From f8b774fbf1f57e520b58ae3828e4b3a1ddf1d97c Mon Sep 17 00:00:00 2001
From: Manish Goregaokar <manishsmail@gmail.com>
Date: Mon, 7 May 2018 09:27:50 -0700
Subject: Add explanation for #[must_use] on mutex guards

---
 src/libstd/sync/mutex.rs  | 2 +-
 src/libstd/sync/rwlock.rs | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

(limited to 'src/libstd/sync')

diff --git a/src/libstd/sync/mutex.rs b/src/libstd/sync/mutex.rs
index 3b4904c98e8..f3503b0b3a6 100644
--- a/src/libstd/sync/mutex.rs
+++ b/src/libstd/sync/mutex.rs
@@ -150,7 +150,7 @@ unsafe impl<T: ?Sized + Send> Sync for Mutex<T> { }
 /// [`lock`]: struct.Mutex.html#method.lock
 /// [`try_lock`]: struct.Mutex.html#method.try_lock
 /// [`Mutex`]: struct.Mutex.html
-#[must_use]
+#[must_use = "if unused the Mutex will immediately unlock"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct MutexGuard<'a, T: ?Sized + 'a> {
     // funny underscores due to how Deref/DerefMut currently work (they
diff --git a/src/libstd/sync/rwlock.rs b/src/libstd/sync/rwlock.rs
index f7fdedc0d21..e3db60cff84 100644
--- a/src/libstd/sync/rwlock.rs
+++ b/src/libstd/sync/rwlock.rs
@@ -94,7 +94,7 @@ unsafe impl<T: ?Sized + Send + Sync> Sync for RwLock<T> {}
 /// [`read`]: struct.RwLock.html#method.read
 /// [`try_read`]: struct.RwLock.html#method.try_read
 /// [`RwLock`]: struct.RwLock.html
-#[must_use]
+#[must_use = "if unused the RwLock will immediately unlock"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct RwLockReadGuard<'a, T: ?Sized + 'a> {
     __lock: &'a RwLock<T>,
@@ -115,7 +115,7 @@ unsafe impl<'a, T: ?Sized + Sync> Sync for RwLockReadGuard<'a, T> {}
 /// [`write`]: struct.RwLock.html#method.write
 /// [`try_write`]: struct.RwLock.html#method.try_write
 /// [`RwLock`]: struct.RwLock.html
-#[must_use]
+#[must_use = "if unused the RwLock will immediately unlock"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct RwLockWriteGuard<'a, T: ?Sized + 'a> {
     __lock: &'a RwLock<T>,
-- 
cgit 1.4.1-3-g733a5