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 Control.Applicative
import Control.Monad.State
import Control.Monad.Error
import Control.Monad.Reader
import qualified Data.Map as M
data NameKind
= Value
| Extern
| Alias ModuleName Ident
| LocalVariable deriving Show
data TypeDeclarationKind
= Data
| ExternData
| TypeSynonym
| DataAlias ModuleName ProperName
| LocalTypeVariable deriving Show
data Environment = Environment
{ names :: M.Map (ModuleName, Ident) (Type, NameKind)
, types :: M.Map (ModuleName, ProperName) (Kind, TypeDeclarationKind)
, dataConstructors :: M.Map (ModuleName, ProperName) Type
, typeSynonyms :: M.Map (ModuleName, ProperName) ([String], Type)
, members :: M.Map (ModuleName, Ident) String
} deriving (Show)
emptyEnvironment :: Environment
emptyEnvironment = Environment M.empty M.empty M.empty M.empty M.empty
bindNames :: (MonadState CheckState m) => M.Map (ModuleName, Ident) (Type, NameKind) -> m a -> m a
bindNames newNames action = do
orig <- get
modify $ \st -> st { checkEnv = (checkEnv st) { names = newNames `M.union` (names . checkEnv $ st) } }
a <- action
modify $ \st -> st { checkEnv = (checkEnv st) { names = names . checkEnv $ orig } }
return a
bindTypes :: (MonadState CheckState m) => M.Map (ModuleName, ProperName) (Kind, TypeDeclarationKind) -> m a -> m a
bindTypes newNames action = do
orig <- get
modify $ \st -> st { checkEnv = (checkEnv st) { types = newNames `M.union` (types . checkEnv $ st) } }
a <- action
modify $ \st -> st { checkEnv = (checkEnv st) { types = types . checkEnv $ orig } }
return a
bindLocalVariables :: (Functor m, MonadState CheckState m) => ModuleName -> [(Ident, Type)] -> m a -> m a
bindLocalVariables moduleName bindings action =
bindNames (M.fromList $ flip map bindings $ \(name, ty) -> ((moduleName, name), (ty, LocalVariable))) action
bindLocalTypeVariables :: (Functor m, MonadState CheckState m) => ModuleName -> [(ProperName, Kind)] -> m a -> m a
bindLocalTypeVariables moduleName bindings action =
bindTypes (M.fromList $ flip map bindings $ \(name, k) -> ((moduleName, name), (k, LocalTypeVariable))) action
lookupVariable :: (Functor m, MonadState CheckState m, MonadError String m) => ModuleName -> Qualified Ident -> m Type
lookupVariable currentModule (Qualified moduleName var) = do
env <- getEnv
case M.lookup (fromMaybe currentModule moduleName, var) (names env) of
Nothing -> throwError $ show var ++ " is undefined"
Just (ty, _) -> return ty
lookupTypeVariable :: (Functor m, MonadState CheckState m, MonadError String m) => ModuleName -> Qualified ProperName -> m Kind
lookupTypeVariable currentModule (Qualified moduleName name) = do
env <- getEnv
case M.lookup (fromMaybe currentModule moduleName, name) (types env) of
Nothing -> throwError $ "Type variable " ++ show name ++ " is undefined"
Just (k, _) -> return k
data AnyUnifiable where
AnyUnifiable :: forall t. (Unifiable t) => t -> AnyUnifiable
data CheckState = CheckState { checkEnv :: Environment
, checkNextVar :: Int
}
newtype Check a = Check { unCheck :: StateT CheckState (Either String) a }
deriving (Functor, Monad, Applicative, MonadPlus, MonadState CheckState, MonadError String)
getEnv :: (Functor m, MonadState CheckState m) => m Environment
getEnv = checkEnv <$> get
putEnv :: (MonadState CheckState m) => Environment -> m ()
putEnv env = modify (\s -> s { checkEnv = env })
modifyEnv :: (MonadState CheckState m) => (Environment -> Environment) -> m ()
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) $ 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)
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 SubstContext = SubstContext { substCurrentModule :: ModuleName } deriving (Show)
newtype Subst a = Subst { unSubst :: ReaderT SubstContext (StateT SubstState Check) a }
deriving (Functor, Monad, Applicative, MonadPlus, MonadReader SubstContext)
instance MonadState CheckState Subst where
get = Subst . lift . lift $ get
put = Subst . lift . lift . put
deriving instance MonadError String Subst
liftCheck :: Check a -> Subst a
liftCheck = Subst . lift . lift
runSubst :: (Unifiable a) => SubstContext -> Subst a -> Check (a, Substitution, [AnyUnifiable])
runSubst context subst = do
(a, s) <- flip runStateT (SubstState mempty []) . flip runReaderT context . 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 ()
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 ()
isUnknown :: t -> Maybe (Unknown t)
apply :: Substitution -> t -> t
unknowns :: t -> [Int]
instance (Unifiable a) => Unifiable [a] where
unknown _ = error "not supported"
(~~) = zipWithM_ (~~)
isUnknown _ = error "not supported"
apply s = map (apply s)
unknowns = concatMap unknowns
occursCheck :: (Unifiable t) => Unknown s -> t -> Subst ()
occursCheck (Unknown u) t =
case isUnknown t of
Nothing -> guardWith "Occurs check fails" (u `notElem` unknowns t)
_ -> return ()
fresh' :: Subst Int
fresh' = do
n <- checkNextVar <$> get
modify $ \s -> s { checkNextVar = succ (checkNextVar s) }
return n
fresh :: (Unifiable t) => Subst t
fresh = unknown . Unknown <$> fresh'
escapeCheckLater :: (Unifiable t) => t -> Subst ()
escapeCheckLater t = Subst . modify $ \s -> s { substFutureEscapeChecks = AnyUnifiable t : substFutureEscapeChecks s }