Method __run

include/stdexec/__detail/__spawn_future.hpp:675–684

      ~__future_operation() {}

      void __run() noexcept(__stop_callback_is_nothrow_constructible<env_of_t<_Receiver>>)
      {
        // this might throw
        std::construct_at(&__callback_,
                          STDEXEC::get_stop_token(STDEXEC::get_env(__rcvr_)),
                          __future_stop_callback{this->__future_.get()});

        // this is no-throw
        this->__future_.release()->__consume(__inner_rcvr_);
      }

      _Receiver __rcvr_;