module Language.PureScript.TypeChecker.Monad where
import Language.PureScript.Types
import Language.PureScript.Kinds
import Language.PureScript.Names
import Language.PureScript.Unknown
import Data.Data
import Data.Maybe
import Data.Monoid
import Data.Typeable
import Control.Applicative
import Control.Monad.State
import Control.Monad.Error
import Control.Arrow ((***), first, second)
import qualified Data.Map as M
data NameKind = Value | Extern | Alias ModulePath Ident deriving Show
data TypeDeclarationKind = Data | ExternData | TypeSynonym deriving Show
data Environment = Environment
{ names :: M.Map (ModulePath, Ident) (Type, NameKind)
, types :: M.Map (ModulePath, ProperName) (Kind, TypeDeclarationKind)
, dataConstructors :: M.Map (ModulePath, ProperName) Type
, typeSynonyms :: M.Map (ModulePath, ProperName) ([String], Type)
, members :: M.Map (ModulePath, Ident) String
} deriving (Show)
emptyEnvironment :: Environment
emptyEnvironment = Environment M.empty M.empty M.empty M.empty M.empty
data AnyUnifiable where
AnyUnifiable :: forall t. (Unifiable t) => t -> AnyUnifiable
data CheckState = CheckState { checkEnv :: Environment
, checkNextVar :: Int
, checkModulePath :: ModulePath
}
newtype Check a = Check { unCheck :: StateT CheckState (Either String) a }
deriving (Functor, Monad, Applicative, MonadPlus, MonadState CheckState, MonadError String)
getEnv :: Check Environment
getEnv = fmap checkEnv get
putEnv :: Environment -> Check ()
putEnv env = modify (\s -> s { checkEnv = env })
modifyEnv :: (Environment -> Environment) -> Check ()
modifyEnv f = modify (\s -> s { checkEnv = f (checkEnv s) })
runCheck :: Check a -> Either String (a, Environment)
runCheck c = do
(a, s) <- flip runStateT (CheckState emptyEnvironment 0 global) $ unCheck c
return (a, checkEnv s)
guardWith :: (MonadError e m) => e -> Bool -> m ()
guardWith _ True = return ()
guardWith e False = throwError e
rethrow :: (MonadError e m) => (e -> e) -> m a -> m a
rethrow f = flip catchError $ \e -> throwError (f e)
withModule :: ProperName -> Check a -> Check a
withModule name act = do
original <- checkModulePath `fmap` get
modify $ \s -> s { checkModulePath = subModule (checkModulePath s) name }
a <- act
modify $ \s -> s { checkModulePath = original }
return a
newtype Substitution = Substitution { runSubstitution :: forall t. (Unifiable t) => Unknown t -> t }
instance Monoid Substitution where
mempty = Substitution unknown
s1 `mappend` s2 = Substitution $ \u -> apply s1 (apply s2 (unknown u))
data SubstState = SubstState { substSubst :: Substitution
, substFutureEscapeChecks :: [AnyUnifiable] }
newtype Subst m a = Subst { unSubst :: StateT SubstState m a }
deriving (Functor, Monad, Applicative, MonadPlus, MonadTrans)
deriving instance (MonadError String m) => MonadError String (Subst m)
runSubst :: (Unifiable a, Monad m) => Subst m a -> m (a, Substitution, [AnyUnifiable])
runSubst subst = do
(a, s) <- flip runStateT (SubstState mempty []) . unSubst $ subst
return (apply (substSubst s) a, substSubst s, substFutureEscapeChecks s)
substituteWith :: (Typeable t) => (Unknown t -> t) -> Substitution
substituteWith f = Substitution $ \u -> fromMaybe (unknown u) $ do
u1 <- cast u
cast (f u1)
substituteOne :: (Unifiable t) => Unknown t -> t -> Substitution
substituteOne u t = substituteWith $ \u1 ->
case u1 of
u2 | u2 == u -> t
| otherwise -> unknown u2
replace :: (Unifiable t) => Unknown t -> t -> Subst Check ()
replace u t' = do
sub <- substSubst <$> Subst get
let t = apply sub t'
occursCheck u t
let current = apply sub $ unknown u
case isUnknown current of
Just u1 | u1 == u -> return ()
_ -> current ~~ t
Subst . modify $ \s -> s { substSubst = substituteOne u t <> substSubst s }
class (Typeable t, Data t, Show t) => Unifiable t where
unknown :: Unknown t -> t
(~~) :: t -> t -> Subst Check ()
isUnknown :: t -> Maybe (Unknown t)
apply :: Substitution -> t -> t
unknowns :: t -> [Int]
occursCheck :: (Unifiable t) => Unknown s -> t -> Subst Check ()
occursCheck (Unknown u) t =
case isUnknown t of
Nothing -> guardWith "Occurs check fails" (u `notElem` unknowns t)
_ -> return ()
fresh' :: Subst Check Int
fresh' = do
n <- lift $ checkNextVar <$> get
lift . modify $ \s -> s { checkNextVar = succ (checkNextVar s) }
return n
fresh :: (Unifiable t) => Subst Check t
fresh = unknown . Unknown <$> fresh'
escapeCheckLater :: (Unifiable t) => t -> Subst Check ()
escapeCheckLater t = Subst . modify $ \s -> s { substFutureEscapeChecks = AnyUnifiable t : substFutureEscapeChecks s }