Delegate Iterator::try_fold for Iterators taken by reference

Author: czipperz

src/libcore/iter/traits/iterator.rs

@@ -2708,4 +2708,9 @@ impl<I: Iterator + ?Sized> Iterator for &mut I {
     fn nth(&mut self, n: usize) -> Option<Self::Item> {
         (**self).nth(n)
     }
+    fn try_fold<B, F, R>(&mut self, init: B, mut f: F) -> R where
+        I: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Ok=B>
+    {
+        (**self).try_fold(init, f)
+    }
 }