Test size hint alongside Powerset counts

Author: Philippe-Cholet

tests/test_std.rs

@@ -994,10 +994,14 @@ fn powerset() {
         let mut it = (0..n).powerset();
         let len = 1 << n;
         assert_eq!(len, it.clone().count());
+        assert_eq!(len, it.size_hint().0);
+        assert_eq!(Some(len), it.size_hint().1);
         for count in (0..len).rev() {
             let elem = it.next();
             assert!(elem.is_some());
             assert_eq!(count, it.clone().count());
+            assert_eq!(count, it.size_hint().0);
+            assert_eq!(Some(count), it.size_hint().1);
         }
         let should_be_none = it.next();
         assert!(should_be_none.is_none());