/* @internal */
namespace ts.FindAllReferences {
    export function findReferencedSymbols(typeChecker: TypeChecker, cancellationToken: CancellationToken, sourceFiles: SourceFile[], sourceFile: SourceFile, position: number, findInStrings: boolean, findInComments: boolean, isForRename: boolean): ReferencedSymbol[] | undefined {
        const node = getTouchingPropertyName(sourceFile, position, /*includeJsDocComment*/ true);
        return getReferencedSymbolsForNode(typeChecker, cancellationToken, node, sourceFiles, findInStrings, findInComments, isForRename);
    }

    export function convertReferences(referenceSymbols: ReferencedSymbol[]): ReferenceEntry[] {
        return referenceSymbols && flatMap(referenceSymbols, r => r.references);
    }

    export function getReferencedSymbolsForNode(typeChecker: TypeChecker, cancellationToken: CancellationToken, node: Node, sourceFiles: SourceFile[], findInStrings?: boolean, findInComments?: boolean, isForRename?: boolean, implementations?: boolean): ReferencedSymbol[] | undefined {
        if (!implementations) {
            const special = getReferencedSymbolsSpecial(node, sourceFiles, typeChecker, cancellationToken);
            if (special) {
                return special;
            }
        }

        // `getSymbolAtLocation` normally returns the symbol of the class when given the constructor keyword,
        // so we have to specify that we want the constructor symbol.
        let symbol = typeChecker.getSymbolAtLocation(node);

        // Could not find a symbol e.g. unknown identifier
        if (!symbol) {
            if (!implementations && node.kind === SyntaxKind.StringLiteral) {
                return getReferencesForStringLiteral(<StringLiteral>node, sourceFiles, typeChecker, cancellationToken);
            }
            // Can't have references to something that we have no symbol for.
            return undefined;
        }

        const declarations = symbol.declarations;

        // The symbol was an internal symbol and does not have a declaration e.g. undefined symbol
        if (!declarations || !declarations.length) {
            return undefined;
        }

        const { symbol: aliasedSymbol, shorthandModuleSymbol } = followAliases(symbol, node, typeChecker, isForRename);
        symbol = aliasedSymbol;

        // Build the set of symbols to search for, initially it has only the current symbol
        const searchSymbols = populateSearchSymbolSet(symbol, node, typeChecker, implementations);
        if (shorthandModuleSymbol) {
            searchSymbols.push(shorthandModuleSymbol);
        }

        // Compute the meaning from the location and the symbol it references
        const searchMeaning = getIntersectingMeaningFromDeclarations(getMeaningFromLocation(node), declarations);

        const result: ReferencedSymbol[] = [];
        // Maps from a symbol ID to the ReferencedSymbol entry in 'result'.
        const symbolToIndex: number[] = [];
        const inheritsFromCache: Map<boolean> = createMap<boolean>();

        // Get the text to search for.
        // Note: if this is an external module symbol, the name doesn't include quotes.
        const declaredName = stripQuotes(getDeclaredName(typeChecker, symbol, node));

        // Try to get the smallest valid scope that we can limit our search to;
        // otherwise we'll need to search globally (i.e. include each file).
        const scope = getSymbolScope(symbol);
        if (scope) {
            getRefs(scope, declaredName);
        }
        else {
            const isDefault = isExportDefaultSymbol(symbol);
            const internedName = isDefault ? symbol.valueDeclaration.localSymbol.name : getInternedName(symbol, node);
            for (const sourceFile of sourceFiles) {
                cancellationToken.throwIfCancellationRequested();
                const searchName = (isDefault ? getDefaultImportName(symbol, sourceFile, typeChecker) : undefined) ||
                    (sourceFileHasName(sourceFile, internedName) ? declaredName : undefined);
                if (searchName !== undefined) {
                    getRefs(sourceFile, searchName);
                }
            }
        }

        return result;

        function getRefs(scope: ts.Node, searchName: string): void {
            getReferencesInNode(scope, symbol, searchName, node, searchMeaning, findInStrings, findInComments, result,
                symbolToIndex, implementations, typeChecker, cancellationToken, searchSymbols, inheritsFromCache);
        }
    }

    /** getReferencedSymbols for special node kinds. */
    function getReferencedSymbolsSpecial(node: Node, sourceFiles: SourceFile[], typeChecker: TypeChecker, cancellationToken: CancellationToken): ReferencedSymbol[] | undefined {
        if (isTypeKeyword(node.kind)) {
            return getAllReferencesForKeyword(sourceFiles, node.kind, cancellationToken);
        }

        // Labels
        if (isLabelName(node)) {
            if (isJumpStatementTarget(node)) {
                const labelDefinition = getTargetLabel((<BreakOrContinueStatement>node.parent), (<Identifier>node).text);
                // if we have a label definition, look within its statement for references, if not, then
                // the label is undefined and we have no results..
                return labelDefinition && getLabelReferencesInNode(labelDefinition.parent, labelDefinition, cancellationToken);
            }
            else {
                // it is a label definition and not a target, search within the parent labeledStatement
                return getLabelReferencesInNode(node.parent, <Identifier>node, cancellationToken);
            }
        }

        if (isThis(node)) {
            return getReferencesForThisKeyword(node, sourceFiles, typeChecker, cancellationToken);
        }

        if (node.kind === SyntaxKind.SuperKeyword) {
            return getReferencesForSuperKeyword(node, typeChecker, cancellationToken);
        }

        return undefined;
    }

    /**
     * Follows aliases to get to the original declaration of a symbol.
     * For a shorthand ambient module, we don't follow the alias to it, but we will need to add it to the set of search symbols.
     */
    function followAliases(symbol: Symbol, node: Node, typeChecker: TypeChecker, isForRename: boolean): { symbol: Symbol, shorthandModuleSymbol?: Symbol } {
        while (true) {
            // When renaming a default import, only rename in the current file
            if (isForRename && isImportDefaultSymbol(symbol)) {
                return { symbol };
            }

            const aliasedSymbol = getAliasSymbolForPropertyNameSymbol(symbol, node, typeChecker);
            // Don't follow alias if it goes to unknown symbol. This can happen if it points to an untyped module.
            if (!aliasedSymbol || !aliasedSymbol.declarations) {
                return { symbol };
            }

            if (ts.isShorthandAmbientModuleSymbol(aliasedSymbol)) {
                return { symbol, shorthandModuleSymbol: aliasedSymbol };
            }

            symbol = aliasedSymbol;
        }
    }

    function sourceFileHasName(sourceFile: SourceFile, name: string): boolean {
        return getNameTable(sourceFile).get(name) !== undefined;
    }

    /**
     * Given a symbol, see if any of the imports in a source file reference it.
     * Only call this if `symbol` is a default export.
     */
    function getDefaultImportName(symbol: Symbol, sourceFile: SourceFile, checker: ts.TypeChecker): string | undefined {
        for (const importSpecifier of sourceFile.imports) {
            const importDecl = importSpecifier.parent as ts.ImportDeclaration;
            Debug.assert(importDecl.moduleSpecifier === importSpecifier);
            const defaultName = importDecl.importClause.name;
            const defaultReferencedSymbol = defaultName && checker.getAliasedSymbol(checker.getSymbolAtLocation(defaultName));
            if (symbol === defaultReferencedSymbol) {
                return defaultName.text;
            }
        }
        return undefined;
    }

    function getDefinition(symbol: Symbol, node: Node, typeChecker: TypeChecker): ReferencedSymbolDefinitionInfo {
        const { displayParts, symbolKind } = SymbolDisplay.getSymbolDisplayPartsDocumentationAndSymbolKind(typeChecker, symbol, node.getSourceFile(), getContainerNode(node), node);
        const name = displayParts.map(p => p.text).join("");
        const declarations = symbol.declarations;
        if (!declarations || declarations.length === 0) {
            return undefined;
        }

        return {
            containerKind: "",
            containerName: "",
            name,
            kind: symbolKind,
            fileName: declarations[0].getSourceFile().fileName,
            textSpan: createTextSpan(declarations[0].getStart(), 0),
            displayParts
        };
    }

    function getAliasSymbolForPropertyNameSymbol(symbol: Symbol, location: Node, typeChecker: TypeChecker): Symbol | undefined {
        if (!(symbol.flags & SymbolFlags.Alias)) {
            return undefined;
        }

        // Default import get alias
        const defaultImport = getDeclarationOfKind(symbol, SyntaxKind.ImportClause);
        if (defaultImport) {
            return typeChecker.getAliasedSymbol(symbol);
        }

        const importOrExportSpecifier = <ImportOrExportSpecifier>forEach(symbol.declarations,
            declaration => (declaration.kind === SyntaxKind.ImportSpecifier ||
                declaration.kind === SyntaxKind.ExportSpecifier) ? declaration : undefined);
        if (importOrExportSpecifier &&
            // export { a }
            (!importOrExportSpecifier.propertyName ||
                // export {a as class } where a is location
                importOrExportSpecifier.propertyName === location)) {
            // If Import specifier -> get alias
            // else Export specifier -> get local target
            return importOrExportSpecifier.kind === SyntaxKind.ImportSpecifier ?
                typeChecker.getAliasedSymbol(symbol) :
                typeChecker.getExportSpecifierLocalTargetSymbol(importOrExportSpecifier);
        }
    }

    function followAliasIfNecessary(symbol: Symbol, location: Node, typeChecker: TypeChecker): Symbol {
        return getAliasSymbolForPropertyNameSymbol(symbol, location, typeChecker) || symbol;
    }

    function getPropertySymbolOfDestructuringAssignment(location: Node, typeChecker: TypeChecker) {
        return isArrayLiteralOrObjectLiteralDestructuringPattern(location.parent.parent) &&
            typeChecker.getPropertySymbolOfDestructuringAssignment(<Identifier>location);
    }

    function isObjectBindingPatternElementWithoutPropertyName(symbol: Symbol) {
        const bindingElement = <BindingElement>getDeclarationOfKind(symbol, SyntaxKind.BindingElement);
        return bindingElement &&
            bindingElement.parent.kind === SyntaxKind.ObjectBindingPattern &&
            !bindingElement.propertyName;
    }

    function getPropertySymbolOfObjectBindingPatternWithoutPropertyName(symbol: Symbol, typeChecker: TypeChecker) {
        if (isObjectBindingPatternElementWithoutPropertyName(symbol)) {
            const bindingElement = <BindingElement>getDeclarationOfKind(symbol, SyntaxKind.BindingElement);
            const typeOfPattern = typeChecker.getTypeAtLocation(bindingElement.parent);
            return typeOfPattern && typeChecker.getPropertyOfType(typeOfPattern, (<Identifier>bindingElement.name).text);
        }
        return undefined;
    }

    function getInternedName(symbol: Symbol, location: Node): string {
        // If this is an export or import specifier it could have been renamed using the 'as' syntax.
        // If so we want to search for whatever under the cursor.
        if (isImportOrExportSpecifierName(location)) {
            return location.text;
        }

        return stripQuotes(symbol.name);
    }

    /**
     * Determines the smallest scope in which a symbol may have named references.
     * Note that not every construct has been accounted for. This function can
     * probably be improved.
     *
     * @returns undefined if the scope cannot be determined, implying that
     * a reference to a symbol can occur anywhere.
     */
    function getSymbolScope(symbol: Symbol): Node {
        // If this is the symbol of a named function expression or named class expression,
        // then named references are limited to its own scope.
        const valueDeclaration = symbol.valueDeclaration;
        if (valueDeclaration && (valueDeclaration.kind === SyntaxKind.FunctionExpression || valueDeclaration.kind === SyntaxKind.ClassExpression)) {
            return valueDeclaration;
        }

        // If this is private property or method, the scope is the containing class
        if (symbol.flags & (SymbolFlags.Property | SymbolFlags.Method)) {
            const privateDeclaration = forEach(symbol.getDeclarations(), d => (getModifierFlags(d) & ModifierFlags.Private) ? d : undefined);
            if (privateDeclaration) {
                return getAncestor(privateDeclaration, SyntaxKind.ClassDeclaration);
            }
        }

        // If the symbol is an import we would like to find it if we are looking for what it imports.
        // So consider it visible outside its declaration scope.
        if (symbol.flags & SymbolFlags.Alias) {
            return undefined;
        }

        // If symbol is of object binding pattern element without property name we would want to
        // look for property too and that could be anywhere
        if (isObjectBindingPatternElementWithoutPropertyName(symbol)) {
            return undefined;
        }

        // if this symbol is visible from its parent container, e.g. exported, then bail out
        // if symbol correspond to the union property - bail out
        if (symbol.parent || (symbol.flags & SymbolFlags.Transient && (<TransientSymbol>symbol).checkFlags & CheckFlags.SyntheticProperty)) {
            return undefined;
        }

        let scope: Node;

        const declarations = symbol.getDeclarations();
        if (declarations) {
            for (const declaration of declarations) {
                const container = getContainerNode(declaration);

                if (!container) {
                    return undefined;
                }

                if (scope && scope !== container) {
                    // Different declarations have different containers, bail out
                    return undefined;
                }

                if (container.kind === SyntaxKind.SourceFile && !isExternalModule(<SourceFile>container)) {
                    // This is a global variable and not an external module, any declaration defined
                    // within this scope is visible outside the file
                    return undefined;
                }

                // The search scope is the container node
                scope = container;
            }
        }

        return scope;
    }

    function getPossibleSymbolReferencePositions(sourceFile: SourceFile, symbolName: string, start: number, end: number, cancellationToken: CancellationToken): number[] {
        const positions: number[] = [];

        /// TODO: Cache symbol existence for files to save text search
        // Also, need to make this work for unicode escapes.

        // Be resilient in the face of a symbol with no name or zero length name
        if (!symbolName || !symbolName.length) {
            return positions;
        }

        const text = sourceFile.text;
        const sourceLength = text.length;
        const symbolNameLength = symbolName.length;

        let position = text.indexOf(symbolName, start);
        while (position >= 0) {
            cancellationToken.throwIfCancellationRequested();

            // If we are past the end, stop looking
            if (position > end) break;

            // We found a match.  Make sure it's not part of a larger word (i.e. the char
            // before and after it have to be a non-identifier char).
            const endPosition = position + symbolNameLength;

            if ((position === 0 || !isIdentifierPart(text.charCodeAt(position - 1), ScriptTarget.Latest)) &&
                (endPosition === sourceLength || !isIdentifierPart(text.charCodeAt(endPosition), ScriptTarget.Latest))) {
                // Found a real match.  Keep searching.
                positions.push(position);
            }
            position = text.indexOf(symbolName, position + symbolNameLength + 1);
        }

        return positions;
    }

    function getLabelReferencesInNode(container: Node, targetLabel: Identifier, cancellationToken: CancellationToken): ReferencedSymbol[] {
        const references: ReferenceEntry[] = [];
        const sourceFile = container.getSourceFile();
        const labelName = targetLabel.text;
        const possiblePositions = getPossibleSymbolReferencePositions(sourceFile, labelName, container.getStart(), container.getEnd(), cancellationToken);
        forEach(possiblePositions, position => {
            cancellationToken.throwIfCancellationRequested();

            const node = getTouchingWord(sourceFile, position);
            if (!node || node.getWidth() !== labelName.length) {
                return;
            }

            // Only pick labels that are either the target label, or have a target that is the target label
            if (node === targetLabel ||
                (isJumpStatementTarget(node) && getTargetLabel(node, labelName) === targetLabel)) {
                references.push(getReferenceEntryFromNode(node));
            }
        });

        const definition: ReferencedSymbolDefinitionInfo = {
            containerKind: "",
            containerName: "",
            fileName: targetLabel.getSourceFile().fileName,
            kind: ScriptElementKind.label,
            name: labelName,
            textSpan: createTextSpanFromNode(targetLabel, sourceFile),
            displayParts: [displayPart(labelName, SymbolDisplayPartKind.text)]
        };

        return [{ definition, references }];
    }

    function isValidReferencePosition(node: Node, searchSymbolName: string): boolean {
        // Compare the length so we filter out strict superstrings of the symbol we are looking for
        switch (node && node.kind) {
            case SyntaxKind.Identifier:
                return node.getWidth() === searchSymbolName.length;

            case SyntaxKind.StringLiteral:
                return (isLiteralNameOfPropertyDeclarationOrIndexAccess(node) || isNameOfExternalModuleImportOrDeclaration(node)) &&
                    // For string literals we have two additional chars for the quotes
                    node.getWidth() === searchSymbolName.length + 2;

            case SyntaxKind.NumericLiteral:
                return isLiteralNameOfPropertyDeclarationOrIndexAccess(node) && node.getWidth() === searchSymbolName.length;

            default:
                return false;
        }
    }

    function getAllReferencesForKeyword(sourceFiles: SourceFile[], keywordKind: ts.SyntaxKind, cancellationToken: CancellationToken): ReferencedSymbol[] {
        const name = tokenToString(keywordKind);
        const references: ReferenceEntry[] = [];
        for (const sourceFile of sourceFiles) {
            cancellationToken.throwIfCancellationRequested();
            addReferencesForKeywordInFile(sourceFile, keywordKind, name, cancellationToken, references);
        }

        if (!references.length) return undefined;

        const definition: ReferencedSymbolDefinitionInfo = {
            containerKind: "",
            containerName: "",
            fileName: references[0].fileName,
            kind: ScriptElementKind.keyword,
            name,
            textSpan: references[0].textSpan,
            displayParts: [{ text: name, kind: ScriptElementKind.keyword }]
        }

        return [{ definition, references }];
    }

    function addReferencesForKeywordInFile(sourceFile: SourceFile, kind: SyntaxKind, searchText: string, cancellationToken: CancellationToken, references: Push<ReferenceEntry>): void {
        const possiblePositions = getPossibleSymbolReferencePositions(sourceFile, searchText, sourceFile.getStart(), sourceFile.getEnd(), cancellationToken);
        for (const position of possiblePositions) {
            cancellationToken.throwIfCancellationRequested();
            const referenceLocation = getTouchingPropertyName(sourceFile, position);
            if (referenceLocation.kind === kind) {
                references.push({
                    textSpan: createTextSpanFromNode(referenceLocation),
                    fileName: sourceFile.fileName,
                    isWriteAccess: false,
                    isDefinition: false,
                });
            }
        }
    }

    /** Search within node "container" for references for a search value, where the search value is defined as a
         * tuple of(searchSymbol, searchText, searchLocation, and searchMeaning).
        * searchLocation: a node where the search value
        */
    function getReferencesInNode(container: Node,
        searchSymbol: Symbol,
        searchText: string,
        searchLocation: Node,
        searchMeaning: SemanticMeaning,
        findInStrings: boolean,
        findInComments: boolean,
        result: ReferencedSymbol[],
        symbolToIndex: number[],
        implementations: boolean,
        typeChecker: TypeChecker,
        cancellationToken: CancellationToken,
        searchSymbols: Symbol[],
        inheritsFromCache: Map<boolean>): void {

        const sourceFile = container.getSourceFile();

        const start = findInComments ? container.getFullStart() : container.getStart();
        const possiblePositions = getPossibleSymbolReferencePositions(sourceFile, searchText, start, container.getEnd(), cancellationToken);

        const parents = getParentSymbolsOfPropertyAccess();

        for (const position of possiblePositions) {
            cancellationToken.throwIfCancellationRequested();

            const referenceLocation = getTouchingPropertyName(sourceFile, position);
            if (!isValidReferencePosition(referenceLocation, searchText)) {
                // This wasn't the start of a token.  Check to see if it might be a
                // match in a comment or string if that's what the caller is asking
                // for.
                if (!implementations && ((findInStrings && isInString(sourceFile, position)) ||
                    (findInComments && isInNonReferenceComment(sourceFile, position)))) {

                    // In the case where we're looking inside comments/strings, we don't have
                    // an actual definition.  So just use 'undefined' here.  Features like
                    // 'Rename' won't care (as they ignore the definitions), and features like
                    // 'FindReferences' will just filter out these results.
                    result.push({
                        definition: undefined,
                        references: [{
                            fileName: sourceFile.fileName,
                            textSpan: createTextSpan(position, searchText.length),
                            isWriteAccess: false,
                            isDefinition: false
                        }]
                    });
                }
                continue;
            }

            if (!(getMeaningFromLocation(referenceLocation) & searchMeaning)) {
                continue;
            }

            const referenceSymbol = typeChecker.getSymbolAtLocation(referenceLocation);
            if (referenceSymbol) {
                const referenceSymbolDeclaration = referenceSymbol.valueDeclaration;
                const shorthandValueSymbol = typeChecker.getShorthandAssignmentValueSymbol(referenceSymbolDeclaration);
                const relatedSymbol = getRelatedSymbol(searchSymbols, referenceSymbol, referenceLocation,
                    /*searchLocationIsConstructor*/ searchLocation.kind === SyntaxKind.ConstructorKeyword, parents, inheritsFromCache, typeChecker);

                if (relatedSymbol) {
                    addReferenceToRelatedSymbol(referenceLocation, relatedSymbol);
                }
                /* Because in short-hand property assignment, an identifier which stored as name of the short-hand property assignment
                 * has two meanings: property name and property value. Therefore when we do findAllReference at the position where
                 * an identifier is declared, the language service should return the position of the variable declaration as well as
                 * the position in short-hand property assignment excluding property accessing. However, if we do findAllReference at the
                 * position of property accessing, the referenceEntry of such position will be handled in the first case.
                 */
                else if (!(referenceSymbol.flags & SymbolFlags.Transient) && contains(searchSymbols, shorthandValueSymbol)) {
                    addReferenceToRelatedSymbol(referenceSymbolDeclaration.name, shorthandValueSymbol);
                }
                else if (searchLocation.kind === SyntaxKind.ConstructorKeyword) {
                    findAdditionalConstructorReferences(referenceSymbol, referenceLocation);
                }
            }
        }
        return;

        /* If we are just looking for implementations and this is a property access expression, we need to get the
         * symbol of the local type of the symbol the property is being accessed on. This is because our search
         * symbol may have a different parent symbol if the local type's symbol does not declare the property
         * being accessed (i.e. it is declared in some parent class or interface)
         */
        function getParentSymbolsOfPropertyAccess(): Symbol[] | undefined {
            if (implementations) {
                const propertyAccessExpression = getPropertyAccessExpressionFromRightHandSide(searchLocation);
                if (propertyAccessExpression) {
                    const localParentType = typeChecker.getTypeAtLocation(propertyAccessExpression.expression);
                    if (localParentType) {
                        if (localParentType.symbol && localParentType.symbol.flags & (SymbolFlags.Class | SymbolFlags.Interface) && localParentType.symbol !== searchSymbol.parent) {
                            return [localParentType.symbol];
                        }
                        else if (localParentType.flags & TypeFlags.UnionOrIntersection) {
                            return getSymbolsForClassAndInterfaceComponents(<UnionOrIntersectionType>localParentType);
                        }
                    }
                }
            }
        }

        /** Adds references when a constructor is used with `new this()` in its own class and `super()` calls in subclasses.  */
        function findAdditionalConstructorReferences(referenceSymbol: Symbol, referenceLocation: Node): void {
            Debug.assert(isClassLike(searchSymbol.valueDeclaration));

            const referenceClass = referenceLocation.parent;
            if (referenceSymbol === searchSymbol && isClassLike(referenceClass)) {
                Debug.assert(referenceClass.name === referenceLocation);
                // This is the class declaration containing the constructor.
                addReferences(findOwnConstructorCalls(searchSymbol, sourceFile));
            }
            else {
                // If this class appears in `extends C`, then the extending class' "super" calls are references.
                const classExtending = tryGetClassByExtendingIdentifier(referenceLocation);
                if (classExtending && isClassLike(classExtending) && followAliasIfNecessary(referenceSymbol, referenceLocation, typeChecker) === searchSymbol) {
                    addReferences(superConstructorAccesses(classExtending));
                }
            }
        }

        function addReferences(references: Node[]): void {
            if (references.length) {
                const referencedSymbol = getReferencedSymbol(searchSymbol);
                addRange(referencedSymbol.references, map(references, getReferenceEntryFromNode));
            }
        }

        function getReferencedSymbol(symbol: Symbol): ReferencedSymbol {
            const symbolId = getSymbolId(symbol);
            let index = symbolToIndex[symbolId];
            if (index === undefined) {
                index = result.length;
                symbolToIndex[symbolId] = index;

                result.push({
                    definition: getDefinition(symbol, searchLocation, typeChecker),
                    references: []
                });
            }

            return result[index];
        }

        function addReferenceToRelatedSymbol(node: Node, relatedSymbol: Symbol) {
            const references = getReferencedSymbol(relatedSymbol).references;
            if (implementations) {
                getImplementationReferenceEntryForNode(node, references, typeChecker);
            }
            else {
                references.push(getReferenceEntryFromNode(node));
            }
        }
    }

    function getPropertyAccessExpressionFromRightHandSide(node: Node): PropertyAccessExpression {
        return isRightSideOfPropertyAccess(node) && <PropertyAccessExpression>node.parent;
    }

    /** `classSymbol` is the class where the constructor was defined.
     * Reference the constructor and all calls to `new this()`.
     */
    function findOwnConstructorCalls(classSymbol: Symbol, sourceFile: SourceFile): Node[] {
        const result: Node[] = [];

        for (const decl of classSymbol.members.get("__constructor").declarations) {
            const ctrKeyword = ts.findChildOfKind(decl, ts.SyntaxKind.ConstructorKeyword, sourceFile)!
            Debug.assert(decl.kind === SyntaxKind.Constructor && !!ctrKeyword);
            result.push(ctrKeyword);
        }

        classSymbol.exports.forEach(member => {
            const decl = member.valueDeclaration;
            if (decl && decl.kind === SyntaxKind.MethodDeclaration) {
                const body = (<MethodDeclaration>decl).body;
                if (body) {
                    forEachDescendantOfKind(body, SyntaxKind.ThisKeyword, thisKeyword => {
                        if (isNewExpressionTarget(thisKeyword)) {
                            result.push(thisKeyword);
                        }
                    });
                }
            }
        });

        return result;
    }

    /** Find references to `super` in the constructor of an extending class.  */
    function superConstructorAccesses(cls: ClassLikeDeclaration): Node[] {
        const symbol = cls.symbol;
        const ctr = symbol.members.get("__constructor");
        if (!ctr) {
            return [];
        }

        const result: Node[] = [];
        for (const decl of ctr.declarations) {
            Debug.assert(decl.kind === SyntaxKind.Constructor);
            const body = (<ConstructorDeclaration>decl).body;
            if (body) {
                forEachDescendantOfKind(body, SyntaxKind.SuperKeyword, node => {
                    if (isCallExpressionTarget(node)) {
                        result.push(node);
                    }
                });
            }
        };
        return result;
    }

    function getImplementationReferenceEntryForNode(refNode: Node, result: ReferenceEntry[], typeChecker: TypeChecker): void {
        // Check if we found a function/propertyAssignment/method with an implementation or initializer
        if (isDeclarationName(refNode) && isImplementation(refNode.parent)) {
            result.push(getReferenceEntryFromNode(refNode.parent));
        }
        else if (refNode.kind === SyntaxKind.Identifier) {
            if (refNode.parent.kind === SyntaxKind.ShorthandPropertyAssignment) {
                // Go ahead and dereference the shorthand assignment by going to its definition
                getReferenceEntriesForShorthandPropertyAssignment(refNode, typeChecker, result);
            }

            // Check if the node is within an extends or implements clause
            const containingClass = getContainingClassIfInHeritageClause(refNode);
            if (containingClass) {
                result.push(getReferenceEntryFromNode(containingClass));
                return;
            }

            // If we got a type reference, try and see if the reference applies to any expressions that can implement an interface
            const containingTypeReference = getContainingTypeReference(refNode);
            if (containingTypeReference) {
                const parent = containingTypeReference.parent;
                if (isVariableLike(parent) && parent.type === containingTypeReference && parent.initializer && isImplementationExpression(parent.initializer)) {
                    maybeAdd(getReferenceEntryFromNode(parent.initializer));
                }
                else if (isFunctionLike(parent) && parent.type === containingTypeReference && parent.body) {
                    if (parent.body.kind === SyntaxKind.Block) {
                        forEachReturnStatement(<Block>parent.body, returnStatement => {
                            if (returnStatement.expression && isImplementationExpression(returnStatement.expression)) {
                                maybeAdd(getReferenceEntryFromNode(returnStatement.expression));
                            }
                        });
                    }
                    else if (isImplementationExpression(<Expression>parent.body)) {
                        maybeAdd(getReferenceEntryFromNode(parent.body));
                    }
                }
                else if (isAssertionExpression(parent) && isImplementationExpression(parent.expression)) {
                    maybeAdd(getReferenceEntryFromNode(parent.expression));
                }
            }
        }

        // Type nodes can contain multiple references to the same type. For example:
        //      let x: Foo & (Foo & Bar) = ...
        // Because we are returning the implementation locations and not the identifier locations,
        // duplicate entries would be returned here as each of the type references is part of
        // the same implementation. For that reason, check before we add a new entry
        function maybeAdd(a: ReferenceEntry) {
            if (!forEach(result, b => a.fileName === b.fileName && a.textSpan.start === b.textSpan.start && a.textSpan.length === b.textSpan.length)) {
                result.push(a);
            }
        }
    }

    function getSymbolsForClassAndInterfaceComponents(type: UnionOrIntersectionType, result: Symbol[] = []): Symbol[] {
        for (const componentType of type.types) {
            if (componentType.symbol && componentType.symbol.getFlags() & (SymbolFlags.Class | SymbolFlags.Interface)) {
                result.push(componentType.symbol);
            }
            if (componentType.getFlags() & TypeFlags.UnionOrIntersection) {
                getSymbolsForClassAndInterfaceComponents(<UnionOrIntersectionType>componentType, result);
            }
        }
        return result;
    }

    function getContainingTypeReference(node: Node): Node {
        let topLevelTypeReference: Node = undefined;

        while (node) {
            if (isTypeNode(node)) {
                topLevelTypeReference = node;
            }
            node = node.parent;
        }

        return topLevelTypeReference;
    }

    function getContainingClassIfInHeritageClause(node: Node): ClassLikeDeclaration {
        if (node && node.parent) {
            if (node.kind === SyntaxKind.ExpressionWithTypeArguments
                && node.parent.kind === SyntaxKind.HeritageClause
                && isClassLike(node.parent.parent)) {
                return node.parent.parent;
            }

            else if (node.kind === SyntaxKind.Identifier || node.kind === SyntaxKind.PropertyAccessExpression) {
                return getContainingClassIfInHeritageClause(node.parent);
            }
        }
        return undefined;
    }

    /**
     * Returns true if this is an expression that can be considered an implementation
     */
    function isImplementationExpression(node: Expression): boolean {
        switch (node.kind) {
            case SyntaxKind.ParenthesizedExpression:
                return isImplementationExpression((<ParenthesizedExpression>node).expression);
            case SyntaxKind.ArrowFunction:
            case SyntaxKind.FunctionExpression:
            case SyntaxKind.ObjectLiteralExpression:
            case SyntaxKind.ClassExpression:
            case SyntaxKind.ArrayLiteralExpression:
                return true;
            default:
                return false;
        }
    }

    /**
     * Determines if the parent symbol occurs somewhere in the child's ancestry. If the parent symbol
     * is an interface, determines if some ancestor of the child symbol extends or inherits from it.
     * Also takes in a cache of previous results which makes this slightly more efficient and is
     * necessary to avoid potential loops like so:
     *     class A extends B { }
     *     class B extends A { }
     *
     * We traverse the AST rather than using the type checker because users are typically only interested
     * in explicit implementations of an interface/class when calling "Go to Implementation". Sibling
     * implementations of types that share a common ancestor with the type whose implementation we are
     * searching for need to be filtered out of the results. The type checker doesn't let us make the
     * distinction between structurally compatible implementations and explicit implementations, so we
     * must use the AST.
     *
     * @param child         A class or interface Symbol
     * @param parent        Another class or interface Symbol
     * @param cachedResults A map of symbol id pairs (i.e. "child,parent") to booleans indicating previous results
     */
    function explicitlyInheritsFrom(child: Symbol, parent: Symbol, cachedResults: Map<boolean>, typeChecker: TypeChecker): boolean {
        const parentIsInterface = parent.getFlags() & SymbolFlags.Interface;
        return searchHierarchy(child);

        function searchHierarchy(symbol: Symbol): boolean {
            if (symbol === parent) {
                return true;
            }

            const key = getSymbolId(symbol) + "," + getSymbolId(parent);
            const cached = cachedResults.get(key);
            if (cached !== undefined) {
                return cached;
            }

            // Set the key so that we don't infinitely recurse
            cachedResults.set(key, false);

            const inherits = forEach(symbol.getDeclarations(), declaration => {
                if (isClassLike(declaration)) {
                    if (parentIsInterface) {
                        const interfaceReferences = getClassImplementsHeritageClauseElements(declaration);
                        if (interfaceReferences) {
                            for (const typeReference of interfaceReferences) {
                                if (searchTypeReference(typeReference)) {
                                    return true;
                                }
                            }
                        }
                    }
                    return searchTypeReference(getClassExtendsHeritageClauseElement(declaration));
                }
                else if (declaration.kind === SyntaxKind.InterfaceDeclaration) {
                    if (parentIsInterface) {
                        return forEach(getInterfaceBaseTypeNodes(<InterfaceDeclaration>declaration), searchTypeReference);
                    }
                }
                return false;
            });

            cachedResults.set(key, inherits);
            return inherits;
        }

        function searchTypeReference(typeReference: ExpressionWithTypeArguments): boolean {
            if (typeReference) {
                const type = typeChecker.getTypeAtLocation(typeReference);
                if (type && type.symbol) {
                    return searchHierarchy(type.symbol);
                }
            }
            return false;
        }
    }

    function getReferencesForSuperKeyword(superKeyword: Node, typeChecker: TypeChecker, cancellationToken: CancellationToken): ReferencedSymbol[] {
        let searchSpaceNode = getSuperContainer(superKeyword, /*stopOnFunctions*/ false);
        if (!searchSpaceNode) {
            return undefined;
        }
        // Whether 'super' occurs in a static context within a class.
        let staticFlag = ModifierFlags.Static;

        switch (searchSpaceNode.kind) {
            case SyntaxKind.PropertyDeclaration:
            case SyntaxKind.PropertySignature:
            case SyntaxKind.MethodDeclaration:
            case SyntaxKind.MethodSignature:
            case SyntaxKind.Constructor:
            case SyntaxKind.GetAccessor:
            case SyntaxKind.SetAccessor:
                staticFlag &= getModifierFlags(searchSpaceNode);
                searchSpaceNode = searchSpaceNode.parent; // re-assign to be the owning class
                break;
            default:
                return undefined;
        }

        const references: ReferenceEntry[] = [];

        const sourceFile = searchSpaceNode.getSourceFile();
        const possiblePositions = getPossibleSymbolReferencePositions(sourceFile, "super", searchSpaceNode.getStart(), searchSpaceNode.getEnd(), cancellationToken);
        for (const position of possiblePositions) {
            cancellationToken.throwIfCancellationRequested();

            const node = getTouchingWord(sourceFile, position);

            if (!node || node.kind !== SyntaxKind.SuperKeyword) {
                continue;
            }

            const container = getSuperContainer(node, /*stopOnFunctions*/ false);

            // If we have a 'super' container, we must have an enclosing class.
            // Now make sure the owning class is the same as the search-space
            // and has the same static qualifier as the original 'super's owner.
            if (container && (ModifierFlags.Static & getModifierFlags(container)) === staticFlag && container.parent.symbol === searchSpaceNode.symbol) {
                references.push(getReferenceEntryFromNode(node));
            }
        }

        const definition = getDefinition(searchSpaceNode.symbol, superKeyword, typeChecker);
        return [{ definition, references }];
    }

    function getReferencesForThisKeyword(thisOrSuperKeyword: Node, sourceFiles: SourceFile[], typeChecker: TypeChecker, cancellationToken: CancellationToken): ReferencedSymbol[] {
        let searchSpaceNode = getThisContainer(thisOrSuperKeyword, /* includeArrowFunctions */ false);

        // Whether 'this' occurs in a static context within a class.
        let staticFlag = ModifierFlags.Static;

        switch (searchSpaceNode.kind) {
            case SyntaxKind.MethodDeclaration:
            case SyntaxKind.MethodSignature:
                if (isObjectLiteralMethod(searchSpaceNode)) {
                    break;
                }
            // fall through
            case SyntaxKind.PropertyDeclaration:
            case SyntaxKind.PropertySignature:
            case SyntaxKind.Constructor:
            case SyntaxKind.GetAccessor:
            case SyntaxKind.SetAccessor:
                staticFlag &= getModifierFlags(searchSpaceNode);
                searchSpaceNode = searchSpaceNode.parent; // re-assign to be the owning class
                break;
            case SyntaxKind.SourceFile:
                if (isExternalModule(<SourceFile>searchSpaceNode)) {
                    return undefined;
                }
            // Fall through
            case SyntaxKind.FunctionDeclaration:
            case SyntaxKind.FunctionExpression:
                break;
            // Computed properties in classes are not handled here because references to this are illegal,
            // so there is no point finding references to them.
            default:
                return undefined;
        }

        const references: ReferenceEntry[] = [];

        let possiblePositions: number[];
        if (searchSpaceNode.kind === SyntaxKind.SourceFile) {
            forEach(sourceFiles, sourceFile => {
                possiblePositions = getPossibleSymbolReferencePositions(sourceFile, "this", sourceFile.getStart(), sourceFile.getEnd(), cancellationToken);
                getThisReferencesInFile(sourceFile, sourceFile, possiblePositions, references);
            });
        }
        else {
            const sourceFile = searchSpaceNode.getSourceFile();
            possiblePositions = getPossibleSymbolReferencePositions(sourceFile, "this", searchSpaceNode.getStart(), searchSpaceNode.getEnd(), cancellationToken);
            getThisReferencesInFile(sourceFile, searchSpaceNode, possiblePositions, references);
        }

        const thisOrSuperSymbol = typeChecker.getSymbolAtLocation(thisOrSuperKeyword);

        const displayParts = thisOrSuperSymbol && SymbolDisplay.getSymbolDisplayPartsDocumentationAndSymbolKind(
            typeChecker, thisOrSuperSymbol, thisOrSuperKeyword.getSourceFile(), getContainerNode(thisOrSuperKeyword), thisOrSuperKeyword).displayParts;

        return [{
            definition: {
                containerKind: "",
                containerName: "",
                fileName: thisOrSuperKeyword.getSourceFile().fileName,
                kind: ScriptElementKind.variableElement,
                name: "this",
                textSpan: createTextSpanFromNode(thisOrSuperKeyword),
                displayParts
            },
            references: references
        }];

        function getThisReferencesInFile(sourceFile: SourceFile, searchSpaceNode: Node, possiblePositions: number[], result: ReferenceEntry[]): void {
            forEach(possiblePositions, position => {
                cancellationToken.throwIfCancellationRequested();

                const node = getTouchingWord(sourceFile, position);
                if (!node || !isThis(node)) {
                    return;
                }

                const container = getThisContainer(node, /* includeArrowFunctions */ false);

                switch (searchSpaceNode.kind) {
                    case SyntaxKind.FunctionExpression:
                    case SyntaxKind.FunctionDeclaration:
                        if (searchSpaceNode.symbol === container.symbol) {
                            result.push(getReferenceEntryFromNode(node));
                        }
                        break;
                    case SyntaxKind.MethodDeclaration:
                    case SyntaxKind.MethodSignature:
                        if (isObjectLiteralMethod(searchSpaceNode) && searchSpaceNode.symbol === container.symbol) {
                            result.push(getReferenceEntryFromNode(node));
                        }
                        break;
                    case SyntaxKind.ClassExpression:
                    case SyntaxKind.ClassDeclaration:
                        // Make sure the container belongs to the same class
                        // and has the appropriate static modifier from the original container.
                        if (container.parent && searchSpaceNode.symbol === container.parent.symbol && (getModifierFlags(container) & ModifierFlags.Static) === staticFlag) {
                            result.push(getReferenceEntryFromNode(node));
                        }
                        break;
                    case SyntaxKind.SourceFile:
                        if (container.kind === SyntaxKind.SourceFile && !isExternalModule(<SourceFile>container)) {
                            result.push(getReferenceEntryFromNode(node));
                        }
                        break;
                }
            });
        }
    }

    function getReferencesForStringLiteral(node: StringLiteral, sourceFiles: SourceFile[], typeChecker: TypeChecker, cancellationToken: CancellationToken): ReferencedSymbol[] {
        const type = getStringLiteralTypeForNode(node, typeChecker);

        if (!type) {
            // nothing to do here. moving on
            return undefined;
        }

        const references: ReferenceEntry[] = [];

        for (const sourceFile of sourceFiles) {
            const possiblePositions = getPossibleSymbolReferencePositions(sourceFile, type.text, sourceFile.getStart(), sourceFile.getEnd(), cancellationToken);
            getReferencesForStringLiteralInFile(sourceFile, type, possiblePositions, references);
        }

        return [{
            definition: {
                containerKind: "",
                containerName: "",
                fileName: node.getSourceFile().fileName,
                kind: ScriptElementKind.variableElement,
                name: type.text,
                textSpan: createTextSpanFromNode(node),
                displayParts: [displayPart(getTextOfNode(node), SymbolDisplayPartKind.stringLiteral)]
            },
            references: references
        }];

        function getReferencesForStringLiteralInFile(sourceFile: SourceFile, searchType: Type, possiblePositions: number[], references: ReferenceEntry[]): void {
            for (const position of possiblePositions) {
                cancellationToken.throwIfCancellationRequested();

                const node = getTouchingWord(sourceFile, position);
                if (!node || node.kind !== SyntaxKind.StringLiteral) {
                    return;
                }

                const type = getStringLiteralTypeForNode(<StringLiteral>node, typeChecker);
                if (type === searchType) {
                    references.push(getReferenceEntryFromNode(node));
                }
            }
        }
    }

    function populateSearchSymbolSet(symbol: Symbol, location: Node, typeChecker: TypeChecker, implementations: boolean): Symbol[] {
        // The search set contains at least the current symbol
        const result = [symbol];

        // If the location is name of property symbol from object literal destructuring pattern
        // Search the property symbol
        //      for ( { property: p2 } of elems) { }
        const containingObjectLiteralElement = getContainingObjectLiteralElement(location);
        if (containingObjectLiteralElement && containingObjectLiteralElement.kind !== SyntaxKind.ShorthandPropertyAssignment) {
            const propertySymbol = getPropertySymbolOfDestructuringAssignment(location, typeChecker);
            if (propertySymbol) {
                result.push(propertySymbol);
            }
        }

        // If the location is in a context sensitive location (i.e. in an object literal) try
        // to get a contextual type for it, and add the property symbol from the contextual
        // type to the search set
        if (containingObjectLiteralElement) {
            forEach(getPropertySymbolsFromContextualType(containingObjectLiteralElement, typeChecker), contextualSymbol => {
                addRange(result, typeChecker.getRootSymbols(contextualSymbol));
            });

            /* Because in short-hand property assignment, location has two meaning : property name and as value of the property
                * When we do findAllReference at the position of the short-hand property assignment, we would want to have references to position of
                * property name and variable declaration of the identifier.
                * Like in below example, when querying for all references for an identifier 'name', of the property assignment, the language service
                * should show both 'name' in 'obj' and 'name' in variable declaration
                *      const name = "Foo";
                *      const obj = { name };
                * In order to do that, we will populate the search set with the value symbol of the identifier as a value of the property assignment
                * so that when matching with potential reference symbol, both symbols from property declaration and variable declaration
                * will be included correctly.
                */
            const shorthandValueSymbol = typeChecker.getShorthandAssignmentValueSymbol(location.parent);
            if (shorthandValueSymbol) {
                result.push(shorthandValueSymbol);
            }
        }

        // If the symbol.valueDeclaration is a property parameter declaration,
        // we should include both parameter declaration symbol and property declaration symbol
        // Parameter Declaration symbol is only visible within function scope, so the symbol is stored in constructor.locals.
        // Property Declaration symbol is a member of the class, so the symbol is stored in its class Declaration.symbol.members
        if (symbol.valueDeclaration && symbol.valueDeclaration.kind === SyntaxKind.Parameter &&
            isParameterPropertyDeclaration(<ParameterDeclaration>symbol.valueDeclaration)) {
            addRange(result, typeChecker.getSymbolsOfParameterPropertyDeclaration(<ParameterDeclaration>symbol.valueDeclaration, symbol.name));
        }

        // If this is symbol of binding element without propertyName declaration in Object binding pattern
        // Include the property in the search
        const bindingElementPropertySymbol = getPropertySymbolOfObjectBindingPatternWithoutPropertyName(symbol, typeChecker);
        if (bindingElementPropertySymbol) {
            result.push(bindingElementPropertySymbol);
        }

        // If this is a union property, add all the symbols from all its source symbols in all unioned types.
        // If the symbol is an instantiation from a another symbol (e.g. widened symbol) , add the root the list
        for (const rootSymbol of typeChecker.getRootSymbols(symbol)) {
            if (rootSymbol !== symbol) {
                result.push(rootSymbol);
            }

            // Add symbol of properties/methods of the same name in base classes and implemented interfaces definitions
            if (!implementations && rootSymbol.parent && rootSymbol.parent.flags & (SymbolFlags.Class | SymbolFlags.Interface)) {
                getPropertySymbolsFromBaseTypes(rootSymbol.parent, rootSymbol.getName(), result, /*previousIterationSymbolsCache*/ createMap<Symbol>(), typeChecker);
            }
        }

        return result;
    }

    /**
     * Find symbol of the given property-name and add the symbol to the given result array
     * @param symbol a symbol to start searching for the given propertyName
     * @param propertyName a name of property to search for
     * @param result an array of symbol of found property symbols
     * @param previousIterationSymbolsCache a cache of symbol from previous iterations of calling this function to prevent infinite revisiting of the same symbol.
     *                                The value of previousIterationSymbol is undefined when the function is first called.
     */
    function getPropertySymbolsFromBaseTypes(symbol: Symbol, propertyName: string, result: Symbol[],
        previousIterationSymbolsCache: SymbolTable, typeChecker: TypeChecker): void {
        if (!symbol) {
            return;
        }

        // If the current symbol is the same as the previous-iteration symbol, we can just return the symbol that has already been visited
        // This is particularly important for the following cases, so that we do not infinitely visit the same symbol.
        // For example:
        //      interface C extends C {
        //          /*findRef*/propName: string;
        //      }
        // The first time getPropertySymbolsFromBaseTypes is called when finding-all-references at propName,
        // the symbol argument will be the symbol of an interface "C" and previousIterationSymbol is undefined,
        // the function will add any found symbol of the property-name, then its sub-routine will call
        // getPropertySymbolsFromBaseTypes again to walk up any base types to prevent revisiting already
        // visited symbol, interface "C", the sub-routine will pass the current symbol as previousIterationSymbol.
        if (previousIterationSymbolsCache.has(symbol.name)) {
            return;
        }

        if (symbol.flags & (SymbolFlags.Class | SymbolFlags.Interface)) {
            forEach(symbol.getDeclarations(), declaration => {
                if (isClassLike(declaration)) {
                    getPropertySymbolFromTypeReference(getClassExtendsHeritageClauseElement(<ClassDeclaration>declaration));
                    forEach(getClassImplementsHeritageClauseElements(<ClassDeclaration>declaration), getPropertySymbolFromTypeReference);
                }
                else if (declaration.kind === SyntaxKind.InterfaceDeclaration) {
                    forEach(getInterfaceBaseTypeNodes(<InterfaceDeclaration>declaration), getPropertySymbolFromTypeReference);
                }
            });
        }
        return;

        function getPropertySymbolFromTypeReference(typeReference: ExpressionWithTypeArguments) {
            if (typeReference) {
                const type = typeChecker.getTypeAtLocation(typeReference);
                if (type) {
                    const propertySymbol = typeChecker.getPropertyOfType(type, propertyName);
                    if (propertySymbol) {
                        result.push(...typeChecker.getRootSymbols(propertySymbol));
                    }

                    // Visit the typeReference as well to see if it directly or indirectly use that property
                    previousIterationSymbolsCache.set(symbol.name, symbol);
                    getPropertySymbolsFromBaseTypes(type.symbol, propertyName, result, previousIterationSymbolsCache, typeChecker);
                }
            }
        }
    }

    function getRelatedSymbol(searchSymbols: Symbol[], referenceSymbol: Symbol, referenceLocation: Node, searchLocationIsConstructor: boolean, parents: Symbol[] | undefined, cache: Map<boolean>, typeChecker: TypeChecker): Symbol | undefined {
        if (contains(searchSymbols, referenceSymbol)) {
            // If we are searching for constructor uses, they must be 'new' expressions.
            return (!searchLocationIsConstructor || isNewExpressionTarget(referenceLocation)) ? referenceSymbol : undefined;
        }

        // If the reference symbol is an alias, check if what it is aliasing is one of the search
        // symbols but by looking up for related symbol of this alias so it can handle multiple level of indirectness.
        const aliasSymbol = getAliasSymbolForPropertyNameSymbol(referenceSymbol, referenceLocation, typeChecker);
        if (aliasSymbol) {
            return getRelatedSymbol(searchSymbols, aliasSymbol, referenceLocation, searchLocationIsConstructor, parents, cache, typeChecker);
        }

        // If the reference location is in an object literal, try to get the contextual type for the
        // object literal, lookup the property symbol in the contextual type, and use this symbol to
        // compare to our searchSymbol
        const containingObjectLiteralElement = getContainingObjectLiteralElement(referenceLocation);
        if (containingObjectLiteralElement) {
            const contextualSymbol = forEach(getPropertySymbolsFromContextualType(containingObjectLiteralElement, typeChecker), contextualSymbol =>
                find(typeChecker.getRootSymbols(contextualSymbol), symbol => contains(searchSymbols, symbol)));

            if (contextualSymbol) {
                return contextualSymbol;
            }

            // If the reference location is the name of property from object literal destructuring pattern
            // Get the property symbol from the object literal's type and look if thats the search symbol
            // In below eg. get 'property' from type of elems iterating type
            //      for ( { property: p2 } of elems) { }
            const propertySymbol = getPropertySymbolOfDestructuringAssignment(referenceLocation, typeChecker);
            if (propertySymbol && contains(searchSymbols, propertySymbol)) {
                return propertySymbol;
            }
        }

        // If the reference location is the binding element and doesn't have property name
        // then include the binding element in the related symbols
        //      let { a } : { a };
        const bindingElementPropertySymbol = getPropertySymbolOfObjectBindingPatternWithoutPropertyName(referenceSymbol, typeChecker);
        if (bindingElementPropertySymbol && contains(searchSymbols, bindingElementPropertySymbol)) {
            return bindingElementPropertySymbol;
        }

        // Unwrap symbols to get to the root (e.g. transient symbols as a result of widening)
        // Or a union property, use its underlying unioned symbols
        return forEach(typeChecker.getRootSymbols(referenceSymbol), rootSymbol => {
            // if it is in the list, then we are done
            if (contains(searchSymbols, rootSymbol)) {
                return rootSymbol;
            }

            // Finally, try all properties with the same name in any type the containing type extended or implemented, and
            // see if any is in the list. If we were passed a parent symbol, only include types that are subtypes of the
            // parent symbol
            if (rootSymbol.parent && rootSymbol.parent.flags & (SymbolFlags.Class | SymbolFlags.Interface)) {
                // Parents will only be defined if implementations is true
                if (parents) {
                    if (!forEach(parents, parent => explicitlyInheritsFrom(rootSymbol.parent, parent, cache, typeChecker))) {
                        return undefined;
                    }
                }

                const result: Symbol[] = [];
                getPropertySymbolsFromBaseTypes(rootSymbol.parent, rootSymbol.getName(), result, /*previousIterationSymbolsCache*/ createMap<Symbol>(), typeChecker);
                return find(result, symbol => contains(searchSymbols, symbol));
            }

            return undefined;
        });
    }

    function getNameFromObjectLiteralElement(node: ObjectLiteralElement) {
        if (node.name.kind === SyntaxKind.ComputedPropertyName) {
            const nameExpression = (<ComputedPropertyName>node.name).expression;
            // treat computed property names where expression is string/numeric literal as just string/numeric literal
            if (isStringOrNumericLiteral(nameExpression)) {
                return (<LiteralExpression>nameExpression).text;
            }
            return undefined;
        }
        return (<Identifier | LiteralExpression>node.name).text;
    }

    /** Gets all symbols for one property. Does not get symbols for every property. */
    function getPropertySymbolsFromContextualType(node: ObjectLiteralElement, typeChecker: TypeChecker): Symbol[] | undefined {
        const objectLiteral = <ObjectLiteralExpression>node.parent;
        const contextualType = typeChecker.getContextualType(objectLiteral);
        const name = getNameFromObjectLiteralElement(node);
        if (name && contextualType) {
            const result: Symbol[] = [];
            const symbol = contextualType.getProperty(name);
            if (symbol) {
                result.push(symbol);
            }

            if (contextualType.flags & TypeFlags.Union) {
                forEach((<UnionType>contextualType).types, t => {
                    const symbol = t.getProperty(name);
                    if (symbol) {
                        result.push(symbol);
                    }
                });
            }
            return result;
        }
        return undefined;
    }

    /**
     * Given an initial searchMeaning, extracted from a location, widen the search scope based on the declarations
     * of the corresponding symbol. e.g. if we are searching for "Foo" in value position, but "Foo" references a class
     * then we need to widen the search to include type positions as well.
     * On the contrary, if we are searching for "Bar" in type position and we trace bar to an interface, and an uninstantiated
     * module, we want to keep the search limited to only types, as the two declarations (interface and uninstantiated module)
     * do not intersect in any of the three spaces.
     */
    function getIntersectingMeaningFromDeclarations(meaning: SemanticMeaning, declarations: Declaration[]): SemanticMeaning {
        if (declarations) {
            let lastIterationMeaning: SemanticMeaning;
            do {
                // The result is order-sensitive, for instance if initialMeaning === Namespace, and declarations = [class, instantiated module]
                // we need to consider both as they initialMeaning intersects with the module in the namespace space, and the module
                // intersects with the class in the value space.
                // To achieve that we will keep iterating until the result stabilizes.

                // Remember the last meaning
                lastIterationMeaning = meaning;

                for (const declaration of declarations) {
                    const declarationMeaning = getMeaningFromDeclaration(declaration);

                    if (declarationMeaning & meaning) {
                        meaning |= declarationMeaning;
                    }
                }
            }
            while (meaning !== lastIterationMeaning);
        }
        return meaning;
    }

    function isImplementation(node: Node): boolean {
        if (!node) {
            return false;
        }
        else if (isVariableLike(node)) {
            if (node.initializer) {
                return true;
            }
            else if (node.kind === SyntaxKind.VariableDeclaration) {
                const parentStatement = getParentStatementOfVariableDeclaration(<VariableDeclaration>node);
                return parentStatement && hasModifier(parentStatement, ModifierFlags.Ambient);
            }
        }
        else if (isFunctionLike(node)) {
            return !!node.body || hasModifier(node, ModifierFlags.Ambient);
        }
        else {
            switch (node.kind) {
                case SyntaxKind.ClassDeclaration:
                case SyntaxKind.ClassExpression:
                case SyntaxKind.EnumDeclaration:
                case SyntaxKind.ModuleDeclaration:
                    return true;
            }
        }
        return false;
    }

    function getParentStatementOfVariableDeclaration(node: VariableDeclaration): VariableStatement {
        if (node.parent && node.parent.parent && node.parent.parent.kind === SyntaxKind.VariableStatement) {
            Debug.assert(node.parent.kind === SyntaxKind.VariableDeclarationList);
            return <VariableStatement>node.parent.parent;
        }
    }

    export function getReferenceEntriesForShorthandPropertyAssignment(node: Node, typeChecker: TypeChecker, result: ReferenceEntry[]): void {
        const refSymbol = typeChecker.getSymbolAtLocation(node);
        const shorthandSymbol = typeChecker.getShorthandAssignmentValueSymbol(refSymbol.valueDeclaration);

        if (shorthandSymbol) {
            for (const declaration of shorthandSymbol.getDeclarations()) {
                if (getMeaningFromDeclaration(declaration) & SemanticMeaning.Value) {
                    result.push(getReferenceEntryFromNode(declaration));
                }
            }
        }
    }

    export function getReferenceEntryFromNode(node: Node): ReferenceEntry {
        let start = node.getStart();
        let end = node.getEnd();

        if (node.kind === SyntaxKind.StringLiteral) {
            start += 1;
            end -= 1;
        }

        return {
            fileName: node.getSourceFile().fileName,
            textSpan: createTextSpanFromBounds(start, end),
            isWriteAccess: isWriteAccess(node),
            isDefinition: isDeclarationName(node) || isLiteralComputedPropertyDeclarationName(node)
        };
    }

    /** A node is considered a writeAccess iff it is a name of a declaration or a target of an assignment */
    function isWriteAccess(node: Node): boolean {
        if (node.kind === SyntaxKind.Identifier && isDeclarationName(node)) {
            return true;
        }

        const parent = node.parent;
        if (parent) {
            if (parent.kind === SyntaxKind.PostfixUnaryExpression || parent.kind === SyntaxKind.PrefixUnaryExpression) {
                return true;
            }
            else if (parent.kind === SyntaxKind.BinaryExpression && (<BinaryExpression>parent).left === node) {
                const operator = (<BinaryExpression>parent).operatorToken.kind;
                return SyntaxKind.FirstAssignment <= operator && operator <= SyntaxKind.LastAssignment;
            }
        }

        return false;
    }

    function forEachDescendantOfKind(node: Node, kind: SyntaxKind, action: (node: Node) => void) {
        forEachChild(node, child => {
            if (child.kind === kind) {
                action(child);
            }
            forEachDescendantOfKind(child, kind, action);
        });
    }

    /**
     * Returns the containing object literal property declaration given a possible name node, e.g. "a" in x = { "a": 1 }
     */
    function getContainingObjectLiteralElement(node: Node): ObjectLiteralElement {
        switch (node.kind) {
            case SyntaxKind.StringLiteral:
            case SyntaxKind.NumericLiteral:
                if (node.parent.kind === SyntaxKind.ComputedPropertyName) {
                    return isObjectLiteralPropertyDeclaration(node.parent.parent) ? node.parent.parent : undefined;
                }
            // intential fall through
            case SyntaxKind.Identifier:
                return isObjectLiteralPropertyDeclaration(node.parent) && node.parent.name === node ? node.parent : undefined;
        }
        return undefined;
    }

    function isObjectLiteralPropertyDeclaration(node: Node): node is ObjectLiteralElement  {
        switch (node.kind) {
            case SyntaxKind.PropertyAssignment:
            case SyntaxKind.ShorthandPropertyAssignment:
            case SyntaxKind.MethodDeclaration:
            case SyntaxKind.GetAccessor:
            case SyntaxKind.SetAccessor:
                return true;
        }
        return false;
    }

    /** Get `C` given `N` if `N` is in the position `class C extends N` or `class C extends foo.N` where `N` is an identifier. */
    function tryGetClassByExtendingIdentifier(node: Node): ClassLikeDeclaration | undefined {
        return tryGetClassExtendingExpressionWithTypeArguments(climbPastPropertyAccess(node).parent);
    }

    function isNameOfExternalModuleImportOrDeclaration(node: Node): boolean {
        if (node.kind === SyntaxKind.StringLiteral) {
            return isNameOfModuleDeclaration(node) || isExpressionOfExternalModuleImportEqualsDeclaration(node);
        }

        return false;
    }

    function isImportDefaultSymbol(symbol: Symbol): boolean {
        return symbol.declarations[0].kind === SyntaxKind.ImportClause;
    }
}