Modernize PR 7240: Use C++20 requires clause and remove redundant executor includes

Author: Hackathon User

libs/core/executors/include/hpx/executors/executor_scheduler.hpp

@@ -14,6 +14,7 @@
 #include <hpx/modules/execution.hpp>
 #include <hpx/modules/execution_base.hpp>
 
+#include <concepts>
 #include <exception>
 #include <type_traits>
 #include <utility>
@@ -109,9 +110,8 @@ namespace hpx::execution::experimental {
 
         constexpr executor_scheduler() = default;
 
-        template <typename Exec,
-            typename = std::enable_if_t<
-                !std::is_same_v<std::decay_t<Exec>, executor_scheduler>>>
+        template <typename Exec>
+            requires(!std::is_same_v<std::decay_t<Exec>, executor_scheduler>)
         explicit executor_scheduler(Exec&& exec)
           : exec_(HPX_FORWARD(Exec, exec))
         {

libs/core/executors/include/hpx/executors/executor_scheduler_bulk.hpp

@@ -8,9 +8,7 @@
 
 #include <hpx/config.hpp>
 
-#if defined(HPX_HAVE_STDEXEC)
 #include <hpx/execution_base/stdexec_forward.hpp>
-#endif
 
 #include <hpx/execution/algorithms/bulk.hpp>
 #include <hpx/execution_base/completion_scheduler.hpp>
@@ -82,7 +80,6 @@ namespace hpx::execution::experimental {
             HPX_NO_UNIQUE_ADDRESS std::decay_t<Shape> shape_;
             HPX_NO_UNIQUE_ADDRESS std::decay_t<F> f_;
 
-#if defined(HPX_HAVE_STDEXEC)
             using sender_concept = hpx::execution::experimental::sender_t;
 
 #if defined(HPX_CLANG_VERSION)
@@ -142,48 +139,7 @@ namespace hpx::execution::experimental {
             {
                 return env{s.sender_, s.exec_};
             }
-#else
-            template <typename Env>
-            struct generate_completion_signatures
-            {
-                template <template <typename...> typename Tuple,
-                    template <typename...> typename Variant>
-                using value_types =
-                    value_types_of_t<Sender, Env, Tuple, Variant>;
-
-                template <template <typename...> typename Variant>
-                using error_types = hpx::util::detail::unique_concat_t<
-                    error_types_of_t<Sender, Env, Variant>,
-                    Variant<std::exception_ptr>>;
-
-                static constexpr bool sends_stopped =
-                    sends_stopped_of_v<Sender, Env>;
-            };
-
-            template <typename Env>
-            friend auto tag_invoke(
-                hpx::execution::experimental::get_completion_signatures_t,
-                executor_bulk_sender const&, Env)
-                -> generate_completion_signatures<Env>;
-
-            template <typename CPO>
-            friend constexpr auto tag_invoke(
-                hpx::execution::experimental::get_completion_scheduler_t<CPO>
-                    tag,
-                executor_bulk_sender const& s)
-            {
-                return tag(s.sender_);
-            }
 
-            friend constexpr auto tag_invoke(
-                hpx::execution::experimental::get_completion_scheduler_t<
-                    hpx::execution::experimental::set_value_t>,
-                executor_bulk_sender const& s)
-            {
-                return hpx::execution::experimental::executor_scheduler<
-                    Executor>{s.exec_};
-            }
-#endif
 
             template <typename Receiver>
             friend auto tag_invoke(connect_t,

libs/core/executors/include/hpx/executors/parallel_executor.hpp

@@ -13,8 +13,6 @@
 #include <hpx/executors/detail/hierarchical_spawning.hpp>
 #include <hpx/executors/detail/index_queue_spawning.hpp>
 #include <hpx/executors/execution_policy_mappings.hpp>
-#include <hpx/executors/executor_scheduler.hpp>
-#include <hpx/executors/executor_scheduler_bulk.hpp>
 #include <hpx/executors/fwd/executor_scheduler_fwd.hpp>
 #include <hpx/modules/allocator_support.hpp>
 #include <hpx/modules/async_base.hpp>
@@ -675,13 +673,13 @@ namespace hpx::execution {
             }
         }
 
-        friend hpx::execution::experimental::executor_scheduler<
-            parallel_policy_executor>
+        template <typename Exec = parallel_policy_executor>
+            requires std::is_same_v<Exec, parallel_policy_executor>
+        friend hpx::execution::experimental::executor_scheduler<Exec>
         tag_invoke(hpx::execution::experimental::get_scheduler_t,
-            parallel_policy_executor const& exec)
+            Exec const& exec)
         {
-            return hpx::execution::experimental::executor_scheduler<
-                parallel_policy_executor>(exec);
+            return hpx::execution::experimental::executor_scheduler<Exec>(exec);
         }
         /// \endcond
 

libs/core/executors/include/hpx/executors/sequenced_executor.hpp

@@ -10,8 +10,6 @@
 
 #include <hpx/config.hpp>
 #include <hpx/executors/execution_policy_mappings.hpp>
-#include <hpx/executors/executor_scheduler.hpp>
-#include <hpx/executors/executor_scheduler_bulk.hpp>
 #include <hpx/executors/fwd/executor_scheduler_fwd.hpp>
 #include <hpx/executors/parallel_executor.hpp>
 #include <hpx/modules/errors.hpp>
@@ -239,13 +237,13 @@ namespace hpx::execution {
 #endif
         }
 
-        friend hpx::execution::experimental::executor_scheduler<
-            sequenced_executor>
+        template <typename Exec = sequenced_executor>
+            requires std::is_same_v<Exec, sequenced_executor>
+        friend hpx::execution::experimental::executor_scheduler<Exec>
         tag_invoke(hpx::execution::experimental::get_scheduler_t,
-            sequenced_executor const& exec)
+            Exec const& exec)
         {
-            return hpx::execution::experimental::executor_scheduler<
-                sequenced_executor>(exec);
+            return hpx::execution::experimental::executor_scheduler<Exec>(exec);
         }
 
     private: