1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 // UNSUPPORTED: c++03, c++11, c++14, c++17
10 
11 // template<class F, class... Args>
12 // concept relation;
13 
14 #include <concepts>
15 
16 struct S1 {};
17 struct S2 {};
18 
19 struct R {
20   bool operator()(S1, S1) const;
21   bool operator()(S1, S2) const;
22   bool operator()(S2, S1) const;
23   bool operator()(S2, S2) const;
24 };
25 
26 // clang-format off
27 template<class F, class T, class U>
28 requires std::predicate<F, T, T> && std::predicate<F, T, U> &&
29          std::predicate<F, U, T> && std::predicate<F, U, U>
30 constexpr bool check_relation_subsumes_predicate() {
31   return false;
32 }
33 
34 template<class F, class T, class U>
35 requires std::relation<F, T, U> && true
36 constexpr bool check_relation_subsumes_predicate() {
37   return true;
38 }
39 // clang-format on
40 
41 static_assert(
42     check_relation_subsumes_predicate<int (*)(int, double), int, int>());
43 static_assert(
44     check_relation_subsumes_predicate<int (*)(int, double), int, double>());
45 static_assert(check_relation_subsumes_predicate<R, S1, S1>());
46 static_assert(check_relation_subsumes_predicate<R, S1, S2>());
47 
48 // clang-format off
49 template<class F, class T, class U>
50 requires std::relation<F, T, T> && std::relation<F, U, U>
51 constexpr bool check_relation_subsumes_itself() {
52   return false;
53 }
54 
55 template<class F, class T, class U>
56 requires std::relation<F, T, U>
57 constexpr bool check_relation_subsumes_itself() {
58   return true;
59 }
60 // clang-format on
61 
62 static_assert(check_relation_subsumes_itself<int (*)(int, double), int, int>());
63 static_assert(check_relation_subsumes_itself<R, S1, S1>());
64