message: add test for layout optimizations
diff: @@ -4,6 +4,7 @@ fn main() {
  basic();
  ref_protector();
  ref_mut_protector();
  + rust_issue_68303();
  }
  fn basic() {
  @@ -66,3 +67,11 @@ fn ref_mut_protector() {
  let rc = RefCell::new(0);
  break_it(&rc, rc.borrow_mut())
  }
  +
  +/// Make sure we do not have bad enum layout optimizations.
  +fn rust_issue_68303() {
  + let optional=Some(RefCell::new(false));
  + let mut handle=optional.as_ref().unwrap().borrow_mut();
  + assert!(optional.is_some());
  + *handle=true;
  +}
  