Merge branch 'master' into fixGenericSignatureRelation

# Conflicts:
#	tests/baselines/reference/keyofAndIndexedAccess2.errors.txt
#	tests/baselines/reference/keyofAndIndexedAccess2.js
#	tests/baselines/reference/keyofAndIndexedAccess2.symbols
#	tests/baselines/reference/keyofAndIndexedAccess2.types
#	tests/cases/conformance/types/keyof/keyofAndIndexedAccess2.ts

Author: ahejlsberg

.github/pull_request_template.md

@@ -1,8 +1,8 @@
 <!--
 Thank you for submitting a pull request!
 
-Here's a checklist you might find useful.
-* [ ] There is an associated issue that is labeled 'Bug' or 'help wanted'
+Please verify that:
+* [ ] There is an associated issue in the `Backlog` milestone (**required**)
 * [ ] Code is up-to-date with the `master` branch
 * [ ] You've successfully run `gulp runtests` locally
 * [ ] There are new or updated unit tests validating the change
@@ -12,4 +12,3 @@ Refer to CONTRIBUTING.MD for more details.
 -->
 
 Fixes #
-

README.md

@@ -7,7 +7,7 @@
 
 [![Join the chat at https://gitter.im/Microsoft/TypeScript](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/Microsoft/TypeScript?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
-[TypeScript](https://www.typescriptlang.org/) is a language for application-scale JavaScript. TypeScript adds optional types to JavaScript that support tools for large-scale JavaScript applications for any browser, for any host, on any OS. TypeScript compiles to readable, standards-based JavaScript. Try it out at the [playground](https://www.typescriptlang.org/play/), and stay up to date via [our blog](https://blogs.msdn.microsoft.com/typescript) and [Twitter account](https://twitter.com/typescriptlang).
+[TypeScript](https://www.typescriptlang.org/) is a language for application-scale JavaScript. TypeScript adds optional types to JavaScript that support tools for large-scale JavaScript applications for any browser, for any host, on any OS. TypeScript compiles to readable, standards-based JavaScript. Try it out at the [playground](https://www.typescriptlang.org/play/), and stay up to date via [our blog](https://blogs.msdn.microsoft.com/typescript) and [Twitter account](https://twitter.com/typescript).
 
 ## Installing
 

src/compiler/binder.ts

@@ -1625,15 +1625,8 @@ namespace ts {
         }
 
         function hasExportDeclarations(node: ModuleDeclaration | SourceFile): boolean {
-            const body = node.kind === SyntaxKind.SourceFile ? node : node.body;
-            if (body && (body.kind === SyntaxKind.SourceFile || body.kind === SyntaxKind.ModuleBlock)) {
-                for (const stat of (<BlockLike>body).statements) {
-                    if (stat.kind === SyntaxKind.ExportDeclaration || stat.kind === SyntaxKind.ExportAssignment) {
-                        return true;
-                    }
-                }
-            }
-            return false;
+            const body = isSourceFile(node) ? node : tryCast(node.body, isModuleBlock);
+            return !!body && body.statements.some(s => isExportDeclaration(s) || isExportAssignment(s));
         }
 
         function setExportContextFlag(node: ModuleDeclaration | SourceFile) {

src/compiler/checker.ts

@@ -16,6 +16,7 @@ namespace ts {
         ["es2017", "lib.es2017.d.ts"],
         ["es2018", "lib.es2018.d.ts"],
         ["es2019", "lib.es2019.d.ts"],
+        ["es2020", "lib.es2020.d.ts"],
         ["esnext", "lib.esnext.d.ts"],
         // Host only
         ["dom", "lib.dom.d.ts"],
@@ -44,8 +45,11 @@ namespace ts {
         ["es2018.promise", "lib.es2018.promise.d.ts"],
         ["es2018.regexp", "lib.es2018.regexp.d.ts"],
         ["es2019.array", "lib.es2019.array.d.ts"],
+        ["es2019.object", "lib.es2019.object.d.ts"],
         ["es2019.string", "lib.es2019.string.d.ts"],
         ["es2019.symbol", "lib.es2019.symbol.d.ts"],
+        ["es2020.string", "lib.es2020.string.d.ts"],
+        ["es2020.symbol.wellknown", "lib.es2020.symbol.wellknown.d.ts"],
         ["esnext.array", "lib.es2019.array.d.ts"],
         ["esnext.symbol", "lib.es2019.symbol.d.ts"],
         ["esnext.asynciterable", "lib.es2018.asynciterable.d.ts"],
@@ -210,10 +214,12 @@ namespace ts {
                 es2017: ScriptTarget.ES2017,
                 es2018: ScriptTarget.ES2018,
                 es2019: ScriptTarget.ES2019,
+                es2020: ScriptTarget.ES2020,
                 esnext: ScriptTarget.ESNext,
             }),
             affectsSourceFile: true,
             affectsModuleResolution: true,
+            affectsEmit: true,
             paramType: Diagnostics.VERSION,
             showInSimplifiedHelpView: true,
             category: Diagnostics.Basic_Options,
@@ -1341,7 +1347,12 @@ namespace ts {
     /**
      * Reads the config file, reports errors if any and exits if the config file cannot be found
      */
-    export function getParsedCommandLineOfConfigFile(configFileName: string, optionsToExtend: CompilerOptions, host: ParseConfigFileHost): ParsedCommandLine | undefined {
+    export function getParsedCommandLineOfConfigFile(
+        configFileName: string,
+        optionsToExtend: CompilerOptions,
+        host: ParseConfigFileHost,
+        extendedConfigCache?: Map<ExtendedConfigCacheEntry>
+    ): ParsedCommandLine | undefined {
         let configFileText: string | undefined;
         try {
             configFileText = host.readFile(configFileName);
@@ -1362,7 +1373,16 @@ namespace ts {
         result.path = toPath(configFileName, cwd, createGetCanonicalFileName(host.useCaseSensitiveFileNames));
         result.resolvedPath = result.path;
         result.originalFileName = result.fileName;
-        return parseJsonSourceFileConfigFileContent(result, host, getNormalizedAbsolutePath(getDirectoryPath(configFileName), cwd), optionsToExtend, getNormalizedAbsolutePath(configFileName, cwd));
+        return parseJsonSourceFileConfigFileContent(
+            result,
+            host,
+            getNormalizedAbsolutePath(getDirectoryPath(configFileName), cwd),
+            optionsToExtend,
+            getNormalizedAbsolutePath(configFileName, cwd),
+            /*resolutionStack*/ undefined,
+            /*extraFileExtension*/ undefined,
+            extendedConfigCache
+        );
     }
 
     /**
@@ -1965,8 +1985,8 @@ namespace ts {
      * @param basePath A root directory to resolve relative path entries in the config
      *    file to. e.g. outDir
      */
-    export function parseJsonConfigFileContent(json: any, host: ParseConfigHost, basePath: string, existingOptions?: CompilerOptions, configFileName?: string, resolutionStack?: Path[], extraFileExtensions?: ReadonlyArray<FileExtensionInfo>): ParsedCommandLine {
-        return parseJsonConfigFileContentWorker(json, /*sourceFile*/ undefined, host, basePath, existingOptions, configFileName, resolutionStack, extraFileExtensions);
+    export function parseJsonConfigFileContent(json: any, host: ParseConfigHost, basePath: string, existingOptions?: CompilerOptions, configFileName?: string, resolutionStack?: Path[], extraFileExtensions?: ReadonlyArray<FileExtensionInfo>, extendedConfigCache?: Map<ExtendedConfigCacheEntry>): ParsedCommandLine {
+        return parseJsonConfigFileContentWorker(json, /*sourceFile*/ undefined, host, basePath, existingOptions, configFileName, resolutionStack, extraFileExtensions, extendedConfigCache);
     }
 
     /**
@@ -1976,8 +1996,8 @@ namespace ts {
      * @param basePath A root directory to resolve relative path entries in the config
      *    file to. e.g. outDir
      */
-    export function parseJsonSourceFileConfigFileContent(sourceFile: TsConfigSourceFile, host: ParseConfigHost, basePath: string, existingOptions?: CompilerOptions, configFileName?: string, resolutionStack?: Path[], extraFileExtensions?: ReadonlyArray<FileExtensionInfo>): ParsedCommandLine {
-        return parseJsonConfigFileContentWorker(/*json*/ undefined, sourceFile, host, basePath, existingOptions, configFileName, resolutionStack, extraFileExtensions);
+    export function parseJsonSourceFileConfigFileContent(sourceFile: TsConfigSourceFile, host: ParseConfigHost, basePath: string, existingOptions?: CompilerOptions, configFileName?: string, resolutionStack?: Path[], extraFileExtensions?: ReadonlyArray<FileExtensionInfo>, extendedConfigCache?: Map<ExtendedConfigCacheEntry>): ParsedCommandLine {
+        return parseJsonConfigFileContentWorker(/*json*/ undefined, sourceFile, host, basePath, existingOptions, configFileName, resolutionStack, extraFileExtensions, extendedConfigCache);
     }
 
     /*@internal*/
@@ -2016,11 +2036,12 @@ namespace ts {
         configFileName?: string,
         resolutionStack: Path[] = [],
         extraFileExtensions: ReadonlyArray<FileExtensionInfo> = [],
+        extendedConfigCache?: Map<ExtendedConfigCacheEntry>
     ): ParsedCommandLine {
         Debug.assert((json === undefined && sourceFile !== undefined) || (json !== undefined && sourceFile === undefined));
         const errors: Diagnostic[] = [];
 
-        const parsedConfig = parseConfig(json, sourceFile, host, basePath, configFileName, resolutionStack, errors);
+        const parsedConfig = parseConfig(json, sourceFile, host, basePath, configFileName, resolutionStack, errors, extendedConfigCache);
         const { raw } = parsedConfig;
         const options = extend(existingOptions, parsedConfig.options || {});
         options.configFilePath = configFileName && normalizeSlashes(configFileName);
@@ -2168,7 +2189,7 @@ namespace ts {
         return existingErrors !== configParseDiagnostics.length;
     }
 
-    interface ParsedTsconfig {
+    export interface ParsedTsconfig {
         raw: any;
         options?: CompilerOptions;
         typeAcquisition?: TypeAcquisition;
@@ -2187,13 +2208,14 @@ namespace ts {
      * It does *not* resolve the included files.
      */
     function parseConfig(
-            json: any,
-            sourceFile: TsConfigSourceFile | undefined,
-            host: ParseConfigHost,
-            basePath: string,
-            configFileName: string | undefined,
-            resolutionStack: string[],
-            errors: Push<Diagnostic>,
+        json: any,
+        sourceFile: TsConfigSourceFile | undefined,
+        host: ParseConfigHost,
+        basePath: string,
+        configFileName: string | undefined,
+        resolutionStack: string[],
+        errors: Push<Diagnostic>,
+        extendedConfigCache?: Map<ExtendedConfigCacheEntry>
     ): ParsedTsconfig {
         basePath = normalizeSlashes(basePath);
         const resolvedPath = getNormalizedAbsolutePath(configFileName || "", basePath);
@@ -2210,7 +2232,7 @@ namespace ts {
         if (ownConfig.extendedConfigPath) {
             // copy the resolution stack so it is never reused between branches in potential diamond-problem scenarios.
             resolutionStack = resolutionStack.concat([resolvedPath]);
-            const extendedConfig = getExtendedConfig(sourceFile, ownConfig.extendedConfigPath, host, basePath, resolutionStack, errors);
+            const extendedConfig = getExtendedConfig(sourceFile, ownConfig.extendedConfigPath, host, basePath, resolutionStack, errors, extendedConfigCache);
             if (extendedConfig && isSuccessfulParsedTsconfig(extendedConfig)) {
                 const baseRaw = extendedConfig.raw;
                 const raw = ownConfig.raw;
@@ -2354,47 +2376,65 @@ namespace ts {
         return undefined;
     }
 
+    export interface ExtendedConfigCacheEntry {
+        extendedResult: TsConfigSourceFile;
+        extendedConfig: ParsedTsconfig | undefined;
+    }
+
     function getExtendedConfig(
         sourceFile: TsConfigSourceFile | undefined,
         extendedConfigPath: string,
         host: ParseConfigHost,
         basePath: string,
         resolutionStack: string[],
         errors: Push<Diagnostic>,
+        extendedConfigCache?: Map<ExtendedConfigCacheEntry>
     ): ParsedTsconfig | undefined {
-        const extendedResult = readJsonConfigFile(extendedConfigPath, path => host.readFile(path));
+        const path = host.useCaseSensitiveFileNames ? extendedConfigPath : toLowerCase(extendedConfigPath);
+        let value: ExtendedConfigCacheEntry | undefined;
+        let extendedResult: TsConfigSourceFile;
+        let extendedConfig: ParsedTsconfig | undefined;
+        if (extendedConfigCache && (value = extendedConfigCache.get(path))) {
+            ({ extendedResult, extendedConfig } = value);
+        }
+        else {
+            extendedResult = readJsonConfigFile(extendedConfigPath, path => host.readFile(path));
+            if (!extendedResult.parseDiagnostics.length) {
+                const extendedDirname = getDirectoryPath(extendedConfigPath);
+                extendedConfig = parseConfig(/*json*/ undefined, extendedResult, host, extendedDirname,
+                    getBaseFileName(extendedConfigPath), resolutionStack, errors, extendedConfigCache);
+
+                if (isSuccessfulParsedTsconfig(extendedConfig)) {
+                    // Update the paths to reflect base path
+                    const relativeDifference = convertToRelativePath(extendedDirname, basePath, identity);
+                    const updatePath = (path: string) => isRootedDiskPath(path) ? path : combinePaths(relativeDifference, path);
+                    const mapPropertiesInRawIfNotUndefined = (propertyName: string) => {
+                        if (raw[propertyName]) {
+                            raw[propertyName] = map(raw[propertyName], updatePath);
+                        }
+                    };
+
+                    const { raw } = extendedConfig;
+                    mapPropertiesInRawIfNotUndefined("include");
+                    mapPropertiesInRawIfNotUndefined("exclude");
+                    mapPropertiesInRawIfNotUndefined("files");
+                }
+            }
+            if (extendedConfigCache) {
+                extendedConfigCache.set(path, { extendedResult, extendedConfig });
+            }
+        }
         if (sourceFile) {
             sourceFile.extendedSourceFiles = [extendedResult.fileName];
+            if (extendedResult.extendedSourceFiles) {
+                sourceFile.extendedSourceFiles.push(...extendedResult.extendedSourceFiles);
+            }
         }
         if (extendedResult.parseDiagnostics.length) {
             errors.push(...extendedResult.parseDiagnostics);
             return undefined;
         }
-
-        const extendedDirname = getDirectoryPath(extendedConfigPath);
-        const extendedConfig = parseConfig(/*json*/ undefined, extendedResult, host, extendedDirname,
-            getBaseFileName(extendedConfigPath), resolutionStack, errors);
-        if (sourceFile && extendedResult.extendedSourceFiles) {
-            sourceFile.extendedSourceFiles!.push(...extendedResult.extendedSourceFiles);
-        }
-
-        if (isSuccessfulParsedTsconfig(extendedConfig)) {
-            // Update the paths to reflect base path
-            const relativeDifference = convertToRelativePath(extendedDirname, basePath, identity);
-            const updatePath = (path: string) => isRootedDiskPath(path) ? path : combinePaths(relativeDifference, path);
-            const mapPropertiesInRawIfNotUndefined = (propertyName: string) => {
-                if (raw[propertyName]) {
-                    raw[propertyName] = map(raw[propertyName], updatePath);
-                }
-            };
-
-            const { raw } = extendedConfig;
-            mapPropertiesInRawIfNotUndefined("include");
-            mapPropertiesInRawIfNotUndefined("exclude");
-            mapPropertiesInRawIfNotUndefined("files");
-        }
-
-        return extendedConfig;
+        return extendedConfig!;
     }
 
     function convertCompileOnSaveOptionFromJson(jsonOption: any, basePath: string, errors: Push<Diagnostic>): boolean {

src/compiler/commandLineParser.ts

@@ -1400,8 +1400,8 @@ namespace ts {
     /** Shims `Array.from`. */
     export function arrayFrom<T, U>(iterator: Iterator<T> | IterableIterator<T>, map: (t: T) => U): U[];
     export function arrayFrom<T>(iterator: Iterator<T> | IterableIterator<T>): T[];
-    export function arrayFrom(iterator: Iterator<any> | IterableIterator<any>, map?: (t: any) => any): any[] {
-        const result: any[] = [];
+    export function arrayFrom<T, U>(iterator: Iterator<T> | IterableIterator<T>, map?: (t: T) => U): (T | U)[] {
+        const result: (T | U)[] = [];
         for (let { value, done } = iterator.next(); !done; { value, done } = iterator.next()) {
             result.push(map ? map(value) : value);
         }
@@ -2284,4 +2284,29 @@ namespace ts {
         }
         return result;
     }
+
+    export function cartesianProduct<T>(arrays: readonly T[][]) {
+        const result: T[][] = [];
+        cartesianProductWorker(arrays, result, /*outer*/ undefined, 0);
+        return result;
+    }
+
+    function cartesianProductWorker<T>(arrays: readonly (readonly T[])[], result: (readonly T[])[], outer: readonly T[] | undefined, index: number) {
+        for (const element of arrays[index]) {
+            let inner: T[];
+            if (outer) {
+                inner = outer.slice();
+                inner.push(element);
+            }
+            else {
+                inner = [element];
+            }
+            if (index === arrays.length - 1) {
+                result.push(inner);
+            }
+            else {
+                cartesianProductWorker(arrays, result, inner, index + 1);
+            }
+        }
+    }
 }

src/compiler/core.ts

@@ -139,7 +139,7 @@
         "category": "Error",
         "code": 1045
     },
-    "A 'declare' modifier is required for a top level declaration in a .d.ts file.": {
+    "Top-level declarations in .d.ts files must start with either a 'declare' or 'export' modifier.": {
         "category": "Error",
         "code": 1046
     },
@@ -691,7 +691,7 @@
         "category": "Error",
         "code": 1218
     },
-    "Experimental support for decorators is a feature that is subject to change in a future release. Set the 'experimentalDecorators' option to remove this warning.": {
+    "Experimental support for decorators is a feature that is subject to change in a future release. Set the 'experimentalDecorators' option in your 'tsconfig' or 'jsconfig' to remove this warning.": {
         "category": "Error",
         "code": 1219
     },
@@ -1035,6 +1035,10 @@
         "category": "Error",
         "code": 1355
     },
+    "Did you mean to mark this function as 'async'?": {
+        "category": "Error",
+        "code": 1356
+    },
 
     "Duplicate identifier '{0}'.": {
         "category": "Error",
@@ -2959,7 +2963,7 @@
         "category": "Error",
         "code": 4104
     },
-    
+
     "The current host does not support the '{0}' option.": {
         "category": "Error",
         "code": 5001
@@ -3096,6 +3100,10 @@
         "category": "Error",
         "code": 5074
     },
+    "'{0}' is assignable to the constraint of type '{1}', but '{1}' could be instantiated with a different subtype of constraint '{2}'.": {
+        "category": "Error",
+        "code": 5075
+    },
 
     "Generates a sourcemap for each corresponding '.d.ts' file.": {
         "category": "Message",
@@ -4272,7 +4280,10 @@
         "category": "Error",
         "code": 7051
     },
-
+    "Element implicitly has an 'any' type because type '{0}' has no index signature. Did you mean to call '{1}' ?": {
+        "category": "Error",
+        "code": 7052
+    },
     "You cannot rename this element.": {
         "category": "Error",
         "code": 8000
@@ -4954,5 +4965,13 @@
     "No value exists in scope for the shorthand property '{0}'. Either declare one or provide an initializer." :{
         "category": "Error",
         "code": 18004
+    },
+    "Quoted constructors have previously been interpreted as methods, which is incorrect. In TypeScript 3.6, they will be correctly parsed as constructors. In the meantime, consider using 'constructor()' to write a constructor, or '[\"constructor\"]()' to write a method.": {
+        "category": "Error",
+        "code": 18005
+    },
+    "Classes may not have a field named 'constructor'.": {
+        "category": "Error",
+        "code": 18006
     }
 }