1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8
9 // UNSUPPORTED: c++03, c++11, c++14
10
11 // template <class T> constexpr add_const<T>& as_const(T& t) noexcept; // C++17
12 // template <class T> add_const<T>& as_const(const T&&) = delete; // C++17
13
14 #include <utility>
15 #include <cassert>
16
17 #include "test_macros.h"
18
19 struct S {int i;};
operator ==(const S & x,const S & y)20 bool operator==(const S& x, const S& y) { return x.i == y.i; }
operator ==(const volatile S & x,const volatile S & y)21 bool operator==(const volatile S& x, const volatile S& y) { return x.i == y.i; }
22
23 template<typename T>
test(T & t)24 void test(T& t)
25 {
26 static_assert(std::is_const<typename std::remove_reference<decltype(std::as_const (t))>::type>::value, "");
27 static_assert(std::is_const<typename std::remove_reference<decltype(std::as_const< T>(t))>::type>::value, "");
28 static_assert(std::is_const<typename std::remove_reference<decltype(std::as_const<const T>(t))>::type>::value, "");
29 static_assert(std::is_const<typename std::remove_reference<decltype(std::as_const<volatile T>(t))>::type>::value, "");
30 static_assert(std::is_const<typename std::remove_reference<decltype(std::as_const<const volatile T>(t))>::type>::value, "");
31
32 assert(std::as_const(t) == t);
33 assert(std::as_const< T>(t) == t);
34 assert(std::as_const<const T>(t) == t);
35 assert(std::as_const<volatile T>(t) == t);
36 assert(std::as_const<const volatile T>(t) == t);
37 }
38
main(int,char **)39 int main(int, char**)
40 {
41 int i = 3;
42 double d = 4.0;
43 S s{2};
44 test(i);
45 test(d);
46 test(s);
47
48 return 0;
49 }
50