binder.ts

/* @internal */
namespace ts {
    export const enum ModuleInstanceState {
        NonInstantiated = 0,
        Instantiated = 1,
        ConstEnumOnly = 2
    }

    interface ActiveLabel {
        next: ActiveLabel | undefined;
        name: __String;
        breakTarget: FlowLabel;
        continueTarget: FlowLabel | undefined;
        referenced: boolean;
    }

    export function getModuleInstanceState(node: ModuleDeclaration, visited?: Map<ModuleInstanceState | undefined>): ModuleInstanceState {
        if (node.body && !node.body.parent) {
            // getModuleInstanceStateForAliasTarget needs to walk up the parent chain, so parent pointers must be set on this tree already
            setParentPointers(node, node.body);
        }
        return node.body ? getModuleInstanceStateCached(node.body, visited) : ModuleInstanceState.Instantiated;
    }

    function getModuleInstanceStateCached(node: Node, visited = createMap<ModuleInstanceState | undefined>()) {
        const nodeId = "" + getNodeId(node);
        if (visited.has(nodeId)) {
            return visited.get(nodeId) || ModuleInstanceState.NonInstantiated;
        }
        visited.set(nodeId, undefined);
        const result = getModuleInstanceStateWorker(node, visited);
        visited.set(nodeId, result);
        return result;
    }

    function getModuleInstanceStateWorker(node: Node, visited: Map<ModuleInstanceState | undefined>): ModuleInstanceState {
        // A module is uninstantiated if it contains only
        switch (node.kind) {
            // 1. interface declarations, type alias declarations
            case SyntaxKind.InterfaceDeclaration:
            case SyntaxKind.TypeAliasDeclaration:
                return ModuleInstanceState.NonInstantiated;
            // 2. const enum declarations
            case SyntaxKind.EnumDeclaration:
                if (isEnumConst(node as EnumDeclaration)) {
                    return ModuleInstanceState.ConstEnumOnly;
                }
                break;
            // 3. non-exported import declarations
            case SyntaxKind.ImportDeclaration:
            case SyntaxKind.ImportEqualsDeclaration:
                if (!(hasModifier(node, ModifierFlags.Export))) {
                    return ModuleInstanceState.NonInstantiated;
                }
                break;
            // 4. Export alias declarations pointing at only uninstantiated modules or things uninstantiated modules contain
            case SyntaxKind.ExportDeclaration:
                const exportDeclaration = node as ExportDeclaration;
                if (!exportDeclaration.moduleSpecifier && exportDeclaration.exportClause && exportDeclaration.exportClause.kind === SyntaxKind.NamedExports) {
                    let state = ModuleInstanceState.NonInstantiated;
                    for (const specifier of exportDeclaration.exportClause.elements) {
                        const specifierState = getModuleInstanceStateForAliasTarget(specifier, visited);
                        if (specifierState > state) {
                            state = specifierState;
                        }
                        if (state === ModuleInstanceState.Instantiated) {
                            return state;
                        }
                    }
                    return state;
                }
                break;
            // 5. other uninstantiated module declarations.
            case SyntaxKind.ModuleBlock: {
                let state = ModuleInstanceState.NonInstantiated;
                forEachChild(node, n => {
                    const childState = getModuleInstanceStateCached(n, visited);
                    switch (childState) {
                        case ModuleInstanceState.NonInstantiated:
                            // child is non-instantiated - continue searching
                            return;
                        case ModuleInstanceState.ConstEnumOnly:
                            // child is const enum only - record state and continue searching
                            state = ModuleInstanceState.ConstEnumOnly;
                            return;
                        case ModuleInstanceState.Instantiated:
                            // child is instantiated - record state and stop
                            state = ModuleInstanceState.Instantiated;
                            return true;
                        default:
                            Debug.assertNever(childState);
                    }
                });
                return state;
            }
            case SyntaxKind.ModuleDeclaration:
                return getModuleInstanceState(node as ModuleDeclaration, visited);
            case SyntaxKind.Identifier:
                // Only jsdoc typedef definition can exist in jsdoc namespace, and it should
                // be considered the same as type alias
                if ((<Identifier>node).isInJSDocNamespace) {
                    return ModuleInstanceState.NonInstantiated;
                }
        }
        return ModuleInstanceState.Instantiated;
    }

    function getModuleInstanceStateForAliasTarget(specifier: ExportSpecifier, visited: Map<ModuleInstanceState | undefined>) {
        const name = specifier.propertyName || specifier.name;
        let p: Node | undefined = specifier.parent;
        while (p) {
            if (isBlock(p) || isModuleBlock(p) || isSourceFile(p)) {
                const statements = p.statements;
                let found: ModuleInstanceState | undefined;
                for (const statement of statements) {
                    if (nodeHasName(statement, name)) {
                        if (!statement.parent) {
                            setParentPointers(p, statement);
                        }
                        const state = getModuleInstanceStateCached(statement, visited);
                        if (found === undefined || state > found) {
                            found = state;
                        }
                        if (found === ModuleInstanceState.Instantiated) {
                            return found;
                        }
                    }
                }
                if (found !== undefined) {
                    return found;
                }
            }
            p = p.parent;
        }
        return ModuleInstanceState.Instantiated; // Couldn't locate, assume could refer to a value
    }

    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,
        IsObjectLiteralOrClassExpressionMethod = 1 << 7,
    }

    function initFlowNode<T extends FlowNode>(node: T) {
        Debug.attachFlowNodeDebugInfo(node);
        return node;
    }

    const binder = createBinder();

    export function bindSourceFile(file: SourceFile, options: CompilerOptions) {
        performance.mark("beforeBind");
        perfLogger.logStartBindFile("" + file.fileName);
        binder(file, options);
        perfLogger.logStopBindFile();
        performance.mark("afterBind");
        performance.measure("Bind", "beforeBind", "afterBind");
    }

    function createBinder(): (file: SourceFile, options: CompilerOptions) => void {
        let file: SourceFile;
        let options: CompilerOptions;
        let languageVersion: ScriptTarget;
        let parent: Node;
        let container: Node;
        let thisParentContainer: Node; // Container one level up
        let blockScopeContainer: Node;
        let lastContainer: Node;
        let delayedTypeAliases: (JSDocTypedefTag | JSDocCallbackTag | JSDocEnumTag)[];
        let seenThisKeyword: boolean;

        // state used by control flow analysis
        let currentFlow: FlowNode;
        let currentBreakTarget: FlowLabel | undefined;
        let currentContinueTarget: FlowLabel | undefined;
        let currentReturnTarget: FlowLabel | undefined;
        let currentTrueTarget: FlowLabel | undefined;
        let currentFalseTarget: FlowLabel | undefined;
        let currentExceptionTarget: FlowLabel | undefined;
        let preSwitchCaseFlow: FlowNode | undefined;
        let activeLabelList: ActiveLabel | undefined;
        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
        // or if compiler options contain alwaysStrict.
        let inStrictMode: boolean;

        let symbolCount = 0;

        let Symbol: new (flags: SymbolFlags, name: __String) => Symbol;
        let classifiableNames: UnderscoreEscapedMap<true>;

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

        // state used to aggregate transform flags during bind.
        let subtreeTransformFlags: TransformFlags = TransformFlags.None;
        let skipTransformFlagAggregation: boolean;

        /**
         * Inside the binder, we may create a diagnostic for an as-yet unbound node (with potentially no parent pointers, implying no accessible source file)
         * If so, the node _must_ be in the current file (as that's the only way anything could have traversed to it to yield it as the error node)
         * This version of `createDiagnosticForNode` uses the binder's context to account for this, and always yields correct diagnostics even in these situations.
         */
        function createDiagnosticForNode(node: Node, message: DiagnosticMessage, arg0?: string | number, arg1?: string | number, arg2?: string | number): DiagnosticWithLocation {
            return createDiagnosticForNodeInSourceFile(getSourceFileOfNode(node) || file, node, message, arg0, arg1, arg2);
        }

        function bindSourceFile(f: SourceFile, opts: CompilerOptions) {
            file = f;
            options = opts;
            languageVersion = getEmitScriptTarget(options);
            inStrictMode = bindInStrictMode(file, opts);
            classifiableNames = createUnderscoreEscapedMap<true>();
            symbolCount = 0;
            skipTransformFlagAggregation = file.isDeclarationFile;

            Symbol = objectAllocator.getSymbolConstructor();

            // Attach debugging information if necessary
            Debug.attachFlowNodeDebugInfo(unreachableFlow);
            Debug.attachFlowNodeDebugInfo(reportedUnreachableFlow);

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

            file = undefined!;
            options = undefined!;
            languageVersion = undefined!;
            parent = undefined!;
            container = undefined!;
            thisParentContainer = undefined!;
            blockScopeContainer = undefined!;
            lastContainer = undefined!;
            delayedTypeAliases = undefined!;
            seenThisKeyword = false;
            currentFlow = undefined!;
            currentBreakTarget = undefined;
            currentContinueTarget = undefined;
            currentReturnTarget = undefined;
            currentTrueTarget = undefined;
            currentFalseTarget = undefined;
            currentExceptionTarget = undefined;
            activeLabelList = undefined;
            hasExplicitReturn = false;
            emitFlags = NodeFlags.None;
            subtreeTransformFlags = TransformFlags.None;
        }

        return bindSourceFile;

        function bindInStrictMode(file: SourceFile, opts: CompilerOptions): boolean {
            if (getStrictOptionValue(opts, "alwaysStrict") && !file.isDeclarationFile) {
                // bind in strict mode source files with alwaysStrict option
                return true;
            }
            else {
                return !!file.externalModuleIndicator;
            }
        }

        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;
            symbol.declarations = appendIfUnique(symbol.declarations, node);

            if (symbolFlags & (SymbolFlags.Class | SymbolFlags.Enum | SymbolFlags.Module | SymbolFlags.Variable) && !symbol.exports) {
                symbol.exports = createSymbolTable();
            }

            if (symbolFlags & (SymbolFlags.Class | SymbolFlags.Interface | SymbolFlags.TypeLiteral | SymbolFlags.ObjectLiteral) && !symbol.members) {
                symbol.members = createSymbolTable();
            }

            // On merge of const enum module with class or function, reset const enum only flag (namespaces will already recalculate)
            if (symbol.constEnumOnlyModule && (symbol.flags & (SymbolFlags.Function | SymbolFlags.Class | SymbolFlags.RegularEnum))) {
                symbol.constEnumOnlyModule = false;
            }

            if (symbolFlags & SymbolFlags.Value) {
                setValueDeclaration(symbol, node);
            }
        }

        function setValueDeclaration(symbol: Symbol, node: Declaration): void {
            const { valueDeclaration } = symbol;
            if (!valueDeclaration ||
                (isAssignmentDeclaration(valueDeclaration) && !isAssignmentDeclaration(node)) ||
                (valueDeclaration.kind !== node.kind && isEffectiveModuleDeclaration(valueDeclaration))) {
                // other kinds of value declarations take precedence over modules and assignment declarations
                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 | undefined {
            if (node.kind === SyntaxKind.ExportAssignment) {
                return (<ExportAssignment>node).isExportEquals ? InternalSymbolName.ExportEquals : InternalSymbolName.Default;
            }

            const name = getNameOfDeclaration(node);
            if (name) {
                if (isAmbientModule(node)) {
                    const moduleName = getTextOfIdentifierOrLiteral(name as Identifier | StringLiteral);
                    return (isGlobalScopeAugmentation(<ModuleDeclaration>node) ? "__global" : `"${moduleName}"`) as __String;
                }
                if (name.kind === SyntaxKind.ComputedPropertyName) {
                    const nameExpression = name.expression;
                    // treat computed property names where expression is string/numeric literal as just string/numeric literal
                    if (isStringOrNumericLiteralLike(nameExpression)) {
                        return escapeLeadingUnderscores(nameExpression.text);
                    }
                    if (isSignedNumericLiteral(nameExpression)) {
                        return tokenToString(nameExpression.operator) + nameExpression.operand.text as __String;
                    }

                    Debug.assert(isWellKnownSymbolSyntactically(nameExpression));
                    return getPropertyNameForKnownSymbolName(idText((<PropertyAccessExpression>nameExpression).name));
                }
                if (isWellKnownSymbolSyntactically(name)) {
                    return getPropertyNameForKnownSymbolName(idText(name.name));
                }
                if (isPrivateIdentifier(name)) {
                    // containingClass exists because private names only allowed inside classes
                    const containingClass = getContainingClass(node);
                    if (!containingClass) {
                        // we can get here in cases where there is already a parse error.
                        return undefined;
                    }
                    const containingClassSymbol = containingClass.symbol;
                    return getSymbolNameForPrivateIdentifier(containingClassSymbol, name.escapedText);
                }
                return isPropertyNameLiteral(name) ? getEscapedTextOfIdentifierOrLiteral(name) : undefined;
            }
            switch (node.kind) {
                case SyntaxKind.Constructor:
                    return InternalSymbolName.Constructor;
                case SyntaxKind.FunctionType:
                case SyntaxKind.CallSignature:
                case SyntaxKind.JSDocSignature:
                    return InternalSymbolName.Call;
                case SyntaxKind.ConstructorType:
                case SyntaxKind.ConstructSignature:
                    return InternalSymbolName.New;
                case SyntaxKind.IndexSignature:
                    return InternalSymbolName.Index;
                case SyntaxKind.ExportDeclaration:
                    return InternalSymbolName.ExportStar;
                case SyntaxKind.SourceFile:
                    // json file should behave as
                    // module.exports = ...
                    return InternalSymbolName.ExportEquals;
                case SyntaxKind.BinaryExpression:
                    if (getAssignmentDeclarationKind(node as BinaryExpression) === AssignmentDeclarationKind.ModuleExports) {
                        // module.exports = ...
                        return InternalSymbolName.ExportEquals;
                    }
                    Debug.fail("Unknown binary declaration kind");
                    break;
                case SyntaxKind.JSDocFunctionType:
                    return (isJSDocConstructSignature(node) ? InternalSymbolName.New : InternalSymbolName.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, "Impossible parameter parent kind", () => `parent is: ${(ts as any).SyntaxKind ? (ts as any).SyntaxKind[node.parent.kind] : node.parent.kind}, expected JSDocFunctionType`);
                    const functionType = <JSDocFunctionType>node.parent;
                    const index = functionType.parameters.indexOf(node as ParameterDeclaration);
                    return "arg" + index as __String;
            }
        }

        function getDisplayName(node: Declaration): string {
            return isNamedDeclaration(node) ? declarationNameToString(node.name) : unescapeLeadingUnderscores(Debug.assertDefined(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 | undefined, node: Declaration, includes: SymbolFlags, excludes: SymbolFlags, isReplaceableByMethod?: boolean): Symbol {
            Debug.assert(!hasDynamicName(node));

            const isDefaultExport = hasModifier(node, ModifierFlags.Default);

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

            let symbol: Symbol | undefined;
            if (name === undefined) {
                symbol = createSymbol(SymbolFlags.None, InternalSymbolName.Missing);
            }
            else {
                // 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.
                //
                // Note that when properties declared in Javascript constructors
                // (marked by isReplaceableByMethod) conflict with another symbol, the property loses.
                // Always. This allows the common Javascript pattern of overwriting a prototype method
                // with an bound instance method of the same type: `this.method = this.method.bind(this)`
                //
                // 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 = symbolTable.get(name);

                if (includes & SymbolFlags.Classifiable) {
                    classifiableNames.set(name, true);
                }

                if (!symbol) {
                    symbolTable.set(name, symbol = createSymbol(SymbolFlags.None, name));
                    if (isReplaceableByMethod) symbol.isReplaceableByMethod = true;
                }
                else if (isReplaceableByMethod && !symbol.isReplaceableByMethod) {
                    // A symbol already exists, so don't add this as a declaration.
                    return symbol;
                }
                else if (symbol.flags & excludes) {
                    if (symbol.isReplaceableByMethod) {
                        // Javascript constructor-declared symbols can be discarded in favor of
                        // prototype symbols like methods.
                        symbolTable.set(name, symbol = createSymbol(SymbolFlags.None, name));
                    }
                    else if (!(includes & SymbolFlags.Variable && symbol.flags & SymbolFlags.Assignment)) {
                        // Assignment declarations are allowed to merge with variables, no matter what other flags they have.
                        if (isNamedDeclaration(node)) {
                            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;
                        let messageNeedsName = true;

                        if (symbol.flags & SymbolFlags.Enum || includes & SymbolFlags.Enum) {
                            message = Diagnostics.Enum_declarations_can_only_merge_with_namespace_or_other_enum_declarations;
                            messageNeedsName = false;
                        }

                        let multipleDefaultExports = false;
                        if (length(symbol.declarations)) {
                            // If the current node is a default export of some sort, then check if
                            // there are any other default exports that we need to error on.
                            // We'll know whether we have other default exports depending on if `symbol` already has a declaration list set.
                            if (isDefaultExport) {
                                message = Diagnostics.A_module_cannot_have_multiple_default_exports;
                                messageNeedsName = false;
                                multipleDefaultExports = true;
                            }
                            else {
                                // This is to properly report an error in the case "export default { }" is after export default of class declaration or function declaration.
                                // Error on multiple export default in the following case:
                                // 1. multiple export default of class declaration or function declaration by checking NodeFlags.Default
                                // 2. multiple export default of export assignment. This one doesn't have NodeFlags.Default on (as export default doesn't considered as modifiers)
                                if (symbol.declarations && symbol.declarations.length &&
                                    (node.kind === SyntaxKind.ExportAssignment && !(<ExportAssignment>node).isExportEquals)) {
                                    message = Diagnostics.A_module_cannot_have_multiple_default_exports;
                                    messageNeedsName = false;
                                    multipleDefaultExports = true;
                                }
                            }
                        }

                        const relatedInformation: DiagnosticRelatedInformation[] = [];
                        if (isTypeAliasDeclaration(node) && nodeIsMissing(node.type) && hasModifier(node, ModifierFlags.Export) && symbol.flags & (SymbolFlags.Alias | SymbolFlags.Type | SymbolFlags.Namespace)) {
                            // export type T; - may have meant export type { T }?
                            relatedInformation.push(createDiagnosticForNode(node, Diagnostics.Did_you_mean_0, `export type { ${unescapeLeadingUnderscores(node.name.escapedText)} }`));
                        }

                        const declarationName = getNameOfDeclaration(node) || node;
                        forEach(symbol.declarations, (declaration, index) => {
                            const decl = getNameOfDeclaration(declaration) || declaration;
                            const diag = createDiagnosticForNode(decl, message, messageNeedsName ? getDisplayName(declaration) : undefined);
                            file.bindDiagnostics.push(
                                multipleDefaultExports ? addRelatedInfo(diag, createDiagnosticForNode(declarationName, index === 0 ? Diagnostics.Another_export_default_is_here : Diagnostics.and_here)) : diag
                            );
                            if (multipleDefaultExports) {
                                relatedInformation.push(createDiagnosticForNode(decl, Diagnostics.The_first_export_default_is_here));
                            }
                        });

                        const diag = createDiagnosticForNode(declarationName, message, messageNeedsName ? getDisplayName(node) : undefined);
                        file.bindDiagnostics.push(addRelatedInfo(diag, ...relatedInformation));

                        symbol = createSymbol(SymbolFlags.None, name);
                    }
                }
            }

            addDeclarationToSymbol(symbol, node, includes);
            if (symbol.parent) {
                Debug.assert(symbol.parent === parent, "Existing symbol parent should match new one");
            }
            else {
                symbol.parent = parent;
            }

            return symbol;
        }

        function declareModuleMember(node: Declaration, symbolFlags: SymbolFlags, symbolExcludes: SymbolFlags): Symbol {
            const hasExportModifier = getCombinedModifierFlags(node) & ModifierFlags.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!, /*parent*/ undefined, node, symbolFlags, symbolExcludes);
                }
            }
            else {
                // Exported module members are given 2 symbols: A local symbol that is classified with an ExportValue 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 (isJSDocTypeAlias(node)) Debug.assert(isInJSFile(node)); // We shouldn't add symbols for JSDoc nodes if not in a JS file.
                if ((!isAmbientModule(node) && (hasExportModifier || container.flags & NodeFlags.ExportContext)) || isJSDocTypeAlias(node)) {
                    if (!container.locals || (hasModifier(node, ModifierFlags.Default) && !getDeclarationName(node))) {
                        return declareSymbol(container.symbol.exports!, container.symbol, node, symbolFlags, symbolExcludes); // No local symbol for an unnamed default!
                    }
                    const exportKind = symbolFlags & SymbolFlags.Value ? SymbolFlags.ExportValue : 0;
                    const local = declareSymbol(container.locals, /*parent*/ 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!, /*parent*/ 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 saveThisParentContainer = thisParentContainer;
            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 eagerly 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) {
                if (node.kind !== SyntaxKind.ArrowFunction) {
                    thisParentContainer = container;
                }
                container = blockScopeContainer = node;
                if (containerFlags & ContainerFlags.HasLocals) {
                    container.locals = createSymbolTable();
                }
                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 saveExceptionTarget = currentExceptionTarget;
                const saveActiveLabelList = activeLabelList;
                const saveHasExplicitReturn = hasExplicitReturn;
                const isIIFE = containerFlags & ContainerFlags.IsFunctionExpression && !hasModifier(node, ModifierFlags.Async) &&
                    !(<FunctionLikeDeclaration>node).asteriskToken && !!getImmediatelyInvokedFunctionExpression(node);
                // A non-async, non-generator 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) {
                    currentFlow = initFlowNode({ flags: FlowFlags.Start });
                    if (containerFlags & (ContainerFlags.IsFunctionExpression | ContainerFlags.IsObjectLiteralOrClassExpressionMethod)) {
                        currentFlow.node = <FunctionExpression | ArrowFunction | MethodDeclaration>node;
                    }
                }
                // We create a return control flow graph for IIFEs and constructors. For constructors
                // we use the return control flow graph in strict property initialization checks.
                currentReturnTarget = isIIFE || node.kind === SyntaxKind.Constructor ? createBranchLabel() : undefined;
                currentExceptionTarget = undefined;
                currentBreakTarget = undefined;
                currentContinueTarget = undefined;
                activeLabelList = undefined;
                hasExplicitReturn = false;
                bindChildren(node);
                // Reset all reachability check related 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;
                    (<FunctionLikeDeclaration>node).endFlowNode = currentFlow;
                }
                if (node.kind === SyntaxKind.SourceFile) {
                    node.flags |= emitFlags;
                }

                if (currentReturnTarget) {
                    addAntecedent(currentReturnTarget, currentFlow);
                    currentFlow = finishFlowLabel(currentReturnTarget);
                    if (node.kind === SyntaxKind.Constructor) {
                        (<ConstructorDeclaration>node).returnFlowNode = currentFlow;
                    }
                }
                if (!isIIFE) {
                    currentFlow = saveCurrentFlow;
                }
                currentBreakTarget = saveBreakTarget;
                currentContinueTarget = saveContinueTarget;
                currentReturnTarget = saveReturnTarget;
                currentExceptionTarget = saveExceptionTarget;
                activeLabelList = saveActiveLabelList;
                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;
            thisParentContainer = saveThisParentContainer;
            blockScopeContainer = savedBlockScopeContainer;
        }

        function bindChildren(node: Node): void {
            if (skipTransformFlagAggregation) {
                bindChildrenWorker(node);
            }
            else if (node.transformFlags & TransformFlags.HasComputedFlags) {
                skipTransformFlagAggregation = true;
                bindChildrenWorker(node);
                skipTransformFlagAggregation = false;
                subtreeTransformFlags |= node.transformFlags & ~getTransformFlagsSubtreeExclusions(node.kind);
            }
            else {
                const savedSubtreeTransformFlags = subtreeTransformFlags;
                subtreeTransformFlags = 0;
                bindChildrenWorker(node);
                subtreeTransformFlags = savedSubtreeTransformFlags | computeTransformFlagsForNode(node, subtreeTransformFlags);
            }
        }

        function bindEachFunctionsFirst(nodes: NodeArray<Node> | undefined): void {
            bindEach(nodes, n => n.kind === SyntaxKind.FunctionDeclaration ? bind(n) : undefined);
            bindEach(nodes, n => n.kind !== SyntaxKind.FunctionDeclaration ? bind(n) : undefined);
        }

        function bindEach(nodes: NodeArray<Node> | undefined, bindFunction: (node: Node) => void = bind): void {
            if (nodes === undefined) {
                return;
            }

            if (skipTransformFlagAggregation) {
                forEach(nodes, bindFunction);
            }
            else {
                const savedSubtreeTransformFlags = subtreeTransformFlags;
                subtreeTransformFlags = TransformFlags.None;
                let nodeArrayFlags = TransformFlags.None;
                for (const node of nodes) {
                    bindFunction(node);
                    nodeArrayFlags |= node.transformFlags & ~TransformFlags.HasComputedFlags;
                }
                nodes.transformFlags = nodeArrayFlags | TransformFlags.HasComputedFlags;
                subtreeTransformFlags |= savedSubtreeTransformFlags;
            }
        }

        function bindEachChild(node: Node) {
            forEachChild(node, bind, bindEach);
        }

        function bindChildrenWorker(node: Node): void {
            if (checkUnreachable(node)) {
                bindEachChild(node);
                bindJSDoc(node);
                return;
            }
            if (node.kind >= SyntaxKind.FirstStatement && node.kind <= SyntaxKind.LastStatement && !options.allowUnreachableCode) {
                node.flowNode = currentFlow;
            }
            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(<ForInOrOfStatement>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.CaseClause:
                    bindCaseClause(<CaseClause>node);
                    break;
                case SyntaxKind.ExpressionStatement:
                    bindExpressionStatement(<ExpressionStatement>node);
                    break;
                case SyntaxKind.LabeledStatement:
                    bindLabeledStatement(<LabeledStatement>node);
                    break;
                case SyntaxKind.PrefixUnaryExpression:
                    bindPrefixUnaryExpressionFlow(<PrefixUnaryExpression>node);
                    break;
                case SyntaxKind.PostfixUnaryExpression:
                    bindPostfixUnaryExpressionFlow(<PostfixUnaryExpression>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.PropertyAccessExpression:
                case SyntaxKind.ElementAccessExpression:
                    bindAccessExpressionFlow(<AccessExpression>node);
                    break;
                case SyntaxKind.CallExpression:
                    bindCallExpressionFlow(<CallExpression>node);
                    break;
                case SyntaxKind.JSDocTypedefTag:
                case SyntaxKind.JSDocCallbackTag:
                case SyntaxKind.JSDocEnumTag:
                    bindJSDocTypeAlias(node as JSDocTypedefTag | JSDocCallbackTag | JSDocEnumTag);
                    break;
                // In source files and blocks, bind functions first to match hoisting that occurs at runtime
                case SyntaxKind.SourceFile: {
                    bindEachFunctionsFirst((node as SourceFile).statements);
                    bind((node as SourceFile).endOfFileToken);
                    break;
                }
                case SyntaxKind.Block:
                case SyntaxKind.ModuleBlock:
                    bindEachFunctionsFirst((node as Block).statements);
                    break;
                default:
                    bindEachChild(node);
                    break;
            }
            bindJSDoc(node);
        }

        function isNarrowingExpression(expr: Expression): boolean {
            switch (expr.kind) {
                case SyntaxKind.Identifier:
                case SyntaxKind.ThisKeyword:
                case SyntaxKind.PropertyAccessExpression:
                case SyntaxKind.ElementAccessExpression:
                    return containsNarrowableReference(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);
                case SyntaxKind.TypeOfExpression:
                    return isNarrowingExpression((<TypeOfExpression>expr).expression);
            }
            return false;
        }

        function isNarrowableReference(expr: Expression): boolean {
            return expr.kind === SyntaxKind.Identifier || expr.kind === SyntaxKind.ThisKeyword || expr.kind === SyntaxKind.SuperKeyword ||
                (isPropertyAccessExpression(expr) || isNonNullExpression(expr) || isParenthesizedExpression(expr)) && isNarrowableReference(expr.expression) ||
                isElementAccessExpression(expr) && isStringOrNumericLiteralLike(expr.argumentExpression) && isNarrowableReference(expr.expression);
        }

        function containsNarrowableReference(expr: Expression): boolean {
            return isNarrowableReference(expr) || isOptionalChain(expr) && containsNarrowableReference(expr.expression);
        }

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

        function isNarrowingTypeofOperands(expr1: Expression, expr2: Expression) {
            return isTypeOfExpression(expr1) && isNarrowableOperand(expr1.expression) && isStringLiteralLike(expr2);
        }

        function isNarrowableInOperands(left: Expression, right: Expression) {
            return isStringLiteralLike(left) && isNarrowingExpression(right);
        }

        function isNarrowingBinaryExpression(expr: BinaryExpression) {
            switch (expr.operatorToken.kind) {
                case SyntaxKind.EqualsToken:
                    return containsNarrowableReference(expr.left);
                case SyntaxKind.EqualsEqualsToken:
                case SyntaxKind.ExclamationEqualsToken:
                case SyntaxKind.EqualsEqualsEqualsToken:
                case SyntaxKind.ExclamationEqualsEqualsToken:
                    return isNarrowableOperand(expr.left) || isNarrowableOperand(expr.right) ||
                        isNarrowingTypeofOperands(expr.right, expr.left) || isNarrowingTypeofOperands(expr.left, expr.right);
                case SyntaxKind.InstanceOfKeyword:
                    return isNarrowableOperand(expr.left);
                case SyntaxKind.InKeyword:
                    return isNarrowableInOperands(expr.left, expr.right);
                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 containsNarrowableReference(expr);
        }

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

        function createLoopLabel(): FlowLabel {
            return initFlowNode({ 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 | undefined): 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) &&
                !isExpressionOfOptionalChainRoot(expression) && !isNullishCoalesce(expression.parent)) {
                return unreachableFlow;
            }
            if (!isNarrowingExpression(expression)) {
                return antecedent;
            }
            setFlowNodeReferenced(antecedent);
            return initFlowNode({ flags, antecedent, node: expression });
        }

        function createFlowSwitchClause(antecedent: FlowNode, switchStatement: SwitchStatement, clauseStart: number, clauseEnd: number): FlowNode {
            setFlowNodeReferenced(antecedent);
            return initFlowNode({ flags: FlowFlags.SwitchClause, antecedent, switchStatement, clauseStart, clauseEnd });
        }

        function createFlowMutation(flags: FlowFlags, antecedent: FlowNode, node: Node): FlowNode {
            setFlowNodeReferenced(antecedent);
            const result = initFlowNode({ flags, antecedent, node });
            if (currentExceptionTarget) {
                addAntecedent(currentExceptionTarget, result);
            }
            return result;
        }

        function createFlowCall(antecedent: FlowNode, node: CallExpression): FlowNode {
            setFlowNodeReferenced(antecedent);
            return initFlowNode({ flags: FlowFlags.Call, 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 ||
                        (<BinaryExpression>node).operatorToken.kind === SyntaxKind.QuestionQuestionToken);
                }
            }
        }

        function isTopLevelLogicalExpression(node: Node): boolean {
            while (isParenthesizedExpression(node.parent) ||
                isPrefixUnaryExpression(node.parent) && node.parent.operator === SyntaxKind.ExclamationToken) {
                node = node.parent;
            }
            return !isStatementCondition(node) &&
                !isLogicalExpression(node.parent) &&
                !(isOptionalChain(node.parent) && node.parent.expression === node);
        }

        function doWithConditionalBranches<T>(action: (value: T) => void, value: T, trueTarget: FlowLabel, falseTarget: FlowLabel) {
            const savedTrueTarget = currentTrueTarget;
            const savedFalseTarget = currentFalseTarget;
            currentTrueTarget = trueTarget;
            currentFalseTarget = falseTarget;
            action(value);
            currentTrueTarget = savedTrueTarget;
            currentFalseTarget = savedFalseTarget;
        }

        function bindCondition(node: Expression | undefined, trueTarget: FlowLabel, falseTarget: FlowLabel) {
            doWithConditionalBranches(bind, node, trueTarget, falseTarget);
            if (!node || !isLogicalExpression(node) && !(isOptionalChain(node) && isOutermostOptionalChain(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 setContinueTarget(node: Node, target: FlowLabel) {
            let label = activeLabelList;
            while (label && node.parent.kind === SyntaxKind.LabeledStatement) {
                label.continueTarget = target;
                label = label.next;
                node = node.parent;
            }
            return target;
        }

        function bindWhileStatement(node: WhileStatement): void {
            const preWhileLabel = setContinueTarget(node, 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 = setContinueTarget(node, 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 = setContinueTarget(node, 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: ForInOrOfStatement): void {
            const preLoopLabel = setContinueTarget(node, createLoopLabel());
            const postLoopLabel = createBranchLabel();
            bind(node.expression);
            addAntecedent(preLoopLabel, currentFlow);
            currentFlow = preLoopLabel;
            if (node.kind === SyntaxKind.ForOfStatement) {
                bind(node.awaitModifier);
            }
            addAntecedent(postLoopLabel, currentFlow);
            bind(node.initializer);
            if (node.initializer.kind !== SyntaxKind.VariableDeclarationList) {
                bindAssignmentTargetFlow(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) {
            for (let label = activeLabelList; label; label = label.next) {
                if (label.name === name) {
                    return label;
                }
            }
            return undefined;
        }

        function bindBreakOrContinueFlow(node: BreakOrContinueStatement, breakTarget: FlowLabel | undefined, continueTarget: FlowLabel | undefined) {
            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.escapedText);
                if (activeLabel) {
                    activeLabel.referenced = true;
                    bindBreakOrContinueFlow(node, activeLabel.breakTarget, activeLabel.continueTarget);
                }
            }
            else {
                bindBreakOrContinueFlow(node, currentBreakTarget, currentContinueTarget);
            }
        }

        function bindTryStatement(node: TryStatement): void {
            const preFinallyLabel = createBranchLabel();
            // We conservatively assume that *any* code in the try block can cause an exception, but we only need
            // to track code that causes mutations (because only mutations widen the possible control flow type of
            // a variable). The currentExceptionTarget is the target label for control flows that result from
            // exceptions. We add all mutation flow nodes as antecedents of this label such that we can analyze them
            // as possible antecedents of the start of catch or finally blocks. Furthermore, we add the current
            // control flow to represent exceptions that occur before any mutations.
            const saveReturnTarget = currentReturnTarget;
            const saveExceptionTarget = currentExceptionTarget;
            currentReturnTarget = createBranchLabel();
            currentExceptionTarget = node.catchClause ? createBranchLabel() : currentReturnTarget;
            addAntecedent(currentExceptionTarget, currentFlow);
            bind(node.tryBlock);
            addAntecedent(preFinallyLabel, currentFlow);
            const flowAfterTry = currentFlow;
            let flowAfterCatch = unreachableFlow;
            if (node.catchClause) {
                // Start of catch clause is the target of exceptions from try block.
                currentFlow = finishFlowLabel(currentExceptionTarget);
                // The currentExceptionTarget now represents control flows from exceptions in the catch clause.
                // Effectively, in a try-catch-finally, if an exception occurs in the try block, the catch block
                // acts like a second try block.
                currentExceptionTarget = currentReturnTarget;
                addAntecedent(currentExceptionTarget, currentFlow);
                bind(node.catchClause);
                addAntecedent(preFinallyLabel, currentFlow);
                flowAfterCatch = currentFlow;
            }
            const exceptionTarget = finishFlowLabel(currentExceptionTarget);
            currentReturnTarget = saveReturnTarget;
            currentExceptionTarget = saveExceptionTarget;
            if (node.finallyBlock) {
                // Possible ways control can reach the finally block:
                // 1) Normal completion of try block of a try-finally or try-catch-finally
                // 2) Normal completion of catch block (following exception in try block) of a try-catch-finally
                // 3) Return in try or catch block of a try-finally or try-catch-finally
                // 4) Exception in try block of a try-finally
                // 5) Exception in catch block of a try-catch-finally
                // When analyzing a control flow graph that starts inside a finally block we want to consider all
                // five possibilities above. However, when analyzing a control flow graph that starts outside (past)
                // the finally block, we only want to consider the first two (if we're past a finally block then it
                // must have completed normally). To make this possible, we inject two extra nodes into the control
                // flow graph: An after-finally with an antecedent of the control flow at the end of the finally
                // block, and a pre-finally with an antecedent that represents all exceptional control flows. The
                // 'lock' property of the pre-finally references the after-finally, and the after-finally has a
                // boolean 'locked' property that we set to true when analyzing a control flow that contained the
                // the after-finally node. When the lock associated with a pre-finally is locked, the antecedent of
                // the pre-finally (i.e. the exceptional control flows) are skipped.
                const preFinallyFlow: PreFinallyFlow = initFlowNode({ flags: FlowFlags.PreFinally, antecedent: exceptionTarget, lock: {} });
                addAntecedent(preFinallyLabel, preFinallyFlow);
                currentFlow = finishFlowLabel(preFinallyLabel);
                bind(node.finallyBlock);
                // If the end of the finally block is reachable, but the end of the try and catch blocks are not,
                // convert the current flow to unreachable. For example, 'try { return 1; } finally { ... }' should
                // result in an unreachable current control flow.
                if (!(currentFlow.flags & FlowFlags.Unreachable)) {
                    if ((flowAfterTry.flags & FlowFlags.Unreachable) && (flowAfterCatch.flags & FlowFlags.Unreachable)) {
                        currentFlow = flowAfterTry === reportedUnreachableFlow || flowAfterCatch === reportedUnreachableFlow
                            ? reportedUnreachableFlow
                            : unreachableFlow;
                    }
                }
                if (!(currentFlow.flags & FlowFlags.Unreachable)) {
                    const afterFinallyFlow: AfterFinallyFlow = initFlowNode({ flags: FlowFlags.AfterFinally, antecedent: currentFlow });
                    preFinallyFlow.lock = afterFinallyFlow;
                    currentFlow = afterFinallyFlow;
                }
            }
            else {
                currentFlow = finishFlowLabel(preFinallyLabel);
            }
        }

        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). Note, we no longer need
            // this property in control flow analysis, it's there only for backwards compatibility.
            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 savedSubtreeTransformFlags = subtreeTransformFlags;
            subtreeTransformFlags = 0;
            const clauses = node.clauses;
            const isNarrowingSwitch = isNarrowingExpression(node.parent.expression);
            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, isNarrowingSwitch ? createFlowSwitchClause(preSwitchCaseFlow!, node.parent, clauseStart, i + 1) : preSwitchCaseFlow!);
                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) {
                    clause.fallthroughFlowNode = currentFlow;
                }
            }
            clauses.transformFlags = subtreeTransformFlags | TransformFlags.HasComputedFlags;
            subtreeTransformFlags |= savedSubtreeTransformFlags;
        }

        function bindCaseClause(node: CaseClause): void {
            const saveCurrentFlow = currentFlow;
            currentFlow = preSwitchCaseFlow!;
            bind(node.expression);
            currentFlow = saveCurrentFlow;
            bindEach(node.statements);
        }

        function bindExpressionStatement(node: ExpressionStatement): void {
            bind(node.expression);
            // A top level call expression with a dotted function name and at least one argument
            // is potentially an assertion and is therefore included in the control flow.
            if (node.expression.kind === SyntaxKind.CallExpression) {
                const call = <CallExpression>node.expression;
                if (isDottedName(call.expression)) {
                    currentFlow = createFlowCall(currentFlow, call);
                }
            }
        }

        function bindLabeledStatement(node: LabeledStatement): void {
            const postStatementLabel = createBranchLabel();
            activeLabelList = {
                next: activeLabelList,
                name: node.label.escapedText,
                breakTarget: postStatementLabel,
                continueTarget: undefined,
                referenced: false
            };
            bind(node.label);
            bind(node.statement);
            if (!activeLabelList.referenced && !options.allowUnusedLabels) {
                errorOrSuggestionOnNode(unusedLabelIsError(options), node.label, Diagnostics.Unused_label);
            }
            activeLabelList = activeLabelList.next;
            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 = createFlowMutation(FlowFlags.Assignment, currentFlow, node);
            }
            else if (node.kind === SyntaxKind.ArrayLiteralExpression) {
                for (const e of (<ArrayLiteralExpression>node).elements) {
                    if (e.kind === SyntaxKind.SpreadElement) {
                        bindAssignmentTargetFlow((<SpreadElement>e).expression);
                    }
                    else {
                        bindDestructuringTargetFlow(e);
                    }
                }
            }
            else if (node.kind === SyntaxKind.ObjectLiteralExpression) {
                for (const p of (<ObjectLiteralExpression>node).properties) {
                    if (p.kind === SyntaxKind.PropertyAssignment) {
                        bindDestructuringTargetFlow(p.initializer);
                    }
                    else if (p.kind === SyntaxKind.ShorthandPropertyAssignment) {
                        bindAssignmentTargetFlow(p.name);
                    }
                    else if (p.kind === SyntaxKind.SpreadAssignment) {
                        bindAssignmentTargetFlow(p.expression);
                    }
                }
            }
        }

        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;
                bindEachChild(node);
                currentFalseTarget = currentTrueTarget;
                currentTrueTarget = saveTrueTarget;
            }
            else {
                bindEachChild(node);
                if (node.operator === SyntaxKind.PlusPlusToken || node.operator === SyntaxKind.MinusMinusToken) {
                    bindAssignmentTargetFlow(node.operand);
                }
            }
        }

        function bindPostfixUnaryExpressionFlow(node: PostfixUnaryExpression) {
            bindEachChild(node);
            if (node.operator === SyntaxKind.PlusPlusToken || node.operator === SyntaxKind.MinusMinusToken) {
                bindAssignmentTargetFlow(node.operand);
            }
        }

        const enum BindBinaryExpressionFlowState {
            BindThenBindChildren,
            MaybeBindLeft,
            BindToken,
            BindRight,
            FinishBind
        }

        function bindBinaryExpressionFlow(node: BinaryExpression) {
            const workStacks: {
                expr: BinaryExpression[],
                state: BindBinaryExpressionFlowState[],
                inStrictMode: (boolean | undefined)[],
                parent: (Node | undefined)[],
                subtreeFlags: (number | undefined)[]
            } = {
                expr: [node],
                state: [BindBinaryExpressionFlowState.MaybeBindLeft],
                inStrictMode: [undefined],
                parent: [undefined],
                subtreeFlags: [undefined]
            };
            let stackIndex = 0;
            while (stackIndex >= 0) {
                node = workStacks.expr[stackIndex];
                switch (workStacks.state[stackIndex]) {
                    case BindBinaryExpressionFlowState.BindThenBindChildren: {
                        // This state is used only when recuring, to emulate the work that `bind` does before
                        // reaching `bindChildren`. A normal call to `bindBinaryExpressionFlow` will already have done this work.
                        node.parent = parent;
                        const saveInStrictMode = inStrictMode;
                        bindWorker(node);
                        const saveParent = parent;
                        parent = node;

                        let subtreeFlagsState: number | undefined;
                        // While this next part does the work of `bindChildren` before it descends into `bindChildrenWorker`
                        // and uses `subtreeFlagsState` to queue up the work that needs to be done once the node is bound.
                        if (skipTransformFlagAggregation) {
                            // do nothing extra
                        }
                        else if (node.transformFlags & TransformFlags.HasComputedFlags) {
                            skipTransformFlagAggregation = true;
                            subtreeFlagsState = -1;
                        }
                        else {
                            const savedSubtreeTransformFlags = subtreeTransformFlags;
                            subtreeTransformFlags = 0;
                            subtreeFlagsState = savedSubtreeTransformFlags;
                        }

                        advanceState(BindBinaryExpressionFlowState.MaybeBindLeft, saveInStrictMode, saveParent, subtreeFlagsState);
                        break;
                    }
                    case BindBinaryExpressionFlowState.MaybeBindLeft: {
                        const operator = node.operatorToken.kind;
                        // TODO: bindLogicalExpression is recursive - if we want to handle deeply nested `&&` expressions
                        // we'll need to handle the `bindLogicalExpression` scenarios in this state machine, too
                        // For now, though, since the common cases are chained `+`, leaving it recursive is fine
                        if (operator === SyntaxKind.AmpersandAmpersandToken || operator === SyntaxKind.BarBarToken || operator === SyntaxKind.QuestionQuestionToken) {
                            if (isTopLevelLogicalExpression(node)) {
                                const postExpressionLabel = createBranchLabel();
                                bindLogicalExpression(node, postExpressionLabel, postExpressionLabel);
                                currentFlow = finishFlowLabel(postExpressionLabel);
                            }
                            else {
                                bindLogicalExpression(node, currentTrueTarget!, currentFalseTarget!);
                            }
                            completeNode();
                        }
                        else {
                            advanceState(BindBinaryExpressionFlowState.BindToken);
                            maybeBind(node.left);
                        }
                        break;
                    }
                    case BindBinaryExpressionFlowState.BindToken: {
                        advanceState(BindBinaryExpressionFlowState.BindRight);
                        maybeBind(node.operatorToken);
                        break;
                    }
                    case BindBinaryExpressionFlowState.BindRight: {
                        advanceState(BindBinaryExpressionFlowState.FinishBind);
                        maybeBind(node.right);
                        break;
                    }
                    case BindBinaryExpressionFlowState.FinishBind: {
                        const operator = node.operatorToken.kind;
                        if (isAssignmentOperator(operator) && !isAssignmentTarget(node)) {
                            bindAssignmentTargetFlow(node.left);
                            if (operator === SyntaxKind.EqualsToken && node.left.kind === SyntaxKind.ElementAccessExpression) {
                                const elementAccess = <ElementAccessExpression>node.left;
                                if (isNarrowableOperand(elementAccess.expression)) {
                                    currentFlow = createFlowMutation(FlowFlags.ArrayMutation, currentFlow, node);
                                }
                            }
                        }
                        completeNode();
                        break;
                    }
                    default: return Debug.fail(`Invalid state ${workStacks.state[stackIndex]} for bindBinaryExpressionFlow`);
                }
            }

            /**
             * Note that `advanceState` sets the _current_ head state, and that `maybeBind` potentially pushes on a new
             * head state; so `advanceState` must be called before any `maybeBind` during a state's execution.
             */
            function advanceState(state: BindBinaryExpressionFlowState, isInStrictMode?: boolean, parent?: Node, subtreeFlags?: number) {
                workStacks.state[stackIndex] = state;
                if (isInStrictMode !== undefined) {
                    workStacks.inStrictMode[stackIndex] = isInStrictMode;
                }
                if (parent !== undefined) {
                    workStacks.parent[stackIndex] = parent;
                }
                if (subtreeFlags !== undefined) {
                    workStacks.subtreeFlags[stackIndex] = subtreeFlags;
                }
            }

            function completeNode() {
                if (workStacks.inStrictMode[stackIndex] !== undefined) {
                    if (workStacks.subtreeFlags[stackIndex] === -1) {
                        skipTransformFlagAggregation = false;
                        subtreeTransformFlags |= node.transformFlags & ~getTransformFlagsSubtreeExclusions(node.kind);
                    }
                    else if (workStacks.subtreeFlags[stackIndex] !== undefined) {
                        subtreeTransformFlags = workStacks.subtreeFlags[stackIndex]! | computeTransformFlagsForNode(node, subtreeTransformFlags);
                    }
                    inStrictMode = workStacks.inStrictMode[stackIndex]!;
                    parent = workStacks.parent[stackIndex]!;
                }
                stackIndex--;
            }

            /**
             * If `node` is a BinaryExpression, adds it to the local work stack, otherwise recursively binds it
             */
            function maybeBind(node: Node) {
                if (node && isBinaryExpression(node)) {
                    stackIndex++;
                    workStacks.expr[stackIndex] = node;
                    workStacks.state[stackIndex] = BindBinaryExpressionFlowState.BindThenBindChildren;
                    workStacks.inStrictMode[stackIndex] = undefined;
                    workStacks.parent[stackIndex] = undefined;
                    workStacks.subtreeFlags[stackIndex] = undefined;
                }
                else {
                    bind(node);
                }
            }
        }

        function bindDeleteExpressionFlow(node: DeleteExpression) {
            bindEachChild(node);
            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.questionToken);
            bind(node.whenTrue);
            addAntecedent(postExpressionLabel, currentFlow);
            currentFlow = finishFlowLabel(falseLabel);
            bind(node.colonToken);
            bind(node.whenFalse);
            addAntecedent(postExpressionLabel, currentFlow);
            currentFlow = finishFlowLabel(postExpressionLabel);
        }

        function bindInitializedVariableFlow(node: VariableDeclaration | ArrayBindingElement) {
            const name = !isOmittedExpression(node) ? node.name : undefined;
            if (isBindingPattern(name)) {
                for (const child of name.elements) {
                    bindInitializedVariableFlow(child);
                }
            }
            else {
                currentFlow = createFlowMutation(FlowFlags.Assignment, currentFlow, node);
            }
        }

        function bindVariableDeclarationFlow(node: VariableDeclaration) {
            bindEachChild(node);
            if (node.initializer || isForInOrOfStatement(node.parent.parent)) {
                bindInitializedVariableFlow(node);
            }
        }

        function bindJSDocTypeAlias(node: JSDocTypedefTag | JSDocCallbackTag | JSDocEnumTag) {
            node.tagName.parent = node;
            if (node.kind !== SyntaxKind.JSDocEnumTag && node.fullName) {
                setParentPointers(node, node.fullName);
            }
        }

        function bindJSDocClassTag(node: JSDocClassTag) {
            bindEachChild(node);
            const host = getHostSignatureFromJSDoc(node);
            if (host && host.kind !== SyntaxKind.MethodDeclaration) {
                addDeclarationToSymbol(host.symbol, host, SymbolFlags.Class);
            }
        }

        function bindOptionalExpression(node: Expression, trueTarget: FlowLabel, falseTarget: FlowLabel) {
            doWithConditionalBranches(bind, node, trueTarget, falseTarget);
            if (!isOptionalChain(node) || isOutermostOptionalChain(node)) {
                addAntecedent(trueTarget, createFlowCondition(FlowFlags.TrueCondition, currentFlow, node));
                addAntecedent(falseTarget, createFlowCondition(FlowFlags.FalseCondition, currentFlow, node));
            }
        }

        function bindOptionalChainRest(node: OptionalChain) {
            bind(node.questionDotToken);
            switch (node.kind) {
                case SyntaxKind.PropertyAccessExpression:
                    bind(node.name);
                    break;
                case SyntaxKind.ElementAccessExpression:
                    bind(node.argumentExpression);
                    break;
                case SyntaxKind.CallExpression:
                    bindEach(node.typeArguments);
                    bindEach(node.arguments);
                    break;
            }
        }

        function bindOptionalChain(node: OptionalChain, trueTarget: FlowLabel, falseTarget: FlowLabel) {
            // For an optional chain, we emulate the behavior of a logical expression:
            //
            // a?.b         -> a && a.b
            // a?.b.c       -> a && a.b.c
            // a?.b?.c      -> a && a.b && a.b.c
            // a?.[x = 1]   -> a && a[x = 1]
            //
            // To do this we descend through the chain until we reach the root of a chain (the expression with a `?.`)
            // and build it's CFA graph as if it were the first condition (`a && ...`). Then we bind the rest
            // of the node as part of the "true" branch, and continue to do so as we ascend back up to the outermost
            // chain node. We then treat the entire node as the right side of the expression.
            const preChainLabel = node.questionDotToken ? createBranchLabel() : undefined;
            bindOptionalExpression(node.expression, preChainLabel || trueTarget, falseTarget);
            if (preChainLabel) {
                currentFlow = finishFlowLabel(preChainLabel);
            }
            doWithConditionalBranches(bindOptionalChainRest, node, trueTarget, falseTarget);
            if (isOutermostOptionalChain(node)) {
                addAntecedent(trueTarget, createFlowCondition(FlowFlags.TrueCondition, currentFlow, node));
                addAntecedent(falseTarget, createFlowCondition(FlowFlags.FalseCondition, currentFlow, node));
            }
        }

        function bindOptionalChainFlow(node: OptionalChain) {
            if (isTopLevelLogicalExpression(node)) {
                const postExpressionLabel = createBranchLabel();
                bindOptionalChain(node, postExpressionLabel, postExpressionLabel);
                currentFlow = finishFlowLabel(postExpressionLabel);
            }
            else {
                bindOptionalChain(node, currentTrueTarget!, currentFalseTarget!);
            }
        }

        function bindAccessExpressionFlow(node: AccessExpression) {
            if (isOptionalChain(node)) {
                bindOptionalChainFlow(node);
            }
            else {
                bindEachChild(node);
            }
        }

        function bindCallExpressionFlow(node: CallExpression) {
            if (isOptionalChain(node)) {
                bindOptionalChainFlow(node);
            }
            else {
                // 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).
                const expr = skipParentheses(node.expression);
                if (expr.kind === SyntaxKind.FunctionExpression || expr.kind === SyntaxKind.ArrowFunction) {
                    bindEach(node.typeArguments);
                    bindEach(node.arguments);
                    bind(node.expression);
                }
                else {
                    bindEachChild(node);
                }
            }
            if (node.expression.kind === SyntaxKind.PropertyAccessExpression) {
                const propertyAccess = <PropertyAccessExpression>node.expression;
                if (isIdentifier(propertyAccess.name) && isNarrowableOperand(propertyAccess.expression) && isPushOrUnshiftIdentifier(propertyAccess.name)) {
                    currentFlow = createFlowMutation(FlowFlags.ArrayMutation, currentFlow, node);
                }
            }
        }

        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.JsxAttributes:
                    return ContainerFlags.IsContainer;

                case SyntaxKind.InterfaceDeclaration:
                    return ContainerFlags.IsContainer | ContainerFlags.IsInterface;

                case SyntaxKind.ModuleDeclaration:
                case SyntaxKind.TypeAliasDeclaration:
                case SyntaxKind.MappedType:
                    return ContainerFlags.IsContainer | ContainerFlags.HasLocals;

                case SyntaxKind.SourceFile:
                    return ContainerFlags.IsContainer | ContainerFlags.IsControlFlowContainer | ContainerFlags.HasLocals;

                case SyntaxKind.MethodDeclaration:
                    if (isObjectLiteralOrClassExpressionMethod(node)) {
                        return ContainerFlags.IsContainer | ContainerFlags.IsControlFlowContainer | ContainerFlags.HasLocals | ContainerFlags.IsFunctionLike | ContainerFlags.IsObjectLiteralOrClassExpressionMethod;
                    }
                    // falls through
                case SyntaxKind.Constructor:
                case SyntaxKind.FunctionDeclaration:
                case SyntaxKind.MethodSignature:
                case SyntaxKind.GetAccessor:
                case SyntaxKind.SetAccessor:
                case SyntaxKind.CallSignature:
                case SyntaxKind.JSDocSignature:
                case SyntaxKind.JSDocFunctionType:
                case SyntaxKind.FunctionType:
                case SyntaxKind.ConstructSignature:
                case SyntaxKind.IndexSignature:
                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 | undefined {
            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.JSDocTypeLiteral:
                case SyntaxKind.ObjectLiteralExpression:
                case SyntaxKind.InterfaceDeclaration:
                case SyntaxKind.JsxAttributes:
                    // 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.JSDocSignature:
                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.JSDocTypedefTag:
                case SyntaxKind.JSDocCallbackTag:
                case SyntaxKind.TypeAliasDeclaration:
                case SyntaxKind.MappedType:
                    // 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 hasModifier(node, ModifierFlags.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!, /*parent*/ undefined, node, symbolFlags, symbolExcludes);
        }

        function hasExportDeclarations(node: ModuleDeclaration | SourceFile): boolean {
            const body = isSourceFile(node) ? node : tryCast(node.body, isModuleBlock);
            return !!body && body.statements.some(s => isExportDeclaration(s) || isExportAssignment(s));
        }

        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 (node.flags & NodeFlags.Ambient && !hasExportDeclarations(node)) {
                node.flags |= NodeFlags.ExportContext;
            }
            else {
                node.flags &= ~NodeFlags.ExportContext;
            }
        }

        function bindModuleDeclaration(node: ModuleDeclaration) {
            setExportContextFlag(node);
            if (isAmbientModule(node)) {
                if (hasModifier(node, ModifierFlags.Export)) {
                    errorOnFirstToken(node, Diagnostics.export_modifier_cannot_be_applied_to_ambient_modules_and_module_augmentations_since_they_are_always_visible);
                }
                if (isModuleAugmentationExternal(node)) {
                    declareModuleSymbol(node);
                }
                else {
                    let pattern: Pattern | undefined;
                    if (node.name.kind === SyntaxKind.StringLiteral) {
                        const { text } = node.name;
                        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)!;
                    file.patternAmbientModules = append<PatternAmbientModule>(file.patternAmbientModules, pattern && { pattern, symbol });
                }
            }
            else {
                const state = declareModuleSymbol(node);
                if (state !== ModuleInstanceState.NonInstantiated) {
                    const { symbol } = node;
                    // if module was already merged with some function, class or non-const enum, treat it as non-const-enum-only
                    symbol.constEnumOnlyModule = (!(symbol.flags & (SymbolFlags.Function | SymbolFlags.Class | SymbolFlags.RegularEnum)))
                        // Current must be `const enum` only
                        && state === ModuleInstanceState.ConstEnumOnly
                        // Can't have been set to 'false' in a previous merged symbol. ('undefined' OK)
                        && symbol.constEnumOnlyModule !== false;
                }
            }
        }

        function declareModuleSymbol(node: ModuleDeclaration): ModuleInstanceState {
            const state = getModuleInstanceState(node);
            const instantiated = state !== ModuleInstanceState.NonInstantiated;
            declareSymbolAndAddToSymbolTable(node,
                instantiated ? SymbolFlags.ValueModule : SymbolFlags.NamespaceModule,
                instantiated ? SymbolFlags.ValueModuleExcludes : SymbolFlags.NamespaceModuleExcludes);
            return state;
        }

        function bindFunctionOrConstructorType(node: SignatureDeclaration | JSDocSignature): 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)!); // TODO: GH#18217
            addDeclarationToSymbol(symbol, node, SymbolFlags.Signature);

            const typeLiteralSymbol = createSymbol(SymbolFlags.TypeLiteral, InternalSymbolName.Type);
            addDeclarationToSymbol(typeLiteralSymbol, node, SymbolFlags.TypeLiteral);
            typeLiteralSymbol.members = createSymbolTable();
            typeLiteralSymbol.members.set(symbol.escapedName, symbol);
        }

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

            if (inStrictMode && !isAssignmentTarget(node)) {
                const seen = createUnderscoreEscapedMap<ElementKind>();

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

                    const 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.get(identifier.escapedText);
                    if (!existingKind) {
                        seen.set(identifier.escapedText, 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, InternalSymbolName.Object);
        }

        function bindJsxAttributes(node: JsxAttributes) {
            return bindAnonymousDeclaration(node, SymbolFlags.ObjectLiteral, InternalSymbolName.JSXAttributes);
        }

        function bindJsxAttribute(node: JsxAttribute, symbolFlags: SymbolFlags, symbolExcludes: SymbolFlags) {
            return declareSymbolAndAddToSymbolTable(node, symbolFlags, symbolExcludes);
        }

        function bindAnonymousDeclaration(node: Declaration, symbolFlags: SymbolFlags, name: __String) {
            const symbol = createSymbol(symbolFlags, name);
            if (symbolFlags & (SymbolFlags.EnumMember | SymbolFlags.ClassMember)) {
                symbol.parent = container.symbol;
            }
            addDeclarationToSymbol(symbol, node, symbolFlags);
            return symbol;
        }

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

        function delayedBindJSDocTypedefTag() {
            if (!delayedTypeAliases) {
                return;
            }
            const saveContainer = container;
            const saveLastContainer = lastContainer;
            const saveBlockScopeContainer = blockScopeContainer;
            const saveParent = parent;
            const saveCurrentFlow = currentFlow;
            for (const typeAlias of delayedTypeAliases) {
                const host = getJSDocHost(typeAlias);
                container = findAncestor(host.parent, n => !!(getContainerFlags(n) & ContainerFlags.IsContainer)) || file;
                blockScopeContainer = getEnclosingBlockScopeContainer(host) || file;
                currentFlow = initFlowNode({ flags: FlowFlags.Start });
                parent = typeAlias;
                bind(typeAlias.typeExpression);
                const declName = getNameOfDeclaration(typeAlias);
                if ((isJSDocEnumTag(typeAlias) || !typeAlias.fullName) && declName && isPropertyAccessEntityNameExpression(declName.parent)) {
                    // typedef anchored to an A.B.C assignment - we need to bind into B's namespace under name C
                    const isTopLevel = isTopLevelNamespaceAssignment(declName.parent);
                    if (isTopLevel) {
                        bindPotentiallyMissingNamespaces(file.symbol, declName.parent, isTopLevel,
                            !!findAncestor(declName, d => isPropertyAccessExpression(d) && d.name.escapedText === "prototype"), /*containerIsClass*/ false);
                        const oldContainer = container;
                        switch (getAssignmentDeclarationPropertyAccessKind(declName.parent)) {
                            case AssignmentDeclarationKind.ExportsProperty:
                            case AssignmentDeclarationKind.ModuleExports:
                                if (!isExternalOrCommonJsModule(file)) {
                                    container = undefined!;
                                }
                                else {
                                    container = file;
                                }
                                break;
                            case AssignmentDeclarationKind.ThisProperty:
                                container = declName.parent.expression;
                                break;
                            case AssignmentDeclarationKind.PrototypeProperty:
                                container = (declName.parent.expression as PropertyAccessExpression).name;
                                break;
                            case AssignmentDeclarationKind.Property:
                                container = isPropertyAccessExpression(declName.parent.expression) ? declName.parent.expression.name : declName.parent.expression;
                                break;
                            case AssignmentDeclarationKind.None:
                                return Debug.fail("Shouldn't have detected typedef or enum on non-assignment declaration");
                        }
                        if (container) {
                            declareModuleMember(typeAlias, SymbolFlags.TypeAlias, SymbolFlags.TypeAliasExcludes);
                        }
                        container = oldContainer;
                    }
                }
                else if (isJSDocEnumTag(typeAlias) || !typeAlias.fullName || typeAlias.fullName.kind === SyntaxKind.Identifier) {
                    parent = typeAlias.parent;
                    bindBlockScopedDeclaration(typeAlias, SymbolFlags.TypeAlias, SymbolFlags.TypeAliasExcludes);
                }
                else {
                    bind(typeAlias.fullName);
                }
            }
            container = saveContainer;
            lastContainer = saveLastContainer;
            blockScopeContainer = saveBlockScopeContainer;
            parent = saveParent;
            currentFlow = saveCurrentFlow;
        }

        // 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) &&
                !(node.flags & NodeFlags.Ambient) &&
                !(node.flags & NodeFlags.JSDoc)) {

                // 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;
        }

        // The binder visits every node, so this is a good place to check for
        // the reserved private name (there is only one)
        function checkPrivateIdentifier(node: PrivateIdentifier) {
            if (node.escapedText === "#constructor") {
                // Report error only if there are no parse errors in file
                if (!file.parseDiagnostics.length) {
                    file.bindDiagnostics.push(createDiagnosticForNode(node,
                        Diagnostics.constructor_is_a_reserved_word, declarationNameToString(node)));
                }
            }
        }

        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 isIdentifier(node) && (node.escapedText === "eval" || node.escapedText === "arguments");
        }

        function checkStrictModeEvalOrArguments(contextNode: Node, name: Node | undefined) {
            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), idText(identifier)));
                }
            }
        }

        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.ES2015) {
                // 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: NumericLiteral) {
            if (inStrictMode && node.numericLiteralFlags & TokenFlags.Octal) {
                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 checkStrictModeLabeledStatement(node: LabeledStatement) {
            // Grammar checking for labeledStatement
            if (inStrictMode && options.target! >= ScriptTarget.ES2015) {
                if (isDeclarationStatement(node.statement) || isVariableStatement(node.statement)) {
                    errorOnFirstToken(node.label, Diagnostics.A_label_is_not_allowed_here);
                }
            }
        }

        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 errorOrSuggestionOnNode(isError: boolean, node: Node, message: DiagnosticMessage): void {
            errorOrSuggestionOnRange(isError, node, node, message);
        }

        function errorOrSuggestionOnRange(isError: boolean, startNode: Node, endNode: Node, message: DiagnosticMessage): void {
            addErrorOrSuggestionDiagnostic(isError, { pos: getTokenPosOfNode(startNode, file), end: endNode.end }, message);
        }

        function addErrorOrSuggestionDiagnostic(isError: boolean, range: TextRange, message: DiagnosticMessage): void {
            const diag = createFileDiagnostic(file, range.pos, range.end - range.pos, message);
            if (isError) {
                file.bindDiagnostics.push(diag);
            }
            else {
                file.bindSuggestionDiagnostics = append(file.bindSuggestionDiagnostics, { ...diag, category: DiagnosticCategory.Suggestion });
            }
        }

        function bind(node: Node | undefined): void {
            if (!node) {
                return;
            }
            node.parent = parent;
            const saveInStrictMode = inStrictMode;

            // Even though in the AST the jsdoc @typedef node belongs to the current node,
            // its symbol might be in the same scope with the current node's symbol. Consider:
            //
            //     /** @typedef {string | number} MyType */
            //     function foo();
            //
            // Here the current node is "foo", which is a container, but the scope of "MyType" should
            // not be inside "foo". Therefore we always bind @typedef before bind the parent node,
            // and skip binding this tag later when binding all the other jsdoc tags.

            // 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;
            }
            else if (!skipTransformFlagAggregation && (node.transformFlags & TransformFlags.HasComputedFlags) === 0) {
                subtreeTransformFlags |= computeTransformFlagsForNode(node, 0);
                const saveParent = parent;
                if (node.kind === SyntaxKind.EndOfFileToken) parent = node;
                bindJSDoc(node);
                parent = saveParent;
            }
            inStrictMode = saveInStrictMode;
        }

        function bindJSDoc(node: Node) {
            if (hasJSDocNodes(node)) {
                if (isInJSFile(node)) {
                    for (const j of node.jsDoc!) {
                        bind(j);
                    }
                }
                else {
                    for (const j of node.jsDoc!) {
                        setParentPointers(node, j);
                    }
                }
            }
        }

        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 = getSourceTextOfNodeFromSourceFile(file, 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:
                    // for typedef type names with namespaces, bind the new jsdoc type symbol here
                    // because it requires all containing namespaces to be in effect, namely the
                    // current "blockScopeContainer" needs to be set to its immediate namespace parent.
                    if ((<Identifier>node).isInJSDocNamespace) {
                        let parentNode = node.parent;
                        while (parentNode && !isJSDocTypeAlias(parentNode)) {
                            parentNode = parentNode.parent;
                        }
                        bindBlockScopedDeclaration(parentNode as Declaration, SymbolFlags.TypeAlias, SymbolFlags.TypeAliasExcludes);
                        break;
                    }
                    // falls through
                case SyntaxKind.ThisKeyword:
                    if (currentFlow && (isExpression(node) || parent.kind === SyntaxKind.ShorthandPropertyAssignment)) {
                        node.flowNode = currentFlow;
                    }
                    return checkStrictModeIdentifier(<Identifier>node);
                case SyntaxKind.PrivateIdentifier:
                    return checkPrivateIdentifier(node as PrivateIdentifier);
                case SyntaxKind.PropertyAccessExpression:
                case SyntaxKind.ElementAccessExpression:
                    const expr = node as PropertyAccessExpression | ElementAccessExpression;
                    if (currentFlow && isNarrowableReference(expr)) {
                        expr.flowNode = currentFlow;
                    }
                    if (isSpecialPropertyDeclaration(expr)) {
                        bindSpecialPropertyDeclaration(expr);
                    }
                    if (isInJSFile(expr) &&
                        file.commonJsModuleIndicator &&
                        isModuleExportsAccessExpression(expr) &&
                        !lookupSymbolForNameWorker(blockScopeContainer, "module" as __String)) {
                        declareSymbol(file.locals!, /*parent*/ undefined, expr.expression,
                            SymbolFlags.FunctionScopedVariable | SymbolFlags.ModuleExports, SymbolFlags.FunctionScopedVariableExcludes);
                    }
                    break;
                case SyntaxKind.BinaryExpression:
                    const specialKind = getAssignmentDeclarationKind(node as BinaryExpression);
                    switch (specialKind) {
                        case AssignmentDeclarationKind.ExportsProperty:
                            bindExportsPropertyAssignment(node as BindableStaticPropertyAssignmentExpression);
                            break;
                        case AssignmentDeclarationKind.ModuleExports:
                            bindModuleExportsAssignment(node as BindablePropertyAssignmentExpression);
                            break;
                        case AssignmentDeclarationKind.PrototypeProperty:
                            bindPrototypePropertyAssignment((node as BindableStaticPropertyAssignmentExpression).left, node);
                            break;
                        case AssignmentDeclarationKind.Prototype:
                            bindPrototypeAssignment(node as BindableStaticPropertyAssignmentExpression);
                            break;
                        case AssignmentDeclarationKind.ThisProperty:
                            bindThisPropertyAssignment(node as BindablePropertyAssignmentExpression);
                            break;
                        case AssignmentDeclarationKind.Property:
                            bindSpecialPropertyAssignment(node as BindablePropertyAssignmentExpression);
                            break;
                        case AssignmentDeclarationKind.None:
                            // Nothing to do
                            break;
                        default:
                            Debug.fail("Unknown binary expression 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(<NumericLiteral>node);
                case SyntaxKind.PostfixUnaryExpression:
                    return checkStrictModePostfixUnaryExpression(<PostfixUnaryExpression>node);
                case SyntaxKind.PrefixUnaryExpression:
                    return checkStrictModePrefixUnaryExpression(<PrefixUnaryExpression>node);
                case SyntaxKind.WithStatement:
                    return checkStrictModeWithStatement(<WithStatement>node);
                case SyntaxKind.LabeledStatement:
                    return checkStrictModeLabeledStatement(<LabeledStatement>node);
                case SyntaxKind.ThisType:
                    seenThisKeyword = true;
                    return;
                case SyntaxKind.TypePredicate:
                    break; // Binding the children will handle everything
                case SyntaxKind.TypeParameter:
                    return bindTypeParameter(node as TypeParameterDeclaration);
                case SyntaxKind.Parameter:
                    return bindParameter(<ParameterDeclaration>node);
                case SyntaxKind.VariableDeclaration:
                    return bindVariableDeclarationOrBindingElement(<VariableDeclaration>node);
                case SyntaxKind.BindingElement:
                    node.flowNode = currentFlow;
                    return bindVariableDeclarationOrBindingElement(<BindingElement>node);
                case SyntaxKind.PropertyDeclaration:
                case SyntaxKind.PropertySignature:
                    return bindPropertyWorker(node as PropertyDeclaration | PropertySignature);
                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.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.JSDocFunctionType:
                case SyntaxKind.JSDocSignature:
                case SyntaxKind.ConstructorType:
                    return bindFunctionOrConstructorType(<SignatureDeclaration | JSDocSignature>node);
                case SyntaxKind.TypeLiteral:
                case SyntaxKind.JSDocTypeLiteral:
                case SyntaxKind.MappedType:
                    return bindAnonymousTypeWorker(node as TypeLiteralNode | MappedTypeNode | JSDocTypeLiteral);
                case SyntaxKind.JSDocClassTag:
                    return bindJSDocClassTag(node as JSDocClassTag);
                case SyntaxKind.ObjectLiteralExpression:
                    return bindObjectLiteralExpression(<ObjectLiteralExpression>node);
                case SyntaxKind.FunctionExpression:
                case SyntaxKind.ArrowFunction:
                    return bindFunctionExpression(<FunctionExpression>node);

                case SyntaxKind.CallExpression:
                    const assignmentKind = getAssignmentDeclarationKind(node as CallExpression);
                    switch (assignmentKind) {
                        case AssignmentDeclarationKind.ObjectDefinePropertyValue:
                            return bindObjectDefinePropertyAssignment(node as BindableObjectDefinePropertyCall);
                        case AssignmentDeclarationKind.ObjectDefinePropertyExports:
                            return bindObjectDefinePropertyExport(node as BindableObjectDefinePropertyCall);
                        case AssignmentDeclarationKind.ObjectDefinePrototypeProperty:
                            return bindObjectDefinePrototypeProperty(node as BindableObjectDefinePropertyCall);
                        case AssignmentDeclarationKind.None:
                            break; // Nothing to do
                        default:
                            return Debug.fail("Unknown call expression assignment declaration kind");
                    }
                    if (isInJSFile(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.TypeAliasDeclaration:
                    return bindBlockScopedDeclaration(<Declaration>node, SymbolFlags.TypeAlias, SymbolFlags.TypeAliasExcludes);
                case SyntaxKind.EnumDeclaration:
                    return bindEnumDeclaration(<EnumDeclaration>node);
                case SyntaxKind.ModuleDeclaration:
                    return bindModuleDeclaration(<ModuleDeclaration>node);
                // Jsx-attributes
                case SyntaxKind.JsxAttributes:
                    return bindJsxAttributes(<JsxAttributes>node);
                case SyntaxKind.JsxAttribute:
                    return bindJsxAttribute(<JsxAttribute>node, SymbolFlags.Property, SymbolFlags.PropertyExcludes);

                // 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;
                    }
                    // falls through
                case SyntaxKind.ModuleBlock:
                    return updateStrictModeStatementList((<Block | ModuleBlock>node).statements);

                case SyntaxKind.JSDocParameterTag:
                    if (node.parent.kind === SyntaxKind.JSDocSignature) {
                        return bindParameter(node as JSDocParameterTag);
                    }
                    if (node.parent.kind !== SyntaxKind.JSDocTypeLiteral) {
                        break;
                    }
                    // falls through
                case SyntaxKind.JSDocPropertyTag:
                    const propTag = node as JSDocPropertyLikeTag;
                    const flags = propTag.isBracketed || propTag.typeExpression && propTag.typeExpression.type.kind === SyntaxKind.JSDocOptionalType ?
                        SymbolFlags.Property | SymbolFlags.Optional :
                        SymbolFlags.Property;
                    return declareSymbolAndAddToSymbolTable(propTag, flags, SymbolFlags.PropertyExcludes);
                case SyntaxKind.JSDocTypedefTag:
                case SyntaxKind.JSDocCallbackTag:
                case SyntaxKind.JSDocEnumTag:
                    return (delayedTypeAliases || (delayedTypeAliases = [])).push(node as JSDocTypedefTag | JSDocCallbackTag | JSDocEnumTag);
            }
        }

        function bindPropertyWorker(node: PropertyDeclaration | PropertySignature) {
            return bindPropertyOrMethodOrAccessor(node, SymbolFlags.Property | (node.questionToken ? SymbolFlags.Optional : SymbolFlags.None), SymbolFlags.PropertyExcludes);
        }

        function bindAnonymousTypeWorker(node: TypeLiteralNode | MappedTypeNode | JSDocTypeLiteral) {
            return bindAnonymousDeclaration(<Declaration>node, SymbolFlags.TypeLiteral, InternalSymbolName.Type);
        }

        function bindSourceFileIfExternalModule() {
            setExportContextFlag(file);
            if (isExternalModule(file)) {
                bindSourceFileAsExternalModule();
            }
            else if (isJsonSourceFile(file)) {
                bindSourceFileAsExternalModule();
                // Create symbol equivalent for the module.exports = {}
                const originalSymbol = file.symbol;
                declareSymbol(file.symbol.exports!, file.symbol, file, SymbolFlags.Property, SymbolFlags.All);
                file.symbol = originalSymbol;
            }
        }

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

        function bindExportAssignment(node: ExportAssignment) {
            if (!container.symbol || !container.symbol.exports) {
                // Export assignment in some sort of block construct
                bindAnonymousDeclaration(node, SymbolFlags.Alias, getDeclarationName(node)!);
            }
            else {
                const flags = exportAssignmentIsAlias(node)
                    // An export default clause with an EntityNameExpression or a class expression exports all meanings of that identifier or expression;
                    ? SymbolFlags.Alias
                    // An export default clause with any other expression exports a value
                    : SymbolFlags.Property;
                // If there is an `export default x;` alias declaration, can't `export default` anything else.
                // (In contrast, you can still have `export default function f() {}` and `export default interface I {}`.)
                const symbol = declareSymbol(container.symbol.exports, container.symbol, node, flags, SymbolFlags.All);

                if (node.isExportEquals) {
                    // Will be an error later, since the module already has other exports. Just make sure this has a valueDeclaration set.
                    setValueDeclaration(symbol, node);
                }
            }
        }

        function bindNamespaceExportDeclaration(node: NamespaceExportDeclaration) {
            if (node.modifiers && node.modifiers.length) {
                file.bindDiagnostics.push(createDiagnosticForNode(node, Diagnostics.Modifiers_cannot_appear_here));
            }
            const diag = !isSourceFile(node.parent) ? Diagnostics.Global_module_exports_may_only_appear_at_top_level
                : !isExternalModule(node.parent) ? Diagnostics.Global_module_exports_may_only_appear_in_module_files
                : !node.parent.isDeclarationFile ? Diagnostics.Global_module_exports_may_only_appear_in_declaration_files
                : undefined;
            if (diag) {
                file.bindDiagnostics.push(createDiagnosticForNode(node, diag));
            }
            else {
                file.symbol.globalExports = file.symbol.globalExports || createSymbolTable();
                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);
            }
            else if (isNamespaceExport(node.exportClause)) {
                // declareSymbol walks up parents to find name text, parent _must_ be set
                // but won't be set by the normal binder walk until `bindChildren` later on.
                node.exportClause.parent = node;
                declareSymbol(container.symbol.exports, container.symbol, node.exportClause, SymbolFlags.Alias, SymbolFlags.AliasExcludes);
            }
        }

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

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

        function bindObjectDefinePropertyExport(node: BindableObjectDefinePropertyCall) {
            if (!setCommonJsModuleIndicator(node)) {
                return;
            }
            const symbol = forEachIdentifierInEntityName(node.arguments[0], /*parent*/ undefined, (id, symbol) => {
                if (symbol) {
                    addDeclarationToSymbol(symbol, id, SymbolFlags.Module | SymbolFlags.Assignment);
                }
                return symbol;
            });
            if (symbol) {
                const flags = SymbolFlags.Property | SymbolFlags.ExportValue;
                declareSymbol(symbol.exports!, symbol, node, flags, SymbolFlags.None);
            }
        }

        function bindExportsPropertyAssignment(node: BindableStaticPropertyAssignmentExpression) {
            // When we create a property via 'exports.foo = bar', the 'exports.foo' property access
            // expression is the declaration
            if (!setCommonJsModuleIndicator(node)) {
                return;
            }
            const symbol = forEachIdentifierInEntityName(node.left.expression, /*parent*/ undefined, (id, symbol) => {
                if (symbol) {
                    addDeclarationToSymbol(symbol, id, SymbolFlags.Module | SymbolFlags.Assignment);
                }
                return symbol;
            });
            if (symbol) {
                const flags = isClassExpression(node.right) ?
                    SymbolFlags.Property | SymbolFlags.ExportValue | SymbolFlags.Class :
                    SymbolFlags.Property | SymbolFlags.ExportValue;
                declareSymbol(symbol.exports!, symbol, node.left, flags, SymbolFlags.None);
            }
        }

        function bindModuleExportsAssignment(node: BindablePropertyAssignmentExpression) {
            // A common practice in node modules is to set 'export = module.exports = {}', this ensures that 'exports'
            // is still pointing to 'module.exports'.
            // We do not want to consider this as 'export=' since a module can have only one of these.
            // Similarly we do not want to treat 'module.exports = exports' as an 'export='.
            if (!setCommonJsModuleIndicator(node)) {
                return;
            }
            const assignedExpression = getRightMostAssignedExpression(node.right);
            if (isEmptyObjectLiteral(assignedExpression) || container === file && isExportsOrModuleExportsOrAlias(file, assignedExpression)) {
                return;
            }

            // 'module.exports = expr' assignment
            const flags = exportAssignmentIsAlias(node)
                ? SymbolFlags.Alias // An export= with an EntityNameExpression or a ClassExpression exports all meanings of that identifier or class
                : SymbolFlags.Property | SymbolFlags.ExportValue | SymbolFlags.ValueModule;
            const symbol = declareSymbol(file.symbol.exports!, file.symbol, node, flags | SymbolFlags.Assignment, SymbolFlags.None);
            setValueDeclaration(symbol, node);
        }

        function bindThisPropertyAssignment(node: BindablePropertyAssignmentExpression | PropertyAccessExpression | LiteralLikeElementAccessExpression) {
            Debug.assert(isInJSFile(node));
            // private identifiers *must* be declared (even in JS files)
            const hasPrivateIdentifier = (isBinaryExpression(node) && isPropertyAccessExpression(node.left) && isPrivateIdentifier(node.left.name))
                || (isPropertyAccessExpression(node) && isPrivateIdentifier(node.name));
            if (hasPrivateIdentifier) {
                return;
            }
            const thisContainer = getThisContainer(node, /*includeArrowFunctions*/ false);
            switch (thisContainer.kind) {
                case SyntaxKind.FunctionDeclaration:
                case SyntaxKind.FunctionExpression:
                    let constructorSymbol: Symbol | undefined = thisContainer.symbol;
                    // For `f.prototype.m = function() { this.x = 0; }`, `this.x = 0` should modify `f`'s members, not the function expression.
                    if (isBinaryExpression(thisContainer.parent) && thisContainer.parent.operatorToken.kind === SyntaxKind.EqualsToken) {
                        const l = thisContainer.parent.left;
                        if (isBindableStaticAccessExpression(l) && isPrototypeAccess(l.expression)) {
                            constructorSymbol = lookupSymbolForPropertyAccess(l.expression.expression, thisParentContainer);
                        }
                    }

                    if (constructorSymbol && constructorSymbol.valueDeclaration) {
                        // Declare a 'member' if the container is an ES5 class or ES6 constructor
                        constructorSymbol.members = constructorSymbol.members || createSymbolTable();
                        // It's acceptable for multiple 'this' assignments of the same identifier to occur
                        if (hasDynamicName(node)) {
                            bindDynamicallyNamedThisPropertyAssignment(node, constructorSymbol);
                        }
                        else {
                            declareSymbol(constructorSymbol.members, constructorSymbol, node, SymbolFlags.Property | SymbolFlags.Assignment, SymbolFlags.PropertyExcludes & ~SymbolFlags.Property);
                        }
                        addDeclarationToSymbol(constructorSymbol, constructorSymbol.valueDeclaration, SymbolFlags.Class);
                    }
                    break;

                case SyntaxKind.Constructor:
                case SyntaxKind.PropertyDeclaration:
                case SyntaxKind.MethodDeclaration:
                case SyntaxKind.GetAccessor:
                case SyntaxKind.SetAccessor:
                    // this.foo assignment in a JavaScript class
                    // Bind this property to the containing class
                    const containingClass = thisContainer.parent;
                    const symbolTable = hasModifier(thisContainer, ModifierFlags.Static) ? containingClass.symbol.exports! : containingClass.symbol.members!;
                    if (hasDynamicName(node)) {
                        bindDynamicallyNamedThisPropertyAssignment(node, containingClass.symbol);
                    }
                    else {
                        declareSymbol(symbolTable, containingClass.symbol, node, SymbolFlags.Property | SymbolFlags.Assignment, SymbolFlags.None, /*isReplaceableByMethod*/ true);
                    }
                    break;
                case SyntaxKind.SourceFile:
                    // this.property = assignment in a source file -- declare symbol in exports for a module, in locals for a script
                    if (hasDynamicName(node)) {
                        break;
                    }
                    else if ((thisContainer as SourceFile).commonJsModuleIndicator) {
                        declareSymbol(thisContainer.symbol.exports!, thisContainer.symbol, node, SymbolFlags.Property | SymbolFlags.ExportValue, SymbolFlags.None);
                    }
                    else {
                        declareSymbolAndAddToSymbolTable(node, SymbolFlags.FunctionScopedVariable, SymbolFlags.FunctionScopedVariableExcludes);
                    }
                    break;

                default:
                    Debug.failBadSyntaxKind(thisContainer);
            }
        }

        function bindDynamicallyNamedThisPropertyAssignment(node: BinaryExpression | DynamicNamedDeclaration, symbol: Symbol) {
            bindAnonymousDeclaration(node, SymbolFlags.Property, InternalSymbolName.Computed);
            addLateBoundAssignmentDeclarationToSymbol(node, symbol);
        }

        function addLateBoundAssignmentDeclarationToSymbol(node: BinaryExpression | DynamicNamedDeclaration, symbol: Symbol | undefined) {
            if (symbol) {
                const members = symbol.assignmentDeclarationMembers || (symbol.assignmentDeclarationMembers = createMap());
                members.set("" + getNodeId(node), node);
            }
        }

        function bindSpecialPropertyDeclaration(node: PropertyAccessExpression | LiteralLikeElementAccessExpression) {
            if (node.expression.kind === SyntaxKind.ThisKeyword) {
                bindThisPropertyAssignment(node);
            }
            else if (isBindableStaticAccessExpression(node) && node.parent.parent.kind === SyntaxKind.SourceFile) {
                if (isPrototypeAccess(node.expression)) {
                    bindPrototypePropertyAssignment(node, node.parent);
                }
                else {
                    bindStaticPropertyAssignment(node);
                }
            }
        }

        /** For `x.prototype = { p, ... }`, declare members p,... if `x` is function/class/{}, or not declared. */
        function bindPrototypeAssignment(node: BindableStaticPropertyAssignmentExpression) {
            node.left.parent = node;
            node.right.parent = node;
            bindPropertyAssignment(node.left.expression, node.left, /*isPrototypeProperty*/ false, /*containerIsClass*/ true);
        }

        function bindObjectDefinePrototypeProperty(node: BindableObjectDefinePropertyCall) {
            const namespaceSymbol = lookupSymbolForPropertyAccess((node.arguments[0] as PropertyAccessExpression).expression as EntityNameExpression);
            if (namespaceSymbol && namespaceSymbol.valueDeclaration) {
                // Ensure the namespace symbol becomes class-like
                addDeclarationToSymbol(namespaceSymbol, namespaceSymbol.valueDeclaration, SymbolFlags.Class);
            }
            bindPotentiallyNewExpandoMemberToNamespace(node, namespaceSymbol, /*isPrototypeProperty*/ true);
        }

        /**
         * For `x.prototype.y = z`, declare a member `y` on `x` if `x` is a function or class, or not declared.
         * Note that jsdoc preceding an ExpressionStatement like `x.prototype.y;` is also treated as a declaration.
         */
        function bindPrototypePropertyAssignment(lhs: BindableStaticAccessExpression, parent: Node) {
            // Look up the function in the local scope, since prototype assignments should
            // follow the function declaration
            const classPrototype = lhs.expression as BindableStaticAccessExpression;
            const constructorFunction = classPrototype.expression;

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

            bindPropertyAssignment(constructorFunction, lhs, /*isPrototypeProperty*/ true, /*containerIsClass*/ true);
        }

        function bindObjectDefinePropertyAssignment(node: BindableObjectDefinePropertyCall) {
            let namespaceSymbol = lookupSymbolForPropertyAccess(node.arguments[0]);
            const isToplevel = node.parent.parent.kind === SyntaxKind.SourceFile;
            namespaceSymbol = bindPotentiallyMissingNamespaces(namespaceSymbol, node.arguments[0], isToplevel, /*isPrototypeProperty*/ false, /*containerIsClass*/ false);
            bindPotentiallyNewExpandoMemberToNamespace(node, namespaceSymbol, /*isPrototypeProperty*/ false);
        }

        function bindSpecialPropertyAssignment(node: BindablePropertyAssignmentExpression) {
            // Class declarations in Typescript do not allow property declarations
            const parentSymbol = lookupSymbolForPropertyAccess(node.left.expression);
            if (!isInJSFile(node) && !isFunctionSymbol(parentSymbol)) {
                return;
            }
            // Fix up parent pointers since we're going to use these nodes before we bind into them
            node.left.parent = node;
            node.right.parent = node;
            if (isIdentifier(node.left.expression) && container === file && isExportsOrModuleExportsOrAlias(file, node.left.expression)) {
                // This can be an alias for the 'exports' or 'module.exports' names, e.g.
                //    var util = module.exports;
                //    util.property = function ...
                bindExportsPropertyAssignment(node as BindableStaticPropertyAssignmentExpression);
            }
            else {
                if (hasDynamicName(node)) {
                    bindAnonymousDeclaration(node, SymbolFlags.Property | SymbolFlags.Assignment, InternalSymbolName.Computed);
                    const sym = bindPotentiallyMissingNamespaces(parentSymbol, node.left.expression, isTopLevelNamespaceAssignment(node.left), /*isPrototype*/ false, /*containerIsClass*/ false);
                    addLateBoundAssignmentDeclarationToSymbol(node, sym);
                }
                else {
                    bindStaticPropertyAssignment(cast(node.left, isBindableStaticAccessExpression));
                }
            }
        }

        /**
         * For nodes like `x.y = z`, declare a member 'y' on 'x' if x is a function (or IIFE) or class or {}, or not declared.
         * Also works for expression statements preceded by JSDoc, like / ** @type number * / x.y;
         */
        function bindStaticPropertyAssignment(node: BindableStaticAccessExpression) {
            node.expression.parent = node;
            bindPropertyAssignment(node.expression, node, /*isPrototypeProperty*/ false, /*containerIsClass*/ false);
        }

        function bindPotentiallyMissingNamespaces(namespaceSymbol: Symbol | undefined, entityName: BindableStaticNameExpression, isToplevel: boolean, isPrototypeProperty: boolean, containerIsClass: boolean) {
            if (isToplevel && !isPrototypeProperty) {
                // make symbols or add declarations for intermediate containers
                const flags = SymbolFlags.Module | SymbolFlags.Assignment;
                const excludeFlags = SymbolFlags.ValueModuleExcludes & ~SymbolFlags.Assignment;
                namespaceSymbol = forEachIdentifierInEntityName(entityName, namespaceSymbol, (id, symbol, parent) => {
                    if (symbol) {
                        addDeclarationToSymbol(symbol, id, flags);
                        return symbol;
                    }
                    else {
                        const table = parent ? parent.exports! :
                            file.jsGlobalAugmentations || (file.jsGlobalAugmentations = createSymbolTable());
                        return declareSymbol(table, parent, id, flags, excludeFlags);
                    }
                });
            }
            if (containerIsClass && namespaceSymbol && namespaceSymbol.valueDeclaration) {
                addDeclarationToSymbol(namespaceSymbol, namespaceSymbol.valueDeclaration, SymbolFlags.Class);
            }
            return namespaceSymbol;
        }

        function bindPotentiallyNewExpandoMemberToNamespace(declaration: BindableStaticAccessExpression | CallExpression, namespaceSymbol: Symbol | undefined, isPrototypeProperty: boolean) {
            if (!namespaceSymbol || !isExpandoSymbol(namespaceSymbol)) {
                return;
            }

            // Set up the members collection if it doesn't exist already
            const symbolTable = isPrototypeProperty ?
                (namespaceSymbol.members || (namespaceSymbol.members = createSymbolTable())) :
                (namespaceSymbol.exports || (namespaceSymbol.exports = createSymbolTable()));

            let includes = SymbolFlags.None;
            let excludes = SymbolFlags.None;
            // Method-like
            if (isFunctionLikeDeclaration(getAssignedExpandoInitializer(declaration)!)) {
                includes = SymbolFlags.Method;
                excludes = SymbolFlags.MethodExcludes;
            }
            // Maybe accessor-like
            else if (isCallExpression(declaration) && isBindableObjectDefinePropertyCall(declaration)) {
                if (some(declaration.arguments[2].properties, p => {
                    const id = getNameOfDeclaration(p);
                    return !!id && isIdentifier(id) && idText(id) === "set";
                })) {
                    // We mix in `SymbolFLags.Property` so in the checker `getTypeOfVariableParameterOrProperty` is used for this
                    // symbol, instead of `getTypeOfAccessor` (which will assert as there is no real accessor declaration)
                    includes |= SymbolFlags.SetAccessor | SymbolFlags.Property;
                    excludes |= SymbolFlags.SetAccessorExcludes;
                }
                if (some(declaration.arguments[2].properties, p => {
                    const id = getNameOfDeclaration(p);
                    return !!id && isIdentifier(id) && idText(id) === "get";
                })) {
                    includes |= SymbolFlags.GetAccessor | SymbolFlags.Property;
                    excludes |= SymbolFlags.GetAccessorExcludes;
                }
            }

            if (includes === SymbolFlags.None) {
                includes = SymbolFlags.Property;
                excludes = SymbolFlags.PropertyExcludes;
            }

            declareSymbol(symbolTable, namespaceSymbol, declaration, includes | SymbolFlags.Assignment, excludes & ~SymbolFlags.Assignment);
        }

        function isTopLevelNamespaceAssignment(propertyAccess: BindableAccessExpression) {
            return isBinaryExpression(propertyAccess.parent)
                ? getParentOfBinaryExpression(propertyAccess.parent).parent.kind === SyntaxKind.SourceFile
                : propertyAccess.parent.parent.kind === SyntaxKind.SourceFile;
        }

        function bindPropertyAssignment(name: BindableStaticNameExpression, propertyAccess: BindableStaticAccessExpression, isPrototypeProperty: boolean, containerIsClass: boolean) {
            let namespaceSymbol = lookupSymbolForPropertyAccess(name);
            const isToplevel = isTopLevelNamespaceAssignment(propertyAccess);
            namespaceSymbol = bindPotentiallyMissingNamespaces(namespaceSymbol, propertyAccess.expression, isToplevel, isPrototypeProperty, containerIsClass);
            bindPotentiallyNewExpandoMemberToNamespace(propertyAccess, namespaceSymbol, isPrototypeProperty);
        }

        /**
         * Javascript expando values are:
         * - Functions
         * - classes
         * - namespaces
         * - variables initialized with function expressions
         * -                       with class expressions
         * -                       with empty object literals
         * -                       with non-empty object literals if assigned to the prototype property
         */
        function isExpandoSymbol(symbol: Symbol): boolean {
            if (symbol.flags & (SymbolFlags.Function | SymbolFlags.Class | SymbolFlags.NamespaceModule)) {
                return true;
            }
            const node = symbol.valueDeclaration;
            if (node && isCallExpression(node)) {
                return !!getAssignedExpandoInitializer(node);
            }
            let init = !node ? undefined :
                isVariableDeclaration(node) ? node.initializer :
                isBinaryExpression(node) ? node.right :
                isPropertyAccessExpression(node) && isBinaryExpression(node.parent) ? node.parent.right :
                undefined;
            init = init && getRightMostAssignedExpression(init);
            if (init) {
                const isPrototypeAssignment = isPrototypeAccess(isVariableDeclaration(node) ? node.name : isBinaryExpression(node) ? node.left : node);
                return !!getExpandoInitializer(isBinaryExpression(init) && (init.operatorToken.kind === SyntaxKind.BarBarToken || init.operatorToken.kind === SyntaxKind.QuestionQuestionToken) ? init.right : init, isPrototypeAssignment);
            }
            return false;
        }

        function getParentOfBinaryExpression(expr: Node) {
            while (isBinaryExpression(expr.parent)) {
                expr = expr.parent;
            }
            return expr.parent;
        }

        function lookupSymbolForPropertyAccess(node: BindableStaticNameExpression, lookupContainer: Node = container): Symbol | undefined {
            if (isIdentifier(node)) {
                return lookupSymbolForNameWorker(lookupContainer, node.escapedText);
            }
            else {
                const symbol = lookupSymbolForPropertyAccess(node.expression);
                return symbol && symbol.exports && symbol.exports.get(getElementOrPropertyAccessName(node));
            }
        }

        function forEachIdentifierInEntityName(e: BindableStaticNameExpression, parent: Symbol | undefined, action: (e: Declaration, symbol: Symbol | undefined, parent: Symbol | undefined) => Symbol | undefined): Symbol | undefined {
            if (isExportsOrModuleExportsOrAlias(file, e)) {
                return file.symbol;
            }
            else if (isIdentifier(e)) {
                return action(e, lookupSymbolForPropertyAccess(e), parent);
            }
            else {
                const s = forEachIdentifierInEntityName(e.expression, parent, action);
                const name = getNameOrArgument(e);
                // unreachable
                if (isPrivateIdentifier(name)) {
                    Debug.fail("unexpected PrivateIdentifier");
                }
                return action(name, s && s.exports && s.exports.get(getElementOrPropertyAccessName(e)), s);
            }
        }

        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, /*checkArgumentIsStringLiteralLike*/ false)) {
                setCommonJsModuleIndicator(node);
            }
        }

        function bindClassLikeDeclaration(node: ClassLikeDeclaration) {
            if (node.kind === SyntaxKind.ClassDeclaration) {
                bindBlockScopedDeclaration(node, SymbolFlags.Class, SymbolFlags.ClassExcludes);
            }
            else {
                const bindingName = node.name ? node.name.escapedText : InternalSymbolName.Class;
                bindAnonymousDeclaration(node, SymbolFlags.Class, bindingName);
                // Add name of class expression into the map for semantic classifier
                if (node.name) {
                    classifiableNames.set(node.name.escapedText, true);
                }
            }

            const { symbol } = node;

            // 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" as __String);
            const symbolExport = symbol.exports!.get(prototypeSymbol.escapedName);
            if (symbolExport) {
                if (node.name) {
                    node.name.parent = node;
                }
                file.bindDiagnostics.push(createDiagnosticForNode(symbolExport.declarations[0], Diagnostics.Duplicate_identifier_0, symbolName(prototypeSymbol)));
            }
            symbol.exports!.set(prototypeSymbol.escapedName, prototypeSymbol);
            prototypeSymbol.parent = symbol;
        }

        function bindEnumDeclaration(node: EnumDeclaration) {
            return isEnumConst(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)) {
                    bindBlockScopedDeclaration(node, SymbolFlags.BlockScopedVariable, SymbolFlags.BlockScopedVariableExcludes);
                }
                else if (isParameterDeclaration(node)) {
                    // It is safe to walk up parent chain to find whether the node is a destructuring 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 | JSDocParameterTag) {
            if (node.kind === SyntaxKind.JSDocParameterTag && container.kind !== SyntaxKind.JSDocSignature) {
                return;
            }
            if (inStrictMode && !(node.flags & NodeFlags.Ambient)) {
                // 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, "__" + (node as ParameterDeclaration).parent.parameters.indexOf(node as ParameterDeclaration) as __String);
            }
            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, node.parent)) {
                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 (!file.isDeclarationFile && !(node.flags & NodeFlags.Ambient)) {
                if (isAsyncFunction(node)) {
                    emitFlags |= NodeFlags.HasAsyncFunctions;
                }
            }

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

        function bindFunctionExpression(node: FunctionExpression) {
            if (!file.isDeclarationFile && !(node.flags & NodeFlags.Ambient)) {
                if (isAsyncFunction(node)) {
                    emitFlags |= NodeFlags.HasAsyncFunctions;
                }
            }
            if (currentFlow) {
                node.flowNode = currentFlow;
            }
            checkStrictModeFunctionName(node);
            const bindingName = node.name ? node.name.escapedText : InternalSymbolName.Function;
            return bindAnonymousDeclaration(node, SymbolFlags.Function, bindingName);
        }

        function bindPropertyOrMethodOrAccessor(node: Declaration, symbolFlags: SymbolFlags, symbolExcludes: SymbolFlags) {
            if (!file.isDeclarationFile && !(node.flags & NodeFlags.Ambient) && isAsyncFunction(node)) {
                emitFlags |= NodeFlags.HasAsyncFunctions;
            }

            if (currentFlow && isObjectLiteralOrClassExpressionMethod(node)) {
                node.flowNode = currentFlow;
            }

            return hasDynamicName(node)
                ? bindAnonymousDeclaration(node, symbolFlags, InternalSymbolName.Computed)
                : declareSymbolAndAddToSymbolTable(node, symbolFlags, symbolExcludes);
        }

        function getInferTypeContainer(node: Node): ConditionalTypeNode | undefined {
            const extendsType = findAncestor(node, n => n.parent && isConditionalTypeNode(n.parent) && n.parent.extendsType === n);
            return extendsType && extendsType.parent as ConditionalTypeNode;
        }

        function bindTypeParameter(node: TypeParameterDeclaration) {
            if (isJSDocTemplateTag(node.parent)) {
                const container = find((node.parent.parent as JSDoc).tags!, isJSDocTypeAlias) || getHostSignatureFromJSDoc(node.parent); // TODO: GH#18217
                if (container) {
                    if (!container.locals) {
                        container.locals = createSymbolTable();
                    }
                    declareSymbol(container.locals, /*parent*/ undefined, node, SymbolFlags.TypeParameter, SymbolFlags.TypeParameterExcludes);
                }
                else {
                    declareSymbolAndAddToSymbolTable(node, SymbolFlags.TypeParameter, SymbolFlags.TypeParameterExcludes);
                }
            }
            else if (node.parent.kind === SyntaxKind.InferType) {
                const container = getInferTypeContainer(node.parent);
                if (container) {
                    if (!container.locals) {
                        container.locals = createSymbolTable();
                    }
                    declareSymbol(container.locals, /*parent*/ undefined, node, SymbolFlags.TypeParameter, SymbolFlags.TypeParameterExcludes);
                }
                else {
                    bindAnonymousDeclaration(node, SymbolFlags.TypeParameter, getDeclarationName(node)!); // TODO: GH#18217
                }
            }
            else {
                declareSymbolAndAddToSymbolTable(node, SymbolFlags.TypeParameter, SymbolFlags.TypeParameterExcludes);
            }
        }

        // 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
                    (isStatementButNotDeclaration(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));

                if (reportError) {
                    currentFlow = reportedUnreachableFlow;

                    if (!options.allowUnreachableCode) {
                        // 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 isError =
                            unreachableCodeIsError(options) &&
                            !(node.flags & NodeFlags.Ambient) &&
                            (
                                !isVariableStatement(node) ||
                                !!(getCombinedNodeFlags(node.declarationList) & NodeFlags.BlockScoped) ||
                                node.declarationList.declarations.some(d => !!d.initializer)
                            );

                        eachUnreachableRange(node, (start, end) => errorOrSuggestionOnRange(isError, start, end, Diagnostics.Unreachable_code_detected));
                    }
                }
            }
            return true;
        }
    }

    function eachUnreachableRange(node: Node, cb: (start: Node, last: Node) => void): void {
        if (isStatement(node) && isExecutableStatement(node) && isBlock(node.parent)) {
            const { statements } = node.parent;
            const slice = sliceAfter(statements, node);
            getRangesWhere(slice, isExecutableStatement, (start, afterEnd) => cb(slice[start], slice[afterEnd - 1]));
        }
        else {
            cb(node, node);
        }
    }
    // As opposed to a pure declaration like an `interface`
    function isExecutableStatement(s: Statement): boolean {
        // Don't remove statements that can validly be used before they appear.
        return !isFunctionDeclaration(s) && !isPurelyTypeDeclaration(s) && !isEnumDeclaration(s) &&
            // `var x;` may declare a variable used above
            !(isVariableStatement(s) && !(getCombinedNodeFlags(s) & (NodeFlags.Let | NodeFlags.Const)) && s.declarationList.declarations.some(d => !d.initializer));
    }

    function isPurelyTypeDeclaration(s: Statement): boolean {
        switch (s.kind) {
            case SyntaxKind.InterfaceDeclaration:
            case SyntaxKind.TypeAliasDeclaration:
                return true;
            case SyntaxKind.ModuleDeclaration:
                return getModuleInstanceState(s as ModuleDeclaration) !== ModuleInstanceState.Instantiated;
            case SyntaxKind.EnumDeclaration:
                return hasModifier(s, ModifierFlags.Const);
            default:
                return false;
        }
    }

    export function isExportsOrModuleExportsOrAlias(sourceFile: SourceFile, node: Expression): boolean {
        let i = 0;
        const q = [node];
        while (q.length && i < 100) {
            i++;
            node = q.shift()!;
            if (isExportsIdentifier(node) || isModuleExportsAccessExpression(node)) {
                return true;
            }
            else if (isIdentifier(node)) {
                const symbol = lookupSymbolForNameWorker(sourceFile, node.escapedText);
                if (!!symbol && !!symbol.valueDeclaration && isVariableDeclaration(symbol.valueDeclaration) && !!symbol.valueDeclaration.initializer) {
                    const init = symbol.valueDeclaration.initializer;
                    q.push(init);
                    if (isAssignmentExpression(init, /*excludeCompoundAssignment*/ true)) {
                        q.push(init.left);
                        q.push(init.right);
                    }
                }
            }
        }
        return false;
    }

    function lookupSymbolForNameWorker(container: Node, name: __String): Symbol | undefined {
        const local = container.locals && container.locals.get(name);
        if (local) {
            return local.exportSymbol || local;
        }
        if (isSourceFile(container) && container.jsGlobalAugmentations && container.jsGlobalAugmentations.has(name)) {
            return container.jsGlobalAugmentations.get(name);
        }
        return container.symbol && container.symbol.exports && container.symbol.exports.get(name);
    }

    /**
     * Computes the transform flags for a node, given the transform flags of its subtree
     *
     * @param node The node to analyze
     * @param subtreeFlags Transform flags computed for this node's subtree
     */
    export function computeTransformFlagsForNode(node: Node, subtreeFlags: TransformFlags): TransformFlags {
        const kind = node.kind;
        switch (kind) {
            case SyntaxKind.CallExpression:
                return computeCallExpression(<CallExpression>node, subtreeFlags);

            case SyntaxKind.NewExpression:
                return computeNewExpression(<NewExpression>node, subtreeFlags);

            case SyntaxKind.ModuleDeclaration:
                return computeModuleDeclaration(<ModuleDeclaration>node, subtreeFlags);

            case SyntaxKind.ParenthesizedExpression:
                return computeParenthesizedExpression(<ParenthesizedExpression>node, subtreeFlags);

            case SyntaxKind.BinaryExpression:
                return computeBinaryExpression(<BinaryExpression>node, subtreeFlags);

            case SyntaxKind.ExpressionStatement:
                return computeExpressionStatement(<ExpressionStatement>node, subtreeFlags);

            case SyntaxKind.Parameter:
                return computeParameter(<ParameterDeclaration>node, subtreeFlags);

            case SyntaxKind.ArrowFunction:
                return computeArrowFunction(<ArrowFunction>node, subtreeFlags);

            case SyntaxKind.FunctionExpression:
                return computeFunctionExpression(<FunctionExpression>node, subtreeFlags);

            case SyntaxKind.FunctionDeclaration:
                return computeFunctionDeclaration(<FunctionDeclaration>node, subtreeFlags);

            case SyntaxKind.VariableDeclaration:
                return computeVariableDeclaration(<VariableDeclaration>node, subtreeFlags);

            case SyntaxKind.VariableDeclarationList:
                return computeVariableDeclarationList(<VariableDeclarationList>node, subtreeFlags);

            case SyntaxKind.VariableStatement:
                return computeVariableStatement(<VariableStatement>node, subtreeFlags);

            case SyntaxKind.LabeledStatement:
                return computeLabeledStatement(<LabeledStatement>node, subtreeFlags);

            case SyntaxKind.ClassDeclaration:
                return computeClassDeclaration(<ClassDeclaration>node, subtreeFlags);

            case SyntaxKind.ClassExpression:
                return computeClassExpression(<ClassExpression>node, subtreeFlags);

            case SyntaxKind.HeritageClause:
                return computeHeritageClause(<HeritageClause>node, subtreeFlags);

            case SyntaxKind.CatchClause:
                return computeCatchClause(<CatchClause>node, subtreeFlags);

            case SyntaxKind.ExpressionWithTypeArguments:
                return computeExpressionWithTypeArguments(<ExpressionWithTypeArguments>node, subtreeFlags);

            case SyntaxKind.Constructor:
                return computeConstructor(<ConstructorDeclaration>node, subtreeFlags);

            case SyntaxKind.PropertyDeclaration:
                return computePropertyDeclaration(<PropertyDeclaration>node, subtreeFlags);

            case SyntaxKind.MethodDeclaration:
                return computeMethod(<MethodDeclaration>node, subtreeFlags);

            case SyntaxKind.GetAccessor:
            case SyntaxKind.SetAccessor:
                return computeAccessor(<AccessorDeclaration>node, subtreeFlags);

            case SyntaxKind.ImportEqualsDeclaration:
                return computeImportEquals(<ImportEqualsDeclaration>node, subtreeFlags);

            case SyntaxKind.PropertyAccessExpression:
                return computePropertyAccess(<PropertyAccessExpression>node, subtreeFlags);

            case SyntaxKind.ElementAccessExpression:
                return computeElementAccess(<ElementAccessExpression>node, subtreeFlags);

            default:
                return computeOther(node, kind, subtreeFlags);
        }
    }

    function computeCallExpression(node: CallExpression, subtreeFlags: TransformFlags) {
        let transformFlags = subtreeFlags;
        const callee = skipOuterExpressions(node.expression);
        const expression = node.expression;

        if (node.flags & NodeFlags.OptionalChain) {
            transformFlags |= TransformFlags.ContainsES2020;
        }

        if (node.typeArguments) {
            transformFlags |= TransformFlags.AssertTypeScript;
        }

        if (subtreeFlags & TransformFlags.ContainsRestOrSpread || isSuperOrSuperProperty(callee)) {
            // If the this node contains a SpreadExpression, or is a super call, then it is an ES6
            // node.
            transformFlags |= TransformFlags.AssertES2015;
            if (isSuperProperty(callee)) {
                transformFlags |= TransformFlags.ContainsLexicalThis;
            }
        }

        if (expression.kind === SyntaxKind.ImportKeyword) {
            transformFlags |= TransformFlags.ContainsDynamicImport;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.ArrayLiteralOrCallOrNewExcludes;
    }

    function computeNewExpression(node: NewExpression, subtreeFlags: TransformFlags) {
        let transformFlags = subtreeFlags;
        if (node.typeArguments) {
            transformFlags |= TransformFlags.AssertTypeScript;
        }
        if (subtreeFlags & TransformFlags.ContainsRestOrSpread) {
            // If the this node contains a SpreadElementExpression then it is an ES6
            // node.
            transformFlags |= TransformFlags.AssertES2015;
        }
        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.ArrayLiteralOrCallOrNewExcludes;
    }

    function computeBinaryExpression(node: BinaryExpression, subtreeFlags: TransformFlags) {
        let transformFlags = subtreeFlags;
        const operatorTokenKind = node.operatorToken.kind;
        const leftKind = node.left.kind;

        if (operatorTokenKind === SyntaxKind.QuestionQuestionToken) {
            transformFlags |= TransformFlags.AssertES2020;
        }
        else if (operatorTokenKind === SyntaxKind.EqualsToken && leftKind === SyntaxKind.ObjectLiteralExpression) {
            // Destructuring object assignments with are ES2015 syntax
            // and possibly ES2018 if they contain rest
            transformFlags |= TransformFlags.AssertES2018 | TransformFlags.AssertES2015 | TransformFlags.AssertDestructuringAssignment;
        }
        else if (operatorTokenKind === SyntaxKind.EqualsToken && leftKind === SyntaxKind.ArrayLiteralExpression) {
            // Destructuring assignments are ES2015 syntax.
            transformFlags |= TransformFlags.AssertES2015 | TransformFlags.AssertDestructuringAssignment;
        }
        else if (operatorTokenKind === SyntaxKind.AsteriskAsteriskToken
            || operatorTokenKind === SyntaxKind.AsteriskAsteriskEqualsToken) {
            // Exponentiation is ES2016 syntax.
            transformFlags |= TransformFlags.AssertES2016;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.NodeExcludes;
    }

    function computeParameter(node: ParameterDeclaration, subtreeFlags: TransformFlags) {
        let transformFlags = subtreeFlags;
        const name = node.name;
        const initializer = node.initializer;
        const dotDotDotToken = node.dotDotDotToken;

        // The '?' token, type annotations, decorators, and 'this' parameters are TypeSCript
        // syntax.
        if (node.questionToken
            || node.type
            || (subtreeFlags & TransformFlags.ContainsTypeScriptClassSyntax && some(node.decorators))
            || isThisIdentifier(name)) {
            transformFlags |= TransformFlags.AssertTypeScript;
        }

        // If a parameter has an accessibility modifier, then it is TypeScript syntax.
        if (hasModifier(node, ModifierFlags.ParameterPropertyModifier)) {
            transformFlags |= TransformFlags.AssertTypeScript | TransformFlags.ContainsTypeScriptClassSyntax;
        }

        // parameters with object rest destructuring are ES2018 syntax
        if (subtreeFlags & TransformFlags.ContainsObjectRestOrSpread) {
            transformFlags |= TransformFlags.AssertES2018;
        }

        // If a parameter has an initializer, a binding pattern or a dotDotDot token, then
        // it is ES6 syntax and its container must emit default value assignments or parameter destructuring downlevel.
        if (subtreeFlags & TransformFlags.ContainsBindingPattern || initializer || dotDotDotToken) {
            transformFlags |= TransformFlags.AssertES2015;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.ParameterExcludes;
    }

    function computeParenthesizedExpression(node: ParenthesizedExpression, subtreeFlags: TransformFlags) {
        let transformFlags = subtreeFlags;
        const expression = node.expression;
        const expressionKind = expression.kind;

        // If the node is synthesized, it means the emitter put the parentheses there,
        // not the user. If we didn't want them, the emitter would not have put them
        // there.
        if (expressionKind === SyntaxKind.AsExpression
            || expressionKind === SyntaxKind.TypeAssertionExpression) {
            transformFlags |= TransformFlags.AssertTypeScript;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.OuterExpressionExcludes;
    }

    function computeClassDeclaration(node: ClassDeclaration, subtreeFlags: TransformFlags) {
        let transformFlags: TransformFlags;

        if (hasModifier(node, ModifierFlags.Ambient)) {
            // An ambient declaration is TypeScript syntax.
            transformFlags = TransformFlags.AssertTypeScript;
        }
        else {
            // A ClassDeclaration is ES6 syntax.
            transformFlags = subtreeFlags | TransformFlags.AssertES2015;

            // A class with a parameter property assignment or decorator is TypeScript syntax.
            // An exported declaration may be TypeScript syntax, but is handled by the visitor
            // for a namespace declaration.
            if ((subtreeFlags & TransformFlags.ContainsTypeScriptClassSyntax)
                || node.typeParameters) {
                transformFlags |= TransformFlags.AssertTypeScript;
            }
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.ClassExcludes;
    }

    function computeClassExpression(node: ClassExpression, subtreeFlags: TransformFlags) {
        // A ClassExpression is ES6 syntax.
        let transformFlags = subtreeFlags | TransformFlags.AssertES2015;

        // A class with a parameter property assignment or decorator is TypeScript syntax.
        if (subtreeFlags & TransformFlags.ContainsTypeScriptClassSyntax
            || node.typeParameters) {
            transformFlags |= TransformFlags.AssertTypeScript;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.ClassExcludes;
    }

    function computeHeritageClause(node: HeritageClause, subtreeFlags: TransformFlags) {
        let transformFlags = subtreeFlags;

        switch (node.token) {
            case SyntaxKind.ExtendsKeyword:
                // An `extends` HeritageClause is ES6 syntax.
                transformFlags |= TransformFlags.AssertES2015;
                break;

            case SyntaxKind.ImplementsKeyword:
                // An `implements` HeritageClause is TypeScript syntax.
                transformFlags |= TransformFlags.AssertTypeScript;
                break;

            default:
                Debug.fail("Unexpected token for heritage clause");
                break;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.NodeExcludes;
    }

    function computeCatchClause(node: CatchClause, subtreeFlags: TransformFlags) {
        let transformFlags = subtreeFlags;

        if (!node.variableDeclaration) {
            transformFlags |= TransformFlags.AssertES2019;
        }
        else if (isBindingPattern(node.variableDeclaration.name)) {
            transformFlags |= TransformFlags.AssertES2015;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.CatchClauseExcludes;
    }

    function computeExpressionWithTypeArguments(node: ExpressionWithTypeArguments, subtreeFlags: TransformFlags) {
        // An ExpressionWithTypeArguments is ES6 syntax, as it is used in the
        // extends clause of a class.
        let transformFlags = subtreeFlags | TransformFlags.AssertES2015;

        // If an ExpressionWithTypeArguments contains type arguments, then it
        // is TypeScript syntax.
        if (node.typeArguments) {
            transformFlags |= TransformFlags.AssertTypeScript;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.NodeExcludes;
    }

    function computeConstructor(node: ConstructorDeclaration, subtreeFlags: TransformFlags) {
        let transformFlags = subtreeFlags;

        // TypeScript-specific modifiers and overloads are TypeScript syntax
        if (hasModifier(node, ModifierFlags.TypeScriptModifier)
            || !node.body) {
            transformFlags |= TransformFlags.AssertTypeScript;
        }

        // function declarations with object rest destructuring are ES2018 syntax
        if (subtreeFlags & TransformFlags.ContainsObjectRestOrSpread) {
            transformFlags |= TransformFlags.AssertES2018;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.ConstructorExcludes;
    }

    function computeMethod(node: MethodDeclaration, subtreeFlags: TransformFlags) {
        // A MethodDeclaration is ES6 syntax.
        let transformFlags = subtreeFlags | TransformFlags.AssertES2015;

        // Decorators, TypeScript-specific modifiers, type parameters, type annotations, and
        // overloads are TypeScript syntax.
        if (node.decorators
            || hasModifier(node, ModifierFlags.TypeScriptModifier)
            || node.typeParameters
            || node.type
            || !node.body
            || node.questionToken) {
            transformFlags |= TransformFlags.AssertTypeScript;
        }

        // function declarations with object rest destructuring are ES2018 syntax
        if (subtreeFlags & TransformFlags.ContainsObjectRestOrSpread) {
            transformFlags |= TransformFlags.AssertES2018;
        }

        // An async method declaration is ES2017 syntax.
        if (hasModifier(node, ModifierFlags.Async)) {
            transformFlags |= node.asteriskToken ? TransformFlags.AssertES2018 : TransformFlags.AssertES2017;
        }

        if (node.asteriskToken) {
            transformFlags |= TransformFlags.AssertGenerator;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return propagatePropertyNameFlags(node.name, transformFlags & ~TransformFlags.MethodOrAccessorExcludes);
    }

    function computeAccessor(node: AccessorDeclaration, subtreeFlags: TransformFlags) {
        let transformFlags = subtreeFlags;

        // Decorators, TypeScript-specific modifiers, type annotations, and overloads are
        // TypeScript syntax.
        if (node.decorators
            || hasModifier(node, ModifierFlags.TypeScriptModifier)
            || node.type
            || !node.body) {
            transformFlags |= TransformFlags.AssertTypeScript;
        }

        // function declarations with object rest destructuring are ES2018 syntax
        if (subtreeFlags & TransformFlags.ContainsObjectRestOrSpread) {
            transformFlags |= TransformFlags.AssertES2018;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return propagatePropertyNameFlags(node.name, transformFlags & ~TransformFlags.MethodOrAccessorExcludes);
    }

    function computePropertyDeclaration(node: PropertyDeclaration, subtreeFlags: TransformFlags) {
        let transformFlags = subtreeFlags | TransformFlags.ContainsClassFields;

        // Decorators, TypeScript-specific modifiers, and type annotations are TypeScript syntax.
        if (some(node.decorators) || hasModifier(node, ModifierFlags.TypeScriptModifier) || node.type || node.questionToken || node.exclamationToken) {
            transformFlags |= TransformFlags.AssertTypeScript;
        }

        // Hoisted variables related to class properties should live within the TypeScript class wrapper.
        if (isComputedPropertyName(node.name) || (hasStaticModifier(node) && node.initializer)) {
            transformFlags |= TransformFlags.ContainsTypeScriptClassSyntax;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return propagatePropertyNameFlags(node.name, transformFlags & ~TransformFlags.PropertyExcludes);
    }

    function computeFunctionDeclaration(node: FunctionDeclaration, subtreeFlags: TransformFlags) {
        let transformFlags: TransformFlags;
        const modifierFlags = getModifierFlags(node);
        const body = node.body;

        if (!body || (modifierFlags & ModifierFlags.Ambient)) {
            // An ambient declaration is TypeScript syntax.
            // A FunctionDeclaration without a body is an overload and is TypeScript syntax.
            transformFlags = TransformFlags.AssertTypeScript;
        }
        else {
            transformFlags = subtreeFlags | TransformFlags.ContainsHoistedDeclarationOrCompletion;

            // TypeScript-specific modifiers, type parameters, and type annotations are TypeScript
            // syntax.
            if (modifierFlags & ModifierFlags.TypeScriptModifier
                || node.typeParameters
                || node.type) {
                transformFlags |= TransformFlags.AssertTypeScript;
            }

            // An async function declaration is ES2017 syntax.
            if (modifierFlags & ModifierFlags.Async) {
                transformFlags |= node.asteriskToken ? TransformFlags.AssertES2018 : TransformFlags.AssertES2017;
            }

            // function declarations with object rest destructuring are ES2018 syntax
            if (subtreeFlags & TransformFlags.ContainsObjectRestOrSpread) {
                transformFlags |= TransformFlags.AssertES2018;
            }

            // If a FunctionDeclaration is generator function and is the body of a
            // transformed async function, then this node can be transformed to a
            // down-level generator.
            // Currently we do not support transforming any other generator functions
            // down level.
            if (node.asteriskToken) {
                transformFlags |= TransformFlags.AssertGenerator;
            }
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.FunctionExcludes;
    }

    function computeFunctionExpression(node: FunctionExpression, subtreeFlags: TransformFlags) {
        let transformFlags = subtreeFlags;

        // TypeScript-specific modifiers, type parameters, and type annotations are TypeScript
        // syntax.
        if (hasModifier(node, ModifierFlags.TypeScriptModifier)
            || node.typeParameters
            || node.type) {
            transformFlags |= TransformFlags.AssertTypeScript;
        }

        // An async function expression is ES2017 syntax.
        if (hasModifier(node, ModifierFlags.Async)) {
            transformFlags |= node.asteriskToken ? TransformFlags.AssertES2018 : TransformFlags.AssertES2017;
        }

        // function expressions with object rest destructuring are ES2018 syntax
        if (subtreeFlags & TransformFlags.ContainsObjectRestOrSpread) {
            transformFlags |= TransformFlags.AssertES2018;
        }

        // If a FunctionExpression is generator function and is the body of a
        // transformed async function, then this node can be transformed to a
        // down-level generator.
        if (node.asteriskToken) {
            transformFlags |= TransformFlags.AssertGenerator;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.FunctionExcludes;
    }

    function computeArrowFunction(node: ArrowFunction, subtreeFlags: TransformFlags) {
        // An ArrowFunction is ES6 syntax, and excludes markers that should not escape the scope of an ArrowFunction.
        let transformFlags = subtreeFlags | TransformFlags.AssertES2015;

        // TypeScript-specific modifiers, type parameters, and type annotations are TypeScript
        // syntax.
        if (hasModifier(node, ModifierFlags.TypeScriptModifier)
            || node.typeParameters
            || node.type) {
            transformFlags |= TransformFlags.AssertTypeScript;
        }

        // An async arrow function is ES2017 syntax.
        if (hasModifier(node, ModifierFlags.Async)) {
            transformFlags |= TransformFlags.AssertES2017;
        }

        // arrow functions with object rest destructuring are ES2018 syntax
        if (subtreeFlags & TransformFlags.ContainsObjectRestOrSpread) {
            transformFlags |= TransformFlags.AssertES2018;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.ArrowFunctionExcludes;
    }

    function computePropertyAccess(node: PropertyAccessExpression, subtreeFlags: TransformFlags) {
        let transformFlags = subtreeFlags;

        if (node.flags & NodeFlags.OptionalChain) {
            transformFlags |= TransformFlags.ContainsES2020;
        }

        // If a PropertyAccessExpression starts with a super keyword, then it is
        // ES6 syntax, and requires a lexical `this` binding.
        if (node.expression.kind === SyntaxKind.SuperKeyword) {
            // super inside of an async function requires hoisting the super access (ES2017).
            // same for super inside of an async generator, which is ES2018.
            transformFlags |= TransformFlags.ContainsES2017 | TransformFlags.ContainsES2018;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.PropertyAccessExcludes;
    }

    function computeElementAccess(node: ElementAccessExpression, subtreeFlags: TransformFlags) {
        let transformFlags = subtreeFlags;

        if (node.flags & NodeFlags.OptionalChain) {
            transformFlags |= TransformFlags.ContainsES2020;
        }

        // If an ElementAccessExpression starts with a super keyword, then it is
        // ES6 syntax, and requires a lexical `this` binding.
        if (node.expression.kind === SyntaxKind.SuperKeyword) {
            // super inside of an async function requires hoisting the super access (ES2017).
            // same for super inside of an async generator, which is ES2018.
            transformFlags |= TransformFlags.ContainsES2017 | TransformFlags.ContainsES2018;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.PropertyAccessExcludes;
    }

    function computeVariableDeclaration(node: VariableDeclaration, subtreeFlags: TransformFlags) {
        let transformFlags = subtreeFlags;
        transformFlags |= TransformFlags.AssertES2015 | TransformFlags.ContainsBindingPattern; // TODO(rbuckton): Why are these set unconditionally?

        // A VariableDeclaration containing ObjectRest is ES2018 syntax
        if (subtreeFlags & TransformFlags.ContainsObjectRestOrSpread) {
            transformFlags |= TransformFlags.AssertES2018;
        }

        // Type annotations are TypeScript syntax.
        if (node.type || node.exclamationToken) {
            transformFlags |= TransformFlags.AssertTypeScript;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.NodeExcludes;
    }

    function computeVariableStatement(node: VariableStatement, subtreeFlags: TransformFlags) {
        let transformFlags: TransformFlags;
        const declarationListTransformFlags = node.declarationList.transformFlags;

        // An ambient declaration is TypeScript syntax.
        if (hasModifier(node, ModifierFlags.Ambient)) {
            transformFlags = TransformFlags.AssertTypeScript;
        }
        else {
            transformFlags = subtreeFlags;

            if (declarationListTransformFlags & TransformFlags.ContainsBindingPattern) {
                transformFlags |= TransformFlags.AssertES2015;
            }
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.NodeExcludes;
    }

    function computeLabeledStatement(node: LabeledStatement, subtreeFlags: TransformFlags) {
        let transformFlags = subtreeFlags;

        // A labeled statement containing a block scoped binding *may* need to be transformed from ES6.
        if (subtreeFlags & TransformFlags.ContainsBlockScopedBinding
            && isIterationStatement(node, /*lookInLabeledStatements*/ true)) {
            transformFlags |= TransformFlags.AssertES2015;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.NodeExcludes;
    }

    function computeImportEquals(node: ImportEqualsDeclaration, subtreeFlags: TransformFlags) {
        let transformFlags = subtreeFlags;

        // An ImportEqualsDeclaration with a namespace reference is TypeScript.
        if (!isExternalModuleImportEqualsDeclaration(node)) {
            transformFlags |= TransformFlags.AssertTypeScript;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.NodeExcludes;
    }

    function computeExpressionStatement(node: ExpressionStatement, subtreeFlags: TransformFlags) {
        const transformFlags = subtreeFlags;
        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.NodeExcludes;
    }

    function computeModuleDeclaration(node: ModuleDeclaration, subtreeFlags: TransformFlags) {
        let transformFlags = TransformFlags.AssertTypeScript;
        const modifierFlags = getModifierFlags(node);

        if ((modifierFlags & ModifierFlags.Ambient) === 0) {
            transformFlags |= subtreeFlags;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.ModuleExcludes;
    }

    function computeVariableDeclarationList(node: VariableDeclarationList, subtreeFlags: TransformFlags) {
        let transformFlags = subtreeFlags | TransformFlags.ContainsHoistedDeclarationOrCompletion;

        if (subtreeFlags & TransformFlags.ContainsBindingPattern) {
            transformFlags |= TransformFlags.AssertES2015;
        }

        // If a VariableDeclarationList is `let` or `const`, then it is ES6 syntax.
        if (node.flags & NodeFlags.BlockScoped) {
            transformFlags |= TransformFlags.AssertES2015 | TransformFlags.ContainsBlockScopedBinding;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~TransformFlags.VariableDeclarationListExcludes;
    }

    function computeOther(node: Node, kind: SyntaxKind, subtreeFlags: TransformFlags) {
        // Mark transformations needed for each node
        let transformFlags = subtreeFlags;
        let excludeFlags = TransformFlags.NodeExcludes;

        switch (kind) {
            case SyntaxKind.AsyncKeyword:
                // async is ES2017 syntax, but may be ES2018 syntax (for async generators)
                transformFlags |= TransformFlags.AssertES2018 | TransformFlags.AssertES2017;
                break;
            case SyntaxKind.AwaitExpression:
                // await is ES2017 syntax, but may be ES2018 syntax (for async generators)
                transformFlags |= TransformFlags.AssertES2018 | TransformFlags.AssertES2017 | TransformFlags.ContainsAwait;
                break;

            case SyntaxKind.TypeAssertionExpression:
            case SyntaxKind.AsExpression:
            case SyntaxKind.PartiallyEmittedExpression:
                // These nodes are TypeScript syntax.
                transformFlags |= TransformFlags.AssertTypeScript;
                excludeFlags = TransformFlags.OuterExpressionExcludes;
                break;
            case SyntaxKind.PublicKeyword:
            case SyntaxKind.PrivateKeyword:
            case SyntaxKind.ProtectedKeyword:
            case SyntaxKind.AbstractKeyword:
            case SyntaxKind.DeclareKeyword:
            case SyntaxKind.ConstKeyword:
            case SyntaxKind.EnumDeclaration:
            case SyntaxKind.EnumMember:
            case SyntaxKind.NonNullExpression:
            case SyntaxKind.ReadonlyKeyword:
                // These nodes are TypeScript syntax.
                transformFlags |= TransformFlags.AssertTypeScript;
                break;

            case SyntaxKind.JsxElement:
            case SyntaxKind.JsxSelfClosingElement:
            case SyntaxKind.JsxOpeningElement:
            case SyntaxKind.JsxText:
            case SyntaxKind.JsxClosingElement:
            case SyntaxKind.JsxFragment:
            case SyntaxKind.JsxOpeningFragment:
            case SyntaxKind.JsxClosingFragment:
            case SyntaxKind.JsxAttribute:
            case SyntaxKind.JsxAttributes:
            case SyntaxKind.JsxSpreadAttribute:
            case SyntaxKind.JsxExpression:
                // These nodes are Jsx syntax.
                transformFlags |= TransformFlags.AssertJsx;
                break;

            case SyntaxKind.NoSubstitutionTemplateLiteral:
            case SyntaxKind.TemplateHead:
            case SyntaxKind.TemplateMiddle:
            case SyntaxKind.TemplateTail:
            case SyntaxKind.TemplateExpression:
            case SyntaxKind.TaggedTemplateExpression:
            case SyntaxKind.ShorthandPropertyAssignment:
            case SyntaxKind.StaticKeyword:
            case SyntaxKind.MetaProperty:
                // These nodes are ES6 syntax.
                transformFlags |= TransformFlags.AssertES2015;
                break;

            case SyntaxKind.StringLiteral:
                if ((<StringLiteral>node).hasExtendedUnicodeEscape) {
                    transformFlags |= TransformFlags.AssertES2015;
                }
                break;

            case SyntaxKind.NumericLiteral:
                if ((<NumericLiteral>node).numericLiteralFlags & TokenFlags.BinaryOrOctalSpecifier) {
                    transformFlags |= TransformFlags.AssertES2015;
                }
                break;

            case SyntaxKind.BigIntLiteral:
                transformFlags |= TransformFlags.AssertESNext;
                break;

            case SyntaxKind.ForOfStatement:
                // This node is either ES2015 syntax or ES2017 syntax (if it is a for-await-of).
                if ((<ForOfStatement>node).awaitModifier) {
                    transformFlags |= TransformFlags.AssertES2018;
                }
                transformFlags |= TransformFlags.AssertES2015;
                break;

            case SyntaxKind.YieldExpression:
                // This node is either ES2015 syntax (in a generator) or ES2017 syntax (in an async
                // generator).
                transformFlags |= TransformFlags.AssertES2018 | TransformFlags.AssertES2015 | TransformFlags.ContainsYield;
                break;

            case SyntaxKind.AnyKeyword:
            case SyntaxKind.NumberKeyword:
            case SyntaxKind.BigIntKeyword:
            case SyntaxKind.NeverKeyword:
            case SyntaxKind.ObjectKeyword:
            case SyntaxKind.StringKeyword:
            case SyntaxKind.BooleanKeyword:
            case SyntaxKind.SymbolKeyword:
            case SyntaxKind.VoidKeyword:
            case SyntaxKind.TypeParameter:
            case SyntaxKind.PropertySignature:
            case SyntaxKind.MethodSignature:
            case SyntaxKind.CallSignature:
            case SyntaxKind.ConstructSignature:
            case SyntaxKind.IndexSignature:
            case SyntaxKind.TypePredicate:
            case SyntaxKind.TypeReference:
            case SyntaxKind.FunctionType:
            case SyntaxKind.ConstructorType:
            case SyntaxKind.TypeQuery:
            case SyntaxKind.TypeLiteral:
            case SyntaxKind.ArrayType:
            case SyntaxKind.TupleType:
            case SyntaxKind.OptionalType:
            case SyntaxKind.RestType:
            case SyntaxKind.UnionType:
            case SyntaxKind.IntersectionType:
            case SyntaxKind.ConditionalType:
            case SyntaxKind.InferType:
            case SyntaxKind.ParenthesizedType:
            case SyntaxKind.InterfaceDeclaration:
            case SyntaxKind.TypeAliasDeclaration:
            case SyntaxKind.ThisType:
            case SyntaxKind.TypeOperator:
            case SyntaxKind.IndexedAccessType:
            case SyntaxKind.MappedType:
            case SyntaxKind.LiteralType:
            case SyntaxKind.NamespaceExportDeclaration:
                // Types and signatures are TypeScript syntax, and exclude all other facts.
                transformFlags = TransformFlags.AssertTypeScript;
                excludeFlags = TransformFlags.TypeExcludes;
                break;

            case SyntaxKind.ComputedPropertyName:
                // Even though computed property names are ES6, we don't treat them as such.
                // This is so that they can flow through PropertyName transforms unaffected.
                // Instead, we mark the container as ES6, so that it can properly handle the transform.
                transformFlags |= TransformFlags.ContainsComputedPropertyName;
                break;

            case SyntaxKind.SpreadElement:
                transformFlags |= TransformFlags.AssertES2015 | TransformFlags.ContainsRestOrSpread;
                break;

            case SyntaxKind.SpreadAssignment:
                transformFlags |= TransformFlags.AssertES2018 | TransformFlags.ContainsObjectRestOrSpread;
                break;

            case SyntaxKind.SuperKeyword:
                // This node is ES6 syntax.
                transformFlags |= TransformFlags.AssertES2015;
                excludeFlags = TransformFlags.OuterExpressionExcludes; // must be set to persist `Super`
                break;

            case SyntaxKind.ThisKeyword:
                // Mark this node and its ancestors as containing a lexical `this` keyword.
                transformFlags |= TransformFlags.ContainsLexicalThis;
                break;

            case SyntaxKind.ObjectBindingPattern:
                transformFlags |= TransformFlags.AssertES2015 | TransformFlags.ContainsBindingPattern;
                if (subtreeFlags & TransformFlags.ContainsRestOrSpread) {
                    transformFlags |= TransformFlags.AssertES2018 | TransformFlags.ContainsObjectRestOrSpread;
                }
                excludeFlags = TransformFlags.BindingPatternExcludes;
                break;

            case SyntaxKind.ArrayBindingPattern:
                transformFlags |= TransformFlags.AssertES2015 | TransformFlags.ContainsBindingPattern;
                excludeFlags = TransformFlags.BindingPatternExcludes;
                break;

            case SyntaxKind.BindingElement:
                transformFlags |= TransformFlags.AssertES2015;
                if ((<BindingElement>node).dotDotDotToken) {
                    transformFlags |= TransformFlags.ContainsRestOrSpread;
                }
                break;

            case SyntaxKind.Decorator:
                // This node is TypeScript syntax, and marks its container as also being TypeScript syntax.
                transformFlags |= TransformFlags.AssertTypeScript | TransformFlags.ContainsTypeScriptClassSyntax;
                break;

            case SyntaxKind.ObjectLiteralExpression:
                excludeFlags = TransformFlags.ObjectLiteralExcludes;
                if (subtreeFlags & TransformFlags.ContainsComputedPropertyName) {
                    // If an ObjectLiteralExpression contains a ComputedPropertyName, then it
                    // is an ES6 node.
                    transformFlags |= TransformFlags.AssertES2015;
                }

                if (subtreeFlags & TransformFlags.ContainsObjectRestOrSpread) {
                    // If an ObjectLiteralExpression contains a spread element, then it
                    // is an ES2018 node.
                    transformFlags |= TransformFlags.AssertES2018;
                }

                break;

            case SyntaxKind.ArrayLiteralExpression:
                excludeFlags = TransformFlags.ArrayLiteralOrCallOrNewExcludes;
                break;

            case SyntaxKind.DoStatement:
            case SyntaxKind.WhileStatement:
            case SyntaxKind.ForStatement:
            case SyntaxKind.ForInStatement:
                // A loop containing a block scoped binding *may* need to be transformed from ES6.
                if (subtreeFlags & TransformFlags.ContainsBlockScopedBinding) {
                    transformFlags |= TransformFlags.AssertES2015;
                }

                break;

            case SyntaxKind.SourceFile:
                break;

            case SyntaxKind.NamespaceExport:
                transformFlags |= TransformFlags.AssertESNext;
                break;

            case SyntaxKind.ReturnStatement:
                // Return statements may require an `await` in ES2018.
                transformFlags |= TransformFlags.ContainsHoistedDeclarationOrCompletion | TransformFlags.AssertES2018;
                break;

            case SyntaxKind.ContinueStatement:
            case SyntaxKind.BreakStatement:
                transformFlags |= TransformFlags.ContainsHoistedDeclarationOrCompletion;
                break;

            case SyntaxKind.PrivateIdentifier:
                transformFlags |= TransformFlags.ContainsClassFields;
                break;
        }

        node.transformFlags = transformFlags | TransformFlags.HasComputedFlags;
        return transformFlags & ~excludeFlags;
    }

    function propagatePropertyNameFlags(node: PropertyName, transformFlags: TransformFlags) {
        return transformFlags | (node.transformFlags & TransformFlags.PropertyNamePropagatingFlags);
    }

    /**
     * Gets the transform flags to exclude when unioning the transform flags of a subtree.
     *
     * NOTE: This needs to be kept up-to-date with the exclusions used in `computeTransformFlagsForNode`.
     *       For performance reasons, `computeTransformFlagsForNode` uses local constant values rather
     *       than calling this function.
     */
    export function getTransformFlagsSubtreeExclusions(kind: SyntaxKind) {
        if (kind >= SyntaxKind.FirstTypeNode && kind <= SyntaxKind.LastTypeNode) {
            return TransformFlags.TypeExcludes;
        }

        switch (kind) {
            case SyntaxKind.CallExpression:
            case SyntaxKind.NewExpression:
            case SyntaxKind.ArrayLiteralExpression:
                return TransformFlags.ArrayLiteralOrCallOrNewExcludes;
            case SyntaxKind.ModuleDeclaration:
                return TransformFlags.ModuleExcludes;
            case SyntaxKind.Parameter:
                return TransformFlags.ParameterExcludes;
            case SyntaxKind.ArrowFunction:
                return TransformFlags.ArrowFunctionExcludes;
            case SyntaxKind.FunctionExpression:
            case SyntaxKind.FunctionDeclaration:
                return TransformFlags.FunctionExcludes;
            case SyntaxKind.VariableDeclarationList:
                return TransformFlags.VariableDeclarationListExcludes;
            case SyntaxKind.ClassDeclaration:
            case SyntaxKind.ClassExpression:
                return TransformFlags.ClassExcludes;
            case SyntaxKind.Constructor:
                return TransformFlags.ConstructorExcludes;
            case SyntaxKind.MethodDeclaration:
            case SyntaxKind.GetAccessor:
            case SyntaxKind.SetAccessor:
                return TransformFlags.MethodOrAccessorExcludes;
            case SyntaxKind.AnyKeyword:
            case SyntaxKind.NumberKeyword:
            case SyntaxKind.BigIntKeyword:
            case SyntaxKind.NeverKeyword:
            case SyntaxKind.StringKeyword:
            case SyntaxKind.ObjectKeyword:
            case SyntaxKind.BooleanKeyword:
            case SyntaxKind.SymbolKeyword:
            case SyntaxKind.VoidKeyword:
            case SyntaxKind.TypeParameter:
            case SyntaxKind.PropertySignature:
            case SyntaxKind.MethodSignature:
            case SyntaxKind.CallSignature:
            case SyntaxKind.ConstructSignature:
            case SyntaxKind.IndexSignature:
            case SyntaxKind.InterfaceDeclaration:
            case SyntaxKind.TypeAliasDeclaration:
                return TransformFlags.TypeExcludes;
            case SyntaxKind.ObjectLiteralExpression:
                return TransformFlags.ObjectLiteralExcludes;
            case SyntaxKind.CatchClause:
                return TransformFlags.CatchClauseExcludes;
            case SyntaxKind.ObjectBindingPattern:
            case SyntaxKind.ArrayBindingPattern:
                return TransformFlags.BindingPatternExcludes;
            case SyntaxKind.TypeAssertionExpression:
            case SyntaxKind.AsExpression:
            case SyntaxKind.PartiallyEmittedExpression:
            case SyntaxKind.ParenthesizedExpression:
            case SyntaxKind.SuperKeyword:
                return TransformFlags.OuterExpressionExcludes;
            case SyntaxKind.PropertyAccessExpression:
            case SyntaxKind.ElementAccessExpression:
                return TransformFlags.PropertyAccessExcludes;
            default:
                return TransformFlags.NodeExcludes;
        }
    }

    /**
     * "Binds" JSDoc nodes in TypeScript code.
     * Since we will never create symbols for JSDoc, we just set parent pointers instead.
     */
    function setParentPointers(parent: Node, child: Node): void {
        child.parent = parent;
        forEachChild(child, grandchild => setParentPointers(child, grandchild));
    }
}