Move complex parameter lists of async function into downlevel generator body (#56296)

Author: rbuckton

src/compiler/checker.ts

@@ -28739,17 +28739,25 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 return errorType;
             }
 
-            const container = getContainingFunction(node)!;
-            if (languageVersion < ScriptTarget.ES2015) {
-                if (container.kind === SyntaxKind.ArrowFunction) {
-                    error(node, Diagnostics.The_arguments_object_cannot_be_referenced_in_an_arrow_function_in_ES3_and_ES5_Consider_using_a_standard_function_expression);
+            let container = getContainingFunction(node);
+            if (container) {
+                if (languageVersion < ScriptTarget.ES2015) {
+                    if (container.kind === SyntaxKind.ArrowFunction) {
+                        error(node, Diagnostics.The_arguments_object_cannot_be_referenced_in_an_arrow_function_in_ES3_and_ES5_Consider_using_a_standard_function_expression);
+                    }
+                    else if (hasSyntacticModifier(container, ModifierFlags.Async)) {
+                        error(node, Diagnostics.The_arguments_object_cannot_be_referenced_in_an_async_function_or_method_in_ES3_and_ES5_Consider_using_a_standard_function_or_method);
+                    }
                 }
-                else if (hasSyntacticModifier(container, ModifierFlags.Async)) {
-                    error(node, Diagnostics.The_arguments_object_cannot_be_referenced_in_an_async_function_or_method_in_ES3_and_ES5_Consider_using_a_standard_function_or_method);
+
+                getNodeLinks(container).flags |= NodeCheckFlags.CaptureArguments;
+                while (container && isArrowFunction(container)) {
+                    container = getContainingFunction(container);
+                    if (container) {
+                        getNodeLinks(container).flags |= NodeCheckFlags.CaptureArguments;
+                    }
                 }
             }
-
-            getNodeLinks(container).flags |= NodeCheckFlags.CaptureArguments;
             return getTypeOfSymbol(symbol);
         }
 

src/compiler/factory/emitHelpers.ts

@@ -26,6 +26,7 @@ import {
     isIdentifier,
     memoize,
     ObjectLiteralElementLike,
+    ParameterDeclaration,
     PrivateIdentifier,
     ScriptTarget,
     setEmitFlags,
@@ -115,7 +116,7 @@ export interface EmitHelperFactory {
     // ES2018 Destructuring Helpers
     createRestHelper(value: Expression, elements: readonly BindingOrAssignmentElement[], computedTempVariables: readonly Expression[] | undefined, location: TextRange): Expression;
     // ES2017 Helpers
-    createAwaiterHelper(hasLexicalThis: boolean, hasLexicalArguments: boolean, promiseConstructor: EntityName | Expression | undefined, body: Block): Expression;
+    createAwaiterHelper(hasLexicalThis: boolean, argumentsExpression: Expression | undefined, promiseConstructor: EntityName | Expression | undefined, parameters: readonly ParameterDeclaration[] | undefined, body: Block): Expression;
     // ES2015 Helpers
     createExtendsHelper(name: Identifier): Expression;
     createTemplateObjectHelper(cooked: ArrayLiteralExpression, raw: ArrayLiteralExpression): Expression;
@@ -497,15 +498,15 @@ export function createEmitHelperFactory(context: TransformationContext): EmitHel
 
     // ES2017 Helpers
 
-    function createAwaiterHelper(hasLexicalThis: boolean, hasLexicalArguments: boolean, promiseConstructor: EntityName | Expression | undefined, body: Block) {
+    function createAwaiterHelper(hasLexicalThis: boolean, argumentsExpression: Expression | undefined, promiseConstructor: EntityName | Expression | undefined, parameters: readonly ParameterDeclaration[], body: Block) {
         context.requestEmitHelper(awaiterHelper);
 
         const generatorFunc = factory.createFunctionExpression(
             /*modifiers*/ undefined,
             factory.createToken(SyntaxKind.AsteriskToken),
             /*name*/ undefined,
             /*typeParameters*/ undefined,
-            /*parameters*/ [],
+            parameters ?? [],
             /*type*/ undefined,
             body,
         );
@@ -518,7 +519,7 @@ export function createEmitHelperFactory(context: TransformationContext): EmitHel
             /*typeArguments*/ undefined,
             [
                 hasLexicalThis ? factory.createThis() : factory.createVoidZero(),
-                hasLexicalArguments ? factory.createIdentifier("arguments") : factory.createVoidZero(),
+                argumentsExpression ?? factory.createVoidZero(),
                 promiseConstructor ? createExpressionFromEntityName(factory, promiseConstructor) : factory.createVoidZero(),
                 generatorFunc,
             ],