asioexec::completion_token & ::use_sender: Non-Dependent Senders

asioexec::completion_token and ::use_sender are completion tokens which
induce an initiating function to return a sender. Previously these
senders were dependent, but this was not necessary: The completion
signatures thereof are not changed by the environment. Updated the
implementation so that the senders yielded by initiating functions
parameterized by asioexec::completion_token or ::use_sender are no
longer dependent.

Author: RobertLeahy

include/asioexec/completion_token.hpp

@@ -365,17 +365,14 @@ namespace asioexec {
         , args_(static_cast<Us&&>(us)...) {
       }
 
-      template <typename Env>
-        requires std::is_copy_constructible_v<Initiation>
-              && std::is_copy_constructible_v<args_type_>
-      constexpr Signatures get_completion_signatures(const Env&) const & noexcept {
-        return {};
-      }
-
-      template <typename Env>
-        requires std::is_move_constructible_v<Initiation>
-              && std::is_move_constructible_v<args_type_>
-      constexpr Signatures get_completion_signatures(const Env&) && noexcept {
+      template <typename Self, typename... Env>
+        requires std::is_constructible_v<
+                   Initiation,
+                   decltype(::STDEXEC::__forward_like<Self>(std::declval<Initiation&>()))>
+              && std::is_constructible_v<
+                   args_type_,
+                   decltype(::STDEXEC::__forward_like<Self>(std::declval<args_type_&>()))>
+      static consteval Signatures get_completion_signatures() noexcept {
         return {};
       }
 

include/asioexec/use_sender.hpp

@@ -158,15 +158,11 @@ namespace asioexec {
 
       using sender_concept = ::STDEXEC::sender_t;
 
-      template <typename Env>
-      constexpr completion_signatures<::STDEXEC::completion_signatures_of_t<Sender, Env>>
-        get_completion_signatures(const Env&) && noexcept {
-        return {};
-      }
-
-      template <typename Env>
-      constexpr completion_signatures<::STDEXEC::completion_signatures_of_t<const Sender&, Env>>
-        get_completion_signatures(const Env&) const & noexcept {
+      template <typename Self, typename... Env>
+      static consteval completion_signatures<::STDEXEC::completion_signatures_of_t<
+        decltype(::STDEXEC::__forward_like<Self>(std::declval<Sender&>())),
+        Env...>>
+        get_completion_signatures() noexcept {
         return {};
       }
 

test/asioexec/test_use_sender.cpp

@@ -83,6 +83,11 @@ namespace {
     asio_impl::system_timer t(ctx);
     t.expires_after(std::chrono::years(1));
     auto sender = t.async_wait(use_sender);
+    static_assert(::STDEXEC::sender_in<decltype(sender)>);
+    static_assert(
+      ::STDEXEC::sender_of<
+        decltype(sender),
+        ::STDEXEC::set_value_t()>);
     static_assert(
       set_equivalent<
         ::STDEXEC::completion_signatures_of_t<decltype(sender), ::STDEXEC::env<>>,