Functor list product or idk

Main.hs

{-# LANGUAGE UndecidableInstances #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE ScopedTypeVariables #-}

import Data.Kind

data HList (ts :: [Type]) where
  HNil :: HList '[]
  HCons :: t -> HList ts -> HList (t ': ts)

type family HProduct (l :: [Type -> Type]) (a :: Type) where
  HProduct '[] _ = '[]
  HProduct (f ': fs) a = f a ': (HProduct fs a)

data WhatTheFuckType fs a =
  WhatTheFuckTerm { unfuck :: HList (HProduct fs a) }

instance Functor (WhatTheFuckType '[]) where
  fmap _ (WhatTheFuckTerm HNil) = WhatTheFuckTerm HNil

instance (Functor f, Functor (WhatTheFuckType fs)) =>
  Functor (WhatTheFuckType (f ': fs))
    where  
      fmap f (WhatTheFuckTerm (HCons xa xas)) = WhatTheFuckTerm $
        HCons
        (fmap f xa)
        (unfuck @fs $ fmap f (WhatTheFuckTerm $ xas))

type MuhFunctors a = WhatTheFuckType '[ Maybe, IO ] a

heck :: MuhFunctors String
heck = fmap show $ WhatTheFuckTerm $
  HCons (Just 12) $
  HCons (length <$> getLine)
  HNil