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 <size_t I, class T> struct variant_alternative; // undefined
14// template <size_t I, class T> struct variant_alternative<I, const T>;
15// template <size_t I, class T> struct variant_alternative<I, volatile T>;
16// template <size_t I, class T> struct variant_alternative<I, const volatile T>;
17// template <size_t I, class T>
18// using variant_alternative_t = typename variant_alternative<I, T>::type;
19//
20// template <size_t I, class... Types>
21// struct variant_alternative<I, variant<Types...>>;
22
23#include <memory>
24#include <type_traits>
25#include <variant>
26
27#include "test_macros.h"
28#include "variant_test_helpers.h"
29
30template <class V, std::size_t I, class E> void test() {
31 static_assert(
32 std::is_same_v<typename std::variant_alternative<I, V>::type, E>, "");
33 static_assert(
34 std::is_same_v<typename std::variant_alternative<I, const V>::type,
35 const E>,
36 "");
37 static_assert(
38 std::is_same_v<typename std::variant_alternative<I, volatile V>::type,
39 volatile E>,
40 "");
41 static_assert(
42 std::is_same_v<
43 typename std::variant_alternative<I, const volatile V>::type,
44 const volatile E>,
45 "");
46 static_assert(std::is_same_v<std::variant_alternative_t<I, V>, E>, "");
47 static_assert(std::is_same_v<std::variant_alternative_t<I, const V>, const E>,
48 "");
49 static_assert(
50 std::is_same_v<std::variant_alternative_t<I, volatile V>, volatile E>,
51 "");
52 static_assert(std::is_same_v<std::variant_alternative_t<I, const volatile V>,
53 const volatile E>,
54 "");
55}
56
57int main(int, char**) {
58 {
59 using V = std::variant<int, void *, const void *, long double>;
60 test<V, 0, int>();
61 test<V, 1, void *>();
62 test<V, 2, const void *>();
63 test<V, 3, long double>();
64 }
65
66 return 0;
67}
68

source code of libcxx/test/std/utilities/variant/variant.helpers/variant_alternative.pass.cpp