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52 lines
1.6 KiB
C++
52 lines
1.6 KiB
C++
// { dg-options "-std=gnu++17" }
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// Copyright (C) 2016-2019 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License along
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// with this library; see the file COPYING3. If not see
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// <http://www.gnu.org/licenses/>.
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#include <optional>
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#include <testsuite_hooks.h>
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class S{}; // No hash specialization
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template<class T>
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auto f(int) -> decltype(std::hash<std::optional<T>>(), std::true_type());
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template<class T>
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auto f(...) -> decltype(std::false_type());
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static_assert(!decltype(f<S>(0))::value, "");
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template<typename T>
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constexpr bool hashable()
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{ return std::is_invocable_v<std::hash<T>&, const T&>; }
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static_assert(!hashable<std::optional<S>>());
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static_assert(!hashable<std::optional<const S>>());
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static_assert(hashable<std::optional<int>>());
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static_assert(hashable<std::optional<const int>>());
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int main()
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{
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int x = 42;
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std::optional<int> x2 = 42;
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VERIFY(std::hash<int>()(x) == std::hash<std::optional<int>>()(x2));
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// PR libstdc++/82262
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std::optional<const int> x3 = x2;
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VERIFY(std::hash<int>()(x) == std::hash<std::optional<const int>>()(x3));
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}
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