From 86a4b27475aab52b998c15f5758540697cc9cff0 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Sebastian=20Dr=C3=B6ge?= 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 --- 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 98b8dca961407..9f98353452006 100644 --- a/library/core/src/iter/adapters/zip.rs +++ b/library/core/src/iter/adapters/zip.rs @@ -198,12 +198,13 @@ where 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