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

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

Index: pkg/analysis_server/test/services/refactoring/rename_import_test.dart
diff --git a/pkg/analysis_server/test/services/refactoring/rename_import_test.dart b/pkg/analysis_server/test/services/refactoring/rename_import_test.dart
index 0e28f419b37f22660842776cef2230fdb2e36ec8..c744b598126a0fbd82416528de1eae5c7f491208 100644
--- a/pkg/analysis_server/test/services/refactoring/rename_import_test.dart
+++ b/pkg/analysis_server/test/services/refactoring/rename_import_test.dart
@@ -93,6 +93,33 @@ main() {
 ''');
   }
 
+  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;