{-# LANGUAGE AllowAmbiguousTypes
           , FlexibleInstances
           , MultiParamTypeClasses
           , ScopedTypeVariables
           , TypeApplications
           , DuplicateRecordFields
           , OverloadedLabels
           , FlexibleContexts
  #-}
module Records where

import GHC.OverloadedLabels
import GHC.Records

instance HasField x r a => IsLabel x (r -> a) where
  fromLabel = getField @x


fb r = if #bar r then #foo r else 0

f1 = fb $ FooBar 42 True
-- 42
f2 = fb $ BarFoo True 24
-- 24

data FooBar = FooBar { foo :: Int, bar :: Bool }
data BarFoo = BarFoo { bar :: Bool, foo :: Int }