migrate most senders to use static consteval version of get_completion_signatures

examples/algorithms/retry.hpp

@@ -119,10 +119,9 @@ struct _retry_sender {
   template <class... Ts>
   using _value = stdexec::completion_signatures<stdexec::set_value_t(Ts...)>;
 
-  template <class Env>
-  auto get_completion_signatures(Env&&) const -> stdexec::transform_completion_signatures_of<
-    S&,
-    Env,
+  template <class Self, class... Env>
+  static consteval auto get_completion_signatures() -> stdexec::transform_completion_signatures<
+    stdexec::completion_signatures_of_t<S&, Env...>,
     stdexec::completion_signatures<stdexec::set_error_t(std::exception_ptr)>,
     _value,
     _error

examples/algorithms/then.hpp

@@ -64,16 +64,15 @@ struct _then_sender {
   using _set_value_t =
     stdexec::completion_signatures<stdexec::set_value_t(std::invoke_result_t<F, Args...>)>;
 
-  template <class Env>
-  using _completions_t = stdexec::transform_completion_signatures_of<
-    S,
-    Env,
+  template <class... Env>
+  using _completions_t = stdexec::transform_completion_signatures<
+    stdexec::completion_signatures_of_t<S, Env...>,
     stdexec::completion_signatures<stdexec::set_error_t(std::exception_ptr)>,
     _set_value_t
   >;
 
-  template <class Env>
-  auto get_completion_signatures(Env&&) && -> _completions_t<Env> {
+  template <class, class... Env>
+  static consteval auto get_completion_signatures() -> _completions_t<Env...> {
     return {};
   }
 

examples/benchmark/static_thread_pool_old.hpp

@@ -494,11 +494,9 @@ namespace exec_old {
     STDEXEC_EXPLICIT_THIS_END(connect)
 
     template <stdexec::__decays_to<bulk_sender> Self, class Env>
-    STDEXEC_EXPLICIT_THIS_BEGIN(auto get_completion_signatures)(this Self&&, Env&&)
-      -> completion_signatures<Self, Env> {
+    static consteval auto get_completion_signatures() -> completion_signatures<Self, Env> {
       return {};
     }
-    STDEXEC_EXPLICIT_THIS_END(get_completion_signatures)
 
     auto get_env() const noexcept -> stdexec::env_of_t<const Sender&> {
       return stdexec::get_env(sndr_);

include/exec/__detail/__basic_sequence.hpp

@@ -74,7 +74,7 @@ namespace exec {
     };
 
     template <class _Tag, class _Data, class... _Child>
-    STDEXEC_ATTRIBUTE(host, device)
+    STDEXEC_HOST_DEVICE_DEDUCTION_GUIDE
     __seqexpr(_Tag, _Data, _Child...)
       -> __seqexpr<STDEXEC_SEXPR_DESCRIPTOR(_Tag, _Data, _Child...)>;
   } // namespace

include/exec/any_sender_of.hpp

@@ -1233,11 +1233,9 @@ namespace exec {
 
       template <STDEXEC::__decays_to_derived_from<any_sender> _Self, class... _Env>
         requires(__any::__satisfies_receiver_query<decltype(_ReceiverQueries), _Env...> && ...)
-      STDEXEC_EXPLICIT_THIS_BEGIN(auto get_completion_signatures)(this _Self&&, _Env&&...) noexcept
-        -> __sender_base::completion_signatures {
+      static consteval auto get_completion_signatures() -> __sender_base::completion_signatures {
         return {};
       }
-      STDEXEC_EXPLICIT_THIS_END(get_completion_signatures)
 
       template <STDEXEC::receiver_of<_Completions> _Receiver>
       auto connect(_Receiver __rcvr) && -> STDEXEC::connect_result_t<__sender_base, _Receiver> {

include/exec/async_scope.hpp

@@ -131,11 +131,10 @@ namespace exec {
         STDEXEC_EXPLICIT_THIS_END(connect)
 
         template <__decays_to<__t> _Self, class... _Env>
-        STDEXEC_EXPLICIT_THIS_BEGIN(auto get_completion_signatures)(this _Self&&, _Env&&...)
+        static consteval auto get_completion_signatures()
           -> __completion_signatures_of_t<__copy_cvref_t<_Self, _Constrained>, __env_t<_Env>...> {
           return {};
         }
-        STDEXEC_EXPLICIT_THIS_END(get_completion_signatures)
 
         const __impl* __scope_;
         STDEXEC_ATTRIBUTE(no_unique_address) _Constrained __c_;
@@ -278,11 +277,10 @@ namespace exec {
         STDEXEC_EXPLICIT_THIS_END(connect)
 
         template <__decays_to<__t> _Self, class... _Env>
-        STDEXEC_EXPLICIT_THIS_BEGIN(auto get_completion_signatures)(this _Self&&, _Env&&...)
+        static consteval auto get_completion_signatures()
           -> __completion_signatures_of_t<__copy_cvref_t<_Self, _Constrained>, __env_t<_Env>...> {
           return {};
         }
-        STDEXEC_EXPLICIT_THIS_END(get_completion_signatures)
       };
     };
 
@@ -684,11 +682,9 @@ namespace exec {
         STDEXEC_EXPLICIT_THIS_END(connect)
 
         template <__decays_to<__t> _Self, class... _OtherEnv>
-        STDEXEC_EXPLICIT_THIS_BEGIN(auto get_completion_signatures)(this _Self&&, _OtherEnv&&...)
-          -> __completions_t<_Self> {
+        static consteval auto get_completion_signatures() -> __completions_t<_Self> {
           return {};
         }
-        STDEXEC_EXPLICIT_THIS_END(get_completion_signatures)
 
        private:
         friend struct async_scope;

include/exec/at_coroutine_exit.hpp

@@ -91,11 +91,9 @@ namespace exec {
           }
 
           template <__same_as<__t> _Self, class... _Env>
-          STDEXEC_EXPLICIT_THIS_BEGIN(auto get_completion_signatures)(this _Self&&, _Env&&...)
-            -> __completions_t<_Env...> {
+          static consteval auto get_completion_signatures() -> __completions_t<_Env...> {
             return {};
           }
-          STDEXEC_EXPLICIT_THIS_END(get_completion_signatures)
 
           auto get_env() const noexcept -> env_of_t<_Sender> {
             return STDEXEC::get_env(__sender_);

include/exec/completion_signatures.hpp

@@ -39,6 +39,17 @@ namespace exec {
       detail::normalize(static_cast<Sigs*>(nullptr))...));
   } // namespace detail
 
+  ///////////////////////////////////////////////////////////////////////////////////////////////////
+  // get_child_completion_signatures
+  template <STDEXEC::sender _Parent, STDEXEC::sender _Child, class... _Env>
+  [[nodiscard]]
+  consteval auto get_child_completion_signatures() {
+    return STDEXEC::get_completion_signatures<
+      STDEXEC::__copy_cvref_t<_Parent, _Child>,
+      STDEXEC::__fwd_env_t<_Env>...
+    >();
+  }
+
   //! Creates a compile-time completion signatures type from explicit and deduced signature types.
   //!
   //! This function is a compile-time helper that constructs a completion signatures type
@@ -213,8 +224,8 @@ namespace exec {
     ErrorFn error_fn = {},
     StoppedFn stopped_fn = {},
     ExtraSigs = {}) {
-    STDEXEC_COMPLSIGS_LET(auto(completions) = Completions{}) {
-      STDEXEC_COMPLSIGS_LET(auto(extra_sigs) = ExtraSigs{}) {
+    STDEXEC_COMPLSIGS_LET(completions, Completions{}) {
+      STDEXEC_COMPLSIGS_LET(extra_sigs, ExtraSigs{}) {
         detail::_transform_one<ValueFn, ErrorFn, StoppedFn> tfx1{value_fn, error_fn, stopped_fn};
         return concat_completion_signatures(
           completions.__apply(detail::_transform_all_fn{tfx1}), extra_sigs);

include/exec/env.hpp

@@ -126,8 +126,8 @@ namespace exec {
       }
       STDEXEC_EXPLICIT_THIS_END(connect)
 
-      template <class _Env>
-      constexpr auto get_completion_signatures(_Env&&) -> __completions_t<_Env> {
+      template <class, class _Env>
+      static consteval auto get_completion_signatures() -> __completions_t<_Env> {
         return {};
       }
     };
@@ -166,12 +166,10 @@ namespace exec {
         }
 
         template <__decays_to<__t> _Self, class... _Env>
-        constexpr STDEXEC_EXPLICIT_THIS_BEGIN(
-          auto get_completion_signatures)(this _Self&&, _Env&&...)
+        static consteval auto get_completion_signatures()
           -> __completion_signatures_of_t<__copy_cvref_t<_Self, _Sender>, _Env...> {
           return {};
         }
-        STDEXEC_EXPLICIT_THIS_END(get_completion_signatures)
 
         template <__decays_to<__t> _Self, class _Receiver>
           requires sender_in<__copy_cvref_t<_Self, _Sender>, env_of_t<_Receiver>>