Implement dependent_sender

include/beman/execution/detail/basic_sender.hpp

@@ -17,6 +17,7 @@ import beman.execution.detail.completion_signatures_for;
 import beman.execution.detail.connect;
 import beman.execution.detail.connect_all;
 import beman.execution.detail.decays_to;
+import beman.execution.detail.dependent_sender;
 import beman.execution.detail.get_completion_signatures;
 import beman.execution.detail.impls_for;
 import beman.execution.detail.product_type;
@@ -28,6 +29,7 @@ import beman.execution.detail.sender_decompose;
 #include <beman/execution/detail/completion_signatures_for.hpp>
 #include <beman/execution/detail/connect.hpp>
 #include <beman/execution/detail/decays_to.hpp>
+#include <beman/execution/detail/dependent_sender.hpp>
 #include <beman/execution/detail/get_completion_signatures.hpp>
 #include <beman/execution/detail/impls_for.hpp>
 #include <beman/execution/detail/product_type.hpp>
@@ -110,6 +112,7 @@ struct basic_sender : ::beman::execution::detail::product_type<Tag, Data, Child.
     }
 #endif
     template <::beman::execution::detail::decays_to<basic_sender> Self, typename... Env>
+        requires(sizeof...(Env) == 1) || (... && !::beman::execution::dependent_sender<Child>)
     static consteval auto get_completion_signatures() noexcept {
         if constexpr (requires { Tag::template get_completion_signatures<Self, Env...>(); })
             return Tag::template get_completion_signatures<Self, Env...>();

include/beman/execution/detail/common.hpp

@@ -17,6 +17,17 @@
 #define BEMAN_SPECIALIZE_EXPORT template <>
 #endif
 
+#define BEMAN_EXECUTION_TRY_EVAL(rcvr, expr)                                                    \
+    do {                                                                                        \
+        try {                                                                                   \
+            (expr);                                                                             \
+        } catch (...) {                                                                         \
+            if constexpr (!noexcept((expr))) {                                                  \
+                ::beman::execution::set_error(::std::move((rcvr)), ::std::current_exception()); \
+            }                                                                                   \
+        }                                                                                       \
+    } while (false)
+
 // ----------------------------------------------------------------------------
 /*!
  * \mainpage Asynchronous Operation Support

include/beman/execution/detail/dependent_sender.hpp

@@ -0,0 +1,41 @@
+// include/beman/execution/detail/dependent_sender.hpp                     -*-C++-*-
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#ifndef INCLUDED_BEMAN_EXECUTION_DETAIL_DEPENDENT_SENDER
+#define INCLUDED_BEMAN_EXECUTION_DETAIL_DEPENDENT_SENDER
+
+#include <beman/execution/detail/common.hpp>
+#ifdef BEMAN_HAS_IMPORT_STD
+import std;
+#else
+#include <concepts>
+#endif
+#ifdef BEMAN_HAS_MODULES
+import beman.execution.detail.get_completion_signatures;
+import beman.execution.detail.sender;
+#else
+#include <beman/execution/detail/get_completion_signatures.hpp>
+#include <beman/execution/detail/sender.hpp>
+#endif
+
+// ----------------------------------------------------------------------------
+
+namespace beman::execution::detail {
+template <auto>
+auto non_dependent_sender_helper() noexcept -> void {}
+
+template <typename Sender>
+concept non_dependent_sender = ::beman::execution::sender<Sender> && requires {
+    ::beman::execution::detail::non_dependent_sender_helper<::beman::execution::get_completion_signatures<Sender>()>();
+};
+} // namespace beman::execution::detail
+
+namespace beman::execution {
+template <typename Sender>
+concept dependent_sender =
+    ::beman::execution::sender<Sender> && !::beman::execution::detail::non_dependent_sender<Sender>;
+} // namespace beman::execution
+
+// ----------------------------------------------------------------------------
+
+#endif // INCLUDED_BEMAN_EXECUTION_DETAIL_DEPENDENT_SENDER

include/beman/execution/detail/into_variant.hpp

@@ -20,13 +20,17 @@ import beman.execution.detail.completion_signatures;
 import beman.execution.detail.completion_signatures_for;
 import beman.execution.detail.decayed_tuple;
 import beman.execution.detail.default_impls;
+import beman.execution.detail.dependent_sender;
+import beman.execution.detail.dependent_sender_error;
+import beman.execution.detail.env;
 import beman.execution.detail.env_of_t;
 import beman.execution.detail.error_types_of_t;
 import beman.execution.detail.get_domain_early;
 import beman.execution.detail.impls_for;
 import beman.execution.detail.make_sender;
 import beman.execution.detail.meta.combine;
 import beman.execution.detail.sender;
+import beman.execution.detail.sender_adaptor_closure;
 import beman.execution.detail.sends_stopped;
 import beman.execution.detail.set_error;
 import beman.execution.detail.set_stopped;
@@ -39,13 +43,17 @@ import beman.execution.detail.variant_or_empty;
 #include <beman/execution/detail/completion_signatures_for.hpp>
 #include <beman/execution/detail/decayed_tuple.hpp>
 #include <beman/execution/detail/default_impls.hpp>
+#include <beman/execution/detail/dependent_sender.hpp>
+#include <beman/execution/detail/dependent_sender_error.hpp>
+#include <beman/execution/detail/env.hpp>
 #include <beman/execution/detail/env_of_t.hpp>
 #include <beman/execution/detail/error_types_of_t.hpp>
 #include <beman/execution/detail/get_domain_early.hpp>
 #include <beman/execution/detail/impls_for.hpp>
 #include <beman/execution/detail/make_sender.hpp>
 #include <beman/execution/detail/meta_combine.hpp>
 #include <beman/execution/detail/sender.hpp>
+#include <beman/execution/detail/sender_adaptor_closure.hpp>
 #include <beman/execution/detail/sends_stopped.hpp>
 #include <beman/execution/detail/set_error.hpp>
 #include <beman/execution/detail/set_value.hpp>
@@ -56,25 +64,25 @@ import beman.execution.detail.variant_or_empty;
 // ----------------------------------------------------------------------------
 
 namespace beman::execution::detail {
-struct into_variant_t {
+struct into_variant_t : ::beman::execution::sender_adaptor_closure<into_variant_t> {
     template <::beman::execution::sender Sender>
     auto operator()(Sender&& sender) const {
-        // auto domain{::beman::execution::detail::get_domain_early(sender)};
-        //(void)domain;
-        return ::beman::execution::detail::make_sender(*this, {}, ::std::forward<Sender>(sender));
-        // return ::beman::execution::transform_sender(
-        //     ::std::move(domain),
-        //     ::beman::execution::detail::make_sender(*this, {}, ::std::forward<Sender>(sender))
-        //);
+        return ::beman::execution::transform_sender(
+            ::beman::execution::detail::get_domain_early(sender),
+            ::beman::execution::detail::make_sender(*this, {}, ::std::forward<Sender>(sender)));
     }
 
+    auto operator()() const noexcept { return ::beman::execution::detail::make_sender_adaptor(*this); }
+
   private:
     template <typename... E>
     using make_error_types = ::beman::execution::completion_signatures<::beman::execution::set_error_t(E)...>;
 
   private:
-    template <typename, typename>
+    template <typename, typename...>
     struct get_signatures;
+    template <typename Sender>
+    struct get_signatures<Sender> : get_signatures<Sender, ::beman::execution::env<>> {};
     template <::beman::execution::sender Child, typename State, typename Env>
     struct get_signatures<
         ::beman::execution::detail::basic_sender<::beman::execution::detail::into_variant_t, State, Child>,
@@ -99,9 +107,9 @@ struct into_variant_t {
     };
 
   public:
-    template <::beman::execution::sender Sender, typename Env>
+    template <::beman::execution::sender Sender, typename... Env>
     static consteval auto get_completion_signatures() {
-        return get_signatures<::std::remove_cvref_t<Sender>, Env>::get();
+        return get_signatures<::std::remove_cvref_t<Sender>, Env...>::get();
     }
     struct impls_for : ::beman::execution::detail::default_impls {
         struct get_state_impl {
@@ -119,14 +127,14 @@ struct into_variant_t {
                 if constexpr (::std::same_as<Tag, ::beman::execution::set_value_t>) {
                     using variant_type = typename State::type;
                     using tuple_type   = ::beman::execution::detail::decayed_tuple<Args...>;
-                    try {
-                        if constexpr (sizeof...(Args) == 0u)
-                            ::beman::execution::set_value(::std::move(receiver));
-                        else
+                    if constexpr (std::same_as<variant_type, ::beman::execution::detail::empty_variant>) {
+                        static_assert(sizeof...(Args) == 0);
+                        BEMAN_EXECUTION_TRY_EVAL(receiver, ::beman::execution::set_value(std::move(receiver)));
+                    } else {
+                        BEMAN_EXECUTION_TRY_EVAL(
+                            receiver,
                             ::beman::execution::set_value(::std::move(receiver),
-                                                          variant_type(tuple_type{::std::forward<Args>(args)...}));
-                    } catch (...) {
-                        ::beman::execution::set_error(::std::move(receiver), ::std::current_exception());
+                                                          variant_type(tuple_type{::std::forward<Args>(args)...})));
                     }
                 } else {
                     Tag()(::std::move(receiver), ::std::forward<Args>(args)...);

include/beman/execution/detail/read_env.hpp

@@ -17,6 +17,7 @@ import beman.execution.detail.basic_sender;
 import beman.execution.detail.completion_signatures;
 import beman.execution.detail.completion_signatures_for;
 import beman.execution.detail.default_impls;
+import beman.execution.detail.env_of_t;
 import beman.execution.detail.get_env;
 import beman.execution.detail.impls_for;
 import beman.execution.detail.make_sender;
@@ -27,6 +28,7 @@ import beman.execution.detail.set_value;
 #include <beman/execution/detail/completion_signatures.hpp>
 #include <beman/execution/detail/completion_signatures_for.hpp>
 #include <beman/execution/detail/default_impls.hpp>
+#include <beman/execution/detail/env_of_t.hpp>
 #include <beman/execution/detail/get_env.hpp>
 #include <beman/execution/detail/impls_for.hpp>
 #include <beman/execution/detail/make_sender.hpp>
@@ -59,18 +61,21 @@ struct read_env_t {
     };
 
   public:
-    template <typename Sender, typename... Env>
+    template <typename Sender, typename Env>
     static consteval auto get_completion_signatures() {
-        return typename get_signatures<::std::remove_cvref_t<Sender>, Env...>::type{};
+        return typename get_signatures<::std::remove_cvref_t<Sender>, Env>::type{};
     }
     struct impls_for : ::beman::execution::detail::default_impls {
         struct start_impl {
-            auto operator()(auto query, auto& receiver) const noexcept -> void {
+            template <typename Query, typename Receiver>
+            auto operator()(Query query, Receiver& receiver) const noexcept -> void {
                 try {
                     auto env{::beman::execution::get_env(receiver)};
                     ::beman::execution::set_value(::std::move(receiver), query(env));
                 } catch (...) {
-                    ::beman::execution::set_error(::std::move(receiver), ::std::current_exception());
+                    if constexpr (!std::is_nothrow_invocable_v<Query, ::beman::execution::env_of_t<Receiver>>) {
+                        ::beman::execution::set_error(::std::move(receiver), ::std::current_exception());
+                    }
                 }
             }
         };

include/beman/execution/detail/sender.hpp

@@ -42,7 +42,10 @@ concept enable_sender =
 } // namespace beman::execution::detail
 namespace beman::execution {
 template <typename Sender>
-concept sender = ::beman::execution::detail::enable_sender<::std::remove_cvref_t<Sender>> &&
+inline constexpr bool enable_sender = ::beman::execution::detail::enable_sender<Sender>;
+
+template <typename Sender>
+concept sender = ::beman::execution::enable_sender<::std::remove_cvref_t<Sender>> &&
                  requires(const ::std::remove_cvref_t<Sender>& sndr) {
                      { ::beman::execution::get_env(sndr) } -> ::beman::execution::detail::queryable;
                  } && ::std::move_constructible<::std::remove_cvref_t<Sender>> &&

include/beman/execution/detail/then.hpp

@@ -21,6 +21,9 @@ import beman.execution.detail.completion_signatures;
 import beman.execution.detail.completion_signatures_for;
 import beman.execution.detail.completion_signatures_of_t;
 import beman.execution.detail.default_impls;
+import beman.execution.detail.dependent_sender;
+import beman.execution.detail.dependent_sender_error;
+import beman.execution.detail.env;
 import beman.execution.detail.get_domain_early;
 import beman.execution.detail.impls_for;
 import beman.execution.detail.make_sender;
@@ -41,6 +44,9 @@ import beman.execution.detail.transform_sender;
 #include <beman/execution/detail/completion_signatures_for.hpp>
 #include <beman/execution/detail/completion_signatures_of_t.hpp>
 #include <beman/execution/detail/default_impls.hpp>
+#include <beman/execution/detail/dependent_sender.hpp>
+#include <beman/execution/detail/dependent_sender_error.hpp>
+#include <beman/execution/detail/env.hpp>
 #include <beman/execution/detail/get_domain_early.hpp>
 #include <beman/execution/detail/impls_for.hpp>
 #include <beman/execution/detail/make_sender.hpp>
@@ -125,17 +131,19 @@ struct then_t : ::beman::execution::sender_adaptor_closure<then_t<Completion>> {
   private:
     template <typename, typename...>
     struct get_signatures;
-    template <typename Comp, typename Fun, typename Child, typename... Env>
+    template <typename Sender>
+    struct get_signatures<Sender> : get_signatures<Sender, ::beman::execution::env<>> {};
+    template <typename Comp, typename Fun, typename Child, typename Env>
     struct get_signatures<
         ::beman::execution::detail::basic_sender<::beman::execution::detail::then_t<Comp>, Fun, Child>,
-        Env...> {
+        Env> {
         using type = ::beman::execution::detail::meta::unique<::beman::execution::detail::meta::combine<
             ::beman::execution::detail::meta::transform<
                 ::beman::execution::detail::then_transform_t<Fun, Comp>::template transform,
-                ::beman::execution::completion_signatures_of_t<Child, Env...>>,
+                ::beman::execution::completion_signatures_of_t<Child, Env>>,
             ::std::conditional_t<
                 ::beman::execution::detail::
-                    then_exception<Comp, Fun, ::beman::execution::completion_signatures_of_t<Child, Env...>>::value,
+                    then_exception<Comp, Fun, ::beman::execution::completion_signatures_of_t<Child, Env>>::value,
                 ::beman::execution::completion_signatures<::beman::execution::set_error_t(::std::exception_ptr)>,
                 ::beman::execution::completion_signatures<>>>>;
     };