Cause.empty type inconsistency

[zeal18]

Hi all! It seems there is a type inconsistency for Cause.empty which makes it impossible to pass it as an argument of type Cause[?].

This can happen because the Cause type is defined as follows:

type Cause[+E] = ParSeq[Nothing, E]

where ParSeq has both type parameters covariant.
But Cause.empty is

case object Empty extends ParSeq[Unit, Nothing]

the first type parameter is Unit which is always Unit > Nothing and this makes Cause.empty > Cause[?]

Can you check if my assumptions are correct?