You're right that your conformance should/could work, but this part is wrong, throwing people off guard. It's the other way around; Any value of type General is, by it's definition, also a value of type A, i.e., you can cast General to A.
So, if we use < as a subtype relationship, then
General<A,- Since function argument is contravariant,
(A) -> Self<(General) -> Self - Now, as class method is covariant w.r.t. its class. It follows that
Sub < Pas we'd like.
The question now is, whether Swift accept the last relationship, because iirc, it doesn't allow methods with subtype signature to satisfy protocol requirement yet.
Well, the requirements form a union, but the typing forms an intersection. So you might be talking past each other here.