CSharpCodeBlock - [0..19)::19 - [@val?[null ?? true]]
    CSharpImplicitExpression - [0..19)::19
        CSharpTransition - [0..1)::1 - Gen<None> - SpanEditHandler;Accepts:None
            Transition;[@];
        CSharpImplicitExpressionBody - [1..19)::18
            CSharpCodeBlock - [1..19)::18
                CSharpExpressionLiteral - [1..19)::18 - [val?[null ?? true]] - Gen<Expr> - ImplicitExpressionEditHandler;Accepts:NonWhitespace;ImplicitExpression[RTD];K14
                    Identifier;[val];
                    QuestionMark;[?];
                    LeftBracket;[[];
                    Keyword;[null];
                    Whitespace;[ ];
                    NullCoalesce;[??];
                    Whitespace;[ ];
                    Keyword;[true];
                    RightBracket;[]];
