anchor.diff:      _className = style == null ? '': style._className;
       _children = children == null ? _emptyList : children;
   
  -    if (_debugWarnings()) {
  +    if (_isInCheckedMode) {
         _debugReportDuplicateIds();
       }
     }
  
positive.code: import 'dart:sky' as sky;
  import 'reflect.dart' as reflect;
  
  bool _checkedMode;
  
  bool _debugWarnings() {
    void testFn(double i) {}
  
    if (_checkedMode == null) {
      _checkedMode = false;
      try {
        testFn('not a double');
      } catch (ex) {
        _checkedMode = true;
      }
    }
  
    return _checkedMode;
  }
  
  class EventHandler {
    final String type;
  
negative.code: 
    _dirtyComponents.clear();
    _renderScheduled = false;
  
    sw.stop();
    if (_shouldLogRenderDuration)
      print("Render took ${sw.elapsedMicroseconds} microseconds");
  }
  
  void _scheduleComponentForRender(Component c) {
  