Compilation (look like to) never end

[flomebul]

Minimized code

This code (look like) to never end.
It finish normally if we use the last line (i.e. "case ? :: ? => ...") inside the previous one (i.e. "case ? => ...")

object ABug:
  sealed trait Bit
  sealed trait B0 extends Bit
  sealed trait B1 extends Bit

  sealed trait Bin
  sealed trait Nil extends Bin
  sealed trait ::[U <: Bit, D <: Bin] extends Bin

  type Zero = B0 :: Nil
  type One  = B1 :: Nil

  type --[B <: Bin] =
    B match
      case B1 :: d => B0 :: d
      case B0 :: B1 :: Nil => B1 :: Nil
      case B0 :: d => B1 :: --[d]

  type ×[N <: Bin, M <: Bin] =
    (N, M) match
      case (Zero, ?) => Zero

  type ![N <: Bin] =
    N match
      case Zero => One
      case One => One
      case ? => ![--[N]] × (N)
//      case ? :: ? => ![--[N]] × (N)

Output

No output at all !!!

Expectation

Terminate in a reasonable time, eventually with an error.

[odersky]

I think this is another case where a counter limiting match type reductions would help.

[flomebul]

With delivery of 3.0.0-M3, I discover that the issue seems to be corrected, but not closed.
Could you check?

[OlivierBlanvillain]

Yes, this seems to be fixed, thanks for the ping!