public override JsonValueSyntax VisitUnknownSymbolSyntax(GreenJsonUnknownSymbolSyntax green, JsonValueWithBackgroundSyntax parent) => new JsonUnknownSymbolSyntax(parent, green);
public virtual TResult VisitUnknownSymbolSyntax(GreenJsonUnknownSymbolSyntax node, T arg) => DefaultVisit(node, arg);