grids-0.3.0.0: src/Data/Grid/Internal/Errors.hs

{-# LANGUAGE UndecidableInstances #-}
module Data.Grid.Internal.Errors where

import Data.Kind
import GHC.TypeLits

type family (b :: Bool) ?! (e :: ErrorMessage) :: Constraint where
  True ?! _ = ()
  False ?! e = TypeError e

infixr 1 ?!