diff --git a/.gitignore b/.gitignore
index 3147b8e8724..58a45545939 100644
--- a/.gitignore
+++ b/.gitignore
@@ -25,6 +25,7 @@ tests/baselines/reference/projectOutput/*
 tests/baselines/local/projectOutput/*
 tests/services/baselines/prototyping/local/*
 tests/services/browser/typescriptServices.js
+scripts/configureNightly.js
 scripts/processDiagnosticMessages.d.ts
 scripts/processDiagnosticMessages.js
 scripts/importDefinitelyTypedTests.js
diff --git a/AUTHORS.md b/AUTHORS.md
new file mode 100644
index 00000000000..0ade4c31221
--- /dev/null
+++ b/AUTHORS.md
@@ -0,0 +1,70 @@
+TypeScript is authored by:
+
+* Adam Freidin
+* Ahmad Farid 
+* Anders Hejlsberg
+* Arnav Singh
+* Arthur Ozga
+* Basarat Ali Syed 
+* Ben Duffield
+* Bill Ticehurst 
+* Bryan Forbes 
+* Caitlin Potter 
+* Chris Bubernak
+* Colby Russell 
+* Colin Snover
+* Cyrus Najmabadi
+* Dan Quirk 
+* Daniel Rosenwasser
+* David Li 
+* Dick van den Brink 
+* Dirk Bäumer 
+* Frank Wallis 
+* Gabriel Isenberg
+* Gilad Peleg 
+* Guillaume Salles 
+* Harald Niesche
+* Ingvar Stepanyan
+* Ivo Gabe de Wolff 
+* James Whitney 
+* Jason Freeman
+* Jason Ramsay 
+* Jed Mao
+* Johannes Rieken 
+* Jonathan Bond-Caron
+* Jonathan Park
+* Jonathan Turner
+* Josh Kalderimis
+* Kagami Sascha Rosylight
+* Keith Mashinter
+* Kenji Imamula
+* Lorant Pinter 
+* Masahiro Wakame
+* Max Deepfield
+* Micah Zoltu 
+* Mohamed Hegazy 
+* Oleg Mihailik
+* Oleksandr Chekhovskyi 
+* Paul van Brenk 
+* Pedro Maltez 
+* Philip Bulley
+* piloopin
+* Ron Buckton 
+* Ryan Cavanaugh 
+* Sheetal Nandi
+* Shengping Zhong
+* Shyyko Serhiy
+* Simon Hürlimann
+* Solal Pirelli
+* Stan Thomas
+* Steve Lucco
+* Tien Hoanhtien
+* Tingan Ho
+* togru
+* Tomas Grubliauskas
+* TruongSinh Tran-Nguyen
+* Vladimir Matveev
+* Wesley Wigham
+* Yui Tanglertsampan
+* Zev Spitz 
+* Zhengbo Li
\ No newline at end of file
diff --git a/Jakefile.js b/Jakefile.js
index bd5074b43d6..8fbefe1b2cc 100644
--- a/Jakefile.js
+++ b/Jakefile.js
@@ -138,6 +138,7 @@ var harnessSources = harnessCoreSources.concat([
     "services/documentRegistry.ts",
     "services/preProcessFile.ts",
     "services/patternMatcher.ts",
+    "session.ts",
     "versionCache.ts",
     "convertToBase64.ts",
     "transpile.ts"
@@ -313,7 +314,7 @@ var processDiagnosticMessagesTs = path.join(scriptsDirectory, "processDiagnostic
 var diagnosticMessagesJson = path.join(compilerDirectory, "diagnosticMessages.json");
 var diagnosticInfoMapTs = path.join(compilerDirectory, "diagnosticInformationMap.generated.ts");
 
-file(processDiagnosticMessagesTs)
+file(processDiagnosticMessagesTs);
 
 // processDiagnosticMessages script
 compileFile(processDiagnosticMessagesJs,
@@ -338,12 +339,50 @@ file(diagnosticInfoMapTs, [processDiagnosticMessagesJs, diagnosticMessagesJson],
         complete();
     });
     ex.run();
-}, {async: true})
+}, {async: true});
 
 desc("Generates a diagnostic file in TypeScript based on an input JSON file");
-task("generate-diagnostics", [diagnosticInfoMapTs])
+task("generate-diagnostics", [diagnosticInfoMapTs]);
 
 
+// Publish nightly
+var configureNightlyJs = path.join(scriptsDirectory, "configureNightly.js");
+var configureNightlyTs = path.join(scriptsDirectory, "configureNightly.ts");
+var packageJson = "package.json";
+var programTs = path.join(compilerDirectory, "program.ts");
+
+file(configureNightlyTs);
+
+compileFile(/*outfile*/configureNightlyJs,
+            /*sources*/ [configureNightlyTs],
+            /*prereqs*/ [configureNightlyTs],
+            /*prefixes*/ [],
+            /*useBuiltCompiler*/ false,
+            /*noOutFile*/ false,
+            /*generateDeclarations*/ false,
+            /*outDir*/ undefined,
+            /*preserveConstEnums*/ undefined,
+            /*keepComments*/ false,
+            /*noResolve*/ false,
+            /*stripInternal*/ false);
+
+task("setDebugMode", function() {
+    useDebugMode = true;
+});
+
+task("configure-nightly", [configureNightlyJs], function() {
+    var cmd = "node " + configureNightlyJs + " " + packageJson + " " + programTs;
+    console.log(cmd);
+    exec(cmd);
+}, { async: true });
+
+desc("Configure, build, test, and publish the nightly release.");
+task("publish-nightly", ["configure-nightly", "LKG", "clean", "setDebugMode", "runtests"], function () {
+    var cmd = "npm publish --tag next";
+    console.log(cmd);
+    exec(cmd);
+});
+
 // Local target to build the compiler and services
 var tscFile = path.join(builtLocalDirectory, compilerFilename);
 compileFile(tscFile, compilerSources, [builtLocalDirectory, copyright].concat(compilerSources), [copyright], /*useBuiltCompiler:*/ false);
@@ -440,11 +479,11 @@ file(specMd, [word2mdJs, specWord], function () {
     child_process.exec(cmd, function () {
         complete();
     });
-}, {async: true})
+}, {async: true});
 
 
 desc("Generates a Markdown version of the Language Specification");
-task("generate-spec", [specMd])
+task("generate-spec", [specMd]);
 
 
 // Makes a new LKG. This target does not build anything, but errors if not all the outputs are present in the built/local directory
@@ -576,7 +615,7 @@ task("runtests", ["tests", builtLocalDirectory], function() {
     exec(cmd, deleteTemporaryProjectOutput);
 }, {async: true});
 
-desc("Generates code coverage data via instanbul")
+desc("Generates code coverage data via instanbul");
 task("generate-code-coverage", ["tests", builtLocalDirectory], function () {
     var cmd = 'istanbul cover node_modules/mocha/bin/_mocha -- -R min -t ' + testTimeout + ' ' + run;
     console.log(cmd);
@@ -619,7 +658,7 @@ task("runtests-browser", ["tests", "browserify", builtLocalDirectory], function(
 function getDiffTool() {
     var program = process.env['DIFF']
     if (!program) {
-        fail("Add the 'DIFF' environment variable to the path of the program you want to use.")
+        fail("Add the 'DIFF' environment variable to the path of the program you want to use.");
     }
     return program;
 }
@@ -628,14 +667,14 @@ function getDiffTool() {
 desc("Diffs the compiler baselines using the diff tool specified by the 'DIFF' environment variable");
 task('diff', function () {
     var cmd = '"' +  getDiffTool()  + '" ' + refBaseline + ' ' + localBaseline;
-    console.log(cmd)
+    console.log(cmd);
     exec(cmd);
 }, {async: true});
 
 desc("Diffs the RWC baselines using the diff tool specified by the 'DIFF' environment variable");
 task('diff-rwc', function () {
     var cmd = '"' +  getDiffTool()  + '" ' + refRwcBaseline + ' ' + localRwcBaseline;
-    console.log(cmd)
+    console.log(cmd);
     exec(cmd);
 }, {async: true});
 
@@ -736,9 +775,9 @@ task("lint", [], function() {
     function failure(f) { return function() { console.log('FAILURE: Please fix linting errors in ' + f + '\n') }};
 
     var lintTargets = compilerSources.concat(harnessCoreSources);
-    for(var i in lintTargets) {
+    for (var i in lintTargets) {
         var f = lintTargets[i];
-        var cmd = 'tslint -f ' + f;
+        var cmd = 'tslint -c tslint.json ' + f;
         exec(cmd, success(f), failure(f));
     }
 }, { async: true });
diff --git a/README.md b/README.md
index 57dfe06c67c..c8bc5936c24 100644
--- a/README.md
+++ b/README.md
@@ -8,6 +8,19 @@
 
 [TypeScript](http://www.typescriptlang.org/) is a language for application-scale JavaScript. TypeScript adds optional types, classes, and modules to JavaScript. TypeScript supports tools for large-scale JavaScript applications for any browser, for any host, on any OS. TypeScript compiles to readable, standards-based JavaScript. Try it out at the [playground](http://www.typescriptlang.org/Playground), and stay up to date via [our blog](http://blogs.msdn.com/typescript) and [twitter account](https://twitter.com/typescriptlang).
 
+## Installing
+
+For the latest stable version:
+
+```
+npm install -g typescript
+```
+
+For our nightly builds:
+
+```
+npm install -g typescript@next
+```
 
 ## Contribute
 
@@ -63,7 +76,8 @@ jake runtests         # Run tests using the built compiler and test infrastructu
                       # Use host=<hostName> or tests=<testPath>. 
 jake runtests-browser # Runs the tests using the built run.js file. Syntax is jake runtests. Optional
                         parameters 'host=', 'tests=[regex], reporter=[list|spec|json|<more>]'.
-jake baseline-accept  # This replaces the baseline test results with the results obtained from jake runtests. 
+jake baseline-accept  # This replaces the baseline test results with the results obtained from jake runtests.
+jake lint             # Runs tslint on the TypeScript source.
 jake -T               # List the above commands. 
 ```
 
diff --git a/package.json b/package.json
index 70ada6fef15..c8b30f9de1c 100644
--- a/package.json
+++ b/package.json
@@ -2,7 +2,7 @@
     "name": "typescript",
     "author": "Microsoft Corp.",
     "homepage": "http://typescriptlang.org/",
-    "version": "1.5.3",
+    "version": "1.6.0",
     "license": "Apache-2.0",
     "description": "TypeScript is a language for application scale JavaScript development",
     "keywords": [
diff --git a/scripts/configureNightly.ts b/scripts/configureNightly.ts
new file mode 100644
index 00000000000..640f330b376
--- /dev/null
+++ b/scripts/configureNightly.ts
@@ -0,0 +1,73 @@
+/// <reference path="../src/compiler/sys.ts" />
+
+/**
+ * A minimal description for a parsed package.json object.
+ */
+interface PackageJson {
+    name: string;
+    version: string;
+    keywords: string[];
+}
+
+function main(): void {
+    const sys = ts.sys;
+    if (sys.args.length < 2) {
+        sys.write("Usage:" + sys.newLine)
+        sys.write("\tnode configureNightly.js <package.json location> <file containing version>" + sys.newLine);
+        return;
+    }
+
+    // Acquire the version from the package.json file and modify it appropriately.
+    const packageJsonFilePath = ts.normalizePath(sys.args[0]);
+    const packageJsonContents = sys.readFile(packageJsonFilePath);
+    const packageJsonValue: PackageJson = JSON.parse(packageJsonContents);
+
+    const nightlyVersion = getNightlyVersionString(packageJsonValue.version);
+
+    // Modify the package.json structure
+    packageJsonValue.version = nightlyVersion;
+
+    // Acquire and modify the source file that exposes the version string.
+    const tsFilePath = ts.normalizePath(sys.args[1]);
+    const tsFileContents = sys.readFile(tsFilePath);
+    const versionAssignmentRegExp = /export\s+const\s+version\s+=\s+".*";/;
+    const modifiedTsFileContents = tsFileContents.replace(versionAssignmentRegExp, `export const version = "${nightlyVersion}";`);
+
+    // Ensure we are actually changing something - the user probably wants to know that the update failed.
+    if (tsFileContents === modifiedTsFileContents) {
+        let err = `\n  '${tsFilePath}' was not updated while configuring for a nightly publish.\n    `;
+
+        if (tsFileContents.match(versionAssignmentRegExp)) {
+            err += `Ensure that you have not already run this script; otherwise, erase your changes using 'git checkout -- "${tsFilePath}"'.`;
+        }
+        else {
+            err += `The file seems to no longer have a string matching '${versionAssignmentRegExp}'.`;
+        }
+
+        throw err + "\n";
+    }
+
+    // Finally write the changes to disk.
+    sys.writeFile(packageJsonFilePath, JSON.stringify(packageJsonValue, /*replacer:*/ undefined, /*space:*/ 4))
+    sys.writeFile(tsFilePath, modifiedTsFileContents);
+}
+
+function getNightlyVersionString(versionString: string): string {
+    // If the version string already contains "-nightly",
+    // then get the base string and update based on that.
+    const dashNightlyPos = versionString.indexOf("-dev");
+    if (dashNightlyPos >= 0) {
+        versionString = versionString.slice(0, dashNightlyPos);
+    }
+
+    // We're going to append a representation of the current time at the end of the current version.
+    // String.prototype.toISOString() returns a 24-character string formatted as 'YYYY-MM-DDTHH:mm:ss.sssZ',
+    // but we'd prefer to just remove separators and limit ourselves to YYYYMMDD.
+    // UTC time will always be implicit here.
+    const now = new Date();
+    const timeStr = now.toISOString().replace(/:|T|\.|-/g, "").slice(0, 8);
+
+    return `${versionString}-dev.${timeStr}`;
+}
+
+main();
\ No newline at end of file
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index c09b069bee6..44266402607 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -68,6 +68,7 @@ namespace ts {
             getPropertyOfType,
             getSignaturesOfType,
             getIndexTypeOfType,
+            getBaseTypes,
             getReturnTypeOfSignature,
             getSymbolsInScope,
             getSymbolAtLocation,
@@ -90,7 +91,8 @@ namespace ts {
             getExportsOfModule: getExportsOfModuleAsArray,
 
             getJsxElementAttributesType,
-            getJsxIntrinsicTagNames
+            getJsxIntrinsicTagNames,
+            isOptionalParameter
         };
 
         let unknownSymbol = createSymbol(SymbolFlags.Property | SymbolFlags.Transient, "unknown");
@@ -112,6 +114,10 @@ namespace ts {
         emptyGenericType.instantiations = {};
 
         let anyFunctionType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
+        // The anyFunctionType contains the anyFunctionType by definition. The flag is further propagated
+        // in getPropagatingFlagsOfTypes, and it is checked in inferFromTypes.
+        anyFunctionType.flags |= TypeFlags.ContainsAnyFunctionType;
+
         let noConstraintType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
 
         let anySignature = createSignature(undefined, undefined, emptyArray, anyType, undefined, 0, false, false);
@@ -1993,15 +1999,15 @@ namespace ts {
             }
 
             return _displayBuilder || (_displayBuilder = {
-                buildSymbolDisplay: buildSymbolDisplay,
-                buildTypeDisplay: buildTypeDisplay,
-                buildTypeParameterDisplay: buildTypeParameterDisplay,
-                buildParameterDisplay: buildParameterDisplay,
-                buildDisplayForParametersAndDelimiters: buildDisplayForParametersAndDelimiters,
-                buildDisplayForTypeParametersAndDelimiters: buildDisplayForTypeParametersAndDelimiters,
-                buildTypeParameterDisplayFromSymbol: buildTypeParameterDisplayFromSymbol,
-                buildSignatureDisplay: buildSignatureDisplay,
-                buildReturnTypeDisplay: buildReturnTypeDisplay
+                buildSymbolDisplay,
+                buildTypeDisplay,
+                buildTypeParameterDisplay,
+                buildParameterDisplay,
+                buildDisplayForParametersAndDelimiters,
+                buildDisplayForTypeParametersAndDelimiters,
+                buildTypeParameterDisplayFromSymbol,
+                buildSignatureDisplay,
+                buildReturnTypeDisplay
             });
         }
 
@@ -3516,7 +3522,19 @@ namespace ts {
         }
 
         function isOptionalParameter(node: ParameterDeclaration) {
-            return hasQuestionToken(node) || !!node.initializer;
+            if (hasQuestionToken(node)) {
+                return true;
+            }
+
+            if (node.initializer) {
+                let signatureDeclaration = <SignatureDeclaration>node.parent;
+                let signature = getSignatureFromDeclaration(signatureDeclaration);
+                let parameterIndex = signatureDeclaration.parameters.indexOf(node);
+                Debug.assert(parameterIndex >= 0);
+                return parameterIndex >= signature.minArgumentCount;
+            }
+
+            return false;
         }
 
         function getSignatureFromDeclaration(declaration: SignatureDeclaration): Signature {
@@ -3534,11 +3552,16 @@ namespace ts {
                     if (param.type && param.type.kind === SyntaxKind.StringLiteral) {
                         hasStringLiterals = true;
                     }
-                    if (minArgumentCount < 0) {
-                        if (param.initializer || param.questionToken || param.dotDotDotToken) {
+
+                    if (param.initializer || param.questionToken || param.dotDotDotToken) {
+                        if (minArgumentCount < 0) {
                             minArgumentCount = i;
                         }
                     }
+                    else {
+                        // If we see any required parameters, it means the prior ones were not in fact optional.
+                        minArgumentCount = -1;
+                    }
                 }
 
                 if (minArgumentCount < 0) {
@@ -3756,22 +3779,23 @@ namespace ts {
             }
         }
 
-        // This function is used to propagate widening flags when creating new object types references and union types.
-        // It is only necessary to do so if a constituent type might be the undefined type, the null type, or the type
-        // of an object literal (since those types have widening related information we need to track).
-        function getWideningFlagsOfTypes(types: Type[]): TypeFlags {
+        // This function is used to propagate certain flags when creating new object type references and union types.
+        // It is only necessary to do so if a constituent type might be the undefined type, the null type, the type
+        // of an object literal or the anyFunctionType. This is because there are operations in the type checker
+        // that care about the presence of such types at arbitrary depth in a containing type.
+        function getPropagatingFlagsOfTypes(types: Type[]): TypeFlags {
             let result: TypeFlags = 0;
             for (let type of types) {
                 result |= type.flags;
             }
-            return result & TypeFlags.RequiresWidening;
+            return result & TypeFlags.PropagatingFlags;
         }
 
         function createTypeReference(target: GenericType, typeArguments: Type[]): TypeReference {
             let id = getTypeListId(typeArguments);
             let type = target.instantiations[id];
             if (!type) {
-                let flags = TypeFlags.Reference | getWideningFlagsOfTypes(typeArguments);
+                let flags = TypeFlags.Reference | getPropagatingFlagsOfTypes(typeArguments);
                 type = target.instantiations[id] = <TypeReference>createObjectType(flags, target.symbol);
                 type.target = target;
                 type.typeArguments = typeArguments;
@@ -4025,7 +4049,7 @@ namespace ts {
             let id = getTypeListId(elementTypes);
             let type = tupleTypes[id];
             if (!type) {
-                type = tupleTypes[id] = <TupleType>createObjectType(TypeFlags.Tuple | getWideningFlagsOfTypes(elementTypes));
+                type = tupleTypes[id] = <TupleType>createObjectType(TypeFlags.Tuple | getPropagatingFlagsOfTypes(elementTypes));
                 type.elementTypes = elementTypes;
             }
             return type;
@@ -4174,7 +4198,7 @@ namespace ts {
             let id = getTypeListId(typeSet);
             let type = unionTypes[id];
             if (!type) {
-                type = unionTypes[id] = <UnionType>createObjectType(TypeFlags.Union | getWideningFlagsOfTypes(typeSet));
+                type = unionTypes[id] = <UnionType>createObjectType(TypeFlags.Union | getPropagatingFlagsOfTypes(typeSet));
                 type.types = typeSet;
             }
             return type;
@@ -4208,7 +4232,7 @@ namespace ts {
             let id = getTypeListId(typeSet);
             let type = intersectionTypes[id];
             if (!type) {
-                type = intersectionTypes[id] = <IntersectionType>createObjectType(TypeFlags.Intersection | getWideningFlagsOfTypes(typeSet));
+                type = intersectionTypes[id] = <IntersectionType>createObjectType(TypeFlags.Intersection | getPropagatingFlagsOfTypes(typeSet));
                 type.types = typeSet;
             }
             return type;
@@ -4363,11 +4387,11 @@ namespace ts {
                         return getInferredType(context, i);
                     }
                 }
-                return t;
+                return t;
             };
             
             mapper.context = context;
-            return mapper;
+            return mapper;
         }
 
         function identityMapper(type: Type): Type {
@@ -5655,11 +5679,17 @@ namespace ts {
             }
 
             function inferFromTypes(source: Type, target: Type) {
-                if (source === anyFunctionType) {
-                    return;
-                }
                 if (target.flags & TypeFlags.TypeParameter) {
-                    // If target is a type parameter, make an inference
+                    // If target is a type parameter, make an inference, unless the source type contains
+                    // the anyFunctionType (the wildcard type that's used to avoid contextually typing functions).
+                    // Because the anyFunctionType is internal, it should not be exposed to the user by adding
+                    // it as an inference candidate. Hopefully, a better candidate will come along that does
+                    // not contain anyFunctionType when we come back to this argument for its second round
+                    // of inference.
+                    if (source.flags & TypeFlags.ContainsAnyFunctionType) {
+                        return;
+                    }
+
                     let typeParameters = context.typeParameters;
                     for (let i = 0; i < typeParameters.length; i++) {
                         if (target === typeParameters[i]) {
@@ -7092,7 +7122,7 @@ namespace ts {
             let stringIndexType = getIndexType(IndexKind.String);
             let numberIndexType = getIndexType(IndexKind.Number);
             let result = createAnonymousType(node.symbol, propertiesTable, emptyArray, emptyArray, stringIndexType, numberIndexType);
-            result.flags |= TypeFlags.ObjectLiteral | TypeFlags.FreshObjectLiteral | TypeFlags.ContainsObjectLiteral | (typeFlags & TypeFlags.ContainsUndefinedOrNull);
+            result.flags |= TypeFlags.ObjectLiteral | TypeFlags.FreshObjectLiteral | TypeFlags.ContainsObjectLiteral | (typeFlags & TypeFlags.PropagatingFlags);
             return result;
 
             function getIndexType(kind: IndexKind) {
@@ -7323,10 +7353,9 @@ namespace ts {
          * For example, in the element <MyClass>, the element instance type is `MyClass` (not `typeof MyClass`).
          */
         function getJsxElementInstanceType(node: JsxOpeningLikeElement) {
-            if (!(getNodeLinks(node).jsxFlags & JsxFlags.ClassElement)) {
-                // There is no such thing as an instance type for a non-class element
-                return undefined;
-            }
+            // There is no such thing as an instance type for a non-class element. This
+            // line shouldn't be hit.
+            Debug.assert(!!(getNodeLinks(node).jsxFlags & JsxFlags.ClassElement), 'Should not call getJsxElementInstanceType on non-class Element');
 
             let classSymbol = getJsxElementTagSymbol(node);
             if (classSymbol === unknownSymbol) {
@@ -7349,16 +7378,11 @@ namespace ts {
                 if (signatures.length === 0) {
                     // We found no signatures at all, which is an error
                     error(node.tagName, Diagnostics.JSX_element_type_0_does_not_have_any_construct_or_call_signatures, getTextOfNode(node.tagName));
-                    return undefined;
+                    return unknownType;
                 }
             }
 
-            // Check that the constructor/factory returns an object type
-            let returnType = getUnionType(signatures.map(s => getReturnTypeOfSignature(s)));
-            if (!isTypeAny(returnType) && !(returnType.flags & TypeFlags.ObjectType)) {
-                error(node.tagName, Diagnostics.The_return_type_of_a_JSX_element_constructor_must_return_an_object_type);
-                return undefined;
-            }
+            let returnType = getUnionType(signatures.map(getReturnTypeOfSignature));
 
             // Issue an error if this return type isn't assignable to JSX.ElementClass
             let elemClassType = getJsxGlobalElementClassType();
@@ -7419,7 +7443,7 @@ namespace ts {
                     let elemInstanceType = getJsxElementInstanceType(node);
 
                     if (isTypeAny(elemInstanceType)) {
-                        return links.resolvedJsxType = anyType;
+                        return links.resolvedJsxType = elemInstanceType;
                     }
 
                     let propsName = getJsxElementPropertiesName();
@@ -10436,10 +10460,19 @@ namespace ts {
             // TS 1.0 spec (April 2014): 8.3.2
             // Constructors of classes with no extends clause may not contain super calls, whereas
             // constructors of derived classes must contain at least one super call somewhere in their function body.
-            if (getClassExtendsHeritageClauseElement(<ClassDeclaration>node.parent)) {
+            let containingClassDecl = <ClassDeclaration>node.parent;
+            if (getClassExtendsHeritageClauseElement(containingClassDecl)) {
+                let containingClassSymbol = getSymbolOfNode(containingClassDecl);
+                let containingClassInstanceType = <InterfaceType>getDeclaredTypeOfSymbol(containingClassSymbol);
+                let baseConstructorType = getBaseConstructorTypeOfClass(containingClassInstanceType);
 
                 if (containsSuperCall(node.body)) {
-                    // The first statement in the body of a constructor must be a super call if both of the following are true:
+                    if (baseConstructorType === nullType) {
+                        error(node, Diagnostics.A_constructor_cannot_contain_a_super_call_when_its_class_extends_null);
+                    }
+
+                    // The first statement in the body of a constructor (excluding prologue directives) must be a super call
+                    // if both of the following are true:
                     // - The containing class is a derived class.
                     // - The constructor declares parameter properties
                     //   or the containing class declares instance member variables with initializers.
@@ -10447,18 +10480,30 @@ namespace ts {
                         forEach((<ClassDeclaration>node.parent).members, isInstancePropertyWithInitializer) ||
                         forEach(node.parameters, p => p.flags & (NodeFlags.Public | NodeFlags.Private | NodeFlags.Protected));
 
+                    // Skip past any prologue directives to find the first statement
+                    // to ensure that it was a super call.
                     if (superCallShouldBeFirst) {
                         let statements = (<Block>node.body).statements;
-                        if (!statements.length || statements[0].kind !== SyntaxKind.ExpressionStatement || !isSuperCallExpression((<ExpressionStatement>statements[0]).expression)) {
-                            error(node, Diagnostics.A_super_call_must_be_the_first_statement_in_the_constructor_when_a_class_contains_initialized_properties_or_has_parameter_properties);
+                        let superCallStatement: ExpressionStatement;
+                        for (let statement of statements) {
+                            if (statement.kind === SyntaxKind.ExpressionStatement && isSuperCallExpression((<ExpressionStatement>statement).expression)) {
+                                superCallStatement = <ExpressionStatement>statement;
+                                break;
+                            }
+                            if (!isPrologueDirective(statement)) {
+                                break;
+                            }
                         }
+                        if (!superCallStatement) {
+                            error(node, Diagnostics.A_super_call_must_be_the_first_statement_in_the_constructor_when_a_class_contains_initialized_properties_or_has_parameter_properties);
+                        } 
                         else {
                             // In such a required super call, it is a compile-time error for argument expressions to reference this.
-                            markThisReferencesAsErrors((<ExpressionStatement>statements[0]).expression);
+                            markThisReferencesAsErrors(superCallStatement.expression);
                         }
                     }
                 }
-                else {
+                else if (baseConstructorType !== nullType) {
                     error(node, Diagnostics.Constructors_for_derived_classes_must_contain_a_super_call);
                 }
             }
@@ -10849,9 +10894,6 @@ namespace ts {
                 return;
             }
 
-            // Exports should be checked only if enclosing module contains both exported and non exported declarations.
-            // In case if all declarations are non-exported check is unnecessary.
-
             // if localSymbol is defined on node then node itself is exported - check is required
             let symbol = node.localSymbol;
             if (!symbol) {
@@ -10871,27 +10913,45 @@ namespace ts {
 
             // we use SymbolFlags.ExportValue, SymbolFlags.ExportType and SymbolFlags.ExportNamespace
             // to denote disjoint declarationSpaces (without making new enum type).
-            let exportedDeclarationSpaces: SymbolFlags = 0;
-            let nonExportedDeclarationSpaces: SymbolFlags = 0;
-            forEach(symbol.declarations, d => {
+            let exportedDeclarationSpaces = SymbolFlags.None;
+            let nonExportedDeclarationSpaces = SymbolFlags.None;
+            let defaultExportedDeclarationSpaces = SymbolFlags.None;
+            for (let d of symbol.declarations) {
                 let declarationSpaces = getDeclarationSpaces(d);
-                if (getEffectiveDeclarationFlags(d, NodeFlags.Export)) {
-                    exportedDeclarationSpaces |= declarationSpaces;
+                let effectiveDeclarationFlags = getEffectiveDeclarationFlags(d, NodeFlags.Export | NodeFlags.Default);
+
+                if (effectiveDeclarationFlags & NodeFlags.Export) {
+                    if (effectiveDeclarationFlags & NodeFlags.Default) {
+                        defaultExportedDeclarationSpaces |= declarationSpaces;
+                    }
+                    else {
+                        exportedDeclarationSpaces |= declarationSpaces;
+                    }
                 }
                 else {
                     nonExportedDeclarationSpaces |= declarationSpaces;
                 }
-            });
+            }
 
-            let commonDeclarationSpace = exportedDeclarationSpaces & nonExportedDeclarationSpaces;
+            // Spaces for anyting not declared a 'default export'.
+            let nonDefaultExportedDeclarationSpaces = exportedDeclarationSpaces | nonExportedDeclarationSpaces;
+            
+            let commonDeclarationSpacesForExportsAndLocals = exportedDeclarationSpaces & nonExportedDeclarationSpaces;
+            let commonDeclarationSpacesForDefaultAndNonDefault = defaultExportedDeclarationSpaces & nonDefaultExportedDeclarationSpaces;
 
-            if (commonDeclarationSpace) {
+            if (commonDeclarationSpacesForExportsAndLocals || commonDeclarationSpacesForDefaultAndNonDefault) {
                 // declaration spaces for exported and non-exported declarations intersect
-                forEach(symbol.declarations, d => {
-                    if (getDeclarationSpaces(d) & commonDeclarationSpace) {
+                for (let d of symbol.declarations) {
+                    let declarationSpaces = getDeclarationSpaces(d);
+                    
+                    // Only error on the declarations that conributed to the intersecting spaces.
+                    if (declarationSpaces & commonDeclarationSpacesForDefaultAndNonDefault) {
+                        error(d.name, Diagnostics.Merged_declaration_0_cannot_include_a_default_export_declaration_Consider_adding_a_separate_export_default_0_declaration_instead, declarationNameToString(d.name));
+                    }
+                    else if (declarationSpaces & commonDeclarationSpacesForExportsAndLocals) {
                         error(d.name, Diagnostics.Individual_declarations_in_merged_declaration_0_must_be_all_exported_or_all_local, declarationNameToString(d.name));
                     }
-                });
+                }
             }
 
             function getDeclarationSpaces(d: Declaration): SymbolFlags {
@@ -12736,28 +12796,7 @@ namespace ts {
                     }
                     let initializer = member.initializer;
                     if (initializer) {
-                        autoValue = getConstantValueForEnumMemberInitializer(initializer);
-                        if (autoValue === undefined) {
-                            if (enumIsConst) {
-                                error(initializer, Diagnostics.In_const_enum_declarations_member_initializer_must_be_constant_expression);
-                            }
-                            else if (!ambient) {
-                                // Only here do we need to check that the initializer is assignable to the enum type.
-                                // If it is a constant value (not undefined), it is syntactically constrained to be a number.
-                                // Also, we do not need to check this for ambients because there is already
-                                // a syntax error if it is not a constant.
-                                checkTypeAssignableTo(checkExpression(initializer), enumType, initializer, /*headMessage*/ undefined);
-                            }
-                        }
-                        else if (enumIsConst) {
-                            if (isNaN(autoValue)) {
-                                error(initializer, Diagnostics.const_enum_member_initializer_was_evaluated_to_disallowed_value_NaN);
-                            }
-                            else if (!isFinite(autoValue)) {
-                                error(initializer, Diagnostics.const_enum_member_initializer_was_evaluated_to_a_non_finite_value);
-                            }
-                        }
-
+                        autoValue = computeConstantValueForEnumMemberInitializer(initializer, enumType, enumIsConst, ambient);
                     }
                     else if (ambient && !enumIsConst) {
                         autoValue = undefined;
@@ -12771,8 +12810,36 @@ namespace ts {
                 nodeLinks.flags |= NodeCheckFlags.EnumValuesComputed;
             }
 
-            function getConstantValueForEnumMemberInitializer(initializer: Expression): number {
-                return evalConstant(initializer);
+            function computeConstantValueForEnumMemberInitializer(initializer: Expression, enumType: Type, enumIsConst: boolean, ambient: boolean): number {
+                // Controls if error should be reported after evaluation of constant value is completed
+                // Can be false if another more precise error was already reported during evaluation.
+                let reportError = true;
+                let value = evalConstant(initializer);
+
+                if (reportError) {
+                    if (value === undefined) {
+                        if (enumIsConst) {
+                            error(initializer, Diagnostics.In_const_enum_declarations_member_initializer_must_be_constant_expression);
+                        }
+                        else if (!ambient) {
+                            // Only here do we need to check that the initializer is assignable to the enum type.
+                            // If it is a constant value (not undefined), it is syntactically constrained to be a number.
+                            // Also, we do not need to check this for ambients because there is already
+                            // a syntax error if it is not a constant.
+                            checkTypeAssignableTo(checkExpression(initializer), enumType, initializer, /*headMessage*/ undefined);
+                        }
+                    }
+                    else if (enumIsConst) {
+                        if (isNaN(value)) {
+                            error(initializer, Diagnostics.const_enum_member_initializer_was_evaluated_to_disallowed_value_NaN);
+                        }
+                        else if (!isFinite(value)) {
+                            error(initializer, Diagnostics.const_enum_member_initializer_was_evaluated_to_a_non_finite_value);
+                        }
+                    }
+                }
+
+                return value;
 
                 function evalConstant(e: Node): number {
                     switch (e.kind) {
@@ -12881,6 +12948,8 @@ namespace ts {
 
                             // illegal case: forward reference
                             if (!isDefinedBefore(propertyDecl, member)) {
+                                reportError = false;
+                                error(e, Diagnostics.A_member_initializer_in_a_const_enum_declaration_cannot_reference_members_declared_after_it_including_members_defined_in_other_const_enums);
                                 return undefined;
                             }
 
@@ -14362,6 +14431,7 @@ namespace ts {
                 getBlockScopedVariableId,
                 getReferencedValueDeclaration,
                 getTypeReferenceSerializationKind,
+                isOptionalParameter
             };
         }
 
@@ -14757,17 +14827,15 @@ namespace ts {
                         return grammarErrorOnNode(parameter.name, Diagnostics.A_rest_parameter_cannot_have_an_initializer);
                     }
                 }
-                else if (parameter.questionToken || parameter.initializer) {
+                else if (parameter.questionToken) {
                     seenOptionalParameter = true;
 
-                    if (parameter.questionToken && parameter.initializer) {
+                    if (parameter.initializer) {
                         return grammarErrorOnNode(parameter.name, Diagnostics.Parameter_cannot_have_question_mark_and_initializer);
                     }
                 }
-                else {
-                    if (seenOptionalParameter) {
-                        return grammarErrorOnNode(parameter.name, Diagnostics.A_required_parameter_cannot_follow_an_optional_parameter);
-                    }
+                else if (seenOptionalParameter && !parameter.initializer) {
+                    return grammarErrorOnNode(parameter.name, Diagnostics.A_required_parameter_cannot_follow_an_optional_parameter);
                 }
             }
         }
diff --git a/src/compiler/declarationEmitter.ts b/src/compiler/declarationEmitter.ts
index 6c0803f8761..63d71b0339e 100644
--- a/src/compiler/declarationEmitter.ts
+++ b/src/compiler/declarationEmitter.ts
@@ -1371,7 +1371,7 @@ namespace ts {
             else {
                 writeTextOfNode(currentSourceFile, node.name);
             }
-            if (node.initializer || hasQuestionToken(node)) {
+            if (resolver.isOptionalParameter(node)) {
                 write("?");
             }
             decreaseIndent();
diff --git a/src/compiler/diagnosticInformationMap.generated.ts b/src/compiler/diagnosticInformationMap.generated.ts
index b91399e8ee1..5ccc0a0db9b 100644
--- a/src/compiler/diagnosticInformationMap.generated.ts
+++ b/src/compiler/diagnosticInformationMap.generated.ts
@@ -294,7 +294,7 @@ namespace ts {
         Multiple_constructor_implementations_are_not_allowed: { code: 2392, category: DiagnosticCategory.Error, key: "Multiple constructor implementations are not allowed." },
         Duplicate_function_implementation: { code: 2393, category: DiagnosticCategory.Error, key: "Duplicate function implementation." },
         Overload_signature_is_not_compatible_with_function_implementation: { code: 2394, category: DiagnosticCategory.Error, key: "Overload signature is not compatible with function implementation." },
-        Individual_declarations_in_merged_declaration_0_must_be_all_exported_or_all_local: { code: 2395, category: DiagnosticCategory.Error, key: "Individual declarations in merged declaration {0} must be all exported or all local." },
+        Individual_declarations_in_merged_declaration_0_must_be_all_exported_or_all_local: { code: 2395, category: DiagnosticCategory.Error, key: "Individual declarations in merged declaration '{0}' must be all exported or all local." },
         Duplicate_identifier_arguments_Compiler_uses_arguments_to_initialize_rest_parameters: { code: 2396, category: DiagnosticCategory.Error, key: "Duplicate identifier 'arguments'. Compiler uses 'arguments' to initialize rest parameters." },
         Duplicate_identifier_this_Compiler_uses_variable_declaration_this_to_capture_this_reference: { code: 2399, category: DiagnosticCategory.Error, key: "Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference." },
         Expression_resolves_to_variable_declaration_this_that_compiler_uses_to_capture_this_reference: { code: 2400, category: DiagnosticCategory.Error, key: "Expression resolves to variable declaration '_this' that compiler uses to capture 'this' reference." },
@@ -425,6 +425,8 @@ namespace ts {
         JSX_element_class_does_not_support_attributes_because_it_does_not_have_a_0_property: { code: 2607, category: DiagnosticCategory.Error, key: "JSX element class does not support attributes because it does not have a '{0}' property" },
         The_global_type_JSX_0_may_not_have_more_than_one_property: { code: 2608, category: DiagnosticCategory.Error, key: "The global type 'JSX.{0}' may not have more than one property" },
         Cannot_emit_namespaced_JSX_elements_in_React: { code: 2650, category: DiagnosticCategory.Error, key: "Cannot emit namespaced JSX elements in React" },
+        A_member_initializer_in_a_const_enum_declaration_cannot_reference_members_declared_after_it_including_members_defined_in_other_const_enums: { code: 2651, category: DiagnosticCategory.Error, key: "A member initializer in a 'const' enum declaration cannot reference members declared after it, including members defined in other 'const' enums." },
+        Merged_declaration_0_cannot_include_a_default_export_declaration_Consider_adding_a_separate_export_default_0_declaration_instead: { code: 2652, category: DiagnosticCategory.Error, key: "Merged declaration '{0}' cannot include a default export declaration. Consider adding a separate 'export default {0}' declaration instead." },
         Import_declaration_0_is_using_private_name_1: { code: 4000, category: DiagnosticCategory.Error, key: "Import declaration '{0}' is using private name '{1}'." },
         Type_parameter_0_of_exported_class_has_or_is_using_private_name_1: { code: 4002, category: DiagnosticCategory.Error, key: "Type parameter '{0}' of exported class has or is using private name '{1}'." },
         Type_parameter_0_of_exported_interface_has_or_is_using_private_name_1: { code: 4004, category: DiagnosticCategory.Error, key: "Type parameter '{0}' of exported interface has or is using private name '{1}'." },
@@ -509,7 +511,6 @@ namespace ts {
         Option_noEmit_cannot_be_specified_with_option_out_or_outDir: { code: 5040, category: DiagnosticCategory.Error, key: "Option 'noEmit' cannot be specified with option 'out' or 'outDir'." },
         Option_noEmit_cannot_be_specified_with_option_declaration: { code: 5041, category: DiagnosticCategory.Error, key: "Option 'noEmit' cannot be specified with option 'declaration'." },
         Option_project_cannot_be_mixed_with_source_files_on_a_command_line: { code: 5042, category: DiagnosticCategory.Error, key: "Option 'project' cannot be mixed with source files on a command line." },
-        Option_sourceMap_cannot_be_specified_with_option_isolatedModules: { code: 5043, category: DiagnosticCategory.Error, key: "Option 'sourceMap' cannot be specified with option 'isolatedModules'." },
         Option_declaration_cannot_be_specified_with_option_isolatedModules: { code: 5044, category: DiagnosticCategory.Error, key: "Option 'declaration' cannot be specified with option 'isolatedModules'." },
         Option_noEmitOnError_cannot_be_specified_with_option_isolatedModules: { code: 5045, category: DiagnosticCategory.Error, key: "Option 'noEmitOnError' cannot be specified with option 'isolatedModules'." },
         Option_out_cannot_be_specified_with_option_isolatedModules: { code: 5046, category: DiagnosticCategory.Error, key: "Option 'out' cannot be specified with option 'isolatedModules'." },
@@ -614,5 +615,6 @@ namespace ts {
         Expected_corresponding_JSX_closing_tag_for_0: { code: 17002, category: DiagnosticCategory.Error, key: "Expected corresponding JSX closing tag for '{0}'." },
         JSX_attribute_expected: { code: 17003, category: DiagnosticCategory.Error, key: "JSX attribute expected." },
         Cannot_use_JSX_unless_the_jsx_flag_is_provided: { code: 17004, category: DiagnosticCategory.Error, key: "Cannot use JSX unless the '--jsx' flag is provided." },
+        A_constructor_cannot_contain_a_super_call_when_its_class_extends_null: { code: 17005, category: DiagnosticCategory.Error, key: "A constructor cannot contain a 'super' call when its class extends 'null'" },
     };
 }
\ No newline at end of file
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 9fda73740ba..e138e2ddac4 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -1,4 +1,4 @@
-{
+ {
     "Unterminated string literal.": {
         "category": "Error",
         "code": 1002
@@ -1165,7 +1165,7 @@
         "category": "Error",
         "code": 2394
     },
-    "Individual declarations in merged declaration {0} must be all exported or all local.": {
+    "Individual declarations in merged declaration '{0}' must be all exported or all local.": {
         "category": "Error",
         "code": 2395
     },
@@ -1689,6 +1689,14 @@
         "category": "Error",
         "code": 2650
     },
+    "A member initializer in a 'const' enum declaration cannot reference members declared after it, including members defined in other 'const' enums.": {
+        "category": "Error",
+        "code": 2651
+    },    
+    "Merged declaration '{0}' cannot include a default export declaration. Consider adding a separate 'export default {0}' declaration instead.": {
+        "category": "Error",
+        "code": 2652
+    },
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",
         "code": 4000
@@ -2025,10 +2033,6 @@
         "category": "Error",
         "code": 5042
     },
-    "Option 'sourceMap' cannot be specified with option 'isolatedModules'.": {
-        "category": "Error",
-        "code": 5043
-    },
     "Option 'declaration' cannot be specified with option 'isolatedModules'.": {
         "category": "Error",
         "code": 5044
@@ -2449,5 +2453,9 @@
     "Cannot use JSX unless the '--jsx' flag is provided.": {
         "category": "Error",
         "code": 17004
+    },
+    "A constructor cannot contain a 'super' call when its class extends 'null'": {
+      "category": "Error",
+      "code": 17005
     }
 }
diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index d55e5ec9464..b1a0c1fff5b 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -6842,6 +6842,11 @@ var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, Promi
                 return leadingComments;
             }
 
+            /**
+             * Removes all but the pinned or triple slash comments.
+             * @param ranges The array to be filtered
+             * @param onlyPinnedOrTripleSlashComments whether the filtering should be performed.
+             */
             function filterComments(ranges: CommentRange[], onlyPinnedOrTripleSlashComments: boolean): CommentRange[] {
                 // If we're removing comments, then we want to strip out all but the pinned or
                 // triple slash comments.
diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 5ce4846b43b..4b1f10eb649 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -8,7 +8,7 @@ namespace ts {
     /* @internal */ export let ioWriteTime = 0;
 
     /** The version of the TypeScript compiler release */
-    export const version = "1.5.3";
+    export const version = "1.6.0";
 
     export function findConfigFile(searchPath: string): string {
         let fileName = "tsconfig.json";
@@ -341,7 +341,7 @@ namespace ts {
             });
         }
 
-        function getDeclarationDiagnosticsForFile(sourceFile: SourceFile, cancellationToken: CancellationToken): Diagnostic[] {
+        function getDeclarationDiagnosticsForFile(sourceFile: SourceFile, cancellationToken: CancellationToken): Diagnostic[] {
             return runWithCancellationToken(() => {
                 if (!isDeclarationFile(sourceFile)) {
                     let resolver = getDiagnosticsProducingTypeChecker().getEmitResolver(sourceFile, cancellationToken);
@@ -350,7 +350,7 @@ namespace ts {
                     return ts.getDeclarationDiagnostics(getEmitHost(writeFile), resolver, sourceFile);
                 }
             });
-        }
+        }
 
         function getOptionsDiagnostics(): Diagnostic[] {
             let allDiagnostics: Diagnostic[] = [];
@@ -602,10 +602,6 @@ namespace ts {
 
         function verifyCompilerOptions() {
             if (options.isolatedModules) {
-                if (options.sourceMap) {
-                    diagnostics.add(createCompilerDiagnostic(Diagnostics.Option_sourceMap_cannot_be_specified_with_option_isolatedModules));
-                }
-
                 if (options.declaration) {
                     diagnostics.add(createCompilerDiagnostic(Diagnostics.Option_declaration_cannot_be_specified_with_option_isolatedModules));
                 }
diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index a657cc8c314..6872c4c876e 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -3,7 +3,7 @@
 
 namespace ts {
     export interface SourceFile {
-        fileWatcher: FileWatcher;
+        fileWatcher?: FileWatcher;
     }
 
     /**
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 8d5596c6f64..c5d7f879c25 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -1404,6 +1404,7 @@ namespace ts {
         getPropertyOfType(type: Type, propertyName: string): Symbol;
         getSignaturesOfType(type: Type, kind: SignatureKind): Signature[];
         getIndexTypeOfType(type: Type, kind: IndexKind): Type;
+        getBaseTypes(type: InterfaceType): ObjectType[];
         getReturnTypeOfSignature(signature: Signature): Type;
 
         getSymbolsInScope(location: Node, meaning: SymbolFlags): Symbol[];
@@ -1430,6 +1431,7 @@ namespace ts {
 
         getJsxElementAttributesType(elementNode: JsxOpeningLikeElement): Type;
         getJsxIntrinsicTagNames(): Symbol[];
+        isOptionalParameter(node: ParameterDeclaration): boolean;
 
         // Should not be called directly.  Should only be accessed through the Program instance.
         /* @internal */ getDiagnostics(sourceFile?: SourceFile, cancellationToken?: CancellationToken): Diagnostic[];
@@ -1573,7 +1575,8 @@ namespace ts {
         getConstantValue(node: EnumMember | PropertyAccessExpression | ElementAccessExpression): number;
         getBlockScopedVariableId(node: Identifier): number;
         getReferencedValueDeclaration(reference: Identifier): Declaration;
-        getTypeReferenceSerializationKind(node: TypeReferenceNode): TypeReferenceSerializationKind; 
+        getTypeReferenceSerializationKind(node: TypeReferenceNode): TypeReferenceSerializationKind;
+        isOptionalParameter(node: ParameterDeclaration): boolean;
     }
 
     export const enum SymbolFlags {
@@ -1767,7 +1770,9 @@ namespace ts {
         ContainsUndefinedOrNull = 0x00200000,  // Type is or contains Undefined or Null type
         /* @internal */
         ContainsObjectLiteral   = 0x00400000,  // Type is or contains object literal type
-        ESSymbol                = 0x00800000,  // Type of symbol primitive introduced in ES6
+        /* @internal */
+        ContainsAnyFunctionType = 0x00800000,  // Type is or contains object literal type
+        ESSymbol                = 0x01000000,  // Type of symbol primitive introduced in ES6
 
         /* @internal */
         Intrinsic = Any | String | Number | Boolean | ESSymbol | Void | Undefined | Null,
@@ -1776,10 +1781,12 @@ namespace ts {
         StringLike = String | StringLiteral,
         NumberLike = Number | Enum,
         ObjectType = Class | Interface | Reference | Tuple | Anonymous,
-        UnionOrIntersection = Union | Intersection,
+        UnionOrIntersection = Union | Intersection,
         StructuredType = ObjectType | Union | Intersection,
+        /* @internal */
+        RequiresWidening = ContainsUndefinedOrNull | ContainsObjectLiteral,
         /* @internal */
-        RequiresWidening = ContainsUndefinedOrNull | ContainsObjectLiteral
+        PropagatingFlags = ContainsUndefinedOrNull | ContainsObjectLiteral | ContainsAnyFunctionType
     }
 
     // Properties common to all types
@@ -1808,7 +1815,9 @@ namespace ts {
         typeParameters: TypeParameter[];           // Type parameters (undefined if non-generic)
         outerTypeParameters: TypeParameter[];      // Outer type parameters (undefined if none)
         localTypeParameters: TypeParameter[];      // Local type parameters (undefined if none)
+        /* @internal */
         resolvedBaseConstructorType?: Type;        // Resolved base constructor type of class
+        /* @internal */
         resolvedBaseTypes: ObjectType[];           // Resolved base types
     }
 
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index 56eb2415cf9..312a3666757 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -988,15 +988,13 @@ namespace ts {
         if (node) {
             switch (node.kind) {
                 case SyntaxKind.Parameter:
-                    return (<ParameterDeclaration>node).questionToken !== undefined;
                 case SyntaxKind.MethodDeclaration:
                 case SyntaxKind.MethodSignature:
-                    return (<MethodDeclaration>node).questionToken !== undefined;
                 case SyntaxKind.ShorthandPropertyAssignment:
                 case SyntaxKind.PropertyAssignment:
                 case SyntaxKind.PropertyDeclaration:
                 case SyntaxKind.PropertySignature:
-                    return (<PropertyDeclaration>node).questionToken !== undefined;
+                    return (<ParameterDeclaration | MethodDeclaration | PropertyDeclaration>node).questionToken !== undefined;
             }
         }
 
diff --git a/src/harness/fourslash.ts b/src/harness/fourslash.ts
index 02ca17cefd7..272f4c1c1dd 100644
--- a/src/harness/fourslash.ts
+++ b/src/harness/fourslash.ts
@@ -1875,7 +1875,7 @@ module FourSlash {
             }
         }
 
-        private verifyProjectInfo(expected: string[]) {
+        public verifyProjectInfo(expected: string[]) {
             if (this.testType === FourSlashTestType.Server) {
                 let actual = (<ts.server.SessionClient>this.languageService).getProjectInfo(
                     this.activeFile.fileName,
@@ -2057,11 +2057,8 @@ module FourSlash {
             return result;
         }
 
-        public verifGetScriptLexicalStructureListContains(
-            name: string,
-            kind: string,
-            markerPosition?: number) {
-            this.taoInvalidReason = 'verifGetScriptLexicalStructureListContains impossible';
+        public verifyGetScriptLexicalStructureListContains(name: string, kind: string) {
+            this.taoInvalidReason = 'verifyGetScriptLexicalStructureListContains impossible';
 
             let items = this.languageService.getNavigationBarItems(this.activeFile.fileName);
 
@@ -2263,7 +2260,7 @@ module FourSlash {
             return 'line ' + (pos.line + 1) + ', col ' + pos.character;
         }
 
-        private getMarkerByName(markerName: string) {
+        public getMarkerByName(markerName: string) {
             let markerPos = this.testData.markerPositions[markerName];
             if (markerPos === undefined) {
                 let markerNames: string[] = [];
@@ -2738,4 +2735,4 @@ module FourSlash {
             fileName: fileName
         };
     }
-}
+}
\ No newline at end of file
diff --git a/src/harness/harness.ts b/src/harness/harness.ts
index 17aa0dd325c..b6c10071cb1 100644
--- a/src/harness/harness.ts
+++ b/src/harness/harness.ts
@@ -29,6 +29,7 @@ var Buffer: BufferConstructor = require('buffer').Buffer;
 // this will work in the browser via browserify
 var _chai: typeof chai = require('chai');
 var assert: typeof _chai.assert = _chai.assert;
+var expect: typeof _chai.expect = _chai.expect;
 declare var __dirname: string; // Node-specific
 var global = <any>Function("return this").call(null);
 
diff --git a/src/server/session.ts b/src/server/session.ts
index d2ac429aa3c..9a5cee32264 100644
--- a/src/server/session.ts
+++ b/src/server/session.ts
@@ -109,13 +109,13 @@ namespace ts.server {
     }
 
     export class Session {
-        projectService: ProjectService;
-        pendingOperation = false;
-        fileHash: ts.Map<number> = {};
-        nextFileId = 1;
-        errorTimer: any; /*NodeJS.Timer | number*/
-        immediateId: any;
-        changeSeq = 0;
+        protected projectService: ProjectService;
+        private pendingOperation = false;
+        private fileHash: ts.Map<number> = {};
+        private nextFileId = 1;
+        private errorTimer: any; /*NodeJS.Timer | number*/
+        private immediateId: any;
+        private changeSeq = 0;
 
         constructor(
             private host: ServerHost, 
@@ -129,7 +129,7 @@ namespace ts.server {
             });
         }
 
-        handleEvent(eventName: string, project: Project, fileName: string) {
+        private handleEvent(eventName: string, project: Project, fileName: string) {
             if (eventName == "context") {
                 this.projectService.log("got context event, updating diagnostics for" + fileName, "Info");
                 this.updateErrorCheck([{ fileName, project }], this.changeSeq,
@@ -137,7 +137,7 @@ namespace ts.server {
             }
         }
 
-        logError(err: Error, cmd: string) {
+        public logError(err: Error, cmd: string) {
             var typedErr = <StackTraceError>err;
             var msg = "Exception on executing command " + cmd;
             if (typedErr.message) {
@@ -149,11 +149,11 @@ namespace ts.server {
             this.projectService.log(msg);
         }
 
-        sendLineToClient(line: string) {
+        private sendLineToClient(line: string) {
             this.host.write(line + this.host.newLine);
         }
 
-        send(msg: protocol.Message) {
+        public send(msg: protocol.Message) {
             var json = JSON.stringify(msg);
             if (this.logger.isVerbose()) {
                 this.logger.info(msg.type + ": " + json);
@@ -162,7 +162,7 @@ namespace ts.server {
                 '\r\n\r\n' + json);
         }
 
-        event(info: any, eventName: string) {
+        public event(info: any, eventName: string) {
             var ev: protocol.Event = {
                 seq: 0,
                 type: "event",
@@ -172,7 +172,7 @@ namespace ts.server {
             this.send(ev);
         }
 
-        response(info: any, cmdName: string, reqSeq = 0, errorMsg?: string) {
+        private response(info: any, cmdName: string, reqSeq = 0, errorMsg?: string) {
             var res: protocol.Response = {
                 seq: 0,
                 type: "response",
@@ -189,11 +189,11 @@ namespace ts.server {
             this.send(res);
         }
 
-        output(body: any, commandName: string, requestSequence = 0, errorMessage?: string) {
+        public output(body: any, commandName: string, requestSequence = 0, errorMessage?: string) {
             this.response(body, commandName, requestSequence, errorMessage);
         }
 
-        semanticCheck(file: string, project: Project) {
+        private semanticCheck(file: string, project: Project) {
             try {
                 var diags = project.compilerService.languageService.getSemanticDiagnostics(file);
 
@@ -207,7 +207,7 @@ namespace ts.server {
             }
         }
 
-        syntacticCheck(file: string, project: Project) {
+        private syntacticCheck(file: string, project: Project) {
             try {
                 var diags = project.compilerService.languageService.getSyntacticDiagnostics(file);
                 if (diags) {
@@ -220,12 +220,12 @@ namespace ts.server {
             }
         }
 
-        errorCheck(file: string, project: Project) {
+        private errorCheck(file: string, project: Project) {
             this.syntacticCheck(file, project);
             this.semanticCheck(file, project);
         }
 
-        updateProjectStructure(seq: number, matchSeq: (seq: number) => boolean, ms = 1500) {
+        private updateProjectStructure(seq: number, matchSeq: (seq: number) => boolean, ms = 1500) {
             setTimeout(() => {
                 if (matchSeq(seq)) {
                     this.projectService.updateProjectStructure();
@@ -233,7 +233,7 @@ namespace ts.server {
             }, ms);
         }
 
-        updateErrorCheck(checkList: PendingErrorCheck[], seq: number,
+        private updateErrorCheck(checkList: PendingErrorCheck[], seq: number,
             matchSeq: (seq: number) => boolean, ms = 1500, followMs = 200) {
             if (followMs > ms) {
                 followMs = ms;
@@ -269,7 +269,7 @@ namespace ts.server {
             }
         }
 
-        getDefinition(line: number, offset: number, fileName: string): protocol.FileSpan[] {
+        private getDefinition(line: number, offset: number, fileName: string): protocol.FileSpan[] {
             var file = ts.normalizePath(fileName);
             var project = this.projectService.getProjectForFile(file);
             if (!project) {
@@ -291,7 +291,7 @@ namespace ts.server {
             }));
         }
 
-        getTypeDefinition(line: number, offset: number, fileName: string): protocol.FileSpan[] {
+        private getTypeDefinition(line: number, offset: number, fileName: string): protocol.FileSpan[] {
             var file = ts.normalizePath(fileName);
             var project = this.projectService.getProjectForFile(file);
             if (!project) {
@@ -313,7 +313,7 @@ namespace ts.server {
             }));
         }
 
-        getOccurrences(line: number, offset: number, fileName: string): protocol.OccurrencesResponseItem[]{
+        private getOccurrences(line: number, offset: number, fileName: string): protocol.OccurrencesResponseItem[]{
             fileName = ts.normalizePath(fileName);
             let project = this.projectService.getProjectForFile(fileName);
 
@@ -343,7 +343,7 @@ namespace ts.server {
             });
         }
 
-        getProjectInfo(fileName: string, needFileNameList: boolean): protocol.ProjectInfo {
+        private getProjectInfo(fileName: string, needFileNameList: boolean): protocol.ProjectInfo {
             fileName = ts.normalizePath(fileName)
             let project = this.projectService.getProjectForFile(fileName)
 
@@ -358,7 +358,7 @@ namespace ts.server {
             return projectInfo;
         }
 
-        getRenameLocations(line: number, offset: number, fileName: string,findInComments: boolean, findInStrings: boolean): protocol.RenameResponseBody {
+        private getRenameLocations(line: number, offset: number, fileName: string,findInComments: boolean, findInStrings: boolean): protocol.RenameResponseBody {
             var file = ts.normalizePath(fileName);
             var project = this.projectService.getProjectForFile(file);
             if (!project) {
@@ -426,7 +426,7 @@ namespace ts.server {
             return { info: renameInfo, locs: bakedRenameLocs };
         }
 
-        getReferences(line: number, offset: number, fileName: string): protocol.ReferencesResponseBody {
+        private getReferences(line: number, offset: number, fileName: string): protocol.ReferencesResponseBody {
             // TODO: get all projects for this file; report refs for all projects deleting duplicates
             // can avoid duplicates by eliminating same ref file from subsequent projects
             var file = ts.normalizePath(fileName);
@@ -473,12 +473,12 @@ namespace ts.server {
             };
         }
 
-        openClientFile(fileName: string) {
+        private openClientFile(fileName: string) {
             var file = ts.normalizePath(fileName);
             this.projectService.openClientFile(file);
         }
 
-        getQuickInfo(line: number, offset: number, fileName: string): protocol.QuickInfoResponseBody {
+        private getQuickInfo(line: number, offset: number, fileName: string): protocol.QuickInfoResponseBody {
             var file = ts.normalizePath(fileName);
             var project = this.projectService.getProjectForFile(file);
             if (!project) {
@@ -504,7 +504,7 @@ namespace ts.server {
             };
         }
 
-        getFormattingEditsForRange(line: number, offset: number, endLine: number, endOffset: number, fileName: string): protocol.CodeEdit[] {
+        private getFormattingEditsForRange(line: number, offset: number, endLine: number, endOffset: number, fileName: string): protocol.CodeEdit[] {
             var file = ts.normalizePath(fileName);
             var project = this.projectService.getProjectForFile(file);
             if (!project) {
@@ -531,7 +531,7 @@ namespace ts.server {
             });
         }
 
-        getFormattingEditsAfterKeystroke(line: number, offset: number, key: string, fileName: string): protocol.CodeEdit[] {
+        private getFormattingEditsAfterKeystroke(line: number, offset: number, key: string, fileName: string): protocol.CodeEdit[] {
             var file = ts.normalizePath(fileName);
 
             var project = this.projectService.getProjectForFile(file);
@@ -607,7 +607,7 @@ namespace ts.server {
             });
         }
 
-        getCompletions(line: number, offset: number, prefix: string, fileName: string): protocol.CompletionEntry[] {
+        private getCompletions(line: number, offset: number, prefix: string, fileName: string): protocol.CompletionEntry[] {
             if (!prefix) {
                 prefix = "";
             }
@@ -633,7 +633,7 @@ namespace ts.server {
             }, []).sort((a, b) => a.name.localeCompare(b.name));
         }
 
-        getCompletionEntryDetails(line: number, offset: number,
+        private getCompletionEntryDetails(line: number, offset: number,
             entryNames: string[], fileName: string): protocol.CompletionEntryDetails[] {
             var file = ts.normalizePath(fileName);
             var project = this.projectService.getProjectForFile(file);
@@ -653,7 +653,7 @@ namespace ts.server {
             }, []);
         }
 
-        getSignatureHelpItems(line: number, offset: number, fileName: string): protocol.SignatureHelpItems {
+        private getSignatureHelpItems(line: number, offset: number, fileName: string): protocol.SignatureHelpItems {
             var file = ts.normalizePath(fileName);
             var project = this.projectService.getProjectForFile(file);
             if (!project) {
@@ -682,7 +682,7 @@ namespace ts.server {
             return result;
         }
                 
-        getDiagnostics(delay: number, fileNames: string[]) {
+        private getDiagnostics(delay: number, fileNames: string[]) {
             var checkList = fileNames.reduce((accum: PendingErrorCheck[], fileName: string) => {
                 fileName = ts.normalizePath(fileName);
                 var project = this.projectService.getProjectForFile(fileName);
@@ -697,7 +697,7 @@ namespace ts.server {
             }
         }
 
-        change(line: number, offset: number, endLine: number, endOffset: number, insertString: string, fileName: string) {
+        private change(line: number, offset: number, endLine: number, endOffset: number, insertString: string, fileName: string) {
             var file = ts.normalizePath(fileName);
             var project = this.projectService.getProjectForFile(file);
             if (project) {
@@ -712,7 +712,7 @@ namespace ts.server {
             }
         }
 
-        reload(fileName: string, tempFileName: string, reqSeq = 0) {
+        private reload(fileName: string, tempFileName: string, reqSeq = 0) {
             var file = ts.normalizePath(fileName);
             var tmpfile = ts.normalizePath(tempFileName);
             var project = this.projectService.getProjectForFile(file);
@@ -725,7 +725,7 @@ namespace ts.server {
             }
         }
 
-        saveToTmp(fileName: string, tempFileName: string) {
+        private saveToTmp(fileName: string, tempFileName: string) {
             var file = ts.normalizePath(fileName);
             var tmpfile = ts.normalizePath(tempFileName);
 
@@ -735,12 +735,12 @@ namespace ts.server {
             }
         }
 
-        closeClientFile(fileName: string) {
+        private closeClientFile(fileName: string) {
             var file = ts.normalizePath(fileName);
             this.projectService.closeClientFile(file);
         }
 
-        decorateNavigationBarItem(project: Project, fileName: string, items: ts.NavigationBarItem[]): protocol.NavigationBarItem[] {
+        private decorateNavigationBarItem(project: Project, fileName: string, items: ts.NavigationBarItem[]): protocol.NavigationBarItem[] {
             if (!items) {
                 return undefined;
             }
@@ -759,7 +759,7 @@ namespace ts.server {
             }));
         }
 
-        getNavigationBarItems(fileName: string): protocol.NavigationBarItem[] {
+        private getNavigationBarItems(fileName: string): protocol.NavigationBarItem[] {
             var file = ts.normalizePath(fileName);
             var project = this.projectService.getProjectForFile(file);
             if (!project) {
@@ -775,7 +775,7 @@ namespace ts.server {
             return this.decorateNavigationBarItem(project, fileName, items);
         }
 
-        getNavigateToItems(searchValue: string, fileName: string, maxResultCount?: number): protocol.NavtoItem[] {
+        private getNavigateToItems(searchValue: string, fileName: string, maxResultCount?: number): protocol.NavtoItem[] {
             var file = ts.normalizePath(fileName);
             var project = this.projectService.getProjectForFile(file);
             if (!project) {
@@ -814,7 +814,7 @@ namespace ts.server {
             });
         }
 
-        getBraceMatching(line: number, offset: number, fileName: string): protocol.TextSpan[] {
+        private getBraceMatching(line: number, offset: number, fileName: string): protocol.TextSpan[] {
             var file = ts.normalizePath(fileName);
             
             var project = this.projectService.getProjectForFile(file);
@@ -836,7 +836,7 @@ namespace ts.server {
             }));
         }
 
-        exit() {
+        public exit() {
         }
 
         private handlers : Map<(request: protocol.Request) => {response?: any, responseRequired?: boolean}> = {
@@ -942,14 +942,14 @@ namespace ts.server {
                 return {response: this.getProjectInfo(file, needFileNameList), responseRequired: true};
             },
         };
-        addProtocolHandler(command: string, handler: (request: protocol.Request) => {response?: any, responseRequired: boolean}) {
+        public addProtocolHandler(command: string, handler: (request: protocol.Request) => {response?: any, responseRequired: boolean}) {
             if (this.handlers[command]) {
                 throw new Error(`Protocol handler already exists for command "${command}"`);
             }
             this.handlers[command] = handler;
         }
 
-        executeCommand(request: protocol.Request) : {response?: any, responseRequired?: boolean} {
+        public executeCommand(request: protocol.Request) : {response?: any, responseRequired?: boolean} {
             var handler = this.handlers[request.command];
             if (handler) {
                 return handler(request);
@@ -960,7 +960,7 @@ namespace ts.server {
             }
         }
 
-        onMessage(message: string) {
+        public onMessage(message: string) {
             if (this.logger.isVerbose()) {
                 this.logger.info("request: " + message);
                 var start = this.hrtime();                
diff --git a/src/services/services.ts b/src/services/services.ts
index 16f5b0b91fe..8e670268498 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -48,6 +48,7 @@ namespace ts {
         getConstructSignatures(): Signature[];
         getStringIndexType(): Type;
         getNumberIndexType(): Type;
+        getBaseTypes(): ObjectType[]
     }
 
     export interface Signature {
@@ -260,26 +261,25 @@ namespace ts {
         }
 
         public getFirstToken(sourceFile?: SourceFile): Node {
-            let children = this.getChildren();
-            for (let child of children) {
-                if (child.kind < SyntaxKind.FirstNode) {
-                    return child;
-                }
-
-                return child.getFirstToken(sourceFile);
+            let children = this.getChildren(sourceFile);
+            if (!children.length) {
+                return undefined;
             }
+
+            let child = children[0];
+
+            return child.kind < SyntaxKind.FirstNode ? child : child.getFirstToken(sourceFile);
         }
 
         public getLastToken(sourceFile?: SourceFile): Node {
             let children = this.getChildren(sourceFile);
-            for (let i = children.length - 1; i >= 0; i--) {
-                let child = children[i];
-                if (child.kind < SyntaxKind.FirstNode) {
-                    return child;
-                }
 
-                return child.getLastToken(sourceFile);
+            let child = lastOrUndefined(children);
+            if (!child) { 
+                return undefined; 
             }
+
+            return child.kind < SyntaxKind.FirstNode ? child : child.getLastToken(sourceFile);
         }
     }
 
@@ -682,6 +682,11 @@ namespace ts {
         getNumberIndexType(): Type {
             return this.checker.getIndexTypeOfType(this, IndexKind.Number);
         }
+        getBaseTypes(): ObjectType[] {
+            return this.flags & (TypeFlags.Class | TypeFlags.Interface)
+                ? this.checker.getBaseTypes(<TypeObject & InterfaceType>this)
+                : undefined;
+        }
     }
 
     class SignatureObject implements Signature {
@@ -1754,18 +1759,31 @@ namespace ts {
         sourceFile.version = version;
         sourceFile.scriptSnapshot = scriptSnapshot;
     }
-
+    
+    export interface TranspileOptions {
+        compilerOptions?: CompilerOptions;
+        fileName?: string;
+        reportDiagnostics?: boolean;
+        moduleName?: string;
+    }
+    
+    export interface TranspileOutput {
+        outputText: string;
+        diagnostics?: Diagnostic[];
+        sourceMapText?: string;
+    }
+    
     /*
      * This function will compile source text from 'input' argument using specified compiler options.
      * If not options are provided - it will use a set of default compiler options.
-     * Extra compiler options that will unconditionally be used bu this function are:
+     * Extra compiler options that will unconditionally be used by this function are:
      * - isolatedModules = true
      * - allowNonTsExtensions = true
      * - noLib = true
      * - noResolve = true
-     */
-    export function transpile(input: string, compilerOptions?: CompilerOptions, fileName?: string, diagnostics?: Diagnostic[], moduleName?: string): string {
-        let options = compilerOptions ? clone(compilerOptions) : getDefaultCompilerOptions();
+     */    
+    export function transpileModule(input: string, transpileOptions?: TranspileOptions): TranspileOutput {
+        let options = transpileOptions.compilerOptions ? clone(transpileOptions.compilerOptions) : getDefaultCompilerOptions();
 
         options.isolatedModules = true;
 
@@ -1781,23 +1799,30 @@ namespace ts {
         options.noResolve = true;
 
         // Parse
-        let inputFileName = fileName || "module.ts";
+        let inputFileName = transpileOptions.fileName || "module.ts";
         let sourceFile = createSourceFile(inputFileName, input, options.target);
-        if (moduleName) {
-            sourceFile.moduleName = moduleName;
+        if (transpileOptions.moduleName) {
+            sourceFile.moduleName = transpileOptions.moduleName;
         }
 
         let newLine = getNewLineCharacter(options);
 
         // Output
         let outputText: string;
+        let sourceMapText: string;
 
         // Create a compilerHost object to allow the compiler to read and write files
         let compilerHost: CompilerHost = {
             getSourceFile: (fileName, target) => fileName === inputFileName ? sourceFile : undefined,
             writeFile: (name, text, writeByteOrderMark) => {
-                Debug.assert(outputText === undefined, "Unexpected multiple outputs for the file: " + name);
-                outputText = text;
+                if (fileExtensionIs(name, ".map")) {
+                    Debug.assert(sourceMapText === undefined, `Unexpected multiple source map outputs for the file '${name}'`);
+                    sourceMapText = text;
+                }
+                else {
+                    Debug.assert(outputText === undefined, "Unexpected multiple outputs for the file: " + name);
+                    outputText = text;
+                }
             },
             getDefaultLibFileName: () => "lib.d.ts",
             useCaseSensitiveFileNames: () => false,
@@ -1807,16 +1832,29 @@ namespace ts {
         };
 
         let program = createProgram([inputFileName], options, compilerHost);
-
-        addRange(/*to*/ diagnostics, /*from*/ program.getSyntacticDiagnostics(sourceFile));
-        addRange(/*to*/ diagnostics, /*from*/ program.getOptionsDiagnostics());
-
+        
+        let diagnostics: Diagnostic[];
+        if (transpileOptions.reportDiagnostics) {
+            diagnostics = [];
+            addRange(/*to*/ diagnostics, /*from*/ program.getSyntacticDiagnostics(sourceFile));
+            addRange(/*to*/ diagnostics, /*from*/ program.getOptionsDiagnostics());
+        }
         // Emit
         program.emit();
 
         Debug.assert(outputText !== undefined, "Output generation failed");
 
-        return outputText;
+        return { outputText, diagnostics, sourceMapText };        
+    }
+
+    /*
+     * This is a shortcut function for transpileModule - it accepts transpileOptions as parameters and returns only outputText part of the result. 
+     */
+    export function transpile(input: string, compilerOptions?: CompilerOptions, fileName?: string, diagnostics?: Diagnostic[], moduleName?: string): string {
+        let output = transpileModule(input, { compilerOptions, fileName, reportDiagnostics: !!diagnostics, moduleName });
+        // addRange correctly handles cases when wither 'from' or 'to' argument is missing
+        addRange(diagnostics, output.diagnostics);
+        return output.outputText;
     }
 
     export function createLanguageServiceSourceFile(fileName: string, scriptSnapshot: IScriptSnapshot, scriptTarget: ScriptTarget, version: string, setNodeParents: boolean): SourceFile {
diff --git a/src/services/signatureHelp.ts b/src/services/signatureHelp.ts
index f44ebade2a7..df321647e5c 100644
--- a/src/services/signatureHelp.ts
+++ b/src/services/signatureHelp.ts
@@ -611,13 +611,11 @@ namespace ts.SignatureHelp {
                 let displayParts = mapToDisplayParts(writer =>
                     typeChecker.getSymbolDisplayBuilder().buildParameterDisplay(parameter, writer, invocation));
 
-                let isOptional = hasQuestionToken(parameter.valueDeclaration);
-
                 return {
                     name: parameter.name,
                     documentation: parameter.getDocumentationComment(),
                     displayParts,
-                    isOptional
+                    isOptional: typeChecker.isOptionalParameter(<ParameterDeclaration>parameter.valueDeclaration)
                 };
             }
 
diff --git a/tests/baselines/reference/classExtendsNull.errors.txt b/tests/baselines/reference/classExtendsNull.errors.txt
new file mode 100644
index 00000000000..7bb44774826
--- /dev/null
+++ b/tests/baselines/reference/classExtendsNull.errors.txt
@@ -0,0 +1,21 @@
+tests/cases/compiler/classExtendsNull.ts(2,5): error TS17005: A constructor cannot contain a 'super' call when its class extends 'null'
+
+
+==== tests/cases/compiler/classExtendsNull.ts (1 errors) ====
+    class C extends null {
+        constructor() {
+        ~~~~~~~~~~~~~~~
+            super();
+    ~~~~~~~~~~~~~~~~
+            return Object.create(null);
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+        }
+    ~~~~~
+!!! error TS17005: A constructor cannot contain a 'super' call when its class extends 'null'
+    }
+    
+    class D extends null {
+        constructor() {
+            return Object.create(null);
+        }
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/classExtendsNull.js b/tests/baselines/reference/classExtendsNull.js
new file mode 100644
index 00000000000..5627f10dca6
--- /dev/null
+++ b/tests/baselines/reference/classExtendsNull.js
@@ -0,0 +1,35 @@
+//// [classExtendsNull.ts]
+class C extends null {
+    constructor() {
+        super();
+        return Object.create(null);
+    }
+}
+
+class D extends null {
+    constructor() {
+        return Object.create(null);
+    }
+}
+
+//// [classExtendsNull.js]
+var __extends = (this && this.__extends) || function (d, b) {
+    for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
+    function __() { this.constructor = d; }
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
+};
+var C = (function (_super) {
+    __extends(C, _super);
+    function C() {
+        _super.call(this);
+        return Object.create(null);
+    }
+    return C;
+})(null);
+var D = (function (_super) {
+    __extends(D, _super);
+    function D() {
+        return Object.create(null);
+    }
+    return D;
+})(null);
diff --git a/tests/baselines/reference/constEnumErrors.errors.txt b/tests/baselines/reference/constEnumErrors.errors.txt
index be7dad54eeb..4236544defa 100644
--- a/tests/baselines/reference/constEnumErrors.errors.txt
+++ b/tests/baselines/reference/constEnumErrors.errors.txt
@@ -1,6 +1,6 @@
 tests/cases/compiler/constEnumErrors.ts(1,12): error TS2300: Duplicate identifier 'E'.
 tests/cases/compiler/constEnumErrors.ts(5,8): error TS2300: Duplicate identifier 'E'.
-tests/cases/compiler/constEnumErrors.ts(12,9): error TS2474: In 'const' enum declarations member initializer must be constant expression.
+tests/cases/compiler/constEnumErrors.ts(12,9): error TS2651: A member initializer in a 'const' enum declaration cannot reference members declared after it, including members defined in other 'const' enums.
 tests/cases/compiler/constEnumErrors.ts(14,9): error TS2474: In 'const' enum declarations member initializer must be constant expression.
 tests/cases/compiler/constEnumErrors.ts(15,10): error TS2474: In 'const' enum declarations member initializer must be constant expression.
 tests/cases/compiler/constEnumErrors.ts(22,13): error TS2476: A const enum member can only be accessed using a string literal.
@@ -31,7 +31,7 @@ tests/cases/compiler/constEnumErrors.ts(42,9): error TS2478: 'const' enum member
         // forward reference to the element of the same enum
         X = Y, 
             ~
-!!! error TS2474: In 'const' enum declarations member initializer must be constant expression.
+!!! error TS2651: A member initializer in a 'const' enum declaration cannot reference members declared after it, including members defined in other 'const' enums.
         // forward reference to the element of the same enum
         Y = E1.Z,
             ~~~~
diff --git a/tests/baselines/reference/defaultExportsCannotMerge01.errors.txt b/tests/baselines/reference/defaultExportsCannotMerge01.errors.txt
new file mode 100644
index 00000000000..be08d976eeb
--- /dev/null
+++ b/tests/baselines/reference/defaultExportsCannotMerge01.errors.txt
@@ -0,0 +1,49 @@
+tests/cases/conformance/es6/modules/m1.ts(2,25): error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+tests/cases/conformance/es6/modules/m1.ts(11,18): error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+tests/cases/conformance/es6/modules/m2.ts(5,8): error TS2304: Cannot find name 'Entity'.
+tests/cases/conformance/es6/modules/m2.ts(6,8): error TS2503: Cannot find namespace 'Entity'.
+tests/cases/conformance/es6/modules/m2.ts(8,8): error TS2339: Property 'x' does not exist on type '() => number'.
+tests/cases/conformance/es6/modules/m2.ts(9,8): error TS2339: Property 'y' does not exist on type '() => number'.
+
+
+==== tests/cases/conformance/es6/modules/m1.ts (2 errors) ====
+    
+    export default function Decl() {
+                            ~~~~
+!!! error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+        return 0;
+    }
+    
+    export interface Decl {
+        p1: number;
+        p2: number;
+    }
+    
+    export namespace Decl {
+                     ~~~~
+!!! error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+        export var x = 10;
+        export var y = 20;
+    
+        interface I {
+        }
+    }
+    
+==== tests/cases/conformance/es6/modules/m2.ts (4 errors) ====
+    import Entity from "m1"
+    
+    Entity();
+    
+    var x: Entity;
+           ~~~~~~
+!!! error TS2304: Cannot find name 'Entity'.
+    var y: Entity.I;
+           ~~~~~~
+!!! error TS2503: Cannot find namespace 'Entity'.
+    
+    Entity.x;
+           ~
+!!! error TS2339: Property 'x' does not exist on type '() => number'.
+    Entity.y;
+           ~
+!!! error TS2339: Property 'y' does not exist on type '() => number'.
\ No newline at end of file
diff --git a/tests/baselines/reference/defaultExportsCannotMerge01.js b/tests/baselines/reference/defaultExportsCannotMerge01.js
new file mode 100644
index 00000000000..99b8ecab1d3
--- /dev/null
+++ b/tests/baselines/reference/defaultExportsCannotMerge01.js
@@ -0,0 +1,50 @@
+//// [tests/cases/conformance/es6/modules/defaultExportsCannotMerge01.ts] ////
+
+//// [m1.ts]
+
+export default function Decl() {
+    return 0;
+}
+
+export interface Decl {
+    p1: number;
+    p2: number;
+}
+
+export namespace Decl {
+    export var x = 10;
+    export var y = 20;
+
+    interface I {
+    }
+}
+
+//// [m2.ts]
+import Entity from "m1"
+
+Entity();
+
+var x: Entity;
+var y: Entity.I;
+
+Entity.x;
+Entity.y;
+
+//// [m1.js]
+function Decl() {
+    return 0;
+}
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.default = Decl;
+var Decl;
+(function (Decl) {
+    Decl.x = 10;
+    Decl.y = 20;
+})(Decl = exports.Decl || (exports.Decl = {}));
+//// [m2.js]
+var m1_1 = require("m1");
+m1_1.default();
+var x;
+var y;
+m1_1.default.x;
+m1_1.default.y;
diff --git a/tests/baselines/reference/defaultExportsCannotMerge02.errors.txt b/tests/baselines/reference/defaultExportsCannotMerge02.errors.txt
new file mode 100644
index 00000000000..ad9b85c7e94
--- /dev/null
+++ b/tests/baselines/reference/defaultExportsCannotMerge02.errors.txt
@@ -0,0 +1,44 @@
+tests/cases/conformance/es6/modules/m1.ts(2,22): error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+tests/cases/conformance/es6/modules/m1.ts(5,18): error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+tests/cases/conformance/es6/modules/m2.ts(3,1): error TS2348: Value of type 'typeof Decl' is not callable. Did you mean to include 'new'?
+tests/cases/conformance/es6/modules/m2.ts(6,8): error TS2503: Cannot find namespace 'Entity'.
+tests/cases/conformance/es6/modules/m2.ts(8,13): error TS2339: Property 'p1' does not exist on type 'Decl'.
+tests/cases/conformance/es6/modules/m2.ts(8,20): error TS2339: Property 'p2' does not exist on type 'Decl'.
+
+
+==== tests/cases/conformance/es6/modules/m1.ts (2 errors) ====
+    
+    export default class Decl {
+                         ~~~~
+!!! error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+    }
+    
+    export interface Decl {
+                     ~~~~
+!!! error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+        p1: number;
+        p2: number;
+    }
+    
+    export namespace Decl {
+        interface I {
+        }
+    }
+    
+==== tests/cases/conformance/es6/modules/m2.ts (4 errors) ====
+    import Entity from "m1"
+    
+    Entity();
+    ~~~~~~~~
+!!! error TS2348: Value of type 'typeof Decl' is not callable. Did you mean to include 'new'?
+    
+    var x: Entity;
+    var y: Entity.I;
+           ~~~~~~
+!!! error TS2503: Cannot find namespace 'Entity'.
+    var z = new Entity();
+    var sum = z.p1 + z.p2
+                ~~
+!!! error TS2339: Property 'p1' does not exist on type 'Decl'.
+                       ~~
+!!! error TS2339: Property 'p2' does not exist on type 'Decl'.
\ No newline at end of file
diff --git a/tests/baselines/reference/defaultExportsCannotMerge02.js b/tests/baselines/reference/defaultExportsCannotMerge02.js
new file mode 100644
index 00000000000..e3897395c74
--- /dev/null
+++ b/tests/baselines/reference/defaultExportsCannotMerge02.js
@@ -0,0 +1,42 @@
+//// [tests/cases/conformance/es6/modules/defaultExportsCannotMerge02.ts] ////
+
+//// [m1.ts]
+
+export default class Decl {
+}
+
+export interface Decl {
+    p1: number;
+    p2: number;
+}
+
+export namespace Decl {
+    interface I {
+    }
+}
+
+//// [m2.ts]
+import Entity from "m1"
+
+Entity();
+
+var x: Entity;
+var y: Entity.I;
+var z = new Entity();
+var sum = z.p1 + z.p2
+
+//// [m1.js]
+var Decl = (function () {
+    function Decl() {
+    }
+    return Decl;
+})();
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.default = Decl;
+//// [m2.js]
+var m1_1 = require("m1");
+m1_1.default();
+var x;
+var y;
+var z = new m1_1.default();
+var sum = z.p1 + z.p2;
diff --git a/tests/baselines/reference/defaultExportsCannotMerge03.errors.txt b/tests/baselines/reference/defaultExportsCannotMerge03.errors.txt
new file mode 100644
index 00000000000..b1d405671e3
--- /dev/null
+++ b/tests/baselines/reference/defaultExportsCannotMerge03.errors.txt
@@ -0,0 +1,47 @@
+tests/cases/conformance/es6/modules/m1.ts(2,22): error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+tests/cases/conformance/es6/modules/m1.ts(5,11): error TS2518: Only an ambient class can be merged with an interface.
+tests/cases/conformance/es6/modules/m1.ts(5,11): error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+tests/cases/conformance/es6/modules/m2.ts(3,1): error TS2348: Value of type 'typeof Decl' is not callable. Did you mean to include 'new'?
+tests/cases/conformance/es6/modules/m2.ts(6,8): error TS2503: Cannot find namespace 'Entity'.
+tests/cases/conformance/es6/modules/m2.ts(8,13): error TS2339: Property 'p1' does not exist on type 'Decl'.
+tests/cases/conformance/es6/modules/m2.ts(8,20): error TS2339: Property 'p2' does not exist on type 'Decl'.
+
+
+==== tests/cases/conformance/es6/modules/m1.ts (3 errors) ====
+    
+    export default class Decl {
+                         ~~~~
+!!! error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+    }
+    
+    interface Decl {
+              ~~~~
+!!! error TS2518: Only an ambient class can be merged with an interface.
+              ~~~~
+!!! error TS2652: Merged declaration 'Decl' cannot include a default export declaration. Consider adding a separate 'export default Decl' declaration instead.
+        p1: number;
+        p2: number;
+    }
+    
+    namespace Decl {
+        interface I {
+        }
+    }
+    
+==== tests/cases/conformance/es6/modules/m2.ts (4 errors) ====
+    import Entity from "m1"
+    
+    Entity();
+    ~~~~~~~~
+!!! error TS2348: Value of type 'typeof Decl' is not callable. Did you mean to include 'new'?
+    
+    var x: Entity;
+    var y: Entity.I;
+           ~~~~~~
+!!! error TS2503: Cannot find namespace 'Entity'.
+    var z = new Entity();
+    var sum = z.p1 + z.p2
+                ~~
+!!! error TS2339: Property 'p1' does not exist on type 'Decl'.
+                       ~~
+!!! error TS2339: Property 'p2' does not exist on type 'Decl'.
\ No newline at end of file
diff --git a/tests/baselines/reference/defaultExportsCannotMerge03.js b/tests/baselines/reference/defaultExportsCannotMerge03.js
new file mode 100644
index 00000000000..05e7de94120
--- /dev/null
+++ b/tests/baselines/reference/defaultExportsCannotMerge03.js
@@ -0,0 +1,42 @@
+//// [tests/cases/conformance/es6/modules/defaultExportsCannotMerge03.ts] ////
+
+//// [m1.ts]
+
+export default class Decl {
+}
+
+interface Decl {
+    p1: number;
+    p2: number;
+}
+
+namespace Decl {
+    interface I {
+    }
+}
+
+//// [m2.ts]
+import Entity from "m1"
+
+Entity();
+
+var x: Entity;
+var y: Entity.I;
+var z = new Entity();
+var sum = z.p1 + z.p2
+
+//// [m1.js]
+var Decl = (function () {
+    function Decl() {
+    }
+    return Decl;
+})();
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.default = Decl;
+//// [m2.js]
+var m1_1 = require("m1");
+m1_1.default();
+var x;
+var y;
+var z = new m1_1.default();
+var sum = z.p1 + z.p2;
diff --git a/tests/baselines/reference/defaultExportsCannotMerge04.errors.txt b/tests/baselines/reference/defaultExportsCannotMerge04.errors.txt
new file mode 100644
index 00000000000..000a9b8f30e
--- /dev/null
+++ b/tests/baselines/reference/defaultExportsCannotMerge04.errors.txt
@@ -0,0 +1,28 @@
+tests/cases/conformance/es6/modules/defaultExportsCannotMerge04.ts(2,25): error TS2652: Merged declaration 'Foo' cannot include a default export declaration. Consider adding a separate 'export default Foo' declaration instead.
+tests/cases/conformance/es6/modules/defaultExportsCannotMerge04.ts(5,11): error TS2652: Merged declaration 'Foo' cannot include a default export declaration. Consider adding a separate 'export default Foo' declaration instead.
+tests/cases/conformance/es6/modules/defaultExportsCannotMerge04.ts(9,11): error TS2395: Individual declarations in merged declaration 'Foo' must be all exported or all local.
+tests/cases/conformance/es6/modules/defaultExportsCannotMerge04.ts(12,18): error TS2395: Individual declarations in merged declaration 'Foo' must be all exported or all local.
+
+
+==== tests/cases/conformance/es6/modules/defaultExportsCannotMerge04.ts (4 errors) ====
+    
+    export default function Foo() {
+                            ~~~
+!!! error TS2652: Merged declaration 'Foo' cannot include a default export declaration. Consider adding a separate 'export default Foo' declaration instead.
+    }
+    
+    namespace Foo {
+              ~~~
+!!! error TS2652: Merged declaration 'Foo' cannot include a default export declaration. Consider adding a separate 'export default Foo' declaration instead.
+        export var x;
+    }
+    
+    interface Foo {
+              ~~~
+!!! error TS2395: Individual declarations in merged declaration 'Foo' must be all exported or all local.
+    }
+    
+    export interface Foo {
+                     ~~~
+!!! error TS2395: Individual declarations in merged declaration 'Foo' must be all exported or all local.
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/defaultExportsCannotMerge04.js b/tests/baselines/reference/defaultExportsCannotMerge04.js
new file mode 100644
index 00000000000..eb1122a8197
--- /dev/null
+++ b/tests/baselines/reference/defaultExportsCannotMerge04.js
@@ -0,0 +1,23 @@
+//// [defaultExportsCannotMerge04.ts]
+
+export default function Foo() {
+}
+
+namespace Foo {
+    export var x;
+}
+
+interface Foo {
+}
+
+export interface Foo {
+}
+
+//// [defaultExportsCannotMerge04.js]
+function Foo() {
+}
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.default = Foo;
+var Foo;
+(function (Foo) {
+})(Foo || (Foo = {}));
diff --git a/tests/baselines/reference/duplicateSymbolsExportMatching.errors.txt b/tests/baselines/reference/duplicateSymbolsExportMatching.errors.txt
index df4f8f13c31..85dd29b78a3 100644
--- a/tests/baselines/reference/duplicateSymbolsExportMatching.errors.txt
+++ b/tests/baselines/reference/duplicateSymbolsExportMatching.errors.txt
@@ -1,21 +1,21 @@
-tests/cases/compiler/duplicateSymbolsExportMatching.ts(24,15): error TS2395: Individual declarations in merged declaration I must be all exported or all local.
-tests/cases/compiler/duplicateSymbolsExportMatching.ts(25,22): error TS2395: Individual declarations in merged declaration I must be all exported or all local.
-tests/cases/compiler/duplicateSymbolsExportMatching.ts(26,22): error TS2395: Individual declarations in merged declaration E must be all exported or all local.
-tests/cases/compiler/duplicateSymbolsExportMatching.ts(27,15): error TS2395: Individual declarations in merged declaration E must be all exported or all local.
-tests/cases/compiler/duplicateSymbolsExportMatching.ts(32,12): error TS2395: Individual declarations in merged declaration inst must be all exported or all local.
-tests/cases/compiler/duplicateSymbolsExportMatching.ts(35,19): error TS2395: Individual declarations in merged declaration inst must be all exported or all local.
-tests/cases/compiler/duplicateSymbolsExportMatching.ts(42,9): error TS2395: Individual declarations in merged declaration v must be all exported or all local.
-tests/cases/compiler/duplicateSymbolsExportMatching.ts(43,16): error TS2395: Individual declarations in merged declaration v must be all exported or all local.
-tests/cases/compiler/duplicateSymbolsExportMatching.ts(44,9): error TS2395: Individual declarations in merged declaration w must be all exported or all local.
-tests/cases/compiler/duplicateSymbolsExportMatching.ts(45,16): error TS2395: Individual declarations in merged declaration w must be all exported or all local.
-tests/cases/compiler/duplicateSymbolsExportMatching.ts(49,12): error TS2395: Individual declarations in merged declaration F must be all exported or all local.
+tests/cases/compiler/duplicateSymbolsExportMatching.ts(24,15): error TS2395: Individual declarations in merged declaration 'I' must be all exported or all local.
+tests/cases/compiler/duplicateSymbolsExportMatching.ts(25,22): error TS2395: Individual declarations in merged declaration 'I' must be all exported or all local.
+tests/cases/compiler/duplicateSymbolsExportMatching.ts(26,22): error TS2395: Individual declarations in merged declaration 'E' must be all exported or all local.
+tests/cases/compiler/duplicateSymbolsExportMatching.ts(27,15): error TS2395: Individual declarations in merged declaration 'E' must be all exported or all local.
+tests/cases/compiler/duplicateSymbolsExportMatching.ts(32,12): error TS2395: Individual declarations in merged declaration 'inst' must be all exported or all local.
+tests/cases/compiler/duplicateSymbolsExportMatching.ts(35,19): error TS2395: Individual declarations in merged declaration 'inst' must be all exported or all local.
+tests/cases/compiler/duplicateSymbolsExportMatching.ts(42,9): error TS2395: Individual declarations in merged declaration 'v' must be all exported or all local.
+tests/cases/compiler/duplicateSymbolsExportMatching.ts(43,16): error TS2395: Individual declarations in merged declaration 'v' must be all exported or all local.
+tests/cases/compiler/duplicateSymbolsExportMatching.ts(44,9): error TS2395: Individual declarations in merged declaration 'w' must be all exported or all local.
+tests/cases/compiler/duplicateSymbolsExportMatching.ts(45,16): error TS2395: Individual declarations in merged declaration 'w' must be all exported or all local.
+tests/cases/compiler/duplicateSymbolsExportMatching.ts(49,12): error TS2395: Individual declarations in merged declaration 'F' must be all exported or all local.
 tests/cases/compiler/duplicateSymbolsExportMatching.ts(49,12): error TS2434: A namespace declaration cannot be located prior to a class or function with which it is merged
-tests/cases/compiler/duplicateSymbolsExportMatching.ts(52,21): error TS2395: Individual declarations in merged declaration F must be all exported or all local.
-tests/cases/compiler/duplicateSymbolsExportMatching.ts(56,11): error TS2395: Individual declarations in merged declaration C must be all exported or all local.
-tests/cases/compiler/duplicateSymbolsExportMatching.ts(57,12): error TS2395: Individual declarations in merged declaration C must be all exported or all local.
-tests/cases/compiler/duplicateSymbolsExportMatching.ts(58,19): error TS2395: Individual declarations in merged declaration C must be all exported or all local.
-tests/cases/compiler/duplicateSymbolsExportMatching.ts(64,11): error TS2395: Individual declarations in merged declaration D must be all exported or all local.
-tests/cases/compiler/duplicateSymbolsExportMatching.ts(65,18): error TS2395: Individual declarations in merged declaration D must be all exported or all local.
+tests/cases/compiler/duplicateSymbolsExportMatching.ts(52,21): error TS2395: Individual declarations in merged declaration 'F' must be all exported or all local.
+tests/cases/compiler/duplicateSymbolsExportMatching.ts(56,11): error TS2395: Individual declarations in merged declaration 'C' must be all exported or all local.
+tests/cases/compiler/duplicateSymbolsExportMatching.ts(57,12): error TS2395: Individual declarations in merged declaration 'C' must be all exported or all local.
+tests/cases/compiler/duplicateSymbolsExportMatching.ts(58,19): error TS2395: Individual declarations in merged declaration 'C' must be all exported or all local.
+tests/cases/compiler/duplicateSymbolsExportMatching.ts(64,11): error TS2395: Individual declarations in merged declaration 'D' must be all exported or all local.
+tests/cases/compiler/duplicateSymbolsExportMatching.ts(65,18): error TS2395: Individual declarations in merged declaration 'D' must be all exported or all local.
 
 
 ==== tests/cases/compiler/duplicateSymbolsExportMatching.ts (18 errors) ====
@@ -44,28 +44,28 @@ tests/cases/compiler/duplicateSymbolsExportMatching.ts(65,18): error TS2395: Ind
     module N2 {
         interface I { }
                   ~
-!!! error TS2395: Individual declarations in merged declaration I must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'I' must be all exported or all local.
         export interface I { } // error
                          ~
-!!! error TS2395: Individual declarations in merged declaration I must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'I' must be all exported or all local.
         export interface E { }
                          ~
-!!! error TS2395: Individual declarations in merged declaration E must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'E' must be all exported or all local.
         interface E { } // error
                   ~
-!!! error TS2395: Individual declarations in merged declaration E must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'E' must be all exported or all local.
     }
     
     // Should report error only once for instantiated module
     module M {
         module inst {
                ~~~~
-!!! error TS2395: Individual declarations in merged declaration inst must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'inst' must be all exported or all local.
             var t;
         }
         export module inst { // one error
                       ~~~~
-!!! error TS2395: Individual declarations in merged declaration inst must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'inst' must be all exported or all local.
             var t;
         }
     }
@@ -74,41 +74,41 @@ tests/cases/compiler/duplicateSymbolsExportMatching.ts(65,18): error TS2395: Ind
     module M2 {
         var v: string;
             ~
-!!! error TS2395: Individual declarations in merged declaration v must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'v' must be all exported or all local.
         export var v: string; // one error (visibility)
                    ~
-!!! error TS2395: Individual declarations in merged declaration v must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'v' must be all exported or all local.
         var w: number;
             ~
-!!! error TS2395: Individual declarations in merged declaration w must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'w' must be all exported or all local.
         export var w: string; // two errors (visibility and type mismatch)
                    ~
-!!! error TS2395: Individual declarations in merged declaration w must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'w' must be all exported or all local.
     }
     
     module M {
         module F {
                ~
-!!! error TS2395: Individual declarations in merged declaration F must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'F' must be all exported or all local.
                ~
 !!! error TS2434: A namespace declaration cannot be located prior to a class or function with which it is merged
             var t;
         }
         export function F() { } // Only one error for duplicate identifier (don't consider visibility)
                         ~
-!!! error TS2395: Individual declarations in merged declaration F must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'F' must be all exported or all local.
     }
     
     module M {
         class C { }
               ~
-!!! error TS2395: Individual declarations in merged declaration C must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'C' must be all exported or all local.
         module C { }
                ~
-!!! error TS2395: Individual declarations in merged declaration C must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'C' must be all exported or all local.
         export module C { // Two visibility errors (one for the clodule symbol, and one for the merged container symbol)
                       ~
-!!! error TS2395: Individual declarations in merged declaration C must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'C' must be all exported or all local.
             var t;
         }
     }
@@ -116,7 +116,7 @@ tests/cases/compiler/duplicateSymbolsExportMatching.ts(65,18): error TS2395: Ind
     // Top level
     interface D { }
               ~
-!!! error TS2395: Individual declarations in merged declaration D must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'D' must be all exported or all local.
     export interface D { }
                      ~
-!!! error TS2395: Individual declarations in merged declaration D must be all exported or all local.
\ No newline at end of file
+!!! error TS2395: Individual declarations in merged declaration 'D' must be all exported or all local.
\ No newline at end of file
diff --git a/tests/baselines/reference/fatarrowfunctionsOptionalArgsErrors1.errors.txt b/tests/baselines/reference/fatarrowfunctionsOptionalArgsErrors1.errors.txt
index 5934ab52ccf..b32a7b67b61 100644
--- a/tests/baselines/reference/fatarrowfunctionsOptionalArgsErrors1.errors.txt
+++ b/tests/baselines/reference/fatarrowfunctionsOptionalArgsErrors1.errors.txt
@@ -1,10 +1,9 @@
 tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors1.ts(1,9): error TS1016: A required parameter cannot follow an optional parameter.
 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.
 
 
-==== tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors1.ts (4 errors) ====
+==== tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors1.ts (3 errors) ====
     (arg1?, arg2) => 101;
             ~~~~
 !!! error TS1016: A required parameter cannot follow an optional parameter.
@@ -16,7 +15,5 @@ tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors1.ts(7,12): error TS1016
         ~~~
 !!! error TS1048: A rest parameter cannot have an initializer.
     
-    // Non optional parameter following an optional one
-    (arg1 = 1, arg2) => 1; 
-               ~~~~
-!!! error TS1016: A required parameter cannot follow an optional parameter.
\ No newline at end of file
+    // Uninitialized parameter makes the initialized one required
+    (arg1 = 1, arg2) => 1; 
\ No newline at end of file
diff --git a/tests/baselines/reference/fatarrowfunctionsOptionalArgsErrors1.js b/tests/baselines/reference/fatarrowfunctionsOptionalArgsErrors1.js
index e746b24a066..4d27f8230eb 100644
--- a/tests/baselines/reference/fatarrowfunctionsOptionalArgsErrors1.js
+++ b/tests/baselines/reference/fatarrowfunctionsOptionalArgsErrors1.js
@@ -4,7 +4,7 @@
 (...arg) => 103;
 (...arg:number [] = []) => 104;
 
-// Non optional parameter following an optional one
+// Uninitialized parameter makes the initialized one required
 (arg1 = 1, arg2) => 1; 
 
 //// [fatarrowfunctionsOptionalArgsErrors1.js]
@@ -30,7 +30,7 @@
     }
     return 104;
 });
-// Non optional parameter following an optional one
+// Uninitialized parameter makes the initialized one required
 (function (arg1, arg2) {
     if (arg1 === void 0) { arg1 = 1; }
     return 1;
diff --git a/tests/baselines/reference/inferentialTypingUsingApparentType2.types b/tests/baselines/reference/inferentialTypingUsingApparentType2.types
index 597f5885f5a..5841e021c3a 100644
--- a/tests/baselines/reference/inferentialTypingUsingApparentType2.types
+++ b/tests/baselines/reference/inferentialTypingUsingApparentType2.types
@@ -13,7 +13,7 @@ function foo<T extends { m(p: string): number }>(x: T): T {
 }
 
 foo({ m(x) { return x.length } });
->foo({ m(x) { return x.length } }) : { }
+>foo({ m(x) { return x.length } }) : { m(x: string): number; }
 >foo : <T extends { m(p: string): number; }>(x: T) => T
 >{ m(x) { return x.length } } : { m(x: string): number; }
 >m : (x: string) => number
diff --git a/tests/baselines/reference/inferringAnyFunctionType1.js b/tests/baselines/reference/inferringAnyFunctionType1.js
new file mode 100644
index 00000000000..6b48cf2db58
--- /dev/null
+++ b/tests/baselines/reference/inferringAnyFunctionType1.js
@@ -0,0 +1,12 @@
+//// [inferringAnyFunctionType1.ts]
+function f<T extends { "0": (p1: number) => number }>(p: T): T {
+    return p;
+}
+
+var v = f([x => x]);
+
+//// [inferringAnyFunctionType1.js]
+function f(p) {
+    return p;
+}
+var v = f([function (x) { return x; }]);
diff --git a/tests/baselines/reference/inferringAnyFunctionType1.symbols b/tests/baselines/reference/inferringAnyFunctionType1.symbols
new file mode 100644
index 00000000000..6a43952d770
--- /dev/null
+++ b/tests/baselines/reference/inferringAnyFunctionType1.symbols
@@ -0,0 +1,19 @@
+=== tests/cases/compiler/inferringAnyFunctionType1.ts ===
+function f<T extends { "0": (p1: number) => number }>(p: T): T {
+>f : Symbol(f, Decl(inferringAnyFunctionType1.ts, 0, 0))
+>T : Symbol(T, Decl(inferringAnyFunctionType1.ts, 0, 11))
+>p1 : Symbol(p1, Decl(inferringAnyFunctionType1.ts, 0, 29))
+>p : Symbol(p, Decl(inferringAnyFunctionType1.ts, 0, 54))
+>T : Symbol(T, Decl(inferringAnyFunctionType1.ts, 0, 11))
+>T : Symbol(T, Decl(inferringAnyFunctionType1.ts, 0, 11))
+
+    return p;
+>p : Symbol(p, Decl(inferringAnyFunctionType1.ts, 0, 54))
+}
+
+var v = f([x => x]);
+>v : Symbol(v, Decl(inferringAnyFunctionType1.ts, 4, 3))
+>f : Symbol(f, Decl(inferringAnyFunctionType1.ts, 0, 0))
+>x : Symbol(x, Decl(inferringAnyFunctionType1.ts, 4, 11))
+>x : Symbol(x, Decl(inferringAnyFunctionType1.ts, 4, 11))
+
diff --git a/tests/baselines/reference/inferringAnyFunctionType1.types b/tests/baselines/reference/inferringAnyFunctionType1.types
new file mode 100644
index 00000000000..16402cc3ced
--- /dev/null
+++ b/tests/baselines/reference/inferringAnyFunctionType1.types
@@ -0,0 +1,22 @@
+=== tests/cases/compiler/inferringAnyFunctionType1.ts ===
+function f<T extends { "0": (p1: number) => number }>(p: T): T {
+>f : <T extends { "0": (p1: number) => number; }>(p: T) => T
+>T : T
+>p1 : number
+>p : T
+>T : T
+>T : T
+
+    return p;
+>p : T
+}
+
+var v = f([x => x]);
+>v : [(x: number) => number]
+>f([x => x]) : [(x: number) => number]
+>f : <T extends { "0": (p1: number) => number; }>(p: T) => T
+>[x => x] : [(x: number) => number]
+>x => x : (x: number) => number
+>x : number
+>x : number
+
diff --git a/tests/baselines/reference/inferringAnyFunctionType2.js b/tests/baselines/reference/inferringAnyFunctionType2.js
new file mode 100644
index 00000000000..3841793233e
--- /dev/null
+++ b/tests/baselines/reference/inferringAnyFunctionType2.js
@@ -0,0 +1,12 @@
+//// [inferringAnyFunctionType2.ts]
+function f<T extends [(p1: number) => number]>(p: T): T {
+    return p;
+}
+
+var v = f([x => x]);
+
+//// [inferringAnyFunctionType2.js]
+function f(p) {
+    return p;
+}
+var v = f([function (x) { return x; }]);
diff --git a/tests/baselines/reference/inferringAnyFunctionType2.symbols b/tests/baselines/reference/inferringAnyFunctionType2.symbols
new file mode 100644
index 00000000000..9bdb627d46d
--- /dev/null
+++ b/tests/baselines/reference/inferringAnyFunctionType2.symbols
@@ -0,0 +1,19 @@
+=== tests/cases/compiler/inferringAnyFunctionType2.ts ===
+function f<T extends [(p1: number) => number]>(p: T): T {
+>f : Symbol(f, Decl(inferringAnyFunctionType2.ts, 0, 0))
+>T : Symbol(T, Decl(inferringAnyFunctionType2.ts, 0, 11))
+>p1 : Symbol(p1, Decl(inferringAnyFunctionType2.ts, 0, 23))
+>p : Symbol(p, Decl(inferringAnyFunctionType2.ts, 0, 47))
+>T : Symbol(T, Decl(inferringAnyFunctionType2.ts, 0, 11))
+>T : Symbol(T, Decl(inferringAnyFunctionType2.ts, 0, 11))
+
+    return p;
+>p : Symbol(p, Decl(inferringAnyFunctionType2.ts, 0, 47))
+}
+
+var v = f([x => x]);
+>v : Symbol(v, Decl(inferringAnyFunctionType2.ts, 4, 3))
+>f : Symbol(f, Decl(inferringAnyFunctionType2.ts, 0, 0))
+>x : Symbol(x, Decl(inferringAnyFunctionType2.ts, 4, 11))
+>x : Symbol(x, Decl(inferringAnyFunctionType2.ts, 4, 11))
+
diff --git a/tests/baselines/reference/inferringAnyFunctionType2.types b/tests/baselines/reference/inferringAnyFunctionType2.types
new file mode 100644
index 00000000000..7884bdfc6ba
--- /dev/null
+++ b/tests/baselines/reference/inferringAnyFunctionType2.types
@@ -0,0 +1,22 @@
+=== tests/cases/compiler/inferringAnyFunctionType2.ts ===
+function f<T extends [(p1: number) => number]>(p: T): T {
+>f : <T extends [(p1: number) => number]>(p: T) => T
+>T : T
+>p1 : number
+>p : T
+>T : T
+>T : T
+
+    return p;
+>p : T
+}
+
+var v = f([x => x]);
+>v : [(x: number) => number]
+>f([x => x]) : [(x: number) => number]
+>f : <T extends [(p1: number) => number]>(p: T) => T
+>[x => x] : [(x: number) => number]
+>x => x : (x: number) => number
+>x : number
+>x : number
+
diff --git a/tests/baselines/reference/inferringAnyFunctionType3.js b/tests/baselines/reference/inferringAnyFunctionType3.js
new file mode 100644
index 00000000000..ed1c4348dfc
--- /dev/null
+++ b/tests/baselines/reference/inferringAnyFunctionType3.js
@@ -0,0 +1,12 @@
+//// [inferringAnyFunctionType3.ts]
+function f<T extends ((p1: number) => number)[]>(p: T): T {
+    return p;
+}
+
+var v = f([x => x]);
+
+//// [inferringAnyFunctionType3.js]
+function f(p) {
+    return p;
+}
+var v = f([function (x) { return x; }]);
diff --git a/tests/baselines/reference/inferringAnyFunctionType3.symbols b/tests/baselines/reference/inferringAnyFunctionType3.symbols
new file mode 100644
index 00000000000..472d170b81d
--- /dev/null
+++ b/tests/baselines/reference/inferringAnyFunctionType3.symbols
@@ -0,0 +1,19 @@
+=== tests/cases/compiler/inferringAnyFunctionType3.ts ===
+function f<T extends ((p1: number) => number)[]>(p: T): T {
+>f : Symbol(f, Decl(inferringAnyFunctionType3.ts, 0, 0))
+>T : Symbol(T, Decl(inferringAnyFunctionType3.ts, 0, 11))
+>p1 : Symbol(p1, Decl(inferringAnyFunctionType3.ts, 0, 23))
+>p : Symbol(p, Decl(inferringAnyFunctionType3.ts, 0, 49))
+>T : Symbol(T, Decl(inferringAnyFunctionType3.ts, 0, 11))
+>T : Symbol(T, Decl(inferringAnyFunctionType3.ts, 0, 11))
+
+    return p;
+>p : Symbol(p, Decl(inferringAnyFunctionType3.ts, 0, 49))
+}
+
+var v = f([x => x]);
+>v : Symbol(v, Decl(inferringAnyFunctionType3.ts, 4, 3))
+>f : Symbol(f, Decl(inferringAnyFunctionType3.ts, 0, 0))
+>x : Symbol(x, Decl(inferringAnyFunctionType3.ts, 4, 11))
+>x : Symbol(x, Decl(inferringAnyFunctionType3.ts, 4, 11))
+
diff --git a/tests/baselines/reference/inferringAnyFunctionType3.types b/tests/baselines/reference/inferringAnyFunctionType3.types
new file mode 100644
index 00000000000..1edcfc34643
--- /dev/null
+++ b/tests/baselines/reference/inferringAnyFunctionType3.types
@@ -0,0 +1,22 @@
+=== tests/cases/compiler/inferringAnyFunctionType3.ts ===
+function f<T extends ((p1: number) => number)[]>(p: T): T {
+>f : <T extends ((p1: number) => number)[]>(p: T) => T
+>T : T
+>p1 : number
+>p : T
+>T : T
+>T : T
+
+    return p;
+>p : T
+}
+
+var v = f([x => x]);
+>v : ((x: number) => number)[]
+>f([x => x]) : ((x: number) => number)[]
+>f : <T extends ((p1: number) => number)[]>(p: T) => T
+>[x => x] : ((x: number) => number)[]
+>x => x : (x: number) => number
+>x : number
+>x : number
+
diff --git a/tests/baselines/reference/inferringAnyFunctionType4.js b/tests/baselines/reference/inferringAnyFunctionType4.js
new file mode 100644
index 00000000000..dccc51920b0
--- /dev/null
+++ b/tests/baselines/reference/inferringAnyFunctionType4.js
@@ -0,0 +1,12 @@
+//// [inferringAnyFunctionType4.ts]
+function f<T extends (p1: number) => number>(p: T): T {
+    return p;
+}
+
+var v = f(x => x);
+
+//// [inferringAnyFunctionType4.js]
+function f(p) {
+    return p;
+}
+var v = f(function (x) { return x; });
diff --git a/tests/baselines/reference/inferringAnyFunctionType4.symbols b/tests/baselines/reference/inferringAnyFunctionType4.symbols
new file mode 100644
index 00000000000..bfbacfc277c
--- /dev/null
+++ b/tests/baselines/reference/inferringAnyFunctionType4.symbols
@@ -0,0 +1,19 @@
+=== tests/cases/compiler/inferringAnyFunctionType4.ts ===
+function f<T extends (p1: number) => number>(p: T): T {
+>f : Symbol(f, Decl(inferringAnyFunctionType4.ts, 0, 0))
+>T : Symbol(T, Decl(inferringAnyFunctionType4.ts, 0, 11))
+>p1 : Symbol(p1, Decl(inferringAnyFunctionType4.ts, 0, 22))
+>p : Symbol(p, Decl(inferringAnyFunctionType4.ts, 0, 45))
+>T : Symbol(T, Decl(inferringAnyFunctionType4.ts, 0, 11))
+>T : Symbol(T, Decl(inferringAnyFunctionType4.ts, 0, 11))
+
+    return p;
+>p : Symbol(p, Decl(inferringAnyFunctionType4.ts, 0, 45))
+}
+
+var v = f(x => x);
+>v : Symbol(v, Decl(inferringAnyFunctionType4.ts, 4, 3))
+>f : Symbol(f, Decl(inferringAnyFunctionType4.ts, 0, 0))
+>x : Symbol(x, Decl(inferringAnyFunctionType4.ts, 4, 10))
+>x : Symbol(x, Decl(inferringAnyFunctionType4.ts, 4, 10))
+
diff --git a/tests/baselines/reference/inferringAnyFunctionType4.types b/tests/baselines/reference/inferringAnyFunctionType4.types
new file mode 100644
index 00000000000..49d46d0433e
--- /dev/null
+++ b/tests/baselines/reference/inferringAnyFunctionType4.types
@@ -0,0 +1,21 @@
+=== tests/cases/compiler/inferringAnyFunctionType4.ts ===
+function f<T extends (p1: number) => number>(p: T): T {
+>f : <T extends (p1: number) => number>(p: T) => T
+>T : T
+>p1 : number
+>p : T
+>T : T
+>T : T
+
+    return p;
+>p : T
+}
+
+var v = f(x => x);
+>v : (x: number) => number
+>f(x => x) : (x: number) => number
+>f : <T extends (p1: number) => number>(p: T) => T
+>x => x : (x: number) => number
+>x : number
+>x : number
+
diff --git a/tests/baselines/reference/inferringAnyFunctionType5.js b/tests/baselines/reference/inferringAnyFunctionType5.js
new file mode 100644
index 00000000000..babbab1be9e
--- /dev/null
+++ b/tests/baselines/reference/inferringAnyFunctionType5.js
@@ -0,0 +1,12 @@
+//// [inferringAnyFunctionType5.ts]
+function f<T extends { q: (p1: number) => number }>(p: T): T {
+    return p;
+}
+
+var v = f({ q: x => x });
+
+//// [inferringAnyFunctionType5.js]
+function f(p) {
+    return p;
+}
+var v = f({ q: function (x) { return x; } });
diff --git a/tests/baselines/reference/inferringAnyFunctionType5.symbols b/tests/baselines/reference/inferringAnyFunctionType5.symbols
new file mode 100644
index 00000000000..abf0fe68f46
--- /dev/null
+++ b/tests/baselines/reference/inferringAnyFunctionType5.symbols
@@ -0,0 +1,21 @@
+=== tests/cases/compiler/inferringAnyFunctionType5.ts ===
+function f<T extends { q: (p1: number) => number }>(p: T): T {
+>f : Symbol(f, Decl(inferringAnyFunctionType5.ts, 0, 0))
+>T : Symbol(T, Decl(inferringAnyFunctionType5.ts, 0, 11))
+>q : Symbol(q, Decl(inferringAnyFunctionType5.ts, 0, 22))
+>p1 : Symbol(p1, Decl(inferringAnyFunctionType5.ts, 0, 27))
+>p : Symbol(p, Decl(inferringAnyFunctionType5.ts, 0, 52))
+>T : Symbol(T, Decl(inferringAnyFunctionType5.ts, 0, 11))
+>T : Symbol(T, Decl(inferringAnyFunctionType5.ts, 0, 11))
+
+    return p;
+>p : Symbol(p, Decl(inferringAnyFunctionType5.ts, 0, 52))
+}
+
+var v = f({ q: x => x });
+>v : Symbol(v, Decl(inferringAnyFunctionType5.ts, 4, 3))
+>f : Symbol(f, Decl(inferringAnyFunctionType5.ts, 0, 0))
+>q : Symbol(q, Decl(inferringAnyFunctionType5.ts, 4, 11))
+>x : Symbol(x, Decl(inferringAnyFunctionType5.ts, 4, 14))
+>x : Symbol(x, Decl(inferringAnyFunctionType5.ts, 4, 14))
+
diff --git a/tests/baselines/reference/inferringAnyFunctionType5.types b/tests/baselines/reference/inferringAnyFunctionType5.types
new file mode 100644
index 00000000000..8f7ae123eac
--- /dev/null
+++ b/tests/baselines/reference/inferringAnyFunctionType5.types
@@ -0,0 +1,24 @@
+=== tests/cases/compiler/inferringAnyFunctionType5.ts ===
+function f<T extends { q: (p1: number) => number }>(p: T): T {
+>f : <T extends { q: (p1: number) => number; }>(p: T) => T
+>T : T
+>q : (p1: number) => number
+>p1 : number
+>p : T
+>T : T
+>T : T
+
+    return p;
+>p : T
+}
+
+var v = f({ q: x => x });
+>v : { q: (x: number) => number; }
+>f({ q: x => x }) : { q: (x: number) => number; }
+>f : <T extends { q: (p1: number) => number; }>(p: T) => T
+>{ q: x => x } : { q: (x: number) => number; }
+>q : (x: number) => number
+>x => x : (x: number) => number
+>x : number
+>x : number
+
diff --git a/tests/baselines/reference/innerModExport2.errors.txt b/tests/baselines/reference/innerModExport2.errors.txt
index 52a9d01c997..f9568bb45a4 100644
--- a/tests/baselines/reference/innerModExport2.errors.txt
+++ b/tests/baselines/reference/innerModExport2.errors.txt
@@ -1,7 +1,7 @@
 tests/cases/compiler/innerModExport2.ts(5,5): error TS2304: Cannot find name 'module'.
 tests/cases/compiler/innerModExport2.ts(5,12): error TS1005: ';' expected.
-tests/cases/compiler/innerModExport2.ts(7,20): error TS2395: Individual declarations in merged declaration export_var must be all exported or all local.
-tests/cases/compiler/innerModExport2.ts(13,9): error TS2395: Individual declarations in merged declaration export_var must be all exported or all local.
+tests/cases/compiler/innerModExport2.ts(7,20): error TS2395: Individual declarations in merged declaration 'export_var' must be all exported or all local.
+tests/cases/compiler/innerModExport2.ts(13,9): error TS2395: Individual declarations in merged declaration 'export_var' must be all exported or all local.
 tests/cases/compiler/innerModExport2.ts(20,7): error TS2339: Property 'NonExportFunc' does not exist on type 'typeof Outer'.
 
 
@@ -18,7 +18,7 @@ tests/cases/compiler/innerModExport2.ts(20,7): error TS2339: Property 'NonExport
             var non_export_var = 0;
             export var export_var = 1;
                        ~~~~~~~~~~
-!!! error TS2395: Individual declarations in merged declaration export_var must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'export_var' must be all exported or all local.
     
             function NonExportFunc() { return 0; }
     
@@ -26,7 +26,7 @@ tests/cases/compiler/innerModExport2.ts(20,7): error TS2339: Property 'NonExport
         }
         var export_var: number;
             ~~~~~~~~~~
-!!! error TS2395: Individual declarations in merged declaration export_var must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'export_var' must be all exported or all local.
     
         export var outer_var_export = 0;
         export function outerFuncExport() { return 0; }
diff --git a/tests/baselines/reference/isolatedModulesSourceMap.errors.txt b/tests/baselines/reference/isolatedModulesSourceMap.errors.txt
deleted file mode 100644
index 6383e85ecd5..00000000000
--- a/tests/baselines/reference/isolatedModulesSourceMap.errors.txt
+++ /dev/null
@@ -1,7 +0,0 @@
-error TS5043: Option 'sourceMap' cannot be specified with option 'isolatedModules'.
-
-
-!!! error TS5043: Option 'sourceMap' cannot be specified with option 'isolatedModules'.
-==== tests/cases/compiler/isolatedModulesSourceMap.ts (0 errors) ====
-    
-    export var x;
\ No newline at end of file
diff --git a/tests/baselines/reference/isolatedModulesSourceMap.js b/tests/baselines/reference/isolatedModulesSourceMap.js
index ca6f4b4190e..2722a3ce7ab 100644
--- a/tests/baselines/reference/isolatedModulesSourceMap.js
+++ b/tests/baselines/reference/isolatedModulesSourceMap.js
@@ -1,7 +1,7 @@
 //// [isolatedModulesSourceMap.ts]
 
-export var x;
+export var x = 1;
 
 //// [isolatedModulesSourceMap.js]
-export var x;
+export var x = 1;
 //# sourceMappingURL=isolatedModulesSourceMap.js.map
\ No newline at end of file
diff --git a/tests/baselines/reference/isolatedModulesSourceMap.js.map b/tests/baselines/reference/isolatedModulesSourceMap.js.map
index 8e505dcda7a..9fa3e0da0d6 100644
--- a/tests/baselines/reference/isolatedModulesSourceMap.js.map
+++ b/tests/baselines/reference/isolatedModulesSourceMap.js.map
@@ -1,2 +1,2 @@
 //// [isolatedModulesSourceMap.js.map]
-{"version":3,"file":"isolatedModulesSourceMap.js","sourceRoot":"","sources":["isolatedModulesSourceMap.ts"],"names":[],"mappings":"AACA,WAAW,CAAC,CAAC"}
\ No newline at end of file
+{"version":3,"file":"isolatedModulesSourceMap.js","sourceRoot":"","sources":["isolatedModulesSourceMap.ts"],"names":[],"mappings":"AACA,WAAW,CAAC,GAAG,CAAC,CAAC"}
\ No newline at end of file
diff --git a/tests/baselines/reference/isolatedModulesSourceMap.sourcemap.txt b/tests/baselines/reference/isolatedModulesSourceMap.sourcemap.txt
index 5c6b7659bc6..d31445505f7 100644
--- a/tests/baselines/reference/isolatedModulesSourceMap.sourcemap.txt
+++ b/tests/baselines/reference/isolatedModulesSourceMap.sourcemap.txt
@@ -8,20 +8,26 @@ sources: isolatedModulesSourceMap.ts
 emittedFile:tests/cases/compiler/isolatedModulesSourceMap.js
 sourceFile:isolatedModulesSourceMap.ts
 -------------------------------------------------------------------
->>>export var x;
+>>>export var x = 1;
 1 >
 2 >^^^^^^^^^^^
 3 >           ^
-4 >            ^
-5 >             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^->
+4 >            ^^^
+5 >               ^
+6 >                ^
+7 >                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^->
 1 >
   >
 2 >export var 
 3 >           x
-4 >            ;
+4 >             = 
+5 >               1
+6 >                ;
 1 >Emitted(1, 1) Source(2, 1) + SourceIndex(0)
 2 >Emitted(1, 12) Source(2, 12) + SourceIndex(0)
 3 >Emitted(1, 13) Source(2, 13) + SourceIndex(0)
-4 >Emitted(1, 14) Source(2, 14) + SourceIndex(0)
+4 >Emitted(1, 16) Source(2, 16) + SourceIndex(0)
+5 >Emitted(1, 17) Source(2, 17) + SourceIndex(0)
+6 >Emitted(1, 18) Source(2, 18) + SourceIndex(0)
 ---
 >>>//# sourceMappingURL=isolatedModulesSourceMap.js.map
\ No newline at end of file
diff --git a/tests/baselines/reference/isolatedModulesSourceMap.symbols b/tests/baselines/reference/isolatedModulesSourceMap.symbols
new file mode 100644
index 00000000000..d4ae3c34cf1
--- /dev/null
+++ b/tests/baselines/reference/isolatedModulesSourceMap.symbols
@@ -0,0 +1,5 @@
+=== tests/cases/compiler/isolatedModulesSourceMap.ts ===
+
+export var x = 1;
+>x : Symbol(x, Decl(isolatedModulesSourceMap.ts, 1, 10))
+
diff --git a/tests/baselines/reference/isolatedModulesSourceMap.types b/tests/baselines/reference/isolatedModulesSourceMap.types
new file mode 100644
index 00000000000..1955fe5da6e
--- /dev/null
+++ b/tests/baselines/reference/isolatedModulesSourceMap.types
@@ -0,0 +1,6 @@
+=== tests/cases/compiler/isolatedModulesSourceMap.ts ===
+
+export var x = 1;
+>x : number
+>1 : number
+
diff --git a/tests/baselines/reference/jsxImportInAttribute.js b/tests/baselines/reference/jsxImportInAttribute.js
new file mode 100644
index 00000000000..40b21e87c3f
--- /dev/null
+++ b/tests/baselines/reference/jsxImportInAttribute.js
@@ -0,0 +1,21 @@
+//// [tests/cases/compiler/jsxImportInAttribute.tsx] ////
+
+//// [component.d.ts]
+
+declare module "Test" {
+	export default class Text { }
+}
+
+//// [consumer.tsx]
+/// <reference path="component.d.ts" />
+import Test from 'Test';
+
+let x = Test; // emit test_1.default
+<anything attr={Test} />; // ?
+
+
+//// [consumer.jsx]
+/// <reference path="component.d.ts" />
+var Test_1 = require('Test');
+var x = Test_1["default"]; // emit test_1.default
+<anything attr={Test_1["default"]}/>; // ?
diff --git a/tests/baselines/reference/jsxImportInAttribute.symbols b/tests/baselines/reference/jsxImportInAttribute.symbols
new file mode 100644
index 00000000000..8481771f085
--- /dev/null
+++ b/tests/baselines/reference/jsxImportInAttribute.symbols
@@ -0,0 +1,19 @@
+=== tests/cases/compiler/consumer.tsx ===
+/// <reference path="component.d.ts" />
+import Test from 'Test';
+>Test : Symbol(Test, Decl(consumer.tsx, 1, 6))
+
+let x = Test; // emit test_1.default
+>x : Symbol(x, Decl(consumer.tsx, 3, 3))
+>Test : Symbol(Test, Decl(consumer.tsx, 1, 6))
+
+<anything attr={Test} />; // ?
+>attr : Symbol(unknown)
+
+=== tests/cases/compiler/component.d.ts ===
+
+declare module "Test" {
+	export default class Text { }
+>Text : Symbol(Text, Decl(component.d.ts, 1, 23))
+}
+
diff --git a/tests/baselines/reference/jsxImportInAttribute.types b/tests/baselines/reference/jsxImportInAttribute.types
new file mode 100644
index 00000000000..8dfbe292fe0
--- /dev/null
+++ b/tests/baselines/reference/jsxImportInAttribute.types
@@ -0,0 +1,22 @@
+=== tests/cases/compiler/consumer.tsx ===
+/// <reference path="component.d.ts" />
+import Test from 'Test';
+>Test : typeof Test
+
+let x = Test; // emit test_1.default
+>x : typeof Test
+>Test : typeof Test
+
+<anything attr={Test} />; // ?
+><anything attr={Test} /> : any
+>anything : any
+>attr : any
+>Test : any
+
+=== tests/cases/compiler/component.d.ts ===
+
+declare module "Test" {
+	export default class Text { }
+>Text : Text
+}
+
diff --git a/tests/baselines/reference/jsxViaImport.errors.txt b/tests/baselines/reference/jsxViaImport.errors.txt
new file mode 100644
index 00000000000..8fa22809a44
--- /dev/null
+++ b/tests/baselines/reference/jsxViaImport.errors.txt
@@ -0,0 +1,27 @@
+tests/cases/compiler/consumer.tsx(5,17): error TS2604: JSX element type 'BaseComponent' does not have any construct or call signatures.
+
+
+==== tests/cases/compiler/consumer.tsx (1 errors) ====
+    /// <reference path="component.d.ts" />
+    import BaseComponent = require('BaseComponent');
+    class TestComponent extends React.Component<any, {}> {
+        render() {
+            return <BaseComponent />;
+                    ~~~~~~~~~~~~~
+!!! error TS2604: JSX element type 'BaseComponent' does not have any construct or call signatures.
+        }
+    }
+    
+==== tests/cases/compiler/component.d.ts (0 errors) ====
+    
+    declare module JSX {
+      interface ElementAttributesProperty { props; }
+    }
+    declare module React {
+      class Component<T, U> { }
+    }
+    declare module "BaseComponent" {
+        var base: React.Component<any, {}>;
+        export = base;
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/jsxViaImport.js b/tests/baselines/reference/jsxViaImport.js
new file mode 100644
index 00000000000..6bf61af67f5
--- /dev/null
+++ b/tests/baselines/reference/jsxViaImport.js
@@ -0,0 +1,43 @@
+//// [tests/cases/compiler/jsxViaImport.tsx] ////
+
+//// [component.d.ts]
+
+declare module JSX {
+  interface ElementAttributesProperty { props; }
+}
+declare module React {
+  class Component<T, U> { }
+}
+declare module "BaseComponent" {
+    var base: React.Component<any, {}>;
+    export = base;
+}
+
+//// [consumer.tsx]
+/// <reference path="component.d.ts" />
+import BaseComponent = require('BaseComponent');
+class TestComponent extends React.Component<any, {}> {
+    render() {
+        return <BaseComponent />;
+    }
+}
+
+
+//// [consumer.jsx]
+var __extends = (this && this.__extends) || function (d, b) {
+    for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
+    function __() { this.constructor = d; }
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
+};
+/// <reference path="component.d.ts" />
+var BaseComponent = require('BaseComponent');
+var TestComponent = (function (_super) {
+    __extends(TestComponent, _super);
+    function TestComponent() {
+        _super.apply(this, arguments);
+    }
+    TestComponent.prototype.render = function () {
+        return <BaseComponent />;
+    };
+    return TestComponent;
+})(React.Component);
diff --git a/tests/baselines/reference/multipleDefaultExports01.errors.txt b/tests/baselines/reference/multipleDefaultExports01.errors.txt
new file mode 100644
index 00000000000..7b49afe1a4e
--- /dev/null
+++ b/tests/baselines/reference/multipleDefaultExports01.errors.txt
@@ -0,0 +1,31 @@
+tests/cases/conformance/es6/modules/m1.ts(2,22): error TS2300: Duplicate identifier 'foo'.
+tests/cases/conformance/es6/modules/m1.ts(6,25): error TS2300: Duplicate identifier 'bar'.
+tests/cases/conformance/es6/modules/m1.ts(11,1): error TS2300: Duplicate identifier 'default'.
+tests/cases/conformance/es6/modules/m2.ts(3,1): error TS2348: Value of type 'typeof foo' is not callable. Did you mean to include 'new'?
+
+
+==== tests/cases/conformance/es6/modules/m1.ts (3 errors) ====
+    
+    export default class foo {
+                         ~~~
+!!! error TS2300: Duplicate identifier 'foo'.
+    
+    }
+    
+    export default function bar() {
+                            ~~~
+!!! error TS2300: Duplicate identifier 'bar'.
+    
+    }
+    
+    var x = 10;
+    export default x;
+    ~~~~~~~~~~~~~~~~~
+!!! error TS2300: Duplicate identifier 'default'.
+    
+==== tests/cases/conformance/es6/modules/m2.ts (1 errors) ====
+    import Entity from "m1"
+    
+    Entity();
+    ~~~~~~~~
+!!! error TS2348: Value of type 'typeof foo' is not callable. Did you mean to include 'new'?
\ No newline at end of file
diff --git a/tests/baselines/reference/multipleDefaultExports01.js b/tests/baselines/reference/multipleDefaultExports01.js
new file mode 100644
index 00000000000..e633cf69f55
--- /dev/null
+++ b/tests/baselines/reference/multipleDefaultExports01.js
@@ -0,0 +1,38 @@
+//// [tests/cases/conformance/es6/modules/multipleDefaultExports01.ts] ////
+
+//// [m1.ts]
+
+export default class foo {
+
+}
+
+export default function bar() {
+
+}
+
+var x = 10;
+export default x;
+
+//// [m2.ts]
+import Entity from "m1"
+
+Entity();
+
+//// [m1.js]
+var foo = (function () {
+    function foo() {
+    }
+    return foo;
+})();
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.default = foo;
+function bar() {
+}
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.default = bar;
+var x = 10;
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.default = x;
+//// [m2.js]
+var m1_1 = require("m1");
+m1_1.default();
diff --git a/tests/baselines/reference/multipleDefaultExports02.errors.txt b/tests/baselines/reference/multipleDefaultExports02.errors.txt
new file mode 100644
index 00000000000..51220ecfae2
--- /dev/null
+++ b/tests/baselines/reference/multipleDefaultExports02.errors.txt
@@ -0,0 +1,22 @@
+tests/cases/conformance/es6/modules/m1.ts(2,25): error TS2393: Duplicate function implementation.
+tests/cases/conformance/es6/modules/m1.ts(6,25): error TS2393: Duplicate function implementation.
+
+
+==== tests/cases/conformance/es6/modules/m1.ts (2 errors) ====
+    
+    export default function foo() {
+                            ~~~
+!!! error TS2393: Duplicate function implementation.
+    
+    }
+    
+    export default function bar() {
+                            ~~~
+!!! error TS2393: Duplicate function implementation.
+    
+    }
+    
+==== tests/cases/conformance/es6/modules/m2.ts (0 errors) ====
+    import Entity from "m1"
+    
+    Entity();
\ No newline at end of file
diff --git a/tests/baselines/reference/multipleDefaultExports02.js b/tests/baselines/reference/multipleDefaultExports02.js
new file mode 100644
index 00000000000..3d1b84ff6a6
--- /dev/null
+++ b/tests/baselines/reference/multipleDefaultExports02.js
@@ -0,0 +1,29 @@
+//// [tests/cases/conformance/es6/modules/multipleDefaultExports02.ts] ////
+
+//// [m1.ts]
+
+export default function foo() {
+
+}
+
+export default function bar() {
+
+}
+
+//// [m2.ts]
+import Entity from "m1"
+
+Entity();
+
+//// [m1.js]
+function foo() {
+}
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.default = foo;
+function bar() {
+}
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.default = bar;
+//// [m2.js]
+var m1_1 = require("m1");
+m1_1.default();
diff --git a/tests/baselines/reference/multivar.errors.txt b/tests/baselines/reference/multivar.errors.txt
index 931e61de5ae..44061b9d74c 100644
--- a/tests/baselines/reference/multivar.errors.txt
+++ b/tests/baselines/reference/multivar.errors.txt
@@ -1,5 +1,5 @@
-tests/cases/compiler/multivar.ts(6,19): error TS2395: Individual declarations in merged declaration b2 must be all exported or all local.
-tests/cases/compiler/multivar.ts(22,9): error TS2395: Individual declarations in merged declaration b2 must be all exported or all local.
+tests/cases/compiler/multivar.ts(6,19): error TS2395: Individual declarations in merged declaration 'b2' must be all exported or all local.
+tests/cases/compiler/multivar.ts(22,9): error TS2395: Individual declarations in merged declaration 'b2' must be all exported or all local.
 
 
 ==== tests/cases/compiler/multivar.ts (2 errors) ====
@@ -10,7 +10,7 @@ tests/cases/compiler/multivar.ts(22,9): error TS2395: Individual declarations in
     
         export var a, b2: number = 10, b;
                       ~~
-!!! error TS2395: Individual declarations in merged declaration b2 must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'b2' must be all exported or all local.
         var m1;
         var a2, b22: number = 10, b222;
         var m3;
@@ -28,7 +28,7 @@ tests/cases/compiler/multivar.ts(22,9): error TS2395: Individual declarations in
         declare var d1, d2;
         var b2;
             ~~
-!!! error TS2395: Individual declarations in merged declaration b2 must be all exported or all local.
+!!! error TS2395: Individual declarations in merged declaration 'b2' must be all exported or all local.
     
         declare var v1;
     }
diff --git a/tests/baselines/reference/optionalParamArgsTest.errors.txt b/tests/baselines/reference/optionalParamArgsTest.errors.txt
index 3c4d2e37be9..05fefa85065 100644
--- a/tests/baselines/reference/optionalParamArgsTest.errors.txt
+++ b/tests/baselines/reference/optionalParamArgsTest.errors.txt
@@ -1,6 +1,6 @@
 tests/cases/compiler/optionalParamArgsTest.ts(31,12): error TS2393: Duplicate function implementation.
-tests/cases/compiler/optionalParamArgsTest.ts(35,12): error TS2393: Duplicate function implementation.
-tests/cases/compiler/optionalParamArgsTest.ts(35,47): error TS1016: A required parameter cannot follow an optional parameter.
+tests/cases/compiler/optionalParamArgsTest.ts(34,12): error TS2393: Duplicate function implementation.
+tests/cases/compiler/optionalParamArgsTest.ts(98,1): error TS2346: Supplied parameters do not match any signature of call target.
 tests/cases/compiler/optionalParamArgsTest.ts(99,1): error TS2346: Supplied parameters do not match any signature of call target.
 tests/cases/compiler/optionalParamArgsTest.ts(100,1): error TS2346: Supplied parameters do not match any signature of call target.
 tests/cases/compiler/optionalParamArgsTest.ts(101,1): error TS2346: Supplied parameters do not match any signature of call target.
@@ -20,10 +20,9 @@ tests/cases/compiler/optionalParamArgsTest.ts(114,1): error TS2346: Supplied par
 tests/cases/compiler/optionalParamArgsTest.ts(115,1): error TS2346: Supplied parameters do not match any signature of call target.
 tests/cases/compiler/optionalParamArgsTest.ts(116,1): error TS2346: Supplied parameters do not match any signature of call target.
 tests/cases/compiler/optionalParamArgsTest.ts(117,1): error TS2346: Supplied parameters do not match any signature of call target.
-tests/cases/compiler/optionalParamArgsTest.ts(118,1): error TS2346: Supplied parameters do not match any signature of call target.
 
 
-==== tests/cases/compiler/optionalParamArgsTest.ts (23 errors) ====
+==== tests/cases/compiler/optionalParamArgsTest.ts (22 errors) ====
     // Optional parameter and default argument tests
     
     // Key:
@@ -58,13 +57,10 @@ tests/cases/compiler/optionalParamArgsTest.ts(118,1): error TS2346: Supplied par
                ~~~~
 !!! error TS2393: Duplicate function implementation.
     
-        // Negative test
-        // "Optional parameters may only be followed by other optional parameters"
+        // Uninitialized parameter makes the initialized one required
         public C1M5(C1M5A1:number,C1M5A2:number=0,C1M5A3:number) { return C1M5A1 + C1M5A2; }
                ~~~~
 !!! error TS2393: Duplicate function implementation.
-                                                  ~~~~~~
-!!! error TS1016: A required parameter cannot follow an optional parameter.
     }
     
     class C2 extends C1 {
diff --git a/tests/baselines/reference/optionalParamArgsTest.js b/tests/baselines/reference/optionalParamArgsTest.js
index 414f474598d..0c5a5d82814 100644
--- a/tests/baselines/reference/optionalParamArgsTest.js
+++ b/tests/baselines/reference/optionalParamArgsTest.js
@@ -31,8 +31,7 @@ class C1 {
 
     public C1M5(C1M5A1:number,C1M5A2:number=0,C1M5A3?:number) { return C1M5A1 + C1M5A2; }
 
-    // Negative test
-    // "Optional parameters may only be followed by other optional parameters"
+    // Uninitialized parameter makes the initialized one required
     public C1M5(C1M5A1:number,C1M5A2:number=0,C1M5A3:number) { return C1M5A1 + C1M5A2; }
 }
 
@@ -152,8 +151,7 @@ var C1 = (function () {
         if (C1M5A2 === void 0) { C1M5A2 = 0; }
         return C1M5A1 + C1M5A2;
     };
-    // Negative test
-    // "Optional parameters may only be followed by other optional parameters"
+    // Uninitialized parameter makes the initialized one required
     C1.prototype.C1M5 = function (C1M5A1, C1M5A2, C1M5A3) {
         if (C1M5A2 === void 0) { C1M5A2 = 0; }
         return C1M5A1 + C1M5A2;
diff --git a/tests/baselines/reference/requiredInitializedParameter1.errors.txt b/tests/baselines/reference/requiredInitializedParameter1.errors.txt
new file mode 100644
index 00000000000..ef958dbdec9
--- /dev/null
+++ b/tests/baselines/reference/requiredInitializedParameter1.errors.txt
@@ -0,0 +1,28 @@
+tests/cases/compiler/requiredInitializedParameter1.ts(11,1): error TS2346: Supplied parameters do not match any signature of call target.
+tests/cases/compiler/requiredInitializedParameter1.ts(16,1): error TS2346: Supplied parameters do not match any signature of call target.
+
+
+==== tests/cases/compiler/requiredInitializedParameter1.ts (2 errors) ====
+    function f1(a, b = 0, c) { }
+    function f2(a, b = 0, c = 0) { }
+    function f3(a, b = 0, c?) { }
+    function f4(a, b = 0, ...c) { }
+    
+    f1(0, 1, 2);
+    f2(0, 1, 2);
+    f3(0, 1, 2);
+    f4(0, 1, 2);
+    
+    f1(0, 1);
+    ~~~~~~~~
+!!! error TS2346: Supplied parameters do not match any signature of call target.
+    f2(0, 1);
+    f3(0, 1);
+    f4(0, 1);
+    
+    f1(0);
+    ~~~~~
+!!! error TS2346: Supplied parameters do not match any signature of call target.
+    f2(0);
+    f3(0);
+    f4(0);
\ No newline at end of file
diff --git a/tests/baselines/reference/requiredInitializedParameter1.js b/tests/baselines/reference/requiredInitializedParameter1.js
new file mode 100644
index 00000000000..0fe07503056
--- /dev/null
+++ b/tests/baselines/reference/requiredInitializedParameter1.js
@@ -0,0 +1,51 @@
+//// [requiredInitializedParameter1.ts]
+function f1(a, b = 0, c) { }
+function f2(a, b = 0, c = 0) { }
+function f3(a, b = 0, c?) { }
+function f4(a, b = 0, ...c) { }
+
+f1(0, 1, 2);
+f2(0, 1, 2);
+f3(0, 1, 2);
+f4(0, 1, 2);
+
+f1(0, 1);
+f2(0, 1);
+f3(0, 1);
+f4(0, 1);
+
+f1(0);
+f2(0);
+f3(0);
+f4(0);
+
+//// [requiredInitializedParameter1.js]
+function f1(a, b, c) {
+    if (b === void 0) { b = 0; }
+}
+function f2(a, b, c) {
+    if (b === void 0) { b = 0; }
+    if (c === void 0) { c = 0; }
+}
+function f3(a, b, c) {
+    if (b === void 0) { b = 0; }
+}
+function f4(a, b) {
+    if (b === void 0) { b = 0; }
+    var c = [];
+    for (var _i = 2; _i < arguments.length; _i++) {
+        c[_i - 2] = arguments[_i];
+    }
+}
+f1(0, 1, 2);
+f2(0, 1, 2);
+f3(0, 1, 2);
+f4(0, 1, 2);
+f1(0, 1);
+f2(0, 1);
+f3(0, 1);
+f4(0, 1);
+f1(0);
+f2(0);
+f3(0);
+f4(0);
diff --git a/tests/baselines/reference/requiredInitializedParameter2.errors.txt b/tests/baselines/reference/requiredInitializedParameter2.errors.txt
new file mode 100644
index 00000000000..5dcec536e1b
--- /dev/null
+++ b/tests/baselines/reference/requiredInitializedParameter2.errors.txt
@@ -0,0 +1,17 @@
+tests/cases/compiler/requiredInitializedParameter2.ts(5,7): error TS2420: Class 'C1' incorrectly implements interface 'I1'.
+  Types of property 'method' are incompatible.
+    Type '(a: number, b: any) => void' is not assignable to type '() => any'.
+
+
+==== tests/cases/compiler/requiredInitializedParameter2.ts (1 errors) ====
+    interface I1 {
+        method();
+    }
+    
+    class C1 implements I1 {
+          ~~
+!!! error TS2420: Class 'C1' incorrectly implements interface 'I1'.
+!!! error TS2420:   Types of property 'method' are incompatible.
+!!! error TS2420:     Type '(a: number, b: any) => void' is not assignable to type '() => any'.
+        method(a = 0, b) { }
+    }
\ No newline at end of file
diff --git a/tests/baselines/reference/requiredInitializedParameter2.js b/tests/baselines/reference/requiredInitializedParameter2.js
new file mode 100644
index 00000000000..3c69d54e1d9
--- /dev/null
+++ b/tests/baselines/reference/requiredInitializedParameter2.js
@@ -0,0 +1,18 @@
+//// [requiredInitializedParameter2.ts]
+interface I1 {
+    method();
+}
+
+class C1 implements I1 {
+    method(a = 0, b) { }
+}
+
+//// [requiredInitializedParameter2.js]
+var C1 = (function () {
+    function C1() {
+    }
+    C1.prototype.method = function (a, b) {
+        if (a === void 0) { a = 0; }
+    };
+    return C1;
+})();
diff --git a/tests/baselines/reference/requiredInitializedParameter3.js b/tests/baselines/reference/requiredInitializedParameter3.js
new file mode 100644
index 00000000000..68e1aa696ea
--- /dev/null
+++ b/tests/baselines/reference/requiredInitializedParameter3.js
@@ -0,0 +1,27 @@
+//// [requiredInitializedParameter3.ts]
+interface I1 {
+    method();
+}
+
+class C1 implements I1 {
+    method(a = 0, b?) { }
+}
+
+//// [requiredInitializedParameter3.js]
+var C1 = (function () {
+    function C1() {
+    }
+    C1.prototype.method = function (a, b) {
+        if (a === void 0) { a = 0; }
+    };
+    return C1;
+})();
+
+
+//// [requiredInitializedParameter3.d.ts]
+interface I1 {
+    method(): any;
+}
+declare class C1 implements I1 {
+    method(a?: number, b?: any): void;
+}
diff --git a/tests/baselines/reference/requiredInitializedParameter3.symbols b/tests/baselines/reference/requiredInitializedParameter3.symbols
new file mode 100644
index 00000000000..e9f35b21bcf
--- /dev/null
+++ b/tests/baselines/reference/requiredInitializedParameter3.symbols
@@ -0,0 +1,17 @@
+=== tests/cases/compiler/requiredInitializedParameter3.ts ===
+interface I1 {
+>I1 : Symbol(I1, Decl(requiredInitializedParameter3.ts, 0, 0))
+
+    method();
+>method : Symbol(method, Decl(requiredInitializedParameter3.ts, 0, 14))
+}
+
+class C1 implements I1 {
+>C1 : Symbol(C1, Decl(requiredInitializedParameter3.ts, 2, 1))
+>I1 : Symbol(I1, Decl(requiredInitializedParameter3.ts, 0, 0))
+
+    method(a = 0, b?) { }
+>method : Symbol(method, Decl(requiredInitializedParameter3.ts, 4, 24))
+>a : Symbol(a, Decl(requiredInitializedParameter3.ts, 5, 11))
+>b : Symbol(b, Decl(requiredInitializedParameter3.ts, 5, 17))
+}
diff --git a/tests/baselines/reference/requiredInitializedParameter3.types b/tests/baselines/reference/requiredInitializedParameter3.types
new file mode 100644
index 00000000000..aa37f5e13dd
--- /dev/null
+++ b/tests/baselines/reference/requiredInitializedParameter3.types
@@ -0,0 +1,18 @@
+=== tests/cases/compiler/requiredInitializedParameter3.ts ===
+interface I1 {
+>I1 : I1
+
+    method();
+>method : () => any
+}
+
+class C1 implements I1 {
+>C1 : C1
+>I1 : I1
+
+    method(a = 0, b?) { }
+>method : (a?: number, b?: any) => void
+>a : number
+>0 : number
+>b : any
+}
diff --git a/tests/baselines/reference/requiredInitializedParameter4.js b/tests/baselines/reference/requiredInitializedParameter4.js
new file mode 100644
index 00000000000..3b23f119391
--- /dev/null
+++ b/tests/baselines/reference/requiredInitializedParameter4.js
@@ -0,0 +1,20 @@
+//// [requiredInitializedParameter4.ts]
+class C1 {
+    method(a = 0, b) { }
+}
+
+//// [requiredInitializedParameter4.js]
+var C1 = (function () {
+    function C1() {
+    }
+    C1.prototype.method = function (a, b) {
+        if (a === void 0) { a = 0; }
+    };
+    return C1;
+})();
+
+
+//// [requiredInitializedParameter4.d.ts]
+declare class C1 {
+    method(a: number, b: any): void;
+}
diff --git a/tests/baselines/reference/requiredInitializedParameter4.symbols b/tests/baselines/reference/requiredInitializedParameter4.symbols
new file mode 100644
index 00000000000..2790b33698c
--- /dev/null
+++ b/tests/baselines/reference/requiredInitializedParameter4.symbols
@@ -0,0 +1,9 @@
+=== tests/cases/compiler/requiredInitializedParameter4.ts ===
+class C1 {
+>C1 : Symbol(C1, Decl(requiredInitializedParameter4.ts, 0, 0))
+
+    method(a = 0, b) { }
+>method : Symbol(method, Decl(requiredInitializedParameter4.ts, 0, 10))
+>a : Symbol(a, Decl(requiredInitializedParameter4.ts, 1, 11))
+>b : Symbol(b, Decl(requiredInitializedParameter4.ts, 1, 17))
+}
diff --git a/tests/baselines/reference/requiredInitializedParameter4.types b/tests/baselines/reference/requiredInitializedParameter4.types
new file mode 100644
index 00000000000..c483146a1ba
--- /dev/null
+++ b/tests/baselines/reference/requiredInitializedParameter4.types
@@ -0,0 +1,10 @@
+=== tests/cases/compiler/requiredInitializedParameter4.ts ===
+class C1 {
+>C1 : C1
+
+    method(a = 0, b) { }
+>method : (a: number, b: any) => void
+>a : number
+>0 : number
+>b : any
+}
diff --git a/tests/baselines/reference/strictModeInConstructor.errors.txt b/tests/baselines/reference/strictModeInConstructor.errors.txt
index 11ba2e26a68..9a80732842a 100644
--- a/tests/baselines/reference/strictModeInConstructor.errors.txt
+++ b/tests/baselines/reference/strictModeInConstructor.errors.txt
@@ -1,8 +1,7 @@
-tests/cases/compiler/strictModeInConstructor.ts(9,5): error TS2376: A 'super' call must be the first statement in the constructor when a class contains initialized properties or has parameter properties.
 tests/cases/compiler/strictModeInConstructor.ts(27,5): error TS2376: A 'super' call must be the first statement in the constructor when a class contains initialized properties or has parameter properties.
 
 
-==== tests/cases/compiler/strictModeInConstructor.ts (2 errors) ====
+==== tests/cases/compiler/strictModeInConstructor.ts (1 errors) ====
     class A {
     }
     
@@ -12,14 +11,9 @@ tests/cases/compiler/strictModeInConstructor.ts(27,5): error TS2376: A 'super' c
         public s: number = 9;
     
         constructor () {
-        ~~~~~~~~~~~~~~~~
             "use strict";   // No error
-    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
             super();
-    ~~~~~~~~~~~~~~~~
         }
-    ~~~~~
-!!! error TS2376: A 'super' call must be the first statement in the constructor when a class contains initialized properties or has parameter properties.
     }
     
     class C extends A {
diff --git a/tests/baselines/reference/tsxElementResolution8.errors.txt b/tests/baselines/reference/tsxElementResolution8.errors.txt
index 5710c4e177d..92ff05d1aed 100644
--- a/tests/baselines/reference/tsxElementResolution8.errors.txt
+++ b/tests/baselines/reference/tsxElementResolution8.errors.txt
@@ -1,10 +1,8 @@
 tests/cases/conformance/jsx/tsxElementResolution8.tsx(8,2): error TS2604: JSX element type 'Div' does not have any construct or call signatures.
-tests/cases/conformance/jsx/tsxElementResolution8.tsx(16,2): error TS2601: The return type of a JSX element constructor must return an object type.
-tests/cases/conformance/jsx/tsxElementResolution8.tsx(29,2): error TS2601: The return type of a JSX element constructor must return an object type.
 tests/cases/conformance/jsx/tsxElementResolution8.tsx(34,2): error TS2604: JSX element type 'Obj3' does not have any construct or call signatures.
 
 
-==== tests/cases/conformance/jsx/tsxElementResolution8.tsx (4 errors) ====
+==== tests/cases/conformance/jsx/tsxElementResolution8.tsx (2 errors) ====
     declare module JSX {
     	interface Element { }
     	interface IntrinsicElements { }
@@ -23,8 +21,6 @@ tests/cases/conformance/jsx/tsxElementResolution8.tsx(34,2): error TS2604: JSX e
     // Error
     function Fnum(): number{ return 42; }
     <Fnum />
-     ~~~~
-!!! error TS2601: The return type of a JSX element constructor must return an object type.
     
     interface Obj1 {
     	new(): {};
@@ -38,8 +34,6 @@ tests/cases/conformance/jsx/tsxElementResolution8.tsx(34,2): error TS2604: JSX e
     }
     var Obj2: Obj2;
     <Obj2 />; // Error
-     ~~~~
-!!! error TS2601: The return type of a JSX element constructor must return an object type.
     
     interface Obj3 {
     }
diff --git a/tests/baselines/reference/tsxElementResolution9.errors.txt b/tests/baselines/reference/tsxElementResolution9.errors.txt
deleted file mode 100644
index 64514eebc00..00000000000
--- a/tests/baselines/reference/tsxElementResolution9.errors.txt
+++ /dev/null
@@ -1,38 +0,0 @@
-tests/cases/conformance/jsx/tsxElementResolution9.tsx(11,2): error TS2601: The return type of a JSX element constructor must return an object type.
-tests/cases/conformance/jsx/tsxElementResolution9.tsx(18,2): error TS2601: The return type of a JSX element constructor must return an object type.
-tests/cases/conformance/jsx/tsxElementResolution9.tsx(25,2): error TS2601: The return type of a JSX element constructor must return an object type.
-
-
-==== tests/cases/conformance/jsx/tsxElementResolution9.tsx (3 errors) ====
-    declare module JSX {
-    	interface Element { }
-    	interface IntrinsicElements { }
-    }
-    
-    interface Obj1 {
-    	new(n: string): { x: number };
-    	new(n: number): { y: string };
-    }
-    var Obj1: Obj1;
-    <Obj1 />; // Error, return type is not an object type
-     ~~~~
-!!! error TS2601: The return type of a JSX element constructor must return an object type.
-    
-    interface Obj2 {
-    	(n: string): { x: number };
-    	(n: number): { y: string };
-    }
-    var Obj2: Obj2;
-    <Obj2 />; // Error, return type is not an object type
-     ~~~~
-!!! error TS2601: The return type of a JSX element constructor must return an object type.
-    
-    interface Obj3 {
-    	(n: string): { x: number };
-    	(n: number): { x: number; y: string };
-    }
-    var Obj3: Obj3;
-    <Obj3 x={42} />; // OK
-     ~~~~
-!!! error TS2601: The return type of a JSX element constructor must return an object type.
-    
\ No newline at end of file
diff --git a/tests/baselines/reference/tsxElementResolution9.symbols b/tests/baselines/reference/tsxElementResolution9.symbols
new file mode 100644
index 00000000000..bfa04219ef9
--- /dev/null
+++ b/tests/baselines/reference/tsxElementResolution9.symbols
@@ -0,0 +1,67 @@
+=== tests/cases/conformance/jsx/tsxElementResolution9.tsx ===
+declare module JSX {
+>JSX : Symbol(JSX, Decl(tsxElementResolution9.tsx, 0, 0))
+
+	interface Element { }
+>Element : Symbol(Element, Decl(tsxElementResolution9.tsx, 0, 20))
+
+	interface IntrinsicElements { }
+>IntrinsicElements : Symbol(IntrinsicElements, Decl(tsxElementResolution9.tsx, 1, 22))
+}
+
+interface Obj1 {
+>Obj1 : Symbol(Obj1, Decl(tsxElementResolution9.tsx, 3, 1), Decl(tsxElementResolution9.tsx, 9, 3))
+
+	new(n: string): { x: number };
+>n : Symbol(n, Decl(tsxElementResolution9.tsx, 6, 5))
+>x : Symbol(x, Decl(tsxElementResolution9.tsx, 6, 18))
+
+	new(n: number): { y: string };
+>n : Symbol(n, Decl(tsxElementResolution9.tsx, 7, 5))
+>y : Symbol(y, Decl(tsxElementResolution9.tsx, 7, 18))
+}
+var Obj1: Obj1;
+>Obj1 : Symbol(Obj1, Decl(tsxElementResolution9.tsx, 3, 1), Decl(tsxElementResolution9.tsx, 9, 3))
+>Obj1 : Symbol(Obj1, Decl(tsxElementResolution9.tsx, 3, 1), Decl(tsxElementResolution9.tsx, 9, 3))
+
+<Obj1 />; // Error, return type is not an object type
+>Obj1 : Symbol(Obj1, Decl(tsxElementResolution9.tsx, 3, 1), Decl(tsxElementResolution9.tsx, 9, 3))
+
+interface Obj2 {
+>Obj2 : Symbol(Obj2, Decl(tsxElementResolution9.tsx, 10, 9), Decl(tsxElementResolution9.tsx, 16, 3))
+
+	(n: string): { x: number };
+>n : Symbol(n, Decl(tsxElementResolution9.tsx, 13, 2))
+>x : Symbol(x, Decl(tsxElementResolution9.tsx, 13, 15))
+
+	(n: number): { y: string };
+>n : Symbol(n, Decl(tsxElementResolution9.tsx, 14, 2))
+>y : Symbol(y, Decl(tsxElementResolution9.tsx, 14, 15))
+}
+var Obj2: Obj2;
+>Obj2 : Symbol(Obj2, Decl(tsxElementResolution9.tsx, 10, 9), Decl(tsxElementResolution9.tsx, 16, 3))
+>Obj2 : Symbol(Obj2, Decl(tsxElementResolution9.tsx, 10, 9), Decl(tsxElementResolution9.tsx, 16, 3))
+
+<Obj2 />; // Error, return type is not an object type
+>Obj2 : Symbol(Obj2, Decl(tsxElementResolution9.tsx, 10, 9), Decl(tsxElementResolution9.tsx, 16, 3))
+
+interface Obj3 {
+>Obj3 : Symbol(Obj3, Decl(tsxElementResolution9.tsx, 17, 9), Decl(tsxElementResolution9.tsx, 23, 3))
+
+	(n: string): { x: number };
+>n : Symbol(n, Decl(tsxElementResolution9.tsx, 20, 2))
+>x : Symbol(x, Decl(tsxElementResolution9.tsx, 20, 15))
+
+	(n: number): { x: number; y: string };
+>n : Symbol(n, Decl(tsxElementResolution9.tsx, 21, 2))
+>x : Symbol(x, Decl(tsxElementResolution9.tsx, 21, 15))
+>y : Symbol(y, Decl(tsxElementResolution9.tsx, 21, 26))
+}
+var Obj3: Obj3;
+>Obj3 : Symbol(Obj3, Decl(tsxElementResolution9.tsx, 17, 9), Decl(tsxElementResolution9.tsx, 23, 3))
+>Obj3 : Symbol(Obj3, Decl(tsxElementResolution9.tsx, 17, 9), Decl(tsxElementResolution9.tsx, 23, 3))
+
+<Obj3 x={42} />; // OK
+>Obj3 : Symbol(Obj3, Decl(tsxElementResolution9.tsx, 17, 9), Decl(tsxElementResolution9.tsx, 23, 3))
+>x : Symbol(unknown)
+
diff --git a/tests/baselines/reference/tsxElementResolution9.types b/tests/baselines/reference/tsxElementResolution9.types
new file mode 100644
index 00000000000..525e4600b2e
--- /dev/null
+++ b/tests/baselines/reference/tsxElementResolution9.types
@@ -0,0 +1,70 @@
+=== tests/cases/conformance/jsx/tsxElementResolution9.tsx ===
+declare module JSX {
+>JSX : any
+
+	interface Element { }
+>Element : Element
+
+	interface IntrinsicElements { }
+>IntrinsicElements : IntrinsicElements
+}
+
+interface Obj1 {
+>Obj1 : Obj1
+
+	new(n: string): { x: number };
+>n : string
+>x : number
+
+	new(n: number): { y: string };
+>n : number
+>y : string
+}
+var Obj1: Obj1;
+>Obj1 : Obj1
+>Obj1 : Obj1
+
+<Obj1 />; // Error, return type is not an object type
+><Obj1 /> : JSX.Element
+>Obj1 : Obj1
+
+interface Obj2 {
+>Obj2 : Obj2
+
+	(n: string): { x: number };
+>n : string
+>x : number
+
+	(n: number): { y: string };
+>n : number
+>y : string
+}
+var Obj2: Obj2;
+>Obj2 : Obj2
+>Obj2 : Obj2
+
+<Obj2 />; // Error, return type is not an object type
+><Obj2 /> : JSX.Element
+>Obj2 : Obj2
+
+interface Obj3 {
+>Obj3 : Obj3
+
+	(n: string): { x: number };
+>n : string
+>x : number
+
+	(n: number): { x: number; y: string };
+>n : number
+>x : number
+>y : string
+}
+var Obj3: Obj3;
+>Obj3 : Obj3
+>Obj3 : Obj3
+
+<Obj3 x={42} />; // OK
+><Obj3 x={42} /> : JSX.Element
+>Obj3 : Obj3
+>x : any
+
diff --git a/tests/cases/compiler/classExtendsNull.ts b/tests/cases/compiler/classExtendsNull.ts
new file mode 100644
index 00000000000..5532fa72702
--- /dev/null
+++ b/tests/cases/compiler/classExtendsNull.ts
@@ -0,0 +1,12 @@
+class C extends null {
+    constructor() {
+        super();
+        return Object.create(null);
+    }
+}
+
+class D extends null {
+    constructor() {
+        return Object.create(null);
+    }
+}
\ No newline at end of file
diff --git a/tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors1.ts b/tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors1.ts
index d8ddcf4bb8f..814f1b41619 100644
--- a/tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors1.ts
+++ b/tests/cases/compiler/fatarrowfunctionsOptionalArgsErrors1.ts
@@ -3,5 +3,5 @@
 (...arg) => 103;
 (...arg:number [] = []) => 104;
 
-// Non optional parameter following an optional one
+// Uninitialized parameter makes the initialized one required
 (arg1 = 1, arg2) => 1; 
\ No newline at end of file
diff --git a/tests/cases/compiler/inferringAnyFunctionType1.ts b/tests/cases/compiler/inferringAnyFunctionType1.ts
new file mode 100644
index 00000000000..bc1e6f68973
--- /dev/null
+++ b/tests/cases/compiler/inferringAnyFunctionType1.ts
@@ -0,0 +1,5 @@
+function f<T extends { "0": (p1: number) => number }>(p: T): T {
+    return p;
+}
+
+var v = f([x => x]);
\ No newline at end of file
diff --git a/tests/cases/compiler/inferringAnyFunctionType2.ts b/tests/cases/compiler/inferringAnyFunctionType2.ts
new file mode 100644
index 00000000000..0984e578f67
--- /dev/null
+++ b/tests/cases/compiler/inferringAnyFunctionType2.ts
@@ -0,0 +1,5 @@
+function f<T extends [(p1: number) => number]>(p: T): T {
+    return p;
+}
+
+var v = f([x => x]);
\ No newline at end of file
diff --git a/tests/cases/compiler/inferringAnyFunctionType3.ts b/tests/cases/compiler/inferringAnyFunctionType3.ts
new file mode 100644
index 00000000000..4576a30898a
--- /dev/null
+++ b/tests/cases/compiler/inferringAnyFunctionType3.ts
@@ -0,0 +1,5 @@
+function f<T extends ((p1: number) => number)[]>(p: T): T {
+    return p;
+}
+
+var v = f([x => x]);
\ No newline at end of file
diff --git a/tests/cases/compiler/inferringAnyFunctionType4.ts b/tests/cases/compiler/inferringAnyFunctionType4.ts
new file mode 100644
index 00000000000..592908bdfec
--- /dev/null
+++ b/tests/cases/compiler/inferringAnyFunctionType4.ts
@@ -0,0 +1,5 @@
+function f<T extends (p1: number) => number>(p: T): T {
+    return p;
+}
+
+var v = f(x => x);
\ No newline at end of file
diff --git a/tests/cases/compiler/inferringAnyFunctionType5.ts b/tests/cases/compiler/inferringAnyFunctionType5.ts
new file mode 100644
index 00000000000..2ff4a325c5a
--- /dev/null
+++ b/tests/cases/compiler/inferringAnyFunctionType5.ts
@@ -0,0 +1,5 @@
+function f<T extends { q: (p1: number) => number }>(p: T): T {
+    return p;
+}
+
+var v = f({ q: x => x });
\ No newline at end of file
diff --git a/tests/cases/compiler/isolatedModulesSourceMap.ts b/tests/cases/compiler/isolatedModulesSourceMap.ts
index 31dd4d9f0cf..465941d9a8b 100644
--- a/tests/cases/compiler/isolatedModulesSourceMap.ts
+++ b/tests/cases/compiler/isolatedModulesSourceMap.ts
@@ -3,4 +3,4 @@
 // @target: es6
 
 // @filename: file1.ts
-export var x;
\ No newline at end of file
+export var x = 1;
\ No newline at end of file
diff --git a/tests/cases/compiler/jsxImportInAttribute.tsx b/tests/cases/compiler/jsxImportInAttribute.tsx
new file mode 100644
index 00000000000..c4f16f55ddb
--- /dev/null
+++ b/tests/cases/compiler/jsxImportInAttribute.tsx
@@ -0,0 +1,14 @@
+//@jsx: preserve
+//@module: commonjs
+
+//@filename: component.d.ts
+declare module "Test" {
+	export default class Text { }
+}
+
+//@filename: consumer.tsx
+/// <reference path="component.d.ts" />
+import Test from 'Test';
+
+let x = Test; // emit test_1.default
+<anything attr={Test} />; // ?
diff --git a/tests/cases/compiler/jsxViaImport.tsx b/tests/cases/compiler/jsxViaImport.tsx
new file mode 100644
index 00000000000..5b3b7e11d83
--- /dev/null
+++ b/tests/cases/compiler/jsxViaImport.tsx
@@ -0,0 +1,23 @@
+//@jsx: preserve
+//@module: commonjs
+
+//@filename: component.d.ts
+declare module JSX {
+  interface ElementAttributesProperty { props; }
+}
+declare module React {
+  class Component<T, U> { }
+}
+declare module "BaseComponent" {
+    var base: React.Component<any, {}>;
+    export = base;
+}
+
+//@filename: consumer.tsx
+/// <reference path="component.d.ts" />
+import BaseComponent = require('BaseComponent');
+class TestComponent extends React.Component<any, {}> {
+    render() {
+        return <BaseComponent />;
+    }
+}
diff --git a/tests/cases/compiler/optionalParamArgsTest.ts b/tests/cases/compiler/optionalParamArgsTest.ts
index ce34acae869..609cbfe4734 100644
--- a/tests/cases/compiler/optionalParamArgsTest.ts
+++ b/tests/cases/compiler/optionalParamArgsTest.ts
@@ -30,8 +30,7 @@ class C1 {
 
     public C1M5(C1M5A1:number,C1M5A2:number=0,C1M5A3?:number) { return C1M5A1 + C1M5A2; }
 
-    // Negative test
-    // "Optional parameters may only be followed by other optional parameters"
+    // Uninitialized parameter makes the initialized one required
     public C1M5(C1M5A1:number,C1M5A2:number=0,C1M5A3:number) { return C1M5A1 + C1M5A2; }
 }
 
diff --git a/tests/cases/compiler/requiredInitializedParameter1.ts b/tests/cases/compiler/requiredInitializedParameter1.ts
new file mode 100644
index 00000000000..35d606426f0
--- /dev/null
+++ b/tests/cases/compiler/requiredInitializedParameter1.ts
@@ -0,0 +1,19 @@
+function f1(a, b = 0, c) { }
+function f2(a, b = 0, c = 0) { }
+function f3(a, b = 0, c?) { }
+function f4(a, b = 0, ...c) { }
+
+f1(0, 1, 2);
+f2(0, 1, 2);
+f3(0, 1, 2);
+f4(0, 1, 2);
+
+f1(0, 1);
+f2(0, 1);
+f3(0, 1);
+f4(0, 1);
+
+f1(0);
+f2(0);
+f3(0);
+f4(0);
\ No newline at end of file
diff --git a/tests/cases/compiler/requiredInitializedParameter2.ts b/tests/cases/compiler/requiredInitializedParameter2.ts
new file mode 100644
index 00000000000..48d42869ee7
--- /dev/null
+++ b/tests/cases/compiler/requiredInitializedParameter2.ts
@@ -0,0 +1,7 @@
+interface I1 {
+    method();
+}
+
+class C1 implements I1 {
+    method(a = 0, b) { }
+}
\ No newline at end of file
diff --git a/tests/cases/compiler/requiredInitializedParameter3.ts b/tests/cases/compiler/requiredInitializedParameter3.ts
new file mode 100644
index 00000000000..803eefb6342
--- /dev/null
+++ b/tests/cases/compiler/requiredInitializedParameter3.ts
@@ -0,0 +1,8 @@
+//@declaration: true
+interface I1 {
+    method();
+}
+
+class C1 implements I1 {
+    method(a = 0, b?) { }
+}
\ No newline at end of file
diff --git a/tests/cases/compiler/requiredInitializedParameter4.ts b/tests/cases/compiler/requiredInitializedParameter4.ts
new file mode 100644
index 00000000000..4ba15878e43
--- /dev/null
+++ b/tests/cases/compiler/requiredInitializedParameter4.ts
@@ -0,0 +1,4 @@
+//@declaration: true
+class C1 {
+    method(a = 0, b) { }
+}
\ No newline at end of file
diff --git a/tests/cases/conformance/es6/modules/defaultExportsCannotMerge01.ts b/tests/cases/conformance/es6/modules/defaultExportsCannotMerge01.ts
new file mode 100644
index 00000000000..7caa9caf574
--- /dev/null
+++ b/tests/cases/conformance/es6/modules/defaultExportsCannotMerge01.ts
@@ -0,0 +1,31 @@
+// @module: commonjs
+// @target: ES5
+
+// @filename: m1.ts
+export default function Decl() {
+    return 0;
+}
+
+export interface Decl {
+    p1: number;
+    p2: number;
+}
+
+export namespace Decl {
+    export var x = 10;
+    export var y = 20;
+
+    interface I {
+    }
+}
+
+// @filename: m2.ts
+import Entity from "m1"
+
+Entity();
+
+var x: Entity;
+var y: Entity.I;
+
+Entity.x;
+Entity.y;
\ No newline at end of file
diff --git a/tests/cases/conformance/es6/modules/defaultExportsCannotMerge02.ts b/tests/cases/conformance/es6/modules/defaultExportsCannotMerge02.ts
new file mode 100644
index 00000000000..f7312ec2e66
--- /dev/null
+++ b/tests/cases/conformance/es6/modules/defaultExportsCannotMerge02.ts
@@ -0,0 +1,26 @@
+// @module: commonjs
+// @target: ES5
+
+// @filename: m1.ts
+export default class Decl {
+}
+
+export interface Decl {
+    p1: number;
+    p2: number;
+}
+
+export namespace Decl {
+    interface I {
+    }
+}
+
+// @filename: m2.ts
+import Entity from "m1"
+
+Entity();
+
+var x: Entity;
+var y: Entity.I;
+var z = new Entity();
+var sum = z.p1 + z.p2
\ No newline at end of file
diff --git a/tests/cases/conformance/es6/modules/defaultExportsCannotMerge03.ts b/tests/cases/conformance/es6/modules/defaultExportsCannotMerge03.ts
new file mode 100644
index 00000000000..dad8431812b
--- /dev/null
+++ b/tests/cases/conformance/es6/modules/defaultExportsCannotMerge03.ts
@@ -0,0 +1,26 @@
+// @module: commonjs
+// @target: ES5
+
+// @filename: m1.ts
+export default class Decl {
+}
+
+interface Decl {
+    p1: number;
+    p2: number;
+}
+
+namespace Decl {
+    interface I {
+    }
+}
+
+// @filename: m2.ts
+import Entity from "m1"
+
+Entity();
+
+var x: Entity;
+var y: Entity.I;
+var z = new Entity();
+var sum = z.p1 + z.p2
\ No newline at end of file
diff --git a/tests/cases/conformance/es6/modules/defaultExportsCannotMerge04.ts b/tests/cases/conformance/es6/modules/defaultExportsCannotMerge04.ts
new file mode 100644
index 00000000000..ab72d10504a
--- /dev/null
+++ b/tests/cases/conformance/es6/modules/defaultExportsCannotMerge04.ts
@@ -0,0 +1,15 @@
+// @module: commonjs
+// @target: ES5
+
+export default function Foo() {
+}
+
+namespace Foo {
+    export var x;
+}
+
+interface Foo {
+}
+
+export interface Foo {
+}
\ No newline at end of file
diff --git a/tests/cases/conformance/es6/modules/multipleDefaultExports01.ts b/tests/cases/conformance/es6/modules/multipleDefaultExports01.ts
new file mode 100644
index 00000000000..84172248e93
--- /dev/null
+++ b/tests/cases/conformance/es6/modules/multipleDefaultExports01.ts
@@ -0,0 +1,19 @@
+// @module: commonjs
+// @target: ES5
+
+// @filename: m1.ts
+export default class foo {
+
+}
+
+export default function bar() {
+
+}
+
+var x = 10;
+export default x;
+
+// @filename: m2.ts
+import Entity from "m1"
+
+Entity();
\ No newline at end of file
diff --git a/tests/cases/conformance/es6/modules/multipleDefaultExports02.ts b/tests/cases/conformance/es6/modules/multipleDefaultExports02.ts
new file mode 100644
index 00000000000..1e9c8dabc13
--- /dev/null
+++ b/tests/cases/conformance/es6/modules/multipleDefaultExports02.ts
@@ -0,0 +1,16 @@
+// @module: commonjs
+// @target: ES5
+
+// @filename: m1.ts
+export default function foo() {
+
+}
+
+export default function bar() {
+
+}
+
+// @filename: m2.ts
+import Entity from "m1"
+
+Entity();
\ No newline at end of file
diff --git a/tests/cases/fourslash/addDeclareToFunction.ts b/tests/cases/fourslash/addDeclareToFunction.ts
index 46e5d123632..a31713fc56f 100644
--- a/tests/cases/fourslash/addDeclareToFunction.ts
+++ b/tests/cases/fourslash/addDeclareToFunction.ts
@@ -1,7 +1,8 @@
+/// <reference path="fourslash.ts" />
+
 //// /*1*/function parseInt(s/*2*/:string):number;
 
 goTo.marker('2');
 edit.deleteAtCaret(':string'.length);
 goTo.marker('1');
-edit.insert('declare ');
-
+edit.insert('declare ');
\ No newline at end of file
diff --git a/tests/cases/fourslash/fourslash.ts b/tests/cases/fourslash/fourslash.ts
index a0463073d8c..cbba2e916ce 100644
--- a/tests/cases/fourslash/fourslash.ts
+++ b/tests/cases/fourslash/fourslash.ts
@@ -29,7 +29,34 @@
 // type 'fs.' as an alternate way of accessing the top-level objects
 // (e.g. 'fs.goTo.eof();')
 
+//---------------------------------------
+// For API editors:
+// When editting this file, and only while editing this file, enable the reference comments
+// and comment out the declarations in this section to get proper type information.
+// Undo these changes before compiling/committing/editing any other fourslash tests.
+// The test suite will likely crash if you try 'jake runtests' with reference comments enabled.
+//
+// Explanation:
+// We want type-completion while we edit this file, but at compile time/while editting fourslash tests,
+// we don't want to include the following reference because we are compiling this file in "--out" mode and don't want to rope
+// in the entire codebase into the compilation each fourslash test. Additionally, we don't want to expose the
+// src/harness/fourslash.ts API's (or the rest of the compiler) because they are unstable and complicate the
+// fourslash testing DSL. Finally, in this case, runtime reflection is (much) faster.
+//
+// TODO: figure out a better solution to the API exposure problem.
+
+// /// <reference path="../../../built/local/typescriptServices.d.ts"/>
+// /// <reference path="../../../src/harness/fourslash.ts"/>
+
 declare var FourSlash;
+module ts {
+    export interface SymbolDisplayPart {
+        text: string;
+        kind: string;
+    }
+}
+
+//---------------------------------------------
 
 // Return code used by getEmitOutput function to indicate status of the function
 // It is a duplicate of the one in types.ts to expose it to testcases in fourslash
@@ -42,7 +69,6 @@ enum EmitReturnStatus {
 }
 
 module FourSlashInterface {
-    declare var FourSlash;
 
     export interface Marker {
         fileName: string;
@@ -201,15 +227,6 @@ module FourSlashInterface {
             FourSlash.currentTestState.verifyReferencesAtPositionListContains(range.fileName, range.start, range.end, isWriteAccess);
         }
 
-        public implementorsCountIs(count: number) {
-            FourSlash.currentTestState.verifyImplementorsCountIs(count);
-        }
-
-        // Add tests for this.
-        public currentParameterIsVariable() {
-            FourSlash.currentTestState.verifyCurrentParameterIsVariable(!this.negative);
-        }
-
         public signatureHelpPresent() {
             FourSlash.currentTestState.verifySignatureHelpPresent(!this.negative);
         }
@@ -361,14 +378,11 @@ module FourSlashInterface {
             FourSlash.currentTestState.verifyNoMatchingBracePosition(bracePosition);
         }
 
-        public setVerifyDocComments(val: boolean) {
-            FourSlash.currentTestState.setVerifyDocComments(val);
-        }
-
         public getScriptLexicalStructureListCount(count: number) {
             FourSlash.currentTestState.verifyGetScriptLexicalStructureListCount(count);
         }
 
+        // TODO: figure out what to do with the unused arguments.
         public getScriptLexicalStructureListContains(
             name: string,
             kind: string,
@@ -376,13 +390,7 @@ module FourSlashInterface {
             parentName?: string,
             isAdditionalSpan?: boolean,
             markerPosition?: number) {
-            FourSlash.currentTestState.verifGetScriptLexicalStructureListContains(
-                name,
-                kind,
-                fileName,
-                parentName,
-                isAdditionalSpan,
-                markerPosition);
+            FourSlash.currentTestState.verifyGetScriptLexicalStructureListContains(name, kind);
         }
 
         public navigationItemsListCount(count: number, searchValue: string, matchKind?: string) {
@@ -698,12 +706,7 @@ module fs {
     export var format = new FourSlashInterface.format();
     export var cancellation = new FourSlashInterface.cancellation();
 }
-module ts {
-    export interface SymbolDisplayPart {
-        text: string;
-        kind: string;
-    }
-}
+
 function verifyOperationIsCancelled(f) {
     FourSlash.verifyOperationIsCancelled(f);
 }
diff --git a/tests/cases/unittests/session.ts b/tests/cases/unittests/session.ts
new file mode 100644
index 00000000000..c1dfd508942
--- /dev/null
+++ b/tests/cases/unittests/session.ts
@@ -0,0 +1,447 @@
+/// <reference path="..\..\..\src\harness\harness.ts" />
+
+namespace ts.server {
+    let lastWrittenToHost: string;
+    const mockHost: ServerHost = {
+        args: [],
+        newLine: "\n",
+        useCaseSensitiveFileNames: true,
+        write(s): void { lastWrittenToHost = s; },
+        readFile(): string { return void 0; },
+        writeFile(): void {},
+        resolvePath(): string { return void 0; },
+        fileExists: () => false,
+        directoryExists: () => false,
+        createDirectory(): void {},
+        getExecutingFilePath(): string { return void 0; },
+        getCurrentDirectory(): string { return void 0; },
+        readDirectory(): string[] { return []; },
+        exit(): void {}
+    };
+    const mockLogger: Logger = {
+        close(): void {},
+        isVerbose(): boolean { return false; },
+        loggingEnabled(): boolean { return false; },
+        perftrc(s: string): void {},
+        info(s: string): void {},
+        startGroup(): void {},
+        endGroup(): void {},
+        msg(s: string, type?: string): void {},
+    };
+    
+    describe("the Session class", () => {
+        let session: Session;
+        let lastSent: protocol.Message;
+
+        beforeEach(() => {
+            session = new Session(mockHost, Buffer.byteLength, process.hrtime, mockLogger);
+            session.send = (msg: protocol.Message) => {
+                lastSent = msg;
+            };
+        });
+
+        describe("executeCommand", () => {
+            it("should throw when commands are executed with invalid arguments", () => {
+                const req: protocol.FileRequest = {
+                    command: CommandNames.Open,
+                    seq: 0,
+                    type: "command",
+                    arguments: {
+                        file: undefined
+                    }
+                };
+
+                expect(() => session.executeCommand(req)).to.throw();
+            });
+            it("should output an error response when a command does not exist", () => {
+                const req: protocol.Request = {
+                    command: "foobar",
+                    seq: 0,
+                    type: "command"
+                };
+
+                session.executeCommand(req);
+
+                expect(lastSent).to.deep.equal(<protocol.Response>{
+                    command: CommandNames.Unknown,
+                    type: "response",
+                    seq: 0,
+                    message: "Unrecognized JSON command: foobar",
+                    request_seq: 0,
+                    success: false
+                });
+            });
+            it("should return a tuple containing the response and if a response is required on success", () => {
+                const req: protocol.ConfigureRequest = {
+                    command: CommandNames.Configure,
+                    seq: 0,
+                    type: "command",
+                    arguments: {
+                        hostInfo: "unit test",
+                        formatOptions: {
+                            newLineCharacter: "`n"
+                        }
+                    }
+                };
+
+                expect(session.executeCommand(req)).to.deep.equal({
+                    responseRequired: false
+                });
+                expect(lastSent).to.deep.equal({
+                    command: CommandNames.Configure,
+                    type: "response",
+                    success: true,
+                    request_seq: 0,
+                    seq: 0,
+                    body: undefined
+                });
+            });
+        });
+
+        describe("onMessage", () => {
+            it("should not throw when commands are executed with invalid arguments", () => {
+                let i = 0;
+                for (name in CommandNames) {
+                    if (!Object.prototype.hasOwnProperty.call(CommandNames, name)) {
+                        continue;
+                    }
+                    const req: protocol.Request = {
+                        command: name,
+                        seq: i++,
+                        type: "command"
+                    };
+                    session.onMessage(JSON.stringify(req));
+                    req.seq = i++;
+                    req.arguments = {};
+                    session.onMessage(JSON.stringify(req));
+                    req.seq = i++;
+                    req.arguments = null;
+                    session.onMessage(JSON.stringify(req));
+                    req.seq = i++;
+                    req.arguments = "";
+                    session.onMessage(JSON.stringify(req));
+                    req.seq = i++;
+                    req.arguments = 0;
+                    session.onMessage(JSON.stringify(req));
+                    req.seq = i++;
+                    req.arguments = [];
+                    session.onMessage(JSON.stringify(req));
+                }
+                session.onMessage("GARBAGE NON_JSON DATA");
+            });
+            it("should output the response for a correctly handled message", () => {
+                const req: protocol.ConfigureRequest = {
+                    command: CommandNames.Configure,
+                    seq: 0,
+                    type: "command",
+                    arguments: {
+                        hostInfo: "unit test",
+                        formatOptions: {
+                            newLineCharacter: "`n"
+                        }
+                    }
+                };
+
+                session.onMessage(JSON.stringify(req));
+
+                expect(lastSent).to.deep.equal(<protocol.ConfigureResponse>{
+                    command: CommandNames.Configure,
+                    type: "response",
+                    success: true,
+                    request_seq: 0,
+                    seq: 0,
+                    body: undefined
+                });
+            });
+        });
+
+        describe("send", () => {
+            it("is an overrideable handle which sends protocol messages over the wire", () => {
+                const msg = {seq: 0, type: "none"};
+                const strmsg = JSON.stringify(msg);
+                const len = 1 + Buffer.byteLength(strmsg, "utf8");
+                const resultMsg = `Content-Length: ${len}\r\n\r\n${strmsg}\n`;
+
+                session.send = Session.prototype.send;
+                assert(session.send);
+                expect(session.send(msg)).to.not.exist;
+                expect(lastWrittenToHost).to.equal(resultMsg);
+            });
+        });
+
+        describe("addProtocolHandler", () => {
+            it("can add protocol handlers", () => {
+                const respBody = {
+                    item: false
+                };
+                const command = "newhandle";
+                const result = {
+                    response: respBody,
+                    responseRequired: true
+                };
+
+                session.addProtocolHandler(command, (req) => result);
+
+                expect(session.executeCommand({
+                    command,
+                    seq: 0,
+                    type: "command"
+                })).to.deep.equal(result);
+            });
+            it("throws when a duplicate handler is passed", () => {
+                const respBody = {
+                    item: false
+                };
+                const resp = {
+                    response: respBody,
+                    responseRequired: true
+                };
+                const command = "newhandle";
+
+                session.addProtocolHandler(command, (req) => resp);
+
+                expect(() => session.addProtocolHandler(command, (req) => resp))
+                .to.throw(`Protocol handler already exists for command "${command}"`);
+            });
+        });
+        
+        describe("event", () => {
+            it("can format event responses and send them", () => {
+                const evt = "notify-test";
+                const info = {
+                    test: true
+                };
+
+                session.event(info, evt);
+
+                expect(lastSent).to.deep.equal({
+                    type: "event",
+                    seq: 0,
+                    event: evt,
+                    body: info
+                });
+            });
+        });
+
+        describe("output", () => {
+            it("can format command responses and send them", () => {
+                const body = {
+                    block: {
+                        key: "value"
+                    }
+                };
+                const command = "test";
+
+                session.output(body, command);
+
+                expect(lastSent).to.deep.equal({
+                    seq: 0,
+                    request_seq: 0,
+                    type: "response",
+                    command,
+                    body: body,
+                    success: true
+                });
+            });
+        });
+    });
+
+    describe("how Session is extendable via subclassing", () => {
+        class TestSession extends Session {
+            lastSent: protocol.Message;
+            customHandler = "testhandler";
+            constructor() {
+                super(mockHost, Buffer.byteLength, process.hrtime, mockLogger);
+                this.addProtocolHandler(this.customHandler, () => {
+                    return {response: undefined, responseRequired: true};
+                });
+            }
+            send(msg: protocol.Message) {
+                this.lastSent = msg;
+            }
+        };
+
+        it("can override methods such as send", () => {
+            const session = new TestSession();
+            const body = {
+                block: {
+                    key: "value"
+                }
+            };
+            const command = "test";
+
+            session.output(body, command);
+
+            expect(session.lastSent).to.deep.equal({
+                seq: 0,
+                request_seq: 0,
+                type: "response",
+                command,
+                body: body,
+                success: true
+            });
+        });
+        it("can add and respond to new protocol handlers", () => {
+            const session = new TestSession();
+
+            expect(session.executeCommand({
+                seq: 0,
+                type: "command",
+                command: session.customHandler
+            })).to.deep.equal({
+                response: undefined,
+                responseRequired: true
+            });
+        });
+        it("has access to the project service", () => {
+            class ServiceSession extends TestSession {
+                constructor() {
+                    super();
+                    assert(this.projectService);
+                    expect(this.projectService).to.be.instanceOf(ProjectService);
+                }
+            };
+            new ServiceSession();
+        });
+    });
+
+    describe("an example of using the Session API to create an in-process server", () => {
+        class InProcSession extends Session {
+            private queue: protocol.Request[] = [];
+            constructor(private client: InProcClient) {
+                super(mockHost, Buffer.byteLength, process.hrtime, mockLogger);
+                this.addProtocolHandler("echo", (req: protocol.Request) => ({
+                    response: req.arguments,
+                    responseRequired: true
+                }));
+            }
+            
+            send(msg: protocol.Message) {
+                this.client.handle(msg);
+            }
+
+            enqueue(msg: protocol.Request) {
+                this.queue.unshift(msg);
+            }
+            
+            handleRequest(msg: protocol.Request) {
+                let response: protocol.Response;
+                try {
+                    ({response} = this.executeCommand(msg));
+                }
+                catch (e) {
+                    this.output(undefined, msg.command, msg.seq, e.toString());
+                    return;
+                }
+                if (response) {
+                    this.output(response, msg.command, msg.seq);
+                }
+            }
+
+            consumeQueue() {
+                while (this.queue.length > 0) {
+                    const elem = this.queue.pop();
+                    this.handleRequest(elem);
+                }
+            }
+        }
+        
+        class InProcClient {
+            private server: InProcSession;
+            private seq = 0;
+            private callbacks: ts.Map<(resp: protocol.Response) => void> = {};
+            private eventHandlers: ts.Map<(args: any) => void> = {};
+
+            handle(msg: protocol.Message): void {
+                if (msg.type === "response") {
+                    const response = <protocol.Response>msg;
+                    if (this.callbacks[response.request_seq]) {
+                        this.callbacks[response.request_seq](response);
+                        delete this.callbacks[response.request_seq];
+                    }
+                }
+                else if (msg.type === "event") {
+                    const event = <protocol.Event>msg;
+                    this.emit(event.event, event.body);
+                }
+            }
+
+            emit(name: string, args: any): void {
+                if (this.eventHandlers[name]) {
+                    this.eventHandlers[name](args);
+                }
+            }
+
+            on(name: string, handler: (args: any) => void): void {
+                this.eventHandlers[name] = handler;
+            }
+
+            connect(session: InProcSession): void {
+                this.server = session;
+            }
+            
+            execute(command: string, args: any, callback: (resp: protocol.Response) => void): void {
+                if (!this.server) {
+                    return;
+                }
+                this.seq++;
+                this.server.enqueue({
+                    seq: this.seq,
+                    type: "command",
+                    command,
+                    arguments: args
+                });
+                this.callbacks[this.seq] = callback;
+            }
+        };
+        
+        it("can be constructed and respond to commands", (done) => {
+            const cli = new InProcClient();
+            const session = new InProcSession(cli);
+            const toEcho = {
+                data: true
+            };
+            const toEvent = {
+                data: false    
+            };
+            let responses = 0;
+
+            // Connect the client
+            cli.connect(session);
+            
+            // Add an event handler
+            cli.on("testevent", (eventinfo) => {
+                expect(eventinfo).to.equal(toEvent);
+                responses++;
+                expect(responses).to.equal(1);
+            });
+            
+            // Trigger said event from the server
+            session.event(toEvent, "testevent");
+            
+            // Queue an echo command
+            cli.execute("echo", toEcho, (resp) => {
+                assert(resp.success, resp.message);
+                responses++;
+                expect(responses).to.equal(2);
+                expect(resp.body).to.deep.equal(toEcho);
+            });
+            
+            // Queue a configure command
+            cli.execute("configure", {
+                hostInfo: "unit test",
+                formatOptions: {
+                    newLineCharacter: "`n"
+                }
+            }, (resp) => {
+                assert(resp.success, resp.message);
+                responses++;
+                expect(responses).to.equal(3);                
+                done();
+            });
+            
+            // Consume the queue and trigger the callbacks
+            session.consumeQueue();
+        });
+    });
+}
\ No newline at end of file
diff --git a/tests/cases/unittests/transpile.ts b/tests/cases/unittests/transpile.ts
index fcce034b227..1fd8c860d01 100644
--- a/tests/cases/unittests/transpile.ts
+++ b/tests/cases/unittests/transpile.ts
@@ -2,58 +2,120 @@
 
 module ts {
     describe("Transpile", () => {
-
-        function runTest(input: string, compilerOptions: ts.CompilerOptions = {}, fileName?: string,  moduleName?: string, expectedOutput?: string, expectedDiagnosticCodes: number[] = []): void {
-            let diagnostics: Diagnostic[] = [];
-            let result = transpile(input, compilerOptions, fileName || "file.ts", diagnostics, moduleName);
-
+        
+        interface TranspileTestSettings {
+            options?: TranspileOptions;
+            expectedOutput?: string;
+            expectedDiagnosticCodes?: number[];
+        }
+        
+        function checkDiagnostics(diagnostics: Diagnostic[], expectedDiagnosticCodes?: number[]) {
+            if(!expectedDiagnosticCodes) {
+                return;
+            }
+            
             for (let i = 0; i < expectedDiagnosticCodes.length; i++) {
                 assert.equal(expectedDiagnosticCodes[i], diagnostics[i] && diagnostics[i].code, `Could not find expeced diagnostic.`);
             }
-            assert.equal(diagnostics.length, expectedDiagnosticCodes.length, "Resuting diagnostics count does not match expected");
-
-            if (expectedOutput !== undefined) {
-                assert.equal(result, expectedOutput);
-            }
+            assert.equal(diagnostics.length, expectedDiagnosticCodes.length, "Resuting diagnostics count does not match expected");            
         }
+        
+        function test(input: string, testSettings: TranspileTestSettings): void {
+            let diagnostics: Diagnostic[] = [];
+            
+            let transpileOptions: TranspileOptions = testSettings.options || {}; 
+            let transpileResult = transpile(input, transpileOptions.compilerOptions, transpileOptions.fileName, diagnostics, transpileOptions.moduleName);
+            
+            transpileOptions.reportDiagnostics = true;
+            let transpileModuleResult = transpileModule(input, transpileOptions);
+            
+            checkDiagnostics(diagnostics, testSettings.expectedDiagnosticCodes);
+            checkDiagnostics(transpileModuleResult.diagnostics, testSettings.expectedDiagnosticCodes);
+            
+            if (testSettings.expectedOutput !== undefined) {
+                assert.equal(transpileResult, testSettings.expectedOutput);
+                assert.equal(transpileModuleResult.outputText, testSettings.expectedOutput);
+            }
+            
+            // check source maps
+            if (!transpileOptions.compilerOptions) {
+                transpileOptions.compilerOptions = {};
+            }
+            
+            if (!transpileOptions.fileName) {
+                transpileOptions.fileName = "file.ts";
+            }
+            
+            transpileOptions.compilerOptions.sourceMap = true;            
+            let transpileModuleResultWithSourceMap = transpileModule(input, transpileOptions);
+            assert.isTrue(transpileModuleResultWithSourceMap.sourceMapText !== undefined);
+            
+            let expectedSourceMapFileName = removeFileExtension(transpileOptions.fileName) + ".js.map";
+            let expectedSourceMappingUrlLine = `//# sourceMappingURL=${expectedSourceMapFileName}`;           
+                        
+            if (testSettings.expectedOutput !== undefined) {
+                assert.equal(transpileModuleResultWithSourceMap.outputText, testSettings.expectedOutput + expectedSourceMappingUrlLine);    
+            }
+            else {
+                // expected output is not set, just verify that output text has sourceMappingURL as a last line
+                let output = transpileModuleResultWithSourceMap.outputText;
+                assert.isTrue(output.length >= expectedSourceMappingUrlLine.length);
+                if (output.length === expectedSourceMappingUrlLine.length) {
+                    assert.equal(output, expectedSourceMappingUrlLine);
+                }
+                else {
+                    let suffix = getNewLineCharacter(transpileOptions.compilerOptions) + expectedSourceMappingUrlLine                                
+                    assert.isTrue(output.indexOf(suffix, output.length - suffix.length) !== -1);
+                }
+            }       
 
+        }
+        
         it("Generates correct compilerOptions diagnostics", () => {
             // Expecting 5047: "Option 'isolatedModules' can only be used when either option'--module' is provided or option 'target' is 'ES6' or higher."
-            runTest(`var x = 0;`, {}, /*fileName*/ undefined, /*moduleName*/undefined, /*expectedOutput*/ undefined, /*expectedDiagnosticCodes*/ [5047]);
+            test(`var x = 0;`, { expectedDiagnosticCodes: [5047] });
         });
 
         it("Generates no diagnostics with valid inputs", () => {
             // No errors
-            runTest(`var x = 0;`, { module: ModuleKind.CommonJS }, /*fileName*/ undefined, /*moduleName*/undefined, /*expectedOutput*/ undefined, /*expectedDiagnosticCodes*/ []);
+            test(`var x = 0;`, { options: { compilerOptions: { module: ModuleKind.CommonJS } } });
         });
 
         it("Generates no diagnostics for missing file references", () => {
-            runTest(`/// <reference path="file2.ts" />
-var x = 0;`,
-                { module: ModuleKind.CommonJS }, /*fileName*/ undefined, /*moduleName*/undefined, /*expectedOutput*/ undefined, /*expectedDiagnosticCodes*/ []);
+            test(`/// <reference path="file2.ts" />
+var x = 0;`, 
+                { options: { compilerOptions: { module: ModuleKind.CommonJS } } });
         });
 
         it("Generates no diagnostics for missing module imports", () => {
-            runTest(`import {a} from "module2";`,
-                { module: ModuleKind.CommonJS }, /*fileName*/ undefined,/*moduleName*/undefined, /*expectedOutput*/ undefined, /*expectedDiagnosticCodes*/ []);
+            test(`import {a} from "module2";`,
+                { options: { compilerOptions: { module: ModuleKind.CommonJS } } });
         });
 
         it("Generates expected syntactic diagnostics", () => {
-            runTest(`a b`,
-                { module: ModuleKind.CommonJS }, /*fileName*/ undefined, /*moduleName*/undefined, /*expectedOutput*/ undefined, /*expectedDiagnosticCodes*/ [1005]); /// 1005: ';' Expected
+            test(`a b`,
+                { options: { compilerOptions: { module: ModuleKind.CommonJS } }, expectedDiagnosticCodes: [1005] }); /// 1005: ';' Expected
         });
 
         it("Does not generate semantic diagnostics", () => {
-            runTest(`var x: string = 0;`,
-                { module: ModuleKind.CommonJS }, /*fileName*/ undefined, /*moduleName*/undefined, /*expectedOutput*/ undefined, /*expectedDiagnosticCodes*/ []);
+            test(`var x: string = 0;`,
+                { options: { compilerOptions: { module: ModuleKind.CommonJS } } });
         });
 
         it("Generates module output", () => {
-            runTest(`var x = 0;`, { module: ModuleKind.AMD }, /*fileName*/ undefined, /*moduleName*/undefined, `define(["require", "exports"], function (require, exports) {\r\n    var x = 0;\r\n});\r\n`);
+            test(`var x = 0;`, 
+                { 
+                    options: { compilerOptions: { module: ModuleKind.AMD } }, 
+                    expectedOutput: `define(["require", "exports"], function (require, exports) {\r\n    var x = 0;\r\n});\r\n`
+                });
         });
 
         it("Uses correct newLine character", () => {
-            runTest(`var x = 0;`, { module: ModuleKind.CommonJS, newLine: NewLineKind.LineFeed }, /*fileName*/ undefined, /*moduleName*/undefined, `var x = 0;\n`, /*expectedDiagnosticCodes*/ []);
+            test(`var x = 0;`, 
+                { 
+                    options: { compilerOptions: { module: ModuleKind.CommonJS, newLine: NewLineKind.LineFeed } }, 
+                    expectedOutput: `var x = 0;\n`
+                });
         });
 
         it("Sets module name", () => {
@@ -66,12 +128,15 @@ var x = 0;`,
                 `        }\n` +
                 `    }\n` +
                 `});\n`;
-            runTest("var x = 1;", { module: ModuleKind.System, newLine: NewLineKind.LineFeed }, /*fileName*/ undefined, "NamedModule", output)
+            test("var x = 1;", 
+                { 
+                    options: { compilerOptions: { module: ModuleKind.System, newLine: NewLineKind.LineFeed }, moduleName: "NamedModule" }, 
+                    expectedOutput: output
+                })
         });
 
         it("No extra errors for file without extension", () => {
-            runTest(`var x = 0;`, { module: ModuleKind.CommonJS }, "file", /*moduleName*/undefined, /*expectedOutput*/ undefined, /*expectedDiagnosticCodes*/[]);
+            test(`var x = 0;`, { options: { compilerOptions: { module: ModuleKind.CommonJS }, fileName: "file" } });
         });
-
     });
 }