anchor.diff:  
           case 1: // Strict line
             if (closeParagraph) {
  -            tight = false;
  -            buildBuffer();
  +            buffer.add('');
             }
             buffer.add(res.value[1]);
             closeParagraph = false;
  
positive.code:       para
    ]);
  
    //
    // Horizontal rule
    //
  
negative.code:   CommonMarkParser();
  
    Map<String, Target> _references;
  
    Map<String, Target> get references => _references; // TODO remove later
  
  