1 //===----------------------------------------------------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is dual licensed under the MIT and the University of Illinois Open
6 // Source Licenses. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9
10 // <functional>
11
12 // reference_wrapper
13
14 // has weak result type
15
16 #include <functional>
17 #include <type_traits>
18
19 template <class Arg, class Result>
20 struct my_unary_function
21 { // std::unary_function was removed in C++17
22 typedef Arg argument_type;
23 typedef Result result_type;
24 };
25
26 template <class Arg1, class Arg2, class Result>
27 struct my_binary_function
28 { // std::binary_function was removed in C++17
29 typedef Arg1 first_argument_type;
30 typedef Arg2 second_argument_type;
31 typedef Result result_type;
32 };
33
34 class functor1
35 : public my_unary_function<int, char>
36 {
37 };
38
39 class functor2
40 : public my_binary_function<char, int, double>
41 {
42 };
43
44 class functor3
45 : public my_unary_function<char, int>,
46 public my_binary_function<char, int, double>
47 {
48 public:
49 typedef float result_type;
50 };
51
52 class functor4
53 : public my_unary_function<char, int>,
54 public my_binary_function<char, int, double>
55 {
56 public:
57 };
58
59 class C {};
60
61 template <class T>
62 struct has_result_type
63 {
64 private:
65 struct two {char _; char __;};
66 template <class U> static two test(...);
67 template <class U> static char test(typename U::result_type* = 0);
68 public:
69 static const bool value = sizeof(test<T>(0)) == 1;
70 };
71
main()72 int main()
73 {
74 static_assert((std::is_same<std::reference_wrapper<functor1>::result_type,
75 char>::value), "");
76 static_assert((std::is_same<std::reference_wrapper<functor2>::result_type,
77 double>::value), "");
78 static_assert((std::is_same<std::reference_wrapper<functor3>::result_type,
79 float>::value), "");
80 static_assert((std::is_same<std::reference_wrapper<void()>::result_type,
81 void>::value), "");
82 static_assert((std::is_same<std::reference_wrapper<int*(double*)>::result_type,
83 int*>::value), "");
84 static_assert((std::is_same<std::reference_wrapper<void(*)()>::result_type,
85 void>::value), "");
86 static_assert((std::is_same<std::reference_wrapper<int*(*)(double*)>::result_type,
87 int*>::value), "");
88 static_assert((std::is_same<std::reference_wrapper<int*(C::*)(double*)>::result_type,
89 int*>::value), "");
90 static_assert((std::is_same<std::reference_wrapper<int (C::*)(double*) const volatile>::result_type,
91 int>::value), "");
92 static_assert((std::is_same<std::reference_wrapper<C()>::result_type,
93 C>::value), "");
94 static_assert(has_result_type<std::reference_wrapper<functor3> >::value, "");
95 static_assert(!has_result_type<std::reference_wrapper<functor4> >::value, "");
96 static_assert(!has_result_type<std::reference_wrapper<C> >::value, "");
97 }
98