anchor.diff:      _channelsMenu?.unlisten('MDCMenu:selected', _handleChannelsMenuSelected);
       _channelsMenu = MDCMenu(menuElement)
         ..setAnchorCorner(AnchorCorner.bottomLeft)
  -      ..setAnchorElement(_channelsDropdownButton as ButtonElement)
  +      ..setAnchorElement(_channelsDropdownButton)
         ..hoistMenuToBody();
   
       _channelsMenu?.listen('MDCMenu:selected', _handleChannelsMenuSelected);
  
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();
  