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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// <utility>
// template <class T1, class T2> struct pair
// void swap(const pair& p) const;
// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
#include <cassert>
#include <utility>
#include "test_macros.h"
// Remarks: The expression inside noexcept is equivalent to
// is_nothrow_swappable_v<const first_type> && is_nothrow_swappable_v<const second_type> for the second overload.
template <class T>
concept ConstMemberSwapNoexcept =
requires(const T& t1, const T& t2) {
{ t1.swap(t2) } noexcept;
};
template <bool canThrow>
struct SwapMayThrow {};
template <bool canThrow>
void swap(const SwapMayThrow<canThrow>&, const SwapMayThrow<canThrow>&) noexcept(!canThrow);
static_assert(ConstMemberSwapNoexcept<std::pair<SwapMayThrow<false>, SwapMayThrow<false>>>);
static_assert(!ConstMemberSwapNoexcept<std::pair<SwapMayThrow<true>, SwapMayThrow<false>>>);
static_assert(!ConstMemberSwapNoexcept<std::pair<SwapMayThrow<false>, SwapMayThrow<true>>>);
static_assert(!ConstMemberSwapNoexcept<std::pair<SwapMayThrow<true>, SwapMayThrow<true>>>);
struct ConstSwappable {
mutable int i;
friend constexpr void swap(const ConstSwappable& lhs, const ConstSwappable& rhs) { std::swap(lhs.i, rhs.i); }
};
constexpr bool test() {
// user defined const swap
{
using P = std::pair<const ConstSwappable, const ConstSwappable>;
const P p1(ConstSwappable{0}, ConstSwappable{1});
const P p2(ConstSwappable{2}, ConstSwappable{3});
p1.swap(p2);
assert(p1.first.i == 2);
assert(p1.second.i == 3);
assert(p2.first.i == 0);
assert(p2.second.i == 1);
}
// pair of references
{
int i1 = 0, i2 = 1, i3 = 2, i4 = 3;
const std::pair<int&, int&> p1{i1, i2};
const std::pair<int&, int&> p2{i3, i4};
p1.swap(p2);
assert(p1.first == 2);
assert(p1.second == 3);
assert(p2.first == 0);
assert(p2.second == 1);
}
return true;
}
int main(int, char**) {
test();
// gcc cannot have mutable member in constant expression
#if !defined(TEST_COMPILER_GCC)
static_assert(test());
#endif
return 0;
}
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