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