Answer by Raoul Supercopter for Lifting class instance in Haskell

GHC implements what you want : Extensions to the deriving mecanism.These modifications are often shown for future standard language extension (As seen on haskell' wiki)

To Enable this extension, you must use the following pragma

{-# GeneralizedNewtypeDeriving #-}

and then use a deriving on your newtype declaration, as usual

data SomeType a = SomeCons a deriving (Num)