std::execution::sender-to(C++26)

namespace std::execution {
  template<class Sndr, class Rcvr>
  concept sender-to =
    sender_in<Sndr, env_of_t<Rcvr>> &&
    receiver-of<Rcvr, completion_signatures_of_t<Sndr, env_of_t<Rcvr>>> &&
    requires (Sndr&& sndr, Rcvr&& rcvr) {
      connect(std::forward<Sndr>(sndr), std::forward<Rcvr>(rcvr));
    };
}