Elements. Migrate ReplaceReturnType.

Change-Id: I7591ae9bfff524bc20aa6ce8a36ea7c20303db1d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/387413
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Samuel Rawlins <srawlins@google.com>
diff --git a/pkg/analysis_server/analyzer_use_new_elements.txt b/pkg/analysis_server/analyzer_use_new_elements.txt
index 83fa5ff..a193405 100644
--- a/pkg/analysis_server/analyzer_use_new_elements.txt
+++ b/pkg/analysis_server/analyzer_use_new_elements.txt
@@ -399,6 +399,7 @@
 lib/src/services/correction/dart/replace_null_check_with_cast.dart
 lib/src/services/correction/dart/replace_null_with_closure.dart
 lib/src/services/correction/dart/replace_null_with_void.dart
+lib/src/services/correction/dart/replace_return_type.dart
 lib/src/services/correction/dart/replace_return_type_future.dart
 lib/src/services/correction/dart/replace_return_type_iterable.dart
 lib/src/services/correction/dart/replace_return_type_stream.dart
diff --git a/pkg/analysis_server/lib/src/services/correction/dart/replace_return_type.dart b/pkg/analysis_server/lib/src/services/correction/dart/replace_return_type.dart
index 8647616..4dec68d 100644
--- a/pkg/analysis_server/lib/src/services/correction/dart/replace_return_type.dart
+++ b/pkg/analysis_server/lib/src/services/correction/dart/replace_return_type.dart
@@ -32,7 +32,7 @@
   Future<void> compute(ChangeBuilder builder) async {
     var node = this.node;
     if (node is Expression) {
-      var typeSystem = libraryElement.typeSystem;
+      var typeSystem = libraryElement2.typeSystem;
 
       var newType = node.staticType;
 
@@ -91,16 +91,16 @@
     if (newType != null) {
       var clazz = method.thisOrAncestorOfType<ClassDeclaration>();
       if (clazz != null) {
-        var classElement = clazz.declaredElement!;
-        var overriddenList = InheritanceManager3().getOverridden2(
+        var classElement = clazz.declaredFragment!.element;
+        var overriddenList = InheritanceManager3().getOverridden4(
             classElement,
-            Name(
-              classElement.library.source.uri,
-              method.declaredElement!.name,
+            Name.forLibrary(
+              classElement.library2,
+              method.declaredFragment!.name!,
             ));
 
         if (overriddenList != null) {
-          var notSubtype = overriddenList.any((element) => !libraryElement
+          var notSubtype = overriddenList.any((element) => !libraryElement2
               .typeSystem
               .isSubtypeOf(newType, element.returnType));
           if (notSubtype) {