Generics are to types what HKT are to type signatures. In functions, they usually map to arity. That is, an arity mismatch is are a higher-kinded type mismatch.

Generics are to types what HKT are to type signatures. In functions, they usually map to arity. That is, an arity mismatch is are a higher-kinded type mismatch. An easy (if not totally accurate) way to view them is like doubly-generic types. If you have some type A, it has the kind * . If you have some function from A -> B, it has the kind * -> * .