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1 | // Copyright (C) 2018-2020 Free Software Foundation, Inc. | |
2 | // | |
3 | // This file is part of the GNU ISO C++ Library. This library is free | |
4 | // software; you can redistribute it and/or modify it under the | |
5 | // terms of the GNU General Public License as published by the | |
6 | // Free Software Foundation; either version 3, or (at your option) | |
7 | // any later version. | |
8 | ||
9 | // This library is distributed in the hope that it will be useful, | |
10 | // but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | // GNU General Public License for more details. | |
13 | ||
14 | // You should have received a copy of the GNU General Public License along | |
15 | // with this library; see the file COPYING3. If not see | |
16 | // <http://www.gnu.org/licenses/>. | |
17 | ||
18 | // { dg-options "-std=gnu++2a" } | |
19 | // { dg-do compile { target c++2a } } | |
20 | ||
21 | #include <type_traits> | |
22 | ||
23 | template<typename T, typename U> struct expect_same; | |
24 | template<typename T> struct expect_same<T, T> : std::true_type { }; | |
25 | ||
26 | template<typename T, typename U = T> | |
27 | constexpr bool check() | |
28 | { | |
29 | using std::unwrap_reference; | |
30 | using T2 = typename unwrap_reference<T>::type; | |
31 | static_assert(expect_same<T2, std::unwrap_reference_t<T2>>::value); | |
32 | return expect_same<T2, U>::value; | |
33 | } | |
34 | ||
35 | void | |
36 | test01() | |
37 | { | |
38 | static_assert( check<int>() ); | |
39 | static_assert( check<const int>() ); | |
40 | static_assert( check<const int&>() ); | |
41 | static_assert( check<const int*>() ); | |
42 | static_assert( check<const int*&>() ); | |
43 | ||
44 | // reference_wrapper types should get unwrapped: | |
45 | static_assert( check<std::reference_wrapper<int>, int&>() ); | |
46 | static_assert( check<std::reference_wrapper<const int>, const int&>() ); | |
47 | static_assert( check<std::reference_wrapper<long>, long&>() ); | |
48 | ||
49 | // But not cv-qualified reference_wrapper types: | |
50 | static_assert( check<const std::reference_wrapper<int>>() ); | |
51 | static_assert( check<volatile std::reference_wrapper<int>>() ); | |
52 | static_assert( check<const volatile std::reference_wrapper<int>>() ); | |
53 | ||
54 | // Or references to reference_wrapper types: | |
55 | static_assert( check<std::reference_wrapper<int>&>() ); | |
56 | static_assert( check<std::reference_wrapper<int>&&>() ); | |
57 | static_assert( check<const std::reference_wrapper<int>&>() ); | |
58 | } |