{-# LANGUAGE DerivingVia #-}
module M where

import Control.Monad.State
import Control.Monad.Except

-- funnily, this is necessary for the `coerce` inherent in DerivingVia to be accepted
import Data.Functor.Identity

newtype M e s a = M (s -> Either e (a, s))
  deriving (Functor, Applicative, Monad, MonadState s, MonadError e) via (StateT s (Except e))