| // { dg-do run { target c++17 } } |
| |
| // Copyright (C) 2016-2021 Free Software Foundation, Inc. |
| // |
| // This file is part of the GNU ISO C++ Library. This library is free |
| // software; you can redistribute it and/or modify it under the |
| // terms of the GNU General Public License as published by the |
| // Free Software Foundation; either version 3, or (at your option) |
| // any later version. |
| |
| // This library is distributed in the hope that it will be useful, |
| // but WITHOUT ANY WARRANTY; without even the implied warranty of |
| // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| // GNU General Public License for more details. |
| |
| // You should have received a copy of the GNU General Public License along |
| // with this library; see the file COPYING3. If not see |
| // <http://www.gnu.org/licenses/>. |
| |
| #include <optional> |
| #include <testsuite_hooks.h> |
| |
| class S{}; // No hash specialization |
| |
| template<class T> |
| auto f(int) -> decltype(std::hash<std::optional<T>>(), std::true_type()); |
| |
| template<class T> |
| auto f(...) -> decltype(std::false_type()); |
| |
| static_assert(!decltype(f<S>(0))::value, ""); |
| |
| template<typename T> |
| constexpr bool hashable() |
| { return std::is_invocable_v<std::hash<T>&, const T&>; } |
| |
| static_assert(!hashable<std::optional<S>>()); |
| static_assert(!hashable<std::optional<const S>>()); |
| static_assert(hashable<std::optional<int>>()); |
| static_assert(hashable<std::optional<const int>>()); |
| |
| int main() |
| { |
| int x = 42; |
| std::optional<int> x2 = 42; |
| VERIFY(std::hash<int>()(x) == std::hash<std::optional<int>>()(x2)); |
| |
| // PR libstdc++/82262 |
| std::optional<const int> x3 = x2; |
| VERIFY(std::hash<int>()(x) == std::hash<std::optional<const int>>()(x3)); |
| } |