Work around VM bug in ClassMirror.superclass.

dart/pkg/serialization/lib/src/mirrors_helpers.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.
 
 /**
  * Provides some additional convenience methods on top of the basic mirrors
  */
 library mirrors_helpers;
 
 // Import and re-export mirrors here to minimize both dependence on mirrors
 // and the number of times we have to be told that mirrors aren't finished yet.
 import 'dart:mirrors';
 export 'dart:mirrors';
 import 'serialization_helpers.dart';
 
+// TODO(alanknight): Remove this method.  It is working around a bug
+// in the Dart VM which incorrectly returns Object as the superclass
+// of Object.
+_getSuperclass(ClassMirror mirror) {
+  var superclass = mirror.superclass;
+  return (superclass == mirror) ? null : superclass;
+}
+
 /**
  * Return a list of all the public fields of a class, including inherited
  * fields.
  */
 Iterable<VariableMirror> publicFields(ClassMirror mirror) {
   var mine = mirror.variables.values.where(
       (x) => !(x.isPrivate || x.isStatic));
-  var mySuperclass = mirror.superclass;
-  if (mySuperclass != mirror) {
-    return append(publicFields(mirror.superclass), mine);
+  var mySuperclass = _getSuperclass(mirror);
+  if (mySuperclass != null) {
+    return append(publicFields(mySuperclass), mine);
   } else {
     return mine;
   }
 }
 
 /** Return true if the class has a field named [name]. Note that this
  * includes private fields, but excludes statics. */
 bool hasField(Symbol name, ClassMirror mirror) {
   if (name == null) return false;
   var field = mirror.variables[name];
   if (field != null && !field.isStatic) return true;
-  var superclass = mirror.superclass;
-  if (superclass == mirror) return false;
+  var superclass = _getSuperclass(mirror);
+  if (superclass == null) return false;
   return hasField(name, superclass);
 }
 
 /**
  * Return a list of all the getters of a class, including inherited
  * getters. Note that this allows private getters, but excludes statics.
  */
 Iterable<MethodMirror> publicGetters(ClassMirror mirror) {
   var mine = mirror.getters.values.where((x) => !(x.isPrivate || x.isStatic));
-  var mySuperclass = mirror.superclass;
-  if (mySuperclass != mirror) {
-    return append(publicGetters(mirror.superclass), mine);
+  var mySuperclass = _getSuperclass(mirror);
+  if (mySuperclass != null) {
+    return append(publicGetters(mySuperclass), mine);
   } else {
     return mine.toList();
   }
 }
 
 /** Return true if the class has a getter named [name] */
 bool hasGetter(Symbol name, ClassMirror mirror) {
   if (name == null) return false;
   var getter = mirror.getters[name];
   if (getter != null && !getter.isStatic) return true;
-  var superclass = mirror.superclass;
-  if (superclass == mirror) return false;
+  var superclass = _getSuperclass(mirror);
+  if (superclass == null) return false;
   return hasField(name, superclass);
 }
 
 /**
  * Return a list of all the public getters of a class which have corresponding
  * setters.
  */
 Iterable<MethodMirror> publicGettersWithMatchingSetters(ClassMirror mirror) {
   var setters = mirror.setters;
   return publicGetters(mirror).where((each) =>
     setters["${each.simpleName}="] != null);
 }
 
 /**
  * A particularly bad case of polyfill, because we cannot yet use type names
  * as literals, so we have to be passed an instance and then extract a
  * ClassMirror from that. Given a horrible name as an extra reminder to fix it.
  */
 ClassMirror turnInstanceIntoSomethingWeCanUse(x) => reflect(x).type;