Cyclic reference with -Ytest-pickler

[OlivierBlanvillain]

a.scala:

trait Filter {
  def info: Info
}

b.scala:

class Info(k: Keyboard)

sealed trait Thing
class Keyboard            extends Thing
class Laptop(k: Keyboard) extends Thing

run -Ytest-pickler -Ystop-after:pickler a.scala b.scala

cannot take signature of (k: Keyboard)Laptop
cannot take signature of ()Keyboard
cannot take signature of (k: Keyboard)Info

exception occurred while compiling a.scala, b.scala
Exception in thread "main" dotty.tools.dotc.core.Types$CyclicReference: cyclic reference involving class Keyboard
        [...]