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