| // { dg-do compile { target c++17 } } |
| |
| // Copyright (C) 2020-2021 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> |
| |
| int i; |
| |
| struct Cont |
| { |
| Cont() noexcept; |
| Cont(Cont&&) noexcept; |
| Cont(const Cont&); |
| Cont(int); |
| Cont(std::initializer_list<int>, int) noexcept; |
| Cont(std::initializer_list<int>, const char*); |
| }; |
| const Cont c{}; |
| |
| template<typename T, typename = void> |
| struct can_make_optional1 |
| : std::false_type |
| { }; |
| |
| template<typename T> |
| struct can_make_optional1<T, |
| std::void_t<decltype(std::make_optional(std::declval<T>()))>> |
| : std::true_type |
| { }; |
| |
| static_assert( can_make_optional1<int>::value ); |
| static_assert( noexcept(std::make_optional(1)) ); |
| static_assert( can_make_optional1<int&>::value ); |
| static_assert( noexcept(std::make_optional(i)) ); |
| static_assert( ! can_make_optional1<void>::value ); |
| static_assert( can_make_optional1<Cont>::value ); |
| static_assert( noexcept(std::make_optional(Cont{})) ); |
| static_assert( can_make_optional1<Cont>::value ); |
| static_assert( ! noexcept(std::make_optional(c)) ); |
| |
| template<typename T, typename Arg, typename = void> |
| struct can_make_optional2 |
| : std::false_type |
| { }; |
| |
| template<typename T, typename Arg> |
| struct can_make_optional2<T, Arg, |
| std::void_t<decltype(std::make_optional<T>(std::declval<Arg>()))>> |
| : std::true_type |
| { }; |
| |
| static_assert( can_make_optional2<int, int>::value ); |
| static_assert( noexcept(std::make_optional<int>(1)) ); |
| static_assert( can_make_optional2<int, int&>::value ); |
| static_assert( noexcept(std::make_optional(i)) ); |
| static_assert( ! can_make_optional2<void, void>::value ); |
| static_assert( can_make_optional2<Cont, Cont>::value ); |
| static_assert( noexcept(std::make_optional<Cont>({})) ); |
| static_assert( can_make_optional2<Cont, const Cont&>::value ); |
| static_assert( ! noexcept(std::make_optional(c)) ); |
| static_assert( can_make_optional2<Cont, int>::value ); |
| static_assert( ! noexcept(std::make_optional<Cont>(1)) ); |
| |
| template<typename T, typename Arg, typename = void> |
| struct can_make_optional3 |
| : std::false_type |
| { }; |
| |
| template<typename T, typename Arg> |
| struct can_make_optional3<T, Arg, |
| std::void_t<decltype(std::make_optional<T>({1,2}, std::declval<Arg>()))>> |
| : std::true_type |
| { }; |
| |
| static_assert( can_make_optional3<Cont, int>::value ); |
| static_assert( noexcept(std::make_optional<Cont>({1,2}, 1)) ); |
| static_assert( can_make_optional3<Cont, char*>::value ); |
| static_assert( ! noexcept(std::make_optional<Cont>({1,2}, "")) ); |
| static_assert( !can_make_optional3<Cont, int*>::value ); |