message: Fix `unused_must_use` inside `Box`
  After this will be linted against (and causes the test to fail).
diff: @@ -21,8 +21,10 @@ pub enum Handler {
  }
  fn main() {
  + #[allow(unused_must_use)] {
  take(Handler::Default, Box::new(main));
  }
  +}
  #[inline(never)]
  pub fn take(h: Handler, f: Box<dyn Fn()>) -> Box<dyn Fn()> {
  