Stop using the Hashable interface.

utils/pub/package.dart

 // Copyright (c) 2012, 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('package');
 
 #import('io.dart');
 #import('pubspec.dart');
 #import('source.dart');
 #import('source_registry.dart');
@@ skipping 76 matching lines @@
 
 /**
  * An unambiguous resolved reference to a package. A package ID contains enough
  * information to correctly install the package.
  *
  * Note that it's possible for multiple distinct package IDs to point to
  * different directories that happen to contain identical packages. For example,
  * the same package may be available from multiple sources. As far as Pub is
  * concerned, those packages are different.
  */
-class PackageId implements Comparable, Hashable {
+class PackageId implements Comparable {
   /// The name of the package being identified.
   final String name;
 
   /**
    * The [Source] used to look up this package given its [description].
    */
   final Source source;
 
   /**
    * The package's version.
@@ skipping 105 matching lines @@
 
 class PubspecNameMismatchException implements Exception {
   final String expectedName;
   final String actualName;
 
   PubspecNameMismatchException(this.expectedName, this.actualName);
 
   String toString() => 'The name you specified for your dependency, '
     '"$expectedName", doesn\'t match the name "$actualName" in its pubspec.';
 }