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Bug 1601251 - Prohibit copies and moves on Maybe<T> where such operations are prohibited on T. r=glandium

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Differential Revision: https://phabricator.services.mozilla.com/D205077
This commit is contained in:
Andreas Pehrson 2024-03-26 08:00:56 +00:00
parent 7298d91b7f
commit 522fd9ad0a
2 changed files with 25 additions and 10 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

27
mfbt/Maybe.h
View file

@ -203,6 +203,8 @@ class Maybe_CopyMove_Enabler<T, false, false, true> {
public:
Maybe_CopyMove_Enabler() = default;
Maybe_CopyMove_Enabler(const Maybe_CopyMove_Enabler&) = delete;
Maybe_CopyMove_Enabler& operator=(const Maybe_CopyMove_Enabler&) = delete;
MOZ_MAYBE_MOVE_OPS()
private:
@ -215,6 +217,8 @@ class Maybe_CopyMove_Enabler<T, false, true, false> {
Maybe_CopyMove_Enabler() = default;
MOZ_MAYBE_COPY_OPS()
Maybe_CopyMove_Enabler(Maybe_CopyMove_Enabler&&) = delete;
Maybe_CopyMove_Enabler& operator=(Maybe_CopyMove_Enabler&&) = delete;
private:
MOZ_MAYBE_DOWNCAST()
@ -392,28 +396,35 @@ class MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS Maybe
* a const U&.
*/
template <typename U,
typename = std::enable_if_t<std::is_constructible_v<T, const U&>>>
std::enable_if_t<std::is_constructible_v<T, const U&>, bool> = true>
MOZ_IMPLICIT Maybe(const Maybe<U>& aOther) {
if (aOther.isSome()) {
emplace(*aOther);
}
}
template <typename U, std::enable_if_t<!std::is_constructible_v<T, const U&>,
bool> = true>
explicit Maybe(const Maybe<U>& aOther) = delete;
/**
* Maybe<T> can be move-constructed from a Maybe<U> if T is constructible from
* a U&&.
*/
template <typename U,
typename = std::enable_if_t<std::is_constructible_v<T, U&&>>>
std::enable_if_t<std::is_constructible_v<T, U&&>, bool> = true>
MOZ_IMPLICIT Maybe(Maybe<U>&& aOther) {
if (aOther.isSome()) {
emplace(std::move(*aOther));
aOther.reset();
}
}
template <typename U,
std::enable_if_t<!std::is_constructible_v<T, U&&>, bool> = true>
explicit Maybe(Maybe<U>&& aOther) = delete;
template <typename U,
typename = std::enable_if_t<std::is_constructible_v<T, const U&>>>
std::enable_if_t<std::is_constructible_v<T, const U&>, bool> = true>
Maybe& operator=(const Maybe<U>& aOther) {
if (aOther.isSome()) {
if (mIsSome) {
@ -427,8 +438,12 @@ class MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS Maybe
return *this;
}
template <typename U, std::enable_if_t<!std::is_constructible_v<T, const U&>,
bool> = true>
Maybe& operator=(const Maybe<U>& aOther) = delete;
template <typename U,
typename = std::enable_if_t<std::is_constructible_v<T, U&&>>>
std::enable_if_t<std::is_constructible_v<T, U&&>, bool> = true>
Maybe& operator=(Maybe<U>&& aOther) {
if (aOther.isSome()) {
if (mIsSome) {
@ -444,6 +459,10 @@ class MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS Maybe
return *this;
}
template <typename U,
std::enable_if_t<!std::is_constructible_v<T, U&&>, bool> = true>
Maybe& operator=(Maybe<U>&& aOther) = delete;
constexpr Maybe& operator=(Nothing) {
reset();
return *this;

8
mfbt/tests/TestMaybe.cpp
View file

@ -519,8 +519,6 @@ static bool TestCopyAndMove() {
{
Maybe<UnmovableValue> mayUnmovableValue = Some(UnmovableValue());
MOZ_RELEASE_ASSERT(mayUnmovableValue->GetStatus() == eWasCopyConstructed);
mayUnmovableValue = Some(UnmovableValue());
MOZ_RELEASE_ASSERT(mayUnmovableValue->GetStatus() == eWasCopyAssigned);
mayUnmovableValue.reset();
mayUnmovableValue.emplace(UnmovableValue());
MOZ_RELEASE_ASSERT(mayUnmovableValue->GetStatus() == eWasCopyConstructed);
@ -530,10 +528,8 @@ static bool TestCopyAndMove() {
static_assert(std::is_copy_constructible_v<Maybe<UnmovableValue>>);
static_assert(std::is_copy_assignable_v<Maybe<UnmovableValue>>);
// TODO(Bug 1601251): Maybe<T> should delete move operations if T does not
// support moves
// static_assert(!std::is_move_constructible_v<Maybe<UnmovableValue>>);
// static_assert(!std::is_move_assignable_v<Maybe<UnmovableValue>>);
static_assert(!std::is_move_constructible_v<Maybe<UnmovableValue>>);
static_assert(!std::is_move_assignable_v<Maybe<UnmovableValue>>);
}
MOZ_RELEASE_ASSERT(0 == sUndestroyedObjects);