From f241c102230fb1a01fff4712228426ef67171115 Mon Sep 17 00:00:00 2001 From: Giacomo Stevanato Date: Sat, 23 Jan 2021 20:52:59 +0100 Subject: [PATCH 1/2] Improve flatten-fuse tests --- library/core/tests/iter/adapters/flatten.rs | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/library/core/tests/iter/adapters/flatten.rs b/library/core/tests/iter/adapters/flatten.rs index bd2c6fd9252df..4bbae6947bf66 100644 --- a/library/core/tests/iter/adapters/flatten.rs +++ b/library/core/tests/iter/adapters/flatten.rs @@ -64,6 +64,14 @@ fn test_flatten_non_fused_outer() { assert_eq!(iter.next_back(), Some(1)); assert_eq!(iter.next(), Some(0)); assert_eq!(iter.next(), None); + assert_eq!(iter.next(), None); + + let mut iter = NonFused::new(once(0..2)).flatten(); + + assert_eq!(iter.next(), Some(0)); + assert_eq!(iter.next_back(), Some(1)); + assert_eq!(iter.next_back(), None); + assert_eq!(iter.next_back(), None); } #[test] @@ -74,6 +82,15 @@ fn test_flatten_non_fused_inner() { assert_eq!(iter.next(), Some(0)); assert_eq!(iter.next(), Some(1)); assert_eq!(iter.next(), None); + assert_eq!(iter.next(), None); + + let mut iter = once(0..1).chain(once(1..3)).flat_map(NonFused::new); + + assert_eq!(iter.next(), Some(0)); + assert_eq!(iter.next_back(), Some(2)); + assert_eq!(iter.next_back(), Some(1)); + assert_eq!(iter.next_back(), None); + assert_eq!(iter.next_back(), None); } #[test] From 5aa625b903a24a270b2676b2b8c2f99902942b31 Mon Sep 17 00:00:00 2001 From: Giacomo Stevanato Date: Sat, 23 Jan 2021 21:00:00 +0100 Subject: [PATCH 2/2] 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), } }