UI to unit test for those using Cell/RefCell/UnsafeCell

library/core/tests/cell.rs

@@ -303,6 +303,30 @@ fn cell_into_inner() {
     assert_eq!("Hello world".to_owned(), cell.into_inner());
 }
 
+#[test]
+fn cell_exterior() {
+    #[derive(Copy, Clone)]
+    #[allow(dead_code)]
+    struct Point {
+        x: isize,
+        y: isize,
+        z: isize,
+    }
+
+    fn f(p: &Cell<Point>) {
+        assert_eq!(p.get().z, 12);
+        p.set(Point { x: 10, y: 11, z: 13 });
+        assert_eq!(p.get().z, 13);
+    }
+
+    let a = Point { x: 10, y: 11, z: 12 };
+    let b = &Cell::new(a);
+    assert_eq!(b.get().z, 12);
+    f(b);
+    assert_eq!(a.z, 12);
+    assert_eq!(b.get().z, 13);
+}
+
 #[test]
 fn refcell_default() {
     let cell: RefCell<u64> = Default::default();

library/core/tests/option.rs

@@ -372,3 +372,34 @@ fn option_const() {
     const IS_NONE: bool = OPTION.is_none();
     assert!(!IS_NONE);
 }
+
+#[test]
+fn test_unwrap_drop() {
+    use std::cell::Cell;
+
+    struct Dtor<'a> {
+        x: &'a Cell<isize>,
+    }
+
+    impl<'a> std::ops::Drop for Dtor<'a> {
+        fn drop(&mut self) {
+            self.x.set(self.x.get() - 1);
+        }
+    }
+
+    fn unwrap<T>(o: Option<T>) -> T {
+        match o {
+            Some(v) => v,
+            None => panic!(),
+        }
+    }
+
+    let x = &Cell::new(1);
+
+    {
+        let b = Some(Dtor { x });
+        let _c = unwrap(b);
+    }
+
+    assert_eq!(x.get(), 0);
+}