36 lines
894 B
Rust
36 lines
894 B
Rust
|
// Copyright 2014 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.
|
||
|
|
|
||
|
|
// A basic test of using a higher-ranked trait bound.
|
||
|
|
|
||
|
|
trait FnLike<A,R> {
|
||
|
|
fn call(&self, arg: A) -> R;
|
||
|
|
}
|
||
|
|
|
||
|
|
struct Identity;
|
||
|
|
|
||
|
|
impl<'a, T> FnLike<&'a T, &'a T> for Identity {
|
||
|
|
fn call(&self, arg: &'a T) -> &'a T {
|
||
|
|
arg
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
fn call_repeatedly<F>(f: F)
|
||
|
|
where F : for<'a> FnLike<&'a int, &'a int>
|
||
|
|
{
|
||
|
|
let x = 3;
|
||
|
|
let y = f.call(&x);
|
||
|
|
assert_eq!(3, *y);
|
||
|
|
}
|
||
|
|
|
||
|
|
fn main() {
|
||
|
|
call_repeatedly(Identity);
|
||
|
|
}
|