Use artificial hashCode values.

pkg/analyzer/lib/src/task/model.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.task.model;
 
 import 'package:analyzer/src/generated/engine.dart' hide AnalysisTask;
 import 'package:analyzer/src/task/inputs.dart';
 import 'package:analyzer/task/model.dart';
 
@@ skipping 19 matching lines @@
 
   @override
   ListTaskInput<E> of(AnalysisTarget target) =>
       new ListTaskInputImpl<E>(target, this);
 }
 
 /**
  * A concrete implementation of a [ResultDescriptor].
  */
 class ResultDescriptorImpl<V> implements ResultDescriptor<V> {
+  static int _NEXT_HASH = 0;
+
+  @override
+  final hashCode = _NEXT_HASH++;
+
   /**
    * The name of the result, used for debugging.
    */
   final String name;
 
   /**
    * Return the default value for results described by this descriptor.
    */
   final V defaultValue;
 
   /**
    * The caching policy for results described by this descriptor.
    */
   final ResultCachingPolicy<V> cachingPolicy;
 
   /**
    * Initialize a newly created analysis result to have the given [name] and
    * [defaultValue]. If a [cachingPolicy] is provided, it will control how long
    * values associated with this result will remain in the cache.
    */
   ResultDescriptorImpl(this.name, this.defaultValue,
       {this.cachingPolicy: DEFAULT_CACHING_POLICY});
 
   @override
+  bool operator ==(Object other) {
+    return other is ResultDescriptorImpl && other.hashCode == hashCode;
+  }
+
+  @override
   TaskInput<V> of(AnalysisTarget target) =>
       new SimpleTaskInput<V>(target, this);
 
   @override
   String toString() => name;
 }
 
 /**
  * A simple [ResultCachingPolicy] implementation that consider all the objects
  * to be of the size `1`.
@@ skipping 50 matching lines @@
   AnalysisTask createTask(AnalysisContext context, AnalysisTarget target,
       Map<String, dynamic> inputs) {
     AnalysisTask task = buildTask(context, target);
     task.inputs = inputs;
     return task;
   }
 
   @override
   String toString() => name;
 }