There are two kinds of reference:

  • Shared reference: &
  • Mutable reference: &mut

Which obey the following rules:

  • A reference cannot outlive its referent
  • A mutable reference cannot be aliased

That's it. That's the whole model references follow.

Of course, we should probably define what aliased means.

error[E0425]: cannot find value `aliased` in this scope
 --> <>:2:20
2 |     println!("{}", aliased);
  |                    ^^^^^^^ not found in this scope

error: aborting due to previous error

Unfortunately, Rust hasn't actually defined its aliasing model. 🙀

While we wait for the Rust devs to specify the semantics of their language, let's use the next section to discuss what aliasing is in general, and why it matters.