libcxx/test/std/utilities/function.objects/refwrap/weak_result.pass.cpp

   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 // <functional>
  10
  11 // reference_wrapper
  12
  13 // has weak result type
  14
  15 // REQUIRES: c++03 || c++11 || c++14 || c++17
  16
  17 // ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_DISABLE_DEPRECATION_WARNINGS
  18
  19 #include <functional>
  20 #include <type_traits>
  21
  22 #include "test_macros.h"
  23
  24 template <class Arg, class Result>
  25 struct my_unary_function
  26 { // std::unary_function was removed in C++17
  27     typedef Arg argument_type;
  28     typedef Result result_type;
  29 };
  30
  31 template <class Arg1, class Arg2, class Result>
  32 struct my_binary_function
  33 { // std::binary_function was removed in C++17
  34     typedef Arg1 first_argument_type;
  35     typedef Arg2 second_argument_type;
  36     typedef Result result_type;
  37 };
  38
  39 class functor1
  40     : public my_unary_function<int, char>
  41 {
  42 };
  43
  44 class functor2
  45     : public my_binary_function<char, int, double>
  46 {
  47 };
  48
  49 class functor3
  50     : public my_unary_function<char, int>,
  51       public my_binary_function<char, int, double>
  52 {
  53 public:
  54     typedef float result_type;
  55 };
  56
  57 class functor4
  58     : public my_unary_function<char, int>,
  59       public my_binary_function<char, int, double>
  60 {
  61 public:
  62 };
  63
  64 class C {};
  65
  66 template <class T>
  67 struct has_result_type
  68 {
  69 private:
  70     struct two {char _; char __;};
  71     template <class U> static two test(...);
  72     template <class U> static char test(typename U::result_type* = 0);
  73 public:
  74     static const bool value = sizeof(test<T>(0)) == 1;
  75 };
  76
  77 int main(int, char**)
  78 {
  79     static_assert((std::is_same<std::reference_wrapper<functor1>::result_type,
  80                                 char>::value), "");
  81     static_assert((std::is_same<std::reference_wrapper<functor2>::result_type,
  82                                 double>::value), "");
  83     static_assert((std::is_same<std::reference_wrapper<functor3>::result_type,
  84                                 float>::value), "");
  85     static_assert((std::is_same<std::reference_wrapper<void()>::result_type,
  86                                 void>::value), "");
  87     static_assert((std::is_same<std::reference_wrapper<int*(double*)>::result_type,
  88                                 int*>::value), "");
  89     static_assert((std::is_same<std::reference_wrapper<void(*)()>::result_type,
  90                                 void>::value), "");
  91     static_assert((std::is_same<std::reference_wrapper<int*(*)(double*)>::result_type,
  92                                 int*>::value), "");
  93     static_assert((std::is_same<std::reference_wrapper<int*(C::*)(double*)>::result_type,
  94                                 int*>::value), "");
  95     static_assert((std::is_same<std::reference_wrapper<int (C::*)(double*) const volatile>::result_type,
  96                                 int>::value), "");
  97     static_assert((std::is_same<std::reference_wrapper<C()>::result_type,
  98                                 C>::value), "");
  99     static_assert(has_result_type<std::reference_wrapper<functor3> >::value, "");
 100     static_assert(!has_result_type<std::reference_wrapper<functor4> >::value, "");
 101     static_assert(!has_result_type<std::reference_wrapper<C> >::value, "");
 102
 103   return 0;
 104 }