// 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 or the MIT license // , at your // option. This file may not be copied, modified, or distributed // except according to those terms. use std::ops::{Deref, DerefMut}; struct Foo; impl Foo { fn foo_mut(&mut self) {} } struct Bar(Foo); impl Deref for Bar { type Target = Foo; fn deref(&self) -> &Foo { &self.0 } } impl DerefMut for Bar { fn deref_mut(&mut self) -> &mut Foo { &mut self.0 } } fn test(mut bar: Box) { bar.foo_mut(); } fn main() {}