diff --git a/Jakefile.js b/Jakefile.js
index 501892bf840..1b5f698529b 100644
--- a/Jakefile.js
+++ b/Jakefile.js
@@ -154,7 +154,8 @@ var harnessSources = harnessCoreSources.concat([
     "tsconfigParsing.ts",
     "commandLineParsing.ts",
     "convertCompilerOptionsFromJson.ts",
-    "convertTypingOptionsFromJson.ts"
+    "convertTypingOptionsFromJson.ts",
+    "tsserverProjectSystem.ts"
 ].map(function (f) {
     return path.join(unittestsDirectory, f);
 })).concat([
diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index fef23770475..8c48d984b78 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -77,12 +77,14 @@ namespace ts {
         //      Blocks (when not parented by functions), Catch clauses, For/For-in/For-of statements...
         IsBlockScopedContainer = 1 << 1,
 
-        HasLocals = 1 << 2,
+        // The current node is the container of a control flow path. The current control flow should
+        // be saved and restored, and a new control flow initialized within the container.
+        IsControlFlowContainer = 1 << 2,
 
-        // If the current node is a container that also container that also contains locals.  Examples:
-        //
-        //      Functions, Methods, Modules, Source-files.
-        IsContainerWithLocals = IsContainer | HasLocals
+        IsFunctionLike = 1 << 3,
+        IsFunctionExpression = 1 << 4,
+        HasLocals = 1 << 5,
+        IsInterface = 1 << 6,
     }
 
     const binder = createBinder();
@@ -103,22 +105,19 @@ namespace ts {
         let lastContainer: Node;
         let seenThisKeyword: boolean;
 
-        // state used by reachability checks
-        let hasExplicitReturn: boolean;
+        // state used by control flow analysis
         let currentFlow: FlowNode;
         let currentBreakTarget: FlowLabel;
         let currentContinueTarget: FlowLabel;
+        let currentReturnTarget: FlowLabel;
         let currentTrueTarget: FlowLabel;
         let currentFalseTarget: FlowLabel;
         let preSwitchCaseFlow: FlowNode;
         let activeLabels: ActiveLabel[];
+        let hasExplicitReturn: boolean;
 
         // state used for emit helpers
-        let hasClassExtends: boolean;
-        let hasAsyncFunctions: boolean;
-        let hasDecorators: boolean;
-        let hasParameterDecorators: boolean;
-        let hasJsxSpreadAttribute: boolean;
+        let emitFlags: NodeFlags;
 
         // If this file is an external module, then it is automatically in strict-mode according to
         // ES6.  If it is not an external module, then we'll determine if it is in strict mode or
@@ -156,18 +155,15 @@ namespace ts {
             blockScopeContainer = undefined;
             lastContainer = undefined;
             seenThisKeyword = false;
-            hasExplicitReturn = false;
             currentFlow = undefined;
             currentBreakTarget = undefined;
             currentContinueTarget = undefined;
+            currentReturnTarget = undefined;
             currentTrueTarget = undefined;
             currentFalseTarget = undefined;
             activeLabels = undefined;
-            hasClassExtends = false;
-            hasAsyncFunctions = false;
-            hasDecorators = false;
-            hasParameterDecorators = false;
-            hasJsxSpreadAttribute = false;
+            hasExplicitReturn = false;
+            emitFlags = NodeFlags.None;
         }
 
         return bindSourceFile;
@@ -267,6 +263,18 @@ namespace ts {
                     let functionType = <JSDocFunctionType>node.parent;
                     let index = indexOf(functionType.parameters, node);
                     return "p" + index;
+                case SyntaxKind.JSDocTypedefTag:
+                    const parentNode = node.parent && node.parent.parent;
+                    let nameFromParentNode: string;
+                    if (parentNode && parentNode.kind === SyntaxKind.VariableStatement) {
+                        if ((<VariableStatement>parentNode).declarationList.declarations.length > 0) {
+                            const nameIdentifier = (<VariableStatement>parentNode).declarationList.declarations[0].name;
+                            if (nameIdentifier.kind === SyntaxKind.Identifier) {
+                                nameFromParentNode = (<Identifier>nameIdentifier).text;
+                            }
+                        }
+                    }
+                    return nameFromParentNode;
             }
         }
 
@@ -400,17 +408,13 @@ namespace ts {
         // All container nodes are kept on a linked list in declaration order. This list is used by
         // the getLocalNameOfContainer function in the type checker to validate that the local name
         // used for a container is unique.
-        function bindChildren(node: Node) {
+        function bindContainer(node: Node, containerFlags: ContainerFlags) {
             // Before we recurse into a node's children, we first save the existing parent, container
             // and block-container.  Then after we pop out of processing the children, we restore
             // these saved values.
-            const saveParent = parent;
             const saveContainer = container;
             const savedBlockScopeContainer = blockScopeContainer;
 
-            // This node will now be set as the parent of all of its children as we recurse into them.
-            parent = node;
-
             // Depending on what kind of node this is, we may have to adjust the current container
             // and block-container.   If the current node is a container, then it is automatically
             // considered the current block-container as well.  Also, for containers that we know
@@ -428,115 +432,90 @@ namespace ts {
             // reusing a node from a previous compilation, that node may have had 'locals' created
             // for it.  We must clear this so we don't accidentally move any stale data forward from
             // a previous compilation.
-            const containerFlags = getContainerFlags(node);
             if (containerFlags & ContainerFlags.IsContainer) {
                 container = blockScopeContainer = node;
-
                 if (containerFlags & ContainerFlags.HasLocals) {
                     container.locals = {};
                 }
-
                 addToContainerChain(container);
             }
             else if (containerFlags & ContainerFlags.IsBlockScopedContainer) {
                 blockScopeContainer = node;
                 blockScopeContainer.locals = undefined;
             }
-
-            let savedHasExplicitReturn: boolean;
-            let savedCurrentFlow: FlowNode;
-            let savedBreakTarget: FlowLabel;
-            let savedContinueTarget: FlowLabel;
-            let savedActiveLabels: ActiveLabel[];
-
-            const kind = node.kind;
-            let flags = node.flags;
-
-            // reset all reachability check related flags on node (for incremental scenarios)
-            flags &= ~NodeFlags.ReachabilityCheckFlags;
-
-            // reset all emit helper flags on node (for incremental scenarios)
-            flags &= ~NodeFlags.EmitHelperFlags;
-
-            if (kind === SyntaxKind.InterfaceDeclaration) {
-                seenThisKeyword = false;
-            }
-
-            const saveState = kind === SyntaxKind.SourceFile || kind === SyntaxKind.ModuleBlock || isFunctionLikeKind(kind);
-            if (saveState) {
-                savedHasExplicitReturn = hasExplicitReturn;
-                savedCurrentFlow = currentFlow;
-                savedBreakTarget = currentBreakTarget;
-                savedContinueTarget = currentContinueTarget;
-                savedActiveLabels = activeLabels;
-
-                hasExplicitReturn = false;
-                currentFlow = { flags: FlowFlags.Start };
+            if (containerFlags & ContainerFlags.IsControlFlowContainer) {
+                const saveCurrentFlow = currentFlow;
+                const saveBreakTarget = currentBreakTarget;
+                const saveContinueTarget = currentContinueTarget;
+                const saveReturnTarget = currentReturnTarget;
+                const saveActiveLabels = activeLabels;
+                const saveHasExplicitReturn = hasExplicitReturn;
+                const isIIFE = containerFlags & ContainerFlags.IsFunctionExpression && !!getImmediatelyInvokedFunctionExpression(node);
+                // An IIFE is considered part of the containing control flow. Return statements behave
+                // similarly to break statements that exit to a label just past the statement body.
+                if (isIIFE) {
+                    currentReturnTarget = createBranchLabel();
+                }
+                else {
+                    currentFlow = { flags: FlowFlags.Start };
+                    if (containerFlags & ContainerFlags.IsFunctionExpression) {
+                        (<FlowStart>currentFlow).container = <FunctionExpression | ArrowFunction>node;
+                    }
+                    currentReturnTarget = undefined;
+                }
                 currentBreakTarget = undefined;
                 currentContinueTarget = undefined;
                 activeLabels = undefined;
-            }
-
-            if (isInJavaScriptFile(node) && node.jsDocComment) {
-                bind(node.jsDocComment);
-            }
-
-            bindReachableStatement(node);
-
-            if (!(currentFlow.flags & FlowFlags.Unreachable) && isFunctionLikeKind(kind) && nodeIsPresent((<FunctionLikeDeclaration>node).body)) {
-                flags |= NodeFlags.HasImplicitReturn;
-                if (hasExplicitReturn) {
-                    flags |= NodeFlags.HasExplicitReturn;
+                hasExplicitReturn = false;
+                bindChildren(node);
+                // Reset all reachability check related flags on node (for incremental scenarios)
+                // Reset all emit helper flags on node (for incremental scenarios)
+                node.flags &= ~NodeFlags.ReachabilityAndEmitFlags;
+                if (!(currentFlow.flags & FlowFlags.Unreachable) && containerFlags & ContainerFlags.IsFunctionLike && nodeIsPresent((<FunctionLikeDeclaration>node).body)) {
+                    node.flags |= NodeFlags.HasImplicitReturn;
+                    if (hasExplicitReturn) node.flags |= NodeFlags.HasExplicitReturn;
                 }
+                if (node.kind === SyntaxKind.SourceFile) {
+                    node.flags |= emitFlags;
+                }
+                if (isIIFE) {
+                    addAntecedent(currentReturnTarget, currentFlow);
+                    currentFlow = finishFlowLabel(currentReturnTarget);
+                }
+                else {
+                    currentFlow = saveCurrentFlow;
+                }
+                currentBreakTarget = saveBreakTarget;
+                currentContinueTarget = saveContinueTarget;
+                currentReturnTarget = saveReturnTarget;
+                activeLabels = saveActiveLabels;
+                hasExplicitReturn = saveHasExplicitReturn;
             }
-
-            if (kind === SyntaxKind.InterfaceDeclaration) {
-                flags = seenThisKeyword ? flags | NodeFlags.ContainsThis : flags & ~NodeFlags.ContainsThis;
+            else if (containerFlags & ContainerFlags.IsInterface) {
+                seenThisKeyword = false;
+                bindChildren(node);
+                node.flags = seenThisKeyword ? node.flags | NodeFlags.ContainsThis : node.flags & ~NodeFlags.ContainsThis;
             }
-
-            if (kind === SyntaxKind.SourceFile) {
-                if (hasClassExtends) {
-                    flags |= NodeFlags.HasClassExtends;
-                }
-                if (hasDecorators) {
-                    flags |= NodeFlags.HasDecorators;
-                }
-                if (hasParameterDecorators) {
-                    flags |= NodeFlags.HasParamDecorators;
-                }
-                if (hasAsyncFunctions) {
-                    flags |= NodeFlags.HasAsyncFunctions;
-                }
-                if (hasJsxSpreadAttribute) {
-                    flags |= NodeFlags.HasJsxSpreadAttribute;
-                }
+            else {
+                bindChildren(node);
             }
-
-            node.flags = flags;
-
-            if (saveState) {
-                hasExplicitReturn = savedHasExplicitReturn;
-                currentFlow = savedCurrentFlow;
-                currentBreakTarget = savedBreakTarget;
-                currentContinueTarget = savedContinueTarget;
-                activeLabels = savedActiveLabels;
-            }
-
             container = saveContainer;
-            parent = saveParent;
             blockScopeContainer = savedBlockScopeContainer;
         }
 
-        /**
-         * Returns true if node and its subnodes were successfully traversed.
-         * Returning false means that node was not examined and caller needs to dive into the node himself.
-         */
-        function bindReachableStatement(node: Node): void {
+        function bindChildren(node: Node): void {
+            // Binding of JsDocComment should be done before the current block scope container changes.
+            // because the scope of JsDocComment should not be affected by whether the current node is a
+            // container or not.
+            if (isInJavaScriptFile(node) && node.jsDocComments) {
+                for (const jsDocComment of node.jsDocComments) {
+                    bind(jsDocComment);
+                }
+            }
             if (checkUnreachable(node)) {
                 forEachChild(node, bind);
                 return;
             }
-
             switch (node.kind) {
                 case SyntaxKind.WhileStatement:
                     bindWhileStatement(<WhileStatement>node);
@@ -589,6 +568,9 @@ namespace ts {
                 case SyntaxKind.VariableDeclaration:
                     bindVariableDeclarationFlow(<VariableDeclaration>node);
                     break;
+                case SyntaxKind.CallExpression:
+                    bindCallExpressionFlow(<CallExpression>node);
+                    break;
                 default:
                     forEachChild(node, bind);
                     break;
@@ -848,6 +830,9 @@ namespace ts {
             bind(node.expression);
             if (node.kind === SyntaxKind.ReturnStatement) {
                 hasExplicitReturn = true;
+                if (currentReturnTarget) {
+                    addAntecedent(currentReturnTarget, currentFlow);
+                }
             }
             currentFlow = unreachableFlow;
         }
@@ -1098,35 +1083,67 @@ namespace ts {
             }
         }
 
+        function bindCallExpressionFlow(node: CallExpression) {
+            // If the target of the call expression is a function expression or arrow function we have
+            // an immediately invoked function expression (IIFE). Initialize the flowNode property to
+            // the current control flow (which includes evaluation of the IIFE arguments).
+            let expr: Expression = node.expression;
+            while (expr.kind === SyntaxKind.ParenthesizedExpression) {
+                expr = (<ParenthesizedExpression>expr).expression;
+            }
+            if (expr.kind === SyntaxKind.FunctionExpression || expr.kind === SyntaxKind.ArrowFunction) {
+                forEach(node.typeArguments, bind);
+                forEach(node.arguments, bind);
+                bind(node.expression);
+            }
+            else {
+                forEachChild(node, bind);
+            }
+        }
+
         function getContainerFlags(node: Node): ContainerFlags {
             switch (node.kind) {
                 case SyntaxKind.ClassExpression:
                 case SyntaxKind.ClassDeclaration:
-                case SyntaxKind.InterfaceDeclaration:
                 case SyntaxKind.EnumDeclaration:
                 case SyntaxKind.ObjectLiteralExpression:
                 case SyntaxKind.TypeLiteral:
+                case SyntaxKind.JSDocTypeLiteral:
                 case SyntaxKind.JSDocRecordType:
                     return ContainerFlags.IsContainer;
 
+                case SyntaxKind.InterfaceDeclaration:
+                    return ContainerFlags.IsContainer | ContainerFlags.IsInterface;
+
+                case SyntaxKind.JSDocFunctionType:
+                case SyntaxKind.ModuleDeclaration:
+                case SyntaxKind.TypeAliasDeclaration:
+                    return ContainerFlags.IsContainer | ContainerFlags.HasLocals;
+
+                case SyntaxKind.SourceFile:
+                    return ContainerFlags.IsContainer | ContainerFlags.IsControlFlowContainer | ContainerFlags.HasLocals;
+
+                case SyntaxKind.Constructor:
+                case SyntaxKind.FunctionDeclaration:
+                case SyntaxKind.MethodDeclaration:
+                case SyntaxKind.MethodSignature:
+                case SyntaxKind.GetAccessor:
+                case SyntaxKind.SetAccessor:
                 case SyntaxKind.CallSignature:
                 case SyntaxKind.ConstructSignature:
                 case SyntaxKind.IndexSignature:
-                case SyntaxKind.MethodDeclaration:
-                case SyntaxKind.MethodSignature:
-                case SyntaxKind.FunctionDeclaration:
-                case SyntaxKind.Constructor:
-                case SyntaxKind.GetAccessor:
-                case SyntaxKind.SetAccessor:
                 case SyntaxKind.FunctionType:
-                case SyntaxKind.JSDocFunctionType:
                 case SyntaxKind.ConstructorType:
+                    return ContainerFlags.IsContainer | ContainerFlags.IsControlFlowContainer | ContainerFlags.HasLocals | ContainerFlags.IsFunctionLike;
+
                 case SyntaxKind.FunctionExpression:
                 case SyntaxKind.ArrowFunction:
-                case SyntaxKind.ModuleDeclaration:
-                case SyntaxKind.SourceFile:
-                case SyntaxKind.TypeAliasDeclaration:
-                    return ContainerFlags.IsContainerWithLocals;
+                    return ContainerFlags.IsContainer | ContainerFlags.IsControlFlowContainer | ContainerFlags.HasLocals | ContainerFlags.IsFunctionLike | ContainerFlags.IsFunctionExpression;
+
+                case SyntaxKind.ModuleBlock:
+                    return ContainerFlags.IsControlFlowContainer;
+                case SyntaxKind.PropertyDeclaration:
+                    return (<PropertyDeclaration>node).initializer ? ContainerFlags.IsControlFlowContainer : 0;
 
                 case SyntaxKind.CatchClause:
                 case SyntaxKind.ForStatement:
@@ -1194,6 +1211,7 @@ namespace ts {
                 case SyntaxKind.ObjectLiteralExpression:
                 case SyntaxKind.InterfaceDeclaration:
                 case SyntaxKind.JSDocRecordType:
+                case SyntaxKind.JSDocTypeLiteral:
                     // Interface/Object-types always have their children added to the 'members' of
                     // their container. They are only accessible through an instance of their
                     // container, and are never in scope otherwise (even inside the body of the
@@ -1222,7 +1240,7 @@ namespace ts {
                     // their container in the tree.  To accomplish this, we simply add their declared
                     // symbol to the 'locals' of the container.  These symbols can then be found as
                     // the type checker walks up the containers, checking them for matching names.
-                    return declareSymbol(container.locals, undefined, node, symbolFlags, symbolExcludes);
+                    return declareSymbol(container.locals, /*parent*/ undefined, node, symbolFlags, symbolExcludes);
             }
         }
 
@@ -1560,15 +1578,9 @@ namespace ts {
             if (!node) {
                 return;
             }
-
             node.parent = parent;
-
-            const savedInStrictMode = inStrictMode;
-            if (!savedInStrictMode) {
-                updateStrictMode(node);
-            }
-
-            // First we bind declaration nodes to a symbol if possible.  We'll both create a symbol
+            const saveInStrictMode = inStrictMode;
+            // First we bind declaration nodes to a symbol if possible. We'll both create a symbol
             // and then potentially add the symbol to an appropriate symbol table. Possible
             // destination symbol tables are:
             //
@@ -1576,47 +1588,40 @@ namespace ts {
             //  2) The 'members' table of the current container's symbol.
             //  3) The 'locals' table of the current container.
             //
-            // However, not all symbols will end up in any of these tables.  'Anonymous' symbols
+            // However, not all symbols will end up in any of these tables. 'Anonymous' symbols
             // (like TypeLiterals for example) will not be put in any table.
             bindWorker(node);
-
-            // Then we recurse into the children of the node to bind them as well.  For certain
-            // symbols we do specialized work when we recurse.  For example, we'll keep track of
-            // the current 'container' node when it changes.  This helps us know which symbol table
-            // a local should go into for example.
-            bindChildren(node);
-
-            inStrictMode = savedInStrictMode;
-        }
-
-        function updateStrictMode(node: Node) {
-            switch (node.kind) {
-                case SyntaxKind.SourceFile:
-                case SyntaxKind.ModuleBlock:
-                    updateStrictModeStatementList((<SourceFile | ModuleBlock>node).statements);
-                    return;
-                case SyntaxKind.Block:
-                    if (isFunctionLike(node.parent)) {
-                        updateStrictModeStatementList((<Block>node).statements);
-                    }
-                    return;
-                case SyntaxKind.ClassDeclaration:
-                case SyntaxKind.ClassExpression:
-                    // All classes are automatically in strict mode in ES6.
-                    inStrictMode = true;
-                    return;
+            // Then we recurse into the children of the node to bind them as well. For certain
+            // symbols we do specialized work when we recurse. For example, we'll keep track of
+            // the current 'container' node when it changes. This helps us know which symbol table
+            // a local should go into for example. Since terminal nodes are known not to have
+            // children, as an optimization we don't process those.
+            if (node.kind > SyntaxKind.LastToken) {
+                const saveParent = parent;
+                parent = node;
+                const containerFlags = getContainerFlags(node);
+                if (containerFlags === ContainerFlags.None) {
+                    bindChildren(node);
+                }
+                else {
+                    bindContainer(node, containerFlags);
+                }
+                parent = saveParent;
             }
+            inStrictMode = saveInStrictMode;
         }
 
         function updateStrictModeStatementList(statements: NodeArray<Statement>) {
-            for (const statement of statements) {
-                if (!isPrologueDirective(statement)) {
-                    return;
-                }
+            if (!inStrictMode) {
+                for (const statement of statements) {
+                    if (!isPrologueDirective(statement)) {
+                        return;
+                    }
 
-                if (isUseStrictPrologueDirective(<ExpressionStatement>statement)) {
-                    inStrictMode = true;
-                    return;
+                    if (isUseStrictPrologueDirective(<ExpressionStatement>statement)) {
+                        inStrictMode = true;
+                        return;
+                    }
                 }
             }
         }
@@ -1696,6 +1701,8 @@ namespace ts {
                 case SyntaxKind.PropertySignature:
                 case SyntaxKind.JSDocRecordMember:
                     return bindPropertyOrMethodOrAccessor(<Declaration>node, SymbolFlags.Property | ((<PropertyDeclaration>node).questionToken ? SymbolFlags.Optional : SymbolFlags.None), SymbolFlags.PropertyExcludes);
+                case SyntaxKind.JSDocPropertyTag:
+                    return bindJSDocProperty(<JSDocPropertyTag>node);
                 case SyntaxKind.PropertyAssignment:
                 case SyntaxKind.ShorthandPropertyAssignment:
                     return bindPropertyOrMethodOrAccessor(<Declaration>node, SymbolFlags.Property, SymbolFlags.PropertyExcludes);
@@ -1703,7 +1710,7 @@ namespace ts {
                     return bindPropertyOrMethodOrAccessor(<Declaration>node, SymbolFlags.EnumMember, SymbolFlags.EnumMemberExcludes);
 
                 case SyntaxKind.JsxSpreadAttribute:
-                    hasJsxSpreadAttribute = true;
+                    emitFlags |= NodeFlags.HasJsxSpreadAttribute;
                     return;
 
                 case SyntaxKind.CallSignature:
@@ -1731,6 +1738,7 @@ namespace ts {
                 case SyntaxKind.JSDocFunctionType:
                     return bindFunctionOrConstructorType(<SignatureDeclaration>node);
                 case SyntaxKind.TypeLiteral:
+                case SyntaxKind.JSDocTypeLiteral:
                 case SyntaxKind.JSDocRecordType:
                     return bindAnonymousDeclaration(<TypeLiteralNode>node, SymbolFlags.TypeLiteral, "__type");
                 case SyntaxKind.ObjectLiteralExpression:
@@ -1748,9 +1756,12 @@ namespace ts {
                 // Members of classes, interfaces, and modules
                 case SyntaxKind.ClassExpression:
                 case SyntaxKind.ClassDeclaration:
+                    // All classes are automatically in strict mode in ES6.
+                    inStrictMode = true;
                     return bindClassLikeDeclaration(<ClassLikeDeclaration>node);
                 case SyntaxKind.InterfaceDeclaration:
                     return bindBlockScopedDeclaration(<Declaration>node, SymbolFlags.Interface, SymbolFlags.InterfaceExcludes);
+                case SyntaxKind.JSDocTypedefTag:
                 case SyntaxKind.TypeAliasDeclaration:
                     return bindBlockScopedDeclaration(<Declaration>node, SymbolFlags.TypeAlias, SymbolFlags.TypeAliasExcludes);
                 case SyntaxKind.EnumDeclaration:
@@ -1773,7 +1784,15 @@ namespace ts {
                 case SyntaxKind.ExportAssignment:
                     return bindExportAssignment(<ExportAssignment>node);
                 case SyntaxKind.SourceFile:
+                    updateStrictModeStatementList((<SourceFile>node).statements);
                     return bindSourceFileIfExternalModule();
+                case SyntaxKind.Block:
+                    if (!isFunctionLike(node.parent)) {
+                        return;
+                    }
+                    // Fall through
+                case SyntaxKind.ModuleBlock:
+                    return updateStrictModeStatementList((<Block | ModuleBlock>node).statements);
             }
         }
 
@@ -1935,10 +1954,10 @@ namespace ts {
         function bindClassLikeDeclaration(node: ClassLikeDeclaration) {
             if (!isDeclarationFile(file) && !isInAmbientContext(node)) {
                 if (getClassExtendsHeritageClauseElement(node) !== undefined) {
-                    hasClassExtends = true;
+                    emitFlags |= NodeFlags.HasClassExtends;
                 }
                 if (nodeIsDecorated(node)) {
-                    hasDecorators = true;
+                    emitFlags |= NodeFlags.HasDecorators;
                 }
             }
 
@@ -2014,8 +2033,7 @@ namespace ts {
             if (!isDeclarationFile(file) &&
                 !isInAmbientContext(node) &&
                 nodeIsDecorated(node)) {
-                hasDecorators = true;
-                hasParameterDecorators = true;
+                emitFlags |= (NodeFlags.HasDecorators | NodeFlags.HasParamDecorators);
             }
 
             if (inStrictMode) {
@@ -2042,7 +2060,7 @@ namespace ts {
         function bindFunctionDeclaration(node: FunctionDeclaration) {
             if (!isDeclarationFile(file) && !isInAmbientContext(node)) {
                 if (isAsyncFunctionLike(node)) {
-                    hasAsyncFunctions = true;
+                    emitFlags |= NodeFlags.HasAsyncFunctions;
                 }
             }
 
@@ -2059,10 +2077,12 @@ namespace ts {
         function bindFunctionExpression(node: FunctionExpression) {
             if (!isDeclarationFile(file) && !isInAmbientContext(node)) {
                 if (isAsyncFunctionLike(node)) {
-                    hasAsyncFunctions = true;
+                    emitFlags |= NodeFlags.HasAsyncFunctions;
                 }
             }
-
+            if (currentFlow) {
+                node.flowNode = currentFlow;
+            }
             checkStrictModeFunctionName(<FunctionExpression>node);
             const bindingName = (<FunctionExpression>node).name ? (<FunctionExpression>node).name.text : "__function";
             return bindAnonymousDeclaration(<FunctionExpression>node, SymbolFlags.Function, bindingName);
@@ -2071,10 +2091,10 @@ namespace ts {
         function bindPropertyOrMethodOrAccessor(node: Declaration, symbolFlags: SymbolFlags, symbolExcludes: SymbolFlags) {
             if (!isDeclarationFile(file) && !isInAmbientContext(node)) {
                 if (isAsyncFunctionLike(node)) {
-                    hasAsyncFunctions = true;
+                    emitFlags |= NodeFlags.HasAsyncFunctions;
                 }
                 if (nodeIsDecorated(node)) {
-                    hasDecorators = true;
+                    emitFlags |= NodeFlags.HasDecorators;
                 }
             }
 
@@ -2083,6 +2103,10 @@ namespace ts {
                 : declareSymbolAndAddToSymbolTable(node, symbolFlags, symbolExcludes);
         }
 
+        function bindJSDocProperty(node: JSDocPropertyTag) {
+            return declareSymbolAndAddToSymbolTable(node, SymbolFlags.Property, SymbolFlags.PropertyExcludes);
+        }
+
         // reachability checks
 
         function shouldReportErrorOnModuleDeclaration(node: ModuleDeclaration): boolean {
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index c87e353e751..b8f078ea9a5 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -110,16 +110,16 @@ namespace ts {
         const unknownSymbol = createSymbol(SymbolFlags.Property | SymbolFlags.Transient, "unknown");
         const resolvingSymbol = createSymbol(SymbolFlags.Transient, "__resolving__");
 
-        const nullableWideningFlags = strictNullChecks ? 0 : TypeFlags.ContainsUndefinedOrNull;
         const anyType = createIntrinsicType(TypeFlags.Any, "any");
         const stringType = createIntrinsicType(TypeFlags.String, "string");
         const numberType = createIntrinsicType(TypeFlags.Number, "number");
         const booleanType = createIntrinsicType(TypeFlags.Boolean, "boolean");
         const esSymbolType = createIntrinsicType(TypeFlags.ESSymbol, "symbol");
         const voidType = createIntrinsicType(TypeFlags.Void, "void");
-        const undefinedType = createIntrinsicType(TypeFlags.Undefined | nullableWideningFlags, "undefined");
-        const nullType = createIntrinsicType(TypeFlags.Null | nullableWideningFlags, "null");
-        const emptyArrayElementType = createIntrinsicType(TypeFlags.Undefined | TypeFlags.ContainsUndefinedOrNull, "undefined");
+        const undefinedType = createIntrinsicType(TypeFlags.Undefined, "undefined");
+        const undefinedWideningType = strictNullChecks ? undefinedType : createIntrinsicType(TypeFlags.Undefined | TypeFlags.ContainsWideningType, "undefined");
+        const nullType = createIntrinsicType(TypeFlags.Null, "null");
+        const nullWideningType = strictNullChecks ? nullType : createIntrinsicType(TypeFlags.Null | TypeFlags.ContainsWideningType, "null");
         const unknownType = createIntrinsicType(TypeFlags.Any, "unknown");
         const neverType = createIntrinsicType(TypeFlags.Never, "never");
 
@@ -3405,7 +3405,7 @@ namespace ts {
                     error(type.symbol.valueDeclaration, Diagnostics._0_is_referenced_directly_or_indirectly_in_its_own_base_expression, symbolToString(type.symbol));
                     return type.resolvedBaseConstructorType = unknownType;
                 }
-                if (baseConstructorType !== unknownType && baseConstructorType !== nullType && !isConstructorType(baseConstructorType)) {
+                if (baseConstructorType !== unknownType && baseConstructorType !== nullWideningType && !isConstructorType(baseConstructorType)) {
                     error(baseTypeNode.expression, Diagnostics.Type_0_is_not_a_constructor_function_type, typeToString(baseConstructorType));
                     return type.resolvedBaseConstructorType = unknownType;
                 }
@@ -3581,8 +3581,22 @@ namespace ts {
                 if (!pushTypeResolution(symbol, TypeSystemPropertyName.DeclaredType)) {
                     return unknownType;
                 }
-                const declaration = <TypeAliasDeclaration>getDeclarationOfKind(symbol, SyntaxKind.TypeAliasDeclaration);
-                let type = getTypeFromTypeNode(declaration.type);
+
+                let type: Type;
+                let declaration: JSDocTypedefTag | TypeAliasDeclaration = <JSDocTypedefTag>getDeclarationOfKind(symbol, SyntaxKind.JSDocTypedefTag);
+                if (declaration) {
+                    if (declaration.jsDocTypeLiteral) {
+                        type = getTypeFromTypeNode(declaration.jsDocTypeLiteral);
+                    }
+                    else {
+                        type = getTypeFromTypeNode(declaration.typeExpression.type);
+                    }
+                }
+                else {
+                    declaration = <TypeAliasDeclaration>getDeclarationOfKind(symbol, SyntaxKind.TypeAliasDeclaration);
+                    type = getTypeFromTypeNode(declaration.type);
+                }
+
                 if (popTypeResolution()) {
                     links.typeParameters = getLocalTypeParametersOfClassOrInterfaceOrTypeAlias(symbol);
                     if (links.typeParameters) {
@@ -4997,6 +5011,7 @@ namespace ts {
             containsAny?: boolean;
             containsUndefined?: boolean;
             containsNull?: boolean;
+            containsNonWideningType?: boolean;
         }
 
         function addTypeToSet(typeSet: TypeSet, type: Type, typeSetKind: TypeFlags) {
@@ -5007,6 +5022,7 @@ namespace ts {
                 if (type.flags & TypeFlags.Any) typeSet.containsAny = true;
                 if (type.flags & TypeFlags.Undefined) typeSet.containsUndefined = true;
                 if (type.flags & TypeFlags.Null) typeSet.containsNull = true;
+                if (!(type.flags & TypeFlags.ContainsWideningType)) typeSet.containsNonWideningType = true;
             }
             else if (type !== neverType && !contains(typeSet, type)) {
                 typeSet.push(type);
@@ -5067,8 +5083,8 @@ namespace ts {
                 removeSubtypes(typeSet);
             }
             if (typeSet.length === 0) {
-                return typeSet.containsNull ? nullType :
-                    typeSet.containsUndefined ? undefinedType :
+                return typeSet.containsNull ? typeSet.containsNonWideningType ? nullType : nullWideningType :
+                    typeSet.containsUndefined ? typeSet.containsNonWideningType ? undefinedType : undefinedWideningType :
                     neverType;
             }
             else if (typeSet.length === 1) {
@@ -5253,6 +5269,7 @@ namespace ts {
                 case SyntaxKind.FunctionType:
                 case SyntaxKind.ConstructorType:
                 case SyntaxKind.TypeLiteral:
+                case SyntaxKind.JSDocTypeLiteral:
                 case SyntaxKind.JSDocFunctionType:
                 case SyntaxKind.JSDocRecordType:
                     return getTypeFromTypeLiteralOrFunctionOrConstructorTypeNode(node);
@@ -5867,7 +5884,7 @@ namespace ts {
                 if (!(target.flags & TypeFlags.Never)) {
                     if (target.flags & TypeFlags.Any || source.flags & TypeFlags.Never) return Ternary.True;
                     if (source.flags & TypeFlags.Undefined) {
-                        if (!strictNullChecks || target.flags & (TypeFlags.Undefined | TypeFlags.Void) || source === emptyArrayElementType) return Ternary.True;
+                        if (!strictNullChecks || target.flags & (TypeFlags.Undefined | TypeFlags.Void)) return Ternary.True;
                     }
                     if (source.flags & TypeFlags.Null) {
                         if (!strictNullChecks || target.flags & TypeFlags.Null) return Ternary.True;
@@ -6957,7 +6974,7 @@ namespace ts {
             if (type.flags & TypeFlags.ObjectLiteral) {
                 for (const p of getPropertiesOfObjectType(type)) {
                     const t = getTypeOfSymbol(p);
-                    if (t.flags & TypeFlags.ContainsUndefinedOrNull) {
+                    if (t.flags & TypeFlags.ContainsWideningType) {
                         if (!reportWideningErrorsInType(t)) {
                             error(p.valueDeclaration, Diagnostics.Object_literal_s_property_0_implicitly_has_an_1_type, p.name, typeToString(getWidenedType(t)));
                         }
@@ -7004,7 +7021,7 @@ namespace ts {
         }
 
         function reportErrorsFromWidening(declaration: Declaration, type: Type) {
-            if (produceDiagnostics && compilerOptions.noImplicitAny && type.flags & TypeFlags.ContainsUndefinedOrNull) {
+            if (produceDiagnostics && compilerOptions.noImplicitAny && type.flags & TypeFlags.ContainsWideningType) {
                 // Report implicit any error within type if possible, otherwise report error on declaration
                 if (!reportWideningErrorsInType(type)) {
                     reportImplicitAnyError(declaration, type);
@@ -7645,7 +7662,7 @@ namespace ts {
                 getInitialTypeOfBindingElement(<BindingElement>node);
         }
 
-        function getFlowTypeOfReference(reference: Node, declaredType: Type, assumeInitialized: boolean) {
+        function getFlowTypeOfReference(reference: Node, declaredType: Type, assumeInitialized: boolean, includeOuterFunctions: boolean) {
             let key: string;
             if (!reference.flowNode || assumeInitialized && !(declaredType.flags & TypeFlags.Narrowable)) {
                 return declaredType;
@@ -7691,15 +7708,21 @@ namespace ts {
                             getTypeAtFlowBranchLabel(<FlowLabel>flow) :
                             getTypeAtFlowLoopLabel(<FlowLabel>flow);
                     }
-                    else if (flow.flags & FlowFlags.Unreachable) {
+                    else if (flow.flags & FlowFlags.Start) {
+                        // Check if we should continue with the control flow of the containing function.
+                        const container = (<FlowStart>flow).container;
+                        if (container && includeOuterFunctions) {
+                            flow = container.flowNode;
+                            continue;
+                        }
+                        // At the top of the flow we have the initial type.
+                        type = initialType;
+                    }
+                    else {
                         // Unreachable code errors are reported in the binding phase. Here we
                         // simply return the declared type to reduce follow-on errors.
                         type = declaredType;
                     }
-                    else {
-                        // At the top of the flow we have the initial type.
-                        type = initialType;
-                    }
                     if (flow.flags & FlowFlags.Shared) {
                         // Record visited node and the associated type in the cache.
                         visitedFlowNodes[visitedFlowCount] = flow;
@@ -8068,6 +8091,17 @@ namespace ts {
             return expression;
         }
 
+        function isDeclarationIncludedInFlow(reference: Node, declaration: Declaration, includeOuterFunctions: boolean) {
+            const declarationContainer = getContainingFunctionOrModule(declaration);
+            let container = getContainingFunctionOrModule(reference);
+            while (container !== declarationContainer &&
+                (container.kind === SyntaxKind.FunctionExpression || container.kind === SyntaxKind.ArrowFunction) &&
+                (includeOuterFunctions || getImmediatelyInvokedFunctionExpression(<FunctionExpression>container))) {
+                container = getContainingFunctionOrModule(container);
+            }
+            return container === declarationContainer;
+        }
+
         function checkIdentifier(node: Identifier): Type {
             const symbol = getResolvedSymbol(node);
 
@@ -8124,10 +8158,11 @@ namespace ts {
                 return type;
             }
             const declaration = localOrExportSymbol.valueDeclaration;
+            const includeOuterFunctions = isReadonlySymbol(localOrExportSymbol);
             const assumeInitialized = !strictNullChecks || (type.flags & TypeFlags.Any) !== 0 || !declaration ||
                 getRootDeclaration(declaration).kind === SyntaxKind.Parameter || isInAmbientContext(declaration) ||
-                getContainingFunctionOrModule(declaration) !== getContainingFunctionOrModule(node);
-            const flowType = getFlowTypeOfReference(node, type, assumeInitialized);
+                !isDeclarationIncludedInFlow(node, declaration, includeOuterFunctions);
+            const flowType = getFlowTypeOfReference(node, type, assumeInitialized, includeOuterFunctions);
             if (!assumeInitialized && !(getNullableKind(type) & TypeFlags.Undefined) && getNullableKind(flowType) & TypeFlags.Undefined) {
                 error(node, Diagnostics.Variable_0_is_used_before_being_assigned, symbolToString(symbol));
                 // Return the declared type to reduce follow-on errors
@@ -8278,7 +8313,7 @@ namespace ts {
             const classInstanceType = <InterfaceType>getDeclaredTypeOfSymbol(classSymbol);
             const baseConstructorType = getBaseConstructorTypeOfClass(classInstanceType);
 
-            return baseConstructorType === nullType;
+            return baseConstructorType === nullWideningType;
         }
 
         function checkThisExpression(node: Node): Type {
@@ -8376,7 +8411,7 @@ namespace ts {
             if (isClassLike(container.parent)) {
                 const symbol = getSymbolOfNode(container.parent);
                 const type = container.flags & NodeFlags.Static ? getTypeOfSymbol(symbol) : (<InterfaceType>getDeclaredTypeOfSymbol(symbol)).thisType;
-                return getFlowTypeOfReference(node, type, /*assumeInitialized*/ true);
+                return getFlowTypeOfReference(node, type, /*assumeInitialized*/ true, /*includeOuterFunctions*/ true);
             }
 
             if (isInJavaScriptFile(node)) {
@@ -8661,20 +8696,6 @@ namespace ts {
             return undefined;
         }
 
-        function getImmediatelyInvokedFunctionExpression(func: FunctionExpression | MethodDeclaration) {
-            if (isFunctionExpressionOrArrowFunction(func)) {
-                let prev: Node = func;
-                let parent: Node = func.parent;
-                while (parent.kind === SyntaxKind.ParenthesizedExpression) {
-                    prev = parent;
-                    parent = parent.parent;
-                }
-                if (parent.kind === SyntaxKind.CallExpression && (parent as CallExpression).expression === prev) {
-                    return parent as CallExpression;
-                }
-            }
-        }
-
         // In a variable, parameter or property declaration with a type annotation,
         //   the contextual type of an initializer expression is the type of the variable, parameter or property.
         // Otherwise, in a parameter declaration of a contextually typed function expression,
@@ -9183,7 +9204,7 @@ namespace ts {
                     }
                 }
             }
-            return createArrayType(elementTypes.length ? getUnionType(elementTypes) : emptyArrayElementType);
+            return createArrayType(elementTypes.length ? getUnionType(elementTypes) : strictNullChecks ? neverType : undefinedWideningType);
         }
 
         function isNumericName(name: DeclarationName): boolean {
@@ -9988,7 +10009,7 @@ namespace ts {
                     return propType;
                 }
             }
-            return getFlowTypeOfReference(node, propType, /*assumeInitialized*/ true);
+            return getFlowTypeOfReference(node, propType, /*assumeInitialized*/ true, /*includeOuterFunctions*/ false);
         }
 
         function isValidPropertyAccess(node: PropertyAccessExpression | QualifiedName, propertyName: string): boolean {
@@ -11983,7 +12004,7 @@ namespace ts {
 
         function checkVoidExpression(node: VoidExpression): Type {
             checkExpression(node.expression);
-            return undefinedType;
+            return undefinedWideningType;
         }
 
         function checkAwaitExpression(node: AwaitExpression): Type {
@@ -12390,7 +12411,7 @@ namespace ts {
                 case SyntaxKind.InKeyword:
                     return checkInExpression(left, right, leftType, rightType);
                 case SyntaxKind.AmpersandAmpersandToken:
-                    return addNullableKind(rightType, getNullableKind(leftType));
+                    return strictNullChecks ? addNullableKind(rightType, getNullableKind(leftType)) : rightType;
                 case SyntaxKind.BarBarToken:
                     return getUnionType([getNonNullableType(leftType), rightType]);
                 case SyntaxKind.EqualsToken:
@@ -12657,7 +12678,7 @@ namespace ts {
                 case SyntaxKind.SuperKeyword:
                     return checkSuperExpression(node);
                 case SyntaxKind.NullKeyword:
-                    return nullType;
+                    return nullWideningType;
                 case SyntaxKind.TrueKeyword:
                 case SyntaxKind.FalseKeyword:
                     return booleanType;
@@ -12715,7 +12736,7 @@ namespace ts {
                 case SyntaxKind.SpreadElementExpression:
                     return checkSpreadElementExpression(<SpreadElementExpression>node, contextualMapper);
                 case SyntaxKind.OmittedExpression:
-                    return undefinedType;
+                    return undefinedWideningType;
                 case SyntaxKind.YieldExpression:
                     return checkYieldExpression(<YieldExpression>node);
                 case SyntaxKind.JsxExpression:
@@ -16724,7 +16745,7 @@ namespace ts {
                 node = node.parent;
             }
 
-            return node.parent && node.parent.kind === SyntaxKind.TypeReference;
+            return node.parent && (node.parent.kind === SyntaxKind.TypeReference || node.parent.kind === SyntaxKind.JSDocTypeReference) ;
         }
 
         function isHeritageClauseElementIdentifier(entityName: Node): boolean {
@@ -16860,7 +16881,7 @@ namespace ts {
                 }
             }
             else if (isTypeReferenceIdentifier(<EntityName>entityName)) {
-                let meaning = entityName.parent.kind === SyntaxKind.TypeReference ? SymbolFlags.Type : SymbolFlags.Namespace;
+                let meaning = (entityName.parent.kind === SyntaxKind.TypeReference || entityName.parent.kind === SyntaxKind.JSDocTypeReference) ? SymbolFlags.Type : SymbolFlags.Namespace;
                 // Include aliases in the meaning, this ensures that we do not follow aliases to where they point and instead
                 // return the alias symbol.
                 meaning |= SymbolFlags.Alias;
@@ -17629,7 +17650,7 @@ namespace ts {
             // Setup global builtins
             addToSymbolTable(globals, builtinGlobals, Diagnostics.Declaration_name_conflicts_with_built_in_global_identifier_0);
 
-            getSymbolLinks(undefinedSymbol).type = undefinedType;
+            getSymbolLinks(undefinedSymbol).type = undefinedWideningType;
             getSymbolLinks(argumentsSymbol).type = getGlobalType("IArguments");
             getSymbolLinks(unknownSymbol).type = unknownType;
 
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index af8dd8ceb69..034bd27b147 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -819,6 +819,10 @@
         "category": "Error",
         "code": 1252
     },
+    "'{0}' tag cannot be used independently as a top level JSDoc tag.": {
+        "category": "Error",
+        "code": 1253
+    },
     "'with' statements are not allowed in an async function block.": {
         "category": "Error",
         "code": 1300
diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index 2672efb647c..b24dd85f2f0 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -401,6 +401,15 @@ namespace ts {
                 return visitNode(cbNode, (<JSDocTypeTag>node).typeExpression);
             case SyntaxKind.JSDocTemplateTag:
                 return visitNodes(cbNodes, (<JSDocTemplateTag>node).typeParameters);
+            case SyntaxKind.JSDocTypedefTag:
+                return visitNode(cbNode, (<JSDocTypedefTag>node).typeExpression) ||
+                    visitNode(cbNode, (<JSDocTypedefTag>node).name) ||
+                    visitNode(cbNode, (<JSDocTypedefTag>node).jsDocTypeLiteral);
+            case SyntaxKind.JSDocTypeLiteral:
+                return visitNodes(cbNodes, (<JSDocTypeLiteral>node).jsDocPropertyTags);
+            case SyntaxKind.JSDocPropertyTag:
+                return visitNode(cbNode, (<JSDocPropertyTag>node).typeExpression) ||
+                    visitNode(cbNode, (<JSDocPropertyTag>node).name);
         }
     }
 
@@ -431,7 +440,14 @@ namespace ts {
 
     /* @internal */
     export function parseIsolatedJSDocComment(content: string, start?: number, length?: number) {
-        return Parser.JSDocParser.parseIsolatedJSDocComment(content, start, length);
+        const result = Parser.JSDocParser.parseIsolatedJSDocComment(content, start, length);
+        if (result && result.jsDocComment) {
+            // because the jsDocComment was parsed out of the source file, it might
+            // not be covered by the fixupParentReferences.
+            Parser.fixupParentReferences(result.jsDocComment);
+        }
+
+        return result;
     }
 
     /* @internal */
@@ -628,9 +644,14 @@ namespace ts {
                 if (comments) {
                     for (const comment of comments) {
                         const jsDocComment = JSDocParser.parseJSDocComment(node, comment.pos, comment.end - comment.pos);
-                        if (jsDocComment) {
-                            node.jsDocComment = jsDocComment;
+                        if (!jsDocComment) {
+                            continue;
                         }
+
+                        if (!node.jsDocComments) {
+                            node.jsDocComments = [];
+                        }
+                        node.jsDocComments.push(jsDocComment);
                     }
                 }
             }
@@ -638,14 +659,14 @@ namespace ts {
             return node;
         }
 
-        export function fixupParentReferences(sourceFile: Node) {
+        export function fixupParentReferences(rootNode: Node) {
             // normally parent references are set during binding. However, for clients that only need
             // a syntax tree, and no semantic features, then the binding process is an unnecessary
             // overhead.  This functions allows us to set all the parents, without all the expense of
             // binding.
 
-            let parent: Node = sourceFile;
-            forEachChild(sourceFile, visitNode);
+            let parent: Node = rootNode;
+            forEachChild(rootNode, visitNode);
             return;
 
             function visitNode(n: Node): void {
@@ -658,6 +679,13 @@ namespace ts {
                     const saveParent = parent;
                     parent = n;
                     forEachChild(n, visitNode);
+                    if (n.jsDocComments) {
+                        for (const jsDocComment of n.jsDocComments) {
+                            jsDocComment.parent = n;
+                            parent = jsDocComment;
+                            forEachChild(jsDocComment, visitNode);
+                        }
+                    }
                     parent = saveParent;
                 }
             }
@@ -2704,7 +2732,7 @@ namespace ts {
             //      1) async[no LineTerminator here]AsyncArrowBindingIdentifier[?Yield][no LineTerminator here]=>AsyncConciseBody[?In]
             //      2) CoverCallExpressionAndAsyncArrowHead[?Yield, ?Await][no LineTerminator here]=>AsyncConciseBody[?In]
             // Production (1) of AsyncArrowFunctionExpression is parsed in "tryParseAsyncSimpleArrowFunctionExpression".
-            // And production (2) is parsed in "tryParseParenthesizedArrowFunctionExpression". 
+            // And production (2) is parsed in "tryParseParenthesizedArrowFunctionExpression".
             //
             // If we do successfully parse arrow-function, we must *not* recurse for productions 1, 2 or 3. An ArrowFunction is
             // not a  LeftHandSideExpression, nor does it start a ConditionalExpression.  So we are done
@@ -3396,8 +3424,8 @@ namespace ts {
                     if (sourceFile.languageVariant !== LanguageVariant.JSX) {
                         return false;
                     }
-                    // We are in JSX context and the token is part of JSXElement.
-                    // Fall through
+                // We are in JSX context and the token is part of JSXElement.
+                // Fall through
                 default:
                     return true;
             }
@@ -4099,9 +4127,9 @@ namespace ts {
             const isAsync = !!(node.flags & NodeFlags.Async);
             node.name =
                 isGenerator && isAsync ? doInYieldAndAwaitContext(parseOptionalIdentifier) :
-                isGenerator ? doInYieldContext(parseOptionalIdentifier) :
-                isAsync ? doInAwaitContext(parseOptionalIdentifier) :
-                parseOptionalIdentifier();
+                    isGenerator ? doInYieldContext(parseOptionalIdentifier) :
+                        isAsync ? doInAwaitContext(parseOptionalIdentifier) :
+                            parseOptionalIdentifier();
 
             fillSignature(SyntaxKind.ColonToken, /*yieldContext*/ isGenerator, /*awaitContext*/ isAsync, /*requireCompleteParameterList*/ false, node);
             node.body = parseFunctionBlock(/*allowYield*/ isGenerator, /*allowAwait*/ isAsync, /*ignoreMissingOpenBrace*/ false);
@@ -5891,7 +5919,7 @@ namespace ts {
             }
 
             function checkForEmptyTypeArgumentList(typeArguments: NodeArray<Node>) {
-                if (parseDiagnostics.length === 0 &&  typeArguments && typeArguments.length === 0) {
+                if (parseDiagnostics.length === 0 && typeArguments && typeArguments.length === 0) {
                     const start = typeArguments.pos - "<".length;
                     const end = skipTrivia(sourceText, typeArguments.end) + ">".length;
                     return parseErrorAtPosition(start, end - start, Diagnostics.Type_argument_list_cannot_be_empty);
@@ -6052,7 +6080,6 @@ namespace ts {
                 Debug.assert(end <= content.length);
 
                 let tags: NodeArray<JSDocTag>;
-
                 let result: JSDocComment;
 
                 // Check for /** (JSDoc opening part)
@@ -6159,6 +6186,8 @@ namespace ts {
                                 return handleTemplateTag(atToken, tagName);
                             case "type":
                                 return handleTypeTag(atToken, tagName);
+                            case "typedef":
+                                return handleTypedefTag(atToken, tagName);
                         }
                     }
 
@@ -6266,6 +6295,122 @@ namespace ts {
                     return finishNode(result);
                 }
 
+                function handlePropertyTag(atToken: Node, tagName: Identifier): JSDocPropertyTag {
+                    const typeExpression = tryParseTypeExpression();
+                    skipWhitespace();
+                    const name = parseJSDocIdentifierName();
+                    if (!name) {
+                        parseErrorAtPosition(scanner.getStartPos(), /*length*/ 0, Diagnostics.Identifier_expected);
+                        return undefined;
+                    }
+
+                    const result = <JSDocPropertyTag>createNode(SyntaxKind.JSDocPropertyTag, atToken.pos);
+                    result.atToken = atToken;
+                    result.tagName = tagName;
+                    result.name = name;
+                    result.typeExpression = typeExpression;
+                    return finishNode(result);
+                }
+
+                function handleTypedefTag(atToken: Node, tagName: Identifier): JSDocTypedefTag {
+                    const typeExpression = tryParseTypeExpression();
+                    skipWhitespace();
+
+                    const typedefTag = <JSDocTypedefTag>createNode(SyntaxKind.JSDocTypedefTag, atToken.pos);
+                    typedefTag.atToken = atToken;
+                    typedefTag.tagName = tagName;
+                    typedefTag.name = parseJSDocIdentifierName();
+                    typedefTag.typeExpression = typeExpression;
+
+                    if (typeExpression) {
+                        if (typeExpression.type.kind === SyntaxKind.JSDocTypeReference) {
+                            const jsDocTypeReference = <JSDocTypeReference>typeExpression.type;
+                            if (jsDocTypeReference.name.kind === SyntaxKind.Identifier) {
+                                const name = <Identifier>jsDocTypeReference.name;
+                                if (name.text === "Object") {
+                                    typedefTag.jsDocTypeLiteral = scanChildTags();
+                                }
+                            }
+                        }
+                        if (!typedefTag.jsDocTypeLiteral) {
+                            typedefTag.jsDocTypeLiteral = typeExpression.type;
+                        }
+                    }
+                    else {
+                        typedefTag.jsDocTypeLiteral = scanChildTags();
+                    }
+
+                    return finishNode(typedefTag);
+
+                    function scanChildTags(): JSDocTypeLiteral {
+                        const jsDocTypeLiteral = <JSDocTypeLiteral>createNode(SyntaxKind.JSDocTypeLiteral, scanner.getStartPos());
+                        let resumePos = scanner.getStartPos();
+                        let canParseTag = true;
+                        let seenAsterisk = false;
+                        let parentTagTerminated = false;
+
+                        while (token !== SyntaxKind.EndOfFileToken && !parentTagTerminated) {
+                            nextJSDocToken();
+                            switch (token) {
+                                case SyntaxKind.AtToken:
+                                    if (canParseTag) {
+                                        parentTagTerminated = !tryParseChildTag(jsDocTypeLiteral);
+                                    }
+                                    seenAsterisk = false;
+                                    break;
+                                case SyntaxKind.NewLineTrivia:
+                                    resumePos = scanner.getStartPos() - 1;
+                                    canParseTag = true;
+                                    seenAsterisk = false;
+                                    break;
+                                case SyntaxKind.AsteriskToken:
+                                    if (seenAsterisk) {
+                                        canParseTag = false;
+                                    }
+                                    seenAsterisk = true;
+                                    break;
+                                case SyntaxKind.Identifier:
+                                    canParseTag = false;
+                                case SyntaxKind.EndOfFileToken:
+                                    break;
+                            }
+                        }
+                        scanner.setTextPos(resumePos);
+                        return finishNode(jsDocTypeLiteral);
+                    }
+                }
+
+                function tryParseChildTag(parentTag: JSDocTypeLiteral): boolean {
+                    Debug.assert(token === SyntaxKind.AtToken);
+                    const atToken = createNode(SyntaxKind.AtToken, scanner.getStartPos());
+                    atToken.end = scanner.getTextPos();
+                    nextJSDocToken();
+
+                    const tagName = parseJSDocIdentifierName();
+                    if (!tagName) {
+                        return false;
+                    }
+
+                    switch (tagName.text) {
+                        case "type":
+                            if (parentTag.jsDocTypeTag) {
+                                // already has a @type tag, terminate the parent tag now.
+                                return false;
+                            }
+                            parentTag.jsDocTypeTag = handleTypeTag(atToken, tagName);
+                            return true;
+                        case "prop":
+                        case "property":
+                            if (!parentTag.jsDocPropertyTags) {
+                                parentTag.jsDocPropertyTags = <NodeArray<JSDocPropertyTag>>[];
+                            }
+                            const propertyTag = handlePropertyTag(atToken, tagName);
+                            parentTag.jsDocPropertyTags.push(propertyTag);
+                            return true;
+                    }
+                    return false;
+                }
+
                 function handleTemplateTag(atToken: Node, tagName: Identifier): JSDocTemplateTag {
                     if (forEach(tags, t => t.kind === SyntaxKind.JSDocTemplateTag)) {
                         parseErrorAtPosition(tagName.pos, scanner.getTokenPos() - tagName.pos, Diagnostics._0_tag_already_specified, tagName.text);
@@ -6435,10 +6580,6 @@ namespace ts {
                     node._children = undefined;
                 }
 
-                if (node.jsDocComment) {
-                    node.jsDocComment = undefined;
-                }
-
                 node.pos += delta;
                 node.end += delta;
 
@@ -6447,6 +6588,11 @@ namespace ts {
                 }
 
                 forEachChild(node, visitNode, visitArray);
+                if (node.jsDocComments) {
+                    for (const jsDocComment of node.jsDocComments) {
+                        forEachChild(jsDocComment, visitNode, visitArray);
+                    }
+                }
                 checkNodePositions(node, aggressiveChecks);
             }
 
diff --git a/src/compiler/scanner.ts b/src/compiler/scanner.ts
index 1a2748b38b1..82359eacc3e 100644
--- a/src/compiler/scanner.ts
+++ b/src/compiler/scanner.ts
@@ -434,7 +434,7 @@ namespace ts {
       }
 
       /* @internal */
-      export function skipTrivia(text: string, pos: number, stopAfterLineBreak?: boolean): number {
+      export function skipTrivia(text: string, pos: number, stopAfterLineBreak?: boolean, stopAtComments = false): number {
           // Using ! with a greater than test is a fast way of testing the following conditions:
           //  pos === undefined || pos === null || isNaN(pos) || pos < 0;
           if (!(pos >= 0)) {
@@ -462,6 +462,9 @@ namespace ts {
                       pos++;
                       continue;
                   case CharacterCodes.slash:
+                      if (stopAtComments) {
+                          break;
+                      }
                       if (text.charCodeAt(pos + 1) === CharacterCodes.slash) {
                           pos += 2;
                           while (pos < text.length) {
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 7613c489920..4c0e7a036db 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -343,6 +343,9 @@ namespace ts {
         JSDocReturnTag,
         JSDocTypeTag,
         JSDocTemplateTag,
+        JSDocTypedefTag,
+        JSDocPropertyTag,
+        JSDocTypeLiteral,
 
         // Synthesized list
         SyntaxList,
@@ -372,6 +375,10 @@ namespace ts {
         FirstBinaryOperator = LessThanToken,
         LastBinaryOperator = CaretEqualsToken,
         FirstNode = QualifiedName,
+        FirstJSDocNode = JSDocTypeExpression,
+        LastJSDocNode = JSDocTypeLiteral,
+        FirstJSDocTagNode = JSDocComment,
+        LastJSDocTagNode = JSDocTypeLiteral
     }
 
     export const enum NodeFlags {
@@ -416,6 +423,7 @@ namespace ts {
 
         ReachabilityCheckFlags = HasImplicitReturn | HasExplicitReturn,
         EmitHelperFlags = HasClassExtends | HasDecorators | HasParamDecorators | HasAsyncFunctions,
+        ReachabilityAndEmitFlags = ReachabilityCheckFlags | EmitHelperFlags,
 
         // Parsing context flags
         ContextFlags = DisallowInContext | YieldContext | DecoratorContext | AwaitContext | JavaScriptFile,
@@ -448,7 +456,7 @@ namespace ts {
         modifiers?: ModifiersArray;                     // Array of modifiers
         /* @internal */ id?: number;                    // Unique id (used to look up NodeLinks)
         parent?: Node;                                  // Parent node (initialized by binding
-        /* @internal */ jsDocComment?: JSDocComment;    // JSDoc for the node, if it has any.  Only for .js files.
+        /* @internal */ jsDocComments?: JSDocComment[]; // JSDoc for the node, if it has any.  Only for .js files.
         /* @internal */ symbol?: Symbol;                // Symbol declared by node (initialized by binding)
         /* @internal */ locals?: SymbolTable;           // Locals associated with node (initialized by binding)
         /* @internal */ nextContainer?: Node;           // Next container in declaration order (initialized by binding)
@@ -612,6 +620,7 @@ namespace ts {
     // SyntaxKind.PropertyAssignment
     // SyntaxKind.ShorthandPropertyAssignment
     // SyntaxKind.EnumMember
+    // SyntaxKind.JSDocPropertyTag
     export interface VariableLikeDeclaration extends Declaration {
         propertyName?: PropertyName;
         dotDotDotToken?: Node;
@@ -1510,6 +1519,25 @@ namespace ts {
         typeExpression: JSDocTypeExpression;
     }
 
+    // @kind(SyntaxKind.JSDocTypedefTag)
+    export interface JSDocTypedefTag extends JSDocTag, Declaration {
+        name?: Identifier;
+        typeExpression?: JSDocTypeExpression;
+        jsDocTypeLiteral?: JSDocTypeLiteral;
+    }
+
+    // @kind(SyntaxKind.JSDocPropertyTag)
+    export interface JSDocPropertyTag extends JSDocTag, TypeElement {
+        name: Identifier;
+        typeExpression: JSDocTypeExpression;
+    }
+
+    // @kind(SyntaxKind.JSDocTypeLiteral)
+    export interface JSDocTypeLiteral extends JSDocType {
+        jsDocPropertyTags?: NodeArray<JSDocPropertyTag>;
+        jsDocTypeTag?: JSDocTypeTag;
+    }
+
     // @kind(SyntaxKind.JSDocParameterTag)
     export interface JSDocParameterTag extends JSDocTag {
         preParameterName?: Identifier;
@@ -1537,6 +1565,13 @@ namespace ts {
         id?: number;     // Node id used by flow type cache in checker
     }
 
+    // FlowStart represents the start of a control flow. For a function expression or arrow
+    // function, the container property references the function (which in turn has a flowNode
+    // property for the containing control flow).
+    export interface FlowStart extends FlowNode {
+        container?: FunctionExpression | ArrowFunction;
+    }
+
     // FlowLabel represents a junction with multiple possible preceding control flows.
     export interface FlowLabel extends FlowNode {
         antecedents: FlowNode[];
@@ -2162,7 +2197,7 @@ namespace ts {
         /* @internal */
         FreshObjectLiteral      = 0x00100000,  // Fresh object literal type
         /* @internal */
-        ContainsUndefinedOrNull = 0x00200000,  // Type is or contains undefined or null type
+        ContainsWideningType    = 0x00200000,  // Type is or contains undefined or null widening type
         /* @internal */
         ContainsObjectLiteral   = 0x00400000,  // Type is or contains object literal type
         /* @internal */
@@ -2185,9 +2220,9 @@ namespace ts {
         StructuredType = ObjectType | Union | Intersection,
         Narrowable = Any | ObjectType | Union | TypeParameter,
         /* @internal */
-        RequiresWidening = ContainsUndefinedOrNull | ContainsObjectLiteral,
+        RequiresWidening = ContainsWideningType | ContainsObjectLiteral,
         /* @internal */
-        PropagatingFlags = ContainsUndefinedOrNull | ContainsObjectLiteral | ContainsAnyFunctionType
+        PropagatingFlags = ContainsWideningType | ContainsObjectLiteral | ContainsAnyFunctionType
     }
 
     export type DestructuringPattern = BindingPattern | ObjectLiteralExpression | ArrayLiteralExpression;
@@ -2875,4 +2910,9 @@ namespace ts {
 
         /* @internal */ reattachFileDiagnostics(newFile: SourceFile): void;
     }
+
+    // SyntaxKind.SyntaxList
+    export interface SyntaxList extends Node {
+        _children: Node[];
+    }
 }
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index 7969389d788..74ea3459b23 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -287,16 +287,36 @@ namespace ts {
         return !nodeIsMissing(node);
     }
 
-    export function getTokenPosOfNode(node: Node, sourceFile?: SourceFile): number {
+    export function getTokenPosOfNode(node: Node, sourceFile?: SourceFile, includeJsDocComment?: boolean): number {
         // With nodes that have no width (i.e. 'Missing' nodes), we actually *don't*
         // want to skip trivia because this will launch us forward to the next token.
         if (nodeIsMissing(node)) {
             return node.pos;
         }
 
+        if (isJSDocNode(node)) {
+            return skipTrivia((sourceFile || getSourceFileOfNode(node)).text, node.pos, /*stopAfterLineBreak*/ false, /*stopAtComments*/ true);
+        }
+
+        if (includeJsDocComment && node.jsDocComments && node.jsDocComments.length > 0) {
+            return getTokenPosOfNode(node.jsDocComments[0]);
+        }
+
+        // For a syntax list, it is possible that one of its children has JSDocComment nodes, while 
+        // the syntax list itself considers them as normal trivia. Therefore if we simply skip 
+        // trivia for the list, we may have skipped the JSDocComment as well. So we should process its
+        // first child to determine the actual position of its first token.
+        if (node.kind === SyntaxKind.SyntaxList && (<SyntaxList>node)._children.length > 0) {
+            return getTokenPosOfNode((<SyntaxList>node)._children[0], sourceFile, includeJsDocComment);
+        }
+
         return skipTrivia((sourceFile || getSourceFileOfNode(node)).text, node.pos);
     }
 
+    export function isJSDocNode(node: Node) {
+        return node.kind >= SyntaxKind.FirstJSDocNode && node.kind <= SyntaxKind.LastJSDocNode;
+    }
+
     export function getNonDecoratorTokenPosOfNode(node: Node, sourceFile?: SourceFile): number {
         if (nodeIsMissing(node) || !node.decorators) {
             return getTokenPosOfNode(node, sourceFile);
@@ -987,6 +1007,20 @@ namespace ts {
         }
     }
 
+    export function getImmediatelyInvokedFunctionExpression(func: Node): CallExpression {
+        if (func.kind === SyntaxKind.FunctionExpression || func.kind === SyntaxKind.ArrowFunction) {
+            let prev = func;
+            let parent = func.parent;
+            while (parent.kind === SyntaxKind.ParenthesizedExpression) {
+                prev = parent;
+                parent = parent.parent;
+            }
+            if (parent.kind === SyntaxKind.CallExpression && (parent as CallExpression).expression === prev) {
+                return parent as CallExpression;
+            }
+        }
+    }
+
     /**
      * Determines whether a node is a property or element access expression for super.
      */
@@ -1322,21 +1356,23 @@ namespace ts {
             return undefined;
         }
 
-        const jsDocComment = getJSDocComment(node, checkParentVariableStatement);
-        if (!jsDocComment) {
+        const jsDocComments = getJSDocComments(node, checkParentVariableStatement);
+        if (!jsDocComments) {
             return undefined;
         }
 
-        for (const tag of jsDocComment.tags) {
-            if (tag.kind === kind) {
-                return tag;
+        for (const jsDocComment of jsDocComments) {
+            for (const tag of jsDocComment.tags) {
+                if (tag.kind === kind) {
+                    return tag;
+                }
             }
         }
     }
 
-    function getJSDocComment(node: Node, checkParentVariableStatement: boolean): JSDocComment {
-        if (node.jsDocComment) {
-            return node.jsDocComment;
+    function getJSDocComments(node: Node, checkParentVariableStatement: boolean): JSDocComment[] {
+        if (node.jsDocComments) {
+            return node.jsDocComments;
         }
         // Try to recognize this pattern when node is initializer of variable declaration and JSDoc comments are on containing variable statement.
         // /**
@@ -1352,7 +1388,7 @@ namespace ts {
 
             const variableStatementNode = isInitializerOfVariableDeclarationInStatement ? node.parent.parent.parent : undefined;
             if (variableStatementNode) {
-                return variableStatementNode.jsDocComment;
+                return variableStatementNode.jsDocComments;
             }
 
             // Also recognize when the node is the RHS of an assignment expression
@@ -1363,12 +1399,12 @@ namespace ts {
                 (parent as BinaryExpression).operatorToken.kind === SyntaxKind.EqualsToken &&
                 parent.parent.kind === SyntaxKind.ExpressionStatement;
             if (isSourceOfAssignmentExpressionStatement) {
-                return parent.parent.jsDocComment;
+                return parent.parent.jsDocComments;
             }
 
             const isPropertyAssignmentExpression = parent && parent.kind === SyntaxKind.PropertyAssignment;
             if (isPropertyAssignmentExpression) {
-                return parent.jsDocComment;
+                return parent.jsDocComments;
             }
         }
 
@@ -1393,14 +1429,16 @@ namespace ts {
             // annotation.
             const parameterName = (<Identifier>parameter.name).text;
 
-            const jsDocComment = getJSDocComment(parameter.parent, /*checkParentVariableStatement*/ true);
-            if (jsDocComment) {
-                for (const tag of jsDocComment.tags) {
-                    if (tag.kind === SyntaxKind.JSDocParameterTag) {
-                        const parameterTag = <JSDocParameterTag>tag;
-                        const name = parameterTag.preParameterName || parameterTag.postParameterName;
-                        if (name.text === parameterName) {
-                            return parameterTag;
+            const jsDocComments = getJSDocComments(parameter.parent, /*checkParentVariableStatement*/ true);
+            if (jsDocComments) {
+                for (const jsDocComment of jsDocComments) {
+                    for (const tag of jsDocComment.tags) {
+                        if (tag.kind === SyntaxKind.JSDocParameterTag) {
+                            const parameterTag = <JSDocParameterTag>tag;
+                            const name = parameterTag.preParameterName || parameterTag.postParameterName;
+                            if (name.text === parameterName) {
+                                return parameterTag;
+                            }
                         }
                     }
                 }
@@ -1525,6 +1563,7 @@ namespace ts {
             case SyntaxKind.TypeAliasDeclaration:
             case SyntaxKind.TypeParameter:
             case SyntaxKind.VariableDeclaration:
+            case SyntaxKind.JSDocTypedefTag:
                 return true;
         }
         return false;
diff --git a/src/harness/fourslash.ts b/src/harness/fourslash.ts
index 4a756ab3b1e..bd556c659c7 100644
--- a/src/harness/fourslash.ts
+++ b/src/harness/fourslash.ts
@@ -1486,6 +1486,12 @@ namespace FourSlash {
             this.fixCaretPosition();
         }
 
+        public formatOnType(pos: number, key: string) {
+            const edits = this.languageService.getFormattingEditsAfterKeystroke(this.activeFile.fileName, pos, key, this.formatCodeOptions);
+            this.currentCaretPosition += this.applyEdits(this.activeFile.fileName, edits, /*isFormattingEdit*/ true);
+            this.fixCaretPosition();
+        }
+
         private updateMarkersForEdit(fileName: string, minChar: number, limChar: number, text: string) {
             for (let i = 0; i < this.testData.markers.length; i++) {
                 const marker = this.testData.markers[i];
@@ -3223,6 +3229,10 @@ namespace FourSlashInterface {
             this.state.formatSelection(this.state.getMarkerByName(startMarker).position, this.state.getMarkerByName(endMarker).position);
         }
 
+        public onType(posMarker: string, key: string) {
+            this.state.formatOnType(this.state.getMarkerByName(posMarker).position, key);
+        }
+
         public setOption(name: string, value: number): void;
         public setOption(name: string, value: string): void;
         public setOption(name: string, value: boolean): void;
diff --git a/src/harness/harness.ts b/src/harness/harness.ts
index d6959c2a54f..5fe5b84ac91 100644
--- a/src/harness/harness.ts
+++ b/src/harness/harness.ts
@@ -1,7 +1,7 @@
 
 //
 // Copyright (c) Microsoft Corporation.  All rights reserved.
-// 
+//
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
@@ -221,6 +221,19 @@ namespace Utils {
                 return k;
             }
 
+            // For some markers in SyntaxKind, we should print its original syntax name instead of
+            // the marker name in tests.
+            if (k === (<any>ts).SyntaxKind.FirstJSDocNode ||
+                k === (<any>ts).SyntaxKind.LastJSDocNode ||
+                k === (<any>ts).SyntaxKind.FirstJSDocTagNode ||
+                k === (<any>ts).SyntaxKind.LastJSDocTagNode) {
+                for (const kindName in (<any>ts).SyntaxKind) {
+                    if ((<any>ts).SyntaxKind[kindName] === k) {
+                        return kindName;
+                    }
+                }
+            }
+
             return (<any>ts).SyntaxKind[k];
         }
 
@@ -350,7 +363,7 @@ namespace Utils {
         assert.equal(node1.end, node2.end, "node1.end !== node2.end");
         assert.equal(node1.kind, node2.kind, "node1.kind !== node2.kind");
 
-        // call this on both nodes to ensure all propagated flags have been set (and thus can be 
+        // call this on both nodes to ensure all propagated flags have been set (and thus can be
         // compared).
         assert.equal(ts.containsParseError(node1), ts.containsParseError(node2));
         assert.equal(node1.flags, node2.flags, "node1.flags !== node2.flags");
@@ -751,7 +764,7 @@ namespace Harness {
         (emittedFile: string, emittedLine: number, emittedColumn: number, sourceFile: string, sourceLine: number, sourceColumn: number, sourceName: string): void;
     }
 
-    // Settings 
+    // Settings
     export let userSpecifiedRoot = "";
     export let lightMode = false;
 
@@ -790,7 +803,7 @@ namespace Harness {
             fileName: string,
             sourceText: string,
             languageVersion: ts.ScriptTarget) {
-            // We'll only assert invariants outside of light mode. 
+            // We'll only assert invariants outside of light mode.
             const shouldAssertInvariants = !Harness.lightMode;
 
             // Only set the parent nodes if we're asserting invariants.  We don't need them otherwise.
@@ -935,7 +948,7 @@ namespace Harness {
             libFiles?: string;
         }
 
-        // Additional options not already in ts.optionDeclarations 
+        // Additional options not already in ts.optionDeclarations
         const harnessOptionDeclarations: ts.CommandLineOption[] = [
             { name: "allowNonTsExtensions", type: "boolean" },
             { name: "useCaseSensitiveFileNames", type: "boolean" },
@@ -1187,7 +1200,7 @@ namespace Harness {
                 errLines.forEach(e => outputLines.push(e));
 
                 // do not count errors from lib.d.ts here, they are computed separately as numLibraryDiagnostics
-                // if lib.d.ts is explicitly included in input files and there are some errors in it (i.e. because of duplicate identifiers) 
+                // if lib.d.ts is explicitly included in input files and there are some errors in it (i.e. because of duplicate identifiers)
                 // then they will be added twice thus triggering 'total errors' assertion with condition
                 // 'totalErrorsReportedInNonLibraryFiles + numLibraryDiagnostics + numTest262HarnessDiagnostics, diagnostics.length
 
@@ -1497,7 +1510,7 @@ namespace Harness {
             };
             testUnitData.push(newTestFile2);
 
-            // unit tests always list files explicitly 
+            // unit tests always list files explicitly
             const parseConfigHost: ts.ParseConfigHost = {
                 readDirectory: (name) => []
             };
diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index b84654f38e1..55079c4896b 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -1131,7 +1131,7 @@ namespace ts.server {
             else {
                 this.log("No config files found.");
             }
-            return {};
+            return configFileName ? { configFileName } : {};
         }
 
         /**
diff --git a/src/services/formatting/formatting.ts b/src/services/formatting/formatting.ts
index 2f5f10752f4..ef8fddcfb3a 100644
--- a/src/services/formatting/formatting.ts
+++ b/src/services/formatting/formatting.ts
@@ -81,6 +81,12 @@ namespace ts.formatting {
         while (isWhiteSpace(sourceFile.text.charCodeAt(endOfFormatSpan)) && !isLineBreak(sourceFile.text.charCodeAt(endOfFormatSpan))) {
             endOfFormatSpan--;
         }
+        // if the character at the end of the span is a line break, we shouldn't include it, because it indicates we don't want to
+        // touch the current line at all. Also, on some OSes the line break consists of two characters (\r\n), we should test if the
+        // previous character before the end of format span is line break character as well.
+        if (isLineBreak(sourceFile.text.charCodeAt(endOfFormatSpan))) {
+            endOfFormatSpan--;
+        }
         const span = {
             // get start position for the previous line
             pos: getStartPositionOfLine(line - 1, sourceFile),
diff --git a/src/services/navigationBar.ts b/src/services/navigationBar.ts
index 57726a45cb0..92cf64eac94 100644
--- a/src/services/navigationBar.ts
+++ b/src/services/navigationBar.ts
@@ -652,6 +652,12 @@ namespace ts.NavigationBar {
                 topItem.childItems.push(newItem);
             }
 
+            if (node.jsDocComments && node.jsDocComments.length > 0) {
+                for (const jsDocComment of node.jsDocComments) {
+                    visitNode(jsDocComment);
+                }
+            }
+
             // Add a level if traversing into a container
             if (newItem && (isFunctionLike(node) || isClassLike(node))) {
                 const lastTop = topItem;
@@ -731,6 +737,27 @@ namespace ts.NavigationBar {
                     }
                     const declName = declarationNameToString(decl.name);
                     return getNavBarItem(declName, ScriptElementKind.constElement, [getNodeSpan(node)]);
+                case SyntaxKind.JSDocTypedefTag:
+                    if ((<JSDocTypedefTag>node).name) {
+                        return getNavBarItem(
+                            (<JSDocTypedefTag>node).name.text,
+                            ScriptElementKind.typeElement,
+                            [getNodeSpan(node)]);
+                    }
+                    else {
+                        const parentNode = node.parent && node.parent.parent;
+                        if (parentNode && parentNode.kind === SyntaxKind.VariableStatement) {
+                            if ((<VariableStatement>parentNode).declarationList.declarations.length > 0) {
+                                const nameIdentifier = (<VariableStatement>parentNode).declarationList.declarations[0].name;
+                                if (nameIdentifier.kind === SyntaxKind.Identifier) {
+                                    return getNavBarItem(
+                                        (<Identifier>nameIdentifier).text,
+                                        ScriptElementKind.typeElement,
+                                        [getNodeSpan(node)]);
+                                }
+                            }
+                        }
+                    }
                 default:
                     return undefined;
             }
@@ -801,7 +828,7 @@ namespace ts.NavigationBar {
         }
 
         function getNodeSpan(node: Node) {
-            return node.kind === SyntaxKind.SourceFile
+           return node.kind === SyntaxKind.SourceFile
                 ? createTextSpanFromBounds(node.getFullStart(), node.getEnd())
                 : createTextSpanFromBounds(node.getStart(), node.getEnd());
         }
diff --git a/src/services/services.ts b/src/services/services.ts
index 35fb0887b3b..90740b257c6 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -20,7 +20,7 @@ namespace ts {
         getChildCount(sourceFile?: SourceFile): number;
         getChildAt(index: number, sourceFile?: SourceFile): Node;
         getChildren(sourceFile?: SourceFile): Node[];
-        getStart(sourceFile?: SourceFile): number;
+        getStart(sourceFile?: SourceFile, includeJsDocComment?: boolean): number;
         getFullStart(): number;
         getEnd(): number;
         getWidth(sourceFile?: SourceFile): number;
@@ -172,6 +172,9 @@ namespace ts {
         "static",
         "throws",
         "type",
+        "typedef",
+        "property",
+        "prop",
         "version"
     ];
     let jsDocCompletionEntries: CompletionEntry[];
@@ -189,6 +192,7 @@ namespace ts {
         public end: number;
         public flags: NodeFlags;
         public parent: Node;
+        public jsDocComments: JSDocComment[];
         private _children: Node[];
 
         constructor(kind: SyntaxKind, pos: number, end: number) {
@@ -203,8 +207,8 @@ namespace ts {
             return getSourceFileOfNode(this);
         }
 
-        public getStart(sourceFile?: SourceFile): number {
-            return getTokenPosOfNode(this, sourceFile);
+        public getStart(sourceFile?: SourceFile, includeJsDocComment?: boolean): number {
+            return getTokenPosOfNode(this, sourceFile, includeJsDocComment);
         }
 
         public getFullStart(): number {
@@ -235,12 +239,14 @@ namespace ts {
             return (sourceFile || this.getSourceFile()).text.substring(this.getStart(), this.getEnd());
         }
 
-        private addSyntheticNodes(nodes: Node[], pos: number, end: number): number {
+        private addSyntheticNodes(nodes: Node[], pos: number, end: number, useJSDocScanner?: boolean): number {
             scanner.setTextPos(pos);
             while (pos < end) {
-                const token = scanner.scan();
+                const token = useJSDocScanner ? scanner.scanJSDocToken() : scanner.scan();
                 const textPos = scanner.getTextPos();
-                nodes.push(createNode(token, pos, textPos, 0, this));
+                if (textPos <= end) {
+                    nodes.push(createNode(token, pos, textPos, 0, this));
+                }
                 pos = textPos;
             }
             return pos;
@@ -270,20 +276,27 @@ namespace ts {
                 scanner.setText((sourceFile || this.getSourceFile()).text);
                 children = [];
                 let pos = this.pos;
+                const useJSDocScanner = this.kind >= SyntaxKind.FirstJSDocTagNode && this.kind <= SyntaxKind.LastJSDocTagNode;
                 const processNode = (node: Node) => {
                     if (pos < node.pos) {
-                        pos = this.addSyntheticNodes(children, pos, node.pos);
+                        pos = this.addSyntheticNodes(children, pos, node.pos, useJSDocScanner);
                     }
                     children.push(node);
                     pos = node.end;
                 };
                 const processNodes = (nodes: NodeArray<Node>) => {
                     if (pos < nodes.pos) {
-                        pos = this.addSyntheticNodes(children, pos, nodes.pos);
+                        pos = this.addSyntheticNodes(children, pos, nodes.pos, useJSDocScanner);
                     }
                     children.push(this.createSyntaxList(<NodeArray<Node>>nodes));
                     pos = nodes.end;
                 };
+                // jsDocComments need to be the first children
+                if (this.jsDocComments) {
+                    for (const jsDocComment of this.jsDocComments) {
+                        processNode(jsDocComment);
+                    }
+                }
                 forEachChild(this, processNode, processNodes);
                 if (pos < this.end) {
                     this.addSyntheticNodes(children, pos, this.end);
@@ -5637,7 +5650,7 @@ namespace ts {
 
             const sourceFile = getValidSourceFile(fileName);
 
-            const node = getTouchingPropertyName(sourceFile, position);
+            const node = getTouchingPropertyName(sourceFile, position, /*includeJsDocComment*/ true);
             if (node === sourceFile) {
                 return undefined;
             }
@@ -5999,7 +6012,8 @@ namespace ts {
                 const sourceFile = container.getSourceFile();
                 const tripleSlashDirectivePrefixRegex = /^\/\/\/\s*</;
 
-                const possiblePositions = getPossibleSymbolReferencePositions(sourceFile, searchText, container.getStart(), container.getEnd());
+                const start = findInComments ? container.getFullStart() : container.getStart();
+                const possiblePositions = getPossibleSymbolReferencePositions(sourceFile, searchText, start, container.getEnd());
 
                 if (possiblePositions.length) {
                     // Build the set of symbols to search for, initially it has only the current symbol
@@ -7829,7 +7843,7 @@ namespace ts {
             const defaultLibFileName = host.getDefaultLibFileName(host.getCompilationSettings());
             const canonicalDefaultLibName = getCanonicalFileName(ts.normalizePath(defaultLibFileName));
 
-            const node = getTouchingWord(sourceFile, position);
+            const node = getTouchingWord(sourceFile, position, /*includeJsDocComment*/ true);
 
             // Can only rename an identifier.
             if (node) {
@@ -7999,6 +8013,11 @@ namespace ts {
                     break;
                 default:
                     forEachChild(node, walk);
+                    if (node.jsDocComments) {
+                        for (const jsDocComment of node.jsDocComments) {
+                            forEachChild(jsDocComment, walk);
+                        }
+                    }
             }
         }
     }
diff --git a/src/services/utilities.ts b/src/services/utilities.ts
index f4617395c43..54372877b9a 100644
--- a/src/services/utilities.ts
+++ b/src/services/utilities.ts
@@ -234,29 +234,29 @@ namespace ts {
     /* Gets the token whose text has range [start, end) and
      * position >= start and (position < end or (position === end && token is keyword or identifier))
      */
-    export function getTouchingWord(sourceFile: SourceFile, position: number): Node {
-        return getTouchingToken(sourceFile, position, n => isWord(n.kind));
+    export function getTouchingWord(sourceFile: SourceFile, position: number, includeJsDocComment = false): Node {
+        return getTouchingToken(sourceFile, position, n => isWord(n.kind), includeJsDocComment);
     }
 
     /* Gets the token whose text has range [start, end) and position >= start
      * and (position < end or (position === end && token is keyword or identifier or numeric/string literal))
      */
-    export function getTouchingPropertyName(sourceFile: SourceFile, position: number): Node {
-        return getTouchingToken(sourceFile, position, n => isPropertyName(n.kind));
+    export function getTouchingPropertyName(sourceFile: SourceFile, position: number, includeJsDocComment = false): Node {
+        return getTouchingToken(sourceFile, position, n => isPropertyName(n.kind), includeJsDocComment);
     }
 
     /** Returns the token if position is in [start, end) or if position === end and includeItemAtEndPosition(token) === true */
-    export function getTouchingToken(sourceFile: SourceFile, position: number, includeItemAtEndPosition?: (n: Node) => boolean): Node {
-        return getTokenAtPositionWorker(sourceFile, position, /*allowPositionInLeadingTrivia*/ false, includeItemAtEndPosition);
+    export function getTouchingToken(sourceFile: SourceFile, position: number, includeItemAtEndPosition?: (n: Node) => boolean, includeJsDocComment = false): Node {
+        return getTokenAtPositionWorker(sourceFile, position, /*allowPositionInLeadingTrivia*/ false, includeItemAtEndPosition, includeJsDocComment);
     }
 
     /** Returns a token if position is in [start-of-leading-trivia, end) */
-    export function getTokenAtPosition(sourceFile: SourceFile, position: number): Node {
-        return getTokenAtPositionWorker(sourceFile, position, /*allowPositionInLeadingTrivia*/ true, /*includeItemAtEndPosition*/ undefined);
+    export function getTokenAtPosition(sourceFile: SourceFile, position: number, includeJsDocComment = false): Node {
+        return getTokenAtPositionWorker(sourceFile, position, /*allowPositionInLeadingTrivia*/ true, /*includeItemAtEndPosition*/ undefined, includeJsDocComment);
     }
 
     /** Get the token whose text contains the position */
-    function getTokenAtPositionWorker(sourceFile: SourceFile, position: number, allowPositionInLeadingTrivia: boolean, includeItemAtEndPosition: (n: Node) => boolean): Node {
+    function getTokenAtPositionWorker(sourceFile: SourceFile, position: number, allowPositionInLeadingTrivia: boolean, includeItemAtEndPosition: (n: Node) => boolean, includeJsDocComment = false): Node {
         let current: Node = sourceFile;
         outer: while (true) {
             if (isToken(current)) {
@@ -264,13 +264,34 @@ namespace ts {
                 return current;
             }
 
+            if (includeJsDocComment) {
+                const jsDocChildren = ts.filter(current.getChildren(), isJSDocNode);
+                for (const jsDocChild of jsDocChildren) {
+                    const start = allowPositionInLeadingTrivia ? jsDocChild.getFullStart() : jsDocChild.getStart(sourceFile, includeJsDocComment);
+                    if (start <= position) {
+                        const end = jsDocChild.getEnd();
+                        if (position < end || (position === end && jsDocChild.kind === SyntaxKind.EndOfFileToken)) {
+                            current = jsDocChild;
+                            continue outer;
+                        }
+                        else if (includeItemAtEndPosition && end === position) {
+                            const previousToken = findPrecedingToken(position, sourceFile, jsDocChild);
+                            if (previousToken && includeItemAtEndPosition(previousToken)) {
+                                return previousToken;
+                            }
+                        }
+                    }
+                }
+            }
+
             // find the child that contains 'position'
             for (let i = 0, n = current.getChildCount(sourceFile); i < n; i++) {
                 const child = current.getChildAt(i);
-                if (position < child.getFullStart() || position > child.getEnd()) {
+                // all jsDocComment nodes were already visited
+                if (isJSDocNode(child)) {
                     continue;
                 }
-                const start = allowPositionInLeadingTrivia ? child.getFullStart() : child.getStart(sourceFile);
+                const start = allowPositionInLeadingTrivia ? child.getFullStart() : child.getStart(sourceFile, includeJsDocComment);
                 if (start <= position) {
                     const end = child.getEnd();
                     if (position < end || (position === end && child.kind === SyntaxKind.EndOfFileToken)) {
@@ -285,6 +306,7 @@ namespace ts {
                     }
                 }
             }
+
             return current;
         }
     }
@@ -423,6 +445,10 @@ namespace ts {
             return false;
         }
 
+        if (token.kind === SyntaxKind.JsxText) {
+            return true;
+        }
+
         // <div>Hello |</div>
         if (token.kind === SyntaxKind.LessThanToken && token.parent.kind === SyntaxKind.JsxText) {
             return true;
@@ -433,7 +459,7 @@ namespace ts {
             return true;
         }
 
-        // <div> { 
+        // <div> {
         // |
         // } < /div>
         if (token && token.kind === SyntaxKind.CloseBraceToken && token.parent.kind === SyntaxKind.JsxExpression) {
@@ -518,11 +544,12 @@ namespace ts {
         }
 
         if (node) {
-            const jsDocComment = node.jsDocComment;
-            if (jsDocComment) {
-                for (const tag of jsDocComment.tags) {
-                    if (tag.pos <= position && position <= tag.end) {
-                        return tag;
+            if (node.jsDocComments) {
+                for (const jsDocComment of node.jsDocComments) {
+                    for (const tag of jsDocComment.tags) {
+                        if (tag.pos <= position && position <= tag.end) {
+                            return tag;
+                        }
                     }
                 }
             }
@@ -646,7 +673,7 @@ namespace ts {
 
             // [a, b, c] of
             // [x, [a, b, c] ] = someExpression
-            // or 
+            // or
             // {x, a: {a, b, c} } = someExpression
             if (isArrayLiteralOrObjectLiteralDestructuringPattern(node.parent.kind === SyntaxKind.PropertyAssignment ? node.parent.parent : node.parent)) {
                 return true;
diff --git a/tests/baselines/reference/arrayLiteralWidened.js b/tests/baselines/reference/arrayLiteralWidened.js
index a250c47849d..5b7346b8738 100644
--- a/tests/baselines/reference/arrayLiteralWidened.js
+++ b/tests/baselines/reference/arrayLiteralWidened.js
@@ -2,6 +2,7 @@
 // array literals are widened upon assignment according to their element type
 
 var a = []; // any[]
+var a = [,,];
 
 var a = [null, null];
 var a = [undefined, undefined];
@@ -12,11 +13,20 @@ var b = [[undefined, undefined]];
 
 var c = [[[]]]; // any[][][]
 var c = [[[null]],[undefined]]
+
+// no widening when one or more elements are non-widening
+
+var x: undefined = undefined;
+
+var d = [x];
+var d = [, x];
+var d = [undefined, x];
 
 
 //// [arrayLiteralWidened.js]
 // array literals are widened upon assignment according to their element type
 var a = []; // any[]
+var a = [, ,];
 var a = [null, null];
 var a = [undefined, undefined];
 var b = [[], [null, null]]; // any[][]
@@ -24,3 +34,8 @@ var b = [[], []];
 var b = [[undefined, undefined]];
 var c = [[[]]]; // any[][][]
 var c = [[[null]], [undefined]];
+// no widening when one or more elements are non-widening
+var x = undefined;
+var d = [x];
+var d = [, x];
+var d = [undefined, x];
diff --git a/tests/baselines/reference/arrayLiteralWidened.symbols b/tests/baselines/reference/arrayLiteralWidened.symbols
index ba058aeded1..48137812a5d 100644
--- a/tests/baselines/reference/arrayLiteralWidened.symbols
+++ b/tests/baselines/reference/arrayLiteralWidened.symbols
@@ -2,31 +2,53 @@
 // array literals are widened upon assignment according to their element type
 
 var a = []; // any[]
->a : Symbol(a, Decl(arrayLiteralWidened.ts, 2, 3), Decl(arrayLiteralWidened.ts, 4, 3), Decl(arrayLiteralWidened.ts, 5, 3))
+>a : Symbol(a, Decl(arrayLiteralWidened.ts, 2, 3), Decl(arrayLiteralWidened.ts, 3, 3), Decl(arrayLiteralWidened.ts, 5, 3), Decl(arrayLiteralWidened.ts, 6, 3))
+
+var a = [,,];
+>a : Symbol(a, Decl(arrayLiteralWidened.ts, 2, 3), Decl(arrayLiteralWidened.ts, 3, 3), Decl(arrayLiteralWidened.ts, 5, 3), Decl(arrayLiteralWidened.ts, 6, 3))
 
 var a = [null, null];
->a : Symbol(a, Decl(arrayLiteralWidened.ts, 2, 3), Decl(arrayLiteralWidened.ts, 4, 3), Decl(arrayLiteralWidened.ts, 5, 3))
+>a : Symbol(a, Decl(arrayLiteralWidened.ts, 2, 3), Decl(arrayLiteralWidened.ts, 3, 3), Decl(arrayLiteralWidened.ts, 5, 3), Decl(arrayLiteralWidened.ts, 6, 3))
 
 var a = [undefined, undefined];
->a : Symbol(a, Decl(arrayLiteralWidened.ts, 2, 3), Decl(arrayLiteralWidened.ts, 4, 3), Decl(arrayLiteralWidened.ts, 5, 3))
+>a : Symbol(a, Decl(arrayLiteralWidened.ts, 2, 3), Decl(arrayLiteralWidened.ts, 3, 3), Decl(arrayLiteralWidened.ts, 5, 3), Decl(arrayLiteralWidened.ts, 6, 3))
 >undefined : Symbol(undefined)
 >undefined : Symbol(undefined)
 
 var b = [[], [null, null]]; // any[][]
->b : Symbol(b, Decl(arrayLiteralWidened.ts, 7, 3), Decl(arrayLiteralWidened.ts, 8, 3), Decl(arrayLiteralWidened.ts, 9, 3))
+>b : Symbol(b, Decl(arrayLiteralWidened.ts, 8, 3), Decl(arrayLiteralWidened.ts, 9, 3), Decl(arrayLiteralWidened.ts, 10, 3))
 
 var b = [[], []];
->b : Symbol(b, Decl(arrayLiteralWidened.ts, 7, 3), Decl(arrayLiteralWidened.ts, 8, 3), Decl(arrayLiteralWidened.ts, 9, 3))
+>b : Symbol(b, Decl(arrayLiteralWidened.ts, 8, 3), Decl(arrayLiteralWidened.ts, 9, 3), Decl(arrayLiteralWidened.ts, 10, 3))
 
 var b = [[undefined, undefined]];
->b : Symbol(b, Decl(arrayLiteralWidened.ts, 7, 3), Decl(arrayLiteralWidened.ts, 8, 3), Decl(arrayLiteralWidened.ts, 9, 3))
+>b : Symbol(b, Decl(arrayLiteralWidened.ts, 8, 3), Decl(arrayLiteralWidened.ts, 9, 3), Decl(arrayLiteralWidened.ts, 10, 3))
 >undefined : Symbol(undefined)
 >undefined : Symbol(undefined)
 
 var c = [[[]]]; // any[][][]
->c : Symbol(c, Decl(arrayLiteralWidened.ts, 11, 3), Decl(arrayLiteralWidened.ts, 12, 3))
+>c : Symbol(c, Decl(arrayLiteralWidened.ts, 12, 3), Decl(arrayLiteralWidened.ts, 13, 3))
 
 var c = [[[null]],[undefined]]
->c : Symbol(c, Decl(arrayLiteralWidened.ts, 11, 3), Decl(arrayLiteralWidened.ts, 12, 3))
+>c : Symbol(c, Decl(arrayLiteralWidened.ts, 12, 3), Decl(arrayLiteralWidened.ts, 13, 3))
 >undefined : Symbol(undefined)
 
+// no widening when one or more elements are non-widening
+
+var x: undefined = undefined;
+>x : Symbol(x, Decl(arrayLiteralWidened.ts, 17, 3))
+>undefined : Symbol(undefined)
+
+var d = [x];
+>d : Symbol(d, Decl(arrayLiteralWidened.ts, 19, 3), Decl(arrayLiteralWidened.ts, 20, 3), Decl(arrayLiteralWidened.ts, 21, 3))
+>x : Symbol(x, Decl(arrayLiteralWidened.ts, 17, 3))
+
+var d = [, x];
+>d : Symbol(d, Decl(arrayLiteralWidened.ts, 19, 3), Decl(arrayLiteralWidened.ts, 20, 3), Decl(arrayLiteralWidened.ts, 21, 3))
+>x : Symbol(x, Decl(arrayLiteralWidened.ts, 17, 3))
+
+var d = [undefined, x];
+>d : Symbol(d, Decl(arrayLiteralWidened.ts, 19, 3), Decl(arrayLiteralWidened.ts, 20, 3), Decl(arrayLiteralWidened.ts, 21, 3))
+>undefined : Symbol(undefined)
+>x : Symbol(x, Decl(arrayLiteralWidened.ts, 17, 3))
+
diff --git a/tests/baselines/reference/arrayLiteralWidened.types b/tests/baselines/reference/arrayLiteralWidened.types
index 83db7046eed..6237cd79a7e 100644
--- a/tests/baselines/reference/arrayLiteralWidened.types
+++ b/tests/baselines/reference/arrayLiteralWidened.types
@@ -5,6 +5,12 @@ var a = []; // any[]
 >a : any[]
 >[] : undefined[]
 
+var a = [,,];
+>a : any[]
+>[,,] : undefined[]
+> : undefined
+> : undefined
+
 var a = [null, null];
 >a : any[]
 >[null, null] : null[]
@@ -53,3 +59,26 @@ var c = [[[null]],[undefined]]
 >[undefined] : undefined[]
 >undefined : undefined
 
+// no widening when one or more elements are non-widening
+
+var x: undefined = undefined;
+>x : undefined
+>undefined : undefined
+
+var d = [x];
+>d : undefined[]
+>[x] : undefined[]
+>x : undefined
+
+var d = [, x];
+>d : undefined[]
+>[, x] : undefined[]
+> : undefined
+>x : undefined
+
+var d = [undefined, x];
+>d : undefined[]
+>[undefined, x] : undefined[]
+>undefined : undefined
+>x : undefined
+
diff --git a/tests/baselines/reference/constLocalsInFunctionExpressions.js b/tests/baselines/reference/constLocalsInFunctionExpressions.js
new file mode 100644
index 00000000000..473de3b1a6c
--- /dev/null
+++ b/tests/baselines/reference/constLocalsInFunctionExpressions.js
@@ -0,0 +1,73 @@
+//// [constLocalsInFunctionExpressions.ts]
+declare function getStringOrNumber(): string | number;
+
+function f1() {
+    const x = getStringOrNumber();
+    if (typeof x === "string") {
+        const f = () => x.length;
+    }
+}
+
+function f2() {
+    const x = getStringOrNumber();
+    if (typeof x !== "string") {
+        return;
+    }
+    const f = () => x.length;
+}
+
+function f3() {
+    const x = getStringOrNumber();
+    if (typeof x === "string") {
+        const f = function() { return x.length; };
+    }
+}
+
+function f4() {
+    const x = getStringOrNumber();
+    if (typeof x !== "string") {
+        return;
+    }
+    const f = function() { return x.length; };
+}
+
+function f5() {
+    const x = getStringOrNumber();
+    if (typeof x === "string") {
+        const f = () => () => x.length;
+    }
+}
+
+//// [constLocalsInFunctionExpressions.js]
+function f1() {
+    var x = getStringOrNumber();
+    if (typeof x === "string") {
+        var f = function () { return x.length; };
+    }
+}
+function f2() {
+    var x = getStringOrNumber();
+    if (typeof x !== "string") {
+        return;
+    }
+    var f = function () { return x.length; };
+}
+function f3() {
+    var x = getStringOrNumber();
+    if (typeof x === "string") {
+        var f = function () { return x.length; };
+    }
+}
+function f4() {
+    var x = getStringOrNumber();
+    if (typeof x !== "string") {
+        return;
+    }
+    var f = function () { return x.length; };
+}
+function f5() {
+    var x = getStringOrNumber();
+    if (typeof x === "string") {
+        var f = function () { return function () { return x.length; }; };
+    }
+}
diff --git a/tests/baselines/reference/constLocalsInFunctionExpressions.symbols b/tests/baselines/reference/constLocalsInFunctionExpressions.symbols
new file mode 100644
index 00000000000..d9465a118aa
--- /dev/null
+++ b/tests/baselines/reference/constLocalsInFunctionExpressions.symbols
@@ -0,0 +1,95 @@
+=== tests/cases/conformance/controlFlow/constLocalsInFunctionExpressions.ts ===
+declare function getStringOrNumber(): string | number;
+>getStringOrNumber : Symbol(getStringOrNumber, Decl(constLocalsInFunctionExpressions.ts, 0, 0))
+
+function f1() {
+>f1 : Symbol(f1, Decl(constLocalsInFunctionExpressions.ts, 0, 54))
+
+    const x = getStringOrNumber();
+>x : Symbol(x, Decl(constLocalsInFunctionExpressions.ts, 3, 9))
+>getStringOrNumber : Symbol(getStringOrNumber, Decl(constLocalsInFunctionExpressions.ts, 0, 0))
+
+    if (typeof x === "string") {
+>x : Symbol(x, Decl(constLocalsInFunctionExpressions.ts, 3, 9))
+
+        const f = () => x.length;
+>f : Symbol(f, Decl(constLocalsInFunctionExpressions.ts, 5, 13))
+>x.length : Symbol(String.length, Decl(lib.d.ts, --, --))
+>x : Symbol(x, Decl(constLocalsInFunctionExpressions.ts, 3, 9))
+>length : Symbol(String.length, Decl(lib.d.ts, --, --))
+    }
+}
+
+function f2() {
+>f2 : Symbol(f2, Decl(constLocalsInFunctionExpressions.ts, 7, 1))
+
+    const x = getStringOrNumber();
+>x : Symbol(x, Decl(constLocalsInFunctionExpressions.ts, 10, 9))
+>getStringOrNumber : Symbol(getStringOrNumber, Decl(constLocalsInFunctionExpressions.ts, 0, 0))
+
+    if (typeof x !== "string") {
+>x : Symbol(x, Decl(constLocalsInFunctionExpressions.ts, 10, 9))
+
+        return;
+    }
+    const f = () => x.length;
+>f : Symbol(f, Decl(constLocalsInFunctionExpressions.ts, 14, 9))
+>x.length : Symbol(String.length, Decl(lib.d.ts, --, --))
+>x : Symbol(x, Decl(constLocalsInFunctionExpressions.ts, 10, 9))
+>length : Symbol(String.length, Decl(lib.d.ts, --, --))
+}
+
+function f3() {
+>f3 : Symbol(f3, Decl(constLocalsInFunctionExpressions.ts, 15, 1))
+
+    const x = getStringOrNumber();
+>x : Symbol(x, Decl(constLocalsInFunctionExpressions.ts, 18, 9))
+>getStringOrNumber : Symbol(getStringOrNumber, Decl(constLocalsInFunctionExpressions.ts, 0, 0))
+
+    if (typeof x === "string") {
+>x : Symbol(x, Decl(constLocalsInFunctionExpressions.ts, 18, 9))
+
+        const f = function() { return x.length; };
+>f : Symbol(f, Decl(constLocalsInFunctionExpressions.ts, 20, 13))
+>x.length : Symbol(String.length, Decl(lib.d.ts, --, --))
+>x : Symbol(x, Decl(constLocalsInFunctionExpressions.ts, 18, 9))
+>length : Symbol(String.length, Decl(lib.d.ts, --, --))
+    }
+}
+
+function f4() {
+>f4 : Symbol(f4, Decl(constLocalsInFunctionExpressions.ts, 22, 1))
+
+    const x = getStringOrNumber();
+>x : Symbol(x, Decl(constLocalsInFunctionExpressions.ts, 25, 9))
+>getStringOrNumber : Symbol(getStringOrNumber, Decl(constLocalsInFunctionExpressions.ts, 0, 0))
+
+    if (typeof x !== "string") {
+>x : Symbol(x, Decl(constLocalsInFunctionExpressions.ts, 25, 9))
+
+        return;
+    }
+    const f = function() { return x.length; };
+>f : Symbol(f, Decl(constLocalsInFunctionExpressions.ts, 29, 9))
+>x.length : Symbol(String.length, Decl(lib.d.ts, --, --))
+>x : Symbol(x, Decl(constLocalsInFunctionExpressions.ts, 25, 9))
+>length : Symbol(String.length, Decl(lib.d.ts, --, --))
+}
+
+function f5() {
+>f5 : Symbol(f5, Decl(constLocalsInFunctionExpressions.ts, 30, 1))
+
+    const x = getStringOrNumber();
+>x : Symbol(x, Decl(constLocalsInFunctionExpressions.ts, 33, 9))
+>getStringOrNumber : Symbol(getStringOrNumber, Decl(constLocalsInFunctionExpressions.ts, 0, 0))
+
+    if (typeof x === "string") {
+>x : Symbol(x, Decl(constLocalsInFunctionExpressions.ts, 33, 9))
+
+        const f = () => () => x.length;
+>f : Symbol(f, Decl(constLocalsInFunctionExpressions.ts, 35, 13))
+>x.length : Symbol(String.length, Decl(lib.d.ts, --, --))
+>x : Symbol(x, Decl(constLocalsInFunctionExpressions.ts, 33, 9))
+>length : Symbol(String.length, Decl(lib.d.ts, --, --))
+    }
+}
diff --git a/tests/baselines/reference/constLocalsInFunctionExpressions.types b/tests/baselines/reference/constLocalsInFunctionExpressions.types
new file mode 100644
index 00000000000..e9f0086f6b1
--- /dev/null
+++ b/tests/baselines/reference/constLocalsInFunctionExpressions.types
@@ -0,0 +1,121 @@
+=== tests/cases/conformance/controlFlow/constLocalsInFunctionExpressions.ts ===
+declare function getStringOrNumber(): string | number;
+>getStringOrNumber : () => string | number
+
+function f1() {
+>f1 : () => void
+
+    const x = getStringOrNumber();
+>x : string | number
+>getStringOrNumber() : string | number
+>getStringOrNumber : () => string | number
+
+    if (typeof x === "string") {
+>typeof x === "string" : boolean
+>typeof x : string
+>x : string | number
+>"string" : string
+
+        const f = () => x.length;
+>f : () => number
+>() => x.length : () => number
+>x.length : number
+>x : string
+>length : number
+    }
+}
+
+function f2() {
+>f2 : () => void
+
+    const x = getStringOrNumber();
+>x : string | number
+>getStringOrNumber() : string | number
+>getStringOrNumber : () => string | number
+
+    if (typeof x !== "string") {
+>typeof x !== "string" : boolean
+>typeof x : string
+>x : string | number
+>"string" : string
+
+        return;
+    }
+    const f = () => x.length;
+>f : () => number
+>() => x.length : () => number
+>x.length : number
+>x : string
+>length : number
+}
+
+function f3() {
+>f3 : () => void
+
+    const x = getStringOrNumber();
+>x : string | number
+>getStringOrNumber() : string | number
+>getStringOrNumber : () => string | number
+
+    if (typeof x === "string") {
+>typeof x === "string" : boolean
+>typeof x : string
+>x : string | number
+>"string" : string
+
+        const f = function() { return x.length; };
+>f : () => number
+>function() { return x.length; } : () => number
+>x.length : number
+>x : string
+>length : number
+    }
+}
+
+function f4() {
+>f4 : () => void
+
+    const x = getStringOrNumber();
+>x : string | number
+>getStringOrNumber() : string | number
+>getStringOrNumber : () => string | number
+
+    if (typeof x !== "string") {
+>typeof x !== "string" : boolean
+>typeof x : string
+>x : string | number
+>"string" : string
+
+        return;
+    }
+    const f = function() { return x.length; };
+>f : () => number
+>function() { return x.length; } : () => number
+>x.length : number
+>x : string
+>length : number
+}
+
+function f5() {
+>f5 : () => void
+
+    const x = getStringOrNumber();
+>x : string | number
+>getStringOrNumber() : string | number
+>getStringOrNumber : () => string | number
+
+    if (typeof x === "string") {
+>typeof x === "string" : boolean
+>typeof x : string
+>x : string | number
+>"string" : string
+
+        const f = () => () => x.length;
+>f : () => () => number
+>() => () => x.length : () => () => number
+>() => x.length : () => number
+>x.length : number
+>x : string
+>length : number
+    }
+}
diff --git a/tests/baselines/reference/controlFlowIIFE.js b/tests/baselines/reference/controlFlowIIFE.js
new file mode 100644
index 00000000000..5d295b57315
--- /dev/null
+++ b/tests/baselines/reference/controlFlowIIFE.js
@@ -0,0 +1,89 @@
+//// [controlFlowIIFE.ts]
+
+declare function getStringOrNumber(): string | number;
+
+function f1() {
+    let x = getStringOrNumber();
+    if (typeof x === "string") {
+        let n = function() {
+            return x.length;
+        }();
+    }
+}
+
+function f2() {
+    let x = getStringOrNumber();
+    if (typeof x === "string") {
+        let n = (function() {
+            return x.length;
+        })();
+    }
+}
+
+function f3() {
+    let x = getStringOrNumber();
+    let y: number;
+    if (typeof x === "string") {
+        let n = (z => x.length + y + z)(y = 1);
+    }
+}
+
+// Repros from #8381
+
+let maybeNumber: number | undefined;
+(function () {
+    maybeNumber = 1;
+})();
+maybeNumber++;
+if (maybeNumber !== undefined) {
+    maybeNumber++;
+}
+
+let test: string | undefined;
+if (!test) {
+    throw new Error('Test is not defined');
+}
+(() => {
+    test.slice(1); // No error
+})();
+
+//// [controlFlowIIFE.js]
+function f1() {
+    var x = getStringOrNumber();
+    if (typeof x === "string") {
+        var n = function () {
+            return x.length;
+        }();
+    }
+}
+function f2() {
+    var x = getStringOrNumber();
+    if (typeof x === "string") {
+        var n = (function () {
+            return x.length;
+        })();
+    }
+}
+function f3() {
+    var x = getStringOrNumber();
+    var y;
+    if (typeof x === "string") {
+        var n = (function (z) { return x.length + y + z; })(y = 1);
+    }
+}
+// Repros from #8381
+var maybeNumber;
+(function () {
+    maybeNumber = 1;
+})();
+maybeNumber++;
+if (maybeNumber !== undefined) {
+    maybeNumber++;
+}
+var test;
+if (!test) {
+    throw new Error('Test is not defined');
+}
+(function () {
+    test.slice(1); // No error
+})();
diff --git a/tests/baselines/reference/controlFlowIIFE.symbols b/tests/baselines/reference/controlFlowIIFE.symbols
new file mode 100644
index 00000000000..b1b2b741158
--- /dev/null
+++ b/tests/baselines/reference/controlFlowIIFE.symbols
@@ -0,0 +1,111 @@
+=== tests/cases/conformance/controlFlow/controlFlowIIFE.ts ===
+
+declare function getStringOrNumber(): string | number;
+>getStringOrNumber : Symbol(getStringOrNumber, Decl(controlFlowIIFE.ts, 0, 0))
+
+function f1() {
+>f1 : Symbol(f1, Decl(controlFlowIIFE.ts, 1, 54))
+
+    let x = getStringOrNumber();
+>x : Symbol(x, Decl(controlFlowIIFE.ts, 4, 7))
+>getStringOrNumber : Symbol(getStringOrNumber, Decl(controlFlowIIFE.ts, 0, 0))
+
+    if (typeof x === "string") {
+>x : Symbol(x, Decl(controlFlowIIFE.ts, 4, 7))
+
+        let n = function() {
+>n : Symbol(n, Decl(controlFlowIIFE.ts, 6, 11))
+
+            return x.length;
+>x.length : Symbol(String.length, Decl(lib.d.ts, --, --))
+>x : Symbol(x, Decl(controlFlowIIFE.ts, 4, 7))
+>length : Symbol(String.length, Decl(lib.d.ts, --, --))
+
+        }();
+    }
+}
+
+function f2() {
+>f2 : Symbol(f2, Decl(controlFlowIIFE.ts, 10, 1))
+
+    let x = getStringOrNumber();
+>x : Symbol(x, Decl(controlFlowIIFE.ts, 13, 7))
+>getStringOrNumber : Symbol(getStringOrNumber, Decl(controlFlowIIFE.ts, 0, 0))
+
+    if (typeof x === "string") {
+>x : Symbol(x, Decl(controlFlowIIFE.ts, 13, 7))
+
+        let n = (function() {
+>n : Symbol(n, Decl(controlFlowIIFE.ts, 15, 11))
+
+            return x.length;
+>x.length : Symbol(String.length, Decl(lib.d.ts, --, --))
+>x : Symbol(x, Decl(controlFlowIIFE.ts, 13, 7))
+>length : Symbol(String.length, Decl(lib.d.ts, --, --))
+
+        })();
+    }
+}
+
+function f3() {
+>f3 : Symbol(f3, Decl(controlFlowIIFE.ts, 19, 1))
+
+    let x = getStringOrNumber();
+>x : Symbol(x, Decl(controlFlowIIFE.ts, 22, 7))
+>getStringOrNumber : Symbol(getStringOrNumber, Decl(controlFlowIIFE.ts, 0, 0))
+
+    let y: number;
+>y : Symbol(y, Decl(controlFlowIIFE.ts, 23, 7))
+
+    if (typeof x === "string") {
+>x : Symbol(x, Decl(controlFlowIIFE.ts, 22, 7))
+
+        let n = (z => x.length + y + z)(y = 1);
+>n : Symbol(n, Decl(controlFlowIIFE.ts, 25, 11))
+>z : Symbol(z, Decl(controlFlowIIFE.ts, 25, 17))
+>x.length : Symbol(String.length, Decl(lib.d.ts, --, --))
+>x : Symbol(x, Decl(controlFlowIIFE.ts, 22, 7))
+>length : Symbol(String.length, Decl(lib.d.ts, --, --))
+>y : Symbol(y, Decl(controlFlowIIFE.ts, 23, 7))
+>z : Symbol(z, Decl(controlFlowIIFE.ts, 25, 17))
+>y : Symbol(y, Decl(controlFlowIIFE.ts, 23, 7))
+    }
+}
+
+// Repros from #8381
+
+let maybeNumber: number | undefined;
+>maybeNumber : Symbol(maybeNumber, Decl(controlFlowIIFE.ts, 31, 3))
+
+(function () {
+    maybeNumber = 1;
+>maybeNumber : Symbol(maybeNumber, Decl(controlFlowIIFE.ts, 31, 3))
+
+})();
+maybeNumber++;
+>maybeNumber : Symbol(maybeNumber, Decl(controlFlowIIFE.ts, 31, 3))
+
+if (maybeNumber !== undefined) {
+>maybeNumber : Symbol(maybeNumber, Decl(controlFlowIIFE.ts, 31, 3))
+>undefined : Symbol(undefined)
+
+    maybeNumber++;
+>maybeNumber : Symbol(maybeNumber, Decl(controlFlowIIFE.ts, 31, 3))
+}
+
+let test: string | undefined;
+>test : Symbol(test, Decl(controlFlowIIFE.ts, 40, 3))
+
+if (!test) {
+>test : Symbol(test, Decl(controlFlowIIFE.ts, 40, 3))
+
+    throw new Error('Test is not defined');
+>Error : Symbol(Error, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+}
+(() => {
+    test.slice(1); // No error
+>test.slice : Symbol(String.slice, Decl(lib.d.ts, --, --))
+>test : Symbol(test, Decl(controlFlowIIFE.ts, 40, 3))
+>slice : Symbol(String.slice, Decl(lib.d.ts, --, --))
+
+})();
diff --git a/tests/baselines/reference/controlFlowIIFE.types b/tests/baselines/reference/controlFlowIIFE.types
new file mode 100644
index 00000000000..c041de04bc7
--- /dev/null
+++ b/tests/baselines/reference/controlFlowIIFE.types
@@ -0,0 +1,153 @@
+=== tests/cases/conformance/controlFlow/controlFlowIIFE.ts ===
+
+declare function getStringOrNumber(): string | number;
+>getStringOrNumber : () => string | number
+
+function f1() {
+>f1 : () => void
+
+    let x = getStringOrNumber();
+>x : string | number
+>getStringOrNumber() : string | number
+>getStringOrNumber : () => string | number
+
+    if (typeof x === "string") {
+>typeof x === "string" : boolean
+>typeof x : string
+>x : string | number
+>"string" : string
+
+        let n = function() {
+>n : number
+>function() {            return x.length;        }() : number
+>function() {            return x.length;        } : () => number
+
+            return x.length;
+>x.length : number
+>x : string
+>length : number
+
+        }();
+    }
+}
+
+function f2() {
+>f2 : () => void
+
+    let x = getStringOrNumber();
+>x : string | number
+>getStringOrNumber() : string | number
+>getStringOrNumber : () => string | number
+
+    if (typeof x === "string") {
+>typeof x === "string" : boolean
+>typeof x : string
+>x : string | number
+>"string" : string
+
+        let n = (function() {
+>n : number
+>(function() {            return x.length;        })() : number
+>(function() {            return x.length;        }) : () => number
+>function() {            return x.length;        } : () => number
+
+            return x.length;
+>x.length : number
+>x : string
+>length : number
+
+        })();
+    }
+}
+
+function f3() {
+>f3 : () => void
+
+    let x = getStringOrNumber();
+>x : string | number
+>getStringOrNumber() : string | number
+>getStringOrNumber : () => string | number
+
+    let y: number;
+>y : number
+
+    if (typeof x === "string") {
+>typeof x === "string" : boolean
+>typeof x : string
+>x : string | number
+>"string" : string
+
+        let n = (z => x.length + y + z)(y = 1);
+>n : number
+>(z => x.length + y + z)(y = 1) : number
+>(z => x.length + y + z) : (z: number) => number
+>z => x.length + y + z : (z: number) => number
+>z : number
+>x.length + y + z : number
+>x.length + y : number
+>x.length : number
+>x : string
+>length : number
+>y : number
+>z : number
+>y = 1 : number
+>y : number
+>1 : number
+    }
+}
+
+// Repros from #8381
+
+let maybeNumber: number | undefined;
+>maybeNumber : number | undefined
+
+(function () {
+>(function () {    maybeNumber = 1;})() : void
+>(function () {    maybeNumber = 1;}) : () => void
+>function () {    maybeNumber = 1;} : () => void
+
+    maybeNumber = 1;
+>maybeNumber = 1 : number
+>maybeNumber : number | undefined
+>1 : number
+
+})();
+maybeNumber++;
+>maybeNumber++ : number
+>maybeNumber : number
+
+if (maybeNumber !== undefined) {
+>maybeNumber !== undefined : boolean
+>maybeNumber : number
+>undefined : undefined
+
+    maybeNumber++;
+>maybeNumber++ : number
+>maybeNumber : number
+}
+
+let test: string | undefined;
+>test : string | undefined
+
+if (!test) {
+>!test : boolean
+>test : string | undefined
+
+    throw new Error('Test is not defined');
+>new Error('Test is not defined') : Error
+>Error : ErrorConstructor
+>'Test is not defined' : string
+}
+(() => {
+>(() => {    test.slice(1); // No error})() : void
+>(() => {    test.slice(1); // No error}) : () => void
+>() => {    test.slice(1); // No error} : () => void
+
+    test.slice(1); // No error
+>test.slice(1) : string
+>test.slice : (start?: number | undefined, end?: number | undefined) => string
+>test : string
+>slice : (start?: number | undefined, end?: number | undefined) => string
+>1 : number
+
+})();
diff --git a/tests/baselines/reference/controlFlowPropertyDeclarations.js b/tests/baselines/reference/controlFlowPropertyDeclarations.js
new file mode 100644
index 00000000000..748f63ea858
--- /dev/null
+++ b/tests/baselines/reference/controlFlowPropertyDeclarations.js
@@ -0,0 +1,291 @@
+//// [controlFlowPropertyDeclarations.ts]
+// Repro from ##8913
+
+declare var require:any;
+
+var HTMLDOMPropertyConfig = require('react/lib/HTMLDOMPropertyConfig');
+
+// Populate property map with ReactJS's attribute and property mappings
+// TODO handle/use .Properties value eg: MUST_USE_PROPERTY is not HTML attr
+for (var propname in HTMLDOMPropertyConfig.Properties) {
+  if (!HTMLDOMPropertyConfig.Properties.hasOwnProperty(propname)) {
+    continue;
+  }
+
+  var mapFrom = HTMLDOMPropertyConfig.DOMAttributeNames[propname] || propname.toLowerCase();
+}
+
+/**
+ * Repeats a string a certain number of times.
+ * Also: the future is bright and consists of native string repetition:
+ * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/repeat
+ *
+ * @param {string} string  String to repeat
+ * @param {number} times   Number of times to repeat string. Integer.
+ * @see http://jsperf.com/string-repeater/2
+ */
+function repeatString(string, times) {
+  if (times === 1) {
+    return string;
+  }
+  if (times < 0) { throw new Error(); }
+  var repeated = '';
+  while (times) {
+    if (times & 1) {
+      repeated += string;
+    }
+    if (times >>= 1) {
+      string += string;
+    }
+  }
+  return repeated;
+}
+
+/**
+ * Determine if the string ends with the specified substring.
+ *
+ * @param {string} haystack String to search in
+ * @param {string} needle   String to search for
+ * @return {boolean}
+ */
+function endsWith(haystack, needle) {
+  return haystack.slice(-needle.length) === needle;
+}
+
+/**
+ * Trim the specified substring off the string. If the string does not end
+ * with the specified substring, this is a no-op.
+ *
+ * @param {string} haystack String to search in
+ * @param {string} needle   String to search for
+ * @return {string}
+ */
+function trimEnd(haystack, needle) {
+  return endsWith(haystack, needle)
+    ? haystack.slice(0, -needle.length)
+    : haystack;
+}
+
+/**
+ * Convert a hyphenated string to camelCase.
+ */
+function hyphenToCamelCase(string) {
+  return string.replace(/-(.)/g, function(match, chr) {
+    return chr.toUpperCase();
+  });
+}
+
+/**
+ * Determines if the specified string consists entirely of whitespace.
+ */
+function isEmpty(string) {
+   return !/[^\s]/.test(string);
+}
+
+/**
+ * Determines if the CSS value can be converted from a
+ * 'px' suffixed string to a numeric value
+ *
+ * @param {string} value CSS property value
+ * @return {boolean}
+ */
+function isConvertiblePixelValue(value) {
+  return /^\d+px$/.test(value);
+}
+
+export class HTMLtoJSX {
+    private output: string;
+    private level: number;
+    private _inPreTag: boolean;
+
+
+  /**
+   * Handles processing of the specified text node
+   *
+   * @param {TextNode} node
+   */
+  _visitText = (node) => {
+    var parentTag = node.parentNode && node.parentNode.tagName.toLowerCase();
+    if (parentTag === 'textarea' || parentTag === 'style') {
+      // Ignore text content of textareas and styles, as it will have already been moved
+      // to a "defaultValue" attribute and "dangerouslySetInnerHTML" attribute respectively.
+      return;
+    }
+
+    var text = ''
+
+    if (this._inPreTag) {
+      // If this text is contained within a <pre>, we need to ensure the JSX
+      // whitespace coalescing rules don't eat the whitespace. This means
+      // wrapping newlines and sequences of two or more spaces in variables.
+      text = text
+        .replace(/\r/g, '')
+        .replace(/( {2,}|\n|\t|\{|\})/g, function(whitespace) {
+          return '{' + JSON.stringify(whitespace) + '}';
+        });
+    } else {
+      // If there's a newline in the text, adjust the indent level
+      if (text.indexOf('\n') > -1) {
+      }
+    }
+    this.output += text;
+  }
+
+
+
+};
+
+/**
+ * Handles parsing of inline styles
+ */
+export class StyleParser {
+  styles = {};
+  toJSXString = () => {
+    for (var key in this.styles) {
+      if (!this.styles.hasOwnProperty(key)) {
+      }
+    }
+  }
+}
+
+//// [controlFlowPropertyDeclarations.js]
+// Repro from ##8913
+"use strict";
+var HTMLDOMPropertyConfig = require('react/lib/HTMLDOMPropertyConfig');
+// Populate property map with ReactJS's attribute and property mappings
+// TODO handle/use .Properties value eg: MUST_USE_PROPERTY is not HTML attr
+for (var propname in HTMLDOMPropertyConfig.Properties) {
+    if (!HTMLDOMPropertyConfig.Properties.hasOwnProperty(propname)) {
+        continue;
+    }
+    var mapFrom = HTMLDOMPropertyConfig.DOMAttributeNames[propname] || propname.toLowerCase();
+}
+/**
+ * Repeats a string a certain number of times.
+ * Also: the future is bright and consists of native string repetition:
+ * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/repeat
+ *
+ * @param {string} string  String to repeat
+ * @param {number} times   Number of times to repeat string. Integer.
+ * @see http://jsperf.com/string-repeater/2
+ */
+function repeatString(string, times) {
+    if (times === 1) {
+        return string;
+    }
+    if (times < 0) {
+        throw new Error();
+    }
+    var repeated = '';
+    while (times) {
+        if (times & 1) {
+            repeated += string;
+        }
+        if (times >>= 1) {
+            string += string;
+        }
+    }
+    return repeated;
+}
+/**
+ * Determine if the string ends with the specified substring.
+ *
+ * @param {string} haystack String to search in
+ * @param {string} needle   String to search for
+ * @return {boolean}
+ */
+function endsWith(haystack, needle) {
+    return haystack.slice(-needle.length) === needle;
+}
+/**
+ * Trim the specified substring off the string. If the string does not end
+ * with the specified substring, this is a no-op.
+ *
+ * @param {string} haystack String to search in
+ * @param {string} needle   String to search for
+ * @return {string}
+ */
+function trimEnd(haystack, needle) {
+    return endsWith(haystack, needle)
+        ? haystack.slice(0, -needle.length)
+        : haystack;
+}
+/**
+ * Convert a hyphenated string to camelCase.
+ */
+function hyphenToCamelCase(string) {
+    return string.replace(/-(.)/g, function (match, chr) {
+        return chr.toUpperCase();
+    });
+}
+/**
+ * Determines if the specified string consists entirely of whitespace.
+ */
+function isEmpty(string) {
+    return !/[^\s]/.test(string);
+}
+/**
+ * Determines if the CSS value can be converted from a
+ * 'px' suffixed string to a numeric value
+ *
+ * @param {string} value CSS property value
+ * @return {boolean}
+ */
+function isConvertiblePixelValue(value) {
+    return /^\d+px$/.test(value);
+}
+var HTMLtoJSX = (function () {
+    function HTMLtoJSX() {
+        var _this = this;
+        /**
+         * Handles processing of the specified text node
+         *
+         * @param {TextNode} node
+         */
+        this._visitText = function (node) {
+            var parentTag = node.parentNode && node.parentNode.tagName.toLowerCase();
+            if (parentTag === 'textarea' || parentTag === 'style') {
+                // Ignore text content of textareas and styles, as it will have already been moved
+                // to a "defaultValue" attribute and "dangerouslySetInnerHTML" attribute respectively.
+                return;
+            }
+            var text = '';
+            if (_this._inPreTag) {
+                // If this text is contained within a <pre>, we need to ensure the JSX
+                // whitespace coalescing rules don't eat the whitespace. This means
+                // wrapping newlines and sequences of two or more spaces in variables.
+                text = text
+                    .replace(/\r/g, '')
+                    .replace(/( {2,}|\n|\t|\{|\})/g, function (whitespace) {
+                    return '{' + JSON.stringify(whitespace) + '}';
+                });
+            }
+            else {
+                // If there's a newline in the text, adjust the indent level
+                if (text.indexOf('\n') > -1) {
+                }
+            }
+            _this.output += text;
+        };
+    }
+    return HTMLtoJSX;
+}());
+exports.HTMLtoJSX = HTMLtoJSX;
+;
+/**
+ * Handles parsing of inline styles
+ */
+var StyleParser = (function () {
+    function StyleParser() {
+        var _this = this;
+        this.styles = {};
+        this.toJSXString = function () {
+            for (var key in _this.styles) {
+                if (!_this.styles.hasOwnProperty(key)) {
+                }
+            }
+        };
+    }
+    return StyleParser;
+}());
+exports.StyleParser = StyleParser;
diff --git a/tests/baselines/reference/controlFlowPropertyDeclarations.symbols b/tests/baselines/reference/controlFlowPropertyDeclarations.symbols
new file mode 100644
index 00000000000..8e87d71ae33
--- /dev/null
+++ b/tests/baselines/reference/controlFlowPropertyDeclarations.symbols
@@ -0,0 +1,288 @@
+=== tests/cases/compiler/controlFlowPropertyDeclarations.ts ===
+// Repro from ##8913
+
+declare var require:any;
+>require : Symbol(require, Decl(controlFlowPropertyDeclarations.ts, 2, 11))
+
+var HTMLDOMPropertyConfig = require('react/lib/HTMLDOMPropertyConfig');
+>HTMLDOMPropertyConfig : Symbol(HTMLDOMPropertyConfig, Decl(controlFlowPropertyDeclarations.ts, 4, 3))
+>require : Symbol(require, Decl(controlFlowPropertyDeclarations.ts, 2, 11))
+
+// Populate property map with ReactJS's attribute and property mappings
+// TODO handle/use .Properties value eg: MUST_USE_PROPERTY is not HTML attr
+for (var propname in HTMLDOMPropertyConfig.Properties) {
+>propname : Symbol(propname, Decl(controlFlowPropertyDeclarations.ts, 8, 8))
+>HTMLDOMPropertyConfig : Symbol(HTMLDOMPropertyConfig, Decl(controlFlowPropertyDeclarations.ts, 4, 3))
+
+  if (!HTMLDOMPropertyConfig.Properties.hasOwnProperty(propname)) {
+>HTMLDOMPropertyConfig : Symbol(HTMLDOMPropertyConfig, Decl(controlFlowPropertyDeclarations.ts, 4, 3))
+>propname : Symbol(propname, Decl(controlFlowPropertyDeclarations.ts, 8, 8))
+
+    continue;
+  }
+
+  var mapFrom = HTMLDOMPropertyConfig.DOMAttributeNames[propname] || propname.toLowerCase();
+>mapFrom : Symbol(mapFrom, Decl(controlFlowPropertyDeclarations.ts, 13, 5))
+>HTMLDOMPropertyConfig : Symbol(HTMLDOMPropertyConfig, Decl(controlFlowPropertyDeclarations.ts, 4, 3))
+>propname : Symbol(propname, Decl(controlFlowPropertyDeclarations.ts, 8, 8))
+>propname.toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+>propname : Symbol(propname, Decl(controlFlowPropertyDeclarations.ts, 8, 8))
+>toLowerCase : Symbol(String.toLowerCase, Decl(lib.d.ts, --, --))
+}
+
+/**
+ * Repeats a string a certain number of times.
+ * Also: the future is bright and consists of native string repetition:
+ * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/repeat
+ *
+ * @param {string} string  String to repeat
+ * @param {number} times   Number of times to repeat string. Integer.
+ * @see http://jsperf.com/string-repeater/2
+ */
+function repeatString(string, times) {
+>repeatString : Symbol(repeatString, Decl(controlFlowPropertyDeclarations.ts, 14, 1))
+>string : Symbol(string, Decl(controlFlowPropertyDeclarations.ts, 25, 22))
+>times : Symbol(times, Decl(controlFlowPropertyDeclarations.ts, 25, 29))
+
+  if (times === 1) {
+>times : Symbol(times, Decl(controlFlowPropertyDeclarations.ts, 25, 29))
+
+    return string;
+>string : Symbol(string, Decl(controlFlowPropertyDeclarations.ts, 25, 22))
+  }
+  if (times < 0) { throw new Error(); }
+>times : Symbol(times, Decl(controlFlowPropertyDeclarations.ts, 25, 29))
+>Error : Symbol(Error, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+
+  var repeated = '';
+>repeated : Symbol(repeated, Decl(controlFlowPropertyDeclarations.ts, 30, 5))
+
+  while (times) {
+>times : Symbol(times, Decl(controlFlowPropertyDeclarations.ts, 25, 29))
+
+    if (times & 1) {
+>times : Symbol(times, Decl(controlFlowPropertyDeclarations.ts, 25, 29))
+
+      repeated += string;
+>repeated : Symbol(repeated, Decl(controlFlowPropertyDeclarations.ts, 30, 5))
+>string : Symbol(string, Decl(controlFlowPropertyDeclarations.ts, 25, 22))
+    }
+    if (times >>= 1) {
+>times : Symbol(times, Decl(controlFlowPropertyDeclarations.ts, 25, 29))
+
+      string += string;
+>string : Symbol(string, Decl(controlFlowPropertyDeclarations.ts, 25, 22))
+>string : Symbol(string, Decl(controlFlowPropertyDeclarations.ts, 25, 22))
+    }
+  }
+  return repeated;
+>repeated : Symbol(repeated, Decl(controlFlowPropertyDeclarations.ts, 30, 5))
+}
+
+/**
+ * Determine if the string ends with the specified substring.
+ *
+ * @param {string} haystack String to search in
+ * @param {string} needle   String to search for
+ * @return {boolean}
+ */
+function endsWith(haystack, needle) {
+>endsWith : Symbol(endsWith, Decl(controlFlowPropertyDeclarations.ts, 40, 1))
+>haystack : Symbol(haystack, Decl(controlFlowPropertyDeclarations.ts, 49, 18))
+>needle : Symbol(needle, Decl(controlFlowPropertyDeclarations.ts, 49, 27))
+
+  return haystack.slice(-needle.length) === needle;
+>haystack : Symbol(haystack, Decl(controlFlowPropertyDeclarations.ts, 49, 18))
+>needle : Symbol(needle, Decl(controlFlowPropertyDeclarations.ts, 49, 27))
+>needle : Symbol(needle, Decl(controlFlowPropertyDeclarations.ts, 49, 27))
+}
+
+/**
+ * Trim the specified substring off the string. If the string does not end
+ * with the specified substring, this is a no-op.
+ *
+ * @param {string} haystack String to search in
+ * @param {string} needle   String to search for
+ * @return {string}
+ */
+function trimEnd(haystack, needle) {
+>trimEnd : Symbol(trimEnd, Decl(controlFlowPropertyDeclarations.ts, 51, 1))
+>haystack : Symbol(haystack, Decl(controlFlowPropertyDeclarations.ts, 61, 17))
+>needle : Symbol(needle, Decl(controlFlowPropertyDeclarations.ts, 61, 26))
+
+  return endsWith(haystack, needle)
+>endsWith : Symbol(endsWith, Decl(controlFlowPropertyDeclarations.ts, 40, 1))
+>haystack : Symbol(haystack, Decl(controlFlowPropertyDeclarations.ts, 61, 17))
+>needle : Symbol(needle, Decl(controlFlowPropertyDeclarations.ts, 61, 26))
+
+    ? haystack.slice(0, -needle.length)
+>haystack : Symbol(haystack, Decl(controlFlowPropertyDeclarations.ts, 61, 17))
+>needle : Symbol(needle, Decl(controlFlowPropertyDeclarations.ts, 61, 26))
+
+    : haystack;
+>haystack : Symbol(haystack, Decl(controlFlowPropertyDeclarations.ts, 61, 17))
+}
+
+/**
+ * Convert a hyphenated string to camelCase.
+ */
+function hyphenToCamelCase(string) {
+>hyphenToCamelCase : Symbol(hyphenToCamelCase, Decl(controlFlowPropertyDeclarations.ts, 65, 1))
+>string : Symbol(string, Decl(controlFlowPropertyDeclarations.ts, 70, 27))
+
+  return string.replace(/-(.)/g, function(match, chr) {
+>string : Symbol(string, Decl(controlFlowPropertyDeclarations.ts, 70, 27))
+>match : Symbol(match, Decl(controlFlowPropertyDeclarations.ts, 71, 42))
+>chr : Symbol(chr, Decl(controlFlowPropertyDeclarations.ts, 71, 48))
+
+    return chr.toUpperCase();
+>chr : Symbol(chr, Decl(controlFlowPropertyDeclarations.ts, 71, 48))
+
+  });
+}
+
+/**
+ * Determines if the specified string consists entirely of whitespace.
+ */
+function isEmpty(string) {
+>isEmpty : Symbol(isEmpty, Decl(controlFlowPropertyDeclarations.ts, 74, 1))
+>string : Symbol(string, Decl(controlFlowPropertyDeclarations.ts, 79, 17))
+
+   return !/[^\s]/.test(string);
+>/[^\s]/.test : Symbol(RegExp.test, Decl(lib.d.ts, --, --))
+>test : Symbol(RegExp.test, Decl(lib.d.ts, --, --))
+>string : Symbol(string, Decl(controlFlowPropertyDeclarations.ts, 79, 17))
+}
+
+/**
+ * Determines if the CSS value can be converted from a
+ * 'px' suffixed string to a numeric value
+ *
+ * @param {string} value CSS property value
+ * @return {boolean}
+ */
+function isConvertiblePixelValue(value) {
+>isConvertiblePixelValue : Symbol(isConvertiblePixelValue, Decl(controlFlowPropertyDeclarations.ts, 81, 1))
+>value : Symbol(value, Decl(controlFlowPropertyDeclarations.ts, 90, 33))
+
+  return /^\d+px$/.test(value);
+>/^\d+px$/.test : Symbol(RegExp.test, Decl(lib.d.ts, --, --))
+>test : Symbol(RegExp.test, Decl(lib.d.ts, --, --))
+>value : Symbol(value, Decl(controlFlowPropertyDeclarations.ts, 90, 33))
+}
+
+export class HTMLtoJSX {
+>HTMLtoJSX : Symbol(HTMLtoJSX, Decl(controlFlowPropertyDeclarations.ts, 92, 1))
+
+    private output: string;
+>output : Symbol(HTMLtoJSX.output, Decl(controlFlowPropertyDeclarations.ts, 94, 24))
+
+    private level: number;
+>level : Symbol(HTMLtoJSX.level, Decl(controlFlowPropertyDeclarations.ts, 95, 27))
+
+    private _inPreTag: boolean;
+>_inPreTag : Symbol(HTMLtoJSX._inPreTag, Decl(controlFlowPropertyDeclarations.ts, 96, 26))
+
+
+  /**
+   * Handles processing of the specified text node
+   *
+   * @param {TextNode} node
+   */
+  _visitText = (node) => {
+>_visitText : Symbol(HTMLtoJSX._visitText, Decl(controlFlowPropertyDeclarations.ts, 97, 31))
+>node : Symbol(node, Decl(controlFlowPropertyDeclarations.ts, 105, 16))
+
+    var parentTag = node.parentNode && node.parentNode.tagName.toLowerCase();
+>parentTag : Symbol(parentTag, Decl(controlFlowPropertyDeclarations.ts, 106, 7))
+>node : Symbol(node, Decl(controlFlowPropertyDeclarations.ts, 105, 16))
+>node : Symbol(node, Decl(controlFlowPropertyDeclarations.ts, 105, 16))
+
+    if (parentTag === 'textarea' || parentTag === 'style') {
+>parentTag : Symbol(parentTag, Decl(controlFlowPropertyDeclarations.ts, 106, 7))
+>parentTag : Symbol(parentTag, Decl(controlFlowPropertyDeclarations.ts, 106, 7))
+
+      // Ignore text content of textareas and styles, as it will have already been moved
+      // to a "defaultValue" attribute and "dangerouslySetInnerHTML" attribute respectively.
+      return;
+    }
+
+    var text = ''
+>text : Symbol(text, Decl(controlFlowPropertyDeclarations.ts, 113, 7))
+
+    if (this._inPreTag) {
+>this._inPreTag : Symbol(HTMLtoJSX._inPreTag, Decl(controlFlowPropertyDeclarations.ts, 96, 26))
+>this : Symbol(HTMLtoJSX, Decl(controlFlowPropertyDeclarations.ts, 92, 1))
+>_inPreTag : Symbol(HTMLtoJSX._inPreTag, Decl(controlFlowPropertyDeclarations.ts, 96, 26))
+
+      // If this text is contained within a <pre>, we need to ensure the JSX
+      // whitespace coalescing rules don't eat the whitespace. This means
+      // wrapping newlines and sequences of two or more spaces in variables.
+      text = text
+>text : Symbol(text, Decl(controlFlowPropertyDeclarations.ts, 113, 7))
+>text        .replace(/\r/g, '')        .replace : Symbol(String.replace, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>text        .replace : Symbol(String.replace, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>text : Symbol(text, Decl(controlFlowPropertyDeclarations.ts, 113, 7))
+
+        .replace(/\r/g, '')
+>replace : Symbol(String.replace, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+
+        .replace(/( {2,}|\n|\t|\{|\})/g, function(whitespace) {
+>replace : Symbol(String.replace, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>whitespace : Symbol(whitespace, Decl(controlFlowPropertyDeclarations.ts, 121, 50))
+
+          return '{' + JSON.stringify(whitespace) + '}';
+>JSON.stringify : Symbol(JSON.stringify, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>JSON : Symbol(JSON, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>stringify : Symbol(JSON.stringify, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>whitespace : Symbol(whitespace, Decl(controlFlowPropertyDeclarations.ts, 121, 50))
+
+        });
+    } else {
+      // If there's a newline in the text, adjust the indent level
+      if (text.indexOf('\n') > -1) {
+>text.indexOf : Symbol(String.indexOf, Decl(lib.d.ts, --, --))
+>text : Symbol(text, Decl(controlFlowPropertyDeclarations.ts, 113, 7))
+>indexOf : Symbol(String.indexOf, Decl(lib.d.ts, --, --))
+      }
+    }
+    this.output += text;
+>this.output : Symbol(HTMLtoJSX.output, Decl(controlFlowPropertyDeclarations.ts, 94, 24))
+>this : Symbol(HTMLtoJSX, Decl(controlFlowPropertyDeclarations.ts, 92, 1))
+>output : Symbol(HTMLtoJSX.output, Decl(controlFlowPropertyDeclarations.ts, 94, 24))
+>text : Symbol(text, Decl(controlFlowPropertyDeclarations.ts, 113, 7))
+  }
+
+
+
+};
+
+/**
+ * Handles parsing of inline styles
+ */
+export class StyleParser {
+>StyleParser : Symbol(StyleParser, Decl(controlFlowPropertyDeclarations.ts, 134, 2))
+
+  styles = {};
+>styles : Symbol(StyleParser.styles, Decl(controlFlowPropertyDeclarations.ts, 139, 26))
+
+  toJSXString = () => {
+>toJSXString : Symbol(StyleParser.toJSXString, Decl(controlFlowPropertyDeclarations.ts, 140, 14))
+
+    for (var key in this.styles) {
+>key : Symbol(key, Decl(controlFlowPropertyDeclarations.ts, 142, 12))
+>this.styles : Symbol(StyleParser.styles, Decl(controlFlowPropertyDeclarations.ts, 139, 26))
+>this : Symbol(StyleParser, Decl(controlFlowPropertyDeclarations.ts, 134, 2))
+>styles : Symbol(StyleParser.styles, Decl(controlFlowPropertyDeclarations.ts, 139, 26))
+
+      if (!this.styles.hasOwnProperty(key)) {
+>this.styles.hasOwnProperty : Symbol(Object.hasOwnProperty, Decl(lib.d.ts, --, --))
+>this.styles : Symbol(StyleParser.styles, Decl(controlFlowPropertyDeclarations.ts, 139, 26))
+>this : Symbol(StyleParser, Decl(controlFlowPropertyDeclarations.ts, 134, 2))
+>styles : Symbol(StyleParser.styles, Decl(controlFlowPropertyDeclarations.ts, 139, 26))
+>hasOwnProperty : Symbol(Object.hasOwnProperty, Decl(lib.d.ts, --, --))
+>key : Symbol(key, Decl(controlFlowPropertyDeclarations.ts, 142, 12))
+      }
+    }
+  }
+}
diff --git a/tests/baselines/reference/controlFlowPropertyDeclarations.types b/tests/baselines/reference/controlFlowPropertyDeclarations.types
new file mode 100644
index 00000000000..81c86e8625d
--- /dev/null
+++ b/tests/baselines/reference/controlFlowPropertyDeclarations.types
@@ -0,0 +1,383 @@
+=== tests/cases/compiler/controlFlowPropertyDeclarations.ts ===
+// Repro from ##8913
+
+declare var require:any;
+>require : any
+
+var HTMLDOMPropertyConfig = require('react/lib/HTMLDOMPropertyConfig');
+>HTMLDOMPropertyConfig : any
+>require('react/lib/HTMLDOMPropertyConfig') : any
+>require : any
+>'react/lib/HTMLDOMPropertyConfig' : string
+
+// Populate property map with ReactJS's attribute and property mappings
+// TODO handle/use .Properties value eg: MUST_USE_PROPERTY is not HTML attr
+for (var propname in HTMLDOMPropertyConfig.Properties) {
+>propname : string
+>HTMLDOMPropertyConfig.Properties : any
+>HTMLDOMPropertyConfig : any
+>Properties : any
+
+  if (!HTMLDOMPropertyConfig.Properties.hasOwnProperty(propname)) {
+>!HTMLDOMPropertyConfig.Properties.hasOwnProperty(propname) : boolean
+>HTMLDOMPropertyConfig.Properties.hasOwnProperty(propname) : any
+>HTMLDOMPropertyConfig.Properties.hasOwnProperty : any
+>HTMLDOMPropertyConfig.Properties : any
+>HTMLDOMPropertyConfig : any
+>Properties : any
+>hasOwnProperty : any
+>propname : string
+
+    continue;
+  }
+
+  var mapFrom = HTMLDOMPropertyConfig.DOMAttributeNames[propname] || propname.toLowerCase();
+>mapFrom : any
+>HTMLDOMPropertyConfig.DOMAttributeNames[propname] || propname.toLowerCase() : any
+>HTMLDOMPropertyConfig.DOMAttributeNames[propname] : any
+>HTMLDOMPropertyConfig.DOMAttributeNames : any
+>HTMLDOMPropertyConfig : any
+>DOMAttributeNames : any
+>propname : string
+>propname.toLowerCase() : string
+>propname.toLowerCase : () => string
+>propname : string
+>toLowerCase : () => string
+}
+
+/**
+ * Repeats a string a certain number of times.
+ * Also: the future is bright and consists of native string repetition:
+ * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/repeat
+ *
+ * @param {string} string  String to repeat
+ * @param {number} times   Number of times to repeat string. Integer.
+ * @see http://jsperf.com/string-repeater/2
+ */
+function repeatString(string, times) {
+>repeatString : (string: any, times: any) => any
+>string : any
+>times : any
+
+  if (times === 1) {
+>times === 1 : boolean
+>times : any
+>1 : number
+
+    return string;
+>string : any
+  }
+  if (times < 0) { throw new Error(); }
+>times < 0 : boolean
+>times : any
+>0 : number
+>new Error() : Error
+>Error : ErrorConstructor
+
+  var repeated = '';
+>repeated : string
+>'' : string
+
+  while (times) {
+>times : any
+
+    if (times & 1) {
+>times & 1 : number
+>times : any
+>1 : number
+
+      repeated += string;
+>repeated += string : string
+>repeated : string
+>string : any
+    }
+    if (times >>= 1) {
+>times >>= 1 : number
+>times : any
+>1 : number
+
+      string += string;
+>string += string : any
+>string : any
+>string : any
+    }
+  }
+  return repeated;
+>repeated : string
+}
+
+/**
+ * Determine if the string ends with the specified substring.
+ *
+ * @param {string} haystack String to search in
+ * @param {string} needle   String to search for
+ * @return {boolean}
+ */
+function endsWith(haystack, needle) {
+>endsWith : (haystack: any, needle: any) => boolean
+>haystack : any
+>needle : any
+
+  return haystack.slice(-needle.length) === needle;
+>haystack.slice(-needle.length) === needle : boolean
+>haystack.slice(-needle.length) : any
+>haystack.slice : any
+>haystack : any
+>slice : any
+>-needle.length : number
+>needle.length : any
+>needle : any
+>length : any
+>needle : any
+}
+
+/**
+ * Trim the specified substring off the string. If the string does not end
+ * with the specified substring, this is a no-op.
+ *
+ * @param {string} haystack String to search in
+ * @param {string} needle   String to search for
+ * @return {string}
+ */
+function trimEnd(haystack, needle) {
+>trimEnd : (haystack: any, needle: any) => any
+>haystack : any
+>needle : any
+
+  return endsWith(haystack, needle)
+>endsWith(haystack, needle)    ? haystack.slice(0, -needle.length)    : haystack : any
+>endsWith(haystack, needle) : boolean
+>endsWith : (haystack: any, needle: any) => boolean
+>haystack : any
+>needle : any
+
+    ? haystack.slice(0, -needle.length)
+>haystack.slice(0, -needle.length) : any
+>haystack.slice : any
+>haystack : any
+>slice : any
+>0 : number
+>-needle.length : number
+>needle.length : any
+>needle : any
+>length : any
+
+    : haystack;
+>haystack : any
+}
+
+/**
+ * Convert a hyphenated string to camelCase.
+ */
+function hyphenToCamelCase(string) {
+>hyphenToCamelCase : (string: any) => any
+>string : any
+
+  return string.replace(/-(.)/g, function(match, chr) {
+>string.replace(/-(.)/g, function(match, chr) {    return chr.toUpperCase();  }) : any
+>string.replace : any
+>string : any
+>replace : any
+>/-(.)/g : RegExp
+>function(match, chr) {    return chr.toUpperCase();  } : (match: any, chr: any) => any
+>match : any
+>chr : any
+
+    return chr.toUpperCase();
+>chr.toUpperCase() : any
+>chr.toUpperCase : any
+>chr : any
+>toUpperCase : any
+
+  });
+}
+
+/**
+ * Determines if the specified string consists entirely of whitespace.
+ */
+function isEmpty(string) {
+>isEmpty : (string: any) => boolean
+>string : any
+
+   return !/[^\s]/.test(string);
+>!/[^\s]/.test(string) : boolean
+>/[^\s]/.test(string) : boolean
+>/[^\s]/.test : (string: string) => boolean
+>/[^\s]/ : RegExp
+>test : (string: string) => boolean
+>string : any
+}
+
+/**
+ * Determines if the CSS value can be converted from a
+ * 'px' suffixed string to a numeric value
+ *
+ * @param {string} value CSS property value
+ * @return {boolean}
+ */
+function isConvertiblePixelValue(value) {
+>isConvertiblePixelValue : (value: any) => boolean
+>value : any
+
+  return /^\d+px$/.test(value);
+>/^\d+px$/.test(value) : boolean
+>/^\d+px$/.test : (string: string) => boolean
+>/^\d+px$/ : RegExp
+>test : (string: string) => boolean
+>value : any
+}
+
+export class HTMLtoJSX {
+>HTMLtoJSX : HTMLtoJSX
+
+    private output: string;
+>output : string
+
+    private level: number;
+>level : number
+
+    private _inPreTag: boolean;
+>_inPreTag : boolean
+
+
+  /**
+   * Handles processing of the specified text node
+   *
+   * @param {TextNode} node
+   */
+  _visitText = (node) => {
+>_visitText : (node: any) => void
+>(node) => {    var parentTag = node.parentNode && node.parentNode.tagName.toLowerCase();    if (parentTag === 'textarea' || parentTag === 'style') {      // Ignore text content of textareas and styles, as it will have already been moved      // to a "defaultValue" attribute and "dangerouslySetInnerHTML" attribute respectively.      return;    }    var text = ''    if (this._inPreTag) {      // If this text is contained within a <pre>, we need to ensure the JSX      // whitespace coalescing rules don't eat the whitespace. This means      // wrapping newlines and sequences of two or more spaces in variables.      text = text        .replace(/\r/g, '')        .replace(/( {2,}|\n|\t|\{|\})/g, function(whitespace) {          return '{' + JSON.stringify(whitespace) + '}';        });    } else {      // If there's a newline in the text, adjust the indent level      if (text.indexOf('\n') > -1) {      }    }    this.output += text;  } : (node: any) => void
+>node : any
+
+    var parentTag = node.parentNode && node.parentNode.tagName.toLowerCase();
+>parentTag : any
+>node.parentNode && node.parentNode.tagName.toLowerCase() : any
+>node.parentNode : any
+>node : any
+>parentNode : any
+>node.parentNode.tagName.toLowerCase() : any
+>node.parentNode.tagName.toLowerCase : any
+>node.parentNode.tagName : any
+>node.parentNode : any
+>node : any
+>parentNode : any
+>tagName : any
+>toLowerCase : any
+
+    if (parentTag === 'textarea' || parentTag === 'style') {
+>parentTag === 'textarea' || parentTag === 'style' : boolean
+>parentTag === 'textarea' : boolean
+>parentTag : any
+>'textarea' : string
+>parentTag === 'style' : boolean
+>parentTag : any
+>'style' : string
+
+      // Ignore text content of textareas and styles, as it will have already been moved
+      // to a "defaultValue" attribute and "dangerouslySetInnerHTML" attribute respectively.
+      return;
+    }
+
+    var text = ''
+>text : string
+>'' : string
+
+    if (this._inPreTag) {
+>this._inPreTag : boolean
+>this : this
+>_inPreTag : boolean
+
+      // If this text is contained within a <pre>, we need to ensure the JSX
+      // whitespace coalescing rules don't eat the whitespace. This means
+      // wrapping newlines and sequences of two or more spaces in variables.
+      text = text
+>text = text        .replace(/\r/g, '')        .replace(/( {2,}|\n|\t|\{|\})/g, function(whitespace) {          return '{' + JSON.stringify(whitespace) + '}';        }) : string
+>text : string
+>text        .replace(/\r/g, '')        .replace(/( {2,}|\n|\t|\{|\})/g, function(whitespace) {          return '{' + JSON.stringify(whitespace) + '}';        }) : string
+>text        .replace(/\r/g, '')        .replace : { (searchValue: string, replaceValue: string): string; (searchValue: string, replacer: (substring: string, ...args: any[]) => string): string; (searchValue: RegExp, replaceValue: string): string; (searchValue: RegExp, replacer: (substring: string, ...args: any[]) => string): string; }
+>text        .replace(/\r/g, '') : string
+>text        .replace : { (searchValue: string, replaceValue: string): string; (searchValue: string, replacer: (substring: string, ...args: any[]) => string): string; (searchValue: RegExp, replaceValue: string): string; (searchValue: RegExp, replacer: (substring: string, ...args: any[]) => string): string; }
+>text : string
+
+        .replace(/\r/g, '')
+>replace : { (searchValue: string, replaceValue: string): string; (searchValue: string, replacer: (substring: string, ...args: any[]) => string): string; (searchValue: RegExp, replaceValue: string): string; (searchValue: RegExp, replacer: (substring: string, ...args: any[]) => string): string; }
+>/\r/g : RegExp
+>'' : string
+
+        .replace(/( {2,}|\n|\t|\{|\})/g, function(whitespace) {
+>replace : { (searchValue: string, replaceValue: string): string; (searchValue: string, replacer: (substring: string, ...args: any[]) => string): string; (searchValue: RegExp, replaceValue: string): string; (searchValue: RegExp, replacer: (substring: string, ...args: any[]) => string): string; }
+>/( {2,}|\n|\t|\{|\})/g : RegExp
+>function(whitespace) {          return '{' + JSON.stringify(whitespace) + '}';        } : (whitespace: string) => string
+>whitespace : string
+
+          return '{' + JSON.stringify(whitespace) + '}';
+>'{' + JSON.stringify(whitespace) + '}' : string
+>'{' + JSON.stringify(whitespace) : string
+>'{' : string
+>JSON.stringify(whitespace) : string
+>JSON.stringify : { (value: any, replacer?: (key: string, value: any) => any, space?: string | number): string; (value: any, replacer?: (number | string)[], space?: string | number): string; }
+>JSON : JSON
+>stringify : { (value: any, replacer?: (key: string, value: any) => any, space?: string | number): string; (value: any, replacer?: (number | string)[], space?: string | number): string; }
+>whitespace : string
+>'}' : string
+
+        });
+    } else {
+      // If there's a newline in the text, adjust the indent level
+      if (text.indexOf('\n') > -1) {
+>text.indexOf('\n') > -1 : boolean
+>text.indexOf('\n') : number
+>text.indexOf : (searchString: string, position?: number) => number
+>text : string
+>indexOf : (searchString: string, position?: number) => number
+>'\n' : string
+>-1 : number
+>1 : number
+      }
+    }
+    this.output += text;
+>this.output += text : string
+>this.output : string
+>this : this
+>output : string
+>text : string
+  }
+
+
+
+};
+
+/**
+ * Handles parsing of inline styles
+ */
+export class StyleParser {
+>StyleParser : StyleParser
+
+  styles = {};
+>styles : {}
+>{} : {}
+
+  toJSXString = () => {
+>toJSXString : () => void
+>() => {    for (var key in this.styles) {      if (!this.styles.hasOwnProperty(key)) {      }    }  } : () => void
+
+    for (var key in this.styles) {
+>key : string
+>this.styles : {}
+>this : this
+>styles : {}
+
+      if (!this.styles.hasOwnProperty(key)) {
+>!this.styles.hasOwnProperty(key) : boolean
+>this.styles.hasOwnProperty(key) : boolean
+>this.styles.hasOwnProperty : (v: string) => boolean
+>this.styles : {}
+>this : this
+>styles : {}
+>hasOwnProperty : (v: string) => boolean
+>key : string
+      }
+    }
+  }
+}
diff --git a/tests/baselines/reference/initializersWidened.js b/tests/baselines/reference/initializersWidened.js
index fce0750a600..3954735ee6e 100644
--- a/tests/baselines/reference/initializersWidened.js
+++ b/tests/baselines/reference/initializersWidened.js
@@ -1,10 +1,44 @@
 //// [initializersWidened.ts]
 // these are widened to any at the point of assignment
 
-var x = null;
-var y = undefined;
+var x1 = null;
+var y1 = undefined;
+var z1 = void 0;
+
+// these are not widened
+
+var x2: null;
+var y2: undefined;
+
+var x3: null = null;
+var y3: undefined = undefined;
+var z3: undefined = void 0;
+
+// widen only when all constituents of union are widening
+
+var x4 = null || null;
+var y4 = undefined || undefined;
+var z4 = void 0 || void 0;
+
+var x5 = null || x2;
+var y5 = undefined || y2;
+var z5 = void 0 || y2;
 
 //// [initializersWidened.js]
 // these are widened to any at the point of assignment
-var x = null;
-var y = undefined;
+var x1 = null;
+var y1 = undefined;
+var z1 = void 0;
+// these are not widened
+var x2;
+var y2;
+var x3 = null;
+var y3 = undefined;
+var z3 = void 0;
+// widen only when all constituents of union are widening
+var x4 = null || null;
+var y4 = undefined || undefined;
+var z4 = void 0 || void 0;
+var x5 = null || x2;
+var y5 = undefined || y2;
+var z5 = void 0 || y2;
diff --git a/tests/baselines/reference/initializersWidened.symbols b/tests/baselines/reference/initializersWidened.symbols
index 625c066a058..252a248bec8 100644
--- a/tests/baselines/reference/initializersWidened.symbols
+++ b/tests/baselines/reference/initializersWidened.symbols
@@ -1,10 +1,57 @@
 === tests/cases/conformance/types/typeRelationships/widenedTypes/initializersWidened.ts ===
 // these are widened to any at the point of assignment
 
-var x = null;
->x : Symbol(x, Decl(initializersWidened.ts, 2, 3))
+var x1 = null;
+>x1 : Symbol(x1, Decl(initializersWidened.ts, 2, 3))
 
-var y = undefined;
->y : Symbol(y, Decl(initializersWidened.ts, 3, 3))
+var y1 = undefined;
+>y1 : Symbol(y1, Decl(initializersWidened.ts, 3, 3))
 >undefined : Symbol(undefined)
 
+var z1 = void 0;
+>z1 : Symbol(z1, Decl(initializersWidened.ts, 4, 3))
+
+// these are not widened
+
+var x2: null;
+>x2 : Symbol(x2, Decl(initializersWidened.ts, 8, 3))
+
+var y2: undefined;
+>y2 : Symbol(y2, Decl(initializersWidened.ts, 9, 3))
+
+var x3: null = null;
+>x3 : Symbol(x3, Decl(initializersWidened.ts, 11, 3))
+
+var y3: undefined = undefined;
+>y3 : Symbol(y3, Decl(initializersWidened.ts, 12, 3))
+>undefined : Symbol(undefined)
+
+var z3: undefined = void 0;
+>z3 : Symbol(z3, Decl(initializersWidened.ts, 13, 3))
+
+// widen only when all constituents of union are widening
+
+var x4 = null || null;
+>x4 : Symbol(x4, Decl(initializersWidened.ts, 17, 3))
+
+var y4 = undefined || undefined;
+>y4 : Symbol(y4, Decl(initializersWidened.ts, 18, 3))
+>undefined : Symbol(undefined)
+>undefined : Symbol(undefined)
+
+var z4 = void 0 || void 0;
+>z4 : Symbol(z4, Decl(initializersWidened.ts, 19, 3))
+
+var x5 = null || x2;
+>x5 : Symbol(x5, Decl(initializersWidened.ts, 21, 3))
+>x2 : Symbol(x2, Decl(initializersWidened.ts, 8, 3))
+
+var y5 = undefined || y2;
+>y5 : Symbol(y5, Decl(initializersWidened.ts, 22, 3))
+>undefined : Symbol(undefined)
+>y2 : Symbol(y2, Decl(initializersWidened.ts, 9, 3))
+
+var z5 = void 0 || y2;
+>z5 : Symbol(z5, Decl(initializersWidened.ts, 23, 3))
+>y2 : Symbol(y2, Decl(initializersWidened.ts, 9, 3))
+
diff --git a/tests/baselines/reference/initializersWidened.types b/tests/baselines/reference/initializersWidened.types
index 15705589246..766f859029a 100644
--- a/tests/baselines/reference/initializersWidened.types
+++ b/tests/baselines/reference/initializersWidened.types
@@ -1,11 +1,80 @@
 === tests/cases/conformance/types/typeRelationships/widenedTypes/initializersWidened.ts ===
 // these are widened to any at the point of assignment
 
-var x = null;
->x : any
+var x1 = null;
+>x1 : any
 >null : null
 
-var y = undefined;
->y : any
+var y1 = undefined;
+>y1 : any
 >undefined : undefined
 
+var z1 = void 0;
+>z1 : any
+>void 0 : undefined
+>0 : number
+
+// these are not widened
+
+var x2: null;
+>x2 : null
+>null : null
+
+var y2: undefined;
+>y2 : undefined
+
+var x3: null = null;
+>x3 : null
+>null : null
+>null : null
+
+var y3: undefined = undefined;
+>y3 : undefined
+>undefined : undefined
+
+var z3: undefined = void 0;
+>z3 : undefined
+>void 0 : undefined
+>0 : number
+
+// widen only when all constituents of union are widening
+
+var x4 = null || null;
+>x4 : any
+>null || null : null
+>null : null
+>null : null
+
+var y4 = undefined || undefined;
+>y4 : any
+>undefined || undefined : undefined
+>undefined : undefined
+>undefined : undefined
+
+var z4 = void 0 || void 0;
+>z4 : any
+>void 0 || void 0 : undefined
+>void 0 : undefined
+>0 : number
+>void 0 : undefined
+>0 : number
+
+var x5 = null || x2;
+>x5 : null
+>null || x2 : null
+>null : null
+>x2 : null
+
+var y5 = undefined || y2;
+>y5 : undefined
+>undefined || y2 : undefined
+>undefined : undefined
+>y2 : undefined
+
+var z5 = void 0 || y2;
+>z5 : undefined
+>void 0 || y2 : undefined
+>void 0 : undefined
+>0 : number
+>y2 : undefined
+
diff --git a/tests/baselines/reference/logicalAndOperatorWithEveryType.types b/tests/baselines/reference/logicalAndOperatorWithEveryType.types
index b2628eed921..bd913e94da5 100644
--- a/tests/baselines/reference/logicalAndOperatorWithEveryType.types
+++ b/tests/baselines/reference/logicalAndOperatorWithEveryType.types
@@ -623,7 +623,7 @@ var rj8 = a8 && undefined;
 
 var rj9 = null && undefined;
 >rj9 : any
->null && undefined : null
+>null && undefined : undefined
 >null : null
 >undefined : undefined
 
diff --git a/tests/baselines/reference/objectLiteralWidened.js b/tests/baselines/reference/objectLiteralWidened.js
index 4de228cb14a..98d79133540 100644
--- a/tests/baselines/reference/objectLiteralWidened.js
+++ b/tests/baselines/reference/objectLiteralWidened.js
@@ -1,29 +1,61 @@
 //// [objectLiteralWidened.ts]
 // object literal properties are widened to any
 
-var x = {
+var x1 = {
     foo: null,
     bar: undefined
 }
 
-var y = {
+var y1 = {
     foo: null,
     bar: {
         baz: null,
         boo: undefined
     }
+}
+
+// these are not widened
+
+var u: undefined = undefined;
+var n: null = null;
+
+var x2 = {
+    foo: n,
+    bar: u
+}
+
+var y2 = {
+    foo: n,
+    bar: {
+        baz: n,
+        boo: u
+    }
 }
 
 //// [objectLiteralWidened.js]
 // object literal properties are widened to any
-var x = {
+var x1 = {
     foo: null,
     bar: undefined
 };
-var y = {
+var y1 = {
     foo: null,
     bar: {
         baz: null,
         boo: undefined
     }
 };
+// these are not widened
+var u = undefined;
+var n = null;
+var x2 = {
+    foo: n,
+    bar: u
+};
+var y2 = {
+    foo: n,
+    bar: {
+        baz: n,
+        boo: u
+    }
+};
diff --git a/tests/baselines/reference/objectLiteralWidened.symbols b/tests/baselines/reference/objectLiteralWidened.symbols
index 0bf077cd9d8..4b2a1b4a001 100644
--- a/tests/baselines/reference/objectLiteralWidened.symbols
+++ b/tests/baselines/reference/objectLiteralWidened.symbols
@@ -1,22 +1,22 @@
 === tests/cases/conformance/types/typeRelationships/widenedTypes/objectLiteralWidened.ts ===
 // object literal properties are widened to any
 
-var x = {
->x : Symbol(x, Decl(objectLiteralWidened.ts, 2, 3))
+var x1 = {
+>x1 : Symbol(x1, Decl(objectLiteralWidened.ts, 2, 3))
 
     foo: null,
->foo : Symbol(foo, Decl(objectLiteralWidened.ts, 2, 9))
+>foo : Symbol(foo, Decl(objectLiteralWidened.ts, 2, 10))
 
     bar: undefined
 >bar : Symbol(bar, Decl(objectLiteralWidened.ts, 3, 14))
 >undefined : Symbol(undefined)
 }
 
-var y = {
->y : Symbol(y, Decl(objectLiteralWidened.ts, 7, 3))
+var y1 = {
+>y1 : Symbol(y1, Decl(objectLiteralWidened.ts, 7, 3))
 
     foo: null,
->foo : Symbol(foo, Decl(objectLiteralWidened.ts, 7, 9))
+>foo : Symbol(foo, Decl(objectLiteralWidened.ts, 7, 10))
 
     bar: {
 >bar : Symbol(bar, Decl(objectLiteralWidened.ts, 8, 14))
@@ -29,3 +29,44 @@ var y = {
 >undefined : Symbol(undefined)
     }
 }
+
+// these are not widened
+
+var u: undefined = undefined;
+>u : Symbol(u, Decl(objectLiteralWidened.ts, 17, 3))
+>undefined : Symbol(undefined)
+
+var n: null = null;
+>n : Symbol(n, Decl(objectLiteralWidened.ts, 18, 3))
+
+var x2 = {
+>x2 : Symbol(x2, Decl(objectLiteralWidened.ts, 20, 3))
+
+    foo: n,
+>foo : Symbol(foo, Decl(objectLiteralWidened.ts, 20, 10))
+>n : Symbol(n, Decl(objectLiteralWidened.ts, 18, 3))
+
+    bar: u
+>bar : Symbol(bar, Decl(objectLiteralWidened.ts, 21, 11))
+>u : Symbol(u, Decl(objectLiteralWidened.ts, 17, 3))
+}
+
+var y2 = {
+>y2 : Symbol(y2, Decl(objectLiteralWidened.ts, 25, 3))
+
+    foo: n,
+>foo : Symbol(foo, Decl(objectLiteralWidened.ts, 25, 10))
+>n : Symbol(n, Decl(objectLiteralWidened.ts, 18, 3))
+
+    bar: {
+>bar : Symbol(bar, Decl(objectLiteralWidened.ts, 26, 11))
+
+        baz: n,
+>baz : Symbol(baz, Decl(objectLiteralWidened.ts, 27, 10))
+>n : Symbol(n, Decl(objectLiteralWidened.ts, 18, 3))
+
+        boo: u
+>boo : Symbol(boo, Decl(objectLiteralWidened.ts, 28, 15))
+>u : Symbol(u, Decl(objectLiteralWidened.ts, 17, 3))
+    }
+}
diff --git a/tests/baselines/reference/objectLiteralWidened.types b/tests/baselines/reference/objectLiteralWidened.types
index 9f47e47795d..66309202617 100644
--- a/tests/baselines/reference/objectLiteralWidened.types
+++ b/tests/baselines/reference/objectLiteralWidened.types
@@ -1,8 +1,8 @@
 === tests/cases/conformance/types/typeRelationships/widenedTypes/objectLiteralWidened.ts ===
 // object literal properties are widened to any
 
-var x = {
->x : { foo: any; bar: any; }
+var x1 = {
+>x1 : { foo: any; bar: any; }
 >{    foo: null,    bar: undefined} : { foo: null; bar: undefined; }
 
     foo: null,
@@ -14,8 +14,8 @@ var x = {
 >undefined : undefined
 }
 
-var y = {
->y : { foo: any; bar: { baz: any; boo: any; }; }
+var y1 = {
+>y1 : { foo: any; bar: { baz: any; boo: any; }; }
 >{    foo: null,    bar: {        baz: null,        boo: undefined    }} : { foo: null; bar: { baz: null; boo: undefined; }; }
 
     foo: null,
@@ -35,3 +35,49 @@ var y = {
 >undefined : undefined
     }
 }
+
+// these are not widened
+
+var u: undefined = undefined;
+>u : undefined
+>undefined : undefined
+
+var n: null = null;
+>n : null
+>null : null
+>null : null
+
+var x2 = {
+>x2 : { foo: null; bar: undefined; }
+>{    foo: n,    bar: u} : { foo: null; bar: undefined; }
+
+    foo: n,
+>foo : null
+>n : null
+
+    bar: u
+>bar : undefined
+>u : undefined
+}
+
+var y2 = {
+>y2 : { foo: null; bar: { baz: null; boo: undefined; }; }
+>{    foo: n,    bar: {        baz: n,        boo: u    }} : { foo: null; bar: { baz: null; boo: undefined; }; }
+
+    foo: n,
+>foo : null
+>n : null
+
+    bar: {
+>bar : { baz: null; boo: undefined; }
+>{        baz: n,        boo: u    } : { baz: null; boo: undefined; }
+
+        baz: n,
+>baz : null
+>n : null
+
+        boo: u
+>boo : undefined
+>u : undefined
+    }
+}
diff --git a/tests/baselines/reference/strictNullChecksNoWidening.js b/tests/baselines/reference/strictNullChecksNoWidening.js
new file mode 100644
index 00000000000..ba26a04fc13
--- /dev/null
+++ b/tests/baselines/reference/strictNullChecksNoWidening.js
@@ -0,0 +1,31 @@
+//// [strictNullChecksNoWidening.ts]
+
+var a1 = null;
+var a2 = undefined;
+var a3 = void 0;
+
+var b1 = [];
+var b2 = [,];
+var b3 = [undefined];
+var b4 = [[], []];
+var b5 = [[], [,]];
+
+declare function f<T>(x: T): T;
+
+var c1 = f(null);
+var c2 = f(undefined);
+var c3 = f([]);
+
+
+//// [strictNullChecksNoWidening.js]
+var a1 = null;
+var a2 = undefined;
+var a3 = void 0;
+var b1 = [];
+var b2 = [,];
+var b3 = [undefined];
+var b4 = [[], []];
+var b5 = [[], [,]];
+var c1 = f(null);
+var c2 = f(undefined);
+var c3 = f([]);
diff --git a/tests/baselines/reference/strictNullChecksNoWidening.symbols b/tests/baselines/reference/strictNullChecksNoWidening.symbols
new file mode 100644
index 00000000000..a23a0d2e926
--- /dev/null
+++ b/tests/baselines/reference/strictNullChecksNoWidening.symbols
@@ -0,0 +1,48 @@
+=== tests/cases/conformance/types/typeRelationships/widenedTypes/strictNullChecksNoWidening.ts ===
+
+var a1 = null;
+>a1 : Symbol(a1, Decl(strictNullChecksNoWidening.ts, 1, 3))
+
+var a2 = undefined;
+>a2 : Symbol(a2, Decl(strictNullChecksNoWidening.ts, 2, 3))
+>undefined : Symbol(undefined)
+
+var a3 = void 0;
+>a3 : Symbol(a3, Decl(strictNullChecksNoWidening.ts, 3, 3))
+
+var b1 = [];
+>b1 : Symbol(b1, Decl(strictNullChecksNoWidening.ts, 5, 3))
+
+var b2 = [,];
+>b2 : Symbol(b2, Decl(strictNullChecksNoWidening.ts, 6, 3))
+
+var b3 = [undefined];
+>b3 : Symbol(b3, Decl(strictNullChecksNoWidening.ts, 7, 3))
+>undefined : Symbol(undefined)
+
+var b4 = [[], []];
+>b4 : Symbol(b4, Decl(strictNullChecksNoWidening.ts, 8, 3))
+
+var b5 = [[], [,]];
+>b5 : Symbol(b5, Decl(strictNullChecksNoWidening.ts, 9, 3))
+
+declare function f<T>(x: T): T;
+>f : Symbol(f, Decl(strictNullChecksNoWidening.ts, 9, 19))
+>T : Symbol(T, Decl(strictNullChecksNoWidening.ts, 11, 19))
+>x : Symbol(x, Decl(strictNullChecksNoWidening.ts, 11, 22))
+>T : Symbol(T, Decl(strictNullChecksNoWidening.ts, 11, 19))
+>T : Symbol(T, Decl(strictNullChecksNoWidening.ts, 11, 19))
+
+var c1 = f(null);
+>c1 : Symbol(c1, Decl(strictNullChecksNoWidening.ts, 13, 3))
+>f : Symbol(f, Decl(strictNullChecksNoWidening.ts, 9, 19))
+
+var c2 = f(undefined);
+>c2 : Symbol(c2, Decl(strictNullChecksNoWidening.ts, 14, 3))
+>f : Symbol(f, Decl(strictNullChecksNoWidening.ts, 9, 19))
+>undefined : Symbol(undefined)
+
+var c3 = f([]);
+>c3 : Symbol(c3, Decl(strictNullChecksNoWidening.ts, 15, 3))
+>f : Symbol(f, Decl(strictNullChecksNoWidening.ts, 9, 19))
+
diff --git a/tests/baselines/reference/strictNullChecksNoWidening.types b/tests/baselines/reference/strictNullChecksNoWidening.types
new file mode 100644
index 00000000000..6dd2ee3fb4c
--- /dev/null
+++ b/tests/baselines/reference/strictNullChecksNoWidening.types
@@ -0,0 +1,67 @@
+=== tests/cases/conformance/types/typeRelationships/widenedTypes/strictNullChecksNoWidening.ts ===
+
+var a1 = null;
+>a1 : null
+>null : null
+
+var a2 = undefined;
+>a2 : undefined
+>undefined : undefined
+
+var a3 = void 0;
+>a3 : undefined
+>void 0 : undefined
+>0 : number
+
+var b1 = [];
+>b1 : never[]
+>[] : never[]
+
+var b2 = [,];
+>b2 : undefined[]
+>[,] : undefined[]
+> : undefined
+
+var b3 = [undefined];
+>b3 : undefined[]
+>[undefined] : undefined[]
+>undefined : undefined
+
+var b4 = [[], []];
+>b4 : never[][]
+>[[], []] : never[][]
+>[] : never[]
+>[] : never[]
+
+var b5 = [[], [,]];
+>b5 : undefined[][]
+>[[], [,]] : undefined[][]
+>[] : never[]
+>[,] : undefined[]
+> : undefined
+
+declare function f<T>(x: T): T;
+>f : <T>(x: T) => T
+>T : T
+>x : T
+>T : T
+>T : T
+
+var c1 = f(null);
+>c1 : null
+>f(null) : null
+>f : <T>(x: T) => T
+>null : null
+
+var c2 = f(undefined);
+>c2 : undefined
+>f(undefined) : undefined
+>f : <T>(x: T) => T
+>undefined : undefined
+
+var c3 = f([]);
+>c3 : never[]
+>f([]) : never[]
+>f : <T>(x: T) => T
+>[] : never[]
+
diff --git a/tests/baselines/reference/typeGuardsInFunctionAndModuleBlock.js b/tests/baselines/reference/typeGuardsInFunctionAndModuleBlock.js
index 91443a9ae78..8ec45de814e 100644
--- a/tests/baselines/reference/typeGuardsInFunctionAndModuleBlock.js
+++ b/tests/baselines/reference/typeGuardsInFunctionAndModuleBlock.js
@@ -41,7 +41,7 @@ function foo4(x: number | string | boolean) {
                 : x.toString(); // number
         })(x); // x here is narrowed to number | boolean
 }
-// Type guards affect nested function expressions and nested function declarations
+// Type guards do not affect nested function declarations
 function foo5(x: number | string | boolean) {
     if (typeof x === "string") {
         var y = x; // string;
@@ -121,7 +121,7 @@ function foo4(x) {
                 : x.toString(); // number
         })(x); // x here is narrowed to number | boolean
 }
-// Type guards affect nested function expressions and nested function declarations
+// Type guards do not affect nested function declarations
 function foo5(x) {
     if (typeof x === "string") {
         var y = x; // string;
diff --git a/tests/baselines/reference/typeGuardsInFunctionAndModuleBlock.symbols b/tests/baselines/reference/typeGuardsInFunctionAndModuleBlock.symbols
index bf21641624e..56eeb22bf9f 100644
--- a/tests/baselines/reference/typeGuardsInFunctionAndModuleBlock.symbols
+++ b/tests/baselines/reference/typeGuardsInFunctionAndModuleBlock.symbols
@@ -27,9 +27,9 @@ function foo(x: number | string | boolean) {
 >toString : Symbol(Object.toString, Decl(lib.d.ts, --, --))
 
                 : x.toString(); // number
->x.toString : Symbol(toString, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>x.toString : Symbol(Number.toString, Decl(lib.d.ts, --, --))
 >x : Symbol(x, Decl(typeGuardsInFunctionAndModuleBlock.ts, 2, 13))
->toString : Symbol(toString, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>toString : Symbol(Number.toString, Decl(lib.d.ts, --, --))
 
         } ();
 }
@@ -60,9 +60,9 @@ function foo2(x: number | string | boolean) {
 >toString : Symbol(Object.toString, Decl(lib.d.ts, --, --))
 
                 : x.toString(); // number
->x.toString : Symbol(toString, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>x.toString : Symbol(Number.toString, Decl(lib.d.ts, --, --))
 >x : Symbol(x, Decl(typeGuardsInFunctionAndModuleBlock.ts, 12, 14))
->toString : Symbol(toString, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>toString : Symbol(Number.toString, Decl(lib.d.ts, --, --))
 
         } (x); // x here is narrowed to number | boolean
 >x : Symbol(x, Decl(typeGuardsInFunctionAndModuleBlock.ts, 12, 14))
@@ -91,9 +91,9 @@ function foo3(x: number | string | boolean) {
 >toString : Symbol(Object.toString, Decl(lib.d.ts, --, --))
 
                 : x.toString(); // number
->x.toString : Symbol(toString, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>x.toString : Symbol(Number.toString, Decl(lib.d.ts, --, --))
 >x : Symbol(x, Decl(typeGuardsInFunctionAndModuleBlock.ts, 22, 14))
->toString : Symbol(toString, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>toString : Symbol(Number.toString, Decl(lib.d.ts, --, --))
 
         })();
 }
@@ -123,14 +123,14 @@ function foo4(x: number | string | boolean) {
 >toString : Symbol(Object.toString, Decl(lib.d.ts, --, --))
 
                 : x.toString(); // number
->x.toString : Symbol(toString, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>x.toString : Symbol(Number.toString, Decl(lib.d.ts, --, --))
 >x : Symbol(x, Decl(typeGuardsInFunctionAndModuleBlock.ts, 32, 14))
->toString : Symbol(toString, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>toString : Symbol(Number.toString, Decl(lib.d.ts, --, --))
 
         })(x); // x here is narrowed to number | boolean
 >x : Symbol(x, Decl(typeGuardsInFunctionAndModuleBlock.ts, 32, 14))
 }
-// Type guards affect nested function expressions and nested function declarations
+// Type guards do not affect nested function declarations
 function foo5(x: number | string | boolean) {
 >foo5 : Symbol(foo5, Decl(typeGuardsInFunctionAndModuleBlock.ts, 41, 1))
 >x : Symbol(x, Decl(typeGuardsInFunctionAndModuleBlock.ts, 43, 14))
diff --git a/tests/baselines/reference/typeGuardsInFunctionAndModuleBlock.types b/tests/baselines/reference/typeGuardsInFunctionAndModuleBlock.types
index 67d1816cfc3..cc9553b9767 100644
--- a/tests/baselines/reference/typeGuardsInFunctionAndModuleBlock.types
+++ b/tests/baselines/reference/typeGuardsInFunctionAndModuleBlock.types
@@ -21,14 +21,14 @@ function foo(x: number | string | boolean) {
 >f : () => string
 
             var b = x; // number | boolean
->b : number | string | boolean
->x : number | string | boolean
+>b : number | boolean
+>x : number | boolean
 
             return typeof x === "boolean"
 >typeof x === "boolean"                ? x.toString() // boolean                : x.toString() : string
 >typeof x === "boolean" : boolean
 >typeof x : string
->x : number | string | boolean
+>x : number | boolean
 >"boolean" : string
 
                 ? x.toString() // boolean
@@ -40,7 +40,7 @@ function foo(x: number | string | boolean) {
                 : x.toString(); // number
 >x.toString() : string
 >x.toString : (radix?: number) => string
->x : number | string
+>x : number
 >toString : (radix?: number) => string
 
         } ();
@@ -66,14 +66,14 @@ function foo2(x: number | string | boolean) {
 >a : number | boolean
 
             var b = x; // new scope - number | boolean
->b : number | string | boolean
->x : number | string | boolean
+>b : number | boolean
+>x : number | boolean
 
             return typeof x === "boolean"
 >typeof x === "boolean"                ? x.toString() // boolean                : x.toString() : string
 >typeof x === "boolean" : boolean
 >typeof x : string
->x : number | string | boolean
+>x : number | boolean
 >"boolean" : string
 
                 ? x.toString() // boolean
@@ -85,7 +85,7 @@ function foo2(x: number | string | boolean) {
                 : x.toString(); // number
 >x.toString() : string
 >x.toString : (radix?: number) => string
->x : number | string
+>x : number
 >toString : (radix?: number) => string
 
         } (x); // x here is narrowed to number | boolean
@@ -111,14 +111,14 @@ function foo3(x: number | string | boolean) {
 >() => {            var b = x; // new scope - number | boolean            return typeof x === "boolean"                ? x.toString() // boolean                : x.toString(); // number        } : () => string
 
             var b = x; // new scope - number | boolean
->b : number | string | boolean
->x : number | string | boolean
+>b : number | boolean
+>x : number | boolean
 
             return typeof x === "boolean"
 >typeof x === "boolean"                ? x.toString() // boolean                : x.toString() : string
 >typeof x === "boolean" : boolean
 >typeof x : string
->x : number | string | boolean
+>x : number | boolean
 >"boolean" : string
 
                 ? x.toString() // boolean
@@ -130,7 +130,7 @@ function foo3(x: number | string | boolean) {
                 : x.toString(); // number
 >x.toString() : string
 >x.toString : (radix?: number) => string
->x : number | string
+>x : number
 >toString : (radix?: number) => string
 
         })();
@@ -156,14 +156,14 @@ function foo4(x: number | string | boolean) {
 >a : number | boolean
 
             var b = x; // new scope - number | boolean
->b : number | string | boolean
->x : number | string | boolean
+>b : number | boolean
+>x : number | boolean
 
             return typeof x === "boolean"
 >typeof x === "boolean"                ? x.toString() // boolean                : x.toString() : string
 >typeof x === "boolean" : boolean
 >typeof x : string
->x : number | string | boolean
+>x : number | boolean
 >"boolean" : string
 
                 ? x.toString() // boolean
@@ -175,13 +175,13 @@ function foo4(x: number | string | boolean) {
                 : x.toString(); // number
 >x.toString() : string
 >x.toString : (radix?: number) => string
->x : number | string
+>x : number
 >toString : (radix?: number) => string
 
         })(x); // x here is narrowed to number | boolean
 >x : number | boolean
 }
-// Type guards affect nested function expressions and nested function declarations
+// Type guards do not affect nested function declarations
 function foo5(x: number | string | boolean) {
 >foo5 : (x: number | string | boolean) => void
 >x : number | string | boolean
diff --git a/tests/cases/compiler/controlFlowPropertyDeclarations.ts b/tests/cases/compiler/controlFlowPropertyDeclarations.ts
new file mode 100644
index 00000000000..5a5e9fb96bf
--- /dev/null
+++ b/tests/cases/compiler/controlFlowPropertyDeclarations.ts
@@ -0,0 +1,148 @@
+// Repro from ##8913
+
+declare var require:any;
+
+var HTMLDOMPropertyConfig = require('react/lib/HTMLDOMPropertyConfig');
+
+// Populate property map with ReactJS's attribute and property mappings
+// TODO handle/use .Properties value eg: MUST_USE_PROPERTY is not HTML attr
+for (var propname in HTMLDOMPropertyConfig.Properties) {
+  if (!HTMLDOMPropertyConfig.Properties.hasOwnProperty(propname)) {
+    continue;
+  }
+
+  var mapFrom = HTMLDOMPropertyConfig.DOMAttributeNames[propname] || propname.toLowerCase();
+}
+
+/**
+ * Repeats a string a certain number of times.
+ * Also: the future is bright and consists of native string repetition:
+ * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/repeat
+ *
+ * @param {string} string  String to repeat
+ * @param {number} times   Number of times to repeat string. Integer.
+ * @see http://jsperf.com/string-repeater/2
+ */
+function repeatString(string, times) {
+  if (times === 1) {
+    return string;
+  }
+  if (times < 0) { throw new Error(); }
+  var repeated = '';
+  while (times) {
+    if (times & 1) {
+      repeated += string;
+    }
+    if (times >>= 1) {
+      string += string;
+    }
+  }
+  return repeated;
+}
+
+/**
+ * Determine if the string ends with the specified substring.
+ *
+ * @param {string} haystack String to search in
+ * @param {string} needle   String to search for
+ * @return {boolean}
+ */
+function endsWith(haystack, needle) {
+  return haystack.slice(-needle.length) === needle;
+}
+
+/**
+ * Trim the specified substring off the string. If the string does not end
+ * with the specified substring, this is a no-op.
+ *
+ * @param {string} haystack String to search in
+ * @param {string} needle   String to search for
+ * @return {string}
+ */
+function trimEnd(haystack, needle) {
+  return endsWith(haystack, needle)
+    ? haystack.slice(0, -needle.length)
+    : haystack;
+}
+
+/**
+ * Convert a hyphenated string to camelCase.
+ */
+function hyphenToCamelCase(string) {
+  return string.replace(/-(.)/g, function(match, chr) {
+    return chr.toUpperCase();
+  });
+}
+
+/**
+ * Determines if the specified string consists entirely of whitespace.
+ */
+function isEmpty(string) {
+   return !/[^\s]/.test(string);
+}
+
+/**
+ * Determines if the CSS value can be converted from a
+ * 'px' suffixed string to a numeric value
+ *
+ * @param {string} value CSS property value
+ * @return {boolean}
+ */
+function isConvertiblePixelValue(value) {
+  return /^\d+px$/.test(value);
+}
+
+export class HTMLtoJSX {
+    private output: string;
+    private level: number;
+    private _inPreTag: boolean;
+
+
+  /**
+   * Handles processing of the specified text node
+   *
+   * @param {TextNode} node
+   */
+  _visitText = (node) => {
+    var parentTag = node.parentNode && node.parentNode.tagName.toLowerCase();
+    if (parentTag === 'textarea' || parentTag === 'style') {
+      // Ignore text content of textareas and styles, as it will have already been moved
+      // to a "defaultValue" attribute and "dangerouslySetInnerHTML" attribute respectively.
+      return;
+    }
+
+    var text = ''
+
+    if (this._inPreTag) {
+      // If this text is contained within a <pre>, we need to ensure the JSX
+      // whitespace coalescing rules don't eat the whitespace. This means
+      // wrapping newlines and sequences of two or more spaces in variables.
+      text = text
+        .replace(/\r/g, '')
+        .replace(/( {2,}|\n|\t|\{|\})/g, function(whitespace) {
+          return '{' + JSON.stringify(whitespace) + '}';
+        });
+    } else {
+      // If there's a newline in the text, adjust the indent level
+      if (text.indexOf('\n') > -1) {
+      }
+    }
+    this.output += text;
+  }
+
+
+
+};
+
+/**
+ * Handles parsing of inline styles
+ */
+export class StyleParser {
+  styles = {};
+  toJSXString = () => {
+    for (var key in this.styles) {
+      if (!this.styles.hasOwnProperty(key)) {
+      }
+    }
+  }
+}
\ No newline at end of file
diff --git a/tests/cases/conformance/controlFlow/constLocalsInFunctionExpressions.ts b/tests/cases/conformance/controlFlow/constLocalsInFunctionExpressions.ts
new file mode 100644
index 00000000000..69b19fcb307
--- /dev/null
+++ b/tests/cases/conformance/controlFlow/constLocalsInFunctionExpressions.ts
@@ -0,0 +1,38 @@
+declare function getStringOrNumber(): string | number;
+
+function f1() {
+    const x = getStringOrNumber();
+    if (typeof x === "string") {
+        const f = () => x.length;
+    }
+}
+
+function f2() {
+    const x = getStringOrNumber();
+    if (typeof x !== "string") {
+        return;
+    }
+    const f = () => x.length;
+}
+
+function f3() {
+    const x = getStringOrNumber();
+    if (typeof x === "string") {
+        const f = function() { return x.length; };
+    }
+}
+
+function f4() {
+    const x = getStringOrNumber();
+    if (typeof x !== "string") {
+        return;
+    }
+    const f = function() { return x.length; };
+}
+
+function f5() {
+    const x = getStringOrNumber();
+    if (typeof x === "string") {
+        const f = () => () => x.length;
+    }
+}
\ No newline at end of file
diff --git a/tests/cases/conformance/controlFlow/controlFlowIIFE.ts b/tests/cases/conformance/controlFlow/controlFlowIIFE.ts
new file mode 100644
index 00000000000..c72f038c1ec
--- /dev/null
+++ b/tests/cases/conformance/controlFlow/controlFlowIIFE.ts
@@ -0,0 +1,48 @@
+// @strictNullChecks: true
+
+declare function getStringOrNumber(): string | number;
+
+function f1() {
+    let x = getStringOrNumber();
+    if (typeof x === "string") {
+        let n = function() {
+            return x.length;
+        }();
+    }
+}
+
+function f2() {
+    let x = getStringOrNumber();
+    if (typeof x === "string") {
+        let n = (function() {
+            return x.length;
+        })();
+    }
+}
+
+function f3() {
+    let x = getStringOrNumber();
+    let y: number;
+    if (typeof x === "string") {
+        let n = (z => x.length + y + z)(y = 1);
+    }
+}
+
+// Repros from #8381
+
+let maybeNumber: number | undefined;
+(function () {
+    maybeNumber = 1;
+})();
+maybeNumber++;
+if (maybeNumber !== undefined) {
+    maybeNumber++;
+}
+
+let test: string | undefined;
+if (!test) {
+    throw new Error('Test is not defined');
+}
+(() => {
+    test.slice(1); // No error
+})();
\ No newline at end of file
diff --git a/tests/cases/conformance/expressions/typeGuards/typeGuardsInFunctionAndModuleBlock.ts b/tests/cases/conformance/expressions/typeGuards/typeGuardsInFunctionAndModuleBlock.ts
index 5dbc925d04b..f1ba854394b 100644
--- a/tests/cases/conformance/expressions/typeGuards/typeGuardsInFunctionAndModuleBlock.ts
+++ b/tests/cases/conformance/expressions/typeGuards/typeGuardsInFunctionAndModuleBlock.ts
@@ -40,7 +40,7 @@ function foo4(x: number | string | boolean) {
                 : x.toString(); // number
         })(x); // x here is narrowed to number | boolean
 }
-// Type guards affect nested function expressions and nested function declarations
+// Type guards do not affect nested function declarations
 function foo5(x: number | string | boolean) {
     if (typeof x === "string") {
         var y = x; // string;
diff --git a/tests/cases/conformance/types/typeRelationships/widenedTypes/arrayLiteralWidened.ts b/tests/cases/conformance/types/typeRelationships/widenedTypes/arrayLiteralWidened.ts
index 8af0a5842cc..05428422129 100644
--- a/tests/cases/conformance/types/typeRelationships/widenedTypes/arrayLiteralWidened.ts
+++ b/tests/cases/conformance/types/typeRelationships/widenedTypes/arrayLiteralWidened.ts
@@ -1,6 +1,7 @@
 // array literals are widened upon assignment according to their element type
 
 var a = []; // any[]
+var a = [,,];
 
 var a = [null, null];
 var a = [undefined, undefined];
@@ -11,3 +12,11 @@ var b = [[undefined, undefined]];
 
 var c = [[[]]]; // any[][][]
 var c = [[[null]],[undefined]]
+
+// no widening when one or more elements are non-widening
+
+var x: undefined = undefined;
+
+var d = [x];
+var d = [, x];
+var d = [undefined, x];
diff --git a/tests/cases/conformance/types/typeRelationships/widenedTypes/initializersWidened.ts b/tests/cases/conformance/types/typeRelationships/widenedTypes/initializersWidened.ts
index e79cdc9e168..2eeb96194b7 100644
--- a/tests/cases/conformance/types/typeRelationships/widenedTypes/initializersWidened.ts
+++ b/tests/cases/conformance/types/typeRelationships/widenedTypes/initializersWidened.ts
@@ -1,4 +1,24 @@
 // these are widened to any at the point of assignment
 
-var x = null;
-var y = undefined;
\ No newline at end of file
+var x1 = null;
+var y1 = undefined;
+var z1 = void 0;
+
+// these are not widened
+
+var x2: null;
+var y2: undefined;
+
+var x3: null = null;
+var y3: undefined = undefined;
+var z3: undefined = void 0;
+
+// widen only when all constituents of union are widening
+
+var x4 = null || null;
+var y4 = undefined || undefined;
+var z4 = void 0 || void 0;
+
+var x5 = null || x2;
+var y5 = undefined || y2;
+var z5 = void 0 || y2;
\ No newline at end of file
diff --git a/tests/cases/conformance/types/typeRelationships/widenedTypes/objectLiteralWidened.ts b/tests/cases/conformance/types/typeRelationships/widenedTypes/objectLiteralWidened.ts
index cde44f91168..8b51e526882 100644
--- a/tests/cases/conformance/types/typeRelationships/widenedTypes/objectLiteralWidened.ts
+++ b/tests/cases/conformance/types/typeRelationships/widenedTypes/objectLiteralWidened.ts
@@ -1,14 +1,32 @@
 // object literal properties are widened to any
 
-var x = {
+var x1 = {
     foo: null,
     bar: undefined
 }
 
-var y = {
+var y1 = {
     foo: null,
     bar: {
         baz: null,
         boo: undefined
     }
+}
+
+// these are not widened
+
+var u: undefined = undefined;
+var n: null = null;
+
+var x2 = {
+    foo: n,
+    bar: u
+}
+
+var y2 = {
+    foo: n,
+    bar: {
+        baz: n,
+        boo: u
+    }
 }
\ No newline at end of file
diff --git a/tests/cases/conformance/types/typeRelationships/widenedTypes/strictNullChecksNoWidening.ts b/tests/cases/conformance/types/typeRelationships/widenedTypes/strictNullChecksNoWidening.ts
new file mode 100644
index 00000000000..8f5b4709abf
--- /dev/null
+++ b/tests/cases/conformance/types/typeRelationships/widenedTypes/strictNullChecksNoWidening.ts
@@ -0,0 +1,17 @@
+// @strictNullChecks: true
+
+var a1 = null;
+var a2 = undefined;
+var a3 = void 0;
+
+var b1 = [];
+var b2 = [,];
+var b3 = [undefined];
+var b4 = [[], []];
+var b5 = [[], [,]];
+
+declare function f<T>(x: T): T;
+
+var c1 = f(null);
+var c2 = f(undefined);
+var c3 = f([]);
diff --git a/tests/cases/fourslash/fourslash.ts b/tests/cases/fourslash/fourslash.ts
index 8a0d2d36364..71e1c3cc5d7 100644
--- a/tests/cases/fourslash/fourslash.ts
+++ b/tests/cases/fourslash/fourslash.ts
@@ -246,6 +246,7 @@ declare namespace FourSlashInterface {
         copyFormatOptions(): FormatCodeOptions;
         setFormatOptions(options: FormatCodeOptions): any;
         selection(startMarker: string, endMarker: string): void;
+        onType(posMarker: string, key: string): void;
         setOption(name: string, value: number): any;
         setOption(name: string, value: string): any;
         setOption(name: string, value: boolean): any;
diff --git a/tests/cases/fourslash/server/formatOnEnter.ts b/tests/cases/fourslash/server/formatOnEnter.ts
new file mode 100644
index 00000000000..f505cf6cec7
--- /dev/null
+++ b/tests/cases/fourslash/server/formatOnEnter.ts
@@ -0,0 +1,17 @@
+/// <reference path="fourslash.ts"/>
+
+/////*3*/function listAPIFiles (path : string): string[] {
+////    /*1*/
+////    /*2*/
+////}
+
+goTo.marker("1");
+format.onType("1", "\n");
+verify.currentLineContentIs("    ");
+
+goTo.marker("2");
+format.onType("2", "\n");
+verify.currentLineContentIs("    ");
+
+goTo.marker("3");
+verify.currentLineContentIs("function listAPIFiles(path: string): string[] {");
\ No newline at end of file
diff --git a/tests/cases/fourslash/server/jsdocTypedefTag.ts b/tests/cases/fourslash/server/jsdocTypedefTag.ts
new file mode 100644
index 00000000000..e645b518020
--- /dev/null
+++ b/tests/cases/fourslash/server/jsdocTypedefTag.ts
@@ -0,0 +1,64 @@
+/// <reference path="../fourslash.ts"/>
+
+// @allowNonTsExtensions: true
+// @Filename: jsdocCompletion_typedef.js
+
+//// /** @typedef {(string | number)} NumberLike */
+////
+//// /**
+////  * @typedef Animal
+////  * @type {Object}
+////  * @property {string} animalName
+////  * @property {number} animalAge
+////  */
+////
+//// /**
+////  * @typedef {Object} Person
+////  * @property {string} personName
+////  * @property {number} personAge
+////  */
+////
+//// /**
+////  * @typedef {Object}
+////  * @property {string} catName
+////  * @property {number} catAge
+////  */
+//// var Cat;
+////
+//// /** @typedef {{ dogName: string, dogAge: number }} */
+//// var Dog;
+////
+//// /** @type {NumberLike} */
+//// var numberLike; numberLike./*numberLike*/
+////
+//// /** @type {Person} */
+//// var p;p./*person*/
+////
+//// /** @type {Animal} */
+//// var a;a./*animal*/
+////
+//// /** @type {Cat} */
+//// var c;c./*cat*/
+////
+//// /** @type {Dog} */
+//// var d;d./*dog*/
+
+goTo.marker('numberLike');
+verify.memberListContains('charAt');
+verify.memberListContains('toExponential');
+
+goTo.marker('person');
+verify.memberListContains('personName');
+verify.memberListContains('personAge');
+
+goTo.marker('animal');
+verify.memberListContains('animalName');
+verify.memberListContains('animalAge');
+
+goTo.marker('dog');
+verify.memberListContains('dogName');
+verify.memberListContains('dogAge');
+
+goTo.marker('cat');
+verify.memberListContains('catName');
+verify.memberListContains('catAge');
\ No newline at end of file
diff --git a/tests/cases/fourslash/server/jsdocTypedefTagGoToDefinition.ts b/tests/cases/fourslash/server/jsdocTypedefTagGoToDefinition.ts
new file mode 100644
index 00000000000..4db14611938
--- /dev/null
+++ b/tests/cases/fourslash/server/jsdocTypedefTagGoToDefinition.ts
@@ -0,0 +1,29 @@
+/// <reference path="../fourslash.ts"/>
+
+// @allowNonTsExtensions: true
+// @Filename: jsdocCompletion_typedef.js
+
+//// /**
+////  * @typedef {Object} Person
+////  * /*1*/@property {string} personName
+////  * @property {number} personAge
+////  */
+////
+//// /**
+////  * @typedef {{ /*2*/animalName: string, animalAge: number }} Animal
+////  */
+////
+//// /** @type {Person} */
+//// var person; person.personName/*3*/
+////
+//// /** @type {Animal} */
+//// var animal; animal.animalName/*4*/
+
+goTo.file('jsdocCompletion_typedef.js');
+goTo.marker('3');
+goTo.definition();
+verify.caretAtMarker('1');
+
+goTo.marker('4');
+goTo.definition();
+verify.caretAtMarker('2');
diff --git a/tests/cases/fourslash/server/jsdocTypedefTagNavigateTo.ts b/tests/cases/fourslash/server/jsdocTypedefTagNavigateTo.ts
new file mode 100644
index 00000000000..77cd75aa44c
--- /dev/null
+++ b/tests/cases/fourslash/server/jsdocTypedefTagNavigateTo.ts
@@ -0,0 +1,30 @@
+/// <reference path="../fourslash.ts"/>
+
+// @allowNonTsExtensions: true
+// @Filename: jsDocTypedef_form2.js
+////
+//// /** @typedef {(string | number)} NumberLike */
+//// /** @typedef {(string | number | string[])} */
+//// var NumberLike2;
+////
+//// /** @type {/*1*/NumberLike} */
+//// var numberLike;
+
+verify.navigationBar([
+  {
+    "text": "NumberLike",
+    "kind": "type"
+  },
+  {
+    "text": "NumberLike2",
+    "kind": "type"
+  },
+  {
+    "text": "NumberLike2",
+    "kind": "var"
+  },
+  {
+    "text": "numberLike",
+    "kind": "var"
+  }
+]);
\ No newline at end of file
diff --git a/tests/cases/fourslash/server/jsdocTypedefTagRename01.ts b/tests/cases/fourslash/server/jsdocTypedefTagRename01.ts
new file mode 100644
index 00000000000..776d0180b06
--- /dev/null
+++ b/tests/cases/fourslash/server/jsdocTypedefTagRename01.ts
@@ -0,0 +1,20 @@
+/// <reference path="../fourslash.ts"/>
+
+// @allowNonTsExtensions: true
+// @Filename: jsDocTypedef_form1.js
+////
+//// /** @typedef {(string | number)} */
+//// var /*1*/[|NumberLike|];
+////
+//// /*2*/[|NumberLike|] = 10;
+////
+//// /** @type {/*3*/[|NumberLike|]} */
+//// var numberLike;
+
+goTo.file('jsDocTypedef_form1.js')
+goTo.marker('1');
+verify.renameLocations(/*findInStrings*/ false, /*findInComments*/ true);
+goTo.marker('2');
+verify.renameLocations(/*findInStrings*/ false, /*findInComments*/ true);
+goTo.marker('3');
+verify.renameLocations(/*findInStrings*/ false, /*findInComments*/ true);
\ No newline at end of file
diff --git a/tests/cases/fourslash/server/jsdocTypedefTagRename02.ts b/tests/cases/fourslash/server/jsdocTypedefTagRename02.ts
new file mode 100644
index 00000000000..7f1d422d971
--- /dev/null
+++ b/tests/cases/fourslash/server/jsdocTypedefTagRename02.ts
@@ -0,0 +1,15 @@
+/// <reference path="../fourslash.ts"/>
+
+// @allowNonTsExtensions: true
+// @Filename: jsDocTypedef_form2.js
+////
+//// /** @typedef {(string | number)} /*1*/[|NumberLike|] */
+////
+//// /** @type {/*2*/[|NumberLike|]} */
+//// var numberLike;
+
+goTo.file('jsDocTypedef_form2.js')
+goTo.marker('1');
+verify.renameLocations(/*findInStrings*/ false, /*findInComments*/ true);
+goTo.marker('2');
+verify.renameLocations(/*findInStrings*/ false, /*findInComments*/ true);
\ No newline at end of file
diff --git a/tests/cases/fourslash/server/jsdocTypedefTagRename03.ts b/tests/cases/fourslash/server/jsdocTypedefTagRename03.ts
new file mode 100644
index 00000000000..c1b38945806
--- /dev/null
+++ b/tests/cases/fourslash/server/jsdocTypedefTagRename03.ts
@@ -0,0 +1,20 @@
+/// <reference path="../fourslash.ts"/>
+
+// @allowNonTsExtensions: true
+// @Filename: jsDocTypedef_form3.js
+////
+//// /** 
+////  * @typedef /*1*/[|Person|]
+////  * @type {Object}
+////  * @property {number} age
+////  * @property {string} name
+////  */
+////
+//// /** @type {/*2*/[|Person|]} */
+//// var person;
+
+goTo.file('jsDocTypedef_form3.js')
+goTo.marker('1');
+verify.renameLocations(/*findInStrings*/ false, /*findInComments*/ true);
+goTo.marker('2');
+verify.renameLocations(/*findInStrings*/ false, /*findInComments*/ true);
\ No newline at end of file
diff --git a/tests/cases/fourslash/server/jsdocTypedefTagRename04.ts b/tests/cases/fourslash/server/jsdocTypedefTagRename04.ts
new file mode 100644
index 00000000000..b7bf220512a
--- /dev/null
+++ b/tests/cases/fourslash/server/jsdocTypedefTagRename04.ts
@@ -0,0 +1,24 @@
+/// <reference path="../fourslash.ts"/>
+
+// @allowNonTsExtensions: true
+// @Filename: jsDocTypedef_form2.js
+////
+//// function test1() {
+////    /** @typedef {(string | number)} NumberLike */
+////
+////    /** @type {/*1*/NumberLike} */
+////    var numberLike;
+//// }
+//// function test2() {
+////    /** @typedef {(string | number)} NumberLike2 */
+////
+////    /** @type {NumberLike2} */
+////    var n/*2*/umberLike2;
+//// }
+
+goTo.marker('2');
+verify.quickInfoExists();
+goTo.marker('1');
+edit.insert('111');
+goTo.marker('2');
+verify.quickInfoExists();
\ No newline at end of file
diff --git a/tests/cases/fourslash/syntacticClassificationForJSDocTemplateTag.ts b/tests/cases/fourslash/syntacticClassificationForJSDocTemplateTag.ts
new file mode 100644
index 00000000000..c3368207d2c
--- /dev/null
+++ b/tests/cases/fourslash/syntacticClassificationForJSDocTemplateTag.ts
@@ -0,0 +1,22 @@
+/// <reference path="fourslash.ts"/>
+
+/////** @template T */
+////function ident<T>: T {
+////}
+
+var c = classification;
+verify.syntacticClassificationsAre(
+    c.comment("/** "),
+    c.punctuation("@"),
+    c.docCommentTagName("template"),
+    c.typeParameterName("T"),
+    c.comment(" */"),
+    c.keyword("function"),
+    c.identifier("ident"),
+    c.punctuation("<"),
+    c.typeParameterName("T"),
+    c.punctuation(">"),
+    c.punctuation(":"),
+    c.identifier("T"),
+    c.punctuation("{"),
+    c.punctuation("}"));
diff --git a/tests/cases/unittests/jsDocParsing.ts b/tests/cases/unittests/jsDocParsing.ts
index 22f679c4ad5..fb75b4d4940 100644
--- a/tests/cases/unittests/jsDocParsing.ts
+++ b/tests/cases/unittests/jsDocParsing.ts
@@ -1004,7 +1004,8 @@ namespace ts {
                 if (result !== expected) {
                     // Turn on a human-readable diff
                     if (typeof require !== "undefined") {
-                        require("chai").config.showDiff = true;
+                        const chai = require("chai");
+                        chai.config.showDiff = true;
                         chai.expect(JSON.parse(result)).equal(JSON.parse(expected));
                     }
                     else {
@@ -2218,4 +2219,4 @@ namespace ts {
             });
         });
     });
-}
+}
\ No newline at end of file
diff --git a/tests/cases/unittests/tsserverProjectSystem.ts b/tests/cases/unittests/tsserverProjectSystem.ts
new file mode 100644
index 00000000000..c69821ced5f
--- /dev/null
+++ b/tests/cases/unittests/tsserverProjectSystem.ts
@@ -0,0 +1,294 @@
+/// <reference path="..\..\..\src\harness\harness.ts" />
+
+namespace ts {
+    function notImplemented(): any {
+        throw new Error("Not yet implemented");
+    }
+
+    const nullLogger: server.Logger = {
+        close: () => void 0,
+        isVerbose: () => void 0,
+        loggingEnabled: () => false,
+        perftrc: () => void 0,
+        info: () => void 0,
+        startGroup: () => void 0,
+        endGroup: () => void 0,
+        msg: () => void 0
+    };
+
+    const { content: libFileContent } = Harness.getDefaultLibraryFile(Harness.IO);
+
+    function getExecutingFilePathFromLibFile(libFile: FileOrFolder): string {
+        return combinePaths(getDirectoryPath(libFile.path), "tsc.js");
+    }
+
+    interface FileOrFolder {
+        path: string;
+        content?: string;
+    }
+
+    interface FSEntry {
+        path: Path;
+        fullPath: string;
+    }
+
+    interface File extends FSEntry {
+        content: string;
+    }
+
+    interface Folder extends FSEntry {
+        entries: FSEntry[];
+    }
+
+    function isFolder(s: FSEntry): s is Folder {
+        return isArray((<Folder>s).entries);
+    }
+
+    function isFile(s: FSEntry): s is File {
+        return typeof (<File>s).content === "string";
+    }
+
+    function addFolder(fullPath: string, toPath: (s: string) => Path, fs: FileMap<FSEntry>): Folder {
+        const path = toPath(fullPath);
+        if (fs.contains(path)) {
+            Debug.assert(isFolder(fs.get(path)));
+            return (<Folder>fs.get(path));
+        }
+
+        const entry: Folder = { path, entries: [], fullPath };
+        fs.set(path, entry);
+
+        const baseFullPath = getDirectoryPath(fullPath);
+        if (fullPath !== baseFullPath) {
+            addFolder(baseFullPath, toPath, fs).entries.push(entry);
+        }
+
+        return entry;
+    }
+
+    function sizeOfMap(map: Map<any>): number {
+        let n = 0;
+        for (const name in map) {
+            if (hasProperty(map, name)) {
+                n++;
+            }
+        }
+        return n;
+    }
+
+    function checkMapKeys(caption: string, map: Map<any>, expectedKeys: string[]) {
+        assert.equal(sizeOfMap(map), expectedKeys.length, `${caption}: incorrect size of map`);
+        for (const name of expectedKeys) {
+            assert.isTrue(hasProperty(map, name), `${caption} is expected to contain ${name}, actual keys: ${getKeys(map)}`);
+        }
+    }
+
+    function checkFileNames(caption: string, actualFileNames: string[], expectedFileNames: string[]) {
+        assert.equal(actualFileNames.length, expectedFileNames.length, `${caption}: incorrect actual number of files, expected ${JSON.stringify(expectedFileNames)}, got ${actualFileNames}`);
+        for (const f of expectedFileNames) {
+            assert.isTrue(contains(actualFileNames, f), `${caption}: expected to find ${f} in ${JSON.stringify(actualFileNames)}`);
+        }
+    }
+
+    function readDirectory(folder: FSEntry, ext: string, excludes: Path[], result: string[]): void {
+        if (!folder || !isFolder(folder) || contains(excludes, folder.path)) {
+            return;
+        }
+        for (const entry of folder.entries) {
+            if (contains(excludes, entry.path)) {
+                continue;
+            }
+            if (isFolder(entry)) {
+                readDirectory(entry, ext, excludes, result);
+            }
+            else if (fileExtensionIs(entry.path, ext)) {
+                result.push(entry.fullPath);
+            }
+        }
+    }
+
+    class TestServerHost implements server.ServerHost {
+        args: string[] = [];
+        newLine: "\n";
+
+        private fs: ts.FileMap<FSEntry>;
+        private getCanonicalFileName: (s: string) => string;
+        private toPath: (f: string) => Path;
+        readonly watchedDirectories: Map<{ cb: DirectoryWatcherCallback, recursive: boolean }[]> = {};
+        readonly watchedFiles: Map<FileWatcherCallback[]> = {};
+
+        constructor(public useCaseSensitiveFileNames: boolean, private executingFilePath: string, private currentDirectory: string, fileOrFolderList: FileOrFolder[]) {
+            this.getCanonicalFileName = createGetCanonicalFileName(useCaseSensitiveFileNames);
+            this.toPath = s => toPath(s, currentDirectory, this.getCanonicalFileName);
+
+            this.reloadFS(fileOrFolderList);
+        }
+
+        reloadFS(filesOrFolders: FileOrFolder[]) {
+            this.fs = createFileMap<FSEntry>();
+            for (const fileOrFolder of filesOrFolders) {
+                const path = this.toPath(fileOrFolder.path);
+                const fullPath = getNormalizedAbsolutePath(fileOrFolder.path, this.currentDirectory);
+                if (typeof fileOrFolder.content === "string") {
+                    const entry = { path, content: fileOrFolder.content, fullPath };
+                    this.fs.set(path, entry);
+                    addFolder(getDirectoryPath(fullPath), this.toPath, this.fs).entries.push(entry);
+                }
+                else {
+                    addFolder(fullPath, this.toPath, this.fs);
+                }
+            }
+        }
+
+        fileExists(s: string) {
+            const path = this.toPath(s);
+            return this.fs.contains(path) && isFile(this.fs.get(path));
+        };
+
+        directoryExists(s: string) {
+            const path = this.toPath(s);
+            return this.fs.contains(path) && isFolder(this.fs.get(path));
+        }
+
+        getDirectories(s: string) {
+            const path = this.toPath(s);
+            if (!this.fs.contains(path)) {
+                return [];
+            }
+            else {
+                const entry = this.fs.get(path);
+                return isFolder(entry) ? map(entry.entries, x => getBaseFileName(x.fullPath)) : [];
+            }
+        }
+
+        readDirectory(path: string, ext: string, excludes: string[]): string[] {
+            const result: string[] = [];
+            readDirectory(this.fs.get(this.toPath(path)), ext, map(excludes, e => toPath(e, path, this.getCanonicalFileName)), result);
+            return result;
+        }
+
+        watchDirectory(directoryName: string, callback: DirectoryWatcherCallback, recursive: boolean): DirectoryWatcher {
+            const path = this.toPath(directoryName);
+            const callbacks = lookUp(this.watchedDirectories, path) || (this.watchedDirectories[path] = []);
+            callbacks.push({ cb: callback, recursive });
+            return {
+                referenceCount: 0,
+                directoryName,
+                close: () => {
+                    for (let i = 0; i < callbacks.length; i++) {
+                        if (callbacks[i].cb === callback) {
+                            callbacks.splice(i, 1);
+                            break;
+                        }
+                    }
+                    if (!callbacks.length) {
+                        delete this.watchedDirectories[path];
+                    }
+                }
+            };
+        }
+
+        watchFile(fileName: string, callback: FileWatcherCallback) {
+            const path = this.toPath(fileName);
+            const callbacks = lookUp(this.watchedFiles, path) || (this.watchedFiles[path] = []);
+            callbacks.push(callback);
+            return {
+                close: () => {
+                    const i = callbacks.indexOf(callback);
+                    callbacks.splice(i, 1);
+                    if (!callbacks.length) {
+                        delete this.watchedFiles[path];
+                    }
+                }
+            };
+        }
+
+        // TOOD: record and invoke callbacks to simulate timer events
+        readonly setTimeout = (callback: (...args: any[]) => void, ms: number, ...args: any[]): any => void 0;
+        readonly clearTimeout = (timeoutId: any): void => void 0;
+        readonly readFile = (s: string) => (<File>this.fs.get(this.toPath(s))).content;
+        readonly resolvePath = (s: string) => s;
+        readonly getExecutingFilePath = () => this.executingFilePath;
+        readonly getCurrentDirectory = () => this.currentDirectory;
+        readonly writeFile = (path: string, content: string) => notImplemented();
+        readonly write = (s: string) => notImplemented();
+        readonly createDirectory = (s: string) => notImplemented();
+        readonly exit = () => notImplemented();
+    }
+
+    describe("tsserver project system:", () => {
+        it("create inferred project", () => {
+            const appFile: FileOrFolder = {
+                path: "/a/b/c/app.ts",
+                content: `
+                import {f} from "./module"
+                console.log(f)
+                `
+            };
+            const libFile: FileOrFolder = {
+                path: "/a/lib/lib.d.ts",
+                content: libFileContent
+            };
+            const moduleFile: FileOrFolder = {
+                path: "/a/b/c/module.d.ts",
+                content: `export let x: number`
+            };
+            const host = new TestServerHost(/*useCaseSensitiveFileNames*/ false, getExecutingFilePathFromLibFile(libFile), "/", [appFile, moduleFile, libFile]);
+            const projectService = new server.ProjectService(host, nullLogger);
+            const { configFileName } = projectService.openClientFile(appFile.path);
+
+            assert(!configFileName, `should not find config, got: '${configFileName}`);
+            assert.equal(projectService.inferredProjects.length, 1, "expected one inferred project");
+            assert.equal(projectService.configuredProjects.length, 0, "expected no configured project");
+
+            const project = projectService.inferredProjects[0];
+
+            checkFileNames("inferred project", project.getFileNames(), [appFile.path, libFile.path, moduleFile.path]);
+            checkMapKeys("watchedDirectories", host.watchedDirectories, ["/a/b/c", "/a/b", "/a"]);
+        });
+
+        it("create configured project without file list", () => {
+            const configFile: FileOrFolder = {
+                path: "/a/b/tsconfig.json",
+                content: `
+                {
+                    "compilerOptions": {},
+                    "exclude": [
+                        "e"
+                    ]
+                }`
+            };
+            const libFile: FileOrFolder = {
+                path: "/a/lib/lib.d.ts",
+                content: libFileContent
+            };
+            const file1: FileOrFolder = {
+                path: "/a/b/c/f1.ts",
+                content: "let x = 1"
+            };
+            const file2: FileOrFolder = {
+                path: "/a/b/d/f2.ts",
+                content: "let y = 1"
+            };
+            const file3: FileOrFolder = {
+                path: "/a/b/e/f3.ts",
+                content: "let z = 1"
+            };
+            const host = new TestServerHost(/*useCaseSensitiveFileNames*/ false, getExecutingFilePathFromLibFile(libFile), "/", [ configFile, libFile, file1, file2, file3 ]);
+            const projectService = new server.ProjectService(host, nullLogger);
+            const { configFileName, configFileErrors } = projectService.openClientFile(file1.path);
+
+            assert(configFileName, "should find config file");
+            assert.isTrue(!configFileErrors, `expect no errors in config file, got ${JSON.stringify(configFileErrors)}`);
+            assert.equal(projectService.inferredProjects.length, 0, "expected no inferred project");
+            assert.equal(projectService.configuredProjects.length, 1, "expected one configured project");
+
+            const project = projectService.configuredProjects[0];
+            checkFileNames("configuredProjects project, actualFileNames", project.getFileNames(), [file1.path, libFile.path, file2.path]);
+            checkFileNames("configuredProjects project, rootFileNames", project.getRootFiles(), [file1.path, file2.path]);
+
+            checkMapKeys("watchedFiles", host.watchedFiles, [configFile.path, file2.path, libFile.path]); // watching all files except one that was open
+            checkMapKeys("watchedDirectories", host.watchedDirectories, [getDirectoryPath(configFile.path)]);
+        });
+    });
+}
\ No newline at end of file