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1 | // |
2 | // cpp14/can_prefer_not_applicable_free_require.cpp | |
3 | // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
4 | // | |
5 | // Copyright (c) 2003-2020 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/prefer.hpp> | |
12 | #include <cassert> | |
13 | ||
14 | template <int> | |
15 | struct prop | |
16 | { | |
17 | static constexpr bool is_preferable = true; | |
18 | }; | |
19 | ||
20 | template <int> | |
21 | struct object | |
22 | { | |
23 | template <int N> | |
24 | friend constexpr object<N> require(const object&, prop<N>) | |
25 | { | |
26 | return object<N>(); | |
27 | } | |
28 | }; | |
29 | ||
30 | int main() | |
31 | { | |
32 | static_assert(!boost::asio::can_prefer_v<object<1>, prop<2>>, ""); | |
33 | static_assert(!boost::asio::can_prefer_v<object<1>, prop<2>, prop<3>>, ""); | |
34 | static_assert(!boost::asio::can_prefer_v<object<1>, prop<2>, prop<3>, prop<4>>, ""); | |
35 | static_assert(!boost::asio::can_prefer_v<const object<1>, prop<2>>, ""); | |
36 | static_assert(!boost::asio::can_prefer_v<const object<1>, prop<2>, prop<3>>, ""); | |
37 | static_assert(!boost::asio::can_prefer_v<const object<1>, prop<2>, prop<3>, prop<4>>, ""); | |
38 | } |