rust/src/test/compile-fail/issue-4972.rs

// Copyright 2013 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.

trait MyTrait { }

pub enum TraitWrapper {
    A(~MyTrait),
}

fn get_tw_map<'lt>(tw: &'lt TraitWrapper) -> &'lt MyTrait {
    match *tw {
        A(~ref map) => map, //~ ERROR found a ~-box pattern
    }
}

pub fn main() {}