Function has_attribute

include/boost/parser/parser.hpp:9984–9990

        template<typename Iter, typename Sentinel, typename Parser>
        auto has_attribute(Iter first, Sentinel last, Parser parser)
        {
            using attr_t = typename attribute_impl<
                BOOST_PARSER_SUBRANGE<Iter, Sentinel>,
                Parser>::type;
            return std::integral_constant<bool, !is_nope_v<attr_t>>{};
        }

        template<typename T>
        constexpr wrapper<T> attr_wrapped_final;