anchor.diff:          .listen((_) => showPackageVersionsDialog());
   
       _initChannelsMenu();
  -    final channelsButton = _channelsDropdownButton;
  -    if (channelsButton is ButtonElement) {
  -      MDCButton(channelsButton)
  -          .onClick
  -          .listen((e) => _toggleMenu(_channelsMenu));
  -    }
  +    MDCButton(_channelsDropdownButton)
  +        .onClick
  +        .listen((e) => _toggleMenu(_channelsMenu));
     }
   
     MDCMenu _initSamplesMenu() {
  
positive.code: 
    MDCMenu get _samplesMenu => _initSamplesMenu();
  
    Element? get _channelsDropdownButton =>
        querySelector('#channels-dropdown-button');
  
    bool get _isCompletionActive => editor.completionActive;
  
  
negative.code:       return;
      }
      queryParams.channel = channel;
      final buttonText =
          _channelsDropdownButton.querySelector('.mdc-button__label')!;
      buttonText.text = '$channel channel';
      dartServices.rootUrl = Channel.urlMapping[channel]!;
      updateVersions();
      performAnalysis();
  