Generate artificial hashCode for often used classes.

pkg/analyzer/lib/src/generated/engine.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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine;
 
 import "dart:math" as math;
@@ skipping 8646 matching lines @@
     _resolutionState._writeOn(buffer);
   }
 }
 
 /**
  * Instances of the class `DataDescriptor` are immutable constants representing data that can
  * be stored in the cache.
  */
 class DataDescriptor<E> {
   /**
+   * The next artificial hash code.
+   */
+  static int _NEXT_HASH_CODE = 0;
+
+  /**
+   * The artifitial hash code for this object.
+   */
+  final int _hashCode = _NEXT_HASH_CODE++;
+
+  /**
    * The name of the descriptor, used for debugging purposes.
    */
   final String _name;
 
   /**
    * The default value used when the data does not exist.
    */
   final E defaultValue;
 
   /**
    * Initialize a newly created descriptor to have the given [name] and
    * [defaultValue].
    */
   DataDescriptor(this._name, [this.defaultValue = null]);
 
   @override
+  int get hashCode => _hashCode;
+
+  @override
   String toString() => _name;
 }
 
 /**
  * Instances of the class `DefaultRetentionPolicy` implement a retention policy that will keep
  * AST's in the cache if there is analysis information that needs to be computed for a source, where
  * the computation is dependent on having the AST.
  */
 class DefaultRetentionPolicy implements CacheRetentionPolicy {
   /**
@@ skipping 3711 matching lines @@
     if (element.id == _id) {
       result = element;
       throw new _ElementByIdFinderException();
     }
     super.visitElement(element);
   }
 }
 
 class _ElementByIdFinderException {
 }