Rollup merge of #58064 - llogiq:vec-deque-try-rfold, r=scottmcm

override `VecDeque::try_rfold`, also update iterator

This keeps the slice based iteration and updates the iterator state after each slice. It also uses a loop to reduce the amount of code.

This uses unsafe code, so some thorough review would be appreciated. Cc @RalfJung

1 files changed, 7 insertions, 0 deletions

diff --git a/src/liballoc/benches/vec_deque.rs b/src/liballoc/benches/vec_deque.rs
index f7aadbdbd82..7d2d3cfa612 100644
--- a/src/liballoc/benches/vec_deque.rs
+++ b/src/liballoc/benches/vec_deque.rs
@@ -45,3 +45,10 @@ fn bench_mut_iter_1000(b: &mut Bencher) {
         black_box(sum);
     })
 }
+
+#[bench]
+fn bench_try_fold(b: &mut Bencher) {
+    let ring: VecDeque<_> = (0..1000).collect();
+
+    b.iter(|| black_box(ring.iter().try_fold(0, |a, b| Some(a + b))))
+}