//@ run-pass
#![allow(non_camel_case_types)]
trait double {
fn double(self: Box<Self>) -> usize;
}
impl double for usize {
fn double(self: Box<usize>) -> usize { *self * 2 }
pub fn main() {
let x: Box<_> = Box::new(3);
assert_eq!(x.double(), 6);