#![feature(rustc_attrs)]
#![allow(unused)]

// revisions: migrate nll
#![cfg_attr(nll, feature(nll))]

fn f() {
    let mut x: Box<()> = Box::new(());

    || {
        &mut x
    };
    //[migrate]~^^ WARNING captured variable cannot escape `FnMut` closure body
    //[migrate]~| WARNING this error has been downgraded to a warning
    //[migrate]~| WARNING this warning will become a hard error in the future
    //[nll]~^^^^^ ERROR captured variable cannot escape `FnMut` closure body
}

#[rustc_error]
fn main() {}
//[migrate]~^ ERROR