1 files changed, 74 insertions, 0 deletions
diff --git a/src/test/ui/span/issue-25199.rs b/src/test/ui/span/issue-25199.rs
new file mode 100644
index 000000000..dbc3b1900
--- /dev/null
+++ b/src/test/ui/span/issue-25199.rs
@@ -0,0 +1,74 @@
+// Regression test for Issue 25199: Check that one cannot hide a
+// destructor's access to borrowed data behind a boxed trait object.
+//
+// Prior to fixing Issue 25199, this example was able to be compiled
+// with rustc, and thus when you ran it, you would see the `Drop` impl
+// for `Test` accessing state that had already been dropping (which is
+// marked explicitly here with checking code within the `Drop` impl
+// for `VecHolder`, but in the general case could just do unsound
+// things like accessing memory that has been freed).
+//
+// Note that I would have liked to encode my go-to example of cyclic
+// structure that accesses its neighbors in drop (and thus is
+// fundamentally unsound) via this trick, but the closest I was able
+// to come was dropck_trait_cycle_checked.rs, which is not quite as
+// "good" as this regression test because the encoding of that example
+// was forced to attach a lifetime to the trait definition itself
+// (`trait Obj<'a>`) while *this* example is solely
+
+use std::cell::RefCell;
+
+trait Obj { }
+
+struct VecHolder {
+    v: Vec<(bool, &'static str)>,
+}
+
+impl Drop for VecHolder {
+    fn drop(&mut self) {
+        println!("Dropping Vec");
+        self.v[30].0 = false;
+        self.v[30].1 = "invalid access: VecHolder dropped already";
+    }
+}
+
+struct Container<'a> {
+    v: VecHolder,
+    d: RefCell<Vec<Box<dyn Obj+'a>>>,
+}
+
+impl<'a> Container<'a> {
+    fn new() -> Container<'a> {
+        Container {
+            d: RefCell::new(Vec::new()),
+            v: VecHolder {
+                v: vec![(true, "valid"); 100]
+            }
+        }
+    }
+
+    fn store<T: Obj+'a>(&'a self, val: T) {
+        self.d.borrow_mut().push(Box::new(val));
+    }
+}
+
+struct Test<'a> {
+    test: &'a Container<'a>,
+}
+
+impl<'a> Obj for Test<'a> { }
+impl<'a> Drop for Test<'a> {
+    fn drop(&mut self) {
+        for e in &self.test.v.v {
+            assert!(e.0, e.1);
+        }
+    }
+}
+
+fn main() {
+    let container = Container::new();
+    let test = Test{test: &container};
+    //~^ ERROR `container` does not live long enough
+    println!("container.v[30]: {:?}", container.v.v[30]);
+    container.store(test);
+}