Function visit

include/daScript/ast/ast.h:644–644

        virtual ~Expression() {}
        friend StringWriter& operator<< (StringWriter& stream, const Expression & func);
        virtual ExpressionPtr visit(Visitor & /*vis*/ )  { DAS_ASSERT(0); return this; };
        virtual ExpressionPtr clone( ExpressionPtr expr = nullptr ) const;
        static ExpressionPtr autoDereference ( ExpressionPtr expr );
        virtual void markNoDiscard() { }