Stop using the Hashable interface.

lib/compiler/implementation/tree/nodes.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.
 
 abstract class Visitor<R> {
   R visitBlock(Block node);
   R visitBreakStatement(BreakStatement node);
   R visitCascade(Cascade node);
   R visitCascadeReceiver(CascadeReceiver node);
   R visitCaseMatch(CaseMatch node);
@@ skipping 66 matching lines @@
  * A node in a syntax tree.
  *
  * The abstract part of "abstract syntax tree" is invalidated when
  * supporting tools such as code formatting. These tools need concrete
  * syntax such as parentheses and no constant folding.
  *
  * We support these tools by storing additional references back to the
  * token stream. These references are stored in fields ending with
  * "Token".
  */
-class Node implements Hashable, Spannable {
+class Node implements Spannable {
   final int _hashCode;
   static int _HASH_COUNTER = 0;
 
   Node() : _hashCode = ++_HASH_COUNTER;
 
   hashCode() => _hashCode;
 
   abstract accept(Visitor visitor);
 
   abstract visitChildren(Visitor visitor);
@@ skipping 1795 matching lines @@
  * argument).
  *
  * TODO(ahe): This method is controversial, the team needs to discuss
  * if top-level methods are acceptable and what naming conventions to
  * use.
  */
 initializerDo(Node node, f(Node node)) {
   SendSet send = node.asSendSet();
   if (send !== null) return f(send.arguments.head);
 }