1 // -*- C++ -*-
2 //===----------------------------------------------------------------------===//
3 //
4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5 // See https://llvm.org/LICENSE.txt for license information.
6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //
8 //===----------------------------------------------------------------------===//
9
10 // UNSUPPORTED: c++03, c++11, c++14
11
12 // <variant>
13
14 // template <size_t I, class T> struct variant_alternative; // undefined
15 // template <size_t I, class T> struct variant_alternative<I, const T>;
16 // template <size_t I, class T> struct variant_alternative<I, volatile T>;
17 // template <size_t I, class T> struct variant_alternative<I, const volatile T>;
18 // template <size_t I, class T>
19 // using variant_alternative_t = typename variant_alternative<I, T>::type;
20 //
21 // template <size_t I, class... Types>
22 // struct variant_alternative<I, variant<Types...>>;
23
24 #include <memory>
25 #include <type_traits>
26 #include <variant>
27
28 #include "test_macros.h"
29 #include "variant_test_helpers.h"
30
test()31 template <class V, size_t I, class E> void test() {
32 static_assert(
33 std::is_same_v<typename std::variant_alternative<I, V>::type, E>, "");
34 static_assert(
35 std::is_same_v<typename std::variant_alternative<I, const V>::type,
36 const E>,
37 "");
38 static_assert(
39 std::is_same_v<typename std::variant_alternative<I, volatile V>::type,
40 volatile E>,
41 "");
42 static_assert(
43 std::is_same_v<
44 typename std::variant_alternative<I, const volatile V>::type,
45 const volatile E>,
46 "");
47 static_assert(std::is_same_v<std::variant_alternative_t<I, V>, E>, "");
48 static_assert(std::is_same_v<std::variant_alternative_t<I, const V>, const E>,
49 "");
50 static_assert(
51 std::is_same_v<std::variant_alternative_t<I, volatile V>, volatile E>,
52 "");
53 static_assert(std::is_same_v<std::variant_alternative_t<I, const volatile V>,
54 const volatile E>,
55 "");
56 }
57
main(int,char **)58 int main(int, char**) {
59 {
60 using V = std::variant<int, void *, const void *, long double>;
61 test<V, 0, int>();
62 test<V, 1, void *>();
63 test<V, 2, const void *>();
64 test<V, 3, long double>();
65 }
66 #if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
67 {
68 using V = std::variant<int, int &, const int &, int &&, long double>;
69 test<V, 0, int>();
70 test<V, 1, int &>();
71 test<V, 2, const int &>();
72 test<V, 3, int &&>();
73 test<V, 4, long double>();
74 }
75 #endif
76
77 return 0;
78 }
79