Defunctionalization and generic traversal https://www.reddit.com/r/haskell/comments/884pe0/higherkinded_data_reasonably_polymorphic/

hkd.hs

{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE UndecidableInstances #-}

import Data.Functor.Identity
import GHC.Generics
import Generics.OneLiner.Binary

-- gvalidate implementation

class (a ~ f b) => F f a b
instance (a ~ f b) => F f a b

gvalidate :: forall t t' f. (ADT t t', Constraints t t' (F f), Applicative f) => t -> f t'
gvalidate t = gtraverse @(F f) id t

-- HKD

type family HKD f a where
  HKD Identity a = a
  HKD f a = f a

-- Example

data Person f = Person
  { name :: HKD f String
  , age :: HKD f Int
  } deriving Generic

deriving instance Show (Person Identity)

john :: Person Maybe
john = Person (Just "John") (Just 43)

main = do
  print (gvalidate john :: Maybe (Person Identity))