Generate artificial hashCode for often used classes.

pkg/analysis_server/lib/src/services/index/index.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 services.index;
 
 import 'dart:async';
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
@@ skipping 302 matching lines @@
  * Relationship between an element and a location. Relationships are identified
  * by a globally unique identifier.
  */
 class Relationship {
   /**
    * A table mapping relationship identifiers to relationships.
    */
   static Map<String, Relationship> _RELATIONSHIP_MAP = {};
 
   /**
+   * The next artificial hash code.
+   */
+  static int _NEXT_HASH_CODE = 0;
+
+  /**
+   * The artifitial hash code for this object.
+   */
+  final int _hashCode = _NEXT_HASH_CODE++;

[kasperl, 2015/02/18 08:04:16]

Have you considered masking here? If you start overflowing the smi limit, you
might get considerably worse performance.

[scheglov, 2015/02/18 17:20:32]

Good question.
See https://codereview.chromium.org/936823002

+
+  /**
    * The unique identifier for this relationship.
    */
   final String identifier;
 
   /**
    * Initialize a newly created relationship with the given unique identifier.
    */
   Relationship(this.identifier);
 
   @override
+  int get hashCode => _hashCode;
+
+  @override
   String toString() => identifier;
 
   /**
    * Returns the relationship with the given unique [identifier].
    */
   static Relationship getRelationship(String identifier) {
     Relationship relationship = _RELATIONSHIP_MAP[identifier];
     if (relationship == null) {
       relationship = new Relationship(identifier);
       _RELATIONSHIP_MAP[identifier] = relationship;
@@ skipping 11 matching lines @@
   static final UniverseElement INSTANCE = new UniverseElement._();
 
   UniverseElement._() : super("--universe--", -1);
 
   @override
   ElementKind get kind => ElementKind.UNIVERSE;
 
   @override
   accept(ElementVisitor visitor) => null;
 }