src/test/ui/traits/object/exclusion.rs

   1 // run-pass
   2 trait Future: 'static {
   3     // The requirement for Self: Sized must prevent instantiation of
   4     // Future::forget in vtables, otherwise there's an infinite type
   5     // recursion through <Map<...> as Future>::forget.
   6     fn forget(self) where Self: Sized {
   7         Box::new(Map(self)) as Box<dyn Future>;
   8     }
   9 }
  10
  11 struct Map<A>(#[allow(unused_tuple_struct_fields)] A);
  12 impl<A: Future> Future for Map<A> {}
  13
  14 pub struct Promise;
  15 impl Future for Promise {}
  16
  17 fn main() {
  18     Promise.forget();
  19 }