Fix deprecation warning (#457)

src/bytes.rs

@@ -1023,24 +1023,24 @@ unsafe fn shallow_clone_vec(
     // `Release` is used synchronize with other threads that
     // will load the `arc` field.
     //
-    // If the `compare_and_swap` fails, then the thread lost the
+    // If the `compare_exchange` fails, then the thread lost the
     // race to promote the buffer to shared. The `Acquire`
-    // ordering will synchronize with the `compare_and_swap`
+    // ordering will synchronize with the `compare_exchange`
     // that happened in the other thread and the `Shared`
     // pointed to by `actual` will be visible.
-    let actual = atom.compare_and_swap(ptr as _, shared as _, Ordering::AcqRel);
+    match atom.compare_exchange(ptr as _, shared as _, Ordering::AcqRel, Ordering::Acquire) {
-
+        Ok(actual) => {
-    if actual as usize == ptr as usize {
+            debug_assert!(actual as usize == ptr as usize);
             // The upgrade was successful, the new handle can be
             // returned.
-        return Bytes {
+            Bytes {
                 ptr: offset,
                 len,
                 data: AtomicPtr::new(shared as _),
                 vtable: &SHARED_VTABLE,
-        };
             }
-
+        }
+        Err(actual) => {
             // The upgrade failed, a concurrent clone happened. Release
             // the allocation that was made in this thread, it will not
             // be needed.
@@ -1051,6 +1051,8 @@ unsafe fn shallow_clone_vec(
             // count.
             shallow_clone_arc(actual as _, offset, len)
         }
+    }
+}
 
 unsafe fn release_shared(ptr: *mut Shared) {
     // `Shared` storage... follow the drop steps from Arc.