Make Comparable generic.

pkg/serialization/lib/src/basic_rule.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.
 
 part of serialization;
 
 // TODO(alanknight): Figure out how to reasonably separate out the things
 // that require reflection without making the API more awkward. Or if that is
 // in fact necessary. Maybe the tree-shaking will just remove it if unused.
 
@@ skipping 253 matching lines @@
   // TODO(alanknight): This, and other places, rely on synchronous access to
   // mirrors. Should be changed to use a synchronous API once one is available,
   // or to be async, but that would be extremely ugly.
   _value(InstanceMirror mirror, _Field field) => field.valueIn(mirror);
 }
 
 /**
  * This represents a field in an object. It is intended to be used as part of
  * a [_FieldList].
  */
-abstract class _Field implements Comparable {
+abstract class _Field implements Comparable<_Field> {
 
   /** The FieldList that contains us. */
   final _FieldList fieldList;
 
   /**
    * Our position in the [contents] collection of [fieldList]. This is used
    * to index into the state, so it's extremely important.
    */
   int index;
 
@@ skipping 338 matching lines @@
   _MapWrapper(this.fieldList) : _map = new Map();
   _MapWrapper.fromMap(this._map, this.fieldList);
 
   operator [](key) => _map[fieldList[key].name];
 
   operator []=(key, value) { _map[fieldList[key].name] = value; }
   get length => _map.length;
 
   asMap() => _map;
 }