From adb7607189e04a20e67fe089d23d418826177186 Mon Sep 17 00:00:00 2001
From: Amanieu d'Antras <amanieu@gmail.com>
Date: Tue, 30 Jan 2024 17:51:20 +0000
Subject: [PATCH] Fix BTreeMap's Cursor::remove_{next,prev}
These would incorrectly leave `current` as `None` after a failed attempt
to remove an element (due to the cursor already being at the start/end).
---
library/alloc/src/collections/btree/map.rs | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/library/alloc/src/collections/btree/map.rs b/library/alloc/src/collections/btree/map.rs
index b585e2082f137..6e0b79b9640f9 100644
--- a/library/alloc/src/collections/btree/map.rs
+++ b/library/alloc/src/collections/btree/map.rs
@@ -3198,9 +3198,15 @@ impl<'a, K: Ord, V, A: Allocator + Clone> CursorMutKey<'a, K, V, A> {
#[unstable(feature = "btree_cursors", issue = "107540")]
pub fn remove_next(&mut self) -> Option<(K, V)> {
let current = self.current.take()?;
+ if current.reborrow().next_kv().is_err() {
+ self.current = Some(current);
+ return None;
+ }
let mut emptied_internal_root = false;
let (kv, pos) = current
.next_kv()
+ // This should be unwrap(), but that doesn't work because NodeRef
+ // doesn't implement Debug. The condition is checked above.
.ok()?
.remove_kv_tracking(|| emptied_internal_root = true, self.alloc.clone());
self.current = Some(pos);
@@ -3221,9 +3227,15 @@ impl<'a, K: Ord, V, A: Allocator + Clone> CursorMutKey<'a, K, V, A> {
#[unstable(feature = "btree_cursors", issue = "107540")]
pub fn remove_prev(&mut self) -> Option<(K, V)> {
let current = self.current.take()?;
+ if current.reborrow().next_back_kv().is_err() {
+ self.current = Some(current);
+ return None;
+ }
let mut emptied_internal_root = false;
let (kv, pos) = current
.next_back_kv()
+ // This should be unwrap(), but that doesn't work because NodeRef
+ // doesn't implement Debug. The condition is checked above.
.ok()?
.remove_kv_tracking(|| emptied_internal_root = true, self.alloc.clone());
self.current = Some(pos);