Auto merge of #42856 - Mark-Simulacrum:rollup, r=Mark-Simulacrum

Rollup of 8 pull requests

- Successful merges: #42777, #42783, #42787, #42821, #42822, #42825, #42829, #42833
- Failed merges:

2 files changed, 21 insertions, 0 deletions

diff --git a/src/libstd/sync/mutex.rs b/src/libstd/sync/mutex.rs
index 9a242a96d46..fc6c7de9ef0 100644
--- a/src/libstd/sync/mutex.rs
+++ b/src/libstd/sync/mutex.rs
@@ -440,6 +440,13 @@ impl<'a, T: ?Sized + fmt::Debug> fmt::Debug for MutexGuard<'a, T> {
     }
 }
 
+#[stable(feature = "std_guard_impls", since = "1.20")]
+impl<'a, T: ?Sized + fmt::Display> fmt::Display for MutexGuard<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
 pub fn guard_lock<'a, T: ?Sized>(guard: &MutexGuard<'a, T>) -> &'a sys::Mutex {
     &guard.__lock.inner
 }
diff --git a/src/libstd/sync/rwlock.rs b/src/libstd/sync/rwlock.rs
index 95bc8d30932..944801e8a3b 100644
--- a/src/libstd/sync/rwlock.rs
+++ b/src/libstd/sync/rwlock.rs
@@ -370,6 +370,13 @@ impl<'a, T: fmt::Debug> fmt::Debug for RwLockReadGuard<'a, T> {
     }
 }
 
+#[stable(feature = "std_guard_impls", since = "1.20")]
+impl<'a, T: ?Sized + fmt::Display> fmt::Display for RwLockReadGuard<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
 #[stable(feature = "std_debug", since = "1.16.0")]
 impl<'a, T: fmt::Debug> fmt::Debug for RwLockWriteGuard<'a, T> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
@@ -379,6 +386,13 @@ impl<'a, T: fmt::Debug> fmt::Debug for RwLockWriteGuard<'a, T> {
     }
 }
 
+#[stable(feature = "std_guard_impls", since = "1.20")]
+impl<'a, T: ?Sized + fmt::Display> fmt::Display for RwLockWriteGuard<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        (**self).fmt(f)
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'rwlock, T: ?Sized> Deref for RwLockReadGuard<'rwlock, T> {
     type Target = T;