Method __get_completion_signatures

include/exec/repeat_until.hpp:327–332

    {
      template <class _CvSender, class... _Env>
      static consteval auto __get_completion_signatures()
      {
        using __child_t  = __call_result_t<then_t, __child_of<_CvSender>, _never>;
        using __parent_t = __call_result_t<repeat_until_t, __child_t>;
        return __repeat_until_impl::__get_completion_signatures<__parent_t, _Env...>();
      }
    };
  }  // namespace __repeat