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llvm-project/libcxx/test/std/utilities/optional/optional.object/optional.object.swap/swap.pass.cpp
William Tran-Viet 9f5efd5d03
[libc++] Correct optional<T&> implementation (#174537) 
Resolves #174350

- Several issues were found in the current implementation of
`optional<T&>`
- `value()`, `operator*()`, `and_then()`, `transform()`, `operator->()`
still provided their ref-qualified versions for rvalues and `const&`.
- Using the listed methods on an rvalue `optional<T&>` would cause a
compile failure due to a mismatch in return types.
- On the latter, `operator*`, `operator->` would return `const` for a
`optional<T&>`, which is an incorrect deep const.
- A few constructors were missing (`optional<U>&`), and most
constructors relevant to `optional<T&>` were missing `noexcept`
- Constructors and `emplace` were not correctly constructing a `T&` as
specified in _`convert-ref-init-val`_
- Also corrects the behavior of `value_or` which should return
`remove_cv_t<T>` (in our case `decay_t<_Tp>`)
- Add several test cases to verify behavior, update `value_or` tests
2026-01-09 16:33:10 +08:00

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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
//
//===----------------------------------------------------------------------===//
// UNSUPPORTED: c++03, c++11, c++14
// <optional>
// void swap(optional&)
// noexcept(is_nothrow_move_constructible<T>::value &&
// is_nothrow_swappable<T>::value)
#include <cassert>
#include <memory>
#include <optional>
#include <type_traits>
#include "test_macros.h"
#include "archetypes.h"
using std::optional;
class X
{
int i_;
public:
static unsigned dtor_called;
X(int i) : i_(i) {}
X(X&& x) = default;
X& operator=(X&&) = default;
~X() {++dtor_called;}
friend bool operator==(const X& x, const X& y) {return x.i_ == y.i_;}
};
unsigned X::dtor_called = 0;
class Y
{
int i_;
public:
static unsigned dtor_called;
Y(int i) : i_(i) {}
Y(Y&&) = default;
~Y() {++dtor_called;}
friend constexpr bool operator==(const Y& x, const Y& y) {return x.i_ == y.i_;}
friend void swap(Y& x, Y& y) {std::swap(x.i_, y.i_);}
};
unsigned Y::dtor_called = 0;
class Z
{
int i_;
public:
Z(int i) : i_(i) {}
Z(Z&&) {TEST_THROW(7);}
friend constexpr bool operator==(const Z& x, const Z& y) {return x.i_ == y.i_;}
friend void swap(Z&, Z&) {TEST_THROW(6);}
};
class W
{
int i_;
public:
constexpr W(int i) : i_(i) {}
friend constexpr bool operator==(const W& x, const W& y) {return x.i_ == y.i_;}
friend TEST_CONSTEXPR_CXX20 void swap(W& x, W& y) noexcept {std::swap(x.i_, y.i_);}
};
template<class T>
TEST_CONSTEXPR_CXX20 bool check_swap()
{
{
optional<T> opt1;
optional<T> opt2;
static_assert(noexcept(opt1.swap(opt2)) == true);
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == false);
opt1.swap(opt2);
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == false);
}
{
optional<T> opt1(1);
optional<T> opt2;
static_assert(noexcept(opt1.swap(opt2)) == true);
assert(static_cast<bool>(opt1) == true);
assert(*opt1 == 1);
assert(static_cast<bool>(opt2) == false);
opt1.swap(opt2);
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == true);
assert(*opt2 == 1);
}
{
optional<T> opt1;
optional<T> opt2(2);
static_assert(noexcept(opt1.swap(opt2)) == true, "");
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == true);
assert(*opt2 == 2);
opt1.swap(opt2);
assert(static_cast<bool>(opt1) == true);
assert(*opt1 == 2);
assert(static_cast<bool>(opt2) == false);
}
{
optional<T> opt1(1);
optional<T> opt2(2);
static_assert(noexcept(opt1.swap(opt2)) == true, "");
assert(static_cast<bool>(opt1) == true);
assert(*opt1 == 1);
assert(static_cast<bool>(opt2) == true);
assert(*opt2 == 2);
opt1.swap(opt2);
assert(static_cast<bool>(opt1) == true);
assert(*opt1 == 2);
assert(static_cast<bool>(opt2) == true);
assert(*opt2 == 1);
}
return true;
}
#if TEST_STD_VER >= 26
template <typename T>
constexpr bool check_swap_ref() {
{
optional<T&> opt1;
optional<T&> opt2;
static_assert(noexcept(opt1.swap(opt2)) == true);
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == false);
opt1.swap(opt2);
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == false);
}
{
T one{1};
optional<T&> opt1(one);
optional<T&> opt2;
static_assert(noexcept(opt1.swap(opt2)) == true);
assert(static_cast<bool>(opt1) == true);
assert(std::addressof(*opt1) == std::addressof(one));
assert(static_cast<bool>(opt2) == false);
opt1.swap(opt2);
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == true);
assert(std::addressof(*opt2) == std::addressof(one));
}
{
T two{2};
optional<T&> opt1;
optional<T&> opt2(two);
static_assert(noexcept(opt1.swap(opt2)) == true);
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == true);
assert(std::addressof(*opt2) == std::addressof(two));
opt1.swap(opt2);
assert(static_cast<bool>(opt1) == true);
assert(std::addressof(*opt1) == std::addressof(two));
assert(static_cast<bool>(opt2) == false);
}
{
T one{1};
T two{2};
optional<T&> opt1(one);
optional<T&> opt2(two);
static_assert(noexcept(opt1.swap(opt2)) == true);
assert(static_cast<bool>(opt1) == true);
assert(*opt1 == 1);
assert(std::addressof(*opt1) == std::addressof(one));
assert(static_cast<bool>(opt2) == true);
assert(*opt2 == 2);
assert(std::addressof(*opt2) == std::addressof(two));
opt1.swap(opt2);
assert(static_cast<bool>(opt1) == true);
assert(*opt1 == 2);
assert(std::addressof(*opt1) == std::addressof(two));
assert(static_cast<bool>(opt2) == true);
assert(*opt2 == 1);
assert(std::addressof(*opt2) == std::addressof(one));
}
return true;
}
#endif
int main(int, char**)
{
check_swap<int>();
check_swap<W>();
#if TEST_STD_VER > 17
static_assert(check_swap<int>());
static_assert(check_swap<W>());
#endif
#if TEST_STD_VER >= 26
static_assert(check_swap_ref<int>());
static_assert(check_swap_ref<W>());
check_swap_ref<int>();
check_swap_ref<W>();
#endif
{
optional<X> opt1;
optional<X> opt2;
static_assert(noexcept(opt1.swap(opt2)) == true, "");
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == false);
opt1.swap(opt2);
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == false);
assert(X::dtor_called == 0);
}
{
optional<X> opt1(1);
optional<X> opt2;
static_assert(noexcept(opt1.swap(opt2)) == true, "");
assert(static_cast<bool>(opt1) == true);
assert(*opt1 == 1);
assert(static_cast<bool>(opt2) == false);
X::dtor_called = 0;
opt1.swap(opt2);
assert(X::dtor_called == 1);
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == true);
assert(*opt2 == 1);
}
{
optional<X> opt1;
optional<X> opt2(2);
static_assert(noexcept(opt1.swap(opt2)) == true, "");
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == true);
assert(*opt2 == 2);
X::dtor_called = 0;
opt1.swap(opt2);
assert(X::dtor_called == 1);
assert(static_cast<bool>(opt1) == true);
assert(*opt1 == 2);
assert(static_cast<bool>(opt2) == false);
}
{
optional<X> opt1(1);
optional<X> opt2(2);
static_assert(noexcept(opt1.swap(opt2)) == true, "");
assert(static_cast<bool>(opt1) == true);
assert(*opt1 == 1);
assert(static_cast<bool>(opt2) == true);
assert(*opt2 == 2);
X::dtor_called = 0;
opt1.swap(opt2);
assert(X::dtor_called == 1); // from inside std::swap
assert(static_cast<bool>(opt1) == true);
assert(*opt1 == 2);
assert(static_cast<bool>(opt2) == true);
assert(*opt2 == 1);
}
{
optional<Y> opt1;
optional<Y> opt2;
static_assert(noexcept(opt1.swap(opt2)) == false, "");
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == false);
opt1.swap(opt2);
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == false);
assert(Y::dtor_called == 0);
}
{
optional<Y> opt1(1);
optional<Y> opt2;
static_assert(noexcept(opt1.swap(opt2)) == false, "");
assert(static_cast<bool>(opt1) == true);
assert(*opt1 == 1);
assert(static_cast<bool>(opt2) == false);
Y::dtor_called = 0;
opt1.swap(opt2);
assert(Y::dtor_called == 1);
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == true);
assert(*opt2 == 1);
}
{
optional<Y> opt1;
optional<Y> opt2(2);
static_assert(noexcept(opt1.swap(opt2)) == false, "");
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == true);
assert(*opt2 == 2);
Y::dtor_called = 0;
opt1.swap(opt2);
assert(Y::dtor_called == 1);
assert(static_cast<bool>(opt1) == true);
assert(*opt1 == 2);
assert(static_cast<bool>(opt2) == false);
}
{
optional<Y> opt1(1);
optional<Y> opt2(2);
static_assert(noexcept(opt1.swap(opt2)) == false, "");
assert(static_cast<bool>(opt1) == true);
assert(*opt1 == 1);
assert(static_cast<bool>(opt2) == true);
assert(*opt2 == 2);
Y::dtor_called = 0;
opt1.swap(opt2);
assert(Y::dtor_called == 0);
assert(static_cast<bool>(opt1) == true);
assert(*opt1 == 2);
assert(static_cast<bool>(opt2) == true);
assert(*opt2 == 1);
}
{
optional<Z> opt1;
optional<Z> opt2;
static_assert(noexcept(opt1.swap(opt2)) == false, "");
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == false);
opt1.swap(opt2);
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == false);
}
#ifndef TEST_HAS_NO_EXCEPTIONS
{
optional<Z> opt1;
opt1.emplace(1);
optional<Z> opt2;
static_assert(noexcept(opt1.swap(opt2)) == false, "");
assert(static_cast<bool>(opt1) == true);
assert(*opt1 == 1);
assert(static_cast<bool>(opt2) == false);
try
{
opt1.swap(opt2);
assert(false);
}
catch (int i)
{
assert(i == 7);
}
assert(static_cast<bool>(opt1) == true);
assert(*opt1 == 1);
assert(static_cast<bool>(opt2) == false);
}
{
optional<Z> opt1;
optional<Z> opt2;
opt2.emplace(2);
static_assert(noexcept(opt1.swap(opt2)) == false, "");
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == true);
assert(*opt2 == 2);
try
{
opt1.swap(opt2);
assert(false);
}
catch (int i)
{
assert(i == 7);
}
assert(static_cast<bool>(opt1) == false);
assert(static_cast<bool>(opt2) == true);
assert(*opt2 == 2);
}
{
optional<Z> opt1;
opt1.emplace(1);
optional<Z> opt2;
opt2.emplace(2);
static_assert(noexcept(opt1.swap(opt2)) == false, "");
assert(static_cast<bool>(opt1) == true);
assert(*opt1 == 1);
assert(static_cast<bool>(opt2) == true);
assert(*opt2 == 2);
try
{
opt1.swap(opt2);
assert(false);
}
catch (int i)
{
assert(i == 6);
}
assert(static_cast<bool>(opt1) == true);
assert(*opt1 == 1);
assert(static_cast<bool>(opt2) == true);
assert(*opt2 == 2);
}
# if TEST_STD_VER >= 26
{
Z z{1};
optional<Z&> opt1{z};
optional<Z&> opt2;
ASSERT_NOEXCEPT(opt1.swap(opt2));
assert(opt1);
assert(*opt1 == 1);
assert(&(*opt1) == &z);
assert(!opt2);
opt1.swap(opt2);
assert(*opt2 == 1);
assert(&(*opt2) == &z);
assert(opt2 && !opt1);
}
{
Z z1{1};
optional<Z&> opt1;
optional<Z&> opt2{z1};
ASSERT_NOEXCEPT(opt1.swap(opt2));
opt1.swap(opt2);
assert(opt1 && !opt2);
assert(*opt1 == 1);
assert(&(*opt1) == &z1);
}
{
Z z1{1};
Z z2{2};
optional<Z&> opt1{z1};
optional<Z&> opt2{z2};
ASSERT_NOEXCEPT(opt1.swap(opt2));
opt1.swap(opt2);
assert(opt1 && opt2);
assert(*opt1 == 2);
assert(*opt2 == 1);
assert(&(*opt1) == &z2);
assert(&(*opt2) == &z1);
}
# endif
#endif
return 0;
}
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