1 files changed, 17 insertions, 2 deletions
diff --git a/library/core/src/iter/adapters/rev.rs b/library/core/src/iter/adapters/rev.rs
index 139fb7bbd..4aaf7c61f 100644
--- a/library/core/src/iter/adapters/rev.rs
+++ b/library/core/src/iter/adapters/rev.rs
@@ -1,4 +1,5 @@
 use crate::iter::{FusedIterator, TrustedLen};
+use crate::num::NonZeroUsize;
 use crate::ops::Try;
 
 /// A double-ended iterator with the direction inverted.
@@ -38,7 +39,7 @@ where
     }
 
     #[inline]
-    fn advance_by(&mut self, n: usize) -> Result<(), usize> {
+    fn advance_by(&mut self, n: usize) -> Result<(), NonZeroUsize> {
         self.iter.advance_back_by(n)
     }
 
@@ -83,7 +84,7 @@ where
     }
 
     #[inline]
-    fn advance_back_by(&mut self, n: usize) -> Result<(), usize> {
+    fn advance_back_by(&mut self, n: usize) -> Result<(), NonZeroUsize> {
         self.iter.advance_by(n)
     }
 
@@ -135,3 +136,17 @@ impl<I> FusedIterator for Rev<I> where I: FusedIterator + DoubleEndedIterator {}
 
 #[unstable(feature = "trusted_len", issue = "37572")]
 unsafe impl<I> TrustedLen for Rev<I> where I: TrustedLen + DoubleEndedIterator {}
+
+#[stable(feature = "default_iters", since = "1.70.0")]
+impl<I: Default> Default for Rev<I> {
+    /// Creates a `Rev` iterator from the default value of `I`
+    /// ```
+    /// # use core::slice;
+    /// # use core::iter::Rev;
+    /// let iter: Rev<slice::Iter<'_, u8>> = Default::default();
+    /// assert_eq!(iter.len(), 0);
+    /// ```
+    fn default() -> Self {
+        Rev::new(Default::default())
+    }
+}