Allow in (or :?) for all quantification

[ChrisJefferson]

At the moment we write forAll x : T, for types, but forAll x in S, for sets. I think it would be easier if we could use 'in' for both.

The other option we be to push all tutorials towards matrix comprehension?

[ozgurakgun]

Same problem with comprehensions. <- works for expressions, : for domains there.

[ott2]

It would seem to make sense to treat x in T as a synonym for x : T when T is a type, and [f(x) | x <- D] as a synonym for [f(x) | x : D] when D is a domain?

[ozgurakgun]

I'll close this as won't fix for now, we can think about this in the future again if we get to rethinking the language...