Avoid creating &muts in Windows ReentrantMutex.

library/std/src/lib.rs

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

library/std/src/sys/windows/mutex.rs

@@ -148,35 +148,35 @@ fn kind() -> Kind {
 }
 
 pub struct ReentrantMutex {
-    inner: UnsafeCell<MaybeUninit<c::CRITICAL_SECTION>>,
+    inner: MaybeUninit<UnsafeCell<c::CRITICAL_SECTION>>,
 }
 
 unsafe impl Send for ReentrantMutex {}
 unsafe impl Sync for ReentrantMutex {}
 
 impl ReentrantMutex {
     pub const fn uninitialized() -> ReentrantMutex {
-        ReentrantMutex { inner: UnsafeCell::new(MaybeUninit::uninit()) }
+        ReentrantMutex { inner: MaybeUninit::uninit() }
     }
 
     pub unsafe fn init(&self) {
-        c::InitializeCriticalSection((&mut *self.inner.get()).as_mut_ptr());
+        c::InitializeCriticalSection(UnsafeCell::raw_get(self.inner.as_ptr()));
     }
 
     pub unsafe fn lock(&self) {
-        c::EnterCriticalSection((&mut *self.inner.get()).as_mut_ptr());
+        c::EnterCriticalSection(UnsafeCell::raw_get(self.inner.as_ptr()));
     }
 
     #[inline]
     pub unsafe fn try_lock(&self) -> bool {
-        c::TryEnterCriticalSection((&mut *self.inner.get()).as_mut_ptr()) != 0
+        c::TryEnterCriticalSection(UnsafeCell::raw_get(self.inner.as_ptr())) != 0
     }
 
     pub unsafe fn unlock(&self) {
-        c::LeaveCriticalSection((&mut *self.inner.get()).as_mut_ptr());
+        c::LeaveCriticalSection(UnsafeCell::raw_get(self.inner.as_ptr()));
     }
 
     pub unsafe fn destroy(&self) {
-        c::DeleteCriticalSection((&mut *self.inner.get()).as_mut_ptr());
+        c::DeleteCriticalSection(UnsafeCell::raw_get(self.inner.as_ptr()));
     }
 }