2 #![allow(non_camel_case_types)]
3 #![feature(box_syntax)]
6 fn double(self) -> usize;
9 impl double for usize {
10 fn double(self) -> usize { self }
13 impl double for Box<usize> {
14 fn double(self) -> usize { *self * 2 }
18 let x: Box<_> = box 3;
19 assert_eq!(x.double(), 6);