1 // 2 // cpp14/can_require_concept_free.cpp 3 // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4 // 5 // Copyright (c) 2003-2021 Christopher M. Kohlhoff (chris at kohlhoff dot com) 6 // 7 // Distributed under the Boost Software License, Version 1.0. (See accompanying 8 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 9 // 10 11 #include <boost/asio/require_concept.hpp> 12 #include <cassert> 13 14 template <int> 15 struct prop 16 { 17 template <typename> static constexpr bool is_applicable_property_v = true; 18 static constexpr bool is_requirable_concept = true; 19 }; 20 21 template <int> 22 struct object 23 { 24 template <int N> require_concept(const object &,prop<N>)25 friend constexpr object<N> require_concept(const object&, prop<N>) 26 { 27 return object<N>(); 28 } 29 }; 30 main()31int main() 32 { 33 static_assert(boost::asio::can_require_concept_v<object<1>, prop<2>>, ""); 34 static_assert(boost::asio::can_require_concept_v<const object<1>, prop<2>>, ""); 35 } 36