libcxx/test/std/utilities/utility/pairs/pairs.spec/non_member_const_swap.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 // <utility>
  10
  11 // template <class T1, class T2>
  12 // void swap(const pair<T1, T2>& x, const pair<T1, T2>& y) const noexcept(noexcept(x.swap(y)));;
  13
  14 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
  15
  16 #include <cassert>
  17 #include <type_traits>
  18 #include <utility>
  19
  20 #include "test_macros.h"
  21
  22 // Constraints:
  23 // For the second overload, is_swappable_v<const T1> is true and is_swappable_v<const T2> is true.
  24 struct NonConstSwappable {
  25   friend constexpr void swap(NonConstSwappable&, NonConstSwappable&);
  26 };
  27
  28 struct ConstSwappable {
  29   mutable int i;
  30   friend constexpr void swap(const ConstSwappable& lhs, const ConstSwappable& rhs) { std::swap(lhs.i, rhs.i); }
  31 };
  32
  33 static_assert(std::is_swappable_v<const std::pair<ConstSwappable, ConstSwappable>>);
  34 static_assert(!std::is_swappable_v<const std::pair<NonConstSwappable, ConstSwappable>>);
  35 static_assert(!std::is_swappable_v<const std::pair<ConstSwappable, NonConstSwappable>>);
  36 static_assert(!std::is_swappable_v<const std::pair<NonConstSwappable, NonConstSwappable>>);
  37
  38 // noexcept(noexcept(x.swap(y)));
  39 template <class T>
  40 concept NonMemberSwapNoexcept =
  41     requires(T t1, T t2) {
  42       { swap(t1, t2) } noexcept;
  43     };
  44
  45 template <bool canThrow>
  46 struct SwapMayThrow {};
  47
  48 template <bool canThrow>
  49 void swap(const SwapMayThrow<canThrow>&, const SwapMayThrow<canThrow>&) noexcept(!canThrow);
  50
  51 static_assert(NonMemberSwapNoexcept<const std::pair<SwapMayThrow<false>, SwapMayThrow<false>>>);
  52 static_assert(!NonMemberSwapNoexcept<const std::pair<SwapMayThrow<true>, SwapMayThrow<false>>>);
  53 static_assert(!NonMemberSwapNoexcept<const std::pair<SwapMayThrow<false>, SwapMayThrow<true>>>);
  54 static_assert(!NonMemberSwapNoexcept<const std::pair<SwapMayThrow<true>, SwapMayThrow<true>>>);
  55
  56 constexpr bool test() {
  57   // user defined const swap
  58   {
  59     using P = std::pair<const ConstSwappable, const ConstSwappable>;
  60     const P p1(ConstSwappable{0}, ConstSwappable{1});
  61     const P p2(ConstSwappable{2}, ConstSwappable{3});
  62     using std::swap;
  63     swap(p1, p2);
  64     assert(p1.first.i == 2);
  65     assert(p1.second.i == 3);
  66     assert(p2.first.i == 0);
  67     assert(p2.second.i == 1);
  68   }
  69
  70   // pair of references
  71   {
  72     int i1 = 0, i2 = 1, i3 = 2, i4 = 3;
  73     const std::pair<int&, int&> p1{i1, i2};
  74     const std::pair<int&, int&> p2{i3, i4};
  75     using std::swap;
  76     swap(p1, p2);
  77     assert(p1.first == 2);
  78     assert(p1.second == 3);
  79     assert(p2.first == 0);
  80     assert(p2.second == 1);
  81   }
  82   return true;
  83 }
  84
  85 int main(int, char**) {
  86   test();
  87
  88 // gcc cannot have mutable member in constant expression
  89 #if !defined(TEST_COMPILER_GCC)
  90   static_assert(test());
  91 #endif
  92
  93   return 0;
  94 }