When user renames 'prefix' in 'prefix.Class' she actually wants to rename ImportElement.

pkg/analysis_server/test/services/refactoring/rename_import_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_import;
 
 import 'package:analysis_server/src/services/correction/status.dart';
 import 'package:analysis_testing/reflective_tests.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:unittest/unittest.dart';
@@ skipping 75 matching lines @@
     // validate change
     return assertSuccessfulRename('''
 import 'dart:math' as test;
 import 'dart:async' as newName;
 main() {
   newName.Future f;
 }
 ''');
   }
 
+  test_createChange_change_onPrefixElement() {
+    indexTestUnit('''
+import 'dart:async' as test;
+import 'dart:math' as test;
+main() {
+  test.Future f;
+  test.PI;
+  test.E;
+}
+''');
+    // configure refactoring
+    createRenameRefactoringAtString('test.PI');
+    expect(refactoring.refactoringName, 'Rename Import Prefix');
+    expect(refactoring.oldName, 'test');
+    refactoring.newName = 'newName';
+    // validate change
+    return assertSuccessfulRename('''
+import 'dart:async' as test;
+import 'dart:math' as newName;
+main() {
+  test.Future f;
+  newName.PI;
+  newName.E;
+}
+''');
+  }
+
   test_createChange_change_function() {
     indexTestUnit('''
 import 'dart:math' as test;
 import 'dart:async' as test;
 main() {
   test.max(1, 2);
   test.Future f;
 }
 ''');
     // configure refactoring
@@ skipping 34 matching lines @@
 }
 ''');
   }
 
   void _createRefactoring(String search) {
     ImportDirective directive =
         findNodeAtString(search, (node) => node is ImportDirective);
     createRenameRefactoringForElement(directive.element);
   }
 }