Fix BTreeSet's range API panic message, document

1 files changed, 23 insertions, 0 deletions

diff --git a/library/alloc/src/collections/btree/set/tests.rs b/library/alloc/src/collections/btree/set/tests.rs
index 429b1644976..502d3e1d126 100644
--- a/library/alloc/src/collections/btree/set/tests.rs
+++ b/library/alloc/src/collections/btree/set/tests.rs
@@ -5,6 +5,7 @@ use crate::vec::Vec;
 use std::cmp::Ordering;
 use std::hash::{Hash, Hasher};
 use std::iter::FromIterator;
+use std::ops::Bound::{Excluded, Included};
 use std::panic::{catch_unwind, AssertUnwindSafe};
 
 #[test]
@@ -831,3 +832,25 @@ fn from_array() {
     let unordered_duplicates = BTreeSet::from([4, 1, 4, 3, 2]);
     assert_eq!(set, unordered_duplicates);
 }
+
+#[should_panic(expected = "range start is greater than range end in BTreeSet")]
+#[test]
+fn test_range_panic_1() {
+    let mut set = BTreeSet::new();
+    set.insert(3);
+    set.insert(5);
+    set.insert(8);
+
+    let _invalid_range = set.range((Included(&8), Included(&3)));
+}
+
+#[should_panic(expected = "range start and end are equal and excluded in BTreeSet")]
+#[test]
+fn test_range_panic_2() {
+    let mut set = BTreeSet::new();
+    set.insert(3);
+    set.insert(5);
+    set.insert(8);
+
+    let _invalid_range = set.range((Excluded(&5), Excluded(&5)));
+}