{-# LANGUAGE DeriveGeneric, ScopedTypeVariables #-}
module Main where
import GHC.Generics (Generic)
import Test.QuickCheck
import Test.QuickCheck.Function
data D a = C1 a | C2 deriving (Eq, Show, Read, Generic)
instance Arbitrary a => Arbitrary (D a)
instance CoArbitrary a => CoArbitrary (D a)
instance (Show a, Read a) => Function (D a) where
function = functionShow
main :: IO ()
main = quickCheck $ \(Fun _ f) ->
f (C1 (2::Int)) `elem` [0, 1 :: Int]