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++98, c++03
10 
11 // test forward
12 
13 #include <utility>
14 #include <type_traits>
15 #include <cassert>
16 
17 #include "test_macros.h"
18 
19 struct A
20 {
21 };
22 
23 A source() noexcept {return A();}
24 const A csource() noexcept {return A();}
25 
26 
27 constexpr bool test_constexpr_forward() {
28 #if TEST_STD_VER > 11
29     int x = 42;
30     const int cx = 101;
31     return std::forward<int&>(x)        == 42
32         && std::forward<int>(x)         == 42
33         && std::forward<const int&>(x)  == 42
34         && std::forward<const int>(x)   == 42
35         && std::forward<int&&>(x)       == 42
36         && std::forward<const int&&>(x) == 42
37         && std::forward<const int&>(cx) == 101
38         && std::forward<const int>(cx)  == 101;
39 #else
40     return true;
41 #endif
42 }
43 
44 int main(int, char**)
45 {
46     A a;
47     const A ca = A();
48 
49     ((void)a); // Prevent unused warning
50     ((void)ca); // Prevent unused warning
51 
52     static_assert(std::is_same<decltype(std::forward<A&>(a)), A&>::value, "");
53     static_assert(std::is_same<decltype(std::forward<A>(a)), A&&>::value, "");
54     static_assert(std::is_same<decltype(std::forward<A>(source())), A&&>::value, "");
55     static_assert(noexcept(std::forward<A&>(a)), "");
56     static_assert(noexcept(std::forward<A>(a)), "");
57     static_assert(noexcept(std::forward<A>(source())), "");
58 
59     static_assert(std::is_same<decltype(std::forward<const A&>(a)), const A&>::value, "");
60     static_assert(std::is_same<decltype(std::forward<const A>(a)), const A&&>::value, "");
61     static_assert(std::is_same<decltype(std::forward<const A>(source())), const A&&>::value, "");
62     static_assert(noexcept(std::forward<const A&>(a)), "");
63     static_assert(noexcept(std::forward<const A>(a)), "");
64     static_assert(noexcept(std::forward<const A>(source())), "");
65 
66     static_assert(std::is_same<decltype(std::forward<const A&>(ca)), const A&>::value, "");
67     static_assert(std::is_same<decltype(std::forward<const A>(ca)), const A&&>::value, "");
68     static_assert(std::is_same<decltype(std::forward<const A>(csource())), const A&&>::value, "");
69     static_assert(noexcept(std::forward<const A&>(ca)), "");
70     static_assert(noexcept(std::forward<const A>(ca)), "");
71     static_assert(noexcept(std::forward<const A>(csource())), "");
72 
73 #if TEST_STD_VER > 11
74     {
75     constexpr int i2 = std::forward<int>(42);
76     static_assert(std::forward<int>(42) == 42, "");
77     static_assert(std::forward<const int&>(i2) == 42, "");
78     static_assert(test_constexpr_forward(), "");
79     }
80 #endif
81 #if TEST_STD_VER == 11 && defined(_LIBCPP_VERSION)
82     // Test that std::forward is constexpr in C++11. This is an extension
83     // provided by both libc++ and libstdc++.
84     {
85     constexpr int i2 = std::forward<int>(42);
86     static_assert(std::forward<int>(42) == 42, "" );
87     static_assert(std::forward<const int&>(i2) == 42, "");
88     }
89 #endif
90 
91   return 0;
92 }
93