From 5aa625b903a24a270b2676b2b8c2f99902942b31 Mon Sep 17 00:00:00 2001 From: Giacomo Stevanato Date: Sat, 23 Jan 2021 21:00:00 +0100 Subject: [PATCH] Manually fuse the inner iterator in FlattenCompat --- library/core/src/iter/adapters/flatten.rs | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/library/core/src/iter/adapters/flatten.rs b/library/core/src/iter/adapters/flatten.rs index 29e191db0f62f..081f282edcf89 100644 --- a/library/core/src/iter/adapters/flatten.rs +++ b/library/core/src/iter/adapters/flatten.rs @@ -265,7 +265,13 @@ where } } match self.iter.next() { - None => return self.backiter.as_mut()?.next(), + None => match self.backiter.as_mut()?.next() { + None => { + self.backiter = None; + return None; + } + elt @ Some(_) => return elt, + }, Some(inner) => self.frontiter = Some(inner.into_iter()), } } @@ -353,7 +359,13 @@ where } } match self.iter.next_back() { - None => return self.frontiter.as_mut()?.next_back(), + None => match self.frontiter.as_mut()?.next_back() { + None => { + self.frontiter = None; + return None; + } + elt @ Some(_) => return elt, + }, next => self.backiter = next.map(IntoIterator::into_iter), } }