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-rw-r--r--mfbt/Maybe.h212
1 files changed, 191 insertions, 21 deletions
diff --git a/mfbt/Maybe.h b/mfbt/Maybe.h
index 100b139c79..2f92f753c0 100644
--- a/mfbt/Maybe.h
+++ b/mfbt/Maybe.h
@@ -9,6 +9,7 @@
#ifndef mozilla_Maybe_h
#define mozilla_Maybe_h
+#include <functional>
#include <new> // for placement new
#include <ostream>
#include <type_traits>
@@ -202,6 +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:
@@ -214,6 +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()
@@ -288,6 +293,15 @@ struct MaybeStorage<T, true> : MaybeStorageBase<T> {
mIsSome{true} {}
};
+template <typename T>
+struct IsMaybeImpl : std::false_type {};
+
+template <typename T>
+struct IsMaybeImpl<Maybe<T>> : std::true_type {};
+
+template <typename T>
+using IsMaybe = IsMaybeImpl<std::decay_t<T>>;
+
} // namespace detail
template <typename T, typename U = typename std::remove_cv<
@@ -382,28 +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) {
@@ -417,8 +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) {
@@ -434,6 +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;
@@ -455,7 +484,7 @@ class MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS Maybe
* without calling the destructor. The internal storage is also reset to
* avoid multiple calls. Unsafe unless |isSome()|.
*/
- T extract() {
+ constexpr T extract() {
MOZ_RELEASE_ASSERT(isSome());
T v = std::move(mStorage.val);
reset();
@@ -597,7 +626,7 @@ class MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS Maybe
/* If |isSome()|, runs the provided function or functor on the contents of
* this Maybe. */
template <typename Func>
- constexpr Maybe& apply(Func&& aFunc) {
+ constexpr Maybe& apply(Func&& aFunc) & {
if (isSome()) {
std::forward<Func>(aFunc)(ref());
}
@@ -605,20 +634,36 @@ class MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS Maybe
}
template <typename Func>
- constexpr const Maybe& apply(Func&& aFunc) const {
+ constexpr const Maybe& apply(Func&& aFunc) const& {
if (isSome()) {
std::forward<Func>(aFunc)(ref());
}
return *this;
}
+ template <typename Func>
+ constexpr Maybe& apply(Func&& aFunc) && {
+ if (isSome()) {
+ std::forward<Func>(aFunc)(extract());
+ }
+ return *this;
+ }
+
+ template <typename Func>
+ constexpr Maybe& apply(Func&& aFunc) const&& {
+ if (isSome()) {
+ std::forward<Func>(aFunc)(extract());
+ }
+ return *this;
+ }
+
/*
* If |isSome()|, runs the provided function and returns the result wrapped
* in a Maybe. If |isNothing()|, returns an empty Maybe value with the same
* value type as what the provided function would have returned.
*/
template <typename Func>
- constexpr auto map(Func&& aFunc) {
+ constexpr auto map(Func&& aFunc) & {
if (isSome()) {
return Some(std::forward<Func>(aFunc)(ref()));
}
@@ -626,13 +671,132 @@ class MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS Maybe
}
template <typename Func>
- constexpr auto map(Func&& aFunc) const {
+ constexpr auto map(Func&& aFunc) const& {
if (isSome()) {
return Some(std::forward<Func>(aFunc)(ref()));
}
return Maybe<decltype(std::forward<Func>(aFunc)(ref()))>{};
}
+ template <typename Func>
+ constexpr auto map(Func&& aFunc) && {
+ if (isSome()) {
+ return Some(std::forward<Func>(aFunc)(extract()));
+ }
+ return Maybe<decltype(std::forward<Func>(aFunc)(extract()))>{};
+ }
+
+ template <typename Func>
+ constexpr auto map(Func&& aFunc) const&& {
+ if (isSome()) {
+ return Some(std::forward<Func>(aFunc)(extract()));
+ }
+ return Maybe<decltype(std::forward<Func>(aFunc)(extract()))>{};
+ }
+
+ /*
+ * If |isSome()|, runs the provided function or functor on the contents of
+ * this Maybe and returns the result. Note that the provided function or
+ * functor must return a Maybe<U> of any type U.
+ * If |isNothing()|, returns an empty Maybe value with the same type as what
+ * the provided function would have returned.
+ */
+ template <typename Func>
+ constexpr auto andThen(Func&& aFunc) & {
+ static_assert(std::is_invocable_v<Func, T&>);
+ using U = std::invoke_result_t<Func, T&>;
+ static_assert(detail::IsMaybe<U>::value);
+ if (isSome()) {
+ return std::invoke(std::forward<Func>(aFunc), ref());
+ }
+ return std::remove_cv_t<std::remove_reference_t<U>>{};
+ }
+
+ template <typename Func>
+ constexpr auto andThen(Func&& aFunc) const& {
+ static_assert(std::is_invocable_v<Func, const T&>);
+ using U = std::invoke_result_t<Func, const T&>;
+ static_assert(detail::IsMaybe<U>::value);
+ if (isSome()) {
+ return std::invoke(std::forward<Func>(aFunc), ref());
+ }
+ return std::remove_cv_t<std::remove_reference_t<U>>{};
+ }
+
+ template <typename Func>
+ constexpr auto andThen(Func&& aFunc) && {
+ static_assert(std::is_invocable_v<Func, T&&>);
+ using U = std::invoke_result_t<Func, T&&>;
+ static_assert(detail::IsMaybe<U>::value);
+ if (isSome()) {
+ return std::invoke(std::forward<Func>(aFunc), extract());
+ }
+ return std::remove_cv_t<std::remove_reference_t<U>>{};
+ }
+
+ template <typename Func>
+ constexpr auto andThen(Func&& aFunc) const&& {
+ static_assert(std::is_invocable_v<Func, const T&&>);
+ using U = std::invoke_result_t<Func, const T&&>;
+ static_assert(detail::IsMaybe<U>::value);
+ if (isSome()) {
+ return std::invoke(std::forward<Func>(aFunc), extract());
+ }
+ return std::remove_cv_t<std::remove_reference_t<U>>{};
+ }
+
+ /*
+ * If |isNothing()|, runs the provided function or functor and returns its
+ * result. If |isSome()|, returns the contained value wrapped in a Maybe.
+ */
+ template <typename Func>
+ constexpr Maybe orElse(Func&& aFunc) & {
+ static_assert(std::is_invocable_v<Func>);
+ using U = std::invoke_result_t<Func>;
+ static_assert(
+ std::is_same_v<Maybe, std::remove_cv_t<std::remove_reference_t<U>>>);
+ if (isSome()) {
+ return *this;
+ }
+ return std::invoke(std::forward<Func>(aFunc));
+ }
+
+ template <typename Func>
+ constexpr Maybe orElse(Func&& aFunc) const& {
+ static_assert(std::is_invocable_v<Func>);
+ using U = std::invoke_result_t<Func>;
+ static_assert(
+ std::is_same_v<Maybe, std::remove_cv_t<std::remove_reference_t<U>>>);
+ if (isSome()) {
+ return *this;
+ }
+ return std::invoke(std::forward<Func>(aFunc));
+ }
+
+ template <typename Func>
+ constexpr Maybe orElse(Func&& aFunc) && {
+ static_assert(std::is_invocable_v<Func>);
+ using U = std::invoke_result_t<Func>;
+ static_assert(
+ std::is_same_v<Maybe, std::remove_cv_t<std::remove_reference_t<U>>>);
+ if (isSome()) {
+ return std::move(*this);
+ }
+ return std::invoke(std::forward<Func>(aFunc));
+ }
+
+ template <typename Func>
+ constexpr Maybe orElse(Func&& aFunc) const&& {
+ static_assert(std::is_invocable_v<Func>);
+ using U = std::invoke_result_t<Func>;
+ static_assert(
+ std::is_same_v<Maybe, std::remove_cv_t<std::remove_reference_t<U>>>);
+ if (isSome()) {
+ return std::move(*this);
+ }
+ return std::invoke(std::forward<Func>(aFunc));
+ }
+
/* If |isSome()|, empties this Maybe and destroys its contents. */
constexpr void reset() {
if (isSome()) {
@@ -705,7 +869,7 @@ class Maybe<T&> {
void reset() { mValue = nullptr; }
template <typename Func>
- Maybe& apply(Func&& aFunc) {
+ const Maybe& apply(Func&& aFunc) const {
if (isSome()) {
std::forward<Func>(aFunc)(ref());
}
@@ -713,29 +877,35 @@ class Maybe<T&> {
}
template <typename Func>
- const Maybe& apply(Func&& aFunc) const {
+ auto map(Func&& aFunc) const {
+ Maybe<decltype(std::forward<Func>(aFunc)(ref()))> val;
if (isSome()) {
- std::forward<Func>(aFunc)(ref());
+ val.emplace(std::forward<Func>(aFunc)(ref()));
}
- return *this;
+ return val;
}
template <typename Func>
- auto map(Func&& aFunc) {
- Maybe<decltype(std::forward<Func>(aFunc)(ref()))> val;
+ constexpr auto andThen(Func&& aFunc) const {
+ static_assert(std::is_invocable_v<Func, T&>);
+ using U = std::invoke_result_t<Func, T&>;
+ static_assert(detail::IsMaybe<U>::value);
if (isSome()) {
- val.emplace(std::forward<Func>(aFunc)(ref()));
+ return std::invoke(std::forward<Func>(aFunc), ref());
}
- return val;
+ return std::remove_cv_t<std::remove_reference_t<U>>{};
}
template <typename Func>
- auto map(Func&& aFunc) const {
- Maybe<decltype(std::forward<Func>(aFunc)(ref()))> val;
+ constexpr Maybe orElse(Func&& aFunc) const {
+ static_assert(std::is_invocable_v<Func>);
+ using U = std::invoke_result_t<Func>;
+ static_assert(
+ std::is_same_v<Maybe, std::remove_cv_t<std::remove_reference_t<U>>>);
if (isSome()) {
- val.emplace(std::forward<Func>(aFunc)(ref()));
+ return *this;
}
- return val;
+ return std::invoke(std::forward<Func>(aFunc));
}
bool refEquals(const Maybe<T&>& aOther) const {
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-23 10:18:02 +0000