From 40d3f2d7ef5835317fe9df9ecc01f4c363def4fd Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Sebastian=20Dr=C3=B6ge?= <sebastian@centricular.com>

Date: Thu, 4 Feb 2021 10:23:01 +0200

Subject: [PATCH] Increment `self.index` before calling

 `Iterator::self.a.__iterator_get_unchecked` in `Zip` `TrustedRandomAccess`

 specialization

Otherwise if `Iterator::self.a.__iterator_get_unchecked` panics the

index would not have been incremented yet and another call to

`Iterator::next` would read from the same index again, which is not

allowed according to the API contract of `TrustedRandomAccess` for

`!Clone`.

Fixes https://github.com/rust-lang/rust/issues/81740

(cherry picked from commit 86a4b27475aab52b998c15f5758540697cc9cff0)

---

 library/core/src/iter/adapters/zip.rs | 7 ++++---

 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/library/core/src/iter/adapters/zip.rs b/library/core/src/iter/adapters/zip.rs

index 98b8dca96140..9f9835345200 100644

--- a/library/core/src/iter/adapters/zip.rs

+++ b/library/core/src/iter/adapters/zip.rs

@@ -198,12 +198,13 @@ fn next(&mut self) -> Option<(A::Item, B::Item)> {

                 Some((self.a.__iterator_get_unchecked(i), self.b.__iterator_get_unchecked(i)))

             }

         } else if A::may_have_side_effect() && self.index < self.a.size() {

+            let i = self.index;

+            self.index += 1;

             // match the base implementation's potential side effects

-            // SAFETY: we just checked that `self.index` < `self.a.len()`

+            // SAFETY: we just checked that `i` < `self.a.len()`

             unsafe {

-                self.a.__iterator_get_unchecked(self.index);

+                self.a.__iterator_get_unchecked(i);

             }

-            self.index += 1;

             None

         } else {

             None

-- 

2.31.1