Use single unit/node/element.

pkg/analysis_server/lib/src/search/search_domain.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 search.domain;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/constants.dart';
@@ skipping 43 matching lines @@
       String searchId = (_nextSearchId++).toString();
       var result = new protocol.SearchFindElementReferencesResult();
       result.id = searchId;
       _sendSearchResult(request, result);
       _sendSearchNotification(searchId, true, <protocol.SearchResult>[]);
       return;
     }
     var params =
         new protocol.SearchFindElementReferencesParams.fromRequest(request);
     await server.onAnalysisComplete;
-    // prepare elements
-    List<Element> elements =
-        server.getElementsAtOffset(params.file, params.offset);
-    elements = elements.map((Element element) {
-      if (element is ImportElement) {
-        return element.prefix;
-      }
-      if (element is FieldFormalParameterElement) {
-        return element.field;
-      }
-      if (element is PropertyAccessorElement) {
-        return element.variable;
-      }
-      return element;
-    }).where((Element element) {
-      return element != null;
-    }).toList();
+    // prepare element
+    Element element = server.getElementAtOffset(params.file, params.offset);
+    if (element is ImportElement) {
+      element = (element as ImportElement).prefix;
+    }
+    if (element is FieldFormalParameterElement) {
+      element = (element as FieldFormalParameterElement).field;
+    }
+    if (element is PropertyAccessorElement) {
+      element = (element as PropertyAccessorElement).variable;
+    }
     // respond
     String searchId = (_nextSearchId++).toString();
     var result = new protocol.SearchFindElementReferencesResult();
-    if (elements.isNotEmpty) {
+    if (element != null) {
       result.id = searchId;
-      result.element = protocol.convertElement(elements.first);
+      result.element = protocol.convertElement(element);
     }
     _sendSearchResult(request, result);
     // search elements
-    elements.forEach((Element element) async {
-      var computer = new ElementReferencesComputer(searchEngine);
-      List<protocol.SearchResult> results =
-          await computer.compute(element, params.includePotential);
-      bool isLast = identical(element, elements.last);
-      _sendSearchNotification(searchId, isLast, results);
-    });
+    var computer = new ElementReferencesComputer(searchEngine);
+    List<protocol.SearchResult> results =
+        await computer.compute(element, params.includePotential);
+    _sendSearchNotification(searchId, true, results);
   }
 
   Future findMemberDeclarations(protocol.Request request) async {
     var params =
         new protocol.SearchFindMemberDeclarationsParams.fromRequest(request);
     await server.onAnalysisComplete;
     // respond
     String searchId = (_nextSearchId++).toString();
     _sendSearchResult(
         request, new protocol.SearchFindMemberDeclarationsResult(searchId));
@@ skipping 57 matching lines @@
     }
     var params = new protocol.SearchGetTypeHierarchyParams.fromRequest(request);
     String file = params.file;
     // wait for analysis
     if (params.superOnly == true) {
       await server.onFileAnalysisComplete(file);
     } else {
       await server.onAnalysisComplete;
     }
     // prepare element
-    List<Element> elements = server.getElementsAtOffset(file, params.offset);
-    if (elements.isEmpty) {
+    Element element = server.getElementAtOffset(file, params.offset);
+    if (element == null) {
       _sendTypeHierarchyNull(request);
       return;
     }
-    Element element = elements.first;
     // maybe supertype hierarchy only
     if (params.superOnly == true) {
       TypeHierarchyComputer computer =
           new TypeHierarchyComputer(searchEngine, element);
       List<protocol.TypeHierarchyItem> items = computer.computeSuper();
       protocol.Response response =
           new protocol.SearchGetTypeHierarchyResult(hierarchyItems: items)
               .toResponse(request.id);
       server.sendResponse(response);
       return;
@@ skipping 55 matching lines @@
   void _sendTypeHierarchyNull(protocol.Request request) {
     protocol.Response response =
         new protocol.SearchGetTypeHierarchyResult().toResponse(request.id);
     server.sendResponse(response);
   }
 
   static protocol.SearchResult toResult(SearchMatch match) {
     return protocol.newSearchResult_fromMatch(match);
   }
 }