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 equivalence_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::relation<F, T, U>
29 constexpr bool check_equivalence_relation_subsumes_relation() {
30   return false;
31 }
32 
33 template<class F, class T, class U>
34 requires std::equivalence_relation<F, T, U> && true
35 constexpr bool check_equivalence_relation_subsumes_relation() {
36   return true;
37 }
38 // clang-format on
39 
40 static_assert(check_equivalence_relation_subsumes_relation<int (*)(int, int), int, int>());
41 static_assert(check_equivalence_relation_subsumes_relation<int (*)(int, double), int, double>());
42 static_assert(check_equivalence_relation_subsumes_relation<R, S1, S1>());
43 static_assert(check_equivalence_relation_subsumes_relation<R, S1, S2>());
44 
45 // clang-format off
46 template<class F, class T, class U>
47 requires std::relation<F, T, U> && true
48 constexpr bool check_relation_subsumes_equivalence_relation() {
49   return true;
50 }
51 
52 template<class F, class T, class U>
53 requires std::equivalence_relation<F, T, U>
54 constexpr bool check_relation_subsumes_equivalence_relation() {
55   return false;
56 }
57 // clang-format on
58 
59 static_assert(check_relation_subsumes_equivalence_relation<int (*)(int, int), int, int>());
60 static_assert(check_relation_subsumes_equivalence_relation<int (*)(int, double), int, double>());
61 static_assert(check_relation_subsumes_equivalence_relation<R, S1, S1>());
62 static_assert(check_relation_subsumes_equivalence_relation<R, S1, S2>());
63 
64 // clang-format off
65 template<class F, class T, class U>
66 requires std::equivalence_relation<F, T, T> && std::equivalence_relation<F, U, U>
67 constexpr bool check_equivalence_relation_subsumes_itself() {
68   return false;
69 }
70 
71 template<class F, class T, class U>
72 requires std::equivalence_relation<F, T, U>
73 constexpr bool check_equivalence_relation_subsumes_itself() {
74   return true;
75 }
76 // clang-format on
77 
78 static_assert(
79     check_equivalence_relation_subsumes_itself<int (*)(int, int), int, int>());
80 static_assert(check_equivalence_relation_subsumes_itself<R, S1, S1>());
81