1 files changed, 50 insertions, 0 deletions
diff --git a/library/alloc/tests/vec_deque.rs b/library/alloc/tests/vec_deque.rs
index d04de5a07..5a0b852e8 100644
--- a/library/alloc/tests/vec_deque.rs
+++ b/library/alloc/tests/vec_deque.rs
@@ -1046,6 +1046,20 @@ fn test_append_double_drop() {
 }
 
 #[test]
+#[should_panic]
+fn test_append_zst_capacity_overflow() {
+    let mut v = Vec::with_capacity(usize::MAX);
+    // note: using resize instead of set_len here would
+    //       be *extremely* slow in unoptimized builds.
+    // SAFETY: `v` has capacity `usize::MAX`, and no initialization
+    //         is needed for empty tuples.
+    unsafe { v.set_len(usize::MAX) };
+    let mut v = VecDeque::from(v);
+    let mut w = vec![()].into();
+    v.append(&mut w);
+}
+
+#[test]
 fn test_retain() {
     let mut buf = VecDeque::new();
     buf.extend(1..5);
@@ -1736,3 +1750,39 @@ fn test_resize_keeps_reserved_space_from_item() {
     d.resize(1, v);
     assert_eq!(d[0].capacity(), 1234);
 }
+
+#[test]
+fn test_collect_from_into_iter_keeps_allocation() {
+    let mut v = Vec::with_capacity(13);
+    v.extend(0..7);
+    check(v.as_ptr(), v.last().unwrap(), v.into_iter());
+
+    let mut v = VecDeque::with_capacity(13);
+    v.extend(0..7);
+    check(&v[0], &v[v.len() - 1], v.into_iter());
+
+    fn check(buf: *const i32, last: *const i32, mut it: impl Iterator<Item = i32>) {
+        assert_eq!(it.next(), Some(0));
+        assert_eq!(it.next(), Some(1));
+
+        let mut v: VecDeque<i32> = it.collect();
+        assert_eq!(v.capacity(), 13);
+        assert_eq!(v.as_slices().0.as_ptr(), buf.wrapping_add(2));
+        assert_eq!(&v[v.len() - 1] as *const _, last);
+
+        assert_eq!(v.as_slices(), ([2, 3, 4, 5, 6].as_slice(), [].as_slice()));
+        v.push_front(7);
+        assert_eq!(v.as_slices(), ([7, 2, 3, 4, 5, 6].as_slice(), [].as_slice()));
+        v.push_front(8);
+        assert_eq!(v.as_slices(), ([8, 7, 2, 3, 4, 5, 6].as_slice(), [].as_slice()));
+
+        // Now that we've adding thing in place of the two that we removed from
+        // the front of the iterator, we're back to matching the buffer pointer.
+        assert_eq!(v.as_slices().0.as_ptr(), buf);
+        assert_eq!(&v[v.len() - 1] as *const _, last);
+
+        v.push_front(9);
+        assert_eq!(v.as_slices(), ([9].as_slice(), [8, 7, 2, 3, 4, 5, 6].as_slice()));
+        assert_eq!(v.capacity(), 13);
+    }
+}