{-# LANGUAGE DeriveAnyClass      #-}
{-# LANGUAGE DeriveGeneric       #-}
{-# LANGUAGE OverloadedStrings   #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeApplications    #-}
{-# LANGUAGE TypeFamilies        #-}
module Example where

import           Development.IDE.Graph
import           Development.IDE.Graph.Classes
import           Development.IDE.Graph.Rule
import           GHC.Generics
import           Type.Reflection               (typeRep)

data Rule a = Rule
    deriving (Eq, Generic, Hashable, NFData)

instance Typeable a => Show (Rule a) where
    show Rule = show $ typeRep @a

type instance RuleResult (Rule a) = a

ruleUnit :: Rules ()
ruleUnit = addRule $ \(Rule :: Rule ()) old mode -> do
    return $ RunResult ChangedRecomputeDiff "" ()

-- | Depends on Rule @()
ruleBool :: Rules ()
ruleBool = addRule $ \Rule old mode -> do
    () <- apply1 Rule
    return $ RunResult ChangedRecomputeDiff "" True