libcxx/test/std/utilities/utility/forward/forward_like.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 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
  10
  11 // test forward_like
  12
  13 #include <cassert>
  14 #include <type_traits>
  15 #include <utility>
  16
  17 struct U {}; // class type so const-qualification is not stripped from a prvalue
  18 using CU = const U;
  19 using T  = int;
  20 using CT = const T;
  21
  22 U u{};
  23 const U& cu = u;
  24
  25 static_assert(std::is_same_v<decltype(std::forward_like<T>(U{})), U&&>);
  26 static_assert(std::is_same_v<decltype(std::forward_like<T>(CU{})), CU&&>);
  27 static_assert(std::is_same_v<decltype(std::forward_like<T>(u)), U&&>);
  28 static_assert(std::is_same_v<decltype(std::forward_like<T>(cu)), CU&&>);
  29 static_assert(std::is_same_v<decltype(std::forward_like<T>(std::move(u))), U&&>);
  30 static_assert(std::is_same_v<decltype(std::forward_like<T>(std::move(cu))), CU&&>);
  31
  32 static_assert(std::is_same_v<decltype(std::forward_like<CT>(U{})), CU&&>);
  33 static_assert(std::is_same_v<decltype(std::forward_like<CT>(CU{})), CU&&>);
  34 static_assert(std::is_same_v<decltype(std::forward_like<CT>(u)), CU&&>);
  35 static_assert(std::is_same_v<decltype(std::forward_like<CT>(cu)), CU&&>);
  36 static_assert(std::is_same_v<decltype(std::forward_like<CT>(std::move(u))), CU&&>);
  37 static_assert(std::is_same_v<decltype(std::forward_like<CT>(std::move(cu))), CU&&>);
  38
  39 static_assert(std::is_same_v<decltype(std::forward_like<T&>(U{})), U&>);
  40 static_assert(std::is_same_v<decltype(std::forward_like<T&>(CU{})), CU&>);
  41 static_assert(std::is_same_v<decltype(std::forward_like<T&>(u)), U&>);
  42 static_assert(std::is_same_v<decltype(std::forward_like<T&>(cu)), CU&>);
  43 static_assert(std::is_same_v<decltype(std::forward_like<T&>(std::move(u))), U&>);
  44 static_assert(std::is_same_v<decltype(std::forward_like<T&>(std::move(cu))), CU&>);
  45
  46 static_assert(std::is_same_v<decltype(std::forward_like<CT&>(U{})), CU&>);
  47 static_assert(std::is_same_v<decltype(std::forward_like<CT&>(CU{})), CU&>);
  48 static_assert(std::is_same_v<decltype(std::forward_like<CT&>(u)), CU&>);
  49 static_assert(std::is_same_v<decltype(std::forward_like<CT&>(cu)), CU&>);
  50 static_assert(std::is_same_v<decltype(std::forward_like<CT&>(std::move(u))), CU&>);
  51 static_assert(std::is_same_v<decltype(std::forward_like<CT&>(std::move(cu))), CU&>);
  52
  53 static_assert(std::is_same_v<decltype(std::forward_like<T&&>(U{})), U&&>);
  54 static_assert(std::is_same_v<decltype(std::forward_like<T&&>(CU{})), CU&&>);
  55 static_assert(std::is_same_v<decltype(std::forward_like<T&&>(u)), U&&>);
  56 static_assert(std::is_same_v<decltype(std::forward_like<T&&>(cu)), CU&&>);
  57 static_assert(std::is_same_v<decltype(std::forward_like<T&&>(std::move(u))), U&&>);
  58 static_assert(std::is_same_v<decltype(std::forward_like<T&&>(std::move(cu))), CU&&>);
  59
  60 static_assert(std::is_same_v<decltype(std::forward_like<CT&&>(U{})), CU&&>);
  61 static_assert(std::is_same_v<decltype(std::forward_like<CT&&>(CU{})), CU&&>);
  62 static_assert(std::is_same_v<decltype(std::forward_like<CT&&>(u)), CU&&>);
  63 static_assert(std::is_same_v<decltype(std::forward_like<CT&&>(cu)), CU&&>);
  64 static_assert(std::is_same_v<decltype(std::forward_like<CT&&>(std::move(u))), CU&&>);
  65 static_assert(std::is_same_v<decltype(std::forward_like<CT&&>(std::move(cu))), CU&&>);
  66
  67 static_assert(noexcept(std::forward_like<T>(u)));
  68
  69 static_assert(std::is_same_v<decltype(std::forward_like<U&>(u)), U&>);
  70 static_assert(std::is_same_v<decltype(std::forward_like<CU&>(cu)), CU&>);
  71 static_assert(std::is_same_v<decltype(std::forward_like<U&&>(std::move(u))), U&&>);
  72 static_assert(std::is_same_v<decltype(std::forward_like<CU&&>(std::move(cu))), CU&&>);
  73
  74 struct NoCtorCopyMove {
  75   NoCtorCopyMove() = delete;
  76   NoCtorCopyMove(const NoCtorCopyMove&) = delete;
  77   NoCtorCopyMove(NoCtorCopyMove&&) = delete;
  78 };
  79
  80 static_assert(std::is_same_v<decltype(std::forward_like<CT&&>(std::declval<NoCtorCopyMove>())), const NoCtorCopyMove&&>);
  81 static_assert(std::is_same_v<decltype(std::forward_like<CT&>(std::declval<NoCtorCopyMove>())), const NoCtorCopyMove&>);
  82 static_assert(std::is_same_v<decltype(std::forward_like<T&&>(std::declval<NoCtorCopyMove>())), NoCtorCopyMove&&>);
  83 static_assert(std::is_same_v<decltype(std::forward_like<T&>(std::declval<NoCtorCopyMove>())), NoCtorCopyMove&>);
  84
  85 static_assert(noexcept(std::forward_like<T>(std::declval<NoCtorCopyMove>())));
  86
  87 constexpr bool test() {
  88   {
  89     int val       = 1729;
  90     auto&& result = std::forward_like<const double&>(val);
  91     static_assert(std::is_same_v<decltype(result), const int&>);
  92     assert(&result == &val);
  93   }
  94   {
  95     int val       = 1729;
  96     auto&& result = std::forward_like<double&>(val);
  97     static_assert(std::is_same_v<decltype(result), int&>);
  98     assert(&result == &val);
  99   }
 100   {
 101     int val       = 1729;
 102     auto&& result = std::forward_like<const double&&>(val);
 103     static_assert(std::is_same_v<decltype(result), const int&&>);
 104     assert(&result == &val);
 105   }
 106   {
 107     int val       = 1729;
 108     auto&& result = std::forward_like<double&&>(val);
 109     static_assert(std::is_same_v<decltype(result), int&&>);
 110     assert(&result == &val);
 111   }
 112   return true;
 113 }
 114
 115 int main(int, char**) {
 116   test();
 117   static_assert(test());
 118
 119   return 0;
 120 }