model the algorithm for normalizing when trait is unknown about chalk

[nikomatsakis]

cc @Garogolun, who expressed some interest here.

[tweerwag]

Adding InScope went scaringly quickly, but maybe I missed something. The commit is here.

If I understand correctly, the next step is to add types such as T::Item (where the trait is not specified), and generate rules to infer <T as Iterator>::Item from T::Item and things like InScope(Iterator)? (I also tried thinking a bit about these rules, but I don't know what rustc does exactly.)

[nikomatsakis]

@Garogolun argh, sorry, I'm having trouble keeping up with GH notifications right now. Feel free to reach out over gitter for faster responses. =)

Anyway, that commit looks pretty reasonable.

Yes, I think that the next step would be to add a new kind of type that is like an associated type but without the trait, and a rule like:

Normalize<Item>(A, B) :-
    InScope(Iterator),
    Normalize<Iterator::Item>(A, B).

[fabric-and-ink]

@Garogolun are you still on it? If not, I am interested in picking this up 🙂

[tweerwag]

@fabric-and-ink I'm actually on it right now. 😄 Should have something soon.

[nikomatsakis]

OK, this is done.