diff --git a/src/liballoc/rc/tests.rs b/src/liballoc/rc/tests.rs
index 56788bb56d550..d847948559082 100644
--- a/src/liballoc/rc/tests.rs
+++ b/src/liballoc/rc/tests.rs
@@ -434,3 +434,23 @@ fn test_array_from_slice() {
     let a: Result<Rc<[u32; 2]>, _> = r.clone().try_into();
     assert!(a.is_err());
 }
+
+#[test]
+fn test_fn() {
+    fn apply_fn_once<T>(v: T, f: impl FnOnce(T)) {
+        f(v)
+    }
+    fn apply_fn_mut<T>(v: T, mut f: impl FnMut(T)) {
+        f(v)
+    }
+    fn apply_fn<T>(v: T, f: impl Fn(T)) {
+        f(v)
+    }
+
+    let x = RefCell::new(0);
+    let f = Rc::new(|v: i32| *x.borrow_mut() += v);
+    apply_fn_once(1, f.clone());
+    apply_fn_mut(2, f.clone());
+    apply_fn(4, f.clone());
+    assert_eq!(*x.borrow(), 7);
+}
diff --git a/src/liballoc/sync/tests.rs b/src/liballoc/sync/tests.rs
index edc2820ee22f1..f4319dabf7ef5 100644
--- a/src/liballoc/sync/tests.rs
+++ b/src/liballoc/sync/tests.rs
@@ -490,3 +490,23 @@ fn test_array_from_slice() {
     let a: Result<Arc<[u32; 2]>, _> = r.clone().try_into();
     assert!(a.is_err());
 }
+
+#[test]
+fn test_fn() {
+    fn apply_fn_once<T>(v: T, f: impl FnOnce(T)) {
+        f(v)
+    }
+    fn apply_fn_mut<T>(v: T, mut f: impl FnMut(T)) {
+        f(v)
+    }
+    fn apply_fn<T>(v: T, f: impl Fn(T)) {
+        f(v)
+    }
+
+    let x = Mutex::new(0);
+    let f = Arc::new(|v: i32| *x.lock().unwrap() += v);
+    apply_fn_once(1, f.clone());
+    apply_fn_mut(2, f.clone());
+    apply_fn(4, f.clone());
+    assert_eq!(*x.lock().unwrap(), 7);
+}