[crimsonalucard]

Thanks for the clarification. I think I get it despite the incorrect notation. You guys are talking about some sort of type of types?

[kmill]

Yeah, the "type of types" is called a kind in Haskell https://wiki.haskell.org/Kind https://en.wikipedia.org/wiki/Kind_(type_theory)

Caveat: there seems to be some reason not to think of kinds as actually being the types of datatypes, but I don't understand why that is.