@@ -0,0 +1,752 @@
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+ do me <- fresh
159+ ty <- infer (M.singleton ident me) val
160+ ty `subsumes` me
161+ return ty
162+ _ -> infer M.empty val
163+ escapeCheck checks ty sub
164+ return $ varIfUnknown $ desaturateAllTypeSynonyms $ setifyAll ty
165+
166+escapeCheck :: [AnyUnifiable] -> Type -> Substitution -> Check ()
167+escapeCheck checks ty sub =
168+ let
169+ visibleUnknowns = nub $ unknowns ty
170+ in
171+ forM_ checks $ \check -> case check of
172+ AnyUnifiable t -> do
173+ let unsolvedUnknowns = nub . unknowns $ apply sub t
174+ guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
175+
176+setify :: Row -> Row
177+setify = rowFromList . first (M.toList . M.fromList) . rowToList
178+
179+setifyAll :: (D.Data d) => d -> d
180+setifyAll = everywhere (mkT setify)
181+
182+findTypeVars :: (D.Data d) => d -> [String]
183+findTypeVars = everything (++) (mkQ [] f)
184+ where
185+ f :: Type -> [String]
186+ f (TypeVar v) = [v]
187+ f _ = []
188+
189+varIfUnknown :: Type -> Type
190+varIfUnknown ty =
191+ let
192+ (ty', m) = flip runState M.empty $ everywhereM (flip extM g $ mkM f) ty
193+ in
194+ mkForAll (sort $ nub $ M.elems m ++ findTypeVars ty) ty'
195+ where
196+ f :: Type -> State (M.Map Int String) Type
197+ f (TUnknown (Unknown n)) = do
198+ m <- get
199+ case M.lookup n m of
200+ Nothing -> do
201+ let name = 't' : show (M.size m)
202+ put $ M.insert n name m
203+ return $ TypeVar name
204+ Just name -> return $ TypeVar name
205+ f t = return t
206+ g :: Row -> State (M.Map Int String) Row
207+ g (RUnknown (Unknown n)) = do
208+ m <- get
209+ case M.lookup n m of
210+ Nothing -> do
211+ let name = 'r' : show (M.size m)
212+ put $ M.insert n name m
213+ return $ RowVar name
214+ Just name -> return $ RowVar name
215+ g r = return r
216+
217+replaceTypeVars :: M.Map String Type -> Type -> Type
218+replaceTypeVars m = everywhere (mkT replace)
219+ where
220+ replace (TypeVar v) = case M.lookup v m of
221+ Just ty -> ty
222+ _ -> TypeVar v
223+ replace t = t
224+
225+replaceRowVars :: M.Map String Row -> Type -> Type
226+replaceRowVars m = everywhere (mkT replace)
227+ where
228+ replace (RowVar v) = case M.lookup v m of
229+ Just r -> r
230+ _ -> RowVar v
231+ replace t = t
232+
233+replaceAllVarsWithUnknowns :: Type -> Subst Check Type
234+replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarsWithUnknowns [ident] ty >>= replaceAllVarsWithUnknowns
235+replaceAllVarsWithUnknowns ty = return ty
236+
237+replaceVarsWithUnknowns :: [String] -> Type -> Subst Check Type
238+replaceVarsWithUnknowns idents = flip evalStateT M.empty . everywhereM (flip extM f $ mkM g)
239+ where
240+ f :: Type -> StateT (M.Map String Int) (Subst Check) Type
241+ f (TypeVar var) | var `elem` idents = do
242+ m <- get
243+ n <- lift fresh'
244+ case M.lookup var m of
245+ Nothing -> do
246+ put (M.insert var n m)
247+ return $ TUnknown (Unknown n)
248+ Just u -> return $ TUnknown (Unknown u)
249+ f t = return t
250+ g :: Row -> StateT (M.Map String Int) (Subst Check) Row
251+ g (RowVar var) | var `elem` idents = do
252+ m <- get
253+ n <- lift fresh'
254+ case M.lookup var m of
255+ Nothing -> do
256+ put (M.insert var n m)
257+ return $ RUnknown (Unknown n)
258+ Just u -> return $ RUnknown (Unknown u)
259+ g r = return r
260+
261+replaceAllTypeSynonyms :: (D.Data d) => d -> Check d
262+replaceAllTypeSynonyms d = do
263+ env <- getEnv
264+ let syns = map (\((path, name), (args, _)) -> (Qualified path name, length args)) . M.toList $ typeSynonyms env
265+ either throwError return $ saturateAllTypeSynonyms syns d
266+
267+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
268+desaturateAllTypeSynonyms = everywhere (mkT replace)
269+ where
270+ replace (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
271+ replace t = t
272+
273+ensureNoDuplicateProperties :: [(String, Value)] -> Check ()
274+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
275+
276+infer :: M.Map Ident Type -> Value -> Subst Check Type
277+infer m val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ do
278+ ty <- infer' m val
279+ escapeCheckLater ty
280+ return ty
281+
282+infer' _ (NumericLiteral _) = return Number
283+infer' _ (StringLiteral _) = return String
284+infer' _ (BooleanLiteral _) = return Boolean
285+infer' m (ArrayLiteral vals) = do
286+ ts <- mapM (infer m) vals
287+ arr <- fresh
288+ forM_ ts $ \t -> arr ~~ Array t
289+ return arr
290+infer' m (Unary op val) = do
291+ t <- infer m val
292+ inferUnary op t
293+infer' m (Binary op left right) = do
294+ t1 <- infer m left
295+ t2 <- infer m right
296+ inferBinary op t1 t2
297+infer' m (ObjectLiteral ps) = do
298+ lift $ ensureNoDuplicateProperties ps
299+ ts <- mapM (infer m . snd) ps
300+ let fields = zipWith (\(name, _) t -> (name, t)) ps ts
301+ return $ Object $ typesToRow fields
302+infer' m (ObjectUpdate o ps) = do
303+ lift $ ensureNoDuplicateProperties ps
304+ obj <- infer m o
305+ row <- fresh
306+ ts <- mapM (infer m . snd) ps
307+ let tys = zipWith (\(name, _) t -> (name, t)) ps ts
308+ obj ~~ Object (rowFromList (tys, row))
309+ return obj
310+infer' m (Indexer index val) = do
311+ el <- fresh
312+ check m index Number
313+ check m val (Array el)
314+ return el
315+infer' m (Accessor prop val) = do
316+ field <- fresh
317+ rest <- fresh
318+ check m val (Object (RCons prop field rest))
319+ return field
320+infer' m (Abs args ret) = do
321+ ts <- replicateM (length args) fresh
322+ let m' = m `M.union` M.fromList (zip args ts)
323+ body <- infer m' ret
324+ return $ Function ts body
325+infer' m app@(App _ _) = do
326+ let (f, argss) = unfoldApplication app
327+ ft <- infer m f
328+ ret <- fresh
329+ checkFunctionApplications m ft argss ret
330+ return ret
331+infer' m (Var var@(Qualified mp name)) = do
332+ case mp of
333+ ModulePath [] ->
334+ case M.lookup name m of
335+ Just ty -> lift $ replaceAllTypeSynonyms ty
336+ Nothing -> lookupGlobal
337+ _ -> lookupGlobal
338+ where
339+ lookupGlobal = do
340+ env <- lift getEnv
341+ modulePath <- checkModulePath `fmap` lift get
342+ case M.lookup (qualify modulePath var) (names env) of
343+ Nothing -> throwError $ show var ++ " is undefined"
344+ Just (ty, _) -> lift $ replaceAllTypeSynonyms ty
345+infer' m (Block ss) = do
346+ ret <- fresh
347+ (allCodePathsReturn, _) <- checkBlock m M.empty ret ss
348+ guardWith "Block is missing a return statement" allCodePathsReturn
349+ return ret
350+infer' m (Constructor c) = do
351+ env <- lift getEnv
352+ modulePath <- checkModulePath `fmap` lift get
353+ case M.lookup (qualify modulePath c) (dataConstructors env) of
354+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
355+ Just ty -> lift $ replaceAllTypeSynonyms ty
356+infer' m (Case val binders) = do
357+ t1 <- infer m val
358+ ret <- fresh
359+ checkBinders m t1 ret binders
360+ return ret
361+infer' m (IfThenElse cond th el) = do
362+ check m cond Boolean
363+ t2 <- infer m th
364+ t3 <- infer m el
365+ t2 ~~ t3
366+ return t2
367+infer' m (TypedValue val ty) = do
368+ kind <- lift $ kindOf ty
369+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
370+ ty' <- lift $ replaceAllTypeSynonyms ty
371+ check m val ty'
372+ return ty'
373+
374+inferUnary :: UnaryOperator -> Type -> Subst Check Type
375+inferUnary op val =
376+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
377+ (valTy, resTy) -> do
378+ val ~~ valTy
379+ return resTy
380+
381+checkUnary :: M.Map Ident Type -> UnaryOperator -> Value -> Type -> Subst Check ()
382+checkUnary m op val res =
383+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
384+ (valTy, resTy) -> do
385+ res ~~ resTy
386+ check m val valTy
387+
388+unaryOps :: [(UnaryOperator, (Type, Type))]
389+unaryOps = [ (Negate, (Number, Number))
390+ , (Not, (Boolean, Boolean))
391+ , (BitwiseNot, (Number, Number))
392+ ]
393+
394+inferBinary :: BinaryOperator -> Type -> Type -> Subst Check Type
395+inferBinary op left right | isEqualityTest op = do
396+ left ~~ right
397+ return Boolean
398+inferBinary op left right =
399+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
400+ (valTy, resTy) -> do
401+ left ~~ valTy
402+ right ~~ valTy
403+ return resTy
404+
405+checkBinary :: M.Map Ident Type -> BinaryOperator -> Value -> Value -> Type -> Subst Check ()
406+checkBinary m op left right res | isEqualityTest op = do
407+ res ~~ Boolean
408+ t1 <- infer m left
409+ t2 <- infer m right
410+ t1 ~~ t2
411+checkBinary m op left right res =
412+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
413+ (valTy, resTy) -> do
414+ res ~~ resTy
415+ check m left valTy
416+ check m right valTy
417+
418+isEqualityTest :: BinaryOperator -> Bool
419+isEqualityTest EqualTo = True
420+isEqualityTest NotEqualTo = True
421+isEqualityTest _ = False
422+
423+binaryOps :: [(BinaryOperator, (Type, Type))]
424+binaryOps = [ (Add, (Number, Number))
425+ , (Subtract, (Number, Number))
426+ , (Multiply, (Number, Number))
427+ , (Divide, (Number, Number))
428+ , (Modulus, (Number, Number))
429+ , (BitwiseAnd, (Number, Number))
430+ , (BitwiseOr, (Number, Number))
431+ , (BitwiseXor, (Number, Number))
432+ , (ShiftRight, (Number, Number))
433+ , (ZeroFillShiftRight, (Number, Number))
434+ , (And, (Boolean, Boolean))
435+ , (Or, (Boolean, Boolean))
436+ , (Concat, (String, String))
437+ , (Modulus, (Number, Number))
438+ , (LessThan, (Number, Boolean))
439+ , (LessThanOrEqualTo, (Number, Boolean))
440+ , (GreaterThan, (Number, Boolean))
441+ , (GreaterThanOrEqualTo, (Number, Boolean))
442+ ]
443+
444+inferBinder :: Type -> Binder -> Subst Check (M.Map Ident Type)
445+inferBinder _ NullBinder = return M.empty
446+inferBinder val (StringBinder _) = val ~~ String >> return M.empty
447+inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
448+inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
449+inferBinder val (VarBinder name) = return $ M.singleton name val
450+inferBinder val (NullaryBinder ctor) = do
451+ env <- lift getEnv
452+ modulePath <- checkModulePath `fmap` lift get
453+ case M.lookup (qualify modulePath ctor) (dataConstructors env) of
454+ Just ty -> do
455+ ty `subsumes` val
456+ return M.empty
457+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
458+inferBinder val (UnaryBinder ctor binder) = do
459+ env <- lift getEnv
460+ modulePath <- checkModulePath `fmap` lift get
461+ case M.lookup (qualify modulePath ctor) (dataConstructors env) of
462+ Just ty -> do
463+ obj <- fresh
464+ ty `subsumes` (Function [obj] val)
465+ inferBinder obj binder
466+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
467+inferBinder val (ObjectBinder props) = do
468+ row <- fresh
469+ rest <- fresh
470+ m1 <- inferRowProperties row rest props
471+ val ~~ Object row
472+ return m1
473+ where
474+ inferRowProperties :: Row -> Row -> [(String, Binder)] -> Subst Check (M.Map Ident Type)
475+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
476+ inferRowProperties nrow row ((name, binder):binders) = do
477+ propTy <- fresh
478+ m1 <- inferBinder propTy binder
479+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
480+ return $ m1 `M.union` m2
481+inferBinder val (ArrayBinder binders rest) = do
482+ el <- fresh
483+ m1 <- M.unions <$> mapM (inferBinder el) binders
484+ val ~~ Array el
485+ case rest of
486+ Nothing -> return m1
487+ Just binder -> do
488+ m2 <- inferBinder val binder
489+ return $ m1 `M.union` m2
490+inferBinder val (NamedBinder name binder) = do
491+ m <- inferBinder val binder
492+ return $ M.insert name val m
493+
494+inferGuardedBinder :: M.Map Ident Type -> Type -> Binder -> Subst Check (M.Map Ident Type)
495+inferGuardedBinder m val (GuardedBinder cond binder) = do
496+ m1 <- inferBinder val binder
497+ ty <- infer (m `M.union` m1) cond
498+ ty ~~ Boolean
499+ return m1
500+inferGuardedBinder m val b = inferBinder val b
501+
502+checkBinders :: M.Map Ident Type -> Type -> Type -> [(Binder, Value)] -> Subst Check ()
503+checkBinders _ _ _ [] = return ()
504+checkBinders m nval ret ((binder, val):bs) = do
505+ m1 <- inferGuardedBinder m nval binder
506+ check (m `M.union` m1) val ret
507+ checkBinders m nval ret bs
508+
509+assignVariable :: Ident -> M.Map Ident Type -> Subst Check ()
510+assignVariable name m =
511+ case M.lookup name m of
512+ Nothing -> return ()
513+ Just _ -> throwError $ "Variable with name " ++ show name ++ " already exists."
514+
515+checkStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> Statement -> Subst Check (Bool, M.Map Ident Type)
516+checkStatement m mass ret (VariableIntroduction name val) = do
517+ assignVariable name (m `M.union` mass)
518+ t <- infer m val
519+ return (False, M.insert name t mass)
520+checkStatement m mass ret (Assignment ident val) = do
521+ t <- infer m val
522+ case M.lookup ident mass of
523+ Nothing -> throwError $ "No local variable with name " ++ show ident
524+ Just ty -> do t ~~ ty
525+ return (False, mass)
526+checkStatement m mass ret (While val inner) = do
527+ check m val Boolean
528+ (allCodePathsReturn, _) <- checkBlock m mass ret inner
529+ return (allCodePathsReturn, mass)
530+checkStatement m mass ret (If ifst) = do
531+ allCodePathsReturn <- checkIfStatement m mass ret ifst
532+ return (allCodePathsReturn, mass)
533+checkStatement m mass ret (For ident start end inner) = do
534+ assignVariable ident (m `M.union` mass)
535+ check (m `M.union` mass) start Number
536+ check (m `M.union` mass) end Number
537+ let mass1 = M.insert ident Number mass
538+ (allCodePathsReturn, _) <- checkBlock (m `M.union` mass1) mass1 ret inner
539+ return (allCodePathsReturn, mass)
540+checkStatement m mass ret (ForEach ident vals inner) = do
541+ assignVariable ident (m `M.union` mass)
542+ val <- fresh
543+ check (m `M.union` mass) vals (Array val)
544+ let mass1 = M.insert ident val mass
545+ (allCodePathsReturn, _) <- checkBlock (m `M.union` mass1) mass1 ret inner
546+ guardWith "Cannot return from within a foreach block" $ not allCodePathsReturn
547+ return (False, mass)
548+checkStatement m mass ret (Return val) = do
549+ check (m `M.union` mass) val ret
550+ return (True, mass)
551+
552+checkIfStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> IfStatement -> Subst Check Bool
553+checkIfStatement m mass ret (IfStatement val thens Nothing) = do
554+ check m val Boolean
555+ _ <- checkBlock m mass ret thens
556+ return False
557+checkIfStatement m mass ret (IfStatement val thens (Just elses)) = do
558+ check m val Boolean
559+ (allCodePathsReturn1, _) <- checkBlock m mass ret thens
560+ allCodePathsReturn2 <- checkElseStatement m mass ret elses
561+ return $ allCodePathsReturn1 && allCodePathsReturn2
562+
563+checkElseStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> ElseStatement -> Subst Check Bool
564+checkElseStatement m mass ret (Else elses) = fst <$> checkBlock m mass ret elses
565+checkElseStatement m mass ret (ElseIf ifst) = checkIfStatement m mass ret ifst
566+
567+checkBlock :: M.Map Ident Type -> M.Map Ident Type -> Type -> [Statement] -> Subst Check (Bool, M.Map Ident Type)
568+checkBlock _ mass _ [] = return (False, mass)
569+checkBlock m mass ret (s:ss) = do
570+ (b1, mass1) <- checkStatement (m `M.union` mass) mass ret s
571+ case (b1, ss) of
572+ (True, []) -> return (True, mass1)
573+ (True, _) -> throwError "Unreachable code"
574+ (False, ss) -> do
575+ (b2, mass2) <- checkBlock m mass1 ret ss
576+ return (b2, mass2)
577+
578+skolemize :: String -> Type -> Subst Check Type
579+skolemize ident ty = do
580+ tsk <- Skolem <$> fresh'
581+ rsk <- RSkolem <$> fresh'
582+ return $ replaceRowVars (M.singleton ident rsk) $ replaceTypeVars (M.singleton ident tsk) ty
583+
584+check :: M.Map Ident Type -> Value -> Type -> Subst Check ()
585+check m val ty = rethrow errorMessage $ check' m val ty
586+ where
587+ errorMessage msg =
588+ "Error checking type of term " ++
589+ prettyPrintValue val ++
590+ " against type " ++
591+ prettyPrintType ty ++
592+ ":\n" ++
593+ msg
594+
595+check' :: M.Map Ident Type -> Value -> Type -> Subst Check ()
596+check' m val (ForAll idents ty) = do
597+ sk <- skolemize idents ty
598+ check m val sk
599+check' m val (SaturatedTypeSynonym name args) = do
600+ env <- lift getEnv
601+ modulePath <- checkModulePath `fmap` lift get
602+ case M.lookup (qualify modulePath name) (typeSynonyms env) of
603+ Just (synArgs, body) -> do
604+ let replaced = replaceTypeVars (M.fromList (zip synArgs args)) body
605+ check m val replaced
606+ Nothing -> error "Type synonym was not defined"
607+check' m val u@(TUnknown _) = do
608+ ty <- infer m val
609+ -- Don't unify an unknown with an inferred polytype
610+ ty' <- replaceAllVarsWithUnknowns ty
611+ ty' ~~ u
612+check' m (NumericLiteral _) Number = return ()
613+check' m (StringLiteral _) String = return ()
614+check' m (BooleanLiteral _) Boolean = return ()
615+check' m (Unary op val) ty = checkUnary m op val ty
616+check' m (Binary op left right) ty = checkBinary m op left right ty
617+check' m (ArrayLiteral vals) (Array ty) = forM_ vals (\val -> check m val ty)
618+check' m (Indexer index vals) ty = check m index Number >> check m vals (Array ty)
619+check' m (Abs args ret) (Function argTys retTy) = do
620+ guardWith "Incorrect number of function arguments" (length args == length argTys)
621+ let bindings = M.fromList (zip args argTys)
622+ check (bindings `M.union` m) ret retTy
623+check' m app@(App _ _) ret = do
624+ let (f, argss) = unfoldApplication app
625+ ft <- infer m f
626+ checkFunctionApplications m ft argss ret
627+check' m v@(Var var@(Qualified mp name)) ty = do
628+ case mp of
629+ ModulePath [] ->
630+ case M.lookup name m of
631+ Just ty1 -> do
632+ repl <- lift $ replaceAllTypeSynonyms ty1
633+ repl `subsumes` ty
634+ Nothing -> lookupGlobal
635+ _ -> lookupGlobal
636+ where
637+ lookupGlobal = do
638+ env <- lift getEnv
639+ modulePath <- checkModulePath `fmap` lift get
640+ case M.lookup (qualify modulePath var) (names env) of
641+ Nothing -> throwError $ show var ++ " is undefined"
642+ Just (ty1, _) -> do
643+ repl <- lift $ replaceAllTypeSynonyms ty1
644+ repl `subsumes` ty
645+check' m (TypedValue val ty1) ty2 = do
646+ kind <- lift $ kindOf ty1
647+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
648+ ty1 `subsumes` ty2
649+ check m val ty1
650+check' m (Case val binders) ret = do
651+ t1 <- infer m val
652+ checkBinders m t1 ret binders
653+check' m (IfThenElse cond th el) ty = do
654+ check m cond Boolean
655+ check m th ty
656+ check m el ty
657+check' m (ObjectLiteral ps) (Object row) = do
658+ lift $ ensureNoDuplicateProperties ps
659+ checkProperties m ps row False
660+check' m (ObjectUpdate obj ps) objTy@(Object row) = do
661+ lift $ ensureNoDuplicateProperties ps
662+ check m obj objTy
663+ checkProperties m ps row True
664+check' m (Accessor prop val) ty = do
665+ rest <- fresh
666+ check m val (Object (RCons prop ty rest))
667+check' m (Block ss) ret = do
668+ (allCodePathsReturn, _) <- checkBlock m M.empty ret ss
669+ guardWith "Block is missing a return statement" allCodePathsReturn
670+check' m (Constructor c) ty = do
671+ env <- lift getEnv
672+ modulePath <- checkModulePath `fmap` lift get
673+ case M.lookup (qualify modulePath c) (dataConstructors env) of
674+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
675+ Just ty1 -> do
676+ repl <- lift $ replaceAllTypeSynonyms ty1
677+ repl `subsumes` ty
678+check' _ val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
679+
680+checkProperties :: M.Map Ident Type -> [(String, Value)] -> Row -> Bool -> Subst Check ()
681+checkProperties m ps row lax = let (ts, r') = rowToList row in go ps ts r' where
682+ go [] [] REmpty = return ()
683+ go [] [] u@(RUnknown _) = u ~~ REmpty
684+ go [] [] (RSkolem _) | lax = return ()
685+ go [] ((p, _): _) _ | lax = return ()
686+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
687+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
688+ go ((p,v):ps) [] u@(RUnknown _) = do
689+ ty <- infer m v
690+ rest <- fresh
691+ u ~~ RCons p ty rest
692+ go ps [] rest
693+ go ((p,v):ps) ts r =
694+ case lookup p ts of
695+ Nothing -> do
696+ ty <- infer m v
697+ rest <- fresh
698+ r ~~ RCons p ty rest
699+ go ps ts rest
700+ Just ty -> do
701+ check m v ty
702+ go ps (delete (p, ty) ts) r
703+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
704+
705+unfoldApplication :: Value -> (Value, [[Value]])
706+unfoldApplication = go []
707+ where
708+ go argss (App f args) = go (args:argss) f
709+ go argss f = (f, argss)
710+
711+checkFunctionApplications :: M.Map Ident Type -> Type -> [[Value]] -> Type -> Subst Check ()
712+checkFunctionApplications _ _ [] _ = error "Nullary function application"
713+checkFunctionApplications m fnTy [args] ret = checkFunctionApplication m fnTy args ret
714+checkFunctionApplications m fnTy (args:argss) ret = do
715+ f <- fresh
716+ checkFunctionApplication m fnTy args f
717+ checkFunctionApplications m f argss ret
718+
719+checkFunctionApplication :: M.Map Ident Type -> Type -> [Value] -> Type -> Subst Check ()
720+checkFunctionApplication m fnTy args ret = rethrow errorMessage $ checkFunctionApplication' m fnTy args ret
721+ where
722+ errorMessage msg = "Error applying function of type "
723+ ++ prettyPrintType fnTy
724+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
725+ ++ ", expecting value of type "
726+ ++ prettyPrintType ret ++ ":\n" ++ msg
727+
728+checkFunctionApplication' :: M.Map Ident Type -> Type -> [Value] -> Type -> Subst Check ()
729+checkFunctionApplication' m (Function argTys retTy) args ret = do
730+ guardWith "Incorrect number of function arguments" (length args == length argTys)
731+ zipWithM (check m) args argTys
732+ retTy `subsumes` ret
733+checkFunctionApplication' m (ForAll ident ty) args ret = do
734+ replaced <- replaceVarsWithUnknowns [ident] ty
735+ checkFunctionApplication m replaced args ret
736+checkFunctionApplication' m u@(TUnknown _) args ret = do
737+ tyArgs <- mapM (\arg -> infer m arg >>= replaceAllVarsWithUnknowns) args
738+ u ~~ Function tyArgs ret
739+checkFunctionApplication' _ fnTy args ret = throwError $ "Cannot apply function of type "
740+ ++ prettyPrintType fnTy
741+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
742+ ++ ". Expecting value of type " ++ prettyPrintType ret ++ "."
743+
744+subsumes :: Type -> Type -> Subst Check ()
745+subsumes (ForAll ident ty1) ty2 = do
746+ replaced <- replaceVarsWithUnknowns [ident] ty1
747+ replaced `subsumes` ty2
748+subsumes (Function args1 ret1) (Function args2 ret2) = do
749+ zipWithM subsumes args2 args1
750+ ret1 `subsumes` ret2
751+subsumes ty1 ty2 = ty1 ~~ ty2
752+