// Copyright 2016 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 or the MIT license // , at your // option. This file may not be copied, modified, or distributed // except according to those terms. use std::fmt; union U { a: u8 } impl fmt::Display for U { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { unsafe { write!(f, "Oh hai {}", self.a) } } } fn main() { assert_eq!(U { a: 2 }.to_string(), "Oh hai 2"); }