Class scoped_base_assign

include/boost/parser/parser.hpp:2377–2386

        template<typename BaseIter, typename Iter>
        struct scoped_base_assign
        {
            scoped_base_assign(BaseIter & base, Iter & it) :
                base_(base), it_(it)
            {}
            ~scoped_base_assign() { base_ = it_.base(); }

            BaseIter & base_;
            Iter & it_;
        };

        template<typename Parser>
        using has_parser_data_member_expr =