68 lines · cpp
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-exception6//7//===----------------------------------------------------------------------===//8 9// UNSUPPORTED: c++03, c++11, c++1410 11// <variant>12 13// template <size_t I, class T> struct variant_alternative; // undefined14// 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