module Language.PureScript.TypeChecker.Synonyms (
saturateTypeSynonym,
saturateAllTypeSynonyms
) where
import Language.PureScript.Types
import Language.PureScript.Names
import Data.Maybe (fromMaybe)
import Data.Data
import Data.Generics
import Data.Generics.Extras
import Control.Monad.Writer
import Control.Monad.Error
buildTypeSubstitution :: Qualified ProperName -> Int -> Type -> Either String (Maybe Type)
buildTypeSubstitution name n = go n []
where
go :: Int -> [Type] -> Type -> Either String (Maybe Type)
go 0 args (TypeConstructor ctor) | name == ctor = return (Just $ SaturatedTypeSynonym ctor args)
go m _ (TypeConstructor ctor) | m > 0 && name == ctor = throwError $ "Partially applied type synonym " ++ show name
go m args (TypeApp f arg) = go (m 1) (arg:args) f
go _ _ _ = return Nothing
saturateTypeSynonym :: (Data d) => Qualified ProperName -> Int -> d -> Either String d
saturateTypeSynonym name n = everywhereM' (mkM replace)
where
replace t = fmap (fromMaybe t) $ buildTypeSubstitution name n t
saturateAllTypeSynonyms :: (Data d) => [(Qualified ProperName, Int)] -> d -> Either String d
saturateAllTypeSynonyms syns d = foldM (\result (name, n) -> saturateTypeSynonym name n result) d syns