1 files changed, 22 insertions, 12 deletions

diff --git a/src/libcore/iter/adapters/mod.rs b/src/libcore/iter/adapters/mod.rs
index 7b46fd686de..58e0a70cefb 100644
--- a/src/libcore/iter/adapters/mod.rs
+++ b/src/libcore/iter/adapters/mod.rs
@@ -2220,6 +2220,20 @@ impl<I: Iterator, F> Inspect<I, F> where F: FnMut(&I::Item) {
     }
 }
 
+fn inspect_fold<T, Acc>(
+    mut f: impl FnMut(&T),
+    mut fold: impl FnMut(Acc, T) -> Acc,
+) -> impl FnMut(Acc, T) -> Acc {
+    move |acc, item| { f(&item); fold(acc, item) }
+}
+
+fn inspect_try_fold<'a, T, Acc, R>(
+    f: &'a mut impl FnMut(&T),
+    mut fold: impl FnMut(Acc, T) -> R + 'a,
+) -> impl FnMut(Acc, T) -> R + 'a {
+    move |acc, item| { f(&item); fold(acc, item) }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<I: Iterator, F> Iterator for Inspect<I, F> where F: FnMut(&I::Item) {
     type Item = I::Item;
@@ -2236,19 +2250,17 @@ impl<I: Iterator, F> Iterator for Inspect<I, F> where F: FnMut(&I::Item) {
     }
 
     #[inline]
-    fn try_fold<Acc, Fold, R>(&mut self, init: Acc, mut fold: Fold) -> R where
+    fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
         Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc>
     {
-        let f = &mut self.f;
-        self.iter.try_fold(init, move |acc, item| { f(&item); fold(acc, item) })
+        self.iter.try_fold(init, inspect_try_fold(&mut self.f, fold))
     }
 
     #[inline]
-    fn fold<Acc, Fold>(self, init: Acc, mut fold: Fold) -> Acc
+    fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc
         where Fold: FnMut(Acc, Self::Item) -> Acc,
     {
-        let mut f = self.f;
-        self.iter.fold(init, move |acc, item| { f(&item); fold(acc, item) })
+        self.iter.fold(init, inspect_fold(self.f, fold))
     }
 }
 
@@ -2263,19 +2275,17 @@ impl<I: DoubleEndedIterator, F> DoubleEndedIterator for Inspect<I, F>
     }
 
     #[inline]
-    fn try_rfold<Acc, Fold, R>(&mut self, init: Acc, mut fold: Fold) -> R where
+    fn try_rfold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
         Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc>
     {
-        let f = &mut self.f;
-        self.iter.try_rfold(init, move |acc, item| { f(&item); fold(acc, item) })
+        self.iter.try_rfold(init, inspect_try_fold(&mut self.f, fold))
     }
 
     #[inline]
-    fn rfold<Acc, Fold>(self, init: Acc, mut fold: Fold) -> Acc
+    fn rfold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc
         where Fold: FnMut(Acc, Self::Item) -> Acc,
     {
-        let mut f = self.f;
-        self.iter.rfold(init, move |acc, item| { f(&item); fold(acc, item) })
+        self.iter.rfold(init, inspect_fold(self.f, fold))
     }
 }