| // Copyright (C) 2019-2021 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/>. |
| |
| // { dg-options "-std=gnu++2a" } |
| // { dg-do compile { target c++2a } } |
| |
| #include <type_traits> |
| |
| template<typename T, typename = void> |
| struct has_type : std::false_type { }; |
| |
| template<typename T> |
| struct has_type<T, std::void_t<typename T::type>> : std::true_type { }; |
| |
| template<typename... T> |
| constexpr bool |
| has_common_ref() |
| { |
| return has_type<std::common_reference<T...>>::value; |
| } |
| |
| using std::is_same_v; |
| using std::common_reference_t; |
| |
| void test01() |
| { |
| |
| static_assert( !has_common_ref<>() ); |
| static_assert( !has_common_ref<char(*)(), int(*)()>() ); |
| static_assert( !has_common_ref<void*, int>() ); |
| |
| static_assert( is_same_v<common_reference_t<int>, int> ); |
| static_assert( is_same_v<common_reference_t<int&>, int&> ); |
| static_assert( is_same_v<common_reference_t<void>, void> ); |
| static_assert( is_same_v<common_reference_t<const void>, const void> ); |
| static_assert( is_same_v<common_reference_t<const void, void>, void> ); |
| static_assert( is_same_v<common_reference_t<void(*const)(), void(*)()>, void(*)()> ); |
| static_assert( is_same_v<common_reference_t<int, int>, int> ); |
| static_assert( is_same_v<common_reference_t<int&, int>, int> ); |
| static_assert( is_same_v<common_reference_t<int, int&>, int> ); |
| static_assert( is_same_v<common_reference_t<int&&, int>, int> ); |
| static_assert( is_same_v<common_reference_t<int&, int&>, int&> ); |
| static_assert( is_same_v<common_reference_t<int&, int&&>, const int&> ); |
| static_assert( is_same_v<common_reference_t<int&&, int&>, const int&> ); |
| static_assert( is_same_v<common_reference_t<int&&, int&&>, int&&> ); |
| static_assert( is_same_v<common_reference_t<int&&, const int&&>, const int&&> ); |
| static_assert( is_same_v<common_reference_t<int&, int&, int&&>, const int&> ); |
| static_assert( is_same_v<common_reference_t<int&&, int&, int&>, const int&> ); |
| static_assert( is_same_v<common_reference_t<char&, int&>, int> ); |
| static_assert( is_same_v<common_reference_t<long&, int&>, long> ); |
| } |
| |
| struct A { }; |
| struct B { }; |
| struct C { }; |
| |
| template<template<typename> class AQual, template<typename> class BQual> |
| struct std::basic_common_reference<A, B, AQual, BQual> |
| { |
| using type = BQual<AQual<C>>; |
| }; |
| |
| static_assert( is_same_v<common_reference_t<A, B>, C> ); |
| static_assert( is_same_v<common_reference_t<A&, B>, C&> ); |
| static_assert( is_same_v<common_reference_t<A&, const B>, C&> ); |
| static_assert( is_same_v<common_reference_t<const A, B&>, const C&> ); |
| static_assert( is_same_v<common_reference_t<const A&, B&&>, const C&> ); |
| static_assert( is_same_v<common_reference_t<const A, B&&>, const C&&> ); |
| |
| struct D { }; |
| struct E { }; |
| struct F { }; |
| |
| template<> struct std::common_type<D, E> { using type = F; }; |
| |
| static_assert( is_same_v<common_reference_t<D, E>, F> ); |
| static_assert( is_same_v<common_reference_t<D&, E>, F> ); |
| static_assert( is_same_v<common_reference_t<D&, E&&>, F> ); |