[steveklabnik]

For comparison, the same thing in Rust:

  fn main() {
      let p = Box::new(5);
      let q = p;
      println!("{}", p);
  }

gives, upon compiling:

    error: use of moved value: `p` [E0382]
    println!("{}", p);
                   ^
    note: in this expansion of format_args!
    note: in this expansion of print! (defined in <std macros>)
    note: in this expansion of println! (defined in <std macros>)
    help: run `rustc --explain E0382` to see a detailed explanation
    note: `p` moved here because it has type `Box<i32>`, which is moved
    by default
    let q = p;
        ^
    help: if you would like to borrow the value instead, use a `ref`
    binding as shown:
    let ref q = p;
    error: aborting due to previous error

Running `rustc --explain E0382` or going to https://doc.rust-lang.org/nightly/error-index.html#E0382 gives you an extended error message as well.