# References

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
     --> <rust.rs>: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.