Merging upstream version 1.70.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 7 insertions, 8 deletions

diff --git a/library/core/src/ops/index_range.rs b/library/core/src/ops/index_range.rs
index 3e06776d2..265022a39 100644
--- a/library/core/src/ops/index_range.rs
+++ b/library/core/src/ops/index_range.rs
@@ -1,5 +1,6 @@
 use crate::intrinsics::{assert_unsafe_precondition, unchecked_add, unchecked_sub};
 use crate::iter::{FusedIterator, TrustedLen};
+use crate::num::NonZeroUsize;
 
 /// Like a `Range<usize>`, but with a safety invariant that `start <= end`.
 ///
@@ -132,10 +133,9 @@ impl Iterator for IndexRange {
     }
 
     #[inline]
-    fn advance_by(&mut self, n: usize) -> Result<(), usize> {
-        let original_len = self.len();
-        self.take_prefix(n);
-        if n > original_len { Err(original_len) } else { Ok(()) }
+    fn advance_by(&mut self, n: usize) -> Result<(), NonZeroUsize> {
+        let taken = self.take_prefix(n);
+        NonZeroUsize::new(n - taken.len()).map_or(Ok(()), Err)
     }
 }
 
@@ -151,10 +151,9 @@ impl DoubleEndedIterator for IndexRange {
     }
 
     #[inline]
-    fn advance_back_by(&mut self, n: usize) -> Result<(), usize> {
-        let original_len = self.len();
-        self.take_suffix(n);
-        if n > original_len { Err(original_len) } else { Ok(()) }
+    fn advance_back_by(&mut self, n: usize) -> Result<(), NonZeroUsize> {
+        let taken = self.take_suffix(n);
+        NonZeroUsize::new(n - taken.len()).map_or(Ok(()), Err)
     }
 }