From 646eace6ec5db397ba97e86df067792c0cb6be03 Mon Sep 17 00:00:00 2001 From: Simonas Kazlauskas Date: Wed, 12 Aug 2015 15:39:49 +0300 Subject: [PATCH] Fix ReentrantMutex documentation wrt DerefMut Initial version of PR had an DerefMut implementation, which was later removed because it may cause mutable reference aliasing. Suggest how to implement mutability with reentrant mutex and remove the claim we implement DerefMut. --- src/libstd/sys/common/remutex.rs | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/src/libstd/sys/common/remutex.rs b/src/libstd/sys/common/remutex.rs index 8f416464173..0674618396f 100644 --- a/src/libstd/sys/common/remutex.rs +++ b/src/libstd/sys/common/remutex.rs @@ -36,11 +36,18 @@ unsafe impl Sync for ReentrantMutex {} /// dropped (falls out of scope), the lock will be unlocked. /// /// The data protected by the mutex can be accessed through this guard via its -/// Deref and DerefMut implementations +/// Deref implementation. +/// +/// # Mutability +/// +/// Unlike `MutexGuard`, `ReentrantMutexGuard` does not implement `DerefMut`, +/// because implementation of the trait would violate Rust’s reference aliasing +/// rules. Use interior mutability (usually `RefCell`) in order to mutate the +/// guarded data. #[must_use] pub struct ReentrantMutexGuard<'a, T: 'a> { - // funny underscores due to how Deref/DerefMut currently work (they - // disregard field privacy). + // funny underscores due to how Deref currently works (it disregards field + // privacy). __lock: &'a ReentrantMutex, __poison: poison::Guard, }