Add TReturn/TNext to Iterable et al

src/compiler/commandLineParser.ts

@@ -915,6 +915,16 @@ const commandOptionsWithoutBuild: CommandLineOption[] = [
         description: Diagnostics.Check_for_class_properties_that_are_declared_but_not_set_in_the_constructor,
         defaultValueDescription: Diagnostics.false_unless_strict_is_set,
     },
+    {
+        name: "strictBuiltinIteratorReturn",
+        type: "boolean",
+        affectsSemanticDiagnostics: true,
+        affectsBuildInfo: true,
+        strictFlag: true,
+        category: Diagnostics.Type_Checking,
+        description: Diagnostics.Built_in_iterators_are_instantiated_with_a_TReturn_type_of_undefined_instead_of_any,
+        defaultValueDescription: Diagnostics.false_unless_strict_is_set,
+    },
     {
         name: "noImplicitThis",
         type: "boolean",

src/compiler/diagnosticMessages.json

@@ -6368,6 +6368,10 @@
         "code": 6719
     },
 
+    "Built-in iterators are instantiated with a 'TReturn' type of 'undefined' instead of 'any'.": {
+        "category": "Message",
+        "code": 6720
+    },
     "Default catch clause variables as 'unknown' instead of 'any'.": {
         "category": "Message",
         "code": 6803

src/compiler/types.ts

@@ -5237,7 +5237,7 @@ export interface TypeChecker {
     /** @internal */ createPromiseType(type: Type): Type;
     /** @internal */ getPromiseType(): Type;
     /** @internal */ getPromiseLikeType(): Type;
-    /** @internal */ getAsyncIterableType(): Type | undefined;
+    /** @internal */ getAnyAsyncIterableType(): Type | undefined;
 
     /**
      * Returns true if the "source" type is assignable to the "target" type.
@@ -7407,6 +7407,7 @@ export interface CompilerOptions {
     strictBindCallApply?: boolean; // Always combine with strict property
     strictNullChecks?: boolean; // Always combine with strict property
     strictPropertyInitialization?: boolean; // Always combine with strict property
+    strictBuiltinIteratorReturn?: boolean; // Always combine with strict property
     stripInternal?: boolean;
     /** @deprecated */
     suppressExcessPropertyErrors?: boolean;

src/compiler/utilities.ts

@@ -9006,6 +9006,12 @@ export const computedOptions = createComputedCompilerOptions({
             return getStrictOptionValue(compilerOptions, "strictPropertyInitialization");
         },
     },
+    strictBuiltinIteratorReturn: {
+        dependencies: ["strict"],
+        computeValue: compilerOptions => {
+            return getStrictOptionValue(compilerOptions, "strictBuiltinIteratorReturn");
+        },
+    },
     alwaysStrict: {
         dependencies: ["strict"],
         computeValue: compilerOptions => {
@@ -9093,6 +9099,7 @@ export type StrictOptionName =
     | "strictFunctionTypes"
     | "strictBindCallApply"
     | "strictPropertyInitialization"
+    | "strictBuiltinIteratorReturn"
     | "alwaysStrict"
     | "useUnknownInCatchVariables";
 

src/harness/collectionsImpl.ts

@@ -132,6 +132,7 @@ export class SortedMap<K, V> {
                 this._copyOnWrite = false;
             }
         }
+        return undefined;
     }
 
     public *values() {
@@ -154,6 +155,7 @@ export class SortedMap<K, V> {
                 this._copyOnWrite = false;
             }
         }
+        return undefined;
     }
 
     public *entries() {
@@ -179,6 +181,7 @@ export class SortedMap<K, V> {
                 this._copyOnWrite = false;
             }
         }
+        return undefined;
     }
 
     public [Symbol.iterator]() {

src/lib/dom.iterable.d.ts

@@ -1,30 +1,30 @@
 /// <reference lib="dom" />
 
 interface DOMTokenList {
-    [Symbol.iterator](): IterableIterator<string>;
+    [Symbol.iterator](): IterableIterator<string, BuiltinIteratorReturn>;
 }
 
 interface Headers {
-    [Symbol.iterator](): IterableIterator<[string, string]>;
+    [Symbol.iterator](): IterableIterator<[string, string], BuiltinIteratorReturn>;
     /**
      * Returns an iterator allowing to go through all key/value pairs contained in this object.
      */
-    entries(): IterableIterator<[string, string]>;
+    entries(): IterableIterator<[string, string], BuiltinIteratorReturn>;
     /**
      * Returns an iterator allowing to go through all keys f the key/value pairs contained in this object.
      */
-    keys(): IterableIterator<string>;
+    keys(): IterableIterator<string, BuiltinIteratorReturn>;
     /**
      * Returns an iterator allowing to go through all values of the key/value pairs contained in this object.
      */
-    values(): IterableIterator<string>;
+    values(): IterableIterator<string, BuiltinIteratorReturn>;
 }
 
 interface NodeList {
     /**
      * Returns an array of key, value pairs for every entry in the list
      */
-    entries(): IterableIterator<[number, Node]>;
+    entries(): IterableIterator<[number, Node], BuiltinIteratorReturn>;
     /**
      * Performs the specified action for each node in an list.
      * @param callbackfn  A function that accepts up to three arguments. forEach calls the callbackfn function one time for each element in the list.
@@ -34,21 +34,21 @@ interface NodeList {
     /**
      * Returns an list of keys in the list
      */
-    keys(): IterableIterator<number>;
+    keys(): IterableIterator<number, BuiltinIteratorReturn>;
 
     /**
      * Returns an list of values in the list
      */
-    values(): IterableIterator<Node>;
+    values(): IterableIterator<Node, BuiltinIteratorReturn>;
 
-    [Symbol.iterator](): IterableIterator<Node>;
+    [Symbol.iterator](): IterableIterator<Node, BuiltinIteratorReturn>;
 }
 
 interface NodeListOf<TNode extends Node> {
     /**
      * Returns an array of key, value pairs for every entry in the list
      */
-    entries(): IterableIterator<[number, TNode]>;
+    entries(): IterableIterator<[number, TNode], BuiltinIteratorReturn>;
 
     /**
      * Performs the specified action for each node in an list.
@@ -59,55 +59,55 @@ interface NodeListOf<TNode extends Node> {
     /**
      * Returns an list of keys in the list
      */
-    keys(): IterableIterator<number>;
+    keys(): IterableIterator<number, BuiltinIteratorReturn>;
     /**
      * Returns an list of values in the list
      */
-    values(): IterableIterator<TNode>;
+    values(): IterableIterator<TNode, BuiltinIteratorReturn>;
 
-    [Symbol.iterator](): IterableIterator<TNode>;
+    [Symbol.iterator](): IterableIterator<TNode, BuiltinIteratorReturn>;
 }
 
 interface HTMLCollectionBase {
-    [Symbol.iterator](): IterableIterator<Element>;
+    [Symbol.iterator](): IterableIterator<Element, BuiltinIteratorReturn>;
 }
 
 interface HTMLCollectionOf<T extends Element> {
-    [Symbol.iterator](): IterableIterator<T>;
+    [Symbol.iterator](): IterableIterator<T, BuiltinIteratorReturn>;
 }
 
 interface FormData {
     /**
      * Returns an array of key, value pairs for every entry in the list
      */
-    entries(): IterableIterator<[string, string | File]>;
+    entries(): IterableIterator<[string, string | File], BuiltinIteratorReturn>;
     /**
      * Returns a list of keys in the list
      */
-    keys(): IterableIterator<string>;
+    keys(): IterableIterator<string, BuiltinIteratorReturn>;
     /**
      * Returns a list of values in the list
      */
-    values(): IterableIterator<string | File>;
+    values(): IterableIterator<string | File, BuiltinIteratorReturn>;
 
-    [Symbol.iterator](): IterableIterator<string | File>;
+    [Symbol.iterator](): IterableIterator<string | File, BuiltinIteratorReturn>;
 }
 
 interface URLSearchParams {
     /**
      * Returns an array of key, value pairs for every entry in the search params
      */
-    entries(): IterableIterator<[string, string]>;
+    entries(): IterableIterator<[string, string], BuiltinIteratorReturn>;
     /**
      * Returns a list of keys in the search params
      */
-    keys(): IterableIterator<string>;
+    keys(): IterableIterator<string, BuiltinIteratorReturn>;
     /**
      * Returns a list of values in the search params
      */
-    values(): IterableIterator<string>;
+    values(): IterableIterator<string, BuiltinIteratorReturn>;
     /**
      * iterate over key/value pairs
      */
-    [Symbol.iterator](): IterableIterator<[string, string]>;
+    [Symbol.iterator](): IterableIterator<[string, string], BuiltinIteratorReturn>;
 }

src/lib/es2015.generator.d.ts

@@ -1,6 +1,6 @@
 /// <reference lib="es2015.iterable" />
 
-interface Generator<T = unknown, TReturn = any, TNext = unknown> extends Iterator<T, TReturn, TNext> {
+interface Generator<T = unknown, TReturn = any, TNext = any> 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>;