Make hashCode a getter and not a method.

runtime/lib/isolate_patch.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.
 
 patch class _ReceivePortFactory {
   /* patch */ factory ReceivePort() {
     return new _ReceivePortImpl();
   }
 }
 
@@ skipping 73 matching lines @@
         completer.complete(value);
       }
     });
     return completer.future;
   }
 
   bool operator==(var other) {
     return (other is _SendPortImpl) && _id == other._id;
   }
 
-  int hashCode() {
+  int get hashCode {
     return _id;
   }
 
   /*--- private implementation ---*/
   const _SendPortImpl(int id) : _id = id;
 
   // _SendPortImpl._create is called from the VM when a new SendPort instance is
   // needed by the VM code.
   static SendPort _create(int id) {
     return new _SendPortImpl(id);
@@ skipping 15 matching lines @@
   if (_portInternal === null) {
     _portInternal = _getPortInternal();
   }
   return _portInternal;
 }
 
 patch spawnFunction(void topLevelFunction()) native "isolate_spawnFunction";
 
 patch spawnUri(String uri) native "isolate_spawnUri";