# Pastebin izOXtZzZ
{-# LANGUAGE AllowAmbiguousTypes #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeApplications #-}

import Data.Typeable

data Foo where
  Foo :: (Typeable a, Show a) => {field :: a} -> Foo

printType :: forall a. Typeable a => String
printType = show $ typeRep (Proxy :: Proxy a)

showFoo :: Foo -> String
showFoo Foo {field = field :: a} = printType @a ++ show field