{-# LANGUAGE LambdaCase #-}

module FooBar where

data FooBar = Foo | Bar

data Impl = MkImpl{ baz_ :: Int, quux_ :: String }

fooImpl :: Impl
fooImpl = MkImpl{ baz_ = 3, quux_ = "foo" }

barImpl :: Impl
barImpl = MkImpl{ baz_ = 5, quux_ = "bar" }

selectImpl :: FooBar -> Impl
selectImpl = \case
  Foo -> fooImpl
  Bar -> barImpl

baz :: FooBar -> Int
baz = baz_ . selectImpl

quux :: FooBar -> String
quux = quux_ . selectImpl