anchor.diff:  
       String raw = res.value[0];
       int level = res.value[1][0] == '=' ? 1 : 2;
  -    // TODO parse inlines
  -
       _UnparsedInlines inlines = new _UnparsedInlines(raw.trim());
       return res.copy(value: [new SetextHeader(level, inlines)]);
     });
  
positive.code:   CommonMarkParser();
  
    Map<String, Target> _references;
  
    Map<String, Target> get references => _references; // TODO remove later
  
    Document parse(String s) {
      // TODO separate preprocess option
  
negative.code:       return textRes;
      }
      String raw = textRes.value.join();
      _UnparsedInlines inlines = new _UnparsedInlines(raw.trim());
      return textRes.copy(value: [new AtxHeader(level, inlines)]);
    });
  