Add unsafe Send and Sync impls to VecDeque's Drain<T>

Author: mystor

src/libcollections/vec_deque.rs

@@ -1800,6 +1800,9 @@ pub struct Drain<'a, T: 'a> {
     deque: *mut VecDeque<T>,
 }
 
+unsafe impl<'a, T: Sync> Sync for Drain<'a, T> {}
+unsafe impl<'a, T: Send> Send for Drain<'a, T> {}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T: 'a> Drop for Drain<'a, T> {
     fn drop(&mut self) {

src/test/run-pass/sync-send-iterators-in-libcollections.rs

@@ -93,7 +93,8 @@ fn main() {
     }
     all_sync_send!(EnumSet::<Foo>::new(), iter);
 
-    all_sync_send!(VecDeque::<usize>::new(), iter, iter_mut, drain, into_iter);
+    all_sync_send!(VecDeque::<usize>::new(), iter, iter_mut, into_iter);
+    is_sync_send!(VecDeque::<usize>::new(), drain(..));
 
     all_sync_send!(Vec::<usize>::new(), into_iter);
     is_sync_send!(Vec::<usize>::new(), drain(..));