Markup block - Gen<None> - 5 - (0:0,0)
    Markup span - Gen<Markup> - [foo ] - SpanEditHandler;Accepts:Any - (0:0,0) - Tokens:2
        SyntaxKind.Text;[foo];
        SyntaxKind.Whitespace;[ ];
    Expression block - Gen<Expr> - 1 - (4:0,4)
        Transition span - Gen<None> - [@] - SpanEditHandler;Accepts:None - (4:0,4) - Tokens:1
            SyntaxKind.Transition;[@];
        Code span - Gen<Expr> - [] - ImplicitExpressionEditHandler;Accepts:NonWhitespace;ImplicitExpression[RTD];K14 - (5:0,5) - Tokens:1
            SyntaxKind.Unknown;[];
    Markup span - Gen<Markup> - [] - SpanEditHandler;Accepts:Any - (5:0,5) - Tokens:1
        SyntaxKind.Unknown;[];
