{-# LANGUAGE DataKinds #-}

module Comparable where

import Data.Kind (Type)


data FunctionArgument
  = ArgLiteral ComparableSansPath

type Comparable         =           Comparable_ S
type ComparableSansPath = forall s. Comparable_ s

data Sub = S

data Comparable_ :: Sub -> Type where
  CmpNumber :: Int          -> Comparable_ s
  CmpString :: String       -> Comparable_ s
  CmpBool   :: Bool         -> Comparable_ s
  CmpNull   ::                 Comparable_ s
  CmpPath   :: SingularPath -> Comparable_ S

data SingularPath = SingularPath String


-- Compiles
test1 :: FunctionArgument
test1 = ArgLiteral CmpNull

-- Does not compile
--test2 :: FunctionArgument
--test2 = ArgLiteral (CmpPath (SingularPath ""))