src/test/ui/not-panic/not-panic-safe.rs

#![allow(dead_code)]
#![feature(recover)]

use std::panic::UnwindSafe;

fn assert<T: UnwindSafe + ?Sized>() {}

fn main() {
    assert::<&mut i32>();
    //~^ ERROR the type `&mut i32` may not be safely transferred across an unwind boundary
}