libcxx/test/std/utilities/function.objects/func.identity/identity.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
  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
  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
  72 int main(int, char**) {
  73   test();
  74   static_assert(test());
  75
  76   return 0;
  77 }