1 files changed, 49 insertions, 0 deletions
diff --git a/library/core/tests/iter/sources.rs b/library/core/tests/iter/sources.rs
index d0114ade6..a15f3a514 100644
--- a/library/core/tests/iter/sources.rs
+++ b/library/core/tests/iter/sources.rs
@@ -106,3 +106,52 @@ fn test_empty() {
     let mut it = empty::<i32>();
     assert_eq!(it.next(), None);
 }
+
+#[test]
+fn test_repeat_n_drop() {
+    #[derive(Clone, Debug)]
+    struct DropCounter<'a>(&'a Cell<usize>);
+    impl Drop for DropCounter<'_> {
+        fn drop(&mut self) {
+            self.0.set(self.0.get() + 1);
+        }
+    }
+
+    // `repeat_n(x, 0)` drops `x` immediately
+    let count = Cell::new(0);
+    let item = DropCounter(&count);
+    let mut it = repeat_n(item, 0);
+    assert_eq!(count.get(), 1);
+    assert!(it.next().is_none());
+    assert_eq!(count.get(), 1);
+    drop(it);
+    assert_eq!(count.get(), 1);
+
+    // Dropping the iterator needs to drop the item if it's non-empty
+    let count = Cell::new(0);
+    let item = DropCounter(&count);
+    let it = repeat_n(item, 3);
+    assert_eq!(count.get(), 0);
+    drop(it);
+    assert_eq!(count.get(), 1);
+
+    // Dropping the iterator doesn't drop the item if it was exhausted
+    let count = Cell::new(0);
+    let item = DropCounter(&count);
+    let mut it = repeat_n(item, 3);
+    assert_eq!(count.get(), 0);
+    let x0 = it.next().unwrap();
+    assert_eq!(count.get(), 0);
+    let x1 = it.next().unwrap();
+    assert_eq!(count.get(), 0);
+    let x2 = it.next().unwrap();
+    assert_eq!(count.get(), 0);
+    assert!(it.next().is_none());
+    assert_eq!(count.get(), 0);
+    assert!(it.next().is_none());
+    assert_eq!(count.get(), 0);
+    drop(it);
+    assert_eq!(count.get(), 0);
+    drop((x0, x1, x2));
+    assert_eq!(count.get(), 3);
+}