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

pkg/analysis_server/lib/src/analysis_server.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 analysis.server;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/file_system/file_system.dart';
@@ skipping 12 matching lines @@
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/source_io.dart';
 import 'package:analyzer/src/generated/java_engine.dart';
 import 'package:analysis_server/src/services/constants.dart';
 import 'package:analysis_server/src/services/correction/change.dart';
 import 'package:analysis_server/src/services/index/index.dart';
 import 'package:analysis_server/src/services/search/search_engine.dart';
 import 'package:analyzer/src/generated/element.dart';
+import 'package:analysis_server/src/services/correction/namespace.dart';
 
 
 class ServerContextManager extends ContextManager {
   final AnalysisServer analysisServer;
 
   /**
    * The default options used to create new analysis contexts.
    */
   AnalysisOptionsImpl defaultOptions = new AnalysisOptionsImpl();
 
@@ skipping 631 matching lines @@
    * offset.
    *
    * May be empty, but not `null`.
    */
   List<Element> getElementsAtOffset(String path, int offset) {
     List<CompilationUnit> units = getResolvedCompilationUnits(path);
     List<Element> elements = <Element>[];
     for (CompilationUnit unit in units) {
       AstNode node = new NodeLocator.con1(offset).searchWithin(unit);
       Element element = ElementLocator.locateWithOffset(node, offset);
+      if (node is SimpleIdentifier && element is PrefixElement) {
+        element = getImportElement(node);
+      }
       if (element != null) {
         elements.add(element);
       }
     }
     return elements;
   }
 
   /**
    * Returns a [Future] completing when [file] has been completely analyzed, in
    * particular, all its errors have been computed.
@@ skipping 138 matching lines @@
 /**
  * An enumeration of the services provided by the server domain.
  */
 class ServerService extends Enum2<ServerService> {
   static const ServerService STATUS = const ServerService('STATUS', 0);
 
   static const List<ServerService> VALUES = const [STATUS];
 
   const ServerService(String name, int ordinal) : super(name, ordinal);
 }