anchor.diff:  // warn about them.
   // Covers anything with leading digits/symbols, empty string, weird punctuation, spaces.
   final RegExp notARealDocReference = new RegExp(r'''(^[^\w]|^[\d]|[,"'/]|^$)''');
  +
  +final HtmlEscape htmlEscape = const HtmlEscape(HtmlEscapeMode.ELEMENT);
   
   final List<md.InlineSyntax> _markdown_syntaxes = [
     new _InlineCodeSyntax(),
  
positive.code:   @override
    bool onMatch(md.InlineParser parser, Match match) {
      var url = match[1];
      var text = md.escapeHtml(url).replaceFirst(_hide_schemes, '');
      var anchor = new md.Element.text('a', text);
      anchor.attributes['href'] = url;
      parser.addNode(anchor);
  
negative.code:   "video",
    "wbr"
  ];
  
  final RegExp nonHTML =
      new RegExp("</?(?!(${validHtmlTags.join("|")})[> ])\\w+[> ]");
  
  