Tracking Issue for mapped_lock_guards (MappedMutexGuard, MappedRwLockReadGuard, MappedRwLockWriteGuard) · Issue #117108 · rust-lang/rust (original) (raw)

Feature gate: #![feature(mapped_lock_guards)]

This is a tracking issue for MappedMutexGuard, MappedRwLockReadGuard, and MappedRwLockWriteGuard.

This adds types analogous to lock_api::MappedMutexGuard, MappedRwLockReadGuard, MappedRwLockWriteGuard) to std::sync, and methods MutexGuard::map and MutexGuard::filter_map (same for `RwLock*Guard) to create them

Public API

// std::sync::mutex

pub struct MappedMutexGuard<'mutex, T: ?Sized>;

impl<'mutex, T: ?Sized> MutexGuard<'mutex, T> { pub fn map<U, F>(orig: Self, f: F) -> MappedMutexGuard<'mutex, U> where F: FnOnce(&mut T) -> &mut U, U: ?Sized; pub fn filter_map<U, F>(orig: Self, f: F) -> Result<MappedMutexGuard<'mutex, U>, Self> where F: FnOnce(&mut T) -> Option<&mut U>, U: ?Sized; }

impl<'mutex, T: ?Sized> MappedMutexGuard<'mutex, T> { pub fn map<U, F>(orig: Self, f: F) -> MappedMutexGuard<'mutex, U> where F: FnOnce(&mut T) -> &mut U, U: ?Sized; pub fn filter_map<U, F>(orig: Self, f: F) -> Result<MappedMutexGuard<'mutex, U>, Self> where F: FnOnce(&mut T) -> Option<&mut U>, U: ?Sized; }

impl<T: ?Sized> Deref/DerefMut for MappedMutexGuard<'_, T>; impl<T: ?Sized + Debug/Display> Debug/Display for MappedMutexGuard<'_, T>;

// std::sync::rwlock

pub struct MappedRwLockReadGuard<'rwlock, T: ?Sized>; pub struct MappedRwLockWriteGuard<'rwlock, T: ?Sized>;

impl<'rwlock, T: ?Sized> RwLockReadGuard<'rwlock, T> { pub fn map<U, F>(orig: Self, f: F) -> MappedRwLockReadGuard<'rwlock, U> where F: FnOnce(&T) -> &U, U: ?Sized; pub fn filter_map<U, F>(orig: Self, f: F) -> Result<MappedRwLockReadGuard<'rwlock, U>, Self> where F: FnOnce(&T) -> Option<&U>, U: ?Sized; } impl<'rwlock, T: ?Sized> MappedRwLockReadGuard<'rwlock, T> { pub fn map<U, F>(orig: Self, f: F) -> MappedRwLockReadGuard<'rwlock, U> where F: FnOnce(&T) -> &U, U: ?Sized; pub fn filter_map<U, F>(orig: Self, f: F) -> Result<MappedRwLockReadGuard<'rwlock, U>, Self> where F: FnOnce(&T) -> Option<&U>, U: ?Sized; }

impl<'rwlock, T: ?Sized> RwLockWriteGuard<'rwlock, T> { pub fn map<U, F>(orig: Self, f: F) -> MappedRwLockWriteGuard<'rwlock, U> where F: FnOnce(&mut T) -> &mut U, U: ?Sized; pub fn filter_map<U, F>(orig: Self, f: F) -> Result<MappedRwLockWriteGuard<'rwlock, U>, Self> where F: FnOnce(&mut T) -> Option<&mut U>, U: ?Sized; } impl<'rwlock, T: ?Sized> MappedRwLockWriteGuard<'rwlock, T> { pub fn map<U, F>(orig: Self, f: F) -> MappedRwLockWriteGuard<'rwlock, U> where F: FnOnce(&mut T) -> &mut U, U: ?Sized; pub fn filter_map<U, F>(orig: Self, f: F) -> Result<MappedRwLockWriteGuard<'rwlock, U>, Self> where F: FnOnce(&mut T) -> Option<&mut U>, U: ?Sized; }

impl<T: ?Sized> Deref for MappedRwLockReadGuard<'_, T>; impl<T: ?Sized> Deref/DerefMut for MappedRwLockWriteGuard<'_, T>; impl<T: ?Sized + Debug/Display> Debug/Display for MappedRwLockReadGuard<'_, T>; impl<T: ?Sized + Debug/Display> Debug/Display for MappedRwLockWriteGuard<'_, T>;

Steps / History

• ACP: Include MappedRwLocKWriteGuard from lock_api or parking_lot libs-team#260
• Implementation: Implement MappedMutexGuard, MappedRwLockReadGuard, and MappedRwLockWriteGuard. #117107
• Rename try_map to filter_map: Rename *Guard::try_map to filter_map. #140536
• Final comment period (FCP)1
• Stabilization PR

Unresolved Questions

• None yet.

1. https://std-dev-guide.rust-lang.org/feature-lifecycle/stabilization.html ↩