Code example in the Guide could be improved

[aochagavia]

There is a code example in section 0.7.1 of the Guide (http://static.rust-lang.org/doc/master/guide.html#expressions-vs.-statements), which could be improved.

We use this:

let mut x = 0i;
let y = x = 5i;

But, in my opinion, it would be better to use this (avoids making x mutable):

let x;
let y = x = 5i;

Is there a reason why we prefer the first code snippet instead of the second? I could submit a PR to fix it.

cc @steveklabnik

[steveklabnik]

I thought it had to be mutable, but rustc does compile things.

Yes, please submit a PR so you get credit. 😄 the text will need a tiny change as well.