Make hashCode a getter and not a method.

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> {
   const Visitor();
 
   abstract R visitNode(Node node);
 
   R visitBlock(Block node) => visitStatement(node);
@@ skipping 91 matching lines @@
  *
  * 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".
  */
 abstract class Node implements Spannable {
-  final int _hashCode;
+  final int hashCode;
   static int _HASH_COUNTER = 0;
 
-  Node() : _hashCode = ++_HASH_COUNTER;
-
-  hashCode() => _hashCode;
+  Node() : hashCode = ++_HASH_COUNTER;
 
   abstract accept(Visitor visitor);
 
   abstract visitChildren(Visitor visitor);
 
   /**
    * Returns this node unparsed to Dart source string.
    */
   toString() => unparse(this);
 
@@ skipping 1889 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);
 }