{-# language AllowAmbiguousTypes, DataKinds, TypeFamilies #-}

import Data.Kind (Constraint, Type)
import Data.Tagged
import GHC.TypeLits (Symbol)

type HList :: [Type] -> Type
data family HList xs
data instance HList '[] = HNil
data instance HList (x ': xs) = x `HCons` HList xs

type Merge :: [Symbol] -> [Type] -> Constraint
class Merge ls ts where
    merge :: HList ts -> HList whatgoeshere -- ????????
instance Merge ls ts => Merge (l : ls) (t : ts) where
    merge (HCons t ts) = HCons (Tagged @l t) (merge @ls ts)
instance Merge '[] '[] where
    merge HNil = HNil