From 12f959ba39ad353ce07971aaf8cef564f86b068d Mon Sep 17 00:00:00 2001
From: pommicket <pommicket@gmail.com>
Date: Sat, 25 Feb 2023 13:50:56 -0500
Subject: [PATCH] Add test for VecDeque::append ZST capacity overflow

---
 library/alloc/tests/vec_deque.rs | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/library/alloc/tests/vec_deque.rs b/library/alloc/tests/vec_deque.rs
index 0b8f5281b785c..5a0b852e8d5e2 100644
--- a/library/alloc/tests/vec_deque.rs
+++ b/library/alloc/tests/vec_deque.rs
@@ -1045,6 +1045,20 @@ fn test_append_double_drop() {
     assert_eq!(count_b, 1);
 }
 
+#[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();