T1496.hs:10:32: error:
    • Couldn't match representation of type: c Int
                               with that of: c Moo
        arising from the coercion of the method ‘isInt’
          from type ‘forall (c :: * -> *). c Int -> c Int’
            to type ‘forall (c :: * -> *). c Int -> c Moo’
      NB: We cannot know what roles the parameters to ‘c’ have;
        we must assume that the role is nominal
    • When deriving the instance for (IsInt Moo)