Auto merge of #86304 - klensy:hex-length, r=jackh726

[rust.git] / library / core / src / iter / adapters / zip.rs

diff --git a/library/core/src/iter/adapters/zip.rs b/library/core/src/iter/adapters/zip.rs
index 46bf93dcc01e2b5a130b5ad2621fbf93b1967d99..3d0401cbebcf72a0fa0ec3a45f3f891897cb0215 100644 (file)
--- a/library/core/src/iter/adapters/zip.rs
+++ b/library/core/src/iter/adapters/zip.rs
@@ -227,6 +227,8 @@ fn new(a: A, b: B) -> Self {
     fn next(&mut self) -> Option<(A::Item, B::Item)> {
         if self.index < self.len {
             let i = self.index;
+            // since get_unchecked executes code which can panic we increment the counters beforehand
+            // so that the same index won't be accessed twice, as required by TrustedRandomAccess
             self.index += 1;
             // SAFETY: `i` is smaller than `self.len`, thus smaller than `self.a.len()` and `self.b.len()`
             unsafe {
@@ -234,6 +236,7 @@ fn next(&mut self) -> Option<(A::Item, B::Item)> {
             }
         } else if A::MAY_HAVE_SIDE_EFFECT && self.index < self.a_len {
             let i = self.index;
+            // as above, increment before executing code that may panic
             self.index += 1;
             self.len += 1;
             // match the base implementation's potential side effects
@@ -259,6 +262,8 @@ fn nth(&mut self, n: usize) -> Option<Self::Item> {
         let end = self.index + delta;
         while self.index < end {
             let i = self.index;
+            // since get_unchecked executes code which can panic we increment the counters beforehand
+            // so that the same index won't be accessed twice, as required by TrustedRandomAccess
             self.index += 1;
             if A::MAY_HAVE_SIDE_EFFECT {
                 // SAFETY: the usage of `cmp::min` to calculate `delta`
@@ -295,6 +300,8 @@ fn next_back(&mut self) -> Option<(A::Item, B::Item)>
                 let sz_a = self.a.size();
                 if A::MAY_HAVE_SIDE_EFFECT && sz_a > self.len {
                     for _ in 0..sz_a - self.len {
+                        // since next_back() may panic we increment the counters beforehand
+                        // to keep Zip's state in sync with the underlying iterator source
                         self.a_len -= 1;
                         self.a.next_back();
                     }
@@ -309,6 +316,8 @@ fn next_back(&mut self) -> Option<(A::Item, B::Item)>
             }
         }
         if self.index < self.len {
+            // since get_unchecked executes code which can panic we increment the counters beforehand
+            // so that the same index won't be accessed twice, as required by TrustedRandomAccess
             self.len -= 1;
             self.a_len -= 1;
             let i = self.len;