From 539d47c570796a8b36ed5e847509e254ea4bd392 Mon Sep 17 00:00:00 2001
From: lionel-rowe <lionel.rowe@gmail.com>
Date: Thu, 23 Nov 2023 15:50:52 +0800
Subject: [PATCH] Add BuiltInIterableIterator for built-in iterables with
 undefined return values

---
 src/lib/es2015.iterable.d.ts                  | 130 +++++++++---------
 src/lib/es2020.bigint.d.ts                    |  16 +--
 src/lib/es2020.string.d.ts                    |   2 +-
 src/lib/es2020.symbol.wellknown.d.ts          |   2 +-
 src/lib/es2022.intl.d.ts                      |   2 +-
 .../reference/YieldStarExpression4_es6.types  |   2 +-
 .../argumentsObjectIterator02_ES6.types       |   8 +-
 tests/baselines/reference/arrayFrom.types     |  12 +-
 .../reference/bigintWithLib.errors.txt        |   4 +-
 ...ructuredLateBoundNameHasCorrectTypes.types |   4 +-
 .../dissallowSymbolAsWeakType.errors.txt      |   8 +-
 ....asyncGenerators.classMethods.es2015.types |   4 +-
 ....asyncGenerators.classMethods.es2018.types |   4 +-
 ...ter.asyncGenerators.classMethods.es5.types |   4 +-
 ...nerators.functionDeclarations.es2015.types |   4 +-
 ...nerators.functionDeclarations.es2018.types |   4 +-
 ...cGenerators.functionDeclarations.es5.types |   4 +-
 ...enerators.functionExpressions.es2015.types |   4 +-
 ...enerators.functionExpressions.es2018.types |   4 +-
 ...ncGenerators.functionExpressions.es5.types |   4 +-
 ...nerators.objectLiteralMethods.es2015.types |   4 +-
 ...nerators.objectLiteralMethods.es2018.types |   4 +-
 ...cGenerators.objectLiteralMethods.es5.types |   4 +-
 tests/baselines/reference/for-of12.types      |   6 +-
 tests/baselines/reference/for-of13.types      |   6 +-
 tests/baselines/reference/for-of39.errors.txt |   4 +-
 .../generatorReturnTypeInference.types        |   2 +-
 ...eneratorReturnTypeInferenceNonStrict.types |   2 +-
 .../reference/generatorTypeCheck19.types      |   2 +-
 .../reference/generatorTypeCheck20.types      |   2 +-
 .../reference/generatorTypeCheck22.types      |   4 +-
 .../reference/generatorTypeCheck23.types      |   4 +-
 .../reference/generatorTypeCheck24.types      |   6 +-
 .../reference/generatorTypeCheck25.types      |   4 +-
 .../reference/generatorTypeCheck26.types      |   2 +-
 .../reference/generatorTypeCheck53.types      |   2 +-
 .../reference/generatorTypeCheck54.types      |   4 +-
 ...rtHelpersNoHelpersForAsyncGenerators.types |   2 +-
 ...indirectGlobalSymbolPartOfObjectType.types |   2 +-
 .../iterableArrayPattern28.errors.txt         |   4 +-
 ...ithAsClauseAndLateBoundProperty.errors.txt |   4 +-
 ...TypeWithAsClauseAndLateBoundProperty.types |   6 +-
 ...edTypeWithAsClauseAndLateBoundProperty2.js |  16 +--
 ...ypeWithAsClauseAndLateBoundProperty2.types |   6 +-
 ...eLibrary_NoErrorDuplicateLibOptions1.types |   6 +-
 ...eLibrary_NoErrorDuplicateLibOptions2.types |   6 +-
 ...dularizeLibrary_TargetES5UsingES6Lib.types |   6 +-
 ...dularizeLibrary_TargetES6UsingES6Lib.types |   6 +-
 ....asyncGenerators.classMethods.es2018.types |   2 +-
 ...nerators.functionDeclarations.es2018.types |   2 +-
 ...enerators.functionExpressions.es2018.types |   2 +-
 ...nerators.objectLiteralMethods.es2018.types |   2 +-
 .../reference/regexMatchAll-esnext.types      |   8 +-
 tests/baselines/reference/regexMatchAll.types |   8 +-
 .../baselines/reference/stringMatchAll.types  |  10 +-
 .../types.asyncGenerators.es2018.1.types      |  28 ++--
 .../types.asyncGenerators.es2018.2.types      |  12 +-
 .../yieldExpressionInControlFlow.types        |   8 +-
 .../yieldExpressionInnerCommentEmit.types     |   4 +-
 59 files changed, 222 insertions(+), 216 deletions(-)

diff --git a/src/lib/es2015.iterable.d.ts b/src/lib/es2015.iterable.d.ts
index d28b8381eec86..48e8dd0d4fd47 100644
--- a/src/lib/es2015.iterable.d.ts
+++ b/src/lib/es2015.iterable.d.ts
@@ -35,24 +35,30 @@ interface IterableIterator<T> extends Iterator<T> {
     [Symbol.iterator](): IterableIterator<T>;
 }
 
+interface BuiltInIterableIterator<T> {
+    // NOTE: 'next' is defined using a tuple to ensure we report the correct assignability errors in all places.
+    next(...args: [] | [undefined]): IteratorResult<T, undefined>;
+    [Symbol.iterator](): BuiltInIterableIterator<T>;
+}
+
 interface Array<T> {
     /** Iterator */
-    [Symbol.iterator](): IterableIterator<T>;
+    [Symbol.iterator](): BuiltInIterableIterator<T>;
 
     /**
      * Returns an iterable of key, value pairs for every entry in the array
      */
-    entries(): IterableIterator<[number, T]>;
+    entries(): BuiltInIterableIterator<[number, T]>;
 
     /**
      * Returns an iterable of keys in the array
      */
-    keys(): IterableIterator<number>;
+    keys(): BuiltInIterableIterator<number>;
 
     /**
      * Returns an iterable of values in the array
      */
-    values(): IterableIterator<T>;
+    values(): BuiltInIterableIterator<T>;
 }
 
 interface ArrayConstructor {
@@ -73,67 +79,67 @@ interface ArrayConstructor {
 
 interface ReadonlyArray<T> {
     /** Iterator of values in the array. */
-    [Symbol.iterator](): IterableIterator<T>;
+    [Symbol.iterator](): BuiltInIterableIterator<T>;
 
     /**
      * Returns an iterable of key, value pairs for every entry in the array
      */
-    entries(): IterableIterator<[number, T]>;
+    entries(): BuiltInIterableIterator<[number, T]>;
 
     /**
      * Returns an iterable of keys in the array
      */
-    keys(): IterableIterator<number>;
+    keys(): BuiltInIterableIterator<number>;
 
     /**
      * Returns an iterable of values in the array
      */
-    values(): IterableIterator<T>;
+    values(): BuiltInIterableIterator<T>;
 }
 
 interface IArguments {
     /** Iterator */
-    [Symbol.iterator](): IterableIterator<any>;
+    [Symbol.iterator](): BuiltInIterableIterator<any>;
 }
 
 interface Map<K, V> {
     /** Returns an iterable of entries in the map. */
-    [Symbol.iterator](): IterableIterator<[K, V]>;
+    [Symbol.iterator](): BuiltInIterableIterator<[K, V]>;
 
     /**
      * Returns an iterable of key, value pairs for every entry in the map.
      */
-    entries(): IterableIterator<[K, V]>;
+    entries(): BuiltInIterableIterator<[K, V]>;
 
     /**
      * Returns an iterable of keys in the map
      */
-    keys(): IterableIterator<K>;
+    keys(): BuiltInIterableIterator<K>;
 
     /**
      * Returns an iterable of values in the map
      */
-    values(): IterableIterator<V>;
+    values(): BuiltInIterableIterator<V>;
 }
 
 interface ReadonlyMap<K, V> {
     /** Returns an iterable of entries in the map. */
-    [Symbol.iterator](): IterableIterator<[K, V]>;
+    [Symbol.iterator](): BuiltInIterableIterator<[K, V]>;
 
     /**
      * Returns an iterable of key, value pairs for every entry in the map.
      */
-    entries(): IterableIterator<[K, V]>;
+    entries(): BuiltInIterableIterator<[K, V]>;
 
     /**
      * Returns an iterable of keys in the map
      */
-    keys(): IterableIterator<K>;
+    keys(): BuiltInIterableIterator<K>;
 
     /**
      * Returns an iterable of values in the map
      */
-    values(): IterableIterator<V>;
+    values(): BuiltInIterableIterator<V>;
 }
 
 interface MapConstructor {
@@ -149,40 +155,40 @@ interface WeakMapConstructor {
 
 interface Set<T> {
     /** Iterates over values in the set. */
-    [Symbol.iterator](): IterableIterator<T>;
+    [Symbol.iterator](): BuiltInIterableIterator<T>;
     /**
      * Returns an iterable of [v,v] pairs for every value `v` in the set.
      */
-    entries(): IterableIterator<[T, T]>;
+    entries(): BuiltInIterableIterator<[T, T]>;
     /**
      * Despite its name, returns an iterable of the values in the set.
      */
-    keys(): IterableIterator<T>;
+    keys(): BuiltInIterableIterator<T>;
 
     /**
      * Returns an iterable of values in the set.
      */
-    values(): IterableIterator<T>;
+    values(): BuiltInIterableIterator<T>;
 }
 
 interface ReadonlySet<T> {
     /** Iterates over values in the set. */
-    [Symbol.iterator](): IterableIterator<T>;
+    [Symbol.iterator](): BuiltInIterableIterator<T>;
 
     /**
      * Returns an iterable of [v,v] pairs for every value `v` in the set.
      */
-    entries(): IterableIterator<[T, T]>;
+    entries(): BuiltInIterableIterator<[T, T]>;
 
     /**
      * Despite its name, returns an iterable of the values in the set.
      */
-    keys(): IterableIterator<T>;
+    keys(): BuiltInIterableIterator<T>;
 
     /**
      * Returns an iterable of values in the set.
      */
-    values(): IterableIterator<T>;
+    values(): BuiltInIterableIterator<T>;
 }
 
 interface SetConstructor {
@@ -217,23 +223,23 @@ interface PromiseConstructor {
 
 interface String {
     /** Iterator */
-    [Symbol.iterator](): IterableIterator<string>;
+    [Symbol.iterator](): BuiltInIterableIterator<string>;
 }
 
 interface Int8Array {
-    [Symbol.iterator](): IterableIterator<number>;
+    [Symbol.iterator](): BuiltInIterableIterator<number>;
     /**
      * Returns an array of key, value pairs for every entry in the array
      */
-    entries(): IterableIterator<[number, number]>;
+    entries(): BuiltInIterableIterator<[number, number]>;
     /**
      * Returns an list of keys in the array
      */
-    keys(): IterableIterator<number>;
+    keys(): BuiltInIterableIterator<number>;
     /**
      * Returns an list of values in the array
      */
-    values(): IterableIterator<number>;
+    values(): BuiltInIterableIterator<number>;
 }
 
 interface Int8ArrayConstructor {
@@ -249,19 +255,19 @@ interface Int8ArrayConstructor {
 }
 
 interface Uint8Array {
-    [Symbol.iterator](): IterableIterator<number>;
+    [Symbol.iterator](): BuiltInIterableIterator<number>;
     /**
      * Returns an array of key, value pairs for every entry in the array
      */
-    entries(): IterableIterator<[number, number]>;
+    entries(): BuiltInIterableIterator<[number, number]>;
     /**
      * Returns an list of keys in the array
      */
-    keys(): IterableIterator<number>;
+    keys(): BuiltInIterableIterator<number>;
     /**
      * Returns an list of values in the array
      */
-    values(): IterableIterator<number>;
+    values(): BuiltInIterableIterator<number>;
 }
 
 interface Uint8ArrayConstructor {
@@ -277,21 +283,21 @@ interface Uint8ArrayConstructor {
 }
 
 interface Uint8ClampedArray {
-    [Symbol.iterator](): IterableIterator<number>;
+    [Symbol.iterator](): BuiltInIterableIterator<number>;
     /**
      * Returns an array of key, value pairs for every entry in the array
      */
-    entries(): IterableIterator<[number, number]>;
+    entries(): BuiltInIterableIterator<[number, number]>;
 
     /**
      * Returns an list of keys in the array
      */
-    keys(): IterableIterator<number>;
+    keys(): BuiltInIterableIterator<number>;
 
     /**
      * Returns an list of values in the array
      */
-    values(): IterableIterator<number>;
+    values(): BuiltInIterableIterator<number>;
 }
 
 interface Uint8ClampedArrayConstructor {
@@ -307,21 +313,21 @@ interface Uint8ClampedArrayConstructor {
 }
 
 interface Int16Array {
-    [Symbol.iterator](): IterableIterator<number>;
+    [Symbol.iterator](): BuiltInIterableIterator<number>;
     /**
      * Returns an array of key, value pairs for every entry in the array
      */
-    entries(): IterableIterator<[number, number]>;
+    entries(): BuiltInIterableIterator<[number, number]>;
 
     /**
      * Returns an list of keys in the array
      */
-    keys(): IterableIterator<number>;
+    keys(): BuiltInIterableIterator<number>;
 
     /**
      * Returns an list of values in the array
      */
-    values(): IterableIterator<number>;
+    values(): BuiltInIterableIterator<number>;
 }
 
 interface Int16ArrayConstructor {
@@ -337,19 +343,19 @@ interface Int16ArrayConstructor {
 }
 
 interface Uint16Array {
-    [Symbol.iterator](): IterableIterator<number>;
+    [Symbol.iterator](): BuiltInIterableIterator<number>;
     /**
      * Returns an array of key, value pairs for every entry in the array
      */
-    entries(): IterableIterator<[number, number]>;
+    entries(): BuiltInIterableIterator<[number, number]>;
     /**
      * Returns an list of keys in the array
      */
-    keys(): IterableIterator<number>;
+    keys(): BuiltInIterableIterator<number>;
     /**
      * Returns an list of values in the array
      */
-    values(): IterableIterator<number>;
+    values(): BuiltInIterableIterator<number>;
 }
 
 interface Uint16ArrayConstructor {
@@ -365,19 +371,19 @@ interface Uint16ArrayConstructor {
 }
 
 interface Int32Array {
-    [Symbol.iterator](): IterableIterator<number>;
+    [Symbol.iterator](): BuiltInIterableIterator<number>;
     /**
      * Returns an array of key, value pairs for every entry in the array
      */
-    entries(): IterableIterator<[number, number]>;
+    entries(): BuiltInIterableIterator<[number, number]>;
     /**
      * Returns an list of keys in the array
      */
-    keys(): IterableIterator<number>;
+    keys(): BuiltInIterableIterator<number>;
     /**
      * Returns an list of values in the array
      */
-    values(): IterableIterator<number>;
+    values(): BuiltInIterableIterator<number>;
 }
 
 interface Int32ArrayConstructor {
@@ -393,19 +399,19 @@ interface Int32ArrayConstructor {
 }
 
 interface Uint32Array {
-    [Symbol.iterator](): IterableIterator<number>;
+    [Symbol.iterator](): BuiltInIterableIterator<number>;
     /**
      * Returns an array of key, value pairs for every entry in the array
      */
-    entries(): IterableIterator<[number, number]>;
+    entries(): BuiltInIterableIterator<[number, number]>;
     /**
      * Returns an list of keys in the array
      */
-    keys(): IterableIterator<number>;
+    keys(): BuiltInIterableIterator<number>;
     /**
      * Returns an list of values in the array
      */
-    values(): IterableIterator<number>;
+    values(): BuiltInIterableIterator<number>;
 }
 
 interface Uint32ArrayConstructor {
@@ -421,19 +427,19 @@ interface Uint32ArrayConstructor {
 }
 
 interface Float32Array {
-    [Symbol.iterator](): IterableIterator<number>;
+    [Symbol.iterator](): BuiltInIterableIterator<number>;
     /**
      * Returns an array of key, value pairs for every entry in the array
      */
-    entries(): IterableIterator<[number, number]>;
+    entries(): BuiltInIterableIterator<[number, number]>;
     /**
      * Returns an list of keys in the array
      */
-    keys(): IterableIterator<number>;
+    keys(): BuiltInIterableIterator<number>;
     /**
      * Returns an list of values in the array
      */
-    values(): IterableIterator<number>;
+    values(): BuiltInIterableIterator<number>;
 }
 
 interface Float32ArrayConstructor {
@@ -449,19 +455,19 @@ interface Float32ArrayConstructor {
 }
 
 interface Float64Array {
-    [Symbol.iterator](): IterableIterator<number>;
+    [Symbol.iterator](): BuiltInIterableIterator<number>;
     /**
      * Returns an array of key, value pairs for every entry in the array
      */
-    entries(): IterableIterator<[number, number]>;
+    entries(): BuiltInIterableIterator<[number, number]>;
     /**
      * Returns an list of keys in the array
      */
-    keys(): IterableIterator<number>;
+    keys(): BuiltInIterableIterator<number>;
     /**
      * Returns an list of values in the array
      */
-    values(): IterableIterator<number>;
+    values(): BuiltInIterableIterator<number>;
 }
 
 interface Float64ArrayConstructor {
diff --git a/src/lib/es2020.bigint.d.ts b/src/lib/es2020.bigint.d.ts
index 597b3822792eb..55417e2dc8e84 100644
--- a/src/lib/es2020.bigint.d.ts
+++ b/src/lib/es2020.bigint.d.ts
@@ -153,7 +153,7 @@ interface BigInt64Array {
     copyWithin(target: number, start: number, end?: number): this;
 
     /** Yields index, value pairs for every entry in the array. */
-    entries(): IterableIterator<[number, bigint]>;
+    entries(): BuiltInIterableIterator<[number, bigint]>;
 
     /**
      * Determines whether all the members of an array satisfy the specified test.
@@ -238,7 +238,7 @@ interface BigInt64Array {
     join(separator?: string): string;
 
     /** Yields each index in the array. */
-    keys(): IterableIterator<number>;
+    keys(): BuiltInIterableIterator<number>;
 
     /**
      * Returns the index of the last occurrence of a value in an array.
@@ -360,9 +360,9 @@ interface BigInt64Array {
     valueOf(): BigInt64Array;
 
     /** Yields each value in the array. */
-    values(): IterableIterator<bigint>;
+    values(): BuiltInIterableIterator<bigint>;
 
-    [Symbol.iterator](): IterableIterator<bigint>;
+    [Symbol.iterator](): BuiltInIterableIterator<bigint>;
 
     readonly [Symbol.toStringTag]: "BigInt64Array";
 
@@ -425,7 +425,7 @@ interface BigUint64Array {
     copyWithin(target: number, start: number, end?: number): this;
 
     /** Yields index, value pairs for every entry in the array. */
-    entries(): IterableIterator<[number, bigint]>;
+    entries(): BuiltInIterableIterator<[number, bigint]>;
 
     /**
      * Determines whether all the members of an array satisfy the specified test.
@@ -510,7 +510,7 @@ interface BigUint64Array {
     join(separator?: string): string;
 
     /** Yields each index in the array. */
-    keys(): IterableIterator<number>;
+    keys(): BuiltInIterableIterator<number>;
 
     /**
      * Returns the index of the last occurrence of a value in an array.
@@ -632,9 +632,9 @@ interface BigUint64Array {
     valueOf(): BigUint64Array;
 
     /** Yields each value in the array. */
-    values(): IterableIterator<bigint>;
+    values(): BuiltInIterableIterator<bigint>;
 
-    [Symbol.iterator](): IterableIterator<bigint>;
+    [Symbol.iterator](): BuiltInIterableIterator<bigint>;
 
     readonly [Symbol.toStringTag]: "BigUint64Array";
 
diff --git a/src/lib/es2020.string.d.ts b/src/lib/es2020.string.d.ts
index 382bc75595e92..4efe9fcd4ae22 100644
--- a/src/lib/es2020.string.d.ts
+++ b/src/lib/es2020.string.d.ts
@@ -6,5 +6,5 @@ interface String {
      * containing the results of that search.
      * @param regexp A variable name or string literal containing the regular expression pattern and flags.
      */
-    matchAll(regexp: RegExp): IterableIterator<RegExpMatchArray>;
+    matchAll(regexp: RegExp): BuiltInIterableIterator<RegExpMatchArray>;
 }
diff --git a/src/lib/es2020.symbol.wellknown.d.ts b/src/lib/es2020.symbol.wellknown.d.ts
index 94a11768256c7..a5d2d1e079b10 100644
--- a/src/lib/es2020.symbol.wellknown.d.ts
+++ b/src/lib/es2020.symbol.wellknown.d.ts
@@ -15,5 +15,5 @@ interface RegExp {
      * containing the results of that search.
      * @param string A string to search within.
      */
-    [Symbol.matchAll](str: string): IterableIterator<RegExpMatchArray>;
+    [Symbol.matchAll](str: string): BuiltInIterableIterator<RegExpMatchArray>;
 }
diff --git a/src/lib/es2022.intl.d.ts b/src/lib/es2022.intl.d.ts
index 7ed03b05e07ca..7064872513037 100644
--- a/src/lib/es2022.intl.d.ts
+++ b/src/lib/es2022.intl.d.ts
@@ -37,7 +37,7 @@ declare namespace Intl {
         containing(codeUnitIndex?: number): SegmentData;
 
         /** Returns an iterator to iterate over the segments. */
-        [Symbol.iterator](): IterableIterator<SegmentData>;
+        [Symbol.iterator](): BuiltInIterableIterator<SegmentData>;
     }
 
     interface SegmentData {
diff --git a/tests/baselines/reference/YieldStarExpression4_es6.types b/tests/baselines/reference/YieldStarExpression4_es6.types
index 6ab7b6205fe6b..b6be82f0fbde5 100644
--- a/tests/baselines/reference/YieldStarExpression4_es6.types
+++ b/tests/baselines/reference/YieldStarExpression4_es6.types
@@ -5,6 +5,6 @@ function *g() {
 >g : () => Generator<any, void, undefined>
 
     yield * [];
->yield * [] : any
+>yield * [] : undefined
 >[] : undefined[]
 }
diff --git a/tests/baselines/reference/argumentsObjectIterator02_ES6.types b/tests/baselines/reference/argumentsObjectIterator02_ES6.types
index 28ea6a9c71106..e9df0cb6b1d77 100644
--- a/tests/baselines/reference/argumentsObjectIterator02_ES6.types
+++ b/tests/baselines/reference/argumentsObjectIterator02_ES6.types
@@ -8,8 +8,8 @@ function doubleAndReturnAsArray(x: number, y: number, z: number): [number, numbe
 >z : number
 
     let blah = arguments[Symbol.iterator];
->blah : () => IterableIterator<any>
->arguments[Symbol.iterator] : () => IterableIterator<any>
+>blah : () => BuiltInIterableIterator<any>
+>arguments[Symbol.iterator] : () => BuiltInIterableIterator<any>
 >arguments : IArguments
 >Symbol.iterator : unique symbol
 >Symbol : SymbolConstructor
@@ -21,8 +21,8 @@ function doubleAndReturnAsArray(x: number, y: number, z: number): [number, numbe
 
     for (let arg of blah()) {
 >arg : any
->blah() : IterableIterator<any>
->blah : () => IterableIterator<any>
+>blah() : BuiltInIterableIterator<any>
+>blah : () => BuiltInIterableIterator<any>
 
         result.push(arg + arg);
 >result.push(arg + arg) : number
diff --git a/tests/baselines/reference/arrayFrom.types b/tests/baselines/reference/arrayFrom.types
index dda3f91d2698f..04f7da5bef950 100644
--- a/tests/baselines/reference/arrayFrom.types
+++ b/tests/baselines/reference/arrayFrom.types
@@ -54,10 +54,10 @@ const result2: A[] = Array.from(inputA.values());
 >Array.from : { <T>(arrayLike: ArrayLike<T>): T[]; <T_1, U>(arrayLike: ArrayLike<T_1>, mapfn: (v: T_1, k: number) => U, thisArg?: any): U[]; <T_2>(iterable: Iterable<T_2> | ArrayLike<T_2>): T_2[]; <T_3, U_1>(iterable: Iterable<T_3> | ArrayLike<T_3>, mapfn: (v: T_3, k: number) => U_1, thisArg?: any): U_1[]; }
 >Array : ArrayConstructor
 >from : { <T>(arrayLike: ArrayLike<T>): T[]; <T_1, U>(arrayLike: ArrayLike<T_1>, mapfn: (v: T_1, k: number) => U, thisArg?: any): U[]; <T_2>(iterable: Iterable<T_2> | ArrayLike<T_2>): T_2[]; <T_3, U_1>(iterable: Iterable<T_3> | ArrayLike<T_3>, mapfn: (v: T_3, k: number) => U_1, thisArg?: any): U_1[]; }
->inputA.values() : IterableIterator<A>
->inputA.values : () => IterableIterator<A>
+>inputA.values() : BuiltInIterableIterator<A>
+>inputA.values : () => BuiltInIterableIterator<A>
 >inputA : A[]
->values : () => IterableIterator<A>
+>values : () => BuiltInIterableIterator<A>
 
 const result3: B[] = Array.from(inputA.values()); // expect error
 >result3 : B[]
@@ -65,10 +65,10 @@ const result3: B[] = Array.from(inputA.values()); // expect error
 >Array.from : { <T>(arrayLike: ArrayLike<T>): T[]; <T_1, U>(arrayLike: ArrayLike<T_1>, mapfn: (v: T_1, k: number) => U, thisArg?: any): U[]; <T_2>(iterable: Iterable<T_2> | ArrayLike<T_2>): T_2[]; <T_3, U_1>(iterable: Iterable<T_3> | ArrayLike<T_3>, mapfn: (v: T_3, k: number) => U_1, thisArg?: any): U_1[]; }
 >Array : ArrayConstructor
 >from : { <T>(arrayLike: ArrayLike<T>): T[]; <T_1, U>(arrayLike: ArrayLike<T_1>, mapfn: (v: T_1, k: number) => U, thisArg?: any): U[]; <T_2>(iterable: Iterable<T_2> | ArrayLike<T_2>): T_2[]; <T_3, U_1>(iterable: Iterable<T_3> | ArrayLike<T_3>, mapfn: (v: T_3, k: number) => U_1, thisArg?: any): U_1[]; }
->inputA.values() : IterableIterator<A>
->inputA.values : () => IterableIterator<A>
+>inputA.values() : BuiltInIterableIterator<A>
+>inputA.values : () => BuiltInIterableIterator<A>
 >inputA : A[]
->values : () => IterableIterator<A>
+>values : () => BuiltInIterableIterator<A>
 
 const result4: A[] = Array.from(inputB, ({ b }): A => ({ a: b }));
 >result4 : A[]
diff --git a/tests/baselines/reference/bigintWithLib.errors.txt b/tests/baselines/reference/bigintWithLib.errors.txt
index aa402ec0cba5c..478c72e8096ec 100644
--- a/tests/baselines/reference/bigintWithLib.errors.txt
+++ b/tests/baselines/reference/bigintWithLib.errors.txt
@@ -5,7 +5,7 @@ bigintWithLib.ts(19,33): error TS2769: No overload matches this call.
   Overload 2 of 3, '(array: Iterable<bigint>): BigInt64Array', gave the following error.
     Argument of type 'number[]' is not assignable to parameter of type 'Iterable<bigint>'.
       The types returned by '[Symbol.iterator]().next(...)' are incompatible between these types.
-        Type 'IteratorResult<number, any>' is not assignable to type 'IteratorResult<bigint, any>'.
+        Type 'IteratorResult<number, undefined>' is not assignable to type 'IteratorResult<bigint, any>'.
           Type 'IteratorYieldResult<number>' is not assignable to type 'IteratorResult<bigint, any>'.
             Type 'IteratorYieldResult<number>' is not assignable to type 'IteratorYieldResult<bigint>'.
               Type 'number' is not assignable to type 'bigint'.
@@ -54,7 +54,7 @@ bigintWithLib.ts(46,26): error TS2345: Argument of type 'number' is not assignab
 !!! error TS2769:   Overload 2 of 3, '(array: Iterable<bigint>): BigInt64Array', gave the following error.
 !!! error TS2769:     Argument of type 'number[]' is not assignable to parameter of type 'Iterable<bigint>'.
 !!! error TS2769:       The types returned by '[Symbol.iterator]().next(...)' are incompatible between these types.
-!!! error TS2769:         Type 'IteratorResult<number, any>' is not assignable to type 'IteratorResult<bigint, any>'.
+!!! error TS2769:         Type 'IteratorResult<number, undefined>' is not assignable to type 'IteratorResult<bigint, any>'.
 !!! error TS2769:           Type 'IteratorYieldResult<number>' is not assignable to type 'IteratorResult<bigint, any>'.
 !!! error TS2769:             Type 'IteratorYieldResult<number>' is not assignable to type 'IteratorYieldResult<bigint>'.
 !!! error TS2769:               Type 'number' is not assignable to type 'bigint'.
diff --git a/tests/baselines/reference/destructuredLateBoundNameHasCorrectTypes.types b/tests/baselines/reference/destructuredLateBoundNameHasCorrectTypes.types
index 35f40b8548fbc..4d6dc3ce6b735 100644
--- a/tests/baselines/reference/destructuredLateBoundNameHasCorrectTypes.types
+++ b/tests/baselines/reference/destructuredLateBoundNameHasCorrectTypes.types
@@ -5,12 +5,12 @@ let { [Symbol.iterator]: destructured } = [];
 >Symbol.iterator : unique symbol
 >Symbol : SymbolConstructor
 >iterator : unique symbol
->destructured : () => IterableIterator<undefined>
+>destructured : () => BuiltInIterableIterator<undefined>
 >[] : undefined[]
 
 void destructured;
 >void destructured : undefined
->destructured : () => IterableIterator<undefined>
+>destructured : () => BuiltInIterableIterator<undefined>
 
 const named = "prop";
 >named : "prop"
diff --git a/tests/baselines/reference/dissallowSymbolAsWeakType.errors.txt b/tests/baselines/reference/dissallowSymbolAsWeakType.errors.txt
index bb5a8b0daf840..a71188490579c 100644
--- a/tests/baselines/reference/dissallowSymbolAsWeakType.errors.txt
+++ b/tests/baselines/reference/dissallowSymbolAsWeakType.errors.txt
@@ -2,7 +2,7 @@ dissallowSymbolAsWeakType.ts(3,12): error TS2769: No overload matches this call.
   Overload 1 of 2, '(iterable: Iterable<object>): WeakSet<object>', gave the following error.
     Argument of type 'symbol[]' is not assignable to parameter of type 'Iterable<object>'.
       The types returned by '[Symbol.iterator]().next(...)' are incompatible between these types.
-        Type 'IteratorResult<symbol, any>' is not assignable to type 'IteratorResult<object, any>'.
+        Type 'IteratorResult<symbol, undefined>' is not assignable to type 'IteratorResult<object, any>'.
           Type 'IteratorYieldResult<symbol>' is not assignable to type 'IteratorResult<object, any>'.
             Type 'IteratorYieldResult<symbol>' is not assignable to type 'IteratorYieldResult<object>'.
               Type 'symbol' is not assignable to type 'object'.
@@ -15,7 +15,7 @@ dissallowSymbolAsWeakType.ts(8,12): error TS2769: No overload matches this call.
   Overload 1 of 2, '(iterable: Iterable<readonly [object, boolean]>): WeakMap<object, boolean>', gave the following error.
     Argument of type '[symbol, false][]' is not assignable to parameter of type 'Iterable<readonly [object, boolean]>'.
       The types returned by '[Symbol.iterator]().next(...)' are incompatible between these types.
-        Type 'IteratorResult<[symbol, false], any>' is not assignable to type 'IteratorResult<readonly [object, boolean], any>'.
+        Type 'IteratorResult<[symbol, false], undefined>' is not assignable to type 'IteratorResult<readonly [object, boolean], any>'.
           Type 'IteratorYieldResult<[symbol, false]>' is not assignable to type 'IteratorResult<readonly [object, boolean], any>'.
             Type 'IteratorYieldResult<[symbol, false]>' is not assignable to type 'IteratorYieldResult<readonly [object, boolean]>'.
               Type '[symbol, false]' is not assignable to type 'readonly [object, boolean]'.
@@ -41,7 +41,7 @@ dissallowSymbolAsWeakType.ts(19,14): error TS2345: Argument of type 'symbol' is
 !!! error TS2769:   Overload 1 of 2, '(iterable: Iterable<object>): WeakSet<object>', gave the following error.
 !!! error TS2769:     Argument of type 'symbol[]' is not assignable to parameter of type 'Iterable<object>'.
 !!! error TS2769:       The types returned by '[Symbol.iterator]().next(...)' are incompatible between these types.
-!!! error TS2769:         Type 'IteratorResult<symbol, any>' is not assignable to type 'IteratorResult<object, any>'.
+!!! error TS2769:         Type 'IteratorResult<symbol, undefined>' is not assignable to type 'IteratorResult<object, any>'.
 !!! error TS2769:           Type 'IteratorYieldResult<symbol>' is not assignable to type 'IteratorResult<object, any>'.
 !!! error TS2769:             Type 'IteratorYieldResult<symbol>' is not assignable to type 'IteratorYieldResult<object>'.
 !!! error TS2769:               Type 'symbol' is not assignable to type 'object'.
@@ -63,7 +63,7 @@ dissallowSymbolAsWeakType.ts(19,14): error TS2345: Argument of type 'symbol' is
 !!! error TS2769:   Overload 1 of 2, '(iterable: Iterable<readonly [object, boolean]>): WeakMap<object, boolean>', gave the following error.
 !!! error TS2769:     Argument of type '[symbol, false][]' is not assignable to parameter of type 'Iterable<readonly [object, boolean]>'.
 !!! error TS2769:       The types returned by '[Symbol.iterator]().next(...)' are incompatible between these types.
-!!! error TS2769:         Type 'IteratorResult<[symbol, false], any>' is not assignable to type 'IteratorResult<readonly [object, boolean], any>'.
+!!! error TS2769:         Type 'IteratorResult<[symbol, false], undefined>' is not assignable to type 'IteratorResult<readonly [object, boolean], any>'.
 !!! error TS2769:           Type 'IteratorYieldResult<[symbol, false]>' is not assignable to type 'IteratorResult<readonly [object, boolean], any>'.
 !!! error TS2769:             Type 'IteratorYieldResult<[symbol, false]>' is not assignable to type 'IteratorYieldResult<readonly [object, boolean]>'.
 !!! error TS2769:               Type '[symbol, false]' is not assignable to type 'readonly [object, boolean]'.
diff --git a/tests/baselines/reference/emitter.asyncGenerators.classMethods.es2015.types b/tests/baselines/reference/emitter.asyncGenerators.classMethods.es2015.types
index d2afa4c32af15..baeec57e5c949 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.classMethods.es2015.types
+++ b/tests/baselines/reference/emitter.asyncGenerators.classMethods.es2015.types
@@ -41,8 +41,8 @@ class C4 {
 >f : () => AsyncGenerator<number, void, undefined>
 
         const x = yield* [1];
->x : any
->yield* [1] : any
+>x : undefined
+>yield* [1] : undefined
 >[1] : number[]
 >1 : 1
     }
diff --git a/tests/baselines/reference/emitter.asyncGenerators.classMethods.es2018.types b/tests/baselines/reference/emitter.asyncGenerators.classMethods.es2018.types
index 28de01dedacc6..35f2112918702 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.classMethods.es2018.types
+++ b/tests/baselines/reference/emitter.asyncGenerators.classMethods.es2018.types
@@ -41,8 +41,8 @@ class C4 {
 >f : () => AsyncGenerator<number, void, undefined>
 
         const x = yield* [1];
->x : any
->yield* [1] : any
+>x : undefined
+>yield* [1] : undefined
 >[1] : number[]
 >1 : 1
     }
diff --git a/tests/baselines/reference/emitter.asyncGenerators.classMethods.es5.types b/tests/baselines/reference/emitter.asyncGenerators.classMethods.es5.types
index 5035ae32a101c..9700e1bc4e0b4 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.classMethods.es5.types
+++ b/tests/baselines/reference/emitter.asyncGenerators.classMethods.es5.types
@@ -41,8 +41,8 @@ class C4 {
 >f : () => AsyncGenerator<number, void, undefined>
 
         const x = yield* [1];
->x : any
->yield* [1] : any
+>x : undefined
+>yield* [1] : undefined
 >[1] : number[]
 >1 : 1
     }
diff --git a/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es2015.types b/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es2015.types
index 4ee98563c28d0..48f8dea6f827c 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es2015.types
+++ b/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es2015.types
@@ -26,8 +26,8 @@ async function * f4() {
 >f4 : () => AsyncGenerator<number, void, undefined>
 
     const x = yield* [1];
->x : any
->yield* [1] : any
+>x : undefined
+>yield* [1] : undefined
 >[1] : number[]
 >1 : 1
 }
diff --git a/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es2018.types b/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es2018.types
index 33c358b70a958..516aba8940f3a 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es2018.types
+++ b/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es2018.types
@@ -26,8 +26,8 @@ async function * f4() {
 >f4 : () => AsyncGenerator<number, void, undefined>
 
     const x = yield* [1];
->x : any
->yield* [1] : any
+>x : undefined
+>yield* [1] : undefined
 >[1] : number[]
 >1 : 1
 }
diff --git a/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es5.types b/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es5.types
index c007f6f625b8f..6a5645d957c59 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es5.types
+++ b/tests/baselines/reference/emitter.asyncGenerators.functionDeclarations.es5.types
@@ -26,8 +26,8 @@ async function * f4() {
 >f4 : () => AsyncGenerator<number, void, undefined>
 
     const x = yield* [1];
->x : any
->yield* [1] : any
+>x : undefined
+>yield* [1] : undefined
 >[1] : number[]
 >1 : 1
 }
diff --git a/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es2015.types b/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es2015.types
index 08dce0ec514ce..778c85e26ed55 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es2015.types
+++ b/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es2015.types
@@ -30,8 +30,8 @@ const f4 = async function * () {
 >async function * () {    const x = yield* [1];} : () => AsyncGenerator<number, void, undefined>
 
     const x = yield* [1];
->x : any
->yield* [1] : any
+>x : undefined
+>yield* [1] : undefined
 >[1] : number[]
 >1 : 1
 }
diff --git a/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es2018.types b/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es2018.types
index b39f6121770c8..ddc1642253775 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es2018.types
+++ b/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es2018.types
@@ -30,8 +30,8 @@ const f4 = async function * () {
 >async function * () {    const x = yield* [1];} : () => AsyncGenerator<number, void, undefined>
 
     const x = yield* [1];
->x : any
->yield* [1] : any
+>x : undefined
+>yield* [1] : undefined
 >[1] : number[]
 >1 : 1
 }
diff --git a/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es5.types b/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es5.types
index 9f31455cb0827..71ecb9028ae85 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es5.types
+++ b/tests/baselines/reference/emitter.asyncGenerators.functionExpressions.es5.types
@@ -30,8 +30,8 @@ const f4 = async function * () {
 >async function * () {    const x = yield* [1];} : () => AsyncGenerator<number, void, undefined>
 
     const x = yield* [1];
->x : any
->yield* [1] : any
+>x : undefined
+>yield* [1] : undefined
 >[1] : number[]
 >1 : 1
 }
diff --git a/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es2015.types b/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es2015.types
index 791e0696c6bb2..9a246dcd105eb 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es2015.types
+++ b/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es2015.types
@@ -45,8 +45,8 @@ const o4 = {
 >f : () => AsyncGenerator<number, void, undefined>
 
         const x = yield* [1];
->x : any
->yield* [1] : any
+>x : undefined
+>yield* [1] : undefined
 >[1] : number[]
 >1 : 1
     }
diff --git a/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es2018.types b/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es2018.types
index 52aebe0074393..39b3c34125b0c 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es2018.types
+++ b/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es2018.types
@@ -45,8 +45,8 @@ const o4 = {
 >f : () => AsyncGenerator<number, void, undefined>
 
         const x = yield* [1];
->x : any
->yield* [1] : any
+>x : undefined
+>yield* [1] : undefined
 >[1] : number[]
 >1 : 1
     }
diff --git a/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es5.types b/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es5.types
index 05afc7251b23e..415f7cb3ea12c 100644
--- a/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es5.types
+++ b/tests/baselines/reference/emitter.asyncGenerators.objectLiteralMethods.es5.types
@@ -45,8 +45,8 @@ const o4 = {
 >f : () => AsyncGenerator<number, void, undefined>
 
         const x = yield* [1];
->x : any
->yield* [1] : any
+>x : undefined
+>yield* [1] : undefined
 >[1] : number[]
 >1 : 1
     }
diff --git a/tests/baselines/reference/for-of12.types b/tests/baselines/reference/for-of12.types
index d9d75ee7fec4e..565c4f6cb1a1b 100644
--- a/tests/baselines/reference/for-of12.types
+++ b/tests/baselines/reference/for-of12.types
@@ -6,10 +6,10 @@ var v: string;
 
 for (v of [0, ""].values()) { }
 >v : string
->[0, ""].values() : IterableIterator<string | number>
->[0, ""].values : () => IterableIterator<string | number>
+>[0, ""].values() : BuiltInIterableIterator<string | number>
+>[0, ""].values : () => BuiltInIterableIterator<string | number>
 >[0, ""] : (string | number)[]
 >0 : 0
 >"" : ""
->values : () => IterableIterator<string | number>
+>values : () => BuiltInIterableIterator<string | number>
 
diff --git a/tests/baselines/reference/for-of13.types b/tests/baselines/reference/for-of13.types
index bf2d5ef7f5b9f..5ced7b8684998 100644
--- a/tests/baselines/reference/for-of13.types
+++ b/tests/baselines/reference/for-of13.types
@@ -6,9 +6,9 @@ var v: string;
 
 for (v of [""].values()) { }
 >v : string
->[""].values() : IterableIterator<string>
->[""].values : () => IterableIterator<string>
+>[""].values() : BuiltInIterableIterator<string>
+>[""].values : () => BuiltInIterableIterator<string>
 >[""] : string[]
 >"" : ""
->values : () => IterableIterator<string>
+>values : () => BuiltInIterableIterator<string>
 
diff --git a/tests/baselines/reference/for-of39.errors.txt b/tests/baselines/reference/for-of39.errors.txt
index 9f36eb6bd4585..05aa3710c4260 100644
--- a/tests/baselines/reference/for-of39.errors.txt
+++ b/tests/baselines/reference/for-of39.errors.txt
@@ -2,7 +2,7 @@ for-of39.ts(1,11): error TS2769: No overload matches this call.
   Overload 1 of 4, '(iterable?: Iterable<readonly [string, boolean]>): Map<string, boolean>', gave the following error.
     Argument of type '([string, number] | [string, true])[]' is not assignable to parameter of type 'Iterable<readonly [string, boolean]>'.
       The types returned by '[Symbol.iterator]().next(...)' are incompatible between these types.
-        Type 'IteratorResult<[string, number] | [string, true], any>' is not assignable to type 'IteratorResult<readonly [string, boolean], any>'.
+        Type 'IteratorResult<[string, number] | [string, true], undefined>' is not assignable to type 'IteratorResult<readonly [string, boolean], any>'.
           Type 'IteratorYieldResult<[string, number] | [string, true]>' is not assignable to type 'IteratorResult<readonly [string, boolean], any>'.
             Type 'IteratorYieldResult<[string, number] | [string, true]>' is not assignable to type 'IteratorYieldResult<readonly [string, boolean]>'.
               Type '[string, number] | [string, true]' is not assignable to type 'readonly [string, boolean]'.
@@ -20,7 +20,7 @@ for-of39.ts(1,11): error TS2769: No overload matches this call.
 !!! error TS2769:   Overload 1 of 4, '(iterable?: Iterable<readonly [string, boolean]>): Map<string, boolean>', gave the following error.
 !!! error TS2769:     Argument of type '([string, number] | [string, true])[]' is not assignable to parameter of type 'Iterable<readonly [string, boolean]>'.
 !!! error TS2769:       The types returned by '[Symbol.iterator]().next(...)' are incompatible between these types.
-!!! error TS2769:         Type 'IteratorResult<[string, number] | [string, true], any>' is not assignable to type 'IteratorResult<readonly [string, boolean], any>'.
+!!! error TS2769:         Type 'IteratorResult<[string, number] | [string, true], undefined>' is not assignable to type 'IteratorResult<readonly [string, boolean], any>'.
 !!! error TS2769:           Type 'IteratorYieldResult<[string, number] | [string, true]>' is not assignable to type 'IteratorResult<readonly [string, boolean], any>'.
 !!! error TS2769:             Type 'IteratorYieldResult<[string, number] | [string, true]>' is not assignable to type 'IteratorYieldResult<readonly [string, boolean]>'.
 !!! error TS2769:               Type '[string, number] | [string, true]' is not assignable to type 'readonly [string, boolean]'.
diff --git a/tests/baselines/reference/generatorReturnTypeInference.types b/tests/baselines/reference/generatorReturnTypeInference.types
index fef5e85f57e4e..069154e78731f 100644
--- a/tests/baselines/reference/generatorReturnTypeInference.types
+++ b/tests/baselines/reference/generatorReturnTypeInference.types
@@ -34,7 +34,7 @@ function* g003() { // Generator<never, void, undefined>
 >g003 : () => Generator<never, void, undefined>
 
     yield* [];
->yield* [] : any
+>yield* [] : undefined
 >[] : never[]
 }
 
diff --git a/tests/baselines/reference/generatorReturnTypeInferenceNonStrict.types b/tests/baselines/reference/generatorReturnTypeInferenceNonStrict.types
index 1a4ccee855436..810d7472ae8c3 100644
--- a/tests/baselines/reference/generatorReturnTypeInferenceNonStrict.types
+++ b/tests/baselines/reference/generatorReturnTypeInferenceNonStrict.types
@@ -36,7 +36,7 @@ function* g003() { // Generator<any (implicit), void, unknown>
     // NOTE: In strict mode, `[]` produces the type `never[]`.
     //       In non-strict mode, `[]` produces the type `undefined[]` which is implicitly any.
     yield* [];
->yield* [] : any
+>yield* [] : undefined
 >[] : undefined[]
 }
 
diff --git a/tests/baselines/reference/generatorTypeCheck19.types b/tests/baselines/reference/generatorTypeCheck19.types
index 1ba4c4d2a5b44..9b69b9f7a40df 100644
--- a/tests/baselines/reference/generatorTypeCheck19.types
+++ b/tests/baselines/reference/generatorTypeCheck19.types
@@ -17,7 +17,7 @@ function* g(): IterableIterator<Foo> {
 >yield : undefined
 
     yield * [new Bar];
->yield * [new Bar] : any
+>yield * [new Bar] : undefined
 >[new Bar] : Bar[]
 >new Bar : Bar
 >Bar : typeof Bar
diff --git a/tests/baselines/reference/generatorTypeCheck20.types b/tests/baselines/reference/generatorTypeCheck20.types
index 62f0620990fb2..463bea37da233 100644
--- a/tests/baselines/reference/generatorTypeCheck20.types
+++ b/tests/baselines/reference/generatorTypeCheck20.types
@@ -16,7 +16,7 @@ function* g(): IterableIterator<Foo> {
 >yield : undefined
 
     yield * [new Baz];
->yield * [new Baz] : any
+>yield * [new Baz] : undefined
 >[new Baz] : Baz[]
 >new Baz : Baz
 >Baz : typeof Baz
diff --git a/tests/baselines/reference/generatorTypeCheck22.types b/tests/baselines/reference/generatorTypeCheck22.types
index 8db577d0039cc..e63be6d92188d 100644
--- a/tests/baselines/reference/generatorTypeCheck22.types
+++ b/tests/baselines/reference/generatorTypeCheck22.types
@@ -31,13 +31,13 @@ function* g3() {
 >Baz : typeof Baz
 
     yield *[new Bar];
->yield *[new Bar] : any
+>yield *[new Bar] : undefined
 >[new Bar] : Bar[]
 >new Bar : Bar
 >Bar : typeof Bar
 
     yield *[new Baz];
->yield *[new Baz] : any
+>yield *[new Baz] : undefined
 >[new Baz] : Baz[]
 >new Baz : Baz
 >Baz : typeof Baz
diff --git a/tests/baselines/reference/generatorTypeCheck23.types b/tests/baselines/reference/generatorTypeCheck23.types
index 30a25445fa745..851b6730f7f9f 100644
--- a/tests/baselines/reference/generatorTypeCheck23.types
+++ b/tests/baselines/reference/generatorTypeCheck23.types
@@ -36,13 +36,13 @@ function* g3() {
 >Baz : typeof Baz
 
     yield *[new Bar];
->yield *[new Bar] : any
+>yield *[new Bar] : undefined
 >[new Bar] : Bar[]
 >new Bar : Bar
 >Bar : typeof Bar
 
     yield *[new Baz];
->yield *[new Baz] : any
+>yield *[new Baz] : undefined
 >[new Baz] : Baz[]
 >new Baz : Baz
 >Baz : typeof Baz
diff --git a/tests/baselines/reference/generatorTypeCheck24.types b/tests/baselines/reference/generatorTypeCheck24.types
index 438db9562e055..8bfc4eaa7ca08 100644
--- a/tests/baselines/reference/generatorTypeCheck24.types
+++ b/tests/baselines/reference/generatorTypeCheck24.types
@@ -21,7 +21,7 @@ function* g3() {
 >yield : any
 
     yield * [new Foo];
->yield * [new Foo] : any
+>yield * [new Foo] : undefined
 >[new Foo] : Foo[]
 >new Foo : Foo
 >Foo : typeof Foo
@@ -37,13 +37,13 @@ function* g3() {
 >Baz : typeof Baz
 
     yield *[new Bar];
->yield *[new Bar] : any
+>yield *[new Bar] : undefined
 >[new Bar] : Bar[]
 >new Bar : Bar
 >Bar : typeof Bar
 
     yield *[new Baz];
->yield *[new Baz] : any
+>yield *[new Baz] : undefined
 >[new Baz] : Baz[]
 >new Baz : Baz
 >Baz : typeof Baz
diff --git a/tests/baselines/reference/generatorTypeCheck25.types b/tests/baselines/reference/generatorTypeCheck25.types
index 5542432c60ee0..007585e9e2848 100644
--- a/tests/baselines/reference/generatorTypeCheck25.types
+++ b/tests/baselines/reference/generatorTypeCheck25.types
@@ -32,13 +32,13 @@ var g3: () => Iterable<Foo> = function* () {
 >Baz : typeof Baz
 
     yield *[new Bar];
->yield *[new Bar] : any
+>yield *[new Bar] : undefined
 >[new Bar] : Bar[]
 >new Bar : Bar
 >Bar : typeof Bar
 
     yield *[new Baz];
->yield *[new Baz] : any
+>yield *[new Baz] : undefined
 >[new Baz] : Baz[]
 >new Baz : Baz
 >Baz : typeof Baz
diff --git a/tests/baselines/reference/generatorTypeCheck26.types b/tests/baselines/reference/generatorTypeCheck26.types
index 57a7fcf694d51..a97faf50b7c30 100644
--- a/tests/baselines/reference/generatorTypeCheck26.types
+++ b/tests/baselines/reference/generatorTypeCheck26.types
@@ -14,7 +14,7 @@ function* g(): IterableIterator<(x: string) => number> {
 >length : number
 
     yield *[x => x.length];
->yield *[x => x.length] : any
+>yield *[x => x.length] : undefined
 >[x => x.length] : ((x: string) => number)[]
 >x => x.length : (x: string) => number
 >x : string
diff --git a/tests/baselines/reference/generatorTypeCheck53.types b/tests/baselines/reference/generatorTypeCheck53.types
index 060a677db7334..d1c2bbec8bfa4 100644
--- a/tests/baselines/reference/generatorTypeCheck53.types
+++ b/tests/baselines/reference/generatorTypeCheck53.types
@@ -18,7 +18,7 @@ function* g() {
 >Foo : typeof Foo
 
     yield* [new Baz];
->yield* [new Baz] : any
+>yield* [new Baz] : undefined
 >[new Baz] : Baz[]
 >new Baz : Baz
 >Baz : typeof Baz
diff --git a/tests/baselines/reference/generatorTypeCheck54.types b/tests/baselines/reference/generatorTypeCheck54.types
index e37a8d8dfd44c..f04f25b8529e1 100644
--- a/tests/baselines/reference/generatorTypeCheck54.types
+++ b/tests/baselines/reference/generatorTypeCheck54.types
@@ -13,13 +13,13 @@ function* g() {
 >g : () => Generator<Foo | Baz, void, undefined>
 
     yield* [new Foo];
->yield* [new Foo] : any
+>yield* [new Foo] : undefined
 >[new Foo] : Foo[]
 >new Foo : Foo
 >Foo : typeof Foo
 
     yield* [new Baz];
->yield* [new Baz] : any
+>yield* [new Baz] : undefined
 >[new Baz] : Baz[]
 >new Baz : Baz
 >Baz : typeof Baz
diff --git a/tests/baselines/reference/importHelpersNoHelpersForAsyncGenerators.types b/tests/baselines/reference/importHelpersNoHelpersForAsyncGenerators.types
index 68e6fab174ffe..979bdedc4c1c3 100644
--- a/tests/baselines/reference/importHelpersNoHelpersForAsyncGenerators.types
+++ b/tests/baselines/reference/importHelpersNoHelpersForAsyncGenerators.types
@@ -13,7 +13,7 @@ export async function * f() {
 >2 : 2
 
     yield* [3];
->yield* [3] : any
+>yield* [3] : undefined
 >[3] : number[]
 >3 : 3
 }
diff --git a/tests/baselines/reference/indirectGlobalSymbolPartOfObjectType.types b/tests/baselines/reference/indirectGlobalSymbolPartOfObjectType.types
index fda5e3866855f..0e0d442155321 100644
--- a/tests/baselines/reference/indirectGlobalSymbolPartOfObjectType.types
+++ b/tests/baselines/reference/indirectGlobalSymbolPartOfObjectType.types
@@ -9,7 +9,7 @@ const Symbol = globalThis.Symbol;
 >Symbol : SymbolConstructor
 
 [][Symbol.iterator];
->[][Symbol.iterator] : () => IterableIterator<undefined>
+>[][Symbol.iterator] : () => BuiltInIterableIterator<undefined>
 >[] : undefined[]
 >Symbol.iterator : unique symbol
 >Symbol : SymbolConstructor
diff --git a/tests/baselines/reference/iterableArrayPattern28.errors.txt b/tests/baselines/reference/iterableArrayPattern28.errors.txt
index 70bab6d9c7d0d..64ed24539485d 100644
--- a/tests/baselines/reference/iterableArrayPattern28.errors.txt
+++ b/tests/baselines/reference/iterableArrayPattern28.errors.txt
@@ -2,7 +2,7 @@ iterableArrayPattern28.ts(2,24): error TS2769: No overload matches this call.
   Overload 1 of 4, '(iterable?: Iterable<readonly [string, number]>): Map<string, number>', gave the following error.
     Argument of type '([string, number] | [string, boolean])[]' is not assignable to parameter of type 'Iterable<readonly [string, number]>'.
       The types returned by '[Symbol.iterator]().next(...)' are incompatible between these types.
-        Type 'IteratorResult<[string, number] | [string, boolean], any>' is not assignable to type 'IteratorResult<readonly [string, number], any>'.
+        Type 'IteratorResult<[string, number] | [string, boolean], undefined>' is not assignable to type 'IteratorResult<readonly [string, number], any>'.
           Type 'IteratorYieldResult<[string, number] | [string, boolean]>' is not assignable to type 'IteratorResult<readonly [string, number], any>'.
             Type 'IteratorYieldResult<[string, number] | [string, boolean]>' is not assignable to type 'IteratorYieldResult<readonly [string, number]>'.
               Type '[string, number] | [string, boolean]' is not assignable to type 'readonly [string, number]'.
@@ -21,7 +21,7 @@ iterableArrayPattern28.ts(2,24): error TS2769: No overload matches this call.
 !!! error TS2769:   Overload 1 of 4, '(iterable?: Iterable<readonly [string, number]>): Map<string, number>', gave the following error.
 !!! error TS2769:     Argument of type '([string, number] | [string, boolean])[]' is not assignable to parameter of type 'Iterable<readonly [string, number]>'.
 !!! error TS2769:       The types returned by '[Symbol.iterator]().next(...)' are incompatible between these types.
-!!! error TS2769:         Type 'IteratorResult<[string, number] | [string, boolean], any>' is not assignable to type 'IteratorResult<readonly [string, number], any>'.
+!!! error TS2769:         Type 'IteratorResult<[string, number] | [string, boolean], undefined>' is not assignable to type 'IteratorResult<readonly [string, number], any>'.
 !!! error TS2769:           Type 'IteratorYieldResult<[string, number] | [string, boolean]>' is not assignable to type 'IteratorResult<readonly [string, number], any>'.
 !!! error TS2769:             Type 'IteratorYieldResult<[string, number] | [string, boolean]>' is not assignable to type 'IteratorYieldResult<readonly [string, number]>'.
 !!! error TS2769:               Type '[string, number] | [string, boolean]' is not assignable to type 'readonly [string, number]'.
diff --git a/tests/baselines/reference/mappedTypeWithAsClauseAndLateBoundProperty.errors.txt b/tests/baselines/reference/mappedTypeWithAsClauseAndLateBoundProperty.errors.txt
index 6dac97e6c4f8e..ab31e1d4e2294 100644
--- a/tests/baselines/reference/mappedTypeWithAsClauseAndLateBoundProperty.errors.txt
+++ b/tests/baselines/reference/mappedTypeWithAsClauseAndLateBoundProperty.errors.txt
@@ -1,4 +1,4 @@
-mappedTypeWithAsClauseAndLateBoundProperty.ts(3,1): error TS2741: Property 'length' is missing in type '{ [x: number]: number; toString: () => string; toLocaleString: () => string; pop: () => number; push: (...items: number[]) => number; concat: { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }; join: (separator?: string) => string; reverse: () => number[]; shift: () => number; slice: (start?: number, end?: number) => number[]; sort: (compareFn?: (a: number, b: number) => number) => number[]; splice: { (start: number, deleteCount?: number): number[]; (start: number, deleteCount: number, ...items: number[]): number[]; }; unshift: (...items: number[]) => number; indexOf: (searchElement: number, fromIndex?: number) => number; lastIndexOf: (searchElement: number, fromIndex?: number) => number; every: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): this is S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): boolean; }; some: (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any) => boolean; forEach: (callbackfn: (value: number, index: number, array: number[]) => void, thisArg?: any) => void; map: <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]; filter: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): number[]; }; 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; }; reduceRight: { (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; }; find: { <S extends number>(predicate: (value: number, index: number, obj: number[]) => value is S, thisArg?: any): S; (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any): number; }; findIndex: (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any) => number; fill: (value: number, start?: number, end?: number) => number[]; copyWithin: (target: number, start: number, end?: number) => number[]; entries: () => IterableIterator<[number, number]>; keys: () => IterableIterator<number>; values: () => IterableIterator<number>; includes: (searchElement: number, fromIndex?: number) => boolean; flatMap: <U, This = undefined>(callback: (this: This, value: number, index: number, array: number[]) => U | readonly U[], thisArg?: This) => U[]; flat: <A, D extends number = 1>(this: A, depth?: D) => FlatArray<A, D>[]; [Symbol.iterator]: () => IterableIterator<number>; readonly [Symbol.unscopables]: { [x: number]: boolean; length?: boolean; toString?: boolean; toLocaleString?: boolean; pop?: boolean; push?: boolean; concat?: boolean; join?: boolean; reverse?: boolean; shift?: boolean; slice?: boolean; sort?: boolean; splice?: boolean; unshift?: boolean; indexOf?: boolean; lastIndexOf?: boolean; every?: boolean; some?: boolean; forEach?: boolean; map?: boolean; filter?: boolean; reduce?: boolean; reduceRight?: boolean; find?: boolean; findIndex?: boolean; fill?: boolean; copyWithin?: boolean; entries?: boolean; keys?: boolean; values?: boolean; includes?: boolean; flatMap?: boolean; flat?: boolean; [Symbol.iterator]?: boolean; readonly [Symbol.unscopables]?: boolean; }; }' but required in type 'number[]'.
+mappedTypeWithAsClauseAndLateBoundProperty.ts(3,1): error TS2741: Property 'length' is missing in type '{ [x: number]: number; toString: () => string; toLocaleString: () => string; pop: () => number; push: (...items: number[]) => number; concat: { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }; join: (separator?: string) => string; reverse: () => number[]; shift: () => number; slice: (start?: number, end?: number) => number[]; sort: (compareFn?: (a: number, b: number) => number) => number[]; splice: { (start: number, deleteCount?: number): number[]; (start: number, deleteCount: number, ...items: number[]): number[]; }; unshift: (...items: number[]) => number; indexOf: (searchElement: number, fromIndex?: number) => number; lastIndexOf: (searchElement: number, fromIndex?: number) => number; every: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): this is S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): boolean; }; some: (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any) => boolean; forEach: (callbackfn: (value: number, index: number, array: number[]) => void, thisArg?: any) => void; map: <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]; filter: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): number[]; }; 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; }; reduceRight: { (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; }; find: { <S extends number>(predicate: (value: number, index: number, obj: number[]) => value is S, thisArg?: any): S; (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any): number; }; findIndex: (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any) => number; fill: (value: number, start?: number, end?: number) => number[]; copyWithin: (target: number, start: number, end?: number) => number[]; entries: () => BuiltInIterableIterator<[number, number]>; keys: () => BuiltInIterableIterator<number>; values: () => BuiltInIterableIterator<number>; includes: (searchElement: number, fromIndex?: number) => boolean; flatMap: <U, This = undefined>(callback: (this: This, value: number, index: number, array: number[]) => U | readonly U[], thisArg?: This) => U[]; flat: <A, D extends number = 1>(this: A, depth?: D) => FlatArray<A, D>[]; [Symbol.iterator]: () => BuiltInIterableIterator<number>; readonly [Symbol.unscopables]: { [x: number]: boolean; length?: boolean; toString?: boolean; toLocaleString?: boolean; pop?: boolean; push?: boolean; concat?: boolean; join?: boolean; reverse?: boolean; shift?: boolean; slice?: boolean; sort?: boolean; splice?: boolean; unshift?: boolean; indexOf?: boolean; lastIndexOf?: boolean; every?: boolean; some?: boolean; forEach?: boolean; map?: boolean; filter?: boolean; reduce?: boolean; reduceRight?: boolean; find?: boolean; findIndex?: boolean; fill?: boolean; copyWithin?: boolean; entries?: boolean; keys?: boolean; values?: boolean; includes?: boolean; flatMap?: boolean; flat?: boolean; [Symbol.iterator]?: boolean; readonly [Symbol.unscopables]?: boolean; }; }' but required in type 'number[]'.
 
 
 ==== mappedTypeWithAsClauseAndLateBoundProperty.ts (1 errors) ====
@@ -6,6 +6,6 @@ mappedTypeWithAsClauseAndLateBoundProperty.ts(3,1): error TS2741: Property 'leng
     declare let src2: { [K in keyof number[] as Exclude<K, "length">]: (number[])[K] };
     tgt2 = src2; // Should error
     ~~~~
-!!! error TS2741: Property 'length' is missing in type '{ [x: number]: number; toString: () => string; toLocaleString: () => string; pop: () => number; push: (...items: number[]) => number; concat: { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }; join: (separator?: string) => string; reverse: () => number[]; shift: () => number; slice: (start?: number, end?: number) => number[]; sort: (compareFn?: (a: number, b: number) => number) => number[]; splice: { (start: number, deleteCount?: number): number[]; (start: number, deleteCount: number, ...items: number[]): number[]; }; unshift: (...items: number[]) => number; indexOf: (searchElement: number, fromIndex?: number) => number; lastIndexOf: (searchElement: number, fromIndex?: number) => number; every: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): this is S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): boolean; }; some: (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any) => boolean; forEach: (callbackfn: (value: number, index: number, array: number[]) => void, thisArg?: any) => void; map: <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]; filter: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): number[]; }; 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; }; reduceRight: { (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; }; find: { <S extends number>(predicate: (value: number, index: number, obj: number[]) => value is S, thisArg?: any): S; (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any): number; }; findIndex: (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any) => number; fill: (value: number, start?: number, end?: number) => number[]; copyWithin: (target: number, start: number, end?: number) => number[]; entries: () => IterableIterator<[number, number]>; keys: () => IterableIterator<number>; values: () => IterableIterator<number>; includes: (searchElement: number, fromIndex?: number) => boolean; flatMap: <U, This = undefined>(callback: (this: This, value: number, index: number, array: number[]) => U | readonly U[], thisArg?: This) => U[]; flat: <A, D extends number = 1>(this: A, depth?: D) => FlatArray<A, D>[]; [Symbol.iterator]: () => IterableIterator<number>; readonly [Symbol.unscopables]: { [x: number]: boolean; length?: boolean; toString?: boolean; toLocaleString?: boolean; pop?: boolean; push?: boolean; concat?: boolean; join?: boolean; reverse?: boolean; shift?: boolean; slice?: boolean; sort?: boolean; splice?: boolean; unshift?: boolean; indexOf?: boolean; lastIndexOf?: boolean; every?: boolean; some?: boolean; forEach?: boolean; map?: boolean; filter?: boolean; reduce?: boolean; reduceRight?: boolean; find?: boolean; findIndex?: boolean; fill?: boolean; copyWithin?: boolean; entries?: boolean; keys?: boolean; values?: boolean; includes?: boolean; flatMap?: boolean; flat?: boolean; [Symbol.iterator]?: boolean; readonly [Symbol.unscopables]?: boolean; }; }' but required in type 'number[]'.
+!!! error TS2741: Property 'length' is missing in type '{ [x: number]: number; toString: () => string; toLocaleString: () => string; pop: () => number; push: (...items: number[]) => number; concat: { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }; join: (separator?: string) => string; reverse: () => number[]; shift: () => number; slice: (start?: number, end?: number) => number[]; sort: (compareFn?: (a: number, b: number) => number) => number[]; splice: { (start: number, deleteCount?: number): number[]; (start: number, deleteCount: number, ...items: number[]): number[]; }; unshift: (...items: number[]) => number; indexOf: (searchElement: number, fromIndex?: number) => number; lastIndexOf: (searchElement: number, fromIndex?: number) => number; every: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): this is S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): boolean; }; some: (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any) => boolean; forEach: (callbackfn: (value: number, index: number, array: number[]) => void, thisArg?: any) => void; map: <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]; filter: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): number[]; }; 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; }; reduceRight: { (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; }; find: { <S extends number>(predicate: (value: number, index: number, obj: number[]) => value is S, thisArg?: any): S; (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any): number; }; findIndex: (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any) => number; fill: (value: number, start?: number, end?: number) => number[]; copyWithin: (target: number, start: number, end?: number) => number[]; entries: () => BuiltInIterableIterator<[number, number]>; keys: () => BuiltInIterableIterator<number>; values: () => BuiltInIterableIterator<number>; includes: (searchElement: number, fromIndex?: number) => boolean; flatMap: <U, This = undefined>(callback: (this: This, value: number, index: number, array: number[]) => U | readonly U[], thisArg?: This) => U[]; flat: <A, D extends number = 1>(this: A, depth?: D) => FlatArray<A, D>[]; [Symbol.iterator]: () => BuiltInIterableIterator<number>; readonly [Symbol.unscopables]: { [x: number]: boolean; length?: boolean; toString?: boolean; toLocaleString?: boolean; pop?: boolean; push?: boolean; concat?: boolean; join?: boolean; reverse?: boolean; shift?: boolean; slice?: boolean; sort?: boolean; splice?: boolean; unshift?: boolean; indexOf?: boolean; lastIndexOf?: boolean; every?: boolean; some?: boolean; forEach?: boolean; map?: boolean; filter?: boolean; reduce?: boolean; reduceRight?: boolean; find?: boolean; findIndex?: boolean; fill?: boolean; copyWithin?: boolean; entries?: boolean; keys?: boolean; values?: boolean; includes?: boolean; flatMap?: boolean; flat?: boolean; [Symbol.iterator]?: boolean; readonly [Symbol.unscopables]?: boolean; }; }' but required in type 'number[]'.
 !!! related TS2728 lib.es5.d.ts:--:--: 'length' is declared here.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/mappedTypeWithAsClauseAndLateBoundProperty.types b/tests/baselines/reference/mappedTypeWithAsClauseAndLateBoundProperty.types
index 4d9bf2b86fb35..56d9da812dcd5 100644
--- a/tests/baselines/reference/mappedTypeWithAsClauseAndLateBoundProperty.types
+++ b/tests/baselines/reference/mappedTypeWithAsClauseAndLateBoundProperty.types
@@ -5,10 +5,10 @@ declare let tgt2: number[];
 >tgt2 : number[]
 
 declare let src2: { [K in keyof number[] as Exclude<K, "length">]: (number[])[K] };
->src2 : { [x: number]: number; toString: () => string; toLocaleString: () => string; pop: () => number; push: (...items: number[]) => number; concat: { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }; join: (separator?: string) => string; reverse: () => number[]; shift: () => number; slice: (start?: number, end?: number) => number[]; sort: (compareFn?: (a: number, b: number) => number) => number[]; splice: { (start: number, deleteCount?: number): number[]; (start: number, deleteCount: number, ...items: number[]): number[]; }; unshift: (...items: number[]) => number; indexOf: (searchElement: number, fromIndex?: number) => number; lastIndexOf: (searchElement: number, fromIndex?: number) => number; every: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): this is S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): boolean; }; some: (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any) => boolean; forEach: (callbackfn: (value: number, index: number, array: number[]) => void, thisArg?: any) => void; map: <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]; filter: { <S_1 extends number>(predicate: (value: number, index: number, array: number[]) => value is S_1, thisArg?: any): S_1[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): number[]; }; 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_1>(callbackfn: (previousValue: U_1, currentValue: number, currentIndex: number, array: number[]) => U_1, initialValue: U_1): U_1; }; reduceRight: { (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_2>(callbackfn: (previousValue: U_2, currentValue: number, currentIndex: number, array: number[]) => U_2, initialValue: U_2): U_2; }; find: { <S_2 extends number>(predicate: (value: number, index: number, obj: number[]) => value is S_2, thisArg?: any): S_2; (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any): number; }; findIndex: (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any) => number; fill: (value: number, start?: number, end?: number) => number[]; copyWithin: (target: number, start: number, end?: number) => number[]; entries: () => IterableIterator<[number, number]>; keys: () => IterableIterator<number>; values: () => IterableIterator<number>; includes: (searchElement: number, fromIndex?: number) => boolean; flatMap: <U_3, This = undefined>(callback: (this: This, value: number, index: number, array: number[]) => U_3 | readonly U_3[], thisArg?: This) => U_3[]; flat: <A, D extends number = 1>(this: A, depth?: D) => FlatArray<A, D>[]; [Symbol.iterator]: () => IterableIterator<number>; readonly [Symbol.unscopables]: { [x: number]: boolean; length?: boolean; toString?: boolean; toLocaleString?: boolean; pop?: boolean; push?: boolean; concat?: boolean; join?: boolean; reverse?: boolean; shift?: boolean; slice?: boolean; sort?: boolean; splice?: boolean; unshift?: boolean; indexOf?: boolean; lastIndexOf?: boolean; every?: boolean; some?: boolean; forEach?: boolean; map?: boolean; filter?: boolean; reduce?: boolean; reduceRight?: boolean; find?: boolean; findIndex?: boolean; fill?: boolean; copyWithin?: boolean; entries?: boolean; keys?: boolean; values?: boolean; includes?: boolean; flatMap?: boolean; flat?: boolean; [Symbol.iterator]?: boolean; readonly [Symbol.unscopables]?: boolean; }; }
+>src2 : { [x: number]: number; toString: () => string; toLocaleString: () => string; pop: () => number; push: (...items: number[]) => number; concat: { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }; join: (separator?: string) => string; reverse: () => number[]; shift: () => number; slice: (start?: number, end?: number) => number[]; sort: (compareFn?: (a: number, b: number) => number) => number[]; splice: { (start: number, deleteCount?: number): number[]; (start: number, deleteCount: number, ...items: number[]): number[]; }; unshift: (...items: number[]) => number; indexOf: (searchElement: number, fromIndex?: number) => number; lastIndexOf: (searchElement: number, fromIndex?: number) => number; every: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): this is S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): boolean; }; some: (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any) => boolean; forEach: (callbackfn: (value: number, index: number, array: number[]) => void, thisArg?: any) => void; map: <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]; filter: { <S_1 extends number>(predicate: (value: number, index: number, array: number[]) => value is S_1, thisArg?: any): S_1[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): number[]; }; 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_1>(callbackfn: (previousValue: U_1, currentValue: number, currentIndex: number, array: number[]) => U_1, initialValue: U_1): U_1; }; reduceRight: { (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_2>(callbackfn: (previousValue: U_2, currentValue: number, currentIndex: number, array: number[]) => U_2, initialValue: U_2): U_2; }; find: { <S_2 extends number>(predicate: (value: number, index: number, obj: number[]) => value is S_2, thisArg?: any): S_2; (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any): number; }; findIndex: (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any) => number; fill: (value: number, start?: number, end?: number) => number[]; copyWithin: (target: number, start: number, end?: number) => number[]; entries: () => BuiltInIterableIterator<[number, number]>; keys: () => BuiltInIterableIterator<number>; values: () => BuiltInIterableIterator<number>; includes: (searchElement: number, fromIndex?: number) => boolean; flatMap: <U_3, This = undefined>(callback: (this: This, value: number, index: number, array: number[]) => U_3 | readonly U_3[], thisArg?: This) => U_3[]; flat: <A, D extends number = 1>(this: A, depth?: D) => FlatArray<A, D>[]; [Symbol.iterator]: () => BuiltInIterableIterator<number>; readonly [Symbol.unscopables]: { [x: number]: boolean; length?: boolean; toString?: boolean; toLocaleString?: boolean; pop?: boolean; push?: boolean; concat?: boolean; join?: boolean; reverse?: boolean; shift?: boolean; slice?: boolean; sort?: boolean; splice?: boolean; unshift?: boolean; indexOf?: boolean; lastIndexOf?: boolean; every?: boolean; some?: boolean; forEach?: boolean; map?: boolean; filter?: boolean; reduce?: boolean; reduceRight?: boolean; find?: boolean; findIndex?: boolean; fill?: boolean; copyWithin?: boolean; entries?: boolean; keys?: boolean; values?: boolean; includes?: boolean; flatMap?: boolean; flat?: boolean; [Symbol.iterator]?: boolean; readonly [Symbol.unscopables]?: boolean; }; }
 
 tgt2 = src2; // Should error
->tgt2 = src2 : { [x: number]: number; toString: () => string; toLocaleString: () => string; pop: () => number; push: (...items: number[]) => number; concat: { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }; join: (separator?: string) => string; reverse: () => number[]; shift: () => number; slice: (start?: number, end?: number) => number[]; sort: (compareFn?: (a: number, b: number) => number) => number[]; splice: { (start: number, deleteCount?: number): number[]; (start: number, deleteCount: number, ...items: number[]): number[]; }; unshift: (...items: number[]) => number; indexOf: (searchElement: number, fromIndex?: number) => number; lastIndexOf: (searchElement: number, fromIndex?: number) => number; every: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): this is S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): boolean; }; some: (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any) => boolean; forEach: (callbackfn: (value: number, index: number, array: number[]) => void, thisArg?: any) => void; map: <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]; filter: { <S_1 extends number>(predicate: (value: number, index: number, array: number[]) => value is S_1, thisArg?: any): S_1[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): number[]; }; 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_1>(callbackfn: (previousValue: U_1, currentValue: number, currentIndex: number, array: number[]) => U_1, initialValue: U_1): U_1; }; reduceRight: { (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_2>(callbackfn: (previousValue: U_2, currentValue: number, currentIndex: number, array: number[]) => U_2, initialValue: U_2): U_2; }; find: { <S_2 extends number>(predicate: (value: number, index: number, obj: number[]) => value is S_2, thisArg?: any): S_2; (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any): number; }; findIndex: (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any) => number; fill: (value: number, start?: number, end?: number) => number[]; copyWithin: (target: number, start: number, end?: number) => number[]; entries: () => IterableIterator<[number, number]>; keys: () => IterableIterator<number>; values: () => IterableIterator<number>; includes: (searchElement: number, fromIndex?: number) => boolean; flatMap: <U_3, This = undefined>(callback: (this: This, value: number, index: number, array: number[]) => U_3 | readonly U_3[], thisArg?: This) => U_3[]; flat: <A, D extends number = 1>(this: A, depth?: D) => FlatArray<A, D>[]; [Symbol.iterator]: () => IterableIterator<number>; readonly [Symbol.unscopables]: { [x: number]: boolean; length?: boolean; toString?: boolean; toLocaleString?: boolean; pop?: boolean; push?: boolean; concat?: boolean; join?: boolean; reverse?: boolean; shift?: boolean; slice?: boolean; sort?: boolean; splice?: boolean; unshift?: boolean; indexOf?: boolean; lastIndexOf?: boolean; every?: boolean; some?: boolean; forEach?: boolean; map?: boolean; filter?: boolean; reduce?: boolean; reduceRight?: boolean; find?: boolean; findIndex?: boolean; fill?: boolean; copyWithin?: boolean; entries?: boolean; keys?: boolean; values?: boolean; includes?: boolean; flatMap?: boolean; flat?: boolean; [Symbol.iterator]?: boolean; readonly [Symbol.unscopables]?: boolean; }; }
+>tgt2 = src2 : { [x: number]: number; toString: () => string; toLocaleString: () => string; pop: () => number; push: (...items: number[]) => number; concat: { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }; join: (separator?: string) => string; reverse: () => number[]; shift: () => number; slice: (start?: number, end?: number) => number[]; sort: (compareFn?: (a: number, b: number) => number) => number[]; splice: { (start: number, deleteCount?: number): number[]; (start: number, deleteCount: number, ...items: number[]): number[]; }; unshift: (...items: number[]) => number; indexOf: (searchElement: number, fromIndex?: number) => number; lastIndexOf: (searchElement: number, fromIndex?: number) => number; every: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): this is S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): boolean; }; some: (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any) => boolean; forEach: (callbackfn: (value: number, index: number, array: number[]) => void, thisArg?: any) => void; map: <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]; filter: { <S_1 extends number>(predicate: (value: number, index: number, array: number[]) => value is S_1, thisArg?: any): S_1[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): number[]; }; 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_1>(callbackfn: (previousValue: U_1, currentValue: number, currentIndex: number, array: number[]) => U_1, initialValue: U_1): U_1; }; reduceRight: { (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_2>(callbackfn: (previousValue: U_2, currentValue: number, currentIndex: number, array: number[]) => U_2, initialValue: U_2): U_2; }; find: { <S_2 extends number>(predicate: (value: number, index: number, obj: number[]) => value is S_2, thisArg?: any): S_2; (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any): number; }; findIndex: (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any) => number; fill: (value: number, start?: number, end?: number) => number[]; copyWithin: (target: number, start: number, end?: number) => number[]; entries: () => BuiltInIterableIterator<[number, number]>; keys: () => BuiltInIterableIterator<number>; values: () => BuiltInIterableIterator<number>; includes: (searchElement: number, fromIndex?: number) => boolean; flatMap: <U_3, This = undefined>(callback: (this: This, value: number, index: number, array: number[]) => U_3 | readonly U_3[], thisArg?: This) => U_3[]; flat: <A, D extends number = 1>(this: A, depth?: D) => FlatArray<A, D>[]; [Symbol.iterator]: () => BuiltInIterableIterator<number>; readonly [Symbol.unscopables]: { [x: number]: boolean; length?: boolean; toString?: boolean; toLocaleString?: boolean; pop?: boolean; push?: boolean; concat?: boolean; join?: boolean; reverse?: boolean; shift?: boolean; slice?: boolean; sort?: boolean; splice?: boolean; unshift?: boolean; indexOf?: boolean; lastIndexOf?: boolean; every?: boolean; some?: boolean; forEach?: boolean; map?: boolean; filter?: boolean; reduce?: boolean; reduceRight?: boolean; find?: boolean; findIndex?: boolean; fill?: boolean; copyWithin?: boolean; entries?: boolean; keys?: boolean; values?: boolean; includes?: boolean; flatMap?: boolean; flat?: boolean; [Symbol.iterator]?: boolean; readonly [Symbol.unscopables]?: boolean; }; }
 >tgt2 : number[]
->src2 : { [x: number]: number; toString: () => string; toLocaleString: () => string; pop: () => number; push: (...items: number[]) => number; concat: { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }; join: (separator?: string) => string; reverse: () => number[]; shift: () => number; slice: (start?: number, end?: number) => number[]; sort: (compareFn?: (a: number, b: number) => number) => number[]; splice: { (start: number, deleteCount?: number): number[]; (start: number, deleteCount: number, ...items: number[]): number[]; }; unshift: (...items: number[]) => number; indexOf: (searchElement: number, fromIndex?: number) => number; lastIndexOf: (searchElement: number, fromIndex?: number) => number; every: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): this is S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): boolean; }; some: (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any) => boolean; forEach: (callbackfn: (value: number, index: number, array: number[]) => void, thisArg?: any) => void; map: <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]; filter: { <S_1 extends number>(predicate: (value: number, index: number, array: number[]) => value is S_1, thisArg?: any): S_1[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): number[]; }; 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_1>(callbackfn: (previousValue: U_1, currentValue: number, currentIndex: number, array: number[]) => U_1, initialValue: U_1): U_1; }; reduceRight: { (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_2>(callbackfn: (previousValue: U_2, currentValue: number, currentIndex: number, array: number[]) => U_2, initialValue: U_2): U_2; }; find: { <S_2 extends number>(predicate: (value: number, index: number, obj: number[]) => value is S_2, thisArg?: any): S_2; (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any): number; }; findIndex: (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any) => number; fill: (value: number, start?: number, end?: number) => number[]; copyWithin: (target: number, start: number, end?: number) => number[]; entries: () => IterableIterator<[number, number]>; keys: () => IterableIterator<number>; values: () => IterableIterator<number>; includes: (searchElement: number, fromIndex?: number) => boolean; flatMap: <U_3, This = undefined>(callback: (this: This, value: number, index: number, array: number[]) => U_3 | readonly U_3[], thisArg?: This) => U_3[]; flat: <A, D extends number = 1>(this: A, depth?: D) => FlatArray<A, D>[]; [Symbol.iterator]: () => IterableIterator<number>; readonly [Symbol.unscopables]: { [x: number]: boolean; length?: boolean; toString?: boolean; toLocaleString?: boolean; pop?: boolean; push?: boolean; concat?: boolean; join?: boolean; reverse?: boolean; shift?: boolean; slice?: boolean; sort?: boolean; splice?: boolean; unshift?: boolean; indexOf?: boolean; lastIndexOf?: boolean; every?: boolean; some?: boolean; forEach?: boolean; map?: boolean; filter?: boolean; reduce?: boolean; reduceRight?: boolean; find?: boolean; findIndex?: boolean; fill?: boolean; copyWithin?: boolean; entries?: boolean; keys?: boolean; values?: boolean; includes?: boolean; flatMap?: boolean; flat?: boolean; [Symbol.iterator]?: boolean; readonly [Symbol.unscopables]?: boolean; }; }
+>src2 : { [x: number]: number; toString: () => string; toLocaleString: () => string; pop: () => number; push: (...items: number[]) => number; concat: { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }; join: (separator?: string) => string; reverse: () => number[]; shift: () => number; slice: (start?: number, end?: number) => number[]; sort: (compareFn?: (a: number, b: number) => number) => number[]; splice: { (start: number, deleteCount?: number): number[]; (start: number, deleteCount: number, ...items: number[]): number[]; }; unshift: (...items: number[]) => number; indexOf: (searchElement: number, fromIndex?: number) => number; lastIndexOf: (searchElement: number, fromIndex?: number) => number; every: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): this is S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): boolean; }; some: (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any) => boolean; forEach: (callbackfn: (value: number, index: number, array: number[]) => void, thisArg?: any) => void; map: <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]; filter: { <S_1 extends number>(predicate: (value: number, index: number, array: number[]) => value is S_1, thisArg?: any): S_1[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): number[]; }; 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_1>(callbackfn: (previousValue: U_1, currentValue: number, currentIndex: number, array: number[]) => U_1, initialValue: U_1): U_1; }; reduceRight: { (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_2>(callbackfn: (previousValue: U_2, currentValue: number, currentIndex: number, array: number[]) => U_2, initialValue: U_2): U_2; }; find: { <S_2 extends number>(predicate: (value: number, index: number, obj: number[]) => value is S_2, thisArg?: any): S_2; (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any): number; }; findIndex: (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any) => number; fill: (value: number, start?: number, end?: number) => number[]; copyWithin: (target: number, start: number, end?: number) => number[]; entries: () => BuiltInIterableIterator<[number, number]>; keys: () => BuiltInIterableIterator<number>; values: () => BuiltInIterableIterator<number>; includes: (searchElement: number, fromIndex?: number) => boolean; flatMap: <U_3, This = undefined>(callback: (this: This, value: number, index: number, array: number[]) => U_3 | readonly U_3[], thisArg?: This) => U_3[]; flat: <A, D extends number = 1>(this: A, depth?: D) => FlatArray<A, D>[]; [Symbol.iterator]: () => BuiltInIterableIterator<number>; readonly [Symbol.unscopables]: { [x: number]: boolean; length?: boolean; toString?: boolean; toLocaleString?: boolean; pop?: boolean; push?: boolean; concat?: boolean; join?: boolean; reverse?: boolean; shift?: boolean; slice?: boolean; sort?: boolean; splice?: boolean; unshift?: boolean; indexOf?: boolean; lastIndexOf?: boolean; every?: boolean; some?: boolean; forEach?: boolean; map?: boolean; filter?: boolean; reduce?: boolean; reduceRight?: boolean; find?: boolean; findIndex?: boolean; fill?: boolean; copyWithin?: boolean; entries?: boolean; keys?: boolean; values?: boolean; includes?: boolean; flatMap?: boolean; flat?: boolean; [Symbol.iterator]?: boolean; readonly [Symbol.unscopables]?: boolean; }; }
 
diff --git a/tests/baselines/reference/mappedTypeWithAsClauseAndLateBoundProperty2.js b/tests/baselines/reference/mappedTypeWithAsClauseAndLateBoundProperty2.js
index 9bfc37222f9a8..70983cd9bfcd3 100644
--- a/tests/baselines/reference/mappedTypeWithAsClauseAndLateBoundProperty2.js
+++ b/tests/baselines/reference/mappedTypeWithAsClauseAndLateBoundProperty2.js
@@ -59,13 +59,13 @@ export declare const thing: {
     findIndex: (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any) => number;
     fill: (value: number, start?: number, end?: number) => number[];
     copyWithin: (target: number, start: number, end?: number) => number[];
-    entries: () => IterableIterator<[number, number]>;
-    keys: () => IterableIterator<number>;
-    values: () => IterableIterator<number>;
+    entries: () => BuiltInIterableIterator<[number, number]>;
+    keys: () => BuiltInIterableIterator<number>;
+    values: () => BuiltInIterableIterator<number>;
     includes: (searchElement: number, fromIndex?: number) => boolean;
     flatMap: <U_3, This = undefined>(callback: (this: This, value: number, index: number, array: number[]) => U_3 | readonly U_3[], thisArg?: This) => U_3[];
     flat: <A, D extends number = 1>(this: A, depth?: D) => FlatArray<A, D>[];
-    [Symbol.iterator]: () => IterableIterator<number>;
+    [Symbol.iterator]: () => BuiltInIterableIterator<number>;
     readonly [Symbol.unscopables]: {
         [x: number]: boolean;
         length?: boolean;
@@ -165,13 +165,13 @@ mappedTypeWithAsClauseAndLateBoundProperty2.d.ts(24,118): error TS2526: A 'this'
         findIndex: (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any) => number;
         fill: (value: number, start?: number, end?: number) => number[];
         copyWithin: (target: number, start: number, end?: number) => number[];
-        entries: () => IterableIterator<[number, number]>;
-        keys: () => IterableIterator<number>;
-        values: () => IterableIterator<number>;
+        entries: () => BuiltInIterableIterator<[number, number]>;
+        keys: () => BuiltInIterableIterator<number>;
+        values: () => BuiltInIterableIterator<number>;
         includes: (searchElement: number, fromIndex?: number) => boolean;
         flatMap: <U_3, This = undefined>(callback: (this: This, value: number, index: number, array: number[]) => U_3 | readonly U_3[], thisArg?: This) => U_3[];
         flat: <A, D extends number = 1>(this: A, depth?: D) => FlatArray<A, D>[];
-        [Symbol.iterator]: () => IterableIterator<number>;
+        [Symbol.iterator]: () => BuiltInIterableIterator<number>;
         readonly [Symbol.unscopables]: {
             [x: number]: boolean;
             length?: boolean;
diff --git a/tests/baselines/reference/mappedTypeWithAsClauseAndLateBoundProperty2.types b/tests/baselines/reference/mappedTypeWithAsClauseAndLateBoundProperty2.types
index 0938c9402a3d6..cd6a0441796c0 100644
--- a/tests/baselines/reference/mappedTypeWithAsClauseAndLateBoundProperty2.types
+++ b/tests/baselines/reference/mappedTypeWithAsClauseAndLateBoundProperty2.types
@@ -2,8 +2,8 @@
 
 === mappedTypeWithAsClauseAndLateBoundProperty2.ts ===
 export const thing = (null as any as { [K in keyof number[] as Exclude<K, "length">]: (number[])[K] });
->thing : { [x: number]: number; toString: () => string; toLocaleString: () => string; pop: () => number; push: (...items: number[]) => number; concat: { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }; join: (separator?: string) => string; reverse: () => number[]; shift: () => number; slice: (start?: number, end?: number) => number[]; sort: (compareFn?: (a: number, b: number) => number) => number[]; splice: { (start: number, deleteCount?: number): number[]; (start: number, deleteCount: number, ...items: number[]): number[]; }; unshift: (...items: number[]) => number; indexOf: (searchElement: number, fromIndex?: number) => number; lastIndexOf: (searchElement: number, fromIndex?: number) => number; every: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): this is S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): boolean; }; some: (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any) => boolean; forEach: (callbackfn: (value: number, index: number, array: number[]) => void, thisArg?: any) => void; map: <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]; filter: { <S_1 extends number>(predicate: (value: number, index: number, array: number[]) => value is S_1, thisArg?: any): S_1[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): number[]; }; 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_1>(callbackfn: (previousValue: U_1, currentValue: number, currentIndex: number, array: number[]) => U_1, initialValue: U_1): U_1; }; reduceRight: { (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_2>(callbackfn: (previousValue: U_2, currentValue: number, currentIndex: number, array: number[]) => U_2, initialValue: U_2): U_2; }; find: { <S_2 extends number>(predicate: (value: number, index: number, obj: number[]) => value is S_2, thisArg?: any): S_2; (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any): number; }; findIndex: (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any) => number; fill: (value: number, start?: number, end?: number) => number[]; copyWithin: (target: number, start: number, end?: number) => number[]; entries: () => IterableIterator<[number, number]>; keys: () => IterableIterator<number>; values: () => IterableIterator<number>; includes: (searchElement: number, fromIndex?: number) => boolean; flatMap: <U_3, This = undefined>(callback: (this: This, value: number, index: number, array: number[]) => U_3 | readonly U_3[], thisArg?: This) => U_3[]; flat: <A, D extends number = 1>(this: A, depth?: D) => FlatArray<A, D>[]; [Symbol.iterator]: () => IterableIterator<number>; readonly [Symbol.unscopables]: { [x: number]: boolean; length?: boolean; toString?: boolean; toLocaleString?: boolean; pop?: boolean; push?: boolean; concat?: boolean; join?: boolean; reverse?: boolean; shift?: boolean; slice?: boolean; sort?: boolean; splice?: boolean; unshift?: boolean; indexOf?: boolean; lastIndexOf?: boolean; every?: boolean; some?: boolean; forEach?: boolean; map?: boolean; filter?: boolean; reduce?: boolean; reduceRight?: boolean; find?: boolean; findIndex?: boolean; fill?: boolean; copyWithin?: boolean; entries?: boolean; keys?: boolean; values?: boolean; includes?: boolean; flatMap?: boolean; flat?: boolean; [Symbol.iterator]?: boolean; readonly [Symbol.unscopables]?: boolean; }; }
->(null as any as { [K in keyof number[] as Exclude<K, "length">]: (number[])[K] }) : { [x: number]: number; toString: () => string; toLocaleString: () => string; pop: () => number; push: (...items: number[]) => number; concat: { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }; join: (separator?: string) => string; reverse: () => number[]; shift: () => number; slice: (start?: number, end?: number) => number[]; sort: (compareFn?: (a: number, b: number) => number) => number[]; splice: { (start: number, deleteCount?: number): number[]; (start: number, deleteCount: number, ...items: number[]): number[]; }; unshift: (...items: number[]) => number; indexOf: (searchElement: number, fromIndex?: number) => number; lastIndexOf: (searchElement: number, fromIndex?: number) => number; every: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): this is S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): boolean; }; some: (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any) => boolean; forEach: (callbackfn: (value: number, index: number, array: number[]) => void, thisArg?: any) => void; map: <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]; filter: { <S_1 extends number>(predicate: (value: number, index: number, array: number[]) => value is S_1, thisArg?: any): S_1[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): number[]; }; 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_1>(callbackfn: (previousValue: U_1, currentValue: number, currentIndex: number, array: number[]) => U_1, initialValue: U_1): U_1; }; reduceRight: { (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_2>(callbackfn: (previousValue: U_2, currentValue: number, currentIndex: number, array: number[]) => U_2, initialValue: U_2): U_2; }; find: { <S_2 extends number>(predicate: (value: number, index: number, obj: number[]) => value is S_2, thisArg?: any): S_2; (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any): number; }; findIndex: (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any) => number; fill: (value: number, start?: number, end?: number) => number[]; copyWithin: (target: number, start: number, end?: number) => number[]; entries: () => IterableIterator<[number, number]>; keys: () => IterableIterator<number>; values: () => IterableIterator<number>; includes: (searchElement: number, fromIndex?: number) => boolean; flatMap: <U_3, This = undefined>(callback: (this: This, value: number, index: number, array: number[]) => U_3 | readonly U_3[], thisArg?: This) => U_3[]; flat: <A, D extends number = 1>(this: A, depth?: D) => FlatArray<A, D>[]; [Symbol.iterator]: () => IterableIterator<number>; readonly [Symbol.unscopables]: { [x: number]: boolean; length?: boolean; toString?: boolean; toLocaleString?: boolean; pop?: boolean; push?: boolean; concat?: boolean; join?: boolean; reverse?: boolean; shift?: boolean; slice?: boolean; sort?: boolean; splice?: boolean; unshift?: boolean; indexOf?: boolean; lastIndexOf?: boolean; every?: boolean; some?: boolean; forEach?: boolean; map?: boolean; filter?: boolean; reduce?: boolean; reduceRight?: boolean; find?: boolean; findIndex?: boolean; fill?: boolean; copyWithin?: boolean; entries?: boolean; keys?: boolean; values?: boolean; includes?: boolean; flatMap?: boolean; flat?: boolean; [Symbol.iterator]?: boolean; readonly [Symbol.unscopables]?: boolean; }; }
->null as any as { [K in keyof number[] as Exclude<K, "length">]: (number[])[K] } : { [x: number]: number; toString: () => string; toLocaleString: () => string; pop: () => number; push: (...items: number[]) => number; concat: { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }; join: (separator?: string) => string; reverse: () => number[]; shift: () => number; slice: (start?: number, end?: number) => number[]; sort: (compareFn?: (a: number, b: number) => number) => number[]; splice: { (start: number, deleteCount?: number): number[]; (start: number, deleteCount: number, ...items: number[]): number[]; }; unshift: (...items: number[]) => number; indexOf: (searchElement: number, fromIndex?: number) => number; lastIndexOf: (searchElement: number, fromIndex?: number) => number; every: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): this is S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): boolean; }; some: (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any) => boolean; forEach: (callbackfn: (value: number, index: number, array: number[]) => void, thisArg?: any) => void; map: <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]; filter: { <S_1 extends number>(predicate: (value: number, index: number, array: number[]) => value is S_1, thisArg?: any): S_1[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): number[]; }; 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_1>(callbackfn: (previousValue: U_1, currentValue: number, currentIndex: number, array: number[]) => U_1, initialValue: U_1): U_1; }; reduceRight: { (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_2>(callbackfn: (previousValue: U_2, currentValue: number, currentIndex: number, array: number[]) => U_2, initialValue: U_2): U_2; }; find: { <S_2 extends number>(predicate: (value: number, index: number, obj: number[]) => value is S_2, thisArg?: any): S_2; (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any): number; }; findIndex: (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any) => number; fill: (value: number, start?: number, end?: number) => number[]; copyWithin: (target: number, start: number, end?: number) => number[]; entries: () => IterableIterator<[number, number]>; keys: () => IterableIterator<number>; values: () => IterableIterator<number>; includes: (searchElement: number, fromIndex?: number) => boolean; flatMap: <U_3, This = undefined>(callback: (this: This, value: number, index: number, array: number[]) => U_3 | readonly U_3[], thisArg?: This) => U_3[]; flat: <A, D extends number = 1>(this: A, depth?: D) => FlatArray<A, D>[]; [Symbol.iterator]: () => IterableIterator<number>; readonly [Symbol.unscopables]: { [x: number]: boolean; length?: boolean; toString?: boolean; toLocaleString?: boolean; pop?: boolean; push?: boolean; concat?: boolean; join?: boolean; reverse?: boolean; shift?: boolean; slice?: boolean; sort?: boolean; splice?: boolean; unshift?: boolean; indexOf?: boolean; lastIndexOf?: boolean; every?: boolean; some?: boolean; forEach?: boolean; map?: boolean; filter?: boolean; reduce?: boolean; reduceRight?: boolean; find?: boolean; findIndex?: boolean; fill?: boolean; copyWithin?: boolean; entries?: boolean; keys?: boolean; values?: boolean; includes?: boolean; flatMap?: boolean; flat?: boolean; [Symbol.iterator]?: boolean; readonly [Symbol.unscopables]?: boolean; }; }
+>thing : { [x: number]: number; toString: () => string; toLocaleString: () => string; pop: () => number; push: (...items: number[]) => number; concat: { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }; join: (separator?: string) => string; reverse: () => number[]; shift: () => number; slice: (start?: number, end?: number) => number[]; sort: (compareFn?: (a: number, b: number) => number) => number[]; splice: { (start: number, deleteCount?: number): number[]; (start: number, deleteCount: number, ...items: number[]): number[]; }; unshift: (...items: number[]) => number; indexOf: (searchElement: number, fromIndex?: number) => number; lastIndexOf: (searchElement: number, fromIndex?: number) => number; every: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): this is S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): boolean; }; some: (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any) => boolean; forEach: (callbackfn: (value: number, index: number, array: number[]) => void, thisArg?: any) => void; map: <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]; filter: { <S_1 extends number>(predicate: (value: number, index: number, array: number[]) => value is S_1, thisArg?: any): S_1[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): number[]; }; 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_1>(callbackfn: (previousValue: U_1, currentValue: number, currentIndex: number, array: number[]) => U_1, initialValue: U_1): U_1; }; reduceRight: { (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_2>(callbackfn: (previousValue: U_2, currentValue: number, currentIndex: number, array: number[]) => U_2, initialValue: U_2): U_2; }; find: { <S_2 extends number>(predicate: (value: number, index: number, obj: number[]) => value is S_2, thisArg?: any): S_2; (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any): number; }; findIndex: (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any) => number; fill: (value: number, start?: number, end?: number) => number[]; copyWithin: (target: number, start: number, end?: number) => number[]; entries: () => BuiltInIterableIterator<[number, number]>; keys: () => BuiltInIterableIterator<number>; values: () => BuiltInIterableIterator<number>; includes: (searchElement: number, fromIndex?: number) => boolean; flatMap: <U_3, This = undefined>(callback: (this: This, value: number, index: number, array: number[]) => U_3 | readonly U_3[], thisArg?: This) => U_3[]; flat: <A, D extends number = 1>(this: A, depth?: D) => FlatArray<A, D>[]; [Symbol.iterator]: () => BuiltInIterableIterator<number>; readonly [Symbol.unscopables]: { [x: number]: boolean; length?: boolean; toString?: boolean; toLocaleString?: boolean; pop?: boolean; push?: boolean; concat?: boolean; join?: boolean; reverse?: boolean; shift?: boolean; slice?: boolean; sort?: boolean; splice?: boolean; unshift?: boolean; indexOf?: boolean; lastIndexOf?: boolean; every?: boolean; some?: boolean; forEach?: boolean; map?: boolean; filter?: boolean; reduce?: boolean; reduceRight?: boolean; find?: boolean; findIndex?: boolean; fill?: boolean; copyWithin?: boolean; entries?: boolean; keys?: boolean; values?: boolean; includes?: boolean; flatMap?: boolean; flat?: boolean; [Symbol.iterator]?: boolean; readonly [Symbol.unscopables]?: boolean; }; }
+>(null as any as { [K in keyof number[] as Exclude<K, "length">]: (number[])[K] }) : { [x: number]: number; toString: () => string; toLocaleString: () => string; pop: () => number; push: (...items: number[]) => number; concat: { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }; join: (separator?: string) => string; reverse: () => number[]; shift: () => number; slice: (start?: number, end?: number) => number[]; sort: (compareFn?: (a: number, b: number) => number) => number[]; splice: { (start: number, deleteCount?: number): number[]; (start: number, deleteCount: number, ...items: number[]): number[]; }; unshift: (...items: number[]) => number; indexOf: (searchElement: number, fromIndex?: number) => number; lastIndexOf: (searchElement: number, fromIndex?: number) => number; every: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): this is S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): boolean; }; some: (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any) => boolean; forEach: (callbackfn: (value: number, index: number, array: number[]) => void, thisArg?: any) => void; map: <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]; filter: { <S_1 extends number>(predicate: (value: number, index: number, array: number[]) => value is S_1, thisArg?: any): S_1[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): number[]; }; 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_1>(callbackfn: (previousValue: U_1, currentValue: number, currentIndex: number, array: number[]) => U_1, initialValue: U_1): U_1; }; reduceRight: { (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_2>(callbackfn: (previousValue: U_2, currentValue: number, currentIndex: number, array: number[]) => U_2, initialValue: U_2): U_2; }; find: { <S_2 extends number>(predicate: (value: number, index: number, obj: number[]) => value is S_2, thisArg?: any): S_2; (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any): number; }; findIndex: (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any) => number; fill: (value: number, start?: number, end?: number) => number[]; copyWithin: (target: number, start: number, end?: number) => number[]; entries: () => BuiltInIterableIterator<[number, number]>; keys: () => BuiltInIterableIterator<number>; values: () => BuiltInIterableIterator<number>; includes: (searchElement: number, fromIndex?: number) => boolean; flatMap: <U_3, This = undefined>(callback: (this: This, value: number, index: number, array: number[]) => U_3 | readonly U_3[], thisArg?: This) => U_3[]; flat: <A, D extends number = 1>(this: A, depth?: D) => FlatArray<A, D>[]; [Symbol.iterator]: () => BuiltInIterableIterator<number>; readonly [Symbol.unscopables]: { [x: number]: boolean; length?: boolean; toString?: boolean; toLocaleString?: boolean; pop?: boolean; push?: boolean; concat?: boolean; join?: boolean; reverse?: boolean; shift?: boolean; slice?: boolean; sort?: boolean; splice?: boolean; unshift?: boolean; indexOf?: boolean; lastIndexOf?: boolean; every?: boolean; some?: boolean; forEach?: boolean; map?: boolean; filter?: boolean; reduce?: boolean; reduceRight?: boolean; find?: boolean; findIndex?: boolean; fill?: boolean; copyWithin?: boolean; entries?: boolean; keys?: boolean; values?: boolean; includes?: boolean; flatMap?: boolean; flat?: boolean; [Symbol.iterator]?: boolean; readonly [Symbol.unscopables]?: boolean; }; }
+>null as any as { [K in keyof number[] as Exclude<K, "length">]: (number[])[K] } : { [x: number]: number; toString: () => string; toLocaleString: () => string; pop: () => number; push: (...items: number[]) => number; concat: { (...items: ConcatArray<number>[]): number[]; (...items: (number | ConcatArray<number>)[]): number[]; }; join: (separator?: string) => string; reverse: () => number[]; shift: () => number; slice: (start?: number, end?: number) => number[]; sort: (compareFn?: (a: number, b: number) => number) => number[]; splice: { (start: number, deleteCount?: number): number[]; (start: number, deleteCount: number, ...items: number[]): number[]; }; unshift: (...items: number[]) => number; indexOf: (searchElement: number, fromIndex?: number) => number; lastIndexOf: (searchElement: number, fromIndex?: number) => number; every: { <S extends number>(predicate: (value: number, index: number, array: number[]) => value is S, thisArg?: any): this is S[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): boolean; }; some: (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any) => boolean; forEach: (callbackfn: (value: number, index: number, array: number[]) => void, thisArg?: any) => void; map: <U>(callbackfn: (value: number, index: number, array: number[]) => U, thisArg?: any) => U[]; filter: { <S_1 extends number>(predicate: (value: number, index: number, array: number[]) => value is S_1, thisArg?: any): S_1[]; (predicate: (value: number, index: number, array: number[]) => unknown, thisArg?: any): number[]; }; 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_1>(callbackfn: (previousValue: U_1, currentValue: number, currentIndex: number, array: number[]) => U_1, initialValue: U_1): U_1; }; reduceRight: { (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_2>(callbackfn: (previousValue: U_2, currentValue: number, currentIndex: number, array: number[]) => U_2, initialValue: U_2): U_2; }; find: { <S_2 extends number>(predicate: (value: number, index: number, obj: number[]) => value is S_2, thisArg?: any): S_2; (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any): number; }; findIndex: (predicate: (value: number, index: number, obj: number[]) => unknown, thisArg?: any) => number; fill: (value: number, start?: number, end?: number) => number[]; copyWithin: (target: number, start: number, end?: number) => number[]; entries: () => BuiltInIterableIterator<[number, number]>; keys: () => BuiltInIterableIterator<number>; values: () => BuiltInIterableIterator<number>; includes: (searchElement: number, fromIndex?: number) => boolean; flatMap: <U_3, This = undefined>(callback: (this: This, value: number, index: number, array: number[]) => U_3 | readonly U_3[], thisArg?: This) => U_3[]; flat: <A, D extends number = 1>(this: A, depth?: D) => FlatArray<A, D>[]; [Symbol.iterator]: () => BuiltInIterableIterator<number>; readonly [Symbol.unscopables]: { [x: number]: boolean; length?: boolean; toString?: boolean; toLocaleString?: boolean; pop?: boolean; push?: boolean; concat?: boolean; join?: boolean; reverse?: boolean; shift?: boolean; slice?: boolean; sort?: boolean; splice?: boolean; unshift?: boolean; indexOf?: boolean; lastIndexOf?: boolean; every?: boolean; some?: boolean; forEach?: boolean; map?: boolean; filter?: boolean; reduce?: boolean; reduceRight?: boolean; find?: boolean; findIndex?: boolean; fill?: boolean; copyWithin?: boolean; entries?: boolean; keys?: boolean; values?: boolean; includes?: boolean; flatMap?: boolean; flat?: boolean; [Symbol.iterator]?: boolean; readonly [Symbol.unscopables]?: boolean; }; }
 >null as any : any
 
diff --git a/tests/baselines/reference/modularizeLibrary_NoErrorDuplicateLibOptions1.types b/tests/baselines/reference/modularizeLibrary_NoErrorDuplicateLibOptions1.types
index 0f884c4ce16c4..d914f95c1934e 100644
--- a/tests/baselines/reference/modularizeLibrary_NoErrorDuplicateLibOptions1.types
+++ b/tests/baselines/reference/modularizeLibrary_NoErrorDuplicateLibOptions1.types
@@ -37,10 +37,10 @@ m.clear();
 
 // Using ES6 iterable
 m.keys();
->m.keys() : IterableIterator<string>
->m.keys : () => IterableIterator<string>
+>m.keys() : BuiltInIterableIterator<string>
+>m.keys : () => BuiltInIterableIterator<string>
 >m : Map<string, number>
->keys : () => IterableIterator<string>
+>keys : () => BuiltInIterableIterator<string>
 
 // Using ES6 function
 function Baz() { }
diff --git a/tests/baselines/reference/modularizeLibrary_NoErrorDuplicateLibOptions2.types b/tests/baselines/reference/modularizeLibrary_NoErrorDuplicateLibOptions2.types
index 37e1440f523be..a5c02bd12ab01 100644
--- a/tests/baselines/reference/modularizeLibrary_NoErrorDuplicateLibOptions2.types
+++ b/tests/baselines/reference/modularizeLibrary_NoErrorDuplicateLibOptions2.types
@@ -37,10 +37,10 @@ m.clear();
 
 // Using ES6 iterable
 m.keys();
->m.keys() : IterableIterator<string>
->m.keys : () => IterableIterator<string>
+>m.keys() : BuiltInIterableIterator<string>
+>m.keys : () => BuiltInIterableIterator<string>
 >m : Map<string, number>
->keys : () => IterableIterator<string>
+>keys : () => BuiltInIterableIterator<string>
 
 // Using ES6 function
 function Baz() { }
diff --git a/tests/baselines/reference/modularizeLibrary_TargetES5UsingES6Lib.types b/tests/baselines/reference/modularizeLibrary_TargetES5UsingES6Lib.types
index 8a55354867061..0824209174c26 100644
--- a/tests/baselines/reference/modularizeLibrary_TargetES5UsingES6Lib.types
+++ b/tests/baselines/reference/modularizeLibrary_TargetES5UsingES6Lib.types
@@ -37,10 +37,10 @@ m.clear();
 
 // Using ES6 iterable
 m.keys();
->m.keys() : IterableIterator<string>
->m.keys : () => IterableIterator<string>
+>m.keys() : BuiltInIterableIterator<string>
+>m.keys : () => BuiltInIterableIterator<string>
 >m : Map<string, number>
->keys : () => IterableIterator<string>
+>keys : () => BuiltInIterableIterator<string>
 
 // Using ES6 function
 function Baz() { }
diff --git a/tests/baselines/reference/modularizeLibrary_TargetES6UsingES6Lib.types b/tests/baselines/reference/modularizeLibrary_TargetES6UsingES6Lib.types
index 53df319fe798a..010c102852ed0 100644
--- a/tests/baselines/reference/modularizeLibrary_TargetES6UsingES6Lib.types
+++ b/tests/baselines/reference/modularizeLibrary_TargetES6UsingES6Lib.types
@@ -37,10 +37,10 @@ m.clear();
 
 // Using ES6 iterable
 m.keys();
->m.keys() : IterableIterator<string>
->m.keys : () => IterableIterator<string>
+>m.keys() : BuiltInIterableIterator<string>
+>m.keys : () => BuiltInIterableIterator<string>
 >m : Map<string, number>
->keys : () => IterableIterator<string>
+>keys : () => BuiltInIterableIterator<string>
 
 // Using ES6 function
 function Baz() { }
diff --git a/tests/baselines/reference/parser.asyncGenerators.classMethods.es2018.types b/tests/baselines/reference/parser.asyncGenerators.classMethods.es2018.types
index f3c8c633c2472..04e4104186b6c 100644
--- a/tests/baselines/reference/parser.asyncGenerators.classMethods.es2018.types
+++ b/tests/baselines/reference/parser.asyncGenerators.classMethods.es2018.types
@@ -172,7 +172,7 @@ class C16 {
 >f : () => AsyncGenerator<any, void, undefined>
 
         yield * [];
->yield * [] : any
+>yield * [] : undefined
 >[] : undefined[]
     }
 }
diff --git a/tests/baselines/reference/parser.asyncGenerators.functionDeclarations.es2018.types b/tests/baselines/reference/parser.asyncGenerators.functionDeclarations.es2018.types
index 162edaf4ac972..96de924f5cd0c 100644
--- a/tests/baselines/reference/parser.asyncGenerators.functionDeclarations.es2018.types
+++ b/tests/baselines/reference/parser.asyncGenerators.functionDeclarations.es2018.types
@@ -109,7 +109,7 @@ async function * f16() {
 >f16 : () => AsyncGenerator<any, void, undefined>
 
     yield * [];
->yield * [] : any
+>yield * [] : undefined
 >[] : undefined[]
 }
 === awaitWithValueIsOk.ts ===
diff --git a/tests/baselines/reference/parser.asyncGenerators.functionExpressions.es2018.types b/tests/baselines/reference/parser.asyncGenerators.functionExpressions.es2018.types
index 48889e73fea1a..4fbf8715bbd05 100644
--- a/tests/baselines/reference/parser.asyncGenerators.functionExpressions.es2018.types
+++ b/tests/baselines/reference/parser.asyncGenerators.functionExpressions.es2018.types
@@ -138,7 +138,7 @@ const f16 = async function * () {
 >async function * () {    yield * [];} : () => AsyncGenerator<any, void, undefined>
 
     yield * [];
->yield * [] : any
+>yield * [] : undefined
 >[] : undefined[]
 
 };
diff --git a/tests/baselines/reference/parser.asyncGenerators.objectLiteralMethods.es2018.types b/tests/baselines/reference/parser.asyncGenerators.objectLiteralMethods.es2018.types
index d6768850e3925..1192d36efb319 100644
--- a/tests/baselines/reference/parser.asyncGenerators.objectLiteralMethods.es2018.types
+++ b/tests/baselines/reference/parser.asyncGenerators.objectLiteralMethods.es2018.types
@@ -188,7 +188,7 @@ const o16 = {
 >f : () => AsyncGenerator<any, void, undefined>
 
         yield * [];
->yield * [] : any
+>yield * [] : undefined
 >[] : undefined[]
     }
 };
diff --git a/tests/baselines/reference/regexMatchAll-esnext.types b/tests/baselines/reference/regexMatchAll-esnext.types
index 5d9872c0eb01f..0cada42cb950e 100644
--- a/tests/baselines/reference/regexMatchAll-esnext.types
+++ b/tests/baselines/reference/regexMatchAll-esnext.types
@@ -2,9 +2,9 @@
 
 === regexMatchAll-esnext.ts ===
 const matches = /\w/g[Symbol.matchAll]("matchAll");
->matches : IterableIterator<RegExpMatchArray>
->/\w/g[Symbol.matchAll]("matchAll") : IterableIterator<RegExpMatchArray>
->/\w/g[Symbol.matchAll] : (str: string) => IterableIterator<RegExpMatchArray>
+>matches : BuiltInIterableIterator<RegExpMatchArray>
+>/\w/g[Symbol.matchAll]("matchAll") : BuiltInIterableIterator<RegExpMatchArray>
+>/\w/g[Symbol.matchAll] : (str: string) => BuiltInIterableIterator<RegExpMatchArray>
 >/\w/g : RegExp
 >Symbol.matchAll : unique symbol
 >Symbol : SymbolConstructor
@@ -15,7 +15,7 @@ const array = [...matches];
 >array : RegExpMatchArray[]
 >[...matches] : RegExpMatchArray[]
 >...matches : RegExpMatchArray
->matches : IterableIterator<RegExpMatchArray>
+>matches : BuiltInIterableIterator<RegExpMatchArray>
 
 const { index, input } = array[0];
 >index : number
diff --git a/tests/baselines/reference/regexMatchAll.types b/tests/baselines/reference/regexMatchAll.types
index 311b26b931bdf..17339af2bf334 100644
--- a/tests/baselines/reference/regexMatchAll.types
+++ b/tests/baselines/reference/regexMatchAll.types
@@ -2,9 +2,9 @@
 
 === regexMatchAll.ts ===
 const matches = /\w/g[Symbol.matchAll]("matchAll");
->matches : IterableIterator<RegExpMatchArray>
->/\w/g[Symbol.matchAll]("matchAll") : IterableIterator<RegExpMatchArray>
->/\w/g[Symbol.matchAll] : (str: string) => IterableIterator<RegExpMatchArray>
+>matches : BuiltInIterableIterator<RegExpMatchArray>
+>/\w/g[Symbol.matchAll]("matchAll") : BuiltInIterableIterator<RegExpMatchArray>
+>/\w/g[Symbol.matchAll] : (str: string) => BuiltInIterableIterator<RegExpMatchArray>
 >/\w/g : RegExp
 >Symbol.matchAll : unique symbol
 >Symbol : SymbolConstructor
@@ -15,7 +15,7 @@ const array = [...matches];
 >array : RegExpMatchArray[]
 >[...matches] : RegExpMatchArray[]
 >...matches : RegExpMatchArray
->matches : IterableIterator<RegExpMatchArray>
+>matches : BuiltInIterableIterator<RegExpMatchArray>
 
 const { index, input } = array[0];
 >index : number
diff --git a/tests/baselines/reference/stringMatchAll.types b/tests/baselines/reference/stringMatchAll.types
index 59c112f5016a6..9e396d3bf5f25 100644
--- a/tests/baselines/reference/stringMatchAll.types
+++ b/tests/baselines/reference/stringMatchAll.types
@@ -2,18 +2,18 @@
 
 === stringMatchAll.ts ===
 const matches = "matchAll".matchAll(/\w/g);
->matches : IterableIterator<RegExpMatchArray>
->"matchAll".matchAll(/\w/g) : IterableIterator<RegExpMatchArray>
->"matchAll".matchAll : (regexp: RegExp) => IterableIterator<RegExpMatchArray>
+>matches : BuiltInIterableIterator<RegExpMatchArray>
+>"matchAll".matchAll(/\w/g) : BuiltInIterableIterator<RegExpMatchArray>
+>"matchAll".matchAll : (regexp: RegExp) => BuiltInIterableIterator<RegExpMatchArray>
 >"matchAll" : "matchAll"
->matchAll : (regexp: RegExp) => IterableIterator<RegExpMatchArray>
+>matchAll : (regexp: RegExp) => BuiltInIterableIterator<RegExpMatchArray>
 >/\w/g : RegExp
 
 const array = [...matches];
 >array : RegExpMatchArray[]
 >[...matches] : RegExpMatchArray[]
 >...matches : RegExpMatchArray
->matches : IterableIterator<RegExpMatchArray>
+>matches : BuiltInIterableIterator<RegExpMatchArray>
 
 const { index, input } = array[0];
 >index : number
diff --git a/tests/baselines/reference/types.asyncGenerators.es2018.1.types b/tests/baselines/reference/types.asyncGenerators.es2018.1.types
index 1dab8448cf487..f74188d86a980 100644
--- a/tests/baselines/reference/types.asyncGenerators.es2018.1.types
+++ b/tests/baselines/reference/types.asyncGenerators.es2018.1.types
@@ -47,7 +47,7 @@ async function * inferReturnType6() {
 >inferReturnType6 : () => AsyncGenerator<number, void, undefined>
 
     yield* [1, 2];
->yield* [1, 2] : any
+>yield* [1, 2] : undefined
 >[1, 2] : number[]
 >1 : 1
 >2 : 2
@@ -56,7 +56,7 @@ async function * inferReturnType7() {
 >inferReturnType7 : () => AsyncGenerator<number, void, undefined>
 
     yield* [Promise.resolve(1)];
->yield* [Promise.resolve(1)] : any
+>yield* [Promise.resolve(1)] : undefined
 >[Promise.resolve(1)] : Promise<number>[]
 >Promise.resolve(1) : Promise<number>
 >Promise.resolve : { (): Promise<void>; <T>(value: T): Promise<Awaited<T>>; <T_1>(value: T_1 | PromiseLike<T_1>): Promise<Awaited<T_1>>; }
@@ -102,7 +102,7 @@ const assignability3: () => AsyncIterableIterator<number> = async function * ()
 >async function * () {    yield* [1, 2];} : () => AsyncGenerator<number, void, undefined>
 
     yield* [1, 2];
->yield* [1, 2] : any
+>yield* [1, 2] : undefined
 >[1, 2] : number[]
 >1 : 1
 >2 : 2
@@ -113,7 +113,7 @@ const assignability4: () => AsyncIterableIterator<number> = async function * ()
 >async function * () {    yield* [Promise.resolve(1)];} : () => AsyncGenerator<number, void, undefined>
 
     yield* [Promise.resolve(1)];
->yield* [Promise.resolve(1)] : any
+>yield* [Promise.resolve(1)] : undefined
 >[Promise.resolve(1)] : Promise<number>[]
 >Promise.resolve(1) : Promise<number>
 >Promise.resolve : { (): Promise<void>; <T>(value: T): Promise<Awaited<T>>; <T_1>(value: T_1 | PromiseLike<T_1>): Promise<Awaited<T_1>>; }
@@ -162,7 +162,7 @@ const assignability8: () => AsyncIterable<number> = async function * () {
 >async function * () {    yield* [1, 2];} : () => AsyncGenerator<number, void, undefined>
 
     yield* [1, 2];
->yield* [1, 2] : any
+>yield* [1, 2] : undefined
 >[1, 2] : number[]
 >1 : 1
 >2 : 2
@@ -173,7 +173,7 @@ const assignability9: () => AsyncIterable<number> = async function * () {
 >async function * () {    yield* [Promise.resolve(1)];} : () => AsyncGenerator<number, void, undefined>
 
     yield* [Promise.resolve(1)];
->yield* [Promise.resolve(1)] : any
+>yield* [Promise.resolve(1)] : undefined
 >[Promise.resolve(1)] : Promise<number>[]
 >Promise.resolve(1) : Promise<number>
 >Promise.resolve : { (): Promise<void>; <T>(value: T): Promise<Awaited<T>>; <T_1>(value: T_1 | PromiseLike<T_1>): Promise<Awaited<T_1>>; }
@@ -222,7 +222,7 @@ const assignability13: () => AsyncIterator<number> = async function * () {
 >async function * () {    yield* [1, 2];} : () => AsyncGenerator<number, void, undefined>
 
     yield* [1, 2];
->yield* [1, 2] : any
+>yield* [1, 2] : undefined
 >[1, 2] : number[]
 >1 : 1
 >2 : 2
@@ -233,7 +233,7 @@ const assignability14: () => AsyncIterator<number> = async function * () {
 >async function * () {    yield* [Promise.resolve(1)];} : () => AsyncGenerator<number, void, undefined>
 
     yield* [Promise.resolve(1)];
->yield* [Promise.resolve(1)] : any
+>yield* [Promise.resolve(1)] : undefined
 >[Promise.resolve(1)] : Promise<number>[]
 >Promise.resolve(1) : Promise<number>
 >Promise.resolve : { (): Promise<void>; <T>(value: T): Promise<Awaited<T>>; <T_1>(value: T_1 | PromiseLike<T_1>): Promise<Awaited<T_1>>; }
@@ -277,7 +277,7 @@ async function * explicitReturnType3(): AsyncIterableIterator<number> {
 >explicitReturnType3 : () => AsyncIterableIterator<number>
 
     yield* [1, 2];
->yield* [1, 2] : any
+>yield* [1, 2] : undefined
 >[1, 2] : number[]
 >1 : 1
 >2 : 2
@@ -286,7 +286,7 @@ async function * explicitReturnType4(): AsyncIterableIterator<number> {
 >explicitReturnType4 : () => AsyncIterableIterator<number>
 
     yield* [Promise.resolve(1)];
->yield* [Promise.resolve(1)] : any
+>yield* [Promise.resolve(1)] : undefined
 >[Promise.resolve(1)] : Promise<number>[]
 >Promise.resolve(1) : Promise<number>
 >Promise.resolve : { (): Promise<void>; <T>(value: T): Promise<Awaited<T>>; <T_1>(value: T_1 | PromiseLike<T_1>): Promise<Awaited<T_1>>; }
@@ -327,7 +327,7 @@ async function * explicitReturnType8(): AsyncIterable<number> {
 >explicitReturnType8 : () => AsyncIterable<number>
 
     yield* [1, 2];
->yield* [1, 2] : any
+>yield* [1, 2] : undefined
 >[1, 2] : number[]
 >1 : 1
 >2 : 2
@@ -336,7 +336,7 @@ async function * explicitReturnType9(): AsyncIterable<number> {
 >explicitReturnType9 : () => AsyncIterable<number>
 
     yield* [Promise.resolve(1)];
->yield* [Promise.resolve(1)] : any
+>yield* [Promise.resolve(1)] : undefined
 >[Promise.resolve(1)] : Promise<number>[]
 >Promise.resolve(1) : Promise<number>
 >Promise.resolve : { (): Promise<void>; <T>(value: T): Promise<Awaited<T>>; <T_1>(value: T_1 | PromiseLike<T_1>): Promise<Awaited<T_1>>; }
@@ -377,7 +377,7 @@ async function * explicitReturnType13(): AsyncIterator<number> {
 >explicitReturnType13 : () => AsyncIterator<number>
 
     yield* [1, 2];
->yield* [1, 2] : any
+>yield* [1, 2] : undefined
 >[1, 2] : number[]
 >1 : 1
 >2 : 2
@@ -386,7 +386,7 @@ async function * explicitReturnType14(): AsyncIterator<number> {
 >explicitReturnType14 : () => AsyncIterator<number>
 
     yield* [Promise.resolve(1)];
->yield* [Promise.resolve(1)] : any
+>yield* [Promise.resolve(1)] : undefined
 >[Promise.resolve(1)] : Promise<number>[]
 >Promise.resolve(1) : Promise<number>
 >Promise.resolve : { (): Promise<void>; <T>(value: T): Promise<Awaited<T>>; <T_1>(value: T_1 | PromiseLike<T_1>): Promise<Awaited<T_1>>; }
diff --git a/tests/baselines/reference/types.asyncGenerators.es2018.2.types b/tests/baselines/reference/types.asyncGenerators.es2018.2.types
index 915189c840378..275e92f3bd36e 100644
--- a/tests/baselines/reference/types.asyncGenerators.es2018.2.types
+++ b/tests/baselines/reference/types.asyncGenerators.es2018.2.types
@@ -43,7 +43,7 @@ const assignability2: () => AsyncIterableIterator<number> = async function * ()
 >async function * () {    yield* ["a", "b"];} : () => AsyncGenerator<string, void, undefined>
 
     yield* ["a", "b"];
->yield* ["a", "b"] : any
+>yield* ["a", "b"] : undefined
 >["a", "b"] : string[]
 >"a" : "a"
 >"b" : "b"
@@ -76,7 +76,7 @@ const assignability5: () => AsyncIterable<number> = async function * () {
 >async function * () {    yield* ["a", "b"];} : () => AsyncGenerator<string, void, undefined>
 
     yield* ["a", "b"];
->yield* ["a", "b"] : any
+>yield* ["a", "b"] : undefined
 >["a", "b"] : string[]
 >"a" : "a"
 >"b" : "b"
@@ -109,7 +109,7 @@ const assignability8: () => AsyncIterator<number> = async function * () {
 >async function * () {    yield* ["a", "b"];} : () => AsyncGenerator<string, void, undefined>
 
     yield* ["a", "b"];
->yield* ["a", "b"] : any
+>yield* ["a", "b"] : undefined
 >["a", "b"] : string[]
 >"a" : "a"
 >"b" : "b"
@@ -139,7 +139,7 @@ async function * explicitReturnType2(): AsyncIterableIterator<number> {
 >explicitReturnType2 : () => AsyncIterableIterator<number>
 
     yield* ["a", "b"];
->yield* ["a", "b"] : any
+>yield* ["a", "b"] : undefined
 >["a", "b"] : string[]
 >"a" : "a"
 >"b" : "b"
@@ -166,7 +166,7 @@ async function * explicitReturnType5(): AsyncIterable<number> {
 >explicitReturnType5 : () => AsyncIterable<number>
 
     yield* ["a", "b"];
->yield* ["a", "b"] : any
+>yield* ["a", "b"] : undefined
 >["a", "b"] : string[]
 >"a" : "a"
 >"b" : "b"
@@ -193,7 +193,7 @@ async function * explicitReturnType8(): AsyncIterator<number> {
 >explicitReturnType8 : () => AsyncIterator<number>
 
     yield* ["a", "b"];
->yield* ["a", "b"] : any
+>yield* ["a", "b"] : undefined
 >["a", "b"] : string[]
 >"a" : "a"
 >"b" : "b"
diff --git a/tests/baselines/reference/yieldExpressionInControlFlow.types b/tests/baselines/reference/yieldExpressionInControlFlow.types
index b4a31e9f9fa97..a4f1a01fb92c5 100644
--- a/tests/baselines/reference/yieldExpressionInControlFlow.types
+++ b/tests/baselines/reference/yieldExpressionInControlFlow.types
@@ -21,7 +21,7 @@ function* f() {
 === alsoFails.ts ===
 // fails in Typescript too
 function* g() {
->g : () => Generator<any, void, any>
+>g : () => Generator<any, void, undefined>
 
     var o = []
 >o : any[]
@@ -31,10 +31,10 @@ function* g() {
 >true : true
 
         o = yield* o
->o = yield* o : any
+>o = yield* o : undefined
+>o : any[]
+>yield* o : undefined
 >o : any[]
->yield* o : any
->o : any
     }
 }
 
diff --git a/tests/baselines/reference/yieldExpressionInnerCommentEmit.types b/tests/baselines/reference/yieldExpressionInnerCommentEmit.types
index 226e8de48b163..3d402dcae47bf 100644
--- a/tests/baselines/reference/yieldExpressionInnerCommentEmit.types
+++ b/tests/baselines/reference/yieldExpressionInnerCommentEmit.types
@@ -17,12 +17,12 @@ function * foo2() {
 >3 : 3
 
     yield */*comment4*/ [4];
->yield */*comment4*/ [4] : any
+>yield */*comment4*/ [4] : undefined
 >[4] : number[]
 >4 : 4
 
     yield /*comment5*/* [5];
->yield /*comment5*/* [5] : any
+>yield /*comment5*/* [5] : undefined
 >[5] : number[]
 >5 : 5
 }