Method __completed

include/stdexec/__detail/__task.hpp:518–523

      }

      [[nodiscard]]
      auto __completed() noexcept -> __std::coroutine_handle<> final
      {
        this->__reset_callback();
        return this->__handle().promise().continuation().handle();
      }

      [[nodiscard]]
      auto __canceled() noexcept -> __std::coroutine_handle<> final