[tom_mellior]

> it's not obvious that your `close()` method will take ownership of `self`

I'm in the middle of reading the Rust book right now, so this may be dumb, but... Isn't this exactly the point of using a naked `self` instead of the reference `&self`? If it's not a reference, `self` is consumed by the method. At least that's my current understanding

If you mean that the one-character difference is very small for such an important semantic distinction, I might agree.

As for the state machine example, I like it a lot as well. It's very similar to the idea of "making illegal states unrepresentable" from the OCaml world: http://fsharpforfunandprofit.com/posts/designing-with-types-... (This particular post is F#, but the idea is general.)

[estefan]

> Isn't this exactly the point of using a naked `self` instead of the reference `&self`?

Yes it is, but you only see it's a naked self if you look into the method. From the outside there's nothing in the name to indicate that it doesn't take a reference. So potentially it means that for every method call you need to check that it takes a reference to `self` instead of ownership. This would be especially annoying with third-party libraries.