data kinds + kind signatures because yolo

asdf.hs

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE KindSignatures #-}

module Main where

import Data.Proxy
import Data.List

data Validity = Validated | NotValidated

class Crap (a :: Validity) where
  whatever :: Proxy a -> String

instance Crap 'Validated where
  whatever _ = "dsfdsf"

newtype MyThing (validity :: Validity) = MyThing String

myThing :: MyThing 'NotValidated
myThing = MyThing "sdfa"

validatePls ::
     MyThing 'NotValidated
  -> Either String (MyThing 'Validated)
validatePls (MyThing s) =
  if "a" `isInfixOf` s
    then Right (MyThing s)
    else Left "sdfsdf"