anchor.diff:  }
   
   _readOptions(options) {
  -  kind = _parseKind(options['kind']);
  -  machineFormat = options['machine'];
  -  overwriteFileContents = options['write'];
  -  selection = _parseSelection(options['selection']);
  +  kind = _parseKind(options[KIND_FLAG]);
  +  machineFormat = options[MACHINE_FLAG];
  +  overwriteFileContents = options[WRITE_FLAG];
  +  selection = _parseSelection(options[SELECTION_FLAG]);
     formatterSettings =
  -      new FormatterOptions(codeTransforms: options['transform']);
  +      new FormatterOptions(codeTransforms: options[TRANSFORM_FLAG],
  +          pageWidth: _toInt(options[MAX_LINE_FLAG]));
   }
   
   CodeKind _parseKind(kindOption) {
  
positive.code: Selection selection;
  final List<String> paths = [];
  
  const FOLLOW_LINKS = false;
  
  
  
negative.code: ArgParser _initArgParser() {
    // NOTE: these flags are placeholders only!
    var parser = new ArgParser();
    parser.addFlag(WRITE_FLAG, abbr: 'w', negatable: false,
        help: 'Write reformatted sources to files (overwriting contents).  '
              'Do not print reformatted sources to standard output.');
    parser.addFlag(TRANSFORM_FLAG, abbr: 't', negatable: false,
        help: 'Perform code transformations.');
    parser.addOption(MAX_LINE_FLAG, abbr: 'l', defaultsTo: '80',
        help: 'Wrap lines longer than this length.');
    parser.addOption(KIND_FLAG, abbr: 'k', defaultsTo: 'cu',
        help: 'Specify source snippet kind ("stmt" or "cu")'
              ' --- [PROVISIONAL API].', hide: true);
    parser.addOption(SELECTION_FLAG, abbr: 's',
        help: 'Specify selection information as an offset,length pair '
              '(e.g., -s "0,4").', hide: true);
    parser.addFlag(MACHINE_FLAG, abbr: 'm', negatable: false,
        help: 'Produce output in a format suitable for parsing.');
    parser.addFlag(HELP_FLAG, abbr: 'h', negatable: false,
        help: 'Print this usage information.');
    return parser;
  }
  