Add roles declarations to allow safe coercions (#194)

Author: kl0tl

src/Effect/Aff.purs

@@ -63,6 +63,8 @@ import Unsafe.Coerce (unsafeCoerce)
 -- | `makeAff` or `liftEffect`.
 foreign import data Aff ∷ Type → Type
 
+type role Aff representational
+
 instance functorAff ∷ Functor Aff where
   map = _map
 
@@ -117,6 +119,8 @@ instance lazyAff ∷ Lazy (Aff a) where
 -- | `ParAff` and back using the `Parallel` class.
 foreign import data ParAff ∷ Type → Type
 
+type role ParAff representational
+
 instance functorParAff ∷ Functor ParAff where
   map = _parAffMap