From cff1182bcdf0f35cdb65d4560270b6afed856064 Mon Sep 17 00:00:00 2001
From: Tim Vermeulen <tvermeulen@me.com>
Date: Thu, 6 Feb 2020 05:58:04 +0100
Subject: [PATCH] Fix FlattenCompat::{next, next_back}

---
 src/libcore/iter/adapters/flatten.rs | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/libcore/iter/adapters/flatten.rs b/src/libcore/iter/adapters/flatten.rs
index 6000214af43e..4202e52448dc 100644
--- a/src/libcore/iter/adapters/flatten.rs
+++ b/src/libcore/iter/adapters/flatten.rs
@@ -264,8 +264,9 @@ where
     fn next(&mut self) -> Option<U::Item> {
         loop {
             if let Some(ref mut inner) = self.frontiter {
-                if let elt @ Some(_) = inner.next() {
-                    return elt;
+                match inner.next() {
+                    None => self.frontiter = None,
+                    elt @ Some(_) => return elt,
                 }
             }
             match self.iter.next() {
@@ -351,8 +352,9 @@ where
     fn next_back(&mut self) -> Option<U::Item> {
         loop {
             if let Some(ref mut inner) = self.backiter {
-                if let elt @ Some(_) = inner.next_back() {
-                    return elt;
+                match inner.next_back() {
+                    None => self.backiter = None,
+                    elt @ Some(_) => return elt,
                 }
             }
             match self.iter.next_back() {