Markup block - Gen<None> - 12 - (0:0,0)
    HtmlComment block - Gen<None> - 12 - (0:0,0)
        Markup span - Gen<Markup> - [<!--] - SpanEditHandler;Accepts:None - (0:0,0) - Symbols:3
            HtmlSymbolType.OpenAngle;[<];
            HtmlSymbolType.Bang;[!];
            HtmlSymbolType.DoubleHyphen;[--];
        Markup span - Gen<Markup> - [ foo ] - SpanEditHandler;Accepts:WhiteSpace - (4:0,4) - Symbols:3
            HtmlSymbolType.WhiteSpace;[ ];
            HtmlSymbolType.Text;[foo];
            HtmlSymbolType.WhiteSpace;[ ];
        Markup span - Gen<Markup> - [-->] - SpanEditHandler;Accepts:None - (9:0,9) - Symbols:2
            HtmlSymbolType.DoubleHyphen;[--];
            HtmlSymbolType.CloseAngle;[>];
