diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 24ca7da87c4..70cbda14f6d 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -8277,8 +8277,8 @@ namespace ts {
                 maybeStack[depth].set(id, RelationComparisonResult.Succeeded);
                 depth++;
                 const saveExpandingFlags = expandingFlags;
-                if (!(expandingFlags & 1) && isDeeplyNestedGeneric(source, sourceStack, depth)) expandingFlags |= 1;
-                if (!(expandingFlags & 2) && isDeeplyNestedGeneric(target, targetStack, depth)) expandingFlags |= 2;
+                if (!(expandingFlags & 1) && isDeeplyNestedType(source, sourceStack, depth)) expandingFlags |= 1;
+                if (!(expandingFlags & 2) && isDeeplyNestedType(target, targetStack, depth)) expandingFlags |= 2;
                 let result: Ternary;
                 if (expandingFlags === 3) {
                     result = Ternary.Maybe;
@@ -8698,21 +8698,23 @@ namespace ts {
             return false;
         }
 
-        // Return true if the given type is part of a deeply nested chain of generic instantiations. We consider this to be the case
-        // when structural type comparisons have been started for 10 or more instantiations of the same generic type. It is possible,
-        // though highly unlikely, for this test to be true in a situation where a chain of instantiations is not infinitely expanding.
-        // Effectively, we will generate a false positive when two types are structurally equal to at least 10 levels, but unequal at
-        // some level beyond that.
-        function isDeeplyNestedGeneric(type: Type, stack: Type[], depth: number): boolean {
-            // We track type references (created by createTypeReference) and instantiated types (created by instantiateType)
-            if (getObjectFlags(type) & (ObjectFlags.Reference | ObjectFlags.Instantiated) && depth >= 5) {
+        // Return true if the given type is deeply nested. We consider this to be the case when structural type comparisons
+        // for 5 or more occurrences or instantiations of the type have been recorded on the given stack. It is possible,
+        // though highly unlikely, for this test to be true in a situation where a chain of instantiations is not infinitely
+        // expanding. Effectively, we will generate a false positive when two types are structurally equal to at least 5
+        // levels, but unequal at some level beyond that.
+        function isDeeplyNestedType(type: Type, stack: Type[], depth: number): boolean {
+            // We track all object types that have an associated symbol (representing the origin of the type)
+            if (depth >= 5 && type.flags & TypeFlags.Object) {
                 const symbol = type.symbol;
-                let count = 0;
-                for (let i = 0; i < depth; i++) {
-                    const t = stack[i];
-                    if (getObjectFlags(t) & (ObjectFlags.Reference | ObjectFlags.Instantiated) && t.symbol === symbol) {
-                        count++;
-                        if (count >= 5) return true;
+                if (symbol) {
+                    let count = 0;
+                    for (let i = 0; i < depth; i++) {
+                        const t = stack[i];
+                        if (t.flags & TypeFlags.Object && t.symbol === symbol) {
+                            count++;
+                            if (count >= 5) return true;
+                        }
                     }
                 }
             }
@@ -9455,7 +9457,7 @@ namespace ts {
                         if (isInProcess(source, target)) {
                             return;
                         }
-                        if (isDeeplyNestedGeneric(source, sourceStack, depth) && isDeeplyNestedGeneric(target, targetStack, depth)) {
+                        if (isDeeplyNestedType(source, sourceStack, depth) && isDeeplyNestedType(target, targetStack, depth)) {
                             return;
                         }
                         const key = source.id + "," + target.id;
@@ -18788,7 +18790,7 @@ namespace ts {
 
             // unknownType is returned i.e. if node.expression is identifier whose name cannot be resolved
             // in this case error about missing name is already reported - do not report extra one
-            if (!isTypeAnyOrAllConstituentTypesHaveKind(rightType, TypeFlags.Object | TypeFlags.TypeVariable)) {
+            if (!isTypeAnyOrAllConstituentTypesHaveKind(rightType, TypeFlags.Object | TypeFlags.TypeVariable | TypeFlags.NonPrimitive)) {
                 error(node.expression, Diagnostics.The_right_hand_side_of_a_for_in_statement_must_be_of_type_any_an_object_type_or_a_type_parameter);
             }
 
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 821402f1f06..da6125f3106 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -3019,7 +3019,6 @@ namespace ts {
         ObjectLiteral    = 1 << 7,  // Originates in an object literal
         EvolvingArray    = 1 << 8,  // Evolving array type
         ObjectLiteralPatternWithComputedProperties = 1 << 9,  // Object literal pattern with computed properties
-        NonPrimitive        = 1 << 10,  // NonPrimitive object type
         ClassOrInterface = Class | Interface
     }
 
diff --git a/src/harness/unittests/tsserverProjectSystem.ts b/src/harness/unittests/tsserverProjectSystem.ts
index 5ea0df91caa..356a7a8962d 100644
--- a/src/harness/unittests/tsserverProjectSystem.ts
+++ b/src/harness/unittests/tsserverProjectSystem.ts
@@ -1007,6 +1007,41 @@ namespace ts.projectSystem {
             checkProjectRootFiles(projectService.configuredProjects[0], [commonFile1.path, commonFile2.path]);
         });
 
+        it("should disable features when the files are too large", () => {
+            const file1 = {
+                path: "/a/b/f1.js",
+                content: "let x =1;",
+                fileSize: 10 * 1024 * 1024
+            };
+            const file2 = {
+                path: "/a/b/f2.js",
+                content: "let y =1;",
+                fileSize: 6 * 1024 * 1024
+            };
+            const file3 = {
+                path: "/a/b/f3.js",
+                content: "let y =1;",
+                fileSize: 6 * 1024 * 1024
+            };
+
+            const proj1name = "proj1", proj2name = "proj2", proj3name = "proj3";
+
+            const host = createServerHost([file1, file2, file3]);
+            const projectService = createProjectService(host);
+
+            projectService.openExternalProject({ rootFiles: toExternalFiles([file1.path]), options: {}, projectFileName: proj1name });
+            const proj1 = projectService.findProject(proj1name);
+            assert.isTrue(proj1.languageServiceEnabled);
+
+            projectService.openExternalProject({ rootFiles: toExternalFiles([file2.path]), options: {}, projectFileName: proj2name });
+            const proj2 = projectService.findProject(proj2name);
+            assert.isTrue(proj2.languageServiceEnabled);
+
+            projectService.openExternalProject({ rootFiles: toExternalFiles([file3.path]), options: {}, projectFileName: proj3name });
+            const proj3 = projectService.findProject(proj3name);
+            assert.isFalse(proj3.languageServiceEnabled);
+        });
+
         it("should use only one inferred project if 'useOneInferredProject' is set", () => {
             const file1 = {
                 path: "/a/b/main.ts",
diff --git a/src/lib/dom.generated.d.ts b/src/lib/dom.generated.d.ts
index 5d4bb9ce6e4..348e52246a7 100644
--- a/src/lib/dom.generated.d.ts
+++ b/src/lib/dom.generated.d.ts
@@ -1396,6 +1396,7 @@ interface AudioNode extends EventTarget {
     readonly numberOfInputs: number;
     readonly numberOfOutputs: number;
     connect(destination: AudioNode, output?: number, input?: number): AudioNode;
+    connect(destination: AudioParam, output?: number): void;
     disconnect(output?: number): void;
     disconnect(destination: AudioNode, output?: number, input?: number): void;
     disconnect(destination: AudioParam, output?: number): void;
@@ -2152,7 +2153,9 @@ interface CanvasRenderingContext2D extends Object, CanvasPathMethods {
     createPattern(image: HTMLImageElement | HTMLCanvasElement | HTMLVideoElement, repetition: string): CanvasPattern;
     createRadialGradient(x0: number, y0: number, r0: number, x1: number, y1: number, r1: number): CanvasGradient;
     drawFocusIfNeeded(element: Element): void;
-    drawImage(image: HTMLImageElement | HTMLCanvasElement | HTMLVideoElement, offsetX: number, offsetY: number, width?: number, height?: number, canvasOffsetX?: number, canvasOffsetY?: number, canvasImageWidth?: number, canvasImageHeight?: number): void;
+    drawImage(image: HTMLImageElement | HTMLCanvasElement | HTMLVideoElement | ImageBitmap, dstX: number, dstY: number): void;
+    drawImage(image: HTMLImageElement | HTMLCanvasElement | HTMLVideoElement | ImageBitmap, dstX: number, dstY: number, dstW: number, dstH: number): void;
+    drawImage(image: HTMLImageElement | HTMLCanvasElement | HTMLVideoElement | ImageBitmap, srcX: number, srcY: number, srcW: number, srcH: number, dstX: number, dstY: number, dstW: number, dstH: number): void;
     fill(fillRule?: string): void;
     fillRect(x: number, y: number, w: number, h: number): void;
     fillText(text: string, x: number, y: number, maxWidth?: number): void;
@@ -2449,10 +2452,10 @@ declare var DOMException: {
 }
 
 interface DOMImplementation {
-    createDocument(namespaceURI: string | null, qualifiedName: string | null, doctype: DocumentType): Document;
+    createDocument(namespaceURI: string | null, qualifiedName: string | null, doctype: DocumentType | null): Document;
     createDocumentType(qualifiedName: string, publicId: string, systemId: string): DocumentType;
     createHTMLDocument(title: string): Document;
-    hasFeature(): boolean;
+    hasFeature(feature: string | null, version: string | null): boolean;
 }
 
 declare var DOMImplementation: {
@@ -3449,6 +3452,7 @@ declare var Document: {
 }
 
 interface DocumentFragment extends Node, NodeSelector, ParentNode {
+    getElementById(elementId: string): HTMLElement | null;
 }
 
 declare var DocumentFragment: {
@@ -11837,7 +11841,7 @@ interface URL {
     protocol: string;
     search: string;
     username: string;
-    readonly searchparams: URLSearchParams;
+    readonly searchParams: URLSearchParams;
     toString(): string;
 }
 
@@ -12161,12 +12165,12 @@ interface WebGLRenderingContext {
     stencilMaskSeparate(face: number, mask: number): void;
     stencilOp(fail: number, zfail: number, zpass: number): void;
     stencilOpSeparate(face: number, fail: number, zfail: number, zpass: number): void;
-    texImage2D(target: number, level: number, internalformat: number, width: number, height: number, border: number, format: number, type: number, pixels?: ArrayBufferView): void;
-    texImage2D(target: number, level: number, internalformat: number, format: number, type: number, pixels?: ImageData | HTMLVideoElement | HTMLImageElement | HTMLCanvasElement): void;
+    texImage2D(target: number, level: number, internalformat: number, width: number, height: number, border: number, format: number, type: number, pixels: ArrayBufferView | null): void;
+    texImage2D(target: number, level: number, internalformat: number, format: number, type: number, pixels: ImageBitmap | ImageData | HTMLVideoElement | HTMLImageElement | HTMLCanvasElement): void;
     texParameterf(target: number, pname: number, param: number): void;
     texParameteri(target: number, pname: number, param: number): void;
-    texSubImage2D(target: number, level: number, xoffset: number, yoffset: number, width: number, height: number, format: number, type: number, pixels?: ArrayBufferView): void;
-    texSubImage2D(target: number, level: number, xoffset: number, yoffset: number, format: number, type: number, pixels?: ImageData | HTMLVideoElement | HTMLImageElement | HTMLCanvasElement): void;
+    texSubImage2D(target: number, level: number, xoffset: number, yoffset: number, width: number, height: number, format: number, type: number, pixels: ArrayBufferView | null): void;
+    texSubImage2D(target: number, level: number, xoffset: number, yoffset: number, format: number, type: number, pixels: ImageBitmap | ImageData | HTMLVideoElement | HTMLImageElement | HTMLCanvasElement): void;
     uniform1f(location: WebGLUniformLocation | null, x: number): void;
     uniform1fv(location: WebGLUniformLocation, v: Float32Array | number[]): void;
     uniform1i(location: WebGLUniformLocation | null, x: number): void;
@@ -13260,6 +13264,8 @@ interface Window extends EventTarget, WindowTimers, WindowSessionStorage, Window
     webkitConvertPointFromNodeToPage(node: Node, pt: WebKitPoint): WebKitPoint;
     webkitConvertPointFromPageToNode(node: Node, pt: WebKitPoint): WebKitPoint;
     webkitRequestAnimationFrame(callback: FrameRequestCallback): number;
+    createImageBitmap(image: HTMLImageElement | SVGImageElement | HTMLVideoElement | HTMLCanvasElement | ImageBitmap | ImageData | Blob, options?: ImageBitmapOptions): Promise<ImageBitmap>;
+    createImageBitmap(image: HTMLImageElement | SVGImageElement | HTMLVideoElement | HTMLCanvasElement | ImageBitmap | ImageData | Blob, sx: number, sy: number, sw: number, sh: number, options?: ImageBitmapOptions): Promise<ImageBitmap>;
     scroll(options?: ScrollToOptions): void;
     scrollTo(options?: ScrollToOptions): void;
     scrollBy(options?: ScrollToOptions): void;
@@ -13473,6 +13479,7 @@ interface Body {
     blob(): Promise<Blob>;
     json(): Promise<any>;
     text(): Promise<string>;
+    formData(): Promise<FormData>;
 }
 
 interface CanvasPathMethods {
@@ -13835,6 +13842,21 @@ interface Canvas2DContextAttributes {
     [attribute: string]: boolean | string | undefined;
 }
 
+interface ImageBitmapOptions {
+    imageOrientation?: "none" | "flipY";
+    premultiplyAlpha?: "none" | "premultiply" | "default";
+    colorSpaceConversion?: "none" | "default";
+    resizeWidth?: number;
+    resizeHeight?: number;
+    resizeQuality?: "pixelated" | "low" | "medium" | "high";
+}
+
+interface ImageBitmap {
+    readonly width: number;
+    readonly height: number;
+    close(): void;
+}
+
 interface URLSearchParams {
     /**
       * Appends a specified key/value pair as a new search parameter.
@@ -13879,6 +13901,7 @@ interface NodeListOf<TNode extends Node> extends NodeList {
 interface HTMLCollectionOf<T extends Element> extends HTMLCollection {
     item(index: number): T;
     namedItem(name: string): T;
+    [index: number]: T;
 }
 
 interface BlobPropertyBag {
@@ -14840,6 +14863,8 @@ declare function webkitCancelAnimationFrame(handle: number): void;
 declare function webkitConvertPointFromNodeToPage(node: Node, pt: WebKitPoint): WebKitPoint;
 declare function webkitConvertPointFromPageToNode(node: Node, pt: WebKitPoint): WebKitPoint;
 declare function webkitRequestAnimationFrame(callback: FrameRequestCallback): number;
+declare function createImageBitmap(image: HTMLImageElement | SVGImageElement | HTMLVideoElement | HTMLCanvasElement | ImageBitmap | ImageData | Blob, options?: ImageBitmapOptions): Promise<ImageBitmap>;
+declare function createImageBitmap(image: HTMLImageElement | SVGImageElement | HTMLVideoElement | HTMLCanvasElement | ImageBitmap | ImageData | Blob, sx: number, sy: number, sw: number, sh: number, options?: ImageBitmapOptions): Promise<ImageBitmap>;
 declare function scroll(options?: ScrollToOptions): void;
 declare function scrollTo(options?: ScrollToOptions): void;
 declare function scrollBy(options?: ScrollToOptions): void;
diff --git a/src/lib/es2015.generator.d.ts b/src/lib/es2015.generator.d.ts
index 2f522ad8770..5637ef816de 100644
--- a/src/lib/es2015.generator.d.ts
+++ b/src/lib/es2015.generator.d.ts
@@ -1,4 +1,29 @@
-interface GeneratorFunction extends Function { }
+interface Generator extends Iterator<any> { }
+
+interface GeneratorFunction {
+    /**
+     * Creates a new Generator object.
+     * @param args A list of arguments the function accepts.
+     */
+    new (...args: any[]): Generator;
+    /**
+     * Creates a new Generator object.
+     * @param args A list of arguments the function accepts.
+     */
+    (...args: any[]): Generator;
+    /**
+     * The length of the arguments.
+     */
+    readonly length: number;
+    /**
+      * Returns the name of the function.
+      */
+    readonly name: string;
+    /**
+      * A reference to the prototype.
+      */
+    readonly prototype: Generator;
+}
 
 interface GeneratorFunctionConstructor {
     /**
@@ -6,7 +31,22 @@ interface GeneratorFunctionConstructor {
       * @param args A list of arguments the function accepts.
       */
     new (...args: string[]): GeneratorFunction;
+    /**
+      * Creates a new Generator function.
+      * @param args A list of arguments the function accepts.
+      */
     (...args: string[]): GeneratorFunction;
+    /**
+     * The length of the arguments.
+     */
+    readonly length: number;
+    /**
+      * Returns the name of the function.
+      */
+    readonly name: string;
+    /**
+      * A reference to the prototype.
+      */
     readonly prototype: GeneratorFunction;
 }
 declare var GeneratorFunction: GeneratorFunctionConstructor;
diff --git a/src/lib/es2015.symbol.wellknown.d.ts b/src/lib/es2015.symbol.wellknown.d.ts
index 71e4cb7c893..5334dae9e01 100644
--- a/src/lib/es2015.symbol.wellknown.d.ts
+++ b/src/lib/es2015.symbol.wellknown.d.ts
@@ -137,7 +137,7 @@ interface Function {
     [Symbol.hasInstance](value: any): boolean;
 }
 
-interface GeneratorFunction extends Function {
+interface GeneratorFunction {
     readonly [Symbol.toStringTag]: "GeneratorFunction";
 }
 
diff --git a/src/lib/webworker.generated.d.ts b/src/lib/webworker.generated.d.ts
index e9563db1bcd..326a3a9546e 100644
--- a/src/lib/webworker.generated.d.ts
+++ b/src/lib/webworker.generated.d.ts
@@ -1407,6 +1407,8 @@ interface WorkerGlobalScope extends EventTarget, WorkerUtils, WindowConsole, Glo
     readonly performance: Performance;
     readonly self: WorkerGlobalScope;
     msWriteProfilerMark(profilerMarkName: string): void;
+    createImageBitmap(image: ImageBitmap | ImageData | Blob, options?: ImageBitmapOptions): Promise<ImageBitmap>;
+    createImageBitmap(image: ImageBitmap | ImageData | Blob, sx: number, sy: number, sw: number, sh: number, options?: ImageBitmapOptions): Promise<ImageBitmap>;
     addEventListener<K extends keyof WorkerGlobalScopeEventMap>(type: K, listener: (this: WorkerGlobalScope, ev: WorkerGlobalScopeEventMap[K]) => any, useCapture?: boolean): void;
     addEventListener(type: string, listener: EventListenerOrEventListenerObject, useCapture?: boolean): void;
 }
@@ -1467,6 +1469,21 @@ interface ErrorEventInit {
     error?: any;
 }
 
+interface ImageBitmapOptions {
+    imageOrientation?: "none" | "flipY";
+    premultiplyAlpha?: "none" | "premultiply" | "default";
+    colorSpaceConversion?: "none" | "default";
+    resizeWidth?: number;
+    resizeHeight?: number;
+    resizeQuality?: "pixelated" | "low" | "medium" | "high";
+}
+
+interface ImageBitmap {
+    readonly width: number;
+    readonly height: number;
+    close(): void;
+}
+
 interface BlobPropertyBag {
     type?: string;
     endings?: string;
@@ -1697,6 +1714,8 @@ declare var onerror: (this: DedicatedWorkerGlobalScope, ev: ErrorEvent) => any;
 declare var performance: Performance;
 declare var self: WorkerGlobalScope;
 declare function msWriteProfilerMark(profilerMarkName: string): void;
+declare function createImageBitmap(image: ImageBitmap | ImageData | Blob, options?: ImageBitmapOptions): Promise<ImageBitmap>;
+declare function createImageBitmap(image: ImageBitmap | ImageData | Blob, sx: number, sy: number, sw: number, sh: number, options?: ImageBitmapOptions): Promise<ImageBitmap>;
 declare function dispatchEvent(evt: Event): boolean;
 declare function removeEventListener(type: string, listener?: EventListenerOrEventListenerObject, useCapture?: boolean): void;
 declare var indexedDB: IDBFactory;
diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index 397de9ead30..8af6fe5d347 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -254,6 +254,7 @@ namespace ts.server {
 
         private compilerOptionsForInferredProjects: CompilerOptions;
         private compileOnSaveForInferredProjects: boolean;
+        private readonly projectToSizeMap: Map<number> = createMap<number>();
         private readonly directoryWatchers: DirectoryWatchers;
         private readonly throttledOperations: ThrottledOperations;
 
@@ -563,9 +564,11 @@ namespace ts.server {
             switch (project.projectKind) {
                 case ProjectKind.External:
                     removeItemFromSet(this.externalProjects, <ExternalProject>project);
+                    this.projectToSizeMap.delete((project as ExternalProject).externalProjectName);
                     break;
                 case ProjectKind.Configured:
                     removeItemFromSet(this.configuredProjects, <ConfiguredProject>project);
+                    this.projectToSizeMap.delete((project as ConfiguredProject).canonicalConfigFilePath);
                     break;
                 case ProjectKind.Inferred:
                     removeItemFromSet(this.inferredProjects, <InferredProject>project);
@@ -852,10 +855,15 @@ namespace ts.server {
             return { success: true, projectOptions, configFileErrors: errors };
         }
 
-        private exceededTotalSizeLimitForNonTsFiles<T>(options: CompilerOptions, fileNames: T[], propertyReader: FilePropertyReader<T>) {
+        private exceededTotalSizeLimitForNonTsFiles<T>(name: string, options: CompilerOptions, fileNames: T[], propertyReader: FilePropertyReader<T>) {
             if (options && options.disableSizeLimit || !this.host.getFileSize) {
                 return false;
             }
+
+            let availableSpace = maxProgramSizeForNonTsFiles;
+            this.projectToSizeMap.set(name, 0);
+            this.projectToSizeMap.forEach(val => (availableSpace -= (val || 0)));
+
             let totalNonTsFileSize = 0;
             for (const f of fileNames) {
                 const fileName = propertyReader.getFileName(f);
@@ -864,9 +872,16 @@ namespace ts.server {
                 }
                 totalNonTsFileSize += this.host.getFileSize(fileName);
                 if (totalNonTsFileSize > maxProgramSizeForNonTsFiles) {
+                    // Keep the size as zero since it's disabled
                     return true;
                 }
             }
+
+            if (totalNonTsFileSize > availableSpace) {
+                return true;
+            }
+
+            this.projectToSizeMap.set(name, totalNonTsFileSize);
             return false;
         }
 
@@ -877,7 +892,7 @@ namespace ts.server {
                 this,
                 this.documentRegistry,
                 compilerOptions,
-                /*languageServiceEnabled*/ !this.exceededTotalSizeLimitForNonTsFiles(compilerOptions, files, externalFilePropertyReader),
+                /*languageServiceEnabled*/ !this.exceededTotalSizeLimitForNonTsFiles(projectFileName, compilerOptions, files, externalFilePropertyReader),
                 options.compileOnSave === undefined ? true : options.compileOnSave);
 
             this.addFilesToProjectAndUpdateGraph(project, files, externalFilePropertyReader, /*clientFileName*/ undefined, typeAcquisition, /*configFileErrors*/ undefined);
@@ -897,7 +912,7 @@ namespace ts.server {
         }
 
         private createAndAddConfiguredProject(configFileName: NormalizedPath, projectOptions: ProjectOptions, configFileErrors: Diagnostic[], clientFileName?: string) {
-            const sizeLimitExceeded = this.exceededTotalSizeLimitForNonTsFiles(projectOptions.compilerOptions, projectOptions.files, fileNamePropertyReader);
+            const sizeLimitExceeded = this.exceededTotalSizeLimitForNonTsFiles(configFileName, projectOptions.compilerOptions, projectOptions.files, fileNamePropertyReader);
             const project = new ConfiguredProject(
                 configFileName,
                 this,
@@ -1050,7 +1065,7 @@ namespace ts.server {
                 return configFileErrors;
             }
 
-            if (this.exceededTotalSizeLimitForNonTsFiles(projectOptions.compilerOptions, projectOptions.files, fileNamePropertyReader)) {
+            if (this.exceededTotalSizeLimitForNonTsFiles(project.canonicalConfigFilePath, projectOptions.compilerOptions, projectOptions.files, fileNamePropertyReader)) {
                 project.setCompilerOptions(projectOptions.compilerOptions);
                 if (!project.languageServiceEnabled) {
                     // language service is already disabled
@@ -1414,7 +1429,7 @@ namespace ts.server {
             if (externalProject) {
                 if (!tsConfigFiles) {
                     const compilerOptions = convertCompilerOptions(proj.options);
-                    if (this.exceededTotalSizeLimitForNonTsFiles(compilerOptions, proj.rootFiles, externalFilePropertyReader)) {
+                    if (this.exceededTotalSizeLimitForNonTsFiles(proj.projectFileName, compilerOptions, proj.rootFiles, externalFilePropertyReader)) {
                         externalProject.disableLanguageService();
                     }
                     else {
diff --git a/src/server/project.ts b/src/server/project.ts
index 385816b1029..e57e605d65b 100644
--- a/src/server/project.ts
+++ b/src/server/project.ts
@@ -1031,7 +1031,7 @@ namespace ts.server {
 
     export class ExternalProject extends Project {
         private typeAcquisition: TypeAcquisition;
-        constructor(externalProjectName: string,
+        constructor(public externalProjectName: string,
             projectService: ProjectService,
             documentRegistry: ts.DocumentRegistry,
             compilerOptions: CompilerOptions,
diff --git a/src/server/session.ts b/src/server/session.ts
index 8dd0411d077..11c99dfe46c 100644
--- a/src/server/session.ts
+++ b/src/server/session.ts
@@ -25,8 +25,14 @@ namespace ts.server {
         return ((1e9 * seconds) + nanoseconds) / 1000000.0;
     }
 
-    function shouldSkipSematicCheck(project: Project) {
-        return (project.projectKind === ProjectKind.Inferred || project.projectKind === ProjectKind.External) && project.isJsOnlyProject();
+    function shouldSkipSemanticCheck(project: Project) {
+        if (project.projectKind === ProjectKind.Inferred || project.projectKind === ProjectKind.External) {
+            return project.isJsOnlyProject();
+        }
+        else {
+            // For configured projects, require that skipLibCheck be set also
+            return project.getCompilerOptions().skipLibCheck && project.isJsOnlyProject();
+        }
     }
 
     interface FileStart {
@@ -447,7 +453,7 @@ namespace ts.server {
         private semanticCheck(file: NormalizedPath, project: Project) {
             try {
                 let diags: Diagnostic[] = [];
-                if (!shouldSkipSematicCheck(project)) {
+                if (!shouldSkipSemanticCheck(project)) {
                     diags = project.getLanguageService().getSemanticDiagnostics(file);
                 }
 
@@ -555,7 +561,7 @@ namespace ts.server {
 
         private getDiagnosticsWorker(args: protocol.FileRequestArgs, isSemantic: boolean, selector: (project: Project, file: string) => Diagnostic[], includeLinePosition: boolean) {
             const { project, file } = this.getFileAndProject(args);
-            if (isSemantic && shouldSkipSematicCheck(project)) {
+            if (isSemantic && shouldSkipSemanticCheck(project)) {
                 return [];
             }
             const scriptInfo = project.getScriptInfoForNormalizedPath(file);
diff --git a/src/services/symbolDisplay.ts b/src/services/symbolDisplay.ts
index b457165b67f..3fcc467f6ab 100644
--- a/src/services/symbolDisplay.ts
+++ b/src/services/symbolDisplay.ts
@@ -419,7 +419,7 @@ namespace ts.SymbolDisplay {
         if (!documentation) {
             documentation = symbol.getDocumentationComment();
             if (documentation.length === 0 && symbol.flags & SymbolFlags.Property) {
-                // For some special property access expressions like `experts.foo = foo` or `module.exports.foo = foo`
+                // For some special property access expressions like `exports.foo = foo` or `module.exports.foo = foo`
                 // there documentation comments might be attached to the right hand side symbol of their declarations.
                 // The pattern of such special property access is that the parent symbol is the symbol of the file.
                 if (symbol.parent && forEach(symbol.parent.declarations, declaration => declaration.kind === SyntaxKind.SourceFile)) {
diff --git a/tests/baselines/reference/deeplyNestedCheck.js b/tests/baselines/reference/deeplyNestedCheck.js
new file mode 100644
index 00000000000..466ae94f12d
--- /dev/null
+++ b/tests/baselines/reference/deeplyNestedCheck.js
@@ -0,0 +1,14 @@
+//// [deeplyNestedCheck.ts]
+// Repro from #14794
+
+interface DataSnapshot<X = {}> {
+  child(path: string): DataSnapshot;
+}
+
+interface Snapshot<T> extends DataSnapshot {
+  child<U extends keyof T>(path: U): Snapshot<T[U]>;
+}
+
+
+//// [deeplyNestedCheck.js]
+// Repro from #14794
diff --git a/tests/baselines/reference/deeplyNestedCheck.symbols b/tests/baselines/reference/deeplyNestedCheck.symbols
new file mode 100644
index 00000000000..a8b5af60880
--- /dev/null
+++ b/tests/baselines/reference/deeplyNestedCheck.symbols
@@ -0,0 +1,29 @@
+=== tests/cases/compiler/deeplyNestedCheck.ts ===
+// Repro from #14794
+
+interface DataSnapshot<X = {}> {
+>DataSnapshot : Symbol(DataSnapshot, Decl(deeplyNestedCheck.ts, 0, 0))
+>X : Symbol(X, Decl(deeplyNestedCheck.ts, 2, 23))
+
+  child(path: string): DataSnapshot;
+>child : Symbol(DataSnapshot.child, Decl(deeplyNestedCheck.ts, 2, 32))
+>path : Symbol(path, Decl(deeplyNestedCheck.ts, 3, 8))
+>DataSnapshot : Symbol(DataSnapshot, Decl(deeplyNestedCheck.ts, 0, 0))
+}
+
+interface Snapshot<T> extends DataSnapshot {
+>Snapshot : Symbol(Snapshot, Decl(deeplyNestedCheck.ts, 4, 1))
+>T : Symbol(T, Decl(deeplyNestedCheck.ts, 6, 19))
+>DataSnapshot : Symbol(DataSnapshot, Decl(deeplyNestedCheck.ts, 0, 0))
+
+  child<U extends keyof T>(path: U): Snapshot<T[U]>;
+>child : Symbol(Snapshot.child, Decl(deeplyNestedCheck.ts, 6, 44))
+>U : Symbol(U, Decl(deeplyNestedCheck.ts, 7, 8))
+>T : Symbol(T, Decl(deeplyNestedCheck.ts, 6, 19))
+>path : Symbol(path, Decl(deeplyNestedCheck.ts, 7, 27))
+>U : Symbol(U, Decl(deeplyNestedCheck.ts, 7, 8))
+>Snapshot : Symbol(Snapshot, Decl(deeplyNestedCheck.ts, 4, 1))
+>T : Symbol(T, Decl(deeplyNestedCheck.ts, 6, 19))
+>U : Symbol(U, Decl(deeplyNestedCheck.ts, 7, 8))
+}
+
diff --git a/tests/baselines/reference/deeplyNestedCheck.types b/tests/baselines/reference/deeplyNestedCheck.types
new file mode 100644
index 00000000000..e500fc75ed1
--- /dev/null
+++ b/tests/baselines/reference/deeplyNestedCheck.types
@@ -0,0 +1,29 @@
+=== tests/cases/compiler/deeplyNestedCheck.ts ===
+// Repro from #14794
+
+interface DataSnapshot<X = {}> {
+>DataSnapshot : DataSnapshot<X>
+>X : X
+
+  child(path: string): DataSnapshot;
+>child : (path: string) => DataSnapshot<{}>
+>path : string
+>DataSnapshot : DataSnapshot<X>
+}
+
+interface Snapshot<T> extends DataSnapshot {
+>Snapshot : Snapshot<T>
+>T : T
+>DataSnapshot : DataSnapshot<X>
+
+  child<U extends keyof T>(path: U): Snapshot<T[U]>;
+>child : <U extends keyof T>(path: U) => Snapshot<T[U]>
+>U : U
+>T : T
+>path : U
+>U : U
+>Snapshot : Snapshot<T>
+>T : T
+>U : U
+}
+
diff --git a/tests/baselines/reference/nonPrimitiveIndexingWithForIn.js b/tests/baselines/reference/nonPrimitiveIndexingWithForIn.js
new file mode 100644
index 00000000000..c5f4319c748
--- /dev/null
+++ b/tests/baselines/reference/nonPrimitiveIndexingWithForIn.js
@@ -0,0 +1,13 @@
+//// [nonPrimitiveIndexingWithForIn.ts]
+var a: object;
+
+for (var key in a) {
+    var value = a[key];
+}
+
+
+//// [nonPrimitiveIndexingWithForIn.js]
+var a;
+for (var key in a) {
+    var value = a[key];
+}
diff --git a/tests/baselines/reference/nonPrimitiveIndexingWithForIn.symbols b/tests/baselines/reference/nonPrimitiveIndexingWithForIn.symbols
new file mode 100644
index 00000000000..3cb41269541
--- /dev/null
+++ b/tests/baselines/reference/nonPrimitiveIndexingWithForIn.symbols
@@ -0,0 +1,14 @@
+=== tests/cases/conformance/types/nonPrimitive/nonPrimitiveIndexingWithForIn.ts ===
+var a: object;
+>a : Symbol(a, Decl(nonPrimitiveIndexingWithForIn.ts, 0, 3))
+
+for (var key in a) {
+>key : Symbol(key, Decl(nonPrimitiveIndexingWithForIn.ts, 2, 8))
+>a : Symbol(a, Decl(nonPrimitiveIndexingWithForIn.ts, 0, 3))
+
+    var value = a[key];
+>value : Symbol(value, Decl(nonPrimitiveIndexingWithForIn.ts, 3, 7))
+>a : Symbol(a, Decl(nonPrimitiveIndexingWithForIn.ts, 0, 3))
+>key : Symbol(key, Decl(nonPrimitiveIndexingWithForIn.ts, 2, 8))
+}
+
diff --git a/tests/baselines/reference/nonPrimitiveIndexingWithForIn.types b/tests/baselines/reference/nonPrimitiveIndexingWithForIn.types
new file mode 100644
index 00000000000..44e2b3f4d50
--- /dev/null
+++ b/tests/baselines/reference/nonPrimitiveIndexingWithForIn.types
@@ -0,0 +1,15 @@
+=== tests/cases/conformance/types/nonPrimitive/nonPrimitiveIndexingWithForIn.ts ===
+var a: object;
+>a : object
+
+for (var key in a) {
+>key : string
+>a : object
+
+    var value = a[key];
+>value : any
+>a[key] : any
+>a : object
+>key : string
+}
+
diff --git a/tests/baselines/reference/nonPrimitiveIndexingWithForInNoImplicitAny.errors.txt b/tests/baselines/reference/nonPrimitiveIndexingWithForInNoImplicitAny.errors.txt
new file mode 100644
index 00000000000..f7f2ee3db16
--- /dev/null
+++ b/tests/baselines/reference/nonPrimitiveIndexingWithForInNoImplicitAny.errors.txt
@@ -0,0 +1,12 @@
+tests/cases/conformance/types/nonPrimitive/nonPrimitiveIndexingWithForInNoImplicitAny.ts(4,17): error TS7017: Element implicitly has an 'any' type because type '{}' has no index signature.
+
+
+==== tests/cases/conformance/types/nonPrimitive/nonPrimitiveIndexingWithForInNoImplicitAny.ts (1 errors) ====
+    var a: object;
+    
+    for (var key in a) {
+        var value = a[key]; // error
+                    ~~~~~~
+!!! error TS7017: Element implicitly has an 'any' type because type '{}' has no index signature.
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/nonPrimitiveIndexingWithForInNoImplicitAny.js b/tests/baselines/reference/nonPrimitiveIndexingWithForInNoImplicitAny.js
new file mode 100644
index 00000000000..e105e5ba9bb
--- /dev/null
+++ b/tests/baselines/reference/nonPrimitiveIndexingWithForInNoImplicitAny.js
@@ -0,0 +1,13 @@
+//// [nonPrimitiveIndexingWithForInNoImplicitAny.ts]
+var a: object;
+
+for (var key in a) {
+    var value = a[key]; // error
+}
+
+
+//// [nonPrimitiveIndexingWithForInNoImplicitAny.js]
+var a;
+for (var key in a) {
+    var value = a[key]; // error
+}
diff --git a/tests/baselines/reference/nonPrimitiveIndexingWithForInSupressError.js b/tests/baselines/reference/nonPrimitiveIndexingWithForInSupressError.js
new file mode 100644
index 00000000000..ce575b2a4d6
--- /dev/null
+++ b/tests/baselines/reference/nonPrimitiveIndexingWithForInSupressError.js
@@ -0,0 +1,13 @@
+//// [nonPrimitiveIndexingWithForInSupressError.ts]
+var a: object;
+
+for (var key in a) {
+    var value = a[key];
+}
+
+
+//// [nonPrimitiveIndexingWithForInSupressError.js]
+var a;
+for (var key in a) {
+    var value = a[key];
+}
diff --git a/tests/baselines/reference/nonPrimitiveIndexingWithForInSupressError.symbols b/tests/baselines/reference/nonPrimitiveIndexingWithForInSupressError.symbols
new file mode 100644
index 00000000000..4e52e66b1c0
--- /dev/null
+++ b/tests/baselines/reference/nonPrimitiveIndexingWithForInSupressError.symbols
@@ -0,0 +1,14 @@
+=== tests/cases/conformance/types/nonPrimitive/nonPrimitiveIndexingWithForInSupressError.ts ===
+var a: object;
+>a : Symbol(a, Decl(nonPrimitiveIndexingWithForInSupressError.ts, 0, 3))
+
+for (var key in a) {
+>key : Symbol(key, Decl(nonPrimitiveIndexingWithForInSupressError.ts, 2, 8))
+>a : Symbol(a, Decl(nonPrimitiveIndexingWithForInSupressError.ts, 0, 3))
+
+    var value = a[key];
+>value : Symbol(value, Decl(nonPrimitiveIndexingWithForInSupressError.ts, 3, 7))
+>a : Symbol(a, Decl(nonPrimitiveIndexingWithForInSupressError.ts, 0, 3))
+>key : Symbol(key, Decl(nonPrimitiveIndexingWithForInSupressError.ts, 2, 8))
+}
+
diff --git a/tests/baselines/reference/nonPrimitiveIndexingWithForInSupressError.types b/tests/baselines/reference/nonPrimitiveIndexingWithForInSupressError.types
new file mode 100644
index 00000000000..3fafa40b596
--- /dev/null
+++ b/tests/baselines/reference/nonPrimitiveIndexingWithForInSupressError.types
@@ -0,0 +1,15 @@
+=== tests/cases/conformance/types/nonPrimitive/nonPrimitiveIndexingWithForInSupressError.ts ===
+var a: object;
+>a : object
+
+for (var key in a) {
+>key : string
+>a : object
+
+    var value = a[key];
+>value : any
+>a[key] : any
+>a : object
+>key : string
+}
+
diff --git a/tests/cases/compiler/deeplyNestedCheck.ts b/tests/cases/compiler/deeplyNestedCheck.ts
new file mode 100644
index 00000000000..e95233af985
--- /dev/null
+++ b/tests/cases/compiler/deeplyNestedCheck.ts
@@ -0,0 +1,9 @@
+// Repro from #14794
+
+interface DataSnapshot<X = {}> {
+  child(path: string): DataSnapshot;
+}
+
+interface Snapshot<T> extends DataSnapshot {
+  child<U extends keyof T>(path: U): Snapshot<T[U]>;
+}
diff --git a/tests/cases/conformance/types/nonPrimitive/nonPrimitiveIndexingWithForIn.ts b/tests/cases/conformance/types/nonPrimitive/nonPrimitiveIndexingWithForIn.ts
new file mode 100644
index 00000000000..2ec8cf83cb7
--- /dev/null
+++ b/tests/cases/conformance/types/nonPrimitive/nonPrimitiveIndexingWithForIn.ts
@@ -0,0 +1,5 @@
+var a: object;
+
+for (var key in a) {
+    var value = a[key];
+}
diff --git a/tests/cases/conformance/types/nonPrimitive/nonPrimitiveIndexingWithForInNoImplicitAny.ts b/tests/cases/conformance/types/nonPrimitive/nonPrimitiveIndexingWithForInNoImplicitAny.ts
new file mode 100644
index 00000000000..1050cdea497
--- /dev/null
+++ b/tests/cases/conformance/types/nonPrimitive/nonPrimitiveIndexingWithForInNoImplicitAny.ts
@@ -0,0 +1,6 @@
+// @noImplicitAny: true
+var a: object;
+
+for (var key in a) {
+    var value = a[key]; // error
+}
diff --git a/tests/cases/conformance/types/nonPrimitive/nonPrimitiveIndexingWithForInSupressError.ts b/tests/cases/conformance/types/nonPrimitive/nonPrimitiveIndexingWithForInSupressError.ts
new file mode 100644
index 00000000000..3f63faee604
--- /dev/null
+++ b/tests/cases/conformance/types/nonPrimitive/nonPrimitiveIndexingWithForInSupressError.ts
@@ -0,0 +1,7 @@
+// @noImplicitAny: true
+// @suppressImplicitAnyIndexErrors: true
+var a: object;
+
+for (var key in a) {
+    var value = a[key];
+}