69 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++14, c++1710 11// struct unreachable_sentinel_t;12// inline constexpr unreachable_sentinel_t unreachable_sentinel;13 14#include <iterator>15 16#include <cassert>17#include <concepts>18#include <type_traits>19 20#include "test_macros.h"21 22template<class T, class U>23concept weakly_equality_comparable_with = requires(const T& t, const U& u) {24 { t == u } -> std::same_as<bool>;25 { t != u } -> std::same_as<bool>;26 { u == t } -> std::same_as<bool>;27 { u != t } -> std::same_as<bool>;28};29 30constexpr bool test() {31 static_assert(std::is_empty_v<std::unreachable_sentinel_t>);32 static_assert(std::semiregular<std::unreachable_sentinel_t>);33 34 static_assert(std::same_as<decltype(std::unreachable_sentinel), const std::unreachable_sentinel_t>);35 36 auto sentinel = std::unreachable_sentinel;37 int i = 42;38 assert(i != sentinel);39 assert(sentinel != i);40 assert(!(i == sentinel));41 assert(!(sentinel == i));42 43 assert(&i != sentinel);44 assert(sentinel != &i);45 assert(!(&i == sentinel));46 assert(!(sentinel == &i));47 48 int *p = nullptr;49 assert(p != sentinel);50 assert(sentinel != p);51 assert(!(p == sentinel));52 assert(!(sentinel == p));53 54 static_assert( weakly_equality_comparable_with<std::unreachable_sentinel_t, int>);55 static_assert( weakly_equality_comparable_with<std::unreachable_sentinel_t, int*>);56 static_assert(!weakly_equality_comparable_with<std::unreachable_sentinel_t, void*>);57 ASSERT_NOEXCEPT(sentinel == p);58 ASSERT_NOEXCEPT(sentinel != p);59 60 return true;61}62 63int main(int, char**) {64 test();65 static_assert(test());66 67 return 0;68}69