anchor.diff:    void _sync(StatefulComponent old, dynamic slot) {
       if (old == null) {
         if (!_isStateInitialized) {
  +        assert(mounted);
  +        assert(!_wasMounted);
           initState();
           _isStateInitialized = true;
         }
  
positive.code: 
  void _debugReportException(String context, dynamic exception, StackTrace stack) {
    print('------------------------------------------------------------------------');
    print('Exception caught while $context');
    print('$exception');
    print('Stack trace:');
    '$stack'.split('\n').forEach(print);
  
negative.code: 
  // TODO(ianh): Move this to Widget
  void _endSyncPhase() {
    try {
      Widget._currentGeneration += 1;
      Widget._notifyMountStatusChanged();
    } catch (e, stack) {
      _debugReportException('sending post-sync notifications', e, stack);
      return null;
    }
  }
  
  // TODO(ianh): Move this to Component
  