Code shared from the Rust Playground

playground.rs

#![feature(box_into_pin)] 
use std::pin::Pin;

trait T {
    fn test(&self) -> usize;
}

struct X {
    _n: i32
}
impl T for X {
    fn test(&self) -> usize {
        self as *const X as usize
    }
}

fn add_inst(vec: &mut Vec<Pin<Box<T>>>) -> &X {
    let x = X { _n: 0};
    let b = Box::into_pin(Box::new(x));
    let ptr = &*b as *const X;
    vec.push(b);
    unsafe { &*ptr }
}

fn main() {
    let mut v = Vec::new();
    let x = add_inst(&mut v);
    let v0 = x.test();
    let y = add_inst(&mut v);
    let v1 = y.test();
    assert!(v[0].test() == v0);
    assert!(v[1].test() == v1);
}