TASTY: no way to access `baseClasses` of `AppliedType`

[pshirshov]

I'm working on re-implementation of izumi-reflect for Dotty.

So far I made some substantial progress but seems like there is a blocker.

The primary problem is: seems like there is no way to get access to baseClasses of a type:

Let's assume that we have the following definitions:

trait X[A, B]
trait A[F[_]]
trait B extends A[X[Int, *]]

On scala2 I can call .baseClasses method on a type of B and get a list containing A[[T] => X[Int, T]].

In dotty AppliedType has only tycon method which does not allow me to inspect applied parents.

See also: 7mind/dotty-typetag-research#2 ; zio/izumi-reflect#22

[pshirshov]

@nicolasstucki could you check this issue please?

[Blaisorblade]

On scala2 I can call .baseClasses method on a type of A

I assume you mean the type of B, or do I miss something? Can you maybe clarify?

[pshirshov]

Yeah, fixed.

[Blaisorblade]

(On the main issue: I’m aware the API is incomplete and extensions are being considered, and things like this should be fine, but I cannot say more).

[jdegoes]

This seems like a useful improvement regardless, but speaking as a ZIO contributor, I know we are relying on this functionality (or its equivalent) for the new environment encoding, which has proven to be a smash hit among ZIO users, but which only has partial support in Dotty.

Thanks for reporting!