DataTypeName.hs

{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE FlexibleContexts #-}

module Test where

import GHC.Generics
import Data.Proxy

typeName :: forall a. (Generic a, GTypeName (Rep a)) => Proxy a -> String
typeName Proxy = gtypename (from (undefined :: a))

class GTypeName f where
  gtypename :: f a -> String

instance (Datatype c) => GTypeName (M1 i c f) where
  gtypename m = datatypeName m

unit :: String
unit = typeName (Proxy :: Proxy ())

int :: String
int = typeName (Proxy :: Proxy Int)