anchor.diff:        querySelector('#editor-panel-footer') as DivElement;
   
     @override
  -  bool get nullSafetyEnabled => _nullSafetyEnabled;
  +  bool get nullSafetyEnabled => true;
  +
  +  /// Whether null safety was enabled for the previous execution.
  +  @override
  +  bool get nullSafetyWasPreviouslyEnabled => true;
   
     @override
     set nullSafetyEnabled(bool v) {
  
positive.code:   late final MDCButton editorUiOutputTab;
    late final MDCButton editorConsoleTab;
    late final MDCButton editorDocsTab;
    final _nullSafetyEnabled = true;
  
    WorkshopUi() {
      _init();
  
negative.code:     // Set up CodeMirror
      editor = (editorFactory as CodeMirrorFactory)
          .createFromElement(_editorHost, options: codeMirrorOptions)
            ..theme = 'darkpad'
            ..mode = 'dart'
            ..showLineNumbers = true;
  
      context = WorkshopDartSourceProvider(editor);
      docHandler = DocHandler(editor, context);
  