Add test to make sure we run custom destructors

Author: eholk

src/test/ui/async-await/dyn-star-trait-drop.rs

@@ -0,0 +1,22 @@
+// run-pass
+// check-run-results
+#![feature(async_fn_in_traits)]
+
+use std::fmt::Debug;
+
+#[derive(Debug)]
+struct Foo(usize);
+
+impl Drop for Foo {
+    fn drop(&mut self) {
+        println!("destructor called");
+    }
+}
+
+fn make_dyn_star(i: Foo) {
+    let _dyn_i: dyn* Debug = i as dyn* Debug;
+}
+
+fn main() {
+    make_dyn_star(Foo(42));
+}

src/test/ui/async-await/dyn-star-trait-drop.run.stdout

@@ -0,0 +1 @@
+destructor called