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, c++17
10 
11 // struct identity;
12 
13 #include <functional>
14 
15 #include <cassert>
16 #include <concepts>
17 #include <utility>
18 
19 #include "MoveOnly.h"
20 
21 static_assert(std::semiregular<std::identity>);
22 static_assert(requires { typename std::identity::is_transparent; });
23 
test()24 constexpr bool test() {
25   std::identity id;
26   int i = 42;
27   assert(id(i) == 42);
28   assert(id(std::move(i)) == 42);
29 
30   MoveOnly m1 = 2;
31   MoveOnly m2 = id(std::move(m1));
32   assert(m2.get() == 2);
33 
34   assert(&id(i) == &i);
35   static_assert(&id(id) == &id);
36 
37   const std::identity idc;
38   assert(idc(1) == 1);
39   assert(std::move(id)(1) == 1);
40   assert(std::move(idc)(1) == 1);
41 
42   id = idc; // run-time checks assignment
43   static_assert(std::is_same_v<decltype(id(i)), int&>);
44   static_assert(std::is_same_v<decltype(id(std::declval<int&&>())), int&&>);
45   static_assert(
46       std::is_same_v<decltype(id(std::declval<int const&>())), int const&>);
47   static_assert(
48       std::is_same_v<decltype(id(std::declval<int const&&>())), int const&&>);
49   static_assert(std::is_same_v<decltype(id(std::declval<int volatile&>())),
50                                int volatile&>);
51   static_assert(std::is_same_v<decltype(id(std::declval<int volatile&&>())),
52                                int volatile&&>);
53   static_assert(
54       std::is_same_v<decltype(id(std::declval<int const volatile&>())),
55                      int const volatile&>);
56   static_assert(
57       std::is_same_v<decltype(id(std::declval<int const volatile&&>())),
58                      int const volatile&&>);
59 
60   struct S {
61     constexpr S() = default;
62     constexpr S(S&&) noexcept(false) {}
63     constexpr S(S const&) noexcept(false) {}
64   };
65   S x;
66   static_assert(noexcept(id(x)));
67   static_assert(noexcept(id(S())));
68 
69   return true;
70 }
71 
main(int,char **)72 int main(int, char**) {
73   test();
74   static_assert(test());
75 
76   return 0;
77 }
78