Rebase conflicts

Author: poliorcetics

library/alloc/tests/vec_deque.rs

@@ -1698,3 +1698,33 @@ fn test_binary_search_by_key() {
     assert_eq!(deque.binary_search_by_key(&3, |&(v,)| v), Ok(2));
     assert_eq!(deque.binary_search_by_key(&4, |&(v,)| v), Err(3));
 }
+
+#[test]
+fn test_zero_sized_push() {
+    const N: usize = 8;
+
+    // Zero sized type
+    struct Zst;
+
+    // Test that for all possible sequences of push_front / push_back,
+    // we end up with a deque of the correct size
+
+    for len in 0..N {
+        let mut tester = VecDeque::with_capacity(len);
+        assert_eq!(tester.len(), 0);
+        assert!(tester.capacity() >= len);
+        for case in 0..(1 << len) {
+            assert_eq!(tester.len(), 0);
+            for bit in 0..len {
+                if case & (1 << bit) != 0 {
+                    tester.push_front(Zst);
+                } else {
+                    tester.push_back(Zst);
+                }
+            }
+            assert_eq!(tester.len(), len);
+            assert_eq!(tester.iter().count(), len);
+            tester.clear();
+        }
+    }
+}