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 // <compare>
12
13 // template <class ...Ts> struct common_comparison_category
14 // template <class ...Ts> using common_comparison_category_t
15
16
17 #include <compare>
18 #include <type_traits>
19 #include <cassert>
20
21 #include "test_macros.h"
22
23 const volatile void* volatile sink;
24
25 template <class Expect, class ...Args>
test_cat()26 void test_cat() {
27 using Cat = std::common_comparison_category<Args...>;
28 using CatT = typename Cat::type;
29 static_assert(std::is_same<CatT, std::common_comparison_category_t<Args...>>::value, "");
30 static_assert(std::is_same<CatT, Expect>::value, "expected different category");
31 };
32
33
34 // [class.spaceship]p4: The 'common comparison type' U of a possibly-empty list
35 // of 'n' types T0, T1, ..., TN, is defined as follows:
main(int,char **)36 int main(int, char**) {
37 using PO = std::partial_ordering;
38 using WO = std::weak_ordering;
39 using SO = std::strong_ordering;
40
41 // [cmp.common]p2: The member typedef-name type denotes the common comparison
42 /// type ([class.spaceship]) of Ts..., the expanded parameter pack, or void if
43 // any element of Ts is not a comparison category type.
44 {
45 test_cat<void, void>();
46 test_cat<void, int*>();
47 test_cat<void, SO&>();
48 test_cat<void, SO const>();
49 test_cat<void, SO*>();
50 test_cat<void, SO, void, SO>();
51 }
52
53 // [class.spaceship]p4.1: If at least one Ti is std::partial_ordering, U is
54 // std::partial_ordering ([cmp.partialord]).
55 {
56 test_cat<PO, PO>();
57 test_cat<PO, SO, PO, SO>();
58 test_cat<PO, WO, PO, SO>();
59 }
60
61 // [class.spaceship]p4.2: Otherwise, if at least one Ti is std::weak_ordering,
62 // U is std::weak_ordering
63 {
64 test_cat<WO, WO>();
65 test_cat<WO, SO, WO, SO>();
66 }
67
68 // [class.spaceship]p4.3: Otherwise, U is std::strong_ordering.
69 {
70 test_cat<SO, SO>();
71 test_cat<SO, SO, SO>();
72 }
73
74 // [cmp.common]p2, note 2: This is std::strong_ordering if the expansion is empty.
75 // [class.spaceship]p4.3, note 2: In particular this is the result when n is 0.
76 {
77 test_cat<SO>(); // empty type list
78 }
79
80 return 0;
81 }
82