Interaction with passing lvalue to set_value when sender sends a value

Tái hiện chẩn đoán bằng lệnh gcc-13 được báo cáo và tệp mẫu set_value.cpp, sau đó kiểm tra khu vực xung quanh việc kiểm tra completion-signature trong stdexec/include/stdexec/execution.hpp. Xác định cách xử lý dự kiến đối với một lvalue được truyền vào set_value khi sender khai báo set_value_t(int), và bổ sung coverage thể hiện hành vi đã thống nhất.

In the sample code below, compiling with gcc-13 ( g++-13 -std=c++20 set_value.cpp -I stdexec/include -c), my bespoke sender claims it completes with set_value_t(int), although the implementation ends up sending an lvalue v, an int declared on the stack.

#include <stdexec/execution.hpp>
#include <exec/finally.hpp>

struct StdexecSender {

  using is_sender = void;

  template <class Receiver>
  struct Operation {
    Receiver r;

    friend auto tag_invoke(stdexec::start_t, Operation& self) noexcept {
      int v = 0;
      stdexec::set_value((Receiver&&)self.r, v);
    };
  };

  template <class Self, class Receiver>
      requires (std::same_as<StdexecSender, std::remove_cv_t<Self>>)
  friend auto tag_invoke(stdexec::connect_t, Self&& self, Receiver&& r) {
    return Operation<std::decay_t<Receiver>>(std::forward<Receiver>(r));
  }

  using completion_signatures = stdexec::completion_signatures<stdexec::set_value_t(int)>;

};
static_assert(stdexec::sender<StdexecSender>);

void foo() {
    stdexec::sync_wait(exec::finally(stdexec::let_value(StdexecSender{}, [](auto&&...) { return StdexecSender{}; }), stdexec::just()));
}

I get the following diagnostic.

./stdexec/include/exec/../stdexec/execution.hpp:1010:38: warning: 'void stdexec::__debug::_ATTENTION_() [with _Warning = stdexec::_WARNING_<_COMPLETION_SIGNATURES_MISMATCH_, _COMPLETION_SIGNATURE_<stdexec::__receivers::set_value_t(int&)>, _IS_NOT_ONE_OF_<stdexec::__receivers::set_error_t(std::__exception_ptr::exception_ptr), stdexec::__receivers::set_value_t(int)>, _SIGNAL_SENT_BY_SENDER_<stdexec::__let::__sender<stdexec::_Yp<StdexecSender>, main()::<lambda(auto:86&& ...)>, stdexec::__let::let_value_t> > >]' is deprecated: The sender claims to send a particular set of completions, but in actual fact it completes with a result that is not one of the declared completion signatures. [-Wdeprecated-declarations]

The key part is

The sender claims to send a particular set of completions, but in actual fact it completes with a result that is not one of the declared completion signatures.

This makes sense given that technically, I should be sending std::move(v) or something of that nature. That said, the lvalue v is convertible to a plain value (I'm not sure what the type category is called here). My understanding is that set_value is akin to returning from a function. A function declared returning int can write return v - should I be able to write set_value(v) here?