Report a fatal error on attempt to rename an element declared in SDK.

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

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library test.services.refactoring.rename_unit_member;
 
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analysis_server/src/services/correction/status.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 import 'package:unittest/unittest.dart';
@@ skipping 206 matching lines @@
   }
 }
 ''');
     createRenameRefactoringAtString('Test {}');
     // check status
     refactoring.newName = 'NewName';
     RefactoringStatus status = await refactoring.checkFinalConditions();
     assertRefactoringStatusOK(status);
   }
 
+  test_checkInitialConditions_inSDK() async {
+    indexTestUnit('''
+main() {
+  String s;
+}
+''');
+    createRenameRefactoringAtString('String s');
+    // check status
+    refactoring.newName = 'NewName';
+    RefactoringStatus status = await refactoring.checkInitialConditions();
+    assertRefactoringStatus(status, RefactoringProblemSeverity.FATAL,
+        expectedMessage:
+            "The class 'String' is defined in the SDK, so cannot be renamed.");
+  }
+
   test_checkNewName_ClassElement() {
     indexTestUnit('''
 class Test {}
 ''');
     createRenameRefactoringAtString('Test {}');
     // null
     refactoring.newName = null;
     assertRefactoringStatus(
         refactoring.checkNewName(), RefactoringProblemSeverity.FATAL,
         expectedMessage: "Class name must not be null.");
@@ skipping 259 matching lines @@
     return assertSuccessfulRefactoring('''
 int newName = 0;
 main() {
   print(newName);
   newName = 1;
   newName += 2;
 }
 ''');
   }
 }