src/test/run-pass/traits/trait-object-exclusion.rs

   1 // Copyright 2016 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // run-pass
  12 trait Future: 'static {
  13     // The requirement for Self: Sized must prevent instantiation of
  14     // Future::forget in vtables, otherwise there's an infinite type
  15     // recursion through <Map<...> as Future>::forget.
  16     fn forget(self) where Self: Sized {
  17         Box::new(Map(self)) as Box<Future>;
  18     }
  19 }
  20
  21 struct Map<A>(A);
  22 impl<A: Future> Future for Map<A> {}
  23
  24 pub struct Promise;
  25 impl Future for Promise {}
  26
  27 fn main() {
  28     Promise.forget();
  29 }