{-# LANGUAGE OverloadedRecordDot #-}
{-# OPTIONS -Wpartial-fields #-}


data Visitor where
  Member :: { _name :: String } -> Visitor
  NonMember :: {} -> Visitor
  
main :: IO ()
main = putStrLn (makeGreeting NonMember {})

makeGreeting :: Visitor -> String
makeGreeting visitor =
  visitor._name