William Tran-Viet 389a23c538
[libc++] Implement P2988R12: std::optional<T&> (#155202)
Resolves #148131

- Unlock `std::optional<T&>` implementation
- Allow instantiations of `optional<T(&)(...)>` and `optional<T(&)[]>`
but disables `value_or()` and `optional::iterator` + all `iterator`
related functions
- Update documentation
- Update tests
2025-11-12 11:00:08 +08:00

85 lines
1.8 KiB
C++

//===----------------------------------------------------------------------===//
//
// 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 reset() noexcept;
#include <optional>
#include <type_traits>
#include <cassert>
#include "test_macros.h"
using std::optional;
struct X
{
static bool dtor_called;
X() = default;
X(const X&) = default;
X& operator=(const X&) = default;
~X() {dtor_called = true;}
};
bool X::dtor_called = false;
TEST_CONSTEXPR_CXX20 bool check_reset() {
{
optional<int> opt;
static_assert(noexcept(opt.reset()) == true, "");
opt.reset();
assert(static_cast<bool>(opt) == false);
}
{
optional<int> opt(3);
opt.reset();
assert(static_cast<bool>(opt) == false);
}
return true;
}
int main(int, char**)
{
check_reset();
#if TEST_STD_VER >= 20
static_assert(check_reset());
#endif
{
optional<X> opt;
static_assert(noexcept(opt.reset()) == true, "");
assert(X::dtor_called == false);
opt.reset();
assert(X::dtor_called == false);
assert(static_cast<bool>(opt) == false);
}
{
optional<X> opt(X{});
X::dtor_called = false;
opt.reset();
assert(X::dtor_called == true);
assert(static_cast<bool>(opt) == false);
X::dtor_called = false;
}
#if TEST_STD_VER >= 26
{
X x{};
optional<X&> opt(x);
X::dtor_called = false;
opt.reset();
assert(X::dtor_called == false);
assert(static_cast<bool>(opt) == false);
}
#endif
return 0;
}