diff --git a/Jakefile b/Jakefile
index f76110bb5f2..207cfce2e7f 100644
--- a/Jakefile
+++ b/Jakefile
@@ -1,6 +1,7 @@
 // This file contains the build logic for the public repo
 
 var fs = require("fs");
+var os = require("os");
 var path = require("path");
 var child_process = require("child_process");
 
@@ -148,7 +149,7 @@ var compilerFilename = "tsc.js";
     * @param useBuiltCompiler: true to use the built compiler, false to use the LKG
     * @param noOutFile: true to compile without using --out
     */
-function compileFile(outFile, sources, prereqs, prefixes, useBuiltCompiler, noOutFile, generateDeclarations) {
+function compileFile(outFile, sources, prereqs, prefixes, useBuiltCompiler, noOutFile, generateDeclarations, callback) {
     file(outFile, prereqs, function() {
         var dir = useBuiltCompiler ? builtLocalDirectory : LKGDirectory;
         var options = "-removeComments --module commonjs -noImplicitAny ";
@@ -180,6 +181,11 @@ function compileFile(outFile, sources, prereqs, prefixes, useBuiltCompiler, noOu
                     prependFile(prefixes[i], outFile);
                 }
             }
+
+            if (callback) {
+                callback();
+            }
+
             complete();
         });
         ex.addListener("error", function() {
@@ -224,7 +230,7 @@ compileFile(processDiagnosticMessagesJs,
             [processDiagnosticMessagesTs],
             [processDiagnosticMessagesTs],
             [],
-            false);
+            /*useBuiltCompiler*/ false);
 
 // The generated diagnostics map; built for the compiler and for the 'generate-diagnostics' task
 file(diagnosticInfoMapTs, [processDiagnosticMessagesJs, diagnosticMessagesJson], function () {
@@ -244,7 +250,6 @@ file(diagnosticInfoMapTs, [processDiagnosticMessagesJs, diagnosticMessagesJson],
     ex.run();
 }, {async: true})
 
-
 desc("Generates a diagnostic file in TypeScript based on an input JSON file");
 task("generate-diagnostics", [diagnosticInfoMapTs])
 
@@ -255,13 +260,24 @@ compileFile(tscFile, compilerSources, [builtLocalDirectory, copyright].concat(co
 
 var servicesFile = path.join(builtLocalDirectory, "typescriptServices.js");
 var servicesDefinitionsFile = path.join(builtLocalDirectory, "typescriptServices.d.ts");
-compileFile(servicesFile, servicesSources, [builtLocalDirectory, copyright].concat(servicesSources), [copyright], /*useBuiltCompiler:*/ true, /*noOutFile:*/ false, /*generateDeclarations:*/ true);
+
+compileFile(servicesFile,
+            servicesSources,
+            [builtLocalDirectory, copyright].concat(servicesSources),
+            [copyright],
+            /*useBuiltCompiler*/ true,
+            /*noOutFile*/ false,
+            /*generateDeclarations*/ true,
+            /*callback*/ fixDeclarationFile);
+
+function fixDeclarationFile() {
+    fs.appendFileSync(servicesDefinitionsFile, os.EOL + "export = ts;")
+}
 
 // Local target to build the compiler and services
 desc("Builds the full compiler and services");
 task("local", ["generate-diagnostics", "lib", tscFile, servicesFile]);
 
-
 // Local target to build the compiler and services
 desc("Sets release mode flag");
 task("release", function() {
@@ -278,7 +294,6 @@ task("clean", function() {
     jake.rmRf(builtDirectory);
 });
 
-
 // Generate Markdown spec
 var word2mdJs = path.join(scriptsDirectory, "word2md.js");
 var word2mdTs = path.join(scriptsDirectory, "word2md.ts");
@@ -292,7 +307,7 @@ compileFile(word2mdJs,
             [word2mdTs],
             [word2mdTs],
             [],
-            false);
+            /*useBuiltCompiler*/ false);
 
 // The generated spec.md; built for the 'generate-spec' task
 file(specMd, [word2mdJs, specWord], function () {
@@ -444,7 +459,7 @@ task("generate-code-coverage", ["tests", builtLocalDirectory], function () {
 // Browser tests
 var nodeServerOutFile = 'tests/webTestServer.js'
 var nodeServerInFile = 'tests/webTestServer.ts'
-compileFile(nodeServerOutFile, [nodeServerInFile], [builtLocalDirectory, tscFile], [], true, true);
+compileFile(nodeServerOutFile, [nodeServerInFile], [builtLocalDirectory, tscFile], [], /*useBuiltCompiler:*/ true, /*noOutFile*/ true);
 
 desc("Runs browserify on run.js to produce a file suitable for running tests in the browser");
 task("browserify", ["tests", builtLocalDirectory, nodeServerOutFile], function() {
@@ -525,7 +540,7 @@ task("baseline-accept-test262", function() {
 // Webhost
 var webhostPath = "tests/webhost/webtsc.ts";
 var webhostJsPath = "tests/webhost/webtsc.js";
-compileFile(webhostJsPath, [webhostPath], [tscFile, webhostPath].concat(libraryTargets), [], true);
+compileFile(webhostJsPath, [webhostPath], [tscFile, webhostPath].concat(libraryTargets), [], /*useBuiltCompiler*/true);
 
 desc("Builds the tsc web host");
 task("webhost", [webhostJsPath], function() {
@@ -535,7 +550,7 @@ task("webhost", [webhostJsPath], function() {
 // Perf compiler
 var perftscPath = "tests/perftsc.ts";
 var perftscJsPath = "built/local/perftsc.js";
-compileFile(perftscJsPath, [perftscPath], [tscFile, perftscPath, "tests/perfsys.ts"].concat(libraryTargets), [], true);
+compileFile(perftscJsPath, [perftscPath], [tscFile, perftscPath, "tests/perfsys.ts"].concat(libraryTargets), [], /*useBuiltCompiler*/ true);
 desc("Builds augmented version of the compiler for perf tests");
 task("perftsc", [perftscJsPath]);
 
@@ -559,7 +574,7 @@ file(loggedIOJsPath, [builtLocalDirectory, loggedIOpath], function() {
 
 var instrumenterPath = harnessDirectory + 'instrumenter.ts';
 var instrumenterJsPath = builtLocalDirectory + 'instrumenter.js';
-compileFile(instrumenterJsPath, [instrumenterPath], [tscFile, instrumenterPath], [], true);
+compileFile(instrumenterJsPath, [instrumenterPath], [tscFile, instrumenterPath], [], /*useBuiltCompiler*/ true);
 
 desc("Builds an instrumented tsc.js");
 task('tsc-instrumented', [loggedIOJsPath, instrumenterJsPath, tscFile], function() {
diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index 469a794d13d..a45561e7ed6 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -348,8 +348,8 @@ module ts {
             bindChildren(node, symbolKind, isBlockScopeContainer);
         }
 
-        function bindCatchVariableDeclaration(node: CatchBlock) {
-            var symbol = createSymbol(SymbolFlags.FunctionScopedVariable, node.variable.text || "__missing");
+        function bindCatchVariableDeclaration(node: CatchClause) {
+            var symbol = createSymbol(SymbolFlags.FunctionScopedVariable, node.name.text || "__missing");
             addDeclarationToSymbol(symbol, node, SymbolFlags.FunctionScopedVariable);
             var saveParent = parent;
             var savedBlockScopeContainer = blockScopeContainer;
@@ -444,8 +444,8 @@ module ts {
                 case SyntaxKind.ArrowFunction:
                     bindAnonymousDeclaration(<FunctionExpression>node, SymbolFlags.Function, "__function", /*isBlockScopeContainer*/ true);
                     break;
-                case SyntaxKind.CatchBlock:
-                    bindCatchVariableDeclaration(<CatchBlock>node);
+                case SyntaxKind.CatchClause:
+                    bindCatchVariableDeclaration(<CatchClause>node);
                     break;
                 case SyntaxKind.ClassDeclaration:
                     bindDeclaration(<Declaration>node, SymbolFlags.Class, SymbolFlags.ClassExcludes, /*isBlockScopeContainer*/ false);
@@ -478,7 +478,7 @@ module ts {
 
                 case SyntaxKind.Block:
                 case SyntaxKind.TryBlock:
-                case SyntaxKind.CatchBlock:
+                case SyntaxKind.CatchClause:
                 case SyntaxKind.FinallyBlock:
                 case SyntaxKind.ForStatement:
                 case SyntaxKind.ForInStatement:
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index a663b038844..0e428b4a4e0 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -85,7 +85,6 @@ module ts {
             getDiagnostics,
             getDeclarationDiagnostics,
             getGlobalDiagnostics,
-            checkProgram,
             getParentOfSymbol,
             getNarrowedTypeOfSymbol,
             getDeclaredTypeOfSymbol,
@@ -415,8 +414,8 @@ module ts {
                             break loop;
                         }
                         break;
-                    case SyntaxKind.CatchBlock:
-                        var id = (<CatchBlock>location).variable;
+                    case SyntaxKind.CatchClause:
+                        var id = (<CatchClause>location).name;
                         if (name === id.text) {
                             result = location.symbol;
                             break loop;
@@ -546,14 +545,18 @@ module ts {
             return moduleName.substr(0, 2) === "./" || moduleName.substr(0, 3) === "../" || moduleName.substr(0, 2) === ".\\" || moduleName.substr(0, 3) === "..\\";
         }
 
-        function resolveExternalModuleName(location: Node, moduleExpression: Expression): Symbol {
-            if (moduleExpression.kind !== SyntaxKind.StringLiteral) {
+        function resolveExternalModuleName(location: Node, moduleReferenceExpression: Expression): Symbol {
+            if (moduleReferenceExpression.kind !== SyntaxKind.StringLiteral) {
                 return;
             }
 
-            var moduleLiteral = <LiteralExpression>moduleExpression;
+            var moduleReferenceLiteral = <LiteralExpression>moduleReferenceExpression;
             var searchPath = getDirectoryPath(getSourceFile(location).filename);
-            var moduleName = moduleLiteral.text;
+
+            // Module names are escaped in our symbol table.  However, string literal values aren't.
+            // Escape the name in the "require(...)" clause to ensure we find the right symbol.
+            var moduleName = escapeIdentifier(moduleReferenceLiteral.text);
+
             if (!moduleName) return;
             var isRelative = isExternalModuleNameRelative(moduleName);
             if (!isRelative) {
@@ -574,10 +577,10 @@ module ts {
                 if (sourceFile.symbol) {
                     return getResolvedExportSymbol(sourceFile.symbol);
                 }
-                error(moduleLiteral, Diagnostics.File_0_is_not_an_external_module, sourceFile.filename);
+                error(moduleReferenceLiteral, Diagnostics.File_0_is_not_an_external_module, sourceFile.filename);
                 return;
             }
-            error(moduleLiteral, Diagnostics.Cannot_find_external_module_0, moduleName);
+            error(moduleReferenceLiteral, Diagnostics.Cannot_find_external_module_0, moduleName);
         }
 
         function getResolvedExportSymbol(moduleSymbol: Symbol): Symbol {
@@ -756,7 +759,7 @@ module ts {
             //
             // x is an optional parameter, but it is a required property.
             return propertySymbol.valueDeclaration &&
-                propertySymbol.valueDeclaration.flags & NodeFlags.QuestionMark &&
+                hasQuestionToken(propertySymbol.valueDeclaration) &&
                 propertySymbol.valueDeclaration.kind !== SyntaxKind.Parameter;
         }
 
@@ -1437,11 +1440,11 @@ module ts {
             }
 
             function buildParameterDisplay(p: Symbol, writer: SymbolWriter, enclosingDeclaration?: Node, flags?: TypeFormatFlags, typeStack?: Type[]) {
-                if (getDeclarationFlagsFromSymbol(p) & NodeFlags.Rest) {
+                if (hasDotDotDotToken(p.valueDeclaration)) {
                     writePunctuation(writer, SyntaxKind.DotDotDotToken);
                 }
                 appendSymbolNameOnly(p, writer);
-                if (p.valueDeclaration.flags & NodeFlags.QuestionMark || (<VariableDeclaration>p.valueDeclaration).initializer) {
+                if (hasQuestionToken(p.valueDeclaration) || (<VariableDeclaration>p.valueDeclaration).initializer) {
                     writePunctuation(writer, SyntaxKind.QuestionToken);
                 }
                 writePunctuation(writer, SyntaxKind.ColonToken);
@@ -1711,7 +1714,7 @@ module ts {
             }
 
             // Rest parameters default to type any[], other parameters default to type any
-            var type = declaration.flags & NodeFlags.Rest ? createArrayType(anyType) : anyType;
+            var type = hasDotDotDotToken(declaration) ? createArrayType(anyType) : anyType;
             checkImplicitAny(type);
             return type;
 
@@ -1733,9 +1736,9 @@ module ts {
                         var diagnostic = Diagnostics.Member_0_implicitly_has_an_1_type;
                         break;
                     case SyntaxKind.Parameter:
-                        var diagnostic = declaration.flags & NodeFlags.Rest ?
-                            Diagnostics.Rest_parameter_0_implicitly_has_an_any_type :
-                            Diagnostics.Parameter_0_implicitly_has_an_1_type;
+                        var diagnostic = hasDotDotDotToken(declaration)
+                            ? Diagnostics.Rest_parameter_0_implicitly_has_an_any_type
+                            : Diagnostics.Parameter_0_implicitly_has_an_1_type;
                         break;
                     default:
                         var diagnostic = Diagnostics.Variable_0_implicitly_has_an_1_type;
@@ -1753,7 +1756,7 @@ module ts {
                 }
                 // Handle catch clause variables
                 var declaration = symbol.valueDeclaration;
-                if (declaration.kind === SyntaxKind.CatchBlock) {
+                if (declaration.kind === SyntaxKind.CatchClause) {
                     return links.type = anyType;
                 }
                 // Handle variable, parameter or property
@@ -2527,7 +2530,7 @@ module ts {
                         hasStringLiterals = true;
                     }
                     if (minArgumentCount < 0) {
-                        if (param.initializer || param.flags & (NodeFlags.QuestionMark | NodeFlags.Rest)) {
+                        if (param.initializer || param.questionToken || param.dotDotDotToken) {
                             minArgumentCount = i;
                         }
                     }
@@ -4375,7 +4378,7 @@ module ts {
                     case SyntaxKind.ThrowStatement:
                     case SyntaxKind.TryStatement:
                     case SyntaxKind.TryBlock:
-                    case SyntaxKind.CatchBlock:
+                    case SyntaxKind.CatchClause:
                     case SyntaxKind.FinallyBlock:
                         return forEachChild(node, isAssignedIn);
                 }
@@ -6673,7 +6676,7 @@ module ts {
                     !(parameterDeclaration.parent.kind === SyntaxKind.Constructor && (<ConstructorDeclaration>parameterDeclaration.parent).body)) {
                     error(parameterDeclaration, Diagnostics.A_parameter_property_is_only_allowed_in_a_constructor_implementation);
                 }
-                if (parameterDeclaration.flags & NodeFlags.Rest) {
+                if (parameterDeclaration.dotDotDotToken) {
                     if (!isArrayType(getTypeOfSymbol(parameterDeclaration.symbol))) {
                         error(parameterDeclaration, Diagnostics.A_rest_parameter_must_be_of_an_array_type);
                     }
@@ -7020,20 +7023,23 @@ module ts {
                 return;
             }
 
+            function getCanonicalOverload(overloads: Declaration[], implementation: FunctionLikeDeclaration) {
+                // Consider the canonical set of flags to be the flags of the bodyDeclaration or the first declaration
+                // Error on all deviations from this canonical set of flags
+                // The caveat is that if some overloads are defined in lib.d.ts, we don't want to
+                // report the errors on those. To achieve this, we will say that the implementation is
+                // the canonical signature only if it is in the same container as the first overload
+                var implementationSharesContainerWithFirstOverload = implementation !== undefined && implementation.parent === overloads[0].parent;
+                return implementationSharesContainerWithFirstOverload ? implementation : overloads[0];
+            }
+
             function checkFlagAgreementBetweenOverloads(overloads: Declaration[], implementation: FunctionLikeDeclaration, flagsToCheck: NodeFlags, someOverloadFlags: NodeFlags, allOverloadFlags: NodeFlags): void {
                 // Error if some overloads have a flag that is not shared by all overloads. To find the
                 // deviations, we XOR someOverloadFlags with allOverloadFlags
                 var someButNotAllOverloadFlags = someOverloadFlags ^ allOverloadFlags;
                 if (someButNotAllOverloadFlags !== 0) {
-                    // Consider the canonical set of flags to be the flags of the bodyDeclaration or the first declaration
-                    // Error on all deviations from this canonical set of flags
-                    // The caveat is that if some overloads are defined in lib.d.ts, we don't want to
-                    // report the errors on those. To achieve this, we will say that the implementation is
-                    // the canonical signature only if it is in the same container as the first overload
-                    var implementationSharesContainerWithFirstOverload = implementation !== undefined && implementation.parent === overloads[0].parent;
-                    var canonicalFlags = implementationSharesContainerWithFirstOverload
-                        ? getEffectiveDeclarationFlags(implementation, flagsToCheck)
-                        : getEffectiveDeclarationFlags(overloads[0], flagsToCheck);
+                    var canonicalFlags = getEffectiveDeclarationFlags(getCanonicalOverload(overloads, implementation), flagsToCheck);
+
                     forEach(overloads, o => {
                         var deviation = getEffectiveDeclarationFlags(o, flagsToCheck) ^ canonicalFlags;
                         if (deviation & NodeFlags.Export) {
@@ -7045,16 +7051,27 @@ module ts {
                         else if (deviation & (NodeFlags.Private | NodeFlags.Protected)) {
                             error(o.name, Diagnostics.Overload_signatures_must_all_be_public_private_or_protected);
                         }
-                        else if (deviation & NodeFlags.QuestionMark) {
+                    });
+                }
+            }
+
+            function checkQuestionTokenAgreementBetweenOverloads(overloads: Declaration[], implementation: FunctionLikeDeclaration, someHaveQuestionToken: boolean, allHaveQuestionToken: boolean): void {
+                if (someHaveQuestionToken !== allHaveQuestionToken) {
+                    var canonicalHasQuestionToken = hasQuestionToken(getCanonicalOverload(overloads, implementation));
+                    forEach(overloads, o => {
+                        var deviation = hasQuestionToken(o) !== canonicalHasQuestionToken;
+                        if (deviation) {
                             error(o.name, Diagnostics.Overload_signatures_must_all_be_optional_or_required);
                         }
                     });
                 }
             }
 
-            var flagsToCheck: NodeFlags = NodeFlags.Export | NodeFlags.Ambient | NodeFlags.Private | NodeFlags.Protected | NodeFlags.QuestionMark;
+            var flagsToCheck: NodeFlags = NodeFlags.Export | NodeFlags.Ambient | NodeFlags.Private | NodeFlags.Protected;
             var someNodeFlags: NodeFlags = 0;
             var allNodeFlags = flagsToCheck;
+            var someHaveQuestionToken = false;
+            var allHaveQuestionToken = true;
             var hasOverloads = false;
             var bodyDeclaration: FunctionLikeDeclaration;
             var lastSeenNonAmbientDeclaration: FunctionLikeDeclaration;
@@ -7128,6 +7145,8 @@ module ts {
                     var currentNodeFlags = getEffectiveDeclarationFlags(node, flagsToCheck);
                     someNodeFlags |= currentNodeFlags;
                     allNodeFlags &= currentNodeFlags;
+                    someHaveQuestionToken = someHaveQuestionToken || hasQuestionToken(node);
+                    allHaveQuestionToken = allHaveQuestionToken && hasQuestionToken(node);
 
                     if (node.body && bodyDeclaration) {
                         if (isConstructor) {
@@ -7176,6 +7195,8 @@ module ts {
 
             if (hasOverloads) {
                 checkFlagAgreementBetweenOverloads(declarations, bodyDeclaration, flagsToCheck, someNodeFlags, allNodeFlags);
+                checkQuestionTokenAgreementBetweenOverloads(declarations, bodyDeclaration, someHaveQuestionToken, allHaveQuestionToken);
+
                 if (bodyDeclaration) {
                     var signatures = getSignaturesOfSymbol(symbol);
                     var bodySignature = getSignatureFromDeclaration(bodyDeclaration);
@@ -7725,13 +7746,14 @@ module ts {
         function checkSwitchStatement(node: SwitchStatement) {
             var expressionType = checkExpression(node.expression);
             forEach(node.clauses, clause => {
-                if (fullTypeCheck && clause.expression) {
+                if (fullTypeCheck && clause.kind === SyntaxKind.CaseClause) {
+                    var caseClause = <CaseClause>clause;
                     // TypeScript 1.0 spec (April 2014):5.9
                     // In a 'switch' statement, each 'case' expression must be of a type that is assignable to or from the type of the 'switch' expression.
-                    var caseType = checkExpression(clause.expression);
+                    var caseType = checkExpression(caseClause.expression);
                     if (!isTypeAssignableTo(expressionType, caseType)) {
                         // check 'expressionType isAssignableTo caseType' failed, try the reversed check and report errors if it fails
-                        checkTypeAssignableTo(caseType, expressionType, clause.expression, /*headMessage*/ undefined);
+                        checkTypeAssignableTo(caseType, expressionType, caseClause.expression, /*headMessage*/ undefined);
                     }
                 }
                 forEach(clause.statements, checkSourceElement);
@@ -7748,7 +7770,7 @@ module ts {
 
         function checkTryStatement(node: TryStatement) {
             checkBlock(node.tryBlock);
-            if (node.catchBlock) checkBlock(node.catchBlock);
+            if (node.catchClause) checkBlock(node.catchClause.block);
             if (node.finallyBlock) checkBlock(node.finallyBlock);
         }
 
@@ -8586,7 +8608,7 @@ module ts {
                 case SyntaxKind.ThrowStatement:
                 case SyntaxKind.TryStatement:
                 case SyntaxKind.TryBlock:
-                case SyntaxKind.CatchBlock:
+                case SyntaxKind.CatchClause:
                 case SyntaxKind.FinallyBlock:
                 case SyntaxKind.VariableDeclaration:
                 case SyntaxKind.ClassDeclaration:
@@ -8634,10 +8656,6 @@ module ts {
             }
         }
 
-        function checkProgram() {
-            forEach(program.getSourceFiles(), checkSourceFile);
-        }
-
         function getSortedDiagnostics(): Diagnostic[]{
             Debug.assert(fullTypeCheck, "diagnostics are available only in the full typecheck mode");
 
@@ -8650,12 +8668,11 @@ module ts {
         }
 
         function getDiagnostics(sourceFile?: SourceFile): Diagnostic[]{
-
             if (sourceFile) {
                 checkSourceFile(sourceFile);
                 return filter(getSortedDiagnostics(), d => d.file === sourceFile);
             }
-            checkProgram();
+            forEach(program.getSourceFiles(), checkSourceFile);
             return getSortedDiagnostics();
         }
 
@@ -8748,8 +8765,8 @@ module ts {
                             copySymbol(location.symbol, meaning);
                         }
                         break;
-                    case SyntaxKind.CatchBlock:
-                        if ((<CatchBlock>location).variable.text) {
+                    case SyntaxKind.CatchClause:
+                        if ((<CatchClause>location).name.text) {
                             copySymbol(location.symbol, meaning);
                         }
                         break;
@@ -9005,7 +9022,7 @@ module ts {
             // This is necessary as an identifier in short-hand property assignment can contains two meaning:
             // property name and property value.
             if (location && location.kind === SyntaxKind.ShorthandPropertyAssignment) {
-                return resolveEntityName(location, (<ShortHandPropertyDeclaration>location).name, SymbolFlags.Value);
+                return resolveEntityName(location, (<ShorthandPropertyDeclaration>location).name, SymbolFlags.Value);
             }
             return undefined;
         }
@@ -9173,9 +9190,9 @@ module ts {
             return isImportResolvedToValue(getSymbolOfNode(node));
         }
 
-        function hasSemanticErrors() {
+        function hasSemanticErrors(sourceFile?: SourceFile) {
             // Return true if there is any semantic error in a file or globally
-            return getDiagnostics().length > 0 || getGlobalDiagnostics().length > 0;
+            return getDiagnostics(sourceFile).length > 0 || getGlobalDiagnostics().length > 0;
         }
 
         function isEmitBlocked(sourceFile?: SourceFile): boolean {
@@ -9293,7 +9310,6 @@ module ts {
 
         function invokeEmitter(targetSourceFile?: SourceFile) {
             var resolver = createResolver();
-            checkProgram();
             return emitFiles(resolver, targetSourceFile);
         }
 
diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index fab0433890a..7193523bf96 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -943,7 +943,7 @@ module ts {
             if (node.kind !== SyntaxKind.VariableDeclaration || resolver.isDeclarationVisible(node)) {
                 writeTextOfNode(currentSourceFile, node.name);
                 // If optional property emit ?
-                if (node.kind === SyntaxKind.Property && (node.flags & NodeFlags.QuestionMark)) {
+                if (node.kind === SyntaxKind.Property && hasQuestionToken(node)) {
                     write("?");
                 }
                 if (node.kind === SyntaxKind.Property && node.parent.kind === SyntaxKind.TypeLiteral) {
@@ -1124,7 +1124,7 @@ module ts {
                 }
                 else {
                     writeTextOfNode(currentSourceFile, node.name);
-                    if (node.flags & NodeFlags.QuestionMark) {
+                    if (hasQuestionToken(node)) {
                         write("?");
                     }
                 }
@@ -1252,11 +1252,11 @@ module ts {
         function emitParameterDeclaration(node: ParameterDeclaration) {
             increaseIndent();
             emitJsDocComments(node);
-            if (node.flags & NodeFlags.Rest) {
+            if (node.dotDotDotToken) {
                 write("...");
             }
             writeTextOfNode(currentSourceFile, node.name);
-            if (node.initializer || (node.flags & NodeFlags.QuestionMark)) {
+            if (node.initializer || hasQuestionToken(node)) {
                 write("?");
             }
             decreaseIndent();
@@ -2142,8 +2142,8 @@ module ts {
                         return false;
                     case SyntaxKind.LabeledStatement:
                         return (<LabeledStatement>node.parent).label === node;
-                    case SyntaxKind.CatchBlock:
-                        return (<CatchBlock>node.parent).variable === node;
+                    case SyntaxKind.CatchClause:
+                        return (<CatchClause>node.parent).name === node;
                 }
             }
 
@@ -2236,33 +2236,35 @@ module ts {
                 emitTrailingComments(node);
             }
 
-            function emitShortHandPropertyAssignment(node: ShortHandPropertyDeclaration) {
-                function emitAsNormalPropertyAssignment() {
-                    emitLeadingComments(node);
-                    // Emit identifier as an identifier
-                    emit(node.name);
-                    write(": ");
-                    // Even though this is stored as identified because it is in short-hand property assignment,
-                    // treated it as expression 
-                    emitExpressionIdentifier(node.name);
-                    emitTrailingComments(node);
-                }
+            function emitDownlevelShorthandPropertyAssignment(node: ShorthandPropertyDeclaration) {
+                emitLeadingComments(node);
+                // Emit identifier as an identifier
+                emit(node.name);
+                write(": ");
+                // Even though this is stored as identifier treat it as an expression
+                // Short-hand, { x }, is equivalent of normal form { x: x }
+                emitExpressionIdentifier(node.name);
+                emitTrailingComments(node);
+            }
 
-                if (compilerOptions.target < ScriptTarget.ES6) {
-                    emitAsNormalPropertyAssignment();
+            function emitShorthandPropertyAssignment(node: ShorthandPropertyDeclaration) {
+                // If short-hand property has a prefix, then regardless of the target version, we will emit it as normal property assignment. For example:
+                //  module m {
+                //      export var y;
+                //  }
+                //  module m {
+                //      export var obj = { y };
+                //  }
+                //  The short-hand property in obj need to emit as such ... = { y : m.y } regardless of the TargetScript version
+                var prefix = resolver.getExpressionNamePrefix(node.name);
+                if (prefix) {
+                    emitDownlevelShorthandPropertyAssignment(node);
                 }
-                else if (compilerOptions.target >= ScriptTarget.ES6) {
-                    // If short-hand property has a prefix, then regardless of the target version, we will emit it as normal property assignment
-                    var prefix = resolver.getExpressionNamePrefix(node.name);
-                    if (prefix) {
-                        emitAsNormalPropertyAssignment();
-                    }
-                    // If short-hand property has no prefix, emit it as short-hand.
-                    else {
-                        emitLeadingComments(node);
-                        emit(node.name);
-                        emitTrailingComments(node);
-                    }
+                // If short-hand property has no prefix, emit it as short-hand.
+                else {
+                    emitLeadingComments(node);
+                    emit(node.name);
+                    emitTrailingComments(node);
                 }
             }
 
@@ -2624,7 +2626,7 @@ module ts {
             function emitCaseOrDefaultClause(node: CaseOrDefaultClause) {
                 if (node.kind === SyntaxKind.CaseClause) {
                     write("case ");
-                    emit(node.expression);
+                    emit((<CaseClause>node).expression);
                     write(":");
                 }
                 else {
@@ -2650,7 +2652,7 @@ module ts {
             function emitTryStatement(node: TryStatement) {
                 write("try ");
                 emit(node.tryBlock);
-                emit(node.catchBlock);
+                emit(node.catchClause);
                 if (node.finallyBlock) {
                     writeLine();
                     write("finally ");
@@ -2658,15 +2660,15 @@ module ts {
                 }
             }
 
-            function emitCatchBlock(node: CatchBlock) {
+            function emitCatchClause(node: CatchClause) {
                 writeLine();
                 var endPos = emitToken(SyntaxKind.CatchKeyword, node.pos);
                 write(" ");
                 emitToken(SyntaxKind.OpenParenToken, endPos);
-                emit(node.variable);
-                emitToken(SyntaxKind.CloseParenToken, node.variable.end);
+                emit(node.name);
+                emitToken(SyntaxKind.CloseParenToken, node.name.end);
                 write(" ");
-                emitBlock(node);
+                emitBlock(node.block);
             }
 
             function emitDebuggerStatement(node: Node) {
@@ -3441,6 +3443,7 @@ module ts {
                 // Start new file on new line
                 writeLine();
                 emitDetachedComments(node);
+
                 // emit prologue directives prior to __extends
                 var startIndex = emitDirectivePrologues(node.statements, /*startWithNewLine*/ false);
                 if (!extendsEmitted && resolver.getNodeCheckFlags(node) & NodeCheckFlags.EmitExtends) {
@@ -3472,6 +3475,8 @@ module ts {
                     emitCaptureThisForNodeIfNecessary(node);
                     emitLinesStartingAt(node.statements, startIndex);
                 }
+
+                emitLeadingComments(node.endOfFileToken);
             }
 
             function emitNode(node: Node): void {
@@ -3483,6 +3488,7 @@ module ts {
                     return emitPinnedOrTripleSlashComments(node);
                 }
 
+                // Check if the node can be emitted regardless of the ScriptTarget
                 switch (node.kind) {
                     case SyntaxKind.Identifier:
                         return emitIdentifier(<Identifier>node);
@@ -3521,8 +3527,6 @@ module ts {
                         return emitObjectLiteral(<ObjectLiteralExpression>node);
                     case SyntaxKind.PropertyAssignment:
                         return emitPropertyAssignment(<PropertyDeclaration>node);
-                    case SyntaxKind.ShorthandPropertyAssignment:
-                        return emitShortHandPropertyAssignment(<ShortHandPropertyDeclaration>node);
                     case SyntaxKind.ComputedPropertyName:
                         return emitComputedPropertyName(<ComputedPropertyName>node);
                     case SyntaxKind.PropertyAccessExpression:
@@ -3599,8 +3603,8 @@ module ts {
                         return emitThrowStatement(<ThrowStatement>node);
                     case SyntaxKind.TryStatement:
                         return emitTryStatement(<TryStatement>node);
-                    case SyntaxKind.CatchBlock:
-                        return emitCatchBlock(<CatchBlock>node);
+                    case SyntaxKind.CatchClause:
+                        return emitCatchClause(<CatchClause>node);
                     case SyntaxKind.DebuggerStatement:
                         return emitDebuggerStatement(node);
                     case SyntaxKind.VariableDeclaration:
@@ -3618,6 +3622,23 @@ module ts {
                     case SyntaxKind.SourceFile:
                         return emitSourceFile(<SourceFile>node);
                 }
+
+                // Emit node which needs to be emitted differently depended on ScriptTarget
+                if (compilerOptions.target < ScriptTarget.ES6) {
+                    // Emit node down-level
+                    switch (node.kind) {
+                        case SyntaxKind.ShorthandPropertyAssignment:
+                            return emitDownlevelShorthandPropertyAssignment(<ShorthandPropertyDeclaration>node);
+                    }
+                }
+                else {
+                    // Emit node natively
+                    Debug.assert(compilerOptions.target >= ScriptTarget.ES6, "Invalid ScriptTarget. We should emit as ES6 or above");
+                    switch (node.kind) {
+                        case SyntaxKind.ShorthandPropertyAssignment:
+                            return emitShorthandPropertyAssignment(<ShorthandPropertyDeclaration>node);
+                    }
+                }
             }
 
             function hasDetachedComments(pos: number) {
@@ -3791,20 +3812,14 @@ module ts {
             }
         }
 
-        var hasSemanticErrors = resolver.hasSemanticErrors();
-        var isEmitBlocked = resolver.isEmitBlocked(targetSourceFile);
-
-        function emitFile(jsFilePath: string, sourceFile?: SourceFile) {
-            if (!isEmitBlocked) {
-                emitJavaScript(jsFilePath, sourceFile);
-                if (!hasSemanticErrors && compilerOptions.declaration) {
-                    writeDeclarationFile(jsFilePath, sourceFile);
-                }
-            }
-        }
+        var hasSemanticErrors: boolean = false;
+        var isEmitBlocked: boolean = false;
 
         if (targetSourceFile === undefined) {
             // No targetSourceFile is specified (e.g. calling emitter from batch compiler)
+            hasSemanticErrors = resolver.hasSemanticErrors();
+            isEmitBlocked = resolver.isEmitBlocked();
+
             forEach(program.getSourceFiles(), sourceFile => {
                 if (shouldEmitToOwnFile(sourceFile, compilerOptions)) {
                     var jsFilePath = getOwnEmitOutputFilePath(sourceFile, program, ".js");
@@ -3820,16 +3835,35 @@ module ts {
             // targetSourceFile is specified (e.g calling emitter from language service or calling getSemanticDiagnostic from language service)
             if (shouldEmitToOwnFile(targetSourceFile, compilerOptions)) {
                 // If shouldEmitToOwnFile returns true or targetSourceFile is an external module file, then emit targetSourceFile in its own output file
+                hasSemanticErrors = resolver.hasSemanticErrors(targetSourceFile);
+                isEmitBlocked = resolver.isEmitBlocked(targetSourceFile);
+
                 var jsFilePath = getOwnEmitOutputFilePath(targetSourceFile, program, ".js");
                 emitFile(jsFilePath, targetSourceFile);
             }
             else if (!isDeclarationFile(targetSourceFile) && compilerOptions.out) {
                 // Otherwise, if --out is specified and targetSourceFile is not a declaration file,
                 // Emit all, non-external-module file, into one single output file
+                forEach(program.getSourceFiles(), sourceFile => {
+                    if (!shouldEmitToOwnFile(sourceFile, compilerOptions)) {
+                        hasSemanticErrors = hasSemanticErrors || resolver.hasSemanticErrors(sourceFile);
+                        isEmitBlocked = isEmitBlocked || resolver.isEmitBlocked(sourceFile);
+                    }
+                });
+
                 emitFile(compilerOptions.out);
             }
         }
        
+        function emitFile(jsFilePath: string, sourceFile?: SourceFile) {
+            if (!isEmitBlocked) {
+                emitJavaScript(jsFilePath, sourceFile);
+                if (!hasSemanticErrors && compilerOptions.declaration) {
+                    writeDeclarationFile(jsFilePath, sourceFile);
+                }
+            }
+        }
+
         // Sort and make the unique list of diagnostics
         diagnostics.sort(compareDiagnostics);
         diagnostics = deduplicateSortedDiagnostics(diagnostics);
diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index 687eab878f3..b36ded65dc4 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -216,13 +216,18 @@ module ts {
                 return child((<TypeParameterDeclaration>node).name) ||
                     child((<TypeParameterDeclaration>node).constraint);
             case SyntaxKind.Parameter:
-                return child((<ParameterDeclaration>node).name) ||
+                return children(node.modifiers) ||
+                    child((<ParameterDeclaration>node).dotDotDotToken) ||
+                    child((<ParameterDeclaration>node).name) ||
+                    child((<ParameterDeclaration>node).questionToken) ||
                     child((<ParameterDeclaration>node).type) ||
                     child((<ParameterDeclaration>node).initializer);
             case SyntaxKind.Property:
             case SyntaxKind.PropertyAssignment:
             case SyntaxKind.ShorthandPropertyAssignment:
-                return child((<PropertyDeclaration>node).name) ||
+                return children(node.modifiers) ||
+                    child((<PropertyDeclaration>node).name) ||
+                    child((<PropertyDeclaration>node).questionToken) ||
                     child((<PropertyDeclaration>node).type) ||
                     child((<PropertyDeclaration>node).initializer);
             case SyntaxKind.FunctionType:
@@ -230,7 +235,8 @@ module ts {
             case SyntaxKind.CallSignature:
             case SyntaxKind.ConstructSignature:
             case SyntaxKind.IndexSignature:
-                return children((<SignatureDeclaration>node).typeParameters) ||
+                return children(node.modifiers) ||
+                    children((<SignatureDeclaration>node).typeParameters) ||
                     children((<SignatureDeclaration>node).parameters) ||
                     child((<SignatureDeclaration>node).type);
             case SyntaxKind.Method:
@@ -240,7 +246,9 @@ module ts {
             case SyntaxKind.FunctionExpression:
             case SyntaxKind.FunctionDeclaration:
             case SyntaxKind.ArrowFunction:
-                return child((<FunctionLikeDeclaration>node).name) ||
+                return children(node.modifiers) ||
+                    child((<FunctionLikeDeclaration>node).name) ||
+                    child((<FunctionLikeDeclaration>node).questionToken) ||
                     children((<FunctionLikeDeclaration>node).typeParameters) ||
                     children((<FunctionLikeDeclaration>node).parameters) ||
                     child((<FunctionLikeDeclaration>node).type) ||
@@ -305,10 +313,13 @@ module ts {
             case SyntaxKind.FinallyBlock:
             case SyntaxKind.FunctionBlock:
             case SyntaxKind.ModuleBlock:
-            case SyntaxKind.SourceFile:
                 return children((<Block>node).statements);
+            case SyntaxKind.SourceFile:
+                return children((<SourceFile>node).statements) ||
+                    child((<SourceFile>node).endOfFileToken);
             case SyntaxKind.VariableStatement:
-                return children((<VariableStatement>node).declarations);
+                return children(node.modifiers) ||
+                    children((<VariableStatement>node).declarations);
             case SyntaxKind.ExpressionStatement:
                 return child((<ExpressionStatement>node).expression);
             case SyntaxKind.IfStatement:
@@ -344,9 +355,10 @@ module ts {
                 return child((<SwitchStatement>node).expression) ||
                     children((<SwitchStatement>node).clauses);
             case SyntaxKind.CaseClause:
+                return child((<CaseClause>node).expression) ||
+                    children((<CaseClause>node).statements);
             case SyntaxKind.DefaultClause:
-                return child((<CaseOrDefaultClause>node).expression) ||
-                    children((<CaseOrDefaultClause>node).statements);
+                return children((<DefaultClause>node).statements);
             case SyntaxKind.LabeledStatement:
                 return child((<LabeledStatement>node).label) ||
                     child((<LabeledStatement>node).statement);
@@ -354,42 +366,51 @@ module ts {
                 return child((<ThrowStatement>node).expression);
             case SyntaxKind.TryStatement:
                 return child((<TryStatement>node).tryBlock) ||
-                    child((<TryStatement>node).catchBlock) ||
+                    child((<TryStatement>node).catchClause) ||
                     child((<TryStatement>node).finallyBlock);
-            case SyntaxKind.CatchBlock:
-                return child((<CatchBlock>node).variable) ||
-                    children((<CatchBlock>node).statements);
+            case SyntaxKind.CatchClause:
+                return child((<CatchClause>node).name) ||
+                    child((<CatchClause>node).type) ||
+                    child((<CatchClause>node).block);
             case SyntaxKind.VariableDeclaration:
-                return child((<VariableDeclaration>node).name) ||
+                return children(node.modifiers) ||
+                    child((<VariableDeclaration>node).name) ||
                     child((<VariableDeclaration>node).type) ||
                     child((<VariableDeclaration>node).initializer);
             case SyntaxKind.ClassDeclaration:
-                return child((<ClassDeclaration>node).name) ||
+                return children(node.modifiers) ||
+                    child((<ClassDeclaration>node).name) ||
                     children((<ClassDeclaration>node).typeParameters) ||
                     children((<ClassDeclaration>node).heritageClauses) ||
                     children((<ClassDeclaration>node).members);
             case SyntaxKind.InterfaceDeclaration:
-                return child((<InterfaceDeclaration>node).name) ||
-                children((<InterfaceDeclaration>node).typeParameters) ||
-                children((<ClassDeclaration>node).heritageClauses) ||
+                return children(node.modifiers) ||
+                    child((<InterfaceDeclaration>node).name) ||
+                    children((<InterfaceDeclaration>node).typeParameters) ||
+                    children((<ClassDeclaration>node).heritageClauses) ||
                     children((<InterfaceDeclaration>node).members);
             case SyntaxKind.TypeAliasDeclaration:
-                return child((<TypeAliasDeclaration>node).name) ||
+                return children(node.modifiers) ||
+                    child((<TypeAliasDeclaration>node).name) ||
                     child((<TypeAliasDeclaration>node).type);
             case SyntaxKind.EnumDeclaration:
-                return child((<EnumDeclaration>node).name) ||
+                return children(node.modifiers) ||
+                    child((<EnumDeclaration>node).name) ||
                     children((<EnumDeclaration>node).members);
             case SyntaxKind.EnumMember:
                 return child((<EnumMember>node).name) ||
                     child((<EnumMember>node).initializer);
             case SyntaxKind.ModuleDeclaration:
-                return child((<ModuleDeclaration>node).name) ||
+                return children(node.modifiers) ||
+                    child((<ModuleDeclaration>node).name) ||
                     child((<ModuleDeclaration>node).body);
             case SyntaxKind.ImportDeclaration:
-                return child((<ImportDeclaration>node).name) ||
+                return children(node.modifiers) ||
+                    child((<ImportDeclaration>node).name) ||
                     child((<ImportDeclaration>node).moduleReference);
             case SyntaxKind.ExportAssignment:
-                return child((<ExportAssignment>node).exportName);
+                return children(node.modifiers) ||
+                    child((<ExportAssignment>node).exportName);
             case SyntaxKind.TemplateExpression:
                 return child((<TemplateExpression>node).head) || children((<TemplateExpression>node).templateSpans);
             case SyntaxKind.TemplateSpan:
@@ -427,7 +448,7 @@ module ts {
                 case SyntaxKind.LabeledStatement:
                 case SyntaxKind.TryStatement:
                 case SyntaxKind.TryBlock:
-                case SyntaxKind.CatchBlock:
+                case SyntaxKind.CatchClause:
                 case SyntaxKind.FinallyBlock:
                     return forEachChild(node, traverse);
             }
@@ -608,8 +629,29 @@ module ts {
         return node.kind === SyntaxKind.ImportDeclaration && (<ImportDeclaration>node).moduleReference.kind !== SyntaxKind.ExternalModuleReference;
     }
 
+    export function hasDotDotDotToken(node: Node) {
+        return node && node.kind === SyntaxKind.Parameter && (<ParameterDeclaration>node).dotDotDotToken !== undefined;
+    }
+
+    export function hasQuestionToken(node: Node) {
+        if (node) {
+            switch (node.kind) {
+                case SyntaxKind.Parameter:
+                    return (<ParameterDeclaration>node).questionToken !== undefined;
+                case SyntaxKind.Method:
+                    return (<MethodDeclaration>node).questionToken !== undefined;
+                case SyntaxKind.ShorthandPropertyAssignment:
+                case SyntaxKind.PropertyAssignment:
+                case SyntaxKind.Property:
+                    return (<PropertyDeclaration>node).questionToken !== undefined;
+            }
+        }
+
+        return false;
+    }
+
     export function hasRestParameters(s: SignatureDeclaration): boolean {
-        return s.parameters.length > 0 && (s.parameters[s.parameters.length - 1].flags & NodeFlags.Rest) !== 0;
+        return s.parameters.length > 0 && s.parameters[s.parameters.length - 1].dotDotDotToken !== undefined;
     }
 
     export function isLiteralKind(kind: SyntaxKind): boolean {
@@ -694,8 +736,8 @@ module ts {
             return (<Declaration>parent).name === name;
         }
 
-        if (parent.kind === SyntaxKind.CatchBlock) {
-            return (<CatchBlock>parent).variable === name;
+        if (parent.kind === SyntaxKind.CatchClause) {
+            return (<CatchClause>parent).name === name;
         }
 
         return false;
@@ -903,7 +945,6 @@ module ts {
     }
 
     export function createSourceFile(filename: string, sourceText: string, languageVersion: ScriptTarget, version: string, isOpen: boolean = false): SourceFile {
-        var file: SourceFile;
         var scanner: Scanner;
         var token: SyntaxKind;
         var parsingContext: ParsingContext;
@@ -1061,22 +1102,22 @@ module ts {
             return getPositionFromLineAndCharacter(getLineStarts(), line, character);
         }
 
-        function error(message: DiagnosticMessage, arg0?: any, arg1?: any, arg2?: any): void {
+        function parseErrorAtCurrentToken(message: DiagnosticMessage, arg0?: any, arg1?: any, arg2?: any): void {
             var start = scanner.getTokenPos();
             var length = scanner.getTextPos() - start;
 
-            errorAtPosition(start, length, message, arg0, arg1, arg2);
+            parseErrorAtPosition(start, length, message, arg0, arg1, arg2);
         }
 
-        function errorAtPosition(start: number, length: number, message: DiagnosticMessage, arg0?: any, arg1?: any, arg2?: any): void {
-            var lastErrorPosition = file.parseDiagnostics.length
-                ? file.parseDiagnostics[file.parseDiagnostics.length - 1].start
+        function parseErrorAtPosition(start: number, length: number, message: DiagnosticMessage, arg0?: any, arg1?: any, arg2?: any): void {
+            var lastErrorPosition = sourceFile.parseDiagnostics.length
+                ? sourceFile.parseDiagnostics[sourceFile.parseDiagnostics.length - 1].start
                 : -1;
 
             // Don't report another error if it would just be at the same position as the last error.
             if (start !== lastErrorPosition) {
-                var diagnostic = createFileDiagnostic(file, start, length, message, arg0, arg1, arg2);
-                file.parseDiagnostics.push(diagnostic);
+                var diagnostic = createFileDiagnostic(sourceFile, start, length, message, arg0, arg1, arg2);
+                sourceFile.parseDiagnostics.push(diagnostic);
             }
 
             if (lookAheadMode === LookAheadMode.NoErrorYet) {
@@ -1086,7 +1127,7 @@ module ts {
 
         function scanError(message: DiagnosticMessage) {
             var pos = scanner.getTextPos();
-            errorAtPosition(pos, 0, message);
+            parseErrorAtPosition(pos, 0, message);
         }
 
         function onComment(pos: number, end: number) {
@@ -1125,7 +1166,7 @@ module ts {
             // Keep track of the state we'll need to rollback to if lookahead fails (or if the 
             // caller asked us to always reset our state).
             var saveToken = token;
-            var saveSyntacticErrorsLength = file.parseDiagnostics.length;
+            var saveSyntacticErrorsLength = sourceFile.parseDiagnostics.length;
 
             // Keep track of the current look ahead mode (this matters if we have nested 
             // speculative parsing).
@@ -1147,7 +1188,7 @@ module ts {
             lookAheadMode = saveLookAheadMode;
             if (!result || alwaysResetState) {
                 token = saveToken;
-                file.parseDiagnostics.length = saveSyntacticErrorsLength;
+                sourceFile.parseDiagnostics.length = saveSyntacticErrorsLength;
             }
 
             return result;
@@ -1196,10 +1237,10 @@ module ts {
 
             // Report specific message if provided with one.  Otherwise, report generic fallback message.
             if (diagnosticMessage) {
-                error(diagnosticMessage, arg0);
+                parseErrorAtCurrentToken(diagnosticMessage, arg0);
             }
             else {
-                error(Diagnostics._0_expected, tokenToString(kind));
+                parseErrorAtCurrentToken(Diagnostics._0_expected, tokenToString(kind));
             }
             return false;
         }
@@ -1267,10 +1308,10 @@ module ts {
 
         function createMissingNode(kind: SyntaxKind, reportAtCurrentPosition: boolean, diagnosticMessage: DiagnosticMessage, arg0?: any): Node {
             if (reportAtCurrentPosition) {
-                errorAtPosition(scanner.getStartPos(), 0, diagnosticMessage, arg0);
+                parseErrorAtPosition(scanner.getStartPos(), 0, diagnosticMessage, arg0);
             }
             else {
-                error(diagnosticMessage, arg0);
+                parseErrorAtCurrentToken(diagnosticMessage, arg0);
             }
 
             return createMissingNodeWithoutError(kind);
@@ -1307,11 +1348,11 @@ module ts {
         }
 
         function parseIdentifierName(): Identifier {
-            return createIdentifier(token >= SyntaxKind.Identifier);
+            return createIdentifier(isIdentifierOrKeyword());
         }
 
         function isLiteralPropertyName(): boolean {
-            return token >= SyntaxKind.Identifier ||
+            return isIdentifierOrKeyword() ||
                 token === SyntaxKind.StringLiteral ||
                 token === SyntaxKind.NumericLiteral;
         }
@@ -1345,6 +1386,7 @@ module ts {
             if (inGeneratorParameterContext()) {
                 setYieldContext(false);
             }
+
             node.expression = allowInAnd(parseExpression);
             if (inGeneratorParameterContext()) {
                 setYieldContext(yieldContext);
@@ -1355,22 +1397,26 @@ module ts {
         }
         
         function parseContextualModifier(t: SyntaxKind): boolean {
-            return token === t && tryParse(() => {
-                nextToken();
-                return canFollowModifier();
-            });
+            return token === t && tryParse(nextTokenCanFollowModifier);
+        }
+
+        function nextTokenCanFollowModifier() {
+            nextToken();
+            return canFollowModifier();
         }
 
         function parseAnyContextualModifier(): boolean {
-            return isModifier(token) && tryParse(() => {
-                if (token === SyntaxKind.ConstKeyword) {
-                    // 'const' is only a modifier if followed by 'enum'.
-                    return nextToken() === SyntaxKind.EnumKeyword;
-                }
+            return isModifier(token) && tryParse(nextTokenCanFollowContextualModifier);
+        }
 
-                nextToken();
-                return canFollowModifier();
-            });
+        function nextTokenCanFollowContextualModifier() {
+            if (token === SyntaxKind.ConstKeyword) {
+                // 'const' is only a modifier if followed by 'enum'.
+                return nextToken() === SyntaxKind.EnumKeyword;
+            }
+
+            nextToken();
+            return canFollowModifier();
         }
 
         function canFollowModifier(): boolean {
@@ -1399,7 +1445,9 @@ module ts {
                 case ParsingContext.ObjectLiteralMembers:
                     return token === SyntaxKind.OpenBracketToken || token === SyntaxKind.AsteriskToken || isLiteralPropertyName();
                 case ParsingContext.TypeReferences:
-                    return isIdentifier() && ((token !== SyntaxKind.ExtendsKeyword && token !== SyntaxKind.ImplementsKeyword) || !lookAhead(() => (nextToken(), isIdentifier())));
+                    // We want to make sure that the "extends" in "extends foo" or the "implements" in
+                    // "implements foo" is not considered a type name.
+                    return isIdentifier() && !isNotHeritageClauseTypeName();
                 case ParsingContext.VariableDeclarations:
                 case ParsingContext.TypeParameters:
                     return isIdentifier();
@@ -1419,6 +1467,21 @@ module ts {
             Debug.fail("Non-exhaustive case in 'isListElement'.");
         }
 
+        function nextTokenIsIdentifier() {
+            nextToken();
+            return isIdentifier();
+        }
+        
+        function isNotHeritageClauseTypeName(): boolean {
+            if (token === SyntaxKind.ImplementsKeyword ||
+                token === SyntaxKind.ExtendsKeyword) {
+
+                return lookAhead(nextTokenIsIdentifier);
+            }
+
+            return false;
+        }
+
         // True if positioned at a list terminator
         function isListTerminator(kind: ParsingContext): boolean {
             if (token === SyntaxKind.EndOfFileToken) {
@@ -1542,7 +1605,7 @@ module ts {
 
         // Returns true if we should abort parsing.
         function abortParsingListOrMoveToNextToken(kind: ParsingContext) {
-            error(parsingContextErrors(kind));
+            parseErrorAtCurrentToken(parsingContextErrors(kind));
             if (isInSomeParsingContext()) {
                 return true;
             }
@@ -1649,10 +1712,7 @@ module ts {
             // In the first case though, ASI will not take effect because there is not a
             // line terminator after the keyword.
             if (scanner.hasPrecedingLineBreak() && scanner.isReservedWord()) {
-                var matchesPattern = lookAhead(() => {
-                    nextToken();
-                    return !scanner.hasPrecedingLineBreak() && (scanner.isIdentifier() || scanner.isReservedWord());
-                });
+                var matchesPattern = lookAhead(nextTokenIsIdentifierOrKeywordOnSameLine);
 
                 if (matchesPattern) {
                     // Report that we need an identifier.  However, report it right after the dot, 
@@ -1665,6 +1725,8 @@ module ts {
             return allowIdentifierNames ? parseIdentifierName() : parseIdentifier();
         }
 
+
+
         function parseTokenNode<T extends Node>(): T {
             var node = <T>createNode(token);
             nextToken();
@@ -1812,11 +1874,8 @@ module ts {
 
         function parseParameter(): ParameterDeclaration {
             var node = <ParameterDeclaration>createNode(SyntaxKind.Parameter);
-            var modifiers = parseModifiers();
-            setModifiers(node, modifiers);
-            if (parseOptional(SyntaxKind.DotDotDotToken)) {
-                node.flags |= NodeFlags.Rest;
-            }
+            setModifiers(node, parseModifiers());
+            node.dotDotDotToken = parseOptionalToken(SyntaxKind.DotDotDotToken);
 
             // SingleNameBinding[Yield,GeneratorParameter] : See 13.2.3
             //      [+GeneratorParameter]BindingIdentifier[Yield]Initializer[In]opt
@@ -1838,9 +1897,7 @@ module ts {
                 nextToken();
             }
 
-            if (parseOptional(SyntaxKind.QuestionToken)) {
-                node.flags |= NodeFlags.QuestionMark;
-            }
+            node.questionToken = parseOptionalToken(SyntaxKind.QuestionToken);
             node.type = parseParameterType();
             node.initializer = inGeneratorParameterContext()
                 ? doOutsideOfYieldContext(parseParameterInitializer)
@@ -1861,22 +1918,17 @@ module ts {
             return parseInitializer(/*inParameter*/ true);
         }
 
-        function parseSignature(kind: SyntaxKind, returnToken: SyntaxKind, returnTokenRequired: boolean, yieldAndGeneratorParameterContext: boolean): ParsedSignature {
+        function parseSignature(yieldAndGeneratorParameterContext: boolean): ParsedSignature {
             var signature = <ParsedSignature>{};
-            fillSignature(kind, returnToken, returnTokenRequired, yieldAndGeneratorParameterContext, signature);
+            fillSignature(SyntaxKind.ColonToken, yieldAndGeneratorParameterContext, signature);
             return signature;
         }
 
         function fillSignature(
-                kind: SyntaxKind,
                 returnToken: SyntaxKind,
-                returnTokenRequired: boolean,
                 yieldAndGeneratorParameterContext: boolean,
                 signature: ParsedSignature): void {
-
-            if (kind === SyntaxKind.ConstructSignature) {
-                parseExpected(SyntaxKind.NewKeyword);
-            }
+            var returnTokenRequired = returnToken === SyntaxKind.EqualsGreaterThanToken;
             signature.typeParameters = parseTypeParameters();
             signature.parameters = parseParameterList(yieldAndGeneratorParameterContext);
 
@@ -1927,9 +1979,12 @@ module ts {
             return createMissingList<ParameterDeclaration>();
         }
 
-        function parseSignatureMember(kind: SyntaxKind, returnToken: SyntaxKind): SignatureDeclaration {
+        function parseSignatureMember(kind: SyntaxKind): SignatureDeclaration {
             var node = <SignatureDeclaration>createNode(kind);
-            fillSignature(kind, returnToken, /* returnTokenRequired */ false, /*yieldAndGeneratorParameterContext:*/ false, node);
+            if (kind === SyntaxKind.ConstructSignature) {
+                parseExpected(SyntaxKind.NewKeyword);
+            }
+            fillSignature(SyntaxKind.ColonToken, /*yieldAndGeneratorParameterContext:*/ false, node);
             parseSemicolon();
             return finishNode(node);
         }
@@ -1939,58 +1994,62 @@ module ts {
                 return false;
             }
 
-            return lookAhead(() => {
-                // The only allowed sequence is:
-                //
-                //   [id:
-                //
-                // However, for error recovery, we also check the following cases:
-                //
-                //   [...
-                //   [id,
-                //   [id?,
-                //   [id?:
-                //   [id?]
-                //   [public id
-                //   [private id
-                //   [protected id
-                //   []
-                //
-                if (nextToken() === SyntaxKind.DotDotDotToken || token === SyntaxKind.CloseBracketToken) {
+            return lookAhead(isUnambiguouslyIndexSignature);
+        }
+
+        function isUnambiguouslyIndexSignature() {
+            // The only allowed sequence is:
+            //
+            //   [id:
+            //
+            // However, for error recovery, we also check the following cases:
+            //
+            //   [...
+            //   [id,
+            //   [id?,
+            //   [id?:
+            //   [id?]
+            //   [public id
+            //   [private id
+            //   [protected id
+            //   []
+            //
+            nextToken();
+            if (token === SyntaxKind.DotDotDotToken || token === SyntaxKind.CloseBracketToken) {
+                return true;
+            }
+
+            if (isModifier(token)) {
+                nextToken();
+                if (isIdentifier()) {
                     return true;
                 }
+            }
+            else if (!isIdentifier()) {
+                return false;
+            }
+            else {
+                // Skip the identifier
+                nextToken();
+            }
 
-                if (isModifier(token)) {
-                    nextToken();
-                    if (isIdentifier()) {
-                        return true;
-                    }
-                }
-                else if (!isIdentifier()) {
-                    return false;
-                }
-                else {
-                    // Skip the identifier
-                    nextToken();
-                }
+            // A colon signifies a well formed indexer
+            // A comma should be a badly formed indexer because comma expressions are not allowed
+            // in computed properties.
+            if (token === SyntaxKind.ColonToken || token === SyntaxKind.CommaToken) {
+                return true;
+            }
 
-                // A colon signifies a well formed indexer
-                // A comma should be a badly formed indexer because comma expressions are not allowed
-                // in computed properties.
-                if (token === SyntaxKind.ColonToken || token === SyntaxKind.CommaToken) {
-                    return true;
-                }
+            // Question mark could be an indexer with an optional property,
+            // or it could be a conditional expression in a computed property.
+            if (token !== SyntaxKind.QuestionToken) {
+                return false;
+            }
 
-                // Question mark could be an indexer with an optional property,
-                // or it could be a conditional expression in a computed property.
-                if (token !== SyntaxKind.QuestionToken) {
-                    return false;
-                }
-
-                // If any of the following tokens are after the question mark, it cannot
-                // be a conditional expression, so treat it as an indexer.
-                return nextToken() === SyntaxKind.ColonToken || token === SyntaxKind.CommaToken || token === SyntaxKind.CloseBracketToken;
-            });
+            // If any of the following tokens are after the question mark, it cannot
+            // be a conditional expression, so treat it as an indexer.
+            nextToken();
+            return token === SyntaxKind.ColonToken || token === SyntaxKind.CommaToken || token === SyntaxKind.CloseBracketToken;
         }
 
         function parseIndexSignatureDeclaration(fullStart: number, modifiers: ModifiersArray): IndexSignatureDeclaration {
@@ -2005,19 +2064,16 @@ module ts {
         function parsePropertyOrMethod(): Declaration {
             var fullStart = scanner.getStartPos();
             var name = parsePropertyName();
-            var flags = 0;
-            if (parseOptional(SyntaxKind.QuestionToken)) {
-                flags = NodeFlags.QuestionMark;
-            }
+            var questionToken = parseOptionalToken(SyntaxKind.QuestionToken);
 
             if (token === SyntaxKind.OpenParenToken || token === SyntaxKind.LessThanToken) {
                 var method = <MethodDeclaration>createNode(SyntaxKind.Method, fullStart);
                 method.name = name;
-                method.flags = flags;
+                method.questionToken = questionToken;
 
                 // Method signatues don't exist in expression contexts.  So they have neither
                 // [Yield] nor [GeneratorParameter]
-                fillSignature(SyntaxKind.CallSignature, SyntaxKind.ColonToken, /* returnTokenRequired */ false, /*yieldAndGeneratorParameterContext:*/ false, method);
+                fillSignature(SyntaxKind.ColonToken, /*yieldAndGeneratorParameterContext:*/ false, method);
 
                 parseSemicolon();
                 return finishNode(method);
@@ -2025,7 +2081,7 @@ module ts {
             else {
                 var property = <PropertyDeclaration>createNode(SyntaxKind.Property, fullStart);
                 property.name = name;
-                property.flags = flags;
+                property.questionToken = questionToken;
                 property.type = parseTypeAnnotation();
                 parseSemicolon();
                 return finishNode(property);
@@ -2039,40 +2095,54 @@ module ts {
                 case SyntaxKind.OpenBracketToken: // Both for indexers and computed properties
                     return true;
                 default:
-                    return isLiteralPropertyName() && lookAhead(() => nextToken() === SyntaxKind.OpenParenToken || token === SyntaxKind.LessThanToken || token === SyntaxKind.QuestionToken ||
-                        token === SyntaxKind.ColonToken || canParseSemicolon());
+                    return isLiteralPropertyName() && lookAhead(isTypeMemberWithLiteralPropertyName);
             }
         }
 
+        function isTypeMemberWithLiteralPropertyName() {
+            nextToken();
+            return token === SyntaxKind.OpenParenToken ||
+                token === SyntaxKind.LessThanToken ||
+                token === SyntaxKind.QuestionToken ||
+                token === SyntaxKind.ColonToken ||
+                canParseSemicolon();
+        }
+
         function parseTypeMember(): Declaration {
             switch (token) {
                 case SyntaxKind.OpenParenToken:
                 case SyntaxKind.LessThanToken:
-                    return parseSignatureMember(SyntaxKind.CallSignature, SyntaxKind.ColonToken);
+                    return parseSignatureMember(SyntaxKind.CallSignature);
                 case SyntaxKind.OpenBracketToken:
                     // Indexer or computed property
                     return isIndexSignature() ? parseIndexSignatureDeclaration(scanner.getStartPos(), /*modifiers:*/ undefined) : parsePropertyOrMethod();
                 case SyntaxKind.NewKeyword:
-                    if (lookAhead(() => nextToken() === SyntaxKind.OpenParenToken || token === SyntaxKind.LessThanToken)) {
-                        return parseSignatureMember(SyntaxKind.ConstructSignature, SyntaxKind.ColonToken);
+                    if (lookAhead(isStartOfConstructSignature)) {
+                        return parseSignatureMember(SyntaxKind.ConstructSignature);
                     }
+                    // fall through.
                 case SyntaxKind.StringLiteral:
                 case SyntaxKind.NumericLiteral:
                     return parsePropertyOrMethod();
                 default:
-                    if (token >= SyntaxKind.Identifier) {
+                    if (isIdentifierOrKeyword()) {
                         return parsePropertyOrMethod();
                     }
             }
         }
 
+        function isStartOfConstructSignature() {
+            nextToken();
+            return token === SyntaxKind.OpenParenToken || token === SyntaxKind.LessThanToken;
+        }
+
         function parseTypeLiteral(): TypeLiteralNode {
             var node = <TypeLiteralNode>createNode(SyntaxKind.TypeLiteral);
-            node.members = parseObjectType();
+            node.members = parseObjectTypeMembers();
             return finishNode(node);
         }
 
-        function parseObjectType(): NodeArray<Declaration> {
+        function parseObjectTypeMembers(): NodeArray<Declaration> {
             var members: NodeArray<Declaration>;
             if (parseExpected(SyntaxKind.OpenBraceToken)) {
                 members = parseList(ParsingContext.TypeMembers, /*checkForStrictMode*/ false, parseTypeMember);
@@ -2091,7 +2161,7 @@ module ts {
             return finishNode(node);
         }
 
-        function parseParenType(): ParenthesizedTypeNode {
+        function parseParenthesizedType(): ParenthesizedTypeNode {
             var node = <ParenthesizedTypeNode>createNode(SyntaxKind.ParenthesizedType);
             parseExpected(SyntaxKind.OpenParenToken);
             node.type = parseType();
@@ -2099,10 +2169,12 @@ module ts {
             return finishNode(node);
         }
 
-        function parseFunctionType(typeKind: SyntaxKind): FunctionOrConstructorTypeNode {
-            var node = <FunctionOrConstructorTypeNode>createNode(typeKind);
-            fillSignature(typeKind === SyntaxKind.FunctionType ? SyntaxKind.CallSignature : SyntaxKind.ConstructSignature,
-                SyntaxKind.EqualsGreaterThanToken, /* returnTokenRequired */ true, /*yieldAndGeneratorParameterContext:*/ false, node);
+        function parseFunctionOrConstructorType(kind: SyntaxKind): FunctionOrConstructorTypeNode {
+            var node = <FunctionOrConstructorTypeNode>createNode(kind);
+            if (kind === SyntaxKind.ConstructorType) {
+                parseExpected(SyntaxKind.NewKeyword);
+            }
+            fillSignature(SyntaxKind.EqualsGreaterThanToken, /*yieldAndGeneratorParameterContext:*/ false, node);
             return finishNode(node);
         }
 
@@ -2129,7 +2201,7 @@ module ts {
                 case SyntaxKind.OpenBracketToken:
                     return parseTupleType();
                 case SyntaxKind.OpenParenToken:
-                    return parseParenType();
+                    return parseParenthesizedType();
                 default:
                     return parseTypeReference();
             }
@@ -2151,16 +2223,18 @@ module ts {
                 case SyntaxKind.OpenParenToken:
                     // Only consider '(' the start of a type if followed by ')', '...', an identifier, a modifier,
                     // or something that starts a type. We don't want to consider things like '(1)' a type.
-                    return lookAhead(() => {
-                        nextToken();
-                        return token === SyntaxKind.CloseParenToken || isStartOfParameter() || isStartOfType();
-                    });
+                    return lookAhead(isStartOfParenthesizedOrFunctionType);
                 default:
                     return isIdentifier();
             }
         }
 
-        function parsePrimaryType(): TypeNode {
+        function isStartOfParenthesizedOrFunctionType() {
+            nextToken();
+            return token === SyntaxKind.CloseParenToken || isStartOfParameter() || isStartOfType();
+        }
+
+        function parseArrayTypeOrHigher(): TypeNode {
             var type = parseNonArrayType();
             while (!scanner.hasPrecedingLineBreak() && parseOptional(SyntaxKind.OpenBracketToken)) {
                 parseExpected(SyntaxKind.CloseBracketToken);
@@ -2171,13 +2245,13 @@ module ts {
             return type;
         }
 
-        function parseUnionType(): TypeNode {
-            var type = parsePrimaryType();
+        function parseUnionTypeOrHigher(): TypeNode {
+            var type = parseArrayTypeOrHigher();
             if (token === SyntaxKind.BarToken) {
                 var types = <NodeArray<TypeNode>>[type];
                 types.pos = type.pos;
                 while (parseOptional(SyntaxKind.BarToken)) {
-                    types.push(parsePrimaryType());
+                    types.push(parseArrayTypeOrHigher());
                 }
                 types.end = getNodeEnd();
                 var node = <UnionTypeNode>createNode(SyntaxKind.UnionType, type.pos);
@@ -2188,35 +2262,41 @@ module ts {
         }
 
         function isStartOfFunctionType(): boolean {
-            return token === SyntaxKind.LessThanToken || token === SyntaxKind.OpenParenToken && lookAhead(() => {
+            if (token === SyntaxKind.LessThanToken) {
+                return true;
+            }
+
+            return token === SyntaxKind.OpenParenToken && lookAhead(isUnambiguouslyStartOfFunctionType);
+        }
+
+        function isUnambiguouslyStartOfFunctionType() {
+            nextToken();
+            if (token === SyntaxKind.CloseParenToken || token === SyntaxKind.DotDotDotToken) {
+                // ( )
+                // ( ...
+                return true;
+            }
+            if (isIdentifier() || isModifier(token)) {
                 nextToken();
-                if (token === SyntaxKind.CloseParenToken || token === SyntaxKind.DotDotDotToken) {
-                    // ( )
-                    // ( ...
+                if (token === SyntaxKind.ColonToken || token === SyntaxKind.CommaToken ||
+                    token === SyntaxKind.QuestionToken || token === SyntaxKind.EqualsToken ||
+                    isIdentifier() || isModifier(token)) {
+                    // ( id :
+                    // ( id ,
+                    // ( id ?
+                    // ( id =
+                    // ( modifier id
                     return true;
                 }
-                if (isIdentifier() || isModifier(token)) {
+                if (token === SyntaxKind.CloseParenToken) {
                     nextToken();
-                    if (token === SyntaxKind.ColonToken || token === SyntaxKind.CommaToken ||
-                        token === SyntaxKind.QuestionToken || token === SyntaxKind.EqualsToken ||
-                        isIdentifier() || isModifier(token)) {
-                        // ( id :
-                        // ( id ,
-                        // ( id ?
-                        // ( id =
-                        // ( modifier id
+                    if (token === SyntaxKind.EqualsGreaterThanToken) {
+                        // ( id ) =>
                         return true;
                     }
-                    if (token === SyntaxKind.CloseParenToken) {
-                        nextToken();
-                        if (token === SyntaxKind.EqualsGreaterThanToken) {
-                            // ( id ) =>
-                            return true;
-                        }
-                    }
                 }
-                return false;
-            });
+            }
+            return false;
         }
 
         function parseType(): TypeNode {
@@ -2238,12 +2318,12 @@ module ts {
 
         function parseTypeWorker(): TypeNode {
             if (isStartOfFunctionType()) {
-                return parseFunctionType(SyntaxKind.FunctionType);
+                return parseFunctionOrConstructorType(SyntaxKind.FunctionType);
             }
             if (token === SyntaxKind.NewKeyword) {
-                return parseFunctionType(SyntaxKind.ConstructorType);
+                return parseFunctionOrConstructorType(SyntaxKind.ConstructorType);
             }
-            return parseUnionType();
+            return parseUnionTypeOrHigher();
         }
 
         function parseTypeAnnotation(): TypeNode {
@@ -2419,15 +2499,17 @@ module ts {
                 // for now we just check if the next token is an identifier.  More heuristics
                 // can be added here later as necessary.  We just need to make sure that we
                 // don't accidently consume something legal.
-                return lookAhead(() => {
-                    nextToken();
-                    return !scanner.hasPrecedingLineBreak() && isIdentifier();
-                });
+                return lookAhead(nextTokenIsIdentifierOnSameLine);
             }
 
             return false;
         }
 
+        function nextTokenIsIdentifierOnSameLine() {
+            nextToken();
+            return !scanner.hasPrecedingLineBreak() && isIdentifier()
+        }
+
         function parseYieldExpression(): YieldExpression {
             var node = <YieldExpression>createNode(SyntaxKind.YieldExpression);
 
@@ -2452,57 +2534,55 @@ module ts {
 
         function parseSimpleArrowFunctionExpression(identifier: Identifier): Expression {
             Debug.assert(token === SyntaxKind.EqualsGreaterThanToken, "parseSimpleArrowFunctionExpression should only have been called if we had a =>");
-            parseExpected(SyntaxKind.EqualsGreaterThanToken);
+
+            var node = <FunctionExpression>createNode(SyntaxKind.ArrowFunction, identifier.pos);
 
             var parameter = <ParameterDeclaration>createNode(SyntaxKind.Parameter, identifier.pos);
             parameter.name = identifier;
             finishNode(parameter);
 
-            var parameters = <NodeArray<ParameterDeclaration>>[];
-            parameters.push(parameter);
-            parameters.pos = parameter.pos;
-            parameters.end = parameter.end;
+            node.parameters = <NodeArray<ParameterDeclaration>>[parameter];
+            node.parameters.pos = parameter.pos;
+            node.parameters.end = parameter.end;
 
-            var signature = <ParsedSignature> { parameters: parameters };
+            parseExpected(SyntaxKind.EqualsGreaterThanToken);
+            node.body = parseArrowFunctionExpressionBody();
 
-            return parseArrowExpressionTail(identifier.pos, signature);
+            return finishNode(node);
         }
 
         function tryParseParenthesizedArrowFunctionExpression(): Expression {
-            // Indicates whether we are certain that we should parse an arrow expression.
             var triState = isParenthesizedArrowFunctionExpression();
 
             if (triState === Tristate.False) {
+                // It's definitely not a parenthesized arrow function expression.
                 return undefined;
             }
 
-            var pos = getNodePos();
+            // If we definitely have an arrow function, then we can just parse one, not requiring a
+            // following => or { token. Otherwise, we *might* have an arrow function.  Try to parse
+            // it out, but don't allow any ambiguity, and return 'undefined' if this could be an
+            // expression instead.
+            var arrowFunction = triState === Tristate.True
+                ? parseParenthesizedArrowFunctionExpressionHead(/*allowAmbiguity:*/ true)
+                : tryParse(parsePossibleParenthesizedArrowFunctionExpressionHead);
 
-            if (triState === Tristate.True) {
-                // Arrow function are never generators.
-                var sig = parseSignature(SyntaxKind.CallSignature, SyntaxKind.ColonToken, /*returnTokenRequired:*/ false, /*yieldAndGeneratorParameterContext:*/ false);
-
-                // If we have an arrow, then try to parse the body.
-                // Even if not, try to parse if we have an opening brace, just in case we're in an error state.
-                if (parseExpected(SyntaxKind.EqualsGreaterThanToken) || token === SyntaxKind.OpenBraceToken) {
-                    return parseArrowExpressionTail(pos, sig);
-                }
-                else {
-                    // If not, we're probably better off bailing out and returning a bogus function expression.
-                    return makeFunctionExpression(SyntaxKind.ArrowFunction, pos, /*asteriskToken:*/ undefined, /*name:*/ undefined, sig, parseIdentifier(Diagnostics.Expression_expected));
-                }
+            if (!arrowFunction) {
+                // Didn't appear to actually be a parenthesized arrow function.  Just bail out.
+                return undefined;
             }
-            
-            // *Maybe* we had an arrow function and we need to try to parse it out,
-            // rolling back and trying other parses if we fail.
-            var sig = tryParseSignatureIfArrowOrBraceFollows();
-            if (sig) {
-                parseExpected(SyntaxKind.EqualsGreaterThanToken);
-                return parseArrowExpressionTail(pos, sig);
+
+            // If we have an arrow, then try to parse the body. Even if not, try to parse if we 
+            // have an opening brace, just in case we're in an error state.
+            if (parseExpected(SyntaxKind.EqualsGreaterThanToken) || token === SyntaxKind.OpenBraceToken) {
+                arrowFunction.body = parseArrowFunctionExpressionBody();
             }
             else {
-                return undefined;
+                // If not, we're probably better off bailing out and returning a bogus function expression.
+                arrowFunction.body = parseIdentifier();
             }
+
+            return finishNode(arrowFunction);
         }
 
         //  True        -> We definitely expect a parenthesized arrow function here.
@@ -2511,66 +2591,9 @@ module ts {
         //                 Speculatively look ahead to be sure, and rollback if not.
         function isParenthesizedArrowFunctionExpression(): Tristate {
             if (token === SyntaxKind.OpenParenToken || token === SyntaxKind.LessThanToken) {
-                return lookAhead(() => {
-                    var first = token;
-                    var second = nextToken();
-
-                    if (first === SyntaxKind.OpenParenToken) {
-                        if (second === SyntaxKind.CloseParenToken) {
-                            // Simple cases: "() =>", "(): ", and  "() {".
-                            // This is an arrow function with no parameters.
-                            // The last one is not actually an arrow function,
-                            // but this is probably what the user intended.
-                            var third = nextToken();
-                            switch (third) {
-                                case SyntaxKind.EqualsGreaterThanToken:
-                                case SyntaxKind.ColonToken:
-                                case SyntaxKind.OpenBraceToken:
-                                    return Tristate.True;
-                                default:
-                                    return Tristate.False;
-                            }
-                        }
-
-                        // Simple case: "(..."
-                        // This is an arrow function with a rest parameter.
-                        if (second === SyntaxKind.DotDotDotToken) {
-                            return Tristate.True;
-                        }
-
-                        // If we had "(" followed by something that's not an identifier,
-                        // then this definitely doesn't look like a lambda.
-                        // Note: we could be a little more lenient and allow
-                        // "(public" or "(private". These would not ever actually be allowed,
-                        // but we could provide a good error message instead of bailing out.
-                        if (!isIdentifier()) {
-                            return Tristate.False;
-                        }
-
-                        // If we have something like "(a:", then we must have a
-                        // type-annotated parameter in an arrow function expression.
-                        if (nextToken() === SyntaxKind.ColonToken) {
-                            return Tristate.True;
-                        }
-
-                        // This *could* be a parenthesized arrow function.
-                        // Return Unknown to let the caller know.
-                        return Tristate.Unknown;
-                    }
-                    else {
-                        Debug.assert(first === SyntaxKind.LessThanToken);
-
-                        // If we have "<" not followed by an identifier,
-                        // then this definitely is not an arrow function.
-                        if (!isIdentifier()) {
-                            return Tristate.False;
-                        }
-
-                        // This *could* be a parenthesized arrow function.
-                        return Tristate.Unknown;
-                    }
-                });
+                return lookAhead(isParenthesizedArrowFunctionExpressionWorker);
             }
+
             if (token === SyntaxKind.EqualsGreaterThanToken) {
                 // ERROR RECOVERY TWEAK:
                 // If we see a standalone => try to parse it as an arrow function expression as that's
@@ -2581,34 +2604,97 @@ module ts {
             return Tristate.False;
         }
 
-        function tryParseSignatureIfArrowOrBraceFollows(): ParsedSignature {
-            return tryParse(() => {
-                // Arrow functions are never generators.
-                var sig = parseSignature(SyntaxKind.CallSignature, SyntaxKind.ColonToken, /* returnTokenRequired */ false, /*yieldAndGeneratorParameterContext:*/ false);
+        function isParenthesizedArrowFunctionExpressionWorker() {
+            var first = token;
+            var second = nextToken();
 
-                // Parsing a signature isn't enough.
-                // Parenthesized arrow signatures often look like other valid expressions.
-                // For instance:
-                //  - "(x = 10)" is an assignment expression parsed as a signature with a default parameter value.
-                //  - "(x,y)" is a comma expression parsed as a signature with two parameters.
-                //  - "a ? (b): c" will have "(b):" parsed as a signature with a return type annotation.
-                //
-                // So we need just a bit of lookahead to ensure that it can only be a signature.
-                if (token === SyntaxKind.EqualsGreaterThanToken || token === SyntaxKind.OpenBraceToken) {
-                    return sig;
+            if (first === SyntaxKind.OpenParenToken) {
+                if (second === SyntaxKind.CloseParenToken) {
+                    // Simple cases: "() =>", "(): ", and  "() {".
+                    // This is an arrow function with no parameters.
+                    // The last one is not actually an arrow function,
+                    // but this is probably what the user intended.
+                    var third = nextToken();
+                    switch (third) {
+                        case SyntaxKind.EqualsGreaterThanToken:
+                        case SyntaxKind.ColonToken:
+                        case SyntaxKind.OpenBraceToken:
+                            return Tristate.True;
+                        default:
+                            return Tristate.False;
+                    }
                 }
 
-                return undefined;
-            });
+                // Simple case: "(..."
+                // This is an arrow function with a rest parameter.
+                if (second === SyntaxKind.DotDotDotToken) {
+                    return Tristate.True;
+                }
+
+                // If we had "(" followed by something that's not an identifier,
+                // then this definitely doesn't look like a lambda.
+                // Note: we could be a little more lenient and allow
+                // "(public" or "(private". These would not ever actually be allowed,
+                // but we could provide a good error message instead of bailing out.
+                if (!isIdentifier()) {
+                    return Tristate.False;
+                }
+
+                // If we have something like "(a:", then we must have a
+                // type-annotated parameter in an arrow function expression.
+                if (nextToken() === SyntaxKind.ColonToken) {
+                    return Tristate.True;
+                }
+
+                // This *could* be a parenthesized arrow function.
+                // Return Unknown to let the caller know.
+                return Tristate.Unknown;
+            }
+            else {
+                Debug.assert(first === SyntaxKind.LessThanToken);
+
+                // If we have "<" not followed by an identifier,
+                // then this definitely is not an arrow function.
+                if (!isIdentifier()) {
+                    return Tristate.False;
+                }
+
+                // This *could* be a parenthesized arrow function.
+                return Tristate.Unknown;
+            }
         }
 
-        function parseArrowExpressionTail(pos: number, sig: ParsedSignature): FunctionExpression {
-            var body: Block | Expression;
+        function parsePossibleParenthesizedArrowFunctionExpressionHead() {
+            return parseParenthesizedArrowFunctionExpressionHead(/*allowAmbiguity:*/ false);
+        }
 
-            if (token === SyntaxKind.OpenBraceToken) {
-                body = parseFunctionBlock(/*allowYield:*/ false, /* ignoreMissingOpenBrace */ false);
+        function parseParenthesizedArrowFunctionExpressionHead(allowAmbiguity: boolean): FunctionExpression {
+            var node = <FunctionExpression>createNode(SyntaxKind.ArrowFunction);
+            // Arrow functions are never generators.
+            fillSignature(SyntaxKind.ColonToken, /*yieldAndGeneratorParameterContext:*/ false, node);
+
+            // Parsing a signature isn't enough.
+            // Parenthesized arrow signatures often look like other valid expressions.
+            // For instance:
+            //  - "(x = 10)" is an assignment expression parsed as a signature with a default parameter value.
+            //  - "(x,y)" is a comma expression parsed as a signature with two parameters.
+            //  - "a ? (b): c" will have "(b):" parsed as a signature with a return type annotation.
+            //
+            // So we need just a bit of lookahead to ensure that it can only be a signature.
+            if (!allowAmbiguity && token !== SyntaxKind.EqualsGreaterThanToken && token !== SyntaxKind.OpenBraceToken) {
+                // Returning undefined here will cause our caller to rewind to where we started from.
+                return undefined;
             }
-            else if (isStatement(/* inErrorRecovery */ true) && !isStartOfExpressionStatement() && token !== SyntaxKind.FunctionKeyword) {
+
+            return node;
+        }
+
+        function parseArrowFunctionExpressionBody(): Block | Expression {
+            if (token === SyntaxKind.OpenBraceToken) {
+                return parseFunctionBlock(/*allowYield:*/ false, /* ignoreMissingOpenBrace */ false);
+            }
+
+            if (isStatement(/* inErrorRecovery */ true) && !isStartOfExpressionStatement() && token !== SyntaxKind.FunctionKeyword) {
                 // Check if we got a plain statement (i.e. no expression-statements, no functions expressions/declarations)
                 //
                 // Here we try to recover from a potential error situation in the case where the 
@@ -2623,13 +2709,10 @@ module ts {
                 // up preemptively closing the containing construct.
                 //
                 // Note: even when 'ignoreMissingOpenBrace' is passed as true, parseBody will still error.
-                body = parseFunctionBlock(/*allowYield:*/ false, /* ignoreMissingOpenBrace */ true);
-            }
-            else {
-                body = parseAssignmentExpressionOrHigher();
+                return parseFunctionBlock(/*allowYield:*/ false, /* ignoreMissingOpenBrace */ true);
             }
 
-            return makeFunctionExpression(SyntaxKind.ArrowFunction, pos, /*asteriskToken:*/ undefined, /*name:*/ undefined, sig, body);
+            return parseAssignmentExpressionOrHigher();
         }
 
         function parseConditionalExpressionRest(leftOperand: Expression): Expression {
@@ -2730,9 +2813,8 @@ module ts {
 
         function parsePrefixUnaryExpression() {
             var node = <PrefixUnaryExpression>createNode(SyntaxKind.PrefixUnaryExpression);
-            var operator = token;
+            node.operator = token;
             nextToken();
-            node.operator = operator;
             node.operand = parseUnaryExpressionOrHigher();
             return finishNode(node);
         }
@@ -2826,13 +2908,9 @@ module ts {
             // the last two CallExpression productions.  Or we have a MemberExpression which either
             // completes the LeftHandSideExpression, or starts the beginning of the first four
             // CallExpression productions.
-            var expression: MemberExpression;
-            if (token === SyntaxKind.SuperKeyword) {
-                expression = parseSuperExpression();
-            }
-            else {
-                expression = parseMemberExpressionOrHigher();
-            }
+            var expression = token === SyntaxKind.SuperKeyword
+                ? parseSuperExpression()
+                : parseMemberExpressionOrHigher();
 
             // Now, we *may* be complete.  However, we might have consumed the start of a 
             // CallExpression.  As such, we need to consume the rest of it here to be complete.
@@ -3098,7 +3176,7 @@ module ts {
             if (asteriskToken || token === SyntaxKind.OpenParenToken || token === SyntaxKind.LessThanToken) {
                 node = <PropertyDeclaration>createNode(SyntaxKind.PropertyAssignment, nodePos);
                 node.name = propertyName;
-                var sig = parseSignature(SyntaxKind.CallSignature, SyntaxKind.ColonToken, /* returnTokenRequired */ false, /*yieldAndGeneratorParameterContext:*/ !!asteriskToken);
+                var sig = parseSignature(/*yieldAndGeneratorParameterContext:*/ !!asteriskToken);
 
                 var body = parseFunctionBlock(!!asteriskToken, /* ignoreMissingOpenBrace */ false);
                 // do not propagate property name as name for function expression
@@ -3110,28 +3188,24 @@ module ts {
                 return finishNode(node);
             }
 
-            var flags: NodeFlags = 0;
-
             // Disallowing of optional property assignments happens in the grammar checker.
-            if (token === SyntaxKind.QuestionToken) {
-                flags |= NodeFlags.QuestionMark;
-                nextToken();
-            }
+            var questionToken = parseOptionalToken(SyntaxKind.QuestionToken);
 
             // Parse to check if it is short-hand property assignment or normal property assignment
             if ((token === SyntaxKind.CommaToken || token === SyntaxKind.CloseBraceToken) && tokenIsIdentifier) {
-                node = <ShortHandPropertyDeclaration>createNode(SyntaxKind.ShorthandPropertyAssignment, nodePos);
-                node.name = propertyName;
+                var shorthandDeclaration = <ShorthandPropertyDeclaration>createNode(SyntaxKind.ShorthandPropertyAssignment, nodePos);
+                shorthandDeclaration.name = <Identifier>propertyName;
+                shorthandDeclaration.questionToken = questionToken;
+                return finishNode(shorthandDeclaration);
             }
             else {
-                node = <PropertyDeclaration>createNode(SyntaxKind.PropertyAssignment, nodePos);
-                node.name = propertyName;
+                var propertyDeclaration = <PropertyDeclaration>createNode(SyntaxKind.PropertyAssignment, nodePos);
+                propertyDeclaration.name = propertyName;
+                propertyDeclaration.questionToken = questionToken;
                 parseExpected(SyntaxKind.ColonToken);
-                (<PropertyDeclaration>node).initializer = allowInAnd(parseAssignmentExpressionOrHigher);
+                propertyDeclaration.initializer = allowInAnd(parseAssignmentExpressionOrHigher);
+                return finishNode(propertyDeclaration);
             }
-
-            node.flags = flags;
-            return finishNode(node);
         }
 
         function parseObjectLiteralMember(): Declaration {
@@ -3161,15 +3235,13 @@ module ts {
             //      function * BindingIdentifier[Yield]opt (FormalParameters[Yield, GeneratorParameter]) { GeneratorBody[Yield] }
             // FunctionExpression:
             //      function BindingIdentifieropt(FormalParameters) { FunctionBody }
-
-            var pos = getNodePos();
+            var node = <FunctionExpression>createNode(SyntaxKind.FunctionExpression);
             parseExpected(SyntaxKind.FunctionKeyword);
-            var asteriskToken = parseOptionalToken(SyntaxKind.AsteriskToken);
-            var name = asteriskToken ? doInYieldContext(parseOptionalIdentifier) : parseOptionalIdentifier();
-            var sig = parseSignature(SyntaxKind.CallSignature, SyntaxKind.ColonToken, /* returnTokenRequired */ false, /*yieldAndGeneratorParameterContext:*/ !!asteriskToken);
-
-            var body = parseFunctionBlock(/*allowYield:*/ !!asteriskToken, /* ignoreMissingOpenBrace */ false);
-            return makeFunctionExpression(SyntaxKind.FunctionExpression, pos, asteriskToken, name, sig, body);
+            node.asteriskToken = parseOptionalToken(SyntaxKind.AsteriskToken);
+            node.name = node.asteriskToken ? doInYieldContext(parseOptionalIdentifier) : parseOptionalIdentifier();
+            fillSignature(SyntaxKind.ColonToken, /*yieldAndGeneratorParameterContext:*/ !!node.asteriskToken, node);
+            node.body = parseFunctionBlock(/*allowYield:*/ !!node.asteriskToken, /* ignoreMissingOpenBrace */ false);
+            return finishNode(node);
         }
 
         function parseOptionalIdentifier() {
@@ -3191,7 +3263,11 @@ module ts {
             var node = <NewExpression>createNode(SyntaxKind.NewExpression);
             parseExpected(SyntaxKind.NewKeyword);
             node.expression = parseMemberExpressionOrHigher();
-            if (parseOptional(SyntaxKind.OpenParenToken) || (token === SyntaxKind.LessThanToken && (node.typeArguments = tryParse(parseTypeArgumentsAndOpenParen)))) {
+            if (token === SyntaxKind.LessThanToken) {
+                node.typeArguments = tryParse(parseTypeArgumentsAndOpenParen);
+            }
+
+            if (node.typeArguments || parseOptional(SyntaxKind.OpenParenToken)) {
                 node.arguments = parseDelimitedList(ParsingContext.ArgumentExpressions, parseArgumentExpression);
                 parseExpected(SyntaxKind.CloseParenToken);
             }
@@ -3357,8 +3433,8 @@ module ts {
             return finishNode(node);
         }
 
-        function parseCaseClause(): CaseOrDefaultClause {
-            var node = <CaseOrDefaultClause>createNode(SyntaxKind.CaseClause);
+        function parseCaseClause(): CaseClause {
+            var node = <CaseClause>createNode(SyntaxKind.CaseClause);
             parseExpected(SyntaxKind.CaseKeyword);
             node.expression = allowInAnd(parseExpression);
             parseExpected(SyntaxKind.ColonToken);
@@ -3366,8 +3442,8 @@ module ts {
             return finishNode(node);
         }
 
-        function parseDefaultClause(): CaseOrDefaultClause {
-            var node = <CaseOrDefaultClause>createNode(SyntaxKind.DefaultClause);
+        function parseDefaultClause(): DefaultClause {
+            var node = <DefaultClause>createNode(SyntaxKind.DefaultClause);
             parseExpected(SyntaxKind.DefaultKeyword);
             parseExpected(SyntaxKind.ColonToken);
             node.statements = parseList(ParsingContext.SwitchClauseStatements, /*checkForStrictMode*/ false, parseStatement);
@@ -3385,9 +3461,7 @@ module ts {
             node.expression = allowInAnd(parseExpression);
             parseExpected(SyntaxKind.CloseParenToken);
             parseExpected(SyntaxKind.OpenBraceToken);
-
             node.clauses = parseList(ParsingContext.SwitchClauses, /*checkForStrictMode*/ false, parseCaseOrDefaultClause);
-
             parseExpected(SyntaxKind.CloseBraceToken);
             return finishNode(node);
         }
@@ -3412,11 +3486,11 @@ module ts {
         function parseTryStatement(): TryStatement {
             var node = <TryStatement>createNode(SyntaxKind.TryStatement);
             node.tryBlock = parseTokenAndBlock(SyntaxKind.TryKeyword);
-            node.catchBlock = token === SyntaxKind.CatchKeyword ? parseCatchBlock() : undefined;
+            node.catchClause = token === SyntaxKind.CatchKeyword ? parseCatchClause() : undefined;
 
             // If we don't have a catch clause, then we must have a finally clause.  Try to parse
             // one out no matter what.
-            node.finallyBlock = !node.catchBlock || token === SyntaxKind.FinallyKeyword
+            node.finallyBlock = !node.catchClause || token === SyntaxKind.FinallyKeyword
                 ? parseTokenAndBlock(SyntaxKind.FinallyKeyword)
                 : undefined;
             return finishNode(node);
@@ -3432,19 +3506,15 @@ module ts {
             return result;
         }
 
-        function parseCatchBlock(): CatchBlock {
-            var pos = getNodePos();
+        function parseCatchClause(): CatchClause {
+            var result = <CatchClause>createNode(SyntaxKind.CatchClause);
             parseExpected(SyntaxKind.CatchKeyword);
             parseExpected(SyntaxKind.OpenParenToken);
-            var variable = parseIdentifier();
-            var typeAnnotation = parseTypeAnnotation();
+            result.name = parseIdentifier();
+            result.type = parseTypeAnnotation();
             parseExpected(SyntaxKind.CloseParenToken);
-            var result = <CatchBlock>parseBlock(SyntaxKind.CatchBlock, /* ignoreMissingOpenBrace */ false, /*checkForStrictMode*/ false);
-            result.pos = pos;
-            result.variable = variable;
-            result.type = typeAnnotation;
-
-            return result;
+            result.block = parseBlock(SyntaxKind.Block, /* ignoreMissingOpenBrace */ false, /*checkForStrictMode*/ false);
+            return finishNode(result);
         }
 
         function parseDebuggerStatement(): Statement {
@@ -3455,7 +3525,11 @@ module ts {
         }
 
         function isLabel(): boolean {
-            return isIdentifier() && lookAhead(() => nextToken() === SyntaxKind.ColonToken);
+            return isIdentifier() && lookAhead(nextTokenIsColonToken);
+        }
+
+        function nextTokenIsColonToken() {
+            return nextToken() === SyntaxKind.ColonToken;
         }
 
         function parseLabeledStatement(): LabeledStatement {
@@ -3508,7 +3582,7 @@ module ts {
                     // const keyword can precede enum keyword when defining constant enums
                     // 'const enum' do not start statement.
                     // In ES 6 'enum' is a future reserved keyword, so it should not be used as identifier
-                    var isConstEnum = lookAhead(() => nextToken() === SyntaxKind.EnumKeyword);
+                    var isConstEnum = lookAhead(nextTokenIsEnumKeyword);
                     return !isConstEnum;
                 case SyntaxKind.InterfaceKeyword:
                 case SyntaxKind.ClassKeyword:
@@ -3527,7 +3601,7 @@ module ts {
                 case SyntaxKind.StaticKeyword:
                     // When followed by an identifier or keyword, these do not start a statement but
                     // might instead be following type members
-                    if (lookAhead(() => nextToken() >= SyntaxKind.Identifier)) {
+                    if (lookAhead(nextTokenIsIdentifierOrKeywordOnSameLine)) {
                         return false;
                     }
                 default:
@@ -3535,6 +3609,16 @@ module ts {
             }
         }
 
+        function nextTokenIsEnumKeyword() {
+            nextToken();
+            return token === SyntaxKind.EnumKeyword
+        }
+
+        function nextTokenIsIdentifierOrKeywordOnSameLine() {
+            nextToken();
+            return isIdentifierOrKeyword() && !scanner.hasPrecedingLineBreak();
+        }
+
         function parseStatement(): Statement {
             switch (token) {
                 case SyntaxKind.OpenBraceToken:
@@ -3641,7 +3725,7 @@ module ts {
             parseExpected(SyntaxKind.FunctionKeyword);
             node.asteriskToken = parseOptionalToken(SyntaxKind.AsteriskToken);
             node.name = parseIdentifier();
-            fillSignature(SyntaxKind.CallSignature, SyntaxKind.ColonToken, /* returnTokenRequired */ false, /*yieldAndGeneratorParameterContext:*/ !!node.asteriskToken, node);
+            fillSignature(SyntaxKind.ColonToken, /*yieldAndGeneratorParameterContext:*/ !!node.asteriskToken, node);
             node.body = parseFunctionBlockOrSemicolon(!!node.asteriskToken);
             return finishNode(node);
         }
@@ -3650,52 +3734,49 @@ module ts {
             var node = <ConstructorDeclaration>createNode(SyntaxKind.Constructor, pos);
             setModifiers(node, modifiers);
             parseExpected(SyntaxKind.ConstructorKeyword);
-            fillSignature(SyntaxKind.CallSignature, SyntaxKind.ColonToken, /* returnTokenRequired */ false, /*yieldAndGeneratorParameterContext:*/ false, node);
+            fillSignature(SyntaxKind.ColonToken, /*yieldAndGeneratorParameterContext:*/ false, node);
             node.body = parseFunctionBlockOrSemicolon(/*isGenerator:*/ false);
             return finishNode(node);
         }
 
         function parsePropertyMemberDeclaration(fullStart: number, modifiers: ModifiersArray): ClassElement {
-            var flags = modifiers ? modifiers.flags : 0;
             var asteriskToken = parseOptionalToken(SyntaxKind.AsteriskToken);
             var name = parsePropertyName();
-            if (parseOptional(SyntaxKind.QuestionToken)) {
-                // Note: this is not legal as per the grammar.  But we allow it in the parser and
-                // report an error in the grammar checker.
-                flags |= NodeFlags.QuestionMark;
-            }
 
+            // Note: this is not legal as per the grammar.  But we allow it in the parser and
+            // report an error in the grammar checker.
+            var questionToken = parseOptionalToken(SyntaxKind.QuestionToken);
             if (asteriskToken || token === SyntaxKind.OpenParenToken || token === SyntaxKind.LessThanToken) {
                 var method = <MethodDeclaration>createNode(SyntaxKind.Method, fullStart);
                 setModifiers(method, modifiers);
-                if (flags) {
-                    method.flags = flags;
-                }
                 method.asteriskToken = asteriskToken;
                 method.name = name;
-                fillSignature(SyntaxKind.CallSignature, SyntaxKind.ColonToken, /* returnTokenRequired */ false, /*yieldAndGeneratorParameterContext:*/ !!asteriskToken, method);
+                method.questionToken = questionToken;
+                fillSignature(SyntaxKind.ColonToken, /*yieldAndGeneratorParameterContext:*/ !!asteriskToken, method);
                 method.body = parseFunctionBlockOrSemicolon(!!asteriskToken);
                 return finishNode(method);
             }
             else {
                 var property = <PropertyDeclaration>createNode(SyntaxKind.Property, fullStart);
                 setModifiers(property, modifiers);
-                if (flags) {
-                    property.flags = flags;
-                }
                 property.name = name;
+                property.questionToken = questionToken;
                 property.type = parseTypeAnnotation();
-                property.initializer = allowInAnd(() => parseInitializer(/*inParameter*/ false));
+                property.initializer = allowInAnd(parseNonParameterInitializer);
                 parseSemicolon();
                 return finishNode(property);
             }
         }
 
+        function parseNonParameterInitializer() {
+            return parseInitializer(/*inParameter*/ false);
+        }
+
         function parseMemberAccessorDeclaration(kind: SyntaxKind, fullStart: number, modifiers: ModifiersArray): MethodDeclaration {
             var node = <MethodDeclaration>createNode(kind, fullStart);
             setModifiers(node, modifiers);
             node.name = parsePropertyName();
-            fillSignature(SyntaxKind.CallSignature, SyntaxKind.ColonToken, /* returnTokenRequired */ false, /*yieldAndGeneratorParameterContext:*/ false, node);
+            fillSignature(SyntaxKind.ColonToken, /*yieldAndGeneratorParameterContext:*/ false, node);
             node.body = parseFunctionBlockOrSemicolon(/*isGenerator:*/ false);
             return finishNode(node);
         }
@@ -3758,7 +3839,7 @@ module ts {
             var flags = 0;
             var modifiers: ModifiersArray;
             while (true) {
-                var modifierStart = scanner.getTokenPos();
+                var modifierStart = scanner.getStartPos();
                 var modifierKind = token;
 
                 if (!parseAnyContextualModifier()) {
@@ -3767,12 +3848,14 @@ module ts {
 
                 if (!modifiers) {
                     modifiers = <ModifiersArray>[];
+                    modifiers.pos = modifierStart;
                 }
                 flags |= modifierToFlag(modifierKind);
                 modifiers.push(finishNode(createNode(modifierKind, modifierStart))); 
             }
             if (modifiers) {
                 modifiers.flags = flags;
+                modifiers.end = scanner.getStartPos();
             }
             return modifiers;
         }
@@ -3794,7 +3877,7 @@ module ts {
             }
             // It is very important that we check this *after* checking indexers because
             // the [ token can start an index signature or a computed property name
-            if (token >= SyntaxKind.Identifier || token === SyntaxKind.StringLiteral || token === SyntaxKind.NumericLiteral ||
+            if (isIdentifierOrKeyword() || token === SyntaxKind.StringLiteral || token === SyntaxKind.NumericLiteral ||
                 token === SyntaxKind.AsteriskToken || token === SyntaxKind.OpenBracketToken) {
                 return parsePropertyMemberDeclaration(fullStart, modifiers);
             }
@@ -3872,7 +3955,7 @@ module ts {
             node.name = parseIdentifier();
             node.typeParameters = parseTypeParameters();
             node.heritageClauses = parseHeritageClauses(/*isClassHeritageClause:*/ false);
-            node.members = parseObjectType();
+            node.members = parseObjectTypeMembers();
             return finishNode(node);
         }
 
@@ -3894,11 +3977,11 @@ module ts {
         function parseEnumMember(): EnumMember {
             var node = <EnumMember>createNode(SyntaxKind.EnumMember, scanner.getStartPos());
             node.name = parsePropertyName();
-            node.initializer = allowInAnd(() => parseInitializer(/*inParameter*/ false));
+            node.initializer = allowInAnd(parseNonParameterInitializer);
             return finishNode(node);
         }
 
-        function parseAndCheckEnumDeclaration(fullStart: number, modifiers: ModifiersArray, flags: NodeFlags): EnumDeclaration {
+        function parseEnumDeclaration(fullStart: number, modifiers: ModifiersArray): EnumDeclaration {
             var node = <EnumDeclaration>createNode(SyntaxKind.EnumDeclaration, fullStart);
             setModifiers(node, modifiers);
             parseExpected(SyntaxKind.EnumKeyword);
@@ -3916,7 +3999,7 @@ module ts {
         function parseModuleBlock(): ModuleBlock {
             var node = <ModuleBlock>createNode(SyntaxKind.ModuleBlock, scanner.getStartPos());
             if (parseExpected(SyntaxKind.OpenBraceToken)) {
-                node.statements = parseList(ParsingContext.ModuleElements, /*checkForStrictMode*/ false, parseModuleElement);
+                node.statements = parseList(ParsingContext.ModuleElements, /*checkForStrictMode*/false, parseModuleElement);
                 parseExpected(SyntaxKind.CloseBraceToken);
             }
             else {
@@ -3936,31 +4019,28 @@ module ts {
             return finishNode(node);
         }
 
-        function parseAmbientExternalModuleDeclaration(fullStart: number, modifiers: ModifiersArray, flags: NodeFlags): ModuleDeclaration {
+        function parseAmbientExternalModuleDeclaration(fullStart: number, modifiers: ModifiersArray): ModuleDeclaration {
             var node = <ModuleDeclaration>createNode(SyntaxKind.ModuleDeclaration, fullStart);
             setModifiers(node, modifiers);
-            node.flags |= flags;
             node.name = parseLiteralNode(/*internName:*/ true);
             node.body = parseModuleBlock();
             return finishNode(node);
         }
 
-        function parseModuleDeclaration(fullStart: number, modifiers: ModifiersArray, flags: NodeFlags): ModuleDeclaration {
+        function parseModuleDeclaration(fullStart: number, modifiers: ModifiersArray): ModuleDeclaration {
             parseExpected(SyntaxKind.ModuleKeyword);
             return token === SyntaxKind.StringLiteral 
-                ? parseAmbientExternalModuleDeclaration(fullStart, modifiers, flags)
-                : parseInternalModuleTail(fullStart, modifiers, flags);
+                ? parseAmbientExternalModuleDeclaration(fullStart, modifiers)
+                : parseInternalModuleTail(fullStart, modifiers, modifiers? modifiers.flags : 0);
         }
 
         function isExternalModuleReference() {
-            if (token === SyntaxKind.RequireKeyword) {
-                return lookAhead(() => {
-                    nextToken();
-                    return token === SyntaxKind.OpenParenToken;
-                });
-            }
+            return token === SyntaxKind.RequireKeyword &&
+                lookAhead(nextTokenIsOpenParen);
+        }
 
-            return false;
+        function nextTokenIsOpenParen() {
+            return nextToken() === SyntaxKind.OpenParenToken;
         }
 
         function parseImportDeclaration(fullStart: number, modifiers: ModifiersArray): ImportDeclaration {
@@ -3989,9 +4069,13 @@ module ts {
             // literals.  We check to ensure that it is only a string literal later in the grammar
             // walker.
             node.expression = parseExpression();
+
+            // Ensure the string being required is in our 'identifier' table.  This will ensure 
+            // that features like 'find refs' will look inside this file when search for its name.
             if (node.expression.kind === SyntaxKind.StringLiteral) {
                 internIdentifier((<LiteralExpression>node.expression).text);
             }
+
             parseExpected(SyntaxKind.CloseParenToken);
             return finishNode(node);
         }
@@ -4017,23 +4101,47 @@ module ts {
                 case SyntaxKind.ImportKeyword:
                 case SyntaxKind.TypeKeyword:
                     // Not true keywords so ensure an identifier follows
-                    return lookAhead(() => nextToken() >= SyntaxKind.Identifier);
+                    return lookAhead(nextTokenIsIdentifierOrKeyword);
                 case SyntaxKind.ModuleKeyword:
                     // Not a true keyword so ensure an identifier or string literal follows
-                    return lookAhead(() => nextToken() >= SyntaxKind.Identifier || token === SyntaxKind.StringLiteral);
+                    return lookAhead(nextTokenIsIdentifierOrKeywordOrStringLiteral);
                 case SyntaxKind.ExportKeyword:
                     // Check for export assignment or modifier on source element
-                    return lookAhead(() => nextToken() === SyntaxKind.EqualsToken || isDeclarationStart());
+                    return lookAhead(nextTokenIsEqualsTokenOrDeclarationStart);
                 case SyntaxKind.DeclareKeyword:
                 case SyntaxKind.PublicKeyword:
                 case SyntaxKind.PrivateKeyword:
                 case SyntaxKind.ProtectedKeyword:
                 case SyntaxKind.StaticKeyword:
                     // Check for modifier on source element
-                    return lookAhead(() => { nextToken(); return isDeclarationStart(); });
+                    return lookAhead(nextTokenIsDeclarationStart);
             }
         }
 
+        function isIdentifierOrKeyword() {
+            return token >= SyntaxKind.Identifier;
+        }
+
+        function nextTokenIsIdentifierOrKeyword() {
+            nextToken();
+            return isIdentifierOrKeyword();
+        }
+
+        function nextTokenIsIdentifierOrKeywordOrStringLiteral() {
+            nextToken();
+            return isIdentifierOrKeyword() || token === SyntaxKind.StringLiteral;
+        }
+
+        function nextTokenIsEqualsTokenOrDeclarationStart() {
+            nextToken();
+            return token === SyntaxKind.EqualsToken || isDeclarationStart();
+        }
+
+        function nextTokenIsDeclarationStart() {
+            nextToken();
+            return isDeclarationStart();
+        }
+
         function parseDeclaration(): ModuleElement {
             var fullStart = getNodePos();
             var modifiers = parseModifiers();
@@ -4044,11 +4152,9 @@ module ts {
                 }
             }
 
-            var flags = modifiers ? modifiers.flags : 0;
             switch (token) {
                 case SyntaxKind.VarKeyword:
                 case SyntaxKind.LetKeyword:
-                    return parseVariableStatement(fullStart, modifiers);
                 case SyntaxKind.ConstKeyword:
                     return parseVariableStatement(fullStart, modifiers);
                 case SyntaxKind.FunctionKeyword:
@@ -4060,9 +4166,9 @@ module ts {
                 case SyntaxKind.TypeKeyword:
                     return parseTypeAliasDeclaration(fullStart, modifiers);
                 case SyntaxKind.EnumKeyword:
-                    return parseAndCheckEnumDeclaration(fullStart, modifiers, flags);
+                    return parseEnumDeclaration(fullStart, modifiers);
                 case SyntaxKind.ModuleKeyword:
-                    return parseModuleDeclaration(fullStart, modifiers, flags);
+                    return parseModuleDeclaration(fullStart, modifiers);
                 case SyntaxKind.ImportKeyword:
                     return parseImportDeclaration(fullStart, modifiers);
                 default:
@@ -4101,13 +4207,13 @@ module ts {
                 var referencePathMatchResult = getFileReferenceFromReferencePath(comment, range);
                 if (referencePathMatchResult) {
                     var fileReference = referencePathMatchResult.fileReference;
-                    file.hasNoDefaultLib = referencePathMatchResult.isNoDefaultLib;
+                    sourceFile.hasNoDefaultLib = referencePathMatchResult.isNoDefaultLib;
                     var diagnosticMessage = referencePathMatchResult.diagnosticMessage;
                     if (fileReference) {
                         referencedFiles.push(fileReference);
                     }
                     if (diagnosticMessage) {
-                        file.parseDiagnostics.push(createFileDiagnostic(file, range.pos, range.end - range.pos, diagnosticMessage));
+                        sourceFile.referenceDiagnostics.push(createFileDiagnostic(sourceFile, range.pos, range.end - range.pos, diagnosticMessage));
                     }
                 }
                 else {
@@ -4115,7 +4221,7 @@ module ts {
                     var amdModuleNameMatchResult = amdModuleNameRegEx.exec(comment);
                     if(amdModuleNameMatchResult) {
                         if(amdModuleName) {
-                            file.parseDiagnostics.push(createFileDiagnostic(file, range.pos, range.end - range.pos, Diagnostics.An_AMD_module_cannot_have_multiple_name_assignments));
+                            sourceFile.referenceDiagnostics.push(createFileDiagnostic(sourceFile, range.pos, range.end - range.pos, Diagnostics.An_AMD_module_cannot_have_multiple_name_assignments));
                         }
                         amdModuleName = amdModuleNameMatchResult[2];
                     }
@@ -4136,7 +4242,7 @@ module ts {
         }
 
         function getExternalModuleIndicator() {
-            return forEach(file.statements, node =>
+            return forEach(sourceFile.statements, node =>
                 node.flags & NodeFlags.Export
                 || node.kind === SyntaxKind.ImportDeclaration && (<ImportDeclaration>node).moduleReference.kind === SyntaxKind.ExternalModuleReference
                 || node.kind === SyntaxKind.ExportAssignment
@@ -4147,15 +4253,15 @@ module ts {
         var syntacticDiagnostics: Diagnostic[];
         function getSyntacticDiagnostics() {
             if (syntacticDiagnostics === undefined) {
-                if (file.parseDiagnostics.length > 0) {
+                if (sourceFile.parseDiagnostics.length > 0) {
                     // Don't bother doing any grammar checks if there are already parser errors.  
                     // Otherwise we may end up with too many cascading errors.
-                    syntacticDiagnostics = file.parseDiagnostics;
+                    syntacticDiagnostics = sourceFile.referenceDiagnostics.concat(sourceFile.parseDiagnostics);
                 }
                 else {
                     // No parser errors were reported.  Perform our stricter grammar checks.
-                    syntacticDiagnostics = file.grammarDiagnostics;
-                    checkGrammar(sourceText, languageVersion, file);
+                    checkGrammar(sourceText, languageVersion, sourceFile);
+                    syntacticDiagnostics = sourceFile.referenceDiagnostics.concat(sourceFile.grammarDiagnostics);
                 }
             }
 
@@ -4168,32 +4274,40 @@ module ts {
         if (fileExtensionIs(filename, ".d.ts")) {
             rootNodeFlags = NodeFlags.DeclarationFile;
         }
-        file = <SourceFile>createRootNode(SyntaxKind.SourceFile, 0, sourceText.length, rootNodeFlags);
-        file.filename = normalizePath(filename);
-        file.text = sourceText;
-        file.getLineAndCharacterFromPosition = getLineAndCharacterFromSourcePosition;
-        file.getPositionFromLineAndCharacter = getPositionFromSourceLineAndCharacter;
-        file.getLineStarts = getLineStarts;
-        file.getSyntacticDiagnostics = getSyntacticDiagnostics;
-        file.parseDiagnostics = [];
-        file.grammarDiagnostics = [];
-        file.semanticDiagnostics = [];
+
+        var sourceFile = <SourceFile>createRootNode(SyntaxKind.SourceFile, 0, sourceText.length, rootNodeFlags);
+
+        sourceFile.getLineAndCharacterFromPosition = getLineAndCharacterFromSourcePosition;
+        sourceFile.getPositionFromLineAndCharacter = getPositionFromSourceLineAndCharacter;
+        sourceFile.getLineStarts = getLineStarts;
+        sourceFile.getSyntacticDiagnostics = getSyntacticDiagnostics;
+
+        sourceFile.filename = normalizePath(filename);
+        sourceFile.text = sourceText;
+
+        sourceFile.referenceDiagnostics = [];
+        sourceFile.parseDiagnostics = [];
+        sourceFile.grammarDiagnostics = [];
+        sourceFile.semanticDiagnostics = [];
 
         var referenceComments = processReferenceComments(); 
-        file.referencedFiles = referenceComments.referencedFiles;
-        file.amdDependencies = referenceComments.amdDependencies;
-        file.amdModuleName = referenceComments.amdModuleName;
+        sourceFile.referencedFiles = referenceComments.referencedFiles;
+        sourceFile.amdDependencies = referenceComments.amdDependencies;
+        sourceFile.amdModuleName = referenceComments.amdModuleName;
 
-        file.statements = parseList(ParsingContext.SourceElements, /*checkForStrictMode*/ true, parseSourceElement);
-        file.externalModuleIndicator = getExternalModuleIndicator();
+        sourceFile.statements = parseList(ParsingContext.SourceElements, /*checkForStrictMode*/ true, parseSourceElement);
+        Debug.assert(token === SyntaxKind.EndOfFileToken);
+        sourceFile.endOfFileToken = parseTokenNode();
 
-        file.nodeCount = nodeCount;
-        file.identifierCount = identifierCount;
-        file.version = version;
-        file.isOpen = isOpen;
-        file.languageVersion = languageVersion;
-        file.identifiers = identifiers;
-        return file;
+        sourceFile.externalModuleIndicator = getExternalModuleIndicator();
+
+        sourceFile.nodeCount = nodeCount;
+        sourceFile.identifierCount = identifierCount;
+        sourceFile.version = version;
+        sourceFile.isOpen = isOpen;
+        sourceFile.languageVersion = languageVersion;
+        sourceFile.identifiers = identifiers;
+        return sourceFile;
     }
 
     function isLeftHandSideExpression(expr: Expression): boolean {
@@ -4304,7 +4418,7 @@ module ts {
 
                 case SyntaxKind.EnumDeclaration:                return checkEnumDeclaration(<EnumDeclaration>node);
                 case SyntaxKind.BinaryExpression:               return checkBinaryExpression(<BinaryExpression>node);
-                case SyntaxKind.CatchBlock:                     return checkCatchBlock(<CatchBlock>node);
+                case SyntaxKind.CatchClause:                    return checkCatchClause(<CatchClause>node);
                 case SyntaxKind.ClassDeclaration:               return checkClassDeclaration(<ClassDeclaration>node);
                 case SyntaxKind.ComputedPropertyName:           return checkComputedPropertyName(<ComputedPropertyName>node);
                 case SyntaxKind.Constructor:                    return checkConstructor(<ConstructorDeclaration>node);
@@ -4333,7 +4447,7 @@ module ts {
                 case SyntaxKind.ReturnStatement:                return checkReturnStatement(<ReturnStatement>node);
                 case SyntaxKind.SetAccessor:                    return checkSetAccessor(<MethodDeclaration>node);
                 case SyntaxKind.SourceFile:                     return checkSourceFile(<SourceFile>node);
-                case SyntaxKind.ShorthandPropertyAssignment:    return checkShorthandPropertyAssignment(<ShortHandPropertyDeclaration>node);
+                case SyntaxKind.ShorthandPropertyAssignment:    return checkShorthandPropertyAssignment(<ShorthandPropertyDeclaration>node);
                 case SyntaxKind.SwitchStatement:                return checkSwitchStatement(<SwitchStatement>node);
                 case SyntaxKind.TaggedTemplateExpression:       return checkTaggedTemplateExpression(<TaggedTemplateExpression>node);
                 case SyntaxKind.ThrowStatement:                 return checkThrowStatement(<ThrowStatement>node);
@@ -4562,15 +4676,15 @@ module ts {
             }
         }
 
-        function checkCatchBlock(node: CatchBlock) {
+        function checkCatchClause(node: CatchClause) {
             if (node.type) {
-                var colonStart = skipTrivia(sourceText, node.variable.end);
+                var colonStart = skipTrivia(sourceText, node.name.end);
                 return grammarErrorAtPos(colonStart, ":".length, Diagnostics.Catch_clause_parameter_cannot_have_a_type_annotation);
             }
-            if (node.parserContextFlags & ParserContextFlags.StrictMode && isEvalOrArgumentsIdentifier(node.variable)) {
+            if (node.parserContextFlags & ParserContextFlags.StrictMode && isEvalOrArgumentsIdentifier(node.name)) {
                 // It is a SyntaxError if a TryStatement with a Catch occurs within strict code and the Identifier of the 
                 // Catch production is eval or arguments
-                return reportInvalidUseInStrictMode(node.variable);
+                return reportInvalidUseInStrictMode(node.name);
             }
         }
 
@@ -4803,14 +4917,14 @@ module ts {
                     return grammarErrorOnNode(node, Diagnostics.An_index_signature_must_have_exactly_one_parameter);
                 }
             }
-            else if (parameter.flags & NodeFlags.Rest) {
-                return grammarErrorOnNode(parameter.name, Diagnostics.An_index_signature_cannot_have_a_rest_parameter);
+            else if (parameter.dotDotDotToken) {
+                return grammarErrorOnNode(parameter.dotDotDotToken, Diagnostics.An_index_signature_cannot_have_a_rest_parameter);
             }
             else if (parameter.flags & NodeFlags.Modifier) {
                 return grammarErrorOnNode(parameter.name, Diagnostics.An_index_signature_parameter_cannot_have_an_accessibility_modifier);
             }
-            else if (parameter.flags & NodeFlags.QuestionMark) {
-                return grammarErrorOnNode(parameter.name, Diagnostics.An_index_signature_parameter_cannot_have_a_question_mark);
+            else if (parameter.questionToken) {
+                return grammarErrorOnNode(parameter.questionToken, Diagnostics.An_index_signature_parameter_cannot_have_a_question_mark);
             }
             else if (parameter.initializer) {
                 return grammarErrorOnNode(parameter.name, Diagnostics.An_index_signature_parameter_cannot_have_an_initializer);
@@ -4862,7 +4976,7 @@ module ts {
                 return true;
             }
             if (node.parent.kind === SyntaxKind.ClassDeclaration) {
-                if (checkForInvalidQuestionMark(node, Diagnostics.A_class_member_cannot_be_declared_optional)) {
+                if (checkForInvalidQuestionMark(node, node.questionToken, Diagnostics.A_class_member_cannot_be_declared_optional)) {
                     return true;
                 }
                 // Technically, computed properties in ambient contexts is disallowed 
@@ -5160,23 +5274,23 @@ module ts {
 
             for (var i = 0; i < parameterCount; i++) {
                 var parameter = parameters[i];
-                if (parameter.flags & NodeFlags.Rest) {
+                if (parameter.dotDotDotToken) {
                     if (i !== (parameterCount - 1)) {
-                        return grammarErrorOnNode(parameter.name, Diagnostics.A_rest_parameter_must_be_last_in_a_parameter_list);
+                        return grammarErrorOnNode(parameter.dotDotDotToken, Diagnostics.A_rest_parameter_must_be_last_in_a_parameter_list);
                     }
 
-                    if (parameter.flags & NodeFlags.QuestionMark) {
-                        return grammarErrorOnNode(parameter.name, Diagnostics.A_rest_parameter_cannot_be_optional);
+                    if (parameter.questionToken) {
+                        return grammarErrorOnNode(parameter.questionToken, Diagnostics.A_rest_parameter_cannot_be_optional);
                     }
 
                     if (parameter.initializer) {
                         return grammarErrorOnNode(parameter.name, Diagnostics.A_rest_parameter_cannot_have_an_initializer);
                     }
                 }
-                else if (parameter.flags & NodeFlags.QuestionMark || parameter.initializer) {
+                else if (parameter.questionToken || parameter.initializer) {
                     seenOptionalParameter = true;
 
-                    if (parameter.flags & NodeFlags.QuestionMark && parameter.initializer) {
+                    if (parameter.questionToken && parameter.initializer) {
                         return grammarErrorOnNode(parameter.name, Diagnostics.Parameter_cannot_have_question_mark_and_initializer);
                     }
                 }
@@ -5210,7 +5324,7 @@ module ts {
 
         function checkProperty(node: PropertyDeclaration) {
             if (node.parent.kind === SyntaxKind.ClassDeclaration) {
-                if (checkForInvalidQuestionMark(node, Diagnostics.A_class_member_cannot_be_declared_optional) ||
+                if (checkForInvalidQuestionMark(node, node.questionToken, Diagnostics.A_class_member_cannot_be_declared_optional) ||
                     checkForDisallowedComputedProperty(node.name, Diagnostics.Computed_property_names_are_not_allowed_in_class_property_declarations)) {
                     return true;
                 }
@@ -5251,13 +5365,12 @@ module ts {
         }
 
         function checkPropertyAssignment(node: PropertyDeclaration) {
-            return checkForInvalidQuestionMark(node, Diagnostics.An_object_member_cannot_be_declared_optional);
+            return checkForInvalidQuestionMark(node, node.questionToken, Diagnostics.An_object_member_cannot_be_declared_optional);
         }
 
-        function checkForInvalidQuestionMark(node: Declaration, message: DiagnosticMessage) {
-            if (node.flags & NodeFlags.QuestionMark) {
-                var pos = skipTrivia(sourceText, node.name.end);
-                return grammarErrorAtPos(pos, "?".length, message);
+        function checkForInvalidQuestionMark(node: Declaration, questionToken: Node, message: DiagnosticMessage) {
+            if (questionToken) {
+                return grammarErrorOnNode(questionToken, message);
             }
         }
 
@@ -5298,14 +5411,14 @@ module ts {
                 }
                 else {
                     var parameter = accessor.parameters[0];
-                    if (parameter.flags & NodeFlags.Rest) {
-                        return grammarErrorOnNode(accessor.name, Diagnostics.A_set_accessor_cannot_have_rest_parameter);
+                    if (parameter.dotDotDotToken) {
+                        return grammarErrorOnNode(parameter.dotDotDotToken, Diagnostics.A_set_accessor_cannot_have_rest_parameter);
                     }
                     else if (parameter.flags & NodeFlags.Modifier) {
                         return grammarErrorOnNode(accessor.name, Diagnostics.A_parameter_property_is_only_allowed_in_a_constructor_implementation);
                     }
-                    else if (parameter.flags & NodeFlags.QuestionMark) {
-                        return grammarErrorOnNode(accessor.name, Diagnostics.A_set_accessor_cannot_have_an_optional_parameter);
+                    else if (parameter.questionToken) {
+                        return grammarErrorOnNode(parameter.questionToken, Diagnostics.A_set_accessor_cannot_have_an_optional_parameter);
                     }
                     else if (parameter.initializer) {
                         return grammarErrorOnNode(accessor.name, Diagnostics.A_set_accessor_parameter_cannot_have_an_initializer);
@@ -5351,8 +5464,8 @@ module ts {
             return grammarErrorOnFirstToken(node, Diagnostics.A_declare_modifier_is_required_for_a_top_level_declaration_in_a_d_ts_file);
         }
 
-        function checkShorthandPropertyAssignment(node: ShortHandPropertyDeclaration): boolean {
-            return checkForInvalidQuestionMark(node, Diagnostics.An_object_member_cannot_be_declared_optional);
+        function checkShorthandPropertyAssignment(node: ShorthandPropertyDeclaration): boolean {
+            return checkForInvalidQuestionMark(node, node.questionToken, Diagnostics.An_object_member_cannot_be_declared_optional);
         }
 
         function checkSwitchStatement(node: SwitchStatement) {
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 277e2cce5ff..edf052a8876 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -208,7 +208,6 @@ module ts {
         ThrowStatement,
         TryStatement,
         TryBlock,
-        CatchBlock,
         FinallyBlock,
         DebuggerStatement,
         VariableDeclaration,
@@ -222,12 +221,16 @@ module ts {
         ModuleBlock,
         ImportDeclaration,
         ExportAssignment,
+
         // Module references
         ExternalModuleReference,
+
         // Clauses
         CaseClause,
         DefaultClause,
         HeritageClause,
+        CatchClause,
+
         // Property assignments
         PropertyAssignment,
         ShorthandPropertyAssignment,
@@ -254,7 +257,7 @@ module ts {
         LastTypeNode = ParenthesizedType,
         FirstPunctuation = OpenBraceToken,
         LastPunctuation = CaretEqualsToken,
-        FirstToken = EndOfFileToken,
+        FirstToken = Unknown,
         LastToken = TypeKeyword,
         FirstTriviaToken = SingleLineCommentTrivia,
         LastTriviaToken = WhitespaceTrivia,
@@ -272,8 +275,6 @@ module ts {
     export const enum NodeFlags {
         Export              = 0x00000001,  // Declarations
         Ambient             = 0x00000002,  // Declarations
-        QuestionMark        = 0x00000004,  // Parameter/Property/Method
-        Rest                = 0x00000008,  // Parameter
         Public              = 0x00000010,  // Property/Method
         Private             = 0x00000020,  // Property/Method
         Protected           = 0x00000040,  // Property/Method
@@ -318,7 +319,7 @@ module ts {
         hasTrailingComma?: boolean;
     }
 
-    export interface ModifiersArray extends Array<Node> {
+    export interface ModifiersArray extends NodeArray<Node> {
         flags: number;
     }
 
@@ -369,12 +370,15 @@ module ts {
     }
 
     export interface ParameterDeclaration extends Declaration {
+        dotDotDotToken?: Node;
         name: Identifier;
+        questionToken?: Node;
         type?: TypeNode | StringLiteralExpression;
         initializer?: Expression;
     }
 
     export interface PropertyDeclaration extends Declaration, ClassElement {
+        questionToken?: Node;
         type?: TypeNode;
         initializer?: Expression;
     }
@@ -382,8 +386,9 @@ module ts {
     export type VariableOrParameterDeclaration = VariableDeclaration | ParameterDeclaration;
     export type VariableOrParameterOrPropertyDeclaration = VariableOrParameterDeclaration | PropertyDeclaration;
 
-    export interface ShortHandPropertyDeclaration extends Declaration {
+    export interface ShorthandPropertyDeclaration extends Declaration {
         name: Identifier;
+        questionToken?: Node;
     }
 
     /**
@@ -398,6 +403,7 @@ module ts {
         _functionLikeDeclarationBrand: any;
 
         asteriskToken?: Node;
+        questionToken?: Node;
         body?: Block | Expression;
     }
 
@@ -668,11 +674,17 @@ module ts {
         clauses: NodeArray<CaseOrDefaultClause>;
     }
 
-    export interface CaseOrDefaultClause extends Node {
+    export interface CaseClause extends Node {
         expression?: Expression;
         statements: NodeArray<Statement>;
     }
 
+    export interface DefaultClause extends Node {
+        statements: NodeArray<Statement>;
+    }
+
+    export type CaseOrDefaultClause = CaseClause | DefaultClause;
+
     export interface LabeledStatement extends Statement {
         label: Identifier;
         statement: Statement;
@@ -684,13 +696,14 @@ module ts {
 
     export interface TryStatement extends Statement {
         tryBlock: Block;
-        catchBlock?: CatchBlock;
+        catchClause?: CatchClause;
         finallyBlock?: Block;
     }
 
-    export interface CatchBlock extends Block, Declaration {
-        variable: Identifier;
+    export interface CatchClause extends Declaration {
+        name: Identifier;
         type?: TypeNode;
+        block: Block;
     }
 
     export interface ModuleElement extends Node {
@@ -773,6 +786,7 @@ module ts {
     // Source files are declarations when they are external modules.
     export interface SourceFile extends Declaration {
         statements: NodeArray<ModuleElement>;
+        endOfFileToken: Node;
 
         filename: string;
         text: string;
@@ -782,17 +796,24 @@ module ts {
         amdDependencies: string[];
         amdModuleName: string;
         referencedFiles: FileReference[];
-        semanticDiagnostics: Diagnostic[];
+
+        // Diagnostics reported about the "///<reference" comments in the file.
+        referenceDiagnostics: Diagnostic[];
 
         // Parse errors refer specifically to things the parser could not understand at all (like 
-        // missing tokens, or tokens it didn't know how to deal with). Grammar errors are for 
-        // things the parser understood, but either the ES6 or TS grammars do not allow (like 
-        // putting an 'public' modifier on a 'class declaration').
+        // missing tokens, or tokens it didn't know how to deal with).
         parseDiagnostics: Diagnostic[];
+
+        // Grammar errors are for  things the parser understood, but either the ES6 or TS grammars
+        // do not allow (like putting an 'public' modifier on a 'class declaration').
         grammarDiagnostics: Diagnostic[];
 
-        // Returns all 
+        // Returns all syntactic diagnostics (i.e. the reference, parser and grammar diagnostics).
         getSyntacticDiagnostics(): Diagnostic[];
+
+        // File level diagnostics reported by the binder.
+        semanticDiagnostics: Diagnostic[];
+
         hasNoDefaultLib: boolean;
         externalModuleIndicator: Node; // The first node that causes this file to be an external module
         nodeCount: number;
@@ -861,7 +882,6 @@ module ts {
         getIdentifierCount(): number;
         getSymbolCount(): number;
         getTypeCount(): number;
-        checkProgram(): void;
         emitFiles(targetSourceFile?: SourceFile): EmitResult;
         getParentOfSymbol(symbol: Symbol): Symbol;
         getNarrowedTypeOfSymbol(symbol: Symbol, node: Node): Type;
@@ -973,7 +993,7 @@ module ts {
         isTopLevelValueImportWithEntityName(node: ImportDeclaration): boolean;
         getNodeCheckFlags(node: Node): NodeCheckFlags;
         getEnumMemberValue(node: EnumMember): number;
-        hasSemanticErrors(): boolean;
+        hasSemanticErrors(sourceFile?: SourceFile): boolean;
         isDeclarationVisible(node: Declaration): boolean;
         isImplementationOfOverload(node: FunctionLikeDeclaration): boolean;
         writeTypeOfDeclaration(declaration: AccessorDeclaration | VariableOrParameterDeclaration, enclosingDeclaration: Node, flags: TypeFormatFlags, writer: SymbolWriter): void;
diff --git a/src/harness/fourslash.ts b/src/harness/fourslash.ts
index 05e65f5648f..7e364730ede 100644
--- a/src/harness/fourslash.ts
+++ b/src/harness/fourslash.ts
@@ -2217,11 +2217,10 @@ module FourSlash {
         // TODO (drosen): We need to enforce checking on these tests.
         var program = ts.createProgram([Harness.Compiler.fourslashFilename, fileName], { out: "fourslashTestOutput.js", noResolve: true }, host);
         var checker = ts.createTypeChecker(program, /*fullTypeCheckMode*/ true);
-        checker.checkProgram();
 
-        var errs = program.getDiagnostics().concat(checker.getDiagnostics());
-        if (errs.length > 0) {
-            throw new Error('Error compiling ' + fileName + ': ' + errs.map(e => e.messageText).join('\r\n'));
+        var errors = program.getDiagnostics().concat(checker.getDiagnostics());
+        if (errors.length > 0) {
+            throw new Error('Error compiling ' + fileName + ': ' + errors.map(e => e.messageText).join('\r\n'));
         }
         checker.emitFiles();
         result = result || ''; // Might have an empty fourslash file
diff --git a/src/harness/harness.ts b/src/harness/harness.ts
index 640d5f0ae53..c0d3ddedce3 100644
--- a/src/harness/harness.ts
+++ b/src/harness/harness.ts
@@ -801,7 +801,6 @@ module Harness {
                     useCaseSensitiveFileNames));
 
                 var checker = program.getTypeChecker(/*fullTypeCheckMode*/ true);
-                checker.checkProgram();
 
                 var isEmitBlocked = checker.isEmitBlocked();
 
diff --git a/src/services/breakpoints.ts b/src/services/breakpoints.ts
index 6cf775487fa..a67a89dd82f 100644
--- a/src/services/breakpoints.ts
+++ b/src/services/breakpoints.ts
@@ -106,11 +106,13 @@ module ts.BreakpointResolver {
 
                     case SyntaxKind.Block:
                     case SyntaxKind.TryBlock:
-                    case SyntaxKind.CatchBlock:
                     case SyntaxKind.FinallyBlock:
                     case SyntaxKind.ModuleBlock:
                         return spanInBlock(<Block>node);
 
+                    case SyntaxKind.CatchClause:
+                        return spanInBlock((<CatchClause>node).block);
+
                     case SyntaxKind.ExpressionStatement:
                         // span on the expression
                         return textSpan((<ExpressionStatement>node).expression);
@@ -297,7 +299,7 @@ module ts.BreakpointResolver {
 
             function canHaveSpanInParameterDeclaration(parameter: ParameterDeclaration): boolean {
                 // Breakpoint is possible on parameter only if it has initializer, is a rest parameter, or has public or private modifier
-                return !!parameter.initializer || !!(parameter.flags & NodeFlags.Rest) ||
+                return !!parameter.initializer || parameter.dotDotDotToken !== undefined ||
                     !!(parameter.flags & NodeFlags.Public) || !!(parameter.flags & NodeFlags.Private);
             }
 
@@ -420,7 +422,7 @@ module ts.BreakpointResolver {
 
                     case SyntaxKind.Block:
                     case SyntaxKind.TryBlock:
-                    case SyntaxKind.CatchBlock:
+                    case SyntaxKind.CatchClause:
                     case SyntaxKind.FinallyBlock:
                         return spanInNode((<Block>node.parent).statements[(<Block>node.parent).statements.length - 1]);;
 
diff --git a/src/services/formatting.ts b/src/services/formatting.ts
index 741b853b7ba..3322ea1e65b 100644
--- a/src/services/formatting.ts
+++ b/src/services/formatting.ts
@@ -155,10 +155,11 @@ module ts.formatting {
             case SyntaxKind.SourceFile:
             case SyntaxKind.Block:
             case SyntaxKind.TryBlock:
-            case SyntaxKind.CatchBlock:
             case SyntaxKind.FinallyBlock:
             case SyntaxKind.ModuleBlock:
-                return rangeContainsRange((<Block>parent).statements, node)
+                return rangeContainsRange((<Block>parent).statements, node);
+            case SyntaxKind.CatchClause:
+                return rangeContainsRange((<CatchClause>parent).block.statements, node);
         }
 
         return false;
@@ -898,7 +899,6 @@ module ts.formatting {
             case SyntaxKind.Block:
             case SyntaxKind.FunctionBlock:
             case SyntaxKind.TryBlock:
-            case SyntaxKind.CatchBlock:
             case SyntaxKind.FinallyBlock:
             case SyntaxKind.ModuleBlock:
                 return true;
diff --git a/src/services/formatting/rules.ts b/src/services/formatting/rules.ts
index 7de7baee6ca..2723b50af7b 100644
--- a/src/services/formatting/rules.ts
+++ b/src/services/formatting/rules.ts
@@ -525,7 +525,6 @@ module ts.formatting {
                 case SyntaxKind.SwitchStatement:
                 case SyntaxKind.ObjectLiteralExpression:
                 case SyntaxKind.TryBlock:
-                case SyntaxKind.CatchBlock:
                 case SyntaxKind.FinallyBlock:
                 case SyntaxKind.FunctionBlock:
                 case SyntaxKind.ModuleBlock:
@@ -581,7 +580,7 @@ module ts.formatting {
                 case SyntaxKind.EnumDeclaration:
                 case SyntaxKind.Block:
                 case SyntaxKind.TryBlock:
-                case SyntaxKind.CatchBlock:
+                case SyntaxKind.CatchClause:
                 case SyntaxKind.FinallyBlock:
                 case SyntaxKind.FunctionBlock:
                 case SyntaxKind.ModuleBlock:
@@ -603,7 +602,7 @@ module ts.formatting {
                 case SyntaxKind.WithStatement:
                 // TODO
                 // case SyntaxKind.ElseClause:
-                case SyntaxKind.CatchBlock:
+                case SyntaxKind.CatchClause:
                 case SyntaxKind.FinallyBlock:
                     return true;
 
diff --git a/src/services/outliningElementsCollector.ts b/src/services/outliningElementsCollector.ts
index 7f071e5c224..68f30bee781 100644
--- a/src/services/outliningElementsCollector.ts
+++ b/src/services/outliningElementsCollector.ts
@@ -79,7 +79,8 @@ module ts {
                             parent.kind === SyntaxKind.ForStatement ||
                             parent.kind === SyntaxKind.IfStatement ||
                             parent.kind === SyntaxKind.WhileStatement ||
-                            parent.kind === SyntaxKind.WithStatement) {
+                            parent.kind === SyntaxKind.WithStatement ||
+                            parent.kind === SyntaxKind.CatchClause) {
                             
                             addOutliningSpan(parent, openBrace, closeBrace, autoCollapse(n));
                         }
@@ -100,7 +101,6 @@ module ts {
                     case SyntaxKind.FunctionBlock:
                     case SyntaxKind.ModuleBlock:
                     case SyntaxKind.TryBlock:
-                    case SyntaxKind.CatchBlock:
                     case SyntaxKind.FinallyBlock:
                         var openBrace = findChildOfKind(n, SyntaxKind.OpenBraceToken, sourceFile);
                         var closeBrace = findChildOfKind(n, SyntaxKind.CloseBraceToken, sourceFile);
diff --git a/src/services/services.ts b/src/services/services.ts
index c12a1f53e02..96817e276e2 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -722,6 +722,9 @@ module ts {
         public filename: string;
         public text: string;
 
+        public statements: NodeArray<Statement>;
+        public endOfFileToken: Node;
+
         // These methods will have their implementation provided by the implementation the 
         // compiler actually exports off of SourceFile.
         public getLineAndCharacterFromPosition: (position: number) => LineAndCharacter;
@@ -732,15 +735,17 @@ module ts {
         public amdDependencies: string[];
         public amdModuleName: string;
         public referencedFiles: FileReference[];
+
+        public referenceDiagnostics: Diagnostic[];
         public parseDiagnostics: Diagnostic[];
         public grammarDiagnostics: Diagnostic[];
         public semanticDiagnostics: Diagnostic[];
+
         public hasNoDefaultLib: boolean;
         public externalModuleIndicator: Node; // The first node that causes this file to be an external module
         public nodeCount: number;
         public identifierCount: number;
         public symbolCount: number;
-        public statements: NodeArray<Statement>;
         public version: string;
         public isOpen: boolean;
         public languageVersion: ScriptTarget;
@@ -2576,7 +2581,7 @@ module ts {
                                 isFunction(containingNodeKind);
 
                         case SyntaxKind.OpenParenToken:
-                            return containingNodeKind === SyntaxKind.CatchBlock ||
+                            return containingNodeKind === SyntaxKind.CatchClause ||
                                 isFunction(containingNodeKind);
 
                         case SyntaxKind.OpenBraceToken:
@@ -3567,8 +3572,8 @@ module ts {
                     else if (node.kind === SyntaxKind.TryStatement) {
                         var tryStatement = <TryStatement>node;
 
-                        if (tryStatement.catchBlock) {
-                            aggregate(tryStatement.catchBlock);
+                        if (tryStatement.catchClause) {
+                            aggregate(tryStatement.catchClause);
                         }
                         else {
                             // Exceptions thrown within a try block lacking a catch clause
@@ -3607,7 +3612,7 @@ module ts {
                     if (parent.kind === SyntaxKind.TryStatement) {
                         var tryStatement = <TryStatement>parent;
 
-                        if (tryStatement.tryBlock === child && tryStatement.catchBlock) {
+                        if (tryStatement.tryBlock === child && tryStatement.catchClause) {
                             return child;
                         }
                     }
@@ -3623,8 +3628,8 @@ module ts {
 
                 pushKeywordIf(keywords, tryStatement.getFirstToken(), SyntaxKind.TryKeyword);
 
-                if (tryStatement.catchBlock) {
-                    pushKeywordIf(keywords, tryStatement.catchBlock.getFirstToken(), SyntaxKind.CatchKeyword);
+                if (tryStatement.catchClause) {
+                    pushKeywordIf(keywords, tryStatement.catchClause.getFirstToken(), SyntaxKind.CatchKeyword);
                 }
 
                 if (tryStatement.finallyBlock) {
@@ -3839,8 +3844,8 @@ module ts {
                 }
 
                 forEach(nodes, node => {
-                    if (node.flags & modifierFlag) {
-                        forEach(node.getChildren(), child => pushKeywordIf(keywords, child, modifier));
+                    if (node.modifiers && node.flags & modifierFlag) {
+                        forEach(node.modifiers, child => pushKeywordIf(keywords, child, modifier));
                     }
                 });
 
@@ -4670,18 +4675,14 @@ module ts {
 
         function getEmitOutput(filename: string): EmitOutput {
             synchronizeHostData();
+
             filename = normalizeSlashes(filename);
-            var compilerOptions = program.getCompilerOptions();
-            var targetSourceFile = program.getSourceFile(filename);  // Current selected file to be output
-            // If --out flag is not specified, shouldEmitToOwnFile is true. Otherwise shouldEmitToOwnFile is false.
-            var shouldEmitToOwnFile = ts.shouldEmitToOwnFile(targetSourceFile, compilerOptions);
-            var emitOutput: EmitOutput = {
-                outputFiles: [],
-                emitOutputStatus: undefined,
-            };
+            var sourceFile = getSourceFile(filename);
+
+            var outputFiles: OutputFile[] = [];
 
             function getEmitOutputWriter(filename: string, data: string, writeByteOrderMark: boolean) {
-                emitOutput.outputFiles.push({
+                outputFiles.push({
                     name: filename,
                     writeByteOrderMark: writeByteOrderMark,
                     text: data
@@ -4691,41 +4692,15 @@ module ts {
             // Initialize writer for CompilerHost.writeFile
             writer = getEmitOutputWriter;
 
-            var containSyntacticErrors = false;
-
-            if (shouldEmitToOwnFile) {
-                // Check only the file we want to emit
-                containSyntacticErrors = containErrors(program.getDiagnostics(targetSourceFile));
-            } else {
-                // Check the syntactic of only sourceFiles that will get emitted into single output
-                // Terminate the process immediately if we encounter a syntax error from one of the sourceFiles
-                containSyntacticErrors = forEach(program.getSourceFiles(), sourceFile => {
-                    if (!isExternalModuleOrDeclarationFile(sourceFile)) {
-                        // If emit to a single file then we will check all files that do not have external module
-                        return containErrors(program.getDiagnostics(sourceFile));
-                    }
-                    return false;
-                });
-            }
-
-            if (containSyntacticErrors) {
-                // If there is a syntax error, terminate the process and report outputStatus
-                emitOutput.emitOutputStatus = EmitReturnStatus.AllOutputGenerationSkipped;
-                // Reset writer back to undefined to make sure that we produce an error message
-                // if CompilerHost.writeFile is called when we are not in getEmitOutput
-                writer = undefined;
-                return emitOutput;
-            }
-
-            // Perform semantic and force a type check before emit to ensure that all symbols are updated
-            // EmitFiles will report if there is an error from TypeChecker and Emitter
-            // Depend whether we will have to emit into a single file or not either emit only selected file in the project, emit all files into a single file
-            var emitFilesResult = getFullTypeCheckChecker().emitFiles(targetSourceFile);
-            emitOutput.emitOutputStatus = emitFilesResult.emitResultStatus;
+            var emitOutput = getFullTypeCheckChecker().emitFiles(sourceFile);
 
             // Reset writer back to undefined to make sure that we produce an error message if CompilerHost.writeFile method is called when we are not in getEmitOutput
             writer = undefined;
-            return emitOutput;
+
+            return {
+                outputFiles,
+                emitOutputStatus: emitOutput.emitResultStatus
+            };
         }
 
         function getMeaningFromDeclaration(node: Node): SemanticMeaning {
@@ -4743,7 +4718,7 @@ module ts {
                 case SyntaxKind.FunctionDeclaration:
                 case SyntaxKind.FunctionExpression:
                 case SyntaxKind.ArrowFunction:
-                case SyntaxKind.CatchBlock:
+                case SyntaxKind.CatchClause:
                     return SemanticMeaning.Value;
 
                 case SyntaxKind.TypeParameter:
diff --git a/src/services/shims.ts b/src/services/shims.ts
index e1e95c1332c..5556743830f 100644
--- a/src/services/shims.ts
+++ b/src/services/shims.ts
@@ -912,6 +912,13 @@ module ts {
             throw new Error("Invalid operation");
         }
     }
+
+    // Here we expose the TypeScript services as an external module
+    // so that it may be consumed easily like a node module.
+    declare var module: any;
+    if (typeof module !== "undefined" && module.exports) {
+        module.exports = ts;
+    }
 }
 
 
@@ -919,4 +926,3 @@ module ts {
 module TypeScript.Services {
     export var TypeScriptServicesFactory = ts.TypeScriptServicesFactory;
 }
-
diff --git a/src/services/signatureHelp.ts b/src/services/signatureHelp.ts
index f3604b3dfdd..93363b4676b 100644
--- a/src/services/signatureHelp.ts
+++ b/src/services/signatureHelp.ts
@@ -524,7 +524,7 @@ module ts.SignatureHelp {
                 var displayParts = mapToDisplayParts(writer =>
                     typeInfoResolver.getSymbolDisplayBuilder().buildParameterDisplay(parameter, writer, invocation));
 
-                var isOptional = !!(parameter.valueDeclaration.flags & NodeFlags.QuestionMark);
+                var isOptional = hasQuestionToken(parameter.valueDeclaration);
 
                 return {
                     name: parameter.name,
diff --git a/src/services/smartIndenter.ts b/src/services/smartIndenter.ts
index 4e32522040e..82226449b96 100644
--- a/src/services/smartIndenter.ts
+++ b/src/services/smartIndenter.ts
@@ -328,7 +328,6 @@ module ts.formatting {
                 case SyntaxKind.Block:
                 case SyntaxKind.FunctionBlock:
                 case SyntaxKind.TryBlock:
-                case SyntaxKind.CatchBlock:
                 case SyntaxKind.FinallyBlock:
                 case SyntaxKind.ModuleBlock:
                 case SyntaxKind.ObjectLiteralExpression:
@@ -404,12 +403,13 @@ module ts.formatting {
                 case SyntaxKind.EnumDeclaration:
                 case SyntaxKind.ObjectLiteralExpression:
                 case SyntaxKind.Block:
-                case SyntaxKind.CatchBlock:
                 case SyntaxKind.FinallyBlock:
                 case SyntaxKind.FunctionBlock:
                 case SyntaxKind.ModuleBlock:
                 case SyntaxKind.SwitchStatement:
                     return nodeEndsWith(n, SyntaxKind.CloseBraceToken, sourceFile);
+                case SyntaxKind.CatchClause:
+                    return isCompletedNode((<CatchClause>n).block, sourceFile);
                 case SyntaxKind.ParenthesizedExpression:
                 case SyntaxKind.CallSignature:
                 case SyntaxKind.CallExpression:
diff --git a/src/services/utilities.ts b/src/services/utilities.ts
index 4a3301312fb..9df0476c105 100644
--- a/src/services/utilities.ts
+++ b/src/services/utilities.ts
@@ -280,10 +280,6 @@ module ts {
     }
 
     function nodeHasTokens(n: Node): boolean {
-        if (n.kind === SyntaxKind.Unknown) {
-            return false;
-        }
-
         // If we have a token or node that has a non-zero width, it must have tokens.
         // Note, that getWidth() does not take trivia into account.
         return n.getWidth() !== 0;
diff --git a/tests/baselines/reference/accessorWithRestParam.errors.txt b/tests/baselines/reference/accessorWithRestParam.errors.txt
index 6162d5a8238..c6f3ef70563 100644
--- a/tests/baselines/reference/accessorWithRestParam.errors.txt
+++ b/tests/baselines/reference/accessorWithRestParam.errors.txt
@@ -1,14 +1,14 @@
-tests/cases/compiler/accessorWithRestParam.ts(3,9): error TS1053: A 'set' accessor cannot have rest parameter.
-tests/cases/compiler/accessorWithRestParam.ts(4,16): error TS1053: A 'set' accessor cannot have rest parameter.
+tests/cases/compiler/accessorWithRestParam.ts(3,11): error TS1053: A 'set' accessor cannot have rest parameter.
+tests/cases/compiler/accessorWithRestParam.ts(4,18): error TS1053: A 'set' accessor cannot have rest parameter.
 
 
 ==== tests/cases/compiler/accessorWithRestParam.ts (2 errors) ====
     
     class C {
         set X(...v) { }
-            ~
+              ~~~
 !!! error TS1053: A 'set' accessor cannot have rest parameter.
         static set X(...v2) { }
-                   ~
+                     ~~~
 !!! error TS1053: A 'set' accessor cannot have rest parameter.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/anyAssignableToEveryType.js b/tests/baselines/reference/anyAssignableToEveryType.js
index 6c117a5054d..75d847709a5 100644
--- a/tests/baselines/reference/anyAssignableToEveryType.js
+++ b/tests/baselines/reference/anyAssignableToEveryType.js
@@ -83,3 +83,8 @@ function foo(x, y, z) {
     y = a;
     z = a;
 }
+//function foo<T, U extends T, V extends Date>(x: T, y: U, z: V) {
+//    x = a;
+//    y = a;
+//    z = a;
+//} 
diff --git a/tests/baselines/reference/augmentedTypesClass3.js b/tests/baselines/reference/augmentedTypesClass3.js
index dd0da2a1646..b42d9dda356 100644
--- a/tests/baselines/reference/augmentedTypesClass3.js
+++ b/tests/baselines/reference/augmentedTypesClass3.js
@@ -52,3 +52,4 @@ var c5c = (function () {
     };
     return c5c;
 })();
+//import c5c = require(''); 
diff --git a/tests/baselines/reference/augmentedTypesEnum.js b/tests/baselines/reference/augmentedTypesEnum.js
index f7a83018cfd..484b0addd58 100644
--- a/tests/baselines/reference/augmentedTypesEnum.js
+++ b/tests/baselines/reference/augmentedTypesEnum.js
@@ -105,3 +105,6 @@ var e6b;
 (function (e6b) {
     e6b.y = 2;
 })(e6b || (e6b = {})); // should be error
+// enum then import, messes with error reporting
+//enum e7 { One }
+//import e7 = require(''); // should be error 
diff --git a/tests/baselines/reference/augmentedTypesEnum2.js b/tests/baselines/reference/augmentedTypesEnum2.js
index 8ab98a7cb7b..434e508f14c 100644
--- a/tests/baselines/reference/augmentedTypesEnum2.js
+++ b/tests/baselines/reference/augmentedTypesEnum2.js
@@ -40,3 +40,5 @@ var e2 = (function () {
     };
     return e2;
 })();
+//enum then enum - covered
+//enum then import - covered 
diff --git a/tests/baselines/reference/augmentedTypesFunction.js b/tests/baselines/reference/augmentedTypesFunction.js
index 078854e227c..34567c77e8c 100644
--- a/tests/baselines/reference/augmentedTypesFunction.js
+++ b/tests/baselines/reference/augmentedTypesFunction.js
@@ -93,3 +93,6 @@ var y5b;
 })(y5b || (y5b = {})); // should be an error
 function y5c() {
 }
+// function then import, messes with other errors
+//function y6() { }
+//import y6 = require(''); 
diff --git a/tests/baselines/reference/augmentedTypesInterface.js b/tests/baselines/reference/augmentedTypesInterface.js
index 709b16d615c..a5039f8b1d0 100644
--- a/tests/baselines/reference/augmentedTypesInterface.js
+++ b/tests/baselines/reference/augmentedTypesInterface.js
@@ -48,3 +48,4 @@ var i3;
     i3[i3["One"] = 0] = "One";
 })(i3 || (i3 = {}));
 ;
+//import i4 = require('');  // error 
diff --git a/tests/baselines/reference/augmentedTypesModules.js b/tests/baselines/reference/augmentedTypesModules.js
index 0c7967b2227..a9bff3fa74b 100644
--- a/tests/baselines/reference/augmentedTypesModules.js
+++ b/tests/baselines/reference/augmentedTypesModules.js
@@ -268,3 +268,4 @@ var m6;
 (function (m6) {
     m6.y = 2;
 })(m6 || (m6 = {}));
+//import m6 = require('');
diff --git a/tests/baselines/reference/augmentedTypesVar.js b/tests/baselines/reference/augmentedTypesVar.js
index 4735d647056..f4404cecb3d 100644
--- a/tests/baselines/reference/augmentedTypesVar.js
+++ b/tests/baselines/reference/augmentedTypesVar.js
@@ -80,3 +80,6 @@ var x6b;
 (function (x6b) {
     x6b.y = 2;
 })(x6b || (x6b = {})); // error
+// var then import, messes with other error reporting
+//var x7 = 1;
+//import x7 = require('');
diff --git a/tests/baselines/reference/baseIndexSignatureResolution.js b/tests/baselines/reference/baseIndexSignatureResolution.js
index 0c1e6c610f3..4c2d63bf2c9 100644
--- a/tests/baselines/reference/baseIndexSignatureResolution.js
+++ b/tests/baselines/reference/baseIndexSignatureResolution.js
@@ -45,3 +45,37 @@ var Derived = (function (_super) {
 })(Base);
 var x = null;
 var y = x[0];
+/*
+// Note - the equivalent for normal interface methods works fine:
+interface A {
+    foo(): Base;
+}
+interface B<TBase extends Base> extends A {
+    foo(): TBase;
+}
+var b: B<Derived> = null;
+var z: Derived = b.foo();
+class Base { private a: string; }
+class Derived extends Base { private b: string; }
+
+// Note - commmenting "extends Foo" prevents the error
+interface Foo {
+    [i: number]: Base;
+}
+interface FooOf<TBase extends Base> extends Foo {
+    [i: number]: TBase;
+}
+var x: FooOf<Derived> = null;
+var y: Derived = x[0];
+
+/*
+// Note - the equivalent for normal interface methods works fine:
+interface A {
+    foo(): Base;
+}
+interface B<TBase extends Base> extends A {
+    foo(): TBase;
+}
+var b: B<Derived> = null;
+var z: Derived = b.foo();
+ 
diff --git a/tests/baselines/reference/castingTuple.errors.txt b/tests/baselines/reference/castingTuple.errors.txt
index f4efed6f1d1..98be259964d 100644
--- a/tests/baselines/reference/castingTuple.errors.txt
+++ b/tests/baselines/reference/castingTuple.errors.txt
@@ -2,19 +2,19 @@ tests/cases/conformance/types/tuple/castingTuple.ts(13,23): error TS2352: Neithe
   Property '2' is missing in type '[number, string]'.
 tests/cases/conformance/types/tuple/castingTuple.ts(16,21): error TS2352: Neither type '[C, D]' nor type '[C, D, A]' is assignable to the other.
   Property '2' is missing in type '[C, D]'.
-tests/cases/conformance/types/tuple/castingTuple.ts(24,10): error TS2352: Neither type '[number, string]' nor type '[number, number]' is assignable to the other.
+tests/cases/conformance/types/tuple/castingTuple.ts(28,10): error TS2352: Neither type '[number, string]' nor type '[number, number]' is assignable to the other.
   Types of property '1' are incompatible.
     Type 'string' is not assignable to type 'number'.
-tests/cases/conformance/types/tuple/castingTuple.ts(25,10): error TS2352: Neither type '[C, D]' nor type '[A, I]' is assignable to the other.
+tests/cases/conformance/types/tuple/castingTuple.ts(29,10): error TS2352: Neither type '[C, D]' nor type '[A, I]' is assignable to the other.
   Types of property '0' are incompatible.
     Type 'C' is not assignable to type 'A'.
-tests/cases/conformance/types/tuple/castingTuple.ts(26,5): error TS2403: Subsequent variable declarations must have the same type.  Variable 'array1' must be of type '{}[]', but here has type 'number[]'.
-tests/cases/conformance/types/tuple/castingTuple.ts(26,14): error TS2352: Neither type '[number, string]' nor type 'number[]' is assignable to the other.
+tests/cases/conformance/types/tuple/castingTuple.ts(30,5): error TS2403: Subsequent variable declarations must have the same type.  Variable 'array1' must be of type '{}[]', but here has type 'number[]'.
+tests/cases/conformance/types/tuple/castingTuple.ts(30,14): error TS2352: Neither type '[number, string]' nor type 'number[]' is assignable to the other.
   Types of property 'pop' are incompatible.
     Type '() => string | number' is not assignable to type '() => number'.
       Type 'string | number' is not assignable to type 'number'.
         Type 'string' is not assignable to type 'number'.
-tests/cases/conformance/types/tuple/castingTuple.ts(27,1): error TS2304: Cannot find name 't4'.
+tests/cases/conformance/types/tuple/castingTuple.ts(31,1): error TS2304: Cannot find name 't4'.
 
 
 ==== tests/cases/conformance/types/tuple/castingTuple.ts (7 errors) ====
@@ -41,10 +41,14 @@ tests/cases/conformance/types/tuple/castingTuple.ts(27,1): error TS2304: Cannot
 !!! error TS2352: Neither type '[C, D]' nor type '[C, D, A]' is assignable to the other.
 !!! error TS2352:   Property '2' is missing in type '[C, D]'.
     var eleFromCDA1 = classCDATuple[2]; // A
-    var eleFromCDA2 = classCDATuple[5]; // {}
+    var eleFromCDA2 = classCDATuple[5]; // C | D | A
     var t10: [E1, E2] = [E1.one, E2.one];
     var t11 = <[number, number]>t10;
     var array1 = <{}[]>emptyObjTuple;
+    var unionTuple: [C, string | number] = [new C(), "foo"];
+    var unionTuple2: [C, string | number, D] = [new C(), "foo", new D()];
+    var unionTuple3: [number, string| number] = [10, "foo"]; 
+    var unionTuple4 = <[number, number]>unionTuple3; 
     
     // error
     var t3 = <[number, number]>numStrTuple;
@@ -68,4 +72,5 @@ tests/cases/conformance/types/tuple/castingTuple.ts(27,1): error TS2304: Cannot
 !!! error TS2352:         Type 'string' is not assignable to type 'number'.
     t4[2] = 10;
     ~~
-!!! error TS2304: Cannot find name 't4'.
\ No newline at end of file
+!!! error TS2304: Cannot find name 't4'.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/castingTuple.js b/tests/baselines/reference/castingTuple.js
index 0671062bb4e..fffadcbc070 100644
--- a/tests/baselines/reference/castingTuple.js
+++ b/tests/baselines/reference/castingTuple.js
@@ -16,16 +16,21 @@ var classCDTuple: [C, D] = [new C(), new D()];
 var interfaceIITuple = <[I, I]>classCDTuple;
 var classCDATuple = <[C, D, A]>classCDTuple;
 var eleFromCDA1 = classCDATuple[2]; // A
-var eleFromCDA2 = classCDATuple[5]; // {}
+var eleFromCDA2 = classCDATuple[5]; // C | D | A
 var t10: [E1, E2] = [E1.one, E2.one];
 var t11 = <[number, number]>t10;
 var array1 = <{}[]>emptyObjTuple;
+var unionTuple: [C, string | number] = [new C(), "foo"];
+var unionTuple2: [C, string | number, D] = [new C(), "foo", new D()];
+var unionTuple3: [number, string| number] = [10, "foo"]; 
+var unionTuple4 = <[number, number]>unionTuple3; 
 
 // error
 var t3 = <[number, number]>numStrTuple;
 var t9 = <[A, I]>classCDTuple;
 var array1 = <number[]>numStrTuple;
-t4[2] = 10;
+t4[2] = 10;
+
 
 //// [castingTuple.js]
 var __extends = this.__extends || function (d, b) {
@@ -84,10 +89,14 @@ var classCDTuple = [new C(), new D()];
 var interfaceIITuple = classCDTuple;
 var classCDATuple = classCDTuple;
 var eleFromCDA1 = classCDATuple[2]; // A
-var eleFromCDA2 = classCDATuple[5]; // {}
+var eleFromCDA2 = classCDATuple[5]; // C | D | A
 var t10 = [0 /* one */, 0 /* one */];
 var t11 = t10;
 var array1 = emptyObjTuple;
+var unionTuple = [new C(), "foo"];
+var unionTuple2 = [new C(), "foo", new D()];
+var unionTuple3 = [10, "foo"];
+var unionTuple4 = unionTuple3;
 // error
 var t3 = numStrTuple;
 var t9 = classCDTuple;
diff --git a/tests/baselines/reference/commentEmitAtEndOfFile1.js b/tests/baselines/reference/commentEmitAtEndOfFile1.js
new file mode 100644
index 00000000000..1a1f7cb8900
--- /dev/null
+++ b/tests/baselines/reference/commentEmitAtEndOfFile1.js
@@ -0,0 +1,22 @@
+//// [commentEmitAtEndOfFile1.ts]
+// test
+var f = ''
+// test #2
+module foo {
+        function bar() { }
+}
+// test #3
+module empty {
+}
+// test #4
+
+//// [commentEmitAtEndOfFile1.js]
+// test
+var f = '';
+// test #2
+var foo;
+(function (foo) {
+    function bar() {
+    }
+})(foo || (foo = {}));
+// test #4 
diff --git a/tests/baselines/reference/commentEmitAtEndOfFile1.types b/tests/baselines/reference/commentEmitAtEndOfFile1.types
new file mode 100644
index 00000000000..76b5c868cb6
--- /dev/null
+++ b/tests/baselines/reference/commentEmitAtEndOfFile1.types
@@ -0,0 +1,17 @@
+=== tests/cases/compiler/commentEmitAtEndOfFile1.ts ===
+// test
+var f = ''
+>f : string
+
+// test #2
+module foo {
+>foo : typeof foo
+
+        function bar() { }
+>bar : () => void
+}
+// test #3
+module empty {
+>empty : unknown
+}
+// test #4
diff --git a/tests/baselines/reference/commentsAtEndOfFile1.js b/tests/baselines/reference/commentsAtEndOfFile1.js
index a0b0fe3731e..2d4dae39e6b 100644
--- a/tests/baselines/reference/commentsAtEndOfFile1.js
+++ b/tests/baselines/reference/commentsAtEndOfFile1.js
@@ -6,3 +6,4 @@ Input:
 
 //// [commentsAtEndOfFile1.js]
 Input: ;
+//Testing two
diff --git a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnCallSignature.js b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnCallSignature.js
index 890add6bc8a..5a00fd85f3c 100644
--- a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnCallSignature.js
+++ b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnCallSignature.js
@@ -501,3 +501,4 @@ var r8b8 = b8 !== a8;
 var r8b9 = b9 !== a9;
 var r8b10 = b10 !== a10;
 var r8b11 = b11 !== a11;
+//var r8b12 = b12 !== a12; 
diff --git a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnConstructorSignature.js b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnConstructorSignature.js
index aefeb6d87ff..cba4f67933b 100644
--- a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnConstructorSignature.js
+++ b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnConstructorSignature.js
@@ -427,3 +427,4 @@ var r8b6 = b6 !== a6;
 var r8b7 = b7 !== a7;
 var r8b8 = b8 !== a8;
 var r8b9 = b9 !== a9;
+//var r8b10 = b10 !== a10; 
diff --git a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnInstantiatedCallSignature.js b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnInstantiatedCallSignature.js
index 1a83da3e663..1f2400f9bea 100644
--- a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnInstantiatedCallSignature.js
+++ b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnInstantiatedCallSignature.js
@@ -316,3 +316,4 @@ var r8b3 = b3 !== a3;
 var r8b4 = b4 !== a4;
 var r8b5 = b5 !== a5;
 var r8b6 = b6 !== a6;
+//var r8b7 = b7 !== a7; 
diff --git a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnInstantiatedConstructorSignature.js b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnInstantiatedConstructorSignature.js
index 393a2485c47..e80480e1a4e 100644
--- a/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnInstantiatedConstructorSignature.js
+++ b/tests/baselines/reference/comparisonOperatorWithSubtypeObjectOnInstantiatedConstructorSignature.js
@@ -316,3 +316,4 @@ var r8b3 = b3 !== a3;
 var r8b4 = b4 !== a4;
 var r8b5 = b5 !== a5;
 var r8b6 = b6 !== a6;
+//var r8b7 = b7 !== a7; 
diff --git a/tests/baselines/reference/concatError.js b/tests/baselines/reference/concatError.js
index e4ae4afdb65..04c0a16b836 100644
--- a/tests/baselines/reference/concatError.js
+++ b/tests/baselines/reference/concatError.js
@@ -43,3 +43,48 @@ interface Array<T> {
 var fa;
 fa = fa.concat([0]);
 fa = fa.concat(0);
+/*
+
+
+
+
+declare class C<T> {
+    public m(p1: C<C<T>>): C<T>;
+    //public p: T;
+}
+
+var c: C<number>;
+var cc: C<C<number>>;
+
+c = c.m(cc);
+var n1: number[];
+/*
+interface Array<T> {
+    concat(...items: T[][]): T[]; // Note: This overload needs to be picked for arrays of arrays, even though both are applicable
+    concat(...items: T[]): T[];
+}
+*/
+var fa: number[];
+
+fa = fa.concat([0]);
+fa = fa.concat(0);
+
+
+
+
+
+/*
+
+
+
+
+declare class C<T> {
+	public m(p1: C<C<T>>): C<T>;
+	//public p: T;
+}
+
+var c: C<number>;
+var cc: C<C<number>>;
+
+c = c.m(cc);
+ 
diff --git a/tests/baselines/reference/conditionalOperatorConditionIsBooleanType.js b/tests/baselines/reference/conditionalOperatorConditionIsBooleanType.js
index ab9dca9023f..d9a8b2daa29 100644
--- a/tests/baselines/reference/conditionalOperatorConditionIsBooleanType.js
+++ b/tests/baselines/reference/conditionalOperatorConditionIsBooleanType.js
@@ -20,6 +20,7 @@ condBoolean ? exprBoolean1 : exprBoolean2;
 condBoolean ? exprNumber1 : exprNumber2;
 condBoolean ? exprString1 : exprString2;
 condBoolean ? exprIsObject1 : exprIsObject2;
+condBoolean ? exprString1 : exprBoolean1; // union
 
 //Cond is a boolean type literal
 true ? exprAny1 : exprAny2;
@@ -27,6 +28,7 @@ false ? exprBoolean1 : exprBoolean2;
 true ? exprNumber1 : exprNumber2;
 false ? exprString1 : exprString2;
 true ? exprIsObject1 : exprIsObject2;
+true ? exprString1 : exprBoolean1; // union
 
 //Cond is a boolean type expression
 !true ? exprAny1 : exprAny2;
@@ -34,6 +36,7 @@ typeof "123" == "string" ? exprBoolean1 : exprBoolean2;
 2 > 1 ? exprNumber1 : exprNumber2;
 null === undefined ? exprString1 : exprString2;
 true || false ? exprIsObject1 : exprIsObject2;
+null === undefined ? exprString1 : exprBoolean1; // union
 
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condBoolean ? exprAny1 : exprAny2;
@@ -41,18 +44,22 @@ var resultIsBoolean1 = condBoolean ? exprBoolean1 : exprBoolean2;
 var resultIsNumber1 = condBoolean ? exprNumber1 : exprNumber2;
 var resultIsString1 = condBoolean ? exprString1 : exprString2;
 var resultIsObject1 = condBoolean ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean1 = condBoolean ? exprString1 : exprBoolean1; // union
 
 var resultIsAny2 = true ? exprAny1 : exprAny2;
 var resultIsBoolean2 = false ? exprBoolean1 : exprBoolean2;
 var resultIsNumber2 = true ? exprNumber1 : exprNumber2;
 var resultIsString2 = false ? exprString1 : exprString2;
 var resultIsObject2 = true ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean2 = true ? exprString1 : exprBoolean1; // union
+var resultIsStringOrBoolean3 = false ? exprString1 : exprBoolean1; // union
 
 var resultIsAny3 = !true ? exprAny1 : exprAny2;
 var resultIsBoolean3 = typeof "123" == "string" ? exprBoolean1 : exprBoolean2;
 var resultIsNumber3 = 2 > 1 ? exprNumber1 : exprNumber2;
 var resultIsString3 = null === undefined ? exprString1 : exprString2;
 var resultIsObject3 = true || false ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean4 = typeof "123" === "string" ? exprString1 : exprBoolean1; // union
 
 
 //// [conditionalOperatorConditionIsBooleanType.js]
@@ -74,31 +81,38 @@ condBoolean ? exprBoolean1 : exprBoolean2;
 condBoolean ? exprNumber1 : exprNumber2;
 condBoolean ? exprString1 : exprString2;
 condBoolean ? exprIsObject1 : exprIsObject2;
+condBoolean ? exprString1 : exprBoolean1; // union
 //Cond is a boolean type literal
 true ? exprAny1 : exprAny2;
 false ? exprBoolean1 : exprBoolean2;
 true ? exprNumber1 : exprNumber2;
 false ? exprString1 : exprString2;
 true ? exprIsObject1 : exprIsObject2;
+true ? exprString1 : exprBoolean1; // union
 //Cond is a boolean type expression
 !true ? exprAny1 : exprAny2;
 typeof "123" == "string" ? exprBoolean1 : exprBoolean2;
 2 > 1 ? exprNumber1 : exprNumber2;
 null === undefined ? exprString1 : exprString2;
 true || false ? exprIsObject1 : exprIsObject2;
+null === undefined ? exprString1 : exprBoolean1; // union
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condBoolean ? exprAny1 : exprAny2;
 var resultIsBoolean1 = condBoolean ? exprBoolean1 : exprBoolean2;
 var resultIsNumber1 = condBoolean ? exprNumber1 : exprNumber2;
 var resultIsString1 = condBoolean ? exprString1 : exprString2;
 var resultIsObject1 = condBoolean ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean1 = condBoolean ? exprString1 : exprBoolean1; // union
 var resultIsAny2 = true ? exprAny1 : exprAny2;
 var resultIsBoolean2 = false ? exprBoolean1 : exprBoolean2;
 var resultIsNumber2 = true ? exprNumber1 : exprNumber2;
 var resultIsString2 = false ? exprString1 : exprString2;
 var resultIsObject2 = true ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean2 = true ? exprString1 : exprBoolean1; // union
+var resultIsStringOrBoolean3 = false ? exprString1 : exprBoolean1; // union
 var resultIsAny3 = !true ? exprAny1 : exprAny2;
 var resultIsBoolean3 = typeof "123" == "string" ? exprBoolean1 : exprBoolean2;
 var resultIsNumber3 = 2 > 1 ? exprNumber1 : exprNumber2;
 var resultIsString3 = null === undefined ? exprString1 : exprString2;
 var resultIsObject3 = true || false ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean4 = typeof "123" === "string" ? exprString1 : exprBoolean1; // union
diff --git a/tests/baselines/reference/conditionalOperatorConditionIsBooleanType.types b/tests/baselines/reference/conditionalOperatorConditionIsBooleanType.types
index b3ca65219cb..44fc9f5ed7b 100644
--- a/tests/baselines/reference/conditionalOperatorConditionIsBooleanType.types
+++ b/tests/baselines/reference/conditionalOperatorConditionIsBooleanType.types
@@ -66,6 +66,12 @@ condBoolean ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+condBoolean ? exprString1 : exprBoolean1; // union
+>condBoolean ? exprString1 : exprBoolean1 : string | boolean
+>condBoolean : boolean
+>exprString1 : string
+>exprBoolean1 : boolean
+
 //Cond is a boolean type literal
 true ? exprAny1 : exprAny2;
 >true ? exprAny1 : exprAny2 : any
@@ -92,6 +98,11 @@ true ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+true ? exprString1 : exprBoolean1; // union
+>true ? exprString1 : exprBoolean1 : string | boolean
+>exprString1 : string
+>exprBoolean1 : boolean
+
 //Cond is a boolean type expression
 !true ? exprAny1 : exprAny2;
 >!true ? exprAny1 : exprAny2 : any
@@ -125,6 +136,13 @@ true || false ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+null === undefined ? exprString1 : exprBoolean1; // union
+>null === undefined ? exprString1 : exprBoolean1 : string | boolean
+>null === undefined : boolean
+>undefined : undefined
+>exprString1 : string
+>exprBoolean1 : boolean
+
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condBoolean ? exprAny1 : exprAny2;
 >resultIsAny1 : any
@@ -161,6 +179,13 @@ var resultIsObject1 = condBoolean ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+var resultIsStringOrBoolean1 = condBoolean ? exprString1 : exprBoolean1; // union
+>resultIsStringOrBoolean1 : string | boolean
+>condBoolean ? exprString1 : exprBoolean1 : string | boolean
+>condBoolean : boolean
+>exprString1 : string
+>exprBoolean1 : boolean
+
 var resultIsAny2 = true ? exprAny1 : exprAny2;
 >resultIsAny2 : any
 >true ? exprAny1 : exprAny2 : any
@@ -191,6 +216,18 @@ var resultIsObject2 = true ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+var resultIsStringOrBoolean2 = true ? exprString1 : exprBoolean1; // union
+>resultIsStringOrBoolean2 : string | boolean
+>true ? exprString1 : exprBoolean1 : string | boolean
+>exprString1 : string
+>exprBoolean1 : boolean
+
+var resultIsStringOrBoolean3 = false ? exprString1 : exprBoolean1; // union
+>resultIsStringOrBoolean3 : string | boolean
+>false ? exprString1 : exprBoolean1 : string | boolean
+>exprString1 : string
+>exprBoolean1 : boolean
+
 var resultIsAny3 = !true ? exprAny1 : exprAny2;
 >resultIsAny3 : any
 >!true ? exprAny1 : exprAny2 : any
@@ -228,3 +265,11 @@ var resultIsObject3 = true || false ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+var resultIsStringOrBoolean4 = typeof "123" === "string" ? exprString1 : exprBoolean1; // union
+>resultIsStringOrBoolean4 : string | boolean
+>typeof "123" === "string" ? exprString1 : exprBoolean1 : string | boolean
+>typeof "123" === "string" : boolean
+>typeof "123" : string
+>exprString1 : string
+>exprBoolean1 : boolean
+
diff --git a/tests/baselines/reference/conditionalOperatorConditionIsNumberType.js b/tests/baselines/reference/conditionalOperatorConditionIsNumberType.js
index 166841f0a89..46a04169e93 100644
--- a/tests/baselines/reference/conditionalOperatorConditionIsNumberType.js
+++ b/tests/baselines/reference/conditionalOperatorConditionIsNumberType.js
@@ -20,6 +20,7 @@ condNumber ? exprBoolean1 : exprBoolean2;
 condNumber ? exprNumber1 : exprNumber2;
 condNumber ? exprString1 : exprString2;
 condNumber ? exprIsObject1 : exprIsObject2;
+condNumber ? exprString1 : exprBoolean1; // Union
 
 //Cond is a number type literal
 1 ? exprAny1 : exprAny2;
@@ -27,6 +28,7 @@ condNumber ? exprIsObject1 : exprIsObject2;
 0.123456789 ? exprNumber1 : exprNumber2;
 - 10000000000000 ? exprString1 : exprString2;
 1000000000000 ? exprIsObject1 : exprIsObject2;
+10000 ? exprString1 : exprBoolean1; // Union
 
 //Cond is a number type expression
 function foo() { return 1 };
@@ -37,6 +39,7 @@ var array = [1, 2, 3];
 "string".length ? exprNumber1 : exprNumber2;
 foo() ? exprString1 : exprString2;
 foo() / array[1] ? exprIsObject1 : exprIsObject2;
+foo() ? exprString1 : exprBoolean1; // Union
 
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condNumber ? exprAny1 : exprAny2;
@@ -44,19 +47,21 @@ var resultIsBoolean1 = condNumber ? exprBoolean1 : exprBoolean2;
 var resultIsNumber1 = condNumber ? exprNumber1 : exprNumber2;
 var resultIsString1 = condNumber ? exprString1 : exprString2;
 var resultIsObject1 = condNumber ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean1 = condNumber ? exprString1 : exprBoolean1; // Union
 
 var resultIsAny2 = 1 ? exprAny1 : exprAny2;
 var resultIsBoolean2 = 0 ? exprBoolean1 : exprBoolean2;
 var resultIsNumber2 = 0.123456789 ? exprNumber1 : exprNumber2;
 var resultIsString2 = - 10000000000000 ? exprString1 : exprString2;
 var resultIsObject2 = 1000000000000 ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean2 = 10000 ? exprString1 : exprBoolean1; // Union
 
 var resultIsAny3 = 1 * 0 ? exprAny1 : exprAny2;
 var resultIsBoolean3 = 1 + 1 ? exprBoolean1 : exprBoolean2;
 var resultIsNumber3 = "string".length ? exprNumber1 : exprNumber2;
 var resultIsString3 = foo() ? exprString1 : exprString2;
 var resultIsObject3 = foo() / array[1] ? exprIsObject1 : exprIsObject2;
-
+var resultIsStringOrBoolean3 = foo() / array[1] ? exprString1 : exprBoolean1; // Union
 
 //// [conditionalOperatorConditionIsNumberType.js]
 //Cond ? Expr1 : Expr2,  Cond is of number type, Expr1 and Expr2 have the same type
@@ -77,12 +82,14 @@ condNumber ? exprBoolean1 : exprBoolean2;
 condNumber ? exprNumber1 : exprNumber2;
 condNumber ? exprString1 : exprString2;
 condNumber ? exprIsObject1 : exprIsObject2;
+condNumber ? exprString1 : exprBoolean1; // Union
 //Cond is a number type literal
 1 ? exprAny1 : exprAny2;
 0 ? exprBoolean1 : exprBoolean2;
 0.123456789 ? exprNumber1 : exprNumber2;
 -10000000000000 ? exprString1 : exprString2;
 1000000000000 ? exprIsObject1 : exprIsObject2;
+10000 ? exprString1 : exprBoolean1; // Union
 //Cond is a number type expression
 function foo() {
     return 1;
@@ -94,19 +101,23 @@ var array = [1, 2, 3];
 "string".length ? exprNumber1 : exprNumber2;
 foo() ? exprString1 : exprString2;
 foo() / array[1] ? exprIsObject1 : exprIsObject2;
+foo() ? exprString1 : exprBoolean1; // Union
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condNumber ? exprAny1 : exprAny2;
 var resultIsBoolean1 = condNumber ? exprBoolean1 : exprBoolean2;
 var resultIsNumber1 = condNumber ? exprNumber1 : exprNumber2;
 var resultIsString1 = condNumber ? exprString1 : exprString2;
 var resultIsObject1 = condNumber ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean1 = condNumber ? exprString1 : exprBoolean1; // Union
 var resultIsAny2 = 1 ? exprAny1 : exprAny2;
 var resultIsBoolean2 = 0 ? exprBoolean1 : exprBoolean2;
 var resultIsNumber2 = 0.123456789 ? exprNumber1 : exprNumber2;
 var resultIsString2 = -10000000000000 ? exprString1 : exprString2;
 var resultIsObject2 = 1000000000000 ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean2 = 10000 ? exprString1 : exprBoolean1; // Union
 var resultIsAny3 = 1 * 0 ? exprAny1 : exprAny2;
 var resultIsBoolean3 = 1 + 1 ? exprBoolean1 : exprBoolean2;
 var resultIsNumber3 = "string".length ? exprNumber1 : exprNumber2;
 var resultIsString3 = foo() ? exprString1 : exprString2;
 var resultIsObject3 = foo() / array[1] ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean3 = foo() / array[1] ? exprString1 : exprBoolean1; // Union
diff --git a/tests/baselines/reference/conditionalOperatorConditionIsNumberType.types b/tests/baselines/reference/conditionalOperatorConditionIsNumberType.types
index 3396885509a..99a81081d6b 100644
--- a/tests/baselines/reference/conditionalOperatorConditionIsNumberType.types
+++ b/tests/baselines/reference/conditionalOperatorConditionIsNumberType.types
@@ -66,6 +66,12 @@ condNumber ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+condNumber ? exprString1 : exprBoolean1; // Union
+>condNumber ? exprString1 : exprBoolean1 : string | boolean
+>condNumber : number
+>exprString1 : string
+>exprBoolean1 : boolean
+
 //Cond is a number type literal
 1 ? exprAny1 : exprAny2;
 >1 ? exprAny1 : exprAny2 : any
@@ -93,6 +99,11 @@ condNumber ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+10000 ? exprString1 : exprBoolean1; // Union
+>10000 ? exprString1 : exprBoolean1 : string | boolean
+>exprString1 : string
+>exprBoolean1 : boolean
+
 //Cond is a number type expression
 function foo() { return 1 };
 >foo : () => number
@@ -137,6 +148,13 @@ foo() / array[1] ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+foo() ? exprString1 : exprBoolean1; // Union
+>foo() ? exprString1 : exprBoolean1 : string | boolean
+>foo() : number
+>foo : () => number
+>exprString1 : string
+>exprBoolean1 : boolean
+
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condNumber ? exprAny1 : exprAny2;
 >resultIsAny1 : any
@@ -173,6 +191,13 @@ var resultIsObject1 = condNumber ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+var resultIsStringOrBoolean1 = condNumber ? exprString1 : exprBoolean1; // Union
+>resultIsStringOrBoolean1 : string | boolean
+>condNumber ? exprString1 : exprBoolean1 : string | boolean
+>condNumber : number
+>exprString1 : string
+>exprBoolean1 : boolean
+
 var resultIsAny2 = 1 ? exprAny1 : exprAny2;
 >resultIsAny2 : any
 >1 ? exprAny1 : exprAny2 : any
@@ -204,6 +229,12 @@ var resultIsObject2 = 1000000000000 ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+var resultIsStringOrBoolean2 = 10000 ? exprString1 : exprBoolean1; // Union
+>resultIsStringOrBoolean2 : string | boolean
+>10000 ? exprString1 : exprBoolean1 : string | boolean
+>exprString1 : string
+>exprBoolean1 : boolean
+
 var resultIsAny3 = 1 * 0 ? exprAny1 : exprAny2;
 >resultIsAny3 : any
 >1 * 0 ? exprAny1 : exprAny2 : any
@@ -245,3 +276,14 @@ var resultIsObject3 = foo() / array[1] ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+var resultIsStringOrBoolean3 = foo() / array[1] ? exprString1 : exprBoolean1; // Union
+>resultIsStringOrBoolean3 : string | boolean
+>foo() / array[1] ? exprString1 : exprBoolean1 : string | boolean
+>foo() / array[1] : number
+>foo() : number
+>foo : () => number
+>array[1] : number
+>array : number[]
+>exprString1 : string
+>exprBoolean1 : boolean
+
diff --git a/tests/baselines/reference/conditionalOperatorConditionIsObjectType.js b/tests/baselines/reference/conditionalOperatorConditionIsObjectType.js
index 3f98398d94d..b628c21bd14 100644
--- a/tests/baselines/reference/conditionalOperatorConditionIsObjectType.js
+++ b/tests/baselines/reference/conditionalOperatorConditionIsObjectType.js
@@ -23,6 +23,7 @@ condObject ? exprBoolean1 : exprBoolean2;
 condObject ? exprNumber1 : exprNumber2;
 condObject ? exprString1 : exprString2;
 condObject ? exprIsObject1 : exprIsObject2;
+condObject ? exprString1 : exprBoolean1; // union
 
 //Cond is an object type literal
 ((a: string) => a.length) ? exprAny1 : exprAny2;
@@ -30,6 +31,7 @@ condObject ? exprIsObject1 : exprIsObject2;
 ({}) ? exprNumber1 : exprNumber2;
 ({ a: 1, b: "s" }) ? exprString1 : exprString2;
 ({ a: 1, b: "s" }) ? exprIsObject1 : exprIsObject2;
+({ a: 1, b: "s" }) ? exprString1: exprBoolean1; // union
 
 //Cond is an object type expression
 foo() ? exprAny1 : exprAny2;
@@ -37,6 +39,7 @@ new Date() ? exprBoolean1 : exprBoolean2;
 new C() ? exprNumber1 : exprNumber2;
 C.doIt() ? exprString1 : exprString2;
 condObject.valueOf() ? exprIsObject1 : exprIsObject2;
+new Date() ? exprString1 : exprBoolean1; // union
 
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condObject ? exprAny1 : exprAny2;
@@ -44,18 +47,21 @@ var resultIsBoolean1 = condObject ? exprBoolean1 : exprBoolean2;
 var resultIsNumber1 = condObject ? exprNumber1 : exprNumber2;
 var resultIsString1 = condObject ? exprString1 : exprString2;
 var resultIsObject1 = condObject ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean1 = condObject ? exprString1 : exprBoolean1; // union
 
 var resultIsAny2 = ((a: string) => a.length) ? exprAny1 : exprAny2;
 var resultIsBoolean2 = ((a: string) => a.length) ? exprBoolean1 : exprBoolean2;
 var resultIsNumber2 = ({}) ? exprNumber1 : exprNumber2;
 var resultIsString2 = ({ a: 1, b: "s" }) ? exprString1 : exprString2;
 var resultIsObject2 = ({ a: 1, b: "s" }) ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean2 = ({ a: 1, b: "s" }) ? exprString1 : exprBoolean1; // union
 
 var resultIsAny3 = foo() ? exprAny1 : exprAny2;
 var resultIsBoolean3 = new Date() ? exprBoolean1 : exprBoolean2;
 var resultIsNumber3 = new C() ? exprNumber1 : exprNumber2;
 var resultIsString3 = C.doIt() ? exprString1 : exprString2;
 var resultIsObject3 = condObject.valueOf() ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean3 = C.doIt() ? exprString1 : exprBoolean1; // union
 
 
 //// [conditionalOperatorConditionIsObjectType.js]
@@ -86,31 +92,37 @@ condObject ? exprBoolean1 : exprBoolean2;
 condObject ? exprNumber1 : exprNumber2;
 condObject ? exprString1 : exprString2;
 condObject ? exprIsObject1 : exprIsObject2;
+condObject ? exprString1 : exprBoolean1; // union
 //Cond is an object type literal
 (function (a) { return a.length; }) ? exprAny1 : exprAny2;
 (function (a) { return a.length; }) ? exprBoolean1 : exprBoolean2;
 ({}) ? exprNumber1 : exprNumber2;
 ({ a: 1, b: "s" }) ? exprString1 : exprString2;
 ({ a: 1, b: "s" }) ? exprIsObject1 : exprIsObject2;
+({ a: 1, b: "s" }) ? exprString1 : exprBoolean1; // union
 //Cond is an object type expression
 foo() ? exprAny1 : exprAny2;
 new Date() ? exprBoolean1 : exprBoolean2;
 new C() ? exprNumber1 : exprNumber2;
 C.doIt() ? exprString1 : exprString2;
 condObject.valueOf() ? exprIsObject1 : exprIsObject2;
+new Date() ? exprString1 : exprBoolean1; // union
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condObject ? exprAny1 : exprAny2;
 var resultIsBoolean1 = condObject ? exprBoolean1 : exprBoolean2;
 var resultIsNumber1 = condObject ? exprNumber1 : exprNumber2;
 var resultIsString1 = condObject ? exprString1 : exprString2;
 var resultIsObject1 = condObject ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean1 = condObject ? exprString1 : exprBoolean1; // union
 var resultIsAny2 = (function (a) { return a.length; }) ? exprAny1 : exprAny2;
 var resultIsBoolean2 = (function (a) { return a.length; }) ? exprBoolean1 : exprBoolean2;
 var resultIsNumber2 = ({}) ? exprNumber1 : exprNumber2;
 var resultIsString2 = ({ a: 1, b: "s" }) ? exprString1 : exprString2;
 var resultIsObject2 = ({ a: 1, b: "s" }) ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean2 = ({ a: 1, b: "s" }) ? exprString1 : exprBoolean1; // union
 var resultIsAny3 = foo() ? exprAny1 : exprAny2;
 var resultIsBoolean3 = new Date() ? exprBoolean1 : exprBoolean2;
 var resultIsNumber3 = new C() ? exprNumber1 : exprNumber2;
 var resultIsString3 = C.doIt() ? exprString1 : exprString2;
 var resultIsObject3 = condObject.valueOf() ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean3 = C.doIt() ? exprString1 : exprBoolean1; // union
diff --git a/tests/baselines/reference/conditionalOperatorConditionIsObjectType.types b/tests/baselines/reference/conditionalOperatorConditionIsObjectType.types
index 199e93c6265..f99c591b593 100644
--- a/tests/baselines/reference/conditionalOperatorConditionIsObjectType.types
+++ b/tests/baselines/reference/conditionalOperatorConditionIsObjectType.types
@@ -74,6 +74,12 @@ condObject ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+condObject ? exprString1 : exprBoolean1; // union
+>condObject ? exprString1 : exprBoolean1 : string | boolean
+>condObject : Object
+>exprString1 : string
+>exprBoolean1 : boolean
+
 //Cond is an object type literal
 ((a: string) => a.length) ? exprAny1 : exprAny2;
 >((a: string) => a.length) ? exprAny1 : exprAny2 : any
@@ -122,6 +128,15 @@ condObject ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+({ a: 1, b: "s" }) ? exprString1: exprBoolean1; // union
+>({ a: 1, b: "s" }) ? exprString1: exprBoolean1 : string | boolean
+>({ a: 1, b: "s" }) : { a: number; b: string; }
+>{ a: 1, b: "s" } : { a: number; b: string; }
+>a : number
+>b : string
+>exprString1 : string
+>exprBoolean1 : boolean
+
 //Cond is an object type expression
 foo() ? exprAny1 : exprAny2;
 >foo() ? exprAny1 : exprAny2 : any
@@ -162,6 +177,13 @@ condObject.valueOf() ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+new Date() ? exprString1 : exprBoolean1; // union
+>new Date() ? exprString1 : exprBoolean1 : string | boolean
+>new Date() : Date
+>Date : DateConstructor
+>exprString1 : string
+>exprBoolean1 : boolean
+
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condObject ? exprAny1 : exprAny2;
 >resultIsAny1 : any
@@ -198,6 +220,13 @@ var resultIsObject1 = condObject ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+var resultIsStringOrBoolean1 = condObject ? exprString1 : exprBoolean1; // union
+>resultIsStringOrBoolean1 : string | boolean
+>condObject ? exprString1 : exprBoolean1 : string | boolean
+>condObject : Object
+>exprString1 : string
+>exprBoolean1 : boolean
+
 var resultIsAny2 = ((a: string) => a.length) ? exprAny1 : exprAny2;
 >resultIsAny2 : any
 >((a: string) => a.length) ? exprAny1 : exprAny2 : any
@@ -250,6 +279,16 @@ var resultIsObject2 = ({ a: 1, b: "s" }) ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+var resultIsStringOrBoolean2 = ({ a: 1, b: "s" }) ? exprString1 : exprBoolean1; // union
+>resultIsStringOrBoolean2 : string | boolean
+>({ a: 1, b: "s" }) ? exprString1 : exprBoolean1 : string | boolean
+>({ a: 1, b: "s" }) : { a: number; b: string; }
+>{ a: 1, b: "s" } : { a: number; b: string; }
+>a : number
+>b : string
+>exprString1 : string
+>exprBoolean1 : boolean
+
 var resultIsAny3 = foo() ? exprAny1 : exprAny2;
 >resultIsAny3 : any
 >foo() ? exprAny1 : exprAny2 : any
@@ -294,3 +333,13 @@ var resultIsObject3 = condObject.valueOf() ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+var resultIsStringOrBoolean3 = C.doIt() ? exprString1 : exprBoolean1; // union
+>resultIsStringOrBoolean3 : string | boolean
+>C.doIt() ? exprString1 : exprBoolean1 : string | boolean
+>C.doIt() : void
+>C.doIt : () => void
+>C : typeof C
+>doIt : () => void
+>exprString1 : string
+>exprBoolean1 : boolean
+
diff --git a/tests/baselines/reference/conditionalOperatorConditoinIsAnyType.js b/tests/baselines/reference/conditionalOperatorConditoinIsAnyType.js
index 5869023d17d..80cfaf97f26 100644
--- a/tests/baselines/reference/conditionalOperatorConditoinIsAnyType.js
+++ b/tests/baselines/reference/conditionalOperatorConditoinIsAnyType.js
@@ -21,6 +21,7 @@ condAny ? exprBoolean1 : exprBoolean2;
 condAny ? exprNumber1 : exprNumber2;
 condAny ? exprString1 : exprString2;
 condAny ? exprIsObject1 : exprIsObject2;
+condAny ? exprString1 : exprBoolean1; // union
 
 //Cond is an any type literal
 null ? exprAny1 : exprAny2;
@@ -28,6 +29,7 @@ null ? exprBoolean1 : exprBoolean2;
 undefined ? exprNumber1 : exprNumber2;
 [null, undefined] ? exprString1 : exprString2;
 [null, undefined] ? exprIsObject1 : exprIsObject2;
+undefined ? exprString1 : exprBoolean1; // union
 
 //Cond is an any type expression
 x.doSomeThing() ? exprAny1 : exprAny2;
@@ -35,6 +37,7 @@ x("x") ? exprBoolean1 : exprBoolean2;
 x(x) ? exprNumber1 : exprNumber2;
 x("x") ? exprString1 : exprString2;
 x.doSomeThing() ? exprIsObject1 : exprIsObject2;
+x.doSomeThing() ? exprString1 : exprBoolean1; // union
 
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condAny ? exprAny1 : exprAny2;
@@ -42,19 +45,23 @@ var resultIsBoolean1 = condAny ? exprBoolean1 : exprBoolean2;
 var resultIsNumber1 = condAny ? exprNumber1 : exprNumber2;
 var resultIsString1 = condAny ? exprString1 : exprString2;
 var resultIsObject1 = condAny ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean1 = condAny ? exprString1 : exprBoolean1; // union
 
 var resultIsAny2 = null ? exprAny1 : exprAny2;
 var resultIsBoolean2 = null ? exprBoolean1 : exprBoolean2;
 var resultIsNumber2 = undefined ? exprNumber1 : exprNumber2;
 var resultIsString2 = [null, undefined] ? exprString1 : exprString2;
 var resultIsObject2 = [null, undefined] ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean2 = null ? exprString1 : exprBoolean1; // union
+var resultIsStringOrBoolean3 = undefined ? exprString1 : exprBoolean1; // union
+var resultIsStringOrBoolean4 = [null, undefined] ? exprString1 : exprBoolean1; // union
 
 var resultIsAny3 = x.doSomeThing() ? exprAny1 : exprAny2;
 var resultIsBoolean3 = x("x") ? exprBoolean1 : exprBoolean2;
 var resultIsNumber3 = x(x) ? exprNumber1 : exprNumber2;
 var resultIsString3 = x("x") ? exprString1 : exprString2;
 var resultIsObject3 = x.doSomeThing() ? exprIsObject1 : exprIsObject2;
-
+var resultIsStringOrBoolean5 = x.doSomeThing() ? exprString1 : exprBoolean1; // union
 
 //// [conditionalOperatorConditoinIsAnyType.js]
 //Cond ? Expr1 : Expr2,  Cond is of any type, Expr1 and Expr2 have the same type
@@ -76,31 +83,39 @@ condAny ? exprBoolean1 : exprBoolean2;
 condAny ? exprNumber1 : exprNumber2;
 condAny ? exprString1 : exprString2;
 condAny ? exprIsObject1 : exprIsObject2;
+condAny ? exprString1 : exprBoolean1; // union
 //Cond is an any type literal
 null ? exprAny1 : exprAny2;
 null ? exprBoolean1 : exprBoolean2;
 undefined ? exprNumber1 : exprNumber2;
 [null, undefined] ? exprString1 : exprString2;
 [null, undefined] ? exprIsObject1 : exprIsObject2;
+undefined ? exprString1 : exprBoolean1; // union
 //Cond is an any type expression
 x.doSomeThing() ? exprAny1 : exprAny2;
 x("x") ? exprBoolean1 : exprBoolean2;
 x(x) ? exprNumber1 : exprNumber2;
 x("x") ? exprString1 : exprString2;
 x.doSomeThing() ? exprIsObject1 : exprIsObject2;
+x.doSomeThing() ? exprString1 : exprBoolean1; // union
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condAny ? exprAny1 : exprAny2;
 var resultIsBoolean1 = condAny ? exprBoolean1 : exprBoolean2;
 var resultIsNumber1 = condAny ? exprNumber1 : exprNumber2;
 var resultIsString1 = condAny ? exprString1 : exprString2;
 var resultIsObject1 = condAny ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean1 = condAny ? exprString1 : exprBoolean1; // union
 var resultIsAny2 = null ? exprAny1 : exprAny2;
 var resultIsBoolean2 = null ? exprBoolean1 : exprBoolean2;
 var resultIsNumber2 = undefined ? exprNumber1 : exprNumber2;
 var resultIsString2 = [null, undefined] ? exprString1 : exprString2;
 var resultIsObject2 = [null, undefined] ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean2 = null ? exprString1 : exprBoolean1; // union
+var resultIsStringOrBoolean3 = undefined ? exprString1 : exprBoolean1; // union
+var resultIsStringOrBoolean4 = [null, undefined] ? exprString1 : exprBoolean1; // union
 var resultIsAny3 = x.doSomeThing() ? exprAny1 : exprAny2;
 var resultIsBoolean3 = x("x") ? exprBoolean1 : exprBoolean2;
 var resultIsNumber3 = x(x) ? exprNumber1 : exprNumber2;
 var resultIsString3 = x("x") ? exprString1 : exprString2;
 var resultIsObject3 = x.doSomeThing() ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean5 = x.doSomeThing() ? exprString1 : exprBoolean1; // union
diff --git a/tests/baselines/reference/conditionalOperatorConditoinIsAnyType.types b/tests/baselines/reference/conditionalOperatorConditoinIsAnyType.types
index 9f5fc9326bb..6542377795f 100644
--- a/tests/baselines/reference/conditionalOperatorConditoinIsAnyType.types
+++ b/tests/baselines/reference/conditionalOperatorConditoinIsAnyType.types
@@ -69,6 +69,12 @@ condAny ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+condAny ? exprString1 : exprBoolean1; // union
+>condAny ? exprString1 : exprBoolean1 : string | boolean
+>condAny : any
+>exprString1 : string
+>exprBoolean1 : boolean
+
 //Cond is an any type literal
 null ? exprAny1 : exprAny2;
 >null ? exprAny1 : exprAny2 : any
@@ -100,6 +106,12 @@ undefined ? exprNumber1 : exprNumber2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+undefined ? exprString1 : exprBoolean1; // union
+>undefined ? exprString1 : exprBoolean1 : string | boolean
+>undefined : undefined
+>exprString1 : string
+>exprBoolean1 : boolean
+
 //Cond is an any type expression
 x.doSomeThing() ? exprAny1 : exprAny2;
 >x.doSomeThing() ? exprAny1 : exprAny2 : any
@@ -141,6 +153,15 @@ x.doSomeThing() ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+x.doSomeThing() ? exprString1 : exprBoolean1; // union
+>x.doSomeThing() ? exprString1 : exprBoolean1 : string | boolean
+>x.doSomeThing() : any
+>x.doSomeThing : any
+>x : any
+>doSomeThing : any
+>exprString1 : string
+>exprBoolean1 : boolean
+
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condAny ? exprAny1 : exprAny2;
 >resultIsAny1 : any
@@ -177,6 +198,13 @@ var resultIsObject1 = condAny ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+var resultIsStringOrBoolean1 = condAny ? exprString1 : exprBoolean1; // union
+>resultIsStringOrBoolean1 : string | boolean
+>condAny ? exprString1 : exprBoolean1 : string | boolean
+>condAny : any
+>exprString1 : string
+>exprBoolean1 : boolean
+
 var resultIsAny2 = null ? exprAny1 : exprAny2;
 >resultIsAny2 : any
 >null ? exprAny1 : exprAny2 : any
@@ -212,6 +240,27 @@ var resultIsObject2 = [null, undefined] ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+var resultIsStringOrBoolean2 = null ? exprString1 : exprBoolean1; // union
+>resultIsStringOrBoolean2 : string | boolean
+>null ? exprString1 : exprBoolean1 : string | boolean
+>exprString1 : string
+>exprBoolean1 : boolean
+
+var resultIsStringOrBoolean3 = undefined ? exprString1 : exprBoolean1; // union
+>resultIsStringOrBoolean3 : string | boolean
+>undefined ? exprString1 : exprBoolean1 : string | boolean
+>undefined : undefined
+>exprString1 : string
+>exprBoolean1 : boolean
+
+var resultIsStringOrBoolean4 = [null, undefined] ? exprString1 : exprBoolean1; // union
+>resultIsStringOrBoolean4 : string | boolean
+>[null, undefined] ? exprString1 : exprBoolean1 : string | boolean
+>[null, undefined] : null[]
+>undefined : undefined
+>exprString1 : string
+>exprBoolean1 : boolean
+
 var resultIsAny3 = x.doSomeThing() ? exprAny1 : exprAny2;
 >resultIsAny3 : any
 >x.doSomeThing() ? exprAny1 : exprAny2 : any
@@ -257,3 +306,13 @@ var resultIsObject3 = x.doSomeThing() ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+var resultIsStringOrBoolean5 = x.doSomeThing() ? exprString1 : exprBoolean1; // union
+>resultIsStringOrBoolean5 : string | boolean
+>x.doSomeThing() ? exprString1 : exprBoolean1 : string | boolean
+>x.doSomeThing() : any
+>x.doSomeThing : any
+>x : any
+>doSomeThing : any
+>exprString1 : string
+>exprBoolean1 : boolean
+
diff --git a/tests/baselines/reference/conditionalOperatorConditoinIsStringType.js b/tests/baselines/reference/conditionalOperatorConditoinIsStringType.js
index 4bd67a40640..02c398e89e1 100644
--- a/tests/baselines/reference/conditionalOperatorConditoinIsStringType.js
+++ b/tests/baselines/reference/conditionalOperatorConditoinIsStringType.js
@@ -20,6 +20,7 @@ condString ? exprBoolean1 : exprBoolean2;
 condString ? exprNumber1 : exprNumber2;
 condString ? exprString1 : exprString2;
 condString ? exprIsObject1 : exprIsObject2;
+condString ? exprString1 : exprBoolean1; // union
 
 //Cond is a string type literal
 "" ? exprAny1 : exprAny2;
@@ -27,6 +28,7 @@ condString ? exprIsObject1 : exprIsObject2;
 'c' ? exprNumber1 : exprNumber2;
 'string' ? exprString1 : exprString2;
 "  " ? exprIsObject1 : exprIsObject2;
+"hello " ? exprString1 : exprBoolean1; // union
 
 //Cond is a string type expression
 function foo() { return "string" };
@@ -37,6 +39,7 @@ condString.toUpperCase ? exprBoolean1 : exprBoolean2;
 condString + "string" ? exprNumber1 : exprNumber2;
 foo() ? exprString1 : exprString2;
 array[1] ? exprIsObject1 : exprIsObject2;
+foo() ? exprString1 : exprBoolean1; // union
 
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condString ? exprAny1 : exprAny2;
@@ -44,19 +47,22 @@ var resultIsBoolean1 = condString ? exprBoolean1 : exprBoolean2;
 var resultIsNumber1 = condString ? exprNumber1 : exprNumber2;
 var resultIsString1 = condString ? exprString1 : exprString2;
 var resultIsObject1 = condString ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean1 = condString ? exprString1 : exprBoolean1; // union
 
 var resultIsAny2 = "" ? exprAny1 : exprAny2;
 var resultIsBoolean2 = "string" ? exprBoolean1 : exprBoolean2;
 var resultIsNumber2 = 'c' ? exprNumber1 : exprNumber2;
 var resultIsString2 = 'string' ? exprString1 : exprString2;
 var resultIsObject2 = "  " ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean2 = "hello" ? exprString1 : exprBoolean1; // union
 
 var resultIsAny3 = typeof condString ? exprAny1 : exprAny2;
 var resultIsBoolean3 = condString.toUpperCase ? exprBoolean1 : exprBoolean2;
 var resultIsNumber3 = condString + "string" ? exprNumber1 : exprNumber2;
 var resultIsString3 = foo() ? exprString1 : exprString2;
 var resultIsObject3 = array[1] ? exprIsObject1 : exprIsObject2;
-
+var resultIsStringOrBoolean3 = typeof condString ? exprString1 : exprBoolean1; // union
+var resultIsStringOrBoolean4 = condString.toUpperCase ? exprString1 : exprBoolean1; // union
 
 //// [conditionalOperatorConditoinIsStringType.js]
 //Cond ? Expr1 : Expr2,  Cond is of string type, Expr1 and Expr2 have the same type
@@ -77,12 +83,14 @@ condString ? exprBoolean1 : exprBoolean2;
 condString ? exprNumber1 : exprNumber2;
 condString ? exprString1 : exprString2;
 condString ? exprIsObject1 : exprIsObject2;
+condString ? exprString1 : exprBoolean1; // union
 //Cond is a string type literal
 "" ? exprAny1 : exprAny2;
 "string" ? exprBoolean1 : exprBoolean2;
 'c' ? exprNumber1 : exprNumber2;
 'string' ? exprString1 : exprString2;
 "  " ? exprIsObject1 : exprIsObject2;
+"hello " ? exprString1 : exprBoolean1; // union
 //Cond is a string type expression
 function foo() {
     return "string";
@@ -94,19 +102,24 @@ condString.toUpperCase ? exprBoolean1 : exprBoolean2;
 condString + "string" ? exprNumber1 : exprNumber2;
 foo() ? exprString1 : exprString2;
 array[1] ? exprIsObject1 : exprIsObject2;
+foo() ? exprString1 : exprBoolean1; // union
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condString ? exprAny1 : exprAny2;
 var resultIsBoolean1 = condString ? exprBoolean1 : exprBoolean2;
 var resultIsNumber1 = condString ? exprNumber1 : exprNumber2;
 var resultIsString1 = condString ? exprString1 : exprString2;
 var resultIsObject1 = condString ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean1 = condString ? exprString1 : exprBoolean1; // union
 var resultIsAny2 = "" ? exprAny1 : exprAny2;
 var resultIsBoolean2 = "string" ? exprBoolean1 : exprBoolean2;
 var resultIsNumber2 = 'c' ? exprNumber1 : exprNumber2;
 var resultIsString2 = 'string' ? exprString1 : exprString2;
 var resultIsObject2 = "  " ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean2 = "hello" ? exprString1 : exprBoolean1; // union
 var resultIsAny3 = typeof condString ? exprAny1 : exprAny2;
 var resultIsBoolean3 = condString.toUpperCase ? exprBoolean1 : exprBoolean2;
 var resultIsNumber3 = condString + "string" ? exprNumber1 : exprNumber2;
 var resultIsString3 = foo() ? exprString1 : exprString2;
 var resultIsObject3 = array[1] ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean3 = typeof condString ? exprString1 : exprBoolean1; // union
+var resultIsStringOrBoolean4 = condString.toUpperCase ? exprString1 : exprBoolean1; // union
diff --git a/tests/baselines/reference/conditionalOperatorConditoinIsStringType.types b/tests/baselines/reference/conditionalOperatorConditoinIsStringType.types
index 668e0fc437c..45a4db8d295 100644
--- a/tests/baselines/reference/conditionalOperatorConditoinIsStringType.types
+++ b/tests/baselines/reference/conditionalOperatorConditoinIsStringType.types
@@ -66,6 +66,12 @@ condString ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+condString ? exprString1 : exprBoolean1; // union
+>condString ? exprString1 : exprBoolean1 : string | boolean
+>condString : string
+>exprString1 : string
+>exprBoolean1 : boolean
+
 //Cond is a string type literal
 "" ? exprAny1 : exprAny2;
 >"" ? exprAny1 : exprAny2 : any
@@ -92,6 +98,11 @@ condString ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+"hello " ? exprString1 : exprBoolean1; // union
+>"hello " ? exprString1 : exprBoolean1 : string | boolean
+>exprString1 : string
+>exprBoolean1 : boolean
+
 //Cond is a string type expression
 function foo() { return "string" };
 >foo : () => string
@@ -136,6 +147,13 @@ array[1] ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+foo() ? exprString1 : exprBoolean1; // union
+>foo() ? exprString1 : exprBoolean1 : string | boolean
+>foo() : string
+>foo : () => string
+>exprString1 : string
+>exprBoolean1 : boolean
+
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condString ? exprAny1 : exprAny2;
 >resultIsAny1 : any
@@ -172,6 +190,13 @@ var resultIsObject1 = condString ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+var resultIsStringOrBoolean1 = condString ? exprString1 : exprBoolean1; // union
+>resultIsStringOrBoolean1 : string | boolean
+>condString ? exprString1 : exprBoolean1 : string | boolean
+>condString : string
+>exprString1 : string
+>exprBoolean1 : boolean
+
 var resultIsAny2 = "" ? exprAny1 : exprAny2;
 >resultIsAny2 : any
 >"" ? exprAny1 : exprAny2 : any
@@ -202,6 +227,12 @@ var resultIsObject2 = "  " ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+var resultIsStringOrBoolean2 = "hello" ? exprString1 : exprBoolean1; // union
+>resultIsStringOrBoolean2 : string | boolean
+>"hello" ? exprString1 : exprBoolean1 : string | boolean
+>exprString1 : string
+>exprBoolean1 : boolean
+
 var resultIsAny3 = typeof condString ? exprAny1 : exprAny2;
 >resultIsAny3 : any
 >typeof condString ? exprAny1 : exprAny2 : any
@@ -243,3 +274,20 @@ var resultIsObject3 = array[1] ? exprIsObject1 : exprIsObject2;
 >exprIsObject1 : Object
 >exprIsObject2 : Object
 
+var resultIsStringOrBoolean3 = typeof condString ? exprString1 : exprBoolean1; // union
+>resultIsStringOrBoolean3 : string | boolean
+>typeof condString ? exprString1 : exprBoolean1 : string | boolean
+>typeof condString : string
+>condString : string
+>exprString1 : string
+>exprBoolean1 : boolean
+
+var resultIsStringOrBoolean4 = condString.toUpperCase ? exprString1 : exprBoolean1; // union
+>resultIsStringOrBoolean4 : string | boolean
+>condString.toUpperCase ? exprString1 : exprBoolean1 : string | boolean
+>condString.toUpperCase : () => string
+>condString : string
+>toUpperCase : () => string
+>exprString1 : string
+>exprBoolean1 : boolean
+
diff --git a/tests/baselines/reference/conditionalOperatorWithoutIdenticalBCT.errors.txt b/tests/baselines/reference/conditionalOperatorWithoutIdenticalBCT.errors.txt
index 954e8af856f..2fa13333058 100644
--- a/tests/baselines/reference/conditionalOperatorWithoutIdenticalBCT.errors.txt
+++ b/tests/baselines/reference/conditionalOperatorWithoutIdenticalBCT.errors.txt
@@ -4,13 +4,13 @@ tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorWithou
 tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorWithoutIdenticalBCT.ts(16,5): error TS2322: Type 'A | B' is not assignable to type 'B'.
   Type 'A' is not assignable to type 'B'.
     Property 'propertyB' is missing in type 'A'.
-tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorWithoutIdenticalBCT.ts(18,5): error TS2322: Type '((m: X) => number) | ((n: X) => string)' is not assignable to type '(t: X) => number'.
+tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorWithoutIdenticalBCT.ts(19,5): error TS2322: Type '((m: X) => number) | ((n: X) => string)' is not assignable to type '(t: X) => number'.
   Type '(n: X) => string' is not assignable to type '(t: X) => number'.
     Type 'string' is not assignable to type 'number'.
-tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorWithoutIdenticalBCT.ts(19,5): error TS2322: Type '((m: X) => number) | ((n: X) => string)' is not assignable to type '(t: X) => string'.
+tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorWithoutIdenticalBCT.ts(20,5): error TS2322: Type '((m: X) => number) | ((n: X) => string)' is not assignable to type '(t: X) => string'.
   Type '(m: X) => number' is not assignable to type '(t: X) => string'.
     Type 'number' is not assignable to type 'string'.
-tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorWithoutIdenticalBCT.ts(20,5): error TS2322: Type '((m: X) => number) | ((n: X) => string)' is not assignable to type '(t: X) => boolean'.
+tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorWithoutIdenticalBCT.ts(21,5): error TS2322: Type '((m: X) => number) | ((n: X) => string)' is not assignable to type '(t: X) => boolean'.
   Type '(m: X) => number' is not assignable to type '(t: X) => boolean'.
     Type 'number' is not assignable to type 'boolean'.
 
@@ -40,6 +40,7 @@ tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorWithou
 !!! error TS2322: Type 'A | B' is not assignable to type 'B'.
 !!! error TS2322:   Type 'A' is not assignable to type 'B'.
 !!! error TS2322:     Property 'propertyB' is missing in type 'A'.
+    var result31: A | B = true ? a : b;
     
     var result4: (t: X) => number = true ? (m) => m.propertyX1 : (n) => n.propertyX2;
         ~~~~~~~
@@ -55,4 +56,6 @@ tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorWithou
         ~~~~~~~
 !!! error TS2322: Type '((m: X) => number) | ((n: X) => string)' is not assignable to type '(t: X) => boolean'.
 !!! error TS2322:   Type '(m: X) => number' is not assignable to type '(t: X) => boolean'.
-!!! error TS2322:     Type 'number' is not assignable to type 'boolean'.
\ No newline at end of file
+!!! error TS2322:     Type 'number' is not assignable to type 'boolean'.
+    var result61: (t: X) => number| string = true ? (m) => m.propertyX1 : (n) => n.propertyX2;
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/conditionalOperatorWithoutIdenticalBCT.js b/tests/baselines/reference/conditionalOperatorWithoutIdenticalBCT.js
index b6376dd781f..83262ed1301 100644
--- a/tests/baselines/reference/conditionalOperatorWithoutIdenticalBCT.js
+++ b/tests/baselines/reference/conditionalOperatorWithoutIdenticalBCT.js
@@ -15,10 +15,13 @@ var result1 = true ? a : b;
 //Be contextually typed and and bct is not identical, results in errors that union type is not assignable to target
 var result2: A = true ? a : b;
 var result3: B = true ? a : b;
+var result31: A | B = true ? a : b;
 
 var result4: (t: X) => number = true ? (m) => m.propertyX1 : (n) => n.propertyX2;
 var result5: (t: X) => string = true ? (m) => m.propertyX1 : (n) => n.propertyX2;
-var result6: (t: X) => boolean = true ? (m) => m.propertyX1 : (n) => n.propertyX2;
+var result6: (t: X) => boolean = true ? (m) => m.propertyX1 : (n) => n.propertyX2;
+var result61: (t: X) => number| string = true ? (m) => m.propertyX1 : (n) => n.propertyX2;
+
 
 //// [conditionalOperatorWithoutIdenticalBCT.js]
 var __extends = this.__extends || function (d, b) {
@@ -59,6 +62,8 @@ var result1 = true ? a : b;
 //Be contextually typed and and bct is not identical, results in errors that union type is not assignable to target
 var result2 = true ? a : b;
 var result3 = true ? a : b;
+var result31 = true ? a : b;
 var result4 = true ? function (m) { return m.propertyX1; } : function (n) { return n.propertyX2; };
 var result5 = true ? function (m) { return m.propertyX1; } : function (n) { return n.propertyX2; };
 var result6 = true ? function (m) { return m.propertyX1; } : function (n) { return n.propertyX2; };
+var result61 = true ? function (m) { return m.propertyX1; } : function (n) { return n.propertyX2; };
diff --git a/tests/baselines/reference/conformanceFunctionOverloads.js b/tests/baselines/reference/conformanceFunctionOverloads.js
index 15dec719e40..b245f6a2c91 100644
--- a/tests/baselines/reference/conformanceFunctionOverloads.js
+++ b/tests/baselines/reference/conformanceFunctionOverloads.js
@@ -25,3 +25,13 @@
 
 //// [conformanceFunctionOverloads.js]
 // Function overloads do not emit code
+// Function overload signature with optional parameter
+// Function overload signature with optional parameter
+// Function overloads with generic and non-generic overloads
+// Function overloads whose only difference is returning different unconstrained generic parameters
+// Function overloads whose only difference is returning different constrained generic parameters
+// Function overloads that differ only by type parameter constraints
+// Function overloads with matching accessibility
+// Function overloads with matching export
+// Function overloads with more params than implementation signature
+// Function overloads where return types are same infinitely recursive type reference
diff --git a/tests/baselines/reference/contextualTypeWithTuple.errors.txt b/tests/baselines/reference/contextualTypeWithTuple.errors.txt
index 875d7b5e20a..ff9ace5a2c0 100644
--- a/tests/baselines/reference/contextualTypeWithTuple.errors.txt
+++ b/tests/baselines/reference/contextualTypeWithTuple.errors.txt
@@ -4,21 +4,27 @@ tests/cases/conformance/types/tuple/contextualTypeWithTuple.ts(3,5): error TS232
       Type 'string | number | boolean' is not assignable to type 'string | number'.
         Type 'boolean' is not assignable to type 'string | number'.
           Type 'boolean' is not assignable to type 'number'.
-tests/cases/conformance/types/tuple/contextualTypeWithTuple.ts(8,1): error TS2322: Type '[number, string, boolean]' is not assignable to type '[number, string]'.
-tests/cases/conformance/types/tuple/contextualTypeWithTuple.ts(11,1): error TS2322: Type '[{}, number]' is not assignable to type '[{ a: string; }, number]'.
+tests/cases/conformance/types/tuple/contextualTypeWithTuple.ts(15,1): error TS2322: Type '[number, string, boolean]' is not assignable to type '[number, string]'.
+tests/cases/conformance/types/tuple/contextualTypeWithTuple.ts(18,1): error TS2322: Type '[{}, number]' is not assignable to type '[{ a: string; }, number]'.
   Types of property '0' are incompatible.
     Type '{}' is not assignable to type '{ a: string; }'.
       Property 'a' is missing in type '{}'.
-tests/cases/conformance/types/tuple/contextualTypeWithTuple.ts(12,1): error TS2322: Type '[number, string]' is not assignable to type '[number, string, boolean]'.
+tests/cases/conformance/types/tuple/contextualTypeWithTuple.ts(19,1): error TS2322: Type '[number, string]' is not assignable to type '[number, string, boolean]'.
   Property '2' is missing in type '[number, string]'.
-tests/cases/conformance/types/tuple/contextualTypeWithTuple.ts(13,5): error TS2322: Type '[string, string, number]' is not assignable to type '[string, string]'.
+tests/cases/conformance/types/tuple/contextualTypeWithTuple.ts(20,5): error TS2322: Type '[string, string, number]' is not assignable to type '[string, string]'.
   Types of property 'pop' are incompatible.
     Type '() => string | number' is not assignable to type '() => string'.
       Type 'string | number' is not assignable to type 'string'.
         Type 'number' is not assignable to type 'string'.
+tests/cases/conformance/types/tuple/contextualTypeWithTuple.ts(24,1): error TS2322: Type '[C, string | number]' is not assignable to type '[C, string | number, D]'.
+  Property '2' is missing in type '[C, string | number]'.
+tests/cases/conformance/types/tuple/contextualTypeWithTuple.ts(25,1): error TS2322: Type '[number, string | number]' is not assignable to type '[number, string]'.
+  Types of property '1' are incompatible.
+    Type 'string | number' is not assignable to type 'string'.
+      Type 'number' is not assignable to type 'string'.
 
 
-==== tests/cases/conformance/types/tuple/contextualTypeWithTuple.ts (5 errors) ====
+==== tests/cases/conformance/types/tuple/contextualTypeWithTuple.ts (7 errors) ====
     // no error
     var numStrTuple: [number, string] = [5, "hello"];
     var numStrTuple2: [number, string] = [5, "foo", true];
@@ -32,6 +38,13 @@ tests/cases/conformance/types/tuple/contextualTypeWithTuple.ts(13,5): error TS23
     var numStrBoolTuple: [number, string, boolean] = [5, "foo", true];
     var objNumTuple: [{ a: string }, number] = [{ a: "world" }, 5];
     var strTupleTuple: [string, [number, {}]] = ["bar", [5, { x: 1, y: 1 }]];
+    class C { }
+    class D { }
+    var unionTuple: [C, string | number] = [new C(), "foo"];
+    var unionTuple1: [C, string | number] = [new C(), "foo"];
+    var unionTuple2: [C, string | number, D] = [new C(), "foo", new D()];
+    var unionTuple3: [number, string| number] = [10, "foo"]; 
+    
     numStrTuple = numStrTuple2;
     numStrTuple = numStrBoolTuple;
     ~~~~~~~~~~~
@@ -55,4 +68,16 @@ tests/cases/conformance/types/tuple/contextualTypeWithTuple.ts(13,5): error TS23
 !!! error TS2322:     Type '() => string | number' is not assignable to type '() => string'.
 !!! error TS2322:       Type 'string | number' is not assignable to type 'string'.
 !!! error TS2322:         Type 'number' is not assignable to type 'string'.
-    
\ No newline at end of file
+    
+    unionTuple = unionTuple1;
+    unionTuple = unionTuple2;
+    unionTuple2 = unionTuple;
+    ~~~~~~~~~~~
+!!! error TS2322: Type '[C, string | number]' is not assignable to type '[C, string | number, D]'.
+!!! error TS2322:   Property '2' is missing in type '[C, string | number]'.
+    numStrTuple = unionTuple3;
+    ~~~~~~~~~~~
+!!! error TS2322: Type '[number, string | number]' is not assignable to type '[number, string]'.
+!!! error TS2322:   Types of property '1' are incompatible.
+!!! error TS2322:     Type 'string | number' is not assignable to type 'string'.
+!!! error TS2322:       Type 'number' is not assignable to type 'string'.
\ No newline at end of file
diff --git a/tests/baselines/reference/contextualTypeWithTuple.js b/tests/baselines/reference/contextualTypeWithTuple.js
index 61a2df5d8ce..cfcdd13f7d0 100644
--- a/tests/baselines/reference/contextualTypeWithTuple.js
+++ b/tests/baselines/reference/contextualTypeWithTuple.js
@@ -5,6 +5,13 @@ var numStrTuple2: [number, string] = [5, "foo", true];
 var numStrBoolTuple: [number, string, boolean] = [5, "foo", true];
 var objNumTuple: [{ a: string }, number] = [{ a: "world" }, 5];
 var strTupleTuple: [string, [number, {}]] = ["bar", [5, { x: 1, y: 1 }]];
+class C { }
+class D { }
+var unionTuple: [C, string | number] = [new C(), "foo"];
+var unionTuple1: [C, string | number] = [new C(), "foo"];
+var unionTuple2: [C, string | number, D] = [new C(), "foo", new D()];
+var unionTuple3: [number, string| number] = [10, "foo"]; 
+
 numStrTuple = numStrTuple2;
 numStrTuple = numStrBoolTuple;
 
@@ -12,7 +19,11 @@ numStrTuple = numStrBoolTuple;
 objNumTuple = [ {}, 5];
 numStrBoolTuple = numStrTuple;
 var strStrTuple: [string, string] = ["foo", "bar", 5];
-
+
+unionTuple = unionTuple1;
+unionTuple = unionTuple2;
+unionTuple2 = unionTuple;
+numStrTuple = unionTuple3;
 
 //// [contextualTypeWithTuple.js]
 // no error
@@ -21,9 +32,27 @@ var numStrTuple2 = [5, "foo", true];
 var numStrBoolTuple = [5, "foo", true];
 var objNumTuple = [{ a: "world" }, 5];
 var strTupleTuple = ["bar", [5, { x: 1, y: 1 }]];
+var C = (function () {
+    function C() {
+    }
+    return C;
+})();
+var D = (function () {
+    function D() {
+    }
+    return D;
+})();
+var unionTuple = [new C(), "foo"];
+var unionTuple1 = [new C(), "foo"];
+var unionTuple2 = [new C(), "foo", new D()];
+var unionTuple3 = [10, "foo"];
 numStrTuple = numStrTuple2;
 numStrTuple = numStrBoolTuple;
 // error
 objNumTuple = [{}, 5];
 numStrBoolTuple = numStrTuple;
 var strStrTuple = ["foo", "bar", 5];
+unionTuple = unionTuple1;
+unionTuple = unionTuple2;
+unionTuple2 = unionTuple;
+numStrTuple = unionTuple3;
diff --git a/tests/baselines/reference/contextualTypeWithUnionTypeCallSignatures.js b/tests/baselines/reference/contextualTypeWithUnionTypeCallSignatures.js
index 2e21235ea0a..e29d4720cbc 100644
--- a/tests/baselines/reference/contextualTypeWithUnionTypeCallSignatures.js
+++ b/tests/baselines/reference/contextualTypeWithUnionTypeCallSignatures.js
@@ -45,42 +45,6 @@ var x = function (a) { return a.toString(); };
 var x2 = function (a) { return a.toString(); }; // Like iWithCallSignatures
 var x2 = function (a) { return a; }; // Like iWithCallSignatures2
 // With call signatures of mismatching parameter type
-var x3 = function (a /*here a should be any*/) { return a.toString(); };
+var x3 = function (a) { return a.toString(); };
 // With call signature count mismatch
-var x4 = function (a //When used as a contextual type, a union type U has those members that are present in any of 
-// its constituent types, with types that are unions of the respective members in the constituent types. 
-
-// Let S be the set of types in U that have call signatures.
-// If S is not empty and the sets of call signatures of the types in S are identical ignoring return types,
-// U has the same set of call signatures, but with return types that are unions of the return types of the respective call signatures from each type in S.
-
-interface IWithNoCallSignatures {
-    foo: string;
-}
-interface IWithCallSignatures {
-    (a: number): string;
-}
-interface IWithCallSignatures2 {
-    (a: number): number;
-}
-interface IWithCallSignatures3 {
-    (b: string): number;
-}
-interface IWithCallSignatures4 {
-    (a: number): string;
-    (a: string, b: number): number;
-}
-
-// With no call signature | callSignatures
-var x: IWithNoCallSignatures | IWithCallSignatures = a => a.toString();
-
-// With call signatures with different return type
-var x2: IWithCallSignatures | IWithCallSignatures2 = a => a.toString(); // Like iWithCallSignatures
-var x2: IWithCallSignatures | IWithCallSignatures2 = a => a; // Like iWithCallSignatures2
-
-// With call signatures of mismatching parameter type
-var x3: IWithCallSignatures | IWithCallSignatures3 = a => /*here a should be any*/ a.toString();
-
-// With call signature count mismatch
-var x4: IWithCallSignatures | IWithCallSignatures4 = a =>
-    ) { return a.toString(); };
+var x4 = function (a) { return a.toString(); };
diff --git a/tests/baselines/reference/emitCommentsOnlyFile.js b/tests/baselines/reference/emitCommentsOnlyFile.js
index 263e9dd2588..d720dc3c191 100644
--- a/tests/baselines/reference/emitCommentsOnlyFile.js
+++ b/tests/baselines/reference/emitCommentsOnlyFile.js
@@ -29,3 +29,29 @@
 
 
 //// [emitCommentsOnlyFile.js]
+/**
+* @name Foo
+* @class
+*/
+/**#@+
+* @memberOf Foo#
+* @field
+*/
+/**
+* @name bar
+* @type Object[]
+*/
+/**#@-*/
+/**
+* @name Foo2
+* @class
+*/
+/**#@+
+* @memberOf Foo2#
+* @field
+*/
+/**
+* @name bar
+* @type Object[]
+*/
+/**#@-*/
diff --git a/tests/baselines/reference/emitPostComments.js b/tests/baselines/reference/emitPostComments.js
index 98d1d59457b..8a5736af00d 100644
--- a/tests/baselines/reference/emitPostComments.js
+++ b/tests/baselines/reference/emitPostComments.js
@@ -31,3 +31,29 @@ var y = 10;
 
 //// [emitPostComments.js]
 var y = 10;
+/**
+* @name Foo
+* @class
+*/
+/**#@+
+* @memberOf Foo#
+* @field
+*/
+/**
+* @name bar
+* @type Object[]
+*/
+/**#@-*/
+/**
+* @name Foo2
+* @class
+*/
+/**#@+
+* @memberOf Foo2#
+* @field
+*/
+/**
+* @name bar
+* @type Object[]
+*/
+/**#@-*/
diff --git a/tests/baselines/reference/emitPreComments.js b/tests/baselines/reference/emitPreComments.js
index 5a79a430175..4ca3297fce7 100644
--- a/tests/baselines/reference/emitPreComments.js
+++ b/tests/baselines/reference/emitPreComments.js
@@ -33,3 +33,29 @@ var y = 10;
 //// [emitPreComments.js]
 // This is pre comment
 var y = 10;
+/**
+* @name Foo
+* @class
+*/
+/**#@+
+* @memberOf Foo#
+* @field
+*/
+/**
+* @name bar
+* @type Object[]
+*/
+/**#@-*/
+/**
+* @name Foo2
+* @class
+*/
+/**#@+
+* @memberOf Foo2#
+* @field
+*/
+/**
+* @name bar
+* @type Object[]
+*/
+/**#@-*/
diff --git a/tests/baselines/reference/errorSupression1.js b/tests/baselines/reference/errorSupression1.js
index 92330a6c074..059530be452 100644
--- a/tests/baselines/reference/errorSupression1.js
+++ b/tests/baselines/reference/errorSupression1.js
@@ -20,3 +20,4 @@ var Foo = (function () {
 var baz = Foo.b;
 // Foo.b won't bind. 
 baz.concat("y");
+// So we don't want an error on 'concat'. 
diff --git a/tests/baselines/reference/everyTypeAssignableToAny.js b/tests/baselines/reference/everyTypeAssignableToAny.js
index 5ff22ce1962..8730167c3ff 100644
--- a/tests/baselines/reference/everyTypeAssignableToAny.js
+++ b/tests/baselines/reference/everyTypeAssignableToAny.js
@@ -113,3 +113,8 @@ function foo(x, y, z) {
     a = y;
     a = z;
 }
+//function foo<T, U extends T, V extends Date>(x: T, y: U, z: V) {
+//    a = x;
+//    a = y;
+//    a = z;
+//} 
diff --git a/tests/baselines/reference/externalModuleReferenceDoubleUnderscore1.js b/tests/baselines/reference/externalModuleReferenceDoubleUnderscore1.js
new file mode 100644
index 00000000000..f6f9572ba6b
--- /dev/null
+++ b/tests/baselines/reference/externalModuleReferenceDoubleUnderscore1.js
@@ -0,0 +1,19 @@
+//// [externalModuleReferenceDoubleUnderscore1.ts]
+declare module 'timezonecomplete' {
+    import basics = require("__timezonecomplete/basics");
+    export import TimeUnit = basics.TimeUnit;
+}
+
+declare module '__timezonecomplete/basics' {
+    export enum TimeUnit {
+        Second = 0,
+        Minute = 1,
+        Hour = 2,
+        Day = 3,
+        Week = 4,
+        Month = 5,
+        Year = 6,
+    }
+}
+
+//// [externalModuleReferenceDoubleUnderscore1.js]
diff --git a/tests/baselines/reference/externalModuleReferenceDoubleUnderscore1.types b/tests/baselines/reference/externalModuleReferenceDoubleUnderscore1.types
new file mode 100644
index 00000000000..e255e64d467
--- /dev/null
+++ b/tests/baselines/reference/externalModuleReferenceDoubleUnderscore1.types
@@ -0,0 +1,37 @@
+=== tests/cases/compiler/externalModuleReferenceDoubleUnderscore1.ts ===
+declare module 'timezonecomplete' {
+    import basics = require("__timezonecomplete/basics");
+>basics : typeof basics
+
+    export import TimeUnit = basics.TimeUnit;
+>TimeUnit : typeof basics.TimeUnit
+>basics : typeof basics
+>TimeUnit : basics.TimeUnit
+}
+
+declare module '__timezonecomplete/basics' {
+    export enum TimeUnit {
+>TimeUnit : TimeUnit
+
+        Second = 0,
+>Second : TimeUnit
+
+        Minute = 1,
+>Minute : TimeUnit
+
+        Hour = 2,
+>Hour : TimeUnit
+
+        Day = 3,
+>Day : TimeUnit
+
+        Week = 4,
+>Week : TimeUnit
+
+        Month = 5,
+>Month : TimeUnit
+
+        Year = 6,
+>Year : TimeUnit
+    }
+}
diff --git a/tests/baselines/reference/fatarrowfunctionsOptionalArgsErrors1.errors.txt b/tests/baselines/reference/fatarrowfunctionsOptionalArgsErrors1.errors.txt
index 309e731e54f..5934ab52ccf 100644
--- a/tests/baselines/reference/fatarrowfunctionsOptionalArgsErrors1.errors.txt
+++ b/tests/baselines/reference/fatarrowfunctionsOptionalArgsErrors1.errors.txt
@@ -1,5 +1,5 @@
 tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors1.ts(1,9): error TS1016: A required parameter cannot follow an optional parameter.
-tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors1.ts(2,5): error TS1047: A rest parameter cannot be optional.
+tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors1.ts(2,8): error TS1047: A rest parameter cannot be optional.
 tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors1.ts(4,5): error TS1048: A rest parameter cannot have an initializer.
 tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors1.ts(7,12): error TS1016: A required parameter cannot follow an optional parameter.
 
@@ -9,7 +9,7 @@ tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors1.ts(7,12): error TS1016
             ~~~~
 !!! error TS1016: A required parameter cannot follow an optional parameter.
     (...arg?) => 102;
-        ~~~
+           ~
 !!! error TS1047: A rest parameter cannot be optional.
     (...arg) => 103;
     (...arg:number [] = []) => 104;
diff --git a/tests/baselines/reference/functionConstraintSatisfaction.js b/tests/baselines/reference/functionConstraintSatisfaction.js
index 452080917db..a16f4d1ed36 100644
--- a/tests/baselines/reference/functionConstraintSatisfaction.js
+++ b/tests/baselines/reference/functionConstraintSatisfaction.js
@@ -113,3 +113,7 @@ function foo2(x, y) {
     foo(x);
     foo(y);
 }
+//function foo2<T extends { (): void }, U extends T>(x: T, y: U) {
+//    foo(x);
+//    foo(y);
+//} 
diff --git a/tests/baselines/reference/functionImplementationErrors.errors.txt b/tests/baselines/reference/functionImplementationErrors.errors.txt
index fbae17a609d..8ebd5aa272d 100644
--- a/tests/baselines/reference/functionImplementationErrors.errors.txt
+++ b/tests/baselines/reference/functionImplementationErrors.errors.txt
@@ -6,9 +6,15 @@ tests/cases/conformance/functions/functionImplementationErrors.ts(25,16): error
 tests/cases/conformance/functions/functionImplementationErrors.ts(30,17): error TS2373: Initializer of parameter 'n' cannot reference identifier 'm' declared after it.
 tests/cases/conformance/functions/functionImplementationErrors.ts(35,17): error TS2373: Initializer of parameter 'n' cannot reference identifier 'm' declared after it.
 tests/cases/conformance/functions/functionImplementationErrors.ts(40,28): error TS2355: A function whose declared type is neither 'void' nor 'any' must return a value or consist of a single 'throw' statement.
+tests/cases/conformance/functions/functionImplementationErrors.ts(49,1): error TS2354: No best common type exists among return expressions.
+tests/cases/conformance/functions/functionImplementationErrors.ts(53,10): error TS2354: No best common type exists among return expressions.
+tests/cases/conformance/functions/functionImplementationErrors.ts(57,11): error TS2354: No best common type exists among return expressions.
+tests/cases/conformance/functions/functionImplementationErrors.ts(61,1): error TS2354: No best common type exists among return expressions.
+tests/cases/conformance/functions/functionImplementationErrors.ts(65,11): error TS2354: No best common type exists among return expressions.
+tests/cases/conformance/functions/functionImplementationErrors.ts(69,11): error TS2354: No best common type exists among return expressions.
 
 
-==== tests/cases/conformance/functions/functionImplementationErrors.ts (8 errors) ====
+==== tests/cases/conformance/functions/functionImplementationErrors.ts (14 errors) ====
     // FunctionExpression with no return type annotation with multiple return statements with unrelated types
     var f1 = function () {
              ~~~~~~~~~~~~~
@@ -83,4 +89,63 @@ tests/cases/conformance/functions/functionImplementationErrors.ts(40,28): error
         throw undefined;
         var x = 4;
     };
+    
+    class Base { private x; }
+    class AnotherClass { private y; }
+    class Derived1 extends Base { private m; }
+    class Derived2 extends Base { private n; }
+    function f8() {
+    ~~~~~~~~~~~~~~~
+        return new Derived1();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~
+        return new Derived2();    
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+    }
+    ~
+!!! error TS2354: No best common type exists among return expressions.
+    var f9 = function () {
+             ~~~~~~~~~~~~~
+        return new Derived1();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~
+        return new Derived2();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~
+    };
+    ~
+!!! error TS2354: No best common type exists among return expressions.
+    var f10 = () => {
+              ~~~~~~~
+        return new Derived1();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~
+        return new Derived2();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~
+    };
+    ~
+!!! error TS2354: No best common type exists among return expressions.
+    function f11() {
+    ~~~~~~~~~~~~~~~~
+        return new Base();
+    ~~~~~~~~~~~~~~~~~~~~~~
+        return new AnotherClass();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+    }
+    ~
+!!! error TS2354: No best common type exists among return expressions.
+    var f12 = function () {
+              ~~~~~~~~~~~~~
+        return new Base();
+    ~~~~~~~~~~~~~~~~~~~~~~
+        return new AnotherClass();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+    };
+    ~
+!!! error TS2354: No best common type exists among return expressions.
+    var f13 = () => {
+              ~~~~~~~
+        return new Base();
+    ~~~~~~~~~~~~~~~~~~~~~~
+        return new AnotherClass();
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+    };
+    ~
+!!! error TS2354: No best common type exists among return expressions.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/functionImplementationErrors.js b/tests/baselines/reference/functionImplementationErrors.js
index 90e1997f396..5eaf9027335 100644
--- a/tests/baselines/reference/functionImplementationErrors.js
+++ b/tests/baselines/reference/functionImplementationErrors.js
@@ -42,9 +42,44 @@ undefined === function (): number {
     throw undefined;
     var x = 4;
 };
+
+class Base { private x; }
+class AnotherClass { private y; }
+class Derived1 extends Base { private m; }
+class Derived2 extends Base { private n; }
+function f8() {
+    return new Derived1();
+    return new Derived2();    
+}
+var f9 = function () {
+    return new Derived1();
+    return new Derived2();
+};
+var f10 = () => {
+    return new Derived1();
+    return new Derived2();
+};
+function f11() {
+    return new Base();
+    return new AnotherClass();
+}
+var f12 = function () {
+    return new Base();
+    return new AnotherClass();
+};
+var f13 = () => {
+    return new Base();
+    return new AnotherClass();
+};
 
 
 //// [functionImplementationErrors.js]
+var __extends = this.__extends || function (d, b) {
+    for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
+    function __() { this.constructor = d; }
+    __.prototype = b.prototype;
+    d.prototype = new __();
+};
 // FunctionExpression with no return type annotation with multiple return statements with unrelated types
 var f1 = function () {
     return '';
@@ -86,3 +121,51 @@ undefined === function () {
     throw undefined;
     var x = 4;
 };
+var Base = (function () {
+    function Base() {
+    }
+    return Base;
+})();
+var AnotherClass = (function () {
+    function AnotherClass() {
+    }
+    return AnotherClass;
+})();
+var Derived1 = (function (_super) {
+    __extends(Derived1, _super);
+    function Derived1() {
+        _super.apply(this, arguments);
+    }
+    return Derived1;
+})(Base);
+var Derived2 = (function (_super) {
+    __extends(Derived2, _super);
+    function Derived2() {
+        _super.apply(this, arguments);
+    }
+    return Derived2;
+})(Base);
+function f8() {
+    return new Derived1();
+    return new Derived2();
+}
+var f9 = function () {
+    return new Derived1();
+    return new Derived2();
+};
+var f10 = function () {
+    return new Derived1();
+    return new Derived2();
+};
+function f11() {
+    return new Base();
+    return new AnotherClass();
+}
+var f12 = function () {
+    return new Base();
+    return new AnotherClass();
+};
+var f13 = function () {
+    return new Base();
+    return new AnotherClass();
+};
diff --git a/tests/baselines/reference/functionImplementations.js b/tests/baselines/reference/functionImplementations.js
index 365ee1d7c0d..7c7b753a880 100644
--- a/tests/baselines/reference/functionImplementations.js
+++ b/tests/baselines/reference/functionImplementations.js
@@ -70,6 +70,10 @@ var n = function () {
     return 5;
 }();
 
+// Otherwise, the inferred return type is the first of the types of the return statement expressions
+// in the function body that is a supertype of each of the others, 
+// ignoring return statements with no expressions.
+// A compile - time error occurs if no return statement expression has a type that is a supertype of each of the others.
 // FunctionExpression with no return type annotation with multiple return statements with subtype relation between returns
 class Base { private m; }
 class Derived extends Base { private q; }
@@ -120,9 +124,37 @@ function f6(): number {
     return;
 }
 
-
-
-
+class Derived2 extends Base { private r: string; }
+class AnotherClass { private x }
+// if f is a contextually typed function expression, the inferred return type is the union type
+// of the types of the return statement expressions in the function body, 
+// ignoring return statements with no expressions.
+var f7: (x: number) => string | number = x => { // should be (x: number) => number | string
+    if (x < 0) { return x; }
+    return x.toString();
+}
+var f8: (x: number) => any = x => { // should be (x: number) => Base
+    return new Base();
+    return new Derived2();
+}
+var f9: (x: number) => any = x => { // should be (x: number) => Base
+    return new Base();
+    return new Derived();
+    return new Derived2();
+}
+var f10: (x: number) => any = x => { // should be (x: number) => Derived | Derived1
+    return new Derived();
+    return new Derived2();
+}
+var f11: (x: number) => any = x => { // should be (x: number) => Base | AnotherClass
+    return new Base();
+    return new AnotherClass();
+}
+var f12: (x: number) => any = x => { // should be (x: number) => Base | AnotherClass
+    return new Base();
+    return; // should be ignored
+    return new AnotherClass();
+}
 
 //// [functionImplementations.js]
 var __extends = this.__extends || function (d, b) {
@@ -192,6 +224,10 @@ var n = function () {
     return 3;
     return 5;
 }();
+// Otherwise, the inferred return type is the first of the types of the return statement expressions
+// in the function body that is a supertype of each of the others, 
+// ignoring return statements with no expressions.
+// A compile - time error occurs if no return statement expression has a type that is a supertype of each of the others.
 // FunctionExpression with no return type annotation with multiple return statements with subtype relation between returns
 var Base = (function () {
     function Base() {
@@ -249,3 +285,46 @@ function opt3(n, m) {
 function f6() {
     return;
 }
+var Derived2 = (function (_super) {
+    __extends(Derived2, _super);
+    function Derived2() {
+        _super.apply(this, arguments);
+    }
+    return Derived2;
+})(Base);
+var AnotherClass = (function () {
+    function AnotherClass() {
+    }
+    return AnotherClass;
+})();
+// if f is a contextually typed function expression, the inferred return type is the union type
+// of the types of the return statement expressions in the function body, 
+// ignoring return statements with no expressions.
+var f7 = function (x) {
+    if (x < 0) {
+        return x;
+    }
+    return x.toString();
+};
+var f8 = function (x) {
+    return new Base();
+    return new Derived2();
+};
+var f9 = function (x) {
+    return new Base();
+    return new Derived();
+    return new Derived2();
+};
+var f10 = function (x) {
+    return new Derived();
+    return new Derived2();
+};
+var f11 = function (x) {
+    return new Base();
+    return new AnotherClass();
+};
+var f12 = function (x) {
+    return new Base();
+    return; // should be ignored
+    return new AnotherClass();
+};
diff --git a/tests/baselines/reference/functionImplementations.types b/tests/baselines/reference/functionImplementations.types
index 29fe7c0e39c..04144e3a65b 100644
--- a/tests/baselines/reference/functionImplementations.types
+++ b/tests/baselines/reference/functionImplementations.types
@@ -168,6 +168,10 @@ var n = function () {
     return 5;
 }();
 
+// Otherwise, the inferred return type is the first of the types of the return statement expressions
+// in the function body that is a supertype of each of the others, 
+// ignoring return statements with no expressions.
+// A compile - time error occurs if no return statement expression has a type that is a supertype of each of the others.
 // FunctionExpression with no return type annotation with multiple return statements with subtype relation between returns
 class Base { private m; }
 >Base : Base
@@ -292,6 +296,107 @@ function f6(): number {
     return;
 }
 
+class Derived2 extends Base { private r: string; }
+>Derived2 : Derived2
+>Base : Base
+>r : string
 
+class AnotherClass { private x }
+>AnotherClass : AnotherClass
+>x : any
 
+// if f is a contextually typed function expression, the inferred return type is the union type
+// of the types of the return statement expressions in the function body, 
+// ignoring return statements with no expressions.
+var f7: (x: number) => string | number = x => { // should be (x: number) => number | string
+>f7 : (x: number) => string | number
+>x : number
+>x => { // should be (x: number) => number | string    if (x < 0) { return x; }    return x.toString();} : (x: number) => string | number
+>x : number
 
+    if (x < 0) { return x; }
+>x < 0 : boolean
+>x : number
+>x : number
+
+    return x.toString();
+>x.toString() : string
+>x.toString : (radix?: number) => string
+>x : number
+>toString : (radix?: number) => string
+}
+var f8: (x: number) => any = x => { // should be (x: number) => Base
+>f8 : (x: number) => any
+>x : number
+>x => { // should be (x: number) => Base    return new Base();    return new Derived2();} : (x: number) => Base
+>x : number
+
+    return new Base();
+>new Base() : Base
+>Base : typeof Base
+
+    return new Derived2();
+>new Derived2() : Derived2
+>Derived2 : typeof Derived2
+}
+var f9: (x: number) => any = x => { // should be (x: number) => Base
+>f9 : (x: number) => any
+>x : number
+>x => { // should be (x: number) => Base    return new Base();    return new Derived();    return new Derived2();} : (x: number) => Base
+>x : number
+
+    return new Base();
+>new Base() : Base
+>Base : typeof Base
+
+    return new Derived();
+>new Derived() : Derived
+>Derived : typeof Derived
+
+    return new Derived2();
+>new Derived2() : Derived2
+>Derived2 : typeof Derived2
+}
+var f10: (x: number) => any = x => { // should be (x: number) => Derived | Derived1
+>f10 : (x: number) => any
+>x : number
+>x => { // should be (x: number) => Derived | Derived1    return new Derived();    return new Derived2();} : (x: number) => Derived | Derived2
+>x : number
+
+    return new Derived();
+>new Derived() : Derived
+>Derived : typeof Derived
+
+    return new Derived2();
+>new Derived2() : Derived2
+>Derived2 : typeof Derived2
+}
+var f11: (x: number) => any = x => { // should be (x: number) => Base | AnotherClass
+>f11 : (x: number) => any
+>x : number
+>x => { // should be (x: number) => Base | AnotherClass    return new Base();    return new AnotherClass();} : (x: number) => Base | AnotherClass
+>x : number
+
+    return new Base();
+>new Base() : Base
+>Base : typeof Base
+
+    return new AnotherClass();
+>new AnotherClass() : AnotherClass
+>AnotherClass : typeof AnotherClass
+}
+var f12: (x: number) => any = x => { // should be (x: number) => Base | AnotherClass
+>f12 : (x: number) => any
+>x : number
+>x => { // should be (x: number) => Base | AnotherClass    return new Base();    return; // should be ignored    return new AnotherClass();} : (x: number) => Base | AnotherClass
+>x : number
+
+    return new Base();
+>new Base() : Base
+>Base : typeof Base
+
+    return; // should be ignored
+    return new AnotherClass();
+>new AnotherClass() : AnotherClass
+>AnotherClass : typeof AnotherClass
+}
diff --git a/tests/baselines/reference/functionOverloadErrorsSyntax.errors.txt b/tests/baselines/reference/functionOverloadErrorsSyntax.errors.txt
index 98e7f4cd714..7c83759d02d 100644
--- a/tests/baselines/reference/functionOverloadErrorsSyntax.errors.txt
+++ b/tests/baselines/reference/functionOverloadErrorsSyntax.errors.txt
@@ -1,6 +1,6 @@
 tests/cases/conformance/functions/functionOverloadErrorsSyntax.ts(2,27): error TS1016: A required parameter cannot follow an optional parameter.
 tests/cases/conformance/functions/functionOverloadErrorsSyntax.ts(5,38): error TS1016: A required parameter cannot follow an optional parameter.
-tests/cases/conformance/functions/functionOverloadErrorsSyntax.ts(9,28): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/functions/functionOverloadErrorsSyntax.ts(9,25): error TS1014: A rest parameter must be last in a parameter list.
 
 
 ==== tests/cases/conformance/functions/functionOverloadErrorsSyntax.ts (3 errors) ====
@@ -17,7 +17,7 @@ tests/cases/conformance/functions/functionOverloadErrorsSyntax.ts(9,28): error T
     
     //Function overload signature with rest param followed by non-optional parameter
     function fn5(x: string, ...y: any[], z: string);
-                               ~
+                            ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
     function fn5() { }
     
\ No newline at end of file
diff --git a/tests/baselines/reference/genericCallWithObjectTypeArgsAndNumericIndexer.js b/tests/baselines/reference/genericCallWithObjectTypeArgsAndNumericIndexer.js
index aa2da602e25..f300e3a8093 100644
--- a/tests/baselines/reference/genericCallWithObjectTypeArgsAndNumericIndexer.js
+++ b/tests/baselines/reference/genericCallWithObjectTypeArgsAndNumericIndexer.js
@@ -57,3 +57,10 @@ function other3(arg) {
     // BUG 821629
     //var u: U = r2[1]; // ok
 }
+//function other3<T extends U, U extends Date>(arg: T) {
+//    var b: { [x: number]: T };
+//    var r2 = foo(b);
+//    var d = r2[1];
+//    // BUG 821629
+//    //var u: U = r2[1]; // ok
+//} 
diff --git a/tests/baselines/reference/genericCallWithObjectTypeArgsAndStringIndexer.js b/tests/baselines/reference/genericCallWithObjectTypeArgsAndStringIndexer.js
index c810ce01fd4..eee87caf3de 100644
--- a/tests/baselines/reference/genericCallWithObjectTypeArgsAndStringIndexer.js
+++ b/tests/baselines/reference/genericCallWithObjectTypeArgsAndStringIndexer.js
@@ -58,3 +58,10 @@ function other3(arg) {
     // BUG 821629
     //var u: U = r2['hm']; // ok
 }
+//function other3<T extends U, U extends Date>(arg: T) {
+//    var b: { [x: string]: T };
+//    var r2 = foo(b);
+//    var d: Date = r2['hm']; // ok
+//    // BUG 821629
+//    //var u: U = r2['hm']; // ok
+//} 
diff --git a/tests/baselines/reference/getEmitOutputWithEarlySyntacticErrors.baseline b/tests/baselines/reference/getEmitOutputWithEarlySyntacticErrors.baseline
new file mode 100644
index 00000000000..a5d5d2eb9d7
--- /dev/null
+++ b/tests/baselines/reference/getEmitOutputWithEarlySyntacticErrors.baseline
@@ -0,0 +1,2 @@
+EmitOutputStatus : AllOutputGenerationSkipped
+
diff --git a/tests/baselines/reference/getEmitOutputWithSemanticErrorsForMultipleFiles.baseline b/tests/baselines/reference/getEmitOutputWithSemanticErrorsForMultipleFiles.baseline
new file mode 100644
index 00000000000..c6396314824
--- /dev/null
+++ b/tests/baselines/reference/getEmitOutputWithSemanticErrorsForMultipleFiles.baseline
@@ -0,0 +1,8 @@
+EmitOutputStatus : Succeeded
+Filename : tests/cases/fourslash/inputFile1.js
+// File to emit, does not contain semantic errors
+// expected to be emitted correctelly regardless of the semantic errors in the other file
+var noErrors = true;
+Filename : tests/cases/fourslash/inputFile1.d.ts
+declare var noErrors: boolean;
+
diff --git a/tests/baselines/reference/getEmitOutputWithSemanticErrorsForMultipleFiles2.baseline b/tests/baselines/reference/getEmitOutputWithSemanticErrorsForMultipleFiles2.baseline
new file mode 100644
index 00000000000..41b16b40e65
--- /dev/null
+++ b/tests/baselines/reference/getEmitOutputWithSemanticErrorsForMultipleFiles2.baseline
@@ -0,0 +1,8 @@
+EmitOutputStatus : DeclarationGenerationSkipped
+Filename : out.js
+// File to emit, does not contain semantic errors, but --out is passed
+// expected to not generate declarations because of the semantic errors in the other file
+var noErrors = true;
+// File not emitted, and contains semantic errors
+var semanticError = "string";
+
diff --git a/tests/baselines/reference/getEmitOutputWithSyntacticErrorsForMultipleFiles.baseline b/tests/baselines/reference/getEmitOutputWithSyntacticErrorsForMultipleFiles.baseline
new file mode 100644
index 00000000000..bf27703890b
--- /dev/null
+++ b/tests/baselines/reference/getEmitOutputWithSyntacticErrorsForMultipleFiles.baseline
@@ -0,0 +1,6 @@
+EmitOutputStatus : Succeeded
+Filename : tests/cases/fourslash/inputFile1.js
+// File to emit, does not contain syntactic errors
+// expected to be emitted correctelly regardless of the syntactic errors in the other file
+var noErrors = true;
+
diff --git a/tests/baselines/reference/getEmitOutputWithSyntacticErrorsForMultipleFiles2.baseline b/tests/baselines/reference/getEmitOutputWithSyntacticErrorsForMultipleFiles2.baseline
new file mode 100644
index 00000000000..a5d5d2eb9d7
--- /dev/null
+++ b/tests/baselines/reference/getEmitOutputWithSyntacticErrorsForMultipleFiles2.baseline
@@ -0,0 +1,2 @@
+EmitOutputStatus : AllOutputGenerationSkipped
+
diff --git a/tests/baselines/reference/heterogeneousArrayLiterals.js b/tests/baselines/reference/heterogeneousArrayLiterals.js
index 8deb3b4b068..4ac929305c0 100644
--- a/tests/baselines/reference/heterogeneousArrayLiterals.js
+++ b/tests/baselines/reference/heterogeneousArrayLiterals.js
@@ -241,3 +241,28 @@ function foo4(t, u) {
     var j = [u, derived]; // Derived[]
     var k = [t, u];
 }
+//function foo3<T extends U, U extends Derived>(t: T, u: U) {
+//    var a = [t, t]; // T[]
+//    var b = [t, null]; // T[]
+//    var c = [t, u]; // {}[]
+//    var d = [t, 1]; // {}[]
+//    var e = [() => t, () => u]; // {}[]
+//    var f = [() => t, () => u, () => null]; // { (): any }[]
+//    var g = [t, base]; // Base[]
+//    var h = [t, derived]; // Derived[]
+//    var i = [u, base]; // Base[]
+//    var j = [u, derived]; // Derived[]
+//}
+//function foo4<T extends U, U extends Base>(t: T, u: U) {
+//    var a = [t, t]; // T[]
+//    var b = [t, null]; // T[]
+//    var c = [t, u]; // BUG 821629
+//    var d = [t, 1]; // {}[]
+//    var e = [() => t, () => u]; // {}[]
+//    var f = [() => t, () => u, () => null]; // { (): any }[]
+//    var g = [t, base]; // Base[]
+//    var h = [t, derived]; // Derived[]
+//    var i = [u, base]; // Base[]
+//    var j = [u, derived]; // Derived[]
+//    var k: Base[] = [t, u];
+//} 
diff --git a/tests/baselines/reference/indexSignatureTypeCheck.errors.txt b/tests/baselines/reference/indexSignatureTypeCheck.errors.txt
index 1cc69f6294b..8a020fde5c6 100644
--- a/tests/baselines/reference/indexSignatureTypeCheck.errors.txt
+++ b/tests/baselines/reference/indexSignatureTypeCheck.errors.txt
@@ -1,5 +1,5 @@
-tests/cases/compiler/indexSignatureTypeCheck.ts(14,6): error TS1019: An index signature parameter cannot have a question mark.
-tests/cases/compiler/indexSignatureTypeCheck.ts(15,9): error TS1017: An index signature cannot have a rest parameter.
+tests/cases/compiler/indexSignatureTypeCheck.ts(14,8): error TS1019: An index signature parameter cannot have a question mark.
+tests/cases/compiler/indexSignatureTypeCheck.ts(15,6): error TS1017: An index signature cannot have a rest parameter.
 tests/cases/compiler/indexSignatureTypeCheck.ts(16,6): error TS1096: An index signature must have exactly one parameter.
 tests/cases/compiler/indexSignatureTypeCheck.ts(17,6): error TS1096: An index signature must have exactly one parameter.
 
@@ -19,10 +19,10 @@ tests/cases/compiler/indexSignatureTypeCheck.ts(17,6): error TS1096: An index si
     
     interface indexErrors {
         [p2?: string];
-         ~~
+           ~
 !!! error TS1019: An index signature parameter cannot have a question mark.
         [...p3: any[]];
-            ~~
+         ~~~
 !!! error TS1017: An index signature cannot have a rest parameter.
         [p4: string, p5?: string];
          ~~
diff --git a/tests/baselines/reference/indexSignatureTypeCheck2.errors.txt b/tests/baselines/reference/indexSignatureTypeCheck2.errors.txt
index 25e3ab94280..0fd594268c5 100644
--- a/tests/baselines/reference/indexSignatureTypeCheck2.errors.txt
+++ b/tests/baselines/reference/indexSignatureTypeCheck2.errors.txt
@@ -1,5 +1,5 @@
-tests/cases/compiler/indexSignatureTypeCheck2.ts(10,6): error TS1019: An index signature parameter cannot have a question mark.
-tests/cases/compiler/indexSignatureTypeCheck2.ts(11,9): error TS1017: An index signature cannot have a rest parameter.
+tests/cases/compiler/indexSignatureTypeCheck2.ts(10,8): error TS1019: An index signature parameter cannot have a question mark.
+tests/cases/compiler/indexSignatureTypeCheck2.ts(11,6): error TS1017: An index signature cannot have a rest parameter.
 tests/cases/compiler/indexSignatureTypeCheck2.ts(12,6): error TS1096: An index signature must have exactly one parameter.
 tests/cases/compiler/indexSignatureTypeCheck2.ts(13,6): error TS1096: An index signature must have exactly one parameter.
 
@@ -15,10 +15,10 @@ tests/cases/compiler/indexSignatureTypeCheck2.ts(13,6): error TS1096: An index s
     
     interface indexErrors {
         [p2?: string];
-         ~~
+           ~
 !!! error TS1019: An index signature parameter cannot have a question mark.
         [...p3: any[]];
-            ~~
+         ~~~
 !!! error TS1017: An index signature cannot have a rest parameter.
         [p4: string, p5?: string];
          ~~
diff --git a/tests/baselines/reference/indexerAsOptional.errors.txt b/tests/baselines/reference/indexerAsOptional.errors.txt
index 101c03acccd..cfd2d08cef9 100644
--- a/tests/baselines/reference/indexerAsOptional.errors.txt
+++ b/tests/baselines/reference/indexerAsOptional.errors.txt
@@ -1,18 +1,18 @@
-tests/cases/compiler/indexerAsOptional.ts(3,6): error TS1019: An index signature parameter cannot have a question mark.
-tests/cases/compiler/indexerAsOptional.ts(8,6): error TS1019: An index signature parameter cannot have a question mark.
+tests/cases/compiler/indexerAsOptional.ts(3,9): error TS1019: An index signature parameter cannot have a question mark.
+tests/cases/compiler/indexerAsOptional.ts(8,9): error TS1019: An index signature parameter cannot have a question mark.
 
 
 ==== tests/cases/compiler/indexerAsOptional.ts (2 errors) ====
     interface indexSig {
         //Index signatures can't be optional
         [idx?: number]: any; //err
-         ~~~
+            ~
 !!! error TS1019: An index signature parameter cannot have a question mark.
     }
     
     class indexSig2 {
         //Index signatures can't be optional
         [idx?: number]: any //err
-         ~~~
+            ~
 !!! error TS1019: An index signature parameter cannot have a question mark.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/indexerSignatureWithRestParam.errors.txt b/tests/baselines/reference/indexerSignatureWithRestParam.errors.txt
index 4743ed8e91c..08c65816416 100644
--- a/tests/baselines/reference/indexerSignatureWithRestParam.errors.txt
+++ b/tests/baselines/reference/indexerSignatureWithRestParam.errors.txt
@@ -1,16 +1,16 @@
-tests/cases/compiler/indexerSignatureWithRestParam.ts(2,9): error TS1017: An index signature cannot have a rest parameter.
-tests/cases/compiler/indexerSignatureWithRestParam.ts(6,9): error TS1017: An index signature cannot have a rest parameter.
+tests/cases/compiler/indexerSignatureWithRestParam.ts(2,6): error TS1017: An index signature cannot have a rest parameter.
+tests/cases/compiler/indexerSignatureWithRestParam.ts(6,6): error TS1017: An index signature cannot have a rest parameter.
 
 
 ==== tests/cases/compiler/indexerSignatureWithRestParam.ts (2 errors) ====
     interface I {
         [...x]: string;
-            ~
+         ~~~
 !!! error TS1017: An index signature cannot have a rest parameter.
     }
     
     class C {
         [...x]: string
-            ~
+         ~~~
 !!! error TS1017: An index signature cannot have a rest parameter.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/indexerWithTuple.js b/tests/baselines/reference/indexerWithTuple.js
index fc82716ba05..91d90792e6d 100644
--- a/tests/baselines/reference/indexerWithTuple.js
+++ b/tests/baselines/reference/indexerWithTuple.js
@@ -1,32 +1,65 @@
 //// [indexerWithTuple.ts]
 var strNumTuple: [string, number] = ["foo", 10]; 
 var numTupleTuple: [number, [string, number]] = [10, ["bar", 20]];
+var unionTuple1: [number, string| number] = [10, "foo"]; 
+var unionTuple2: [boolean, string| number] = [true, "foo"]; 
 
 // no error
 var idx0 = 0;
 var idx1 = 1;
 var ele10 = strNumTuple[0]; // string
 var ele11 = strNumTuple[1]; // number
-var ele12 = strNumTuple[2]; // {}
-var ele13 = strNumTuple[idx0]; // {}
-var ele14 = strNumTuple[idx1]; // {}
+var ele12 = strNumTuple[2]; // string | number
+var ele13 = strNumTuple[idx0]; // string | number
+var ele14 = strNumTuple[idx1]; // string | number
 var ele15 = strNumTuple["0"]; // string
 var ele16 = strNumTuple["1"]; // number
 var strNumTuple1 = numTupleTuple[1];  //[string, number];
-var ele17 = numTupleTuple[2]; // {}
+var ele17 = numTupleTuple[2]; // number | [string, number]
+var eleUnion10 = unionTuple1[0]; // number
+var eleUnion11 = unionTuple1[1]; // string | number
+var eleUnion12 = unionTuple1[2]; // string | number
+var eleUnion13 = unionTuple1[idx0]; // string | number
+var eleUnion14 = unionTuple1[idx1]; // string | number
+var eleUnion15 = unionTuple1["0"]; // number
+var eleUnion16 = unionTuple1["1"]; // string | number
+
+var eleUnion20 = unionTuple2[0]; // boolean
+var eleUnion21 = unionTuple2[1]; // string | number
+var eleUnion22 = unionTuple2[2]; // string | number | boolean
+var eleUnion23 = unionTuple2[idx0]; // string | number | boolean
+var eleUnion24 = unionTuple2[idx1]; // string | number | boolean
+var eleUnion25 = unionTuple2["0"]; // boolean
+var eleUnion26 = unionTuple2["1"]; // string | number
 
 //// [indexerWithTuple.js]
 var strNumTuple = ["foo", 10];
 var numTupleTuple = [10, ["bar", 20]];
+var unionTuple1 = [10, "foo"];
+var unionTuple2 = [true, "foo"];
 // no error
 var idx0 = 0;
 var idx1 = 1;
 var ele10 = strNumTuple[0]; // string
 var ele11 = strNumTuple[1]; // number
-var ele12 = strNumTuple[2]; // {}
-var ele13 = strNumTuple[idx0]; // {}
-var ele14 = strNumTuple[idx1]; // {}
+var ele12 = strNumTuple[2]; // string | number
+var ele13 = strNumTuple[idx0]; // string | number
+var ele14 = strNumTuple[idx1]; // string | number
 var ele15 = strNumTuple["0"]; // string
 var ele16 = strNumTuple["1"]; // number
 var strNumTuple1 = numTupleTuple[1]; //[string, number];
-var ele17 = numTupleTuple[2]; // {}
+var ele17 = numTupleTuple[2]; // number | [string, number]
+var eleUnion10 = unionTuple1[0]; // number
+var eleUnion11 = unionTuple1[1]; // string | number
+var eleUnion12 = unionTuple1[2]; // string | number
+var eleUnion13 = unionTuple1[idx0]; // string | number
+var eleUnion14 = unionTuple1[idx1]; // string | number
+var eleUnion15 = unionTuple1["0"]; // number
+var eleUnion16 = unionTuple1["1"]; // string | number
+var eleUnion20 = unionTuple2[0]; // boolean
+var eleUnion21 = unionTuple2[1]; // string | number
+var eleUnion22 = unionTuple2[2]; // string | number | boolean
+var eleUnion23 = unionTuple2[idx0]; // string | number | boolean
+var eleUnion24 = unionTuple2[idx1]; // string | number | boolean
+var eleUnion25 = unionTuple2["0"]; // boolean
+var eleUnion26 = unionTuple2["1"]; // string | number
diff --git a/tests/baselines/reference/indexerWithTuple.types b/tests/baselines/reference/indexerWithTuple.types
index 28053a33081..75b89ca6088 100644
--- a/tests/baselines/reference/indexerWithTuple.types
+++ b/tests/baselines/reference/indexerWithTuple.types
@@ -8,6 +8,14 @@ var numTupleTuple: [number, [string, number]] = [10, ["bar", 20]];
 >[10, ["bar", 20]] : [number, [string, number]]
 >["bar", 20] : [string, number]
 
+var unionTuple1: [number, string| number] = [10, "foo"]; 
+>unionTuple1 : [number, string | number]
+>[10, "foo"] : [number, string]
+
+var unionTuple2: [boolean, string| number] = [true, "foo"]; 
+>unionTuple2 : [boolean, string | number]
+>[true, "foo"] : [boolean, string]
+
 // no error
 var idx0 = 0;
 >idx0 : number
@@ -25,18 +33,18 @@ var ele11 = strNumTuple[1]; // number
 >strNumTuple[1] : number
 >strNumTuple : [string, number]
 
-var ele12 = strNumTuple[2]; // {}
+var ele12 = strNumTuple[2]; // string | number
 >ele12 : string | number
 >strNumTuple[2] : string | number
 >strNumTuple : [string, number]
 
-var ele13 = strNumTuple[idx0]; // {}
+var ele13 = strNumTuple[idx0]; // string | number
 >ele13 : string | number
 >strNumTuple[idx0] : string | number
 >strNumTuple : [string, number]
 >idx0 : number
 
-var ele14 = strNumTuple[idx1]; // {}
+var ele14 = strNumTuple[idx1]; // string | number
 >ele14 : string | number
 >strNumTuple[idx1] : string | number
 >strNumTuple : [string, number]
@@ -57,8 +65,82 @@ var strNumTuple1 = numTupleTuple[1];  //[string, number];
 >numTupleTuple[1] : [string, number]
 >numTupleTuple : [number, [string, number]]
 
-var ele17 = numTupleTuple[2]; // {}
+var ele17 = numTupleTuple[2]; // number | [string, number]
 >ele17 : number | [string, number]
 >numTupleTuple[2] : number | [string, number]
 >numTupleTuple : [number, [string, number]]
 
+var eleUnion10 = unionTuple1[0]; // number
+>eleUnion10 : number
+>unionTuple1[0] : number
+>unionTuple1 : [number, string | number]
+
+var eleUnion11 = unionTuple1[1]; // string | number
+>eleUnion11 : string | number
+>unionTuple1[1] : string | number
+>unionTuple1 : [number, string | number]
+
+var eleUnion12 = unionTuple1[2]; // string | number
+>eleUnion12 : string | number
+>unionTuple1[2] : string | number
+>unionTuple1 : [number, string | number]
+
+var eleUnion13 = unionTuple1[idx0]; // string | number
+>eleUnion13 : string | number
+>unionTuple1[idx0] : string | number
+>unionTuple1 : [number, string | number]
+>idx0 : number
+
+var eleUnion14 = unionTuple1[idx1]; // string | number
+>eleUnion14 : string | number
+>unionTuple1[idx1] : string | number
+>unionTuple1 : [number, string | number]
+>idx1 : number
+
+var eleUnion15 = unionTuple1["0"]; // number
+>eleUnion15 : number
+>unionTuple1["0"] : number
+>unionTuple1 : [number, string | number]
+
+var eleUnion16 = unionTuple1["1"]; // string | number
+>eleUnion16 : string | number
+>unionTuple1["1"] : string | number
+>unionTuple1 : [number, string | number]
+
+var eleUnion20 = unionTuple2[0]; // boolean
+>eleUnion20 : boolean
+>unionTuple2[0] : boolean
+>unionTuple2 : [boolean, string | number]
+
+var eleUnion21 = unionTuple2[1]; // string | number
+>eleUnion21 : string | number
+>unionTuple2[1] : string | number
+>unionTuple2 : [boolean, string | number]
+
+var eleUnion22 = unionTuple2[2]; // string | number | boolean
+>eleUnion22 : string | number | boolean
+>unionTuple2[2] : string | number | boolean
+>unionTuple2 : [boolean, string | number]
+
+var eleUnion23 = unionTuple2[idx0]; // string | number | boolean
+>eleUnion23 : string | number | boolean
+>unionTuple2[idx0] : string | number | boolean
+>unionTuple2 : [boolean, string | number]
+>idx0 : number
+
+var eleUnion24 = unionTuple2[idx1]; // string | number | boolean
+>eleUnion24 : string | number | boolean
+>unionTuple2[idx1] : string | number | boolean
+>unionTuple2 : [boolean, string | number]
+>idx1 : number
+
+var eleUnion25 = unionTuple2["0"]; // boolean
+>eleUnion25 : boolean
+>unionTuple2["0"] : boolean
+>unionTuple2 : [boolean, string | number]
+
+var eleUnion26 = unionTuple2["1"]; // string | number
+>eleUnion26 : string | number
+>unionTuple2["1"] : string | number
+>unionTuple2 : [boolean, string | number]
+
diff --git a/tests/baselines/reference/innerTypeParameterShadowingOuterOne.js b/tests/baselines/reference/innerTypeParameterShadowingOuterOne.js
index 81ed990532c..74354468e32 100644
--- a/tests/baselines/reference/innerTypeParameterShadowingOuterOne.js
+++ b/tests/baselines/reference/innerTypeParameterShadowingOuterOne.js
@@ -47,3 +47,11 @@ function f2() {
     var x;
     x.getDate();
 }
+//function f2<T extends Date, U extends T>() {
+//    function g<T extends Number, U extends T>() {
+//        var x: U;
+//        x.toFixed();
+//    }
+//    var x: U;
+//    x.getDate();
+//} 
diff --git a/tests/baselines/reference/innerTypeParameterShadowingOuterOne2.js b/tests/baselines/reference/innerTypeParameterShadowingOuterOne2.js
index 8a5a9448f18..36a250d365d 100644
--- a/tests/baselines/reference/innerTypeParameterShadowingOuterOne2.js
+++ b/tests/baselines/reference/innerTypeParameterShadowingOuterOne2.js
@@ -66,3 +66,13 @@ var C2 = (function () {
     };
     return C2;
 })();
+//class C2<T extends Date, U extends T> {
+//    g<T extends Number, U extends T>() {
+//        var x: U;
+//        x.toFixed();
+//    }
+//    h() {
+//        var x: U;
+//        x.getDate();
+//    }
+//} 
diff --git a/tests/baselines/reference/logicalOrOperatorWithEveryType.js b/tests/baselines/reference/logicalOrOperatorWithEveryType.js
index bf7a641882e..78601374c22 100644
--- a/tests/baselines/reference/logicalOrOperatorWithEveryType.js
+++ b/tests/baselines/reference/logicalOrOperatorWithEveryType.js
@@ -28,77 +28,77 @@ var ra10 = undefined || a1; // undefined || any is any
 
 var rb1 = a1 || a2;         // any       || boolean is any
 var rb2 = a2 || a2;         // boolean   || boolean is boolean
-var rb3 = a3 || a2;         // number    || boolean is {}
-var rb4 = a4 || a2;         // string    || boolean is {}
-var rb5 = a5 || a2;         // void      || boolean is {}
-var rb6 = a6 || a2;         // enum      || boolean is {}
-var rb7 = a7 || a2;         // object    || boolean is {}
-var rb8 = a8 || a2;         // array     || boolean is {}
+var rb3 = a3 || a2;         // number    || boolean is number | boolean
+var rb4 = a4 || a2;         // string    || boolean is string | boolean
+var rb5 = a5 || a2;         // void      || boolean is void | boolean
+var rb6 = a6 || a2;         // enum      || boolean is E | boolean
+var rb7 = a7 || a2;         // object    || boolean is object | boolean
+var rb8 = a8 || a2;         // array     || boolean is array | boolean
 var rb9 = null || a2;       // null      || boolean is boolean
 var rb10= undefined || a2;  // undefined || boolean is boolean
 
 var rc1 = a1 || a3;         // any       || number is any
-var rc2 = a2 || a3;         // boolean   || number is {}
+var rc2 = a2 || a3;         // boolean   || number is boolean | number
 var rc3 = a3 || a3;         // number    || number is number
-var rc4 = a4 || a3;         // string    || number is {}
-var rc5 = a5 || a3;         // void      || number is {}
+var rc4 = a4 || a3;         // string    || number is string | number
+var rc5 = a5 || a3;         // void      || number is void | number
 var rc6 = a6 || a3;         // enum      || number is number
-var rc7 = a7 || a3;         // object    || number is {}
-var rc8 = a8 || a3;         // array     || number is {}
+var rc7 = a7 || a3;         // object    || number is object | number
+var rc8 = a8 || a3;         // array     || number is array | number
 var rc9 = null || a3;       // null      || number is number
 var rc10 = undefined || a3; // undefined || number is number
 
 var rd1 = a1 || a4;         // any       || string is any
-var rd2 = a2 || a4;         // boolean   || string is {}
-var rd3 = a3 || a4;         // number    || string is {}
+var rd2 = a2 || a4;         // boolean   || string is boolean | string
+var rd3 = a3 || a4;         // number    || string is number | string
 var rd4 = a4 || a4;         // string    || string is string
-var rd5 = a5 || a4;         // void      || string is {}
-var rd6 = a6 || a4;         // enum      || string is {}
-var rd7 = a7 || a4;         // object    || string is {}
-var rd8 = a8 || a4;         // array     || string is {}
+var rd5 = a5 || a4;         // void      || string is void | string
+var rd6 = a6 || a4;         // enum      || string is enum | string
+var rd7 = a7 || a4;         // object    || string is object | string
+var rd8 = a8 || a4;         // array     || string is array | string
 var rd9 = null || a4;       // null      || string is string
 var rd10 = undefined || a4; // undefined || string is string
 
 var re1 = a1 || a5;         // any       || void is any
-var re2 = a2 || a5;         // boolean   || void is {}
-var re3 = a3 || a5;         // number    || void is {}
-var re4 = a4 || a5;         // string    || void is {}
+var re2 = a2 || a5;         // boolean   || void is boolean | void
+var re3 = a3 || a5;         // number    || void is number | void
+var re4 = a4 || a5;         // string    || void is string | void
 var re5 = a5 || a5;         // void      || void is void
-var re6 = a6 || a5;         // enum      || void is {}
-var re7 = a7 || a5;         // object    || void is {}
-var re8 = a8 || a5;         // array     || void is {}
+var re6 = a6 || a5;         // enum      || void is enum | void
+var re7 = a7 || a5;         // object    || void is object | void
+var re8 = a8 || a5;         // array     || void is array | void
 var re9 = null || a5;       // null      || void is void
 var re10 = undefined || a5; // undefined || void is void
 
 var rg1 = a1 || a6;         // any       || enum is any
-var rg2 = a2 || a6;         // boolean   || enum is {}
+var rg2 = a2 || a6;         // boolean   || enum is boolean | enum
 var rg3 = a3 || a6;         // number    || enum is number
-var rg4 = a4 || a6;         // string    || enum is {}
-var rg5 = a5 || a6;         // void      || enum is {}
+var rg4 = a4 || a6;         // string    || enum is string | enum
+var rg5 = a5 || a6;         // void      || enum is void | enum
 var rg6 = a6 || a6;         // enum      || enum is E
-var rg7 = a7 || a6;         // object    || enum is {}
-var rg8 = a8 || a6;         // array     || enum is {}
+var rg7 = a7 || a6;         // object    || enum is object | enum
+var rg8 = a8 || a6;         // array     || enum is array | enum
 var rg9 = null || a6;       // null      || enum is E
 var rg10 = undefined || a6; // undefined || enum is E
 
 var rh1 = a1 || a7;         // any       || object is any
-var rh2 = a2 || a7;         // boolean   || object is {}
-var rh3 = a3 || a7;         // number    || object is {}
-var rh4 = a4 || a7;         // string    || object is {}
-var rh5 = a5 || a7;         // void      || object is {}
-var rh6 = a6 || a7;         // enum      || object is {}
+var rh2 = a2 || a7;         // boolean   || object is boolean | object
+var rh3 = a3 || a7;         // number    || object is number | object
+var rh4 = a4 || a7;         // string    || object is string | object
+var rh5 = a5 || a7;         // void      || object is void | object
+var rh6 = a6 || a7;         // enum      || object is enum | object
 var rh7 = a7 || a7;         // object    || object is object
-var rh8 = a8 || a7;         // array     || object is {}
+var rh8 = a8 || a7;         // array     || object is array | object
 var rh9 = null || a7;       // null      || object is object
 var rh10 = undefined || a7; // undefined || object is object
 
 var ri1 = a1 || a8;         // any       || array is any
-var ri2 = a2 || a8;         // boolean   || array is {}
-var ri3 = a3 || a8;         // number    || array is {}
-var ri4 = a4 || a8;         // string    || array is {}
-var ri5 = a5 || a8;         // void      || array is {}
-var ri6 = a6 || a8;         // enum      || array is {}
-var ri7 = a7 || a8;         // object    || array is {}
+var ri2 = a2 || a8;         // boolean   || array is boolean | array
+var ri3 = a3 || a8;         // number    || array is number | array
+var ri4 = a4 || a8;         // string    || array is string | array
+var ri5 = a5 || a8;         // void      || array is void | array
+var ri6 = a6 || a8;         // enum      || array is enum | array
+var ri7 = a7 || a8;         // object    || array is object | array
 var ri8 = a8 || a8;         // array     || array is array
 var ri9 = null || a8;       // null      || array is array
 var ri10 = undefined || a8; // undefined || array is array
@@ -156,71 +156,71 @@ var ra9 = null || a1; // null      || any is any
 var ra10 = undefined || a1; // undefined || any is any
 var rb1 = a1 || a2; // any       || boolean is any
 var rb2 = a2 || a2; // boolean   || boolean is boolean
-var rb3 = a3 || a2; // number    || boolean is {}
-var rb4 = a4 || a2; // string    || boolean is {}
-var rb5 = a5 || a2; // void      || boolean is {}
-var rb6 = a6 || a2; // enum      || boolean is {}
-var rb7 = a7 || a2; // object    || boolean is {}
-var rb8 = a8 || a2; // array     || boolean is {}
+var rb3 = a3 || a2; // number    || boolean is number | boolean
+var rb4 = a4 || a2; // string    || boolean is string | boolean
+var rb5 = a5 || a2; // void      || boolean is void | boolean
+var rb6 = a6 || a2; // enum      || boolean is E | boolean
+var rb7 = a7 || a2; // object    || boolean is object | boolean
+var rb8 = a8 || a2; // array     || boolean is array | boolean
 var rb9 = null || a2; // null      || boolean is boolean
 var rb10 = undefined || a2; // undefined || boolean is boolean
 var rc1 = a1 || a3; // any       || number is any
-var rc2 = a2 || a3; // boolean   || number is {}
+var rc2 = a2 || a3; // boolean   || number is boolean | number
 var rc3 = a3 || a3; // number    || number is number
-var rc4 = a4 || a3; // string    || number is {}
-var rc5 = a5 || a3; // void      || number is {}
+var rc4 = a4 || a3; // string    || number is string | number
+var rc5 = a5 || a3; // void      || number is void | number
 var rc6 = a6 || a3; // enum      || number is number
-var rc7 = a7 || a3; // object    || number is {}
-var rc8 = a8 || a3; // array     || number is {}
+var rc7 = a7 || a3; // object    || number is object | number
+var rc8 = a8 || a3; // array     || number is array | number
 var rc9 = null || a3; // null      || number is number
 var rc10 = undefined || a3; // undefined || number is number
 var rd1 = a1 || a4; // any       || string is any
-var rd2 = a2 || a4; // boolean   || string is {}
-var rd3 = a3 || a4; // number    || string is {}
+var rd2 = a2 || a4; // boolean   || string is boolean | string
+var rd3 = a3 || a4; // number    || string is number | string
 var rd4 = a4 || a4; // string    || string is string
-var rd5 = a5 || a4; // void      || string is {}
-var rd6 = a6 || a4; // enum      || string is {}
-var rd7 = a7 || a4; // object    || string is {}
-var rd8 = a8 || a4; // array     || string is {}
+var rd5 = a5 || a4; // void      || string is void | string
+var rd6 = a6 || a4; // enum      || string is enum | string
+var rd7 = a7 || a4; // object    || string is object | string
+var rd8 = a8 || a4; // array     || string is array | string
 var rd9 = null || a4; // null      || string is string
 var rd10 = undefined || a4; // undefined || string is string
 var re1 = a1 || a5; // any       || void is any
-var re2 = a2 || a5; // boolean   || void is {}
-var re3 = a3 || a5; // number    || void is {}
-var re4 = a4 || a5; // string    || void is {}
+var re2 = a2 || a5; // boolean   || void is boolean | void
+var re3 = a3 || a5; // number    || void is number | void
+var re4 = a4 || a5; // string    || void is string | void
 var re5 = a5 || a5; // void      || void is void
-var re6 = a6 || a5; // enum      || void is {}
-var re7 = a7 || a5; // object    || void is {}
-var re8 = a8 || a5; // array     || void is {}
+var re6 = a6 || a5; // enum      || void is enum | void
+var re7 = a7 || a5; // object    || void is object | void
+var re8 = a8 || a5; // array     || void is array | void
 var re9 = null || a5; // null      || void is void
 var re10 = undefined || a5; // undefined || void is void
 var rg1 = a1 || a6; // any       || enum is any
-var rg2 = a2 || a6; // boolean   || enum is {}
+var rg2 = a2 || a6; // boolean   || enum is boolean | enum
 var rg3 = a3 || a6; // number    || enum is number
-var rg4 = a4 || a6; // string    || enum is {}
-var rg5 = a5 || a6; // void      || enum is {}
+var rg4 = a4 || a6; // string    || enum is string | enum
+var rg5 = a5 || a6; // void      || enum is void | enum
 var rg6 = a6 || a6; // enum      || enum is E
-var rg7 = a7 || a6; // object    || enum is {}
-var rg8 = a8 || a6; // array     || enum is {}
+var rg7 = a7 || a6; // object    || enum is object | enum
+var rg8 = a8 || a6; // array     || enum is array | enum
 var rg9 = null || a6; // null      || enum is E
 var rg10 = undefined || a6; // undefined || enum is E
 var rh1 = a1 || a7; // any       || object is any
-var rh2 = a2 || a7; // boolean   || object is {}
-var rh3 = a3 || a7; // number    || object is {}
-var rh4 = a4 || a7; // string    || object is {}
-var rh5 = a5 || a7; // void      || object is {}
-var rh6 = a6 || a7; // enum      || object is {}
+var rh2 = a2 || a7; // boolean   || object is boolean | object
+var rh3 = a3 || a7; // number    || object is number | object
+var rh4 = a4 || a7; // string    || object is string | object
+var rh5 = a5 || a7; // void      || object is void | object
+var rh6 = a6 || a7; // enum      || object is enum | object
 var rh7 = a7 || a7; // object    || object is object
-var rh8 = a8 || a7; // array     || object is {}
+var rh8 = a8 || a7; // array     || object is array | object
 var rh9 = null || a7; // null      || object is object
 var rh10 = undefined || a7; // undefined || object is object
 var ri1 = a1 || a8; // any       || array is any
-var ri2 = a2 || a8; // boolean   || array is {}
-var ri3 = a3 || a8; // number    || array is {}
-var ri4 = a4 || a8; // string    || array is {}
-var ri5 = a5 || a8; // void      || array is {}
-var ri6 = a6 || a8; // enum      || array is {}
-var ri7 = a7 || a8; // object    || array is {}
+var ri2 = a2 || a8; // boolean   || array is boolean | array
+var ri3 = a3 || a8; // number    || array is number | array
+var ri4 = a4 || a8; // string    || array is string | array
+var ri5 = a5 || a8; // void      || array is void | array
+var ri6 = a6 || a8; // enum      || array is enum | array
+var ri7 = a7 || a8; // object    || array is object | array
 var ri8 = a8 || a8; // array     || array is array
 var ri9 = null || a8; // null      || array is array
 var ri10 = undefined || a8; // undefined || array is array
diff --git a/tests/baselines/reference/logicalOrOperatorWithEveryType.types b/tests/baselines/reference/logicalOrOperatorWithEveryType.types
index 3e3b0dcf37f..ae8dab8c71c 100644
--- a/tests/baselines/reference/logicalOrOperatorWithEveryType.types
+++ b/tests/baselines/reference/logicalOrOperatorWithEveryType.types
@@ -107,37 +107,37 @@ var rb2 = a2 || a2;         // boolean   || boolean is boolean
 >a2 : boolean
 >a2 : boolean
 
-var rb3 = a3 || a2;         // number    || boolean is {}
+var rb3 = a3 || a2;         // number    || boolean is number | boolean
 >rb3 : number | boolean
 >a3 || a2 : number | boolean
 >a3 : number
 >a2 : boolean
 
-var rb4 = a4 || a2;         // string    || boolean is {}
+var rb4 = a4 || a2;         // string    || boolean is string | boolean
 >rb4 : string | boolean
 >a4 || a2 : string | boolean
 >a4 : string
 >a2 : boolean
 
-var rb5 = a5 || a2;         // void      || boolean is {}
+var rb5 = a5 || a2;         // void      || boolean is void | boolean
 >rb5 : boolean | void
 >a5 || a2 : boolean | void
 >a5 : void
 >a2 : boolean
 
-var rb6 = a6 || a2;         // enum      || boolean is {}
+var rb6 = a6 || a2;         // enum      || boolean is E | boolean
 >rb6 : boolean | E
 >a6 || a2 : boolean | E
 >a6 : E
 >a2 : boolean
 
-var rb7 = a7 || a2;         // object    || boolean is {}
+var rb7 = a7 || a2;         // object    || boolean is object | boolean
 >rb7 : boolean | { a: string; }
 >a7 || a2 : boolean | { a: string; }
 >a7 : { a: string; }
 >a2 : boolean
 
-var rb8 = a8 || a2;         // array     || boolean is {}
+var rb8 = a8 || a2;         // array     || boolean is array | boolean
 >rb8 : boolean | string[]
 >a8 || a2 : boolean | string[]
 >a8 : string[]
@@ -160,7 +160,7 @@ var rc1 = a1 || a3;         // any       || number is any
 >a1 : any
 >a3 : number
 
-var rc2 = a2 || a3;         // boolean   || number is {}
+var rc2 = a2 || a3;         // boolean   || number is boolean | number
 >rc2 : number | boolean
 >a2 || a3 : number | boolean
 >a2 : boolean
@@ -172,13 +172,13 @@ var rc3 = a3 || a3;         // number    || number is number
 >a3 : number
 >a3 : number
 
-var rc4 = a4 || a3;         // string    || number is {}
+var rc4 = a4 || a3;         // string    || number is string | number
 >rc4 : string | number
 >a4 || a3 : string | number
 >a4 : string
 >a3 : number
 
-var rc5 = a5 || a3;         // void      || number is {}
+var rc5 = a5 || a3;         // void      || number is void | number
 >rc5 : number | void
 >a5 || a3 : number | void
 >a5 : void
@@ -190,13 +190,13 @@ var rc6 = a6 || a3;         // enum      || number is number
 >a6 : E
 >a3 : number
 
-var rc7 = a7 || a3;         // object    || number is {}
+var rc7 = a7 || a3;         // object    || number is object | number
 >rc7 : number | { a: string; }
 >a7 || a3 : number | { a: string; }
 >a7 : { a: string; }
 >a3 : number
 
-var rc8 = a8 || a3;         // array     || number is {}
+var rc8 = a8 || a3;         // array     || number is array | number
 >rc8 : number | string[]
 >a8 || a3 : number | string[]
 >a8 : string[]
@@ -219,13 +219,13 @@ var rd1 = a1 || a4;         // any       || string is any
 >a1 : any
 >a4 : string
 
-var rd2 = a2 || a4;         // boolean   || string is {}
+var rd2 = a2 || a4;         // boolean   || string is boolean | string
 >rd2 : string | boolean
 >a2 || a4 : string | boolean
 >a2 : boolean
 >a4 : string
 
-var rd3 = a3 || a4;         // number    || string is {}
+var rd3 = a3 || a4;         // number    || string is number | string
 >rd3 : string | number
 >a3 || a4 : string | number
 >a3 : number
@@ -237,25 +237,25 @@ var rd4 = a4 || a4;         // string    || string is string
 >a4 : string
 >a4 : string
 
-var rd5 = a5 || a4;         // void      || string is {}
+var rd5 = a5 || a4;         // void      || string is void | string
 >rd5 : string | void
 >a5 || a4 : string | void
 >a5 : void
 >a4 : string
 
-var rd6 = a6 || a4;         // enum      || string is {}
+var rd6 = a6 || a4;         // enum      || string is enum | string
 >rd6 : string | E
 >a6 || a4 : string | E
 >a6 : E
 >a4 : string
 
-var rd7 = a7 || a4;         // object    || string is {}
+var rd7 = a7 || a4;         // object    || string is object | string
 >rd7 : string | { a: string; }
 >a7 || a4 : string | { a: string; }
 >a7 : { a: string; }
 >a4 : string
 
-var rd8 = a8 || a4;         // array     || string is {}
+var rd8 = a8 || a4;         // array     || string is array | string
 >rd8 : string | string[]
 >a8 || a4 : string | string[]
 >a8 : string[]
@@ -278,19 +278,19 @@ var re1 = a1 || a5;         // any       || void is any
 >a1 : any
 >a5 : void
 
-var re2 = a2 || a5;         // boolean   || void is {}
+var re2 = a2 || a5;         // boolean   || void is boolean | void
 >re2 : boolean | void
 >a2 || a5 : boolean | void
 >a2 : boolean
 >a5 : void
 
-var re3 = a3 || a5;         // number    || void is {}
+var re3 = a3 || a5;         // number    || void is number | void
 >re3 : number | void
 >a3 || a5 : number | void
 >a3 : number
 >a5 : void
 
-var re4 = a4 || a5;         // string    || void is {}
+var re4 = a4 || a5;         // string    || void is string | void
 >re4 : string | void
 >a4 || a5 : string | void
 >a4 : string
@@ -302,19 +302,19 @@ var re5 = a5 || a5;         // void      || void is void
 >a5 : void
 >a5 : void
 
-var re6 = a6 || a5;         // enum      || void is {}
+var re6 = a6 || a5;         // enum      || void is enum | void
 >re6 : void | E
 >a6 || a5 : void | E
 >a6 : E
 >a5 : void
 
-var re7 = a7 || a5;         // object    || void is {}
+var re7 = a7 || a5;         // object    || void is object | void
 >re7 : void | { a: string; }
 >a7 || a5 : void | { a: string; }
 >a7 : { a: string; }
 >a5 : void
 
-var re8 = a8 || a5;         // array     || void is {}
+var re8 = a8 || a5;         // array     || void is array | void
 >re8 : void | string[]
 >a8 || a5 : void | string[]
 >a8 : string[]
@@ -337,7 +337,7 @@ var rg1 = a1 || a6;         // any       || enum is any
 >a1 : any
 >a6 : E
 
-var rg2 = a2 || a6;         // boolean   || enum is {}
+var rg2 = a2 || a6;         // boolean   || enum is boolean | enum
 >rg2 : boolean | E
 >a2 || a6 : boolean | E
 >a2 : boolean
@@ -349,13 +349,13 @@ var rg3 = a3 || a6;         // number    || enum is number
 >a3 : number
 >a6 : E
 
-var rg4 = a4 || a6;         // string    || enum is {}
+var rg4 = a4 || a6;         // string    || enum is string | enum
 >rg4 : string | E
 >a4 || a6 : string | E
 >a4 : string
 >a6 : E
 
-var rg5 = a5 || a6;         // void      || enum is {}
+var rg5 = a5 || a6;         // void      || enum is void | enum
 >rg5 : void | E
 >a5 || a6 : void | E
 >a5 : void
@@ -367,13 +367,13 @@ var rg6 = a6 || a6;         // enum      || enum is E
 >a6 : E
 >a6 : E
 
-var rg7 = a7 || a6;         // object    || enum is {}
+var rg7 = a7 || a6;         // object    || enum is object | enum
 >rg7 : E | { a: string; }
 >a7 || a6 : E | { a: string; }
 >a7 : { a: string; }
 >a6 : E
 
-var rg8 = a8 || a6;         // array     || enum is {}
+var rg8 = a8 || a6;         // array     || enum is array | enum
 >rg8 : string[] | E
 >a8 || a6 : string[] | E
 >a8 : string[]
@@ -396,31 +396,31 @@ var rh1 = a1 || a7;         // any       || object is any
 >a1 : any
 >a7 : { a: string; }
 
-var rh2 = a2 || a7;         // boolean   || object is {}
+var rh2 = a2 || a7;         // boolean   || object is boolean | object
 >rh2 : boolean | { a: string; }
 >a2 || a7 : boolean | { a: string; }
 >a2 : boolean
 >a7 : { a: string; }
 
-var rh3 = a3 || a7;         // number    || object is {}
+var rh3 = a3 || a7;         // number    || object is number | object
 >rh3 : number | { a: string; }
 >a3 || a7 : number | { a: string; }
 >a3 : number
 >a7 : { a: string; }
 
-var rh4 = a4 || a7;         // string    || object is {}
+var rh4 = a4 || a7;         // string    || object is string | object
 >rh4 : string | { a: string; }
 >a4 || a7 : string | { a: string; }
 >a4 : string
 >a7 : { a: string; }
 
-var rh5 = a5 || a7;         // void      || object is {}
+var rh5 = a5 || a7;         // void      || object is void | object
 >rh5 : void | { a: string; }
 >a5 || a7 : void | { a: string; }
 >a5 : void
 >a7 : { a: string; }
 
-var rh6 = a6 || a7;         // enum      || object is {}
+var rh6 = a6 || a7;         // enum      || object is enum | object
 >rh6 : E | { a: string; }
 >a6 || a7 : E | { a: string; }
 >a6 : E
@@ -432,7 +432,7 @@ var rh7 = a7 || a7;         // object    || object is object
 >a7 : { a: string; }
 >a7 : { a: string; }
 
-var rh8 = a8 || a7;         // array     || object is {}
+var rh8 = a8 || a7;         // array     || object is array | object
 >rh8 : string[] | { a: string; }
 >a8 || a7 : string[] | { a: string; }
 >a8 : string[]
@@ -455,37 +455,37 @@ var ri1 = a1 || a8;         // any       || array is any
 >a1 : any
 >a8 : string[]
 
-var ri2 = a2 || a8;         // boolean   || array is {}
+var ri2 = a2 || a8;         // boolean   || array is boolean | array
 >ri2 : boolean | string[]
 >a2 || a8 : boolean | string[]
 >a2 : boolean
 >a8 : string[]
 
-var ri3 = a3 || a8;         // number    || array is {}
+var ri3 = a3 || a8;         // number    || array is number | array
 >ri3 : number | string[]
 >a3 || a8 : number | string[]
 >a3 : number
 >a8 : string[]
 
-var ri4 = a4 || a8;         // string    || array is {}
+var ri4 = a4 || a8;         // string    || array is string | array
 >ri4 : string | string[]
 >a4 || a8 : string | string[]
 >a4 : string
 >a8 : string[]
 
-var ri5 = a5 || a8;         // void      || array is {}
+var ri5 = a5 || a8;         // void      || array is void | array
 >ri5 : void | string[]
 >a5 || a8 : void | string[]
 >a5 : void
 >a8 : string[]
 
-var ri6 = a6 || a8;         // enum      || array is {}
+var ri6 = a6 || a8;         // enum      || array is enum | array
 >ri6 : string[] | E
 >a6 || a8 : string[] | E
 >a6 : E
 >a8 : string[]
 
-var ri7 = a7 || a8;         // object    || array is {}
+var ri7 = a7 || a8;         // object    || array is object | array
 >ri7 : string[] | { a: string; }
 >a7 || a8 : string[] | { a: string; }
 >a7 : { a: string; }
diff --git a/tests/baselines/reference/moduleIdentifiers.js b/tests/baselines/reference/moduleIdentifiers.js
index e2050d98f5d..04d39019482 100644
--- a/tests/baselines/reference/moduleIdentifiers.js
+++ b/tests/baselines/reference/moduleIdentifiers.js
@@ -18,3 +18,5 @@ var M;
 //var p: M.P;
 //var m: M = M;
 var x1 = M.a;
+//var x2 = m.a;
+//var q: m.P; 
diff --git a/tests/baselines/reference/nullAssignableToEveryType.js b/tests/baselines/reference/nullAssignableToEveryType.js
index 4901f4837bb..9917ebeac9e 100644
--- a/tests/baselines/reference/nullAssignableToEveryType.js
+++ b/tests/baselines/reference/nullAssignableToEveryType.js
@@ -80,3 +80,8 @@ function foo(x, y, z) {
     y = null;
     z = null;
 }
+//function foo<T, U extends T, V extends Date>(x: T, y: U, z: V) {
+//    x = null;
+//    y = null;
+//    z = null;
+//} 
diff --git a/tests/baselines/reference/parserIndexSignature1.errors.txt b/tests/baselines/reference/parserIndexSignature1.errors.txt
index 74f5d0e0921..cde7259c7bd 100644
--- a/tests/baselines/reference/parserIndexSignature1.errors.txt
+++ b/tests/baselines/reference/parserIndexSignature1.errors.txt
@@ -1,9 +1,9 @@
-tests/cases/conformance/parser/ecmascript5/IndexSignatures/parserIndexSignature1.ts(2,7): error TS1017: An index signature cannot have a rest parameter.
+tests/cases/conformance/parser/ecmascript5/IndexSignatures/parserIndexSignature1.ts(2,4): error TS1017: An index signature cannot have a rest parameter.
 
 
 ==== tests/cases/conformance/parser/ecmascript5/IndexSignatures/parserIndexSignature1.ts (1 errors) ====
     interface I {
       [...a]
-          ~
+       ~~~
 !!! error TS1017: An index signature cannot have a rest parameter.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/parserIndexSignature3.errors.txt b/tests/baselines/reference/parserIndexSignature3.errors.txt
index bc552fd6a1d..27310e4d0a4 100644
--- a/tests/baselines/reference/parserIndexSignature3.errors.txt
+++ b/tests/baselines/reference/parserIndexSignature3.errors.txt
@@ -1,9 +1,9 @@
-tests/cases/conformance/parser/ecmascript5/IndexSignatures/parserIndexSignature3.ts(2,4): error TS1019: An index signature parameter cannot have a question mark.
+tests/cases/conformance/parser/ecmascript5/IndexSignatures/parserIndexSignature3.ts(2,5): error TS1019: An index signature parameter cannot have a question mark.
 
 
 ==== tests/cases/conformance/parser/ecmascript5/IndexSignatures/parserIndexSignature3.ts (1 errors) ====
     interface I {
       [a?]
-       ~
+        ~
 !!! error TS1019: An index signature parameter cannot have a question mark.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/parserMemberAccessorDeclaration17.errors.txt b/tests/baselines/reference/parserMemberAccessorDeclaration17.errors.txt
index 6edb9b98b7b..2d7f6e3be30 100644
--- a/tests/baselines/reference/parserMemberAccessorDeclaration17.errors.txt
+++ b/tests/baselines/reference/parserMemberAccessorDeclaration17.errors.txt
@@ -1,9 +1,9 @@
-tests/cases/conformance/parser/ecmascript5/MemberAccessorDeclarations/parserMemberAccessorDeclaration17.ts(2,8): error TS1051: A 'set' accessor cannot have an optional parameter.
+tests/cases/conformance/parser/ecmascript5/MemberAccessorDeclarations/parserMemberAccessorDeclaration17.ts(2,13): error TS1051: A 'set' accessor cannot have an optional parameter.
 
 
 ==== tests/cases/conformance/parser/ecmascript5/MemberAccessorDeclarations/parserMemberAccessorDeclaration17.ts (1 errors) ====
     class C {
        set Foo(a?: number) { }
-           ~~~
+                ~
 !!! error TS1051: A 'set' accessor cannot have an optional parameter.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/parserMemberAccessorDeclaration18.errors.txt b/tests/baselines/reference/parserMemberAccessorDeclaration18.errors.txt
index 54d39a6d663..8296a087bab 100644
--- a/tests/baselines/reference/parserMemberAccessorDeclaration18.errors.txt
+++ b/tests/baselines/reference/parserMemberAccessorDeclaration18.errors.txt
@@ -1,9 +1,9 @@
-tests/cases/conformance/parser/ecmascript5/MemberAccessorDeclarations/parserMemberAccessorDeclaration18.ts(2,8): error TS1053: A 'set' accessor cannot have rest parameter.
+tests/cases/conformance/parser/ecmascript5/MemberAccessorDeclarations/parserMemberAccessorDeclaration18.ts(2,12): error TS1053: A 'set' accessor cannot have rest parameter.
 
 
 ==== tests/cases/conformance/parser/ecmascript5/MemberAccessorDeclarations/parserMemberAccessorDeclaration18.ts (1 errors) ====
     class C {
        set Foo(...a) { }
-           ~~~
+               ~~~
 !!! error TS1053: A 'set' accessor cannot have rest parameter.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/parserParameterList1.errors.txt b/tests/baselines/reference/parserParameterList1.errors.txt
index 3b01ee02168..a7e9a533f63 100644
--- a/tests/baselines/reference/parserParameterList1.errors.txt
+++ b/tests/baselines/reference/parserParameterList1.errors.txt
@@ -1,9 +1,9 @@
-tests/cases/conformance/parser/ecmascript5/ParameterLists/parserParameterList1.ts(2,9): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/parser/ecmascript5/ParameterLists/parserParameterList1.ts(2,6): error TS1014: A rest parameter must be last in a parameter list.
 
 
 ==== tests/cases/conformance/parser/ecmascript5/ParameterLists/parserParameterList1.ts (1 errors) ====
     class C {
        F(...A, B) { }
-            ~
+         ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/parserParameterList11.errors.txt b/tests/baselines/reference/parserParameterList11.errors.txt
index 1fcede6c398..2cb8def201d 100644
--- a/tests/baselines/reference/parserParameterList11.errors.txt
+++ b/tests/baselines/reference/parserParameterList11.errors.txt
@@ -1,7 +1,7 @@
-tests/cases/conformance/parser/ecmascript5/ParameterLists/parserParameterList11.ts(1,5): error TS1047: A rest parameter cannot be optional.
+tests/cases/conformance/parser/ecmascript5/ParameterLists/parserParameterList11.ts(1,8): error TS1047: A rest parameter cannot be optional.
 
 
 ==== tests/cases/conformance/parser/ecmascript5/ParameterLists/parserParameterList11.ts (1 errors) ====
     (...arg?) => 102;
-        ~~~
+           ~
 !!! error TS1047: A rest parameter cannot be optional.
\ No newline at end of file
diff --git a/tests/baselines/reference/parserParameterList9.errors.txt b/tests/baselines/reference/parserParameterList9.errors.txt
index 2db96373cd0..5f670148faa 100644
--- a/tests/baselines/reference/parserParameterList9.errors.txt
+++ b/tests/baselines/reference/parserParameterList9.errors.txt
@@ -1,9 +1,9 @@
-tests/cases/conformance/parser/ecmascript5/ParameterLists/parserParameterList9.ts(2,11): error TS1047: A rest parameter cannot be optional.
+tests/cases/conformance/parser/ecmascript5/ParameterLists/parserParameterList9.ts(2,14): error TS1047: A rest parameter cannot be optional.
 
 
 ==== tests/cases/conformance/parser/ecmascript5/ParameterLists/parserParameterList9.ts (1 errors) ====
     class C {
        foo(...bar?) { }
-              ~~~
+                 ~
 !!! error TS1047: A rest parameter cannot be optional.
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/parserS7.6.1.1_A1.10.js b/tests/baselines/reference/parserS7.6.1.1_A1.10.js
index 04e0076b16a..6465281d88d 100644
--- a/tests/baselines/reference/parserS7.6.1.1_A1.10.js
+++ b/tests/baselines/reference/parserS7.6.1.1_A1.10.js
@@ -17,3 +17,11 @@
 //// [parserS7.6.1.1_A1.10.js]
 // Copyright 2009 the Sputnik authors.  All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
+/**
+ * The "for" token can not be used as identifier
+ *
+ * @path ch07/7.6/7.6.1/7.6.1.1/S7.6.1.1_A1.10.js
+ * @description Checking if execution of "for=1" fails
+ * @negative
+ */
+//for = 1;
diff --git a/tests/baselines/reference/parserSyntaxWalker.generated.js b/tests/baselines/reference/parserSyntaxWalker.generated.js
index 3b78baa0f74..392b5545830 100644
--- a/tests/baselines/reference/parserSyntaxWalker.generated.js
+++ b/tests/baselines/reference/parserSyntaxWalker.generated.js
@@ -289,3 +289,220 @@
 //        [index: number]: string;
 //    }
 //}
+//import fs = module("fs");
+//module TypeScriptAllInOne {
+//    export class Program {
+//        static Main(...args: string[]) {
+//            try {
+//                var bfs = new BasicFeatures();
+//                var retValue: number = 0;
+//                retValue = bfs.VARIABLES();
+//                if (retValue != 0) {
+//                    return 1;
+//                }
+//                retValue = bfs.STATEMENTS(4);
+//                if (retValue != 0) {
+//                    return 1;
+//                }
+//                retValue = bfs.TYPES();
+//                if (retValue != 0) {
+//                    return 1;
+//                }
+//                retValue = bfs.OPERATOR();
+//                if (retValue != 0) {
+//                    return 1;
+//                }
+//            }
+//            catch (e) {
+//                console.log(e);
+//            }
+//            finally {
+//            }
+//            console.log('Done');
+//            return 0;
+//        }
+//    }
+//    class BasicFeatures {
+//        /// <summary>
+//        /// Test various of variables. Including nullable,key world as variable,special format
+//        /// </summary>
+//        /// <returns></returns>
+//        public VARIABLES(): number {
+//            var local = Number.MAX_VALUE;
+//            var min = Number.MIN_VALUE;
+//            var inf = Number.NEGATIVE_INFINITY;
+//            var nan = Number.NaN;
+//            var undef = undefined;
+//            var п = local;
+//            var м = local;
+//            var local5 = <fs.File>null;
+//            var local6 = local5 instanceof fs.File;
+//            var hex = 0xBADC0DE, Hex = 0XDEADBEEF;
+//            var float = 6.02e23, float2 = 6.02E-23
+//            var char = 'c', \u0066 = '\u0066', hexchar = '\x42';
+//            var quoted = '"', quoted2 = "'";
+//            var reg = /\w*/;
+//            var objLit = { "var": number = 42, equals: function (x) { return x["var"] === 42; }, toString: () => 'objLit{42}' };
+//            var weekday = Weekdays.Monday;
+//            var con = char + f + hexchar + float.toString() + float2.toString() + reg.toString() + objLit + weekday;
+//            //
+//            var any = 0;
+//            var boolean = 0;
+//            var declare = 0;
+//            var constructor = 0;
+//            var get = 0;
+//            var implements = 0;
+//            var interface = 0;
+//            var let = 0;
+//            var module = 0;
+//            var number = 0;
+//            var package = 0;
+//            var private = 0;
+//            var protected = 0;
+//            var public = 0;
+//            var set = 0;
+//            var static = 0;
+//            var string = 0;
+//            var yield = 0;
+//            var sum3 = any + boolean + declare + constructor + get + implements + interface + let + module + number + package + private + protected + public + set + static + string + yield;
+//            return 0;
+//        }
+//        /// <summary>
+//        /// Test different statements. Including if-else,swith,foreach,(un)checked,lock,using,try-catch-finally
+//        /// </summary>
+//        /// <param name="i"></param>
+//        /// <returns></returns>
+//        STATEMENTS(i: number): number {
+//            var retVal = 0;
+//            if (i == 1)
+//                retVal = 1;
+//            else
+//                retVal = 0;
+//            switch (i) {
+//                case 2:
+//                    retVal = 1;
+//                    break;
+//                case 3:
+//                    retVal = 1;
+//                    break;
+//                default:
+//                    break;
+//            }
+//            for (var x in { x: 0, y: 1 }) {
+//            }
+//            try {
+//                throw null;
+//            }
+//            catch (Exception) {
+//            }
+//            finally {
+//                try { }
+//                catch (Exception) { }
+//            }
+//            return retVal;
+//        }
+//        /// <summary>
+//        /// Test types in ts language. Including class,struct,interface,delegate,anonymous type
+//        /// </summary>
+//        /// <returns></returns>
+//        public TYPES(): number {
+//            var retVal = 0;
+//            var c = new CLASS();
+//            var xx: IF = c;
+//            retVal += c.Property;
+//            retVal += c.Member();
+//            retVal += xx ^= Foo() ? 0 : 1;
+//            //anonymous type
+//            var anony = { a: new CLASS() };
+//            retVal += anony.a.d();
+//            return retVal;
+//        }
+//        ///// <summary>
+//        ///// Test different operators
+//        ///// </summary>
+//        ///// <returns></returns>
+//        public OPERATOR(): number {
+//            var a: number[] = [1, 2, 3, 4,  implements , ];/*[] bug*/ // YES []
+//            var i = a[1];/*[]*/
+//            i = i + i - i * i / i % i & i | i ^ i;/*+ - * / % & | ^*/
+//            var b = true && false || true ^ false;/*& | ^*/
+//            b = !b;/*!*/
+//            i = ~i;/*~i*/
+//            b = i < (i -  continue ) && (i + 1) > i;/*< && >*/
+//            var f = true ? 1 : 0;/*? :*/   // YES :
+//            i++;/*++*/
+//            i--;/*--*/
+//            b = true && false || true;/*&& ||*/
+//            i = i << 5;/*<<*/
+//            i = i >> 5;/*>>*/
+//            var j = i;
+//            b = i == j && i != j && i <= j && i >= j;/*= == && != <= >=*/
+//            i += <number>5.0;/*+=*/
+//            i -= i;/*-=*/
+//            i *= i;/**=*/
+//            if (i == 0)
+//                i++;
+//            i /= i;/*/=*/
+//            i %= i;/*%=*/
+//            i &= i;/*&=*/
+//            i |= i;/*|=*/
+//            i ^= i;/*^=*/
+//            i <<= i;/*<<=*/
+//            i >>= i;/*>>=*/
+//            if (i == 0 && !b && f == 1)
+//                return 0;
+//            else return 1;
+//        }
+//    }
+//    interface IF {
+//        Foo <!-- ): boolean;
+//    }
+//    class CLASS implements IF {
+//        public d = () =>  '  return 0; };
+//        public get Property() { return 0; }
+//        public Member() {
+//            return 0;
+//        }
+//        public Foo(): boolean {
+//            var myEvent = () => { return 1; };
+//            if (myEvent() == 1)
+//                return true;
+//            else
+//                return false;
+//        }
+//    }
+//    // todo: use these
+//    class A {
+//        public method1(val:number) {
+//            return val;
+//        }
+//        public method2() {
+//            return 2 * this.method1(2);
+//        }
+//    }
+//    class B extends A {
+//        public method2() {
+//            return this.method1(2);
+//        }
+//    }
+//    class Overloading {
+//        private otherValue = 42;
+//        constructor(private value: number, public name: string) { }
+//        public Overloads(value: string);
+//        public Overloads(value: string, ...rest: string[]) { }
+//        public DefaultValue(value?: string = "Hello") { }
+//    }
+//}
+//enum Weekdays {
+//    Monday,
+//    Tuesday,
+//    Weekend,
+//}
+//enum Fruit {
+//    Apple,
+//    Pear
+//}
+//interface IDisposable {
+//    Dispose(): void;
+//}
+//TypeScriptAllInOne.Program.Main();
diff --git a/tests/baselines/reference/recursivelySpecializedConstructorDeclaration.js b/tests/baselines/reference/recursivelySpecializedConstructorDeclaration.js
index 492c9bea3c1..dd8028b086a 100644
--- a/tests/baselines/reference/recursivelySpecializedConstructorDeclaration.js
+++ b/tests/baselines/reference/recursivelySpecializedConstructorDeclaration.js
@@ -62,3 +62,44 @@ var MsPortal;
         })(Base = Controls.Base || (Controls.Base = {}));
     })(Controls = MsPortal.Controls || (MsPortal.Controls = {}));
 })(MsPortal || (MsPortal = {}));
+// Generates:
+/*
+declare module MsPortal.Controls.Base.ItemList {
+    interface Interface<TValue> {
+        options: ViewModel<TValue>;
+    }
+    class ItemValue<T> {
+        constructor(value: T);
+    }
+    class ViewModel<TValue> extends ItemValue<TValue> {
+    }
+}
+module MsPortal.Controls.Base.ItemList {
+
+    export interface Interface<TValue> {
+        // Removing this line fixes the constructor of ItemValue
+        options: ViewModel<TValue>;
+    }    
+
+    export class ItemValue<T> {
+        constructor(value: T) {
+        }
+    }    
+ 
+    export class ViewModel<TValue> extends ItemValue<TValue> {
+    }
+}
+
+// Generates:
+/*
+declare module MsPortal.Controls.Base.ItemList {
+    interface Interface<TValue> {
+        options: ViewModel<TValue>;
+    }
+    class ItemValue<T> {
+        constructor(value: T);
+    }
+    class ViewModel<TValue> extends ItemValue<TValue> {
+    }
+}
+ 
diff --git a/tests/baselines/reference/restParamAsOptional.errors.txt b/tests/baselines/reference/restParamAsOptional.errors.txt
index ac061e5d98e..9ab684f0944 100644
--- a/tests/baselines/reference/restParamAsOptional.errors.txt
+++ b/tests/baselines/reference/restParamAsOptional.errors.txt
@@ -1,10 +1,10 @@
-tests/cases/compiler/restParamAsOptional.ts(1,15): error TS1047: A rest parameter cannot be optional.
+tests/cases/compiler/restParamAsOptional.ts(1,16): error TS1047: A rest parameter cannot be optional.
 tests/cases/compiler/restParamAsOptional.ts(2,16): error TS1048: A rest parameter cannot have an initializer.
 
 
 ==== tests/cases/compiler/restParamAsOptional.ts (2 errors) ====
     function f(...x?) { }
-                  ~
+                   ~
 !!! error TS1047: A rest parameter cannot be optional.
     function f2(...x = []) { }
                    ~
diff --git a/tests/baselines/reference/restParameterNotLast.errors.txt b/tests/baselines/reference/restParameterNotLast.errors.txt
index a5b91d05795..0d69ef154ba 100644
--- a/tests/baselines/reference/restParameterNotLast.errors.txt
+++ b/tests/baselines/reference/restParameterNotLast.errors.txt
@@ -1,7 +1,7 @@
-tests/cases/compiler/restParameterNotLast.ts(1,15): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/compiler/restParameterNotLast.ts(1,12): error TS1014: A rest parameter must be last in a parameter list.
 
 
 ==== tests/cases/compiler/restParameterNotLast.ts (1 errors) ====
     function f(...x, y) { }
-                  ~
+               ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
\ No newline at end of file
diff --git a/tests/baselines/reference/restParameterWithoutAnnotationIsAnyArray.errors.txt b/tests/baselines/reference/restParameterWithoutAnnotationIsAnyArray.errors.txt
index e021204341e..0177f1e9a1c 100644
--- a/tests/baselines/reference/restParameterWithoutAnnotationIsAnyArray.errors.txt
+++ b/tests/baselines/reference/restParameterWithoutAnnotationIsAnyArray.errors.txt
@@ -1,6 +1,6 @@
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParameterWithoutAnnotationIsAnyArray.ts(5,14): error TS1014: A rest parameter must be last in a parameter list.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParameterWithoutAnnotationIsAnyArray.ts(13,12): error TS1014: A rest parameter must be last in a parameter list.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParameterWithoutAnnotationIsAnyArray.ts(23,24): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParameterWithoutAnnotationIsAnyArray.ts(5,11): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParameterWithoutAnnotationIsAnyArray.ts(13,9): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParameterWithoutAnnotationIsAnyArray.ts(23,21): error TS1014: A rest parameter must be last in a parameter list.
 
 
 ==== tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParameterWithoutAnnotationIsAnyArray.ts (3 errors) ====
@@ -9,7 +9,7 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParameterWith
     function foo(...x) { }
     var f = function foo(...x) { }
     var f2 = (...x, ...y) => { }
-                 ~
+              ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
     
     class C {
@@ -19,7 +19,7 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParameterWith
     interface I {
         (...x);
         foo(...x, ...y);
-               ~
+            ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
     }
     
@@ -31,7 +31,7 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParameterWith
     var b = {
         foo(...x) { },
         a: function foo(...x, ...y) { },
-                           ~
+                        ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
         b: (...x) => { }
     }
diff --git a/tests/baselines/reference/restParametersOfNonArrayTypes.errors.txt b/tests/baselines/reference/restParametersOfNonArrayTypes.errors.txt
index 2c7db9973d9..12cbd865d1c 100644
--- a/tests/baselines/reference/restParametersOfNonArrayTypes.errors.txt
+++ b/tests/baselines/reference/restParametersOfNonArrayTypes.errors.txt
@@ -1,6 +1,6 @@
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes.ts(5,14): error TS1014: A rest parameter must be last in a parameter list.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes.ts(13,12): error TS1014: A rest parameter must be last in a parameter list.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes.ts(23,24): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes.ts(5,11): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes.ts(13,9): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes.ts(23,21): error TS1014: A rest parameter must be last in a parameter list.
 tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes.ts(3,14): error TS2370: A rest parameter must be of an array type.
 tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes.ts(4,22): error TS2370: A rest parameter must be of an array type.
 tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes.ts(5,11): error TS2370: A rest parameter must be of an array type.
@@ -27,7 +27,7 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfN
                          ~~~~~~~~~~~~
 !!! error TS2370: A rest parameter must be of an array type.
     var f2 = (...x: Date, ...y: boolean) => { }
-                 ~
+              ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
               ~~~~~~~~~~
 !!! error TS2370: A rest parameter must be of an array type.
@@ -45,7 +45,7 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfN
          ~~~~~~~~~~~~
 !!! error TS2370: A rest parameter must be of an array type.
         foo(...x: number, ...y: number);
-               ~
+            ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
             ~~~~~~~~~~~~
 !!! error TS2370: A rest parameter must be of an array type.
@@ -67,7 +67,7 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfN
             ~~~~~~~~~~~~
 !!! error TS2370: A rest parameter must be of an array type.
         a: function foo(...x: number, ...y: Date) { },
-                           ~
+                        ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
                         ~~~~~~~~~~~~
 !!! error TS2370: A rest parameter must be of an array type.
diff --git a/tests/baselines/reference/restParametersOfNonArrayTypes2.errors.txt b/tests/baselines/reference/restParametersOfNonArrayTypes2.errors.txt
index 592993076fd..eef052e5cdf 100644
--- a/tests/baselines/reference/restParametersOfNonArrayTypes2.errors.txt
+++ b/tests/baselines/reference/restParametersOfNonArrayTypes2.errors.txt
@@ -1,9 +1,9 @@
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes2.ts(9,14): error TS1014: A rest parameter must be last in a parameter list.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes2.ts(17,12): error TS1014: A rest parameter must be last in a parameter list.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes2.ts(27,24): error TS1014: A rest parameter must be last in a parameter list.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes2.ts(36,14): error TS1014: A rest parameter must be last in a parameter list.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes2.ts(44,12): error TS1014: A rest parameter must be last in a parameter list.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes2.ts(54,24): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes2.ts(9,11): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes2.ts(17,9): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes2.ts(27,21): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes2.ts(36,11): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes2.ts(44,9): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes2.ts(54,21): error TS1014: A rest parameter must be last in a parameter list.
 tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes2.ts(7,14): error TS2370: A rest parameter must be of an array type.
 tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes2.ts(8,22): error TS2370: A rest parameter must be of an array type.
 tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfNonArrayTypes2.ts(9,11): error TS2370: A rest parameter must be of an array type.
@@ -48,7 +48,7 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfN
                          ~~~~~~~~~~~~~
 !!! error TS2370: A rest parameter must be of an array type.
     var f2 = (...x: MyThing, ...y: MyThing) => { }
-                 ~
+              ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
               ~~~~~~~~~~~~~
 !!! error TS2370: A rest parameter must be of an array type.
@@ -66,7 +66,7 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfN
          ~~~~~~~~~~~~~
 !!! error TS2370: A rest parameter must be of an array type.
         foo(...x: MyThing, ...y: MyThing);
-               ~
+            ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
             ~~~~~~~~~~~~~
 !!! error TS2370: A rest parameter must be of an array type.
@@ -88,7 +88,7 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfN
             ~~~~~~~~~~~~~
 !!! error TS2370: A rest parameter must be of an array type.
         a: function foo(...x: MyThing, ...y: MyThing) { },
-                           ~
+                        ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
                         ~~~~~~~~~~~~~
 !!! error TS2370: A rest parameter must be of an array type.
@@ -109,7 +109,7 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfN
                           ~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS2370: A rest parameter must be of an array type.
     var f4 = (...x: MyThing2<string>, ...y: MyThing2<string>) => { }
-                 ~
+              ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
               ~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS2370: A rest parameter must be of an array type.
@@ -127,7 +127,7 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfN
          ~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS2370: A rest parameter must be of an array type.
         foo(...x: MyThing2<string>, ...y: MyThing2<string>);
-               ~
+            ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
             ~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS2370: A rest parameter must be of an array type.
@@ -149,7 +149,7 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersOfN
             ~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS2370: A rest parameter must be of an array type.
         a: function foo(...x: MyThing2<string>, ...y: MyThing2<string>) { },
-                           ~
+                        ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
                         ~~~~~~~~~~~~~~~~~~~~~~
 !!! error TS2370: A rest parameter must be of an array type.
diff --git a/tests/baselines/reference/restParametersWithArrayTypeAnnotations.errors.txt b/tests/baselines/reference/restParametersWithArrayTypeAnnotations.errors.txt
index 65afe52efa1..06b2caefb9d 100644
--- a/tests/baselines/reference/restParametersWithArrayTypeAnnotations.errors.txt
+++ b/tests/baselines/reference/restParametersWithArrayTypeAnnotations.errors.txt
@@ -1,9 +1,9 @@
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersWithArrayTypeAnnotations.ts(5,14): error TS1014: A rest parameter must be last in a parameter list.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersWithArrayTypeAnnotations.ts(13,12): error TS1014: A rest parameter must be last in a parameter list.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersWithArrayTypeAnnotations.ts(23,24): error TS1014: A rest parameter must be last in a parameter list.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersWithArrayTypeAnnotations.ts(32,14): error TS1014: A rest parameter must be last in a parameter list.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersWithArrayTypeAnnotations.ts(40,12): error TS1014: A rest parameter must be last in a parameter list.
-tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersWithArrayTypeAnnotations.ts(50,24): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersWithArrayTypeAnnotations.ts(5,11): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersWithArrayTypeAnnotations.ts(13,9): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersWithArrayTypeAnnotations.ts(23,21): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersWithArrayTypeAnnotations.ts(32,11): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersWithArrayTypeAnnotations.ts(40,9): error TS1014: A rest parameter must be last in a parameter list.
+tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersWithArrayTypeAnnotations.ts(50,21): error TS1014: A rest parameter must be last in a parameter list.
 
 
 ==== tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersWithArrayTypeAnnotations.ts (6 errors) ====
@@ -12,7 +12,7 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersWit
     function foo(...x: number[]) { }
     var f = function foo(...x: number[]) { }
     var f2 = (...x: number[], ...y: number[]) => { }
-                 ~
+              ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
     
     class C {
@@ -22,7 +22,7 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersWit
     interface I {
         (...x: number[]);
         foo(...x: number[], ...y: number[]);
-               ~
+            ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
     }
     
@@ -34,7 +34,7 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersWit
     var b = {
         foo(...x: number[]) { },
         a: function foo(...x: number[], ...y: number[]) { },
-                           ~
+                        ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
         b: (...x: number[]) => { }
     }
@@ -45,7 +45,7 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersWit
     function foo2(...x: Array<string>) { }
     var f3 = function foo(...x: Array<string>) { }
     var f4 = (...x: Array<string>, ...y: Array<string>) => { }
-                 ~
+              ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
     
     class C2 {
@@ -55,7 +55,7 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersWit
     interface I2 {
         (...x: Array<string>);
         foo(...x: Array<string>, ...y: Array<string>);
-               ~
+            ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
     }
     
@@ -67,7 +67,7 @@ tests/cases/conformance/types/objectTypeLiteral/callSignatures/restParametersWit
     var b2 = {
         foo(...x: Array<string>) { },
         a: function foo(...x: Array<string>, ...y: Array<string>) { },
-                           ~
+                        ~~~
 !!! error TS1014: A rest parameter must be last in a parameter list.
         b: (...x: Array<string>) => { }
     }
\ No newline at end of file
diff --git a/tests/baselines/reference/sourceMap-Comment1.js b/tests/baselines/reference/sourceMap-Comment1.js
index 38442d279aa..071e54b5716 100644
--- a/tests/baselines/reference/sourceMap-Comment1.js
+++ b/tests/baselines/reference/sourceMap-Comment1.js
@@ -2,4 +2,5 @@
 // Comment
 
 //// [sourceMap-Comment1.js]
+// Comment 
 //# sourceMappingURL=sourceMap-Comment1.js.map
\ No newline at end of file
diff --git a/tests/baselines/reference/sourceMap-Comment1.js.map b/tests/baselines/reference/sourceMap-Comment1.js.map
index b87751ea973..66cd9d65a7d 100644
--- a/tests/baselines/reference/sourceMap-Comment1.js.map
+++ b/tests/baselines/reference/sourceMap-Comment1.js.map
@@ -1,2 +1,2 @@
 //// [sourceMap-Comment1.js.map]
-{"version":3,"file":"sourceMap-Comment1.js","sourceRoot":"","sources":["sourceMap-Comment1.ts"],"names":[],"mappings":""}
\ No newline at end of file
+{"version":3,"file":"sourceMap-Comment1.js","sourceRoot":"","sources":["sourceMap-Comment1.ts"],"names":[],"mappings":"AAAA,UAAU"}
\ No newline at end of file
diff --git a/tests/baselines/reference/sourceMap-Comment1.sourcemap.txt b/tests/baselines/reference/sourceMap-Comment1.sourcemap.txt
index cf774ed7093..4d427d1de89 100644
--- a/tests/baselines/reference/sourceMap-Comment1.sourcemap.txt
+++ b/tests/baselines/reference/sourceMap-Comment1.sourcemap.txt
@@ -4,4 +4,17 @@ mapUrl: sourceMap-Comment1.js.map
 sourceRoot: 
 sources: sourceMap-Comment1.ts
 ===================================================================
+-------------------------------------------------------------------
+emittedFile:tests/cases/compiler/sourceMap-Comment1.js
+sourceFile:sourceMap-Comment1.ts
+-------------------------------------------------------------------
+>>>// Comment 
+1 >
+2 >^^^^^^^^^^
+3 >          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^->
+1 >
+2 >// Comment
+1 >Emitted(1, 1) Source(1, 1) + SourceIndex(0)
+2 >Emitted(1, 11) Source(1, 11) + SourceIndex(0)
+---
 >>>//# sourceMappingURL=sourceMap-Comment1.js.map
\ No newline at end of file
diff --git a/tests/baselines/reference/sourceMapValidationStatements.js.map b/tests/baselines/reference/sourceMapValidationStatements.js.map
index 02b5c0bb806..8eb99944914 100644
--- a/tests/baselines/reference/sourceMapValidationStatements.js.map
+++ b/tests/baselines/reference/sourceMapValidationStatements.js.map
@@ -1,2 +1,2 @@
 //// [sourceMapValidationStatements.js.map]
-{"version":3,"file":"sourceMapValidationStatements.js","sourceRoot":"","sources":["sourceMapValidationStatements.ts"],"names":["f"],"mappings":"AAAA,SAAS,CAAC;IACNA,IAAIA,CAACA,CAACA;IACNA,IAAIA,CAACA,GAAGA,CAACA,CAACA;IACVA,GAAGA,CAACA,CAACA,GAAGA,CAACA,CAACA,GAAGA,CAACA,EAAEA,CAACA,GAAGA,EAAEA,EAAEA,CAACA,EAAEA,EAAEA,CAACA;QAC1BA,CAACA,IAAIA,CAACA,CAACA;QACPA,CAACA,IAAIA,CAACA,CAACA;IACXA,CAACA;IACDA,EAAEA,CAACA,CAACA,CAACA,GAAGA,EAAEA,CAACA,CAACA,CAACA;QACTA,CAACA,IAAIA,CAACA,CAACA;IACXA,CAACA;IAACA,IAAIA,CAACA,CAACA;QACJA,CAACA,IAAIA,EAAEA,CAACA;QACRA,CAACA,EAAEA,CAACA;IACRA,CAACA;IACDA,IAAIA,CAACA,GAAGA;QACJA,CAACA;QACDA,CAACA;QACDA,CAACA;KACJA,CAACA;IACFA,IAAIA,GAAGA,GAAGA;QACNA,CAACA,EAAEA,CAACA;QACJA,CAACA,EAAEA,OAAOA;KACbA,CAACA;IACFA,GAAGA,CAACA,CAACA,GAAGA,CAACA,CAACA,IAAIA,CAACA,CAACA,CAACA,CAACA;QACdA,GAAGA,CAACA,CAACA,GAAGA,CAACA,CAACA,CAACA,CAACA,CAACA;QACbA,IAAIA,CAACA,GAAGA,EAAEA,CAACA;IACfA,CAACA;IACDA,IAAAA,CAACA;QACGA,GAAGA,CAACA,CAACA,GAAGA,MAAMA,CAACA;IACnBA,CAAEA;IAAAA,KAAKA,CAACA,CAACA,CAACA,CAACA,CAATA,CAACA;QACCA,EAAEA,CAACA,CAACA,GAAGA,CAACA,CAACA,GAAGA,EAAEA,CAACA,CAACA,CAACA;YACbA,GAAGA,CAACA,CAACA,GAAGA,EAAEA,CAACA;QACfA,CAACA;QAACA,IAAIA,CAACA,CAACA;YACJA,GAAGA,CAACA,CAACA,GAAGA,KAAKA,CAACA;QAClBA,CAACA;IACLA,CAACA;IACDA,IAAAA,CAACA;QACGA,MAAMA,IAAIA,KAAKA,EAAEA,CAACA;IACtBA,CAAEA;IAAAA,KAAKA,CAACA,CAACA,EAAEA,CAACA,CAAVA,CAACA;QACCA,IAAIA,CAACA,GAAGA,EAAEA,CAACA;IACfA,CAACA;YAACA,CAACA;QACCA,CAACA,GAAGA,EAAEA,CAACA;IACXA,CAACA;IACDA,MAAMA,GAAGA,EAAEA,CAACA;QACRA,CAACA,GAAGA,CAACA,CAACA;QACNA,CAACA,GAAGA,EAAEA,CAACA;IACXA,CAACA;IACDA,MAAMA,CAACA,CAACA,GAAGA,CAACA,CAACA,CAACA,CAACA,CAACA;QACZA,KAAKA,CAACA,EAAEA,CAACA;YACLA,CAACA,EAAEA,CAACA;YACJA,KAAKA,CAACA;QAEVA,CAACA;QACDA,KAAKA,CAACA,EAAEA,CAACA;YACLA,CAACA,EAAEA,CAACA;YACJA,KAAKA,CAACA;QAEVA,CAACA;QACDA,SAASA,CAACA;YACNA,CAACA,IAAIA,CAACA,CAACA;YACPA,CAACA,GAAGA,EAAEA,CAACA;YACPA,KAAKA,CAACA;QAEVA,CAACA;IACLA,CAACA;IACDA,OAAOA,CAACA,GAAGA,EAAEA,EAAEA,CAACA;QACZA,CAACA,EAAEA,CAACA;IACRA,CAACA;IACDA,GAAGA,CAACA;QACAA,CAACA,EAAEA,CAACA;IACRA,CAACA,QAAQA,CAACA,GAAGA,CAACA,EAACA;IACfA,CAACA,GAAGA,CAACA,CAACA;IACNA,IAAIA,CAACA,GAAGA,CAACA,CAACA,IAAIA,CAACA,CAACA,GAAGA,CAACA,GAAGA,CAACA,GAAGA,CAACA,GAAGA,CAACA,CAACA;IACjCA,CAACA,CAACA,IAAIA,CAACA,CAACA,GAAGA,CAACA,GAAGA,CAACA,GAAGA,CAACA,GAAGA,CAACA,CAACA;IACzBA,CAACA,KAAKA,CAACA,CAACA;IACRA,CAACA,GAAGA,CAACA,GAAGA,EAAEA,CAACA;IACXA,IAAIA,CAACA,GAAGA,CAACA,CAACA;IACVA,MAAMA,CAACA;AACXA,CAACA;AACD,IAAI,CAAC,GAAG;IACJ,IAAI,CAAC,GAAG,EAAE,CAAC;IACX,CAAC,GAAG,CAAC,GAAG,CAAC,CAAC;AACd,CAAC,CAAC;AACF,CAAC,EAAE,CAAC"}
\ No newline at end of file
+{"version":3,"file":"sourceMapValidationStatements.js","sourceRoot":"","sources":["sourceMapValidationStatements.ts"],"names":["f"],"mappings":"AAAA,SAAS,CAAC;IACNA,IAAIA,CAACA,CAACA;IACNA,IAAIA,CAACA,GAAGA,CAACA,CAACA;IACVA,GAAGA,CAACA,CAACA,GAAGA,CAACA,CAACA,GAAGA,CAACA,EAAEA,CAACA,GAAGA,EAAEA,EAAEA,CAACA,EAAEA,EAAEA,CAACA;QAC1BA,CAACA,IAAIA,CAACA,CAACA;QACPA,CAACA,IAAIA,CAACA,CAACA;IACXA,CAACA;IACDA,EAAEA,CAACA,CAACA,CAACA,GAAGA,EAAEA,CAACA,CAACA,CAACA;QACTA,CAACA,IAAIA,CAACA,CAACA;IACXA,CAACA;IAACA,IAAIA,CAACA,CAACA;QACJA,CAACA,IAAIA,EAAEA,CAACA;QACRA,CAACA,EAAEA,CAACA;IACRA,CAACA;IACDA,IAAIA,CAACA,GAAGA;QACJA,CAACA;QACDA,CAACA;QACDA,CAACA;KACJA,CAACA;IACFA,IAAIA,GAAGA,GAAGA;QACNA,CAACA,EAAEA,CAACA;QACJA,CAACA,EAAEA,OAAOA;KACbA,CAACA;IACFA,GAAGA,CAACA,CAACA,GAAGA,CAACA,CAACA,IAAIA,CAACA,CAACA,CAACA,CAACA;QACdA,GAAGA,CAACA,CAACA,GAAGA,CAACA,CAACA,CAACA,CAACA,CAACA;QACbA,IAAIA,CAACA,GAAGA,EAAEA,CAACA;IACfA,CAACA;IACDA,IAAAA,CAACA;QACGA,GAAGA,CAACA,CAACA,GAAGA,MAAMA,CAACA;IACnBA,CAAEA;IAAAA,KAAKA,CAACA,CAACA,CAACA,CAACA,CAACA,CAACA;QACTA,EAAEA,CAACA,CAACA,GAAGA,CAACA,CAACA,GAAGA,EAAEA,CAACA,CAACA,CAACA;YACbA,GAAGA,CAACA,CAACA,GAAGA,EAAEA,CAACA;QACfA,CAACA;QAACA,IAAIA,CAACA,CAACA;YACJA,GAAGA,CAACA,CAACA,GAAGA,KAAKA,CAACA;QAClBA,CAACA;IACLA,CAACA;IACDA,IAAAA,CAACA;QACGA,MAAMA,IAAIA,KAAKA,EAAEA,CAACA;IACtBA,CAAEA;IAAAA,KAAKA,CAACA,CAACA,EAAEA,CAACA,CAACA,CAACA;QACVA,IAAIA,CAACA,GAAGA,EAAEA,CAACA;IACfA,CAACA;YAACA,CAACA;QACCA,CAACA,GAAGA,EAAEA,CAACA;IACXA,CAACA;IACDA,MAAMA,GAAGA,EAAEA,CAACA;QACRA,CAACA,GAAGA,CAACA,CAACA;QACNA,CAACA,GAAGA,EAAEA,CAACA;IACXA,CAACA;IACDA,MAAMA,CAACA,CAACA,GAAGA,CAACA,CAACA,CAACA,CAACA,CAACA;QACZA,KAAKA,CAACA,EAAEA,CAACA;YACLA,CAACA,EAAEA,CAACA;YACJA,KAAKA,CAACA;QAEVA,CAACA;QACDA,KAAKA,CAACA,EAAEA,CAACA;YACLA,CAACA,EAAEA,CAACA;YACJA,KAAKA,CAACA;QAEVA,CAACA;QACDA,SAASA,CAACA;YACNA,CAACA,IAAIA,CAACA,CAACA;YACPA,CAACA,GAAGA,EAAEA,CAACA;YACPA,KAAKA,CAACA;QAEVA,CAACA;IACLA,CAACA;IACDA,OAAOA,CAACA,GAAGA,EAAEA,EAAEA,CAACA;QACZA,CAACA,EAAEA,CAACA;IACRA,CAACA;IACDA,GAAGA,CAACA;QACAA,CAACA,EAAEA,CAACA;IACRA,CAACA,QAAQA,CAACA,GAAGA,CAACA,EAACA;IACfA,CAACA,GAAGA,CAACA,CAACA;IACNA,IAAIA,CAACA,GAAGA,CAACA,CAACA,IAAIA,CAACA,CAACA,GAAGA,CAACA,GAAGA,CAACA,GAAGA,CAACA,GAAGA,CAACA,CAACA;IACjCA,CAACA,CAACA,IAAIA,CAACA,CAACA,GAAGA,CAACA,GAAGA,CAACA,GAAGA,CAACA,GAAGA,CAACA,CAACA;IACzBA,CAACA,KAAKA,CAACA,CAACA;IACRA,CAACA,GAAGA,CAACA,GAAGA,EAAEA,CAACA;IACXA,IAAIA,CAACA,GAAGA,CAACA,CAACA;IACVA,MAAMA,CAACA;AACXA,CAACA;AACD,IAAI,CAAC,GAAG;IACJ,IAAI,CAAC,GAAG,EAAE,CAAC;IACX,CAAC,GAAG,CAAC,GAAG,CAAC,CAAC;AACd,CAAC,CAAC;AACF,CAAC,EAAE,CAAC"}
\ No newline at end of file
diff --git a/tests/baselines/reference/sourceMapValidationStatements.sourcemap.txt b/tests/baselines/reference/sourceMapValidationStatements.sourcemap.txt
index 1a288e3a830..ef7aef275c0 100644
--- a/tests/baselines/reference/sourceMapValidationStatements.sourcemap.txt
+++ b/tests/baselines/reference/sourceMapValidationStatements.sourcemap.txt
@@ -557,16 +557,16 @@ sourceFile:sourceMapValidationStatements.ts
 4 >          (
 5 >           e
 6 >            )
-7 >             
-8 >              c
+7 >              
+8 >              {
 1->Emitted(31, 5) Source(29, 7) + SourceIndex(0) name (f)
 2 >Emitted(31, 10) Source(29, 12) + SourceIndex(0) name (f)
 3 >Emitted(31, 11) Source(29, 13) + SourceIndex(0) name (f)
 4 >Emitted(31, 12) Source(29, 14) + SourceIndex(0) name (f)
 5 >Emitted(31, 13) Source(29, 15) + SourceIndex(0) name (f)
 6 >Emitted(31, 14) Source(29, 16) + SourceIndex(0) name (f)
-7 >Emitted(31, 15) Source(29, 7) + SourceIndex(0) name (f)
-8 >Emitted(31, 16) Source(29, 8) + SourceIndex(0) name (f)
+7 >Emitted(31, 15) Source(29, 17) + SourceIndex(0) name (f)
+8 >Emitted(31, 16) Source(29, 18) + SourceIndex(0) name (f)
 ---
 >>>        if (obj.z < 10) {
 1->^^^^^^^^
@@ -581,7 +581,7 @@ sourceFile:sourceMapValidationStatements.ts
 10>                      ^
 11>                       ^
 12>                        ^
-1->atch (e) {
+1->
   >        
 2 >        if
 3 >           
@@ -759,16 +759,16 @@ sourceFile:sourceMapValidationStatements.ts
 4 >          (
 5 >           e1
 6 >             )
-7 >              
-8 >               c
+7 >               
+8 >               {
 1->Emitted(42, 5) Source(38, 7) + SourceIndex(0) name (f)
 2 >Emitted(42, 10) Source(38, 12) + SourceIndex(0) name (f)
 3 >Emitted(42, 11) Source(38, 13) + SourceIndex(0) name (f)
 4 >Emitted(42, 12) Source(38, 14) + SourceIndex(0) name (f)
 5 >Emitted(42, 14) Source(38, 16) + SourceIndex(0) name (f)
 6 >Emitted(42, 15) Source(38, 17) + SourceIndex(0) name (f)
-7 >Emitted(42, 16) Source(38, 7) + SourceIndex(0) name (f)
-8 >Emitted(42, 17) Source(38, 8) + SourceIndex(0) name (f)
+7 >Emitted(42, 16) Source(38, 18) + SourceIndex(0) name (f)
+8 >Emitted(42, 17) Source(38, 19) + SourceIndex(0) name (f)
 ---
 >>>        var b = e1;
 1->^^^^^^^^
@@ -777,7 +777,7 @@ sourceFile:sourceMapValidationStatements.ts
 4 >             ^^^
 5 >                ^^
 6 >                  ^
-1->atch (e1) {
+1->
   >        
 2 >        var 
 3 >            b
diff --git a/tests/baselines/reference/sourceMapValidationTryCatchFinally.js.map b/tests/baselines/reference/sourceMapValidationTryCatchFinally.js.map
index 24b7b84a3d0..89716807538 100644
--- a/tests/baselines/reference/sourceMapValidationTryCatchFinally.js.map
+++ b/tests/baselines/reference/sourceMapValidationTryCatchFinally.js.map
@@ -1,2 +1,2 @@
 //// [sourceMapValidationTryCatchFinally.js.map]
-{"version":3,"file":"sourceMapValidationTryCatchFinally.js","sourceRoot":"","sources":["sourceMapValidationTryCatchFinally.ts"],"names":[],"mappings":"AAAA,IAAI,CAAC,GAAG,EAAE,CAAC;AACX,IAAA,CAAC;IACG,CAAC,GAAG,CAAC,GAAG,CAAC,CAAC;AACd,CAAE;AAAA,KAAK,CAAC,CAAC,CAAC,CAAC,CAAT,CAAC;IACC,CAAC,GAAG,CAAC,GAAG,CAAC,CAAC;AACd,CAAC;QAAC,CAAC;IACC,CAAC,GAAG,CAAC,GAAG,EAAE,CAAC;AACf,CAAC;AACD,IAAA,CAAC;IAEG,CAAC,GAAG,CAAC,GAAG,CAAC,CAAC;IACV,MAAM,IAAI,KAAK,EAAE,CAAC;AACtB,CACA;AAAA,KAAK,CAAC,CAAC,CAAC,CAAC,CAAT,CAAC;IAEG,CAAC,GAAG,CAAC,GAAG,CAAC,CAAC;AACd,CAAC;QACD,CAAC;IAEG,CAAC,GAAG,CAAC,GAAG,EAAE,CAAC;AACf,CAAC"}
\ No newline at end of file
+{"version":3,"file":"sourceMapValidationTryCatchFinally.js","sourceRoot":"","sources":["sourceMapValidationTryCatchFinally.ts"],"names":[],"mappings":"AAAA,IAAI,CAAC,GAAG,EAAE,CAAC;AACX,IAAA,CAAC;IACG,CAAC,GAAG,CAAC,GAAG,CAAC,CAAC;AACd,CAAE;AAAA,KAAK,CAAC,CAAC,CAAC,CAAC,CAAC,CAAC;IACT,CAAC,GAAG,CAAC,GAAG,CAAC,CAAC;AACd,CAAC;QAAC,CAAC;IACC,CAAC,GAAG,CAAC,GAAG,EAAE,CAAC;AACf,CAAC;AACD,IAAA,CAAC;IAEG,CAAC,GAAG,CAAC,GAAG,CAAC,CAAC;IACV,MAAM,IAAI,KAAK,EAAE,CAAC;AACtB,CACA;AAAA,KAAK,CAAC,CAAC,CAAC,CAAC,CACT,CAAC;IACG,CAAC,GAAG,CAAC,GAAG,CAAC,CAAC;AACd,CAAC;QACD,CAAC;IAEG,CAAC,GAAG,CAAC,GAAG,EAAE,CAAC;AACf,CAAC"}
\ No newline at end of file
diff --git a/tests/baselines/reference/sourceMapValidationTryCatchFinally.sourcemap.txt b/tests/baselines/reference/sourceMapValidationTryCatchFinally.sourcemap.txt
index aa0b846ece8..25dee4fbc45 100644
--- a/tests/baselines/reference/sourceMapValidationTryCatchFinally.sourcemap.txt
+++ b/tests/baselines/reference/sourceMapValidationTryCatchFinally.sourcemap.txt
@@ -91,16 +91,16 @@ sourceFile:sourceMapValidationTryCatchFinally.ts
 4 >      (
 5 >       e
 6 >        )
-7 >         
-8 >          c
+7 >          
+8 >          {
 1->Emitted(5, 1) Source(4, 3) + SourceIndex(0)
 2 >Emitted(5, 6) Source(4, 8) + SourceIndex(0)
 3 >Emitted(5, 7) Source(4, 9) + SourceIndex(0)
 4 >Emitted(5, 8) Source(4, 10) + SourceIndex(0)
 5 >Emitted(5, 9) Source(4, 11) + SourceIndex(0)
 6 >Emitted(5, 10) Source(4, 12) + SourceIndex(0)
-7 >Emitted(5, 11) Source(4, 3) + SourceIndex(0)
-8 >Emitted(5, 12) Source(4, 4) + SourceIndex(0)
+7 >Emitted(5, 11) Source(4, 13) + SourceIndex(0)
+8 >Emitted(5, 12) Source(4, 14) + SourceIndex(0)
 ---
 >>>    x = x - 1;
 1->^^^^
@@ -110,7 +110,7 @@ sourceFile:sourceMapValidationTryCatchFinally.ts
 5 >         ^^^
 6 >            ^
 7 >             ^
-1->atch (e) {
+1->
   >    
 2 >    x
 3 >      = 
@@ -266,16 +266,17 @@ sourceFile:sourceMapValidationTryCatchFinally.ts
 4 >      (
 5 >       e
 6 >        )
-7 >         
-8 >          c
+7 >         
+  >         
+8 >          {
 1->Emitted(15, 1) Source(14, 1) + SourceIndex(0)
 2 >Emitted(15, 6) Source(14, 6) + SourceIndex(0)
 3 >Emitted(15, 7) Source(14, 7) + SourceIndex(0)
 4 >Emitted(15, 8) Source(14, 8) + SourceIndex(0)
 5 >Emitted(15, 9) Source(14, 9) + SourceIndex(0)
 6 >Emitted(15, 10) Source(14, 10) + SourceIndex(0)
-7 >Emitted(15, 11) Source(14, 1) + SourceIndex(0)
-8 >Emitted(15, 12) Source(14, 2) + SourceIndex(0)
+7 >Emitted(15, 11) Source(15, 1) + SourceIndex(0)
+8 >Emitted(15, 12) Source(15, 2) + SourceIndex(0)
 ---
 >>>    x = x - 1;
 1->^^^^
@@ -285,8 +286,7 @@ sourceFile:sourceMapValidationTryCatchFinally.ts
 5 >         ^^^
 6 >            ^
 7 >             ^
-1->atch (e)
-  >{
+1->
   >    
 2 >    x
 3 >      = 
diff --git a/tests/baselines/reference/subtypesOfUnion.errors.txt b/tests/baselines/reference/subtypesOfUnion.errors.txt
new file mode 100644
index 00000000000..fade5377814
--- /dev/null
+++ b/tests/baselines/reference/subtypesOfUnion.errors.txt
@@ -0,0 +1,142 @@
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(16,5): error TS2411: Property 'foo4' of type 'boolean' is not assignable to string index type 'string | number'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(18,5): error TS2411: Property 'foo6' of type 'Date' is not assignable to string index type 'string | number'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(19,5): error TS2411: Property 'foo7' of type 'RegExp' is not assignable to string index type 'string | number'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(20,5): error TS2411: Property 'foo8' of type '{ bar: number; }' is not assignable to string index type 'string | number'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(21,5): error TS2411: Property 'foo9' of type 'I8' is not assignable to string index type 'string | number'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(22,5): error TS2411: Property 'foo10' of type 'A' is not assignable to string index type 'string | number'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(23,5): error TS2411: Property 'foo11' of type 'A2<number>' is not assignable to string index type 'string | number'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(24,5): error TS2411: Property 'foo12' of type '(x: any) => number' is not assignable to string index type 'string | number'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(25,5): error TS2411: Property 'foo13' of type '<T>(x: T) => T' is not assignable to string index type 'string | number'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(26,5): error TS2411: Property 'foo14' of type 'typeof f' is not assignable to string index type 'string | number'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(27,5): error TS2411: Property 'foo15' of type 'typeof c' is not assignable to string index type 'string | number'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(28,5): error TS2411: Property 'foo16' of type 'T' is not assignable to string index type 'string | number'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(29,5): error TS2411: Property 'foo17' of type 'Object' is not assignable to string index type 'string | number'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(30,5): error TS2411: Property 'foo18' of type '{}' is not assignable to string index type 'string | number'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(35,5): error TS2411: Property 'foo2' of type 'string' is not assignable to string index type 'number | E'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(37,5): error TS2411: Property 'foo4' of type 'boolean' is not assignable to string index type 'number | E'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(39,5): error TS2411: Property 'foo6' of type 'Date' is not assignable to string index type 'number | E'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(40,5): error TS2411: Property 'foo7' of type 'RegExp' is not assignable to string index type 'number | E'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(41,5): error TS2411: Property 'foo8' of type '{ bar: number; }' is not assignable to string index type 'number | E'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(42,5): error TS2411: Property 'foo9' of type 'I8' is not assignable to string index type 'number | E'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(43,5): error TS2411: Property 'foo10' of type 'A' is not assignable to string index type 'number | E'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(44,5): error TS2411: Property 'foo11' of type 'A2<number>' is not assignable to string index type 'number | E'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(45,5): error TS2411: Property 'foo12' of type '(x: any) => number' is not assignable to string index type 'number | E'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(46,5): error TS2411: Property 'foo13' of type '<T>(x: T) => T' is not assignable to string index type 'number | E'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(47,5): error TS2411: Property 'foo14' of type 'typeof f' is not assignable to string index type 'number | E'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(48,5): error TS2411: Property 'foo15' of type 'typeof c' is not assignable to string index type 'number | E'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(49,5): error TS2411: Property 'foo16' of type 'T' is not assignable to string index type 'number | E'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(50,5): error TS2411: Property 'foo17' of type 'Object' is not assignable to string index type 'number | E'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts(51,5): error TS2411: Property 'foo18' of type '{}' is not assignable to string index type 'number | E'.
+
+
+==== tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts (29 errors) ====
+    enum E { e1, e2 }
+    interface I8 { [x: string]: number[]; }
+    class A { foo: number; }
+    class A2<T> { foo: T; }
+    function f() { }
+    module f { export var bar = 1; }
+    class c { baz: string }
+    module c { export var bar = 1; }
+    
+    // A type T is a subtype of a union type U if T is a subtype of any type in U.
+    interface I1<T> {
+        [x: string]: string | number;
+        foo: any; // ok
+        foo2: string; // ok
+        foo3: number; // ok
+        foo4: boolean; // error 
+        ~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo4' of type 'boolean' is not assignable to string index type 'string | number'.
+        foo5: E; // ok - subtype of number 
+        foo6: Date; // error
+        ~~~~~~~~~~~
+!!! error TS2411: Property 'foo6' of type 'Date' is not assignable to string index type 'string | number'.
+        foo7: RegExp; // error
+        ~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo7' of type 'RegExp' is not assignable to string index type 'string | number'.
+        foo8: { bar: number }; // error
+        ~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo8' of type '{ bar: number; }' is not assignable to string index type 'string | number'.
+        foo9: I8; // error
+        ~~~~~~~~~
+!!! error TS2411: Property 'foo9' of type 'I8' is not assignable to string index type 'string | number'.
+        foo10: A; // error
+        ~~~~~~~~~
+!!! error TS2411: Property 'foo10' of type 'A' is not assignable to string index type 'string | number'.
+        foo11: A2<number>; // error
+        ~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo11' of type 'A2<number>' is not assignable to string index type 'string | number'.
+        foo12: (x) => number; //error
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo12' of type '(x: any) => number' is not assignable to string index type 'string | number'.
+        foo13: <T>(x: T) => T; // error
+        ~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo13' of type '<T>(x: T) => T' is not assignable to string index type 'string | number'.
+        foo14: typeof f; // error
+        ~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo14' of type 'typeof f' is not assignable to string index type 'string | number'.
+        foo15: typeof c; // error
+        ~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo15' of type 'typeof c' is not assignable to string index type 'string | number'.
+        foo16: T; // error
+        ~~~~~~~~~
+!!! error TS2411: Property 'foo16' of type 'T' is not assignable to string index type 'string | number'.
+        foo17: Object; // error
+        ~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo17' of type 'Object' is not assignable to string index type 'string | number'.
+        foo18: {}; // error
+        ~~~~~~~~~~
+!!! error TS2411: Property 'foo18' of type '{}' is not assignable to string index type 'string | number'.
+    }
+    interface I2<T> {
+        [x: string]: E | number;
+        foo: any; // ok
+        foo2: string; // error
+        ~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo2' of type 'string' is not assignable to string index type 'number | E'.
+        foo3: number; // ok
+        foo4: boolean; // error 
+        ~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo4' of type 'boolean' is not assignable to string index type 'number | E'.
+        foo5: E; // ok
+        foo6: Date; // error
+        ~~~~~~~~~~~
+!!! error TS2411: Property 'foo6' of type 'Date' is not assignable to string index type 'number | E'.
+        foo7: RegExp; // error
+        ~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo7' of type 'RegExp' is not assignable to string index type 'number | E'.
+        foo8: { bar: number }; // error
+        ~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo8' of type '{ bar: number; }' is not assignable to string index type 'number | E'.
+        foo9: I8; // error
+        ~~~~~~~~~
+!!! error TS2411: Property 'foo9' of type 'I8' is not assignable to string index type 'number | E'.
+        foo10: A; // error
+        ~~~~~~~~~
+!!! error TS2411: Property 'foo10' of type 'A' is not assignable to string index type 'number | E'.
+        foo11: A2<number>; // error
+        ~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo11' of type 'A2<number>' is not assignable to string index type 'number | E'.
+        foo12: (x) => number; //error
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo12' of type '(x: any) => number' is not assignable to string index type 'number | E'.
+        foo13: <T>(x: T) => T; // error
+        ~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo13' of type '<T>(x: T) => T' is not assignable to string index type 'number | E'.
+        foo14: typeof f; // error
+        ~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo14' of type 'typeof f' is not assignable to string index type 'number | E'.
+        foo15: typeof c; // error
+        ~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo15' of type 'typeof c' is not assignable to string index type 'number | E'.
+        foo16: T; // error
+        ~~~~~~~~~
+!!! error TS2411: Property 'foo16' of type 'T' is not assignable to string index type 'number | E'.
+        foo17: Object; // error
+        ~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo17' of type 'Object' is not assignable to string index type 'number | E'.
+        foo18: {}; // error
+        ~~~~~~~~~~
+!!! error TS2411: Property 'foo18' of type '{}' is not assignable to string index type 'number | E'.
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/subtypesOfUnion.js b/tests/baselines/reference/subtypesOfUnion.js
new file mode 100644
index 00000000000..a18ebb944b9
--- /dev/null
+++ b/tests/baselines/reference/subtypesOfUnion.js
@@ -0,0 +1,85 @@
+//// [subtypesOfUnion.ts]
+enum E { e1, e2 }
+interface I8 { [x: string]: number[]; }
+class A { foo: number; }
+class A2<T> { foo: T; }
+function f() { }
+module f { export var bar = 1; }
+class c { baz: string }
+module c { export var bar = 1; }
+
+// A type T is a subtype of a union type U if T is a subtype of any type in U.
+interface I1<T> {
+    [x: string]: string | number;
+    foo: any; // ok
+    foo2: string; // ok
+    foo3: number; // ok
+    foo4: boolean; // error 
+    foo5: E; // ok - subtype of number 
+    foo6: Date; // error
+    foo7: RegExp; // error
+    foo8: { bar: number }; // error
+    foo9: I8; // error
+    foo10: A; // error
+    foo11: A2<number>; // error
+    foo12: (x) => number; //error
+    foo13: <T>(x: T) => T; // error
+    foo14: typeof f; // error
+    foo15: typeof c; // error
+    foo16: T; // error
+    foo17: Object; // error
+    foo18: {}; // error
+}
+interface I2<T> {
+    [x: string]: E | number;
+    foo: any; // ok
+    foo2: string; // error
+    foo3: number; // ok
+    foo4: boolean; // error 
+    foo5: E; // ok
+    foo6: Date; // error
+    foo7: RegExp; // error
+    foo8: { bar: number }; // error
+    foo9: I8; // error
+    foo10: A; // error
+    foo11: A2<number>; // error
+    foo12: (x) => number; //error
+    foo13: <T>(x: T) => T; // error
+    foo14: typeof f; // error
+    foo15: typeof c; // error
+    foo16: T; // error
+    foo17: Object; // error
+    foo18: {}; // error
+}
+
+//// [subtypesOfUnion.js]
+var E;
+(function (E) {
+    E[E["e1"] = 0] = "e1";
+    E[E["e2"] = 1] = "e2";
+})(E || (E = {}));
+var A = (function () {
+    function A() {
+    }
+    return A;
+})();
+var A2 = (function () {
+    function A2() {
+    }
+    return A2;
+})();
+function f() {
+}
+var f;
+(function (f) {
+    f.bar = 1;
+})(f || (f = {}));
+var c = (function () {
+    function c() {
+    }
+    return c;
+})();
+var c;
+(function (c) {
+    c.bar = 1;
+})(c || (c = {}));
diff --git a/tests/baselines/reference/typeParameterAsTypeArgument.js b/tests/baselines/reference/typeParameterAsTypeArgument.js
index ab88221c312..cc9bd485852 100644
--- a/tests/baselines/reference/typeParameterAsTypeArgument.js
+++ b/tests/baselines/reference/typeParameterAsTypeArgument.js
@@ -39,3 +39,13 @@ var C = (function () {
     }
     return C;
 })();
+//function foo<T, U extends T>(x: T, y: U) {
+//    foo<U, U>(y, y);
+//    return new C<U, T>();
+//}
+//class C<T extends U, U> {
+//    x: T;
+//}
+//interface I<T, U extends T> {
+//    x: C<U, T>;
+//}
diff --git a/tests/baselines/reference/typeParameterUsedAsTypeParameterConstraint3.js b/tests/baselines/reference/typeParameterUsedAsTypeParameterConstraint3.js
index 1ce6304d3b9..95c65d5f3a9 100644
--- a/tests/baselines/reference/typeParameterUsedAsTypeParameterConstraint3.js
+++ b/tests/baselines/reference/typeParameterUsedAsTypeParameterConstraint3.js
@@ -53,3 +53,15 @@ interface I2<V, T, U> {
 //// [typeParameterUsedAsTypeParameterConstraint3.js]
 // Type parameters are in scope in their own and other type parameter lists
 // Object types
+//interface I < T, U extends T, V extends U > {
+//    x: T;
+//    y: U;
+//    z: V;
+//    foo<W extends V>(x: W): T;
+//}
+//interface I2<V extends U, T, U extends T> {
+//    x: T;
+//    y: U;
+//    z: V;
+//    foo<W extends V>(x: W): T;
+//} 
diff --git a/tests/baselines/reference/undefinedAssignableToEveryType.js b/tests/baselines/reference/undefinedAssignableToEveryType.js
index c3ed6d679dd..08e1c4f1070 100644
--- a/tests/baselines/reference/undefinedAssignableToEveryType.js
+++ b/tests/baselines/reference/undefinedAssignableToEveryType.js
@@ -79,3 +79,8 @@ function foo(x, y, z) {
     y = undefined;
     z = undefined;
 }
+//function foo<T, U extends T, V extends Date>(x: T, y: U, z: V) {
+//    x = undefined;
+//    y = undefined;
+//    z = undefined;
+//} 
diff --git a/tests/baselines/reference/unionSubtypeIfEveryConstituentTypeIsSubtype.errors.txt b/tests/baselines/reference/unionSubtypeIfEveryConstituentTypeIsSubtype.errors.txt
new file mode 100644
index 00000000000..013b5d9a990
--- /dev/null
+++ b/tests/baselines/reference/unionSubtypeIfEveryConstituentTypeIsSubtype.errors.txt
@@ -0,0 +1,239 @@
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(15,5): error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'number'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(21,5): error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'string'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(22,5): error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'string'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(28,5): error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'boolean'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(29,5): error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'boolean'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(35,5): error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'Date'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(36,5): error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'Date'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(42,5): error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'RegExp'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(43,5): error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'RegExp'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(49,5): error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type '{ bar: number; }'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(50,5): error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type '{ bar: number; }'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(56,5): error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'number[]'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(57,5): error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'number[]'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(63,5): error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'I8'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(64,5): error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'I8'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(70,5): error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'A'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(71,5): error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'A'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(77,5): error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'A2<number>'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(78,5): error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'A2<number>'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(84,5): error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type '(x: any) => number'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(85,5): error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type '(x: any) => number'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(91,5): error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type '<T>(x: T) => T'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(92,5): error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type '<T>(x: T) => T'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(99,5): error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'E2'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(100,5): error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'E2'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(110,5): error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'typeof f'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(111,5): error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'typeof f'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(121,5): error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'typeof c'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(122,5): error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'typeof c'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(128,5): error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'T'.
+tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts(129,5): error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'T'.
+
+
+==== tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts (31 errors) ====
+    enum e {
+        e1,
+        e2
+    }
+    
+    // A union type U is a subtype of a type T if each type in U is a subtype of T
+    interface I {
+        [x: string]: any;
+        foo: string | number; // ok
+        foo2: e | number; // ok
+    }
+    interface I2 {
+        [x: string]: number;
+        // S is union type and each constituent type of S is a subtype of T
+        foo: string | number; // error string is not subtype of number
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'number'.
+        foo2: e | number; // ok e and number both subtype of number
+    }
+    
+    interface I3 {
+        [x: string]: string;
+        foo: string | number; // error numer is not subtype of string
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'string'.
+        foo2: e | number; // error e and number both not subtype of string
+        ~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'string'.
+    }
+    
+    // error cases
+    interface I4 {
+        [x: string]: boolean;
+        foo: string | number;
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'boolean'.
+        foo2: e | number;
+        ~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'boolean'.
+    }
+    
+    
+    interface I5 {
+        [x: string]: Date;
+        foo: string | number;
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'Date'.
+        foo2: e | number;
+        ~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'Date'.
+    }
+    
+    
+    interface I6 {
+        [x: string]: RegExp;
+        foo: string | number;
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'RegExp'.
+        foo2: e | number;
+        ~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'RegExp'.
+    }
+    
+    
+    interface I7 {
+        [x: string]: { bar: number };
+        foo: string | number;
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type '{ bar: number; }'.
+        foo2: e | number;
+        ~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type '{ bar: number; }'.
+    }
+    
+    
+    interface I8 {
+        [x: string]: number[];
+        foo: string | number;
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'number[]'.
+        foo2: e | number;
+        ~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'number[]'.
+    }
+    
+    
+    interface I9 {
+        [x: string]: I8;
+        foo: string | number;
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'I8'.
+        foo2: e | number;
+        ~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'I8'.
+    }
+    
+    class A { foo: number; }
+    interface I10 {
+        [x: string]: A;
+        foo: string | number;
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'A'.
+        foo2: e | number;
+        ~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'A'.
+    }
+    
+    class A2<T> { foo: T; }
+    interface I11 {
+        [x: string]: A2<number>;
+        foo: string | number;
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'A2<number>'.
+        foo2: e | number;
+        ~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'A2<number>'.
+    }
+    
+    
+    interface I12 {
+        [x: string]: (x) => number;
+        foo: string | number;
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type '(x: any) => number'.
+        foo2: e | number;
+        ~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type '(x: any) => number'.
+    }
+    
+    
+    interface I13 {
+        [x: string]: <T>(x: T) => T;
+        foo: string | number;
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type '<T>(x: T) => T'.
+        foo2: e | number;
+        ~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type '<T>(x: T) => T'.
+    }
+    
+    
+    enum E2 { A }
+    interface I14 {
+        [x: string]: E2;
+        foo: string | number;
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'E2'.
+        foo2: e | number;
+        ~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'E2'.
+    }
+    
+    
+    function f() { }
+    module f {
+        export var bar = 1;
+    }
+    interface I15 {
+        [x: string]: typeof f;
+        foo: string | number;
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'typeof f'.
+        foo2: e | number;
+        ~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'typeof f'.
+    }
+    
+    
+    class c { baz: string }
+    module c {
+        export var bar = 1;
+    }
+    interface I16 {
+        [x: string]: typeof c;
+        foo: string | number;
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'typeof c'.
+        foo2: e | number;
+        ~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'typeof c'.
+    }
+    
+    
+    interface I17<T> {
+        [x: string]: T;
+        foo: string | number;
+        ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo' of type 'string | number' is not assignable to string index type 'T'.
+        foo2: e | number;
+        ~~~~~~~~~~~~~~~~~
+!!! error TS2411: Property 'foo2' of type 'number | e' is not assignable to string index type 'T'.
+    }
+    
+    interface I19 {
+        [x: string]: Object;
+        foo: string | number;
+        foo2: e | number;
+    }
+    
+    
+    interface I20 {
+        [x: string]: {};
+        foo: string | number;
+        foo2: e | number;
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/unionSubtypeIfEveryConstituentTypeIsSubtype.js b/tests/baselines/reference/unionSubtypeIfEveryConstituentTypeIsSubtype.js
new file mode 100644
index 00000000000..0c9ffeb5653
--- /dev/null
+++ b/tests/baselines/reference/unionSubtypeIfEveryConstituentTypeIsSubtype.js
@@ -0,0 +1,180 @@
+//// [unionSubtypeIfEveryConstituentTypeIsSubtype.ts]
+enum e {
+    e1,
+    e2
+}
+
+// A union type U is a subtype of a type T if each type in U is a subtype of T
+interface I {
+    [x: string]: any;
+    foo: string | number; // ok
+    foo2: e | number; // ok
+}
+interface I2 {
+    [x: string]: number;
+    // S is union type and each constituent type of S is a subtype of T
+    foo: string | number; // error string is not subtype of number
+    foo2: e | number; // ok e and number both subtype of number
+}
+
+interface I3 {
+    [x: string]: string;
+    foo: string | number; // error numer is not subtype of string
+    foo2: e | number; // error e and number both not subtype of string
+}
+
+// error cases
+interface I4 {
+    [x: string]: boolean;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+interface I5 {
+    [x: string]: Date;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+interface I6 {
+    [x: string]: RegExp;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+interface I7 {
+    [x: string]: { bar: number };
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+interface I8 {
+    [x: string]: number[];
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+interface I9 {
+    [x: string]: I8;
+    foo: string | number;
+    foo2: e | number;
+}
+
+class A { foo: number; }
+interface I10 {
+    [x: string]: A;
+    foo: string | number;
+    foo2: e | number;
+}
+
+class A2<T> { foo: T; }
+interface I11 {
+    [x: string]: A2<number>;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+interface I12 {
+    [x: string]: (x) => number;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+interface I13 {
+    [x: string]: <T>(x: T) => T;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+enum E2 { A }
+interface I14 {
+    [x: string]: E2;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+function f() { }
+module f {
+    export var bar = 1;
+}
+interface I15 {
+    [x: string]: typeof f;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+class c { baz: string }
+module c {
+    export var bar = 1;
+}
+interface I16 {
+    [x: string]: typeof c;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+interface I17<T> {
+    [x: string]: T;
+    foo: string | number;
+    foo2: e | number;
+}
+
+interface I19 {
+    [x: string]: Object;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+interface I20 {
+    [x: string]: {};
+    foo: string | number;
+    foo2: e | number;
+}
+
+//// [unionSubtypeIfEveryConstituentTypeIsSubtype.js]
+var e;
+(function (e) {
+    e[e["e1"] = 0] = "e1";
+    e[e["e2"] = 1] = "e2";
+})(e || (e = {}));
+var A = (function () {
+    function A() {
+    }
+    return A;
+})();
+var A2 = (function () {
+    function A2() {
+    }
+    return A2;
+})();
+var E2;
+(function (E2) {
+    E2[E2["A"] = 0] = "A";
+})(E2 || (E2 = {}));
+function f() {
+}
+var f;
+(function (f) {
+    f.bar = 1;
+})(f || (f = {}));
+var c = (function () {
+    function c() {
+    }
+    return c;
+})();
+var c;
+(function (c) {
+    c.bar = 1;
+})(c || (c = {}));
diff --git a/tests/baselines/reference/unionTypeCallSignatures.errors.txt b/tests/baselines/reference/unionTypeCallSignatures.errors.txt
new file mode 100644
index 00000000000..313cd477187
--- /dev/null
+++ b/tests/baselines/reference/unionTypeCallSignatures.errors.txt
@@ -0,0 +1,178 @@
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(9,43): error TS2345: Argument of type 'string' is not assignable to parameter of type 'number'.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(10,29): error TS2345: Argument of type 'boolean' is not assignable to parameter of type 'string'.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(15,29): error TS2345: Argument of type 'boolean' is not assignable to parameter of type 'string'.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(16,1): error TS2346: Supplied parameters do not match any signature of call target.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(19,1): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(20,1): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(21,1): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(24,1): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(25,1): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(26,1): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(29,1): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(30,1): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(31,1): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(36,49): error TS2345: Argument of type 'string' is not assignable to parameter of type 'number'.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(37,12): error TS2346: Supplied parameters do not match any signature of call target.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(40,12): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(41,12): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(42,12): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(43,12): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(46,12): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(47,12): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(48,12): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(49,12): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(55,45): error TS2345: Argument of type 'string' is not assignable to parameter of type 'number'.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(56,12): error TS2346: Supplied parameters do not match any signature of call target.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(59,12): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(60,12): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(61,12): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(62,12): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(63,12): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(66,12): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(67,12): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(68,12): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(69,12): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeCallSignatures.ts(70,12): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+
+
+==== tests/cases/conformance/types/union/unionTypeCallSignatures.ts (35 errors) ====
+    var numOrDate: number | Date;
+    var strOrBoolean: string | boolean;
+    var strOrNum: string | number;
+    
+    // If each type in U has call signatures and the sets of call signatures are identical ignoring return types, 
+    // U has the same set of call signatures, but with return types that are unions of the return types of the respective call signatures from each type in U.
+    var unionOfDifferentReturnType: { (a: number): number; } | { (a: number): Date; };
+    numOrDate = unionOfDifferentReturnType(10);
+    strOrBoolean = unionOfDifferentReturnType("hello"); // error 
+                                              ~~~~~~~
+!!! error TS2345: Argument of type 'string' is not assignable to parameter of type 'number'.
+    unionOfDifferentReturnType1(true); // error in type of parameter
+                                ~~~~
+!!! error TS2345: Argument of type 'boolean' is not assignable to parameter of type 'string'.
+    
+    var unionOfDifferentReturnType1: { (a: number): number; (a: string): string; } | { (a: number): Date; (a: string): boolean; };
+    numOrDate = unionOfDifferentReturnType1(10);
+    strOrBoolean = unionOfDifferentReturnType1("hello");
+    unionOfDifferentReturnType1(true); // error in type of parameter
+                                ~~~~
+!!! error TS2345: Argument of type 'boolean' is not assignable to parameter of type 'string'.
+    unionOfDifferentReturnType1(); // error missing parameter
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2346: Supplied parameters do not match any signature of call target.
+    
+    var unionOfDifferentParameterTypes: { (a: number): number; } | { (a: string): Date; };
+    unionOfDifferentParameterTypes(10);// error - no call signatures
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    unionOfDifferentParameterTypes("hello");// error - no call signatures
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    unionOfDifferentParameterTypes();// error - no call signatures
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    
+    var unionOfDifferentNumberOfSignatures: { (a: number): number; } | { (a: number): Date; (a: string): boolean; };
+    unionOfDifferentNumberOfSignatures(); // error - no call signatures
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    unionOfDifferentNumberOfSignatures(10); // error - no call signatures
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    unionOfDifferentNumberOfSignatures("hello"); // error - no call signatures
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    
+        var unionWithDifferentParameterCount: { (a: string): string; } | { (a: string, b: number): number; } ;
+    unionWithDifferentParameterCount();// no  call signature
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    unionWithDifferentParameterCount("hello");// no  call signature
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    unionWithDifferentParameterCount("hello", 10);// no  call signature
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    
+        var unionWithOptionalParameter1: { (a: string, b?: number): string; } | { (a: string, b?: number): number; };
+    strOrNum = unionWithOptionalParameter1('hello');
+    strOrNum = unionWithOptionalParameter1('hello', 10);
+    strOrNum = unionWithOptionalParameter1('hello', "hello"); // error in parameter type
+                                                    ~~~~~~~
+!!! error TS2345: Argument of type 'string' is not assignable to parameter of type 'number'.
+    strOrNum = unionWithOptionalParameter1(); // error
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2346: Supplied parameters do not match any signature of call target.
+    
+    var unionWithOptionalParameter2: { (a: string, b?: number): string; } | { (a: string, b: number): number };
+    strOrNum = unionWithOptionalParameter2('hello'); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    strOrNum = unionWithOptionalParameter2('hello', 10); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    strOrNum = unionWithOptionalParameter2('hello', "hello"); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    strOrNum = unionWithOptionalParameter2(); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    
+    var unionWithOptionalParameter3: { (a: string, b?: number): string; } | { (a: string): number; };
+    strOrNum = unionWithOptionalParameter3('hello'); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    strOrNum = unionWithOptionalParameter3('hello', 10); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    strOrNum = unionWithOptionalParameter3('hello', "hello"); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    strOrNum = unionWithOptionalParameter3(); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    
+    var unionWithRestParameter1: { (a: string, ...b: number[]): string; } | { (a: string, ...b: number[]): number };
+    strOrNum = unionWithRestParameter1('hello');
+    strOrNum = unionWithRestParameter1('hello', 10);
+    strOrNum = unionWithRestParameter1('hello', 10, 11);
+    strOrNum = unionWithRestParameter1('hello', "hello"); // error in parameter type
+                                                ~~~~~~~
+!!! error TS2345: Argument of type 'string' is not assignable to parameter of type 'number'.
+    strOrNum = unionWithRestParameter1(); // error
+               ~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2346: Supplied parameters do not match any signature of call target.
+    
+    var unionWithRestParameter2: { (a: string, ...b: number[]): string; } | { (a: string, b: number): number };
+    strOrNum = unionWithRestParameter2('hello'); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    strOrNum = unionWithRestParameter2('hello', 10); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    strOrNum = unionWithRestParameter2('hello', 10, 11); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    strOrNum = unionWithRestParameter2('hello', "hello"); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    strOrNum = unionWithRestParameter2(); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    
+    var unionWithRestParameter3: { (a: string, ...b: number[]): string; } | { (a: string): number };
+    strOrNum = unionWithRestParameter3('hello'); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    strOrNum = unionWithRestParameter3('hello', 10); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    strOrNum = unionWithRestParameter3('hello', 10, 11); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    strOrNum = unionWithRestParameter3('hello', "hello"); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+    strOrNum = unionWithRestParameter3(); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
\ No newline at end of file
diff --git a/tests/baselines/reference/unionTypeCallSignatures.js b/tests/baselines/reference/unionTypeCallSignatures.js
new file mode 100644
index 00000000000..a4000038ce6
--- /dev/null
+++ b/tests/baselines/reference/unionTypeCallSignatures.js
@@ -0,0 +1,132 @@
+//// [unionTypeCallSignatures.ts]
+var numOrDate: number | Date;
+var strOrBoolean: string | boolean;
+var strOrNum: string | number;
+
+// If each type in U has call signatures and the sets of call signatures are identical ignoring return types, 
+// U has the same set of call signatures, but with return types that are unions of the return types of the respective call signatures from each type in U.
+var unionOfDifferentReturnType: { (a: number): number; } | { (a: number): Date; };
+numOrDate = unionOfDifferentReturnType(10);
+strOrBoolean = unionOfDifferentReturnType("hello"); // error 
+unionOfDifferentReturnType1(true); // error in type of parameter
+
+var unionOfDifferentReturnType1: { (a: number): number; (a: string): string; } | { (a: number): Date; (a: string): boolean; };
+numOrDate = unionOfDifferentReturnType1(10);
+strOrBoolean = unionOfDifferentReturnType1("hello");
+unionOfDifferentReturnType1(true); // error in type of parameter
+unionOfDifferentReturnType1(); // error missing parameter
+
+var unionOfDifferentParameterTypes: { (a: number): number; } | { (a: string): Date; };
+unionOfDifferentParameterTypes(10);// error - no call signatures
+unionOfDifferentParameterTypes("hello");// error - no call signatures
+unionOfDifferentParameterTypes();// error - no call signatures
+
+var unionOfDifferentNumberOfSignatures: { (a: number): number; } | { (a: number): Date; (a: string): boolean; };
+unionOfDifferentNumberOfSignatures(); // error - no call signatures
+unionOfDifferentNumberOfSignatures(10); // error - no call signatures
+unionOfDifferentNumberOfSignatures("hello"); // error - no call signatures
+
+    var unionWithDifferentParameterCount: { (a: string): string; } | { (a: string, b: number): number; } ;
+unionWithDifferentParameterCount();// no  call signature
+unionWithDifferentParameterCount("hello");// no  call signature
+unionWithDifferentParameterCount("hello", 10);// no  call signature
+
+    var unionWithOptionalParameter1: { (a: string, b?: number): string; } | { (a: string, b?: number): number; };
+strOrNum = unionWithOptionalParameter1('hello');
+strOrNum = unionWithOptionalParameter1('hello', 10);
+strOrNum = unionWithOptionalParameter1('hello', "hello"); // error in parameter type
+strOrNum = unionWithOptionalParameter1(); // error
+
+var unionWithOptionalParameter2: { (a: string, b?: number): string; } | { (a: string, b: number): number };
+strOrNum = unionWithOptionalParameter2('hello'); // error no call signature
+strOrNum = unionWithOptionalParameter2('hello', 10); // error no call signature
+strOrNum = unionWithOptionalParameter2('hello', "hello"); // error no call signature
+strOrNum = unionWithOptionalParameter2(); // error no call signature
+
+var unionWithOptionalParameter3: { (a: string, b?: number): string; } | { (a: string): number; };
+strOrNum = unionWithOptionalParameter3('hello'); // error no call signature
+strOrNum = unionWithOptionalParameter3('hello', 10); // error no call signature
+strOrNum = unionWithOptionalParameter3('hello', "hello"); // error no call signature
+strOrNum = unionWithOptionalParameter3(); // error no call signature
+
+var unionWithRestParameter1: { (a: string, ...b: number[]): string; } | { (a: string, ...b: number[]): number };
+strOrNum = unionWithRestParameter1('hello');
+strOrNum = unionWithRestParameter1('hello', 10);
+strOrNum = unionWithRestParameter1('hello', 10, 11);
+strOrNum = unionWithRestParameter1('hello', "hello"); // error in parameter type
+strOrNum = unionWithRestParameter1(); // error
+
+var unionWithRestParameter2: { (a: string, ...b: number[]): string; } | { (a: string, b: number): number };
+strOrNum = unionWithRestParameter2('hello'); // error no call signature
+strOrNum = unionWithRestParameter2('hello', 10); // error no call signature
+strOrNum = unionWithRestParameter2('hello', 10, 11); // error no call signature
+strOrNum = unionWithRestParameter2('hello', "hello"); // error no call signature
+strOrNum = unionWithRestParameter2(); // error no call signature
+
+var unionWithRestParameter3: { (a: string, ...b: number[]): string; } | { (a: string): number };
+strOrNum = unionWithRestParameter3('hello'); // error no call signature
+strOrNum = unionWithRestParameter3('hello', 10); // error no call signature
+strOrNum = unionWithRestParameter3('hello', 10, 11); // error no call signature
+strOrNum = unionWithRestParameter3('hello', "hello"); // error no call signature
+strOrNum = unionWithRestParameter3(); // error no call signature
+
+//// [unionTypeCallSignatures.js]
+var numOrDate;
+var strOrBoolean;
+var strOrNum;
+// If each type in U has call signatures and the sets of call signatures are identical ignoring return types, 
+// U has the same set of call signatures, but with return types that are unions of the return types of the respective call signatures from each type in U.
+var unionOfDifferentReturnType;
+numOrDate = unionOfDifferentReturnType(10);
+strOrBoolean = unionOfDifferentReturnType("hello"); // error 
+unionOfDifferentReturnType1(true); // error in type of parameter
+var unionOfDifferentReturnType1;
+numOrDate = unionOfDifferentReturnType1(10);
+strOrBoolean = unionOfDifferentReturnType1("hello");
+unionOfDifferentReturnType1(true); // error in type of parameter
+unionOfDifferentReturnType1(); // error missing parameter
+var unionOfDifferentParameterTypes;
+unionOfDifferentParameterTypes(10); // error - no call signatures
+unionOfDifferentParameterTypes("hello"); // error - no call signatures
+unionOfDifferentParameterTypes(); // error - no call signatures
+var unionOfDifferentNumberOfSignatures;
+unionOfDifferentNumberOfSignatures(); // error - no call signatures
+unionOfDifferentNumberOfSignatures(10); // error - no call signatures
+unionOfDifferentNumberOfSignatures("hello"); // error - no call signatures
+var unionWithDifferentParameterCount;
+unionWithDifferentParameterCount(); // no  call signature
+unionWithDifferentParameterCount("hello"); // no  call signature
+unionWithDifferentParameterCount("hello", 10); // no  call signature
+var unionWithOptionalParameter1;
+strOrNum = unionWithOptionalParameter1('hello');
+strOrNum = unionWithOptionalParameter1('hello', 10);
+strOrNum = unionWithOptionalParameter1('hello', "hello"); // error in parameter type
+strOrNum = unionWithOptionalParameter1(); // error
+var unionWithOptionalParameter2;
+strOrNum = unionWithOptionalParameter2('hello'); // error no call signature
+strOrNum = unionWithOptionalParameter2('hello', 10); // error no call signature
+strOrNum = unionWithOptionalParameter2('hello', "hello"); // error no call signature
+strOrNum = unionWithOptionalParameter2(); // error no call signature
+var unionWithOptionalParameter3;
+strOrNum = unionWithOptionalParameter3('hello'); // error no call signature
+strOrNum = unionWithOptionalParameter3('hello', 10); // error no call signature
+strOrNum = unionWithOptionalParameter3('hello', "hello"); // error no call signature
+strOrNum = unionWithOptionalParameter3(); // error no call signature
+var unionWithRestParameter1;
+strOrNum = unionWithRestParameter1('hello');
+strOrNum = unionWithRestParameter1('hello', 10);
+strOrNum = unionWithRestParameter1('hello', 10, 11);
+strOrNum = unionWithRestParameter1('hello', "hello"); // error in parameter type
+strOrNum = unionWithRestParameter1(); // error
+var unionWithRestParameter2;
+strOrNum = unionWithRestParameter2('hello'); // error no call signature
+strOrNum = unionWithRestParameter2('hello', 10); // error no call signature
+strOrNum = unionWithRestParameter2('hello', 10, 11); // error no call signature
+strOrNum = unionWithRestParameter2('hello', "hello"); // error no call signature
+strOrNum = unionWithRestParameter2(); // error no call signature
+var unionWithRestParameter3;
+strOrNum = unionWithRestParameter3('hello'); // error no call signature
+strOrNum = unionWithRestParameter3('hello', 10); // error no call signature
+strOrNum = unionWithRestParameter3('hello', 10, 11); // error no call signature
+strOrNum = unionWithRestParameter3('hello', "hello"); // error no call signature
+strOrNum = unionWithRestParameter3(); // error no call signature
diff --git a/tests/baselines/reference/unionTypeConstructSignatures.errors.txt b/tests/baselines/reference/unionTypeConstructSignatures.errors.txt
new file mode 100644
index 00000000000..dd46564d779
--- /dev/null
+++ b/tests/baselines/reference/unionTypeConstructSignatures.errors.txt
@@ -0,0 +1,178 @@
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(9,47): error TS2345: Argument of type 'string' is not assignable to parameter of type 'number'.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(10,33): error TS2345: Argument of type 'boolean' is not assignable to parameter of type 'string'.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(15,33): error TS2345: Argument of type 'boolean' is not assignable to parameter of type 'string'.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(16,1): error TS2346: Supplied parameters do not match any signature of call target.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(19,1): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(20,1): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(21,1): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(24,1): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(25,1): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(26,1): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(29,1): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(30,1): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(31,1): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(36,53): error TS2345: Argument of type 'string' is not assignable to parameter of type 'number'.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(37,12): error TS2346: Supplied parameters do not match any signature of call target.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(40,12): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(41,12): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(42,12): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(43,12): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(46,12): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(47,12): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(48,12): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(49,12): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(55,49): error TS2345: Argument of type 'string' is not assignable to parameter of type 'number'.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(56,12): error TS2346: Supplied parameters do not match any signature of call target.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(59,12): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(60,12): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(61,12): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(62,12): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(63,12): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(66,12): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(67,12): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(68,12): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(69,12): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+tests/cases/conformance/types/union/unionTypeConstructSignatures.ts(70,12): error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+
+
+==== tests/cases/conformance/types/union/unionTypeConstructSignatures.ts (35 errors) ====
+    var numOrDate: number | Date;
+    var strOrBoolean: string | boolean;
+    var strOrNum: string | number;
+    
+    // If each type in U has construct signatures and the sets of construct signatures are identical ignoring return types, 
+    // U has the same set of construct signatures, but with return types that are unions of the return types of the respective construct signatures from each type in U.
+    var unionOfDifferentReturnType: { new (a: number): number; } | { new (a: number): Date; };
+    numOrDate = new unionOfDifferentReturnType(10);
+    strOrBoolean = new unionOfDifferentReturnType("hello"); // error 
+                                                  ~~~~~~~
+!!! error TS2345: Argument of type 'string' is not assignable to parameter of type 'number'.
+    new unionOfDifferentReturnType1(true); // error in type of parameter
+                                    ~~~~
+!!! error TS2345: Argument of type 'boolean' is not assignable to parameter of type 'string'.
+    
+    var unionOfDifferentReturnType1: { new (a: number): number; new (a: string): string; } | { new (a: number): Date; new (a: string): boolean; };
+    numOrDate = new unionOfDifferentReturnType1(10);
+    strOrBoolean = new unionOfDifferentReturnType1("hello");
+    new unionOfDifferentReturnType1(true); // error in type of parameter
+                                    ~~~~
+!!! error TS2345: Argument of type 'boolean' is not assignable to parameter of type 'string'.
+    new unionOfDifferentReturnType1(); // error missing parameter
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2346: Supplied parameters do not match any signature of call target.
+    
+    var unionOfDifferentParameterTypes: { new (a: number): number; } | { new (a: string): Date; };
+    new unionOfDifferentParameterTypes(10);// error - no call signatures
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    new unionOfDifferentParameterTypes("hello");// error - no call signatures
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    new unionOfDifferentParameterTypes();// error - no call signatures
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    
+    var unionOfDifferentNumberOfSignatures: { new (a: number): number; } | { new (a: number): Date; new (a: string): boolean; };
+    new unionOfDifferentNumberOfSignatures(); // error - no call signatures
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    new unionOfDifferentNumberOfSignatures(10); // error - no call signatures
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    new unionOfDifferentNumberOfSignatures("hello"); // error - no call signatures
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    
+    var unionWithDifferentParameterCount: { new (a: string): string; } | { new (a: string, b: number): number; };
+    new unionWithDifferentParameterCount();// no  call signature
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    new unionWithDifferentParameterCount("hello");// no  call signature
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    new unionWithDifferentParameterCount("hello", 10);// no  call signature
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    
+    var unionWithOptionalParameter1: { new (a: string, b?: number): string; } | { new (a: string, b?: number): number; };
+    strOrNum = new unionWithOptionalParameter1('hello');
+    strOrNum = new unionWithOptionalParameter1('hello', 10);
+    strOrNum = new unionWithOptionalParameter1('hello', "hello"); // error in parameter type
+                                                        ~~~~~~~
+!!! error TS2345: Argument of type 'string' is not assignable to parameter of type 'number'.
+    strOrNum = new unionWithOptionalParameter1(); // error
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2346: Supplied parameters do not match any signature of call target.
+    
+    var unionWithOptionalParameter2: { new (a: string, b?: number): string; } | { new (a: string, b: number): number };
+    strOrNum = new unionWithOptionalParameter2('hello'); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    strOrNum = new unionWithOptionalParameter2('hello', 10); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    strOrNum = new unionWithOptionalParameter2('hello', "hello"); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    strOrNum = new unionWithOptionalParameter2(); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    
+    var unionWithOptionalParameter3: { new (a: string, b?: number): string; } | { new (a: string): number; };
+    strOrNum = new unionWithOptionalParameter3('hello'); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    strOrNum = new unionWithOptionalParameter3('hello', 10); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    strOrNum = new unionWithOptionalParameter3('hello', "hello"); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    strOrNum = new unionWithOptionalParameter3(); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    
+    var unionWithRestParameter1: { new (a: string, ...b: number[]): string; } | { new (a: string, ...b: number[]): number };
+    strOrNum = new unionWithRestParameter1('hello');
+    strOrNum = new unionWithRestParameter1('hello', 10);
+    strOrNum = new unionWithRestParameter1('hello', 10, 11);
+    strOrNum = new unionWithRestParameter1('hello', "hello"); // error in parameter type
+                                                    ~~~~~~~
+!!! error TS2345: Argument of type 'string' is not assignable to parameter of type 'number'.
+    strOrNum = new unionWithRestParameter1(); // error
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2346: Supplied parameters do not match any signature of call target.
+    
+    var unionWithRestParameter2: { new (a: string, ...b: number[]): string; } | { new (a: string, b: number): number };
+    strOrNum = new unionWithRestParameter2('hello'); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    strOrNum = new unionWithRestParameter2('hello', 10); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    strOrNum = new unionWithRestParameter2('hello', 10, 11); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    strOrNum = new unionWithRestParameter2('hello', "hello"); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    strOrNum = new unionWithRestParameter2(); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    
+    var unionWithRestParameter3: { new (a: string, ...b: number[]): string; } | { new (a: string): number };
+    strOrNum = new unionWithRestParameter3('hello'); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    strOrNum = new unionWithRestParameter3('hello', 10); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    strOrNum = new unionWithRestParameter3('hello', 10, 11); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    strOrNum = new unionWithRestParameter3('hello', "hello"); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
+    strOrNum = new unionWithRestParameter3(); // error no call signature
+               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2351: Cannot use 'new' with an expression whose type lacks a call or construct signature.
\ No newline at end of file
diff --git a/tests/baselines/reference/unionTypeConstructSignatures.js b/tests/baselines/reference/unionTypeConstructSignatures.js
new file mode 100644
index 00000000000..83c3df44603
--- /dev/null
+++ b/tests/baselines/reference/unionTypeConstructSignatures.js
@@ -0,0 +1,132 @@
+//// [unionTypeConstructSignatures.ts]
+var numOrDate: number | Date;
+var strOrBoolean: string | boolean;
+var strOrNum: string | number;
+
+// If each type in U has construct signatures and the sets of construct signatures are identical ignoring return types, 
+// U has the same set of construct signatures, but with return types that are unions of the return types of the respective construct signatures from each type in U.
+var unionOfDifferentReturnType: { new (a: number): number; } | { new (a: number): Date; };
+numOrDate = new unionOfDifferentReturnType(10);
+strOrBoolean = new unionOfDifferentReturnType("hello"); // error 
+new unionOfDifferentReturnType1(true); // error in type of parameter
+
+var unionOfDifferentReturnType1: { new (a: number): number; new (a: string): string; } | { new (a: number): Date; new (a: string): boolean; };
+numOrDate = new unionOfDifferentReturnType1(10);
+strOrBoolean = new unionOfDifferentReturnType1("hello");
+new unionOfDifferentReturnType1(true); // error in type of parameter
+new unionOfDifferentReturnType1(); // error missing parameter
+
+var unionOfDifferentParameterTypes: { new (a: number): number; } | { new (a: string): Date; };
+new unionOfDifferentParameterTypes(10);// error - no call signatures
+new unionOfDifferentParameterTypes("hello");// error - no call signatures
+new unionOfDifferentParameterTypes();// error - no call signatures
+
+var unionOfDifferentNumberOfSignatures: { new (a: number): number; } | { new (a: number): Date; new (a: string): boolean; };
+new unionOfDifferentNumberOfSignatures(); // error - no call signatures
+new unionOfDifferentNumberOfSignatures(10); // error - no call signatures
+new unionOfDifferentNumberOfSignatures("hello"); // error - no call signatures
+
+var unionWithDifferentParameterCount: { new (a: string): string; } | { new (a: string, b: number): number; };
+new unionWithDifferentParameterCount();// no  call signature
+new unionWithDifferentParameterCount("hello");// no  call signature
+new unionWithDifferentParameterCount("hello", 10);// no  call signature
+
+var unionWithOptionalParameter1: { new (a: string, b?: number): string; } | { new (a: string, b?: number): number; };
+strOrNum = new unionWithOptionalParameter1('hello');
+strOrNum = new unionWithOptionalParameter1('hello', 10);
+strOrNum = new unionWithOptionalParameter1('hello', "hello"); // error in parameter type
+strOrNum = new unionWithOptionalParameter1(); // error
+
+var unionWithOptionalParameter2: { new (a: string, b?: number): string; } | { new (a: string, b: number): number };
+strOrNum = new unionWithOptionalParameter2('hello'); // error no call signature
+strOrNum = new unionWithOptionalParameter2('hello', 10); // error no call signature
+strOrNum = new unionWithOptionalParameter2('hello', "hello"); // error no call signature
+strOrNum = new unionWithOptionalParameter2(); // error no call signature
+
+var unionWithOptionalParameter3: { new (a: string, b?: number): string; } | { new (a: string): number; };
+strOrNum = new unionWithOptionalParameter3('hello'); // error no call signature
+strOrNum = new unionWithOptionalParameter3('hello', 10); // error no call signature
+strOrNum = new unionWithOptionalParameter3('hello', "hello"); // error no call signature
+strOrNum = new unionWithOptionalParameter3(); // error no call signature
+
+var unionWithRestParameter1: { new (a: string, ...b: number[]): string; } | { new (a: string, ...b: number[]): number };
+strOrNum = new unionWithRestParameter1('hello');
+strOrNum = new unionWithRestParameter1('hello', 10);
+strOrNum = new unionWithRestParameter1('hello', 10, 11);
+strOrNum = new unionWithRestParameter1('hello', "hello"); // error in parameter type
+strOrNum = new unionWithRestParameter1(); // error
+
+var unionWithRestParameter2: { new (a: string, ...b: number[]): string; } | { new (a: string, b: number): number };
+strOrNum = new unionWithRestParameter2('hello'); // error no call signature
+strOrNum = new unionWithRestParameter2('hello', 10); // error no call signature
+strOrNum = new unionWithRestParameter2('hello', 10, 11); // error no call signature
+strOrNum = new unionWithRestParameter2('hello', "hello"); // error no call signature
+strOrNum = new unionWithRestParameter2(); // error no call signature
+
+var unionWithRestParameter3: { new (a: string, ...b: number[]): string; } | { new (a: string): number };
+strOrNum = new unionWithRestParameter3('hello'); // error no call signature
+strOrNum = new unionWithRestParameter3('hello', 10); // error no call signature
+strOrNum = new unionWithRestParameter3('hello', 10, 11); // error no call signature
+strOrNum = new unionWithRestParameter3('hello', "hello"); // error no call signature
+strOrNum = new unionWithRestParameter3(); // error no call signature
+
+//// [unionTypeConstructSignatures.js]
+var numOrDate;
+var strOrBoolean;
+var strOrNum;
+// If each type in U has construct signatures and the sets of construct signatures are identical ignoring return types, 
+// U has the same set of construct signatures, but with return types that are unions of the return types of the respective construct signatures from each type in U.
+var unionOfDifferentReturnType;
+numOrDate = new unionOfDifferentReturnType(10);
+strOrBoolean = new unionOfDifferentReturnType("hello"); // error 
+new unionOfDifferentReturnType1(true); // error in type of parameter
+var unionOfDifferentReturnType1;
+numOrDate = new unionOfDifferentReturnType1(10);
+strOrBoolean = new unionOfDifferentReturnType1("hello");
+new unionOfDifferentReturnType1(true); // error in type of parameter
+new unionOfDifferentReturnType1(); // error missing parameter
+var unionOfDifferentParameterTypes;
+new unionOfDifferentParameterTypes(10); // error - no call signatures
+new unionOfDifferentParameterTypes("hello"); // error - no call signatures
+new unionOfDifferentParameterTypes(); // error - no call signatures
+var unionOfDifferentNumberOfSignatures;
+new unionOfDifferentNumberOfSignatures(); // error - no call signatures
+new unionOfDifferentNumberOfSignatures(10); // error - no call signatures
+new unionOfDifferentNumberOfSignatures("hello"); // error - no call signatures
+var unionWithDifferentParameterCount;
+new unionWithDifferentParameterCount(); // no  call signature
+new unionWithDifferentParameterCount("hello"); // no  call signature
+new unionWithDifferentParameterCount("hello", 10); // no  call signature
+var unionWithOptionalParameter1;
+strOrNum = new unionWithOptionalParameter1('hello');
+strOrNum = new unionWithOptionalParameter1('hello', 10);
+strOrNum = new unionWithOptionalParameter1('hello', "hello"); // error in parameter type
+strOrNum = new unionWithOptionalParameter1(); // error
+var unionWithOptionalParameter2;
+strOrNum = new unionWithOptionalParameter2('hello'); // error no call signature
+strOrNum = new unionWithOptionalParameter2('hello', 10); // error no call signature
+strOrNum = new unionWithOptionalParameter2('hello', "hello"); // error no call signature
+strOrNum = new unionWithOptionalParameter2(); // error no call signature
+var unionWithOptionalParameter3;
+strOrNum = new unionWithOptionalParameter3('hello'); // error no call signature
+strOrNum = new unionWithOptionalParameter3('hello', 10); // error no call signature
+strOrNum = new unionWithOptionalParameter3('hello', "hello"); // error no call signature
+strOrNum = new unionWithOptionalParameter3(); // error no call signature
+var unionWithRestParameter1;
+strOrNum = new unionWithRestParameter1('hello');
+strOrNum = new unionWithRestParameter1('hello', 10);
+strOrNum = new unionWithRestParameter1('hello', 10, 11);
+strOrNum = new unionWithRestParameter1('hello', "hello"); // error in parameter type
+strOrNum = new unionWithRestParameter1(); // error
+var unionWithRestParameter2;
+strOrNum = new unionWithRestParameter2('hello'); // error no call signature
+strOrNum = new unionWithRestParameter2('hello', 10); // error no call signature
+strOrNum = new unionWithRestParameter2('hello', 10, 11); // error no call signature
+strOrNum = new unionWithRestParameter2('hello', "hello"); // error no call signature
+strOrNum = new unionWithRestParameter2(); // error no call signature
+var unionWithRestParameter3;
+strOrNum = new unionWithRestParameter3('hello'); // error no call signature
+strOrNum = new unionWithRestParameter3('hello', 10); // error no call signature
+strOrNum = new unionWithRestParameter3('hello', 10, 11); // error no call signature
+strOrNum = new unionWithRestParameter3('hello', "hello"); // error no call signature
+strOrNum = new unionWithRestParameter3(); // error no call signature
diff --git a/tests/baselines/reference/unionTypeEquivalence.js b/tests/baselines/reference/unionTypeEquivalence.js
new file mode 100644
index 00000000000..f9fdf2e58d7
--- /dev/null
+++ b/tests/baselines/reference/unionTypeEquivalence.js
@@ -0,0 +1,56 @@
+//// [unionTypeEquivalence.ts]
+// A | B is equivalent to A if B is a subtype of A
+class C { }
+class D extends C { foo() { } }
+var x: C;
+var x : C | D;
+
+// A | B is equivalent to B | A.
+var y: string | number;
+var y : number | string;
+
+// AB | C is equivalent to A | BC, where AB is A | B and BC is B | C.
+var z : string | number | boolean;
+var z : (string | number) | boolean;
+var z : string | (number | boolean);
+var AB : string | number;
+var BC : number | boolean;
+var z1: typeof AB | boolean;
+var z1: string | typeof BC;
+
+
+//// [unionTypeEquivalence.js]
+var __extends = this.__extends || function (d, b) {
+    for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
+    function __() { this.constructor = d; }
+    __.prototype = b.prototype;
+    d.prototype = new __();
+};
+// A | B is equivalent to A if B is a subtype of A
+var C = (function () {
+    function C() {
+    }
+    return C;
+})();
+var D = (function (_super) {
+    __extends(D, _super);
+    function D() {
+        _super.apply(this, arguments);
+    }
+    D.prototype.foo = function () {
+    };
+    return D;
+})(C);
+var x;
+var x;
+// A | B is equivalent to B | A.
+var y;
+var y;
+// AB | C is equivalent to A | BC, where AB is A | B and BC is B | C.
+var z;
+var z;
+var z;
+var AB;
+var BC;
+var z1;
+var z1;
diff --git a/tests/baselines/reference/unionTypeEquivalence.types b/tests/baselines/reference/unionTypeEquivalence.types
new file mode 100644
index 00000000000..c4990a58132
--- /dev/null
+++ b/tests/baselines/reference/unionTypeEquivalence.types
@@ -0,0 +1,50 @@
+=== tests/cases/conformance/types/union/unionTypeEquivalence.ts ===
+// A | B is equivalent to A if B is a subtype of A
+class C { }
+>C : C
+
+class D extends C { foo() { } }
+>D : D
+>C : C
+>foo : () => void
+
+var x: C;
+>x : C
+>C : C
+
+var x : C | D;
+>x : C
+>C : C
+>D : D
+
+// A | B is equivalent to B | A.
+var y: string | number;
+>y : string | number
+
+var y : number | string;
+>y : string | number
+
+// AB | C is equivalent to A | BC, where AB is A | B and BC is B | C.
+var z : string | number | boolean;
+>z : string | number | boolean
+
+var z : (string | number) | boolean;
+>z : string | number | boolean
+
+var z : string | (number | boolean);
+>z : string | number | boolean
+
+var AB : string | number;
+>AB : string | number
+
+var BC : number | boolean;
+>BC : number | boolean
+
+var z1: typeof AB | boolean;
+>z1 : string | number | boolean
+>AB : string | number
+
+var z1: string | typeof BC;
+>z1 : string | number | boolean
+>BC : number | boolean
+
diff --git a/tests/baselines/reference/unionTypeFromArrayLiteral.js b/tests/baselines/reference/unionTypeFromArrayLiteral.js
new file mode 100644
index 00000000000..e0410a65229
--- /dev/null
+++ b/tests/baselines/reference/unionTypeFromArrayLiteral.js
@@ -0,0 +1,79 @@
+//// [unionTypeFromArrayLiteral.ts]
+// The resulting type an array literal expression is determined as follows:
+// If the array literal is empty, the resulting type is an array type with the element type Undefined.
+// Otherwise, if the array literal is contextually typed by a type that has a property with the numeric name ‘0’, the resulting type is a tuple type constructed from the types of the element expressions.
+// Otherwise, the resulting type is an array type with an element type that is the union of the types of the element expressions.
+
+var arr1 = [1, 2]; // number[]
+var arr2 = ["hello", true]; // (string | number)[]
+var arr3Tuple: [number, string] = [3, "three"]; // [number, string]
+var arr4Tuple: [number, string] = [3, "three", "hello"]; // [number, string, string]
+var arrEmpty = [];
+var arr5Tuple: {
+    0: string;
+    5: number;
+} = ["hello", true, false, " hello", true, 10, "any"]; // Tuple
+class C { foo() { } }
+class D { foo2() { } }
+class E extends C { foo3() { } }
+class F extends C { foo4() { } }
+var c: C, d: D, e: E, f: F;
+var arr6 = [c, d];  // (C | D)[]
+var arr7 = [c, d, e]; // (C | D)[]
+var arr8 = [c, e]; // C[]
+var arr9 = [e, f]; // (E|F)[]
+
+//// [unionTypeFromArrayLiteral.js]
+// The resulting type an array literal expression is determined as follows:
+// If the array literal is empty, the resulting type is an array type with the element type Undefined.
+// Otherwise, if the array literal is contextually typed by a type that has a property with the numeric name ‘0’, the resulting type is a tuple type constructed from the types of the element expressions.
+// Otherwise, the resulting type is an array type with an element type that is the union of the types of the element expressions.
+var __extends = this.__extends || function (d, b) {
+    for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
+    function __() { this.constructor = d; }
+    __.prototype = b.prototype;
+    d.prototype = new __();
+};
+var arr1 = [1, 2]; // number[]
+var arr2 = ["hello", true]; // (string | number)[]
+var arr3Tuple = [3, "three"]; // [number, string]
+var arr4Tuple = [3, "three", "hello"]; // [number, string, string]
+var arrEmpty = [];
+var arr5Tuple = ["hello", true, false, " hello", true, 10, "any"]; // Tuple
+var C = (function () {
+    function C() {
+    }
+    C.prototype.foo = function () {
+    };
+    return C;
+})();
+var D = (function () {
+    function D() {
+    }
+    D.prototype.foo2 = function () {
+    };
+    return D;
+})();
+var E = (function (_super) {
+    __extends(E, _super);
+    function E() {
+        _super.apply(this, arguments);
+    }
+    E.prototype.foo3 = function () {
+    };
+    return E;
+})(C);
+var F = (function (_super) {
+    __extends(F, _super);
+    function F() {
+        _super.apply(this, arguments);
+    }
+    F.prototype.foo4 = function () {
+    };
+    return F;
+})(C);
+var c, d, e, f;
+var arr6 = [c, d]; // (C | D)[]
+var arr7 = [c, d, e]; // (C | D)[]
+var arr8 = [c, e]; // C[]
+var arr9 = [e, f]; // (E|F)[]
diff --git a/tests/baselines/reference/unionTypeFromArrayLiteral.types b/tests/baselines/reference/unionTypeFromArrayLiteral.types
new file mode 100644
index 00000000000..7cb09b3ce6a
--- /dev/null
+++ b/tests/baselines/reference/unionTypeFromArrayLiteral.types
@@ -0,0 +1,87 @@
+=== tests/cases/conformance/types/union/unionTypeFromArrayLiteral.ts ===
+// The resulting type an array literal expression is determined as follows:
+// If the array literal is empty, the resulting type is an array type with the element type Undefined.
+// Otherwise, if the array literal is contextually typed by a type that has a property with the numeric name ‘0’, the resulting type is a tuple type constructed from the types of the element expressions.
+// Otherwise, the resulting type is an array type with an element type that is the union of the types of the element expressions.
+
+var arr1 = [1, 2]; // number[]
+>arr1 : number[]
+>[1, 2] : number[]
+
+var arr2 = ["hello", true]; // (string | number)[]
+>arr2 : (string | boolean)[]
+>["hello", true] : (string | boolean)[]
+
+var arr3Tuple: [number, string] = [3, "three"]; // [number, string]
+>arr3Tuple : [number, string]
+>[3, "three"] : [number, string]
+
+var arr4Tuple: [number, string] = [3, "three", "hello"]; // [number, string, string]
+>arr4Tuple : [number, string]
+>[3, "three", "hello"] : [number, string, string]
+
+var arrEmpty = [];
+>arrEmpty : any[]
+>[] : undefined[]
+
+var arr5Tuple: {
+>arr5Tuple : { 0: string; 5: number; }
+
+    0: string;
+    5: number;
+} = ["hello", true, false, " hello", true, 10, "any"]; // Tuple
+>["hello", true, false, " hello", true, 10, "any"] : [string, boolean, boolean, string, boolean, number, string]
+
+class C { foo() { } }
+>C : C
+>foo : () => void
+
+class D { foo2() { } }
+>D : D
+>foo2 : () => void
+
+class E extends C { foo3() { } }
+>E : E
+>C : C
+>foo3 : () => void
+
+class F extends C { foo4() { } }
+>F : F
+>C : C
+>foo4 : () => void
+
+var c: C, d: D, e: E, f: F;
+>c : C
+>C : C
+>d : D
+>D : D
+>e : E
+>E : E
+>f : F
+>F : F
+
+var arr6 = [c, d];  // (C | D)[]
+>arr6 : (C | D)[]
+>[c, d] : (C | D)[]
+>c : C
+>d : D
+
+var arr7 = [c, d, e]; // (C | D)[]
+>arr7 : (C | D)[]
+>[c, d, e] : (C | D)[]
+>c : C
+>d : D
+>e : E
+
+var arr8 = [c, e]; // C[]
+>arr8 : C[]
+>[c, e] : C[]
+>c : C
+>e : E
+
+var arr9 = [e, f]; // (E|F)[]
+>arr9 : (E | F)[]
+>[e, f] : (E | F)[]
+>e : E
+>f : F
+
diff --git a/tests/baselines/reference/unionTypeIdentity.errors.txt b/tests/baselines/reference/unionTypeIdentity.errors.txt
new file mode 100644
index 00000000000..77d25bd78d1
--- /dev/null
+++ b/tests/baselines/reference/unionTypeIdentity.errors.txt
@@ -0,0 +1,20 @@
+tests/cases/conformance/types/typeRelationships/typeAndMemberIdentity/unionTypeIdentity.ts(6,5): error TS2403: Subsequent variable declarations must have the same type.  Variable 'strOrNum' must be of type 'string | boolean', but here has type 'string'.
+tests/cases/conformance/types/typeRelationships/typeAndMemberIdentity/unionTypeIdentity.ts(7,5): error TS2403: Subsequent variable declarations must have the same type.  Variable 'strOrNum' must be of type 'string | boolean', but here has type 'boolean'.
+tests/cases/conformance/types/typeRelationships/typeAndMemberIdentity/unionTypeIdentity.ts(8,5): error TS2403: Subsequent variable declarations must have the same type.  Variable 'strOrNum' must be of type 'string | boolean', but here has type 'number'.
+
+
+==== tests/cases/conformance/types/typeRelationships/typeAndMemberIdentity/unionTypeIdentity.ts (3 errors) ====
+    // Two types are considered identical when
+    // they are union types with identical sets of constituent types, or
+    var strOrNum: string | boolean;
+    var strOrNum: boolean | string;
+    var strOrNum: boolean | string | boolean;
+    var strOrNum: string; // error
+        ~~~~~~~~
+!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'strOrNum' must be of type 'string | boolean', but here has type 'string'.
+    var strOrNum: boolean; // error
+        ~~~~~~~~
+!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'strOrNum' must be of type 'string | boolean', but here has type 'boolean'.
+    var strOrNum: number; // error
+        ~~~~~~~~
+!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'strOrNum' must be of type 'string | boolean', but here has type 'number'.
\ No newline at end of file
diff --git a/tests/baselines/reference/unionTypeIdentity.js b/tests/baselines/reference/unionTypeIdentity.js
new file mode 100644
index 00000000000..82cad827979
--- /dev/null
+++ b/tests/baselines/reference/unionTypeIdentity.js
@@ -0,0 +1,19 @@
+//// [unionTypeIdentity.ts]
+// Two types are considered identical when
+// they are union types with identical sets of constituent types, or
+var strOrNum: string | boolean;
+var strOrNum: boolean | string;
+var strOrNum: boolean | string | boolean;
+var strOrNum: string; // error
+var strOrNum: boolean; // error
+var strOrNum: number; // error
+
+//// [unionTypeIdentity.js]
+// Two types are considered identical when
+// they are union types with identical sets of constituent types, or
+var strOrNum;
+var strOrNum;
+var strOrNum;
+var strOrNum; // error
+var strOrNum; // error
+var strOrNum; // error
diff --git a/tests/baselines/reference/unionTypeIndexSignature.js b/tests/baselines/reference/unionTypeIndexSignature.js
new file mode 100644
index 00000000000..b39a42e76a4
--- /dev/null
+++ b/tests/baselines/reference/unionTypeIndexSignature.js
@@ -0,0 +1,44 @@
+//// [unionTypeIndexSignature.ts]
+var numOrDate: number | Date;
+var anyVar: number;
+
+// If each type in U has a string index signature, 
+// U has a string index signature of a union type of the types of the string index signatures from each type in U.
+
+var unionOfDifferentReturnType: { [a: string]: number; } | { [a: string]: Date; };
+numOrDate = unionOfDifferentReturnType["hello"]; // number | Date
+numOrDate = unionOfDifferentReturnType[10]; // number | Date
+
+var unionOfTypesWithAndWithoutStringSignature: { [a: string]: number; } | boolean;
+anyVar = unionOfTypesWithAndWithoutStringSignature["hello"]; // any
+anyVar = unionOfTypesWithAndWithoutStringSignature[10]; // any
+
+// If each type in U has a numeric index signature, 
+// U has a numeric index signature of a union type of the types of the numeric index signatures from each type in U.
+var unionOfDifferentReturnType1: { [a: number]: number; } | { [a: number]: Date; };
+numOrDate = unionOfDifferentReturnType1["hello"]; // any
+numOrDate = unionOfDifferentReturnType1[10]; // number | Date
+
+var unionOfTypesWithAndWithoutStringSignature1: { [a: number]: number; } | boolean;
+anyVar = unionOfTypesWithAndWithoutStringSignature1["hello"]; // any
+anyVar = unionOfTypesWithAndWithoutStringSignature1[10]; // any
+
+//// [unionTypeIndexSignature.js]
+var numOrDate;
+var anyVar;
+// If each type in U has a string index signature, 
+// U has a string index signature of a union type of the types of the string index signatures from each type in U.
+var unionOfDifferentReturnType;
+numOrDate = unionOfDifferentReturnType["hello"]; // number | Date
+numOrDate = unionOfDifferentReturnType[10]; // number | Date
+var unionOfTypesWithAndWithoutStringSignature;
+anyVar = unionOfTypesWithAndWithoutStringSignature["hello"]; // any
+anyVar = unionOfTypesWithAndWithoutStringSignature[10]; // any
+// If each type in U has a numeric index signature, 
+// U has a numeric index signature of a union type of the types of the numeric index signatures from each type in U.
+var unionOfDifferentReturnType1;
+numOrDate = unionOfDifferentReturnType1["hello"]; // any
+numOrDate = unionOfDifferentReturnType1[10]; // number | Date
+var unionOfTypesWithAndWithoutStringSignature1;
+anyVar = unionOfTypesWithAndWithoutStringSignature1["hello"]; // any
+anyVar = unionOfTypesWithAndWithoutStringSignature1[10]; // any
diff --git a/tests/baselines/reference/unionTypeIndexSignature.types b/tests/baselines/reference/unionTypeIndexSignature.types
new file mode 100644
index 00000000000..96453cffcb4
--- /dev/null
+++ b/tests/baselines/reference/unionTypeIndexSignature.types
@@ -0,0 +1,81 @@
+=== tests/cases/conformance/types/union/unionTypeIndexSignature.ts ===
+var numOrDate: number | Date;
+>numOrDate : number | Date
+>Date : Date
+
+var anyVar: number;
+>anyVar : number
+
+// If each type in U has a string index signature, 
+// U has a string index signature of a union type of the types of the string index signatures from each type in U.
+
+var unionOfDifferentReturnType: { [a: string]: number; } | { [a: string]: Date; };
+>unionOfDifferentReturnType : { [x: string]: number; } | { [x: string]: Date; }
+>a : string
+>a : string
+>Date : Date
+
+numOrDate = unionOfDifferentReturnType["hello"]; // number | Date
+>numOrDate = unionOfDifferentReturnType["hello"] : number | Date
+>numOrDate : number | Date
+>unionOfDifferentReturnType["hello"] : number | Date
+>unionOfDifferentReturnType : { [x: string]: number; } | { [x: string]: Date; }
+
+numOrDate = unionOfDifferentReturnType[10]; // number | Date
+>numOrDate = unionOfDifferentReturnType[10] : number | Date
+>numOrDate : number | Date
+>unionOfDifferentReturnType[10] : number | Date
+>unionOfDifferentReturnType : { [x: string]: number; } | { [x: string]: Date; }
+
+var unionOfTypesWithAndWithoutStringSignature: { [a: string]: number; } | boolean;
+>unionOfTypesWithAndWithoutStringSignature : boolean | { [x: string]: number; }
+>a : string
+
+anyVar = unionOfTypesWithAndWithoutStringSignature["hello"]; // any
+>anyVar = unionOfTypesWithAndWithoutStringSignature["hello"] : any
+>anyVar : number
+>unionOfTypesWithAndWithoutStringSignature["hello"] : any
+>unionOfTypesWithAndWithoutStringSignature : boolean | { [x: string]: number; }
+
+anyVar = unionOfTypesWithAndWithoutStringSignature[10]; // any
+>anyVar = unionOfTypesWithAndWithoutStringSignature[10] : any
+>anyVar : number
+>unionOfTypesWithAndWithoutStringSignature[10] : any
+>unionOfTypesWithAndWithoutStringSignature : boolean | { [x: string]: number; }
+
+// If each type in U has a numeric index signature, 
+// U has a numeric index signature of a union type of the types of the numeric index signatures from each type in U.
+var unionOfDifferentReturnType1: { [a: number]: number; } | { [a: number]: Date; };
+>unionOfDifferentReturnType1 : { [x: number]: number; } | { [x: number]: Date; }
+>a : number
+>a : number
+>Date : Date
+
+numOrDate = unionOfDifferentReturnType1["hello"]; // any
+>numOrDate = unionOfDifferentReturnType1["hello"] : any
+>numOrDate : number | Date
+>unionOfDifferentReturnType1["hello"] : any
+>unionOfDifferentReturnType1 : { [x: number]: number; } | { [x: number]: Date; }
+
+numOrDate = unionOfDifferentReturnType1[10]; // number | Date
+>numOrDate = unionOfDifferentReturnType1[10] : number | Date
+>numOrDate : number | Date
+>unionOfDifferentReturnType1[10] : number | Date
+>unionOfDifferentReturnType1 : { [x: number]: number; } | { [x: number]: Date; }
+
+var unionOfTypesWithAndWithoutStringSignature1: { [a: number]: number; } | boolean;
+>unionOfTypesWithAndWithoutStringSignature1 : boolean | { [x: number]: number; }
+>a : number
+
+anyVar = unionOfTypesWithAndWithoutStringSignature1["hello"]; // any
+>anyVar = unionOfTypesWithAndWithoutStringSignature1["hello"] : any
+>anyVar : number
+>unionOfTypesWithAndWithoutStringSignature1["hello"] : any
+>unionOfTypesWithAndWithoutStringSignature1 : boolean | { [x: number]: number; }
+
+anyVar = unionOfTypesWithAndWithoutStringSignature1[10]; // any
+>anyVar = unionOfTypesWithAndWithoutStringSignature1[10] : any
+>anyVar : number
+>unionOfTypesWithAndWithoutStringSignature1[10] : any
+>unionOfTypesWithAndWithoutStringSignature1 : boolean | { [x: number]: number; }
+
diff --git a/tests/baselines/reference/unionTypeLiterals.js b/tests/baselines/reference/unionTypeLiterals.js
new file mode 100644
index 00000000000..3e23d47d152
--- /dev/null
+++ b/tests/baselines/reference/unionTypeLiterals.js
@@ -0,0 +1,29 @@
+//// [unionTypeLiterals.ts]
+// basic valid forms of union literals
+
+var simpleUnion: string | number;
+var unionOfUnion: string | number | boolean;
+
+var arrayOfUnions: (string | number)[];
+var arrayOfUnions: Array<string | number>;
+
+var unionOfFunctionType: (() => string) | (() => number);
+var unionOfFunctionType: { (): string } | { (): number };
+var unionOfFunctionType: () => string | number;
+
+var unionOfConstructorType: (new () => string) | (new () => number);
+var unionOfConstructorType: { new (): string } | { new (): number };
+var unionOfConstructorType: new () => string | number;
+
+//// [unionTypeLiterals.js]
+// basic valid forms of union literals
+var simpleUnion;
+var unionOfUnion;
+var arrayOfUnions;
+var arrayOfUnions;
+var unionOfFunctionType;
+var unionOfFunctionType;
+var unionOfFunctionType;
+var unionOfConstructorType;
+var unionOfConstructorType;
+var unionOfConstructorType;
diff --git a/tests/baselines/reference/unionTypeLiterals.types b/tests/baselines/reference/unionTypeLiterals.types
new file mode 100644
index 00000000000..90bc4649aa7
--- /dev/null
+++ b/tests/baselines/reference/unionTypeLiterals.types
@@ -0,0 +1,34 @@
+=== tests/cases/conformance/types/specifyingTypes/typeLiterals/unionTypeLiterals.ts ===
+// basic valid forms of union literals
+
+var simpleUnion: string | number;
+>simpleUnion : string | number
+
+var unionOfUnion: string | number | boolean;
+>unionOfUnion : string | number | boolean
+
+var arrayOfUnions: (string | number)[];
+>arrayOfUnions : (string | number)[]
+
+var arrayOfUnions: Array<string | number>;
+>arrayOfUnions : (string | number)[]
+>Array : T[]
+
+var unionOfFunctionType: (() => string) | (() => number);
+>unionOfFunctionType : (() => string) | (() => number)
+
+var unionOfFunctionType: { (): string } | { (): number };
+>unionOfFunctionType : (() => string) | (() => number)
+
+var unionOfFunctionType: () => string | number;
+>unionOfFunctionType : (() => string) | (() => number)
+
+var unionOfConstructorType: (new () => string) | (new () => number);
+>unionOfConstructorType : (new () => string) | (new () => number)
+
+var unionOfConstructorType: { new (): string } | { new (): number };
+>unionOfConstructorType : (new () => string) | (new () => number)
+
+var unionOfConstructorType: new () => string | number;
+>unionOfConstructorType : (new () => string) | (new () => number)
+
diff --git a/tests/baselines/reference/unionTypeMembers.errors.txt b/tests/baselines/reference/unionTypeMembers.errors.txt
new file mode 100644
index 00000000000..21f1204ac6d
--- /dev/null
+++ b/tests/baselines/reference/unionTypeMembers.errors.txt
@@ -0,0 +1,72 @@
+tests/cases/conformance/types/union/unionTypeMembers.ts(44,1): error TS2349: Cannot invoke an expression whose type lacks a call signature.
+tests/cases/conformance/types/union/unionTypeMembers.ts(51,3): error TS2339: Property 'propertyOnlyInI1' does not exist on type 'I1<number> | I2<number>'.
+tests/cases/conformance/types/union/unionTypeMembers.ts(52,3): error TS2339: Property 'propertyOnlyInI2' does not exist on type 'I1<number> | I2<number>'.
+tests/cases/conformance/types/union/unionTypeMembers.ts(53,3): error TS2339: Property 'methodOnlyInI1' does not exist on type 'I1<number> | I2<number>'.
+tests/cases/conformance/types/union/unionTypeMembers.ts(54,3): error TS2339: Property 'methodOnlyInI2' does not exist on type 'I1<number> | I2<number>'.
+
+
+==== tests/cases/conformance/types/union/unionTypeMembers.ts (5 errors) ====
+    interface I1<T> {
+        commonMethodType(a: string): string;
+        commonPropertyType: string;
+    
+        commonMethodDifferentParameterType(a: string): string;
+        commonMethodDifferentReturnType(a: string): string;
+        commonPropertyDifferenType: string;
+    
+        commonMethodWithTypeParameter(a: T): T;
+        commonMethodWithOwnTypeParameter<U>(a: U): U;
+    
+        methodOnlyInI1(a: string): string;
+        propertyOnlyInI1: string;
+    }
+    
+    interface I2<T> {
+        commonMethodType(a: string): string;
+        commonPropertyType: string;
+    
+        commonMethodDifferentParameterType(a: number): number;
+        commonMethodDifferentReturnType(a: string): number;
+        commonPropertyDifferenType: number;
+    
+        commonMethodWithTypeParameter(a: T): T;
+        commonMethodWithOwnTypeParameter<U>(a: U): U;
+    
+        methodOnlyInI2(a: string): string;
+        propertyOnlyInI2: string;
+    }
+    
+    // a union type U has those members that are present in every one of its constituent types, 
+    // with types that are unions of the respective members in the constituent types
+    var x : I1<number> | I2<number>;
+    var str: string;
+    var num: number;
+    var strOrNum: string | number;
+    
+    // If each type in U has a property P, U has a property P of a union type of the types of P from each type in U.
+    str = x.commonPropertyType; // string
+    str = x.commonMethodType(str); // (a: string) => string so result should be string
+    strOrNum = x.commonPropertyDifferenType;
+    strOrNum = x.commonMethodDifferentReturnType(str); // string | union
+    x.commonMethodDifferentParameterType; // No error - property exists
+    x.commonMethodDifferentParameterType(strOrNum); // error - no call signatures because the type of this property is ((a: string) => string) | (a: number) => number
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2349: Cannot invoke an expression whose type lacks a call signature.
+                                                    // and the call signatures arent identical
+    num = x.commonMethodWithTypeParameter(num);
+    num = x.commonMethodWithOwnTypeParameter(num);
+    str = x.commonMethodWithOwnTypeParameter(str);
+    strOrNum = x.commonMethodWithOwnTypeParameter(strOrNum);
+    
+    x.propertyOnlyInI1; // error
+      ~~~~~~~~~~~~~~~~
+!!! error TS2339: Property 'propertyOnlyInI1' does not exist on type 'I1<number> | I2<number>'.
+    x.propertyOnlyInI2; // error
+      ~~~~~~~~~~~~~~~~
+!!! error TS2339: Property 'propertyOnlyInI2' does not exist on type 'I1<number> | I2<number>'.
+    x.methodOnlyInI1("hello"); // error
+      ~~~~~~~~~~~~~~
+!!! error TS2339: Property 'methodOnlyInI1' does not exist on type 'I1<number> | I2<number>'.
+    x.methodOnlyInI2(10); // error
+      ~~~~~~~~~~~~~~
+!!! error TS2339: Property 'methodOnlyInI2' does not exist on type 'I1<number> | I2<number>'.
\ No newline at end of file
diff --git a/tests/baselines/reference/unionTypeMembers.js b/tests/baselines/reference/unionTypeMembers.js
new file mode 100644
index 00000000000..b03572246b4
--- /dev/null
+++ b/tests/baselines/reference/unionTypeMembers.js
@@ -0,0 +1,79 @@
+//// [unionTypeMembers.ts]
+interface I1<T> {
+    commonMethodType(a: string): string;
+    commonPropertyType: string;
+
+    commonMethodDifferentParameterType(a: string): string;
+    commonMethodDifferentReturnType(a: string): string;
+    commonPropertyDifferenType: string;
+
+    commonMethodWithTypeParameter(a: T): T;
+    commonMethodWithOwnTypeParameter<U>(a: U): U;
+
+    methodOnlyInI1(a: string): string;
+    propertyOnlyInI1: string;
+}
+
+interface I2<T> {
+    commonMethodType(a: string): string;
+    commonPropertyType: string;
+
+    commonMethodDifferentParameterType(a: number): number;
+    commonMethodDifferentReturnType(a: string): number;
+    commonPropertyDifferenType: number;
+
+    commonMethodWithTypeParameter(a: T): T;
+    commonMethodWithOwnTypeParameter<U>(a: U): U;
+
+    methodOnlyInI2(a: string): string;
+    propertyOnlyInI2: string;
+}
+
+// a union type U has those members that are present in every one of its constituent types, 
+// with types that are unions of the respective members in the constituent types
+var x : I1<number> | I2<number>;
+var str: string;
+var num: number;
+var strOrNum: string | number;
+
+// If each type in U has a property P, U has a property P of a union type of the types of P from each type in U.
+str = x.commonPropertyType; // string
+str = x.commonMethodType(str); // (a: string) => string so result should be string
+strOrNum = x.commonPropertyDifferenType;
+strOrNum = x.commonMethodDifferentReturnType(str); // string | union
+x.commonMethodDifferentParameterType; // No error - property exists
+x.commonMethodDifferentParameterType(strOrNum); // error - no call signatures because the type of this property is ((a: string) => string) | (a: number) => number
+                                                // and the call signatures arent identical
+num = x.commonMethodWithTypeParameter(num);
+num = x.commonMethodWithOwnTypeParameter(num);
+str = x.commonMethodWithOwnTypeParameter(str);
+strOrNum = x.commonMethodWithOwnTypeParameter(strOrNum);
+
+x.propertyOnlyInI1; // error
+x.propertyOnlyInI2; // error
+x.methodOnlyInI1("hello"); // error
+x.methodOnlyInI2(10); // error
+
+//// [unionTypeMembers.js]
+// a union type U has those members that are present in every one of its constituent types, 
+// with types that are unions of the respective members in the constituent types
+var x;
+var str;
+var num;
+var strOrNum;
+// If each type in U has a property P, U has a property P of a union type of the types of P from each type in U.
+str = x.commonPropertyType; // string
+str = x.commonMethodType(str); // (a: string) => string so result should be string
+strOrNum = x.commonPropertyDifferenType;
+strOrNum = x.commonMethodDifferentReturnType(str); // string | union
+x.commonMethodDifferentParameterType; // No error - property exists
+x.commonMethodDifferentParameterType(strOrNum); // error - no call signatures because the type of this property is ((a: string) => string) | (a: number) => number
+// and the call signatures arent identical
+num = x.commonMethodWithTypeParameter(num);
+num = x.commonMethodWithOwnTypeParameter(num);
+str = x.commonMethodWithOwnTypeParameter(str);
+strOrNum = x.commonMethodWithOwnTypeParameter(strOrNum);
+x.propertyOnlyInI1; // error
+x.propertyOnlyInI2; // error
+x.methodOnlyInI1("hello"); // error
+x.methodOnlyInI2(10); // error
diff --git a/tests/baselines/reference/unionTypesAssignability.errors.txt b/tests/baselines/reference/unionTypesAssignability.errors.txt
new file mode 100644
index 00000000000..f1ede4c10fb
--- /dev/null
+++ b/tests/baselines/reference/unionTypesAssignability.errors.txt
@@ -0,0 +1,154 @@
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts(18,1): error TS2322: Type 'E' is not assignable to type 'D'.
+  Property 'foo1' is missing in type 'E'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts(19,1): error TS2322: Type 'D | E' is not assignable to type 'D'.
+  Type 'E' is not assignable to type 'D'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts(20,1): error TS2322: Type 'D' is not assignable to type 'E'.
+  Property 'foo2' is missing in type 'D'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts(22,1): error TS2322: Type 'D | E' is not assignable to type 'E'.
+  Type 'D' is not assignable to type 'E'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts(24,1): error TS2322: Type 'string' is not assignable to type 'number'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts(25,1): error TS2322: Type 'string | number' is not assignable to type 'number'.
+  Type 'string' is not assignable to type 'number'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts(26,1): error TS2322: Type 'number' is not assignable to type 'string'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts(28,1): error TS2322: Type 'string | number' is not assignable to type 'string'.
+  Type 'number' is not assignable to type 'string'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts(31,1): error TS2322: Type 'C' is not assignable to type 'D'.
+  Property 'foo1' is missing in type 'C'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts(32,1): error TS2322: Type 'C' is not assignable to type 'E'.
+  Property 'foo2' is missing in type 'C'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts(33,1): error TS2322: Type 'C' is not assignable to type 'D | E'.
+  Type 'C' is not assignable to type 'E'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts(35,1): error TS2322: Type 'D' is not assignable to type 'E'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts(37,1): error TS2322: Type 'E' is not assignable to type 'D'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts(41,1): error TS2322: Type 'number' is not assignable to type 'string'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts(43,1): error TS2322: Type 'string' is not assignable to type 'number'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts(64,5): error TS2322: Type 'U' is not assignable to type 'T'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts(65,5): error TS2322: Type 'T' is not assignable to type 'U'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts(69,5): error TS2322: Type 'T | U' is not assignable to type 'T'.
+  Type 'U' is not assignable to type 'T'.
+tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts(70,5): error TS2322: Type 'T | U' is not assignable to type 'U'.
+  Type 'T' is not assignable to type 'U'.
+
+
+==== tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts (19 errors) ====
+    var unionNumberString: number | string;
+    class C { }
+    class D extends C { foo1() { } }
+    class E extends C { foo2() { } }
+    var unionDE: D | E;
+    
+    var num: number;
+    var str: string;
+    var c: C;
+    var d: D;
+    var e: E;
+    
+    // A union type U is assignable to a type T if each type in U is assignable to T
+    c = d;
+    c = e;
+    c = unionDE; // ok
+    d = d;
+    d = e;
+    ~
+!!! error TS2322: Type 'E' is not assignable to type 'D'.
+!!! error TS2322:   Property 'foo1' is missing in type 'E'.
+    d = unionDE; // error e is not assignable to d
+    ~
+!!! error TS2322: Type 'D | E' is not assignable to type 'D'.
+!!! error TS2322:   Type 'E' is not assignable to type 'D'.
+    e = d;
+    ~
+!!! error TS2322: Type 'D' is not assignable to type 'E'.
+!!! error TS2322:   Property 'foo2' is missing in type 'D'.
+    e = e;
+    e = unionDE; // error d is not assignable to e
+    ~
+!!! error TS2322: Type 'D | E' is not assignable to type 'E'.
+!!! error TS2322:   Type 'D' is not assignable to type 'E'.
+    num = num;
+    num = str;
+    ~~~
+!!! error TS2322: Type 'string' is not assignable to type 'number'.
+    num = unionNumberString; // error string is not assignable to number
+    ~~~
+!!! error TS2322: Type 'string | number' is not assignable to type 'number'.
+!!! error TS2322:   Type 'string' is not assignable to type 'number'.
+    str = num;
+    ~~~
+!!! error TS2322: Type 'number' is not assignable to type 'string'.
+    str = str;
+    str = unionNumberString; // error since number is not assignable to string
+    ~~~
+!!! error TS2322: Type 'string | number' is not assignable to type 'string'.
+!!! error TS2322:   Type 'number' is not assignable to type 'string'.
+    
+    // A type T is assignable to a union type U if T is assignable to any type in U
+    d = c;
+    ~
+!!! error TS2322: Type 'C' is not assignable to type 'D'.
+!!! error TS2322:   Property 'foo1' is missing in type 'C'.
+    e = c;
+    ~
+!!! error TS2322: Type 'C' is not assignable to type 'E'.
+!!! error TS2322:   Property 'foo2' is missing in type 'C'.
+    unionDE = c; // error since C is not assinable to either D or E
+    ~~~~~~~
+!!! error TS2322: Type 'C' is not assignable to type 'D | E'.
+!!! error TS2322:   Type 'C' is not assignable to type 'E'.
+    d = d;
+    e = d;
+    ~
+!!! error TS2322: Type 'D' is not assignable to type 'E'.
+    unionDE = d; // ok
+    d = e;
+    ~
+!!! error TS2322: Type 'E' is not assignable to type 'D'.
+    e = e;
+    unionDE = e; // ok
+    num = num;
+    str = num;
+    ~~~
+!!! error TS2322: Type 'number' is not assignable to type 'string'.
+    unionNumberString = num; // ok 
+    num = str;
+    ~~~
+!!! error TS2322: Type 'string' is not assignable to type 'number'.
+    str = str;
+    unionNumberString = str; // ok
+    
+    // Any
+    var anyVar: any;
+    anyVar = unionDE;
+    anyVar = unionNumberString;
+    unionDE = anyVar;
+    unionNumberString = anyVar;
+    
+    // null
+    unionDE = null;
+    unionNumberString = null;
+    
+    // undefined
+    unionDE = undefined;
+    unionNumberString = undefined;
+    
+    // type parameters
+    function foo<T, U>(t: T, u: U) {
+        t = u; // error
+        ~
+!!! error TS2322: Type 'U' is not assignable to type 'T'.
+        u = t; // error
+        ~
+!!! error TS2322: Type 'T' is not assignable to type 'U'.
+        var x : T | U;
+        x = t; // ok
+        x = u; // ok
+        t = x; // error U not assignable to T
+        ~
+!!! error TS2322: Type 'T | U' is not assignable to type 'T'.
+!!! error TS2322:   Type 'U' is not assignable to type 'T'.
+        u = x; // error T not assignable to U
+        ~
+!!! error TS2322: Type 'T | U' is not assignable to type 'U'.
+!!! error TS2322:   Type 'T' is not assignable to type 'U'.
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/unionTypesAssignability.js b/tests/baselines/reference/unionTypesAssignability.js
new file mode 100644
index 00000000000..a67f23bb09f
--- /dev/null
+++ b/tests/baselines/reference/unionTypesAssignability.js
@@ -0,0 +1,165 @@
+//// [unionTypesAssignability.ts]
+var unionNumberString: number | string;
+class C { }
+class D extends C { foo1() { } }
+class E extends C { foo2() { } }
+var unionDE: D | E;
+
+var num: number;
+var str: string;
+var c: C;
+var d: D;
+var e: E;
+
+// A union type U is assignable to a type T if each type in U is assignable to T
+c = d;
+c = e;
+c = unionDE; // ok
+d = d;
+d = e;
+d = unionDE; // error e is not assignable to d
+e = d;
+e = e;
+e = unionDE; // error d is not assignable to e
+num = num;
+num = str;
+num = unionNumberString; // error string is not assignable to number
+str = num;
+str = str;
+str = unionNumberString; // error since number is not assignable to string
+
+// A type T is assignable to a union type U if T is assignable to any type in U
+d = c;
+e = c;
+unionDE = c; // error since C is not assinable to either D or E
+d = d;
+e = d;
+unionDE = d; // ok
+d = e;
+e = e;
+unionDE = e; // ok
+num = num;
+str = num;
+unionNumberString = num; // ok 
+num = str;
+str = str;
+unionNumberString = str; // ok
+
+// Any
+var anyVar: any;
+anyVar = unionDE;
+anyVar = unionNumberString;
+unionDE = anyVar;
+unionNumberString = anyVar;
+
+// null
+unionDE = null;
+unionNumberString = null;
+
+// undefined
+unionDE = undefined;
+unionNumberString = undefined;
+
+// type parameters
+function foo<T, U>(t: T, u: U) {
+    t = u; // error
+    u = t; // error
+    var x : T | U;
+    x = t; // ok
+    x = u; // ok
+    t = x; // error U not assignable to T
+    u = x; // error T not assignable to U
+}
+
+
+//// [unionTypesAssignability.js]
+var __extends = this.__extends || function (d, b) {
+    for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
+    function __() { this.constructor = d; }
+    __.prototype = b.prototype;
+    d.prototype = new __();
+};
+var unionNumberString;
+var C = (function () {
+    function C() {
+    }
+    return C;
+})();
+var D = (function (_super) {
+    __extends(D, _super);
+    function D() {
+        _super.apply(this, arguments);
+    }
+    D.prototype.foo1 = function () {
+    };
+    return D;
+})(C);
+var E = (function (_super) {
+    __extends(E, _super);
+    function E() {
+        _super.apply(this, arguments);
+    }
+    E.prototype.foo2 = function () {
+    };
+    return E;
+})(C);
+var unionDE;
+var num;
+var str;
+var c;
+var d;
+var e;
+// A union type U is assignable to a type T if each type in U is assignable to T
+c = d;
+c = e;
+c = unionDE; // ok
+d = d;
+d = e;
+d = unionDE; // error e is not assignable to d
+e = d;
+e = e;
+e = unionDE; // error d is not assignable to e
+num = num;
+num = str;
+num = unionNumberString; // error string is not assignable to number
+str = num;
+str = str;
+str = unionNumberString; // error since number is not assignable to string
+// A type T is assignable to a union type U if T is assignable to any type in U
+d = c;
+e = c;
+unionDE = c; // error since C is not assinable to either D or E
+d = d;
+e = d;
+unionDE = d; // ok
+d = e;
+e = e;
+unionDE = e; // ok
+num = num;
+str = num;
+unionNumberString = num; // ok 
+num = str;
+str = str;
+unionNumberString = str; // ok
+// Any
+var anyVar;
+anyVar = unionDE;
+anyVar = unionNumberString;
+unionDE = anyVar;
+unionNumberString = anyVar;
+// null
+unionDE = null;
+unionNumberString = null;
+// undefined
+unionDE = undefined;
+unionNumberString = undefined;
+// type parameters
+function foo(t, u) {
+    t = u; // error
+    u = t; // error
+    var x;
+    x = t; // ok
+    x = u; // ok
+    t = x; // error U not assignable to T
+    u = x; // error T not assignable to U
+}
diff --git a/tests/baselines/reference/witness.js b/tests/baselines/reference/witness.js
index e686efc535f..607c2415044 100644
--- a/tests/baselines/reference/witness.js
+++ b/tests/baselines/reference/witness.js
@@ -269,3 +269,4 @@ var C3 = (function () {
 })();
 var qq = C3.q;
 var qq;
+// Parentheses - tested a bunch above
diff --git a/tests/cases/compiler/commentEmitAtEndOfFile1.ts b/tests/cases/compiler/commentEmitAtEndOfFile1.ts
new file mode 100644
index 00000000000..b1b863890d5
--- /dev/null
+++ b/tests/cases/compiler/commentEmitAtEndOfFile1.ts
@@ -0,0 +1,10 @@
+// test
+var f = ''
+// test #2
+module foo {
+        function bar() { }
+}
+// test #3
+module empty {
+}
+// test #4
\ No newline at end of file
diff --git a/tests/cases/compiler/externalModuleReferenceDoubleUnderscore1.ts b/tests/cases/compiler/externalModuleReferenceDoubleUnderscore1.ts
new file mode 100644
index 00000000000..1ff020b4919
--- /dev/null
+++ b/tests/cases/compiler/externalModuleReferenceDoubleUnderscore1.ts
@@ -0,0 +1,16 @@
+declare module 'timezonecomplete' {
+    import basics = require("__timezonecomplete/basics");
+    export import TimeUnit = basics.TimeUnit;
+}
+
+declare module '__timezonecomplete/basics' {
+    export enum TimeUnit {
+        Second = 0,
+        Minute = 1,
+        Hour = 2,
+        Day = 3,
+        Week = 4,
+        Month = 5,
+        Year = 6,
+    }
+}
\ No newline at end of file
diff --git a/tests/cases/conformance/expressions/binaryOperators/logicalOrOperator/logicalOrOperatorWithEveryType.ts b/tests/cases/conformance/expressions/binaryOperators/logicalOrOperator/logicalOrOperatorWithEveryType.ts
index 2db2b854f6a..9ec124449f3 100644
--- a/tests/cases/conformance/expressions/binaryOperators/logicalOrOperator/logicalOrOperatorWithEveryType.ts
+++ b/tests/cases/conformance/expressions/binaryOperators/logicalOrOperator/logicalOrOperatorWithEveryType.ts
@@ -27,77 +27,77 @@ var ra10 = undefined || a1; // undefined || any is any
 
 var rb1 = a1 || a2;         // any       || boolean is any
 var rb2 = a2 || a2;         // boolean   || boolean is boolean
-var rb3 = a3 || a2;         // number    || boolean is {}
-var rb4 = a4 || a2;         // string    || boolean is {}
-var rb5 = a5 || a2;         // void      || boolean is {}
-var rb6 = a6 || a2;         // enum      || boolean is {}
-var rb7 = a7 || a2;         // object    || boolean is {}
-var rb8 = a8 || a2;         // array     || boolean is {}
+var rb3 = a3 || a2;         // number    || boolean is number | boolean
+var rb4 = a4 || a2;         // string    || boolean is string | boolean
+var rb5 = a5 || a2;         // void      || boolean is void | boolean
+var rb6 = a6 || a2;         // enum      || boolean is E | boolean
+var rb7 = a7 || a2;         // object    || boolean is object | boolean
+var rb8 = a8 || a2;         // array     || boolean is array | boolean
 var rb9 = null || a2;       // null      || boolean is boolean
 var rb10= undefined || a2;  // undefined || boolean is boolean
 
 var rc1 = a1 || a3;         // any       || number is any
-var rc2 = a2 || a3;         // boolean   || number is {}
+var rc2 = a2 || a3;         // boolean   || number is boolean | number
 var rc3 = a3 || a3;         // number    || number is number
-var rc4 = a4 || a3;         // string    || number is {}
-var rc5 = a5 || a3;         // void      || number is {}
+var rc4 = a4 || a3;         // string    || number is string | number
+var rc5 = a5 || a3;         // void      || number is void | number
 var rc6 = a6 || a3;         // enum      || number is number
-var rc7 = a7 || a3;         // object    || number is {}
-var rc8 = a8 || a3;         // array     || number is {}
+var rc7 = a7 || a3;         // object    || number is object | number
+var rc8 = a8 || a3;         // array     || number is array | number
 var rc9 = null || a3;       // null      || number is number
 var rc10 = undefined || a3; // undefined || number is number
 
 var rd1 = a1 || a4;         // any       || string is any
-var rd2 = a2 || a4;         // boolean   || string is {}
-var rd3 = a3 || a4;         // number    || string is {}
+var rd2 = a2 || a4;         // boolean   || string is boolean | string
+var rd3 = a3 || a4;         // number    || string is number | string
 var rd4 = a4 || a4;         // string    || string is string
-var rd5 = a5 || a4;         // void      || string is {}
-var rd6 = a6 || a4;         // enum      || string is {}
-var rd7 = a7 || a4;         // object    || string is {}
-var rd8 = a8 || a4;         // array     || string is {}
+var rd5 = a5 || a4;         // void      || string is void | string
+var rd6 = a6 || a4;         // enum      || string is enum | string
+var rd7 = a7 || a4;         // object    || string is object | string
+var rd8 = a8 || a4;         // array     || string is array | string
 var rd9 = null || a4;       // null      || string is string
 var rd10 = undefined || a4; // undefined || string is string
 
 var re1 = a1 || a5;         // any       || void is any
-var re2 = a2 || a5;         // boolean   || void is {}
-var re3 = a3 || a5;         // number    || void is {}
-var re4 = a4 || a5;         // string    || void is {}
+var re2 = a2 || a5;         // boolean   || void is boolean | void
+var re3 = a3 || a5;         // number    || void is number | void
+var re4 = a4 || a5;         // string    || void is string | void
 var re5 = a5 || a5;         // void      || void is void
-var re6 = a6 || a5;         // enum      || void is {}
-var re7 = a7 || a5;         // object    || void is {}
-var re8 = a8 || a5;         // array     || void is {}
+var re6 = a6 || a5;         // enum      || void is enum | void
+var re7 = a7 || a5;         // object    || void is object | void
+var re8 = a8 || a5;         // array     || void is array | void
 var re9 = null || a5;       // null      || void is void
 var re10 = undefined || a5; // undefined || void is void
 
 var rg1 = a1 || a6;         // any       || enum is any
-var rg2 = a2 || a6;         // boolean   || enum is {}
+var rg2 = a2 || a6;         // boolean   || enum is boolean | enum
 var rg3 = a3 || a6;         // number    || enum is number
-var rg4 = a4 || a6;         // string    || enum is {}
-var rg5 = a5 || a6;         // void      || enum is {}
+var rg4 = a4 || a6;         // string    || enum is string | enum
+var rg5 = a5 || a6;         // void      || enum is void | enum
 var rg6 = a6 || a6;         // enum      || enum is E
-var rg7 = a7 || a6;         // object    || enum is {}
-var rg8 = a8 || a6;         // array     || enum is {}
+var rg7 = a7 || a6;         // object    || enum is object | enum
+var rg8 = a8 || a6;         // array     || enum is array | enum
 var rg9 = null || a6;       // null      || enum is E
 var rg10 = undefined || a6; // undefined || enum is E
 
 var rh1 = a1 || a7;         // any       || object is any
-var rh2 = a2 || a7;         // boolean   || object is {}
-var rh3 = a3 || a7;         // number    || object is {}
-var rh4 = a4 || a7;         // string    || object is {}
-var rh5 = a5 || a7;         // void      || object is {}
-var rh6 = a6 || a7;         // enum      || object is {}
+var rh2 = a2 || a7;         // boolean   || object is boolean | object
+var rh3 = a3 || a7;         // number    || object is number | object
+var rh4 = a4 || a7;         // string    || object is string | object
+var rh5 = a5 || a7;         // void      || object is void | object
+var rh6 = a6 || a7;         // enum      || object is enum | object
 var rh7 = a7 || a7;         // object    || object is object
-var rh8 = a8 || a7;         // array     || object is {}
+var rh8 = a8 || a7;         // array     || object is array | object
 var rh9 = null || a7;       // null      || object is object
 var rh10 = undefined || a7; // undefined || object is object
 
 var ri1 = a1 || a8;         // any       || array is any
-var ri2 = a2 || a8;         // boolean   || array is {}
-var ri3 = a3 || a8;         // number    || array is {}
-var ri4 = a4 || a8;         // string    || array is {}
-var ri5 = a5 || a8;         // void      || array is {}
-var ri6 = a6 || a8;         // enum      || array is {}
-var ri7 = a7 || a8;         // object    || array is {}
+var ri2 = a2 || a8;         // boolean   || array is boolean | array
+var ri3 = a3 || a8;         // number    || array is number | array
+var ri4 = a4 || a8;         // string    || array is string | array
+var ri5 = a5 || a8;         // void      || array is void | array
+var ri6 = a6 || a8;         // enum      || array is enum | array
+var ri7 = a7 || a8;         // object    || array is object | array
 var ri8 = a8 || a8;         // array     || array is array
 var ri9 = null || a8;       // null      || array is array
 var ri10 = undefined || a8; // undefined || array is array
diff --git a/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditionIsBooleanType.ts b/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditionIsBooleanType.ts
index 80c2a8e8ec8..67b609e03e9 100644
--- a/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditionIsBooleanType.ts
+++ b/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditionIsBooleanType.ts
@@ -19,6 +19,7 @@ condBoolean ? exprBoolean1 : exprBoolean2;
 condBoolean ? exprNumber1 : exprNumber2;
 condBoolean ? exprString1 : exprString2;
 condBoolean ? exprIsObject1 : exprIsObject2;
+condBoolean ? exprString1 : exprBoolean1; // union
 
 //Cond is a boolean type literal
 true ? exprAny1 : exprAny2;
@@ -26,6 +27,7 @@ false ? exprBoolean1 : exprBoolean2;
 true ? exprNumber1 : exprNumber2;
 false ? exprString1 : exprString2;
 true ? exprIsObject1 : exprIsObject2;
+true ? exprString1 : exprBoolean1; // union
 
 //Cond is a boolean type expression
 !true ? exprAny1 : exprAny2;
@@ -33,6 +35,7 @@ typeof "123" == "string" ? exprBoolean1 : exprBoolean2;
 2 > 1 ? exprNumber1 : exprNumber2;
 null === undefined ? exprString1 : exprString2;
 true || false ? exprIsObject1 : exprIsObject2;
+null === undefined ? exprString1 : exprBoolean1; // union
 
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condBoolean ? exprAny1 : exprAny2;
@@ -40,15 +43,19 @@ var resultIsBoolean1 = condBoolean ? exprBoolean1 : exprBoolean2;
 var resultIsNumber1 = condBoolean ? exprNumber1 : exprNumber2;
 var resultIsString1 = condBoolean ? exprString1 : exprString2;
 var resultIsObject1 = condBoolean ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean1 = condBoolean ? exprString1 : exprBoolean1; // union
 
 var resultIsAny2 = true ? exprAny1 : exprAny2;
 var resultIsBoolean2 = false ? exprBoolean1 : exprBoolean2;
 var resultIsNumber2 = true ? exprNumber1 : exprNumber2;
 var resultIsString2 = false ? exprString1 : exprString2;
 var resultIsObject2 = true ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean2 = true ? exprString1 : exprBoolean1; // union
+var resultIsStringOrBoolean3 = false ? exprString1 : exprBoolean1; // union
 
 var resultIsAny3 = !true ? exprAny1 : exprAny2;
 var resultIsBoolean3 = typeof "123" == "string" ? exprBoolean1 : exprBoolean2;
 var resultIsNumber3 = 2 > 1 ? exprNumber1 : exprNumber2;
 var resultIsString3 = null === undefined ? exprString1 : exprString2;
 var resultIsObject3 = true || false ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean4 = typeof "123" === "string" ? exprString1 : exprBoolean1; // union
diff --git a/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditionIsNumberType.ts b/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditionIsNumberType.ts
index 5ec1beb9342..2e2c39ef316 100644
--- a/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditionIsNumberType.ts
+++ b/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditionIsNumberType.ts
@@ -19,6 +19,7 @@ condNumber ? exprBoolean1 : exprBoolean2;
 condNumber ? exprNumber1 : exprNumber2;
 condNumber ? exprString1 : exprString2;
 condNumber ? exprIsObject1 : exprIsObject2;
+condNumber ? exprString1 : exprBoolean1; // Union
 
 //Cond is a number type literal
 1 ? exprAny1 : exprAny2;
@@ -26,6 +27,7 @@ condNumber ? exprIsObject1 : exprIsObject2;
 0.123456789 ? exprNumber1 : exprNumber2;
 - 10000000000000 ? exprString1 : exprString2;
 1000000000000 ? exprIsObject1 : exprIsObject2;
+10000 ? exprString1 : exprBoolean1; // Union
 
 //Cond is a number type expression
 function foo() { return 1 };
@@ -36,6 +38,7 @@ var array = [1, 2, 3];
 "string".length ? exprNumber1 : exprNumber2;
 foo() ? exprString1 : exprString2;
 foo() / array[1] ? exprIsObject1 : exprIsObject2;
+foo() ? exprString1 : exprBoolean1; // Union
 
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condNumber ? exprAny1 : exprAny2;
@@ -43,15 +46,18 @@ var resultIsBoolean1 = condNumber ? exprBoolean1 : exprBoolean2;
 var resultIsNumber1 = condNumber ? exprNumber1 : exprNumber2;
 var resultIsString1 = condNumber ? exprString1 : exprString2;
 var resultIsObject1 = condNumber ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean1 = condNumber ? exprString1 : exprBoolean1; // Union
 
 var resultIsAny2 = 1 ? exprAny1 : exprAny2;
 var resultIsBoolean2 = 0 ? exprBoolean1 : exprBoolean2;
 var resultIsNumber2 = 0.123456789 ? exprNumber1 : exprNumber2;
 var resultIsString2 = - 10000000000000 ? exprString1 : exprString2;
 var resultIsObject2 = 1000000000000 ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean2 = 10000 ? exprString1 : exprBoolean1; // Union
 
 var resultIsAny3 = 1 * 0 ? exprAny1 : exprAny2;
 var resultIsBoolean3 = 1 + 1 ? exprBoolean1 : exprBoolean2;
 var resultIsNumber3 = "string".length ? exprNumber1 : exprNumber2;
 var resultIsString3 = foo() ? exprString1 : exprString2;
 var resultIsObject3 = foo() / array[1] ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean3 = foo() / array[1] ? exprString1 : exprBoolean1; // Union
\ No newline at end of file
diff --git a/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditionIsObjectType.ts b/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditionIsObjectType.ts
index 5c8dcf0a13e..24b6970e12b 100644
--- a/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditionIsObjectType.ts
+++ b/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditionIsObjectType.ts
@@ -22,6 +22,7 @@ condObject ? exprBoolean1 : exprBoolean2;
 condObject ? exprNumber1 : exprNumber2;
 condObject ? exprString1 : exprString2;
 condObject ? exprIsObject1 : exprIsObject2;
+condObject ? exprString1 : exprBoolean1; // union
 
 //Cond is an object type literal
 ((a: string) => a.length) ? exprAny1 : exprAny2;
@@ -29,6 +30,7 @@ condObject ? exprIsObject1 : exprIsObject2;
 ({}) ? exprNumber1 : exprNumber2;
 ({ a: 1, b: "s" }) ? exprString1 : exprString2;
 ({ a: 1, b: "s" }) ? exprIsObject1 : exprIsObject2;
+({ a: 1, b: "s" }) ? exprString1: exprBoolean1; // union
 
 //Cond is an object type expression
 foo() ? exprAny1 : exprAny2;
@@ -36,6 +38,7 @@ new Date() ? exprBoolean1 : exprBoolean2;
 new C() ? exprNumber1 : exprNumber2;
 C.doIt() ? exprString1 : exprString2;
 condObject.valueOf() ? exprIsObject1 : exprIsObject2;
+new Date() ? exprString1 : exprBoolean1; // union
 
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condObject ? exprAny1 : exprAny2;
@@ -43,15 +46,18 @@ var resultIsBoolean1 = condObject ? exprBoolean1 : exprBoolean2;
 var resultIsNumber1 = condObject ? exprNumber1 : exprNumber2;
 var resultIsString1 = condObject ? exprString1 : exprString2;
 var resultIsObject1 = condObject ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean1 = condObject ? exprString1 : exprBoolean1; // union
 
 var resultIsAny2 = ((a: string) => a.length) ? exprAny1 : exprAny2;
 var resultIsBoolean2 = ((a: string) => a.length) ? exprBoolean1 : exprBoolean2;
 var resultIsNumber2 = ({}) ? exprNumber1 : exprNumber2;
 var resultIsString2 = ({ a: 1, b: "s" }) ? exprString1 : exprString2;
 var resultIsObject2 = ({ a: 1, b: "s" }) ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean2 = ({ a: 1, b: "s" }) ? exprString1 : exprBoolean1; // union
 
 var resultIsAny3 = foo() ? exprAny1 : exprAny2;
 var resultIsBoolean3 = new Date() ? exprBoolean1 : exprBoolean2;
 var resultIsNumber3 = new C() ? exprNumber1 : exprNumber2;
 var resultIsString3 = C.doIt() ? exprString1 : exprString2;
 var resultIsObject3 = condObject.valueOf() ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean3 = C.doIt() ? exprString1 : exprBoolean1; // union
diff --git a/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditoinIsAnyType.ts b/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditoinIsAnyType.ts
index 67ef99da141..3a03dfdacaa 100644
--- a/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditoinIsAnyType.ts
+++ b/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditoinIsAnyType.ts
@@ -20,6 +20,7 @@ condAny ? exprBoolean1 : exprBoolean2;
 condAny ? exprNumber1 : exprNumber2;
 condAny ? exprString1 : exprString2;
 condAny ? exprIsObject1 : exprIsObject2;
+condAny ? exprString1 : exprBoolean1; // union
 
 //Cond is an any type literal
 null ? exprAny1 : exprAny2;
@@ -27,6 +28,7 @@ null ? exprBoolean1 : exprBoolean2;
 undefined ? exprNumber1 : exprNumber2;
 [null, undefined] ? exprString1 : exprString2;
 [null, undefined] ? exprIsObject1 : exprIsObject2;
+undefined ? exprString1 : exprBoolean1; // union
 
 //Cond is an any type expression
 x.doSomeThing() ? exprAny1 : exprAny2;
@@ -34,6 +36,7 @@ x("x") ? exprBoolean1 : exprBoolean2;
 x(x) ? exprNumber1 : exprNumber2;
 x("x") ? exprString1 : exprString2;
 x.doSomeThing() ? exprIsObject1 : exprIsObject2;
+x.doSomeThing() ? exprString1 : exprBoolean1; // union
 
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condAny ? exprAny1 : exprAny2;
@@ -41,15 +44,20 @@ var resultIsBoolean1 = condAny ? exprBoolean1 : exprBoolean2;
 var resultIsNumber1 = condAny ? exprNumber1 : exprNumber2;
 var resultIsString1 = condAny ? exprString1 : exprString2;
 var resultIsObject1 = condAny ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean1 = condAny ? exprString1 : exprBoolean1; // union
 
 var resultIsAny2 = null ? exprAny1 : exprAny2;
 var resultIsBoolean2 = null ? exprBoolean1 : exprBoolean2;
 var resultIsNumber2 = undefined ? exprNumber1 : exprNumber2;
 var resultIsString2 = [null, undefined] ? exprString1 : exprString2;
 var resultIsObject2 = [null, undefined] ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean2 = null ? exprString1 : exprBoolean1; // union
+var resultIsStringOrBoolean3 = undefined ? exprString1 : exprBoolean1; // union
+var resultIsStringOrBoolean4 = [null, undefined] ? exprString1 : exprBoolean1; // union
 
 var resultIsAny3 = x.doSomeThing() ? exprAny1 : exprAny2;
 var resultIsBoolean3 = x("x") ? exprBoolean1 : exprBoolean2;
 var resultIsNumber3 = x(x) ? exprNumber1 : exprNumber2;
 var resultIsString3 = x("x") ? exprString1 : exprString2;
 var resultIsObject3 = x.doSomeThing() ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean5 = x.doSomeThing() ? exprString1 : exprBoolean1; // union
\ No newline at end of file
diff --git a/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditoinIsStringType.ts b/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditoinIsStringType.ts
index 37fd9102922..e8f026d52e3 100644
--- a/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditoinIsStringType.ts
+++ b/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorConditoinIsStringType.ts
@@ -19,6 +19,7 @@ condString ? exprBoolean1 : exprBoolean2;
 condString ? exprNumber1 : exprNumber2;
 condString ? exprString1 : exprString2;
 condString ? exprIsObject1 : exprIsObject2;
+condString ? exprString1 : exprBoolean1; // union
 
 //Cond is a string type literal
 "" ? exprAny1 : exprAny2;
@@ -26,6 +27,7 @@ condString ? exprIsObject1 : exprIsObject2;
 'c' ? exprNumber1 : exprNumber2;
 'string' ? exprString1 : exprString2;
 "  " ? exprIsObject1 : exprIsObject2;
+"hello " ? exprString1 : exprBoolean1; // union
 
 //Cond is a string type expression
 function foo() { return "string" };
@@ -36,6 +38,7 @@ condString.toUpperCase ? exprBoolean1 : exprBoolean2;
 condString + "string" ? exprNumber1 : exprNumber2;
 foo() ? exprString1 : exprString2;
 array[1] ? exprIsObject1 : exprIsObject2;
+foo() ? exprString1 : exprBoolean1; // union
 
 //Results shoud be same as Expr1 and Expr2
 var resultIsAny1 = condString ? exprAny1 : exprAny2;
@@ -43,15 +46,19 @@ var resultIsBoolean1 = condString ? exprBoolean1 : exprBoolean2;
 var resultIsNumber1 = condString ? exprNumber1 : exprNumber2;
 var resultIsString1 = condString ? exprString1 : exprString2;
 var resultIsObject1 = condString ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean1 = condString ? exprString1 : exprBoolean1; // union
 
 var resultIsAny2 = "" ? exprAny1 : exprAny2;
 var resultIsBoolean2 = "string" ? exprBoolean1 : exprBoolean2;
 var resultIsNumber2 = 'c' ? exprNumber1 : exprNumber2;
 var resultIsString2 = 'string' ? exprString1 : exprString2;
 var resultIsObject2 = "  " ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean2 = "hello" ? exprString1 : exprBoolean1; // union
 
 var resultIsAny3 = typeof condString ? exprAny1 : exprAny2;
 var resultIsBoolean3 = condString.toUpperCase ? exprBoolean1 : exprBoolean2;
 var resultIsNumber3 = condString + "string" ? exprNumber1 : exprNumber2;
 var resultIsString3 = foo() ? exprString1 : exprString2;
 var resultIsObject3 = array[1] ? exprIsObject1 : exprIsObject2;
+var resultIsStringOrBoolean3 = typeof condString ? exprString1 : exprBoolean1; // union
+var resultIsStringOrBoolean4 = condString.toUpperCase ? exprString1 : exprBoolean1; // union
\ No newline at end of file
diff --git a/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorWithoutIdenticalBCT.ts b/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorWithoutIdenticalBCT.ts
index feaa3c5a280..f529b4fb9a0 100644
--- a/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorWithoutIdenticalBCT.ts
+++ b/tests/cases/conformance/expressions/conditonalOperator/conditionalOperatorWithoutIdenticalBCT.ts
@@ -14,7 +14,9 @@ var result1 = true ? a : b;
 //Be contextually typed and and bct is not identical, results in errors that union type is not assignable to target
 var result2: A = true ? a : b;
 var result3: B = true ? a : b;
+var result31: A | B = true ? a : b;
 
 var result4: (t: X) => number = true ? (m) => m.propertyX1 : (n) => n.propertyX2;
 var result5: (t: X) => string = true ? (m) => m.propertyX1 : (n) => n.propertyX2;
-var result6: (t: X) => boolean = true ? (m) => m.propertyX1 : (n) => n.propertyX2;
\ No newline at end of file
+var result6: (t: X) => boolean = true ? (m) => m.propertyX1 : (n) => n.propertyX2;
+var result61: (t: X) => number| string = true ? (m) => m.propertyX1 : (n) => n.propertyX2;
diff --git a/tests/cases/conformance/functions/functionImplementationErrors.ts b/tests/cases/conformance/functions/functionImplementationErrors.ts
index 6db4f6ed7e1..ddd3ba0a2c1 100644
--- a/tests/cases/conformance/functions/functionImplementationErrors.ts
+++ b/tests/cases/conformance/functions/functionImplementationErrors.ts
@@ -41,3 +41,32 @@ undefined === function (): number {
     throw undefined;
     var x = 4;
 };
+
+class Base { private x; }
+class AnotherClass { private y; }
+class Derived1 extends Base { private m; }
+class Derived2 extends Base { private n; }
+function f8() {
+    return new Derived1();
+    return new Derived2();    
+}
+var f9 = function () {
+    return new Derived1();
+    return new Derived2();
+};
+var f10 = () => {
+    return new Derived1();
+    return new Derived2();
+};
+function f11() {
+    return new Base();
+    return new AnotherClass();
+}
+var f12 = function () {
+    return new Base();
+    return new AnotherClass();
+};
+var f13 = () => {
+    return new Base();
+    return new AnotherClass();
+};
diff --git a/tests/cases/conformance/functions/functionImplementations.ts b/tests/cases/conformance/functions/functionImplementations.ts
index d49b4780772..df36a0b4457 100644
--- a/tests/cases/conformance/functions/functionImplementations.ts
+++ b/tests/cases/conformance/functions/functionImplementations.ts
@@ -69,6 +69,10 @@ var n = function () {
     return 5;
 }();
 
+// Otherwise, the inferred return type is the first of the types of the return statement expressions
+// in the function body that is a supertype of each of the others, 
+// ignoring return statements with no expressions.
+// A compile - time error occurs if no return statement expression has a type that is a supertype of each of the others.
 // FunctionExpression with no return type annotation with multiple return statements with subtype relation between returns
 class Base { private m; }
 class Derived extends Base { private q; }
@@ -119,5 +123,34 @@ function f6(): number {
     return;
 }
 
-
-
+class Derived2 extends Base { private r: string; }
+class AnotherClass { private x }
+// if f is a contextually typed function expression, the inferred return type is the union type
+// of the types of the return statement expressions in the function body, 
+// ignoring return statements with no expressions.
+var f7: (x: number) => string | number = x => { // should be (x: number) => number | string
+    if (x < 0) { return x; }
+    return x.toString();
+}
+var f8: (x: number) => any = x => { // should be (x: number) => Base
+    return new Base();
+    return new Derived2();
+}
+var f9: (x: number) => any = x => { // should be (x: number) => Base
+    return new Base();
+    return new Derived();
+    return new Derived2();
+}
+var f10: (x: number) => any = x => { // should be (x: number) => Derived | Derived1
+    return new Derived();
+    return new Derived2();
+}
+var f11: (x: number) => any = x => { // should be (x: number) => Base | AnotherClass
+    return new Base();
+    return new AnotherClass();
+}
+var f12: (x: number) => any = x => { // should be (x: number) => Base | AnotherClass
+    return new Base();
+    return; // should be ignored
+    return new AnotherClass();
+}
\ No newline at end of file
diff --git a/tests/cases/conformance/types/specifyingTypes/typeLiterals/unionTypeLiterals.ts b/tests/cases/conformance/types/specifyingTypes/typeLiterals/unionTypeLiterals.ts
new file mode 100644
index 00000000000..7d52182beb3
--- /dev/null
+++ b/tests/cases/conformance/types/specifyingTypes/typeLiterals/unionTypeLiterals.ts
@@ -0,0 +1,15 @@
+// basic valid forms of union literals
+
+var simpleUnion: string | number;
+var unionOfUnion: string | number | boolean;
+
+var arrayOfUnions: (string | number)[];
+var arrayOfUnions: Array<string | number>;
+
+var unionOfFunctionType: (() => string) | (() => number);
+var unionOfFunctionType: { (): string } | { (): number };
+var unionOfFunctionType: () => string | number;
+
+var unionOfConstructorType: (new () => string) | (new () => number);
+var unionOfConstructorType: { new (): string } | { new (): number };
+var unionOfConstructorType: new () => string | number;
\ No newline at end of file
diff --git a/tests/cases/conformance/types/tuple/castingTuple.ts b/tests/cases/conformance/types/tuple/castingTuple.ts
index f154e5f00c8..cf5c58af346 100644
--- a/tests/cases/conformance/types/tuple/castingTuple.ts
+++ b/tests/cases/conformance/types/tuple/castingTuple.ts
@@ -15,13 +15,17 @@ var classCDTuple: [C, D] = [new C(), new D()];
 var interfaceIITuple = <[I, I]>classCDTuple;
 var classCDATuple = <[C, D, A]>classCDTuple;
 var eleFromCDA1 = classCDATuple[2]; // A
-var eleFromCDA2 = classCDATuple[5]; // {}
+var eleFromCDA2 = classCDATuple[5]; // C | D | A
 var t10: [E1, E2] = [E1.one, E2.one];
 var t11 = <[number, number]>t10;
 var array1 = <{}[]>emptyObjTuple;
+var unionTuple: [C, string | number] = [new C(), "foo"];
+var unionTuple2: [C, string | number, D] = [new C(), "foo", new D()];
+var unionTuple3: [number, string| number] = [10, "foo"]; 
+var unionTuple4 = <[number, number]>unionTuple3; 
 
 // error
 var t3 = <[number, number]>numStrTuple;
 var t9 = <[A, I]>classCDTuple;
 var array1 = <number[]>numStrTuple;
-t4[2] = 10;
\ No newline at end of file
+t4[2] = 10;
diff --git a/tests/cases/conformance/types/tuple/contextualTypeWithTuple.ts b/tests/cases/conformance/types/tuple/contextualTypeWithTuple.ts
index 7e9575d7f82..9600ebcd671 100644
--- a/tests/cases/conformance/types/tuple/contextualTypeWithTuple.ts
+++ b/tests/cases/conformance/types/tuple/contextualTypeWithTuple.ts
@@ -4,6 +4,13 @@ var numStrTuple2: [number, string] = [5, "foo", true];
 var numStrBoolTuple: [number, string, boolean] = [5, "foo", true];
 var objNumTuple: [{ a: string }, number] = [{ a: "world" }, 5];
 var strTupleTuple: [string, [number, {}]] = ["bar", [5, { x: 1, y: 1 }]];
+class C { }
+class D { }
+var unionTuple: [C, string | number] = [new C(), "foo"];
+var unionTuple1: [C, string | number] = [new C(), "foo"];
+var unionTuple2: [C, string | number, D] = [new C(), "foo", new D()];
+var unionTuple3: [number, string| number] = [10, "foo"]; 
+
 numStrTuple = numStrTuple2;
 numStrTuple = numStrBoolTuple;
 
@@ -11,3 +18,8 @@ numStrTuple = numStrBoolTuple;
 objNumTuple = [ {}, 5];
 numStrBoolTuple = numStrTuple;
 var strStrTuple: [string, string] = ["foo", "bar", 5];
+
+unionTuple = unionTuple1;
+unionTuple = unionTuple2;
+unionTuple2 = unionTuple;
+numStrTuple = unionTuple3;
\ No newline at end of file
diff --git a/tests/cases/conformance/types/tuple/indexerWithTuple.ts b/tests/cases/conformance/types/tuple/indexerWithTuple.ts
index 0b51ecd32ee..930ca56402c 100644
--- a/tests/cases/conformance/types/tuple/indexerWithTuple.ts
+++ b/tests/cases/conformance/types/tuple/indexerWithTuple.ts
@@ -1,15 +1,32 @@
 var strNumTuple: [string, number] = ["foo", 10]; 
 var numTupleTuple: [number, [string, number]] = [10, ["bar", 20]];
+var unionTuple1: [number, string| number] = [10, "foo"]; 
+var unionTuple2: [boolean, string| number] = [true, "foo"]; 
 
 // no error
 var idx0 = 0;
 var idx1 = 1;
 var ele10 = strNumTuple[0]; // string
 var ele11 = strNumTuple[1]; // number
-var ele12 = strNumTuple[2]; // {}
-var ele13 = strNumTuple[idx0]; // {}
-var ele14 = strNumTuple[idx1]; // {}
+var ele12 = strNumTuple[2]; // string | number
+var ele13 = strNumTuple[idx0]; // string | number
+var ele14 = strNumTuple[idx1]; // string | number
 var ele15 = strNumTuple["0"]; // string
 var ele16 = strNumTuple["1"]; // number
 var strNumTuple1 = numTupleTuple[1];  //[string, number];
-var ele17 = numTupleTuple[2]; // {}
\ No newline at end of file
+var ele17 = numTupleTuple[2]; // number | [string, number]
+var eleUnion10 = unionTuple1[0]; // number
+var eleUnion11 = unionTuple1[1]; // string | number
+var eleUnion12 = unionTuple1[2]; // string | number
+var eleUnion13 = unionTuple1[idx0]; // string | number
+var eleUnion14 = unionTuple1[idx1]; // string | number
+var eleUnion15 = unionTuple1["0"]; // number
+var eleUnion16 = unionTuple1["1"]; // string | number
+
+var eleUnion20 = unionTuple2[0]; // boolean
+var eleUnion21 = unionTuple2[1]; // string | number
+var eleUnion22 = unionTuple2[2]; // string | number | boolean
+var eleUnion23 = unionTuple2[idx0]; // string | number | boolean
+var eleUnion24 = unionTuple2[idx1]; // string | number | boolean
+var eleUnion25 = unionTuple2["0"]; // boolean
+var eleUnion26 = unionTuple2["1"]; // string | number
\ No newline at end of file
diff --git a/tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts b/tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts
new file mode 100644
index 00000000000..9ceee8845a5
--- /dev/null
+++ b/tests/cases/conformance/types/typeRelationships/assignmentCompatibility/unionTypesAssignability.ts
@@ -0,0 +1,71 @@
+var unionNumberString: number | string;
+class C { }
+class D extends C { foo1() { } }
+class E extends C { foo2() { } }
+var unionDE: D | E;
+
+var num: number;
+var str: string;
+var c: C;
+var d: D;
+var e: E;
+
+// A union type U is assignable to a type T if each type in U is assignable to T
+c = d;
+c = e;
+c = unionDE; // ok
+d = d;
+d = e;
+d = unionDE; // error e is not assignable to d
+e = d;
+e = e;
+e = unionDE; // error d is not assignable to e
+num = num;
+num = str;
+num = unionNumberString; // error string is not assignable to number
+str = num;
+str = str;
+str = unionNumberString; // error since number is not assignable to string
+
+// A type T is assignable to a union type U if T is assignable to any type in U
+d = c;
+e = c;
+unionDE = c; // error since C is not assinable to either D or E
+d = d;
+e = d;
+unionDE = d; // ok
+d = e;
+e = e;
+unionDE = e; // ok
+num = num;
+str = num;
+unionNumberString = num; // ok 
+num = str;
+str = str;
+unionNumberString = str; // ok
+
+// Any
+var anyVar: any;
+anyVar = unionDE;
+anyVar = unionNumberString;
+unionDE = anyVar;
+unionNumberString = anyVar;
+
+// null
+unionDE = null;
+unionNumberString = null;
+
+// undefined
+unionDE = undefined;
+unionNumberString = undefined;
+
+// type parameters
+function foo<T, U>(t: T, u: U) {
+    t = u; // error
+    u = t; // error
+    var x : T | U;
+    x = t; // ok
+    x = u; // ok
+    t = x; // error U not assignable to T
+    u = x; // error T not assignable to U
+}
diff --git a/tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts b/tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts
new file mode 100644
index 00000000000..c20bafeeabf
--- /dev/null
+++ b/tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/subtypesOfUnion.ts
@@ -0,0 +1,52 @@
+enum E { e1, e2 }
+interface I8 { [x: string]: number[]; }
+class A { foo: number; }
+class A2<T> { foo: T; }
+function f() { }
+module f { export var bar = 1; }
+class c { baz: string }
+module c { export var bar = 1; }
+
+// A type T is a subtype of a union type U if T is a subtype of any type in U.
+interface I1<T> {
+    [x: string]: string | number;
+    foo: any; // ok
+    foo2: string; // ok
+    foo3: number; // ok
+    foo4: boolean; // error 
+    foo5: E; // ok - subtype of number 
+    foo6: Date; // error
+    foo7: RegExp; // error
+    foo8: { bar: number }; // error
+    foo9: I8; // error
+    foo10: A; // error
+    foo11: A2<number>; // error
+    foo12: (x) => number; //error
+    foo13: <T>(x: T) => T; // error
+    foo14: typeof f; // error
+    foo15: typeof c; // error
+    foo16: T; // error
+    foo17: Object; // error
+    foo18: {}; // error
+}
+interface I2<T> {
+    [x: string]: E | number;
+    foo: any; // ok
+    foo2: string; // error
+    foo3: number; // ok
+    foo4: boolean; // error 
+    foo5: E; // ok
+    foo6: Date; // error
+    foo7: RegExp; // error
+    foo8: { bar: number }; // error
+    foo9: I8; // error
+    foo10: A; // error
+    foo11: A2<number>; // error
+    foo12: (x) => number; //error
+    foo13: <T>(x: T) => T; // error
+    foo14: typeof f; // error
+    foo15: typeof c; // error
+    foo16: T; // error
+    foo17: Object; // error
+    foo18: {}; // error
+}
\ No newline at end of file
diff --git a/tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts b/tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts
new file mode 100644
index 00000000000..7caa26a2959
--- /dev/null
+++ b/tests/cases/conformance/types/typeRelationships/subtypesAndSuperTypes/unionSubtypeIfEveryConstituentTypeIsSubtype.ts
@@ -0,0 +1,143 @@
+enum e {
+    e1,
+    e2
+}
+
+// A union type U is a subtype of a type T if each type in U is a subtype of T
+interface I {
+    [x: string]: any;
+    foo: string | number; // ok
+    foo2: e | number; // ok
+}
+interface I2 {
+    [x: string]: number;
+    // S is union type and each constituent type of S is a subtype of T
+    foo: string | number; // error string is not subtype of number
+    foo2: e | number; // ok e and number both subtype of number
+}
+
+interface I3 {
+    [x: string]: string;
+    foo: string | number; // error numer is not subtype of string
+    foo2: e | number; // error e and number both not subtype of string
+}
+
+// error cases
+interface I4 {
+    [x: string]: boolean;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+interface I5 {
+    [x: string]: Date;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+interface I6 {
+    [x: string]: RegExp;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+interface I7 {
+    [x: string]: { bar: number };
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+interface I8 {
+    [x: string]: number[];
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+interface I9 {
+    [x: string]: I8;
+    foo: string | number;
+    foo2: e | number;
+}
+
+class A { foo: number; }
+interface I10 {
+    [x: string]: A;
+    foo: string | number;
+    foo2: e | number;
+}
+
+class A2<T> { foo: T; }
+interface I11 {
+    [x: string]: A2<number>;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+interface I12 {
+    [x: string]: (x) => number;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+interface I13 {
+    [x: string]: <T>(x: T) => T;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+enum E2 { A }
+interface I14 {
+    [x: string]: E2;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+function f() { }
+module f {
+    export var bar = 1;
+}
+interface I15 {
+    [x: string]: typeof f;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+class c { baz: string }
+module c {
+    export var bar = 1;
+}
+interface I16 {
+    [x: string]: typeof c;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+interface I17<T> {
+    [x: string]: T;
+    foo: string | number;
+    foo2: e | number;
+}
+
+interface I19 {
+    [x: string]: Object;
+    foo: string | number;
+    foo2: e | number;
+}
+
+
+interface I20 {
+    [x: string]: {};
+    foo: string | number;
+    foo2: e | number;
+}
\ No newline at end of file
diff --git a/tests/cases/conformance/types/typeRelationships/typeAndMemberIdentity/unionTypeIdentity.ts b/tests/cases/conformance/types/typeRelationships/typeAndMemberIdentity/unionTypeIdentity.ts
new file mode 100644
index 00000000000..79100f476bc
--- /dev/null
+++ b/tests/cases/conformance/types/typeRelationships/typeAndMemberIdentity/unionTypeIdentity.ts
@@ -0,0 +1,8 @@
+// Two types are considered identical when
+// they are union types with identical sets of constituent types, or
+var strOrNum: string | boolean;
+var strOrNum: boolean | string;
+var strOrNum: boolean | string | boolean;
+var strOrNum: string; // error
+var strOrNum: boolean; // error
+var strOrNum: number; // error
\ No newline at end of file
diff --git a/tests/cases/conformance/types/union/unionTypeCallSignatures.ts b/tests/cases/conformance/types/union/unionTypeCallSignatures.ts
new file mode 100644
index 00000000000..1261de3299e
--- /dev/null
+++ b/tests/cases/conformance/types/union/unionTypeCallSignatures.ts
@@ -0,0 +1,70 @@
+var numOrDate: number | Date;
+var strOrBoolean: string | boolean;
+var strOrNum: string | number;
+
+// If each type in U has call signatures and the sets of call signatures are identical ignoring return types, 
+// U has the same set of call signatures, but with return types that are unions of the return types of the respective call signatures from each type in U.
+var unionOfDifferentReturnType: { (a: number): number; } | { (a: number): Date; };
+numOrDate = unionOfDifferentReturnType(10);
+strOrBoolean = unionOfDifferentReturnType("hello"); // error 
+unionOfDifferentReturnType1(true); // error in type of parameter
+
+var unionOfDifferentReturnType1: { (a: number): number; (a: string): string; } | { (a: number): Date; (a: string): boolean; };
+numOrDate = unionOfDifferentReturnType1(10);
+strOrBoolean = unionOfDifferentReturnType1("hello");
+unionOfDifferentReturnType1(true); // error in type of parameter
+unionOfDifferentReturnType1(); // error missing parameter
+
+var unionOfDifferentParameterTypes: { (a: number): number; } | { (a: string): Date; };
+unionOfDifferentParameterTypes(10);// error - no call signatures
+unionOfDifferentParameterTypes("hello");// error - no call signatures
+unionOfDifferentParameterTypes();// error - no call signatures
+
+var unionOfDifferentNumberOfSignatures: { (a: number): number; } | { (a: number): Date; (a: string): boolean; };
+unionOfDifferentNumberOfSignatures(); // error - no call signatures
+unionOfDifferentNumberOfSignatures(10); // error - no call signatures
+unionOfDifferentNumberOfSignatures("hello"); // error - no call signatures
+
+    var unionWithDifferentParameterCount: { (a: string): string; } | { (a: string, b: number): number; } ;
+unionWithDifferentParameterCount();// no  call signature
+unionWithDifferentParameterCount("hello");// no  call signature
+unionWithDifferentParameterCount("hello", 10);// no  call signature
+
+    var unionWithOptionalParameter1: { (a: string, b?: number): string; } | { (a: string, b?: number): number; };
+strOrNum = unionWithOptionalParameter1('hello');
+strOrNum = unionWithOptionalParameter1('hello', 10);
+strOrNum = unionWithOptionalParameter1('hello', "hello"); // error in parameter type
+strOrNum = unionWithOptionalParameter1(); // error
+
+var unionWithOptionalParameter2: { (a: string, b?: number): string; } | { (a: string, b: number): number };
+strOrNum = unionWithOptionalParameter2('hello'); // error no call signature
+strOrNum = unionWithOptionalParameter2('hello', 10); // error no call signature
+strOrNum = unionWithOptionalParameter2('hello', "hello"); // error no call signature
+strOrNum = unionWithOptionalParameter2(); // error no call signature
+
+var unionWithOptionalParameter3: { (a: string, b?: number): string; } | { (a: string): number; };
+strOrNum = unionWithOptionalParameter3('hello'); // error no call signature
+strOrNum = unionWithOptionalParameter3('hello', 10); // error no call signature
+strOrNum = unionWithOptionalParameter3('hello', "hello"); // error no call signature
+strOrNum = unionWithOptionalParameter3(); // error no call signature
+
+var unionWithRestParameter1: { (a: string, ...b: number[]): string; } | { (a: string, ...b: number[]): number };
+strOrNum = unionWithRestParameter1('hello');
+strOrNum = unionWithRestParameter1('hello', 10);
+strOrNum = unionWithRestParameter1('hello', 10, 11);
+strOrNum = unionWithRestParameter1('hello', "hello"); // error in parameter type
+strOrNum = unionWithRestParameter1(); // error
+
+var unionWithRestParameter2: { (a: string, ...b: number[]): string; } | { (a: string, b: number): number };
+strOrNum = unionWithRestParameter2('hello'); // error no call signature
+strOrNum = unionWithRestParameter2('hello', 10); // error no call signature
+strOrNum = unionWithRestParameter2('hello', 10, 11); // error no call signature
+strOrNum = unionWithRestParameter2('hello', "hello"); // error no call signature
+strOrNum = unionWithRestParameter2(); // error no call signature
+
+var unionWithRestParameter3: { (a: string, ...b: number[]): string; } | { (a: string): number };
+strOrNum = unionWithRestParameter3('hello'); // error no call signature
+strOrNum = unionWithRestParameter3('hello', 10); // error no call signature
+strOrNum = unionWithRestParameter3('hello', 10, 11); // error no call signature
+strOrNum = unionWithRestParameter3('hello', "hello"); // error no call signature
+strOrNum = unionWithRestParameter3(); // error no call signature
\ No newline at end of file
diff --git a/tests/cases/conformance/types/union/unionTypeConstructSignatures.ts b/tests/cases/conformance/types/union/unionTypeConstructSignatures.ts
new file mode 100644
index 00000000000..a02ba610ff7
--- /dev/null
+++ b/tests/cases/conformance/types/union/unionTypeConstructSignatures.ts
@@ -0,0 +1,70 @@
+var numOrDate: number | Date;
+var strOrBoolean: string | boolean;
+var strOrNum: string | number;
+
+// If each type in U has construct signatures and the sets of construct signatures are identical ignoring return types, 
+// U has the same set of construct signatures, but with return types that are unions of the return types of the respective construct signatures from each type in U.
+var unionOfDifferentReturnType: { new (a: number): number; } | { new (a: number): Date; };
+numOrDate = new unionOfDifferentReturnType(10);
+strOrBoolean = new unionOfDifferentReturnType("hello"); // error 
+new unionOfDifferentReturnType1(true); // error in type of parameter
+
+var unionOfDifferentReturnType1: { new (a: number): number; new (a: string): string; } | { new (a: number): Date; new (a: string): boolean; };
+numOrDate = new unionOfDifferentReturnType1(10);
+strOrBoolean = new unionOfDifferentReturnType1("hello");
+new unionOfDifferentReturnType1(true); // error in type of parameter
+new unionOfDifferentReturnType1(); // error missing parameter
+
+var unionOfDifferentParameterTypes: { new (a: number): number; } | { new (a: string): Date; };
+new unionOfDifferentParameterTypes(10);// error - no call signatures
+new unionOfDifferentParameterTypes("hello");// error - no call signatures
+new unionOfDifferentParameterTypes();// error - no call signatures
+
+var unionOfDifferentNumberOfSignatures: { new (a: number): number; } | { new (a: number): Date; new (a: string): boolean; };
+new unionOfDifferentNumberOfSignatures(); // error - no call signatures
+new unionOfDifferentNumberOfSignatures(10); // error - no call signatures
+new unionOfDifferentNumberOfSignatures("hello"); // error - no call signatures
+
+var unionWithDifferentParameterCount: { new (a: string): string; } | { new (a: string, b: number): number; };
+new unionWithDifferentParameterCount();// no  call signature
+new unionWithDifferentParameterCount("hello");// no  call signature
+new unionWithDifferentParameterCount("hello", 10);// no  call signature
+
+var unionWithOptionalParameter1: { new (a: string, b?: number): string; } | { new (a: string, b?: number): number; };
+strOrNum = new unionWithOptionalParameter1('hello');
+strOrNum = new unionWithOptionalParameter1('hello', 10);
+strOrNum = new unionWithOptionalParameter1('hello', "hello"); // error in parameter type
+strOrNum = new unionWithOptionalParameter1(); // error
+
+var unionWithOptionalParameter2: { new (a: string, b?: number): string; } | { new (a: string, b: number): number };
+strOrNum = new unionWithOptionalParameter2('hello'); // error no call signature
+strOrNum = new unionWithOptionalParameter2('hello', 10); // error no call signature
+strOrNum = new unionWithOptionalParameter2('hello', "hello"); // error no call signature
+strOrNum = new unionWithOptionalParameter2(); // error no call signature
+
+var unionWithOptionalParameter3: { new (a: string, b?: number): string; } | { new (a: string): number; };
+strOrNum = new unionWithOptionalParameter3('hello'); // error no call signature
+strOrNum = new unionWithOptionalParameter3('hello', 10); // error no call signature
+strOrNum = new unionWithOptionalParameter3('hello', "hello"); // error no call signature
+strOrNum = new unionWithOptionalParameter3(); // error no call signature
+
+var unionWithRestParameter1: { new (a: string, ...b: number[]): string; } | { new (a: string, ...b: number[]): number };
+strOrNum = new unionWithRestParameter1('hello');
+strOrNum = new unionWithRestParameter1('hello', 10);
+strOrNum = new unionWithRestParameter1('hello', 10, 11);
+strOrNum = new unionWithRestParameter1('hello', "hello"); // error in parameter type
+strOrNum = new unionWithRestParameter1(); // error
+
+var unionWithRestParameter2: { new (a: string, ...b: number[]): string; } | { new (a: string, b: number): number };
+strOrNum = new unionWithRestParameter2('hello'); // error no call signature
+strOrNum = new unionWithRestParameter2('hello', 10); // error no call signature
+strOrNum = new unionWithRestParameter2('hello', 10, 11); // error no call signature
+strOrNum = new unionWithRestParameter2('hello', "hello"); // error no call signature
+strOrNum = new unionWithRestParameter2(); // error no call signature
+
+var unionWithRestParameter3: { new (a: string, ...b: number[]): string; } | { new (a: string): number };
+strOrNum = new unionWithRestParameter3('hello'); // error no call signature
+strOrNum = new unionWithRestParameter3('hello', 10); // error no call signature
+strOrNum = new unionWithRestParameter3('hello', 10, 11); // error no call signature
+strOrNum = new unionWithRestParameter3('hello', "hello"); // error no call signature
+strOrNum = new unionWithRestParameter3(); // error no call signature
\ No newline at end of file
diff --git a/tests/cases/conformance/types/union/unionTypeEquivalence.ts b/tests/cases/conformance/types/union/unionTypeEquivalence.ts
new file mode 100644
index 00000000000..71fd6d91b65
--- /dev/null
+++ b/tests/cases/conformance/types/union/unionTypeEquivalence.ts
@@ -0,0 +1,18 @@
+// A | B is equivalent to A if B is a subtype of A
+class C { }
+class D extends C { foo() { } }
+var x: C;
+var x : C | D;
+
+// A | B is equivalent to B | A.
+var y: string | number;
+var y : number | string;
+
+// AB | C is equivalent to A | BC, where AB is A | B and BC is B | C.
+var z : string | number | boolean;
+var z : (string | number) | boolean;
+var z : string | (number | boolean);
+var AB : string | number;
+var BC : number | boolean;
+var z1: typeof AB | boolean;
+var z1: string | typeof BC;
diff --git a/tests/cases/conformance/types/union/unionTypeFromArrayLiteral.ts b/tests/cases/conformance/types/union/unionTypeFromArrayLiteral.ts
new file mode 100644
index 00000000000..c6b57584673
--- /dev/null
+++ b/tests/cases/conformance/types/union/unionTypeFromArrayLiteral.ts
@@ -0,0 +1,23 @@
+// The resulting type an array literal expression is determined as follows:
+// If the array literal is empty, the resulting type is an array type with the element type Undefined.
+// Otherwise, if the array literal is contextually typed by a type that has a property with the numeric name ‘0’, the resulting type is a tuple type constructed from the types of the element expressions.
+// Otherwise, the resulting type is an array type with an element type that is the union of the types of the element expressions.
+
+var arr1 = [1, 2]; // number[]
+var arr2 = ["hello", true]; // (string | number)[]
+var arr3Tuple: [number, string] = [3, "three"]; // [number, string]
+var arr4Tuple: [number, string] = [3, "three", "hello"]; // [number, string, string]
+var arrEmpty = [];
+var arr5Tuple: {
+    0: string;
+    5: number;
+} = ["hello", true, false, " hello", true, 10, "any"]; // Tuple
+class C { foo() { } }
+class D { foo2() { } }
+class E extends C { foo3() { } }
+class F extends C { foo4() { } }
+var c: C, d: D, e: E, f: F;
+var arr6 = [c, d];  // (C | D)[]
+var arr7 = [c, d, e]; // (C | D)[]
+var arr8 = [c, e]; // C[]
+var arr9 = [e, f]; // (E|F)[]
\ No newline at end of file
diff --git a/tests/cases/conformance/types/union/unionTypeIndexSignature.ts b/tests/cases/conformance/types/union/unionTypeIndexSignature.ts
new file mode 100644
index 00000000000..698da7449f4
--- /dev/null
+++ b/tests/cases/conformance/types/union/unionTypeIndexSignature.ts
@@ -0,0 +1,23 @@
+var numOrDate: number | Date;
+var anyVar: number;
+
+// If each type in U has a string index signature, 
+// U has a string index signature of a union type of the types of the string index signatures from each type in U.
+
+var unionOfDifferentReturnType: { [a: string]: number; } | { [a: string]: Date; };
+numOrDate = unionOfDifferentReturnType["hello"]; // number | Date
+numOrDate = unionOfDifferentReturnType[10]; // number | Date
+
+var unionOfTypesWithAndWithoutStringSignature: { [a: string]: number; } | boolean;
+anyVar = unionOfTypesWithAndWithoutStringSignature["hello"]; // any
+anyVar = unionOfTypesWithAndWithoutStringSignature[10]; // any
+
+// If each type in U has a numeric index signature, 
+// U has a numeric index signature of a union type of the types of the numeric index signatures from each type in U.
+var unionOfDifferentReturnType1: { [a: number]: number; } | { [a: number]: Date; };
+numOrDate = unionOfDifferentReturnType1["hello"]; // any
+numOrDate = unionOfDifferentReturnType1[10]; // number | Date
+
+var unionOfTypesWithAndWithoutStringSignature1: { [a: number]: number; } | boolean;
+anyVar = unionOfTypesWithAndWithoutStringSignature1["hello"]; // any
+anyVar = unionOfTypesWithAndWithoutStringSignature1[10]; // any
\ No newline at end of file
diff --git a/tests/cases/conformance/types/union/unionTypeMembers.ts b/tests/cases/conformance/types/union/unionTypeMembers.ts
new file mode 100644
index 00000000000..73c6867e9ac
--- /dev/null
+++ b/tests/cases/conformance/types/union/unionTypeMembers.ts
@@ -0,0 +1,54 @@
+interface I1<T> {
+    commonMethodType(a: string): string;
+    commonPropertyType: string;
+
+    commonMethodDifferentParameterType(a: string): string;
+    commonMethodDifferentReturnType(a: string): string;
+    commonPropertyDifferenType: string;
+
+    commonMethodWithTypeParameter(a: T): T;
+    commonMethodWithOwnTypeParameter<U>(a: U): U;
+
+    methodOnlyInI1(a: string): string;
+    propertyOnlyInI1: string;
+}
+
+interface I2<T> {
+    commonMethodType(a: string): string;
+    commonPropertyType: string;
+
+    commonMethodDifferentParameterType(a: number): number;
+    commonMethodDifferentReturnType(a: string): number;
+    commonPropertyDifferenType: number;
+
+    commonMethodWithTypeParameter(a: T): T;
+    commonMethodWithOwnTypeParameter<U>(a: U): U;
+
+    methodOnlyInI2(a: string): string;
+    propertyOnlyInI2: string;
+}
+
+// a union type U has those members that are present in every one of its constituent types, 
+// with types that are unions of the respective members in the constituent types
+var x : I1<number> | I2<number>;
+var str: string;
+var num: number;
+var strOrNum: string | number;
+
+// If each type in U has a property P, U has a property P of a union type of the types of P from each type in U.
+str = x.commonPropertyType; // string
+str = x.commonMethodType(str); // (a: string) => string so result should be string
+strOrNum = x.commonPropertyDifferenType;
+strOrNum = x.commonMethodDifferentReturnType(str); // string | union
+x.commonMethodDifferentParameterType; // No error - property exists
+x.commonMethodDifferentParameterType(strOrNum); // error - no call signatures because the type of this property is ((a: string) => string) | (a: number) => number
+                                                // and the call signatures arent identical
+num = x.commonMethodWithTypeParameter(num);
+num = x.commonMethodWithOwnTypeParameter(num);
+str = x.commonMethodWithOwnTypeParameter(str);
+strOrNum = x.commonMethodWithOwnTypeParameter(strOrNum);
+
+x.propertyOnlyInI1; // error
+x.propertyOnlyInI2; // error
+x.methodOnlyInI1("hello"); // error
+x.methodOnlyInI2(10); // error
\ No newline at end of file
diff --git a/tests/cases/fourslash/getEmitOutputWithEarlySemanticErrors.ts b/tests/cases/fourslash/getEmitOutputWithEarlySemanticErrors.ts
new file mode 100644
index 00000000000..2946fffb808
--- /dev/null
+++ b/tests/cases/fourslash/getEmitOutputWithEarlySemanticErrors.ts
@@ -0,0 +1,10 @@
+/// <reference path="fourslash.ts" />
+
+// @BaselineFile: getEmitOutputWithEarlySyntacticErrors.baseline
+
+// @Filename: inputFile1.ts
+// @emitThisFile: true
+//// // File contains early errors. All outputs should be skipped.
+//// const uninitialized_const_error;
+
+verify.baselineGetEmitOutput();
\ No newline at end of file
diff --git a/tests/cases/fourslash/getEmitOutputWithSemanticErrorsForMultipleFiles.ts b/tests/cases/fourslash/getEmitOutputWithSemanticErrorsForMultipleFiles.ts
new file mode 100644
index 00000000000..5cfacc36715
--- /dev/null
+++ b/tests/cases/fourslash/getEmitOutputWithSemanticErrorsForMultipleFiles.ts
@@ -0,0 +1,16 @@
+/// <reference path="fourslash.ts" />
+
+// @BaselineFile: getEmitOutputWithSemanticErrorsForMultipleFiles.baseline
+// @declaration: true
+
+// @Filename: inputFile1.ts
+// @emitThisFile: true
+//// // File to emit, does not contain semantic errors
+//// // expected to be emitted correctelly regardless of the semantic errors in the other file
+//// var noErrors = true;
+
+// @Filename: inputFile2.ts
+//// // File not emitted, and contains semantic errors
+//// var semanticError: boolean = "string";
+
+verify.baselineGetEmitOutput();
\ No newline at end of file
diff --git a/tests/cases/fourslash/getEmitOutputWithSemanticErrorsForMultipleFiles2.ts b/tests/cases/fourslash/getEmitOutputWithSemanticErrorsForMultipleFiles2.ts
new file mode 100644
index 00000000000..d5cfd1346ca
--- /dev/null
+++ b/tests/cases/fourslash/getEmitOutputWithSemanticErrorsForMultipleFiles2.ts
@@ -0,0 +1,17 @@
+/// <reference path="fourslash.ts" />
+
+// @BaselineFile: getEmitOutputWithSemanticErrorsForMultipleFiles2.baseline
+// @declaration: true
+// @out: out.js
+
+// @Filename: inputFile1.ts
+// @emitThisFile: true
+//// // File to emit, does not contain semantic errors, but --out is passed
+//// // expected to not generate declarations because of the semantic errors in the other file
+//// var noErrors = true;
+
+// @Filename: inputFile2.ts
+//// // File not emitted, and contains semantic errors
+//// var semanticError: boolean = "string";
+
+verify.baselineGetEmitOutput();
\ No newline at end of file
diff --git a/tests/cases/fourslash/getEmitOutputWithSyntacticErrorsForMultipleFiles.ts b/tests/cases/fourslash/getEmitOutputWithSyntacticErrorsForMultipleFiles.ts
new file mode 100644
index 00000000000..3b3d01eaac8
--- /dev/null
+++ b/tests/cases/fourslash/getEmitOutputWithSyntacticErrorsForMultipleFiles.ts
@@ -0,0 +1,15 @@
+/// <reference path="fourslash.ts" />
+
+// @BaselineFile: getEmitOutputWithSyntacticErrorsForMultipleFiles.baseline
+
+// @Filename: inputFile1.ts
+// @emitThisFile: true
+//// // File to emit, does not contain syntactic errors
+//// // expected to be emitted correctelly regardless of the syntactic errors in the other file
+//// var noErrors = true;
+
+// @Filename: inputFile2.ts
+//// // File not emitted, and contains syntactic errors
+//// var syntactic Error;
+
+verify.baselineGetEmitOutput();
\ No newline at end of file
diff --git a/tests/cases/fourslash/getEmitOutputWithSyntacticErrorsForMultipleFiles2.ts b/tests/cases/fourslash/getEmitOutputWithSyntacticErrorsForMultipleFiles2.ts
new file mode 100644
index 00000000000..ce82f958b91
--- /dev/null
+++ b/tests/cases/fourslash/getEmitOutputWithSyntacticErrorsForMultipleFiles2.ts
@@ -0,0 +1,16 @@
+/// <reference path="fourslash.ts" />
+
+// @BaselineFile: getEmitOutputWithSyntacticErrorsForMultipleFiles2.baseline
+// @out: out.js
+
+// @Filename: inputFile1.ts
+// @emitThisFile: true
+//// // File to emit, does not contain syntactic errors, but --out is passed
+//// // expected to not generate outputs because of the syntactic errors in the other file.
+//// var noErrors = true;
+
+// @Filename: inputFile2.ts
+//// // File not emitted, and contains syntactic errors
+//// var syntactic Error;
+
+verify.baselineGetEmitOutput();
\ No newline at end of file
diff --git a/tests/cases/fourslash/signatureHelpWithUnknown.ts b/tests/cases/fourslash/signatureHelpWithUnknown.ts
new file mode 100644
index 00000000000..00a031b2673
--- /dev/null
+++ b/tests/cases/fourslash/signatureHelpWithUnknown.ts
@@ -0,0 +1,6 @@
+/// <reference path='fourslash.ts'/>
+
+////eval(\/*1*/
+
+goTo.marker("1");
+verify.signatureHelpCountIs(1);