simplify mmdeploy::Expand sender adaptor

csrc/mmdeploy/execution/expand.h

@@ -11,66 +11,39 @@ namespace mmdeploy {
 
 namespace _expand {
 
-template <typename Sender, typename Receiver>
-struct _Operation {
-  struct type;
-};
-template <typename Sender, typename Receiver>
-using operation_t = typename _Operation<Sender, remove_cvref_t<Receiver>>::type;
-
 template <typename Sender, typename Receiver>
 struct _Receiver {
-  struct type;
+  struct type {
+    Receiver receiver_;
+    template <class Tuple>
+    friend void tag_invoke(set_value_t, type&& self, Tuple&& tup) noexcept {
+      std::apply(
+          [&](auto&&... args) {
+            SetValue((Receiver &&) self.receiver_, (decltype(args)&&)args...);
+          },
+          (Tuple &&) tup);
+    }
+  };
 };
 template <typename Sender, typename Receiver>
-using receiver_t = typename _Receiver<Sender, Receiver>::type;
-
-template <typename Sender, typename Receiver>
-struct _Receiver<Sender, Receiver>::type {
-  operation_t<Sender, Receiver>* op_state_;
-
-  template <class Tuple>
-  friend void tag_invoke(set_value_t, type&& self, Tuple&& tup) noexcept {
-    std::apply(
-        [&](auto&&... args) {
-          SetValue((Receiver &&) self.op_state_->receiver_, (decltype(args)&&)args...);
-        },
-        (Tuple &&) tup);
-  }
-};
-
-template <typename Sender, typename Receiver>
-struct _Operation<Sender, Receiver>::type {
-  connect_result_t<Sender, receiver_t<Sender, Receiver>> op_state2_;
-  Receiver receiver_;
-
-  template <typename Sender2>
-  type(Sender2&& sender, Receiver&& receiver)
-      : op_state2_(Connect((Sender2 &&) sender, receiver_t<Sender, Receiver>{this})),
-        receiver_((Receiver &&) receiver) {}
-
-  friend void tag_invoke(start_t, type& op_state) { Start(op_state.op_state2_); }
-};
+using receiver_t = typename _Receiver<Sender, remove_cvref_t<Receiver>>::type;
 
 template <typename Sender>
 struct _Sender {
-  struct type;
+  struct type {
+    using value_types = std::tuple_element_t<0, completion_signatures_of_t<Sender>>;
+    Sender sender_;
+
+    template <typename Self, typename Receiver, _decays_to<Self, type, bool> = true>
+    friend auto tag_invoke(connect_t, Self&& self, Receiver&& receiver) {
+      return Connect(((Self &&) self).sender_,
+                     receiver_t<Sender, Receiver>{(Receiver &&) receiver});
+    }
+  };
 };
 template <typename Sender>
 using sender_t = typename _Sender<remove_cvref_t<Sender>>::type;
 
-template <typename Sender>
-struct _Sender<Sender>::type {
-  using value_types = std::tuple_element_t<0, completion_signatures_of_t<Sender>>;
-  Sender sender_;
-
-  template <typename Self, typename Receiver, _decays_to<Self, type, bool> = true>
-  friend auto tag_invoke(connect_t, Self&& self, Receiver&& receiver)
-      -> operation_t<Sender, Receiver> {
-    return operation_t<Sender, Receiver>(((Self &&) self).sender_, (Receiver &&) receiver);
-  }
-};
-
 struct expand_t {
   template <typename Sender, std::enable_if_t<_is_sender<Sender>, int> = 0>
   auto operator()(Sender&& sender) const {