From cdd982955623f697f759f548ce11f886a413f4f6 Mon Sep 17 00:00:00 2001
From: marc0246 <40955683+marc0246@users.noreply.github.com>
Date: Wed, 12 Apr 2023 19:21:40 +0200
Subject: [PATCH] Fix btree `CursorMut::insert_after` check

---
 library/alloc/src/collections/btree/map.rs    |  2 +-
 .../alloc/src/collections/btree/map/tests.rs  | 64 +++++++++++++++++++
 2 files changed, 65 insertions(+), 1 deletion(-)

diff --git a/library/alloc/src/collections/btree/map.rs b/library/alloc/src/collections/btree/map.rs
index 61db46314b780..da675379cd58b 100644
--- a/library/alloc/src/collections/btree/map.rs
+++ b/library/alloc/src/collections/btree/map.rs
@@ -3183,7 +3183,7 @@ impl<'a, K: Ord, V, A: Allocator + Clone> CursorMut<'a, K, V, A> {
                 panic!("key must be ordered above the current element");
             }
         }
-        if let Some((next, _)) = self.peek_prev() {
+        if let Some((next, _)) = self.peek_next() {
             if &key >= next {
                 panic!("key must be ordered below the next element");
             }
diff --git a/library/alloc/src/collections/btree/map/tests.rs b/library/alloc/src/collections/btree/map/tests.rs
index 76c2f27b46634..4311f21c925cd 100644
--- a/library/alloc/src/collections/btree/map/tests.rs
+++ b/library/alloc/src/collections/btree/map/tests.rs
@@ -2385,3 +2385,67 @@ fn test_cursor_mut() {
     assert_eq!(cur.key(), Some(&4));
     assert_eq!(map, BTreeMap::from([(0, '?'), (1, 'a'), (3, 'c'), (4, 'd')]));
 }
+
+#[should_panic(expected = "key must be ordered above the previous element")]
+#[test]
+fn test_cursor_mut_insert_before_1() {
+    let mut map = BTreeMap::from([(1, 'a'), (2, 'b'), (3, 'c')]);
+    let mut cur = map.upper_bound_mut(Bound::Included(&2));
+    cur.insert_before(0, 'd');
+}
+
+#[should_panic(expected = "key must be ordered above the previous element")]
+#[test]
+fn test_cursor_mut_insert_before_2() {
+    let mut map = BTreeMap::from([(1, 'a'), (2, 'b'), (3, 'c')]);
+    let mut cur = map.upper_bound_mut(Bound::Included(&2));
+    cur.insert_before(1, 'd');
+}
+
+#[should_panic(expected = "key must be ordered below the current element")]
+#[test]
+fn test_cursor_mut_insert_before_3() {
+    let mut map = BTreeMap::from([(1, 'a'), (2, 'b'), (3, 'c')]);
+    let mut cur = map.upper_bound_mut(Bound::Included(&2));
+    cur.insert_before(2, 'd');
+}
+
+#[should_panic(expected = "key must be ordered below the current element")]
+#[test]
+fn test_cursor_mut_insert_before_4() {
+    let mut map = BTreeMap::from([(1, 'a'), (2, 'b'), (3, 'c')]);
+    let mut cur = map.upper_bound_mut(Bound::Included(&2));
+    cur.insert_before(3, 'd');
+}
+
+#[should_panic(expected = "key must be ordered above the current element")]
+#[test]
+fn test_cursor_mut_insert_after_1() {
+    let mut map = BTreeMap::from([(1, 'a'), (2, 'b'), (3, 'c')]);
+    let mut cur = map.upper_bound_mut(Bound::Included(&2));
+    cur.insert_after(1, 'd');
+}
+
+#[should_panic(expected = "key must be ordered above the current element")]
+#[test]
+fn test_cursor_mut_insert_after_2() {
+    let mut map = BTreeMap::from([(1, 'a'), (2, 'b'), (3, 'c')]);
+    let mut cur = map.upper_bound_mut(Bound::Included(&2));
+    cur.insert_after(2, 'd');
+}
+
+#[should_panic(expected = "key must be ordered below the next element")]
+#[test]
+fn test_cursor_mut_insert_after_3() {
+    let mut map = BTreeMap::from([(1, 'a'), (2, 'b'), (3, 'c')]);
+    let mut cur = map.upper_bound_mut(Bound::Included(&2));
+    cur.insert_after(3, 'd');
+}
+
+#[should_panic(expected = "key must be ordered below the next element")]
+#[test]
+fn test_cursor_mut_insert_after_4() {
+    let mut map = BTreeMap::from([(1, 'a'), (2, 'b'), (3, 'c')]);
+    let mut cur = map.upper_bound_mut(Bound::Included(&2));
+    cur.insert_after(4, 'd');
+}