Support general serializing of functions between JS and Dart

lib/isolate/serialization.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.
 
 class _MessageTraverserVisitedMap {
 
   operator[](var object) => null;
   void operator[]=(var object, var info) { }
 
   void reset() { }
@@ skipping 19 matching lines @@
     }
     return result;
   }
 
   _dispatch(var x) {
     if (isPrimitive(x)) return visitPrimitive(x);
     if (x is List) return visitList(x);
     if (x is Map) return visitMap(x);
     if (x is SendPort) return visitSendPort(x);
     if (x is SendPortSync) return visitSendPortSync(x);
-    if (x is Function) return visitFunction(x);
 
-    // TODO(floitsch): make this a real exception. (which one)?
-    throw "Message serialization: Illegal value $x passed";
+    // Overridable fallback.
+    return visitObject(x);
   }
 
   abstract visitPrimitive(x);
   abstract visitList(List x);
   abstract visitMap(Map x);
   abstract visitSendPort(SendPort x);
   abstract visitSendPortSync(SendPortSync x);
 
-  visitFunction(Function func) {
-    throw "Serialization of functions is not allowed.";
+  visitObject(Object x) {
+    // TODO(floitsch): make this a real exception. (which one)?
+    throw "Message serialization: Illegal value $x passed";
   }
 
   static bool isPrimitive(x) {
     return (x === null) || (x is String) || (x is num) || (x is bool);
   }
 }
 
 
 /** A visitor that recursively copies a message. */
 class _Copier extends _MessageTraverser {
@@ skipping 87 matching lines @@
   }
 
   _deserializeHelper(x) {
     if (isPrimitive(x)) return x;
     assert(x is List);
     switch (x[0]) {
       case 'ref': return _deserializeRef(x);
       case 'list': return _deserializeList(x);
       case 'map': return _deserializeMap(x);
       case 'sendport': return deserializeSendPort(x);
-      // TODO(floitsch): Use real exception (which one?).
-      default: throw "Unexpected serialized object";
+      default: return deserializeObject(x);
     }
   }
 
   _deserializeRef(List x) {
     int id = x[1];
     var result = _deserialized[id];
     assert(result !== null);
     return result;
   }
 
@@ skipping 20 matching lines @@
     for (int i = 0; i < len; i++) {
       var key = _deserializeHelper(keys[i]);
       var value = _deserializeHelper(values[i]);
       result[key] = value;
     }
     return result;
   }
 
   abstract deserializeSendPort(List x);
 
+  deserializeObject(List x) {
+    // TODO(floitsch): Use real exception (which one?).
+    throw "Unexpected serialized object";
+  }
 }