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