Use Set instead of List for 'dependentResults'.

pkg/analyzer/lib/src/context/cache.dart

 // Copyright (c) 2015, 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 analyzer.src.context.cache;
 
 import 'dart:collection';
 
 import 'package:analyzer/src/generated/engine.dart'
     show AnalysisEngine, CacheState, InternalAnalysisContext, RetentionPriority;
@@ skipping 449 matching lines @@
     }
     // Stop depending on other results.
     TargetedResult thisResult = new TargetedResult(target, descriptor);
     thisData.dependedOnResults.forEach((TargetedResult dependedOnResult) {
       ResultData data = _partition._getDataFor(dependedOnResult, orNull: true);
       if (data != null) {
         data.dependentResults.remove(thisResult);
       }
     });
     // Invalidate results that depend on this result.
-    List<TargetedResult> dependentResults = thisData.dependentResults;
-    thisData.dependentResults = <TargetedResult>[];
+    Set<TargetedResult> dependentResults = thisData.dependentResults;
+    thisData.dependentResults = new Set<TargetedResult>();
     dependentResults.forEach((TargetedResult dependentResult) {
       CacheEntry entry = _partition.get(dependentResult.target);
       if (entry != null) {
         entry._invalidate(dependentResult.result);
       }
     });
     // If empty, remove the entry altogether.
     if (_resultMap.isEmpty) {
       _partition._targetMap.remove(target);
       _partition._removeIfSource(target);
@@ skipping 446 matching lines @@
   Object value;
 
   /**
    * A list of the results on which this result depends.
    */
   List<TargetedResult> dependedOnResults = <TargetedResult>[];
 
   /**
    * A list of the results that depend on this result.
    */
-  List<TargetedResult> dependentResults = <TargetedResult>[];
+  Set<TargetedResult> dependentResults = new Set<TargetedResult>();
 
   /**
    * Initialize a newly created result holder to represent the value of data
    * described by the given [descriptor].
    */
   ResultData(this.descriptor) {
     state = CacheState.INVALID;
     value = descriptor.defaultValue;
   }
 
@@ skipping 92 matching lines @@
   void resultAccessed(TargetedResult result) {}
 
   @override
   List<TargetedResult> resultStored(TargetedResult newResult, newValue) {
     return TargetedResult.EMPTY_LIST;
   }
 
   @override
   void targetRemoved(AnalysisTarget target) {}
 }