From 2514d02c55b87712a26eff25dbce9fb08e353888 Mon Sep 17 00:00:00 2001
From: ltdk <usr@ltdk.xyz>
Date: Wed, 4 Jan 2023 15:44:51 -0500
Subject: [PATCH] Use try_fold and try_rfold in default implementations of fold
 and rfold

---
 library/core/src/iter/traits/double_ended.rs | 10 +++-------
 library/core/src/iter/traits/iterator.rs     | 10 +++-------
 2 files changed, 6 insertions(+), 14 deletions(-)

diff --git a/library/core/src/iter/traits/double_ended.rs b/library/core/src/iter/traits/double_ended.rs
index 7a10dea500a96..a244cc1884853 100644
--- a/library/core/src/iter/traits/double_ended.rs
+++ b/library/core/src/iter/traits/double_ended.rs
@@ -1,5 +1,5 @@
 use crate::marker::Destruct;
-use crate::ops::{ControlFlow, Try};
+use crate::ops::{ControlFlow, NeverShortCircuit, Try};
 
 /// An iterator able to yield elements from both ends.
 ///
@@ -297,16 +297,12 @@ pub trait DoubleEndedIterator: Iterator {
     #[inline]
     #[stable(feature = "iter_rfold", since = "1.27.0")]
     #[rustc_do_not_const_check]
-    fn rfold<B, F>(mut self, init: B, mut f: F) -> B
+    fn rfold<B, F>(mut self, init: B, f: F) -> B
     where
         Self: Sized,
         F: FnMut(B, Self::Item) -> B,
     {
-        let mut accum = init;
-        while let Some(x) = self.next_back() {
-            accum = f(accum, x);
-        }
-        accum
+        self.try_rfold(init, NeverShortCircuit::wrap_mut_2(f)).0
     }
 
     /// Searches for an element of an iterator from the back that satisfies a predicate.
diff --git a/library/core/src/iter/traits/iterator.rs b/library/core/src/iter/traits/iterator.rs
index 16c9f668b8ea8..537d7b7470fd6 100644
--- a/library/core/src/iter/traits/iterator.rs
+++ b/library/core/src/iter/traits/iterator.rs
@@ -1,7 +1,7 @@
 use crate::array;
 use crate::cmp::{self, Ordering};
 use crate::marker::Destruct;
-use crate::ops::{ChangeOutputType, ControlFlow, FromResidual, Residual, Try};
+use crate::ops::{ChangeOutputType, ControlFlow, FromResidual, NeverShortCircuit, Residual, Try};
 
 use super::super::try_process;
 use super::super::ByRefSized;
@@ -2472,16 +2472,12 @@ pub trait Iterator {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_do_not_const_check]
-    fn fold<B, F>(mut self, init: B, mut f: F) -> B
+    fn fold<B, F>(mut self, init: B, f: F) -> B
     where
         Self: Sized,
         F: FnMut(B, Self::Item) -> B,
     {
-        let mut accum = init;
-        while let Some(x) = self.next() {
-            accum = f(accum, x);
-        }
-        accum
+        self.try_fold(init, NeverShortCircuit::wrap_mut_2(f)).0
     }
 
     /// Reduces the elements to a single one, by repeatedly applying a reducing