[DAS] Fixes make return type nullable fix

Fixes: #61299
Change-Id: Ic65f13728836475afcb528f03b542b21a216ff49
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/444902
Reviewed-by: Samuel Rawlins <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>
Commit-Queue: Samuel Rawlins <[email protected]>
Auto-Submit: Felipe Morschel <[email protected]>

Author: FMorschel

pkg/analysis_server/lib/src/services/correction/dart/make_return_type_nullable.dart

@@ -5,6 +5,7 @@
 import 'package:analysis_server/src/services/correction/fix.dart';
 import 'package:analysis_server_plugin/edit/dart/correction_producer.dart';
 import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/element/nullability_suffix.dart';
 import 'package:analyzer/src/dart/ast/extensions.dart';
 import 'package:analyzer_plugin/utilities/change_builder/change_builder_core.dart';
 import 'package:analyzer_plugin/utilities/fixes/fixes.dart';
@@ -47,8 +48,8 @@ class MakeReturnTypeNullable extends ResolvedCorrectionProducer {
 
     if (node is! NullLiteral &&
         !typeSystem.isAssignableTo(
-          returnType.typeOrThrow,
-          typeSystem.promoteToNonNull(type),
+          type,
+          returnType.typeOrThrow.withNullability(NullabilitySuffix.question),
           strictCasts: analysisOptions.strictCasts,
         )) {
       return;

pkg/analysis_server/lib/src/services/correction/dart/replace_return_type.dart

@@ -32,8 +32,6 @@ class ReplaceReturnType extends ResolvedCorrectionProducer {
   Future<void> compute(ChangeBuilder builder) async {
     var node = this.node;
     if (node is Expression) {
-      var typeSystem = libraryElement2.typeSystem;
-
       var newType = node.staticType;
 
       void updateNewType(SyntacticEntity entity) {

pkg/analysis_server/test/src/services/correction/fix/make_return_type_nullable_test.dart

@@ -4,6 +4,7 @@
 
 import 'package:analysis_server/src/services/correction/fix.dart';
 import 'package:analyzer_plugin/utilities/fixes/fixes.dart';
+import 'package:analyzer_testing/utilities/utilities.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import 'fix_processor.dart';
@@ -146,6 +147,21 @@ class B extends A {
     await assertNoFix();
   }
 
+  Future<void> test_nullable_type() async {
+    await resolveTestCode('''
+int? f(String v) => v;
+''');
+    await assertNoFix();
+  }
+
+  Future<void> test_nullable_type_dynamic() async {
+    writeAnalysisOptionsFile(analysisOptionsContent(strictCasts: true));
+    await resolveTestCode('''
+int? f(dynamic v) => v;
+''');
+    await assertNoFix();
+  }
+
   Future<void> test_returnTypeHasTypeArguments() async {
     await resolveTestCode('''
 List<String> f() {
@@ -158,4 +174,12 @@ List<String>? f() {
 }
 ''');
   }
+
+  Future<void> test_unrelated_types() async {
+    writeAnalysisOptionsFile(analysisOptionsContent(strictCasts: true));
+    await resolveTestCode('''
+int f(dynamic v) => v;
+''');
+    await assertNoFix();
+  }
 }

pkg/analyzer/lib/src/dart/element/type_system.dart

@@ -713,7 +713,10 @@ class TypeSystemImpl implements TypeSystem {
     required covariant InterfaceElementImpl element,
     required NullabilitySuffix nullabilitySuffix,
   }) {
-    return instantiateInterfaceToBounds(element: element, nullabilitySuffix: nullabilitySuffix);
+    return instantiateInterfaceToBounds(
+      element: element,
+      nullabilitySuffix: nullabilitySuffix,
+    );
   }
 
   /// Given a [DartType] [type] and a list of types
@@ -753,7 +756,10 @@ class TypeSystemImpl implements TypeSystem {
     required covariant TypeAliasElementImpl element,
     required NullabilitySuffix nullabilitySuffix,
   }) {
-    return instantiateTypeAliasToBounds(element: element, nullabilitySuffix: nullabilitySuffix);
+    return instantiateTypeAliasToBounds(
+      element: element,
+      nullabilitySuffix: nullabilitySuffix,
+    );
   }
 
   /// Given uninstantiated [typeFormals], instantiate them to their bounds.