test/std/utilities/variant/variant.helpers/variant_alternative.fail.cpp

// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

// UNSUPPORTED: c++98, c++03, c++11, c++14

// <variant>

// template <size_t I, class T> struct variant_alternative; // undefined
// template <size_t I, class T> struct variant_alternative<I, const T>;
// template <size_t I, class T> struct variant_alternative<I, volatile T>;
// template <size_t I, class T> struct variant_alternative<I, const volatile T>;
// template <size_t I, class T>
//   using variant_alternative_t = typename variant_alternative<I, T>::type;
//
// template <size_t I, class... Types>
//    struct variant_alternative<I, variant<Types...>>;

#include <memory>
#include <type_traits>
#include <variant>

int main() {
    using V = std::variant<int, void *, const void *, long double>;
    std::variant_alternative<4, V>::type foo;  // expected-error@variant:* {{Index out of bounds in std::variant_alternative<>}}
}