From 5222e2ba2d97cd716a379b4ae6bc62c5f7c2dd36 Mon Sep 17 00:00:00 2001
From: Giacomo Stevanato <giaco.stevanato@gmail.com>
Date: Fri, 19 Feb 2021 12:15:37 +0100
Subject: [PATCH 1/3] Increment self.len in specialized ZipImpl to avoid
 underflow in size_hint

(cherry picked from commit 66a260617a88ed1ad55a46f03c5a90d5ad3004d3)
---
 library/core/src/iter/adapters/zip.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/library/core/src/iter/adapters/zip.rs b/library/core/src/iter/adapters/zip.rs
index 9f9835345200..f08bfac837fe 100644
--- a/library/core/src/iter/adapters/zip.rs
+++ b/library/core/src/iter/adapters/zip.rs
@@ -200,6 +200,7 @@ fn next(&mut self) -> Option<(A::Item, B::Item)> {
         } else if A::may_have_side_effect() && self.index < self.a.size() {
             let i = self.index;
             self.index += 1;
+            self.len += 1;
             // match the base implementation's potential side effects
             // SAFETY: we just checked that `i` < `self.a.len()`
             unsafe {
-- 
2.31.1


From d39669fc8282830a374d19d204f7b4ee8eb1e381 Mon Sep 17 00:00:00 2001
From: Giacomo Stevanato <giaco.stevanato@gmail.com>
Date: Fri, 19 Feb 2021 12:16:12 +0100
Subject: [PATCH 2/3] Add test for underflow in specialized Zip's size_hint

(cherry picked from commit 8b9ac4d4155c74db5b317046033ab9c05a09e351)
---
 library/core/tests/iter/adapters/zip.rs | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/library/core/tests/iter/adapters/zip.rs b/library/core/tests/iter/adapters/zip.rs
index 1fce0951e365..a59771039295 100644
--- a/library/core/tests/iter/adapters/zip.rs
+++ b/library/core/tests/iter/adapters/zip.rs
@@ -245,3 +245,23 @@ fn test_double_ended_zip() {
     assert_eq!(it.next_back(), Some((3, 3)));
     assert_eq!(it.next(), None);
 }
+
+#[test]
+fn test_issue_82282() {
+    fn overflowed_zip(arr: &[i32]) -> impl Iterator<Item = (i32, &())> {
+        static UNIT_EMPTY_ARR: [(); 0] = [];
+
+        let mapped = arr.into_iter().map(|i| *i);
+        let mut zipped = mapped.zip(UNIT_EMPTY_ARR.iter());
+        zipped.next();
+        zipped
+    }
+
+    let arr = [1, 2, 3];
+    let zip = overflowed_zip(&arr).zip(overflowed_zip(&arr));
+
+    assert_eq!(zip.size_hint(), (0, Some(0)));
+    for _ in zip {
+        panic!();
+    }
+}
-- 
2.31.1


From 4b382167dd5ed5a6eac0cf314bfb86e3704b6e76 Mon Sep 17 00:00:00 2001
From: Giacomo Stevanato <giaco.stevanato@gmail.com>
Date: Fri, 19 Feb 2021 12:17:48 +0100
Subject: [PATCH 3/3] Remove useless comparison since now self.index <=
 self.len is an invariant

(cherry picked from commit aeb4ea739efb70e0002a4a9c4c7b8027dd0620b3)
---
 library/core/src/iter/adapters/zip.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/library/core/src/iter/adapters/zip.rs b/library/core/src/iter/adapters/zip.rs
index f08bfac837fe..dcbcb1ce7200 100644
--- a/library/core/src/iter/adapters/zip.rs
+++ b/library/core/src/iter/adapters/zip.rs
@@ -261,7 +261,7 @@ fn next_back(&mut self) -> Option<(A::Item, B::Item)>
             if sz_a != sz_b {
                 let sz_a = self.a.size();
                 if a_side_effect && sz_a > self.len {
-                    for _ in 0..sz_a - cmp::max(self.len, self.index) {
+                    for _ in 0..sz_a - self.len {
                         self.a.next_back();
                     }
                 }
-- 
2.31.1