This is the second of a series of articles on “Type Parameters and Type Members”. If you haven’t yet, you should start at the beginning, which introduces code we refer to throughout this article without further ado. In the last part, we just saw two method types that, though different, are effectively the same: those of plengthT and plengthE. We have rules for deciding when an existential parameter can be lifted into a method type parameter—or a method type parameter lowered to an exi...
