Function prefix_parse

include/boost/parser/parser.hpp:9295–9323

            detail::is_equality_comparable_with_v<I, S>>>
#endif
    auto prefix_parse(
        I & first,
        S last,
        parser_interface<Parser, GlobalState, ErrorHandler> const & parser,
        trace trace_mode = trace::off)
    {
        if constexpr (!detail::is_char8_iter_v<I>) {
            if (trace_mode == trace::on) {
                return detail::parse_impl<(true && BOOST_PARSER_DO_TRACE)>(
                    first, last, parser, parser.error_handler_);
            } else {
                return detail::parse_impl<false>(
                    first, last, parser, parser.error_handler_);
            }
        } else {
            auto r =
                BOOST_PARSER_SUBRANGE(first, last) | detail::text::as_utf32;
            auto f = r.begin();
            auto const l = r.end();
            auto _ = detail::scoped_base_assign(first, f);
            if (trace_mode == trace::on) {
                return detail::parse_impl<(true && BOOST_PARSER_DO_TRACE)>(
                    f, l, parser, parser.error_handler_);
            } else {
                return detail::parse_impl<false>(
                    f, l, parser, parser.error_handler_);
            }
        }
    }

    /** Parses `r` using `parser`.  Returns a `std::optional` containing the
        attribute produced by `parser` on parse success, and `std::nullopt` on