diff --git a/.mailmap b/.mailmap
index 4f27b3087b8..774aa4174c3 100644
--- a/.mailmap
+++ b/.mailmap
@@ -139,7 +139,6 @@ Michael  <maykelchiche@gmail.com>
 Mike Busyrev  <busyrev@gmail.com>
 Mine Starks  <minestarks@users.noreply.github.com> Mine Starks  <mineyalc@microsoft.com>
 Mohamed Hegazy <mhegazy@microsoft.com>
-ncoley  <nrcoley@gmail.com> # Natalie Coley
 Nathan Shively-Sanders <nathansa@microsoft.com> Nathan Shively-Sanders  <293473+sandersn@users.noreply.github.com>
 Nathan Yee <ny.nathan.yee@gmail.com>
 Nima Zahedi <nima.zahedee@gmail.com>
diff --git a/Gulpfile.js b/Gulpfile.js
index 1ba05048578..89fe32fed2e 100644
--- a/Gulpfile.js
+++ b/Gulpfile.js
@@ -128,7 +128,7 @@ const generatedLCGFile = "built/local/enu/diagnosticMessages.generated.json.lcg"
  *    2. 'src\compiler\diagnosticMessages.generated.json' => 'built\local\ENU\diagnosticMessages.generated.json.lcg'
  *       generate the lcg file (source of messages to localize) from the diagnosticMessages.generated.json
  */
-const localizationTargets = ["cs", "de", "es", "fr", "it", "ja", "ko", "pl", "pt-br", "ru", "tr", "zh-cn", "zh-tw"]
+const localizationTargets = ["cs", "de", "es", "fr", "it", "ja", "ko", "pl", "pt-BR", "ru", "tr", "zh-CN", "zh-TW"]
     .map(f => `built/local/${f}/diagnosticMessages.generated.json`)
     .concat(generatedLCGFile);
 
diff --git a/Jakefile.js b/Jakefile.js
index 0793659183b..ce5576036f4 100644
--- a/Jakefile.js
+++ b/Jakefile.js
@@ -21,7 +21,7 @@ else if (process.env.PATH !== undefined) {
 
 const host = process.env.TYPESCRIPT_HOST || process.env.host || "node";
 
-const locales = ["cs", "de", "es", "fr", "it", "ja", "ko", "pl", "pt-br", "ru", "tr", "zh-cn", "zh-tw"];
+const locales = ["cs", "de", "es", "fr", "it", "ja", "ko", "pl", "pt-BR", "ru", "tr", "zh-CN", "zh-TW"];
 
 const defaultTestTimeout = 40000;
 
@@ -69,10 +69,10 @@ Paths.tsserverLibraryDefinitionFile = "built/local/tsserverlibrary.d.ts";
 Paths.baselines = {};
 Paths.baselines.local = "tests/baselines/local";
 Paths.baselines.localTest262 = "tests/baselines/test262/local";
-Paths.baselines.localRwc = "tests/baselines/rwc/local";
+Paths.baselines.localRwc = "internal/baselines/rwc/local";
 Paths.baselines.reference = "tests/baselines/reference";
 Paths.baselines.referenceTest262 = "tests/baselines/test262/reference";
-Paths.baselines.referenceRwc = "tests/baselines/rwc/reference";
+Paths.baselines.referenceRwc = "internal/baselines/rwc/reference";
 Paths.copyright = "CopyrightNotice.txt";
 Paths.thirdParty = "ThirdPartyNoticeText.txt";
 Paths.processDiagnosticMessagesJs = "scripts/processDiagnosticMessages.js";
@@ -174,7 +174,7 @@ task(TaskNames.lkg, [
         if (sizeAfter > (sizeBefore * 1.10)) {
             throw new Error("The lib folder increased by 10% or more. This likely indicates a bug.");
         }
-    
+
         complete();
     });
 }, { async: true });
@@ -349,7 +349,7 @@ file(Paths.servicesDefinitionFile, [TaskNames.coreBuild], function() {
         },
         files
     };
-    
+
     const configFilePath = `built/local/typescriptServices.tsconfig.json`;
     fs.writeFileSync(configFilePath, JSON.stringify(config, undefined, 2));
     tsbuild(configFilePath, false, () => {
@@ -696,8 +696,8 @@ function diagnosticsToString(diagnostics, pretty) {
 
 /**
  * Concatenate a list of sourceFiles to a destinationFile
- * @param {string} destinationFile 
- * @param {string[]} sourceFiles 
+ * @param {string} destinationFile
+ * @param {string[]} sourceFiles
  * @param {string} extraContent
  */
 function concatenateFiles(destinationFile, sourceFiles, extraContent) {
@@ -724,8 +724,8 @@ function appendToFile(path, content) {
 }
 
 /**
- * 
- * @param {string} path 
+ *
+ * @param {string} path
  * @returns string
  */
 function readFileSync(path) {
@@ -742,7 +742,7 @@ function getDiffTool() {
 
 /**
  * Replaces const enum declarations with non-const enums
- * @param {string} text 
+ * @param {string} text
  */
 function removeConstModifierFromEnumDeclarations(text) {
     return text.replace(/^(\s*)(export )?const enum (\S+) {(\s*)$/gm, '$1$2enum $3 {$4');
diff --git a/scripts/generateLocalizedDiagnosticMessages.ts b/scripts/generateLocalizedDiagnosticMessages.ts
index 566eb557fd5..09d117d533b 100644
--- a/scripts/generateLocalizedDiagnosticMessages.ts
+++ b/scripts/generateLocalizedDiagnosticMessages.ts
@@ -65,11 +65,10 @@ function main(): void {
      * There are three exceptions, zh-CN, zh-TW and pt-BR.
      */
     function getPreferedLocaleName(localeName: string) {
-        localeName = localeName.toLowerCase();
         switch (localeName) {
-            case "zh-cn":
-            case "zh-tw":
-            case "pt-br":
+            case "zh-CN":
+            case "zh-TW":
+            case "pt-BR":
                 return localeName;
             default:
                 return localeName.split("-")[0];
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 1ecf30690a0..3867a26c023 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -2283,16 +2283,24 @@ namespace ts {
         }
 
         function errorOnImplicitAnyModule(isError: boolean, errorNode: Node, { packageId, resolvedFileName }: ResolvedModuleFull, moduleReference: string): void {
-            const errorInfo = packageId && chainDiagnosticMessages(
-                /*details*/ undefined,
-                Diagnostics.Try_npm_install_types_Slash_0_if_it_exists_or_add_a_new_declaration_d_ts_file_containing_declare_module_0,
-                getMangledNameForScopedPackage(packageId.name));
+            const errorInfo = packageId
+                ? chainDiagnosticMessages(
+                    /*details*/ undefined,
+                    typesPackageExists(packageId.name)
+                        ? Diagnostics.If_the_0_package_actually_exposes_this_module_consider_sending_a_pull_request_to_amend_https_Colon_Slash_Slashgithub_com_SlashDefinitelyTyped_SlashDefinitelyTyped_Slashtree_Slashmaster_Slashtypes_Slash_0
+                        : Diagnostics.Try_npm_install_types_Slash_0_if_it_exists_or_add_a_new_declaration_d_ts_file_containing_declare_module_0,
+                    getMangledNameForScopedPackage(packageId.name))
+                : undefined;
             errorOrSuggestion(isError, errorNode, chainDiagnosticMessages(
                 errorInfo,
                 Diagnostics.Could_not_find_a_declaration_file_for_module_0_1_implicitly_has_an_any_type,
                 moduleReference,
                 resolvedFileName));
         }
+        function typesPackageExists(packageName: string): boolean {
+            return host.getSourceFiles().some(sf => !!sf.resolvedModules && !!forEachEntry(sf.resolvedModules, r =>
+                r && r.packageId && r.packageId.name === getTypesPackageName(packageName)));
+        }
 
         // An external module with an 'export =' declaration resolves to the target of the 'export =' declaration,
         // and an external module with no 'export =' declaration resolves to the module itself.
@@ -2589,7 +2597,7 @@ namespace ts {
             return type;
         }
 
-        function createBooleanType(trueFalseTypes: Type[]): IntrinsicType & UnionType {
+        function createBooleanType(trueFalseTypes: ReadonlyArray<Type>): IntrinsicType & UnionType {
             const type = <IntrinsicType & UnionType>getUnionType(trueFalseTypes);
             type.flags |= TypeFlags.Boolean;
             type.intrinsicName = "boolean";
@@ -2631,7 +2639,7 @@ namespace ts {
             return result || emptyArray;
         }
 
-        function setStructuredTypeMembers(type: StructuredType, members: SymbolTable, callSignatures: Signature[], constructSignatures: Signature[], stringIndexInfo: IndexInfo | undefined, numberIndexInfo: IndexInfo | undefined): ResolvedType {
+        function setStructuredTypeMembers(type: StructuredType, members: SymbolTable, callSignatures: ReadonlyArray<Signature>, constructSignatures: ReadonlyArray<Signature>, stringIndexInfo: IndexInfo | undefined, numberIndexInfo: IndexInfo | undefined): ResolvedType {
             (<ResolvedType>type).members = members;
             (<ResolvedType>type).properties = getNamedMembers(members);
             (<ResolvedType>type).callSignatures = callSignatures;
@@ -2641,7 +2649,7 @@ namespace ts {
             return <ResolvedType>type;
         }
 
-        function createAnonymousType(symbol: Symbol | undefined, members: SymbolTable, callSignatures: Signature[], constructSignatures: Signature[], stringIndexInfo: IndexInfo | undefined, numberIndexInfo: IndexInfo | undefined): ResolvedType {
+        function createAnonymousType(symbol: Symbol | undefined, members: SymbolTable, callSignatures: ReadonlyArray<Signature>, constructSignatures: ReadonlyArray<Signature>, stringIndexInfo: IndexInfo | undefined, numberIndexInfo: IndexInfo | undefined): ResolvedType {
             return setStructuredTypeMembers(createObjectType(ObjectFlags.Anonymous, symbol),
                 members, callSignatures, constructSignatures, stringIndexInfo, numberIndexInfo);
         }
@@ -3387,7 +3395,7 @@ namespace ts {
                 }
 
                 function typeReferenceToTypeNode(type: TypeReference) {
-                    const typeArguments: Type[] = type.typeArguments || emptyArray;
+                    const typeArguments: ReadonlyArray<Type> = type.typeArguments || emptyArray;
                     if (type.target === globalArrayType) {
                         if (context.flags & NodeBuilderFlags.WriteArrayAsGenericType) {
                             const typeArgumentNode = typeToTypeNodeHelper(typeArguments[0], context);
@@ -3583,7 +3591,7 @@ namespace ts {
                 }
             }
 
-            function mapToTypeNodes(types: Type[] | undefined, context: NodeBuilderContext): TypeNode[] | undefined {
+            function mapToTypeNodes(types: ReadonlyArray<Type> | undefined, context: NodeBuilderContext): TypeNode[] | undefined {
                 if (some(types)) {
                     const result = [];
                     for (const type of types) {
@@ -3992,7 +4000,7 @@ namespace ts {
             }
         }
 
-        function formatUnionTypes(types: Type[]): Type[] {
+        function formatUnionTypes(types: ReadonlyArray<Type>): Type[] {
             const result: Type[] = [];
             let flags: TypeFlags = 0;
             for (let i = 0; i < types.length; i++) {
@@ -4110,15 +4118,14 @@ namespace ts {
                 if (declaration.parent && declaration.parent.kind === SyntaxKind.VariableDeclaration) {
                     return declarationNameToString((<VariableDeclaration>declaration.parent).name);
                 }
-                if (context && !context.encounteredError && !(context.flags & NodeBuilderFlags.AllowAnonymousIdentifier)) {
-                    context.encounteredError = true;
-                }
                 switch (declaration.kind) {
                     case SyntaxKind.ClassExpression:
-                        return "(Anonymous class)";
                     case SyntaxKind.FunctionExpression:
                     case SyntaxKind.ArrowFunction:
-                        return "(Anonymous function)";
+                        if (context && !context.encounteredError && !(context.flags & NodeBuilderFlags.AllowAnonymousIdentifier)) {
+                            context.encounteredError = true;
+                        }
+                        return declaration.kind === SyntaxKind.ClassExpression ? "(Anonymous class)" : "(Anonymous function)";
                 }
             }
             const nameType = symbol.nameType;
@@ -5393,26 +5400,17 @@ namespace ts {
         }
 
         function getBaseTypeNodeOfClass(type: InterfaceType): ExpressionWithTypeArguments | undefined {
-            const decl = <ClassLikeDeclaration>type.symbol.valueDeclaration;
-            if (isInJavaScriptFile(decl)) {
-                // Prefer an @augments tag because it may have type parameters.
-                const tag = getJSDocAugmentsTag(decl);
-                if (tag) {
-                    return tag.class;
-                }
-            }
-
-            return getClassExtendsHeritageClauseElement(decl);
+            return getEffectiveBaseTypeNode(type.symbol.valueDeclaration as ClassLikeDeclaration);
         }
 
-        function getConstructorsForTypeArguments(type: Type, typeArgumentNodes: ReadonlyArray<TypeNode> | undefined, location: Node): Signature[] {
+        function getConstructorsForTypeArguments(type: Type, typeArgumentNodes: ReadonlyArray<TypeNode> | undefined, location: Node): ReadonlyArray<Signature> {
             const typeArgCount = length(typeArgumentNodes);
             const isJavaScript = isInJavaScriptFile(location);
             return filter(getSignaturesOfType(type, SignatureKind.Construct),
                 sig => (isJavaScript || typeArgCount >= getMinTypeArgumentCount(sig.typeParameters)) && typeArgCount <= length(sig.typeParameters));
         }
 
-        function getInstantiatedConstructorsForTypeArguments(type: Type, typeArgumentNodes: ReadonlyArray<TypeNode> | undefined, location: Node): Signature[] {
+        function getInstantiatedConstructorsForTypeArguments(type: Type, typeArgumentNodes: ReadonlyArray<TypeNode> | undefined, location: Node): ReadonlyArray<Signature> {
             const signatures = getConstructorsForTypeArguments(type, typeArgumentNodes, location);
             const typeArguments = map(typeArgumentNodes, getTypeFromTypeNode);
             return sameMap<Signature>(signatures, sig => some(sig.typeParameters) ? getSignatureInstantiation(sig, typeArguments, isInJavaScriptFile(location)) : sig);
@@ -5429,7 +5427,7 @@ namespace ts {
         function getBaseConstructorTypeOfClass(type: InterfaceType): Type {
             if (!type.resolvedBaseConstructorType) {
                 const decl = <ClassLikeDeclaration>type.symbol.valueDeclaration;
-                const extended = getClassExtendsHeritageClauseElement(decl);
+                const extended = getEffectiveBaseTypeNode(decl);
                 const baseTypeNode = getBaseTypeNodeOfClass(type);
                 if (!baseTypeNode) {
                     return type.resolvedBaseConstructorType = undefinedType;
@@ -6162,11 +6160,11 @@ namespace ts {
             return needApparentType ? getApparentType(type) : type;
         }
 
-        function resolveObjectTypeMembers(type: ObjectType, source: InterfaceTypeWithDeclaredMembers, typeParameters: TypeParameter[], typeArguments: Type[]) {
+        function resolveObjectTypeMembers(type: ObjectType, source: InterfaceTypeWithDeclaredMembers, typeParameters: ReadonlyArray<TypeParameter>, typeArguments: ReadonlyArray<Type>) {
             let mapper: TypeMapper;
             let members: SymbolTable;
-            let callSignatures: Signature[];
-            let constructSignatures: Signature[] | undefined;
+            let callSignatures: ReadonlyArray<Signature>;
+            let constructSignatures: ReadonlyArray<Signature> | undefined;
             let stringIndexInfo: IndexInfo | undefined;
             let numberIndexInfo: IndexInfo | undefined;
             if (rangeEquals(typeParameters, typeArguments, 0, typeParameters.length)) {
@@ -6222,9 +6220,9 @@ namespace ts {
 
         function createSignature(
             declaration: SignatureDeclaration | JSDocSignature | undefined,
-            typeParameters: TypeParameter[] | undefined,
+            typeParameters: ReadonlyArray<TypeParameter> | undefined,
             thisParameter: Symbol | undefined,
-            parameters: Symbol[],
+            parameters: ReadonlyArray<Symbol>,
             resolvedReturnType: Type | undefined,
             resolvedTypePredicate: TypePredicate | undefined,
             minArgumentCount: number,
@@ -6275,7 +6273,7 @@ namespace ts {
             return result;
         }
 
-        function findMatchingSignature(signatureList: Signature[], signature: Signature, partialMatch: boolean, ignoreThisTypes: boolean, ignoreReturnTypes: boolean): Signature | undefined {
+        function findMatchingSignature(signatureList: ReadonlyArray<Signature>, signature: Signature, partialMatch: boolean, ignoreThisTypes: boolean, ignoreReturnTypes: boolean): Signature | undefined {
             for (const s of signatureList) {
                 if (compareSignaturesIdentical(s, signature, partialMatch, ignoreThisTypes, ignoreReturnTypes, compareTypesIdentical)) {
                     return s;
@@ -6283,7 +6281,7 @@ namespace ts {
             }
         }
 
-        function findMatchingSignatures(signatureLists: Signature[][], signature: Signature, listIndex: number): Signature[] | undefined {
+        function findMatchingSignatures(signatureLists: ReadonlyArray<ReadonlyArray<Signature>>, signature: Signature, listIndex: number): Signature[] | undefined {
             if (signature.typeParameters) {
                 // We require an exact match for generic signatures, so we only return signatures from the first
                 // signature list and only if they have exact matches in the other signature lists.
@@ -6313,7 +6311,7 @@ namespace ts {
         // Generic signatures must match exactly, but non-generic signatures are allowed to have extra optional
         // parameters and may differ in return types. When signatures differ in return types, the resulting return
         // type is the union of the constituent return types.
-        function getUnionSignatures(types: Type[], kind: SignatureKind): Signature[] {
+        function getUnionSignatures(types: ReadonlyArray<Type>, kind: SignatureKind): Signature[] {
             const signatureLists = map(types, t => getSignaturesOfType(t, kind));
             let result: Signature[] | undefined;
             for (let i = 0; i < signatureLists.length; i++) {
@@ -6343,7 +6341,7 @@ namespace ts {
             return result || emptyArray;
         }
 
-        function getUnionIndexInfo(types: Type[], kind: IndexKind): IndexInfo | undefined {
+        function getUnionIndexInfo(types: ReadonlyArray<Type>, kind: IndexKind): IndexInfo | undefined {
             const indexTypes: Type[] = [];
             let isAnyReadonly = false;
             for (const type of types) {
@@ -6383,7 +6381,7 @@ namespace ts {
                 getUnionType([info1.type, info2.type]), info1.isReadonly || info2.isReadonly);
         }
 
-        function includeMixinType(type: Type, types: Type[], index: number): Type {
+        function includeMixinType(type: Type, types: ReadonlyArray<Type>, index: number): Type {
             const mixedTypes: Type[] = [];
             for (let i = 0; i < types.length; i++) {
                 if (i === index) {
@@ -6399,8 +6397,8 @@ namespace ts {
         function resolveIntersectionTypeMembers(type: IntersectionType) {
             // The members and properties collections are empty for intersection types. To get all properties of an
             // intersection type use getPropertiesOfType (only the language service uses this).
-            let callSignatures: Signature[] = emptyArray;
-            let constructSignatures: Signature[] = emptyArray;
+            let callSignatures: ReadonlyArray<Signature> = emptyArray;
+            let constructSignatures: ReadonlyArray<Signature> = emptyArray;
             let stringIndexInfo: IndexInfo | undefined;
             let numberIndexInfo: IndexInfo | undefined;
             const types = type.types;
@@ -6738,7 +6736,7 @@ namespace ts {
                 getPropertiesOfObjectType(type);
         }
 
-        function getAllPossiblePropertiesOfTypes(types: Type[]): Symbol[] {
+        function getAllPossiblePropertiesOfTypes(types: ReadonlyArray<Type>): Symbol[] {
             const unionType = getUnionType(types);
             if (!(unionType.flags & TypeFlags.Union)) {
                 return getAugmentedPropertiesOfType(unionType);
@@ -7142,7 +7140,7 @@ namespace ts {
             return undefined;
         }
 
-        function getSignaturesOfStructuredType(type: Type, kind: SignatureKind): Signature[] {
+        function getSignaturesOfStructuredType(type: Type, kind: SignatureKind): ReadonlyArray<Signature> {
             if (type.flags & TypeFlags.StructuredType) {
                 const resolved = resolveStructuredTypeMembers(<ObjectType>type);
                 return kind === SignatureKind.Call ? resolved.callSignatures : resolved.constructSignatures;
@@ -7154,7 +7152,7 @@ namespace ts {
          * Return the signatures of the given kind in the given type. Creates synthetic union signatures when necessary and
          * maps primitive types and type parameters are to their apparent types.
          */
-        function getSignaturesOfType(type: Type, kind: SignatureKind): Signature[] {
+        function getSignaturesOfType(type: Type, kind: SignatureKind): ReadonlyArray<Signature> {
             return getSignaturesOfStructuredType(getApparentType(type), kind);
         }
 
@@ -7289,7 +7287,7 @@ namespace ts {
          * Gets the minimum number of type arguments needed to satisfy all non-optional type
          * parameters.
          */
-        function getMinTypeArgumentCount(typeParameters: TypeParameter[] | undefined): number {
+        function getMinTypeArgumentCount(typeParameters: ReadonlyArray<TypeParameter> | undefined): number {
             let minTypeArgumentCount = 0;
             if (typeParameters) {
                 for (let i = 0; i < typeParameters.length; i++) {
@@ -7309,9 +7307,9 @@ namespace ts {
          * @param typeParameters The requested type parameters.
          * @param minTypeArgumentCount The minimum number of required type arguments.
          */
-        function fillMissingTypeArguments(typeArguments: Type[], typeParameters: TypeParameter[] | undefined, minTypeArgumentCount: number, isJavaScriptImplicitAny: boolean): Type[];
-        function fillMissingTypeArguments(typeArguments: Type[] | undefined, typeParameters: TypeParameter[] | undefined, minTypeArgumentCount: number, isJavaScriptImplicitAny: boolean): Type[] | undefined;
-        function fillMissingTypeArguments(typeArguments: Type[] | undefined, typeParameters: TypeParameter[] | undefined, minTypeArgumentCount: number, isJavaScriptImplicitAny: boolean) {
+        function fillMissingTypeArguments(typeArguments: Type[], typeParameters: ReadonlyArray<TypeParameter> | undefined, minTypeArgumentCount: number, isJavaScriptImplicitAny: boolean): Type[];
+        function fillMissingTypeArguments(typeArguments: Type[] | undefined, typeParameters: ReadonlyArray<TypeParameter> | undefined, minTypeArgumentCount: number, isJavaScriptImplicitAny: boolean): Type[] | undefined;
+        function fillMissingTypeArguments(typeArguments: Type[] | undefined, typeParameters: ReadonlyArray<TypeParameter> | undefined, minTypeArgumentCount: number, isJavaScriptImplicitAny: boolean) {
             const numTypeParameters = length(typeParameters);
             if (numTypeParameters) {
                 const numTypeArguments = length(typeArguments);
@@ -7606,7 +7604,9 @@ namespace ts {
         }
 
         function getSignatureInstantiation(signature: Signature, typeArguments: Type[] | undefined, isJavascript: boolean): Signature {
-            typeArguments = fillMissingTypeArguments(typeArguments, signature.typeParameters, getMinTypeArgumentCount(signature.typeParameters), isJavascript)!;
+            return getSignatureInstantiationWithoutFillingInTypeArguments(signature, fillMissingTypeArguments(typeArguments, signature.typeParameters, getMinTypeArgumentCount(signature.typeParameters), isJavascript));
+        }
+        function getSignatureInstantiationWithoutFillingInTypeArguments(signature: Signature, typeArguments: ReadonlyArray<Type> | undefined): Signature {
             const instantiations = signature.instantiations || (signature.instantiations = createMap<Signature>());
             const id = getTypeListId(typeArguments);
             let instantiation = instantiations.get(id);
@@ -7616,10 +7616,10 @@ namespace ts {
             return instantiation;
         }
 
-        function createSignatureInstantiation(signature: Signature, typeArguments: Type[]): Signature {
+        function createSignatureInstantiation(signature: Signature, typeArguments: ReadonlyArray<Type> | undefined): Signature {
             return instantiateSignature(signature, createSignatureTypeMapper(signature, typeArguments), /*eraseTypeParameters*/ true);
         }
-        function createSignatureTypeMapper(signature: Signature, typeArguments: Type[]): TypeMapper {
+        function createSignatureTypeMapper(signature: Signature, typeArguments: ReadonlyArray<Type> | undefined): TypeMapper {
             return createTypeMapper(signature.typeParameters!, typeArguments);
         }
 
@@ -7776,7 +7776,7 @@ namespace ts {
             return getSymbolOfNode(getDeclarationOfKind(typeParameter.symbol, SyntaxKind.TypeParameter)!.parent);
         }
 
-        function getTypeListId(types: Type[] | undefined) {
+        function getTypeListId(types: ReadonlyArray<Type> | undefined) {
             let result = "";
             if (types) {
                 const length = types.length;
@@ -7804,7 +7804,7 @@ namespace ts {
         // It is only necessary to do so if a constituent type might be the undefined type, the null type, the type
         // of an object literal or the anyFunctionType. This is because there are operations in the type checker
         // that care about the presence of such types at arbitrary depth in a containing type.
-        function getPropagatingFlagsOfTypes(types: Type[], excludeKinds: TypeFlags): TypeFlags {
+        function getPropagatingFlagsOfTypes(types: ReadonlyArray<Type>, excludeKinds: TypeFlags): TypeFlags {
             let result: TypeFlags = 0;
             for (const type of types) {
                 if (!(type.flags & excludeKinds)) {
@@ -7814,7 +7814,7 @@ namespace ts {
             return result & TypeFlags.PropagatingFlags;
         }
 
-        function createTypeReference(target: GenericType, typeArguments: Type[] | undefined): TypeReference {
+        function createTypeReference(target: GenericType, typeArguments: ReadonlyArray<Type> | undefined): TypeReference {
             const id = getTypeListId(typeArguments);
             let type = target.instantiations.get(id);
             if (!type) {
@@ -8261,7 +8261,7 @@ namespace ts {
         /**
          * Instantiates a global type that is generic with some element type, and returns that instantiation.
          */
-        function createTypeFromGenericGlobalType(genericGlobalType: GenericType, typeArguments: Type[]): ObjectType {
+        function createTypeFromGenericGlobalType(genericGlobalType: GenericType, typeArguments: ReadonlyArray<Type>): ObjectType {
             return genericGlobalType !== emptyGenericType ? createTypeReference(genericGlobalType, typeArguments) : emptyObjectType;
         }
 
@@ -8340,7 +8340,7 @@ namespace ts {
             return tupleTypes[arity] || (tupleTypes[arity] = createTupleTypeOfArity(arity));
         }
 
-        function createTupleType(elementTypes: Type[]) {
+        function createTupleType(elementTypes: ReadonlyArray<Type>) {
             return createTypeReference(getTupleTypeOfArity(elementTypes.length), elementTypes);
         }
 
@@ -8356,7 +8356,7 @@ namespace ts {
             return type.id;
         }
 
-        function containsType(types: Type[], type: Type): boolean {
+        function containsType(types: ReadonlyArray<Type>, type: Type): boolean {
             return binarySearch(types, type, getTypeId, compareValues) >= 0;
         }
 
@@ -8420,14 +8420,14 @@ namespace ts {
 
         // Add the given types to the given type set. Order is preserved, duplicates are removed,
         // and nested types of the given kind are flattened into the set.
-        function addTypesToUnion(typeSet: Type[], includes: TypeFlags, types: Type[]): TypeFlags {
+        function addTypesToUnion(typeSet: Type[], includes: TypeFlags, types: ReadonlyArray<Type>): TypeFlags {
             for (const type of types) {
                 includes = addTypeToUnion(typeSet, includes, type);
             }
             return includes;
         }
 
-        function containsIdenticalType(types: Type[], type: Type) {
+        function containsIdenticalType(types: ReadonlyArray<Type>, type: Type) {
             for (const t of types) {
                 if (isTypeIdenticalTo(t, type)) {
                     return true;
@@ -8436,7 +8436,7 @@ namespace ts {
             return false;
         }
 
-        function isSubtypeOfAny(source: Type, targets: Type[]): boolean {
+        function isSubtypeOfAny(source: Type, targets: ReadonlyArray<Type>): boolean {
             for (const target of targets) {
                 if (source !== target && isTypeSubtypeOf(source, target) && (
                     !(getObjectFlags(getTargetType(source)) & ObjectFlags.Class) ||
@@ -8448,7 +8448,7 @@ namespace ts {
             return false;
         }
 
-        function isSetOfLiteralsFromSameEnum(types: Type[]): boolean {
+        function isSetOfLiteralsFromSameEnum(types: ReadonlyArray<Type>): boolean {
             const first = types[0];
             if (first.flags & TypeFlags.EnumLiteral) {
                 const firstEnum = getParentOfSymbol(first.symbol);
@@ -8500,7 +8500,7 @@ namespace ts {
         // expression constructs such as array literals and the || and ?: operators). Named types can
         // circularly reference themselves and therefore cannot be subtype reduced during their declaration.
         // For example, "type Item = string | (() => Item" is a named type that circularly references itself.
-        function getUnionType(types: Type[], unionReduction: UnionReduction = UnionReduction.Literal, aliasSymbol?: Symbol, aliasTypeArguments?: Type[]): Type {
+        function getUnionType(types: ReadonlyArray<Type>, unionReduction: UnionReduction = UnionReduction.Literal, aliasSymbol?: Symbol, aliasTypeArguments?: ReadonlyArray<Type>): Type {
             if (types.length === 0) {
                 return neverType;
             }
@@ -8567,7 +8567,7 @@ namespace ts {
         }
 
         // This function assumes the constituent type list is sorted and deduplicated.
-        function getUnionTypeFromSortedList(types: Type[], unionOfUnitTypes: TypeFlags, aliasSymbol?: Symbol, aliasTypeArguments?: Type[]): Type {
+        function getUnionTypeFromSortedList(types: Type[], unionOfUnitTypes: TypeFlags, aliasSymbol?: Symbol, aliasTypeArguments?: ReadonlyArray<Type>): Type {
             if (types.length === 0) {
                 return neverType;
             }
@@ -8628,7 +8628,7 @@ namespace ts {
 
         // Add the given types to the given type set. Order is preserved, freshness is removed from literal
         // types, duplicates are removed, and nested types of the given kind are flattened into the set.
-        function addTypesToIntersection(typeSet: Type[], includes: TypeFlags, types: Type[]) {
+        function addTypesToIntersection(typeSet: Type[], includes: TypeFlags, types: ReadonlyArray<Type>) {
             for (const type of types) {
                 includes = addTypeToIntersection(typeSet, includes, getRegularTypeOfLiteralType(type));
             }
@@ -8683,7 +8683,7 @@ namespace ts {
         // a type alias of the form "type List<T> = T & { next: List<T> }" cannot be reduced during its declaration.
         // Also, unlike union types, the order of the constituent types is preserved in order that overload resolution
         // for intersections of types with signatures can be deterministic.
-        function getIntersectionType(types: Type[], aliasSymbol?: Symbol, aliasTypeArguments?: Type[]): Type {
+        function getIntersectionType(types: ReadonlyArray<Type>, aliasSymbol?: Symbol, aliasTypeArguments?: ReadonlyArray<Type>): Type {
             const typeSet: Type[] = [];
             const includes = addTypesToIntersection(typeSet, 0, types);
             if (includes & TypeFlags.Never) {
@@ -9586,9 +9586,9 @@ namespace ts {
             }
         }
 
-        function instantiateList<T>(items: T[], mapper: TypeMapper, instantiator: (item: T, mapper: TypeMapper) => T): T[];
-        function instantiateList<T>(items: T[] | undefined, mapper: TypeMapper, instantiator: (item: T, mapper: TypeMapper) => T): T[] | undefined;
-        function instantiateList<T>(items: T[] | undefined, mapper: TypeMapper, instantiator: (item: T, mapper: TypeMapper) => T): T[] | undefined {
+        function instantiateList<T>(items: ReadonlyArray<T>, mapper: TypeMapper, instantiator: (item: T, mapper: TypeMapper) => T): ReadonlyArray<T>;
+        function instantiateList<T>(items: ReadonlyArray<T> | undefined, mapper: TypeMapper, instantiator: (item: T, mapper: TypeMapper) => T): ReadonlyArray<T> | undefined;
+        function instantiateList<T>(items: ReadonlyArray<T> | undefined, mapper: TypeMapper, instantiator: (item: T, mapper: TypeMapper) => T): ReadonlyArray<T> | undefined {
             if (items && items.length) {
                 for (let i = 0; i < items.length; i++) {
                     const item = items[i];
@@ -9606,14 +9606,14 @@ namespace ts {
             return items;
         }
 
-        function instantiateTypes(types: Type[], mapper: TypeMapper): Type[];
-        function instantiateTypes(types: Type[] | undefined, mapper: TypeMapper): Type[] | undefined;
-        function instantiateTypes(types: Type[] | undefined, mapper: TypeMapper) {
-            return instantiateList(types, mapper, instantiateType);
+        function instantiateTypes(types: ReadonlyArray<Type>, mapper: TypeMapper): ReadonlyArray<Type>;
+        function instantiateTypes(types: ReadonlyArray<Type> | undefined, mapper: TypeMapper): ReadonlyArray<Type> | undefined;
+        function instantiateTypes(types: ReadonlyArray<Type> | undefined, mapper: TypeMapper): ReadonlyArray<Type> | undefined {
+            return instantiateList<Type>(types, mapper, instantiateType);
         }
 
-        function instantiateSignatures(signatures: Signature[], mapper: TypeMapper): Signature[] {
-            return instantiateList(signatures, mapper, instantiateSignature);
+        function instantiateSignatures(signatures: ReadonlyArray<Signature>, mapper: TypeMapper): ReadonlyArray<Signature> {
+            return instantiateList<Signature>(signatures, mapper, instantiateSignature);
         }
 
         function makeUnaryTypeMapper(source: Type, target: Type) {
@@ -9624,7 +9624,7 @@ namespace ts {
             return (t: Type) => t === source1 ? target1 : t === source2 ? target2 : t;
         }
 
-        function makeArrayTypeMapper(sources: Type[], targets: Type[] | undefined) {
+        function makeArrayTypeMapper(sources: ReadonlyArray<Type>, targets: ReadonlyArray<Type> | undefined) {
             return (t: Type) => {
                 for (let i = 0; i < sources.length; i++) {
                     if (t === sources[i]) {
@@ -9635,14 +9635,14 @@ namespace ts {
             };
         }
 
-        function createTypeMapper(sources: TypeParameter[], targets: Type[] | undefined): TypeMapper {
+        function createTypeMapper(sources: ReadonlyArray<TypeParameter>, targets: ReadonlyArray<Type> | undefined): TypeMapper {
             Debug.assert(targets === undefined || sources.length === targets.length);
             return sources.length === 1 ? makeUnaryTypeMapper(sources[0], targets ? targets[0] : anyType) :
                 sources.length === 2 ? makeBinaryTypeMapper(sources[0], targets ? targets[0] : anyType, sources[1], targets ? targets[1] : anyType) :
                 makeArrayTypeMapper(sources, targets);
         }
 
-        function createTypeEraser(sources: TypeParameter[]): TypeMapper {
+        function createTypeEraser(sources: ReadonlyArray<TypeParameter>): TypeMapper {
             return createTypeMapper(sources, /*targets*/ undefined);
         }
 
@@ -9650,7 +9650,7 @@ namespace ts {
          * Maps forward-references to later types parameters to the empty object type.
          * This is used during inference when instantiating type parameter defaults.
          */
-        function createBackreferenceMapper(typeParameters: TypeParameter[], index: number): TypeMapper {
+        function createBackreferenceMapper(typeParameters: ReadonlyArray<TypeParameter>, index: number): TypeMapper {
             return t => typeParameters.indexOf(t) >= index ? emptyObjectType : t;
         }
 
@@ -12414,7 +12414,7 @@ namespace ts {
             }
         }
 
-        function createInferenceContext(typeParameters: TypeParameter[], signature: Signature | undefined, flags: InferenceFlags, compareTypes?: TypeComparer, baseInferences?: InferenceInfo[]): InferenceContext {
+        function createInferenceContext(typeParameters: ReadonlyArray<TypeParameter>, signature: Signature | undefined, flags: InferenceFlags, compareTypes?: TypeComparer, baseInferences?: InferenceInfo[]): InferenceContext {
             const inferences = baseInferences ? baseInferences.map(cloneInferenceInfo) : typeParameters.map(createInferenceInfo);
             const context = mapper as InferenceContext;
             context.typeParameters = typeParameters;
@@ -14257,7 +14257,7 @@ namespace ts {
 
                 if (!targetType) {
                     // Target type is type of construct signature
-                    let constructSignatures: Signature[] | undefined;
+                    let constructSignatures: ReadonlyArray<Signature> | undefined;
                     if (getObjectFlags(rightType) & ObjectFlags.Interface) {
                         constructSignatures = resolveDeclaredMembers(<InterfaceType>rightType).declaredConstructSignatures;
                     }
@@ -14765,7 +14765,7 @@ namespace ts {
 
         function checkThisBeforeSuper(node: Node, container: Node, diagnosticMessage: DiagnosticMessage) {
             const containingClassDecl = <ClassDeclaration>container.parent;
-            const baseTypeNode = getClassExtendsHeritageClauseElement(containingClassDecl);
+            const baseTypeNode = getEffectiveBaseTypeNode(containingClassDecl);
 
             // If a containing class does not have extends clause or the class extends null
             // skip checking whether super statement is called before "this" accessing.
@@ -15041,7 +15041,7 @@ namespace ts {
 
             // at this point the only legal case for parent is ClassLikeDeclaration
             const classLikeDeclaration = <ClassLikeDeclaration>container.parent;
-            if (!getClassExtendsHeritageClauseElement(classLikeDeclaration)) {
+            if (!getEffectiveBaseTypeNode(classLikeDeclaration)) {
                 error(node, Diagnostics.super_can_only_be_referenced_in_a_derived_class);
                 return errorType;
             }
@@ -16454,7 +16454,7 @@ namespace ts {
             return links.resolvedSymbol;
         }
 
-        function instantiateJsxSignatures(node: JsxOpeningLikeElement, signatures: Signature[]) {
+        function instantiateJsxSignatures(node: JsxOpeningLikeElement, signatures: ReadonlyArray<Signature>) {
             const instantiatedSignatures = [];
             let candidateForTypeArgumentError: Signature | undefined;
             let hasTypeArgumentError: boolean = !!node.typeArguments;
@@ -17684,7 +17684,7 @@ namespace ts {
         // interface B extends A { (x: 'foo'): string }
         // const b: B;
         // b('foo') // <- here overloads should be processed as [(x:'foo'): string, (x: string): void]
-        function reorderCandidates(signatures: Signature[], result: Signature[]): void {
+        function reorderCandidates(signatures: ReadonlyArray<Signature>, result: Signature[]): void {
             let lastParent: Node | undefined;
             let lastSymbol: Symbol | undefined;
             let cutoffIndex = 0;
@@ -17893,7 +17893,7 @@ namespace ts {
                     // Above, the type of the 'value' parameter is inferred to be 'A'.
                     const contextualSignature = getSingleCallSignature(instantiatedType);
                     const inferenceSourceType = contextualSignature && contextualSignature.typeParameters ?
-                        getOrCreateTypeFromSignature(getSignatureInstantiation(contextualSignature, contextualSignature.typeParameters, isInJavaScriptFile(node))) :
+                        getOrCreateTypeFromSignature(getSignatureInstantiationWithoutFillingInTypeArguments(contextualSignature, contextualSignature.typeParameters)) :
                         instantiatedType;
                     const inferenceTargetType = getReturnTypeOfSignature(signature);
                      // Inferences made from return types have lower priority than all other inferences.
@@ -18383,7 +18383,7 @@ namespace ts {
             }
         }
 
-        function getTypeArgumentArityError(node: Node, signatures: Signature[], typeArguments: NodeArray<TypeNode>) {
+        function getTypeArgumentArityError(node: Node, signatures: ReadonlyArray<Signature>, typeArguments: NodeArray<TypeNode>) {
             let min = Infinity;
             let max = -Infinity;
             for (const sig of signatures) {
@@ -18394,7 +18394,7 @@ namespace ts {
             return createDiagnosticForNodeArray(getSourceFileOfNode(node), typeArguments, Diagnostics.Expected_0_type_arguments_but_got_1, paramCount, typeArguments.length);
         }
 
-        function resolveCall(node: CallLikeExpression, signatures: Signature[], candidatesOutArray: Signature[] | undefined, fallbackError?: DiagnosticMessage): Signature {
+        function resolveCall(node: CallLikeExpression, signatures: ReadonlyArray<Signature>, candidatesOutArray: Signature[] | undefined, fallbackError?: DiagnosticMessage): Signature {
             const isTaggedTemplate = node.kind === SyntaxKind.TaggedTemplateExpression;
             const isDecorator = node.kind === SyntaxKind.Decorator;
             const isJsxOpeningOrSelfClosingElement = isJsxOpeningLikeElement(node);
@@ -18679,7 +18679,7 @@ namespace ts {
                 if (superType !== errorType) {
                     // In super call, the candidate signatures are the matching arity signatures of the base constructor function instantiated
                     // with the type arguments specified in the extends clause.
-                    const baseTypeNode = getClassExtendsHeritageClauseElement(getContainingClass(node)!);
+                    const baseTypeNode = getEffectiveBaseTypeNode(getContainingClass(node)!);
                     if (baseTypeNode) {
                         const baseConstructors = getInstantiatedConstructorsForTypeArguments(superType, baseTypeNode.typeArguments, baseTypeNode);
                         return resolveCall(node, baseConstructors, candidatesOutArray);
@@ -18979,7 +18979,7 @@ namespace ts {
          * but is receiving too many arguments as part of the decorator invocation.
          * In those cases, a user may have meant to *call* the expression before using it as a decorator.
          */
-        function isPotentiallyUncalledDecorator(decorator: Decorator, signatures: Signature[]) {
+        function isPotentiallyUncalledDecorator(decorator: Decorator, signatures: ReadonlyArray<Signature>) {
             return signatures.length && every(signatures, signature =>
                 signature.minArgumentCount === 0 &&
                 !signature.hasRestParameter &&
@@ -21475,7 +21475,7 @@ namespace ts {
             // Constructors of classes with no extends clause may not contain super calls, whereas
             // constructors of derived classes must contain at least one super call somewhere in their function body.
             const containingClassDecl = <ClassDeclaration>node.parent;
-            if (getClassExtendsHeritageClauseElement(containingClassDecl)) {
+            if (getEffectiveBaseTypeNode(containingClassDecl)) {
                 captureLexicalThis(node.parent, containingClassDecl);
                 const classExtendsNull = classDeclarationExtendsNull(containingClassDecl);
                 const superCall = getSuperCallInConstructor(node);
@@ -21580,12 +21580,12 @@ namespace ts {
             checkDecorators(node);
         }
 
-        function getEffectiveTypeArguments(node: TypeReferenceNode | ExpressionWithTypeArguments, typeParameters: TypeParameter[]): Type[] {
+        function getEffectiveTypeArguments(node: TypeReferenceNode | ExpressionWithTypeArguments, typeParameters: ReadonlyArray<TypeParameter>): Type[] {
             return fillMissingTypeArguments(map(node.typeArguments!, getTypeFromTypeNode), typeParameters,
                 getMinTypeArgumentCount(typeParameters), isInJavaScriptFile(node));
         }
 
-        function checkTypeArgumentConstraints(node: TypeReferenceNode | ExpressionWithTypeArguments, typeParameters: TypeParameter[]): boolean {
+        function checkTypeArgumentConstraints(node: TypeReferenceNode | ExpressionWithTypeArguments, typeParameters: ReadonlyArray<TypeParameter>): boolean {
             let typeArguments: Type[] | undefined;
             let mapper: TypeMapper | undefined;
             let result = true;
@@ -22652,7 +22652,7 @@ namespace ts {
             }
 
             const name = getIdentifierFromEntityNameExpression(node.class.expression);
-            const extend = getClassExtendsHeritageClauseElement(classLike);
+            const extend = getClassExtendsHeritageElement(classLike);
             if (extend) {
                 const className = getIdentifierFromEntityNameExpression(extend.expression);
                 if (className && name.escapedText !== className.escapedText) {
@@ -22815,11 +22815,7 @@ namespace ts {
             addDiagnostic(UnusedKind.Local, createDiagnosticForNode(node, message, name));
         }
 
-        function parameterNameStartsWithUnderscore(parameterName: DeclarationName) {
-            return parameterName && isIdentifierThatStartsWithUnderScore(parameterName);
-        }
-
-        function isIdentifierThatStartsWithUnderScore(node: Node) {
+        function isIdentifierThatStartsWithUnderscore(node: Node) {
             return isIdentifier(node) && idText(node).charCodeAt(0) === CharacterCodes._;
         }
 
@@ -22867,7 +22863,7 @@ namespace ts {
             const typeParameters = getEffectiveTypeParameterDeclarations(node);
             if (!(node.flags & NodeFlags.Ambient) && last(getSymbolOfNode(node).declarations) === node) {
                 for (const typeParameter of typeParameters) {
-                    if (!(getMergedSymbol(typeParameter.symbol).isReferenced! & SymbolFlags.TypeParameter) && !isIdentifierThatStartsWithUnderScore(typeParameter.name)) {
+                    if (!(getMergedSymbol(typeParameter.symbol).isReferenced! & SymbolFlags.TypeParameter) && !isIdentifierThatStartsWithUnderscore(typeParameter.name)) {
                         addDiagnostic(UnusedKind.Parameter, createDiagnosticForNode(typeParameter.name, Diagnostics._0_is_declared_but_its_value_is_never_read, symbolName(typeParameter.symbol)));
                     }
                 }
@@ -22905,7 +22901,7 @@ namespace ts {
 
                 for (const declaration of local.declarations) {
                     if (isAmbientModule(declaration) ||
-                        (isVariableDeclaration(declaration) && isForInOrOfStatement(declaration.parent.parent) || isImportedDeclaration(declaration)) && isIdentifierThatStartsWithUnderScore(declaration.name!)) {
+                        (isVariableDeclaration(declaration) && isForInOrOfStatement(declaration.parent.parent) || isImportedDeclaration(declaration)) && isIdentifierThatStartsWithUnderscore(declaration.name!)) {
                         continue;
                     }
 
@@ -22924,9 +22920,9 @@ namespace ts {
                     }
                     else {
                         const parameter = local.valueDeclaration && tryGetRootParameterDeclaration(local.valueDeclaration);
-                        if (parameter) {
-                            const name = getNameOfDeclaration(local.valueDeclaration);
-                            if (!isParameterPropertyDeclaration(parameter) && !parameterIsThisKeyword(parameter) && !parameterNameStartsWithUnderscore(name)) {
+                        const name = getNameOfDeclaration(local.valueDeclaration);
+                        if (parameter && name) {
+                            if (!isParameterPropertyDeclaration(parameter) && !parameterIsThisKeyword(parameter) && !isIdentifierThatStartsWithUnderscore(name)) {
                                 addDiagnostic(UnusedKind.Parameter, createDiagnosticForNode(name, Diagnostics._0_is_declared_but_its_value_is_never_read, symbolName(local)));
                             }
                         }
@@ -24221,18 +24217,19 @@ namespace ts {
                 }
 
                 const propDeclaration = prop.valueDeclaration;
+                const name = getNameOfDeclaration(propDeclaration);
 
                 // index is numeric and property name is not valid numeric literal
-                if (indexKind === IndexKind.Number && !(propDeclaration ? isNumericName(getNameOfDeclaration(propDeclaration)) : isNumericLiteralName(prop.escapedName))) {
+                if (indexKind === IndexKind.Number && !(name ? isNumericName(name) : isNumericLiteralName(prop.escapedName))) {
                     return;
                 }
 
                 // perform property check if property or indexer is declared in 'type'
                 // this allows us to rule out cases when both property and indexer are inherited from the base class
                 let errorNode: Node | undefined;
-                if (propDeclaration &&
+                if (propDeclaration && name &&
                     (propDeclaration.kind === SyntaxKind.BinaryExpression ||
-                     getNameOfDeclaration(propDeclaration).kind === SyntaxKind.ComputedPropertyName ||
+                     name.kind === SyntaxKind.ComputedPropertyName ||
                      prop.parent === containingType.symbol)) {
                     errorNode = propDeclaration;
                 }
@@ -24427,7 +24424,7 @@ namespace ts {
                 checkClassForStaticPropertyNameConflicts(node);
             }
 
-            const baseTypeNode = getClassExtendsHeritageClauseElement(node);
+            const baseTypeNode = getEffectiveBaseTypeNode(node);
             if (baseTypeNode) {
                 if (languageVersion < ScriptTarget.ES2015) {
                     checkExternalEmitHelpers(baseTypeNode.parent, ExternalEmitHelpers.Extends);
@@ -24440,6 +24437,10 @@ namespace ts {
                     const staticBaseType = getApparentType(baseConstructorType);
                     checkBaseTypeAccessibility(staticBaseType, baseTypeNode);
                     checkSourceElement(baseTypeNode.expression);
+                    const extendsNode = getClassExtendsHeritageElement(node);
+                    if (extendsNode && extendsNode !== baseTypeNode) {
+                        checkExpression(extendsNode.expression);
+                    }
                     if (some(baseTypeNode.typeArguments)) {
                         forEach(baseTypeNode.typeArguments, checkSourceElement);
                         for (const constructor of getConstructorsForTypeArguments(staticBaseType, baseTypeNode.typeArguments, baseTypeNode)) {
@@ -27353,7 +27354,7 @@ namespace ts {
                 }
                 switch (modifier.kind) {
                     case SyntaxKind.ConstKeyword:
-                        if (node.kind !== SyntaxKind.EnumDeclaration && node.parent.kind === SyntaxKind.ClassDeclaration) {
+                        if (node.kind !== SyntaxKind.EnumDeclaration) {
                             return grammarErrorOnNode(node, Diagnostics.A_class_member_cannot_have_the_0_keyword, tokenToString(SyntaxKind.ConstKeyword));
                         }
                         break;
diff --git a/src/compiler/commandLineParser.ts b/src/compiler/commandLineParser.ts
index f8648636c8a..98cbaca5e6f 100644
--- a/src/compiler/commandLineParser.ts
+++ b/src/compiler/commandLineParser.ts
@@ -44,6 +44,7 @@ namespace ts {
         ["esnext.array", "lib.esnext.array.d.ts"],
         ["esnext.symbol", "lib.esnext.symbol.d.ts"],
         ["esnext.asynciterable", "lib.esnext.asynciterable.d.ts"],
+        ["esnext.intl", "lib.esnext.intl.d.ts"]
     ];
 
     /**
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 24b3031b877..7d08fd5caf1 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -3636,7 +3636,7 @@
         "category": "Message",
         "code": 6353
     },
-    
+
     "Project '{0}' is up to date with .d.ts files from its dependencies": {
         "category": "Message",
         "code": 6354
@@ -3836,6 +3836,10 @@
         "category": "Error",
         "code": 7039
     },
+    "If the '{0}' package actually exposes this module, consider sending a pull request to amend 'https://github.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/{0}`": {
+        "category": "Error",
+        "code": 7040
+    },
     "You cannot rename this element.": {
         "category": "Error",
         "code": 8000
diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index 7269462578e..1857fa05f60 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -192,6 +192,11 @@ namespace ts {
             // Setup and perform the transformation to retrieve declarations from the input files
             const nonJsFiles = filter(sourceFiles, isSourceFileNotJavaScript);
             const inputListOrBundle = (compilerOptions.outFile || compilerOptions.out) ? [createBundle(nonJsFiles, !isSourceFile(sourceFileOrBundle) ? sourceFileOrBundle.prepends : undefined)] : nonJsFiles;
+            if (emitOnlyDtsFiles && !compilerOptions.declaration) {
+                // Checker wont collect the linked aliases since thats only done when declaration is enabled.
+                // Do that here when emitting only dts files
+                nonJsFiles.forEach(collectLinkedAliases);
+            }
             const declarationTransform = transformNodes(resolver, host, compilerOptions, inputListOrBundle, concatenate([transformDeclarations], declarationTransformers), /*allowDtsFiles*/ false);
             if (length(declarationTransform.diagnostics)) {
                 for (const diagnostic of declarationTransform.diagnostics!) {
@@ -221,6 +226,20 @@ namespace ts {
             declarationTransform.dispose();
         }
 
+        function collectLinkedAliases(node: Node) {
+            if (isExportAssignment(node)) {
+                if (node.expression.kind === SyntaxKind.Identifier) {
+                    resolver.collectLinkedAliases(node.expression as Identifier, /*setVisibility*/ true);
+                }
+                return;
+            }
+            else if (isExportSpecifier(node)) {
+                resolver.collectLinkedAliases(node.propertyName || node.name, /*setVisibility*/ true);
+                return;
+            }
+            forEachChild(node, collectLinkedAliases);
+        }
+
         function printSourceFileOrBundle(jsFilePath: string, sourceMapFilePath: string | undefined, sourceFileOrBundle: SourceFile | Bundle, bundleInfoPath: string | undefined, printer: Printer, mapRecorder: SourceMapWriter) {
             const bundle = sourceFileOrBundle.kind === SyntaxKind.Bundle ? sourceFileOrBundle : undefined;
             const sourceFile = sourceFileOrBundle.kind === SyntaxKind.SourceFile ? sourceFileOrBundle : undefined;
diff --git a/src/compiler/factory.ts b/src/compiler/factory.ts
index 91ff766678a..7b8a50ef603 100644
--- a/src/compiler/factory.ts
+++ b/src/compiler/factory.ts
@@ -194,10 +194,10 @@ namespace ts {
     }
 
     /** Create a unique name generated for a node. */
-    export function getGeneratedNameForNode(node: Node): Identifier;
-    /* @internal */ export function getGeneratedNameForNode(node: Node, flags: GeneratedIdentifierFlags): Identifier; // tslint:disable-line unified-signatures
-    export function getGeneratedNameForNode(node: Node, flags?: GeneratedIdentifierFlags): Identifier {
-        const name = createIdentifier(isIdentifier(node) ? idText(node) : "");
+    export function getGeneratedNameForNode(node: Node | undefined): Identifier;
+    /* @internal */ export function getGeneratedNameForNode(node: Node | undefined, flags: GeneratedIdentifierFlags): Identifier; // tslint:disable-line unified-signatures
+    export function getGeneratedNameForNode(node: Node | undefined, flags?: GeneratedIdentifierFlags): Identifier {
+        const name = createIdentifier(node && isIdentifier(node) ? idText(node) : "");
         name.autoGenerateFlags = GeneratedIdentifierFlags.Node | flags!;
         name.autoGenerateId = nextAutoGenerateId;
         name.original = node;
diff --git a/src/compiler/transformers/declarations.ts b/src/compiler/transformers/declarations.ts
index 8e2e3727c60..35fb8e99170 100644
--- a/src/compiler/transformers/declarations.ts
+++ b/src/compiler/transformers/declarations.ts
@@ -1022,7 +1022,7 @@ namespace ts {
                     }
                     const members = createNodeArray(concatenate(parameterProperties, visitNodes(input.members, visitDeclarationSubtree)));
 
-                    const extendsClause = getClassExtendsHeritageClauseElement(input);
+                    const extendsClause = getEffectiveBaseTypeNode(input);
                     if (extendsClause && !isEntityNameExpression(extendsClause.expression) && extendsClause.expression.kind !== SyntaxKind.NullKeyword) {
                         // We must add a temporary declaration for the extends clause expression
 
diff --git a/src/compiler/transformers/es2015.ts b/src/compiler/transformers/es2015.ts
index 8624beae643..8e2b487f13f 100644
--- a/src/compiler/transformers/es2015.ts
+++ b/src/compiler/transformers/es2015.ts
@@ -770,7 +770,7 @@ namespace ts {
                 enableSubstitutionsForBlockScopedBindings();
             }
 
-            const extendsClauseElement = getClassExtendsHeritageClauseElement(node);
+            const extendsClauseElement = getEffectiveBaseTypeNode(node);
             const classFunction = createFunctionExpression(
                 /*modifiers*/ undefined,
                 /*asteriskToken*/ undefined,
diff --git a/src/compiler/transformers/ts.ts b/src/compiler/transformers/ts.ts
index 6d41e3d36cd..4712be940fe 100644
--- a/src/compiler/transformers/ts.ts
+++ b/src/compiler/transformers/ts.ts
@@ -586,7 +586,7 @@ namespace ts {
         function getClassFacts(node: ClassDeclaration, staticProperties: ReadonlyArray<PropertyDeclaration>) {
             let facts = ClassFacts.None;
             if (some(staticProperties)) facts |= ClassFacts.HasStaticInitializedProperties;
-            const extendsClauseElement = getClassExtendsHeritageClauseElement(node);
+            const extendsClauseElement = getEffectiveBaseTypeNode(node);
             if (extendsClauseElement && skipOuterExpressions(extendsClauseElement.expression).kind !== SyntaxKind.NullKeyword) facts |= ClassFacts.IsDerivedClass;
             if (shouldEmitDecorateCallForClass(node)) facts |= ClassFacts.HasConstructorDecorators;
             if (childIsDecorated(node)) facts |= ClassFacts.HasMemberDecorators;
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 764aadc37af..7cd4e50365c 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -2861,7 +2861,7 @@ namespace ts {
         getPropertiesOfType(type: Type): Symbol[];
         getPropertyOfType(type: Type, propertyName: string): Symbol | undefined;
         getIndexInfoOfType(type: Type, kind: IndexKind): IndexInfo | undefined;
-        getSignaturesOfType(type: Type, kind: SignatureKind): Signature[];
+        getSignaturesOfType(type: Type, kind: SignatureKind): ReadonlyArray<Signature>;
         getIndexTypeOfType(type: Type, kind: IndexKind): Type | undefined;
         getBaseTypes(type: InterfaceType): BaseType[];
         getBaseTypeOfLiteralType(type: Type): Type;
@@ -3073,6 +3073,7 @@ namespace ts {
         Subtype
     }
 
+    // NOTE: If modifying this enum, must modify `TypeFormatFlags` too!
     export const enum NodeBuilderFlags {
         None                                    = 0,
         // Options
@@ -3337,7 +3338,7 @@ namespace ts {
         getNodeCheckFlags(node: Node): NodeCheckFlags;
         isDeclarationVisible(node: Declaration | AnyImportSyntax): boolean;
         isLateBound(node: Declaration): node is LateBoundDeclaration;
-        collectLinkedAliases(node: Identifier): Node[] | undefined;
+        collectLinkedAliases(node: Identifier, setVisibility?: boolean): Node[] | undefined;
         isImplementationOfOverload(node: FunctionLike): boolean | undefined;
         isRequiredInitializedParameter(node: ParameterDeclaration): boolean;
         isOptionalUninitializedParameterProperty(node: ParameterDeclaration): boolean;
@@ -3741,7 +3742,7 @@ namespace ts {
         symbol: Symbol;                  // Symbol associated with type (if any)
         pattern?: DestructuringPattern;  // Destructuring pattern represented by type (if any)
         aliasSymbol?: Symbol;            // Alias associated with type
-        aliasTypeArguments?: Type[];     // Alias type arguments (if any)
+        aliasTypeArguments?: ReadonlyArray<Type>;     // Alias type arguments (if any)
         /* @internal */
         wildcardInstantiation?: Type;    // Instantiation with type parameters mapped to wildcard type
     }
@@ -3835,7 +3836,7 @@ namespace ts {
      */
     export interface TypeReference extends ObjectType {
         target: GenericType;    // Type reference target
-        typeArguments?: Type[];  // Type reference type arguments (undefined if none)
+        typeArguments?: ReadonlyArray<Type>;  // Type reference type arguments (undefined if none)
     }
 
     /* @internal */
@@ -3912,8 +3913,8 @@ namespace ts {
     export interface ResolvedType extends ObjectType, UnionOrIntersectionType {
         members: SymbolTable;             // Properties by name
         properties: Symbol[];             // Properties
-        callSignatures: Signature[];      // Call signatures of type
-        constructSignatures: Signature[]; // Construct signatures of type
+        callSignatures: ReadonlyArray<Signature>;      // Call signatures of type
+        constructSignatures: ReadonlyArray<Signature>; // Construct signatures of type
         stringIndexInfo?: IndexInfo;      // String indexing info
         numberIndexInfo?: IndexInfo;      // Numeric indexing info
     }
@@ -4038,8 +4039,8 @@ namespace ts {
 
     export interface Signature {
         declaration?: SignatureDeclaration | JSDocSignature; // Originating declaration
-        typeParameters?: TypeParameter[];   // Type parameters (undefined if non-generic)
-        parameters: Symbol[];               // Parameters
+        typeParameters?: ReadonlyArray<TypeParameter>;   // Type parameters (undefined if non-generic)
+        parameters: ReadonlyArray<Symbol>;               // Parameters
         /* @internal */
         thisParameter?: Symbol;             // symbol of this-type parameter
         /* @internal */
@@ -4138,11 +4139,11 @@ namespace ts {
 
     /* @internal */
     export interface InferenceContext extends TypeMapper {
-        typeParameters: TypeParameter[];    // Type parameters for which inferences are made
-        signature?: Signature;              // Generic signature for which inferences are made (if any)
-        inferences: InferenceInfo[];        // Inferences made for each type parameter
-        flags: InferenceFlags;              // Inference flags
-        compareTypes: TypeComparer;         // Type comparer function
+        typeParameters: ReadonlyArray<TypeParameter>; // Type parameters for which inferences are made
+        signature?: Signature;                        // Generic signature for which inferences are made (if any)
+        inferences: InferenceInfo[];                  // Inferences made for each type parameter
+        flags: InferenceFlags;                        // Inference flags
+        compareTypes: TypeComparer;                   // Type comparer function
     }
 
     /* @internal */
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index 49769953f02..93415815e74 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -745,8 +745,8 @@ namespace ts {
     // Return display name of an identifier
     // Computed property names will just be emitted as "[<expr>]", where <expr> is the source
     // text of the expression in the computed property.
-    export function declarationNameToString(name: DeclarationName | QualifiedName) {
-        return getFullWidth(name) === 0 ? "(Missing)" : getTextOfNode(name);
+    export function declarationNameToString(name: DeclarationName | QualifiedName | undefined) {
+        return !name || getFullWidth(name) === 0 ? "(Missing)" : getTextOfNode(name);
     }
 
     export function getNameFromIndexInfo(info: IndexInfo): string | undefined {
@@ -2067,53 +2067,51 @@ namespace ts {
 
     export function getJSDocCommentsAndTags(hostNode: Node): ReadonlyArray<JSDoc | JSDocTag> {
         let result: (JSDoc | JSDocTag)[] | undefined;
-        getJSDocCommentsAndTagsWorker(hostNode);
-        return result || emptyArray;
+        // Pull parameter comments from declaring function as well
+        if (isVariableLike(hostNode) && hasInitializer(hostNode) && hasJSDocNodes(hostNode.initializer!)) {
+            result = addRange(result, (hostNode.initializer as HasJSDoc).jsDoc!);
+        }
 
-        function getJSDocCommentsAndTagsWorker(node: Node): void {
-            const parent = node.parent;
-            if (!parent) return;
-            if (parent.kind === SyntaxKind.PropertyAssignment || parent.kind === SyntaxKind.PropertyDeclaration || getNestedModuleDeclaration(parent)) {
-                getJSDocCommentsAndTagsWorker(parent);
-            }
-            // Try to recognize this pattern when node is initializer of variable declaration and JSDoc comments are on containing variable statement.
-            // /**
-            //   * @param {number} name
-            //   * @returns {number}
-            //   */
-            // var x = function(name) { return name.length; }
-            if (parent.parent && (getSingleVariableOfVariableStatement(parent.parent) === node)) {
-                getJSDocCommentsAndTagsWorker(parent.parent);
-            }
-            if (parent.parent && parent.parent.parent &&
-                (getSingleVariableOfVariableStatement(parent.parent.parent) ||
-                    getSingleInitializerOfVariableStatementOrPropertyDeclaration(parent.parent.parent) === node ||
-                    getSourceOfDefaultedAssignment(parent.parent.parent))) {
-                getJSDocCommentsAndTagsWorker(parent.parent.parent);
-            }
-            if (isBinaryExpression(node) && node.operatorToken.kind === SyntaxKind.EqualsToken ||
-                isBinaryExpression(parent) && parent.operatorToken.kind === SyntaxKind.EqualsToken ||
-                node.kind === SyntaxKind.PropertyAccessExpression && node.parent && node.parent.kind === SyntaxKind.ExpressionStatement) {
-                if (isBinaryExpression(parent)) {
-                    getJSDocCommentsAndTagsWorker(parent.parent);
-                }
-                else {
-                    getJSDocCommentsAndTagsWorker(parent);
-                }
+        let node: Node | undefined = hostNode;
+        while (node && node.parent) {
+            if (hasJSDocNodes(node)) {
+                result = addRange(result, node.jsDoc!);
             }
 
-            // Pull parameter comments from declaring function as well
             if (node.kind === SyntaxKind.Parameter) {
                 result = addRange(result, getJSDocParameterTags(node as ParameterDeclaration));
+                break;
             }
+            node = getNextJSDocCommentLocation(node);
+        }
+        return result || emptyArray;
+    }
 
-            if (isVariableLike(node) && hasInitializer(node) && node.initializer !== hostNode && hasJSDocNodes(node.initializer!)) {
-                result = addRange(result, (node.initializer as HasJSDoc).jsDoc);
-            }
-
-            if (hasJSDocNodes(node)) {
-                result = addRange(result, node.jsDoc);
-            }
+    function getNextJSDocCommentLocation(node: Node) {
+        const parent = node.parent;
+        if (parent.kind === SyntaxKind.PropertyAssignment ||
+            parent.kind === SyntaxKind.PropertyDeclaration ||
+            parent.kind === SyntaxKind.ExpressionStatement && node.kind === SyntaxKind.PropertyAccessExpression ||
+            getNestedModuleDeclaration(parent) ||
+            isBinaryExpression(node) && node.operatorToken.kind === SyntaxKind.EqualsToken) {
+            return parent;
+        }
+        // Try to recognize this pattern when node is initializer of variable declaration and JSDoc comments are on containing variable statement.
+        // /**
+        //   * @param {number} name
+        //   * @returns {number}
+        //   */
+        // var x = function(name) { return name.length; }
+        else if (parent.parent &&
+            (getSingleVariableOfVariableStatement(parent.parent) === node ||
+            isBinaryExpression(parent) && parent.operatorToken.kind === SyntaxKind.EqualsToken)) {
+            return parent.parent;
+        }
+        else if (parent.parent && parent.parent.parent &&
+            (getSingleVariableOfVariableStatement(parent.parent.parent) ||
+            getSingleInitializerOfVariableStatementOrPropertyDeclaration(parent.parent.parent) === node ||
+            getSourceOfDefaultedAssignment(parent.parent.parent))) {
+            return parent.parent.parent;
         }
     }
 
@@ -2415,7 +2413,18 @@ namespace ts {
         return isEntityNameExpression(e) || isClassExpression(e);
     }
 
-    export function getClassExtendsHeritageClauseElement(node: ClassLikeDeclaration | InterfaceDeclaration) {
+    export function getEffectiveBaseTypeNode(node: ClassLikeDeclaration | InterfaceDeclaration) {
+        if (isInJavaScriptFile(node)) {
+            // Prefer an @augments tag because it may have type parameters.
+            const tag = getJSDocAugmentsTag(node);
+            if (tag) {
+                return tag.class;
+            }
+        }
+        return getClassExtendsHeritageElement(node);
+    }
+
+    export function getClassExtendsHeritageElement(node: ClassLikeDeclaration | InterfaceDeclaration) {
         const heritageClause = getHeritageClause(node.heritageClauses, SyntaxKind.ExtendsKeyword);
         return heritageClause && heritageClause.types.length > 0 ? heritageClause.types[0] : undefined;
     }
@@ -2428,7 +2437,7 @@ namespace ts {
     /** Returns the node in an `extends` or `implements` clause of a class or interface. */
     export function getAllSuperTypeNodes(node: Node): ReadonlyArray<TypeNode> {
         return isInterfaceDeclaration(node) ? getInterfaceBaseTypeNodes(node) || emptyArray
-            : isClassLike(node) ? concatenate(singleElementArray(getClassExtendsHeritageClauseElement(node)), getClassImplementsHeritageClauseElements(node)) || emptyArray
+            : isClassLike(node) ? concatenate(singleElementArray(getEffectiveBaseTypeNode(node)), getClassImplementsHeritageClauseElements(node)) || emptyArray
                 : emptyArray;
     }
 
@@ -4849,7 +4858,7 @@ namespace ts {
 
     function getDeclarationIdentifier(node: Declaration | Expression): Identifier | undefined {
         const name = getNameOfDeclaration(node);
-        return isIdentifier(name) ? name : undefined;
+        return name && isIdentifier(name) ? name : undefined;
     }
 
     export function getNameOfJSDocTypedef(declaration: JSDocTypedefTag): Identifier | undefined {
@@ -4861,16 +4870,15 @@ namespace ts {
         return !!(node as NamedDeclaration).name; // A 'name' property should always be a DeclarationName.
     }
 
-    // TODO: GH#18217 This is often used as if it returns a defined result
-    export function getNameOfDeclaration(declaration: Declaration | Expression): DeclarationName {
+    export function getNameOfDeclaration(declaration: Declaration | Expression): DeclarationName | undefined {
         if (!declaration) {
-            return undefined!;
+            return undefined;
         }
         switch (declaration.kind) {
             case SyntaxKind.ClassExpression:
             case SyntaxKind.FunctionExpression:
                 if (!(declaration as ClassExpression | FunctionExpression).name) {
-                    return getAssignedName(declaration)!;
+                    return getAssignedName(declaration);
                 }
                 break;
             case SyntaxKind.Identifier:
@@ -4892,19 +4900,19 @@ namespace ts {
                     case SpecialPropertyAssignmentKind.PrototypeProperty:
                         return (expr.left as PropertyAccessExpression).name;
                     default:
-                        return undefined!;
+                        return undefined;
                 }
             }
             case SyntaxKind.JSDocCallbackTag:
-                return (declaration as JSDocCallbackTag).name!;
+                return (declaration as JSDocCallbackTag).name;
             case SyntaxKind.JSDocTypedefTag:
-                return getNameOfJSDocTypedef(declaration as JSDocTypedefTag)!;
+                return getNameOfJSDocTypedef(declaration as JSDocTypedefTag);
             case SyntaxKind.ExportAssignment: {
                 const { expression } = declaration as ExportAssignment;
-                return isIdentifier(expression) ? expression : undefined!;
+                return isIdentifier(expression) ? expression : undefined;
             }
         }
-        return (declaration as NamedDeclaration).name!;
+        return (declaration as NamedDeclaration).name;
     }
 
     function getAssignedName(node: Node): DeclarationName | undefined {
diff --git a/src/harness/fourslash.ts b/src/harness/fourslash.ts
index 0ca37715b9f..177d98c37ba 100644
--- a/src/harness/fourslash.ts
+++ b/src/harness/fourslash.ts
@@ -3045,6 +3045,10 @@ Actual: ${stringify(fullActual)}`);
             }
         }
 
+        public verifyRefactorsAvailable(names: ReadonlyArray<string>): void {
+            assert.deepEqual(unique(this.getApplicableRefactors(this.getSelection()), r => r.name), names);
+        }
+
         public verifyRefactor({ name, actionName, refactors }: FourSlashInterface.VerifyRefactorOptions) {
             const actualRefactors = this.getApplicableRefactors(this.getSelection()).filter(r => r.name === name && r.actions.some(a => a.name === actionName));
             this.assertObjectsEqual(actualRefactors, refactors);
@@ -3815,7 +3819,7 @@ ${code}
     }
 
     /** Collects an array of unique outputs. */
-    function unique<T>(inputs: T[], getOutput: (t: T) => string): string[] {
+    function unique<T>(inputs: ReadonlyArray<T>, getOutput: (t: T) => string): string[] {
         const set = ts.createMap<true>();
         for (const input of inputs) {
             const out = getOutput(input);
@@ -4106,6 +4110,10 @@ namespace FourSlashInterface {
             this.state.verifyApplicableRefactorAvailableForRange(this.negative);
         }
 
+        public refactorsAvailable(names: ReadonlyArray<string>): void {
+            this.state.verifyRefactorsAvailable(names);
+        }
+
         public refactor(options: VerifyRefactorOptions) {
             this.state.verifyRefactor(options);
         }
diff --git a/src/harness/virtualFileSystemWithWatch.ts b/src/harness/virtualFileSystemWithWatch.ts
index 467a3474100..6645e12c832 100644
--- a/src/harness/virtualFileSystemWithWatch.ts
+++ b/src/harness/virtualFileSystemWithWatch.ts
@@ -571,7 +571,9 @@ interface Array<T> {}`
         }
 
         private addFileOrFolderInFolder(folder: FsFolder, fileOrDirectory: FsFile | FsFolder | FsSymLink, ignoreWatch?: boolean) {
-            insertSorted(folder.entries, fileOrDirectory, (a, b) => compareStringsCaseSensitive(getBaseFileName(a.path), getBaseFileName(b.path)));
+            if (!this.fs.has(fileOrDirectory.path)) {
+                insertSorted(folder.entries, fileOrDirectory, (a, b) => compareStringsCaseSensitive(getBaseFileName(a.path), getBaseFileName(b.path)));
+            }
             folder.modifiedTime = this.now();
             this.fs.set(fileOrDirectory.path, fileOrDirectory);
 
diff --git a/src/lib/esnext.d.ts b/src/lib/esnext.d.ts
index 99e71158f6a..970e1b32b3e 100644
--- a/src/lib/esnext.d.ts
+++ b/src/lib/esnext.d.ts
@@ -2,3 +2,4 @@
 /// <reference lib="esnext.asynciterable" />
 /// <reference lib="esnext.array" />
 /// <reference lib="esnext.symbol" />
+/// <reference lib="esnext.intl" />
diff --git a/src/lib/esnext.intl.d.ts b/src/lib/esnext.intl.d.ts
new file mode 100644
index 00000000000..99e202bd91b
--- /dev/null
+++ b/src/lib/esnext.intl.d.ts
@@ -0,0 +1,12 @@
+declare namespace Intl {
+    type NumberFormatPartTypes = "currency" | "decimal" | "fraction" | "group" | "infinity" | "integer" | "literal" | "minusSign" | "nan" | "plusSign" | "percentSign";
+
+    interface NumberFormatPart {
+        type: NumberFormatPartTypes;
+        value: string;
+    }
+
+    interface NumberFormat {
+        formatToParts(number?: number): NumberFormatPart[];
+    }
+  }
diff --git a/src/lib/libs.json b/src/lib/libs.json
index 07c99278c14..1f2079e33a3 100644
--- a/src/lib/libs.json
+++ b/src/lib/libs.json
@@ -35,6 +35,7 @@
         "esnext.asynciterable",
         "esnext.array",
         "esnext.symbol",
+        "esnext.intl",
         // Default libraries
         "es5.full",
         "es2015.full",
@@ -50,4 +51,4 @@
         "es5.full": "lib.d.ts",
         "es2015.full": "lib.es6.d.ts"
     }
-}
\ No newline at end of file
+}
diff --git a/src/loc/lcl/cht/diagnosticMessages/diagnosticMessages.generated.json.lcl b/src/loc/lcl/cht/diagnosticMessages/diagnosticMessages.generated.json.lcl
index 5f7122bd70c..c735834474e 100644
--- a/src/loc/lcl/cht/diagnosticMessages/diagnosticMessages.generated.json.lcl
+++ b/src/loc/lcl/cht/diagnosticMessages/diagnosticMessages.generated.json.lcl
@@ -487,7 +487,7 @@
         <Str Cat="Text">
           <Val><![CDATA[A non-dry build would build project '{0}']]></Val>
           <Tgt Cat="Text" Stat="Loc" Orig="New">
-            <Val><![CDATA[非 DRY 的組建會建置專案 '{0}']]></Val>
+            <Val><![CDATA[非 -dry 組建會建置專案 '{0}']]></Val>
           </Tgt>
         </Str>
         <Disp Icon="Str" />
@@ -496,7 +496,7 @@
         <Str Cat="Text">
           <Val><![CDATA[A non-dry build would delete the following files: {0}]]></Val>
           <Tgt Cat="Text" Stat="Loc" Orig="New">
-            <Val><![CDATA[非 DRY 的組建會刪除下列檔案: {0}]]></Val>
+            <Val><![CDATA[非 -dry 組建會刪除下列檔案: {0}]]></Val>
           </Tgt>
         </Str>
         <Disp Icon="Str" />
diff --git a/src/loc/lcl/plk/diagnosticMessages/diagnosticMessages.generated.json.lcl b/src/loc/lcl/plk/diagnosticMessages/diagnosticMessages.generated.json.lcl
index 43e457e6907..e0e6e4a2b1a 100644
--- a/src/loc/lcl/plk/diagnosticMessages/diagnosticMessages.generated.json.lcl
+++ b/src/loc/lcl/plk/diagnosticMessages/diagnosticMessages.generated.json.lcl
@@ -480,7 +480,7 @@
         <Str Cat="Text">
           <Val><![CDATA[A non-dry build would build project '{0}']]></Val>
           <Tgt Cat="Text" Stat="Loc" Orig="New">
-            <Val><![CDATA[Kompilacja inna niż DRY spowodowałaby skompilowanie projektu „{0}”]]></Val>
+            <Val><![CDATA[Kompilacja inna niż -dry spowodowałaby skompilowanie projektu „{0}”]]></Val>
           </Tgt>
         </Str>
         <Disp Icon="Str" />
@@ -489,7 +489,7 @@
         <Str Cat="Text">
           <Val><![CDATA[A non-dry build would delete the following files: {0}]]></Val>
           <Tgt Cat="Text" Stat="Loc" Orig="New">
-            <Val><![CDATA[Kompilacja inna niż DRY spowodowałaby usunięcie następujących plików: {0}]]></Val>
+            <Val><![CDATA[Kompilacja inna niż -dry spowodowałaby usunięcie następujących plików: {0}]]></Val>
           </Tgt>
         </Str>
         <Disp Icon="Str" />
diff --git a/src/loc/lcl/ptb/diagnosticMessages/diagnosticMessages.generated.json.lcl b/src/loc/lcl/ptb/diagnosticMessages/diagnosticMessages.generated.json.lcl
index 54b82d0468e..d0086211c52 100644
--- a/src/loc/lcl/ptb/diagnosticMessages/diagnosticMessages.generated.json.lcl
+++ b/src/loc/lcl/ptb/diagnosticMessages/diagnosticMessages.generated.json.lcl
@@ -480,7 +480,7 @@
         <Str Cat="Text">
           <Val><![CDATA[A non-dry build would build project '{0}']]></Val>
           <Tgt Cat="Text" Stat="Loc" Orig="New">
-            <Val><![CDATA[Um build não dry compilaria o projeto '{0}']]></Val>
+            <Val><![CDATA[Um build não -dry compilaria o projeto '{0}']]></Val>
           </Tgt>
         </Str>
         <Disp Icon="Str" />
@@ -489,7 +489,7 @@
         <Str Cat="Text">
           <Val><![CDATA[A non-dry build would delete the following files: {0}]]></Val>
           <Tgt Cat="Text" Stat="Loc" Orig="New">
-            <Val><![CDATA[Um build não dry excluiria os seguintes arquivos: {0}]]></Val>
+            <Val><![CDATA[Um build não -dry excluiria os seguintes arquivos: {0}]]></Val>
           </Tgt>
         </Str>
         <Disp Icon="Str" />
diff --git a/src/server/protocol.ts b/src/server/protocol.ts
index 2f128aa1663..49fb54a6b10 100644
--- a/src/server/protocol.ts
+++ b/src/server/protocol.ts
@@ -14,7 +14,9 @@ namespace ts.server.protocol {
         GetSpanOfEnclosingComment = "getSpanOfEnclosingComment",
         Change = "change",
         Close = "close",
+        /** @deprecated Prefer CompletionInfo -- see comment on CompletionsResponse */
         Completions = "completions",
+        CompletionInfo = "completionInfo",
         /* @internal */
         CompletionsFull = "completions-full",
         CompletionDetails = "completionEntryDetails",
@@ -1943,10 +1945,22 @@ namespace ts.server.protocol {
         source?: SymbolDisplayPart[];
     }
 
+    /** @deprecated Prefer CompletionInfoResponse, which supports several top-level fields in addition to the array of entries. */
     export interface CompletionsResponse extends Response {
         body?: CompletionEntry[];
     }
 
+    export interface CompletionInfoResponse extends Response {
+        body?: CompletionInfo;
+    }
+
+    export interface CompletionInfo {
+        readonly isGlobalCompletion: boolean;
+        readonly isMemberCompletion: boolean;
+        readonly isNewIdentifierLocation: boolean;
+        readonly entries: ReadonlyArray<CompletionEntry>;
+    }
+
     export interface CompletionDetailsResponse extends Response {
         body?: CompletionEntryDetails[];
     }
diff --git a/src/server/session.ts b/src/server/session.ts
index 74629d97e48..c6934bb8d82 100644
--- a/src/server/session.ts
+++ b/src/server/session.ts
@@ -1343,8 +1343,7 @@ namespace ts.server {
             });
         }
 
-        private getCompletions(args: protocol.CompletionsRequestArgs, simplifiedResult: boolean): ReadonlyArray<protocol.CompletionEntry> | CompletionInfo | undefined {
-            const prefix = args.prefix || "";
+        private getCompletions(args: protocol.CompletionsRequestArgs, kind: protocol.CommandTypes.CompletionInfo | protocol.CommandTypes.Completions | protocol.CommandTypes.CompletionsFull): ReadonlyArray<protocol.CompletionEntry> | protocol.CompletionInfo | CompletionInfo | undefined {
             const { file, project } = this.getFileAndProject(args);
             const scriptInfo = this.projectService.getScriptInfoForNormalizedPath(file)!;
             const position = this.getPosition(args, scriptInfo);
@@ -1355,19 +1354,27 @@ namespace ts.server {
                 includeExternalModuleExports: args.includeExternalModuleExports,
                 includeInsertTextCompletions: args.includeInsertTextCompletions
             });
-            if (simplifiedResult) {
-                return mapDefined<CompletionEntry, protocol.CompletionEntry>(completions && completions.entries, entry => {
-                    if (completions!.isMemberCompletion || startsWith(entry.name.toLowerCase(), prefix.toLowerCase())) {
-                        const { name, kind, kindModifiers, sortText, insertText, replacementSpan, hasAction, source, isRecommended } = entry;
-                        const convertedSpan = replacementSpan ? this.toLocationTextSpan(replacementSpan, scriptInfo) : undefined;
-                        // Use `hasAction || undefined` to avoid serializing `false`.
-                        return { name, kind, kindModifiers, sortText, insertText, replacementSpan: convertedSpan, hasAction: hasAction || undefined, source, isRecommended };
-                    }
-                }).sort((a, b) => compareStringsCaseSensitiveUI(a.name, b.name));
-            }
-            else {
-                return completions;
-            }
+            if (completions === undefined) return undefined;
+
+            if (kind === protocol.CommandTypes.CompletionsFull) return completions;
+
+            const prefix = args.prefix || "";
+            const entries = mapDefined<CompletionEntry, protocol.CompletionEntry>(completions.entries, entry => {
+                if (completions.isMemberCompletion || startsWith(entry.name.toLowerCase(), prefix.toLowerCase())) {
+                    const { name, kind, kindModifiers, sortText, insertText, replacementSpan, hasAction, source, isRecommended } = entry;
+                    const convertedSpan = replacementSpan ? this.toLocationTextSpan(replacementSpan, scriptInfo) : undefined;
+                    // Use `hasAction || undefined` to avoid serializing `false`.
+                    return { name, kind, kindModifiers, sortText, insertText, replacementSpan: convertedSpan, hasAction: hasAction || undefined, source, isRecommended };
+                }
+            }).sort((a, b) => compareStringsCaseSensitiveUI(a.name, b.name));
+
+            if (kind === protocol.CommandTypes.Completions) return entries;
+
+            const res: protocol.CompletionInfo = {
+                ...completions,
+                entries,
+            };
+            return res;
         }
 
         private getCompletionEntryDetails(args: protocol.CompletionDetailsRequestArgs, simplifiedResult: boolean): ReadonlyArray<protocol.CompletionEntryDetails> | ReadonlyArray<CompletionEntryDetails> {
@@ -2035,11 +2042,14 @@ namespace ts.server {
             [CommandNames.FormatRangeFull]: (request: protocol.FormatRequest) => {
                 return this.requiredResponse(this.getFormattingEditsForRangeFull(request.arguments));
             },
+            [CommandNames.CompletionInfo]: (request: protocol.CompletionsRequest) => {
+                return this.requiredResponse(this.getCompletions(request.arguments, CommandNames.CompletionInfo));
+            },
             [CommandNames.Completions]: (request: protocol.CompletionsRequest) => {
-                return this.requiredResponse(this.getCompletions(request.arguments, /*simplifiedResult*/ true));
+                return this.requiredResponse(this.getCompletions(request.arguments, CommandNames.Completions));
             },
             [CommandNames.CompletionsFull]: (request: protocol.CompletionsRequest) => {
-                return this.requiredResponse(this.getCompletions(request.arguments, /*simplifiedResult*/ false));
+                return this.requiredResponse(this.getCompletions(request.arguments, CommandNames.CompletionsFull));
             },
             [CommandNames.CompletionDetails]: (request: protocol.CompletionDetailsRequest) => {
                 return this.requiredResponse(this.getCompletionEntryDetails(request.arguments, /*simplifiedResult*/ true));
diff --git a/src/services/codefixes/fixAddMissingMember.ts b/src/services/codefixes/fixAddMissingMember.ts
index 53492211042..7dbb43b94c7 100644
--- a/src/services/codefixes/fixAddMissingMember.ts
+++ b/src/services/codefixes/fixAddMissingMember.ts
@@ -32,7 +32,7 @@ namespace ts.codefix {
 
                 // Always prefer to add a method declaration if possible.
                 if (call) {
-                    addMethodDeclaration(changes, classDeclarationSourceFile, classDeclaration, token, call, makeStatic, inJs, preferences);
+                    addMethodDeclaration(context, changes, classDeclarationSourceFile, classDeclaration, token, call, makeStatic, inJs, preferences);
                 }
                 else {
                     if (inJs) {
@@ -184,11 +184,12 @@ namespace ts.codefix {
         inJs: boolean,
         preferences: UserPreferences,
     ): CodeFixAction | undefined {
-        const changes = textChanges.ChangeTracker.with(context, t => addMethodDeclaration(t, classDeclarationSourceFile, classDeclaration, token, callExpression, makeStatic, inJs, preferences));
+        const changes = textChanges.ChangeTracker.with(context, t => addMethodDeclaration(context, t, classDeclarationSourceFile, classDeclaration, token, callExpression, makeStatic, inJs, preferences));
         return createCodeFixAction(fixName, changes, [makeStatic ? Diagnostics.Declare_static_method_0 : Diagnostics.Declare_method_0, token.text], fixId, Diagnostics.Add_all_missing_members);
     }
 
     function addMethodDeclaration(
+        context: CodeFixContextBase,
         changeTracker: textChanges.ChangeTracker,
         classDeclarationSourceFile: SourceFile,
         classDeclaration: ClassLikeDeclaration,
@@ -198,7 +199,7 @@ namespace ts.codefix {
         inJs: boolean,
         preferences: UserPreferences,
     ): void {
-        const methodDeclaration = createMethodFromCallExpression(callExpression, token.text, inJs, makeStatic, preferences);
+        const methodDeclaration = createMethodFromCallExpression(context, callExpression, token.text, inJs, makeStatic, preferences);
         const containingMethodDeclaration = getAncestor(callExpression, SyntaxKind.MethodDeclaration);
 
         if (containingMethodDeclaration && containingMethodDeclaration.parent === classDeclaration) {
diff --git a/src/services/codefixes/fixClassDoesntImplementInheritedAbstractMember.ts b/src/services/codefixes/fixClassDoesntImplementInheritedAbstractMember.ts
index 95de8857eb2..c0624c5529b 100644
--- a/src/services/codefixes/fixClassDoesntImplementInheritedAbstractMember.ts
+++ b/src/services/codefixes/fixClassDoesntImplementInheritedAbstractMember.ts
@@ -33,7 +33,7 @@ namespace ts.codefix {
     }
 
     function addMissingMembers(classDeclaration: ClassLikeDeclaration, sourceFile: SourceFile, checker: TypeChecker, changeTracker: textChanges.ChangeTracker, preferences: UserPreferences): void {
-        const extendsNode = getClassExtendsHeritageClauseElement(classDeclaration)!;
+        const extendsNode = getEffectiveBaseTypeNode(classDeclaration)!;
         const instantiatedExtendsType = checker.getTypeAtLocation(extendsNode)!;
 
         // Note that this is ultimately derived from a map indexed by symbol names,
diff --git a/src/services/codefixes/fixClassIncorrectlyImplementsInterface.ts b/src/services/codefixes/fixClassIncorrectlyImplementsInterface.ts
index 781f14566c9..ad093de6327 100644
--- a/src/services/codefixes/fixClassIncorrectlyImplementsInterface.ts
+++ b/src/services/codefixes/fixClassIncorrectlyImplementsInterface.ts
@@ -71,7 +71,7 @@ namespace ts.codefix {
     }
 
     function getHeritageClauseSymbolTable (classDeclaration: ClassLikeDeclaration, checker: TypeChecker): SymbolTable {
-        const heritageClauseNode = getClassExtendsHeritageClauseElement(classDeclaration);
+        const heritageClauseNode = getEffectiveBaseTypeNode(classDeclaration);
         if (!heritageClauseNode) return createSymbolTable();
         const heritageClauseType = checker.getTypeAtLocation(heritageClauseNode) as InterfaceType;
         const heritageClauseTypeSymbols = checker.getPropertiesOfType(heritageClauseType);
diff --git a/src/services/codefixes/fixUnusedIdentifier.ts b/src/services/codefixes/fixUnusedIdentifier.ts
index ad3e2e36f5b..505a09813c3 100644
--- a/src/services/codefixes/fixUnusedIdentifier.ts
+++ b/src/services/codefixes/fixUnusedIdentifier.ts
@@ -173,8 +173,8 @@ namespace ts.codefix {
                 const typeParameters = getEffectiveTypeParameterDeclarations(<DeclarationWithTypeParameters>parent.parent);
                 if (typeParameters.length === 1) {
                     const { pos, end } = cast(typeParameters, isNodeArray);
-                    const previousToken = getTokenAtPosition(sourceFile, pos - 1, /*includeJsDocComment*/ false);
-                    const nextToken = getTokenAtPosition(sourceFile, end, /*includeJsDocComment*/ false);
+                    const previousToken = getTokenAtPosition(sourceFile, pos - 1, /*includeJsDocComment*/ true);
+                    const nextToken = getTokenAtPosition(sourceFile, end, /*includeJsDocComment*/ true);
                     Debug.assert(previousToken.kind === SyntaxKind.LessThanToken);
                     Debug.assert(nextToken.kind === SyntaxKind.GreaterThanToken);
 
diff --git a/src/services/codefixes/helpers.ts b/src/services/codefixes/helpers.ts
index 58e0d2bebbf..5f26336a117 100644
--- a/src/services/codefixes/helpers.ts
+++ b/src/services/codefixes/helpers.ts
@@ -111,12 +111,27 @@ namespace ts.codefix {
     }
 
     export function createMethodFromCallExpression(
+        context: CodeFixContextBase,
         { typeArguments, arguments: args, parent: parent }: CallExpression,
         methodName: string,
         inJs: boolean,
         makeStatic: boolean,
         preferences: UserPreferences,
     ): MethodDeclaration {
+        const checker = context.program.getTypeChecker();
+        const types = map(args,
+            arg => {
+                let type = checker.getTypeAtLocation(arg);
+                if (type === undefined) {
+                    return undefined;
+                }
+                // Widen the type so we don't emit nonsense annotations like "function fn(x: 3) {"
+                type = checker.getBaseTypeOfLiteralType(type);
+                return checker.typeToTypeNode(type);
+            });
+        const names = map(args, arg =>
+            isIdentifier(arg) ? arg.text :
+            isPropertyAccessExpression(arg) ? arg.name.text : undefined);
         return createMethod(
             /*decorators*/ undefined,
             /*modifiers*/ makeStatic ? [createToken(SyntaxKind.StaticKeyword)] : undefined,
@@ -125,12 +140,12 @@ namespace ts.codefix {
             /*questionToken*/ undefined,
             /*typeParameters*/ inJs ? undefined : map(typeArguments, (_, i) =>
                 createTypeParameterDeclaration(CharacterCodes.T + typeArguments!.length - 1 <= CharacterCodes.Z ? String.fromCharCode(CharacterCodes.T + i) : `T${i}`)),
-            /*parameters*/ createDummyParameters(args.length, /*names*/ undefined, /*minArgumentCount*/ undefined, inJs),
+            /*parameters*/ createDummyParameters(args.length, names, types, /*minArgumentCount*/ undefined, inJs),
             /*type*/ inJs ? undefined : createKeywordTypeNode(SyntaxKind.AnyKeyword),
             createStubbedMethodBody(preferences));
     }
 
-    function createDummyParameters(argCount: number, names: string[] | undefined, minArgumentCount: number | undefined, inJs: boolean): ParameterDeclaration[] {
+    function createDummyParameters(argCount: number, names: (string | undefined)[] | undefined, types: (TypeNode | undefined)[] | undefined, minArgumentCount: number | undefined, inJs: boolean): ParameterDeclaration[] {
         const parameters: ParameterDeclaration[] = [];
         for (let i = 0; i < argCount; i++) {
             const newParameter = createParameter(
@@ -139,7 +154,7 @@ namespace ts.codefix {
                 /*dotDotDotToken*/ undefined,
                 /*name*/ names && names[i] || `arg${i}`,
                 /*questionToken*/ minArgumentCount !== undefined && i >= minArgumentCount ? createToken(SyntaxKind.QuestionToken) : undefined,
-                /*type*/ inJs ? undefined : createKeywordTypeNode(SyntaxKind.AnyKeyword),
+                /*type*/ inJs ? undefined : types && types[i] || createKeywordTypeNode(SyntaxKind.AnyKeyword),
                 /*initializer*/ undefined);
             parameters.push(newParameter);
         }
@@ -172,7 +187,7 @@ namespace ts.codefix {
         const maxNonRestArgs = maxArgsSignature.parameters.length - (maxArgsSignature.hasRestParameter ? 1 : 0);
         const maxArgsParameterSymbolNames = maxArgsSignature.parameters.map(symbol => symbol.name);
 
-        const parameters = createDummyParameters(maxNonRestArgs, maxArgsParameterSymbolNames, minArgumentCount, /*inJs*/ false);
+        const parameters = createDummyParameters(maxNonRestArgs, maxArgsParameterSymbolNames, /* types */ undefined, minArgumentCount, /*inJs*/ false);
 
         if (someSigHasRestParameter) {
             const anyArrayType = createArrayTypeNode(createKeywordTypeNode(SyntaxKind.AnyKeyword));
diff --git a/src/services/codefixes/inferFromUsage.ts b/src/services/codefixes/inferFromUsage.ts
index c58c001b403..3e26e4cdd32 100644
--- a/src/services/codefixes/inferFromUsage.ts
+++ b/src/services/codefixes/inferFromUsage.ts
@@ -33,8 +33,9 @@ namespace ts.codefix {
             const token = getTokenAtPosition(sourceFile, start, /*includeJsDocComment*/ false);
             let declaration!: Declaration | undefined;
             const changes = textChanges.ChangeTracker.with(context, changes => { declaration = doChange(changes, sourceFile, token, errorCode, program, cancellationToken, /*markSeenseen*/ returnTrue); });
-            return changes.length === 0 ? undefined
-                : [createCodeFixAction(fixId, changes, [getDiagnostic(errorCode, token), getNameOfDeclaration(declaration!).getText(sourceFile)], fixId, Diagnostics.Infer_all_types_from_usage)];
+            const name = getNameOfDeclaration(declaration!);
+            return !name || changes.length === 0 ? undefined
+                : [createCodeFixAction(fixId, changes, [getDiagnostic(errorCode, token), name.getText(sourceFile)], fixId, Diagnostics.Infer_all_types_from_usage)];
         },
         fixIds: [fixId],
         getAllCodeActions(context) {
diff --git a/src/services/completions.ts b/src/services/completions.ts
index e31ac4e81f3..21d704661b2 100644
--- a/src/services/completions.ts
+++ b/src/services/completions.ts
@@ -1122,7 +1122,7 @@ namespace ts.Completions {
             // If this is e.g. [Symbol.iterator], add a completion for `Symbol`.
             const symbolSymbol = firstDefined(symbol.declarations, decl => {
                 const name = getNameOfDeclaration(decl);
-                const leftName = name.kind === SyntaxKind.ComputedPropertyName ? getLeftMostName(name.expression) : undefined;
+                const leftName = name && name.kind === SyntaxKind.ComputedPropertyName ? getLeftMostName(name.expression) : undefined;
                 return leftName && typeChecker.getSymbolAtLocation(leftName);
             });
             if (symbolSymbol) {
@@ -1966,7 +1966,7 @@ namespace ts.Completions {
                     // NOTE: if one only performs this step when m.name is an identifier,
                     // things like '__proto__' are not filtered out.
                     const name = getNameOfDeclaration(m);
-                    existingName = isPropertyNameLiteral(name) ? getEscapedTextOfIdentifierOrLiteral(name) : undefined;
+                    existingName = name && isPropertyNameLiteral(name) ? getEscapedTextOfIdentifierOrLiteral(name) : undefined;
                 }
 
                 existingMemberNames.set(existingName!, true); // TODO: GH#18217
diff --git a/src/services/findAllReferences.ts b/src/services/findAllReferences.ts
index 46dd83851c1..0fbcd5cd6e9 100644
--- a/src/services/findAllReferences.ts
+++ b/src/services/findAllReferences.ts
@@ -981,6 +981,7 @@ namespace ts.FindAllReferences.Core {
 
     function getReferenceForShorthandProperty({ flags, valueDeclaration }: Symbol, search: Search, state: State): void {
         const shorthandValueSymbol = state.checker.getShorthandAssignmentValueSymbol(valueDeclaration)!;
+        const name = getNameOfDeclaration(valueDeclaration);
         /*
          * 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
@@ -988,8 +989,8 @@ namespace ts.FindAllReferences.Core {
          * 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.
          */
-        if (!(flags & SymbolFlags.Transient) && search.includes(shorthandValueSymbol)) {
-            addReference(getNameOfDeclaration(valueDeclaration), shorthandValueSymbol, state);
+        if (!(flags & SymbolFlags.Transient) && name && search.includes(shorthandValueSymbol)) {
+            addReference(name, shorthandValueSymbol, state);
         }
     }
 
diff --git a/src/services/formatting/formatting.ts b/src/services/formatting/formatting.ts
index eeec4b15ea7..f37fb1bc5dd 100644
--- a/src/services/formatting/formatting.ts
+++ b/src/services/formatting/formatting.ts
@@ -512,7 +512,10 @@ namespace ts.formatting {
                 // falls through
                 case SyntaxKind.PropertyDeclaration:
                 case SyntaxKind.Parameter:
-                    return getNameOfDeclaration(<Declaration>node).kind;
+                    const name = getNameOfDeclaration(<Declaration>node);
+                    if (name) {
+                        return name.kind;
+                    }
             }
         }
 
diff --git a/src/services/navigateTo.ts b/src/services/navigateTo.ts
index 723d7f59b3a..dc03c736f3c 100644
--- a/src/services/navigateTo.ts
+++ b/src/services/navigateTo.ts
@@ -113,7 +113,7 @@ namespace ts.NavigateTo {
         // First, if we started with a computed property name, then add all but the last
         // portion into the container array.
         const name = getNameOfDeclaration(declaration);
-        if (name.kind === SyntaxKind.ComputedPropertyName && !tryAddComputedPropertyName(name.expression, containers, /*includeLastPortion*/ false)) {
+        if (name && name.kind === SyntaxKind.ComputedPropertyName && !tryAddComputedPropertyName(name.expression, containers, /*includeLastPortion*/ false)) {
             return undefined;
         }
 
diff --git a/src/services/navigationBar.ts b/src/services/navigationBar.ts
index f381be9b7d1..d97004b80c5 100644
--- a/src/services/navigationBar.ts
+++ b/src/services/navigationBar.ts
@@ -277,7 +277,7 @@ namespace ts.NavigationBar {
                     case SpecialPropertyAssignmentKind.PrototypeProperty:
                     case SpecialPropertyAssignmentKind.Prototype:
                         addNodeWithRecursiveChild(node, (node as BinaryExpression).right);
-                        break;
+                        return;
                     case SpecialPropertyAssignmentKind.ThisProperty:
                     case SpecialPropertyAssignmentKind.Property:
                     case SpecialPropertyAssignmentKind.None:
diff --git a/src/services/refactors/generateGetAccessorAndSetAccessor.ts b/src/services/refactors/generateGetAccessorAndSetAccessor.ts
index 2e4f11c4b27..b7240f2e985 100644
--- a/src/services/refactors/generateGetAccessorAndSetAccessor.ts
+++ b/src/services/refactors/generateGetAccessorAndSetAccessor.ts
@@ -9,20 +9,19 @@ namespace ts.refactor.generateGetAccessorAndSetAccessor {
     type ContainerDeclaration = ClassLikeDeclaration | ObjectLiteralExpression;
 
     interface Info {
-        container: ContainerDeclaration;
-        isStatic: boolean;
-        isReadonly: boolean;
-        type: TypeNode | undefined;
-        declaration: AcceptedDeclaration;
-        fieldName: AcceptedNameType;
-        accessorName: AcceptedNameType;
-        originalName: AcceptedNameType;
-        renameAccessor: boolean;
+        readonly container: ContainerDeclaration;
+        readonly isStatic: boolean;
+        readonly isReadonly: boolean;
+        readonly type: TypeNode | undefined;
+        readonly declaration: AcceptedDeclaration;
+        readonly fieldName: AcceptedNameType;
+        readonly accessorName: AcceptedNameType;
+        readonly originalName: AcceptedNameType;
+        readonly renameAccessor: boolean;
     }
 
     function getAvailableActions(context: RefactorContext): ApplicableRefactorInfo[] | undefined {
-        const { file } = context;
-        if (!getConvertibleFieldAtPosition(context, file)) return undefined;
+        if (!getConvertibleFieldAtPosition(context)) return undefined;
 
         return [{
             name: actionName,
@@ -39,7 +38,7 @@ namespace ts.refactor.generateGetAccessorAndSetAccessor {
     function getEditsForAction(context: RefactorContext, _actionName: string): RefactorEditInfo | undefined {
         const { file } = context;
 
-        const fieldInfo = getConvertibleFieldAtPosition(context, file);
+        const fieldInfo = getConvertibleFieldAtPosition(context);
         if (!fieldInfo) return undefined;
 
         const isJS = isSourceFileJavaScript(file);
@@ -117,14 +116,14 @@ namespace ts.refactor.generateGetAccessorAndSetAccessor {
         return name.charCodeAt(0) === CharacterCodes._;
     }
 
-    function getConvertibleFieldAtPosition(context: RefactorContext, file: SourceFile): Info | undefined {
-        const { startPosition, endPosition } = context;
+    function getConvertibleFieldAtPosition(context: RefactorContext): Info | undefined {
+        const { file, startPosition, endPosition } = context;
 
         const node = getTokenAtPosition(file, startPosition, /*includeJsDocComment*/ false);
         const declaration = findAncestor(node.parent, isAcceptedDeclaration);
         // make sure declaration have AccessibilityModifier or Static Modifier or Readonly Modifier
         const meaning = ModifierFlags.AccessibilityModifier | ModifierFlags.Static | ModifierFlags.Readonly;
-        if (!declaration || !rangeOverlapsWithStartEnd(declaration.name, startPosition, endPosition!) // TODO: GH#18217
+        if (!declaration || !nodeOverlapsWithStartEnd(declaration.name, file, startPosition, endPosition!) // TODO: GH#18217
             || !isConvertibleName(declaration.name) || (getModifierFlags(declaration) | meaning) !== meaning) return undefined;
 
         const name = declaration.name.text;
diff --git a/src/services/services.ts b/src/services/services.ts
index 24feaac17c6..2e275813585 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -391,10 +391,10 @@ namespace ts {
         getApparentProperties(): Symbol[] {
             return this.checker.getAugmentedPropertiesOfType(this);
         }
-        getCallSignatures(): Signature[] {
+        getCallSignatures(): ReadonlyArray<Signature> {
             return this.checker.getSignaturesOfType(this, SignatureKind.Call);
         }
-        getConstructSignatures(): Signature[] {
+        getConstructSignatures(): ReadonlyArray<Signature> {
             return this.checker.getSignaturesOfType(this, SignatureKind.Construct);
         }
         getStringIndexType(): Type | undefined {
diff --git a/src/services/symbolDisplay.ts b/src/services/symbolDisplay.ts
index 2945d641c09..5eb26dc21d6 100644
--- a/src/services/symbolDisplay.ts
+++ b/src/services/symbolDisplay.ts
@@ -600,7 +600,7 @@ namespace ts.SymbolDisplay {
             }
         }
 
-        function addSignatureDisplayParts(signature: Signature, allSignatures: Signature[], flags = TypeFormatFlags.None) {
+        function addSignatureDisplayParts(signature: Signature, allSignatures: ReadonlyArray<Signature>, flags = TypeFormatFlags.None) {
             addRange(displayParts, signatureToDisplayParts(typeChecker, signature, enclosingDeclaration, flags | TypeFormatFlags.WriteTypeArgumentsOfSignature));
             if (allSignatures.length > 1) {
                 displayParts.push(spacePart());
diff --git a/src/services/types.ts b/src/services/types.ts
index 9ae51a4ea61..be897f20cd4 100644
--- a/src/services/types.ts
+++ b/src/services/types.ts
@@ -44,8 +44,8 @@ namespace ts {
         getProperties(): Symbol[];
         getProperty(propertyName: string): Symbol | undefined;
         getApparentProperties(): Symbol[];
-        getCallSignatures(): Signature[];
-        getConstructSignatures(): Signature[];
+        getCallSignatures(): ReadonlyArray<Signature>;
+        getConstructSignatures(): ReadonlyArray<Signature>;
         getStringIndexType(): Type | undefined;
         getNumberIndexType(): Type | undefined;
         getBaseTypes(): BaseType[] | undefined;
diff --git a/src/services/utilities.ts b/src/services/utilities.ts
index 9715d124d7e..481d20e91bd 100644
--- a/src/services/utilities.ts
+++ b/src/services/utilities.ts
@@ -439,6 +439,10 @@ namespace ts {
         return startEndOverlapsWithStartEnd(r1.pos, r1.end, start, end);
     }
 
+    export function nodeOverlapsWithStartEnd(node: Node, sourceFile: SourceFile, start: number, end: number) {
+        return startEndOverlapsWithStartEnd(node.getStart(sourceFile), node.end, start, end);
+    }
+
     export function startEndOverlapsWithStartEnd(start1: number, end1: number, start2: number, end2: number) {
         const start = Math.max(start1, start2);
         const end = Math.min(end1, end2);
@@ -944,7 +948,7 @@ namespace ts {
                     token = findPrecedingToken(token.getFullStart(), sourceFile);
                     if (!token || !isIdentifier(token)) return undefined;
                     if (!remainingLessThanTokens) {
-                        return { called: token, nTypeArguments };
+                        return isDeclarationName(token) ? undefined : { called: token, nTypeArguments };
                     }
                     remainingLessThanTokens--;
                     break;
diff --git a/src/testRunner/unittests/commandLineParsing.ts b/src/testRunner/unittests/commandLineParsing.ts
index cf7cabdd26d..7145b9e5ec4 100644
--- a/src/testRunner/unittests/commandLineParsing.ts
+++ b/src/testRunner/unittests/commandLineParsing.ts
@@ -57,7 +57,7 @@ namespace ts {
             assertParseResult(["--lib", "es5,invalidOption", "0.ts"],
                 {
                     errors: [{
-                        messageText: "Argument for '--lib' option must be: 'es5', 'es6', 'es2015', 'es7', 'es2016', 'es2017', 'es2018', 'esnext', 'dom', 'dom.iterable', 'webworker', 'webworker.importscripts', 'scripthost', 'es2015.core', 'es2015.collection', 'es2015.generator', 'es2015.iterable', 'es2015.promise', 'es2015.proxy', 'es2015.reflect', 'es2015.symbol', 'es2015.symbol.wellknown', 'es2016.array.include', 'es2017.object', 'es2017.sharedmemory', 'es2017.string', 'es2017.intl', 'es2017.typedarrays', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable'.",
+                        messageText: "Argument for '--lib' option must be: 'es5', 'es6', 'es2015', 'es7', 'es2016', 'es2017', 'es2018', 'esnext', 'dom', 'dom.iterable', 'webworker', 'webworker.importscripts', 'scripthost', 'es2015.core', 'es2015.collection', 'es2015.generator', 'es2015.iterable', 'es2015.promise', 'es2015.proxy', 'es2015.reflect', 'es2015.symbol', 'es2015.symbol.wellknown', 'es2016.array.include', 'es2017.object', 'es2017.sharedmemory', 'es2017.string', 'es2017.intl', 'es2017.typedarrays', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable', 'esnext.intl'.",
                         category: Diagnostics.Argument_for_0_option_must_be_Colon_1.category,
                         code: Diagnostics.Argument_for_0_option_must_be_Colon_1.code,
                         file: undefined,
@@ -259,7 +259,7 @@ namespace ts {
             assertParseResult(["--lib", "es5,", "es7", "0.ts"],
                 {
                     errors: [{
-                        messageText: "Argument for '--lib' option must be: 'es5', 'es6', 'es2015', 'es7', 'es2016', 'es2017', 'es2018', 'esnext', 'dom', 'dom.iterable', 'webworker', 'webworker.importscripts', 'scripthost', 'es2015.core', 'es2015.collection', 'es2015.generator', 'es2015.iterable', 'es2015.promise', 'es2015.proxy', 'es2015.reflect', 'es2015.symbol', 'es2015.symbol.wellknown', 'es2016.array.include', 'es2017.object', 'es2017.sharedmemory', 'es2017.string', 'es2017.intl', 'es2017.typedarrays', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable'.",
+                        messageText: "Argument for '--lib' option must be: 'es5', 'es6', 'es2015', 'es7', 'es2016', 'es2017', 'es2018', 'esnext', 'dom', 'dom.iterable', 'webworker', 'webworker.importscripts', 'scripthost', 'es2015.core', 'es2015.collection', 'es2015.generator', 'es2015.iterable', 'es2015.promise', 'es2015.proxy', 'es2015.reflect', 'es2015.symbol', 'es2015.symbol.wellknown', 'es2016.array.include', 'es2017.object', 'es2017.sharedmemory', 'es2017.string', 'es2017.intl', 'es2017.typedarrays', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable', 'esnext.intl'.",
                         category: Diagnostics.Argument_for_0_option_must_be_Colon_1.category,
                         code: Diagnostics.Argument_for_0_option_must_be_Colon_1.code,
                         file: undefined,
@@ -278,7 +278,7 @@ namespace ts {
             assertParseResult(["--lib", "es5, ", "es7", "0.ts"],
                 {
                     errors: [{
-                        messageText: "Argument for '--lib' option must be: 'es5', 'es6', 'es2015', 'es7', 'es2016', 'es2017', 'es2018', 'esnext', 'dom', 'dom.iterable', 'webworker', 'webworker.importscripts', 'scripthost', 'es2015.core', 'es2015.collection', 'es2015.generator', 'es2015.iterable', 'es2015.promise', 'es2015.proxy', 'es2015.reflect', 'es2015.symbol', 'es2015.symbol.wellknown', 'es2016.array.include', 'es2017.object', 'es2017.sharedmemory', 'es2017.string', 'es2017.intl', 'es2017.typedarrays', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable'.",
+                        messageText: "Argument for '--lib' option must be: 'es5', 'es6', 'es2015', 'es7', 'es2016', 'es2017', 'es2018', 'esnext', 'dom', 'dom.iterable', 'webworker', 'webworker.importscripts', 'scripthost', 'es2015.core', 'es2015.collection', 'es2015.generator', 'es2015.iterable', 'es2015.promise', 'es2015.proxy', 'es2015.reflect', 'es2015.symbol', 'es2015.symbol.wellknown', 'es2016.array.include', 'es2017.object', 'es2017.sharedmemory', 'es2017.string', 'es2017.intl', 'es2017.typedarrays', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable', 'esnext.intl'.",
                         category: Diagnostics.Argument_for_0_option_must_be_Colon_1.category,
                         code: Diagnostics.Argument_for_0_option_must_be_Colon_1.code,
                         file: undefined,
diff --git a/src/testRunner/unittests/convertCompilerOptionsFromJson.ts b/src/testRunner/unittests/convertCompilerOptionsFromJson.ts
index b1695ad01f5..3b422e9a645 100644
--- a/src/testRunner/unittests/convertCompilerOptionsFromJson.ts
+++ b/src/testRunner/unittests/convertCompilerOptionsFromJson.ts
@@ -263,7 +263,7 @@ namespace ts {
                         file: undefined,
                         start: 0,
                         length: 0,
-                        messageText: "Argument for '--lib' option must be: 'es5', 'es6', 'es2015', 'es7', 'es2016', 'es2017', 'es2018', 'esnext', 'dom', 'dom.iterable', 'webworker', 'webworker.importscripts', 'scripthost', 'es2015.core', 'es2015.collection', 'es2015.generator', 'es2015.iterable', 'es2015.promise', 'es2015.proxy', 'es2015.reflect', 'es2015.symbol', 'es2015.symbol.wellknown', 'es2016.array.include', 'es2017.object', 'es2017.sharedmemory', 'es2017.string', 'es2017.intl', 'es2017.typedarrays', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable'.",
+                        messageText: "Argument for '--lib' option must be: 'es5', 'es6', 'es2015', 'es7', 'es2016', 'es2017', 'es2018', 'esnext', 'dom', 'dom.iterable', 'webworker', 'webworker.importscripts', 'scripthost', 'es2015.core', 'es2015.collection', 'es2015.generator', 'es2015.iterable', 'es2015.promise', 'es2015.proxy', 'es2015.reflect', 'es2015.symbol', 'es2015.symbol.wellknown', 'es2016.array.include', 'es2017.object', 'es2017.sharedmemory', 'es2017.string', 'es2017.intl', 'es2017.typedarrays', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable', 'esnext.intl'.",
                         code: Diagnostics.Argument_for_0_option_must_be_Colon_1.code,
                         category: Diagnostics.Argument_for_0_option_must_be_Colon_1.category
                     }]
@@ -294,7 +294,7 @@ namespace ts {
                         file: undefined,
                         start: 0,
                         length: 0,
-                        messageText: "Argument for '--lib' option must be: 'es5', 'es6', 'es2015', 'es7', 'es2016', 'es2017', 'es2018', 'esnext', 'dom', 'dom.iterable', 'webworker', 'webworker.importscripts', 'scripthost', 'es2015.core', 'es2015.collection', 'es2015.generator', 'es2015.iterable', 'es2015.promise', 'es2015.proxy', 'es2015.reflect', 'es2015.symbol', 'es2015.symbol.wellknown', 'es2016.array.include', 'es2017.object', 'es2017.sharedmemory', 'es2017.string', 'es2017.intl', 'es2017.typedarrays', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable'.",
+                        messageText: "Argument for '--lib' option must be: 'es5', 'es6', 'es2015', 'es7', 'es2016', 'es2017', 'es2018', 'esnext', 'dom', 'dom.iterable', 'webworker', 'webworker.importscripts', 'scripthost', 'es2015.core', 'es2015.collection', 'es2015.generator', 'es2015.iterable', 'es2015.promise', 'es2015.proxy', 'es2015.reflect', 'es2015.symbol', 'es2015.symbol.wellknown', 'es2016.array.include', 'es2017.object', 'es2017.sharedmemory', 'es2017.string', 'es2017.intl', 'es2017.typedarrays', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable', 'esnext.intl'.",
                         code: Diagnostics.Argument_for_0_option_must_be_Colon_1.code,
                         category: Diagnostics.Argument_for_0_option_must_be_Colon_1.category
                     }]
@@ -325,7 +325,7 @@ namespace ts {
                         file: undefined,
                         start: 0,
                         length: 0,
-                        messageText: "Argument for '--lib' option must be: 'es5', 'es6', 'es2015', 'es7', 'es2016', 'es2017', 'es2018', 'esnext', 'dom', 'dom.iterable', 'webworker', 'webworker.importscripts', 'scripthost', 'es2015.core', 'es2015.collection', 'es2015.generator', 'es2015.iterable', 'es2015.promise', 'es2015.proxy', 'es2015.reflect', 'es2015.symbol', 'es2015.symbol.wellknown', 'es2016.array.include', 'es2017.object', 'es2017.sharedmemory', 'es2017.string', 'es2017.intl', 'es2017.typedarrays', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable'.",
+                        messageText: "Argument for '--lib' option must be: 'es5', 'es6', 'es2015', 'es7', 'es2016', 'es2017', 'es2018', 'esnext', 'dom', 'dom.iterable', 'webworker', 'webworker.importscripts', 'scripthost', 'es2015.core', 'es2015.collection', 'es2015.generator', 'es2015.iterable', 'es2015.promise', 'es2015.proxy', 'es2015.reflect', 'es2015.symbol', 'es2015.symbol.wellknown', 'es2016.array.include', 'es2017.object', 'es2017.sharedmemory', 'es2017.string', 'es2017.intl', 'es2017.typedarrays', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable', 'esnext.intl'.",
                         code: Diagnostics.Argument_for_0_option_must_be_Colon_1.code,
                         category: Diagnostics.Argument_for_0_option_must_be_Colon_1.category
                     }]
@@ -356,7 +356,7 @@ namespace ts {
                         file: undefined,
                         start: 0,
                         length: 0,
-                        messageText: "Argument for '--lib' option must be: 'es5', 'es6', 'es2015', 'es7', 'es2016', 'es2017', 'es2018', 'esnext', 'dom', 'dom.iterable', 'webworker', 'webworker.importscripts', 'scripthost', 'es2015.core', 'es2015.collection', 'es2015.generator', 'es2015.iterable', 'es2015.promise', 'es2015.proxy', 'es2015.reflect', 'es2015.symbol', 'es2015.symbol.wellknown', 'es2016.array.include', 'es2017.object', 'es2017.sharedmemory', 'es2017.string', 'es2017.intl', 'es2017.typedarrays', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable'.",
+                        messageText: "Argument for '--lib' option must be: 'es5', 'es6', 'es2015', 'es7', 'es2016', 'es2017', 'es2018', 'esnext', 'dom', 'dom.iterable', 'webworker', 'webworker.importscripts', 'scripthost', 'es2015.core', 'es2015.collection', 'es2015.generator', 'es2015.iterable', 'es2015.promise', 'es2015.proxy', 'es2015.reflect', 'es2015.symbol', 'es2015.symbol.wellknown', 'es2016.array.include', 'es2017.object', 'es2017.sharedmemory', 'es2017.string', 'es2017.intl', 'es2017.typedarrays', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable', 'esnext.intl'.",
                         code: Diagnostics.Argument_for_0_option_must_be_Colon_1.code,
                         category: Diagnostics.Argument_for_0_option_must_be_Colon_1.category
                     }]
diff --git a/src/testRunner/unittests/tscWatchMode.ts b/src/testRunner/unittests/tscWatchMode.ts
index 2aaef43f2d9..ed03c6ad48d 100644
--- a/src/testRunner/unittests/tscWatchMode.ts
+++ b/src/testRunner/unittests/tscWatchMode.ts
@@ -1218,6 +1218,58 @@ namespace ts.tscWatch {
                 checkWatchedFiles(host, files.map(f => f.path));
             }
         });
+
+        it("updates errors correctly when declaration emit is disabled in compiler options", () => {
+            const currentDirectory = "/user/username/projects/myproject";
+            const aFile: File = {
+                path: `${currentDirectory}/a.ts`,
+                content: `import test from './b';
+test(4, 5);`
+            };
+            const bFileContent = `function test(x: number, y: number) {
+    return x + y / 5;
+}
+export default test;`;
+            const bFile: File = {
+                path: `${currentDirectory}/b.ts`,
+                content: bFileContent
+            };
+            const tsconfigFile: File = {
+                path: `${currentDirectory}/tsconfig.json`,
+                content: JSON.stringify({
+                    compilerOptions: {
+                        module: "commonjs",
+                        noEmit: true,
+                        strict: true,
+                    }
+                })
+            };
+            const files = [aFile, bFile, libFile, tsconfigFile];
+            const host = createWatchedSystem(files, { currentDirectory });
+            const watch = createWatchOfConfigFile("tsconfig.json", host);
+            checkOutputErrorsInitial(host, emptyArray);
+
+            changeParameterType("x", "string", [
+                getDiagnosticOfFileFromProgram(watch(), aFile.path, aFile.content.indexOf("4"), 1, Diagnostics.Argument_of_type_0_is_not_assignable_to_parameter_of_type_1, "4", "string")
+            ]);
+            changeParameterType("y", "string", [
+                getDiagnosticOfFileFromProgram(watch(), aFile.path, aFile.content.indexOf("5"), 1, Diagnostics.Argument_of_type_0_is_not_assignable_to_parameter_of_type_1, "5", "string"),
+                getDiagnosticOfFileFromProgram(watch(), bFile.path, bFile.content.indexOf("y /"), 1, Diagnostics.The_left_hand_side_of_an_arithmetic_operation_must_be_of_type_any_number_or_an_enum_type)
+            ]);
+
+            function changeParameterType(parameterName: string, toType: string, expectedErrors: ReadonlyArray<Diagnostic>) {
+                const newContent = bFileContent.replace(new RegExp(`${parameterName}\: [a-z]*`), `${parameterName}: ${toType}`);
+
+                verifyErrorsWithBFileContents(newContent, expectedErrors);
+                verifyErrorsWithBFileContents(bFileContent, emptyArray);
+            }
+
+            function verifyErrorsWithBFileContents(content: string, expectedErrors: ReadonlyArray<Diagnostic>) {
+                host.writeFile(bFile.path, content);
+                host.runQueuedTimeoutCallbacks();
+                checkOutputErrorsIncremental(host, expectedErrors);
+            }
+        });
     });
 
     describe("tsc-watch emit with outFile or out setting", () => {
diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
index f5e20f96480..2946e354f4d 100644
--- a/tests/baselines/reference/api/tsserverlibrary.d.ts
+++ b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -2552,7 +2552,7 @@ declare namespace ts {
         getPropertiesOfType(type: Type): Symbol[];
         getPropertyOfType(type: Type, propertyName: string): Symbol | undefined;
         getIndexInfoOfType(type: Type, kind: IndexKind): IndexInfo | undefined;
-        getSignaturesOfType(type: Type, kind: SignatureKind): Signature[];
+        getSignaturesOfType(type: Type, kind: SignatureKind): ReadonlyArray<Signature>;
         getIndexTypeOfType(type: Type, kind: IndexKind): Type | undefined;
         getBaseTypes(type: InterfaceType): BaseType[];
         getBaseTypeOfLiteralType(type: Type): Type;
@@ -2923,7 +2923,7 @@ declare namespace ts {
         getNodeCheckFlags(node: Node): NodeCheckFlags;
         isDeclarationVisible(node: Declaration | AnyImportSyntax): boolean;
         isLateBound(node: Declaration): node is LateBoundDeclaration;
-        collectLinkedAliases(node: Identifier): Node[] | undefined;
+        collectLinkedAliases(node: Identifier, setVisibility?: boolean): Node[] | undefined;
         isImplementationOfOverload(node: FunctionLike): boolean | undefined;
         isRequiredInitializedParameter(node: ParameterDeclaration): boolean;
         isOptionalUninitializedParameterProperty(node: ParameterDeclaration): boolean;
@@ -3254,7 +3254,7 @@ declare namespace ts {
         symbol: Symbol;
         pattern?: DestructuringPattern;
         aliasSymbol?: Symbol;
-        aliasTypeArguments?: Type[];
+        aliasTypeArguments?: ReadonlyArray<Type>;
         wildcardInstantiation?: Type;
     }
     interface IntrinsicType extends Type {
@@ -3325,7 +3325,7 @@ declare namespace ts {
      */
     interface TypeReference extends ObjectType {
         target: GenericType;
-        typeArguments?: Type[];
+        typeArguments?: ReadonlyArray<Type>;
     }
     enum Variance {
         Invariant = 0,
@@ -3375,8 +3375,8 @@ declare namespace ts {
     interface ResolvedType extends ObjectType, UnionOrIntersectionType {
         members: SymbolTable;
         properties: Symbol[];
-        callSignatures: Signature[];
-        constructSignatures: Signature[];
+        callSignatures: ReadonlyArray<Signature>;
+        constructSignatures: ReadonlyArray<Signature>;
         stringIndexInfo?: IndexInfo;
         numberIndexInfo?: IndexInfo;
     }
@@ -3455,8 +3455,8 @@ declare namespace ts {
     }
     interface Signature {
         declaration?: SignatureDeclaration | JSDocSignature;
-        typeParameters?: TypeParameter[];
-        parameters: Symbol[];
+        typeParameters?: ReadonlyArray<TypeParameter>;
+        parameters: ReadonlyArray<Symbol>;
         thisParameter?: Symbol;
         resolvedReturnType?: Type;
         resolvedTypePredicate?: TypePredicate;
@@ -3522,7 +3522,7 @@ declare namespace ts {
     }
     type TypeComparer = (s: Type, t: Type, reportErrors?: boolean) => Ternary;
     interface InferenceContext extends TypeMapper {
-        typeParameters: TypeParameter[];
+        typeParameters: ReadonlyArray<TypeParameter>;
         signature?: Signature;
         inferences: InferenceInfo[];
         flags: InferenceFlags;
@@ -5768,6 +5768,7 @@ declare namespace ts {
         Enables_emit_interoperability_between_CommonJS_and_ES_Modules_via_creation_of_namespace_objects_for_all_imports_Implies_allowSyntheticDefaultImports: DiagnosticMessage;
         Type_originates_at_this_import_A_namespace_style_import_cannot_be_called_or_constructed_and_will_cause_a_failure_at_runtime_Consider_using_a_default_import_or_import_require_here_instead: DiagnosticMessage;
         Mapped_object_type_implicitly_has_an_any_template_type: DiagnosticMessage;
+        If_the_0_package_actually_exposes_this_module_consider_sending_a_pull_request_to_amend_https_Colon_Slash_Slashgithub_com_SlashDefinitelyTyped_SlashDefinitelyTyped_Slashtree_Slashmaster_Slashtypes_Slash_0: DiagnosticMessage;
         You_cannot_rename_this_element: DiagnosticMessage;
         You_cannot_rename_elements_that_are_defined_in_the_standard_TypeScript_library: DiagnosticMessage;
         import_can_only_be_used_in_a_ts_file: DiagnosticMessage;
@@ -6122,7 +6123,7 @@ declare namespace ts {
     function isLateVisibilityPaintedStatement(node: Node): node is LateVisibilityPaintedStatement;
     function isAnyImportOrReExport(node: Node): node is AnyImportOrReExport;
     function getEnclosingBlockScopeContainer(node: Node): Node;
-    function declarationNameToString(name: DeclarationName | QualifiedName): string;
+    function declarationNameToString(name: DeclarationName | QualifiedName | undefined): string;
     function getNameFromIndexInfo(info: IndexInfo): string | undefined;
     function getTextOfPropertyName(name: PropertyName): __String;
     function entityNameToString(name: EntityNameOrEntityNameExpression): string;
@@ -6309,7 +6310,8 @@ declare namespace ts {
     function isIdentifierName(node: Identifier): boolean;
     function isAliasSymbolDeclaration(node: Node): boolean;
     function exportAssignmentIsAlias(node: ExportAssignment | BinaryExpression): boolean;
-    function getClassExtendsHeritageClauseElement(node: ClassLikeDeclaration | InterfaceDeclaration): ExpressionWithTypeArguments | undefined;
+    function getEffectiveBaseTypeNode(node: ClassLikeDeclaration | InterfaceDeclaration): ExpressionWithTypeArguments | undefined;
+    function getClassExtendsHeritageElement(node: ClassLikeDeclaration | InterfaceDeclaration): ExpressionWithTypeArguments | undefined;
     function getClassImplementsHeritageClauseElements(node: ClassLikeDeclaration): NodeArray<ExpressionWithTypeArguments> | undefined;
     /** Returns the node in an `extends` or `implements` clause of a class or interface. */
     function getAllSuperTypeNodes(node: Node): ReadonlyArray<TypeNode>;
@@ -6700,7 +6702,7 @@ declare namespace ts {
     function isNamedDeclaration(node: Node): node is NamedDeclaration & {
         name: DeclarationName;
     };
-    function getNameOfDeclaration(declaration: Declaration | Expression): DeclarationName;
+    function getNameOfDeclaration(declaration: Declaration | Expression): DeclarationName | undefined;
     /**
      * Gets the JSDoc parameter tags for the node if present.
      *
@@ -7717,8 +7719,8 @@ declare namespace ts {
     /** Create a unique name based on the supplied text. This does not consider names injected by the transformer. */
     function createFileLevelUniqueName(text: string): Identifier;
     /** Create a unique name generated for a node. */
-    function getGeneratedNameForNode(node: Node): Identifier;
-    function getGeneratedNameForNode(node: Node, flags: GeneratedIdentifierFlags): Identifier;
+    function getGeneratedNameForNode(node: Node | undefined): Identifier;
+    function getGeneratedNameForNode(node: Node | undefined, flags: GeneratedIdentifierFlags): Identifier;
     function createToken<TKind extends SyntaxKind>(token: TKind): Token<TKind>;
     function createSuper(): SuperExpression;
     function createThis(): ThisExpression & Token<SyntaxKind.ThisKeyword>;
@@ -9813,8 +9815,8 @@ declare namespace ts {
         getProperties(): Symbol[];
         getProperty(propertyName: string): Symbol | undefined;
         getApparentProperties(): Symbol[];
-        getCallSignatures(): Signature[];
-        getConstructSignatures(): Signature[];
+        getCallSignatures(): ReadonlyArray<Signature>;
+        getConstructSignatures(): ReadonlyArray<Signature>;
         getStringIndexType(): Type | undefined;
         getNumberIndexType(): Type | undefined;
         getBaseTypes(): BaseType[] | undefined;
@@ -10684,6 +10686,7 @@ declare namespace ts {
     function startEndContainsRange(start: number, end: number, range: TextRange): boolean;
     function rangeContainsStartEnd(range: TextRange, start: number, end: number): boolean;
     function rangeOverlapsWithStartEnd(r1: TextRange, start: number, end: number): boolean;
+    function nodeOverlapsWithStartEnd(node: Node, sourceFile: SourceFile, start: number, end: number): boolean;
     function startEndOverlapsWithStartEnd(start1: number, end1: number, start2: number, end2: number): boolean;
     /**
      * Assumes `candidate.start <= position` holds.
@@ -11639,7 +11642,7 @@ declare namespace ts.codefix {
      * @returns Empty string iff there are no member insertions.
      */
     function createMissingMemberNodes(classDeclaration: ClassLikeDeclaration, possiblyMissingSymbols: ReadonlyArray<Symbol>, checker: TypeChecker, preferences: UserPreferences, out: (node: ClassElement) => void): void;
-    function createMethodFromCallExpression({ typeArguments, arguments: args, parent: parent }: CallExpression, methodName: string, inJs: boolean, makeStatic: boolean, preferences: UserPreferences): MethodDeclaration;
+    function createMethodFromCallExpression(context: CodeFixContextBase, { typeArguments, arguments: args, parent: parent }: CallExpression, methodName: string, inJs: boolean, makeStatic: boolean, preferences: UserPreferences): MethodDeclaration;
 }
 declare namespace ts.codefix {
 }
@@ -12188,6 +12191,7 @@ declare namespace ts.server.protocol {
         Change = "change",
         Close = "close",
         Completions = "completions",
+        CompletionInfo = "completionInfo",
         CompletionsFull = "completions-full",
         CompletionDetails = "completionEntryDetails",
         CompletionDetailsFull = "completionEntryDetails-full",
@@ -12889,6 +12893,15 @@ declare namespace ts.server.protocol {
     interface CompletionsResponse extends Response {
         body?: CompletionEntry[];
     }
+    interface CompletionInfoResponse extends Response {
+        body?: CompletionInfo;
+    }
+    interface CompletionInfo {
+        readonly isGlobalCompletion: boolean;
+        readonly isMemberCompletion: boolean;
+        readonly isNewIdentifierLocation: boolean;
+        readonly entries: ReadonlyArray<CompletionEntry>;
+    }
     interface CompletionDetailsResponse extends Response {
         body?: CompletionEntryDetails[];
     }
diff --git a/tests/baselines/reference/api/typescript.d.ts b/tests/baselines/reference/api/typescript.d.ts
index 62413b0753b..86215a7b7ba 100644
--- a/tests/baselines/reference/api/typescript.d.ts
+++ b/tests/baselines/reference/api/typescript.d.ts
@@ -1822,7 +1822,7 @@ declare namespace ts {
         getPropertiesOfType(type: Type): Symbol[];
         getPropertyOfType(type: Type, propertyName: string): Symbol | undefined;
         getIndexInfoOfType(type: Type, kind: IndexKind): IndexInfo | undefined;
-        getSignaturesOfType(type: Type, kind: SignatureKind): Signature[];
+        getSignaturesOfType(type: Type, kind: SignatureKind): ReadonlyArray<Signature>;
         getIndexTypeOfType(type: Type, kind: IndexKind): Type | undefined;
         getBaseTypes(type: InterfaceType): BaseType[];
         getBaseTypeOfLiteralType(type: Type): Type;
@@ -2198,7 +2198,7 @@ declare namespace ts {
         symbol: Symbol;
         pattern?: DestructuringPattern;
         aliasSymbol?: Symbol;
-        aliasTypeArguments?: Type[];
+        aliasTypeArguments?: ReadonlyArray<Type>;
     }
     interface LiteralType extends Type {
         value: string | number;
@@ -2263,7 +2263,7 @@ declare namespace ts {
      */
     interface TypeReference extends ObjectType {
         target: GenericType;
-        typeArguments?: Type[];
+        typeArguments?: ReadonlyArray<Type>;
     }
     interface GenericType extends InterfaceType, TypeReference {
     }
@@ -2323,8 +2323,8 @@ declare namespace ts {
     }
     interface Signature {
         declaration?: SignatureDeclaration | JSDocSignature;
-        typeParameters?: TypeParameter[];
-        parameters: Symbol[];
+        typeParameters?: ReadonlyArray<TypeParameter>;
+        parameters: ReadonlyArray<Symbol>;
     }
     enum IndexKind {
         String = 0,
@@ -3204,7 +3204,7 @@ declare namespace ts {
      */
     function unescapeIdentifier(id: string): string;
     function getNameOfJSDocTypedef(declaration: JSDocTypedefTag): Identifier | undefined;
-    function getNameOfDeclaration(declaration: Declaration | Expression): DeclarationName;
+    function getNameOfDeclaration(declaration: Declaration | Expression): DeclarationName | undefined;
     /**
      * Gets the JSDoc parameter tags for the node if present.
      *
@@ -3639,7 +3639,7 @@ declare namespace ts {
     /** Create a unique name based on the supplied text. This does not consider names injected by the transformer. */
     function createFileLevelUniqueName(text: string): Identifier;
     /** Create a unique name generated for a node. */
-    function getGeneratedNameForNode(node: Node): Identifier;
+    function getGeneratedNameForNode(node: Node | undefined): Identifier;
     function createToken<TKind extends SyntaxKind>(token: TKind): Token<TKind>;
     function createSuper(): SuperExpression;
     function createThis(): ThisExpression & Token<SyntaxKind.ThisKeyword>;
@@ -4613,8 +4613,8 @@ declare namespace ts {
         getProperties(): Symbol[];
         getProperty(propertyName: string): Symbol | undefined;
         getApparentProperties(): Symbol[];
-        getCallSignatures(): Signature[];
-        getConstructSignatures(): Signature[];
+        getCallSignatures(): ReadonlyArray<Signature>;
+        getConstructSignatures(): ReadonlyArray<Signature>;
         getStringIndexType(): Type | undefined;
         getNumberIndexType(): Type | undefined;
         getBaseTypes(): BaseType[] | undefined;
diff --git a/tests/baselines/reference/constInClassExpression.errors.txt b/tests/baselines/reference/constInClassExpression.errors.txt
new file mode 100644
index 00000000000..b3b66cba3a5
--- /dev/null
+++ b/tests/baselines/reference/constInClassExpression.errors.txt
@@ -0,0 +1,10 @@
+tests/cases/compiler/constInClassExpression.ts(2,11): error TS1248: A class member cannot have the 'const' keyword.
+
+
+==== tests/cases/compiler/constInClassExpression.ts (1 errors) ====
+    let C = class {
+        const a = 4;
+              ~
+!!! error TS1248: A class member cannot have the 'const' keyword.
+    };
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/constInClassExpression.js b/tests/baselines/reference/constInClassExpression.js
new file mode 100644
index 00000000000..1da4605687a
--- /dev/null
+++ b/tests/baselines/reference/constInClassExpression.js
@@ -0,0 +1,13 @@
+//// [constInClassExpression.ts]
+let C = class {
+    const a = 4;
+};
+
+
+//// [constInClassExpression.js]
+var C = /** @class */ (function () {
+    function class_1() {
+        this.a = 4;
+    }
+    return class_1;
+}());
diff --git a/tests/baselines/reference/constInClassExpression.symbols b/tests/baselines/reference/constInClassExpression.symbols
new file mode 100644
index 00000000000..7468772edfb
--- /dev/null
+++ b/tests/baselines/reference/constInClassExpression.symbols
@@ -0,0 +1,9 @@
+=== tests/cases/compiler/constInClassExpression.ts ===
+let C = class {
+>C : Symbol(C, Decl(constInClassExpression.ts, 0, 3))
+
+    const a = 4;
+>a : Symbol(C.a, Decl(constInClassExpression.ts, 0, 15))
+
+};
+
diff --git a/tests/baselines/reference/constInClassExpression.types b/tests/baselines/reference/constInClassExpression.types
new file mode 100644
index 00000000000..1efe8527e04
--- /dev/null
+++ b/tests/baselines/reference/constInClassExpression.types
@@ -0,0 +1,11 @@
+=== tests/cases/compiler/constInClassExpression.ts ===
+let C = class {
+>C : typeof C
+>class {    const a = 4;} : typeof C
+
+    const a = 4;
+>a : number
+>4 : 4
+
+};
+
diff --git a/tests/baselines/reference/extendsTag1.symbols b/tests/baselines/reference/extendsTag1.symbols
new file mode 100644
index 00000000000..f38683338b1
--- /dev/null
+++ b/tests/baselines/reference/extendsTag1.symbols
@@ -0,0 +1,9 @@
+=== tests/cases/conformance/jsdoc/bug25101.js ===
+/**
+ * @template T
+ * @extends {Set<T>} Should prefer this Set<T>, not the Set in the heritage clause
+ */
+class My extends Set {}
+>My : Symbol(My, Decl(bug25101.js, 0, 0))
+>Set : Symbol(Set, Decl(lib.es2015.collection.d.ts, --, --), Decl(lib.es2015.collection.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.symbol.wellknown.d.ts, --, --))
+
diff --git a/tests/baselines/reference/extendsTag1.types b/tests/baselines/reference/extendsTag1.types
new file mode 100644
index 00000000000..440861dd47b
--- /dev/null
+++ b/tests/baselines/reference/extendsTag1.types
@@ -0,0 +1,9 @@
+=== tests/cases/conformance/jsdoc/bug25101.js ===
+/**
+ * @template T
+ * @extends {Set<T>} Should prefer this Set<T>, not the Set in the heritage clause
+ */
+class My extends Set {}
+>My : My<T>
+>Set : Set<T>
+
diff --git a/tests/baselines/reference/typedefInnerNamepaths.errors.txt b/tests/baselines/reference/typedefInnerNamepaths.errors.txt
new file mode 100644
index 00000000000..179c36b0edd
--- /dev/null
+++ b/tests/baselines/reference/typedefInnerNamepaths.errors.txt
@@ -0,0 +1,28 @@
+tests/cases/conformance/jsdoc/bug25104.js(1,7): error TS2300: Duplicate identifier 'C'.
+tests/cases/conformance/jsdoc/bug25104.js(3,19): error TS1005: '}' expected.
+tests/cases/conformance/jsdoc/bug25104.js(4,26): error TS2300: Duplicate identifier 'C'.
+tests/cases/conformance/jsdoc/bug25104.js(6,18): error TS8024: JSDoc '@param' tag has name '', but there is no parameter with that name.
+tests/cases/conformance/jsdoc/bug25104.js(6,18): error TS1005: '}' expected.
+
+
+==== tests/cases/conformance/jsdoc/bug25104.js (5 errors) ====
+    class C {
+          ~
+!!! error TS2300: Duplicate identifier 'C'.
+        /**
+         * @typedef {C~A} C~B
+                      ~
+!!! error TS1005: '}' expected.
+         * @typedef {object} C~A
+                             ~
+!!! error TS2300: Duplicate identifier 'C'.
+         */
+        /** @param {C~A} o */
+                     
+!!! error TS8024: JSDoc '@param' tag has name '', but there is no parameter with that name.
+                     ~
+!!! error TS1005: '}' expected.
+        constructor(o) {
+        }
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/typedefInnerNamepaths.symbols b/tests/baselines/reference/typedefInnerNamepaths.symbols
new file mode 100644
index 00000000000..2ddcf419734
--- /dev/null
+++ b/tests/baselines/reference/typedefInnerNamepaths.symbols
@@ -0,0 +1,14 @@
+=== tests/cases/conformance/jsdoc/bug25104.js ===
+class C {
+>C : Symbol(C, Decl(bug25104.js, 0, 0))
+
+    /**
+     * @typedef {C~A} C~B
+     * @typedef {object} C~A
+     */
+    /** @param {C~A} o */
+    constructor(o) {
+>o : Symbol(o, Decl(bug25104.js, 6, 16))
+    }
+}
+
diff --git a/tests/baselines/reference/typedefInnerNamepaths.types b/tests/baselines/reference/typedefInnerNamepaths.types
new file mode 100644
index 00000000000..16e8ab556a7
--- /dev/null
+++ b/tests/baselines/reference/typedefInnerNamepaths.types
@@ -0,0 +1,14 @@
+=== tests/cases/conformance/jsdoc/bug25104.js ===
+class C {
+>C : C
+
+    /**
+     * @typedef {C~A} C~B
+     * @typedef {object} C~A
+     */
+    /** @param {C~A} o */
+    constructor(o) {
+>o : any
+    }
+}
+
diff --git a/tests/baselines/reference/untypedModuleImport_noImplicitAny_typesForPackageExist.errors.txt b/tests/baselines/reference/untypedModuleImport_noImplicitAny_typesForPackageExist.errors.txt
new file mode 100644
index 00000000000..ef5997f8f5e
--- /dev/null
+++ b/tests/baselines/reference/untypedModuleImport_noImplicitAny_typesForPackageExist.errors.txt
@@ -0,0 +1,35 @@
+/a.ts(2,25): error TS7016: Could not find a declaration file for module 'foo/sub'. '/node_modules/foo/sub.js' implicitly has an 'any' type.
+  If the 'foo' package actually exposes this module, consider sending a pull request to amend 'https://github.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/foo`
+/a.ts(3,25): error TS7016: Could not find a declaration file for module 'bar/sub'. '/node_modules/bar/sub.js' implicitly has an 'any' type.
+  Try `npm install @types/bar` if it exists or add a new declaration (.d.ts) file containing `declare module 'bar';`
+
+
+==== /a.ts (2 errors) ====
+    import * as foo from "foo";
+    import * as fooSub from "foo/sub";
+                            ~~~~~~~~~
+!!! error TS7016: Could not find a declaration file for module 'foo/sub'. '/node_modules/foo/sub.js' implicitly has an 'any' type.
+!!! error TS7016:   If the 'foo' package actually exposes this module, consider sending a pull request to amend 'https://github.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/foo`
+    import * as barSub from "bar/sub";
+                            ~~~~~~~~~
+!!! error TS7016: Could not find a declaration file for module 'bar/sub'. '/node_modules/bar/sub.js' implicitly has an 'any' type.
+!!! error TS7016:   Try `npm install @types/bar` if it exists or add a new declaration (.d.ts) file containing `declare module 'bar';`
+    
+==== /node_modules/@types/foo/index.d.ts (0 errors) ====
+    export const foo: number;
+    
+==== /node_modules/@types/foo/package.json (0 errors) ====
+    { "name": "@types/foo", "version": "1.2.3" }
+    
+==== /node_modules/foo/sub.js (0 errors) ====
+    const x = 0;
+    
+==== /node_modules/foo/package.json (0 errors) ====
+    { "name": "foo", "version": "1.2.3" }
+    
+==== /node_modules/bar/sub.js (0 errors) ====
+    const x = 0;
+    
+==== /node_modules/bar/package.json (0 errors) ====
+    { "name": "bar", "version": "1.2.3" }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/untypedModuleImport_noImplicitAny_typesForPackageExist.js b/tests/baselines/reference/untypedModuleImport_noImplicitAny_typesForPackageExist.js
new file mode 100644
index 00000000000..fe1a85730cd
--- /dev/null
+++ b/tests/baselines/reference/untypedModuleImport_noImplicitAny_typesForPackageExist.js
@@ -0,0 +1,29 @@
+//// [tests/cases/conformance/moduleResolution/untypedModuleImport_noImplicitAny_typesForPackageExist.ts] ////
+
+//// [index.d.ts]
+export const foo: number;
+
+//// [package.json]
+{ "name": "@types/foo", "version": "1.2.3" }
+
+//// [sub.js]
+const x = 0;
+
+//// [package.json]
+{ "name": "foo", "version": "1.2.3" }
+
+//// [sub.js]
+const x = 0;
+
+//// [package.json]
+{ "name": "bar", "version": "1.2.3" }
+
+//// [a.ts]
+import * as foo from "foo";
+import * as fooSub from "foo/sub";
+import * as barSub from "bar/sub";
+
+
+//// [a.js]
+"use strict";
+exports.__esModule = true;
diff --git a/tests/baselines/reference/untypedModuleImport_noImplicitAny_typesForPackageExist.symbols b/tests/baselines/reference/untypedModuleImport_noImplicitAny_typesForPackageExist.symbols
new file mode 100644
index 00000000000..59153d03f54
--- /dev/null
+++ b/tests/baselines/reference/untypedModuleImport_noImplicitAny_typesForPackageExist.symbols
@@ -0,0 +1,14 @@
+=== /a.ts ===
+import * as foo from "foo";
+>foo : Symbol(foo, Decl(a.ts, 0, 6))
+
+import * as fooSub from "foo/sub";
+>fooSub : Symbol(fooSub, Decl(a.ts, 1, 6))
+
+import * as barSub from "bar/sub";
+>barSub : Symbol(barSub, Decl(a.ts, 2, 6))
+
+=== /node_modules/@types/foo/index.d.ts ===
+export const foo: number;
+>foo : Symbol(foo, Decl(index.d.ts, 0, 12))
+
diff --git a/tests/baselines/reference/untypedModuleImport_noImplicitAny_typesForPackageExist.types b/tests/baselines/reference/untypedModuleImport_noImplicitAny_typesForPackageExist.types
new file mode 100644
index 00000000000..9a6b7b7e690
--- /dev/null
+++ b/tests/baselines/reference/untypedModuleImport_noImplicitAny_typesForPackageExist.types
@@ -0,0 +1,14 @@
+=== /a.ts ===
+import * as foo from "foo";
+>foo : typeof foo
+
+import * as fooSub from "foo/sub";
+>fooSub : any
+
+import * as barSub from "bar/sub";
+>barSub : any
+
+=== /node_modules/@types/foo/index.d.ts ===
+export const foo: number;
+>foo : number
+
diff --git a/tests/baselines/reference/user/TypeScript-Node-Starter.log b/tests/baselines/reference/user/TypeScript-Node-Starter.log
index affbd99af1e..9a0b3b00726 100644
--- a/tests/baselines/reference/user/TypeScript-Node-Starter.log
+++ b/tests/baselines/reference/user/TypeScript-Node-Starter.log
@@ -1,7 +1,5 @@
 Exit Code: 1
 Standard output:
-node_modules/@types/jquery/index.d.ts(6366,66): error TS2344: Type '"timeout" | "onreadystatechange" | "responseType" | "withCredentials" | "msCaching"' does not satisfy the constraint '"abort" | "open" | "timeout" | "send" | "DONE" | "response" | "getAllResponseHeaders" | "getRespo...'.
-  Type '"msCaching"' is not assignable to type '"abort" | "open" | "timeout" | "send" | "DONE" | "response" | "getAllResponseHeaders" | "getRespo...'.
 node_modules/@types/passport-facebook/index.d.ts(50,31): error TS2689: Cannot extend an interface 'passport.Strategy'. Did you mean 'implements'?
 
 
diff --git a/tests/baselines/reference/user/uglify-js.log b/tests/baselines/reference/user/uglify-js.log
index 4fb7b01a2c9..f37d91c289a 100644
--- a/tests/baselines/reference/user/uglify-js.log
+++ b/tests/baselines/reference/user/uglify-js.log
@@ -1,95 +1,95 @@
 Exit Code: 1
 Standard output:
-node_modules/uglify-js/lib/ast.js(210,23): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/ast.js(332,33): error TS2339: Property 'transform' does not exist on type 'string'.
-node_modules/uglify-js/lib/ast.js(877,5): error TS2322: Type '{ [x: string]: any; _visit: (node: any, descend: any) => any; parent: (n: any) => any; push: type...' is not assignable to type 'TreeWalker'.
+node_modules/uglify-js/lib/ast.js(209,23): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/ast.js(331,33): error TS2339: Property 'transform' does not exist on type 'string'.
+node_modules/uglify-js/lib/ast.js(872,5): error TS2322: Type '{ [x: string]: any; _visit: (node: any, descend: any) => any; parent: (n: any) => any; push: type...' is not assignable to type 'TreeWalker'.
   Object literal may only specify known properties, but '_visit' does not exist in type 'TreeWalker'. Did you mean to write 'visit'?
 node_modules/uglify-js/lib/compress.js(165,27): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(514,26): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(829,18): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(1084,38): error TS2339: Property 'parent' does not exist on type 'TreeTransformer'.
-node_modules/uglify-js/lib/compress.js(1098,51): error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'true | ((node: any) => any)' has no compatible call signatures.
-node_modules/uglify-js/lib/compress.js(1162,53): error TS2339: Property 'parent' does not exist on type 'TreeTransformer'.
-node_modules/uglify-js/lib/compress.js(1204,112): error TS2532: Object is possibly 'undefined'.
-node_modules/uglify-js/lib/compress.js(1205,29): error TS2532: Object is possibly 'undefined'.
-node_modules/uglify-js/lib/compress.js(1214,87): error TS2322: Type 'false' is not assignable to type 'number'.
-node_modules/uglify-js/lib/compress.js(1222,29): error TS2322: Type 'false' is not assignable to type 'never'.
-node_modules/uglify-js/lib/compress.js(1325,38): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(1417,38): error TS2339: Property 'parent' does not exist on type 'TreeTransformer'.
-node_modules/uglify-js/lib/compress.js(1514,27): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(1546,26): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(1960,44): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(2152,19): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(2412,27): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(3152,23): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(3165,33): error TS2322: Type '"f"' is not assignable to type 'boolean'.
-node_modules/uglify-js/lib/compress.js(3302,18): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(3312,33): error TS2339: Property 'add' does not exist on type 'Dictionary'.
-node_modules/uglify-js/lib/compress.js(3316,32): error TS2339: Property 'add' does not exist on type 'Dictionary'.
-node_modules/uglify-js/lib/compress.js(3322,40): error TS2339: Property 'add' does not exist on type 'Dictionary'.
-node_modules/uglify-js/lib/compress.js(3331,41): error TS2339: Property 'add' does not exist on type 'Dictionary'.
-node_modules/uglify-js/lib/compress.js(3348,14): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(3350,40): error TS2339: Property 'get' does not exist on type 'Dictionary'.
-node_modules/uglify-js/lib/compress.js(3358,33): error TS2339: Property 'parent' does not exist on type 'TreeTransformer'.
-node_modules/uglify-js/lib/compress.js(3432,63): error TS2339: Property 'get' does not exist on type 'Dictionary'.
-node_modules/uglify-js/lib/compress.js(3621,23): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(3638,36): error TS2339: Property 'parent' does not exist on type 'TreeTransformer'.
-node_modules/uglify-js/lib/compress.js(3644,38): error TS2339: Property 'set' does not exist on type 'Dictionary'.
-node_modules/uglify-js/lib/compress.js(3648,40): error TS2339: Property 'parent' does not exist on type 'TreeTransformer'.
-node_modules/uglify-js/lib/compress.js(3673,22): error TS2339: Property 'each' does not exist on type 'Dictionary'.
-node_modules/uglify-js/lib/compress.js(3678,30): error TS2339: Property 'del' does not exist on type 'Dictionary'.
-node_modules/uglify-js/lib/compress.js(3683,30): error TS2339: Property 'set' does not exist on type 'Dictionary'.
-node_modules/uglify-js/lib/compress.js(3694,41): error TS2339: Property 'has' does not exist on type 'Dictionary'.
-node_modules/uglify-js/lib/compress.js(3696,48): error TS2339: Property 'get' does not exist on type 'Dictionary'.
-node_modules/uglify-js/lib/compress.js(3708,41): error TS2339: Property 'has' does not exist on type 'Dictionary'.
-node_modules/uglify-js/lib/compress.js(3710,48): error TS2339: Property 'get' does not exist on type 'Dictionary'.
-node_modules/uglify-js/lib/compress.js(3816,21): error TS2403: Subsequent variable declarations must have the same type.  Variable 'defs' must be of type 'Dictionary', but here has type 'any'.
-node_modules/uglify-js/lib/compress.js(3818,36): error TS2339: Property 'get' does not exist on type 'Dictionary'.
-node_modules/uglify-js/lib/compress.js(3847,22): error TS2339: Property 'set' does not exist on type 'Dictionary'.
-node_modules/uglify-js/lib/compress.js(3867,17): error TS2447: The '|=' operator is not allowed for boolean types. Consider using '||' instead.
-node_modules/uglify-js/lib/compress.js(3892,30): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(4030,18): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(4329,17): error TS2403: Subsequent variable declarations must have the same type.  Variable 'body' must be of type 'any[]', but here has type 'any'.
-node_modules/uglify-js/lib/compress.js(4413,22): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(4761,30): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(4768,25): error TS2403: Subsequent variable declarations must have the same type.  Variable 'code' must be of type 'string', but here has type '{ [x: string]: any; get: () => string; toString: () => string; indent: () => void; indentation: (...'.
-node_modules/uglify-js/lib/compress.js(4772,36): error TS2532: Object is possibly 'undefined'.
-node_modules/uglify-js/lib/compress.js(4777,41): error TS2339: Property 'get' does not exist on type 'string'.
-node_modules/uglify-js/lib/compress.js(5264,18): error TS2454: Variable 'is_strict_comparison' is used before being assigned.
-node_modules/uglify-js/lib/compress.js(5703,25): error TS2365: Operator '==' cannot be applied to types 'boolean' and '"f"'.
-node_modules/uglify-js/lib/compress.js(5730,32): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(5790,24): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(5862,24): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(5868,26): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/compress.js(6218,43): error TS2454: Variable 'property' is used before being assigned.
-node_modules/uglify-js/lib/compress.js(6232,25): error TS2403: Subsequent variable declarations must have the same type.  Variable 'value' must be of type 'number', but here has type 'any'.
-node_modules/uglify-js/lib/compress.js(6235,46): error TS2339: Property 'has_side_effects' does not exist on type 'number'.
-node_modules/uglify-js/lib/compress.js(6242,25): error TS2403: Subsequent variable declarations must have the same type.  Variable 'value' must be of type 'number', but here has type 'any'.
-node_modules/uglify-js/lib/compress.js(6295,19): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(501,26): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(816,18): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(1071,38): error TS2339: Property 'parent' does not exist on type 'TreeTransformer'.
+node_modules/uglify-js/lib/compress.js(1085,51): error TS2349: Cannot invoke an expression whose type lacks a call signature. Type 'true | ((node: any) => any)' has no compatible call signatures.
+node_modules/uglify-js/lib/compress.js(1149,53): error TS2339: Property 'parent' does not exist on type 'TreeTransformer'.
+node_modules/uglify-js/lib/compress.js(1191,112): error TS2532: Object is possibly 'undefined'.
+node_modules/uglify-js/lib/compress.js(1192,29): error TS2532: Object is possibly 'undefined'.
+node_modules/uglify-js/lib/compress.js(1201,87): error TS2322: Type 'false' is not assignable to type 'number'.
+node_modules/uglify-js/lib/compress.js(1209,29): error TS2322: Type 'false' is not assignable to type 'never'.
+node_modules/uglify-js/lib/compress.js(1312,38): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(1407,38): error TS2339: Property 'parent' does not exist on type 'TreeTransformer'.
+node_modules/uglify-js/lib/compress.js(1503,27): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(1535,26): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(1949,44): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(2141,19): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(2401,27): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(3141,23): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(3154,33): error TS2322: Type '"f"' is not assignable to type 'boolean'.
+node_modules/uglify-js/lib/compress.js(3291,18): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(3301,33): error TS2339: Property 'add' does not exist on type 'Dictionary'.
+node_modules/uglify-js/lib/compress.js(3305,32): error TS2339: Property 'add' does not exist on type 'Dictionary'.
+node_modules/uglify-js/lib/compress.js(3311,40): error TS2339: Property 'add' does not exist on type 'Dictionary'.
+node_modules/uglify-js/lib/compress.js(3320,41): error TS2339: Property 'add' does not exist on type 'Dictionary'.
+node_modules/uglify-js/lib/compress.js(3337,14): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(3339,40): error TS2339: Property 'get' does not exist on type 'Dictionary'.
+node_modules/uglify-js/lib/compress.js(3347,33): error TS2339: Property 'parent' does not exist on type 'TreeTransformer'.
+node_modules/uglify-js/lib/compress.js(3421,63): error TS2339: Property 'get' does not exist on type 'Dictionary'.
+node_modules/uglify-js/lib/compress.js(3608,23): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(3629,24): error TS2339: Property 'parent' does not exist on type 'TreeTransformer'.
+node_modules/uglify-js/lib/compress.js(3635,26): error TS2339: Property 'set' does not exist on type 'Dictionary'.
+node_modules/uglify-js/lib/compress.js(3639,28): error TS2339: Property 'parent' does not exist on type 'TreeTransformer'.
+node_modules/uglify-js/lib/compress.js(3657,18): error TS2339: Property 'each' does not exist on type 'Dictionary'.
+node_modules/uglify-js/lib/compress.js(3662,26): error TS2339: Property 'del' does not exist on type 'Dictionary'.
+node_modules/uglify-js/lib/compress.js(3667,26): error TS2339: Property 'set' does not exist on type 'Dictionary'.
+node_modules/uglify-js/lib/compress.js(3678,37): error TS2339: Property 'has' does not exist on type 'Dictionary'.
+node_modules/uglify-js/lib/compress.js(3680,44): error TS2339: Property 'get' does not exist on type 'Dictionary'.
+node_modules/uglify-js/lib/compress.js(3692,37): error TS2339: Property 'has' does not exist on type 'Dictionary'.
+node_modules/uglify-js/lib/compress.js(3694,44): error TS2339: Property 'get' does not exist on type 'Dictionary'.
+node_modules/uglify-js/lib/compress.js(3798,21): error TS2403: Subsequent variable declarations must have the same type.  Variable 'defs' must be of type 'Dictionary', but here has type 'any'.
+node_modules/uglify-js/lib/compress.js(3800,36): error TS2339: Property 'get' does not exist on type 'Dictionary'.
+node_modules/uglify-js/lib/compress.js(3830,22): error TS2339: Property 'set' does not exist on type 'Dictionary'.
+node_modules/uglify-js/lib/compress.js(3850,17): error TS2447: The '|=' operator is not allowed for boolean types. Consider using '||' instead.
+node_modules/uglify-js/lib/compress.js(3875,30): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(4013,18): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(4312,17): error TS2403: Subsequent variable declarations must have the same type.  Variable 'body' must be of type 'any[]', but here has type 'any'.
+node_modules/uglify-js/lib/compress.js(4396,22): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(4746,30): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(4753,25): error TS2403: Subsequent variable declarations must have the same type.  Variable 'code' must be of type 'string', but here has type '{ [x: string]: any; get: () => string; toString: () => string; indent: () => void; indentation: (...'.
+node_modules/uglify-js/lib/compress.js(4757,36): error TS2532: Object is possibly 'undefined'.
+node_modules/uglify-js/lib/compress.js(4762,41): error TS2339: Property 'get' does not exist on type 'string'.
+node_modules/uglify-js/lib/compress.js(5249,18): error TS2454: Variable 'is_strict_comparison' is used before being assigned.
+node_modules/uglify-js/lib/compress.js(5688,25): error TS2365: Operator '==' cannot be applied to types 'boolean' and '"f"'.
+node_modules/uglify-js/lib/compress.js(5715,32): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(5775,24): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(5847,24): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(5853,26): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/compress.js(6213,43): error TS2454: Variable 'property' is used before being assigned.
+node_modules/uglify-js/lib/compress.js(6228,25): error TS2403: Subsequent variable declarations must have the same type.  Variable 'value' must be of type 'number', but here has type 'any'.
+node_modules/uglify-js/lib/compress.js(6231,46): error TS2339: Property 'has_side_effects' does not exist on type 'number'.
+node_modules/uglify-js/lib/compress.js(6237,25): error TS2403: Subsequent variable declarations must have the same type.  Variable 'value' must be of type 'number', but here has type 'any'.
+node_modules/uglify-js/lib/compress.js(6290,19): error TS2554: Expected 0 arguments, but got 1.
 node_modules/uglify-js/lib/minify.js(170,75): error TS2339: Property 'compress' does not exist on type 'Compressor'.
-node_modules/uglify-js/lib/mozilla-ast.js(569,18): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/mozilla-ast.js(566,18): error TS2554: Expected 0 arguments, but got 1.
 node_modules/uglify-js/lib/output.js(481,22): error TS2554: Expected 0 arguments, but got 1.
 node_modules/uglify-js/lib/output.js(774,23): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/output.js(1186,29): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/output.js(1480,58): error TS2362: The left-hand side of an arithmetic operation must be of type 'any', 'number' or an enum type.
-node_modules/uglify-js/lib/parse.js(365,20): error TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'.
+node_modules/uglify-js/lib/output.js(1170,29): error TS2554: Expected 0 arguments, but got 1.
+node_modules/uglify-js/lib/output.js(1452,58): error TS2362: The left-hand side of an arithmetic operation must be of type 'any', 'number' or an enum type.
+node_modules/uglify-js/lib/parse.js(367,20): error TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'.
   Type 'undefined' is not assignable to type 'number'.
-node_modules/uglify-js/lib/parse.js(447,32): error TS2345: Argument of type 'any' is not assignable to parameter of type 'never'.
-node_modules/uglify-js/lib/parse.js(458,32): error TS2345: Argument of type 'any' is not assignable to parameter of type 'never'.
-node_modules/uglify-js/lib/parse.js(509,20): error TS2339: Property 'raw_source' does not exist on type 'RegExp'.
-node_modules/uglify-js/lib/parse.js(620,57): error TS2339: Property 'push' does not exist on type 'never'.
-node_modules/uglify-js/lib/parse.js(630,32): error TS2345: Argument of type 'never[]' is not assignable to parameter of type 'never'.
-node_modules/uglify-js/lib/parse.js(636,40): error TS2339: Property 'length' does not exist on type 'never'.
-node_modules/uglify-js/lib/parse.js(740,13): error TS2531: Object is possibly 'null'.
-node_modules/uglify-js/lib/parse.js(772,52): error TS2531: Object is possibly 'null'.
-node_modules/uglify-js/lib/parse.js(772,74): error TS2531: Object is possibly 'null'.
-node_modules/uglify-js/lib/parse.js(814,31): error TS2531: Object is possibly 'null'.
-node_modules/uglify-js/lib/parse.js(820,17): error TS2531: Object is possibly 'null'.
-node_modules/uglify-js/lib/parse.js(824,21): error TS2531: Object is possibly 'null'.
-node_modules/uglify-js/lib/parse.js(829,43): error TS2531: Object is possibly 'null'.
-node_modules/uglify-js/lib/parse.js(848,21): error TS2531: Object is possibly 'null'.
-node_modules/uglify-js/lib/parse.js(867,21): error TS2531: Object is possibly 'null'.
-node_modules/uglify-js/lib/parse.js(982,23): error TS2345: Argument of type 'any' is not assignable to parameter of type 'never'.
+node_modules/uglify-js/lib/parse.js(449,32): error TS2345: Argument of type 'any' is not assignable to parameter of type 'never'.
+node_modules/uglify-js/lib/parse.js(460,32): error TS2345: Argument of type 'any' is not assignable to parameter of type 'never'.
+node_modules/uglify-js/lib/parse.js(511,20): error TS2339: Property 'raw_source' does not exist on type 'RegExp'.
+node_modules/uglify-js/lib/parse.js(622,57): error TS2339: Property 'push' does not exist on type 'never'.
+node_modules/uglify-js/lib/parse.js(632,32): error TS2345: Argument of type 'never[]' is not assignable to parameter of type 'never'.
+node_modules/uglify-js/lib/parse.js(638,40): error TS2339: Property 'length' does not exist on type 'never'.
+node_modules/uglify-js/lib/parse.js(739,13): error TS2531: Object is possibly 'null'.
+node_modules/uglify-js/lib/parse.js(771,52): error TS2531: Object is possibly 'null'.
+node_modules/uglify-js/lib/parse.js(771,74): error TS2531: Object is possibly 'null'.
+node_modules/uglify-js/lib/parse.js(815,31): error TS2531: Object is possibly 'null'.
+node_modules/uglify-js/lib/parse.js(821,17): error TS2531: Object is possibly 'null'.
+node_modules/uglify-js/lib/parse.js(825,21): error TS2531: Object is possibly 'null'.
+node_modules/uglify-js/lib/parse.js(830,43): error TS2531: Object is possibly 'null'.
+node_modules/uglify-js/lib/parse.js(849,21): error TS2531: Object is possibly 'null'.
+node_modules/uglify-js/lib/parse.js(868,21): error TS2531: Object is possibly 'null'.
+node_modules/uglify-js/lib/parse.js(983,23): error TS2345: Argument of type 'any' is not assignable to parameter of type 'never'.
 node_modules/uglify-js/lib/parse.js(1097,9): error TS2322: Type 'any[]' is not assignable to type 'never[]'.
   Type 'any' is not assignable to type 'never'.
 node_modules/uglify-js/lib/parse.js(1156,17): error TS2531: Object is possibly 'null'.
@@ -111,8 +111,8 @@ node_modules/uglify-js/lib/scope.js(202,19): error TS2554: Expected 0 arguments,
 node_modules/uglify-js/lib/scope.js(410,14): error TS2554: Expected 0 arguments, but got 1.
 node_modules/uglify-js/lib/scope.js(465,15): error TS2554: Expected 0 arguments, but got 1.
 node_modules/uglify-js/lib/scope.js(490,15): error TS2554: Expected 0 arguments, but got 1.
-node_modules/uglify-js/lib/sourcemap.js(56,25): error TS2304: Cannot find name 'MOZ_SourceMap'.
-node_modules/uglify-js/lib/sourcemap.js(62,23): error TS2304: Cannot find name 'MOZ_SourceMap'.
+node_modules/uglify-js/lib/sourcemap.js(55,25): error TS2304: Cannot find name 'MOZ_SourceMap'.
+node_modules/uglify-js/lib/sourcemap.js(61,23): error TS2304: Cannot find name 'MOZ_SourceMap'.
 node_modules/uglify-js/tools/exit.js(7,32): error TS2339: Property 'bufferSize' does not exist on type 'WriteStream'.
 node_modules/uglify-js/tools/exit.js(7,61): error TS2339: Property 'bufferSize' does not exist on type 'WriteStream'.
 node_modules/uglify-js/tools/node.js(68,27): error TS2339: Property 'minify' does not exist on type 'typeof import("/uglify-js/node_modules/uglify-js/tools/node")'.
diff --git a/tests/cases/compiler/constInClassExpression.ts b/tests/cases/compiler/constInClassExpression.ts
new file mode 100644
index 00000000000..b00b085e079
--- /dev/null
+++ b/tests/cases/compiler/constInClassExpression.ts
@@ -0,0 +1,3 @@
+let C = class {
+    const a = 4;
+};
diff --git a/tests/cases/conformance/jsdoc/extendsTag1.ts b/tests/cases/conformance/jsdoc/extendsTag1.ts
new file mode 100644
index 00000000000..194982760e9
--- /dev/null
+++ b/tests/cases/conformance/jsdoc/extendsTag1.ts
@@ -0,0 +1,10 @@
+// @noEmit: true
+// @allowJs: true
+// @checkJs: true
+// @lib: esnext
+// @Filename: bug25101.js
+/**
+ * @template T
+ * @extends {Set<T>} Should prefer this Set<T>, not the Set in the heritage clause
+ */
+class My extends Set {}
diff --git a/tests/cases/compiler/jsdocAugmentsMissingType.ts b/tests/cases/conformance/jsdoc/jsdocAugmentsMissingType.ts
similarity index 100%
rename from tests/cases/compiler/jsdocAugmentsMissingType.ts
rename to tests/cases/conformance/jsdoc/jsdocAugmentsMissingType.ts
diff --git a/tests/cases/compiler/jsdocAugments_errorInExtendsExpression.ts b/tests/cases/conformance/jsdoc/jsdocAugments_errorInExtendsExpression.ts
similarity index 100%
rename from tests/cases/compiler/jsdocAugments_errorInExtendsExpression.ts
rename to tests/cases/conformance/jsdoc/jsdocAugments_errorInExtendsExpression.ts
diff --git a/tests/cases/compiler/jsdocAugments_nameMismatch.ts b/tests/cases/conformance/jsdoc/jsdocAugments_nameMismatch.ts
similarity index 100%
rename from tests/cases/compiler/jsdocAugments_nameMismatch.ts
rename to tests/cases/conformance/jsdoc/jsdocAugments_nameMismatch.ts
diff --git a/tests/cases/compiler/jsdocAugments_noExtends.ts b/tests/cases/conformance/jsdoc/jsdocAugments_noExtends.ts
similarity index 100%
rename from tests/cases/compiler/jsdocAugments_noExtends.ts
rename to tests/cases/conformance/jsdoc/jsdocAugments_noExtends.ts
diff --git a/tests/cases/compiler/jsdocAugments_notAClass.ts b/tests/cases/conformance/jsdoc/jsdocAugments_notAClass.ts
similarity index 100%
rename from tests/cases/compiler/jsdocAugments_notAClass.ts
rename to tests/cases/conformance/jsdoc/jsdocAugments_notAClass.ts
diff --git a/tests/cases/compiler/jsdocAugments_qualifiedName.ts b/tests/cases/conformance/jsdoc/jsdocAugments_qualifiedName.ts
similarity index 100%
rename from tests/cases/compiler/jsdocAugments_qualifiedName.ts
rename to tests/cases/conformance/jsdoc/jsdocAugments_qualifiedName.ts
diff --git a/tests/cases/compiler/jsdocAugments_withTypeParameter.ts b/tests/cases/conformance/jsdoc/jsdocAugments_withTypeParameter.ts
similarity index 100%
rename from tests/cases/compiler/jsdocAugments_withTypeParameter.ts
rename to tests/cases/conformance/jsdoc/jsdocAugments_withTypeParameter.ts
diff --git a/tests/cases/conformance/jsdoc/typedefInnerNamepaths.ts b/tests/cases/conformance/jsdoc/typedefInnerNamepaths.ts
new file mode 100644
index 00000000000..ee71909c2ed
--- /dev/null
+++ b/tests/cases/conformance/jsdoc/typedefInnerNamepaths.ts
@@ -0,0 +1,13 @@
+// @noEmit: true
+// @allowJs: true
+// @checkJs: true
+// @Filename: bug25104.js
+class C {
+    /**
+     * @typedef {C~A} C~B
+     * @typedef {object} C~A
+     */
+    /** @param {C~A} o */
+    constructor(o) {
+    }
+}
diff --git a/tests/cases/conformance/moduleResolution/untypedModuleImport_noImplicitAny_typesForPackageExist.ts b/tests/cases/conformance/moduleResolution/untypedModuleImport_noImplicitAny_typesForPackageExist.ts
new file mode 100644
index 00000000000..74e9da10804
--- /dev/null
+++ b/tests/cases/conformance/moduleResolution/untypedModuleImport_noImplicitAny_typesForPackageExist.ts
@@ -0,0 +1,25 @@
+// @noImplicitReferences: true
+// @strict: true
+
+// @Filename: /node_modules/@types/foo/index.d.ts
+export const foo: number;
+
+// @Filename: /node_modules/@types/foo/package.json
+{ "name": "@types/foo", "version": "1.2.3" }
+
+// @Filename: /node_modules/foo/sub.js
+const x = 0;
+
+// @Filename: /node_modules/foo/package.json
+{ "name": "foo", "version": "1.2.3" }
+
+// @Filename: /node_modules/bar/sub.js
+const x = 0;
+
+// @Filename: /node_modules/bar/package.json
+{ "name": "bar", "version": "1.2.3" }
+
+// @Filename: /a.ts
+import * as foo from "foo";
+import * as fooSub from "foo/sub";
+import * as barSub from "bar/sub";
diff --git a/tests/cases/fourslash/codeFixAddMissingMember9.ts b/tests/cases/fourslash/codeFixAddMissingMember9.ts
new file mode 100644
index 00000000000..b583cd28e9a
--- /dev/null
+++ b/tests/cases/fourslash/codeFixAddMissingMember9.ts
@@ -0,0 +1,25 @@
+/// <reference path='fourslash.ts' />
+
+////class C {
+////    z: boolean = true;
+////    method() {
+////        const x = 0;
+////        this.y(x, "a", this.z);
+////    }
+////}
+
+verify.codeFixAll({
+    fixId: "addMissingMember",
+    fixAllDescription: "Add all missing members",
+    newFileContent:
+`class C {
+    z: boolean = true;
+    method() {
+        const x = 0;
+        this.y(x, "a", this.z);
+    }
+    y(x: number, arg1: string, z: boolean): any {
+        throw new Error("Method not implemented.");
+    }
+}`,
+});
diff --git a/tests/cases/fourslash/codeFixClassImplementInterface_typeInOtherFile.ts b/tests/cases/fourslash/codeFixClassImplementInterface_typeInOtherFile.ts
new file mode 100644
index 00000000000..712bf48e059
--- /dev/null
+++ b/tests/cases/fourslash/codeFixClassImplementInterface_typeInOtherFile.ts
@@ -0,0 +1,25 @@
+/// <reference path='fourslash.ts' />
+
+// @Filename: /I.ts
+////export interface J {}
+////export interface I {
+////    x: J;
+////    m(): J;
+////}
+
+// @Filename: /C.ts
+////import { I } from "./I";
+////export class C implements I {}
+
+goTo.file("/C.ts");
+verify.codeFix({
+    description: "Implement interface 'I'",
+    newFileContent:
+`import { I } from "./I";
+export class C implements I {
+    x: import("/I").J;
+    m(): import("/I").J {
+        throw new Error("Method not implemented.");
+    }
+}`,
+});
diff --git a/tests/cases/fourslash/codeFixInferFromUsageSetterWithInaccessibleType.ts b/tests/cases/fourslash/codeFixInferFromUsageSetterWithInaccessibleType.ts
index 9e56fc70734..b56c6e05f69 100644
--- a/tests/cases/fourslash/codeFixInferFromUsageSetterWithInaccessibleType.ts
+++ b/tests/cases/fourslash/codeFixInferFromUsageSetterWithInaccessibleType.ts
@@ -13,4 +13,13 @@
 ////}
 
 goTo.file("/b.ts");
-verify.not.codeFixAvailable();
+verify.codeFix({
+    index: 0,
+    description: "Infer type of 'x' from usage",
+    newFileContent:
+`export class C {
+    set x(val: Promise<typeof import("/a")>) { val; }
+    method() { this.x = import("./a"); }
+}`,
+});
+
diff --git a/tests/cases/fourslash/codeFixUndeclaredAcrossFiles1.ts b/tests/cases/fourslash/codeFixUndeclaredAcrossFiles1.ts
index 29dcc2a5048..0b2669e41f8 100644
--- a/tests/cases/fourslash/codeFixUndeclaredAcrossFiles1.ts
+++ b/tests/cases/fourslash/codeFixUndeclaredAcrossFiles1.ts
@@ -10,6 +10,7 @@
 //// let c = new X.C;
 //// c.m1();
 //// c.y = {};
+//// c.m2(c);
 
 // @Filename: f1.ts
 //// export class C {[|
@@ -21,14 +22,18 @@ verify.getAndApplyCodeFix(/*errorCode*/undefined, 0);
 verify.getAndApplyCodeFix(/*errorCode*/undefined, 0);
 verify.getAndApplyCodeFix(/*errorCode*/undefined, 0);
 verify.getAndApplyCodeFix(/*errorCode*/undefined, 0);
+verify.getAndApplyCodeFix(/*errorCode*/undefined, 0);
 
 verify.rangeIs(`
+    m2(c: C): any {
+        throw new Error("Method not implemented.");
+    }
     y: { [x: string]: any; };
     m1(): any {
         throw new Error("Method not implemented.");
     }
     static x: any;
-    static m0(arg0: any, arg1: any, arg2: any): any {
+    static m0(arg0: number, arg1: string, arg2: undefined[]): any {
         throw new Error("Method not implemented.");
     }
 `);
diff --git a/tests/cases/fourslash/codeFixUndeclaredAcrossFiles3.ts b/tests/cases/fourslash/codeFixUndeclaredAcrossFiles3.ts
new file mode 100644
index 00000000000..2b07493f923
--- /dev/null
+++ b/tests/cases/fourslash/codeFixUndeclaredAcrossFiles3.ts
@@ -0,0 +1,26 @@
+/// <reference path='fourslash.ts' />
+
+// @allowJs: true
+// @checkJs: true
+
+// @Filename: f3.ts
+//// import { C } from "./f1";
+//// import { D } from "./f2";
+//// const c = new C();
+//// c.m0(new D());
+
+// @Filename: f2.ts
+//// export class D { }
+
+// @Filename: f1.ts
+//// export class C {[|
+////     |]x: number;
+//// }
+
+verify.getAndApplyCodeFix(/*errorCode*/ undefined, 0);
+
+verify.rangeIs(`
+    m0(arg0: D): any {
+        throw new Error("Method not implemented.");
+    }
+`);
\ No newline at end of file
diff --git a/tests/cases/fourslash/codeFixUndeclaredInStaticMethod.ts b/tests/cases/fourslash/codeFixUndeclaredInStaticMethod.ts
index 9faa15745fc..a4ac2488350 100644
--- a/tests/cases/fourslash/codeFixUndeclaredInStaticMethod.ts
+++ b/tests/cases/fourslash/codeFixUndeclaredInStaticMethod.ts
@@ -20,7 +20,7 @@ verify.codeFix({
         this.prop1 = 10;
         A.prop2 = "asdf";
     }
-    static m1(arg0: any, arg1: any, arg2: any): any {
+    static m1(arg0: number, arg1: number, arg2: number): any {
         throw new Error("Method not implemented.");
     }
 }`,
@@ -37,10 +37,10 @@ verify.codeFix({
         this.prop1 = 10;
         A.prop2 = "asdf";
     }
-    static m2(arg0: any, arg1: any): any {
+    static m2(arg0: number, arg1: number): any {
         throw new Error("Method not implemented.");
     }
-    static m1(arg0: any, arg1: any, arg2: any): any {
+    static m1(arg0: number, arg1: number, arg2: number): any {
         throw new Error("Method not implemented.");
     }
 }`,
@@ -58,10 +58,10 @@ verify.codeFix({
         this.prop1 = 10;
         A.prop2 = "asdf";
     }
-    static m2(arg0: any, arg1: any): any {
+    static m2(arg0: number, arg1: number): any {
         throw new Error("Method not implemented.");
     }
-    static m1(arg0: any, arg1: any, arg2: any): any {
+    static m1(arg0: number, arg1: number, arg2: number): any {
         throw new Error("Method not implemented.");
     }
 }`,
@@ -80,10 +80,10 @@ verify.codeFix({
         this.prop1 = 10;
         A.prop2 = "asdf";
     }
-    static m2(arg0: any, arg1: any): any {
+    static m2(arg0: number, arg1: number): any {
         throw new Error("Method not implemented.");
     }
-    static m1(arg0: any, arg1: any, arg2: any): any {
+    static m1(arg0: number, arg1: number, arg2: number): any {
         throw new Error("Method not implemented.");
     }
 }`,
diff --git a/tests/cases/fourslash/codeFixUndeclaredMethod.ts b/tests/cases/fourslash/codeFixUndeclaredMethod.ts
index 41e27dcf207..bf276379b0a 100644
--- a/tests/cases/fourslash/codeFixUndeclaredMethod.ts
+++ b/tests/cases/fourslash/codeFixUndeclaredMethod.ts
@@ -15,7 +15,7 @@ verify.codeFix({
     index: 0,
     newFileContent:
 `class A {
-    foo1(arg0: any, arg1: any, arg2: any): any {
+    foo1(arg0: number, arg1: number, arg2: number): any {
         throw new Error("Method not implemented.");
     }
     constructor() {
@@ -36,7 +36,7 @@ verify.codeFix({
     foo2<T, U, V, W, X, Y, Z>(): any {
         throw new Error("Method not implemented.");
     }
-    foo1(arg0: any, arg1: any, arg2: any): any {
+    foo1(arg0: number, arg1: number, arg2: number): any {
         throw new Error("Method not implemented.");
     }
     constructor() {
@@ -60,7 +60,7 @@ verify.codeFix({
     foo2<T, U, V, W, X, Y, Z>(): any {
         throw new Error("Method not implemented.");
     }
-    foo1(arg0: any, arg1: any, arg2: any): any {
+    foo1(arg0: number, arg1: number, arg2: number): any {
         throw new Error("Method not implemented.");
     }
     constructor() {
diff --git a/tests/cases/fourslash/codeFixUndeclaredMethodFunctionArgs.ts b/tests/cases/fourslash/codeFixUndeclaredMethodFunctionArgs.ts
new file mode 100644
index 00000000000..1c06cfc3afd
--- /dev/null
+++ b/tests/cases/fourslash/codeFixUndeclaredMethodFunctionArgs.ts
@@ -0,0 +1,31 @@
+/// <reference path='fourslash.ts' />
+
+//// class A {[|
+////     |]constructor() {
+////         this.foo1(() => 1, () => "2", () => false);
+////         this.foo2((a: number) => a, (b: string) => b, (c: boolean) => c);
+////     }
+//// }
+
+verify.codeFix({
+    description: "Declare method 'foo1'",
+    index: 0,
+    newRangeContent: `
+    foo1(arg0: () => number, arg1: () => string, arg2: () => boolean): any {
+        throw new Error("Method not implemented.");
+    }
+    `,
+});
+
+verify.codeFix({
+    description: "Declare method 'foo2'",
+    index: 0,
+    newRangeContent: `
+    foo2(arg0: (a: number) => number, arg1: (b: string) => string, arg2: (c: boolean) => boolean): any {
+        throw new Error("Method not implemented.");
+    }
+    foo1(arg0: () => number, arg1: () => string, arg2: () => boolean): any {
+        throw new Error("Method not implemented.");
+    }
+    `
+});
diff --git a/tests/cases/fourslash/codeFixUndeclaredMethodObjectLiteralArgs.ts b/tests/cases/fourslash/codeFixUndeclaredMethodObjectLiteralArgs.ts
new file mode 100644
index 00000000000..bd434cf9d9d
--- /dev/null
+++ b/tests/cases/fourslash/codeFixUndeclaredMethodObjectLiteralArgs.ts
@@ -0,0 +1,17 @@
+/// <reference path='fourslash.ts' />
+
+//// class A {[|
+////     |]constructor() {
+////         this.foo1(null, {}, { a: 1, b: "2"});
+////     }
+//// }
+
+verify.codeFix({
+    description: "Declare method 'foo1'",
+    index: 0,
+    newRangeContent: `
+    foo1(arg0: null, arg1: {}, arg2: { a: number; b: string; }): any {
+        throw new Error("Method not implemented.");
+    }
+    `
+});
diff --git a/tests/cases/fourslash/commentsClassMembers.ts b/tests/cases/fourslash/commentsClassMembers.ts
index 6b598ab458c..b0ed3e9e48b 100644
--- a/tests/cases/fourslash/commentsClassMembers.ts
+++ b/tests/cases/fourslash/commentsClassMembers.ts
@@ -572,12 +572,12 @@ verify.quickInfos({
 });
 
 goTo.marker('114');
-verify.completionListContains("a", "(property) cWithConstructorProperty.a: number", "this is first parameter a\nmore info about a");
-verify.quickInfoIs("(property) cWithConstructorProperty.a: number", "this is first parameter a\nmore info about a");
+verify.completionListContains("a", "(property) cWithConstructorProperty.a: number", "more info about a\nthis is first parameter a");
+verify.quickInfoIs("(property) cWithConstructorProperty.a: number", "more info about a\nthis is first parameter a");
 
 goTo.marker('115');
-verify.completionListContains("a", "(parameter) a: number", "this is first parameter a\nmore info about a");
-verify.quickInfoIs("(parameter) a: number", "this is first parameter a\nmore info about a");
+verify.completionListContains("a", "(parameter) a: number", "more info about a\nthis is first parameter a");
+verify.quickInfoIs("(parameter) a: number", "more info about a\nthis is first parameter a");
 
 verify.quickInfos({
     116: "this: this",
diff --git a/tests/cases/fourslash/commentsCommentParsing.ts b/tests/cases/fourslash/commentsCommentParsing.ts
index 6b0c880e9bb..bba86fea299 100644
--- a/tests/cases/fourslash/commentsCommentParsing.ts
+++ b/tests/cases/fourslash/commentsCommentParsing.ts
@@ -420,7 +420,7 @@ verify.signatureHelp({ marker: "38", docComment: concatDoc, parameterDocComment:
 verify.quickInfoAt("38aq", "(parameter) bar: string", "is second string");
 
 goTo.marker('39');
-verify.completionListContains("a", "(parameter) a: number", "it is first parameter\nthis is inline comment for a ");
+verify.completionListContains("a", "(parameter) a: number", "this is inline comment for a \nit is first parameter");
 verify.completionListContains("b", "(parameter) b: number", "this is inline comment for b");
 verify.completionListContains("c", "(parameter) c: number", "it is third parameter");
 verify.completionListContains("d", "(parameter) d: number", "");
@@ -430,7 +430,7 @@ const jsdocTestTags: ReadonlyArray<FourSlashInterface.JSDocTagInfo> = [
     { name: "param", text: "a it is first parameter" },
     { name: "param", text: "c it is third parameter" },
 ];
-verify.signatureHelp({ marker: "40", docComment: jsdocTestDocComment, parameterDocComment: "it is first parameter\nthis is inline comment for a ", tags: jsdocTestTags });
+verify.signatureHelp({ marker: "40", docComment: jsdocTestDocComment, parameterDocComment: "this is inline comment for a \nit is first parameter", tags: jsdocTestTags });
 verify.quickInfos({
     "40q": [
         "function jsDocParamTest(a: number, b: number, c: number, d: number): number",
@@ -438,7 +438,7 @@ verify.quickInfos({
     ],
     "40aq": [
         "(parameter) a: number",
-        "it is first parameter\nthis is inline comment for a "
+        "this is inline comment for a \nit is first parameter"
     ]
 });
 
diff --git a/tests/cases/fourslash/commentsFunctionExpression.ts b/tests/cases/fourslash/commentsFunctionExpression.ts
index bd9a5c93433..257b8345756 100644
--- a/tests/cases/fourslash/commentsFunctionExpression.ts
+++ b/tests/cases/fourslash/commentsFunctionExpression.ts
@@ -32,7 +32,7 @@
 ////}
 ////assig/*16*/ned/*17*/(/*18*/"hey");
 
-verify.quickInfoAt("1", "var lambdaFoo: (a: number, b: number) => number", "lambdaFoo var comment\nthis is lambda comment");
+verify.quickInfoAt("1", "var lambdaFoo: (a: number, b: number) => number", "this is lambda comment\nlambdaFoo var comment");
 
 goTo.marker('2');
 verify.completionListContains('a', '(parameter) a: number', 'param a');
@@ -42,18 +42,18 @@ verify.completionListContains('b', '(parameter) b: number', 'param b');
 verify.quickInfoAt("3", "var lambddaNoVarComment: (a: number, b: number) => number", "this is lambda multiplication");
 
 goTo.marker('4');
-verify.completionListContains('lambdaFoo', 'var lambdaFoo: (a: number, b: number) => number', 'lambdaFoo var comment\nthis is lambda comment');
+verify.completionListContains('lambdaFoo', 'var lambdaFoo: (a: number, b: number) => number', "this is lambda comment\nlambdaFoo var comment");
 verify.completionListContains('lambddaNoVarComment', 'var lambddaNoVarComment: (a: number, b: number) => number', 'this is lambda multiplication');
 
 verify.signatureHelp(
     {
         marker: "5",
-        docComment: "lambdaFoo var comment\nthis is lambda comment",
+        docComment: "this is lambda comment\nlambdaFoo var comment",
         parameterDocComment: "param a",
     },
     {
         marker: "6",
-        docComment: "lambdaFoo var comment\nthis is lambda comment",
+        docComment: "this is lambda comment\nlambdaFoo var comment",
         parameterDocComment: "param b",
     },
 );
@@ -61,31 +61,31 @@ verify.signatureHelp(
 // no documentation from nested lambda
 verify.quickInfos({
     7: "function anotherFunc(a: number): string",
-    8: ["(local var) lambdaVar: (b: string) => string", "documentation\ninner docs "],
+    8: ["(local var) lambdaVar: (b: string) => string", "inner docs \ndocumentation"],
     9: ["(parameter) b: string", "inner parameter "],
     10: "(local var) localVar: string",
     11: "(local var) localVar: string",
     12: ["(parameter) b: string", "inner parameter "],
-    13: ["(local var) lambdaVar: (b: string) => string", "documentation\ninner docs "],
+    13: ["(local var) lambdaVar: (b: string) => string", "inner docs \ndocumentation"],
     14: [
         "var assigned: (s: string) => number",
-        "On variable\nSummary on expression"
+        "Summary on expression\nOn variable"
     ]
 });
 
 goTo.marker('15');
-verify.completionListContains('s', '(parameter) s: string', "the first parameter!\nparam on expression\nOn parameter ");
-verify.quickInfoAt("16", "var assigned: (s: string) => number", "On variable\nSummary on expression");
+verify.completionListContains('s', '(parameter) s: string', "On parameter \nparam on expression\nthe first parameter!");
+verify.quickInfoAt("16", "var assigned: (s: string) => number", "Summary on expression\nOn variable");
 goTo.marker('17');
-verify.completionListContains("assigned", "var assigned: (s: string) => number", "On variable\nSummary on expression");
+verify.completionListContains("assigned", "var assigned: (s: string) => number", "Summary on expression\nOn variable");
 verify.signatureHelp({
     marker: "18",
-    docComment: "On variable\nSummary on expression",
-    parameterDocComment: "the first parameter!\nparam on expression\nOn parameter ",
+    docComment: "Summary on expression\nOn variable",
+    parameterDocComment: "On parameter \nparam on expression\nthe first parameter!",
     tags: [
-        { name: "param", text: "s the first parameter!" },
-        { name: "returns", text: "the parameter's length" },
         { name: "param", text: "s param on expression" },
         { name: "returns", text: "return on expression" },
+        { name: "param", text: "s the first parameter!" },
+        { name: "returns", text: "the parameter's length" },
     ],
 });
diff --git a/tests/cases/fourslash/fixUnusedIdentifier_jsdocTypeParameter.ts b/tests/cases/fourslash/fixUnusedIdentifier_jsdocTypeParameter.ts
new file mode 100644
index 00000000000..efa096e81a1
--- /dev/null
+++ b/tests/cases/fourslash/fixUnusedIdentifier_jsdocTypeParameter.ts
@@ -0,0 +1,18 @@
+/// <reference path='fourslash.ts' />
+
+// @allowJs: true
+
+// @Filename: /a.js
+/////**
+//// * @type {<T>() => void}
+//// */
+////export const x = 0;
+
+verify.codeFix({
+    description: "Remove declaration for: 'T'",
+    newFileContent:
+`/**
+ * @type {() => void}
+ */
+export const x = 0;`,
+});
diff --git a/tests/cases/fourslash/fourslash.ts b/tests/cases/fourslash/fourslash.ts
index a70d6dcf424..89e1948ce77 100644
--- a/tests/cases/fourslash/fourslash.ts
+++ b/tests/cases/fourslash/fourslash.ts
@@ -190,6 +190,7 @@ declare namespace FourSlashInterface {
         applicableRefactorAvailableForRange(): void;
 
         refactorAvailable(name: string, actionName?: string): void;
+        refactorsAvailable(names: ReadonlyArray<string>): void;
         refactor(options: {
             name: string;
             actionName: string;
diff --git a/tests/cases/fourslash/navbarNestedCommonJsExports.ts b/tests/cases/fourslash/navbarNestedCommonJsExports.ts
new file mode 100644
index 00000000000..3c2d4499172
--- /dev/null
+++ b/tests/cases/fourslash/navbarNestedCommonJsExports.ts
@@ -0,0 +1,35 @@
+/// <reference path="fourslash.ts" />
+
+// @allowJs: true
+
+// @Filename: /a.js
+////exports.a = exports.b = exports.c = 0;
+
+verify.navigationTree({
+    text: "<global>",
+    kind: "script",
+    childItems: [
+        {
+            text: "a",
+            kind: "const",
+            childItems: [
+                {
+                    text: "b",
+                    kind: "const",
+                    childItems: [{ text: "c", kind: "const" }],
+                },
+            ],
+        },
+    ],
+});
+
+verify.navigationBar([
+    {
+        text: "<global>",
+        kind: "script",
+        childItems: [
+            { text: "a", kind: "const" },
+        ],
+    },
+]);
+
diff --git a/tests/cases/fourslash/refactorConvertToGetAccessAndSetAccess_notOnWhitespace.ts b/tests/cases/fourslash/refactorConvertToGetAccessAndSetAccess_notOnWhitespace.ts
new file mode 100644
index 00000000000..9ba208b8e95
--- /dev/null
+++ b/tests/cases/fourslash/refactorConvertToGetAccessAndSetAccess_notOnWhitespace.ts
@@ -0,0 +1,8 @@
+/// <reference path='fourslash.ts' />
+
+////class A {
+/////*a*/    /*b*/p = 0;
+////}
+
+goTo.select("a", "b");
+verify.refactorsAvailable([]);
diff --git a/tests/cases/fourslash/signatureHelpOnDeclaration.ts b/tests/cases/fourslash/signatureHelpOnDeclaration.ts
new file mode 100644
index 00000000000..7fc68174383
--- /dev/null
+++ b/tests/cases/fourslash/signatureHelpOnDeclaration.ts
@@ -0,0 +1,6 @@
+/// <reference path='fourslash.ts' />
+
+////function f</**/
+////x
+
+verify.noSignatureHelp("");