Change traits to take &mut self instead of &self

[f-bro]

See #2 (comment)

[japaric]

Thanks for the pull request @f-bro!

With these changes all the futures examples will need to be updated to take e.g. S by value otherwise code like this won't compile:

fn test<'a, S>(s: &'a mut S) -> impl Future<Item = (), Error = S::Error> + 'a
where
    S: Serial,
{
    write(s, b'H').and_then(move |_| write(s, b'e'))
}

error[E0504]: cannot move `s` into closure because it is borrowed
  --> src/main.rs:33:44
   |
33 |     write(s, b'H').and_then(move |_| write(s, b'e'))
   |           - borrow of `*s` occurs here     ^ move into closure occurs here

error: aborting due to previous error(s)

This is known futures "issue" (well not an issue if follows from how futures work).

For example write will have to be changed to look like this:

fn write<S>(mut s: S, byte: u8) -> impl Future<Item = S, Error = S::Error>
where
    S: Serial,
{
    future::poll_fn(move || {
        try_nb!(s.write(byte));
        Ok(Async::Ready(s))
    })
}

Except that that doesn't work either so you'll have to figure out some solution. Once that works then we should be able to rewrite foo to look like this:

fn test<'a, S>(s: S) -> impl Future<Item = S, Error = S::Error>
where
    S: Serial,
{
    write(s, b'H').and_then(move |s| write(s, b'e'))
}

[homunkulus]

☔ The latest upstream changes (presumably 7d904f5) made this pull request unmergeable. Please resolve the merge conflicts.

[hannobraun]

@japaric This pull request has been inactive for a while, and the changes have been made in another pull request. I think this can be closed.

[japaric]

Yes, thanks for the heads up @hannobraun.

@f-bro Thanks for the original implementation!