StackOverflow in typer

[hobwekiva]

I have a good reason to believe that the majority of the examples given in scala/scala3#4368 will stack overflow or hang in Scala2 (I checked that the first 3 hang in scastie).

[SethTisue]

The simplest of the reproductions:

trait X {
  type A = B
  type B
}
trait Y {
  type A
  type B = A
}
trait Z extends X with Y

does still give a stack overflow in Scala 2.13.10.

I imagine it's likely the others do as well.