Code shared from the Rust Playground

playground.rs

#![feature(ptr_internals)]
use std::ptr::Unique;

fn main() {
    let mut arr = [1u8, 2, 3];
    let slice = &mut arr[..];
    let unique : Unique<[u8]> = Unique::new(slice as *mut [u8]).unwrap();
    // Cast unique to an usize
    let ptr = unsafe { (&(*unique.as_ptr())[0] as *const u8 as usize) };
    println!("{:?} {:x}", unique, ptr);
}