GeneralizedNewtypeDeriving and roles

GNTD.hs

class A a where
  a :: Monad m => a -> m a

instance A Int where
  a = pure

newtype MyNewtype = MyNewtype Int deriving A
-- ^ 
-- error:
--    • Couldn't match representation of type ‘m Int’
--                               with that of ‘m MyNewtype’
--        arising from the coercion of the method ‘a’
--          from type ‘forall (m :: * -> *). Monad m => Int -> m Int’
--            to type ‘forall (m :: * -> *). Monad m => MyNewtype -> m MyNewtype’
--      NB: We cannot know what roles the parameters to ‘m’ have;
--        we must assume that the role is nominal
--    • When deriving the instance for (A MyNewtype)