Merge branch 'master' of https://github.com/Microsoft/TypeScript into feature/eslint

src/compiler/builderState.ts

@@ -429,8 +429,8 @@ namespace ts.BuilderState {
                 const references = state.referencedMap.get(path);
                 if (references) {
                     const iterator = references.keys();
-                    for (let { value, done } = iterator.next(); !done; { value, done } = iterator.next()) {
-                        queue.push(value as Path);
+                    for (let iterResult = iterator.next(); !iterResult.done; iterResult = iterator.next()) {
+                        queue.push(iterResult.value as Path);
                     }
                 }
             }

src/compiler/commandLineParser.ts

@@ -40,6 +40,7 @@ namespace ts {
         ["es2017.string", "lib.es2017.string.d.ts"],
         ["es2017.intl", "lib.es2017.intl.d.ts"],
         ["es2017.typedarrays", "lib.es2017.typedarrays.d.ts"],
+        ["es2018.asyncgenerator", "lib.es2018.asyncgenerator.d.ts"],
         ["es2018.asynciterable", "lib.es2018.asynciterable.d.ts"],
         ["es2018.intl", "lib.es2018.intl.d.ts"],
         ["es2018.promise", "lib.es2018.promise.d.ts"],
@@ -1899,7 +1900,9 @@ namespace ts {
                 case "object":
                     return {};
                 default:
-                    return option.type.keys().next().value;
+                    const iterResult = option.type.keys().next();
+                    if (!iterResult.done) return iterResult.value;
+                    return Debug.fail("Expected 'option.type' to have entries.");
             }
         }
 

src/compiler/core.ts

@@ -25,7 +25,6 @@ namespace ts {
         " __sortedArrayBrand": any;
     }
 
-
     /** ES6 Map interface, only read methods included. */
     export interface ReadonlyMap<T> {
         get(key: string): T | undefined;
@@ -46,7 +45,7 @@ namespace ts {
 
     /** ES6 Iterator type. */
     export interface Iterator<T> {
-        next(): { value: T, done: false } | { value: never, done: true };
+        next(): { value: T, done?: false } | { value: never, done: true };
     }
 
     /** Array that is only intended to be pushed to, never read. */
@@ -299,12 +298,13 @@ namespace ts {
             forEach(action: (value: T, key: string) => void): void {
                 const iterator = this.entries();
                 while (true) {
-                    const { value: entry, done } = iterator.next();
-                    if (done) {
+                    const iterResult = iterator.next();
+                    if (iterResult.done) {
                         break;
                     }
 
-                    action(entry[1], entry[0]);
+                    const [key, value] = iterResult.value;
+                    action(value, key);
                 }
             }
         };
@@ -348,11 +348,11 @@ namespace ts {
 
     export function firstDefinedIterator<T, U>(iter: Iterator<T>, callback: (element: T) => U | undefined): U | undefined {
         while (true) {
-            const { value, done } = iter.next();
-            if (done) {
+            const iterResult = iter.next();
+            if (iterResult.done) {
                 return undefined;
             }
-            const result = callback(value);
+            const result = callback(iterResult.value);
             if (result !== undefined) {
                 return result;
             }
@@ -377,7 +377,7 @@ namespace ts {
                     return { value: undefined as never, done: true };
                 }
                 i++;
-                return { value: [arrayA[i - 1], arrayB[i - 1]], done: false };
+                return { value: [arrayA[i - 1], arrayB[i - 1]] as [T, U], done: false };
             }
         };
     }
@@ -569,7 +569,7 @@ namespace ts {
         return {
             next() {
                 const iterRes = iter.next();
-                return iterRes.done ? iterRes : { value: mapFn(iterRes.value), done: false };
+                return iterRes.done ? iterRes as { done: true, value: never } : { value: mapFn(iterRes.value), done: false };
             }
         };
     }
@@ -680,7 +680,7 @@ namespace ts {
                     }
                     const iterRes = iter.next();
                     if (iterRes.done) {
-                        return iterRes;
+                        return iterRes as { done: true, value: never };
                     }
                     currentIter = getIterator(iterRes.value);
                 }
@@ -755,7 +755,7 @@ namespace ts {
                 while (true) {
                     const res = iter.next();
                     if (res.done) {
-                        return res;
+                        return res as { done: true, value: never };
                     }
                     const value = mapFn(res.value);
                     if (value !== undefined) {
@@ -1081,6 +1081,7 @@ namespace ts {
      * @param value The value to append to the array. If `value` is `undefined`, nothing is
      * appended.
      */
+    export function append<TArray extends any[] | undefined, TValue extends NonNullable<TArray>[number] | undefined>(to: TArray, value: TValue): [undefined, undefined] extends [TArray, TValue] ? TArray : NonNullable<TArray>[number][];
     export function append<T>(to: T[], value: T | undefined): T[];
     export function append<T>(to: T[] | undefined, value: T): T[];
     export function append<T>(to: T[] | undefined, value: T | undefined): T[] | undefined;
@@ -1405,8 +1406,8 @@ namespace ts {
     export function arrayFrom<T>(iterator: Iterator<T> | IterableIterator<T>): T[];
     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);
+        for (let iterResult = iterator.next(); !iterResult.done; iterResult = iterator.next()) {
+            result.push(map ? map(iterResult.value) : iterResult.value);
         }
         return result;
     }

src/compiler/diagnosticMessages.json

@@ -1764,7 +1764,7 @@
         "category": "Error",
         "code": 2489
     },
-    "The type returned by the 'next()' method of an iterator must have a 'value' property.": {
+    "The type returned by the '{0}()' method of an iterator must have a 'value' property.": {
         "category": "Error",
         "code": 2490
     },
@@ -1992,7 +1992,7 @@
         "category": "Error",
         "code": 2546
     },
-    "The type returned by the 'next()' method of an async iterator must be a promise for a type with a 'value' property.": {
+    "The type returned by the '{0}()' method of an async iterator must be a promise for a type with a 'value' property.": {
         "category": "Error",
         "code": 2547
     },
@@ -2653,6 +2653,30 @@
         "category": "Error",
         "code": 2762
     },
+    "Cannot iterate value because the 'next' method of its iterator expects type '{1}', but for-of will always send '{0}'.": {
+        "category": "Error",
+        "code": 2763
+    },
+    "Cannot iterate value because the 'next' method of its iterator expects type '{1}', but array spread will always send '{0}'.": {
+        "category": "Error",
+        "code": 2764
+    },
+    "Cannot iterate value because the 'next' method of its iterator expects type '{1}', but array destructuring will always send '{0}'.": {
+        "category": "Error",
+        "code": 2765
+    },
+    "Cannot delegate iteration to value because the 'next' method of its iterator expects type '{1}', but the containing generator will always send '{0}'.": {
+        "category": "Error",
+        "code": 2766
+    },
+    "The '{0}' property of an iterator must be a method.": {
+        "category": "Error",
+        "code": 2767
+    },
+    "The '{0}' property of an async iterator must be a method.": {
+        "category": "Error",
+        "code": 2768
+    },
 
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",
@@ -4214,7 +4238,7 @@
         "category": "Error",
         "code": 7024
     },
-    "Generator implicitly has type '{0}' because it does not yield any values. Consider supplying a return type.": {
+    "Generator implicitly has yield type '{0}' because it does not yield any values. Consider supplying a return type annotation.": {
         "category": "Error",
         "code": 7025
     },
@@ -4336,6 +4360,11 @@
         "category": "Error",
         "code": 7054
     },
+    "'{0}', which lacks return-type annotation, implicitly has an '{1}' yield type.": {
+        "category": "Error",
+        "code": 7055
+    },
+
     "You cannot rename this element.": {
         "category": "Error",
         "code": 8000

src/compiler/parser.ts

@@ -466,6 +466,8 @@ namespace ts {
                             visitNode(cbNode, (<JSDocPropertyLikeTag>node).typeExpression)
                         : visitNode(cbNode, (<JSDocPropertyLikeTag>node).typeExpression) ||
                             visitNode(cbNode, (<JSDocPropertyLikeTag>node).name));
+            case SyntaxKind.JSDocAuthorTag:
+                return visitNode(cbNode, (node as JSDocTag).tagName);
             case SyntaxKind.JSDocAugmentsTag:
                 return visitNode(cbNode, (node as JSDocTag).tagName) ||
                     visitNode(cbNode, (<JSDocAugmentsTag>node).class);
@@ -6616,6 +6618,9 @@ namespace ts {
 
                     let tag: JSDocTag | undefined;
                     switch (tagName.escapedText) {
+                        case "author":
+                            tag = parseAuthorTag(start, tagName, margin);
+                            break;
                         case "augments":
                         case "extends":
                             tag = parseAugmentsTag(start, tagName);
@@ -6895,6 +6900,69 @@ namespace ts {
                     return finishNode(result);
                 }
 
+                function parseAuthorTag(start: number, tagName: Identifier, indent: number): JSDocAuthorTag {
+                    const result = <JSDocAuthorTag>createNode(SyntaxKind.JSDocAuthorTag, start);
+                    result.tagName = tagName;
+
+                    const authorInfoWithEmail = tryParse(() => tryParseAuthorNameAndEmail());
+                    if (!authorInfoWithEmail) {
+                        return finishNode(result);
+                    }
+
+                    result.comment = authorInfoWithEmail;
+
+                    if (lookAhead(() => nextToken() !== SyntaxKind.NewLineTrivia)) {
+                        const comment = parseTagComments(indent);
+                        if (comment) {
+                            result.comment += comment;
+                        }
+                    }
+
+                    return finishNode(result);
+                }
+
+                function tryParseAuthorNameAndEmail(): string | undefined {
+                    const comments: string[] = [];
+                    let seenLessThan = false;
+                    let seenGreaterThan = false;
+                    let token = scanner.getToken();
+
+                    loop: while (true) {
+                        switch (token) {
+                            case SyntaxKind.Identifier:
+                            case SyntaxKind.WhitespaceTrivia:
+                            case SyntaxKind.DotToken:
+                            case SyntaxKind.AtToken:
+                                comments.push(scanner.getTokenText());
+                                break;
+                            case SyntaxKind.LessThanToken:
+                                if (seenLessThan || seenGreaterThan) {
+                                    return;
+                                }
+                                seenLessThan = true;
+                                comments.push(scanner.getTokenText());
+                                break;
+                            case SyntaxKind.GreaterThanToken:
+                                if (!seenLessThan || seenGreaterThan) {
+                                    return;
+                                }
+                                seenGreaterThan = true;
+                                comments.push(scanner.getTokenText());
+                                scanner.setTextPos(scanner.getTokenPos() + 1);
+                                break loop;
+                            case SyntaxKind.NewLineTrivia:
+                            case SyntaxKind.EndOfFileToken:
+                                break loop;
+                        }
+
+                        token = nextTokenJSDoc();
+                    }
+
+                    if (seenLessThan && seenGreaterThan) {
+                        return comments.length === 0 ? undefined : comments.join("");
+                    }
+                }
+
                 function parseAugmentsTag(start: number, tagName: Identifier): JSDocAugmentsTag {
                     const result = <JSDocAugmentsTag>createNode(SyntaxKind.JSDocAugmentsTag, start);
                     result.tagName = tagName;

src/compiler/scanner.ts

@@ -2087,6 +2087,8 @@ namespace ts {
                     return token = SyntaxKind.CloseBracketToken;
                 case CharacterCodes.lessThan:
                     return token = SyntaxKind.LessThanToken;
+                case CharacterCodes.greaterThan:
+                    return token = SyntaxKind.GreaterThanToken;
                 case CharacterCodes.equals:
                     return token = SyntaxKind.EqualsToken;
                 case CharacterCodes.comma:

src/compiler/sourcemap.ts

@@ -148,7 +148,8 @@ namespace ts {
             const sourceIndexToNewSourceIndexMap: number[] = [];
             let nameIndexToNewNameIndexMap: number[] | undefined;
             const mappingIterator = decodeMappings(map.mappings);
-            for (let { value: raw, done } = mappingIterator.next(); !done; { value: raw, done } = mappingIterator.next()) {
+            for (let iterResult = mappingIterator.next(); !iterResult.done; iterResult = mappingIterator.next()) {
+                const raw = iterResult.value;
                 if (end && (
                     raw.generatedLine > end.line ||
                     (raw.generatedLine === end.line && raw.generatedCharacter > end.character))) {

src/compiler/types.ts

@@ -17,6 +17,7 @@ namespace ts {
         | SyntaxKind.OpenBraceToken
         | SyntaxKind.CloseBraceToken
         | SyntaxKind.LessThanToken
+        | SyntaxKind.GreaterThanToken
         | SyntaxKind.OpenBracketToken
         | SyntaxKind.CloseBracketToken
         | SyntaxKind.EqualsToken
@@ -459,6 +460,7 @@ namespace ts {
         JSDocSignature,
         JSDocTag,
         JSDocAugmentsTag,
+        JSDocAuthorTag,
         JSDocClassTag,
         JSDocCallbackTag,
         JSDocEnumTag,
@@ -2456,6 +2458,10 @@ namespace ts {
         class: ExpressionWithTypeArguments & { expression: Identifier | PropertyAccessEntityNameExpression };
     }
 
+    export interface JSDocAuthorTag extends JSDocTag {
+        kind: SyntaxKind.JSDocAuthorTag;
+    }
+
     export interface JSDocClassTag extends JSDocTag {
         kind: SyntaxKind.JSDocClassTag;
     }
@@ -4289,13 +4295,23 @@ namespace ts {
         regularType: ResolvedType;  // Regular version of fresh type
     }
 
+    /* @internal */
+    export interface IterationTypes {
+        readonly yieldType: Type;
+        readonly returnType: Type;
+        readonly nextType: Type;
+    }
+
     // Just a place to cache element types of iterables and iterators
     /* @internal */
     export interface IterableOrIteratorType extends ObjectType, UnionType {
-        iteratedTypeOfIterable?: Type;
-        iteratedTypeOfIterator?: Type;
-        iteratedTypeOfAsyncIterable?: Type;
-        iteratedTypeOfAsyncIterator?: Type;
+        iterationTypesOfGeneratorReturnType?: IterationTypes;
+        iterationTypesOfAsyncGeneratorReturnType?: IterationTypes;
+        iterationTypesOfIterable?: IterationTypes;
+        iterationTypesOfIterator?: IterationTypes;
+        iterationTypesOfAsyncIterable?: IterationTypes;
+        iterationTypesOfAsyncIterator?: IterationTypes;
+        iterationTypesOfIteratorResult?: IterationTypes;
     }
 
     /* @internal */

src/compiler/utilities.ts

@@ -151,8 +151,8 @@ namespace ts {
     export function forEachEntry<T, U>(map: ReadonlyMap<T>, callback: (value: T, key: string) => U | undefined): U | undefined;
     export function forEachEntry<T, U>(map: ReadonlyUnderscoreEscapedMap<T> | ReadonlyMap<T>, callback: (value: T, key: (string & __String)) => U | undefined): U | undefined {
         const iterator = map.entries();
-        for (let { value: pair, done } = iterator.next(); !done; { value: pair, done } = iterator.next()) {
-            const [key, value] = pair;
+        for (let iterResult = iterator.next(); !iterResult.done; iterResult = iterator.next()) {
+            const [key, value] = iterResult.value;
             const result = callback(value, key as (string & __String));
             if (result) {
                 return result;
@@ -166,8 +166,8 @@ namespace ts {
     export function forEachKey<T>(map: ReadonlyMap<{}>, callback: (key: string) => T | undefined): T | undefined;
     export function forEachKey<T>(map: ReadonlyUnderscoreEscapedMap<{}> | ReadonlyMap<{}>, callback: (key: string & __String) => T | undefined): T | undefined {
         const iterator = map.keys();
-        for (let { value: key, done } = iterator.next(); !done; { value: key, done } = iterator.next()) {
-            const result = callback(key as string & __String);
+        for (let iterResult = iterator.next(); !iterResult.done; iterResult = iterator.next()) {
+            const result = callback(iterResult.value as string & __String);
             if (result) {
                 return result;
             }
@@ -6078,6 +6078,10 @@ namespace ts {
         return node.kind === SyntaxKind.JSDocComment;
     }
 
+    export function isJSDocAuthorTag(node: Node): node is JSDocAuthorTag {
+        return node.kind === SyntaxKind.JSDocAuthorTag;
+    }
+
     export function isJSDocAugmentsTag(node: Node): node is JSDocAugmentsTag {
         return node.kind === SyntaxKind.JSDocAugmentsTag;
     }

src/harness/sourceMapRecorder.ts

@@ -301,7 +301,8 @@ namespace Harness.SourceMapRecorder {
 
             SourceMapSpanWriter.initializeSourceMapSpanWriter(sourceMapRecorder, sourceMapData.sourceMap, currentFile);
             const mapper = ts.decodeMappings(sourceMapData.sourceMap.mappings);
-            for (let { value: decodedSourceMapping, done } = mapper.next(); !done; { value: decodedSourceMapping, done } = mapper.next()) {
+            for (let iterResult = mapper.next(); !iterResult.done; iterResult = mapper.next()) {
+                const decodedSourceMapping = iterResult.value;
                 const currentSourceFile = ts.isSourceMapping(decodedSourceMapping)
                     ? program.getSourceFile(sourceMapData.inputSourceFileNames[decodedSourceMapping.sourceIndex])
                     : undefined;
@@ -335,7 +336,8 @@ namespace Harness.SourceMapRecorder {
 
             SourceMapSpanWriter.initializeSourceMapSpanWriter(sourceMapRecorder, sourceMap, currentFile);
             const mapper = ts.decodeMappings(sourceMap.mappings);
-            for (let { value: decodedSourceMapping, done } = mapper.next(); !done; { value: decodedSourceMapping, done } = mapper.next()) {
+            for (let iterResult = mapper.next(); !iterResult.done; iterResult = mapper.next()) {
+                const decodedSourceMapping = iterResult.value;
                 const currentSourceFile = ts.isSourceMapping(decodedSourceMapping)
                     ? getFile(sourceFileAbsolutePaths[decodedSourceMapping.sourceIndex])
                     : undefined;

src/harness/vfs.ts

@@ -682,7 +682,7 @@ namespace vfs {
 
             if (isDirectory(node)) throw createIOError("EISDIR");
             if (!isFile(node)) throw createIOError("EBADF");
-            node.buffer = Buffer.isBuffer(data) ? data.slice() : ts.sys.bufferFrom!("" + data, encoding || "utf8");
+            node.buffer = Buffer.isBuffer(data) ? data.slice() : ts.sys.bufferFrom!("" + data, encoding || "utf8") as Buffer;
             node.size = node.buffer.byteLength;
             node.mtimeMs = time;
             node.ctimeMs = time;
@@ -1203,7 +1203,7 @@ namespace vfs {
                 }
             },
             readFileSync(path: string): Buffer {
-                return ts.sys.bufferFrom!(host.readFile(path)!, "utf8"); // TODO: GH#18217
+                return ts.sys.bufferFrom!(host.readFile(path)!, "utf8") as Buffer; // TODO: GH#18217
             }
         };
     }

src/lib/es2015.generator.d.ts

@@ -1,4 +1,12 @@
-interface Generator extends Iterator<any> { }
+/// <reference lib="es2015.iterable" />
+
+interface Generator<T = unknown, TReturn = any, TNext = unknown> extends Iterator<T, TReturn, TNext> {
+    // NOTE: 'next' is defined using a tuple to ensure we report the correct assignability errors in all places.
+    next(...args: [] | [TNext]): IteratorResult<T, TReturn>;
+    return(value: TReturn): IteratorResult<T, TReturn>;
+    throw(e: any): IteratorResult<T, TReturn>;
+    [Symbol.iterator](): Generator<T, TReturn, TNext>;
+}
 
 interface GeneratorFunction {
     /**

src/lib/es2015.iterable.d.ts

@@ -8,15 +8,23 @@ interface SymbolConstructor {
     readonly iterator: symbol;
 }
 
-interface IteratorResult<T> {
-    done: boolean;
-    value: T;
+interface IteratorYieldResult<TYield> {
+    done?: false;
+    value: TYield;
 }
 
-interface Iterator<T> {
-    next(value?: any): IteratorResult<T>;
-    return?(value?: any): IteratorResult<T>;
-    throw?(e?: any): IteratorResult<T>;
+interface IteratorReturnResult<TReturn> {
+    done: true;
+    value: TReturn;
+}
+
+type IteratorResult<T, TReturn = any> = IteratorYieldResult<T> | IteratorReturnResult<TReturn>;
+
+interface Iterator<T, TReturn = any, TNext = undefined> {
+    // NOTE: 'next' is defined using a tuple to ensure we report the correct assignability errors in all places.
+    next(...args: [] | [TNext]): IteratorResult<T, TReturn>;
+    return?(value?: TReturn): IteratorResult<T, TReturn>;
+    throw?(e?: any): IteratorResult<T, TReturn>;
 }
 
 interface Iterable<T> {

src/lib/es2018.asyncgenerator.d.ts

@@ -0,0 +1,59 @@
+/// <reference lib="es2018.asynciterable" />
+
+interface AsyncGenerator<T = unknown, TReturn = any, TNext = unknown> extends AsyncIterator<T, TReturn, TNext> {
+    // NOTE: 'next' is defined using a tuple to ensure we report the correct assignability errors in all places.
+    next(...args: [] | [TNext | PromiseLike<TNext>]): Promise<IteratorResult<T, TReturn>>;
+    return(value: TReturn | PromiseLike<TReturn>): Promise<IteratorResult<T, TReturn>>;
+    throw(e: any): Promise<IteratorResult<T, TReturn>>;
+    [Symbol.asyncIterator](): AsyncGenerator<T, TReturn, TNext>;
+}
+
+interface AsyncGeneratorFunction {
+    /**
+     * Creates a new AsyncGenerator object.
+     * @param args A list of arguments the function accepts.
+     */
+    new (...args: any[]): AsyncGenerator;
+    /**
+     * Creates a new AsyncGenerator object.
+     * @param args A list of arguments the function accepts.
+     */
+    (...args: any[]): AsyncGenerator;
+    /**
+     * The length of the arguments.
+     */
+    readonly length: number;
+    /**
+     * Returns the name of the function.
+     */
+    readonly name: string;
+    /**
+     * A reference to the prototype.
+     */
+    readonly prototype: AsyncGenerator;
+}
+
+interface AsyncGeneratorFunctionConstructor {
+    /**
+     * Creates a new AsyncGenerator function.
+     * @param args A list of arguments the function accepts.
+     */
+    new (...args: string[]): AsyncGeneratorFunction;
+    /**
+     * Creates a new AsyncGenerator function.
+     * @param args A list of arguments the function accepts.
+     */
+    (...args: string[]): AsyncGeneratorFunction;
+    /**
+     * The length of the arguments.
+     */
+    readonly length: number;
+    /**
+     * Returns the name of the function.
+     */
+    readonly name: string;
+    /**
+     * A reference to the prototype.
+     */
+    readonly prototype: AsyncGeneratorFunction;
+}

src/lib/es2018.asynciterable.d.ts

@@ -9,10 +9,11 @@ interface SymbolConstructor {
     readonly asyncIterator: symbol;
 }
 
-interface AsyncIterator<T> {
-    next(value?: any): Promise<IteratorResult<T>>;
-    return?(value?: any): Promise<IteratorResult<T>>;
-    throw?(e?: any): Promise<IteratorResult<T>>;
+interface AsyncIterator<T, TReturn = any, TNext = undefined> {
+    // NOTE: 'next' is defined using a tuple to ensure we report the correct assignability errors in all places.
+    next(...args: [] | [TNext | PromiseLike<TNext>]): Promise<IteratorResult<T, TReturn>>;
+    return?(value?: TReturn | PromiseLike<TReturn>): Promise<IteratorResult<T, TReturn>>;
+    throw?(e?: any): Promise<IteratorResult<T, TReturn>>;
 }
 
 interface AsyncIterable<T> {

src/lib/es2018.d.ts

@@ -1,4 +1,5 @@
 /// <reference lib="es2017" />
+/// <reference lib="es2018.asyncgenerator" />
 /// <reference lib="es2018.asynciterable" />
 /// <reference lib="es2018.promise" />
 /// <reference lib="es2018.regexp" />

src/lib/libs.json

@@ -31,6 +31,7 @@
         "es2017.string",
         "es2017.intl",
         "es2017.typedarrays",
+        "es2018.asyncgenerator",
         "es2018.asynciterable",
         "es2018.regexp",
         "es2018.promise",

src/server/editorServices.ts

@@ -2831,8 +2831,9 @@ namespace ts.server {
             let assignOrphanScriptInfosToInferredProject = false;
             if (openFiles) {
                 while (true) {
-                    const { value: file, done } = openFiles.next();
-                    if (done) break;
+                    const iterResult = openFiles.next();
+                    if (iterResult.done) break;
+                    const file = iterResult.value;
                     const scriptInfo = this.getScriptInfo(file.fileName);
                     Debug.assert(!scriptInfo || !scriptInfo.isScriptOpen(), "Script should not exist and not be open already");
                     // Create script infos so we have the new content for all the open files before we do any updates to projects
@@ -2849,8 +2850,9 @@ namespace ts.server {
 
             if (changedFiles) {
                 while (true) {
-                    const { value: file, done } = changedFiles.next();
-                    if (done) break;
+                    const iterResult = changedFiles.next();
+                    if (iterResult.done) break;
+                    const file = iterResult.value;
                     const scriptInfo = this.getScriptInfo(file.fileName)!;
                     Debug.assert(!!scriptInfo);
                     // Make edits to script infos and marks containing project as dirty
@@ -2886,8 +2888,9 @@ namespace ts.server {
         /* @internal */
         applyChangesToFile(scriptInfo: ScriptInfo, changes: Iterator<TextChange>) {
             while (true) {
-                const { value: change, done } = changes.next();
-                if (done) break;
+                const iterResult = changes.next();
+                if (iterResult.done) break;
+                const change = iterResult.value;
                 scriptInfo.editContent(change.span.start, change.span.start + change.span.length, change.newText);
             }
         }

src/testRunner/parallel/host.ts

@@ -291,8 +291,8 @@ namespace Harness.Parallel.Host {
                     worker.accumulatedOutput += d.toString();
                     console.log(`[Worker ${i}]`, d.toString());
                 };
-                worker.process.stderr.on("data", appendOutput);
-                worker.process.stdout.on("data", appendOutput);
+                worker.process.stderr!.on("data", appendOutput);
+                worker.process.stdout!.on("data", appendOutput);
                 const killChild = (timeout: TaskTimeout) => {
                     worker.process.kill();
                     console.error(`Worker exceeded ${timeout.duration}ms timeout ${worker.currentTasks && worker.currentTasks.length ? `while running test '${worker.currentTasks[0].file}'.` : `during test setup.`}`);

src/testRunner/unittests/config/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', 'es2019', 'es2020', '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.asynciterable', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'es2019.array', 'es2019.object', 'es2019.string', 'es2019.symbol', 'es2020.string', 'es2020.symbol.wellknown', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable', 'esnext.intl', 'esnext.bigint'.",
+                        messageText: "Argument for '--lib' option must be: 'es5', 'es6', 'es2015', 'es7', 'es2016', 'es2017', 'es2018', 'es2019', 'es2020', '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.asyncgenerator', 'es2018.asynciterable', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'es2019.array', 'es2019.object', 'es2019.string', 'es2019.symbol', 'es2020.string', 'es2020.symbol.wellknown', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable', 'esnext.intl', 'esnext.bigint'.",
                         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', 'es2019', 'es2020', '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.asynciterable', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'es2019.array', 'es2019.object', 'es2019.string', 'es2019.symbol', 'es2020.string', 'es2020.symbol.wellknown', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable', 'esnext.intl', 'esnext.bigint'.",
+                        messageText: "Argument for '--lib' option must be: 'es5', 'es6', 'es2015', 'es7', 'es2016', 'es2017', 'es2018', 'es2019', 'es2020', '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.asyncgenerator', 'es2018.asynciterable', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'es2019.array', 'es2019.object', 'es2019.string', 'es2019.symbol', 'es2020.string', 'es2020.symbol.wellknown', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable', 'esnext.intl', 'esnext.bigint'.",
                         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', 'es2019', 'es2020', '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.asynciterable', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'es2019.array', 'es2019.object', 'es2019.string', 'es2019.symbol', 'es2020.string', 'es2020.symbol.wellknown', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable', 'esnext.intl', 'esnext.bigint'.",
+                        messageText: "Argument for '--lib' option must be: 'es5', 'es6', 'es2015', 'es7', 'es2016', 'es2017', 'es2018', 'es2019', 'es2020', '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.asyncgenerator', 'es2018.asynciterable', 'es2018.intl', 'es2018.promise', 'es2018.regexp', 'es2019.array', 'es2019.object', 'es2019.string', 'es2019.symbol', 'es2020.string', 'es2020.symbol.wellknown', 'esnext.array', 'esnext.symbol', 'esnext.asynciterable', 'esnext.intl', 'esnext.bigint'.",
                         category: Diagnostics.Argument_for_0_option_must_be_Colon_1.category,
                         code: Diagnostics.Argument_for_0_option_must_be_Colon_1.code,
                         file: undefined,

src/testRunner/unittests/config/showConfig.ts

@@ -133,7 +133,9 @@ namespace ts {
                     break;
                 }
                 default: {
-                    const val = option.type.keys().next().value;
+                    const iterResult = option.type.keys().next();
+                    if (iterResult.done) return Debug.fail("Expected 'option.type' to have entries");
+                    const val = iterResult.value;
                     if (option.isTSConfigOnly) {
                         args = ["-p", "tsconfig.json"];
                         configObject = { compilerOptions: { [option.name]: val } };

src/testRunner/unittests/jsDocParsing.ts

@@ -315,6 +315,11 @@ namespace ts {
  * {@link first link}
  * Inside {@link link text} thing
  * @see {@link second link text} and {@link Foo|a foo} as well.
+ */`);
+                parsesCorrectly("authorTag",
+`/**
+ * @author John Doe <john.doe@example.com>
+ * @author John Doe <john.doe@example.com> unexpected comment
  */`);
             });
         });

src/testRunner/unittests/shimMap.ts

@@ -68,12 +68,13 @@ namespace ts {
                 // Use an iterator.
                 const iterator = map.entries();
                 while (true) {
-                    const { value: tuple, done } = iterator.next();
-                    if (done) {
+                    const iterResult = iterator.next();
+                    if (iterResult.done) {
                         break;
                     }
 
-                    doForEach(tuple[1], tuple[0]);
+                    const [key, value] = iterResult.value;
+                    doForEach(value, key);
                 }
             }
 

src/testRunner/unittests/tsserver/helpers.ts

@@ -438,10 +438,13 @@ namespace ts.projectSystem {
     export function configuredProjectAt(projectService: server.ProjectService, index: number) {
         const values = projectService.configuredProjects.values();
         while (index > 0) {
-            values.next();
+            const iterResult = values.next();
+            if (iterResult.done) return Debug.fail("Expected a result.");
             index--;
         }
-        return values.next().value;
+        const iterResult = values.next();
+        if (iterResult.done) return Debug.fail("Expected a result.");
+        return iterResult.value;
     }
 
     export function checkProjectActualFiles(project: server.Project, expectedFiles: ReadonlyArray<string>) {

src/tsconfig-base.json

@@ -1,7 +1,7 @@
 {
     "compilerOptions": {
         "pretty": true,
-        "lib": ["es2015.iterable", "es5"],
+        "lib": ["es2015.iterable", "es2015.generator", "es5"],
         "target": "es5",
         "rootDir": ".",
 

tests/baselines/reference/FunctionDeclaration11_es6.types

@@ -1,4 +1,4 @@
 === tests/cases/conformance/es6/functionDeclarations/FunctionDeclaration11_es6.ts ===
 function * yield() {
->yield : () => IterableIterator<any>
+>yield : () => Generator<never, void, unknown>
 }

tests/baselines/reference/FunctionDeclaration13_es6.types

@@ -1,6 +1,6 @@
 === tests/cases/conformance/es6/functionDeclarations/FunctionDeclaration13_es6.ts ===
 function * foo() {
->foo : () => IterableIterator<any>
+>foo : () => Generator<never, void, unknown>
 
    // Legal to use 'yield' in a type context.
    var v: yield;

tests/baselines/reference/FunctionDeclaration1_es6.types

@@ -1,4 +1,4 @@
 === tests/cases/conformance/es6/functionDeclarations/FunctionDeclaration1_es6.ts ===
 function * foo() {
->foo : () => IterableIterator<any>
+>foo : () => Generator<never, void, unknown>
 }

tests/baselines/reference/FunctionDeclaration6_es6.types

@@ -1,6 +1,6 @@
 === tests/cases/conformance/es6/functionDeclarations/FunctionDeclaration6_es6.ts ===
 function*foo(a = yield) {
->foo : (a?: any) => IterableIterator<any>
+>foo : (a?: any) => Generator<never, void, unknown>
 >a : any
 >yield : any
 }

tests/baselines/reference/FunctionDeclaration7_es6.types

@@ -1,10 +1,10 @@
 === tests/cases/conformance/es6/functionDeclarations/FunctionDeclaration7_es6.ts ===
 function*bar() {
->bar : () => IterableIterator<any>
+>bar : () => Generator<never, void, unknown>
 
   // 'yield' here is an identifier, and not a yield expression.
   function*foo(a = yield) {
->foo : (a?: any) => IterableIterator<any>
+>foo : (a?: any) => Generator<never, void, unknown>
 >a : any
 >yield : any
   }

tests/baselines/reference/FunctionDeclaration9_es6.types

@@ -1,11 +1,11 @@
 === tests/cases/conformance/es6/functionDeclarations/FunctionDeclaration9_es6.ts ===
 function * foo() {
->foo : () => IterableIterator<any>
+>foo : () => Generator<any, void, unknown>
 
   var v = { [yield]: foo }
->v : { [x: number]: () => IterableIterator<any>; }
->{ [yield]: foo } : { [x: number]: () => IterableIterator<any>; }
->[yield] : () => IterableIterator<any>
+>v : { [x: number]: () => Generator<any, void, unknown>; }
+>{ [yield]: foo } : { [x: number]: () => Generator<any, void, unknown>; }
+>[yield] : () => Generator<any, void, unknown>
 >yield : any
->foo : () => IterableIterator<any>
+>foo : () => Generator<any, void, unknown>
 }

tests/baselines/reference/FunctionExpression1_es6.types

@@ -1,5 +1,5 @@
 === tests/cases/conformance/es6/functionExpressions/FunctionExpression1_es6.ts ===
 var v = function * () { }
->v : () => IterableIterator<any>
->function * () { } : () => IterableIterator<any>
+>v : () => Generator<never, void, unknown>
+>function * () { } : () => Generator<never, void, unknown>
 

tests/baselines/reference/FunctionExpression2_es6.types

@@ -1,6 +1,6 @@
 === tests/cases/conformance/es6/functionExpressions/FunctionExpression2_es6.ts ===
 var v = function * foo() { }
->v : () => IterableIterator<any>
->function * foo() { } : () => IterableIterator<any>
->foo : () => IterableIterator<any>
+>v : () => Generator<never, void, unknown>
+>function * foo() { } : () => Generator<never, void, unknown>
+>foo : () => Generator<never, void, unknown>
 

tests/baselines/reference/FunctionPropertyAssignments1_es6.types

@@ -1,6 +1,6 @@
 === tests/cases/conformance/es6/functionPropertyAssignments/FunctionPropertyAssignments1_es6.ts ===
 var v = { *foo() { } }
->v : { foo(): IterableIterator<any>; }
->{ *foo() { } } : { foo(): IterableIterator<any>; }
->foo : () => IterableIterator<any>
+>v : { foo(): Generator<never, void, unknown>; }
+>{ *foo() { } } : { foo(): Generator<never, void, unknown>; }
+>foo : () => Generator<never, void, unknown>
 

tests/baselines/reference/FunctionPropertyAssignments2_es6.types

@@ -1,6 +1,6 @@
 === tests/cases/conformance/es6/functionPropertyAssignments/FunctionPropertyAssignments2_es6.ts ===
 var v = { *() { } }
->v : { (Missing)(): IterableIterator<any>; }
->{ *() { } } : { (Missing)(): IterableIterator<any>; }
-> : () => IterableIterator<any>
+>v : { (Missing)(): Generator<never, void, unknown>; }
+>{ *() { } } : { (Missing)(): Generator<never, void, unknown>; }
+> : () => Generator<never, void, unknown>
 

tests/baselines/reference/FunctionPropertyAssignments3_es6.types

@@ -1,6 +1,6 @@
 === tests/cases/conformance/es6/functionPropertyAssignments/FunctionPropertyAssignments3_es6.ts ===
 var v = { *{ } }
->v : { (Missing)(): IterableIterator<any>; }
->{ *{ } } : { (Missing)(): IterableIterator<any>; }
-> : () => IterableIterator<any>
+>v : { (Missing)(): Generator<never, void, unknown>; }
+>{ *{ } } : { (Missing)(): Generator<never, void, unknown>; }
+> : () => Generator<never, void, unknown>
 

tests/baselines/reference/FunctionPropertyAssignments5_es6.types

@@ -1,8 +1,8 @@
 === tests/cases/conformance/es6/functionPropertyAssignments/FunctionPropertyAssignments5_es6.ts ===
 var v = { *[foo()]() { } }
->v : { [x: number]: () => IterableIterator<any>; }
->{ *[foo()]() { } } : { [x: number]: () => IterableIterator<any>; }
->[foo()] : () => IterableIterator<any>
+>v : { [x: number]: () => Generator<never, void, unknown>; }
+>{ *[foo()]() { } } : { [x: number]: () => Generator<never, void, unknown>; }
+>[foo()] : () => Generator<never, void, unknown>
 >foo() : any
 >foo : any
 

tests/baselines/reference/FunctionPropertyAssignments6_es6.types

@@ -1,6 +1,6 @@
 === tests/cases/conformance/es6/functionPropertyAssignments/FunctionPropertyAssignments6_es6.ts ===
 var v = { *<T>() { } }
->v : { (Missing)<T>(): IterableIterator<any>; }
->{ *<T>() { } } : { (Missing)<T>(): IterableIterator<any>; }
-> : <T>() => IterableIterator<any>
+>v : { (Missing)<T>(): Generator<never, void, unknown>; }
+>{ *<T>() { } } : { (Missing)<T>(): Generator<never, void, unknown>; }
+> : <T>() => Generator<never, void, unknown>
 

tests/baselines/reference/JSDocParsing/DocComments.parsesCorrectly.authorTag.json

@@ -0,0 +1,44 @@
+{
+    "kind": "JSDocComment",
+    "pos": 0,
+    "end": 112,
+    "modifierFlagsCache": 0,
+    "transformFlags": 0,
+    "tags": {
+        "0": {
+            "kind": "JSDocAuthorTag",
+            "pos": 7,
+            "end": 50,
+            "modifierFlagsCache": 0,
+            "transformFlags": 0,
+            "tagName": {
+                "kind": "Identifier",
+                "pos": 8,
+                "end": 14,
+                "modifierFlagsCache": 0,
+                "transformFlags": 0,
+                "escapedText": "author"
+            },
+            "comment": "John Doe <john.doe@example.com>"
+        },
+        "1": {
+            "kind": "JSDocAuthorTag",
+            "pos": 50,
+            "end": 110,
+            "modifierFlagsCache": 0,
+            "transformFlags": 0,
+            "tagName": {
+                "kind": "Identifier",
+                "pos": 51,
+                "end": 57,
+                "modifierFlagsCache": 0,
+                "transformFlags": 0,
+                "escapedText": "author"
+            },
+            "comment": "John Doe <john.doe@example.com> unexpected comment"
+        },
+        "length": 2,
+        "pos": 7,
+        "end": 110
+    }
+}

tests/baselines/reference/MemberFunctionDeclaration1_es6.types

@@ -3,5 +3,5 @@ class C {
 >C : C
 
    *foo() { }
->foo : () => IterableIterator<any>
+>foo : () => Generator<never, void, unknown>
 }

tests/baselines/reference/MemberFunctionDeclaration2_es6.types

@@ -3,5 +3,5 @@ class C {
 >C : C
 
    public * foo() { }
->foo : () => IterableIterator<any>
+>foo : () => Generator<never, void, unknown>
 }

tests/baselines/reference/MemberFunctionDeclaration3_es6.types

@@ -3,6 +3,6 @@ class C {
 >C : C
 
    *[foo]() { }
->[foo] : () => IterableIterator<any>
+>[foo] : () => Generator<never, void, unknown>
 >foo : any
 }

tests/baselines/reference/MemberFunctionDeclaration4_es6.types

@@ -3,5 +3,5 @@ class C {
 >C : C
 
    *() { }
-> : () => IterableIterator<any>
+> : () => Generator<never, void, unknown>
 }

tests/baselines/reference/MemberFunctionDeclaration7_es6.types

@@ -3,5 +3,5 @@ class C {
 >C : C
 
    *foo<T>() { }
->foo : <T>() => IterableIterator<any>
+>foo : <T>() => Generator<never, void, unknown>
 }

tests/baselines/reference/YieldExpression10_es6.types

@@ -1,8 +1,8 @@
 === tests/cases/conformance/es6/yieldExpressions/YieldExpression10_es6.ts ===
 var v = { * foo() {
->v : { foo(): IterableIterator<any>; }
->{ * foo() {    yield(foo);  }} : { foo(): IterableIterator<any>; }
->foo : () => IterableIterator<any>
+>v : { foo(): Generator<any, void, unknown>; }
+>{ * foo() {    yield(foo);  }} : { foo(): Generator<any, void, unknown>; }
+>foo : () => Generator<any, void, unknown>
 
     yield(foo);
 >yield(foo) : any

tests/baselines/reference/YieldExpression11_es6.types

@@ -3,7 +3,7 @@ class C {
 >C : C
 
   *foo() {
->foo : () => IterableIterator<any>
+>foo : () => Generator<any, void, unknown>
 
     yield(foo);
 >yield(foo) : any

tests/baselines/reference/YieldExpression13_es6.types

@@ -1,5 +1,5 @@
 === tests/cases/conformance/es6/yieldExpressions/YieldExpression13_es6.ts ===
 function* foo() { yield }
->foo : () => IterableIterator<any>
+>foo : () => Generator<any, void, unknown>
 >yield : any
 

tests/baselines/reference/YieldExpression16_es6.types

@@ -1,12 +1,12 @@
 === tests/cases/conformance/es6/yieldExpressions/YieldExpression16_es6.ts ===
 function* foo() {
->foo : () => IterableIterator<any>
+>foo : () => Generator<never, void, unknown>
 
   function bar() {
 >bar : () => void
 
     yield foo;
 >yield foo : any
->foo : () => IterableIterator<any>
+>foo : () => Generator<never, void, unknown>
   }
 }

tests/baselines/reference/YieldExpression19_es6.types

@@ -1,17 +1,17 @@
 === tests/cases/conformance/es6/yieldExpressions/YieldExpression19_es6.ts ===
 function*foo() {
->foo : () => IterableIterator<any>
+>foo : () => Generator<never, void, unknown>
 
   function bar() {
 >bar : () => void
 
     function* quux() {
->quux : () => IterableIterator<() => IterableIterator<any>>
+>quux : () => Generator<() => Generator<never, void, unknown>, void, unknown>
 
       yield(foo);
 >yield(foo) : any
->(foo) : () => IterableIterator<any>
->foo : () => IterableIterator<any>
+>(foo) : () => Generator<never, void, unknown>
+>foo : () => Generator<never, void, unknown>
     }
   }
 }

tests/baselines/reference/YieldExpression3_es6.types

@@ -1,6 +1,6 @@
 === tests/cases/conformance/es6/yieldExpressions/YieldExpression3_es6.ts ===
 function* foo() {
->foo : () => IterableIterator<any>
+>foo : () => Generator<any, void, unknown>
 
   yield
 >yield : any

tests/baselines/reference/YieldExpression4_es6.types

@@ -1,6 +1,6 @@
 === tests/cases/conformance/es6/yieldExpressions/YieldExpression4_es6.ts ===
 function* foo() {
->foo : () => IterableIterator<any>
+>foo : () => Generator<any, void, unknown>
 
   yield;
 >yield : any

tests/baselines/reference/YieldExpression5_es6.types

@@ -1,6 +1,6 @@
 === tests/cases/conformance/es6/yieldExpressions/YieldExpression5_es6.ts ===
 function* foo() {
->foo : () => IterableIterator<any>
+>foo : () => Generator<any, void, any>
 
   yield*
 >yield* : any

tests/baselines/reference/YieldExpression7_es6.types

@@ -1,8 +1,8 @@
 === tests/cases/conformance/es6/yieldExpressions/YieldExpression7_es6.ts ===
 function* foo() {
->foo : () => IterableIterator<typeof foo>
+>foo : () => Generator<typeof foo, void, unknown>
 
   yield foo
 >yield foo : any
->foo : () => IterableIterator<typeof foo>
+>foo : () => Generator<typeof foo, void, unknown>
 }

tests/baselines/reference/YieldExpression8_es6.types

@@ -2,13 +2,13 @@
 yield(foo);
 >yield(foo) : any
 >yield : any
->foo : () => IterableIterator<typeof foo>
+>foo : () => Generator<typeof foo, void, unknown>
 
 function* foo() {
->foo : () => IterableIterator<typeof foo>
+>foo : () => Generator<typeof foo, void, unknown>
 
   yield(foo);
 >yield(foo) : any
->(foo) : () => IterableIterator<typeof foo>
->foo : () => IterableIterator<typeof foo>
+>(foo) : () => Generator<typeof foo, void, unknown>
+>foo : () => Generator<typeof foo, void, unknown>
 }

tests/baselines/reference/YieldExpression9_es6.types

@@ -1,7 +1,7 @@
 === tests/cases/conformance/es6/yieldExpressions/YieldExpression9_es6.ts ===
 var v = function*() {
->v : () => IterableIterator<any>
->function*() {  yield(foo);} : () => IterableIterator<any>
+>v : () => Generator<any, void, unknown>
+>function*() {  yield(foo);} : () => Generator<any, void, unknown>
 
   yield(foo);
 >yield(foo) : any

tests/baselines/reference/YieldStarExpression3_es6.types

@@ -1,6 +1,6 @@
 === tests/cases/conformance/es6/yieldExpressions/YieldStarExpression3_es6.ts ===
 function *g() {
->g : () => IterableIterator<any>
+>g : () => Generator<any, void, any>
 
     yield *;
 >yield * : any

tests/baselines/reference/YieldStarExpression4_es6.types

@@ -1,6 +1,6 @@
 === tests/cases/conformance/es6/yieldExpressions/YieldStarExpression4_es6.ts ===
 function *g() {
->g : () => IterableIterator<any>
+>g : () => Generator<any, void, undefined>
 
     yield * [];
 >yield * [] : any

tests/baselines/reference/api/tsserverlibrary.d.ts

@@ -53,7 +53,7 @@ declare namespace ts {
     interface Iterator<T> {
         next(): {
             value: T;
-            done: false;
+            done?: false;
         } | {
             value: never;
             done: true;
@@ -72,7 +72,7 @@ declare namespace ts {
         pos: number;
         end: number;
     }
-    type JSDocSyntaxKind = SyntaxKind.EndOfFileToken | SyntaxKind.WhitespaceTrivia | SyntaxKind.AtToken | SyntaxKind.NewLineTrivia | SyntaxKind.AsteriskToken | SyntaxKind.OpenBraceToken | SyntaxKind.CloseBraceToken | SyntaxKind.LessThanToken | SyntaxKind.OpenBracketToken | SyntaxKind.CloseBracketToken | SyntaxKind.EqualsToken | SyntaxKind.CommaToken | SyntaxKind.DotToken | SyntaxKind.Identifier | SyntaxKind.BacktickToken | SyntaxKind.Unknown | KeywordSyntaxKind;
+    type JSDocSyntaxKind = SyntaxKind.EndOfFileToken | SyntaxKind.WhitespaceTrivia | SyntaxKind.AtToken | SyntaxKind.NewLineTrivia | SyntaxKind.AsteriskToken | SyntaxKind.OpenBraceToken | SyntaxKind.CloseBraceToken | SyntaxKind.LessThanToken | SyntaxKind.GreaterThanToken | SyntaxKind.OpenBracketToken | SyntaxKind.CloseBracketToken | SyntaxKind.EqualsToken | SyntaxKind.CommaToken | SyntaxKind.DotToken | SyntaxKind.Identifier | SyntaxKind.BacktickToken | SyntaxKind.Unknown | KeywordSyntaxKind;
     type KeywordSyntaxKind = SyntaxKind.AbstractKeyword | SyntaxKind.AnyKeyword | SyntaxKind.AsKeyword | SyntaxKind.BigIntKeyword | SyntaxKind.BooleanKeyword | SyntaxKind.BreakKeyword | SyntaxKind.CaseKeyword | SyntaxKind.CatchKeyword | SyntaxKind.ClassKeyword | SyntaxKind.ContinueKeyword | SyntaxKind.ConstKeyword | SyntaxKind.ConstructorKeyword | SyntaxKind.DebuggerKeyword | SyntaxKind.DeclareKeyword | SyntaxKind.DefaultKeyword | SyntaxKind.DeleteKeyword | SyntaxKind.DoKeyword | SyntaxKind.ElseKeyword | SyntaxKind.EnumKeyword | SyntaxKind.ExportKeyword | SyntaxKind.ExtendsKeyword | SyntaxKind.FalseKeyword | SyntaxKind.FinallyKeyword | SyntaxKind.ForKeyword | SyntaxKind.FromKeyword | SyntaxKind.FunctionKeyword | SyntaxKind.GetKeyword | SyntaxKind.IfKeyword | SyntaxKind.ImplementsKeyword | SyntaxKind.ImportKeyword | SyntaxKind.InKeyword | SyntaxKind.InferKeyword | SyntaxKind.InstanceOfKeyword | SyntaxKind.InterfaceKeyword | SyntaxKind.IsKeyword | SyntaxKind.KeyOfKeyword | SyntaxKind.LetKeyword | SyntaxKind.ModuleKeyword | SyntaxKind.NamespaceKeyword | SyntaxKind.NeverKeyword | SyntaxKind.NewKeyword | SyntaxKind.NullKeyword | SyntaxKind.NumberKeyword | SyntaxKind.ObjectKeyword | SyntaxKind.PackageKeyword | SyntaxKind.PrivateKeyword | SyntaxKind.ProtectedKeyword | SyntaxKind.PublicKeyword | SyntaxKind.ReadonlyKeyword | SyntaxKind.RequireKeyword | SyntaxKind.GlobalKeyword | SyntaxKind.ReturnKeyword | SyntaxKind.SetKeyword | SyntaxKind.StaticKeyword | SyntaxKind.StringKeyword | SyntaxKind.SuperKeyword | SyntaxKind.SwitchKeyword | SyntaxKind.SymbolKeyword | SyntaxKind.ThisKeyword | SyntaxKind.ThrowKeyword | SyntaxKind.TrueKeyword | SyntaxKind.TryKeyword | SyntaxKind.TypeKeyword | SyntaxKind.TypeOfKeyword | SyntaxKind.UndefinedKeyword | SyntaxKind.UniqueKeyword | SyntaxKind.UnknownKeyword | SyntaxKind.VarKeyword | SyntaxKind.VoidKeyword | SyntaxKind.WhileKeyword | SyntaxKind.WithKeyword | SyntaxKind.YieldKeyword | SyntaxKind.AsyncKeyword | SyntaxKind.AwaitKeyword | SyntaxKind.OfKeyword;
     type JsxTokenSyntaxKind = SyntaxKind.LessThanSlashToken | SyntaxKind.EndOfFileToken | SyntaxKind.ConflictMarkerTrivia | SyntaxKind.JsxText | SyntaxKind.JsxTextAllWhiteSpaces | SyntaxKind.OpenBraceToken | SyntaxKind.LessThanToken;
     enum SyntaxKind {
@@ -379,23 +379,24 @@ declare namespace ts {
         JSDocSignature = 299,
         JSDocTag = 300,
         JSDocAugmentsTag = 301,
-        JSDocClassTag = 302,
-        JSDocCallbackTag = 303,
-        JSDocEnumTag = 304,
-        JSDocParameterTag = 305,
-        JSDocReturnTag = 306,
-        JSDocThisTag = 307,
-        JSDocTypeTag = 308,
-        JSDocTemplateTag = 309,
-        JSDocTypedefTag = 310,
-        JSDocPropertyTag = 311,
-        SyntaxList = 312,
-        NotEmittedStatement = 313,
-        PartiallyEmittedExpression = 314,
-        CommaListExpression = 315,
-        MergeDeclarationMarker = 316,
-        EndOfDeclarationMarker = 317,
-        Count = 318,
+        JSDocAuthorTag = 302,
+        JSDocClassTag = 303,
+        JSDocCallbackTag = 304,
+        JSDocEnumTag = 305,
+        JSDocParameterTag = 306,
+        JSDocReturnTag = 307,
+        JSDocThisTag = 308,
+        JSDocTypeTag = 309,
+        JSDocTemplateTag = 310,
+        JSDocTypedefTag = 311,
+        JSDocPropertyTag = 312,
+        SyntaxList = 313,
+        NotEmittedStatement = 314,
+        PartiallyEmittedExpression = 315,
+        CommaListExpression = 316,
+        MergeDeclarationMarker = 317,
+        EndOfDeclarationMarker = 318,
+        Count = 319,
         FirstAssignment = 60,
         LastAssignment = 72,
         FirstCompoundAssignment = 61,
@@ -422,9 +423,9 @@ declare namespace ts {
         LastBinaryOperator = 72,
         FirstNode = 149,
         FirstJSDocNode = 289,
-        LastJSDocNode = 311,
+        LastJSDocNode = 312,
         FirstJSDocTagNode = 300,
-        LastJSDocTagNode = 311,
+        LastJSDocTagNode = 312,
     }
     enum NodeFlags {
         None = 0,
@@ -1581,6 +1582,9 @@ declare namespace ts {
             expression: Identifier | PropertyAccessEntityNameExpression;
         };
     }
+    interface JSDocAuthorTag extends JSDocTag {
+        kind: SyntaxKind.JSDocAuthorTag;
+    }
     interface JSDocClassTag extends JSDocTag {
         kind: SyntaxKind.JSDocClassTag;
     }
@@ -3532,6 +3536,7 @@ declare namespace ts {
     function isJSDocFunctionType(node: Node): node is JSDocFunctionType;
     function isJSDocVariadicType(node: Node): node is JSDocVariadicType;
     function isJSDoc(node: Node): node is JSDoc;
+    function isJSDocAuthorTag(node: Node): node is JSDocAuthorTag;
     function isJSDocAugmentsTag(node: Node): node is JSDocAugmentsTag;
     function isJSDocClassTag(node: Node): node is JSDocClassTag;
     function isJSDocEnumTag(node: Node): node is JSDocEnumTag;

tests/baselines/reference/api/typescript.d.ts

@@ -53,7 +53,7 @@ declare namespace ts {
     interface Iterator<T> {
         next(): {
             value: T;
-            done: false;
+            done?: false;
         } | {
             value: never;
             done: true;
@@ -72,7 +72,7 @@ declare namespace ts {
         pos: number;
         end: number;
     }
-    type JSDocSyntaxKind = SyntaxKind.EndOfFileToken | SyntaxKind.WhitespaceTrivia | SyntaxKind.AtToken | SyntaxKind.NewLineTrivia | SyntaxKind.AsteriskToken | SyntaxKind.OpenBraceToken | SyntaxKind.CloseBraceToken | SyntaxKind.LessThanToken | SyntaxKind.OpenBracketToken | SyntaxKind.CloseBracketToken | SyntaxKind.EqualsToken | SyntaxKind.CommaToken | SyntaxKind.DotToken | SyntaxKind.Identifier | SyntaxKind.BacktickToken | SyntaxKind.Unknown | KeywordSyntaxKind;
+    type JSDocSyntaxKind = SyntaxKind.EndOfFileToken | SyntaxKind.WhitespaceTrivia | SyntaxKind.AtToken | SyntaxKind.NewLineTrivia | SyntaxKind.AsteriskToken | SyntaxKind.OpenBraceToken | SyntaxKind.CloseBraceToken | SyntaxKind.LessThanToken | SyntaxKind.GreaterThanToken | SyntaxKind.OpenBracketToken | SyntaxKind.CloseBracketToken | SyntaxKind.EqualsToken | SyntaxKind.CommaToken | SyntaxKind.DotToken | SyntaxKind.Identifier | SyntaxKind.BacktickToken | SyntaxKind.Unknown | KeywordSyntaxKind;
     type KeywordSyntaxKind = SyntaxKind.AbstractKeyword | SyntaxKind.AnyKeyword | SyntaxKind.AsKeyword | SyntaxKind.BigIntKeyword | SyntaxKind.BooleanKeyword | SyntaxKind.BreakKeyword | SyntaxKind.CaseKeyword | SyntaxKind.CatchKeyword | SyntaxKind.ClassKeyword | SyntaxKind.ContinueKeyword | SyntaxKind.ConstKeyword | SyntaxKind.ConstructorKeyword | SyntaxKind.DebuggerKeyword | SyntaxKind.DeclareKeyword | SyntaxKind.DefaultKeyword | SyntaxKind.DeleteKeyword | SyntaxKind.DoKeyword | SyntaxKind.ElseKeyword | SyntaxKind.EnumKeyword | SyntaxKind.ExportKeyword | SyntaxKind.ExtendsKeyword | SyntaxKind.FalseKeyword | SyntaxKind.FinallyKeyword | SyntaxKind.ForKeyword | SyntaxKind.FromKeyword | SyntaxKind.FunctionKeyword | SyntaxKind.GetKeyword | SyntaxKind.IfKeyword | SyntaxKind.ImplementsKeyword | SyntaxKind.ImportKeyword | SyntaxKind.InKeyword | SyntaxKind.InferKeyword | SyntaxKind.InstanceOfKeyword | SyntaxKind.InterfaceKeyword | SyntaxKind.IsKeyword | SyntaxKind.KeyOfKeyword | SyntaxKind.LetKeyword | SyntaxKind.ModuleKeyword | SyntaxKind.NamespaceKeyword | SyntaxKind.NeverKeyword | SyntaxKind.NewKeyword | SyntaxKind.NullKeyword | SyntaxKind.NumberKeyword | SyntaxKind.ObjectKeyword | SyntaxKind.PackageKeyword | SyntaxKind.PrivateKeyword | SyntaxKind.ProtectedKeyword | SyntaxKind.PublicKeyword | SyntaxKind.ReadonlyKeyword | SyntaxKind.RequireKeyword | SyntaxKind.GlobalKeyword | SyntaxKind.ReturnKeyword | SyntaxKind.SetKeyword | SyntaxKind.StaticKeyword | SyntaxKind.StringKeyword | SyntaxKind.SuperKeyword | SyntaxKind.SwitchKeyword | SyntaxKind.SymbolKeyword | SyntaxKind.ThisKeyword | SyntaxKind.ThrowKeyword | SyntaxKind.TrueKeyword | SyntaxKind.TryKeyword | SyntaxKind.TypeKeyword | SyntaxKind.TypeOfKeyword | SyntaxKind.UndefinedKeyword | SyntaxKind.UniqueKeyword | SyntaxKind.UnknownKeyword | SyntaxKind.VarKeyword | SyntaxKind.VoidKeyword | SyntaxKind.WhileKeyword | SyntaxKind.WithKeyword | SyntaxKind.YieldKeyword | SyntaxKind.AsyncKeyword | SyntaxKind.AwaitKeyword | SyntaxKind.OfKeyword;
     type JsxTokenSyntaxKind = SyntaxKind.LessThanSlashToken | SyntaxKind.EndOfFileToken | SyntaxKind.ConflictMarkerTrivia | SyntaxKind.JsxText | SyntaxKind.JsxTextAllWhiteSpaces | SyntaxKind.OpenBraceToken | SyntaxKind.LessThanToken;
     enum SyntaxKind {
@@ -379,23 +379,24 @@ declare namespace ts {
         JSDocSignature = 299,
         JSDocTag = 300,
         JSDocAugmentsTag = 301,
-        JSDocClassTag = 302,
-        JSDocCallbackTag = 303,
-        JSDocEnumTag = 304,
-        JSDocParameterTag = 305,
-        JSDocReturnTag = 306,
-        JSDocThisTag = 307,
-        JSDocTypeTag = 308,
-        JSDocTemplateTag = 309,
-        JSDocTypedefTag = 310,
-        JSDocPropertyTag = 311,
-        SyntaxList = 312,
-        NotEmittedStatement = 313,
-        PartiallyEmittedExpression = 314,
-        CommaListExpression = 315,
-        MergeDeclarationMarker = 316,
-        EndOfDeclarationMarker = 317,
-        Count = 318,
+        JSDocAuthorTag = 302,
+        JSDocClassTag = 303,
+        JSDocCallbackTag = 304,
+        JSDocEnumTag = 305,
+        JSDocParameterTag = 306,
+        JSDocReturnTag = 307,
+        JSDocThisTag = 308,
+        JSDocTypeTag = 309,
+        JSDocTemplateTag = 310,
+        JSDocTypedefTag = 311,
+        JSDocPropertyTag = 312,
+        SyntaxList = 313,
+        NotEmittedStatement = 314,
+        PartiallyEmittedExpression = 315,
+        CommaListExpression = 316,
+        MergeDeclarationMarker = 317,
+        EndOfDeclarationMarker = 318,
+        Count = 319,
         FirstAssignment = 60,
         LastAssignment = 72,
         FirstCompoundAssignment = 61,
@@ -422,9 +423,9 @@ declare namespace ts {
         LastBinaryOperator = 72,
         FirstNode = 149,
         FirstJSDocNode = 289,
-        LastJSDocNode = 311,
+        LastJSDocNode = 312,
         FirstJSDocTagNode = 300,
-        LastJSDocTagNode = 311,
+        LastJSDocTagNode = 312,
     }
     enum NodeFlags {
         None = 0,
@@ -1581,6 +1582,9 @@ declare namespace ts {
             expression: Identifier | PropertyAccessEntityNameExpression;
         };
     }
+    interface JSDocAuthorTag extends JSDocTag {
+        kind: SyntaxKind.JSDocAuthorTag;
+    }
     interface JSDocClassTag extends JSDocTag {
         kind: SyntaxKind.JSDocClassTag;
     }
@@ -3532,6 +3536,7 @@ declare namespace ts {
     function isJSDocFunctionType(node: Node): node is JSDocFunctionType;
     function isJSDocVariadicType(node: Node): node is JSDocVariadicType;
     function isJSDoc(node: Node): node is JSDoc;
+    function isJSDocAuthorTag(node: Node): node is JSDocAuthorTag;
     function isJSDocAugmentsTag(node: Node): node is JSDocAugmentsTag;
     function isJSDocClassTag(node: Node): node is JSDocClassTag;
     function isJSDocEnumTag(node: Node): node is JSDocEnumTag;

tests/baselines/reference/asyncImportNestedYield.types

@@ -1,6 +1,6 @@
 === tests/cases/compiler/asyncImportNestedYield.ts ===
 async function* foo() {
->foo : () => AsyncIterableIterator<string>
+>foo : () => AsyncGenerator<string, void, string>
 
     import((await import(yield "foo")).default);
 >import((await import(yield "foo")).default) : Promise<any>

tests/baselines/reference/asyncMethodWithSuper_es6.types

@@ -336,7 +336,7 @@ class B extends A {
     }
 
     async * property_access_only_read_only_in_generator() {
->property_access_only_read_only_in_generator : () => AsyncIterableIterator<any>
+>property_access_only_read_only_in_generator : () => AsyncGenerator<never, void, unknown>
 
         // call with property access
         super.x();
@@ -372,7 +372,7 @@ class B extends A {
     }
 
     async * property_access_only_write_only_in_generator() {
->property_access_only_write_only_in_generator : () => AsyncIterableIterator<any>
+>property_access_only_write_only_in_generator : () => AsyncGenerator<never, void, unknown>
 
         const f = () => {};
 >f : () => void
@@ -420,7 +420,7 @@ class B extends A {
     }
 
     async * element_access_only_read_only_in_generator() {
->element_access_only_read_only_in_generator : () => AsyncIterableIterator<any>
+>element_access_only_read_only_in_generator : () => AsyncGenerator<never, void, unknown>
 
         // call with element access
         super["x"]();
@@ -456,7 +456,7 @@ class B extends A {
     }
 
     async * element_access_only_write_only_in_generator() {
->element_access_only_write_only_in_generator : () => AsyncIterableIterator<any>
+>element_access_only_write_only_in_generator : () => AsyncGenerator<never, void, unknown>
 
         const f = () => {};
 >f : () => void

tests/baselines/reference/awaitInNonAsyncFunction.types

@@ -57,7 +57,7 @@ const arrowFunc = (p: Promise<number>) => {
 };
 
 function* generatorFunc(p: Promise<number>) {
->generatorFunc : (p: Promise<number>) => IterableIterator<number>
+>generatorFunc : (p: Promise<number>) => Generator<number, void, unknown>
 >p : Promise<number>
 
   for await (const _ of []);

tests/baselines/reference/blockScopedBindingsInDownlevelGenerator.types

@@ -1,6 +1,6 @@
 === tests/cases/compiler/blockScopedBindingsInDownlevelGenerator.ts ===
 function* a() {
->a : () => IterableIterator<number>
+>a : () => Generator<number, void, unknown>
 
   for (const i of [1,2,3]) {
 >i : number

tests/baselines/reference/capturedParametersInInitializers1.types

@@ -82,11 +82,11 @@ function foo6(y = () => (() => z)(), z = 1) {
 
 // ok - used inside immediately invoked generator function
 function foo7(y = (function*() {yield z})(), z = 1) {
->foo7 : (y?: IterableIterator<number>, z?: number) => void
->y : IterableIterator<number>
->(function*() {yield z})() : IterableIterator<number>
->(function*() {yield z}) : () => IterableIterator<number>
->function*() {yield z} : () => IterableIterator<number>
+>foo7 : (y?: Generator<number, void, unknown>, z?: number) => void
+>y : Generator<number, void, unknown>
+>(function*() {yield z})() : Generator<number, void, unknown>
+>(function*() {yield z}) : () => Generator<number, void, unknown>
+>function*() {yield z} : () => Generator<number, void, unknown>
 >yield z : any
 >z : number
 >z : number

tests/baselines/reference/castOfYield.errors.txt

@@ -1,8 +1,8 @@
-error TS2318: Cannot find global type 'IterableIterator'.
+error TS2318: Cannot find global type 'Generator'.
 tests/cases/compiler/castOfYield.ts(4,14): error TS1109: Expression expected.
 
 
-!!! error TS2318: Cannot find global type 'IterableIterator'.
+!!! error TS2318: Cannot find global type 'Generator'.
 ==== tests/cases/compiler/castOfYield.ts (1 errors) ====
     function* f() {
         <number> (yield 0);

tests/baselines/reference/conditionalTypeRelaxingConstraintAssignability.js

@@ -21,7 +21,21 @@ export class Elem<
 new Elem(undefined as ElChildren.Void);
 new Elem('' as ElChildren.Text);
 new Elem('' as ElChildren.Void | ElChildren.Text); // error
-new Elem('' as ElChildren); // error
+new Elem('' as ElChildren); // error
+
+// Repro from #31766
+
+interface I { a: string }
+
+type DeepPartial<T> =
+    T extends object ? {[K in keyof T]?: DeepPartial<T[K]>} : T;
+
+declare function f<T>(t: T, partial: DeepPartial<T>): T;
+
+function g(p1: I, p2: Partial<I>): I {
+  return f(p1, p2);
+}
+
 
 //// [conditionalTypeRelaxingConstraintAssignability.js]
 "use strict";
@@ -37,3 +51,6 @@ new Elem(undefined);
 new Elem('');
 new Elem(''); // error
 new Elem(''); // error
+function g(p1, p2) {
+    return f(p1, p2);
+}

tests/baselines/reference/conditionalTypeRelaxingConstraintAssignability.symbols

@@ -71,3 +71,47 @@ new Elem('' as ElChildren); // error
 >Elem : Symbol(Elem, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 8, 83))
 >ElChildren : Symbol(ElChildren, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 0, 0), Decl(conditionalTypeRelaxingConstraintAssignability.ts, 2, 20))
 
+// Repro from #31766
+
+interface I { a: string }
+>I : Symbol(I, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 22, 27))
+>a : Symbol(I.a, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 26, 13))
+
+type DeepPartial<T> =
+>DeepPartial : Symbol(DeepPartial, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 26, 25))
+>T : Symbol(T, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 28, 17))
+
+    T extends object ? {[K in keyof T]?: DeepPartial<T[K]>} : T;
+>T : Symbol(T, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 28, 17))
+>K : Symbol(K, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 29, 25))
+>T : Symbol(T, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 28, 17))
+>DeepPartial : Symbol(DeepPartial, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 26, 25))
+>T : Symbol(T, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 28, 17))
+>K : Symbol(K, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 29, 25))
+>T : Symbol(T, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 28, 17))
+
+declare function f<T>(t: T, partial: DeepPartial<T>): T;
+>f : Symbol(f, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 29, 64))
+>T : Symbol(T, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 31, 19))
+>t : Symbol(t, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 31, 22))
+>T : Symbol(T, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 31, 19))
+>partial : Symbol(partial, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 31, 27))
+>DeepPartial : Symbol(DeepPartial, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 26, 25))
+>T : Symbol(T, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 31, 19))
+>T : Symbol(T, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 31, 19))
+
+function g(p1: I, p2: Partial<I>): I {
+>g : Symbol(g, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 31, 56))
+>p1 : Symbol(p1, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 33, 11))
+>I : Symbol(I, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 22, 27))
+>p2 : Symbol(p2, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 33, 17))
+>Partial : Symbol(Partial, Decl(lib.es5.d.ts, --, --))
+>I : Symbol(I, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 22, 27))
+>I : Symbol(I, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 22, 27))
+
+  return f(p1, p2);
+>f : Symbol(f, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 29, 64))
+>p1 : Symbol(p1, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 33, 11))
+>p2 : Symbol(p2, Decl(conditionalTypeRelaxingConstraintAssignability.ts, 33, 17))
+}
+

tests/baselines/reference/conditionalTypeRelaxingConstraintAssignability.types

@@ -62,3 +62,30 @@ new Elem('' as ElChildren); // error
 >'' as ElChildren : ElChildren
 >'' : ""
 
+// Repro from #31766
+
+interface I { a: string }
+>a : string
+
+type DeepPartial<T> =
+>DeepPartial : DeepPartial<T>
+
+    T extends object ? {[K in keyof T]?: DeepPartial<T[K]>} : T;
+
+declare function f<T>(t: T, partial: DeepPartial<T>): T;
+>f : <T>(t: T, partial: DeepPartial<T>) => T
+>t : T
+>partial : DeepPartial<T>
+
+function g(p1: I, p2: Partial<I>): I {
+>g : (p1: I, p2: Partial<I>) => I
+>p1 : I
+>p2 : Partial<I>
+
+  return f(p1, p2);
+>f(p1, p2) : I
+>f : <T>(t: T, partial: DeepPartial<T>) => T
+>p1 : I
+>p2 : Partial<I>
+}
+

tests/baselines/reference/controlFlowIIFE.types

@@ -181,9 +181,9 @@ function f5() {
 >v : number
 
     (function*() {
->(function*() {        yield 1;        v = 1;    })() : IterableIterator<number>
->(function*() {        yield 1;        v = 1;    }) : () => IterableIterator<number>
->function*() {        yield 1;        v = 1;    } : () => IterableIterator<number>
+>(function*() {        yield 1;        v = 1;    })() : Generator<number, void, unknown>
+>(function*() {        yield 1;        v = 1;    }) : () => Generator<number, void, unknown>
+>function*() {        yield 1;        v = 1;    } : () => Generator<number, void, unknown>
 
         yield 1;
 >yield 1 : any

tests/baselines/reference/declarationEmitDestructuringArrayPattern2.errors.txt

@@ -1,6 +1,6 @@
-tests/cases/compiler/declarationEmitDestructuringArrayPattern2.ts(4,6): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
-tests/cases/compiler/declarationEmitDestructuringArrayPattern2.ts(4,11): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
-tests/cases/compiler/declarationEmitDestructuringArrayPattern2.ts(4,16): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+tests/cases/compiler/declarationEmitDestructuringArrayPattern2.ts(4,6): error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
+tests/cases/compiler/declarationEmitDestructuringArrayPattern2.ts(4,11): error TS2493: Tuple type '[]' of length '0' has no element at index '1'.
+tests/cases/compiler/declarationEmitDestructuringArrayPattern2.ts(4,16): error TS2493: Tuple type '[]' of length '0' has no element at index '2'.
 
 
 ==== tests/cases/compiler/declarationEmitDestructuringArrayPattern2.ts (3 errors) ====
@@ -9,11 +9,11 @@ tests/cases/compiler/declarationEmitDestructuringArrayPattern2.ts(4,16): error T
     var [x11 = 0, y11 = ""] = [1, "hello"];
     var [a11, b11, c11] = [];
          ~~~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
               ~~~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '1'.
                    ~~~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '2'.
     
     var [a2, [b2, { x12, y12: c2 }]=["abc", { x12: 10, y12: false }]] = [1, ["hello", { x12: 5, y12: true }]];
     

tests/baselines/reference/declarationEmitDestructuringArrayPattern2.js

@@ -22,7 +22,7 @@ var _m = [[x13, y13], { x: x13, y: y13 }], a3 = _m[0], b3 = _m[1];
 //// [declarationEmitDestructuringArrayPattern2.d.ts]
 declare var x10: number, y10: string, z10: boolean;
 declare var x11: number, y11: string;
-declare var a11: any, b11: any, c11: any;
+declare var a11: undefined, b11: undefined, c11: undefined;
 declare var a2: number, b2: string, x12: number, c2: boolean;
 declare var x13: number, y13: string;
 declare var a3: (string | number)[], b3: {

tests/baselines/reference/declarationEmitDestructuringArrayPattern2.types

@@ -20,10 +20,10 @@ var [x11 = 0, y11 = ""] = [1, "hello"];
 >"hello" : "hello"
 
 var [a11, b11, c11] = [];
->a11 : any
->b11 : any
->c11 : any
->[] : [undefined?, undefined?, undefined?]
+>a11 : undefined
+>b11 : undefined
+>c11 : undefined
+>[] : []
 
 var [a2, [b2, { x12, y12: c2 }]=["abc", { x12: 10, y12: false }]] = [1, ["hello", { x12: 5, y12: true }]];
 >a2 : number

tests/baselines/reference/declarationsAndAssignments.errors.txt

@@ -1,4 +1,4 @@
-tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(5,16): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(5,16): error TS2493: Tuple type '[number, string]' of length '2' has no element at index '2'.
 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(22,17): error TS2353: Object literal may only specify known properties, and 'x' does not exist in type '{}'.
 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(22,23): error TS2353: Object literal may only specify known properties, and 'y' does not exist in type '{}'.
 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(23,25): error TS2353: Object literal may only specify known properties, and 'y' does not exist in type '{ x: any; }'.
@@ -6,11 +6,11 @@ tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(24,19):
 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(28,28): error TS2353: Object literal may only specify known properties, and 'y' does not exist in type '{ x: any; }'.
 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(29,22): error TS2353: Object literal may only specify known properties, and 'x' does not exist in type '{ y: any; }'.
 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(58,9): error TS2403: Subsequent variable declarations must have the same type.  Variable 'y' must be of type 'string | number', but here has type 'string'.
-tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(62,10): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
-tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(62,13): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
-tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(62,16): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
-tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(63,13): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
-tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(63,16): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(62,10): error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
+tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(62,13): error TS2493: Tuple type '[]' of length '0' has no element at index '1'.
+tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(62,16): error TS2493: Tuple type '[]' of length '0' has no element at index '2'.
+tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(63,13): error TS2493: Tuple type '[number]' of length '1' has no element at index '1'.
+tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(63,16): error TS2493: Tuple type '[number]' of length '1' has no element at index '2'.
 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(67,9): error TS2461: Type '{}' is not an array type.
 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(68,9): error TS2461: Type '{ 0: number; 1: number; }' is not an array type.
 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(73,11): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
@@ -29,7 +29,7 @@ tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(138,9):
         var [x, y] = [1, "hello"];
         var [x, y, z] = [1, "hello"];
                    ~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[number, string]' of length '2' has no element at index '2'.
         var [,, x] = [0, 1, 2];
         var x: number;
         var y: string;
@@ -103,16 +103,16 @@ tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(138,9):
     function f8() {
         var [a, b, c] = [];   // Error, [] is an empty tuple
              ~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
                 ~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '1'.
                    ~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '2'.
         var [d, e, f] = [1];  // Error, [1] is a tuple
                 ~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[number]' of length '1' has no element at index '1'.
                    ~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[number]' of length '1' has no element at index '2'.
     }
     
     function f9() {

tests/baselines/reference/declarationsAndAssignments.types

@@ -23,8 +23,8 @@ function f0() {
     var [x, y, z] = [1, "hello"];
 >x : number
 >y : string
->z : any
->[1, "hello"] : [number, string, undefined?]
+>z : undefined
+>[1, "hello"] : [number, string]
 >1 : 1
 >"hello" : "hello"
 
@@ -255,16 +255,16 @@ function f8() {
 >f8 : () => void
 
     var [a, b, c] = [];   // Error, [] is an empty tuple
->a : any
->b : any
->c : any
->[] : [undefined?, undefined?, undefined?]
+>a : undefined
+>b : undefined
+>c : undefined
+>[] : []
 
     var [d, e, f] = [1];  // Error, [1] is a tuple
 >d : number
->e : any
->f : any
->[1] : [number, undefined?, undefined?]
+>e : undefined
+>f : undefined
+>[1] : [number]
 >1 : 1
 }
 

tests/baselines/reference/destructuringArrayBindingPatternAndAssignment1ES5.errors.txt

@@ -1,6 +1,6 @@
-tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES5.ts(43,6): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
-tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES5.ts(44,8): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
-tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES5.ts(44,18): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES5.ts(43,6): error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
+tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES5.ts(44,8): error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
+tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES5.ts(44,18): error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
 
 
 ==== tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES5.ts (3 errors) ====
@@ -48,12 +48,12 @@ tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAss
     var [c0, c1] = [...temp];
     var [c2] = [];
          ~~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
     var [[[c3]], [[[[c4]]]]] = [[[]], [[[[]]]]]
            ~~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
                      ~~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
     var [[c5], c6]: [[string|number], boolean] = [[1], true];
     var [, c7] = [1, 2, 3];
     var [,,, c8] = [1, 2, 3, 4];

tests/baselines/reference/destructuringArrayBindingPatternAndAssignment1ES5.types

@@ -92,19 +92,19 @@ var [c0, c1] = [...temp];
 >temp : number[]
 
 var [c2] = [];
->c2 : any
->[] : [undefined?]
+>c2 : undefined
+>[] : []
 
 var [[[c3]], [[[[c4]]]]] = [[[]], [[[[]]]]]
->c3 : any
->c4 : any
->[[[]], [[[[]]]]] : [[[undefined?]], [[[[undefined?]]]]]
->[[]] : [[undefined?]]
->[] : [undefined?]
->[[[[]]]] : [[[[undefined?]]]]
->[[[]]] : [[[undefined?]]]
->[[]] : [[undefined?]]
->[] : [undefined?]
+>c3 : undefined
+>c4 : undefined
+>[[[]], [[[[]]]]] : [[[]], [[[[]]]]]
+>[[]] : [[]]
+>[] : []
+>[[[[]]]] : [[[[]]]]
+>[[[]]] : [[[]]]
+>[[]] : [[]]
+>[] : []
 
 var [[c5], c6]: [[string|number], boolean] = [[1], true];
 >c5 : string | number

tests/baselines/reference/destructuringArrayBindingPatternAndAssignment1ES5iterable.errors.txt

@@ -1,6 +1,6 @@
-tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES5iterable.ts(43,6): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
-tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES5iterable.ts(44,8): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
-tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES5iterable.ts(44,18): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES5iterable.ts(43,6): error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
+tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES5iterable.ts(44,8): error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
+tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES5iterable.ts(44,18): error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
 
 
 ==== tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES5iterable.ts (3 errors) ====
@@ -48,12 +48,12 @@ tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAss
     var [c0, c1] = [...temp];
     var [c2] = [];
          ~~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
     var [[[c3]], [[[[c4]]]]] = [[[]], [[[[]]]]]
            ~~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
                      ~~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
     var [[c5], c6]: [[string|number], boolean] = [[1], true];
     var [, c7] = [1, 2, 3];
     var [,,, c8] = [1, 2, 3, 4];

tests/baselines/reference/destructuringArrayBindingPatternAndAssignment1ES5iterable.types

@@ -92,19 +92,19 @@ var [c0, c1] = [...temp];
 >temp : number[]
 
 var [c2] = [];
->c2 : any
->[] : [undefined?]
+>c2 : undefined
+>[] : []
 
 var [[[c3]], [[[[c4]]]]] = [[[]], [[[[]]]]]
->c3 : any
->c4 : any
->[[[]], [[[[]]]]] : [[[undefined?]], [[[[undefined?]]]]]
->[[]] : [[undefined?]]
->[] : [undefined?]
->[[[[]]]] : [[[[undefined?]]]]
->[[[]]] : [[[undefined?]]]
->[[]] : [[undefined?]]
->[] : [undefined?]
+>c3 : undefined
+>c4 : undefined
+>[[[]], [[[[]]]]] : [[[]], [[[[]]]]]
+>[[]] : [[]]
+>[] : []
+>[[[[]]]] : [[[[]]]]
+>[[[]]] : [[[]]]
+>[[]] : [[]]
+>[] : []
 
 var [[c5], c6]: [[string|number], boolean] = [[1], true];
 >c5 : string | number

tests/baselines/reference/destructuringArrayBindingPatternAndAssignment1ES6.errors.txt

@@ -1,6 +1,6 @@
-tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES6.ts(43,6): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
-tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES6.ts(44,8): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
-tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES6.ts(44,18): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES6.ts(43,6): error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
+tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES6.ts(44,8): error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
+tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES6.ts(44,18): error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
 
 
 ==== tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment1ES6.ts (3 errors) ====
@@ -48,12 +48,12 @@ tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAss
     var [c0, c1] = [...temp];
     var [c2] = [];
          ~~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
     var [[[c3]], [[[[c4]]]]] = [[[]], [[[[]]]]]
            ~~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
                      ~~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
     var [[c5], c6]: [[string|number], boolean] = [[1], true];
     var [, c7] = [1, 2, 3];
     var [,,, c8] = [1, 2, 3, 4];

tests/baselines/reference/destructuringArrayBindingPatternAndAssignment1ES6.types

@@ -92,19 +92,19 @@ var [c0, c1] = [...temp];
 >temp : number[]
 
 var [c2] = [];
->c2 : any
->[] : [undefined?]
+>c2 : undefined
+>[] : []
 
 var [[[c3]], [[[[c4]]]]] = [[[]], [[[[]]]]]
->c3 : any
->c4 : any
->[[[]], [[[[]]]]] : [[[undefined?]], [[[[undefined?]]]]]
->[[]] : [[undefined?]]
->[] : [undefined?]
->[[[[]]]] : [[[[undefined?]]]]
->[[[]]] : [[[undefined?]]]
->[[]] : [[undefined?]]
->[] : [undefined?]
+>c3 : undefined
+>c4 : undefined
+>[[[]], [[[[]]]]] : [[[]], [[[[]]]]]
+>[[]] : [[]]
+>[] : []
+>[[[[]]]] : [[[[]]]]
+>[[[]]] : [[[]]]
+>[[]] : [[]]
+>[] : []
 
 var [[c5], c6]: [[string|number], boolean] = [[1], true];
 >c5 : string | number

tests/baselines/reference/destructuringArrayBindingPatternAndAssignment2.errors.txt

@@ -1,7 +1,7 @@
 tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment2.ts(3,6): error TS2461: Type 'undefined' is not an array type.
-tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment2.ts(3,6): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment2.ts(3,6): error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
 tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment2.ts(3,12): error TS2461: Type 'undefined' is not an array type.
-tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment2.ts(3,12): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment2.ts(3,12): error TS2493: Tuple type '[]' of length '0' has no element at index '1'.
 tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment2.ts(4,5): error TS2461: Type 'undefined' is not an array type.
 tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment2.ts(9,51): error TS2322: Type 'number' is not assignable to type 'boolean'.
 tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAssignment2.ts(22,5): error TS2739: Type 'number[]' is missing the following properties from type '[number, number]': 0, 1
@@ -16,11 +16,11 @@ tests/cases/conformance/es6/destructuring/destructuringArrayBindingPatternAndAss
          ~~~~
 !!! error TS2461: Type 'undefined' is not an array type.
          ~~~~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
                ~~~~~~
 !!! error TS2461: Type 'undefined' is not an array type.
                ~~~~~~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '1'.
     var [[a2], [[a3]]] = undefined  // Error
         ~~~~~~~~~~~~~~
 !!! error TS2461: Type 'undefined' is not an array type.

tests/baselines/reference/destructuringArrayBindingPatternAndAssignment2.types

@@ -4,7 +4,7 @@
 var [[a0], [[a1]]] = []         // Error
 >a0 : any
 >a1 : any
->[] : [undefined?, undefined?]
+>[] : []
 
 var [[a2], [[a3]]] = undefined  // Error
 >a2 : any

tests/baselines/reference/destructuringArrayBindingPatternAndAssignment3.types

@@ -3,7 +3,7 @@ const [a, b = a] = [1]; // ok
 >a : any
 >b : any
 >a : any
->[1] : [number, any?]
+>[1] : [number]
 >1 : 1
 
 const [c, d = c, e = e] = [1]; // error for e = e
@@ -12,7 +12,7 @@ const [c, d = c, e = e] = [1]; // error for e = e
 >c : any
 >e : any
 >e : any
->[1] : [number, any?, any?]
+>[1] : [number]
 >1 : 1
 
 const [f, g = f, h = i, i = f] = [1]; // error for h = i
@@ -23,7 +23,7 @@ const [f, g = f, h = i, i = f] = [1]; // error for h = i
 >i : any
 >i : any
 >f : any
->[1] : [number, any?, any?, any?]
+>[1] : [number]
 >1 : 1
 
 (function ([a, b = a]) { // ok

tests/baselines/reference/destructuringTuple.errors.txt

@@ -0,0 +1,23 @@
+tests/cases/compiler/destructuringTuple.ts(11,8): error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
+tests/cases/compiler/destructuringTuple.ts(11,60): error TS2345: Argument of type 'number' is not assignable to parameter of type 'ConcatArray<never>'.
+
+
+==== tests/cases/compiler/destructuringTuple.ts (2 errors) ====
+    declare var tuple: [boolean, number, ...string[]];
+    
+    const [a, b, c, ...rest] = tuple;
+    
+    declare var receiver: typeof tuple;
+    
+    [...receiver] = tuple;
+    
+    // Repros from #32140
+    
+    const [oops1] = [1, 2, 3].reduce((accu, el) => accu.concat(el), []);
+           ~~~~~
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
+                                                               ~~
+!!! error TS2345: Argument of type 'number' is not assignable to parameter of type 'ConcatArray<never>'.
+    
+    const [oops2] = [1, 2, 3].reduce((acc: number[], e) => acc.concat(e), []);
+    

tests/baselines/reference/destructuringTuple.js

@@ -6,9 +6,18 @@ const [a, b, c, ...rest] = tuple;
 declare var receiver: typeof tuple;
 
 [...receiver] = tuple;
+
+// Repros from #32140
+
+const [oops1] = [1, 2, 3].reduce((accu, el) => accu.concat(el), []);
+
+const [oops2] = [1, 2, 3].reduce((acc: number[], e) => acc.concat(e), []);
 
 
 //// [destructuringTuple.js]
 "use strict";
 var a = tuple[0], b = tuple[1], c = tuple[2], rest = tuple.slice(3);
 receiver = tuple.slice(0);
+// Repros from #32140
+var oops1 = [1, 2, 3].reduce(function (accu, el) { return accu.concat(el); }, [])[0];
+var oops2 = [1, 2, 3].reduce(function (acc, e) { return acc.concat(e); }, [])[0];

tests/baselines/reference/destructuringTuple.symbols

@@ -17,3 +17,27 @@ declare var receiver: typeof tuple;
 >receiver : Symbol(receiver, Decl(destructuringTuple.ts, 4, 11))
 >tuple : Symbol(tuple, Decl(destructuringTuple.ts, 0, 11))
 
+// Repros from #32140
+
+const [oops1] = [1, 2, 3].reduce((accu, el) => accu.concat(el), []);
+>oops1 : Symbol(oops1, Decl(destructuringTuple.ts, 10, 7))
+>[1, 2, 3].reduce : Symbol(Array.reduce, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>reduce : Symbol(Array.reduce, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>accu : Symbol(accu, Decl(destructuringTuple.ts, 10, 34))
+>el : Symbol(el, Decl(destructuringTuple.ts, 10, 39))
+>accu.concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>accu : Symbol(accu, Decl(destructuringTuple.ts, 10, 34))
+>concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>el : Symbol(el, Decl(destructuringTuple.ts, 10, 39))
+
+const [oops2] = [1, 2, 3].reduce((acc: number[], e) => acc.concat(e), []);
+>oops2 : Symbol(oops2, Decl(destructuringTuple.ts, 12, 7))
+>[1, 2, 3].reduce : Symbol(Array.reduce, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>reduce : Symbol(Array.reduce, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>acc : Symbol(acc, Decl(destructuringTuple.ts, 12, 34))
+>e : Symbol(e, Decl(destructuringTuple.ts, 12, 48))
+>acc.concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>acc : Symbol(acc, Decl(destructuringTuple.ts, 12, 34))
+>concat : Symbol(Array.concat, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>e : Symbol(e, Decl(destructuringTuple.ts, 12, 48))
+

tests/baselines/reference/destructuringTuple.types

@@ -20,3 +20,43 @@ declare var receiver: typeof tuple;
 >receiver : [boolean, number, ...string[]]
 >tuple : [boolean, number, ...string[]]
 
+// Repros from #32140
+
+const [oops1] = [1, 2, 3].reduce((accu, el) => accu.concat(el), []);
+>oops1 : undefined
+>[1, 2, 3].reduce((accu, el) => accu.concat(el), []) : []
+>[1, 2, 3].reduce : { (callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: number[]) => number): number; (callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: number[]) => number, initialValue: number): number; <U>(callbackfn: (previousValue: U, currentValue: number, currentIndex: number, array: number[]) => U, initialValue: U): U; }
+>[1, 2, 3] : number[]
+>1 : 1
+>2 : 2
+>3 : 3
+>reduce : { (callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: number[]) => number): number; (callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: number[]) => number, initialValue: number): number; <U>(callbackfn: (previousValue: U, currentValue: number, currentIndex: number, array: number[]) => U, initialValue: U): U; }
+>(accu, el) => accu.concat(el) : (accu: [], el: number) => any
+>accu : []
+>el : number
+>accu.concat(el) : any
+>accu.concat : { (...items: ConcatArray<never>[]): never[]; (...items: ConcatArray<never>[]): never[]; }
+>accu : []
+>concat : { (...items: ConcatArray<never>[]): never[]; (...items: ConcatArray<never>[]): never[]; }
+>el : number
+>[] : []
+
+const [oops2] = [1, 2, 3].reduce((acc: number[], e) => acc.concat(e), []);
+>oops2 : number
+>[1, 2, 3].reduce((acc: number[], e) => acc.concat(e), []) : number[]
+>[1, 2, 3].reduce : { (callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: number[]) => number): number; (callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: number[]) => number, initialValue: number): number; <U>(callbackfn: (previousValue: U, currentValue: number, currentIndex: number, array: number[]) => U, initialValue: U): U; }
+>[1, 2, 3] : number[]
+>1 : 1
+>2 : 2
+>3 : 3
+>reduce : { (callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: number[]) => number): number; (callbackfn: (previousValue: number, currentValue: number, currentIndex: number, array: number[]) => number, initialValue: number): number; <U>(callbackfn: (previousValue: U, currentValue: number, currentIndex: number, array: number[]) => U, initialValue: U): U; }
+>(acc: number[], e) => acc.concat(e) : (acc: number[], e: number) => number[]
+>acc : number[]
+>e : number
+>acc.concat(e) : number[]
+>acc.concat : { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }
+>acc : number[]
+>concat : { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }
+>e : number
+>[] : never[]
+

tests/baselines/reference/destructuringVariableDeclaration1ES5.types

@@ -151,9 +151,9 @@ var {f: [f1, f2, { f3: f4, f5 }, , ]} = { f: [1, 2, { f3: 4, f5: 0 }] };
 >f4 : number
 >f5 : number
 > : undefined
->{ f: [1, 2, { f3: 4, f5: 0 }] } : { f: [number, number, { f3: number; f5: number; }, undefined?]; }
->f : [number, number, { f3: number; f5: number; }, undefined?]
->[1, 2, { f3: 4, f5: 0 }] : [number, number, { f3: number; f5: number; }, undefined?]
+>{ f: [1, 2, { f3: 4, f5: 0 }] } : { f: [number, number, { f3: number; f5: number; }]; }
+>f : [number, number, { f3: number; f5: number; }]
+>[1, 2, { f3: 4, f5: 0 }] : [number, number, { f3: number; f5: number; }]
 >1 : 1
 >2 : 2
 >{ f3: 4, f5: 0 } : { f3: number; f5: number; }

tests/baselines/reference/destructuringVariableDeclaration1ES5iterable.types

@@ -151,9 +151,9 @@ var {f: [f1, f2, { f3: f4, f5 }, , ]} = { f: [1, 2, { f3: 4, f5: 0 }] };
 >f4 : number
 >f5 : number
 > : undefined
->{ f: [1, 2, { f3: 4, f5: 0 }] } : { f: [number, number, { f3: number; f5: number; }, undefined?]; }
->f : [number, number, { f3: number; f5: number; }, undefined?]
->[1, 2, { f3: 4, f5: 0 }] : [number, number, { f3: number; f5: number; }, undefined?]
+>{ f: [1, 2, { f3: 4, f5: 0 }] } : { f: [number, number, { f3: number; f5: number; }]; }
+>f : [number, number, { f3: number; f5: number; }]
+>[1, 2, { f3: 4, f5: 0 }] : [number, number, { f3: number; f5: number; }]
 >1 : 1
 >2 : 2
 >{ f3: 4, f5: 0 } : { f3: number; f5: number; }

tests/baselines/reference/destructuringVariableDeclaration1ES6.types

@@ -151,9 +151,9 @@ var {f: [f1, f2, { f3: f4, f5 }, , ]} = { f: [1, 2, { f3: 4, f5: 0 }] };
 >f4 : number
 >f5 : number
 > : undefined
->{ f: [1, 2, { f3: 4, f5: 0 }] } : { f: [number, number, { f3: number; f5: number; }, undefined?]; }
->f : [number, number, { f3: number; f5: number; }, undefined?]
->[1, 2, { f3: 4, f5: 0 }] : [number, number, { f3: number; f5: number; }, undefined?]
+>{ f: [1, 2, { f3: 4, f5: 0 }] } : { f: [number, number, { f3: number; f5: number; }]; }
+>f : [number, number, { f3: number; f5: number; }]
+>[1, 2, { f3: 4, f5: 0 }] : [number, number, { f3: number; f5: number; }]
 >1 : 1
 >2 : 2
 >{ f3: 4, f5: 0 } : { f3: number; f5: number; }

tests/baselines/reference/destructuringVariableDeclaration2.types

@@ -60,7 +60,7 @@ var [c1, c2, { c3: c4, c5 }, , ...c6] = [1, 2, { c3: 4, c5: 0 }];  // Error
 >c5 : number
 > : undefined
 >c6 : []
->[1, 2, { c3: 4, c5: 0 }] : [number, number, { c3: number; c5: number; }, undefined?]
+>[1, 2, { c3: 4, c5: 0 }] : [number, number, { c3: number; c5: number; }]
 >1 : 1
 >2 : 2
 >{ c3: 4, c5: 0 } : { c3: number; c5: number; }

tests/baselines/reference/destructuringWithLiteralInitializers.types

@@ -274,7 +274,7 @@ function g4([x, y = 0] = [0]) { }
 >x : number
 >y : number
 >0 : 0
->[0] : [number, number?]
+>[0] : [number]
 >0 : 0
 
 g4();
@@ -295,7 +295,7 @@ function g5([x = 0, y = 0] = []) { }
 >0 : 0
 >y : number
 >0 : 0
->[] : [number?, number?]
+>[] : []
 
 g5();
 >g5() : void

tests/baselines/reference/destructuringWithLiteralInitializers2.errors.txt

@@ -0,0 +1,55 @@
+tests/cases/conformance/es6/destructuring/destructuringWithLiteralInitializers2.ts(1,15): error TS7031: Binding element 'x' implicitly has an 'any' type.
+tests/cases/conformance/es6/destructuring/destructuringWithLiteralInitializers2.ts(1,18): error TS7031: Binding element 'y' implicitly has an 'any' type.
+tests/cases/conformance/es6/destructuring/destructuringWithLiteralInitializers2.ts(2,15): error TS7031: Binding element 'x' implicitly has an 'any' type.
+tests/cases/conformance/es6/destructuring/destructuringWithLiteralInitializers2.ts(2,18): error TS7031: Binding element 'y' implicitly has an 'any' type.
+tests/cases/conformance/es6/destructuring/destructuringWithLiteralInitializers2.ts(3,18): error TS7031: Binding element 'y' implicitly has an 'any' type.
+tests/cases/conformance/es6/destructuring/destructuringWithLiteralInitializers2.ts(6,22): error TS7031: Binding element 'y' implicitly has an 'any' type.
+tests/cases/conformance/es6/destructuring/destructuringWithLiteralInitializers2.ts(7,22): error TS7031: Binding element 'y' implicitly has an 'any' type.
+tests/cases/conformance/es6/destructuring/destructuringWithLiteralInitializers2.ts(8,22): error TS7031: Binding element 'y' implicitly has an 'any' type.
+
+
+==== tests/cases/conformance/es6/destructuring/destructuringWithLiteralInitializers2.ts (8 errors) ====
+    function f00([x, y]) {}
+                  ~
+!!! error TS7031: Binding element 'x' implicitly has an 'any' type.
+                     ~
+!!! error TS7031: Binding element 'y' implicitly has an 'any' type.
+    function f01([x, y] = []) {}
+                  ~
+!!! error TS7031: Binding element 'x' implicitly has an 'any' type.
+                     ~
+!!! error TS7031: Binding element 'y' implicitly has an 'any' type.
+    function f02([x, y] = [1]) {}
+                     ~
+!!! error TS7031: Binding element 'y' implicitly has an 'any' type.
+    function f03([x, y] = [1, 'foo']) {}
+    
+    function f10([x = 0, y]) {}
+                         ~
+!!! error TS7031: Binding element 'y' implicitly has an 'any' type.
+    function f11([x = 0, y] = []) {}
+                         ~
+!!! error TS7031: Binding element 'y' implicitly has an 'any' type.
+    function f12([x = 0, y] = [1]) {}
+                         ~
+!!! error TS7031: Binding element 'y' implicitly has an 'any' type.
+    function f13([x = 0, y] = [1, 'foo']) {}
+    
+    function f20([x = 0, y = 'bar']) {}
+    function f21([x = 0, y = 'bar'] = []) {}
+    function f22([x = 0, y = 'bar'] = [1]) {}
+    function f23([x = 0, y = 'bar'] = [1, 'foo']) {}
+    
+    declare const nx: number | undefined;
+    declare const sx: string | undefined;
+    
+    function f30([x = 0, y = 'bar']) {}
+    function f31([x = 0, y = 'bar'] = []) {}
+    function f32([x = 0, y = 'bar'] = [nx]) {}
+    function f33([x = 0, y = 'bar'] = [nx, sx]) {}
+    
+    function f40([x = 0, y = 'bar']) {}
+    function f41([x = 0, y = 'bar'] = []) {}
+    function f42([x = 0, y = 'bar'] = [sx]) {}
+    function f43([x = 0, y = 'bar'] = [sx, nx]) {}
+    

tests/baselines/reference/destructuringWithLiteralInitializers2.js

@@ -0,0 +1,92 @@
+//// [destructuringWithLiteralInitializers2.ts]
+function f00([x, y]) {}
+function f01([x, y] = []) {}
+function f02([x, y] = [1]) {}
+function f03([x, y] = [1, 'foo']) {}
+
+function f10([x = 0, y]) {}
+function f11([x = 0, y] = []) {}
+function f12([x = 0, y] = [1]) {}
+function f13([x = 0, y] = [1, 'foo']) {}
+
+function f20([x = 0, y = 'bar']) {}
+function f21([x = 0, y = 'bar'] = []) {}
+function f22([x = 0, y = 'bar'] = [1]) {}
+function f23([x = 0, y = 'bar'] = [1, 'foo']) {}
+
+declare const nx: number | undefined;
+declare const sx: string | undefined;
+
+function f30([x = 0, y = 'bar']) {}
+function f31([x = 0, y = 'bar'] = []) {}
+function f32([x = 0, y = 'bar'] = [nx]) {}
+function f33([x = 0, y = 'bar'] = [nx, sx]) {}
+
+function f40([x = 0, y = 'bar']) {}
+function f41([x = 0, y = 'bar'] = []) {}
+function f42([x = 0, y = 'bar'] = [sx]) {}
+function f43([x = 0, y = 'bar'] = [sx, nx]) {}
+
+
+//// [destructuringWithLiteralInitializers2.js]
+"use strict";
+function f00(_a) {
+    var x = _a[0], y = _a[1];
+}
+function f01(_a) {
+    var _b = _a === void 0 ? [] : _a, x = _b[0], y = _b[1];
+}
+function f02(_a) {
+    var _b = _a === void 0 ? [1] : _a, x = _b[0], y = _b[1];
+}
+function f03(_a) {
+    var _b = _a === void 0 ? [1, 'foo'] : _a, x = _b[0], y = _b[1];
+}
+function f10(_a) {
+    var _b = _a[0], x = _b === void 0 ? 0 : _b, y = _a[1];
+}
+function f11(_a) {
+    var _b = _a === void 0 ? [] : _a, _c = _b[0], x = _c === void 0 ? 0 : _c, y = _b[1];
+}
+function f12(_a) {
+    var _b = _a === void 0 ? [1] : _a, _c = _b[0], x = _c === void 0 ? 0 : _c, y = _b[1];
+}
+function f13(_a) {
+    var _b = _a === void 0 ? [1, 'foo'] : _a, _c = _b[0], x = _c === void 0 ? 0 : _c, y = _b[1];
+}
+function f20(_a) {
+    var _b = _a[0], x = _b === void 0 ? 0 : _b, _c = _a[1], y = _c === void 0 ? 'bar' : _c;
+}
+function f21(_a) {
+    var _b = _a === void 0 ? [] : _a, _c = _b[0], x = _c === void 0 ? 0 : _c, _d = _b[1], y = _d === void 0 ? 'bar' : _d;
+}
+function f22(_a) {
+    var _b = _a === void 0 ? [1] : _a, _c = _b[0], x = _c === void 0 ? 0 : _c, _d = _b[1], y = _d === void 0 ? 'bar' : _d;
+}
+function f23(_a) {
+    var _b = _a === void 0 ? [1, 'foo'] : _a, _c = _b[0], x = _c === void 0 ? 0 : _c, _d = _b[1], y = _d === void 0 ? 'bar' : _d;
+}
+function f30(_a) {
+    var _b = _a[0], x = _b === void 0 ? 0 : _b, _c = _a[1], y = _c === void 0 ? 'bar' : _c;
+}
+function f31(_a) {
+    var _b = _a === void 0 ? [] : _a, _c = _b[0], x = _c === void 0 ? 0 : _c, _d = _b[1], y = _d === void 0 ? 'bar' : _d;
+}
+function f32(_a) {
+    var _b = _a === void 0 ? [nx] : _a, _c = _b[0], x = _c === void 0 ? 0 : _c, _d = _b[1], y = _d === void 0 ? 'bar' : _d;
+}
+function f33(_a) {
+    var _b = _a === void 0 ? [nx, sx] : _a, _c = _b[0], x = _c === void 0 ? 0 : _c, _d = _b[1], y = _d === void 0 ? 'bar' : _d;
+}
+function f40(_a) {
+    var _b = _a[0], x = _b === void 0 ? 0 : _b, _c = _a[1], y = _c === void 0 ? 'bar' : _c;
+}
+function f41(_a) {
+    var _b = _a === void 0 ? [] : _a, _c = _b[0], x = _c === void 0 ? 0 : _c, _d = _b[1], y = _d === void 0 ? 'bar' : _d;
+}
+function f42(_a) {
+    var _b = _a === void 0 ? [sx] : _a, _c = _b[0], x = _c === void 0 ? 0 : _c, _d = _b[1], y = _d === void 0 ? 'bar' : _d;
+}
+function f43(_a) {
+    var _b = _a === void 0 ? [sx, nx] : _a, _c = _b[0], x = _c === void 0 ? 0 : _c, _d = _b[1], y = _d === void 0 ? 'bar' : _d;
+}

tests/baselines/reference/destructuringWithLiteralInitializers2.symbols

@@ -0,0 +1,113 @@
+=== tests/cases/conformance/es6/destructuring/destructuringWithLiteralInitializers2.ts ===
+function f00([x, y]) {}
+>f00 : Symbol(f00, Decl(destructuringWithLiteralInitializers2.ts, 0, 0))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 0, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 0, 16))
+
+function f01([x, y] = []) {}
+>f01 : Symbol(f01, Decl(destructuringWithLiteralInitializers2.ts, 0, 23))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 1, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 1, 16))
+
+function f02([x, y] = [1]) {}
+>f02 : Symbol(f02, Decl(destructuringWithLiteralInitializers2.ts, 1, 28))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 2, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 2, 16))
+
+function f03([x, y] = [1, 'foo']) {}
+>f03 : Symbol(f03, Decl(destructuringWithLiteralInitializers2.ts, 2, 29))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 3, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 3, 16))
+
+function f10([x = 0, y]) {}
+>f10 : Symbol(f10, Decl(destructuringWithLiteralInitializers2.ts, 3, 36))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 5, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 5, 20))
+
+function f11([x = 0, y] = []) {}
+>f11 : Symbol(f11, Decl(destructuringWithLiteralInitializers2.ts, 5, 27))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 6, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 6, 20))
+
+function f12([x = 0, y] = [1]) {}
+>f12 : Symbol(f12, Decl(destructuringWithLiteralInitializers2.ts, 6, 32))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 7, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 7, 20))
+
+function f13([x = 0, y] = [1, 'foo']) {}
+>f13 : Symbol(f13, Decl(destructuringWithLiteralInitializers2.ts, 7, 33))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 8, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 8, 20))
+
+function f20([x = 0, y = 'bar']) {}
+>f20 : Symbol(f20, Decl(destructuringWithLiteralInitializers2.ts, 8, 40))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 10, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 10, 20))
+
+function f21([x = 0, y = 'bar'] = []) {}
+>f21 : Symbol(f21, Decl(destructuringWithLiteralInitializers2.ts, 10, 35))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 11, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 11, 20))
+
+function f22([x = 0, y = 'bar'] = [1]) {}
+>f22 : Symbol(f22, Decl(destructuringWithLiteralInitializers2.ts, 11, 40))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 12, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 12, 20))
+
+function f23([x = 0, y = 'bar'] = [1, 'foo']) {}
+>f23 : Symbol(f23, Decl(destructuringWithLiteralInitializers2.ts, 12, 41))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 13, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 13, 20))
+
+declare const nx: number | undefined;
+>nx : Symbol(nx, Decl(destructuringWithLiteralInitializers2.ts, 15, 13))
+
+declare const sx: string | undefined;
+>sx : Symbol(sx, Decl(destructuringWithLiteralInitializers2.ts, 16, 13))
+
+function f30([x = 0, y = 'bar']) {}
+>f30 : Symbol(f30, Decl(destructuringWithLiteralInitializers2.ts, 16, 37))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 18, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 18, 20))
+
+function f31([x = 0, y = 'bar'] = []) {}
+>f31 : Symbol(f31, Decl(destructuringWithLiteralInitializers2.ts, 18, 35))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 19, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 19, 20))
+
+function f32([x = 0, y = 'bar'] = [nx]) {}
+>f32 : Symbol(f32, Decl(destructuringWithLiteralInitializers2.ts, 19, 40))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 20, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 20, 20))
+>nx : Symbol(nx, Decl(destructuringWithLiteralInitializers2.ts, 15, 13))
+
+function f33([x = 0, y = 'bar'] = [nx, sx]) {}
+>f33 : Symbol(f33, Decl(destructuringWithLiteralInitializers2.ts, 20, 42))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 21, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 21, 20))
+>nx : Symbol(nx, Decl(destructuringWithLiteralInitializers2.ts, 15, 13))
+>sx : Symbol(sx, Decl(destructuringWithLiteralInitializers2.ts, 16, 13))
+
+function f40([x = 0, y = 'bar']) {}
+>f40 : Symbol(f40, Decl(destructuringWithLiteralInitializers2.ts, 21, 46))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 23, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 23, 20))
+
+function f41([x = 0, y = 'bar'] = []) {}
+>f41 : Symbol(f41, Decl(destructuringWithLiteralInitializers2.ts, 23, 35))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 24, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 24, 20))
+
+function f42([x = 0, y = 'bar'] = [sx]) {}
+>f42 : Symbol(f42, Decl(destructuringWithLiteralInitializers2.ts, 24, 40))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 25, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 25, 20))
+>sx : Symbol(sx, Decl(destructuringWithLiteralInitializers2.ts, 16, 13))
+
+function f43([x = 0, y = 'bar'] = [sx, nx]) {}
+>f43 : Symbol(f43, Decl(destructuringWithLiteralInitializers2.ts, 25, 42))
+>x : Symbol(x, Decl(destructuringWithLiteralInitializers2.ts, 26, 14))
+>y : Symbol(y, Decl(destructuringWithLiteralInitializers2.ts, 26, 20))
+>sx : Symbol(sx, Decl(destructuringWithLiteralInitializers2.ts, 16, 13))
+>nx : Symbol(nx, Decl(destructuringWithLiteralInitializers2.ts, 15, 13))
+

tests/baselines/reference/destructuringWithLiteralInitializers2.types

@@ -0,0 +1,165 @@
+=== tests/cases/conformance/es6/destructuring/destructuringWithLiteralInitializers2.ts ===
+function f00([x, y]) {}
+>f00 : ([x, y]: [any, any]) => void
+>x : any
+>y : any
+
+function f01([x, y] = []) {}
+>f01 : ([x, y]?: [any?, any?]) => void
+>x : any
+>y : any
+>[] : []
+
+function f02([x, y] = [1]) {}
+>f02 : ([x, y]?: [number, any?]) => void
+>x : number
+>y : any
+>[1] : [number]
+>1 : 1
+
+function f03([x, y] = [1, 'foo']) {}
+>f03 : ([x, y]?: [number, string]) => void
+>x : number
+>y : string
+>[1, 'foo'] : [number, string]
+>1 : 1
+>'foo' : "foo"
+
+function f10([x = 0, y]) {}
+>f10 : ([x, y]: [number | undefined, any]) => void
+>x : number
+>0 : 0
+>y : any
+
+function f11([x = 0, y] = []) {}
+>f11 : ([x, y]?: [(number | undefined)?, any?]) => void
+>x : number
+>0 : 0
+>y : any
+>[] : []
+
+function f12([x = 0, y] = [1]) {}
+>f12 : ([x, y]?: [number, any?]) => void
+>x : number
+>0 : 0
+>y : any
+>[1] : [number]
+>1 : 1
+
+function f13([x = 0, y] = [1, 'foo']) {}
+>f13 : ([x, y]?: [number, string]) => void
+>x : number
+>0 : 0
+>y : string
+>[1, 'foo'] : [number, string]
+>1 : 1
+>'foo' : "foo"
+
+function f20([x = 0, y = 'bar']) {}
+>f20 : ([x, y]: [(number | undefined)?, (string | undefined)?]) => void
+>x : number
+>0 : 0
+>y : string
+>'bar' : "bar"
+
+function f21([x = 0, y = 'bar'] = []) {}
+>f21 : ([x, y]?: [(number | undefined)?, (string | undefined)?]) => void
+>x : number
+>0 : 0
+>y : string
+>'bar' : "bar"
+>[] : []
+
+function f22([x = 0, y = 'bar'] = [1]) {}
+>f22 : ([x, y]?: [number, (string | undefined)?]) => void
+>x : number
+>0 : 0
+>y : string
+>'bar' : "bar"
+>[1] : [number]
+>1 : 1
+
+function f23([x = 0, y = 'bar'] = [1, 'foo']) {}
+>f23 : ([x, y]?: [number, string]) => void
+>x : number
+>0 : 0
+>y : string
+>'bar' : "bar"
+>[1, 'foo'] : [number, string]
+>1 : 1
+>'foo' : "foo"
+
+declare const nx: number | undefined;
+>nx : number | undefined
+
+declare const sx: string | undefined;
+>sx : string | undefined
+
+function f30([x = 0, y = 'bar']) {}
+>f30 : ([x, y]: [(number | undefined)?, (string | undefined)?]) => void
+>x : number
+>0 : 0
+>y : string
+>'bar' : "bar"
+
+function f31([x = 0, y = 'bar'] = []) {}
+>f31 : ([x, y]?: [(number | undefined)?, (string | undefined)?]) => void
+>x : number
+>0 : 0
+>y : string
+>'bar' : "bar"
+>[] : []
+
+function f32([x = 0, y = 'bar'] = [nx]) {}
+>f32 : ([x, y]?: [number | undefined, (string | undefined)?]) => void
+>x : number
+>0 : 0
+>y : string
+>'bar' : "bar"
+>[nx] : [number | undefined]
+>nx : number | undefined
+
+function f33([x = 0, y = 'bar'] = [nx, sx]) {}
+>f33 : ([x, y]?: [number | undefined, string | undefined]) => void
+>x : number
+>0 : 0
+>y : string
+>'bar' : "bar"
+>[nx, sx] : [number | undefined, string | undefined]
+>nx : number | undefined
+>sx : string | undefined
+
+function f40([x = 0, y = 'bar']) {}
+>f40 : ([x, y]: [(number | undefined)?, (string | undefined)?]) => void
+>x : number
+>0 : 0
+>y : string
+>'bar' : "bar"
+
+function f41([x = 0, y = 'bar'] = []) {}
+>f41 : ([x, y]?: [(number | undefined)?, (string | undefined)?]) => void
+>x : number
+>0 : 0
+>y : string
+>'bar' : "bar"
+>[] : []
+
+function f42([x = 0, y = 'bar'] = [sx]) {}
+>f42 : ([x, y]?: [string | undefined, (string | undefined)?]) => void
+>x : string | number
+>0 : 0
+>y : string
+>'bar' : "bar"
+>[sx] : [string | undefined]
+>sx : string | undefined
+
+function f43([x = 0, y = 'bar'] = [sx, nx]) {}
+>f43 : ([x, y]?: [string | undefined, number | undefined]) => void
+>x : string | number
+>0 : 0
+>y : string | number
+>'bar' : "bar"
+>[sx, nx] : [string | undefined, number | undefined]
+>sx : string | undefined
+>nx : number | undefined
+

tests/baselines/reference/downlevelLetConst12.errors.txt

@@ -1,5 +1,5 @@
-tests/cases/compiler/downlevelLetConst12.ts(6,6): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
-tests/cases/compiler/downlevelLetConst12.ts(9,8): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+tests/cases/compiler/downlevelLetConst12.ts(6,6): error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
+tests/cases/compiler/downlevelLetConst12.ts(9,8): error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
 
 
 ==== tests/cases/compiler/downlevelLetConst12.ts (2 errors) ====
@@ -10,10 +10,10 @@ tests/cases/compiler/downlevelLetConst12.ts(9,8): error TS2525: Initializer prov
     
     let [baz] = [];
          ~~~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
     let {a: baz2} = { a: 1 };
     
     const [baz3] = []
            ~~~~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
     const {a: baz4} = { a: 1 };

tests/baselines/reference/downlevelLetConst12.types

@@ -11,8 +11,8 @@ const bar = 1;
 >1 : 1
 
 let [baz] = [];
->baz : any
->[] : [undefined?]
+>baz : undefined
+>[] : []
 
 let {a: baz2} = { a: 1 };
 >a : any
@@ -22,8 +22,8 @@ let {a: baz2} = { a: 1 };
 >1 : 1
 
 const [baz3] = []
->baz3 : any
->[] : [undefined?]
+>baz3 : undefined
+>[] : []
 
 const {a: baz4} = { a: 1 };
 >a : any

tests/baselines/reference/downlevelLetConst16.errors.txt

@@ -1,5 +1,5 @@
-tests/cases/compiler/downlevelLetConst16.ts(151,15): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
-tests/cases/compiler/downlevelLetConst16.ts(164,17): error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+tests/cases/compiler/downlevelLetConst16.ts(151,15): error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
+tests/cases/compiler/downlevelLetConst16.ts(164,17): error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
 tests/cases/compiler/downlevelLetConst16.ts(195,14): error TS2461: Type 'undefined' is not an array type.
 tests/cases/compiler/downlevelLetConst16.ts(202,15): error TS2339: Property 'a' does not exist on type 'undefined'.
 tests/cases/compiler/downlevelLetConst16.ts(216,16): error TS2461: Type 'undefined' is not an array type.
@@ -159,7 +159,7 @@ tests/cases/compiler/downlevelLetConst16.ts(223,17): error TS2339: Property 'a'
         }
         for (let [y] = []; ;) {
                   ~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
             use(y);
         }
         for (let {a: z} = {a: 1}; ;) {
@@ -174,7 +174,7 @@ tests/cases/compiler/downlevelLetConst16.ts(223,17): error TS2339: Property 'a'
         }
         for (const [y] = []; ;) {
                     ~
-!!! error TS2525: Initializer provides no value for this binding element and the binding element has no default value.
+!!! error TS2493: Tuple type '[]' of length '0' has no element at index '0'.
             use(y);
         }
         for (const {a: z} = { a: 1 }; ;) {