9f5efd5d03
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
27 lines
1.1 KiB
C++
27 lines
1.1 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
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
// REQUIRES: std-at-least-c++26
|
|
// <optional>
|
|
|
|
// template <class U> T& optional<T&>::emplace(U&& arg);
|
|
// Ensure that emplace isn't found if reference_constructs_From_temporary_v == true or is_constructible_v<_Tp&, U> == false
|
|
#include <optional>
|
|
#include <type_traits>
|
|
|
|
struct X {};
|
|
void test() {
|
|
int i = 1;
|
|
std::optional<X&> f{};
|
|
static_assert(!std::is_constructible_v<X&, int>); // is_constructible_v<_Tp&, U> == false
|
|
f.emplace(i); // expected-error {{no matching member function for call to 'emplace'}}
|
|
|
|
std::optional<const int&> t{}; // reference_constructs_from_temporary_v == false
|
|
t.emplace(1); // expected-error {{no matching member function for call to 'emplace'}}
|
|
}
|