HasSuperClasses for Constraint product.

HasSuperClassesProduct.hs

class (c x, d x) => (c :&: d) x
instance (c x, d x) => (c :&: d) x
instance (HasSuperClasses c, HasSuperClasses d, Distr (SuperClasses c)) => HasSuperClasses (c :&: d) where
  type SuperClasses (c :&: d) = (c :&: d) ': SuperClasses c ++ SuperClasses d
  superClasses = h superClasses superClasses
    where
      h :: forall x. c x :- FoldConstraints (SuperClasses c) x
        -> d x :- FoldConstraints (SuperClasses d) x
        -> (c :&: d) x :- FoldConstraints (SuperClasses (c :&: d)) x
      h l r = Sub $ case (h2 (Proxy :: Proxy x) (l . Sub Dict) (r . Sub Dict)) of Dict -> Dict
      h2 :: forall x. (c x, d x) => Proxy x
        -> (c :&: d) x :- FoldConstraints (SuperClasses c) x
        -> (c :&: d) x :- FoldConstraints (SuperClasses d) x
        -> Dict (FoldConstraints (SuperClasses c ++ SuperClasses d) x)
      h2 p (Sub Dict) (Sub Dict) = distr p (Proxy :: Proxy (SuperClasses c)) (Proxy :: Proxy (SuperClasses d))
  containsSelf = Sub Dict

class Distr cs where
  distr :: (FoldConstraints cs x, FoldConstraints ds x) => Proxy x -> Proxy cs -> Proxy ds -> Dict (FoldConstraints (cs ++ ds) x)
instance Distr '[] where
  distr _ _ _ = Dict
instance Distr cs => Distr (c ': cs) where
  distr x _ ds = case distr x (Proxy :: Proxy cs) ds of Dict -> Dict