Function move_back

include/boost/parser/parser.hpp:2150–2155

        template<typename Container, typename T>
        constexpr void move_back(Container & c, T && x, bool gen_attrs)
        {
            if (!gen_attrs)
                return;
            detail::move_back_impl(c, (T &&)x);
        }

        template<typename Container>
        constexpr void move_back(Container & c, Container & x, bool gen_attrs)