There's a pretty decent explanation in the release-notes: http://get-scala.org/2.12#partial-unification-of-type-constructors http://get-scala.org/2.12#partial-u

There's a pretty decent explanation in the release-notes: http://get-scala.org/2.12#partial-unification-of-type-constructors http://get-scala.org/2.12#partial-unification-of-type-constr...