| // Copyright 2015 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. |
| |
| // pretty-expanded FIXME #23616 |
| |
| #![allow(dead_code)] |
| |
| // Get<T> is covariant in T |
| trait Get<T> { |
| fn get(&self) -> T; |
| } |
| |
| struct Cloner<T:Clone> { |
| t: T |
| } |
| |
| impl<T:Clone> Get<T> for Cloner<T> { |
| fn get(&self) -> T { |
| self.t.clone() |
| } |
| } |
| |
| fn get<'a, G>(get: &G) -> i32 |
| where G : Get<&'a i32> |
| { |
| // This fails to type-check because, without variance, we can't |
| // use `G : Get<&'a i32>` as evidence that `G : Get<&'b i32>`, |
| // even if `'a : 'b`. |
| pick(get, &22) //~ ERROR cannot infer |
| } |
| |
| fn pick<'b, G>(get: &'b G, if_odd: &'b i32) -> i32 |
| where G : Get<&'b i32> |
| { |
| let v = *get.get(); |
| if v % 2 != 0 { v } else { *if_odd } |
| } |
| |
| fn main() { |
| let x = Cloner { t: &23 }; |
| let y = get(&x); |
| assert_eq!(y, 23); |
| } |