anchor.diff:        },
       );
     }
  -
  -  @override
  -  bool get wantKeepAlive => true;
   }
   
   final _pathSeparatorRegExp = RegExp(r'[/\\]');
  
positive.code:         final file = _files[index];
          if (file.isDirectory()) {
            final directory = file.asDirectory();
            return Directory(directory, onTap: () => _browseTo(directory.path));
          } else {
            assert(file.isSong());
            return Song(file.asSong());
  
negative.code: 
    @override
    Widget build(BuildContext context) {
      if (_files == null) {
        return Center(child: CircularProgressIndicator());
      }
  