anchor.diff:    bool _isKeyboardEvent = false;
   
     /// Whether focus should be drawn.
  +  @visibleForTemplate
     bool get showFocus => _isFocused && _isKeyboardEvent;
   
     @HostListener('focus')
  +  @visibleForTesting
  +  @visibleForTemplate
     void onFocus() {
       _isFocused = true;
       if (_group != null) _group.focusSelection.select(this);
     }
   
     @HostListener('blur')
  +  @visibleForTemplate
  +  @visibleForTesting
     void onBlur() {
       _isFocused = false;
       if (_group != null) _group.focusSelection.deselect(this);
  
positive.code:     cd?.valueAccessor = this;
    }
  
    @HostBinding('class')
    static const hostClass = 'themeable';
  
  
negative.code:   bool _checked = false;
  
    /// Current icon, depends on the state of [checked].
    @visibleForTemplate
    Icon get icon => _checked ? checkedIcon : uncheckedIcon;
  
    /// Current tab index, depends on state of [disabled] and selection status
    /// if in group.
    @HostBinding('attr.tabindex')
    @visibleForTesting
    @visibleForTemplate
    int get tabIndex => disabled ? -1 : _enabledTabIndex;
  
    int _enabledTabIndex = 0;
  