anchor.diff:      'machine',
       '--sdk-warnings',
       '--no-hints',
  +    '--enable-experiment',
  +    'non-nullable',
       emptyProgramUri.toFilePath()
     ]);
   
  
positive.code:           'This name matches one of the possible targets in libraries.json '
            'and it is used to pick which patch files will be applied.',
        allowed: ['dartdevc', 'dart2js', 'dart2js_server', 'vm', 'flutter'],
        defaultsTo: 'dartdevc');
  
negative.code: 
  void main(List<String> argv) {
    var args = _parser.parse(argv);
    if (args['help'] as bool || argv.isEmpty) {
      print('Apply patch file to the SDK and report analysis errors from the '
          'resulting libraries.\n\n'
          'Usage: ${Platform.script.pathSegments.last} [options...]\n\n'
          '${_parser.usage}');
      return;
    }
    String baseDir = args['out'] as String;
    if (baseDir == null) {
      var tmp = Directory.systemTemp.createTempSync('check_sdk-');
  