Add SearchEngine.membersOfSubtypes().

pkg/analysis_server/lib/src/services/search/search_engine_internal.dart

 // Copyright (c) 2016, 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.
 
 import 'dart:async';
 
 import 'package:analysis_server/src/services/search/search_engine.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart';
 import 'package:analyzer/src/dart/analysis/search.dart';
 import 'package:analyzer/src/generated/source.dart' show Source, SourceRange;
 import 'package:meta/meta.dart';
 
 /**
  * A [SearchEngine] implementation.
  */
 class SearchEngineImpl implements SearchEngine {
   final Iterable<AnalysisDriver> _drivers;
 
   SearchEngineImpl(this._drivers);
 
   @override
+  Future<Set<String>> membersOfSubtypes(ClassElement type) async {
+    List<AnalysisDriver> drivers = _drivers.toList();
+
+    bool hasSubtypes = false;
+    Set<String> visitedIds = new Set<String>();
+    Set<String> members = new Set<String>();
+
+    Future<Null> addMembers(ClassElement type, SubtypeResult subtype) async {
+      if (subtype != null && !visitedIds.add(subtype.id)) {
+        return;
+      }
+      for (AnalysisDriver driver in drivers) {
+        List<SubtypeResult> subtypes =
+            await driver.search.subtypes(type: type, subtype: subtype);
+        for (var subtype in subtypes) {
+          hasSubtypes = true;
+          members.addAll(subtype.members);
+          await addMembers(null, subtype);
+        }
+      }
+    }
+
+    await addMembers(type, null);
+
+    if (!hasSubtypes) {
+      return null;
+    }
+    return members;
+  }
+
+  @override
   Future<Set<ClassElement>> searchAllSubtypes(ClassElement type) async {
     Set<ClassElement> allSubtypes = new Set<ClassElement>();
 
     Future<Null> addSubtypes(ClassElement type) async {
       List<SearchResult> directResults = await _searchDirectSubtypes(type);
       for (SearchResult directResult in directResults) {
         var directSubtype = directResult.enclosingElement as ClassElement;
         if (allSubtypes.add(directSubtype)) {
           await addSubtypes(directSubtype);
         }
@@ skipping 162 matching lines @@
     }
     if (kind == SearchResultKind.WRITE) {
       return MatchKind.WRITE;
     }
     if (kind == SearchResultKind.INVOCATION) {
       return MatchKind.INVOCATION;
     }
     return MatchKind.REFERENCE;
   }
 }