Add execution::executor_of concept and execution::is_executor trait.

asio/include/asio/execution/executor.hpp

@@ -33,6 +33,31 @@
 
 namespace asio {
 namespace execution {
+namespace detail {
+
+template <typename T, typename F>
+struct is_executor_of_impl :
+  integral_constant<bool,
+    conditional<true, true_type,
+        typename result_of<typename decay<F>::type&()>::type
+      >::type::value
+      && is_constructible<typename decay<F>::type, F>::value
+      && is_move_constructible<typename decay<F>::type>::value
+      && can_execute<T, F>::value
+#if defined(ASIO_HAS_NOEXCEPT)
+      && is_nothrow_copy_constructible<T>::value
+      && is_nothrow_destructible<T>::value
+#else // defined(ASIO_HAS_NOEXCEPT)
+      && is_copy_constructible<T>::value
+      && is_destructible<T>::value
+#endif // defined(ASIO_HAS_NOEXCEPT)
+      && traits::equality_comparable<T>::is_valid
+      && traits::equality_comparable<T>::is_noexcept
+  >
+{
+};
+
+} // namespace detail
 
 /// The is_executor trait detects whether a type T satisfies the
 /// execution::executor concept.
@@ -46,18 +71,7 @@ struct is_executor :
 #if defined(GENERATING_DOCUMENTATION)
   integral_constant<bool, automatically_determined>
 #else // defined(GENERATING_DOCUMENTATION)
-  integral_constant<bool,
+  detail::is_executor_of_impl<T, invocable_archetype>
-    can_execute<const T, invocable_archetype>::value
-#if defined(ASIO_HAS_NOEXCEPT)
-      && is_nothrow_copy_constructible<T>::value
-      && is_nothrow_destructible<T>::value
-#else // defined(ASIO_HAS_NOEXCEPT)
-      && is_copy_constructible<T>::value
-      && is_destructible<T>::value
-#endif // defined(ASIO_HAS_NOEXCEPT)
-      && traits::equality_comparable<typename decay<T>::type>::is_valid
-      && traits::equality_comparable<typename decay<T>::type>::is_noexcept
-  >
 #endif // defined(GENERATING_DOCUMENTATION)
 {
 };
@@ -82,6 +96,47 @@ ASIO_CONCEPT executor = is_executor<T>::value;
 
 #endif // defined(ASIO_HAS_CONCEPTS)
 
+/// The is_executor_of trait detects whether a type T satisfies the
+/// execution::executor_of concept for some set of value arguments.
+/**
+ * Class template @c is_executor_of is a type trait that is derived from @c
+ * true_type if the type @c T meets the concept definition for a executor for
+ * value arguments @c Vs, otherwise @c false_type.
+ */
+template <typename T, typename F>
+struct is_executor_of :
+#if defined(GENERATING_DOCUMENTATION)
+  integral_constant<bool, automatically_determined>
+#else // defined(GENERATING_DOCUMENTATION)
+  integral_constant<bool,
+    is_executor<T>::value && detail::is_executor_of_impl<T, F>::value
+  >
+#endif // defined(GENERATING_DOCUMENTATION)
+{
+};
+
+#if defined(ASIO_HAS_VARIABLE_TEMPLATES)
+
+template <typename T, typename F>
+ASIO_CONSTEXPR const bool is_executor_of_v =
+  is_executor_of<T, F>::value;
+
+#endif // defined(ASIO_HAS_VARIABLE_TEMPLATES)
+
+#if defined(ASIO_HAS_CONCEPTS)
+
+template <typename T, typename F>
+ASIO_CONCEPT executor_of = is_executor_of<T, F>::value;
+
+#define ASIO_EXECUTION_EXECUTOR_OF(f) \
+  ::asio::execution::executor_of<f>
+
+#else // defined(ASIO_HAS_CONCEPTS)
+
+#define ASIO_EXECUTION_EXECUTOR_OF typename
+
+#endif // defined(ASIO_HAS_CONCEPTS)
+
 } // namespace execution
 } // namespace asio
 

asio/src/Makefile.msc

@@ -153,6 +153,7 @@ UNIT_TEST_EXES = \
 	tests\unit\execution\bulk_guarantee.exe \
 	tests\unit\execution\context_as.exe \
 	tests\unit\execution\execute.exe \
+	tests\unit\execution\executor.exe \
 	tests\unit\execution\invocable_archetype.exe \
 	tests\unit\execution\mapping.exe \
 	tests\unit\execution\outstanding_work.exe \

asio/src/tests/Makefile.am

@@ -49,6 +49,7 @@ check_PROGRAMS = \
 	unit/execution/bulk_guarantee \
 	unit/execution/context_as \
 	unit/execution/execute \
+	unit/execution/executor \
 	unit/execution/invocable_archetype \
 	unit/execution/mapping \
 	unit/execution/outstanding_work \
@@ -206,6 +207,7 @@ TESTS = \
 	unit/execution/bulk_guarantee \
 	unit/execution/context_as \
 	unit/execution/execute \
+	unit/execution/executor \
 	unit/execution/invocable_archetype \
 	unit/execution/mapping \
 	unit/execution/outstanding_work \
@@ -363,6 +365,7 @@ unit_execution_blocking_adaptation_SOURCES = unit/execution/blocking_adaptation.
 unit_execution_bulk_guarantee_SOURCES = unit/execution/bulk_guarantee.cpp
 unit_execution_context_as_SOURCES = unit/execution/context_as.cpp
 unit_execution_execute_SOURCES = unit/execution/execute.cpp
+unit_execution_executor_SOURCES = unit/execution/executor.cpp
 unit_execution_invocable_archetype_SOURCES = unit/execution/invocable_archetype.cpp
 unit_execution_mapping_SOURCES = unit/execution/mapping.cpp
 unit_execution_outstanding_work_SOURCES = unit/execution/outstanding_work.cpp

asio/src/tests/unit/execution/.gitignore

@@ -13,6 +13,7 @@ blocking_adaptation
 bulk_guarantee
 context_as
 execute
+executor
 invocable_archetype
 mapping
 outstanding_work

asio/src/tests/unit/execution/executor.cpp

@@ -0,0 +1,119 @@
+//
+// executor.cpp
+// ~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2020 Christopher M. Kohlhoff (chris at kohlhoff dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+// Disable autolinking for unit tests.
+#if !defined(BOOST_ALL_NO_LIB)
+#define BOOST_ALL_NO_LIB 1
+#endif // !defined(BOOST_ALL_NO_LIB)
+
+// Test that header file is self-contained.
+#include "asio/execution/executor.hpp"
+
+#include "../unit_test.hpp"
+
+struct not_an_executor
+{
+};
+
+struct executor
+{
+  executor()
+  {
+  }
+
+  executor(const executor&) ASIO_NOEXCEPT
+  {
+  }
+
+#if defined(ASIO_HAS_MOVE)
+  executor(executor&&) ASIO_NOEXCEPT
+  {
+  }
+#endif // defined(ASIO_HAS_MOVE)
+
+  template <typename F>
+  void execute(ASIO_MOVE_ARG(F) f) const ASIO_NOEXCEPT
+  {
+    (void)f;
+  }
+
+  bool operator==(const executor&) const ASIO_NOEXCEPT
+  {
+    return true;
+  }
+
+  bool operator!=(const executor&) const ASIO_NOEXCEPT
+  {
+    return false;
+  }
+};
+
+namespace asio {
+namespace traits {
+
+#if !defined(ASIO_HAS_DEDUCED_EXECUTE_MEMBER_TRAIT)
+
+template <typename F>
+struct execute_member<executor, F>
+{
+  ASIO_STATIC_CONSTEXPR(bool, is_valid = true);
+  ASIO_STATIC_CONSTEXPR(bool, is_noexcept = true);
+  typedef void result_type;
+};
+
+#endif // !defined(ASIO_HAS_DEDUCED_SET_ERROR_MEMBER_TRAIT)
+#if !defined(ASIO_HAS_DEDUCED_EQUALITY_COMPARABLE_TRAIT)
+
+template <>
+struct equality_comparable<executor>
+{
+  ASIO_STATIC_CONSTEXPR(bool, is_valid = true);
+  ASIO_STATIC_CONSTEXPR(bool, is_noexcept = true);
+};
+
+#endif // !defined(ASIO_HAS_DEDUCED_EQUALITY_COMPARABLE_TRAIT)
+
+} // namespace traits
+} // namespace asio
+
+void is_executor_test()
+{
+  ASIO_CHECK((
+      !asio::execution::is_executor<
+        not_an_executor
+      >::value));
+
+  ASIO_CHECK((
+      asio::execution::is_executor<
+        executor
+      >::value));
+}
+
+void is_executor_of_test()
+{
+  ASIO_CHECK((
+      !asio::execution::is_executor_of<
+        not_an_executor,
+        void(*)()
+      >::value));
+
+  ASIO_CHECK((
+      asio::execution::is_executor_of<
+        executor,
+        void(*)()
+      >::value));
+}
+
+ASIO_TEST_SUITE
+(
+  "executor",
+  ASIO_TEST_CASE(is_executor_test)
+  ASIO_TEST_CASE(is_executor_of_test)
+)