Replace unneeded `unsafe` calls to `.get()` with calls to `.get_mut()`

library/core/src/cell.rs

@@ -496,10 +496,7 @@ impl<T: ?Sized> Cell<T> {
     #[inline]
     #[stable(feature = "cell_get_mut", since = "1.11.0")]
     pub fn get_mut(&mut self) -> &mut T {
-        // SAFETY: This can cause data races if called from a separate thread,
-        // but `Cell` is `!Sync` so this won't happen, and `&mut` guarantees
-        // unique access.
-        unsafe { &mut *self.value.get() }
+        self.value.get_mut()
     }
 
     /// Returns a `&Cell<T>` from a `&mut T`
@@ -945,8 +942,7 @@ impl<T: ?Sized> RefCell<T> {
     #[inline]
     #[stable(feature = "cell_get_mut", since = "1.11.0")]
     pub fn get_mut(&mut self) -> &mut T {
-        // SAFETY: `&mut` guarantees unique access.
-        unsafe { &mut *self.value.get() }
+        self.value.get_mut()
     }
 
     /// Undo the effect of leaked guards on the borrow state of the `RefCell`.

library/core/src/sync/atomic.rs

@@ -838,8 +838,7 @@ impl<T> AtomicPtr<T> {
     #[inline]
     #[stable(feature = "atomic_access", since = "1.15.0")]
     pub fn get_mut(&mut self) -> &mut *mut T {
-        // SAFETY: the mutable reference guarantees unique ownership.
-        unsafe { &mut *self.p.get() }
+        self.p.get_mut()
     }
 
     /// Get atomic access to a pointer.
@@ -1275,8 +1274,7 @@ assert_eq!(some_var.load(Ordering::SeqCst), 5);
                 #[inline]
                 #[$stable_access]
                 pub fn get_mut(&mut self) -> &mut $int_type {
-                    // SAFETY: the mutable reference guarantees unique ownership.
-                    unsafe { &mut *self.v.get() }
+                    self.v.get_mut()
                 }
             }
 

library/std/src/lib.rs

@@ -315,6 +315,7 @@
 #![feature(try_reserve)]
 #![feature(unboxed_closures)]
 #![feature(unsafe_block_in_unsafe_fn)]
+#![feature(unsafe_cell_get_mut)]
 #![feature(unsafe_cell_raw_get)]
 #![feature(untagged_unions)]
 #![feature(unwind_attributes)]

library/std/src/sync/mutex.rs

@@ -406,9 +406,7 @@ impl<T: ?Sized> Mutex<T> {
     /// ```
     #[stable(feature = "mutex_get_mut", since = "1.6.0")]
     pub fn get_mut(&mut self) -> LockResult<&mut T> {
-        // We know statically that there are no other references to `self`, so
-        // there's no need to lock the inner mutex.
-        let data = unsafe { &mut *self.data.get() };
+        let data = self.data.get_mut();
         poison::map_result(self.poison.borrow(), |_| data)
     }
 }

library/std/src/sync/rwlock.rs

@@ -404,9 +404,7 @@ impl<T: ?Sized> RwLock<T> {
     /// ```
     #[stable(feature = "rwlock_get_mut", since = "1.6.0")]
     pub fn get_mut(&mut self) -> LockResult<&mut T> {
-        // We know statically that there are no other references to `self`, so
-        // there's no need to lock the inner lock.
-        let data = unsafe { &mut *self.data.get() };
+        let data = self.data.get_mut();
         poison::map_result(self.poison.borrow(), |_| data)
     }
 }