binder.ts

/// <reference path="utilities.ts"/>
/// <reference path="parser.ts"/>

/* @internal */
namespace ts {
    export let bindTime = 0;

    export const enum ModuleInstanceState {
        NonInstantiated = 0,
        Instantiated = 1,
        ConstEnumOnly = 2
    }

    interface ActiveLabel {
        name: string;
        breakTarget: FlowLabel;
        continueTarget: FlowLabel;
        referenced: boolean;
    }

    export function getModuleInstanceState(node: Node): ModuleInstanceState {
        // A module is uninstantiated if it contains only
        // 1. interface declarations, type alias declarations
        if (node.kind === SyntaxKind.InterfaceDeclaration || node.kind === SyntaxKind.TypeAliasDeclaration) {
            return ModuleInstanceState.NonInstantiated;
        }
        // 2. const enum declarations
        else if (isConstEnumDeclaration(node)) {
            return ModuleInstanceState.ConstEnumOnly;
        }
        // 3. non-exported import declarations
        else if ((node.kind === SyntaxKind.ImportDeclaration || node.kind === SyntaxKind.ImportEqualsDeclaration) && !(node.flags & NodeFlags.Export)) {
            return ModuleInstanceState.NonInstantiated;
        }
        // 4. other uninstantiated module declarations.
        else if (node.kind === SyntaxKind.ModuleBlock) {
            let state = ModuleInstanceState.NonInstantiated;
            forEachChild(node, n => {
                switch (getModuleInstanceState(n)) {
                    case ModuleInstanceState.NonInstantiated:
                        // child is non-instantiated - continue searching
                        return false;
                    case ModuleInstanceState.ConstEnumOnly:
                        // child is const enum only - record state and continue searching
                        state = ModuleInstanceState.ConstEnumOnly;
                        return false;
                    case ModuleInstanceState.Instantiated:
                        // child is instantiated - record state and stop
                        state = ModuleInstanceState.Instantiated;
                        return true;
                }
            });
            return state;
        }
        else if (node.kind === SyntaxKind.ModuleDeclaration) {
            const body = (<ModuleDeclaration>node).body;
            return body ? getModuleInstanceState(body) : ModuleInstanceState.Instantiated;
        }
        else {
            return ModuleInstanceState.Instantiated;
        }
    }

    const enum ContainerFlags {
        // The current node is not a container, and no container manipulation should happen before
        // recursing into it.
        None = 0,

        // The current node is a container.  It should be set as the current container (and block-
        // container) before recursing into it.  The current node does not have locals.  Examples:
        //
        //      Classes, ObjectLiterals, TypeLiterals, Interfaces...
        IsContainer = 1 << 0,

        // The current node is a block-scoped-container.  It should be set as the current block-
        // container before recursing into it.  Examples:
        //
        //      Blocks (when not parented by functions), Catch clauses, For/For-in/For-of statements...
        IsBlockScopedContainer = 1 << 1,

        // 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,

        IsFunctionLike = 1 << 3,
        IsFunctionExpression = 1 << 4,
        HasLocals = 1 << 5,
        IsInterface = 1 << 6,
    }

    const binder = createBinder();

    export function bindSourceFile(file: SourceFile, options: CompilerOptions) {
        const start = new Date().getTime();
        binder(file, options);
        bindTime += new Date().getTime() - start;
    }

    function createBinder(): (file: SourceFile, options: CompilerOptions) => void {
        let file: SourceFile;
        let options: CompilerOptions;
        let languageVersion: ScriptTarget;
        let parent: Node;
        let container: Node;
        let blockScopeContainer: Node;
        let lastContainer: Node;
        let seenThisKeyword: 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 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
        // not depending on if we see "use strict" in certain places (or if we hit a class/namespace).
        let inStrictMode: boolean;

        let symbolCount = 0;
        let Symbol: { new (flags: SymbolFlags, name: string): Symbol };
        let classifiableNames: Map<string>;

        const unreachableFlow: FlowNode = { flags: FlowFlags.Unreachable };
        const reportedUnreachableFlow: FlowNode = { flags: FlowFlags.Unreachable };

        function bindSourceFile(f: SourceFile, opts: CompilerOptions) {
            file = f;
            options = opts;
            languageVersion = getEmitScriptTarget(options);
            inStrictMode = !!file.externalModuleIndicator;
            classifiableNames = {};
            symbolCount = 0;

            Symbol = objectAllocator.getSymbolConstructor();

            if (!file.locals) {
                bind(file);
                file.symbolCount = symbolCount;
                file.classifiableNames = classifiableNames;
            }

            file = undefined;
            options = undefined;
            languageVersion = undefined;
            parent = undefined;
            container = undefined;
            blockScopeContainer = undefined;
            lastContainer = undefined;
            seenThisKeyword = false;
            currentFlow = undefined;
            currentBreakTarget = undefined;
            currentContinueTarget = undefined;
            currentReturnTarget = undefined;
            currentTrueTarget = undefined;
            currentFalseTarget = undefined;
            activeLabels = undefined;
            hasExplicitReturn = false;
            emitFlags = NodeFlags.None;
        }

        return bindSourceFile;

        function createSymbol(flags: SymbolFlags, name: string): Symbol {
            symbolCount++;
            return new Symbol(flags, name);
        }

        function addDeclarationToSymbol(symbol: Symbol, node: Declaration, symbolFlags: SymbolFlags) {
            symbol.flags |= symbolFlags;

            node.symbol = symbol;

            if (!symbol.declarations) {
                symbol.declarations = [];
            }
            symbol.declarations.push(node);

            if (symbolFlags & SymbolFlags.HasExports && !symbol.exports) {
                symbol.exports = {};
            }

            if (symbolFlags & SymbolFlags.HasMembers && !symbol.members) {
                symbol.members = {};
            }

            if (symbolFlags & SymbolFlags.Value) {
                const valueDeclaration = symbol.valueDeclaration;
                if (!valueDeclaration ||
                    (valueDeclaration.kind !== node.kind && valueDeclaration.kind === SyntaxKind.ModuleDeclaration)) {
                    // other kinds of value declarations take precedence over modules
                    symbol.valueDeclaration = node;
                }
        }
        }

        // Should not be called on a declaration with a computed property name,
        // unless it is a well known Symbol.
        function getDeclarationName(node: Declaration): string {
            if (node.name) {
                if (isAmbientModule(node)) {
                    return isGlobalScopeAugmentation(<ModuleDeclaration>node) ? "__global" : `"${(<LiteralExpression>node.name).text}"`;
                }
                if (node.name.kind === SyntaxKind.ComputedPropertyName) {
                    const nameExpression = (<ComputedPropertyName>node.name).expression;
                    // treat computed property names where expression is string/numeric literal as just string/numeric literal
                    if (isStringOrNumericLiteral(nameExpression.kind)) {
                        return (<LiteralExpression>nameExpression).text;
                    }

                    Debug.assert(isWellKnownSymbolSyntactically(nameExpression));
                    return getPropertyNameForKnownSymbolName((<PropertyAccessExpression>nameExpression).name.text);
                }
                return (<Identifier | LiteralExpression>node.name).text;
            }
            switch (node.kind) {
                case SyntaxKind.Constructor:
                    return "__constructor";
                case SyntaxKind.FunctionType:
                case SyntaxKind.CallSignature:
                    return "__call";
                case SyntaxKind.ConstructorType:
                case SyntaxKind.ConstructSignature:
                    return "__new";
                case SyntaxKind.IndexSignature:
                    return "__index";
                case SyntaxKind.ExportDeclaration:
                    return "__export";
                case SyntaxKind.ExportAssignment:
                    return (<ExportAssignment>node).isExportEquals ? "export=" : "default";
                case SyntaxKind.BinaryExpression:
                    switch (getSpecialPropertyAssignmentKind(node)) {
                        case SpecialPropertyAssignmentKind.ModuleExports:
                            // module.exports = ...
                            return "export=";
                        case SpecialPropertyAssignmentKind.ExportsProperty:
                        case SpecialPropertyAssignmentKind.ThisProperty:
                            // exports.x = ... or this.y = ...
                            return ((node as BinaryExpression).left as PropertyAccessExpression).name.text;
                        case SpecialPropertyAssignmentKind.PrototypeProperty:
                            // className.prototype.methodName = ...
                            return (((node as BinaryExpression).left as PropertyAccessExpression).expression as PropertyAccessExpression).name.text;
                    }
                    Debug.fail("Unknown binary declaration kind");
                    break;

                case SyntaxKind.FunctionDeclaration:
                case SyntaxKind.ClassDeclaration:
                    return node.flags & NodeFlags.Default ? "default" : undefined;
                case SyntaxKind.JSDocFunctionType:
                    return isJSDocConstructSignature(node) ? "__new" : "__call";
                case SyntaxKind.Parameter:
                    // Parameters with names are handled at the top of this function.  Parameters
                    // without names can only come from JSDocFunctionTypes.
                    Debug.assert(node.parent.kind === SyntaxKind.JSDocFunctionType);
                    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;
            }
        }

        function getDisplayName(node: Declaration): string {
            return node.name ? declarationNameToString(node.name) : getDeclarationName(node);
        }

        /**
         * Declares a Symbol for the node and adds it to symbols. Reports errors for conflicting identifier names.
         * @param symbolTable - The symbol table which node will be added to.
         * @param parent - node's parent declaration.
         * @param node - The declaration to be added to the symbol table
         * @param includes - The SymbolFlags that node has in addition to its declaration type (eg: export, ambient, etc.)
         * @param excludes - The flags which node cannot be declared alongside in a symbol table. Used to report forbidden declarations.
         */
        function declareSymbol(symbolTable: SymbolTable, parent: Symbol, node: Declaration, includes: SymbolFlags, excludes: SymbolFlags): Symbol {
            Debug.assert(!hasDynamicName(node));

            const isDefaultExport = node.flags & NodeFlags.Default;

            // The exported symbol for an export default function/class node is always named "default"
            const name = isDefaultExport && parent ? "default" : getDeclarationName(node);

            let symbol: Symbol;
            if (name !== undefined) {

                // Check and see if the symbol table already has a symbol with this name.  If not,
                // create a new symbol with this name and add it to the table.  Note that we don't
                // give the new symbol any flags *yet*.  This ensures that it will not conflict
                // with the 'excludes' flags we pass in.
                //
                // If we do get an existing symbol, see if it conflicts with the new symbol we're
                // creating.  For example, a 'var' symbol and a 'class' symbol will conflict within
                // the same symbol table.  If we have a conflict, report the issue on each
                // declaration we have for this symbol, and then create a new symbol for this
                // declaration.
                //
                // If we created a new symbol, either because we didn't have a symbol with this name
                // in the symbol table, or we conflicted with an existing symbol, then just add this
                // node as the sole declaration of the new symbol.
                //
                // Otherwise, we'll be merging into a compatible existing symbol (for example when
                // you have multiple 'vars' with the same name in the same container).  In this case
                // just add this node into the declarations list of the symbol.
                symbol = hasProperty(symbolTable, name)
                    ? symbolTable[name]
                    : (symbolTable[name] = createSymbol(SymbolFlags.None, name));

                if (name && (includes & SymbolFlags.Classifiable)) {
                    classifiableNames[name] = name;
                }

                if (symbol.flags & excludes) {
                    if (node.name) {
                        node.name.parent = node;
                    }

                    // Report errors every position with duplicate declaration
                    // Report errors on previous encountered declarations
                    let message = symbol.flags & SymbolFlags.BlockScopedVariable
                        ? Diagnostics.Cannot_redeclare_block_scoped_variable_0
                        : Diagnostics.Duplicate_identifier_0;

                    forEach(symbol.declarations, declaration => {
                        if (declaration.flags & NodeFlags.Default) {
                            message = Diagnostics.A_module_cannot_have_multiple_default_exports;
                        }
                    });

                    forEach(symbol.declarations, declaration => {
                        file.bindDiagnostics.push(createDiagnosticForNode(declaration.name || declaration, message, getDisplayName(declaration)));
                    });
                    file.bindDiagnostics.push(createDiagnosticForNode(node.name || node, message, getDisplayName(node)));

                    symbol = createSymbol(SymbolFlags.None, name);
                }
            }
            else {
                symbol = createSymbol(SymbolFlags.None, "__missing");
            }

            addDeclarationToSymbol(symbol, node, includes);
            symbol.parent = parent;

            return symbol;
        }

        function declareModuleMember(node: Declaration, symbolFlags: SymbolFlags, symbolExcludes: SymbolFlags): Symbol {
            const hasExportModifier = getCombinedNodeFlags(node) & NodeFlags.Export;
            if (symbolFlags & SymbolFlags.Alias) {
                if (node.kind === SyntaxKind.ExportSpecifier || (node.kind === SyntaxKind.ImportEqualsDeclaration && hasExportModifier)) {
                    return declareSymbol(container.symbol.exports, container.symbol, node, symbolFlags, symbolExcludes);
                }
                else {
                    return declareSymbol(container.locals, undefined, node, symbolFlags, symbolExcludes);
                }
            }
            else {
                // Exported module members are given 2 symbols: A local symbol that is classified with an ExportValue,
                // ExportType, or ExportContainer flag, and an associated export symbol with all the correct flags set
                // on it. There are 2 main reasons:
                //
                //   1. We treat locals and exports of the same name as mutually exclusive within a container.
                //      That means the binder will issue a Duplicate Identifier error if you mix locals and exports
                //      with the same name in the same container.
                //      TODO: Make this a more specific error and decouple it from the exclusion logic.
                //   2. When we checkIdentifier in the checker, we set its resolved symbol to the local symbol,
                //      but return the export symbol (by calling getExportSymbolOfValueSymbolIfExported). That way
                //      when the emitter comes back to it, it knows not to qualify the name if it was found in a containing scope.

                // NOTE: Nested ambient modules always should go to to 'locals' table to prevent their automatic merge
                //       during global merging in the checker. Why? The only case when ambient module is permitted inside another module is module augmentation
                //       and this case is specially handled. Module augmentations should only be merged with original module definition
                //       and should never be merged directly with other augmentation, and the latter case would be possible if automatic merge is allowed.
                if (!isAmbientModule(node) && (hasExportModifier || container.flags & NodeFlags.ExportContext)) {
                    const exportKind =
                        (symbolFlags & SymbolFlags.Value ? SymbolFlags.ExportValue : 0) |
                        (symbolFlags & SymbolFlags.Type ? SymbolFlags.ExportType : 0) |
                        (symbolFlags & SymbolFlags.Namespace ? SymbolFlags.ExportNamespace : 0);
                    const local = declareSymbol(container.locals, undefined, node, exportKind, symbolExcludes);
                    local.exportSymbol = declareSymbol(container.symbol.exports, container.symbol, node, symbolFlags, symbolExcludes);
                    node.localSymbol = local;
                    return local;
                }
                else {
                    return declareSymbol(container.locals, undefined, node, symbolFlags, symbolExcludes);
                }
            }
        }

        // 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 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 saveContainer = container;
            const savedBlockScopeContainer = blockScopeContainer;

            // 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
            // may contain locals, we proactively initialize the .locals field. We do this because
            // it's highly likely that the .locals will be needed to place some child in (for example,
            // a parameter, or variable declaration).
            //
            // However, we do not proactively create the .locals for block-containers because it's
            // totally normal and common for block-containers to never actually have a block-scoped
            // variable in them.  We don't want to end up allocating an object for every 'block' we
            // run into when most of them won't be necessary.
            //
            // Finally, if this is a block-container, then we clear out any existing .locals object
            // it may contain within it.  This happens in incremental scenarios.  Because we can be
            // 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.
            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;
            }
            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;
                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;
            }
            else if (containerFlags & ContainerFlags.IsInterface) {
                seenThisKeyword = false;
                bindChildren(node);
                node.flags = seenThisKeyword ? node.flags | NodeFlags.ContainsThis : node.flags & ~NodeFlags.ContainsThis;
            }
            else {
                bindChildren(node);
            }
            container = saveContainer;
            blockScopeContainer = savedBlockScopeContainer;
        }

        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);
                    break;
                case SyntaxKind.DoStatement:
                    bindDoStatement(<DoStatement>node);
                    break;
                case SyntaxKind.ForStatement:
                    bindForStatement(<ForStatement>node);
                    break;
                case SyntaxKind.ForInStatement:
                case SyntaxKind.ForOfStatement:
                    bindForInOrForOfStatement(<ForInStatement | ForOfStatement>node);
                    break;
                case SyntaxKind.IfStatement:
                    bindIfStatement(<IfStatement>node);
                    break;
                case SyntaxKind.ReturnStatement:
                case SyntaxKind.ThrowStatement:
                    bindReturnOrThrow(<ReturnStatement | ThrowStatement>node);
                    break;
                case SyntaxKind.BreakStatement:
                case SyntaxKind.ContinueStatement:
                    bindBreakOrContinueStatement(<BreakOrContinueStatement>node);
                    break;
                case SyntaxKind.TryStatement:
                    bindTryStatement(<TryStatement>node);
                    break;
                case SyntaxKind.SwitchStatement:
                    bindSwitchStatement(<SwitchStatement>node);
                    break;
                case SyntaxKind.CaseBlock:
                    bindCaseBlock(<CaseBlock>node);
                    break;
                case SyntaxKind.LabeledStatement:
                    bindLabeledStatement(<LabeledStatement>node);
                    break;
                case SyntaxKind.PrefixUnaryExpression:
                    bindPrefixUnaryExpressionFlow(<PrefixUnaryExpression>node);
                    break;
                case SyntaxKind.BinaryExpression:
                    bindBinaryExpressionFlow(<BinaryExpression>node);
                    break;
                case SyntaxKind.DeleteExpression:
                    bindDeleteExpressionFlow(<DeleteExpression>node);
                    break;
                case SyntaxKind.ConditionalExpression:
                    bindConditionalExpressionFlow(<ConditionalExpression>node);
                    break;
                case SyntaxKind.VariableDeclaration:
                    bindVariableDeclarationFlow(<VariableDeclaration>node);
                    break;
                case SyntaxKind.CallExpression:
                    bindCallExpressionFlow(<CallExpression>node);
                    break;
                default:
                    forEachChild(node, bind);
                    break;
            }
        }

        function isNarrowingExpression(expr: Expression): boolean {
            switch (expr.kind) {
                case SyntaxKind.Identifier:
                case SyntaxKind.ThisKeyword:
                case SyntaxKind.PropertyAccessExpression:
                    return isNarrowableReference(expr);
                case SyntaxKind.CallExpression:
                    return hasNarrowableArgument(<CallExpression>expr);
                case SyntaxKind.ParenthesizedExpression:
                    return isNarrowingExpression((<ParenthesizedExpression>expr).expression);
                case SyntaxKind.BinaryExpression:
                    return isNarrowingBinaryExpression(<BinaryExpression>expr);
                case SyntaxKind.PrefixUnaryExpression:
                    return (<PrefixUnaryExpression>expr).operator === SyntaxKind.ExclamationToken && isNarrowingExpression((<PrefixUnaryExpression>expr).operand);
            }
            return false;
        }

        function isNarrowableReference(expr: Expression): boolean {
            return expr.kind === SyntaxKind.Identifier ||
                expr.kind === SyntaxKind.ThisKeyword ||
                expr.kind === SyntaxKind.PropertyAccessExpression && isNarrowableReference((<PropertyAccessExpression>expr).expression);
        }

        function hasNarrowableArgument(expr: CallExpression) {
            if (expr.arguments) {
                for (const argument of expr.arguments) {
                    if (isNarrowableReference(argument)) {
                        return true;
                    }
                }
            }
            if (expr.expression.kind === SyntaxKind.PropertyAccessExpression &&
                isNarrowableReference((<PropertyAccessExpression>expr.expression).expression)) {
                return true;
            }
            return false;
        }

        function isNarrowingNullCheckOperands(expr1: Expression, expr2: Expression) {
            return (expr1.kind === SyntaxKind.NullKeyword || expr1.kind === SyntaxKind.Identifier && (<Identifier>expr1).text === "undefined") && isNarrowableOperand(expr2);
        }

        function isNarrowingTypeofOperands(expr1: Expression, expr2: Expression) {
            return expr1.kind === SyntaxKind.TypeOfExpression && isNarrowableOperand((<TypeOfExpression>expr1).expression) && expr2.kind === SyntaxKind.StringLiteral;
        }

        function isNarrowingDiscriminant(expr: Expression) {
            return expr.kind === SyntaxKind.PropertyAccessExpression && isNarrowableReference((<PropertyAccessExpression>expr).expression);
        }

        function isNarrowingBinaryExpression(expr: BinaryExpression) {
            switch (expr.operatorToken.kind) {
                case SyntaxKind.EqualsToken:
                    return isNarrowableReference(expr.left);
                case SyntaxKind.EqualsEqualsToken:
                case SyntaxKind.ExclamationEqualsToken:
                case SyntaxKind.EqualsEqualsEqualsToken:
                case SyntaxKind.ExclamationEqualsEqualsToken:
                    return isNarrowingNullCheckOperands(expr.right, expr.left) || isNarrowingNullCheckOperands(expr.left, expr.right) ||
                        isNarrowingTypeofOperands(expr.right, expr.left) || isNarrowingTypeofOperands(expr.left, expr.right) ||
                        isNarrowingDiscriminant(expr.left) || isNarrowingDiscriminant(expr.right);
                case SyntaxKind.InstanceOfKeyword:
                    return isNarrowableOperand(expr.left);
                case SyntaxKind.CommaToken:
                    return isNarrowingExpression(expr.right);
            }
            return false;
        }

        function isNarrowableOperand(expr: Expression): boolean {
            switch (expr.kind) {
                case SyntaxKind.ParenthesizedExpression:
                    return isNarrowableOperand((<ParenthesizedExpression>expr).expression);
                case SyntaxKind.BinaryExpression:
                    switch ((<BinaryExpression>expr).operatorToken.kind) {
                        case SyntaxKind.EqualsToken:
                            return isNarrowableOperand((<BinaryExpression>expr).left);
                        case SyntaxKind.CommaToken:
                            return isNarrowableOperand((<BinaryExpression>expr).right);
                    }
            }
            return isNarrowableReference(expr);
        }

        function isNarrowingSwitchStatement(switchStatement: SwitchStatement) {
            const expr = switchStatement.expression;
            return expr.kind === SyntaxKind.PropertyAccessExpression && isNarrowableReference((<PropertyAccessExpression>expr).expression);
        }

        function createBranchLabel(): FlowLabel {
            return {
                flags: FlowFlags.BranchLabel,
                antecedents: undefined
            };
        }

        function createLoopLabel(): FlowLabel {
            return {
                flags: FlowFlags.LoopLabel,
                antecedents: undefined
            };
        }

        function setFlowNodeReferenced(flow: FlowNode) {
            // On first reference we set the Referenced flag, thereafter we set the Shared flag
            flow.flags |= flow.flags & FlowFlags.Referenced ? FlowFlags.Shared : FlowFlags.Referenced;
        }

        function addAntecedent(label: FlowLabel, antecedent: FlowNode): void {
            if (!(antecedent.flags & FlowFlags.Unreachable) && !contains(label.antecedents, antecedent)) {
                (label.antecedents || (label.antecedents = [])).push(antecedent);
                setFlowNodeReferenced(antecedent);
            }
        }

        function createFlowCondition(flags: FlowFlags, antecedent: FlowNode, expression: Expression): FlowNode {
            if (antecedent.flags & FlowFlags.Unreachable) {
                return antecedent;
            }
            if (!expression) {
                return flags & FlowFlags.TrueCondition ? antecedent : unreachableFlow;
            }
            if (expression.kind === SyntaxKind.TrueKeyword && flags & FlowFlags.FalseCondition ||
                expression.kind === SyntaxKind.FalseKeyword && flags & FlowFlags.TrueCondition) {
                return unreachableFlow;
            }
            if (!isNarrowingExpression(expression)) {
                return antecedent;
            }
            setFlowNodeReferenced(antecedent);
            return <FlowCondition>{
                flags,
                expression,
                antecedent
            };
        }

        function createFlowSwitchClause(antecedent: FlowNode, switchStatement: SwitchStatement, clauseStart: number, clauseEnd: number): FlowNode {
            if (!isNarrowingSwitchStatement(switchStatement)) {
                return antecedent;
            }
            setFlowNodeReferenced(antecedent);
            return <FlowSwitchClause>{
                flags: FlowFlags.SwitchClause,
                switchStatement,
                clauseStart,
                clauseEnd,
                antecedent
            };
        }

        function createFlowAssignment(antecedent: FlowNode, node: Expression | VariableDeclaration | BindingElement): FlowNode {
            setFlowNodeReferenced(antecedent);
            return <FlowAssignment>{
                flags: FlowFlags.Assignment,
                antecedent,
                node
            };
        }

        function finishFlowLabel(flow: FlowLabel): FlowNode {
            const antecedents = flow.antecedents;
            if (!antecedents) {
                return unreachableFlow;
            }
            if (antecedents.length === 1) {
                return antecedents[0];
            }
            return flow;
        }

        function isStatementCondition(node: Node) {
            const parent = node.parent;
            switch (parent.kind) {
                case SyntaxKind.IfStatement:
                case SyntaxKind.WhileStatement:
                case SyntaxKind.DoStatement:
                    return (<IfStatement | WhileStatement | DoStatement>parent).expression === node;
                case SyntaxKind.ForStatement:
                case SyntaxKind.ConditionalExpression:
                    return (<ForStatement | ConditionalExpression>parent).condition === node;
            }
            return false;
        }

        function isLogicalExpression(node: Node) {
            while (true) {
                if (node.kind === SyntaxKind.ParenthesizedExpression) {
                    node = (<ParenthesizedExpression>node).expression;
                }
                else if (node.kind === SyntaxKind.PrefixUnaryExpression && (<PrefixUnaryExpression>node).operator === SyntaxKind.ExclamationToken) {
                    node = (<PrefixUnaryExpression>node).operand;
                }
                else {
                    return node.kind === SyntaxKind.BinaryExpression && (
                        (<BinaryExpression>node).operatorToken.kind === SyntaxKind.AmpersandAmpersandToken ||
                        (<BinaryExpression>node).operatorToken.kind === SyntaxKind.BarBarToken);
                }
            }
        }

        function isTopLevelLogicalExpression(node: Node): boolean {
            while (node.parent.kind === SyntaxKind.ParenthesizedExpression ||
                node.parent.kind === SyntaxKind.PrefixUnaryExpression &&
                (<PrefixUnaryExpression>node.parent).operator === SyntaxKind.ExclamationToken) {
                node = node.parent;
            }
            return !isStatementCondition(node) && !isLogicalExpression(node.parent);
        }

        function bindCondition(node: Expression, trueTarget: FlowLabel, falseTarget: FlowLabel) {
            const saveTrueTarget = currentTrueTarget;
            const saveFalseTarget = currentFalseTarget;
            currentTrueTarget = trueTarget;
            currentFalseTarget = falseTarget;
            bind(node);
            currentTrueTarget = saveTrueTarget;
            currentFalseTarget = saveFalseTarget;
            if (!node || !isLogicalExpression(node)) {
                addAntecedent(trueTarget, createFlowCondition(FlowFlags.TrueCondition, currentFlow, node));
                addAntecedent(falseTarget, createFlowCondition(FlowFlags.FalseCondition, currentFlow, node));
            }
        }

        function bindIterativeStatement(node: Statement, breakTarget: FlowLabel, continueTarget: FlowLabel): void {
            const saveBreakTarget = currentBreakTarget;
            const saveContinueTarget = currentContinueTarget;
            currentBreakTarget = breakTarget;
            currentContinueTarget = continueTarget;
            bind(node);
            currentBreakTarget = saveBreakTarget;
            currentContinueTarget = saveContinueTarget;
        }

        function bindWhileStatement(node: WhileStatement): void {
            const preWhileLabel = createLoopLabel();
            const preBodyLabel = createBranchLabel();
            const postWhileLabel = createBranchLabel();
            addAntecedent(preWhileLabel, currentFlow);
            currentFlow = preWhileLabel;
            bindCondition(node.expression, preBodyLabel, postWhileLabel);
            currentFlow = finishFlowLabel(preBodyLabel);
            bindIterativeStatement(node.statement, postWhileLabel, preWhileLabel);
            addAntecedent(preWhileLabel, currentFlow);
            currentFlow = finishFlowLabel(postWhileLabel);
        }

        function bindDoStatement(node: DoStatement): void {
            const preDoLabel = createLoopLabel();
            const preConditionLabel = createBranchLabel();
            const postDoLabel = createBranchLabel();
            addAntecedent(preDoLabel, currentFlow);
            currentFlow = preDoLabel;
            bindIterativeStatement(node.statement, postDoLabel, preConditionLabel);
            addAntecedent(preConditionLabel, currentFlow);
            currentFlow = finishFlowLabel(preConditionLabel);
            bindCondition(node.expression, preDoLabel, postDoLabel);
            currentFlow = finishFlowLabel(postDoLabel);
        }

        function bindForStatement(node: ForStatement): void {
            const preLoopLabel = createLoopLabel();
            const preBodyLabel = createBranchLabel();
            const postLoopLabel = createBranchLabel();
            bind(node.initializer);
            addAntecedent(preLoopLabel, currentFlow);
            currentFlow = preLoopLabel;
            bindCondition(node.condition, preBodyLabel, postLoopLabel);
            currentFlow = finishFlowLabel(preBodyLabel);
            bindIterativeStatement(node.statement, postLoopLabel, preLoopLabel);
            bind(node.incrementor);
            addAntecedent(preLoopLabel, currentFlow);
            currentFlow = finishFlowLabel(postLoopLabel);
        }

        function bindForInOrForOfStatement(node: ForInStatement | ForOfStatement): void {
            const preLoopLabel = createLoopLabel();
            const postLoopLabel = createBranchLabel();
            addAntecedent(preLoopLabel, currentFlow);
            currentFlow = preLoopLabel;
            bind(node.expression);
            addAntecedent(postLoopLabel, currentFlow);
            bind(node.initializer);
            if (node.initializer.kind !== SyntaxKind.VariableDeclarationList) {
                bindAssignmentTargetFlow(<Expression>node.initializer);
            }
            bindIterativeStatement(node.statement, postLoopLabel, preLoopLabel);
            addAntecedent(preLoopLabel, currentFlow);
            currentFlow = finishFlowLabel(postLoopLabel);
        }

        function bindIfStatement(node: IfStatement): void {
            const thenLabel = createBranchLabel();
            const elseLabel = createBranchLabel();
            const postIfLabel = createBranchLabel();
            bindCondition(node.expression, thenLabel, elseLabel);
            currentFlow = finishFlowLabel(thenLabel);
            bind(node.thenStatement);
            addAntecedent(postIfLabel, currentFlow);
            currentFlow = finishFlowLabel(elseLabel);
            bind(node.elseStatement);
            addAntecedent(postIfLabel, currentFlow);
            currentFlow = finishFlowLabel(postIfLabel);
        }

        function bindReturnOrThrow(node: ReturnStatement | ThrowStatement): void {
            bind(node.expression);
            if (node.kind === SyntaxKind.ReturnStatement) {
                hasExplicitReturn = true;
                if (currentReturnTarget) {
                    addAntecedent(currentReturnTarget, currentFlow);
                }
            }
            currentFlow = unreachableFlow;
        }

        function findActiveLabel(name: string) {
            if (activeLabels) {
                for (const label of activeLabels) {
                    if (label.name === name) {
                        return label;
                    }
                }
            }
            return undefined;
        }

        function bindbreakOrContinueFlow(node: BreakOrContinueStatement, breakTarget: FlowLabel, continueTarget: FlowLabel) {
            const flowLabel = node.kind === SyntaxKind.BreakStatement ? breakTarget : continueTarget;
            if (flowLabel) {
                addAntecedent(flowLabel, currentFlow);
                currentFlow = unreachableFlow;
            }
        }

        function bindBreakOrContinueStatement(node: BreakOrContinueStatement): void {
            bind(node.label);
            if (node.label) {
                const activeLabel = findActiveLabel(node.label.text);
                if (activeLabel) {
                    activeLabel.referenced = true;
                    bindbreakOrContinueFlow(node, activeLabel.breakTarget, activeLabel.continueTarget);
                }
            }
            else {
                bindbreakOrContinueFlow(node, currentBreakTarget, currentContinueTarget);
            }
        }

        function bindTryStatement(node: TryStatement): void {
            const postFinallyLabel = createBranchLabel();
            const preTryFlow = currentFlow;
            // TODO: Every statement in try block is potentially an exit point!
            bind(node.tryBlock);
            addAntecedent(postFinallyLabel, currentFlow);
            if (node.catchClause) {
                currentFlow = preTryFlow;
                bind(node.catchClause);
                addAntecedent(postFinallyLabel, currentFlow);
            }
            if (node.finallyBlock) {
                currentFlow = preTryFlow;
                bind(node.finallyBlock);
            }
            currentFlow = finishFlowLabel(postFinallyLabel);
        }

        function bindSwitchStatement(node: SwitchStatement): void {
            const postSwitchLabel = createBranchLabel();
            bind(node.expression);
            const saveBreakTarget = currentBreakTarget;
            const savePreSwitchCaseFlow = preSwitchCaseFlow;
            currentBreakTarget = postSwitchLabel;
            preSwitchCaseFlow = currentFlow;
            bind(node.caseBlock);
            addAntecedent(postSwitchLabel, currentFlow);
            const hasDefault = forEach(node.caseBlock.clauses, c => c.kind === SyntaxKind.DefaultClause);
            // We mark a switch statement as possibly exhaustive if it has no default clause and if all
            // case clauses have unreachable end points (e.g. they all return).
            node.possiblyExhaustive = !hasDefault && !postSwitchLabel.antecedents;
            if (!hasDefault) {
                addAntecedent(postSwitchLabel, createFlowSwitchClause(preSwitchCaseFlow, node, 0, 0));
            }
            currentBreakTarget = saveBreakTarget;
            preSwitchCaseFlow = savePreSwitchCaseFlow;
            currentFlow = finishFlowLabel(postSwitchLabel);
        }

        function bindCaseBlock(node: CaseBlock): void {
            const clauses = node.clauses;
            let fallthroughFlow = unreachableFlow;
            for (let i = 0; i < clauses.length; i++) {
                const clauseStart = i;
                while (!clauses[i].statements.length && i + 1 < clauses.length) {
                    bind(clauses[i]);
                    i++;
                }
                const preCaseLabel = createBranchLabel();
                addAntecedent(preCaseLabel, createFlowSwitchClause(preSwitchCaseFlow, <SwitchStatement>node.parent, clauseStart, i + 1));
                addAntecedent(preCaseLabel, fallthroughFlow);
                currentFlow = finishFlowLabel(preCaseLabel);
                const clause = clauses[i];
                bind(clause);
                fallthroughFlow = currentFlow;
                if (!(currentFlow.flags & FlowFlags.Unreachable) && i !== clauses.length - 1 && options.noFallthroughCasesInSwitch) {
                    errorOnFirstToken(clause, Diagnostics.Fallthrough_case_in_switch);
                }
            }
        }

        function pushActiveLabel(name: string, breakTarget: FlowLabel, continueTarget: FlowLabel): ActiveLabel {
            const activeLabel = {
                name,
                breakTarget,
                continueTarget,
                referenced: false
            };
            (activeLabels || (activeLabels = [])).push(activeLabel);
            return activeLabel;
        }

        function popActiveLabel() {
            activeLabels.pop();
        }

        function bindLabeledStatement(node: LabeledStatement): void {
            const preStatementLabel = createLoopLabel();
            const postStatementLabel = createBranchLabel();
            bind(node.label);
            addAntecedent(preStatementLabel, currentFlow);
            const activeLabel = pushActiveLabel(node.label.text, postStatementLabel, preStatementLabel);
            bind(node.statement);
            popActiveLabel();
            if (!activeLabel.referenced && !options.allowUnusedLabels) {
                file.bindDiagnostics.push(createDiagnosticForNode(node.label, Diagnostics.Unused_label));
            }
            addAntecedent(postStatementLabel, currentFlow);
            currentFlow = finishFlowLabel(postStatementLabel);
        }

        function bindDestructuringTargetFlow(node: Expression) {
            if (node.kind === SyntaxKind.BinaryExpression && (<BinaryExpression>node).operatorToken.kind === SyntaxKind.EqualsToken) {
                bindAssignmentTargetFlow((<BinaryExpression>node).left);
            }
            else {
                bindAssignmentTargetFlow(node);
            }
        }

        function bindAssignmentTargetFlow(node: Expression) {
            if (isNarrowableReference(node)) {
                currentFlow = createFlowAssignment(currentFlow, node);
            }
            else if (node.kind === SyntaxKind.ArrayLiteralExpression) {
                for (const e of (<ArrayLiteralExpression>node).elements) {
                    if (e.kind === SyntaxKind.SpreadElementExpression) {
                        bindAssignmentTargetFlow((<SpreadElementExpression>e).expression);
                    }
                    else {
                        bindDestructuringTargetFlow(e);
                    }
                }
            }
            else if (node.kind === SyntaxKind.ObjectLiteralExpression) {
                for (const p of (<ObjectLiteralExpression>node).properties) {
                    if (p.kind === SyntaxKind.PropertyAssignment) {
                        bindDestructuringTargetFlow((<PropertyAssignment>p).initializer);
                    }
                    else if (p.kind === SyntaxKind.ShorthandPropertyAssignment) {
                        bindAssignmentTargetFlow((<ShorthandPropertyAssignment>p).name);
                    }
                }
            }
        }

        function bindLogicalExpression(node: BinaryExpression, trueTarget: FlowLabel, falseTarget: FlowLabel) {
            const preRightLabel = createBranchLabel();
            if (node.operatorToken.kind === SyntaxKind.AmpersandAmpersandToken) {
                bindCondition(node.left, preRightLabel, falseTarget);
            }
            else {
                bindCondition(node.left, trueTarget, preRightLabel);
            }
            currentFlow = finishFlowLabel(preRightLabel);
            bind(node.operatorToken);
            bindCondition(node.right, trueTarget, falseTarget);
        }

        function bindPrefixUnaryExpressionFlow(node: PrefixUnaryExpression) {
            if (node.operator === SyntaxKind.ExclamationToken) {
                const saveTrueTarget = currentTrueTarget;
                currentTrueTarget = currentFalseTarget;
                currentFalseTarget = saveTrueTarget;
                forEachChild(node, bind);
                currentFalseTarget = currentTrueTarget;
                currentTrueTarget = saveTrueTarget;
            }
            else {
                forEachChild(node, bind);
            }
        }

        function bindBinaryExpressionFlow(node: BinaryExpression) {
            const operator = node.operatorToken.kind;
            if (operator === SyntaxKind.AmpersandAmpersandToken || operator === SyntaxKind.BarBarToken) {
                if (isTopLevelLogicalExpression(node)) {
                    const postExpressionLabel = createBranchLabel();
                    bindLogicalExpression(node, postExpressionLabel, postExpressionLabel);
                    currentFlow = finishFlowLabel(postExpressionLabel);
                }
                else {
                    bindLogicalExpression(node, currentTrueTarget, currentFalseTarget);
                }
            }
            else {
                forEachChild(node, bind);
                if (operator === SyntaxKind.EqualsToken && !isAssignmentTarget(node)) {
                    bindAssignmentTargetFlow(node.left);
                }
            }
        }

        function bindDeleteExpressionFlow(node: DeleteExpression) {
            forEachChild(node, bind);
            if (node.expression.kind === SyntaxKind.PropertyAccessExpression) {
                bindAssignmentTargetFlow(node.expression);
            }
        }

        function bindConditionalExpressionFlow(node: ConditionalExpression) {
            const trueLabel = createBranchLabel();
            const falseLabel = createBranchLabel();
            const postExpressionLabel = createBranchLabel();
            bindCondition(node.condition, trueLabel, falseLabel);
            currentFlow = finishFlowLabel(trueLabel);
            bind(node.whenTrue);
            addAntecedent(postExpressionLabel, currentFlow);
            currentFlow = finishFlowLabel(falseLabel);
            bind(node.whenFalse);
            addAntecedent(postExpressionLabel, currentFlow);
            currentFlow = finishFlowLabel(postExpressionLabel);
        }

        function bindInitializedVariableFlow(node: VariableDeclaration | BindingElement) {
            const name = node.name;
            if (isBindingPattern(name)) {
                for (const child of name.elements) {
                    bindInitializedVariableFlow(child);
                }
            }
            else {
                currentFlow = createFlowAssignment(currentFlow, node);
            }
        }

        function bindVariableDeclarationFlow(node: VariableDeclaration) {
            forEachChild(node, bind);
            if (node.initializer || node.parent.parent.kind === SyntaxKind.ForInStatement || node.parent.parent.kind === SyntaxKind.ForOfStatement) {
                bindInitializedVariableFlow(node);
            }
        }

        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.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.FunctionType:
                case SyntaxKind.ConstructorType:
                    return ContainerFlags.IsContainer | ContainerFlags.IsControlFlowContainer | ContainerFlags.HasLocals | ContainerFlags.IsFunctionLike;

                case SyntaxKind.FunctionExpression:
                case SyntaxKind.ArrowFunction:
                    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:
                case SyntaxKind.ForInStatement:
                case SyntaxKind.ForOfStatement:
                case SyntaxKind.CaseBlock:
                    return ContainerFlags.IsBlockScopedContainer;

                case SyntaxKind.Block:
                    // do not treat blocks directly inside a function as a block-scoped-container.
                    // Locals that reside in this block should go to the function locals. Otherwise 'x'
                    // would not appear to be a redeclaration of a block scoped local in the following
                    // example:
                    //
                    //      function foo() {
                    //          var x;
                    //          let x;
                    //      }
                    //
                    // If we placed 'var x' into the function locals and 'let x' into the locals of
                    // the block, then there would be no collision.
                    //
                    // By not creating a new block-scoped-container here, we ensure that both 'var x'
                    // and 'let x' go into the Function-container's locals, and we do get a collision
                    // conflict.
                    return isFunctionLike(node.parent) ? ContainerFlags.None : ContainerFlags.IsBlockScopedContainer;
            }

            return ContainerFlags.None;
        }

        function addToContainerChain(next: Node) {
            if (lastContainer) {
                lastContainer.nextContainer = next;
            }

            lastContainer = next;
        }

        function declareSymbolAndAddToSymbolTable(node: Declaration, symbolFlags: SymbolFlags, symbolExcludes: SymbolFlags): Symbol {
            // Just call this directly so that the return type of this function stays "void".
            return declareSymbolAndAddToSymbolTableWorker(node, symbolFlags, symbolExcludes);
        }

        function declareSymbolAndAddToSymbolTableWorker(node: Declaration, symbolFlags: SymbolFlags, symbolExcludes: SymbolFlags): Symbol {
            switch (container.kind) {
                // Modules, source files, and classes need specialized handling for how their
                // members are declared (for example, a member of a class will go into a specific
                // symbol table depending on if it is static or not). We defer to specialized
                // handlers to take care of declaring these child members.
                case SyntaxKind.ModuleDeclaration:
                    return declareModuleMember(node, symbolFlags, symbolExcludes);

                case SyntaxKind.SourceFile:
                    return declareSourceFileMember(node, symbolFlags, symbolExcludes);

                case SyntaxKind.ClassExpression:
                case SyntaxKind.ClassDeclaration:
                    return declareClassMember(node, symbolFlags, symbolExcludes);

                case SyntaxKind.EnumDeclaration:
                    return declareSymbol(container.symbol.exports, container.symbol, node, symbolFlags, symbolExcludes);

                case SyntaxKind.TypeLiteral:
                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
                    // object / type / interface declaring them). An exception is type parameters,
                    // which are in scope without qualification (similar to 'locals').
                    return declareSymbol(container.symbol.members, container.symbol, node, symbolFlags, symbolExcludes);

                case SyntaxKind.FunctionType:
                case SyntaxKind.ConstructorType:
                case SyntaxKind.CallSignature:
                case SyntaxKind.ConstructSignature:
                case SyntaxKind.IndexSignature:
                case SyntaxKind.MethodDeclaration:
                case SyntaxKind.MethodSignature:
                case SyntaxKind.Constructor:
                case SyntaxKind.GetAccessor:
                case SyntaxKind.SetAccessor:
                case SyntaxKind.FunctionDeclaration:
                case SyntaxKind.FunctionExpression:
                case SyntaxKind.ArrowFunction:
                case SyntaxKind.JSDocFunctionType:
                case SyntaxKind.TypeAliasDeclaration:
                    // All the children of these container types are never visible through another
                    // symbol (i.e. through another symbol's 'exports' or 'members').  Instead,
                    // they're only accessed 'lexically' (i.e. from code that exists underneath
                    // 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, /*parent*/ undefined, node, symbolFlags, symbolExcludes);
            }
        }

        function declareClassMember(node: Declaration, symbolFlags: SymbolFlags, symbolExcludes: SymbolFlags) {
            return node.flags & NodeFlags.Static
                ? declareSymbol(container.symbol.exports, container.symbol, node, symbolFlags, symbolExcludes)
                : declareSymbol(container.symbol.members, container.symbol, node, symbolFlags, symbolExcludes);
        }

        function declareSourceFileMember(node: Declaration, symbolFlags: SymbolFlags, symbolExcludes: SymbolFlags) {
            return isExternalModule(file)
                ? declareModuleMember(node, symbolFlags, symbolExcludes)
                : declareSymbol(file.locals, undefined, node, symbolFlags, symbolExcludes);
        }

        function hasExportDeclarations(node: ModuleDeclaration | SourceFile): boolean {
            const body = node.kind === SyntaxKind.SourceFile ? node : (<ModuleDeclaration>node).body;
            if (body && (body.kind === SyntaxKind.SourceFile || body.kind === SyntaxKind.ModuleBlock)) {
                for (const stat of (<Block>body).statements) {
                    if (stat.kind === SyntaxKind.ExportDeclaration || stat.kind === SyntaxKind.ExportAssignment) {
                        return true;
                    }
                }
            }
            return false;
        }

        function setExportContextFlag(node: ModuleDeclaration | SourceFile) {
            // A declaration source file or ambient module declaration that contains no export declarations (but possibly regular
            // declarations with export modifiers) is an export context in which declarations are implicitly exported.
            if (isInAmbientContext(node) && !hasExportDeclarations(node)) {
                node.flags |= NodeFlags.ExportContext;
            }
            else {
                node.flags &= ~NodeFlags.ExportContext;
            }
        }

        function bindModuleDeclaration(node: ModuleDeclaration) {
            setExportContextFlag(node);
            if (isAmbientModule(node)) {
                if (node.flags & NodeFlags.Export) {
                    errorOnFirstToken(node, Diagnostics.export_modifier_cannot_be_applied_to_ambient_modules_and_module_augmentations_since_they_are_always_visible);
                }
                if (isExternalModuleAugmentation(node)) {
                    declareSymbolAndAddToSymbolTable(node, SymbolFlags.NamespaceModule, SymbolFlags.NamespaceModuleExcludes);
                }
                else {
                    let pattern: Pattern | undefined;
                    if (node.name.kind === SyntaxKind.StringLiteral) {
                        const text = (<StringLiteral>node.name).text;
                        if (hasZeroOrOneAsteriskCharacter(text)) {
                            pattern = tryParsePattern(text);
                        }
                        else {
                            errorOnFirstToken(node.name, Diagnostics.Pattern_0_can_have_at_most_one_Asterisk_character, text);
                        }
                    }

                    const symbol = declareSymbolAndAddToSymbolTable(node, SymbolFlags.ValueModule, SymbolFlags.ValueModuleExcludes);

                    if (pattern) {
                        (file.patternAmbientModules || (file.patternAmbientModules = [])).push({ pattern, symbol });
                    }
                }
            }
            else {
                const state = getModuleInstanceState(node);
                if (state === ModuleInstanceState.NonInstantiated) {
                    declareSymbolAndAddToSymbolTable(node, SymbolFlags.NamespaceModule, SymbolFlags.NamespaceModuleExcludes);
                }
                else {
                    declareSymbolAndAddToSymbolTable(node, SymbolFlags.ValueModule, SymbolFlags.ValueModuleExcludes);
                    if (node.symbol.flags & (SymbolFlags.Function | SymbolFlags.Class | SymbolFlags.RegularEnum)) {
                        // if module was already merged with some function, class or non-const enum
                        // treat is a non-const-enum-only
                        node.symbol.constEnumOnlyModule = false;
                    }
                    else {
                        const currentModuleIsConstEnumOnly = state === ModuleInstanceState.ConstEnumOnly;
                        if (node.symbol.constEnumOnlyModule === undefined) {
                            // non-merged case - use the current state
                            node.symbol.constEnumOnlyModule = currentModuleIsConstEnumOnly;
                        }
                        else {
                            // merged case: module is const enum only if all its pieces are non-instantiated or const enum
                            node.symbol.constEnumOnlyModule = node.symbol.constEnumOnlyModule && currentModuleIsConstEnumOnly;
                        }
                    }
                }
            }
        }

        function bindFunctionOrConstructorType(node: SignatureDeclaration): void {
            // For a given function symbol "<...>(...) => T" we want to generate a symbol identical
            // to the one we would get for: { <...>(...): T }
            //
            // We do that by making an anonymous type literal symbol, and then setting the function
            // symbol as its sole member. To the rest of the system, this symbol will be  indistinguishable
            // from an actual type literal symbol you would have gotten had you used the long form.
            const symbol = createSymbol(SymbolFlags.Signature, getDeclarationName(node));
            addDeclarationToSymbol(symbol, node, SymbolFlags.Signature);

            const typeLiteralSymbol = createSymbol(SymbolFlags.TypeLiteral, "__type");
            addDeclarationToSymbol(typeLiteralSymbol, node, SymbolFlags.TypeLiteral);
            typeLiteralSymbol.members = { [symbol.name]: symbol };
        }

        function bindObjectLiteralExpression(node: ObjectLiteralExpression) {
            const enum ElementKind {
                Property = 1,
                Accessor = 2
            }

            if (inStrictMode) {
                const seen: Map<ElementKind> = {};

                for (const prop of node.properties) {
                    if (prop.name.kind !== SyntaxKind.Identifier) {
                        continue;
                    }

                    const identifier = <Identifier>prop.name;

                    // ECMA-262 11.1.5 Object Initializer
                    // If previous is not undefined then throw a SyntaxError exception if any of the following conditions are true
                    // a.This production is contained in strict code and IsDataDescriptor(previous) is true and
                    // IsDataDescriptor(propId.descriptor) is true.
                    //    b.IsDataDescriptor(previous) is true and IsAccessorDescriptor(propId.descriptor) is true.
                    //    c.IsAccessorDescriptor(previous) is true and IsDataDescriptor(propId.descriptor) is true.
                    //    d.IsAccessorDescriptor(previous) is true and IsAccessorDescriptor(propId.descriptor) is true
                    // and either both previous and propId.descriptor have[[Get]] fields or both previous and propId.descriptor have[[Set]] fields
                    const currentKind = prop.kind === SyntaxKind.PropertyAssignment || prop.kind === SyntaxKind.ShorthandPropertyAssignment || prop.kind === SyntaxKind.MethodDeclaration
                        ? ElementKind.Property
                        : ElementKind.Accessor;

                    const existingKind = seen[identifier.text];
                    if (!existingKind) {
                        seen[identifier.text] = currentKind;
                        continue;
                    }

                    if (currentKind === ElementKind.Property && existingKind === ElementKind.Property) {
                        const span = getErrorSpanForNode(file, identifier);
                        file.bindDiagnostics.push(createFileDiagnostic(file, span.start, span.length,
                            Diagnostics.An_object_literal_cannot_have_multiple_properties_with_the_same_name_in_strict_mode));
                    }
                }
            }

            return bindAnonymousDeclaration(node, SymbolFlags.ObjectLiteral, "__object");
        }

        function bindAnonymousDeclaration(node: Declaration, symbolFlags: SymbolFlags, name: string) {
            const symbol = createSymbol(symbolFlags, name);
            addDeclarationToSymbol(symbol, node, symbolFlags);
        }

        function bindBlockScopedDeclaration(node: Declaration, symbolFlags: SymbolFlags, symbolExcludes: SymbolFlags) {
            switch (blockScopeContainer.kind) {
                case SyntaxKind.ModuleDeclaration:
                    declareModuleMember(node, symbolFlags, symbolExcludes);
                    break;
                case SyntaxKind.SourceFile:
                    if (isExternalModule(<SourceFile>container)) {
                        declareModuleMember(node, symbolFlags, symbolExcludes);
                        break;
                    }
                // fall through.
                default:
                    if (!blockScopeContainer.locals) {
                        blockScopeContainer.locals = {};
                        addToContainerChain(blockScopeContainer);
                    }
                    declareSymbol(blockScopeContainer.locals, undefined, node, symbolFlags, symbolExcludes);
            }
        }

        function bindBlockScopedVariableDeclaration(node: Declaration) {
            bindBlockScopedDeclaration(node, SymbolFlags.BlockScopedVariable, SymbolFlags.BlockScopedVariableExcludes);
        }

        // The binder visits every node in the syntax tree so it is a convenient place to perform a single localized
        // check for reserved words used as identifiers in strict mode code.
        function checkStrictModeIdentifier(node: Identifier) {
            if (inStrictMode &&
                node.originalKeywordKind >= SyntaxKind.FirstFutureReservedWord &&
                node.originalKeywordKind <= SyntaxKind.LastFutureReservedWord &&
                !isIdentifierName(node) &&
                !isInAmbientContext(node)) {

                // Report error only if there are no parse errors in file
                if (!file.parseDiagnostics.length) {
                    file.bindDiagnostics.push(createDiagnosticForNode(node,
                        getStrictModeIdentifierMessage(node), declarationNameToString(node)));
                }
            }
        }

        function getStrictModeIdentifierMessage(node: Node) {
            // Provide specialized messages to help the user understand why we think they're in
            // strict mode.
            if (getContainingClass(node)) {
                return Diagnostics.Identifier_expected_0_is_a_reserved_word_in_strict_mode_Class_definitions_are_automatically_in_strict_mode;
            }

            if (file.externalModuleIndicator) {
                return Diagnostics.Identifier_expected_0_is_a_reserved_word_in_strict_mode_Modules_are_automatically_in_strict_mode;
            }

            return Diagnostics.Identifier_expected_0_is_a_reserved_word_in_strict_mode;
        }

        function checkStrictModeBinaryExpression(node: BinaryExpression) {
            if (inStrictMode && isLeftHandSideExpression(node.left) && isAssignmentOperator(node.operatorToken.kind)) {
                // ECMA 262 (Annex C) The identifier eval or arguments may not appear as the LeftHandSideExpression of an
                // Assignment operator(11.13) or of a PostfixExpression(11.3)
                checkStrictModeEvalOrArguments(node, <Identifier>node.left);
            }
        }

        function checkStrictModeCatchClause(node: CatchClause) {
            // It is a SyntaxError if a TryStatement with a Catch occurs within strict code and the Identifier of the
            // Catch production is eval or arguments
            if (inStrictMode && node.variableDeclaration) {
                checkStrictModeEvalOrArguments(node, node.variableDeclaration.name);
            }
        }

        function checkStrictModeDeleteExpression(node: DeleteExpression) {
            // Grammar checking
            if (inStrictMode && node.expression.kind === SyntaxKind.Identifier) {
                // When a delete operator occurs within strict mode code, a SyntaxError is thrown if its
                // UnaryExpression is a direct reference to a variable, function argument, or function name
                const span = getErrorSpanForNode(file, node.expression);
                file.bindDiagnostics.push(createFileDiagnostic(file, span.start, span.length, Diagnostics.delete_cannot_be_called_on_an_identifier_in_strict_mode));
            }
        }

        function isEvalOrArgumentsIdentifier(node: Node): boolean {
            return node.kind === SyntaxKind.Identifier &&
                ((<Identifier>node).text === "eval" || (<Identifier>node).text === "arguments");
        }

        function checkStrictModeEvalOrArguments(contextNode: Node, name: Node) {
            if (name && name.kind === SyntaxKind.Identifier) {
                const identifier = <Identifier>name;
                if (isEvalOrArgumentsIdentifier(identifier)) {
                    // We check first if the name is inside class declaration or class expression; if so give explicit message
                    // otherwise report generic error message.
                    const span = getErrorSpanForNode(file, name);
                    file.bindDiagnostics.push(createFileDiagnostic(file, span.start, span.length,
                        getStrictModeEvalOrArgumentsMessage(contextNode), identifier.text));
                }
            }
        }

        function getStrictModeEvalOrArgumentsMessage(node: Node) {
            // Provide specialized messages to help the user understand why we think they're in
            // strict mode.
            if (getContainingClass(node)) {
                return Diagnostics.Invalid_use_of_0_Class_definitions_are_automatically_in_strict_mode;
            }

            if (file.externalModuleIndicator) {
                return Diagnostics.Invalid_use_of_0_Modules_are_automatically_in_strict_mode;
            }

            return Diagnostics.Invalid_use_of_0_in_strict_mode;
        }

        function checkStrictModeFunctionName(node: FunctionLikeDeclaration) {
            if (inStrictMode) {
                // It is a SyntaxError if the identifier eval or arguments appears within a FormalParameterList of a strict mode FunctionDeclaration or FunctionExpression (13.1))
                checkStrictModeEvalOrArguments(node, node.name);
            }
        }

        function getStrictModeBlockScopeFunctionDeclarationMessage(node: Node) {
            // Provide specialized messages to help the user understand why we think they're in
            // strict mode.
            if (getContainingClass(node)) {
                return Diagnostics.Function_declarations_are_not_allowed_inside_blocks_in_strict_mode_when_targeting_ES3_or_ES5_Class_definitions_are_automatically_in_strict_mode;
            }

            if (file.externalModuleIndicator) {
                return Diagnostics.Function_declarations_are_not_allowed_inside_blocks_in_strict_mode_when_targeting_ES3_or_ES5_Modules_are_automatically_in_strict_mode;
            }

            return Diagnostics.Function_declarations_are_not_allowed_inside_blocks_in_strict_mode_when_targeting_ES3_or_ES5;
        }

        function checkStrictModeFunctionDeclaration(node: FunctionDeclaration) {
            if (languageVersion < ScriptTarget.ES6) {
                // Report error if function is not top level function declaration
                if (blockScopeContainer.kind !== SyntaxKind.SourceFile &&
                    blockScopeContainer.kind !== SyntaxKind.ModuleDeclaration &&
                    !isFunctionLike(blockScopeContainer)) {
                    // We check first if the name is inside class declaration or class expression; if so give explicit message
                    // otherwise report generic error message.
                    const errorSpan = getErrorSpanForNode(file, node);
                    file.bindDiagnostics.push(createFileDiagnostic(file, errorSpan.start, errorSpan.length,
                        getStrictModeBlockScopeFunctionDeclarationMessage(node)));
                }
            }
        }

        function checkStrictModeNumericLiteral(node: LiteralExpression) {
            if (inStrictMode && node.isOctalLiteral) {
                file.bindDiagnostics.push(createDiagnosticForNode(node, Diagnostics.Octal_literals_are_not_allowed_in_strict_mode));
            }
        }

        function checkStrictModePostfixUnaryExpression(node: PostfixUnaryExpression) {
            // Grammar checking
            // The identifier eval or arguments may not appear as the LeftHandSideExpression of an
            // Assignment operator(11.13) or of a PostfixExpression(11.3) or as the UnaryExpression
            // operated upon by a Prefix Increment(11.4.4) or a Prefix Decrement(11.4.5) operator.
            if (inStrictMode) {
                checkStrictModeEvalOrArguments(node, <Identifier>node.operand);
            }
        }

        function checkStrictModePrefixUnaryExpression(node: PrefixUnaryExpression) {
            // Grammar checking
            if (inStrictMode) {
                if (node.operator === SyntaxKind.PlusPlusToken || node.operator === SyntaxKind.MinusMinusToken) {
                    checkStrictModeEvalOrArguments(node, <Identifier>node.operand);
                }
            }
        }

        function checkStrictModeWithStatement(node: WithStatement) {
            // Grammar checking for withStatement
            if (inStrictMode) {
                errorOnFirstToken(node, Diagnostics.with_statements_are_not_allowed_in_strict_mode);
            }
        }

        function errorOnFirstToken(node: Node, message: DiagnosticMessage, arg0?: any, arg1?: any, arg2?: any) {
            const span = getSpanOfTokenAtPosition(file, node.pos);
            file.bindDiagnostics.push(createFileDiagnostic(file, span.start, span.length, message, arg0, arg1, arg2));
        }

        function getDestructuringParameterName(node: Declaration) {
            return "__" + indexOf((<SignatureDeclaration>node.parent).parameters, node);
        }

        function bind(node: Node): void {
            if (!node) {
                return;
            }
            node.parent = parent;
            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:
            //
            //  1) The 'exports' table of the current container's symbol.
            //  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
            // (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. 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>) {
            if (!inStrictMode) {
                for (const statement of statements) {
                    if (!isPrologueDirective(statement)) {
                        return;
                    }

                    if (isUseStrictPrologueDirective(<ExpressionStatement>statement)) {
                        inStrictMode = true;
                        return;
                    }
                }
            }
        }

        /// Should be called only on prologue directives (isPrologueDirective(node) should be true)
        function isUseStrictPrologueDirective(node: ExpressionStatement): boolean {
            const nodeText = getTextOfNodeFromSourceText(file.text, node.expression);

            // Note: the node text must be exactly "use strict" or 'use strict'.  It is not ok for the
            // string to contain unicode escapes (as per ES5).
            return nodeText === '"use strict"' || nodeText === "'use strict'";
        }

        function bindWorker(node: Node) {
            switch (node.kind) {
                /* Strict mode checks */
                case SyntaxKind.Identifier:
                case SyntaxKind.ThisKeyword:
                    if (currentFlow && (isExpression(node) || parent.kind === SyntaxKind.ShorthandPropertyAssignment)) {
                        node.flowNode = currentFlow;
                    }
                    return checkStrictModeIdentifier(<Identifier>node);
                case SyntaxKind.PropertyAccessExpression:
                    if (currentFlow && isNarrowableReference(<Expression>node)) {
                        node.flowNode = currentFlow;
                    }
                    break;
                case SyntaxKind.BinaryExpression:
                    if (isInJavaScriptFile(node)) {
                        const specialKind = getSpecialPropertyAssignmentKind(node);
                        switch (specialKind) {
                            case SpecialPropertyAssignmentKind.ExportsProperty:
                                bindExportsPropertyAssignment(<BinaryExpression>node);
                                break;
                            case SpecialPropertyAssignmentKind.ModuleExports:
                                bindModuleExportsAssignment(<BinaryExpression>node);
                                break;
                            case SpecialPropertyAssignmentKind.PrototypeProperty:
                                bindPrototypePropertyAssignment(<BinaryExpression>node);
                                break;
                            case SpecialPropertyAssignmentKind.ThisProperty:
                                bindThisPropertyAssignment(<BinaryExpression>node);
                                break;
                            case SpecialPropertyAssignmentKind.None:
                                // Nothing to do
                                break;
                            default:
                                Debug.fail("Unknown special property assignment kind");
                        }
                    }
                    return checkStrictModeBinaryExpression(<BinaryExpression>node);
                case SyntaxKind.CatchClause:
                    return checkStrictModeCatchClause(<CatchClause>node);
                case SyntaxKind.DeleteExpression:
                    return checkStrictModeDeleteExpression(<DeleteExpression>node);
                case SyntaxKind.NumericLiteral:
                    return checkStrictModeNumericLiteral(<LiteralExpression>node);
                case SyntaxKind.PostfixUnaryExpression:
                    return checkStrictModePostfixUnaryExpression(<PostfixUnaryExpression>node);
                case SyntaxKind.PrefixUnaryExpression:
                    return checkStrictModePrefixUnaryExpression(<PrefixUnaryExpression>node);
                case SyntaxKind.WithStatement:
                    return checkStrictModeWithStatement(<WithStatement>node);
                case SyntaxKind.ThisType:
                    seenThisKeyword = true;
                    return;
                case SyntaxKind.TypePredicate:
                    return checkTypePredicate(node as TypePredicateNode);
                case SyntaxKind.TypeParameter:
                    return declareSymbolAndAddToSymbolTable(<Declaration>node, SymbolFlags.TypeParameter, SymbolFlags.TypeParameterExcludes);
                case SyntaxKind.Parameter:
                    return bindParameter(<ParameterDeclaration>node);
                case SyntaxKind.VariableDeclaration:
                case SyntaxKind.BindingElement:
                    return bindVariableDeclarationOrBindingElement(<VariableDeclaration | BindingElement>node);
                case SyntaxKind.PropertyDeclaration:
                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);
                case SyntaxKind.EnumMember:
                    return bindPropertyOrMethodOrAccessor(<Declaration>node, SymbolFlags.EnumMember, SymbolFlags.EnumMemberExcludes);

                case SyntaxKind.JsxSpreadAttribute:
                    emitFlags |= NodeFlags.HasJsxSpreadAttribute;
                    return;

                case SyntaxKind.CallSignature:
                case SyntaxKind.ConstructSignature:
                case SyntaxKind.IndexSignature:
                    return declareSymbolAndAddToSymbolTable(<Declaration>node, SymbolFlags.Signature, SymbolFlags.None);
                case SyntaxKind.MethodDeclaration:
                case SyntaxKind.MethodSignature:
                    // If this is an ObjectLiteralExpression method, then it sits in the same space
                    // as other properties in the object literal.  So we use SymbolFlags.PropertyExcludes
                    // so that it will conflict with any other object literal members with the same
                    // name.
                    return bindPropertyOrMethodOrAccessor(<Declaration>node, SymbolFlags.Method | ((<MethodDeclaration>node).questionToken ? SymbolFlags.Optional : SymbolFlags.None),
                        isObjectLiteralMethod(node) ? SymbolFlags.PropertyExcludes : SymbolFlags.MethodExcludes);
                case SyntaxKind.FunctionDeclaration:
                    return bindFunctionDeclaration(<FunctionDeclaration>node);
                case SyntaxKind.Constructor:
                    return declareSymbolAndAddToSymbolTable(<Declaration>node, SymbolFlags.Constructor, /*symbolExcludes:*/ SymbolFlags.None);
                case SyntaxKind.GetAccessor:
                    return bindPropertyOrMethodOrAccessor(<Declaration>node, SymbolFlags.GetAccessor, SymbolFlags.GetAccessorExcludes);
                case SyntaxKind.SetAccessor:
                    return bindPropertyOrMethodOrAccessor(<Declaration>node, SymbolFlags.SetAccessor, SymbolFlags.SetAccessorExcludes);
                case SyntaxKind.FunctionType:
                case SyntaxKind.ConstructorType:
                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:
                    return bindObjectLiteralExpression(<ObjectLiteralExpression>node);
                case SyntaxKind.FunctionExpression:
                case SyntaxKind.ArrowFunction:
                    return bindFunctionExpression(<FunctionExpression>node);

                case SyntaxKind.CallExpression:
                    if (isInJavaScriptFile(node)) {
                        bindCallExpression(<CallExpression>node);
                    }
                    break;

                // 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:
                    return bindEnumDeclaration(<EnumDeclaration>node);
                case SyntaxKind.ModuleDeclaration:
                    return bindModuleDeclaration(<ModuleDeclaration>node);

                // Imports and exports
                case SyntaxKind.ImportEqualsDeclaration:
                case SyntaxKind.NamespaceImport:
                case SyntaxKind.ImportSpecifier:
                case SyntaxKind.ExportSpecifier:
                    return declareSymbolAndAddToSymbolTable(<Declaration>node, SymbolFlags.Alias, SymbolFlags.AliasExcludes);
                case SyntaxKind.NamespaceExportDeclaration:
                    return bindNamespaceExportDeclaration(<NamespaceExportDeclaration>node);
                case SyntaxKind.ImportClause:
                    return bindImportClause(<ImportClause>node);
                case SyntaxKind.ExportDeclaration:
                    return bindExportDeclaration(<ExportDeclaration>node);
                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);
            }
        }

        function checkTypePredicate(node: TypePredicateNode) {
            const { parameterName, type } = node;
            if (parameterName && parameterName.kind === SyntaxKind.Identifier) {
                checkStrictModeIdentifier(parameterName as Identifier);
            }
            if (parameterName && parameterName.kind === SyntaxKind.ThisType) {
                seenThisKeyword = true;
            }
            bind(type);
        }

        function bindSourceFileIfExternalModule() {
            setExportContextFlag(file);
            if (isExternalModule(file)) {
                bindSourceFileAsExternalModule();
            }
        }

        function bindSourceFileAsExternalModule() {
            bindAnonymousDeclaration(file, SymbolFlags.ValueModule, `"${removeFileExtension(file.fileName) }"`);
        }

        function bindExportAssignment(node: ExportAssignment | BinaryExpression) {
            const boundExpression = node.kind === SyntaxKind.ExportAssignment ? (<ExportAssignment>node).expression : (<BinaryExpression>node).right;
            if (!container.symbol || !container.symbol.exports) {
                // Export assignment in some sort of block construct
                bindAnonymousDeclaration(node, SymbolFlags.Alias, getDeclarationName(node));
            }
            else if (boundExpression.kind === SyntaxKind.Identifier && node.kind === SyntaxKind.ExportAssignment) {
                // An export default clause with an identifier exports all meanings of that identifier
                declareSymbol(container.symbol.exports, container.symbol, node, SymbolFlags.Alias, SymbolFlags.PropertyExcludes | SymbolFlags.AliasExcludes);
            }
            else {
                // An export default clause with an expression exports a value
                declareSymbol(container.symbol.exports, container.symbol, node, SymbolFlags.Property, SymbolFlags.PropertyExcludes | SymbolFlags.AliasExcludes);
            }
        }

        function bindNamespaceExportDeclaration(node: NamespaceExportDeclaration) {
            if (node.modifiers && node.modifiers.length) {
                file.bindDiagnostics.push(createDiagnosticForNode(node, Diagnostics.Modifiers_cannot_appear_here));
            }

            if (node.parent.kind !== SyntaxKind.SourceFile) {
                file.bindDiagnostics.push(createDiagnosticForNode(node, Diagnostics.Global_module_exports_may_only_appear_at_top_level));
                return;
            }
            else {
                const parent = node.parent as SourceFile;

                if (!isExternalModule(parent)) {
                    file.bindDiagnostics.push(createDiagnosticForNode(node, Diagnostics.Global_module_exports_may_only_appear_in_module_files));
                    return;
                }

                if (!parent.isDeclarationFile) {
                    file.bindDiagnostics.push(createDiagnosticForNode(node, Diagnostics.Global_module_exports_may_only_appear_in_declaration_files));
                    return;
                }
            }

            file.symbol.globalExports = file.symbol.globalExports || {};
            declareSymbol(file.symbol.globalExports, file.symbol, node, SymbolFlags.Alias, SymbolFlags.AliasExcludes);
        }

        function bindExportDeclaration(node: ExportDeclaration) {
            if (!container.symbol || !container.symbol.exports) {
                // Export * in some sort of block construct
                bindAnonymousDeclaration(node, SymbolFlags.ExportStar, getDeclarationName(node));
            }
            else if (!node.exportClause) {
                // All export * declarations are collected in an __export symbol
                declareSymbol(container.symbol.exports, container.symbol, node, SymbolFlags.ExportStar, SymbolFlags.None);
            }
        }

        function bindImportClause(node: ImportClause) {
            if (node.name) {
                declareSymbolAndAddToSymbolTable(node, SymbolFlags.Alias, SymbolFlags.AliasExcludes);
            }
        }

        function setCommonJsModuleIndicator(node: Node) {
            if (!file.commonJsModuleIndicator) {
                file.commonJsModuleIndicator = node;
                bindSourceFileAsExternalModule();
            }
        }

        function bindExportsPropertyAssignment(node: BinaryExpression) {
            // When we create a property via 'exports.foo = bar', the 'exports.foo' property access
            // expression is the declaration
            setCommonJsModuleIndicator(node);
            declareSymbol(file.symbol.exports, file.symbol, <PropertyAccessExpression>node.left, SymbolFlags.Property | SymbolFlags.Export, SymbolFlags.None);
        }

        function bindModuleExportsAssignment(node: BinaryExpression) {
            // 'module.exports = expr' assignment
            setCommonJsModuleIndicator(node);
            declareSymbol(file.symbol.exports, file.symbol, node, SymbolFlags.Property | SymbolFlags.Export | SymbolFlags.ValueModule, SymbolFlags.None);
        }

        function bindThisPropertyAssignment(node: BinaryExpression) {
            // Declare a 'member' in case it turns out the container was an ES5 class or ES6 constructor
            let assignee: Node;
            if (container.kind === SyntaxKind.FunctionDeclaration || container.kind === SyntaxKind.FunctionDeclaration) {
                assignee = container;
            }
            else if (container.kind === SyntaxKind.Constructor) {
                assignee = container.parent;
            }
            else {
                return;
            }
            assignee.symbol.members = assignee.symbol.members || {};
            // It's acceptable for multiple 'this' assignments of the same identifier to occur
            declareSymbol(assignee.symbol.members, assignee.symbol, node, SymbolFlags.Property, SymbolFlags.PropertyExcludes & ~SymbolFlags.Property);
        }

        function bindPrototypePropertyAssignment(node: BinaryExpression) {
            // We saw a node of the form 'x.prototype.y = z'. Declare a 'member' y on x if x was a function.

            // Look up the function in the local scope, since prototype assignments should
            // follow the function declaration
            const leftSideOfAssignment = node.left as PropertyAccessExpression;
            const classPrototype = leftSideOfAssignment.expression as PropertyAccessExpression;
            const constructorFunction = classPrototype.expression as Identifier;

            // Fix up parent pointers since we're going to use these nodes before we bind into them
            leftSideOfAssignment.parent = node;
            constructorFunction.parent = classPrototype;
            classPrototype.parent = leftSideOfAssignment;

            const funcSymbol = container.locals[constructorFunction.text];
            if (!funcSymbol || !(funcSymbol.flags & SymbolFlags.Function)) {
                return;
            }

            // Set up the members collection if it doesn't exist already
            if (!funcSymbol.members) {
                funcSymbol.members = {};
            }

            // Declare the method/property
            declareSymbol(funcSymbol.members, funcSymbol, leftSideOfAssignment, SymbolFlags.Property, SymbolFlags.PropertyExcludes);
        }

        function bindCallExpression(node: CallExpression) {
            // We're only inspecting call expressions to detect CommonJS modules, so we can skip
            // this check if we've already seen the module indicator
            if (!file.commonJsModuleIndicator && isRequireCall(node, /*checkArgumentIsStringLiteral*/false)) {
                setCommonJsModuleIndicator(node);
            }
        }

        function bindClassLikeDeclaration(node: ClassLikeDeclaration) {
            if (!isDeclarationFile(file) && !isInAmbientContext(node)) {
                if (getClassExtendsHeritageClauseElement(node) !== undefined) {
                    emitFlags |= NodeFlags.HasClassExtends;
                }
                if (nodeIsDecorated(node)) {
                    emitFlags |= NodeFlags.HasDecorators;
                }
            }

            if (node.kind === SyntaxKind.ClassDeclaration) {
                bindBlockScopedDeclaration(node, SymbolFlags.Class, SymbolFlags.ClassExcludes);
            }
            else {
                const bindingName = node.name ? node.name.text : "__class";
                bindAnonymousDeclaration(node, SymbolFlags.Class, bindingName);
                // Add name of class expression into the map for semantic classifier
                if (node.name) {
                    classifiableNames[node.name.text] = node.name.text;
                }
            }

            const symbol = node.symbol;

            // TypeScript 1.0 spec (April 2014): 8.4
            // Every class automatically contains a static property member named 'prototype', the
            // type of which is an instantiation of the class type with type Any supplied as a type
            // argument for each type parameter. It is an error to explicitly declare a static
            // property member with the name 'prototype'.
            //
            // Note: we check for this here because this class may be merging into a module.  The
            // module might have an exported variable called 'prototype'.  We can't allow that as
            // that would clash with the built-in 'prototype' for the class.
            const prototypeSymbol = createSymbol(SymbolFlags.Property | SymbolFlags.Prototype, "prototype");
            if (hasProperty(symbol.exports, prototypeSymbol.name)) {
                if (node.name) {
                    node.name.parent = node;
                }
                file.bindDiagnostics.push(createDiagnosticForNode(symbol.exports[prototypeSymbol.name].declarations[0],
                    Diagnostics.Duplicate_identifier_0, prototypeSymbol.name));
            }
            symbol.exports[prototypeSymbol.name] = prototypeSymbol;
            prototypeSymbol.parent = symbol;
        }

        function bindEnumDeclaration(node: EnumDeclaration) {
            return isConst(node)
                ? bindBlockScopedDeclaration(node, SymbolFlags.ConstEnum, SymbolFlags.ConstEnumExcludes)
                : bindBlockScopedDeclaration(node, SymbolFlags.RegularEnum, SymbolFlags.RegularEnumExcludes);
        }

        function bindVariableDeclarationOrBindingElement(node: VariableDeclaration | BindingElement) {
            if (inStrictMode) {
                checkStrictModeEvalOrArguments(node, node.name);
            }

            if (!isBindingPattern(node.name)) {
                if (isBlockOrCatchScoped(node)) {
                    bindBlockScopedVariableDeclaration(node);
                }
                else if (isParameterDeclaration(node)) {
                    // It is safe to walk up parent chain to find whether the node is a destructing parameter declaration
                    // because its parent chain has already been set up, since parents are set before descending into children.
                    //
                    // If node is a binding element in parameter declaration, we need to use ParameterExcludes.
                    // Using ParameterExcludes flag allows the compiler to report an error on duplicate identifiers in Parameter Declaration
                    // For example:
                    //      function foo([a,a]) {} // Duplicate Identifier error
                    //      function bar(a,a) {}   // Duplicate Identifier error, parameter declaration in this case is handled in bindParameter
                    //                             // which correctly set excluded symbols
                    declareSymbolAndAddToSymbolTable(node, SymbolFlags.FunctionScopedVariable, SymbolFlags.ParameterExcludes);
                }
                else {
                    declareSymbolAndAddToSymbolTable(node, SymbolFlags.FunctionScopedVariable, SymbolFlags.FunctionScopedVariableExcludes);
                }
            }
        }

        function bindParameter(node: ParameterDeclaration) {
            if (!isDeclarationFile(file) &&
                !isInAmbientContext(node) &&
                nodeIsDecorated(node)) {
                emitFlags |= (NodeFlags.HasDecorators | NodeFlags.HasParamDecorators);
            }

            if (inStrictMode) {
                // It is a SyntaxError if the identifier eval or arguments appears within a FormalParameterList of a
                // strict mode FunctionLikeDeclaration or FunctionExpression(13.1)
                checkStrictModeEvalOrArguments(node, node.name);
            }

            if (isBindingPattern(node.name)) {
                bindAnonymousDeclaration(node, SymbolFlags.FunctionScopedVariable, getDestructuringParameterName(node));
            }
            else {
                declareSymbolAndAddToSymbolTable(node, SymbolFlags.FunctionScopedVariable, SymbolFlags.ParameterExcludes);
            }

            // If this is a property-parameter, then also declare the property symbol into the
            // containing class.
            if (isParameterPropertyDeclaration(node)) {
                const classDeclaration = <ClassLikeDeclaration>node.parent.parent;
                declareSymbol(classDeclaration.symbol.members, classDeclaration.symbol, node, SymbolFlags.Property | (node.questionToken ? SymbolFlags.Optional : SymbolFlags.None), SymbolFlags.PropertyExcludes);
            }
        }

        function bindFunctionDeclaration(node: FunctionDeclaration) {
            if (!isDeclarationFile(file) && !isInAmbientContext(node)) {
                if (isAsyncFunctionLike(node)) {
                    emitFlags |= NodeFlags.HasAsyncFunctions;
                }
            }

            checkStrictModeFunctionName(<FunctionDeclaration>node);
            if (inStrictMode) {
                checkStrictModeFunctionDeclaration(node);
                bindBlockScopedDeclaration(node, SymbolFlags.Function, SymbolFlags.FunctionExcludes);
            }
            else {
                declareSymbolAndAddToSymbolTable(<Declaration>node, SymbolFlags.Function, SymbolFlags.FunctionExcludes);
            }
        }

        function bindFunctionExpression(node: FunctionExpression) {
            if (!isDeclarationFile(file) && !isInAmbientContext(node)) {
                if (isAsyncFunctionLike(node)) {
                    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);
        }

        function bindPropertyOrMethodOrAccessor(node: Declaration, symbolFlags: SymbolFlags, symbolExcludes: SymbolFlags) {
            if (!isDeclarationFile(file) && !isInAmbientContext(node)) {
                if (isAsyncFunctionLike(node)) {
                    emitFlags |= NodeFlags.HasAsyncFunctions;
                }
                if (nodeIsDecorated(node)) {
                    emitFlags |= NodeFlags.HasDecorators;
                }
            }

            return hasDynamicName(node)
                ? bindAnonymousDeclaration(node, symbolFlags, "__computed")
                : declareSymbolAndAddToSymbolTable(node, symbolFlags, symbolExcludes);
        }

        function bindJSDocProperty(node: JSDocPropertyTag) {
            return declareSymbolAndAddToSymbolTable(node, SymbolFlags.Property, SymbolFlags.PropertyExcludes);
        }

        // reachability checks

        function shouldReportErrorOnModuleDeclaration(node: ModuleDeclaration): boolean {
            const instanceState = getModuleInstanceState(node);
            return instanceState === ModuleInstanceState.Instantiated || (instanceState === ModuleInstanceState.ConstEnumOnly && options.preserveConstEnums);
        }

        function checkUnreachable(node: Node): boolean {
            if (!(currentFlow.flags & FlowFlags.Unreachable)) {
                return false;
            }
            if (currentFlow === unreachableFlow) {
                const reportError =
                    // report error on all statements except empty ones
                    (isStatement(node) && node.kind !== SyntaxKind.EmptyStatement) ||
                    // report error on class declarations
                    node.kind === SyntaxKind.ClassDeclaration ||
                    // report error on instantiated modules or const-enums only modules if preserveConstEnums is set
                    (node.kind === SyntaxKind.ModuleDeclaration && shouldReportErrorOnModuleDeclaration(<ModuleDeclaration>node)) ||
                    // report error on regular enums and const enums if preserveConstEnums is set
                    (node.kind === SyntaxKind.EnumDeclaration && (!isConstEnumDeclaration(node) || options.preserveConstEnums));

                if (reportError) {
                    currentFlow = reportedUnreachableFlow;

                    // unreachable code is reported if
                    // - user has explicitly asked about it AND
                    // - statement is in not ambient context (statements in ambient context is already an error
                    //   so we should not report extras) AND
                    //   - node is not variable statement OR
                    //   - node is block scoped variable statement OR
                    //   - node is not block scoped variable statement and at least one variable declaration has initializer
                    //   Rationale: we don't want to report errors on non-initialized var's since they are hoisted
                    //   On the other side we do want to report errors on non-initialized 'lets' because of TDZ
                    const reportUnreachableCode =
                        !options.allowUnreachableCode &&
                        !isInAmbientContext(node) &&
                        (
                            node.kind !== SyntaxKind.VariableStatement ||
                            getCombinedNodeFlags((<VariableStatement>node).declarationList) & NodeFlags.BlockScoped ||
                            forEach((<VariableStatement>node).declarationList.declarations, d => d.initializer)
                        );

                    if (reportUnreachableCode) {
                        errorOnFirstToken(node, Diagnostics.Unreachable_code_detected);
                    }
                }
            }
            return true;
        }
    }
}