5 files changed, 88 insertions, 0 deletions
diff --git a/src/liballoc/collections/binary_heap.rs b/src/liballoc/collections/binary_heap.rs
index 8c142a3d317..2b1e52cbf05 100644
--- a/src/liballoc/collections/binary_heap.rs
+++ b/src/liballoc/collections/binary_heap.rs
@@ -968,6 +968,11 @@ impl<'a, T> Iterator for Iter<'a, T> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.iter.size_hint()
     }
+
+    #[inline]
+    fn last(mut self) -> Option<&'a T> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -1023,6 +1028,11 @@ impl<T> Iterator for IntoIter<T> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.iter.size_hint()
     }
+
+    #[inline]
+    fn last(mut self) -> Option<T> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -1069,6 +1079,11 @@ impl<T> Iterator for Drain<'_, T> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.iter.size_hint()
     }
+
+    #[inline]
+    fn last(mut self) -> Option<T> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "drain", since = "1.6.0")]
diff --git a/src/liballoc/collections/btree/map.rs b/src/liballoc/collections/btree/map.rs
index 6b079fc87cc..414abb00ef1 100644
--- a/src/liballoc/collections/btree/map.rs
+++ b/src/liballoc/collections/btree/map.rs
@@ -1193,6 +1193,11 @@ impl<'a, K: 'a, V: 'a> Iterator for Iter<'a, K, V> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         (self.length, Some(self.length))
     }
+
+    #[inline]
+    fn last(mut self) -> Option<(&'a K, &'a V)> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "fused", since = "1.26.0")]
@@ -1253,6 +1258,11 @@ impl<'a, K: 'a, V: 'a> Iterator for IterMut<'a, K, V> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         (self.length, Some(self.length))
     }
+
+    #[inline]
+    fn last(mut self) -> Option<(&'a K, &'a mut V)> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -1359,6 +1369,11 @@ impl<K, V> Iterator for IntoIter<K, V> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         (self.length, Some(self.length))
     }
+
+    #[inline]
+    fn last(mut self) -> Option<(K, V)> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -1421,6 +1436,11 @@ impl<'a, K, V> Iterator for Keys<'a, K, V> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.inner.size_hint()
     }
+
+    #[inline]
+    fn last(mut self) -> Option<&'a K> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -1458,6 +1478,11 @@ impl<'a, K, V> Iterator for Values<'a, K, V> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.inner.size_hint()
     }
+
+    #[inline]
+    fn last(mut self) -> Option<&'a V> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -1495,6 +1520,11 @@ impl<'a, K, V> Iterator for Range<'a, K, V> {
             unsafe { Some(self.next_unchecked()) }
         }
     }
+
+    #[inline]
+    fn last(mut self) -> Option<(&'a K, &'a V)> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "map_values_mut", since = "1.10.0")]
@@ -1508,6 +1538,11 @@ impl<'a, K, V> Iterator for ValuesMut<'a, K, V> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.inner.size_hint()
     }
+
+    #[inline]
+    fn last(mut self) -> Option<&'a mut V> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "map_values_mut", since = "1.10.0")]
@@ -1626,6 +1661,11 @@ impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
             unsafe { Some(self.next_unchecked()) }
         }
     }
+
+    #[inline]
+    fn last(mut self) -> Option<(&'a K, &'a mut V)> {
+        self.next_back()
+    }
 }
 
 impl<'a, K, V> RangeMut<'a, K, V> {
diff --git a/src/liballoc/collections/btree/set.rs b/src/liballoc/collections/btree/set.rs
index 16a96ca19b8..6f2467dfd6b 100644
--- a/src/liballoc/collections/btree/set.rs
+++ b/src/liballoc/collections/btree/set.rs
@@ -1019,6 +1019,11 @@ impl<'a, T> Iterator for Iter<'a, T> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.iter.size_hint()
     }
+
+    #[inline]
+    fn last(mut self) -> Option<&'a T> {
+        self.next_back()
+    }
 }
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T> DoubleEndedIterator for Iter<'a, T> {
@@ -1044,6 +1049,11 @@ impl<T> Iterator for IntoIter<T> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.iter.size_hint()
     }
+
+    #[inline]
+    fn last(mut self) -> Option<T> {
+        self.next_back()
+    }
 }
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> DoubleEndedIterator for IntoIter<T> {
@@ -1073,6 +1083,11 @@ impl<'a, T> Iterator for Range<'a, T> {
     fn next(&mut self) -> Option<&'a T> {
         self.iter.next().map(|(k, _)| k)
     }
+
+    #[inline]
+    fn last(mut self) -> Option<&'a T> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "btree_range", since = "1.17.0")]
diff --git a/src/liballoc/string.rs b/src/liballoc/string.rs
index a3e2098695f..f01610a7c3f 100644
--- a/src/liballoc/string.rs
+++ b/src/liballoc/string.rs
@@ -2367,6 +2367,10 @@ impl Iterator for Drain<'_> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.iter.size_hint()
     }
+    #[inline]
+    fn last(mut self) -> Option<char> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "drain", since = "1.6.0")]
diff --git a/src/liballoc/vec.rs b/src/liballoc/vec.rs
index cd62c3e0524..50bb37b6ed2 100644
--- a/src/liballoc/vec.rs
+++ b/src/liballoc/vec.rs
@@ -2385,6 +2385,11 @@ impl<T> Iterator for IntoIter<T> {
     fn count(self) -> usize {
         self.len()
     }
+
+    #[inline]
+    fn last(mut self) -> Option<T> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -2504,6 +2509,11 @@ impl<T> Iterator for Drain<'_, T> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.iter.size_hint()
     }
+
+    #[inline]
+    fn last(mut self) -> Option<T> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "drain", since = "1.6.0")]
@@ -2573,6 +2583,10 @@ impl<I: Iterator> Iterator for Splice<'_, I> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.drain.size_hint()
     }
+
+    fn last(mut self) -> Option<Self::Item> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "vec_splice", since = "1.21.0")]