module Language.PureScript.TypeChecker.Synonyms (
saturateAllTypeSynonyms
) where
import Language.PureScript.Types
import Language.PureScript.Names
import Control.Applicative ((<$>))
import Data.Maybe (fromMaybe)
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 :: Qualified ProperName -> Int -> Type -> Either String Type
saturateTypeSynonym name n = everywhereOnTypesTopDownM replace
where
replace t = fromMaybe t <$> buildTypeSubstitution name n t
saturateAllTypeSynonyms :: [(Qualified ProperName, Int)] -> Type -> Either String Type
saturateAllTypeSynonyms syns d = foldM (\result (name, n) -> saturateTypeSynonym name n result) d syns