Issue 50604. Fix renaming extension at its declaration.

Bug: https://github.com/dart-lang/sdk/issues/50604
Change-Id: I1c685ea7545ef120e5fc23fe6a507ded8c4f4cb9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/274083
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

pkg/analysis_server/lib/src/services/refactoring/legacy/refactoring.dart

@@ -464,6 +464,8 @@ abstract class RenameRefactoring implements Refactoring {
       nameNode = node;
     } else if (node is EnumConstantDeclaration) {
       nameNode = node.name;
+    } else if (node is ExtensionDeclaration) {
+      nameNode = node.name;
     } else if (node is FieldFormalParameter) {
       nameNode = node.name;
     } else if (node is ImportDirective) {

pkg/analysis_server/lib/src/services/refactoring/legacy/rename_unit_member.dart

@@ -51,6 +51,9 @@ class RenameUnitMemberRefactoringImpl extends RenameRefactoringImpl {
 
   @override
   String get refactoringName {
+    if (element is ExtensionElement) {
+      return 'Rename Extension';
+    }
     if (element is FunctionElement) {
       return 'Rename Top-Level Function';
     }

pkg/analysis_server/test/edit/refactoring_test.dart

@@ -1971,6 +1971,64 @@ enum E {
     );
   }
 
+  Future<void> test_extension_atDeclaration() {
+    addTestFile('''
+extension Test on int {
+  void foo() {}
+}
+void f() {
+  Test(0).foo();
+}
+''');
+    return assertSuccessfulRefactoring(
+      () {
+        return sendRenameRequest('Test on int', 'NewName');
+      },
+      '''
+extension NewName on int {
+  void foo() {}
+}
+void f() {
+  NewName(0).foo();
+}
+''',
+      feedbackValidator: (feedback) {
+        var renameFeedback = feedback as RenameFeedback;
+        expect(renameFeedback.offset, 10);
+        expect(renameFeedback.length, 4);
+      },
+    );
+  }
+
+  Future<void> test_extension_atReference() {
+    addTestFile('''
+extension Test on int {
+  void foo() {}
+}
+void f() {
+  Test(0).foo();
+}
+''');
+    return assertSuccessfulRefactoring(
+      () {
+        return sendRenameRequest('Test(0)', 'NewName');
+      },
+      '''
+extension NewName on int {
+  void foo() {}
+}
+void f() {
+  NewName(0).foo();
+}
+''',
+      feedbackValidator: (feedback) {
+        var renameFeedback = feedback as RenameFeedback;
+        expect(renameFeedback.offset, 55);
+        expect(renameFeedback.length, 4);
+      },
+    );
+  }
+
   Future<void> test_feedback() {
     addTestFile('''
 class Test {}

pkg/analysis_server/test/services/refactoring/legacy/rename_unit_member_test.dart

@@ -619,6 +619,58 @@ void f(NewName t) {}
 ''');
   }
 
+  Future<void> test_createChange_ExtensionElement_atDeclaration() async {
+    await indexTestUnit('''
+extension Test on int {
+  void foo() {}
+}
+void f() {
+  Test(0).foo();
+}
+''');
+    // configure refactoring
+    createRenameRefactoringAtString('Test on int');
+    expect(refactoring.refactoringName, 'Rename Extension');
+    expect(refactoring.elementKindName, 'extension');
+    expect(refactoring.oldName, 'Test');
+    refactoring.newName = 'NewName';
+    // validate change
+    return assertSuccessfulRefactoring('''
+extension NewName on int {
+  void foo() {}
+}
+void f() {
+  NewName(0).foo();
+}
+''');
+  }
+
+  Future<void> test_createChange_ExtensionElement_atReference() async {
+    await indexTestUnit('''
+extension Test on int {
+  void foo() {}
+}
+void f() {
+  Test(0).foo();
+}
+''');
+    // configure refactoring
+    createRenameRefactoringAtString('Test(0)');
+    expect(refactoring.refactoringName, 'Rename Extension');
+    expect(refactoring.elementKindName, 'extension');
+    expect(refactoring.oldName, 'Test');
+    refactoring.newName = 'NewName';
+    // validate change
+    return assertSuccessfulRefactoring('''
+extension NewName on int {
+  void foo() {}
+}
+void f() {
+  NewName(0).foo();
+}
+''');
+  }
+
   Future<void> test_createChange_FunctionElement() async {
     await indexTestUnit('''
 test() {}