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// { dg-do compile { target c++17 } }
// Copyright (C) 2020-2023 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 );
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