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1+-----------------------------------------------------------------------------
2+--
3+-- Module : Language.PureScript.TypeChecker.Types
4+-- Copyright : (c) Phil Freeman 2013
5+-- License : MIT
6+--
7+-- Maintainer : Phil Freeman <paf31@cantab.net>
8+-- Stability : experimental
9+-- Portability :
10+--
11+-- |
12+--
13+-----------------------------------------------------------------------------
14+
15+{-# LANGUAGE DeriveDataTypeable #-}
16+
17+module Language.PureScript.TypeChecker.Types (
18+ typeOf
19+) where
20+
21+import Data.List
22+import Data.Maybe (isJust, fromMaybe)
23+import Data.Function
24+import qualified Data.Data as D
25+import Data.Generics (everywhere, everywhereM, everything, mkT, mkM, mkQ, extM, extQ)
26+
27+import Language.PureScript.Values
28+import Language.PureScript.Types
29+import Language.PureScript.Kinds
30+import Language.PureScript.Names
31+import Language.PureScript.TypeChecker.Monad
32+import Language.PureScript.TypeChecker.Kinds
33+import Language.PureScript.TypeChecker.Synonyms
34+import Language.PureScript.Pretty
35+import Language.PureScript.Unknown
36+
37+import Control.Monad.State
38+import Control.Monad.Error
39+
40+import Control.Applicative
41+import Control.Arrow (Arrow(..), Kleisli(..), (***), (&&&), second)
42+import qualified Control.Category as C
43+
44+import qualified Data.Map as M
45+
46+instance Unifiable Type where
47+ unknown = TUnknown
48+ isUnknown (TUnknown u) = Just u
49+ isUnknown _ = Nothing
50+ (~~) = unifyTypes
51+ apply s (TUnknown u) = runSubstitution s u
52+ apply s (SaturatedTypeSynonym name tys) = SaturatedTypeSynonym name $ map (apply s) tys
53+ apply s (ForAll idents ty) = ForAll idents $ apply s ty
54+ apply s (Array t) = Array (apply s t)
55+ apply s (Object r) = Object (apply s r)
56+ apply s (Function args ret) = Function (map (apply s) args) (apply s ret)
57+ apply s (TypeApp t1 t2) = TypeApp (apply s t1) (apply s t2)
58+ apply _ t = t
59+ unknowns (TUnknown (Unknown u)) = [u]
60+ unknowns (SaturatedTypeSynonym _ tys) = concatMap unknowns tys
61+ unknowns (ForAll idents ty) = unknowns ty
62+ unknowns (Array t) = unknowns t
63+ unknowns (Object r) = unknowns r
64+ unknowns (Function args ret) = concatMap unknowns args ++ unknowns ret
65+ unknowns (TypeApp t1 t2) = unknowns t1 ++ unknowns t2
66+ unknowns _ = []
67+
68+instance Unifiable Row where
69+ unknown = RUnknown
70+ isUnknown (RUnknown u) = Just u
71+ isUnknown _ = Nothing
72+ r1 ~~ r2 =
73+ let
74+ (s1, r1') = rowToList r1
75+ (s2, r2') = rowToList r2
76+ int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
77+ sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
78+ sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
79+ in do
80+ forM_ int (uncurry (~~))
81+ unifyRows sd1 r1' sd2 r2'
82+ where
83+ unifyRows :: [(String, Type)] -> Row -> [(String, Type)] -> Row -> Subst Check ()
84+ unifyRows [] (RUnknown u) sd r = replace u (rowFromList (sd, r))
85+ unifyRows sd r [] (RUnknown u) = replace u (rowFromList (sd, r))
86+ unifyRows ns@((name, ty):row) r others u@(RUnknown un) = do
87+ occursCheck un ty
88+ forM row $ \(_, ty) -> occursCheck un ty
89+ u' <- fresh
90+ u ~~ RCons name ty u'
91+ unifyRows row r others u'
92+ unifyRows [] REmpty [] REmpty = return ()
93+ unifyRows [] (RowVar v1) [] (RowVar v2) | v1 == v2 = return ()
94+ unifyRows [] (RSkolem s1) [] (RSkolem s2) | s1 == s2 = return ()
95+ unifyRows sd1 r1 sd2 r2 = throwError $ "Cannot unify " ++ prettyPrintRow (rowFromList (sd1, r1)) ++ " with " ++ prettyPrintRow (rowFromList (sd2, r2)) ++ "."
96+ apply s (RUnknown u) = runSubstitution s u
97+ apply s (RCons name ty r) = RCons name (apply s ty) (apply s r)
98+ apply _ r = r
99+ unknowns (RUnknown (Unknown u)) = [u]
100+ unknowns (RCons _ ty r) = unknowns ty ++ unknowns r
101+ unknowns _ = []
102+
103+unifyTypes :: Type -> Type -> Subst Check ()
104+unifyTypes t1 t2 = rethrow (\e -> "Error unifying type " ++ prettyPrintType t1 ++ " with type " ++ prettyPrintType t2 ++ ":\n" ++ e) $ do
105+ unifyTypes' t1 t2
106+ where
107+ unifyTypes' (TUnknown u1) (TUnknown u2) | u1 == u2 = return ()
108+ unifyTypes' (TUnknown u) t = replace u t
109+ unifyTypes' t (TUnknown u) = replace u t
110+ unifyTypes' (SaturatedTypeSynonym name1 args1) (SaturatedTypeSynonym name2 args2)
111+ | name1 == name2 = zipWithM_ unifyTypes args1 args2
112+ unifyTypes' (SaturatedTypeSynonym name args) ty = do
113+ env <- lift getEnv
114+ modulePath <- checkModulePath `fmap` lift get
115+ case M.lookup (qualify modulePath name) (typeSynonyms env) of
116+ Just (synArgs, body) -> do
117+ let m = M.fromList $ zip synArgs args
118+ let replaced = replaceTypeVars m body
119+ replaced `unifyTypes` ty
120+ Nothing -> error "Type synonym was not defined"
121+ unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
122+ unifyTypes' (ForAll ident1 ty1) (ForAll ident2 ty2) = do
123+ sk <- skolemize ident1 ty1
124+ replaced <- replaceVarsWithUnknowns [ident2] ty2
125+ sk `unifyTypes` replaced
126+ unifyTypes' (ForAll ident ty1) ty2 = do
127+ sk <- skolemize ident ty1
128+ sk `unifyTypes` ty2
129+ unifyTypes' ty f@(ForAll _ _) = f `unifyTypes` ty
130+ unifyTypes' Number Number = return ()
131+ unifyTypes' String String = return ()
132+ unifyTypes' Boolean Boolean = return ()
133+ unifyTypes' (Array s) (Array t) = s `unifyTypes` t
134+ unifyTypes' (Object row1) (Object row2) = row1 ~~ row2
135+ unifyTypes' (Function args1 ret1) (Function args2 ret2) = do
136+ guardWith "Function applied to incorrect number of args" $ length args1 == length args2
137+ zipWithM_ unifyTypes args1 args2
138+ ret1 `unifyTypes` ret2
139+ unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
140+ unifyTypes' (TypeConstructor c1) (TypeConstructor c2) = do
141+ modulePath <- checkModulePath `fmap` lift get
142+ guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (qualify modulePath c1 == qualify modulePath c2)
143+ unifyTypes' (TypeApp t1 t2) (TypeApp t3 t4) = do
144+ t1 `unifyTypes` t3
145+ t2 `unifyTypes` t4
146+ unifyTypes' (Skolem s1) (Skolem s2) | s1 == s2 = return ()
147+ unifyTypes' t1 t2 = throwError $ "Cannot unify " ++ prettyPrintType t1 ++ " with " ++ prettyPrintType t2 ++ "."
148+
149+isFunction :: Value -> Bool
150+isFunction (Abs _ _) = True
151+isFunction (TypedValue untyped _) = isFunction untyped
152+isFunction _ = False
153+
154+typeOf :: Maybe Ident -> Value -> Check Type
155+typeOf name val = do
156+ (ty, sub, checks) <- runSubst $ case name of
157+ Just ident | isFunction val ->
158+ case val of
159+ TypedValue val ty -> do
160+ kind <- lift $ kindOf ty
161+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
162+ ty' <- lift $ replaceAllTypeSynonyms ty
163+ check (M.singleton ident ty) val ty'
164+ return ty'
165+ _ -> do
166+ me <- fresh
167+ ty <- infer (M.singleton ident me) val
168+ ty ~~ me
169+ return ty
170+ _ -> infer M.empty val
171+ escapeCheck checks ty sub
172+ return $ varIfUnknown $ desaturateAllTypeSynonyms $ setifyAll ty
173+
174+escapeCheck :: [AnyUnifiable] -> Type -> Substitution -> Check ()
175+escapeCheck checks ty sub =
176+ let
177+ visibleUnknowns = nub $ unknowns ty
178+ in
179+ forM_ checks $ \check -> case check of
180+ AnyUnifiable t -> do
181+ let unsolvedUnknowns = nub . unknowns $ apply sub t
182+ guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
183+
184+setify :: Row -> Row
185+setify = rowFromList . first (M.toList . M.fromList) . rowToList
186+
187+setifyAll :: (D.Data d) => d -> d
188+setifyAll = everywhere (mkT setify)
189+
190+varIfUnknown :: Type -> Type
191+varIfUnknown ty = mkForAll (sort . map ((:) 'u' . show) . nub $ unknowns ty) ty
192+
193+replaceTypeVars :: M.Map String Type -> Type -> Type
194+replaceTypeVars m = everywhere (mkT replace)
195+ where
196+ replace (TypeVar v) = case M.lookup v m of
197+ Just ty -> ty
198+ _ -> TypeVar v
199+ replace t = t
200+
201+replaceRowVars :: M.Map String Row -> Type -> Type
202+replaceRowVars m = everywhere (mkT replace)
203+ where
204+ replace (RowVar v) = case M.lookup v m of
205+ Just r -> r
206+ _ -> RowVar v
207+ replace t = t
208+
209+replaceAllVarsWithUnknowns :: Type -> Subst Check Type
210+replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarsWithUnknowns [ident] ty >>= replaceAllVarsWithUnknowns
211+replaceAllVarsWithUnknowns ty = return ty
212+
213+replaceVarsWithUnknowns :: [String] -> Type -> Subst Check Type
214+replaceVarsWithUnknowns idents = flip evalStateT M.empty . everywhereM (flip extM f $ mkM g)
215+ where
216+ f :: Type -> StateT (M.Map String Int) (Subst Check) Type
217+ f (TypeVar var) | var `elem` idents = do
218+ m <- get
219+ n <- lift fresh'
220+ case M.lookup var m of
221+ Nothing -> do
222+ put (M.insert var n m)
223+ return $ TUnknown (Unknown n)
224+ Just u -> return $ TUnknown (Unknown u)
225+ f t = return t
226+ g :: Row -> StateT (M.Map String Int) (Subst Check) Row
227+ g (RowVar var) | var `elem` idents = do
228+ m <- get
229+ n <- lift fresh'
230+ case M.lookup var m of
231+ Nothing -> do
232+ put (M.insert var n m)
233+ return $ RUnknown (Unknown n)
234+ Just u -> return $ RUnknown (Unknown u)
235+ g r = return r
236+
237+replaceAllTypeSynonyms :: (D.Data d) => d -> Check d
238+replaceAllTypeSynonyms d = do
239+ env <- getEnv
240+ let syns = map (\((path, name), (args, _)) -> (Qualified path name, length args)) . M.toList $ typeSynonyms env
241+ either throwError return $ saturateAllTypeSynonyms syns d
242+
243+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
244+desaturateAllTypeSynonyms = everywhere (mkT replace)
245+ where
246+ replace (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
247+ replace t = t
248+
249+ensureNoDuplicateProperties :: [(String, Value)] -> Check ()
250+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
251+
252+infer :: M.Map Ident Type -> Value -> Subst Check Type
253+infer m val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ do
254+ ty <- infer' m val
255+ escapeCheckLater ty
256+ return ty
257+
258+infer' _ (NumericLiteral _) = return Number
259+infer' _ (StringLiteral _) = return String
260+infer' _ (BooleanLiteral _) = return Boolean
261+infer' m (ArrayLiteral vals) = do
262+ ts <- mapM (infer m) vals
263+ arr <- fresh
264+ forM_ ts $ \t -> arr ~~ Array t
265+ return arr
266+infer' m (Unary op val) = do
267+ t <- infer m val
268+ inferUnary op t
269+infer' m (Binary op left right) = do
270+ t1 <- infer m left
271+ t2 <- infer m right
272+ inferBinary op t1 t2
273+infer' m (ObjectLiteral ps) = do
274+ lift $ ensureNoDuplicateProperties ps
275+ ts <- mapM (infer m . snd) ps
276+ let fields = zipWith (\(name, _) t -> (name, t)) ps ts
277+ return $ Object $ typesToRow fields
278+infer' m (ObjectUpdate o ps) = do
279+ lift $ ensureNoDuplicateProperties ps
280+ obj <- infer m o
281+ row <- fresh
282+ ts <- mapM (infer m . snd) ps
283+ let tys = zipWith (\(name, _) t -> (name, t)) ps ts
284+ obj ~~ Object (rowFromList (tys, row))
285+ return obj
286+infer' m (Indexer index val) = do
287+ el <- fresh
288+ check m index Number
289+ check m val (Array el)
290+ return el
291+infer' m (Accessor prop val) = do
292+ field <- fresh
293+ rest <- fresh
294+ check m val (Object (RCons prop field rest))
295+ return field
296+infer' m (Abs args ret) = do
297+ ts <- replicateM (length args) fresh
298+ let m' = m `M.union` M.fromList (zip args ts)
299+ body <- infer m' ret
300+ return $ Function ts body
301+infer' m app@(App _ _) = do
302+ let (f, argss) = unfoldApplication app
303+ ft <- infer m f
304+ ret <- fresh
305+ checkFunctionApplications m ft argss ret
306+ return ret
307+infer' m (Var var@(Qualified mp name)) = do
308+ case mp of
309+ ModulePath [] ->
310+ case M.lookup name m of
311+ Just ty -> lift $ replaceAllTypeSynonyms ty
312+ Nothing -> lookupGlobal
313+ _ -> lookupGlobal
314+ where
315+ lookupGlobal = do
316+ env <- lift getEnv
317+ modulePath <- checkModulePath `fmap` lift get
318+ case M.lookup (qualify modulePath var) (names env) of
319+ Nothing -> throwError $ show var ++ " is undefined"
320+ Just (ty, _) -> lift $ replaceAllTypeSynonyms ty
321+infer' m (Block ss) = do
322+ ret <- fresh
323+ (allCodePathsReturn, _) <- checkBlock m M.empty ret ss
324+ guardWith "Block is missing a return statement" allCodePathsReturn
325+ return ret
326+infer' m (Constructor c) = do
327+ env <- lift getEnv
328+ modulePath <- checkModulePath `fmap` lift get
329+ case M.lookup (qualify modulePath c) (dataConstructors env) of
330+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
331+ Just ty -> lift $ replaceAllTypeSynonyms ty
332+infer' m (Case val binders) = do
333+ t1 <- infer m val
334+ ret <- fresh
335+ checkBinders m t1 ret binders
336+ return ret
337+infer' m (IfThenElse cond th el) = do
338+ check m cond Boolean
339+ t2 <- infer m th
340+ t3 <- infer m el
341+ t2 ~~ t3
342+ return t2
343+infer' m (TypedValue val ty) = do
344+ kind <- lift $ kindOf ty
345+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
346+ ty' <- lift $ replaceAllTypeSynonyms ty
347+ check m val ty'
348+ return ty'
349+
350+inferUnary :: UnaryOperator -> Type -> Subst Check Type
351+inferUnary op val =
352+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
353+ (valTy, resTy) -> do
354+ val ~~ valTy
355+ return resTy
356+
357+checkUnary :: M.Map Ident Type -> UnaryOperator -> Value -> Type -> Subst Check ()
358+checkUnary m op val res =
359+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
360+ (valTy, resTy) -> do
361+ res ~~ resTy
362+ check m val valTy
363+
364+unaryOps :: [(UnaryOperator, (Type, Type))]
365+unaryOps = [ (Negate, (Number, Number))
366+ , (Not, (Boolean, Boolean))
367+ , (BitwiseNot, (Number, Number))
368+ ]
369+
370+inferBinary :: BinaryOperator -> Type -> Type -> Subst Check Type
371+inferBinary op left right | isEqualityTest op = do
372+ left ~~ right
373+ return Boolean
374+inferBinary op left right =
375+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
376+ (valTy, resTy) -> do
377+ left ~~ valTy
378+ right ~~ valTy
379+ return resTy
380+
381+checkBinary :: M.Map Ident Type -> BinaryOperator -> Value -> Value -> Type -> Subst Check ()
382+checkBinary m op left right res | isEqualityTest op = do
383+ res ~~ Boolean
384+ t1 <- infer m left
385+ t2 <- infer m right
386+ t1 ~~ t2
387+checkBinary m op left right res =
388+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
389+ (valTy, resTy) -> do
390+ res ~~ resTy
391+ check m left valTy
392+ check m right valTy
393+
394+isEqualityTest :: BinaryOperator -> Bool
395+isEqualityTest EqualTo = True
396+isEqualityTest NotEqualTo = True
397+isEqualityTest _ = False
398+
399+binaryOps :: [(BinaryOperator, (Type, Type))]
400+binaryOps = [ (Add, (Number, Number))
401+ , (Subtract, (Number, Number))
402+ , (Multiply, (Number, Number))
403+ , (Divide, (Number, Number))
404+ , (Modulus, (Number, Number))
405+ , (BitwiseAnd, (Number, Number))
406+ , (BitwiseOr, (Number, Number))
407+ , (BitwiseXor, (Number, Number))
408+ , (ShiftRight, (Number, Number))
409+ , (ZeroFillShiftRight, (Number, Number))
410+ , (And, (Boolean, Boolean))
411+ , (Or, (Boolean, Boolean))
412+ , (Concat, (String, String))
413+ , (Modulus, (Number, Number))
414+ , (LessThan, (Number, Boolean))
415+ , (LessThanOrEqualTo, (Number, Boolean))
416+ , (GreaterThan, (Number, Boolean))
417+ , (GreaterThanOrEqualTo, (Number, Boolean))
418+ ]
419+
420+inferBinder :: Type -> Binder -> Subst Check (M.Map Ident Type)
421+inferBinder _ NullBinder = return M.empty
422+inferBinder val (StringBinder _) = val ~~ String >> return M.empty
423+inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
424+inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
425+inferBinder val (VarBinder name) = return $ M.singleton name val
426+inferBinder val (NullaryBinder ctor) = do
427+ env <- lift getEnv
428+ modulePath <- checkModulePath `fmap` lift get
429+ case M.lookup (qualify modulePath ctor) (dataConstructors env) of
430+ Just ty -> do
431+ ty `subsumes` val
432+ return M.empty
433+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
434+inferBinder val (UnaryBinder ctor binder) = do
435+ env <- lift getEnv
436+ modulePath <- checkModulePath `fmap` lift get
437+ case M.lookup (qualify modulePath ctor) (dataConstructors env) of
438+ Just ty -> do
439+ obj <- fresh
440+ ty `subsumes` (Function [obj] val)
441+ inferBinder obj binder
442+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
443+inferBinder val (ObjectBinder props) = do
444+ row <- fresh
445+ rest <- fresh
446+ m1 <- inferRowProperties row rest props
447+ val ~~ Object row
448+ return m1
449+ where
450+ inferRowProperties :: Row -> Row -> [(String, Binder)] -> Subst Check (M.Map Ident Type)
451+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
452+ inferRowProperties nrow row ((name, binder):binders) = do
453+ propTy <- fresh
454+ m1 <- inferBinder propTy binder
455+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
456+ return $ m1 `M.union` m2
457+inferBinder val (ArrayBinder binders rest) = do
458+ el <- fresh
459+ m1 <- M.unions <$> mapM (inferBinder el) binders
460+ val ~~ Array el
461+ case rest of
462+ Nothing -> return m1
463+ Just binder -> do
464+ m2 <- inferBinder val binder
465+ return $ m1 `M.union` m2
466+inferBinder val (NamedBinder name binder) = do
467+ m <- inferBinder val binder
468+ return $ M.insert name val m
469+
470+inferGuardedBinder :: M.Map Ident Type -> Type -> Binder -> Subst Check (M.Map Ident Type)
471+inferGuardedBinder m val (GuardedBinder cond binder) = do
472+ m1 <- inferBinder val binder
473+ ty <- infer (m `M.union` m1) cond
474+ ty ~~ Boolean
475+ return m1
476+inferGuardedBinder m val b = inferBinder val b
477+
478+checkBinders :: M.Map Ident Type -> Type -> Type -> [(Binder, Value)] -> Subst Check ()
479+checkBinders _ _ _ [] = return ()
480+checkBinders m nval ret ((binder, val):bs) = do
481+ m1 <- inferGuardedBinder m nval binder
482+ check (m `M.union` m1) val ret
483+ checkBinders m nval ret bs
484+
485+assignVariable :: Ident -> M.Map Ident Type -> Subst Check ()
486+assignVariable name m =
487+ case M.lookup name m of
488+ Nothing -> return ()
489+ Just _ -> throwError $ "Variable with name " ++ show name ++ " already exists."
490+
491+checkStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> Statement -> Subst Check (Bool, M.Map Ident Type)
492+checkStatement m mass ret (VariableIntroduction name val) = do
493+ assignVariable name (m `M.union` mass)
494+ t <- infer m val
495+ return (False, M.insert name t mass)
496+checkStatement m mass ret (Assignment ident val) = do
497+ t <- infer m val
498+ case M.lookup ident mass of
499+ Nothing -> throwError $ "No local variable with name " ++ show ident
500+ Just ty -> do t ~~ ty
501+ return (False, mass)
502+checkStatement m mass ret (While val inner) = do
503+ check m val Boolean
504+ (allCodePathsReturn, _) <- checkBlock m mass ret inner
505+ return (allCodePathsReturn, mass)
506+checkStatement m mass ret (If ifst) = do
507+ allCodePathsReturn <- checkIfStatement m mass ret ifst
508+ return (allCodePathsReturn, mass)
509+checkStatement m mass ret (For ident start end inner) = do
510+ assignVariable ident (m `M.union` mass)
511+ check (m `M.union` mass) start Number
512+ check (m `M.union` mass) end Number
513+ let mass1 = M.insert ident Number mass
514+ (allCodePathsReturn, _) <- checkBlock (m `M.union` mass1) mass1 ret inner
515+ return (allCodePathsReturn, mass)
516+checkStatement m mass ret (ForEach ident vals inner) = do
517+ assignVariable ident (m `M.union` mass)
518+ val <- fresh
519+ check (m `M.union` mass) vals (Array val)
520+ let mass1 = M.insert ident val mass
521+ (allCodePathsReturn, _) <- checkBlock (m `M.union` mass1) mass1 ret inner
522+ guardWith "Cannot return from within a foreach block" $ not allCodePathsReturn
523+ return (False, mass)
524+checkStatement m mass ret (Return val) = do
525+ check (m `M.union` mass) val ret
526+ return (True, mass)
527+
528+checkIfStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> IfStatement -> Subst Check Bool
529+checkIfStatement m mass ret (IfStatement val thens Nothing) = do
530+ check m val Boolean
531+ _ <- checkBlock m mass ret thens
532+ return False
533+checkIfStatement m mass ret (IfStatement val thens (Just elses)) = do
534+ check m val Boolean
535+ (allCodePathsReturn1, _) <- checkBlock m mass ret thens
536+ allCodePathsReturn2 <- checkElseStatement m mass ret elses
537+ return $ allCodePathsReturn1 && allCodePathsReturn2
538+
539+checkElseStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> ElseStatement -> Subst Check Bool
540+checkElseStatement m mass ret (Else elses) = fst <$> checkBlock m mass ret elses
541+checkElseStatement m mass ret (ElseIf ifst) = checkIfStatement m mass ret ifst
542+
543+checkBlock :: M.Map Ident Type -> M.Map Ident Type -> Type -> [Statement] -> Subst Check (Bool, M.Map Ident Type)
544+checkBlock _ mass _ [] = return (False, mass)
545+checkBlock m mass ret (s:ss) = do
546+ (b1, mass1) <- checkStatement (m `M.union` mass) mass ret s
547+ case (b1, ss) of
548+ (True, []) -> return (True, mass1)
549+ (True, _) -> throwError "Unreachable code"
550+ (False, ss) -> do
551+ (b2, mass2) <- checkBlock m mass1 ret ss
552+ return (b2, mass2)
553+
554+skolemize :: String -> Type -> Subst Check Type
555+skolemize ident ty = do
556+ tsk <- Skolem <$> fresh'
557+ rsk <- RSkolem <$> fresh'
558+ return $ replaceRowVars (M.singleton ident rsk) $ replaceTypeVars (M.singleton ident tsk) ty
559+
560+check :: M.Map Ident Type -> Value -> Type -> Subst Check ()
561+check m val ty = rethrow errorMessage $ check' m val ty
562+ where
563+ errorMessage msg =
564+ "Error checking type of term " ++
565+ prettyPrintValue val ++
566+ " against type " ++
567+ prettyPrintType ty ++
568+ ":\n" ++
569+ msg
570+
571+check' :: M.Map Ident Type -> Value -> Type -> Subst Check ()
572+check' m val (ForAll idents ty) = do
573+ sk <- skolemize idents ty
574+ check m val sk
575+check' m val (SaturatedTypeSynonym name args) = do
576+ env <- lift getEnv
577+ modulePath <- checkModulePath `fmap` lift get
578+ case M.lookup (qualify modulePath name) (typeSynonyms env) of
579+ Just (synArgs, body) -> do
580+ let replaced = replaceTypeVars (M.fromList (zip synArgs args)) body
581+ check m val replaced
582+ Nothing -> error "Type synonym was not defined"
583+check' m val u@(TUnknown _) = do
584+ ty <- infer m val
585+ -- Don't unify an unknown with an inferred polytype
586+ ty' <- replaceAllVarsWithUnknowns ty
587+ ty' ~~ u
588+check' m (NumericLiteral _) Number = return ()
589+check' m (StringLiteral _) String = return ()
590+check' m (BooleanLiteral _) Boolean = return ()
591+check' m (Unary op val) ty = checkUnary m op val ty
592+check' m (Binary op left right) ty = checkBinary m op left right ty
593+check' m (ArrayLiteral vals) (Array ty) = forM_ vals (\val -> check m val ty)
594+check' m (Indexer index vals) ty = check m index Number >> check m vals (Array ty)
595+check' m (Abs args ret) (Function argTys retTy) = do
596+ guardWith "Incorrect number of function arguments" (length args == length argTys)
597+ let bindings = M.fromList (zip args argTys)
598+ check (bindings `M.union` m) ret retTy
599+check' m app@(App _ _) ret = do
600+ let (f, argss) = unfoldApplication app
601+ ft <- infer m f
602+ checkFunctionApplications m ft argss ret
603+check' m v@(Var var@(Qualified mp name)) ty = do
604+ case mp of
605+ ModulePath [] ->
606+ case M.lookup name m of
607+ Just ty1 -> do
608+ repl <- lift $ replaceAllTypeSynonyms ty1
609+ repl `subsumes` ty
610+ Nothing -> lookupGlobal
611+ _ -> lookupGlobal
612+ where
613+ lookupGlobal = do
614+ env <- lift getEnv
615+ modulePath <- checkModulePath `fmap` lift get
616+ case M.lookup (qualify modulePath var) (names env) of
617+ Nothing -> throwError $ show var ++ " is undefined"
618+ Just (ty1, _) -> do
619+ repl <- lift $ replaceAllTypeSynonyms ty1
620+ repl `subsumes` ty
621+check' m (TypedValue val ty1) ty2 = do
622+ kind <- lift $ kindOf ty1
623+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
624+ ty1 `subsumes` ty2
625+ check m val ty1
626+check' m (Case val binders) ret = do
627+ t1 <- infer m val
628+ checkBinders m t1 ret binders
629+check' m (IfThenElse cond th el) ty = do
630+ check m cond Boolean
631+ check m th ty
632+ check m el ty
633+check' m (ObjectLiteral ps) (Object row) = do
634+ lift $ ensureNoDuplicateProperties ps
635+ checkProperties m ps row False
636+check' m (ObjectUpdate obj ps) objTy@(Object row) = do
637+ lift $ ensureNoDuplicateProperties ps
638+ check m obj objTy
639+ checkProperties m ps row True
640+check' m (Accessor prop val) ty = do
641+ rest <- fresh
642+ check m val (Object (RCons prop ty rest))
643+check' m (Block ss) ret = do
644+ (allCodePathsReturn, _) <- checkBlock m M.empty ret ss
645+ guardWith "Block is missing a return statement" allCodePathsReturn
646+check' m (Constructor c) ty = do
647+ env <- lift getEnv
648+ modulePath <- checkModulePath `fmap` lift get
649+ case M.lookup (qualify modulePath c) (dataConstructors env) of
650+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
651+ Just ty1 -> do
652+ repl <- lift $ replaceAllTypeSynonyms ty1
653+ repl `subsumes` ty
654+check' _ val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
655+
656+checkProperties :: M.Map Ident Type -> [(String, Value)] -> Row -> Bool -> Subst Check ()
657+checkProperties m ps row lax = let (ts, r') = rowToList row in go ps ts r' where
658+ go [] [] REmpty = return ()
659+ go [] [] u@(RUnknown _) = u ~~ REmpty
660+ go [] [] (RSkolem _) | lax = return ()
661+ go [] ((p, _): _) _ | lax = return ()
662+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
663+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
664+ go ((p,v):ps) [] u@(RUnknown _) = do
665+ ty <- infer m v
666+ rest <- fresh
667+ u ~~ RCons p ty rest
668+ go ps [] rest
669+ go ((p,v):ps) ts r =
670+ case lookup p ts of
671+ Nothing -> do
672+ ty <- infer m v
673+ rest <- fresh
674+ r ~~ RCons p ty rest
675+ go ps ts rest
676+ Just ty -> do
677+ check m v ty
678+ go ps (delete (p, ty) ts) r
679+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
680+
681+unfoldApplication :: Value -> (Value, [[Value]])
682+unfoldApplication = go []
683+ where
684+ go argss (App f args) = go (args:argss) f
685+ go argss f = (f, argss)
686+
687+checkFunctionApplications :: M.Map Ident Type -> Type -> [[Value]] -> Type -> Subst Check ()
688+checkFunctionApplications _ _ [] _ = error "Nullary function application"
689+checkFunctionApplications m fnTy [args] ret = checkFunctionApplication m fnTy args ret
690+checkFunctionApplications m fnTy (args:argss) ret = do
691+ f <- fresh
692+ checkFunctionApplication m fnTy args f
693+ checkFunctionApplications m f argss ret
694+
695+checkFunctionApplication :: M.Map Ident Type -> Type -> [Value] -> Type -> Subst Check ()
696+checkFunctionApplication m fnTy args ret = rethrow errorMessage $ checkFunctionApplication' m fnTy args ret
697+ where
698+ errorMessage msg = "Error applying function of type "
699+ ++ prettyPrintType fnTy
700+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
701+ ++ ", expecting value of type "
702+ ++ prettyPrintType ret ++ ":\n" ++ msg
703+
704+checkFunctionApplication' :: M.Map Ident Type -> Type -> [Value] -> Type -> Subst Check ()
705+checkFunctionApplication' m (Function argTys retTy) args ret = do
706+ guardWith "Incorrect number of function arguments" (length args == length argTys)
707+ zipWithM (check m) args argTys
708+ retTy `subsumes` ret
709+checkFunctionApplication' m (ForAll ident ty) args ret = do
710+ replaced <- replaceVarsWithUnknowns [ident] ty
711+ checkFunctionApplication m replaced args ret
712+checkFunctionApplication' m u@(TUnknown _) args ret = do
713+ tyArgs <- mapM (\arg -> infer m arg >>= replaceAllVarsWithUnknowns) args
714+ u ~~ Function tyArgs ret
715+checkFunctionApplication' _ fnTy args ret = throwError $ "Cannot apply function of type "
716+ ++ prettyPrintType fnTy
717+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
718+ ++ ". Expecting value of type " ++ prettyPrintType ret ++ "."
719+
720+subsumes :: Type -> Type -> Subst Check ()
721+subsumes (ForAll ident ty1) ty2 = do
722+ replaced <- replaceVarsWithUnknowns [ident] ty1
723+ replaced `subsumes` ty2
724+subsumes (Function args1 ret1) (Function args2 ret2) = do
725+ zipWithM subsumes args2 args1
726+ ret1 `subsumes` ret2
727+subsumes ty1 ty2 = ty1 ~~ ty2
728+