Add execution::operation_state concept and execution::is_operation_state trait.

asio/include/Makefile.am

@@ -308,6 +308,7 @@ nobase_include_HEADERS = \
 	asio/execution/invocable_archetype.hpp \
 	asio/execution/mapping.hpp \
 	asio/execution/occupancy.hpp \
+	asio/execution/operation_state.hpp \
 	asio/execution/outstanding_work.hpp \
 	asio/execution/prefer_only.hpp \
 	asio/execution/receiver.hpp \

asio/include/asio.hpp

@@ -66,6 +66,7 @@
 #include "asio/execution/invocable_archetype.hpp"
 #include "asio/execution/mapping.hpp"
 #include "asio/execution/occupancy.hpp"
+#include "asio/execution/operation_state.hpp"
 #include "asio/execution/outstanding_work.hpp"
 #include "asio/execution/prefer_only.hpp"
 #include "asio/execution/receiver.hpp"

asio/include/asio/detail/type_traits.hpp

@@ -36,6 +36,7 @@
 # include <boost/type_traits/is_copy_constructible.hpp>
 # include <boost/type_traits/is_destructible.hpp>
 # include <boost/type_traits/is_function.hpp>
+# include <boost/type_traits/is_object.hpp>
 # include <boost/type_traits/is_same.hpp>
 # include <boost/type_traits/remove_cv.hpp>
 # include <boost/type_traits/remove_pointer.hpp>
@@ -68,6 +69,7 @@ using std::is_function;
 using std::is_move_constructible;
 using std::is_nothrow_copy_constructible;
 using std::is_nothrow_destructible;
+using std::is_object;
 using std::is_reference;
 using std::is_same;
 using std::is_scalar;
@@ -114,6 +116,7 @@ template <typename T>
 struct is_nothrow_copy_constructible : boost::has_nothrow_copy<T> {};
 template <typename T>
 struct is_nothrow_destructible : boost::has_nothrow_destructor<T> {};
+using boost::is_object;
 using boost::is_reference;
 using boost::is_same;
 using boost::is_scalar;

asio/include/asio/execution.hpp

@@ -28,6 +28,7 @@
 #include "asio/execution/invocable_archetype.hpp"
 #include "asio/execution/mapping.hpp"
 #include "asio/execution/occupancy.hpp"
+#include "asio/execution/operation_state.hpp"
 #include "asio/execution/outstanding_work.hpp"
 #include "asio/execution/prefer_only.hpp"
 #include "asio/execution/receiver.hpp"

asio/include/asio/execution/operation_state.hpp

@@ -0,0 +1,82 @@
+//
+// execution/operation_state.hpp
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+//
+// 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)
+//
+
+#ifndef ASIO_EXECUTION_OPERATION_STATE_HPP
+#define ASIO_EXECUTION_OPERATION_STATE_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include "asio/detail/config.hpp"
+#include "asio/detail/type_traits.hpp"
+#include "asio/execution/start.hpp"
+
+#if defined(ASIO_HAS_DEDUCED_START_FREE_TRAIT) \
+  && defined(ASIO_HAS_DEDUCED_START_MEMBER_TRAIT)
+# define ASIO_HAS_DEDUCED_EXECUTION_IS_OPERATION_STATE_TRAIT 1
+#endif // defined(ASIO_HAS_DEDUCED_START_FREE_TRAIT)
+       //   && defined(ASIO_HAS_DEDUCED_START_MEMBER_TRAIT)
+
+#include "asio/detail/push_options.hpp"
+
+namespace asio {
+namespace execution {
+
+/// The is_operation_state trait detects whether a type T satisfies the
+/// execution::operation_state concept.
+/**
+ * Class template @c is_operation_state is a type trait that is derived from
+ * @c true_type if the type @c T meets the concept definition for an
+ * @c operation_state, otherwise @c false_type.
+ */
+template <typename T>
+struct is_operation_state :
+#if defined(GENERATING_DOCUMENTATION)
+  integral_constant<bool, automatically_determined>
+#else // defined(GENERATING_DOCUMENTATION)
+  integral_constant<bool,
+    is_destructible<T>::value
+      && is_object<T>::value
+      && can_start<T&>::value
+      && is_nothrow_start<T&>::value
+  >
+#endif // defined(GENERATING_DOCUMENTATION)
+{
+};
+
+#if defined(ASIO_HAS_VARIABLE_TEMPLATES)
+
+template <typename T>
+ASIO_CONSTEXPR const bool is_operation_state_v =
+  is_operation_state<T>::value;
+
+#endif // defined(ASIO_HAS_VARIABLE_TEMPLATES)
+
+#if defined(ASIO_HAS_CONCEPTS)
+
+template <typename T>
+ASIO_CONCEPT operation_state = is_operation_state<T>::value;
+
+#define ASIO_EXECUTION_OPERATION_STATE \
+  ::asio::execution::operation_state
+
+#else // defined(ASIO_HAS_CONCEPTS)
+
+#define ASIO_EXECUTION_OPERATION_STATE typename
+
+#endif // defined(ASIO_HAS_CONCEPTS)
+
+} // namespace execution
+} // namespace asio
+
+#include "asio/detail/pop_options.hpp"
+
+#endif // ASIO_EXECUTION_OPERATION_STATE_HPP

asio/src/Makefile.msc

@@ -156,6 +156,7 @@ UNIT_TEST_EXES = \
 	tests\unit\execution\executor.exe \
 	tests\unit\execution\invocable_archetype.exe \
 	tests\unit\execution\mapping.exe \
+	tests\unit\execution\operation_state.exe \
 	tests\unit\execution\outstanding_work.exe \
 	tests\unit\execution\prefer_only.exe \
 	tests\unit\execution\receiver.exe \

asio/src/tests/Makefile.am

@@ -52,6 +52,7 @@ check_PROGRAMS = \
 	unit/execution/executor \
 	unit/execution/invocable_archetype \
 	unit/execution/mapping \
+	unit/execution/operation_state \
 	unit/execution/outstanding_work \
 	unit/execution/prefer_only \
 	unit/execution/receiver \
@@ -211,6 +212,7 @@ TESTS = \
 	unit/execution/executor \
 	unit/execution/invocable_archetype \
 	unit/execution/mapping \
+	unit/execution/operation_state \
 	unit/execution/outstanding_work \
 	unit/execution/prefer_only \
 	unit/execution/receiver \
@@ -371,6 +373,7 @@ 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
+unit_execution_operation_state_SOURCES = unit/execution/operation_state.cpp
 unit_execution_prefer_only_SOURCES = unit/execution/prefer_only.cpp
 unit_execution_receiver_SOURCES = unit/execution/receiver.cpp
 unit_execution_relationship_SOURCES = unit/execution/relationship.cpp

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

@@ -16,6 +16,7 @@ execute
 executor
 invocable_archetype
 mapping
+operation_state
 outstanding_work
 prefer_only
 receiver

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

@@ -0,0 +1,99 @@
+//
+// operation_state.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/operation_state.hpp"
+
+#include <string>
+#include "asio/error_code.hpp"
+#include "../unit_test.hpp"
+
+struct not_an_operation_state_1
+{
+};
+
+struct not_an_operation_state_2
+{
+  void start()
+  {
+  }
+};
+
+namespace asio {
+namespace traits {
+
+#if !defined(ASIO_HAS_DEDUCED_START_MEMBER_TRAIT)
+
+template <>
+struct start_member<not_an_operation_state_2>
+{
+  ASIO_STATIC_CONSTEXPR(bool, is_valid = true);
+  ASIO_STATIC_CONSTEXPR(bool, is_noexcept = false);
+  typedef void result_type;
+};
+
+#endif // !defined(ASIO_HAS_DEDUCED_START_MEMBER_TRAIT)
+
+} // namespace traits
+} // namespace asio
+
+struct operation_state
+{
+  void start() ASIO_NOEXCEPT
+  {
+  }
+};
+
+namespace asio {
+namespace traits {
+
+#if !defined(ASIO_HAS_DEDUCED_START_MEMBER_TRAIT)
+
+template <>
+struct start_member<operation_state>
+{
+  ASIO_STATIC_CONSTEXPR(bool, is_valid = true);
+  ASIO_STATIC_CONSTEXPR(bool, is_noexcept = true);
+  typedef void result_type;
+};
+
+#endif // !defined(ASIO_HAS_DEDUCED_START_MEMBER_TRAIT)
+
+} // namespace traits
+} // namespace asio
+
+void is_operation_state_test()
+{
+  ASIO_CHECK((
+      !asio::execution::is_operation_state<
+        not_an_operation_state_1
+      >::value));
+
+  ASIO_CHECK((
+      !asio::execution::is_operation_state<
+        not_an_operation_state_2
+      >::value));
+
+  ASIO_CHECK((
+      asio::execution::is_operation_state<
+        operation_state
+      >::value));
+}
+
+ASIO_TEST_SUITE
+(
+  "operation_state",
+  ASIO_TEST_CASE(is_operation_state_test)
+)