Unreasonably slow (or even non-terminating) compilation of pattern match involving GADT reasoning on nested types #16785
Description
Compiler version
3.2.2
3.3.0-RC2
Reproduction steps
git clone https://github.com/TomasMikula/libretto.git
cd libretto
git checkout 075f9f1911652ccaaa77dbf16e0b35ebd4a9dfc3
sbt core/compile
Note that I hit this bug in the middle of a refactoring session, so most likely the code should not compile just yet.
It is hard to minimize, because whatever I undo, I do get an actual compiler error. I'm hoping you could detect where it's looping, anyway.
UPDATE: Here's a minimization:
class VarImpl[P, A]()
class ContextImpl[Var[_]]()
trait Lambdas[F[_, _], P] {
type Var[A] = VarImpl[P, A]
}
class LambdasImpl[F[_, _], P] extends Lambdas[F, P] {
opaque type Context = ContextImpl[Var]
sealed trait Foo[A]
case class Bar[T, U]() extends Foo[F[Var[T], Var[U]]]
def go[X](that: Foo[Var[X]]): Unit =
that match
case _ => ()
}Output
After a while, compilation hangs with 100% of 1 CPU core.