module Language.PureScript.TypeChecker.Types (
typesOf
) where
import Data.List
import Data.Maybe (maybeToList, isNothing, isJust, fromMaybe)
import qualified Data.Data as D
import Data.Generics
(everythingWithContext, mkM, everywhereM, everything, mkT,
something, everywhere, mkQ)
import Data.Generics.Extras
import Language.PureScript.Values
import Language.PureScript.Types
import Language.PureScript.Kinds
import Language.PureScript.Names
import Language.PureScript.TypeChecker.Monad
import Language.PureScript.TypeChecker.Kinds
import Language.PureScript.TypeChecker.Synonyms
import Language.PureScript.Pretty
import Control.Monad.State
import Control.Monad.Error
import Control.Monad.Unify
import Control.Applicative
import Control.Arrow (Arrow(..))
import qualified Data.Map as M
import Data.Function (on)
import Data.Ord (comparing)
instance Partial Type where
unknown = TUnknown
isUnknown (TUnknown u) = Just u
isUnknown _ = Nothing
instance Unifiable Check Type where
(=?=) = unifyTypes
unifyTypes :: Type -> Type -> UnifyT Type Check ()
unifyTypes t1 t2 = rethrow (\e -> "Error unifying type " ++ prettyPrintType t1 ++ " with type " ++ prettyPrintType t2 ++ ":\n" ++ e) $
unifyTypes' t1 t2
where
unifyTypes' (TUnknown u1) (TUnknown u2) | u1 == u2 = return ()
unifyTypes' (TUnknown u) t = u =:= t
unifyTypes' t (TUnknown u) = u =:= t
unifyTypes' (SaturatedTypeSynonym name args) ty = do
ty1 <- introduceSkolemScope <=< expandTypeSynonym name $ args
ty1 `unifyTypes` ty
unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
unifyTypes' (ForAll ident1 ty1 sc1) (ForAll ident2 ty2 sc2) =
case (sc1, sc2) of
(Just sc1', Just sc2') -> do
sko <- newSkolemConstant
let sk1 = skolemize ident1 sko sc1' ty1
let sk2 = skolemize ident2 sko sc2' ty2
sk1 `unifyTypes` sk2
_ -> throwError (prettyPrintType ty1)
unifyTypes' (ForAll ident ty1 (Just sc)) ty2 = do
sko <- newSkolemConstant
let sk = skolemize ident sko sc ty1
sk `unifyTypes` ty2
unifyTypes' ForAll{} _ = throwError "Skolem variable scope is unspecified"
unifyTypes' ty f@ForAll{} = f `unifyTypes` ty
unifyTypes' (Object row1) (Object row2) = row1 =?= row2
unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
unifyTypes' (TypeConstructor c1) (TypeConstructor c2) = do
env <- getEnv
Just moduleName <- checkCurrentModule <$> get
guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (typeConstructorsAreEqual env moduleName c1 c2)
unifyTypes' (TypeApp t3 t4) (TypeApp t5 t6) = do
t3 `unifyTypes` t5
t4 `unifyTypes` t6
unifyTypes' (Skolem s1 _) (Skolem s2 _) | s1 == s2 = return ()
unifyTypes' r1@RCons{} r2 = unifyRows r1 r2
unifyTypes' r1 r2@RCons{} = unifyRows r1 r2
unifyTypes' r1@REmpty r2 = unifyRows r1 r2
unifyTypes' r1 r2@REmpty = unifyRows r1 r2
unifyTypes' t3 t4 = throwError $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
unifyRows :: Type -> Type -> UnifyT Type Check ()
unifyRows r1 r2 =
let
(s1, r1') = rowToList r1
(s2, r2') = rowToList r2
int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
in do
forM_ int (uncurry (=?=))
unifyRows' sd1 r1' sd2 r2'
where
unifyRows' :: [(String, Type)] -> Type -> [(String, Type)] -> Type -> UnifyT Type Check ()
unifyRows' [] (TUnknown u) sd r = u =:= rowFromList (sd, r)
unifyRows' sd r [] (TUnknown u) = u =:= rowFromList (sd, r)
unifyRows' ((name, ty):row) r others u@(TUnknown un) = do
occursCheck un ty
forM_ row $ \(_, t) -> occursCheck un t
u' <- fresh
u =?= RCons name ty u'
unifyRows' row r others u'
unifyRows' [] REmpty [] REmpty = return ()
unifyRows' [] (TypeVar v1) [] (TypeVar v2) | v1 == v2 = return ()
unifyRows' [] (Skolem s1 _) [] (Skolem s2 _) | s1 == s2 = return ()
unifyRows' sd3 r3 sd4 r4 = throwError $ "Cannot unify (" ++ prettyPrintRow (rowFromList (sd3, r3)) ++ ") with (" ++ prettyPrintRow (rowFromList (sd4, r4)) ++ ")."
typeConstructorsAreEqual :: Environment -> ModuleName -> Qualified ProperName -> Qualified ProperName -> Bool
typeConstructorsAreEqual env moduleName = (==) `on` canonicalizeType moduleName env
typesOf :: Maybe ModuleName -> ModuleName -> [(Ident, Value)] -> Check [(Ident, (Value, Type))]
typesOf mainModuleName moduleName vals = do
tys <- fmap tidyUp . liftUnify $ do
let
es = map isTyped vals
typed = filter (isJust . snd . snd) es
untyped = filter (isNothing . snd . snd) es
typedDict = map (\(ident, (_, Just (ty, _))) -> (ident, ty)) typed
untypedNames <- replicateM (length untyped) fresh
let
untypedDict = zip (map fst untyped) untypedNames
dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ typedDict ++ untypedDict)
forM es $ \e@(_, (val, _)) -> do
let dict' = if isFunction val then dict else M.empty
triple@(_, (val', ty)) <- case e of
(ident, (val', Just (ty, checkType))) -> do
kind <- liftCheck $ kindOf moduleName ty
guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
val'' <- bindNames dict' $ if checkType
then TypedValue True <$> check val' ty' <*> pure ty'
else return (TypedValue False val' ty')
return (ident, (val'', ty'))
(ident, (val', Nothing)) -> do
TypedValue _ val'' ty <- bindNames dict' $ infer val'
ty =?= fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
return (ident, (TypedValue True val'' ty, ty))
when (Just moduleName == mainModuleName && fst e == Ident "main") $ do
[eff, a] <- replicateM 2 fresh
ty =?= TypeApp (TypeApp (TypeConstructor (Qualified (Just (ModuleName [ProperName "Control", ProperName "Monad", ProperName "Eff"])) (ProperName "Eff"))) eff) a
escapeCheck val' ty
return triple
forM tys $ \(ident, (val, ty)) -> do
val' <- replaceTypeClassDictionaries moduleName val
skolemEscapeCheck val'
let val'' = overTypes (desaturateAllTypeSynonyms . setifyAll) val'
ty' = varIfUnknown . desaturateAllTypeSynonyms . setifyAll $ ty
return (ident, (val'', ty'))
where
tidyUp (ts, sub) = map (\(i, (val, ty)) -> (i, (overTypes (sub $?) val, sub $? ty))) ts
isFunction :: Value -> Bool
isFunction (Abs _ _) = True
isFunction (TypedValue _ val _) = isFunction val
isFunction _ = False
isTyped :: (Ident, Value) -> (Ident, (Value, Maybe (Type, Bool)))
isTyped (name, TypedValue checkType value ty) = (name, (value, Just (ty, checkType)))
isTyped (name, value) = (name, (value, Nothing))
overTypes :: (Type -> Type) -> Value -> Value
overTypes f = everywhere (mkT f)
replaceTypeClassDictionaries :: ModuleName -> Value -> Check Value
replaceTypeClassDictionaries mn = everywhereM' (mkM go)
where
go (TypeClassDictionary constraint dicts) = entails mn dicts constraint
go other = return other
entails :: ModuleName -> [TypeClassDictionaryInScope] -> (Qualified ProperName, [Type]) -> Check Value
entails moduleName context goal@(className, tys) = do
env <- getEnv
case go env goal of
[] -> throwError $ "No " ++ show className ++ " instance found for " ++ intercalate ", " (map prettyPrintType tys)
(dict : _) -> return dict
where
go env (className', tys') =
[ mkDictionary (canonicalizeDictionary tcd) args
| tcd <- context
, filterModule tcd
, typeConstructorsAreEqual env moduleName className' (tcdClassName tcd)
, subst <- maybeToList . (>>= verifySubstitution) . fmap concat $ zipWithM (typeHeadsAreEqual moduleName env) tys' (tcdInstanceTypes tcd)
, args <- solveSubgoals env subst (tcdDependencies tcd) ]
solveSubgoals :: Environment -> [(String, Type)] -> Maybe [(Qualified ProperName, [Type])] -> [Maybe [Value]]
solveSubgoals _ _ Nothing = return Nothing
solveSubgoals env subst (Just subgoals) = do
dict <- mapM (go env . second (map (replaceAllTypeVars subst))) subgoals
return $ Just dict
mkDictionary :: Qualified Ident -> Maybe [Value] -> Value
mkDictionary fnName Nothing = Var fnName
mkDictionary fnName (Just []) = App (Var fnName) (ObjectLiteral [])
mkDictionary fnName (Just dicts) = foldl App (Var fnName) dicts
filterModule :: TypeClassDictionaryInScope -> Bool
filterModule (TypeClassDictionaryInScope { tcdName = Qualified (Just mn) _ }) | mn == moduleName = True
filterModule (TypeClassDictionaryInScope { tcdName = Qualified Nothing _ }) = True
filterModule _ = False
canonicalizeDictionary :: TypeClassDictionaryInScope -> Qualified Ident
canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDRegular, tcdName = nm }) = nm
canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDAlias nm }) = nm
verifySubstitution :: [(String, Type)] -> Maybe [(String, Type)]
verifySubstitution subst = do
let grps = groupBy ((==) `on` fst) subst
guard (all ((==) 1 . length . nubBy ((==) `on` snd)) grps)
return $ map head grps
typeHeadsAreEqual :: ModuleName -> Environment -> Type -> Type -> Maybe [(String, Type)]
typeHeadsAreEqual _ _ (Skolem s1 _) (Skolem s2 _) | s1 == s2 = Just []
typeHeadsAreEqual _ _ (TypeVar v) t = Just [(v, t)]
typeHeadsAreEqual _ _ t (TypeVar v) = Just [(v, t)]
typeHeadsAreEqual m e (TypeConstructor c1) (TypeConstructor c2) | typeConstructorsAreEqual e m c1 c2 = Just []
typeHeadsAreEqual m e (TypeApp h1 (TypeVar v)) (TypeApp h2 arg) = (:) (v, arg) <$> typeHeadsAreEqual m e h1 h2
typeHeadsAreEqual m e t1@(TypeApp _ _) t2@(TypeApp _ (TypeVar _)) = typeHeadsAreEqual m e t2 t1
typeHeadsAreEqual m e (SaturatedTypeSynonym name args) t2 = case expandTypeSynonym' e m name args of
Left _ -> Nothing
Right t1 -> typeHeadsAreEqual m e t1 t2
typeHeadsAreEqual _ _ _ _ = Nothing
escapeCheck :: Value -> Type -> UnifyT Type Check ()
escapeCheck value ty = do
subst <- unifyCurrentSubstitution <$> UnifyT get
let visibleUnknowns = nub $ unknowns $ subst $? ty
let allUnknowns = findAllTypes value
forM_ allUnknowns $ \t -> do
let unsolvedUnknowns = nub . unknowns $ subst $? t
guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
findAllTypes :: Value -> [Type]
findAllTypes = everything (++) (mkQ [] go)
where
go (TypedValue _ _ ty) = [ty]
go _ = []
skolemEscapeCheck :: Value -> Check ()
skolemEscapeCheck (TypedValue False _ _) = return ()
skolemEscapeCheck root@TypedValue{} =
case everythingWithContext [] (++) (mkQ ((,) []) go) root of
[] -> return ()
((binding, val) : _) -> throwError $ "Rigid/skolem type variable bound by " ++ maybe "<unknown>" prettyPrintValue binding ++ " has escaped at " ++ prettyPrintValue val
where
go :: Value -> [(SkolemScope, Value)] -> ([(Maybe Value, Value)], [(SkolemScope, Value)])
go val@(TypedValue _ _ (ForAll _ _ (Just sco))) scos = ([], (sco, val) : scos)
go val@(TypedValue _ _ ty) scos = case collectSkolems ty \\ map fst scos of
(sco : _) -> ([(findBindingScope sco, val)], scos)
_ -> ([], scos)
where
collectSkolems :: Type -> [SkolemScope]
collectSkolems = nub . everything (++) (mkQ [] collect)
where
collect (Skolem _ scope) = [scope]
collect _ = []
go _ scos = ([], scos)
findBindingScope :: SkolemScope -> Maybe Value
findBindingScope sco = something (mkQ Nothing go') root
where
go' val@(TypedValue _ _ (ForAll _ _ (Just sco'))) | sco == sco' = Just val
go' _ = Nothing
skolemEscapeCheck val = throwError $ "Untyped value passed to skolemEscapeCheck: " ++ prettyPrintValue val
setify :: Type -> Type
setify = rowFromList . first (M.toList . M.fromList) . rowToList
setifyAll :: (D.Data d) => d -> d
setifyAll = everywhere (mkT setify)
varIfUnknown :: Type -> Type
varIfUnknown ty =
let unks = nub $ unknowns ty
toName = (:) 't' . show
ty' = everywhere (mkT typeToVar) ty
typeToVar :: Type -> Type
typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
typeToVar t = t
in mkForAll (sort . map (toName . runUnknown) $ unks) ty'
instantiatePolyTypeWithUnknowns :: Value -> Type -> UnifyT Type Check (Value, Type)
instantiatePolyTypeWithUnknowns val (ForAll ident ty _) = do
ty' <- replaceVarWithUnknown ident ty
instantiatePolyTypeWithUnknowns val ty'
instantiatePolyTypeWithUnknowns val (ConstrainedType constraints ty) = do
env <- getEnv
Just moduleName <- checkCurrentModule <$> get
dicts <- getTypeClassDictionaries
(_, ty') <- instantiatePolyTypeWithUnknowns (error "Types under a constraint cannot themselves be constrained") ty
return (foldl App val (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints)), ty')
instantiatePolyTypeWithUnknowns val ty = return (val, ty)
replaceVarWithUnknown :: String -> Type -> UnifyT Type Check Type
replaceVarWithUnknown ident ty = do
tu <- fresh
return $ replaceTypeVars ident tu ty
replaceAllTypeSynonyms' :: (D.Data d) => Environment -> ModuleName -> d -> Either String d
replaceAllTypeSynonyms' env moduleName d =
let
syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
in
saturateAllTypeSynonyms env moduleName syns d
replaceAllTypeSynonyms :: (Functor m, Monad m, MonadState CheckState m, MonadError String m) => (D.Data d) => d -> m d
replaceAllTypeSynonyms d = do
env <- getEnv
Just moduleName <- checkCurrentModule <$> get
either throwError return $ replaceAllTypeSynonyms' env moduleName d
desaturateAllTypeSynonyms :: (D.Data d) => d -> d
desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
where
replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
replaceSaturatedTypeSynonym t = t
expandTypeSynonym' :: Environment -> ModuleName -> Qualified ProperName -> [Type] -> Either String Type
expandTypeSynonym' env moduleName name args =
case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
Just (synArgs, body) -> do
let repl = replaceAllTypeVars (zip synArgs args) body
replaceAllTypeSynonyms' env moduleName repl
Nothing -> error "Type synonym was not defined"
expandTypeSynonym :: (Functor m, Monad m, MonadState CheckState m, MonadError String m) => Qualified ProperName -> [Type] -> m Type
expandTypeSynonym name args = do
env <- getEnv
Just moduleName <- checkCurrentModule <$> get
either throwError return $ expandTypeSynonym' env moduleName name args
ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
infer :: Value -> UnifyT Type Check Value
infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ infer' val
infer' :: Value -> UnifyT Type Check Value
infer' v@(NumericLiteral _) = return $ TypedValue True v tyNumber
infer' v@(StringLiteral _) = return $ TypedValue True v tyString
infer' v@(BooleanLiteral _) = return $ TypedValue True v tyBoolean
infer' (ArrayLiteral vals) = do
ts <- mapM infer vals
els <- fresh
forM_ ts $ \(TypedValue _ _ t) -> els =?= TypeApp tyArray t
return $ TypedValue True (ArrayLiteral ts) els
infer' (ObjectLiteral ps) = do
ensureNoDuplicateProperties ps
ts <- mapM (infer . snd) ps
let fields = zipWith (\name (TypedValue _ _ t) -> (name, t)) (map fst ps) ts
ty = Object $ rowFromList (fields, REmpty)
return $ TypedValue True (ObjectLiteral (zip (map fst ps) ts)) ty
infer' (ObjectUpdate o ps) = do
ensureNoDuplicateProperties ps
row <- fresh
newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
let newTys = map (\(name, TypedValue _ _ ty) -> (name, ty)) newVals
oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
let oldTy = Object $ rowFromList (oldTys, row)
o' <- TypedValue True <$> check o oldTy <*> pure oldTy
return $ TypedValue True (ObjectUpdate o' newVals) $ Object $ rowFromList (newTys, row)
infer' (Accessor prop val) = do
typed@(TypedValue _ _ objTy) <- infer val
propTy <- inferProperty objTy prop
case propTy of
Nothing -> do
field <- fresh
rest <- fresh
_ <- subsumes Nothing objTy (Object (RCons prop field rest))
return $ TypedValue True (Accessor prop typed) field
Just ty -> return $ TypedValue True (Accessor prop typed) ty
infer' (Abs (Left arg) ret) = do
ty <- fresh
Just moduleName <- checkCurrentModule <$> get
bindLocalVariables moduleName [(arg, ty)] $ do
body@(TypedValue _ _ bodyTy) <- infer' ret
return $ TypedValue True (Abs (Left arg) body) $ function ty bodyTy
infer' (Abs (Right _) _) = error "Binder was not desugared"
infer' (App f arg) = do
f'@(TypedValue _ _ ft) <- infer f
(ret, app) <- checkFunctionApplication f' ft arg
return $ TypedValue True app ret
infer' (Var var) = do
Just moduleName <- checkCurrentModule <$> get
ty <- introduceSkolemScope <=< replaceAllTypeSynonyms <=< lookupVariable moduleName $ var
case ty of
ConstrainedType constraints ty' -> do
env <- getEnv
dicts <- getTypeClassDictionaries
return $ TypedValue True (foldl App (Var var) (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) ty'
_ -> return $ TypedValue True (Var var) ty
infer' v@(Constructor c) = do
env <- getEnv
Just moduleName <- checkCurrentModule <$> get
case M.lookup (qualify moduleName c) (dataConstructors env) of
Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
Just (ty, _) -> do ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
return $ TypedValue True v ty'
infer' (Case vals binders) = do
ts <- mapM infer vals
ret <- fresh
binders' <- checkBinders (map (\(TypedValue _ _ t) -> t) ts) ret binders
return $ TypedValue True (Case ts binders') ret
infer' (IfThenElse cond th el) = do
cond' <- check cond tyBoolean
v2@(TypedValue _ _ t2) <- infer th
v3@(TypedValue _ _ t3) <- infer el
t2 =?= t3
return $ TypedValue True (IfThenElse cond' v2 v3) t2
infer' (TypedValue checkType val ty) = do
Just moduleName <- checkCurrentModule <$> get
kind <- liftCheck $ kindOf moduleName ty
guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
val' <- if checkType then check val ty' else return val
return $ TypedValue True val' ty'
infer' _ = error "Invalid argument to infer"
inferProperty :: Type -> String -> UnifyT Type Check (Maybe Type)
inferProperty (Object row) prop = do
let (props, _) = rowToList row
return $ lookup prop props
inferProperty (SaturatedTypeSynonym name args) prop = do
replaced <- introduceSkolemScope <=< expandTypeSynonym name $ args
inferProperty replaced prop
inferProperty (ForAll ident ty _) prop = do
replaced <- replaceVarWithUnknown ident ty
inferProperty replaced prop
inferProperty _ _ = return Nothing
inferBinder :: Type -> Binder -> UnifyT Type Check (M.Map Ident Type)
inferBinder _ NullBinder = return M.empty
inferBinder val (StringBinder _) = val =?= tyString >> return M.empty
inferBinder val (NumberBinder _) = val =?= tyNumber >> return M.empty
inferBinder val (BooleanBinder _) = val =?= tyBoolean >> return M.empty
inferBinder val (VarBinder name) = return $ M.singleton name val
inferBinder val (ConstructorBinder ctor binders) = do
env <- getEnv
Just moduleName <- checkCurrentModule <$> get
case M.lookup (qualify moduleName ctor) (dataConstructors env) of
Just (ty, _) -> do
(_, fn) <- instantiatePolyTypeWithUnknowns (error "Data constructor types cannot contains constraints") ty
go binders fn
where
go [] ty' = do
subsumes Nothing val ty'
return M.empty
go (binder : binders') (TypeApp (TypeApp t obj) ret) | t == tyFunction =
M.union <$> inferBinder obj binder <*> go binders' ret
go _ _ = throwError $ "Wrong number of arguments to constructor " ++ show ctor
_ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
inferBinder val (ObjectBinder props) = do
row <- fresh
rest <- fresh
m1 <- inferRowProperties row rest props
val =?= Object row
return m1
where
inferRowProperties :: Type -> Type -> [(String, Binder)] -> UnifyT Type Check (M.Map Ident Type)
inferRowProperties nrow row [] = nrow =?= row >> return M.empty
inferRowProperties nrow row ((name, binder):binders) = do
propTy <- fresh
m1 <- inferBinder propTy binder
m2 <- inferRowProperties nrow (RCons name propTy row) binders
return $ m1 `M.union` m2
inferBinder val (ArrayBinder binders) = do
el <- fresh
m1 <- M.unions <$> mapM (inferBinder el) binders
val =?= TypeApp tyArray el
return m1
inferBinder val (ConsBinder headBinder tailBinder) = do
el <- fresh
m1 <- inferBinder el headBinder
m2 <- inferBinder val tailBinder
val =?= TypeApp tyArray el
return $ m1 `M.union` m2
inferBinder val (NamedBinder name binder) = do
m <- inferBinder val binder
return $ M.insert name val m
checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> UnifyT Type Check [([Binder], Maybe Guard, Value)]
checkBinders _ _ [] = return []
checkBinders nvals ret ((binders, grd, val):bs) = do
Just moduleName <- checkCurrentModule <$> get
m1 <- M.unions <$> zipWithM inferBinder nvals binders
r <- bindLocalVariables moduleName (M.toList m1) $ do
val' <- TypedValue True <$> check val ret <*> pure ret
case grd of
Nothing -> return (binders, Nothing, val')
Just g -> do
g' <- check g tyBoolean
return (binders, Just g', val')
rs <- checkBinders nvals ret bs
return $ r : rs
assignVariable :: Ident -> UnifyT Type Check ()
assignVariable name = do
env <- checkEnv <$> get
Just moduleName <- checkCurrentModule <$> get
case M.lookup (moduleName, name) (names env) of
Just _ -> UnifyT . lift . throwError $ "Variable with name " ++ show name ++ " already exists."
_ -> return ()
newSkolemConstant :: UnifyT Type Check Int
newSkolemConstant = runUnknown <$> fresh'
newSkolemScope :: UnifyT Type Check SkolemScope
newSkolemScope = SkolemScope . runUnknown <$> fresh'
skolemize :: String -> Int -> SkolemScope -> Type -> Type
skolemize ident sko scope = replaceTypeVars ident (Skolem sko scope)
introduceSkolemScope :: Type -> UnifyT Type Check Type
introduceSkolemScope = everywhereM (mkM go)
where
go (ForAll ident ty Nothing) = ForAll ident ty <$> (Just <$> newSkolemScope)
go other = return other
check :: Value -> Type -> UnifyT Type Check Value
check val ty = rethrow errorMessage $ check' val ty
where
errorMessage msg =
"Error checking type of term " ++
prettyPrintValue val ++
" against type " ++
prettyPrintType ty ++
":\n" ++
msg
check' :: Value -> Type -> UnifyT Type Check Value
check' val (ForAll ident ty _) = do
scope <- newSkolemScope
sko <- newSkolemConstant
let sk = skolemize ident sko scope ty
val' <- check val sk
return $ TypedValue True val' (ForAll ident ty (Just scope))
check' val t@(ConstrainedType constraints ty) = do
env <- getEnv
Just moduleName <- checkCurrentModule <$> get
dictNames <- forM constraints $ \(Qualified _ (ProperName className), _) -> do
n <- liftCheck freshDictionaryName
return $ Ident $ "__dict_" ++ className ++ "_" ++ show n
val' <- withTypeClassDictionaries (zipWith (\name (className, instanceTy) ->
TypeClassDictionaryInScope name className instanceTy Nothing TCDRegular) (map (Qualified Nothing) dictNames)
(qualifyAllUnqualifiedNames moduleName env constraints)) $
check val ty
return $ TypedValue True (foldr (Abs . Left) val' dictNames) t
check' val (SaturatedTypeSynonym name args) = do
ty <- introduceSkolemScope <=< expandTypeSynonym name $ args
val' <- check val ty
return $ TypedValue True val' ty
check' val u@(TUnknown _) = do
val'@(TypedValue _ _ ty) <- infer val
(val'', ty') <- instantiatePolyTypeWithUnknowns val' ty
ty' =?= u
return $ TypedValue True val'' ty'
check' v@(NumericLiteral _) t | t == tyNumber =
return $ TypedValue True v t
check' v@(StringLiteral _) t | t == tyString =
return $ TypedValue True v t
check' v@(BooleanLiteral _) t | t == tyBoolean =
return $ TypedValue True v t
check' (ArrayLiteral vals) t@(TypeApp a ty) | a == tyArray = do
array <- ArrayLiteral <$> forM vals (`check` ty)
return $ TypedValue True array t
check' (Abs (Left arg) ret) ty@(TypeApp (TypeApp t argTy) retTy) | t == tyFunction = do
Just moduleName <- checkCurrentModule <$> get
ret' <- bindLocalVariables moduleName [(arg, argTy)] $ check ret retTy
return $ TypedValue True (Abs (Left arg) ret') ty
check' (Abs (Right _) _) _ = error "Binder was not desugared"
check' (App f arg) ret = do
f'@(TypedValue _ _ ft) <- infer f
(ret', app) <- checkFunctionApplication f' ft arg
subsumes Nothing ret' ret
return $ TypedValue True app ret
check' v@(Var var) ty = do
Just moduleName <- checkCurrentModule <$> get
repl <- introduceSkolemScope <=< replaceAllTypeSynonyms <=< lookupVariable moduleName $ var
ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
v' <- subsumes (Just v) repl ty'
case v' of
Nothing -> throwError "Unable to check type subsumption"
Just v'' -> return $ TypedValue True v'' ty'
check' (TypedValue checkType val ty1) ty2 = do
Just moduleName <- checkCurrentModule <$> get
kind <- liftCheck $ kindOf moduleName ty1
guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
ty1' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty1
val' <- subsumes (Just val) ty1' ty2
case val' of
Nothing -> throwError "Unable to check type subsumption"
Just val'' -> do
val''' <- if checkType then check val'' ty1 else return val''
return $ TypedValue checkType (TypedValue True val''' ty1) ty2
check' (Case vals binders) ret = do
vals' <- mapM infer vals
let ts = map (\(TypedValue _ _ t) -> t) vals'
binders' <- checkBinders ts ret binders
return $ TypedValue True (Case vals' binders') ret
check' (IfThenElse cond th el) ty = do
cond' <- check cond tyBoolean
th' <- check th ty
el' <- check el ty
return $ TypedValue True (IfThenElse cond' th' el') ty
check' (ObjectLiteral ps) t@(Object row) = do
ensureNoDuplicateProperties ps
ps' <- checkProperties ps row False
return $ TypedValue True (ObjectLiteral ps') t
check' (ObjectUpdate obj ps) t@(Object row) = do
ensureNoDuplicateProperties ps
us <- zip (map fst ps) <$> replicateM (length ps) fresh
let (propsToCheck, rest) = rowToList row
propsToRemove = map fst ps
remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
obj' <- check obj (Object (rowFromList (us ++ remainingProps, rest)))
ps' <- checkProperties ps row True
return $ TypedValue True (ObjectUpdate obj' ps') t
check' (Accessor prop val) ty = do
rest <- fresh
val' <- check val (Object (RCons prop ty rest))
return $ TypedValue True (Accessor prop val') ty
check' (Constructor c) ty = do
env <- getEnv
Just moduleName <- checkCurrentModule <$> get
case M.lookup (qualify moduleName c) (dataConstructors env) of
Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
Just (ty1, _) -> do
repl <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty1
_ <- subsumes Nothing repl ty
return $ TypedValue True (Constructor c) ty
check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
checkProperties :: [(String, Value)] -> Type -> Bool -> UnifyT Type Check [(String, Value)]
checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
go [] [] REmpty = return []
go [] [] u@(TUnknown _) = do u =?= REmpty
return []
go [] [] (Skolem _ _) | lax = return []
go [] ((p, _): _) _ | lax = return []
| otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
go ((p,v):ps') [] u@(TUnknown _) = do
v'@(TypedValue _ _ ty) <- infer v
rest <- fresh
u =?= RCons p ty rest
ps'' <- go ps' [] rest
return $ (p, v') : ps''
go ((p,v):ps') ts r =
case lookup p ts of
Nothing -> do
v'@(TypedValue _ _ ty) <- infer v
rest <- fresh
r =?= RCons p ty rest
ps'' <- go ps' ts rest
return $ (p, v') : ps''
Just ty -> do
v' <- check v ty
ps'' <- go ps' (delete (p, ty) ts) r
return $ (p, v') : ps''
go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
checkFunctionApplication :: Value -> Type -> Value -> UnifyT Type Check (Type, Value)
checkFunctionApplication fn fnTy arg = rethrow errorMessage $ checkFunctionApplication' fn fnTy arg
where
errorMessage msg = "Error applying function of type "
++ prettyPrintType fnTy
++ " to argument " ++ prettyPrintValue arg
++ ":\n" ++ msg
checkFunctionApplication' :: Value -> Type -> Value -> UnifyT Type Check (Type, Value)
checkFunctionApplication' fn (TypeApp (TypeApp tyFunction' argTy) retTy) arg = do
tyFunction' =?= tyFunction
arg' <- check arg argTy
return (retTy, App fn arg')
checkFunctionApplication' fn (ForAll ident ty _) arg = do
replaced <- replaceVarWithUnknown ident ty
checkFunctionApplication fn replaced arg
checkFunctionApplication' fn u@(TUnknown _) arg = do
arg' <- do
TypedValue _ arg' t <- infer arg
(arg'', t') <- instantiatePolyTypeWithUnknowns arg' t
return $ TypedValue True arg'' t'
let ty = (\(TypedValue _ _ t) -> t) arg'
ret <- fresh
u =?= function ty ret
return (ret, App fn arg')
checkFunctionApplication' fn (SaturatedTypeSynonym name tyArgs) arg = do
ty <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
checkFunctionApplication fn ty arg
checkFunctionApplication' fn (ConstrainedType constraints fnTy) arg = do
env <- getEnv
dicts <- getTypeClassDictionaries
Just moduleName <- checkCurrentModule <$> get
checkFunctionApplication' (foldl App fn (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) fnTy arg
checkFunctionApplication' _ fnTy arg = throwError $ "Cannot apply a function of type "
++ prettyPrintType fnTy
++ " to argument " ++ prettyPrintValue arg
subsumes :: Maybe Value -> Type -> Type -> UnifyT Type Check (Maybe Value)
subsumes val ty1 ty2 = rethrow errorMessage $ subsumes' val ty1 ty2
where
errorMessage msg = "Error checking that type "
++ prettyPrintType ty1
++ " subsumes type "
++ prettyPrintType ty2
++ ":\n" ++ msg
subsumes' :: Maybe Value -> Type -> Type -> UnifyT Type Check (Maybe Value)
subsumes' val (ForAll ident ty1 _) ty2 = do
replaced <- replaceVarWithUnknown ident ty1
subsumes val replaced ty2
subsumes' val ty1 (ForAll ident ty2 sco) =
case sco of
Just sco' -> do
sko <- newSkolemConstant
let sk = skolemize ident sko sco' ty2
subsumes val ty1 sk
Nothing -> throwError "Skolem variable scope is unspecified"
subsumes' val (TypeApp (TypeApp f1 arg1) ret1) (TypeApp (TypeApp f2 arg2) ret2) | f1 == tyFunction && f2 == tyFunction = do
subsumes Nothing arg2 arg1
subsumes Nothing ret1 ret2
return val
subsumes' val (SaturatedTypeSynonym name tyArgs) ty2 = do
ty1 <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
subsumes val ty1 ty2
subsumes' val ty1 (SaturatedTypeSynonym name tyArgs) = do
ty2 <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
subsumes val ty1 ty2
subsumes' (Just val) (ConstrainedType constraints ty1) ty2 = do
env <- getEnv
dicts <- getTypeClassDictionaries
Just moduleName <- checkCurrentModule <$> get
_ <- subsumes' Nothing ty1 ty2
return . Just $ foldl App val (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))
subsumes' val (Object r1) (Object r2) = do
let
(ts1, r1') = rowToList r1
(ts2, r2') = rowToList r2
ts1' = sortBy (comparing fst) ts1
ts2' = sortBy (comparing fst) ts2
go ts1' ts2' r1' r2'
return val
where
go [] ts2 r1' r2' = r1' =?= rowFromList (ts2, r2')
go ts1 [] r1' r2' = r2' =?= rowFromList (ts1, r1')
go ((p1, ty1) : ts1) ((p2, ty2) : ts2) r1' r2'
| p1 == p2 = do subsumes Nothing ty1 ty2
go ts1 ts2 r1' r2'
| p1 < p2 = do rest <- fresh
r2' =?= RCons p1 ty1 rest
go ts1 ((p2, ty2) : ts2) r1' rest
| p1 > p2 = do rest <- fresh
r1' =?= RCons p2 ty2 rest
go ((p1, ty1) : ts1) ts2 rest r2'
subsumes' val ty1 ty2@(Object _) = subsumes val ty2 ty1
subsumes' val ty1 ty2 = do
ty1 =?= ty2
return val