Invalid ITF accepted

[jstolarek]

Consider this definition:

type family Gc (a :: k) (b :: k) = r | r -> k where
    Gc a b = Int

It should be rejected with an error message:

T6018failclosed12.hs:7:5:
    Type family equation violates injectivity annotation.
    Injective kind variable ‘k’ is not inferable from the RHS type variables.
    In the RHS of type family equation:
      forall (k :: BOX) (a :: k) (b :: k). Gc a b = Int
    In the equations for closed type family ‘Gc’
    In the type family declaration for ‘Gc’

But it gets accepted. Even more surprisingly open type family variant is rejected:

type family Gc (a :: k) (b :: k) = r | r -> k
type instance Gc a b = Int

Type family equation violates injectivity annotation.
Injective kind variable ‘k’ is not inferable from the RHS type variables.
In the RHS of type family equation:
forall (k :: BOX) (a :: k) (b :: k). Gc a b = Int

@simonpj this happened after your refactoring. I'm looking into this at the moment but please tell if you have any ideas what might have changed here.

[jstolarek]

7dd5c250993288d750ba404f3c7804ad3f6e850b is the culprit. @simonpj, I understand little of what changes in that commit do so you'll have to fix.