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
10
11 // <variant>
12
13 // template <class ...Types> class variant;
14
15 // constexpr variant() noexcept(see below);
16
17 #include <cassert>
18 #include <type_traits>
19 #include <variant>
20 #include <string>
21
22 #include "test_macros.h"
23 #include "variant_test_helpers.h"
24
25 struct NonDefaultConstructible {
NonDefaultConstructibleNonDefaultConstructible26 constexpr NonDefaultConstructible(int) {}
27 };
28
29 struct NotNoexcept {
NotNoexceptNotNoexcept30 NotNoexcept() noexcept(false) {}
31 };
32
33 #ifndef TEST_HAS_NO_EXCEPTIONS
34 struct DefaultCtorThrows {
DefaultCtorThrowsDefaultCtorThrows35 DefaultCtorThrows() { throw 42; }
36 };
37 #endif
38
test_default_ctor_sfinae()39 constexpr void test_default_ctor_sfinae() {
40 {
41 using V = std::variant<std::monostate, int>;
42 static_assert(std::is_default_constructible<V>::value, "");
43 }
44 {
45 using V = std::variant<NonDefaultConstructible, int>;
46 static_assert(!std::is_default_constructible<V>::value, "");
47 }
48 }
49
test_default_ctor_noexcept()50 constexpr void test_default_ctor_noexcept() {
51 {
52 using V = std::variant<int>;
53 static_assert(std::is_nothrow_default_constructible<V>::value, "");
54 }
55 {
56 using V = std::variant<NotNoexcept>;
57 static_assert(!std::is_nothrow_default_constructible<V>::value, "");
58 }
59 }
60
test_default_ctor_throws()61 void test_default_ctor_throws() {
62 #ifndef TEST_HAS_NO_EXCEPTIONS
63 using V = std::variant<DefaultCtorThrows, int>;
64 try {
65 V v;
66 assert(false);
67 } catch (const int& ex) {
68 assert(ex == 42);
69 } catch (...) {
70 assert(false);
71 }
72 #endif
73 }
74
test_default_ctor_basic()75 constexpr void test_default_ctor_basic() {
76 {
77 std::variant<int> v;
78 assert(v.index() == 0);
79 assert(std::get<0>(v) == 0);
80 }
81 {
82 std::variant<int, long> v;
83 assert(v.index() == 0);
84 assert(std::get<0>(v) == 0);
85 }
86 {
87 std::variant<int, NonDefaultConstructible> v;
88 assert(v.index() == 0);
89 assert(std::get<0>(v) == 0);
90 }
91 {
92 using V = std::variant<int, long>;
93 constexpr V v;
94 static_assert(v.index() == 0, "");
95 static_assert(std::get<0>(v) == 0, "");
96 }
97 {
98 using V = std::variant<int, long>;
99 constexpr V v;
100 static_assert(v.index() == 0, "");
101 static_assert(std::get<0>(v) == 0, "");
102 }
103 {
104 using V = std::variant<int, NonDefaultConstructible>;
105 constexpr V v;
106 static_assert(v.index() == 0, "");
107 static_assert(std::get<0>(v) == 0, "");
108 }
109 }
110
issue_86686()111 constexpr void issue_86686() {
112 #if TEST_STD_VER >= 20
113 static_assert(std::variant<std::string>{}.index() == 0);
114 #endif
115 }
116
test()117 constexpr bool test() {
118 test_default_ctor_basic();
119 test_default_ctor_sfinae();
120 test_default_ctor_noexcept();
121 issue_86686();
122
123 return true;
124 }
125
main(int,char **)126 int main(int, char**) {
127 test();
128 test_default_ctor_throws();
129 static_assert(test());
130 return 0;
131 }
132