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)