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From a707db8193b30b6cc4a3d10ee946f7f245e07097 Mon Sep 17 00:00:00 2001
From: Christopher Kohlhoff <chris@kohlhoff.com>
Date: Tue, 7 Apr 2020 11:18:31 +1000
Subject: [PATCH] Support C++20 concept syntax.
---
include/boost/asio/async_result.hpp | 18 +++++++++++-------
include/boost/asio/detail/config.hpp | 10 +++++++---
2 files changed, 18 insertions(+), 10 deletions(-)
diff --git a/include/boost/asio/async_result.hpp b/include/boost/asio/async_result.hpp
index 2f4b337d1..0eea0f471 100644
--- boost/asio/async_result.hpp
+++ boost/asio/async_result.hpp
@@ -66,9 +66,10 @@ BOOST_ASIO_CONCEPT completion_signature =
#define BOOST_ASIO_COMPLETION_SIGNATURE \
::boost::asio::completion_signature
-template <typename T, completion_signature Signature>
+template <typename T, typename Signature>
BOOST_ASIO_CONCEPT completion_handler_for =
- detail::is_completion_handler_for<T, Signature>::value;
+ detail::is_completion_signature<Signature>::value
+ && detail::is_completion_handler_for<T, Signature>::value;
#define BOOST_ASIO_COMPLETION_HANDLER_FOR(s) \
::boost::asio::completion_handler_for<s>
@@ -488,11 +489,14 @@ struct initiation_archetype
} // namespace detail
-template <typename T, completion_signature Signature>
-BOOST_ASIO_CONCEPT completion_token_for = requires(T&& t)
-{
- async_initiate<T, Signature>(detail::initiation_archetype<Signature>{}, t);
-};
+template <typename T, typename Signature>
+BOOST_ASIO_CONCEPT completion_token_for =
+ detail::is_completion_signature<Signature>::value
+ &&
+ requires(T&& t)
+ {
+ async_initiate<T, Signature>(detail::initiation_archetype<Signature>{}, t);
+ };
#define BOOST_ASIO_COMPLETION_TOKEN_FOR(s) \
::boost::asio::completion_token_for<s>
diff --git a/include/boost/asio/detail/config.hpp b/include/boost/asio/detail/config.hpp
index 27d1d6753..6b85cccea 100644
--- boost/asio/detail/config.hpp
+++ boost/asio/detail/config.hpp
@@ -343,10 +343,14 @@
// Support concepts on compilers known to allow them.
#if !defined(BOOST_ASIO_HAS_CONCEPTS)
# if !defined(BOOST_ASIO_DISABLE_CONCEPTS)
-# if __cpp_concepts
+# if defined(__cpp_concepts)
# define BOOST_ASIO_HAS_CONCEPTS 1
-# define BOOST_ASIO_CONCEPT concept bool
-# endif // __cpp_concepts
+# if (__cpp_concepts >= 201707)
+# define BOOST_ASIO_CONCEPT concept
+# else // (__cpp_concepts >= 201707)
+# define BOOST_ASIO_CONCEPT concept bool
+# endif // (__cpp_concepts >= 201707)
+# endif // defined(__cpp_concepts)
# endif // !defined(BOOST_ASIO_DISABLE_CONCEPTS)
#endif // !defined(BOOST_ASIO_HAS_CONCEPTS)
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