fix(api): unbound R from Send and Sync

src/raw/mutex.rs

@@ -148,8 +148,8 @@ pub struct Mutex<T: ?Sized, R> {
 }
 
 // Same unsafe impls as `std::sync::Mutex`.
-unsafe impl<T: ?Sized + Send, R> Sync for Mutex<T, R> {}
 unsafe impl<T: ?Sized + Send, R> Send for Mutex<T, R> {}
+unsafe impl<T: ?Sized + Send, R> Sync for Mutex<T, R> {}
 
 impl<T, R> Mutex<T, R> {
     /// Creates a new mutex in an unlocked state ready for use.
@@ -585,7 +585,10 @@ pub struct MutexGuard<'a, T: ?Sized, R: Relax> {
     node: &'a MutexNodeInit,
 }
 
-// Same unsafe impl as `std::sync::MutexGuard`.
+// `std::sync::MutexGuard` is not Send for pthread compatibility, but this
+// implementation is safe to be Send.
+unsafe impl<T: ?Sized + Send, R: Relax> Send for MutexGuard<'_, T, R> {}
+// Same unsafe Sync impl as `std::sync::MutexGuard`.
 unsafe impl<T: ?Sized + Sync, R: Relax> Sync for MutexGuard<'_, T, R> {}
 
 impl<'a, T: ?Sized, R: Relax> MutexGuard<'a, T, R> {
@@ -652,7 +655,7 @@ impl<'a, T: ?Sized, R: Relax> core::ops::DerefMut for MutexGuard<'a, T, R> {
 unsafe impl<T: ?Sized, R: Relax> crate::loom::Guard for MutexGuard<'_, T, R> {
     type Target = T;
 
-    fn get(&self) -> &UnsafeCell<Self::Target> {
+    fn get(&self) -> &loom::cell::UnsafeCell<Self::Target> {
         &self.lock.data
     }
 }

src/thread_local/mutex.rs

@@ -105,6 +105,10 @@ fn panic_already_held(caller: &Location<'static>) -> ! {
 /// [`try_lock_with`]: Mutex::try_lock_with
 pub struct Mutex<T: ?Sized, R>(RawMutex<T, R>);
 
+// Same unsafe impls as `crate::raw::Mutex`.
+unsafe impl<T: ?Sized + Send, R> Send for Mutex<T, R> {}
+unsafe impl<T: ?Sized + Send, R> Sync for Mutex<T, R> {}
+
 impl<T, R> Mutex<T, R> {
     /// Creates a new mutex in an unlocked state ready for use.
     ///
@@ -697,7 +701,7 @@ pub struct MutexGuard<'a, T: ?Sized, R: Relax> {
 }
 
 // SAFETY: Guard only access thread local storage during drop call, can be Sync.
-unsafe impl<'a, T: ?Sized + Sync, R: Relax> Sync for MutexGuard<'a, T, R> {}
+unsafe impl<T: ?Sized + Sync, R: Relax> Sync for MutexGuard<'_, T, R> {}
 
 impl<'a, T: ?Sized, R: Relax> MutexGuard<'a, T, R> {
     /// Creates a new guard instance from a raw guard.