Cleaned up a few analyzer warnings

sky/sdk/lib/widgets/widget.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:mirrors';
 import 'dart:sky' as sky;
 
 import '../app/view.dart';
@@ skipping 91 matching lines @@
     return ancestor;
   }
 
   void removeChild(Widget node) {
     node.remove();
   }
 
   // Returns the child which should be retained as the child of this node.
   Widget syncChild(Widget node, Widget oldNode, dynamic slot) {
 
-    assert(oldNode is! Component || !oldNode._disqualifiedFromEverAppearingAgain);
+    assert(oldNode is! Component || 
+        !(oldNode as Component)._disqualifiedFromEverAppearingAgain);

[Hixie, 2015/06/17 17:11:17]

this warning is a bug in the analyzer, you should leave it as it was.

[hansmuller, 2015/06/17 17:35:39]

Done.

 
     if (node == oldNode) {
       assert(node == null || node.mounted);
       return node; // Nothing to do. Subtrees must be identical.
     }
 
     if (node == null) {
       // the child in this slot has gone away
       assert(oldNode.mounted);
       removeChild(oldNode);
@@ skipping 717 matching lines @@
     if (root.parent == null) {
       // we haven't attached it yet
       assert(_container.child == null);
       _container.child = root;
     }
     assert(root.parent == _container);
   }
 
   Widget build() => builder();
 }