{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE MultiParamTypeClasses #-}
import Control.Monad.Reader
newtype T a x = T (Reader a x)
    deriving (Monad, MonadReader a)

{-
[1 of 1] Compiling Main             ( bug.hs, interpreted )
mkUsageInfo: internal name? a{tv amy}
Ok, modules loaded: Main.
-}