| // Copyright 2016 The Rust Project Developers. See the COPYRIGHT |
| // file at the top-level directory of this distribution and at |
| // http://rust-lang.org/COPYRIGHT. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| trait Future: 'static { |
| // The requirement for Self: Sized must prevent instantiation of |
| // Future::forget in vtables, otherwise there's an infinite type |
| // recursion through <Map<...> as Future>::forget. |
| fn forget(self) where Self: Sized { |
| Box::new(Map(self)) as Box<Future>; |
| } |
| } |
| |
| struct Map<A>(A); |
| impl<A: Future> Future for Map<A> {} |
| |
| pub struct Promise; |
| impl Future for Promise {} |
| |
| fn main() { |
| Promise.forget(); |
| } |
