Shared via Rust Playground

playground.rs

#![feature(unsize)]

use std::fmt::Debug;
use std::marker::Unsize;

fn foo<T: Unsize<Debug> + 'static>(mut t: T) {
    let t = unsafe { Box::from_raw(&mut t as *mut _) } as Box<Debug>;
    println!("{:?}", t);
}

fn main() {
    foo(123);
}