Automatic inference of an instance using newtype

(A related question Even more generalized new type inference )

I like the wrapper types

{-# LANGUAGE GeneralizedNewtypeDeriving #-}
newtype Foo = Foo { unFoo :: Int } deriving (Eq, Ord, Enum, Real, Num, Read, Integral, Show)
newtype Var = Var { unVar :: Int } deriving (Eq, Ord, Enum, Real, Num, Read, Integral, Show)

      

        
        
        
      

    

to prevent

doSomething :: Int -> Int -> Int
doSomething someFoo otherVar

      

        
        
        
      

    

Is it possible to automatically get all possible instances?

(Not recommended ?, Is there a better way?)

Thank!