From 79bd844d9b32a8e1d31998a72fc2365305107ff5 Mon Sep 17 00:00:00 2001
From: Ron Buckton <ron.buckton@microsoft.com>
Date: Fri, 19 Jul 2024 19:02:54 -0400
Subject: [PATCH] Add fast paths for 'BuiltinIterator' and
 'AsyncBuiltinIterator' (#59368)

---
 src/compiler/checker.ts | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index b31f54a89b7b8..8372bdcb7c342 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -1176,6 +1176,7 @@ interface IterationTypesResolver {
     getGlobalIteratorType: (reportErrors: boolean) => GenericType;
     getGlobalIterableType: (reportErrors: boolean) => GenericType;
     getGlobalIterableIteratorType: (reportErrors: boolean) => GenericType;
+    getGlobalBuiltinIteratorType: (reportErrors: boolean) => GenericType;
     getGlobalGeneratorType: (reportErrors: boolean) => GenericType;
     resolveIterationType: (type: Type, errorNode: Node | undefined) => Type | undefined;
     mustHaveANextMethodDiagnostic: DiagnosticMessage;
@@ -2159,6 +2160,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         getGlobalIteratorType: getGlobalAsyncIteratorType,
         getGlobalIterableType: getGlobalAsyncIterableType,
         getGlobalIterableIteratorType: getGlobalAsyncIterableIteratorType,
+        getGlobalBuiltinIteratorType: getGlobalAsyncBuiltinIteratorType,
         getGlobalGeneratorType: getGlobalAsyncGeneratorType,
         resolveIterationType: (type, errorNode) => getAwaitedType(type, errorNode, Diagnostics.Type_of_await_operand_must_either_be_a_valid_promise_or_must_not_contain_a_callable_then_member),
         mustHaveANextMethodDiagnostic: Diagnostics.An_async_iterator_must_have_a_next_method,
@@ -2173,6 +2175,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         getGlobalIteratorType,
         getGlobalIterableType,
         getGlobalIterableIteratorType,
+        getGlobalBuiltinIteratorType,
         getGlobalGeneratorType,
         resolveIterationType: (type, _errorNode) => type,
         mustHaveANextMethodDiagnostic: Diagnostics.An_iterator_must_have_a_next_method,
@@ -2234,12 +2237,14 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     var deferredGlobalIterableType: GenericType | undefined;
     var deferredGlobalIteratorType: GenericType | undefined;
     var deferredGlobalIterableIteratorType: GenericType | undefined;
+    var deferredGlobalBuiltinIteratorType: GenericType | undefined;
     var deferredGlobalGeneratorType: GenericType | undefined;
     var deferredGlobalIteratorYieldResultType: GenericType | undefined;
     var deferredGlobalIteratorReturnResultType: GenericType | undefined;
     var deferredGlobalAsyncIterableType: GenericType | undefined;
     var deferredGlobalAsyncIteratorType: GenericType | undefined;
     var deferredGlobalAsyncIterableIteratorType: GenericType | undefined;
+    var deferredGlobalAsyncBuiltinIteratorType: GenericType | undefined;
     var deferredGlobalAsyncGeneratorType: GenericType | undefined;
     var deferredGlobalTemplateStringsArrayType: ObjectType | undefined;
     var deferredGlobalImportMetaType: ObjectType;
@@ -16930,6 +16935,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         return (deferredGlobalAsyncIterableIteratorType ||= getGlobalType("AsyncIterableIterator" as __String, /*arity*/ 3, reportErrors)) || emptyGenericType;
     }
 
+    function getGlobalAsyncBuiltinIteratorType(reportErrors: boolean) {
+        return (deferredGlobalAsyncBuiltinIteratorType ||= getGlobalType("AsyncBuiltinIterator" as __String, /*arity*/ 3, reportErrors)) || emptyGenericType;
+    }
+
     function getGlobalAsyncGeneratorType(reportErrors: boolean) {
         return (deferredGlobalAsyncGeneratorType ||= getGlobalType("AsyncGenerator" as __String, /*arity*/ 3, reportErrors)) || emptyGenericType;
     }
@@ -16946,6 +16955,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         return (deferredGlobalIterableIteratorType ||= getGlobalType("IterableIterator" as __String, /*arity*/ 3, reportErrors)) || emptyGenericType;
     }
 
+    function getGlobalBuiltinIteratorType(reportErrors: boolean) {
+        return (deferredGlobalBuiltinIteratorType ||= getGlobalType("BuiltinIterator" as __String, /*arity*/ 3, reportErrors)) || emptyGenericType;
+    }
+
     function getGlobalGeneratorType(reportErrors: boolean) {
         return (deferredGlobalGeneratorType ||= getGlobalType("Generator" as __String, /*arity*/ 3, reportErrors)) || emptyGenericType;
     }
@@ -44773,10 +44786,12 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         // As an optimization, if the type is an instantiation of the following global type, then
         // just grab its related type arguments:
         // - `Iterable<T, TReturn, TNext>` or `AsyncIterable<T, TReturn, TNext>`
+        // - `BuiltinIterator<T, TReturn, TNext>` or `AsyncBuiltinIterator<T, TReturn, TNext>`
         // - `IterableIterator<T, TReturn, TNext>` or `AsyncIterableIterator<T, TReturn, TNext>`
         // - `Generator<T, TReturn, TNext>` or `AsyncGenerator<T, TReturn, TNext>`
         if (
             isReferenceToType(type, resolver.getGlobalIterableType(/*reportErrors*/ false)) ||
+            isReferenceToType(type, resolver.getGlobalBuiltinIteratorType(/*reportErrors*/ false)) ||
             isReferenceToType(type, resolver.getGlobalIterableIteratorType(/*reportErrors*/ false)) ||
             isReferenceToType(type, resolver.getGlobalGeneratorType(/*reportErrors*/ false))
         ) {
@@ -44899,9 +44914,11 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         // As an optimization, if the type is an instantiation of one of the following global types,
         // then just grab its related type arguments:
         // - `IterableIterator<T, TReturn, TNext>` or `AsyncIterableIterator<T, TReturn, TNext>`
+        // - `BuiltinIterator<T, TReturn, TNext>` or `AsyncBuiltinIterator<T, TReturn, TNext>`
         // - `Iterator<T, TReturn, TNext>` or `AsyncIterator<T, TReturn, TNext>`
         // - `Generator<T, TReturn, TNext>` or `AsyncGenerator<T, TReturn, TNext>`
         if (
+            isReferenceToType(type, resolver.getGlobalBuiltinIteratorType(/*reportErrors*/ false)) ||
             isReferenceToType(type, resolver.getGlobalIterableIteratorType(/*reportErrors*/ false)) ||
             isReferenceToType(type, resolver.getGlobalIteratorType(/*reportErrors*/ false)) ||
             isReferenceToType(type, resolver.getGlobalGeneratorType(/*reportErrors*/ false))