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// friend constexpr void swap(unexpected& x, unexpected& y) noexcept(noexcept(x.swap(y)));
12//
13// Constraints: is_swappable_v<E> is true.
14//
15// Effects: Equivalent to x.swap(y).
16
17#include <cassert>
18#include <concepts>
19#include <expected>
20#include <type_traits>
21#include <utility>
22
23// test noexcept
24struct NoexceptSwap {
25 friend void swap(NoexceptSwap&, NoexceptSwap&) noexcept;
26};
27
28struct MayThrowSwap {
29 friend void swap(MayThrowSwap&, MayThrowSwap&);
30};
31
32template <class T>
33concept ADLSwapNoexcept =
34 requires(T& t1, T& t2) {
35 { swap(t1, t2) } noexcept;
36 };
37
38static_assert(ADLSwapNoexcept<std::unexpected<NoexceptSwap>>);
39static_assert(!ADLSwapNoexcept<std::unexpected<MayThrowSwap>>);
40
41// test constraint
42struct NonSwappable {
43 NonSwappable& operator=(const NonSwappable&) = delete;
44};
45
46static_assert(std::is_swappable_v<std::unexpected<int>>);
47static_assert(std::is_swappable_v<std::unexpected<MayThrowSwap>>);
48static_assert(!std::is_swappable_v<std::unexpected<NonSwappable>>);
49
50struct ADLSwap {
51 constexpr ADLSwap(int ii) : i(ii) {}
52 ADLSwap& operator=(const ADLSwap&) = delete;
53 int i;
54 constexpr friend void swap(ADLSwap& x, ADLSwap& y) { std::swap(a&: x.i, b&: y.i); }
55};
56
57constexpr bool test() {
58 std::unexpected<ADLSwap> unex1(5);
59 std::unexpected<ADLSwap> unex2(6);
60 swap(unex1, unex2);
61 assert(unex1.error().i == 6);
62 assert(unex2.error().i == 5);
63 return true;
64}
65
66int main(int, char**) {
67 test();
68 static_assert(test());
69 return 0;
70}
71

source code of libcxx/test/std/utilities/expected/expected.unexpected/swap/swap.free.pass.cpp