@@ -0,0 +1,753 @@
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+ ty1 <- expandTypeSynonym name args
114+ ty1 `unifyTypes` ty
115+ unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
116+ unifyTypes' (ForAll ident1 ty1) (ForAll ident2 ty2) = do
117+ sk <- skolemize ident1 ty1
118+ replaced <- replaceVarsWithUnknowns [ident2] ty2
119+ sk `unifyTypes` replaced
120+ unifyTypes' (ForAll ident ty1) ty2 = do
121+ sk <- skolemize ident ty1
122+ sk `unifyTypes` ty2
123+ unifyTypes' ty f@(ForAll _ _) = f `unifyTypes` ty
124+ unifyTypes' Number Number = return ()
125+ unifyTypes' String String = return ()
126+ unifyTypes' Boolean Boolean = return ()
127+ unifyTypes' (Array s) (Array t) = s `unifyTypes` t
128+ unifyTypes' (Object row1) (Object row2) = row1 ~~ row2
129+ unifyTypes' (Function args1 ret1) (Function args2 ret2) = do
130+ guardWith "Function applied to incorrect number of args" $ length args1 == length args2
131+ zipWithM_ unifyTypes args1 args2
132+ ret1 `unifyTypes` ret2
133+ unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
134+ unifyTypes' (TypeConstructor c1) (TypeConstructor c2) = do
135+ modulePath <- checkModulePath `fmap` lift get
136+ guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (qualify modulePath c1 == qualify modulePath c2)
137+ unifyTypes' (TypeApp t1 t2) (TypeApp t3 t4) = do
138+ t1 `unifyTypes` t3
139+ t2 `unifyTypes` t4
140+ unifyTypes' (Skolem s1) (Skolem s2) | s1 == s2 = return ()
141+ unifyTypes' t1 t2 = throwError $ "Cannot unify " ++ prettyPrintType t1 ++ " with " ++ prettyPrintType t2 ++ "."
142+
143+isFunction :: Value -> Bool
144+isFunction (Abs _ _) = True
145+isFunction (TypedValue untyped _) = isFunction untyped
146+isFunction _ = False
147+
148+-- TODO: check skolems don't escape
149+typeOf :: Maybe Ident -> Value -> Check Type
150+typeOf name val = do
151+ (ty, sub, checks) <- runSubst $ case name of
152+ Just ident | isFunction val ->
153+ case val of
154+ TypedValue val ty -> do
155+ kind <- lift $ kindOf ty
156+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
157+ ty' <- lift $ replaceAllTypeSynonyms ty
158+ check (M.singleton ident ty) val ty'
159+ return ty'
160+ _ -> do
161+ me <- fresh
162+ ty <- infer (M.singleton ident me) val
163+ ty ~~ me
164+ return ty
165+ _ -> infer M.empty val
166+ escapeCheck checks ty sub
167+ return $ varIfUnknown $ desaturateAllTypeSynonyms $ setifyAll ty
168+
169+escapeCheck :: [AnyUnifiable] -> Type -> Substitution -> Check ()
170+escapeCheck checks ty sub =
171+ let
172+ visibleUnknowns = nub $ unknowns ty
173+ in
174+ forM_ checks $ \check -> case check of
175+ AnyUnifiable t -> do
176+ let unsolvedUnknowns = nub . unknowns $ apply sub t
177+ guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
178+
179+setify :: Row -> Row
180+setify = rowFromList . first (M.toList . M.fromList) . rowToList
181+
182+setifyAll :: (D.Data d) => d -> d
183+setifyAll = everywhere (mkT setify)
184+
185+varIfUnknown :: Type -> Type
186+varIfUnknown ty = mkForAll (sort . map ((:) 'u' . show) . nub $ unknowns ty) ty
187+
188+replaceTypeVars :: M.Map String Type -> Type -> Type
189+replaceTypeVars m = everywhere (mkT replace)
190+ where
191+ replace (TypeVar v) = case M.lookup v m of
192+ Just ty -> ty
193+ _ -> TypeVar v
194+ replace t = t
195+
196+replaceRowVars :: M.Map String Row -> Type -> Type
197+replaceRowVars m = everywhere (mkT replace)
198+ where
199+ replace (RowVar v) = case M.lookup v m of
200+ Just r -> r
201+ _ -> RowVar v
202+ replace t = t
203+
204+replaceAllVarsWithUnknowns :: Type -> Subst Check Type
205+replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarsWithUnknowns [ident] ty >>= replaceAllVarsWithUnknowns
206+replaceAllVarsWithUnknowns ty = return ty
207+
208+-- TODO: need to be careful inside a forall, since variables might be renamed
209+replaceVarsWithUnknowns :: [String] -> Type -> Subst Check Type
210+replaceVarsWithUnknowns idents = flip evalStateT M.empty . everywhereM (flip extM f $ mkM g)
211+ where
212+ f :: Type -> StateT (M.Map String Int) (Subst Check) Type
213+ f (TypeVar var) | var `elem` idents = do
214+ m <- get
215+ n <- lift fresh'
216+ case M.lookup var m of
217+ Nothing -> do
218+ put (M.insert var n m)
219+ return $ TUnknown (Unknown n)
220+ Just u -> return $ TUnknown (Unknown u)
221+ f t = return t
222+ g :: Row -> StateT (M.Map String Int) (Subst Check) Row
223+ g (RowVar var) | var `elem` idents = do
224+ m <- get
225+ n <- lift fresh'
226+ case M.lookup var m of
227+ Nothing -> do
228+ put (M.insert var n m)
229+ return $ RUnknown (Unknown n)
230+ Just u -> return $ RUnknown (Unknown u)
231+ g r = return r
232+
233+replaceAllTypeSynonyms :: (D.Data d) => d -> Check d
234+replaceAllTypeSynonyms d = do
235+ env <- getEnv
236+ let syns = map (\((path, name), (args, _)) -> (Qualified path name, length args)) . M.toList $ typeSynonyms env
237+ either throwError return $ saturateAllTypeSynonyms syns d
238+
239+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
240+desaturateAllTypeSynonyms = everywhere (mkT replace)
241+ where
242+ replace (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
243+ replace t = t
244+
245+expandAllTypeSynonyms :: Type -> Subst Check Type
246+expandAllTypeSynonyms (SaturatedTypeSynonym name args) = expandTypeSynonym name args >>= expandAllTypeSynonyms
247+expandAllTypeSynonyms ty = return ty
248+
249+expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Check Type
250+expandTypeSynonym name args = do
251+ env <- lift getEnv
252+ modulePath <- checkModulePath `fmap` lift get
253+ case M.lookup (qualify modulePath name) (typeSynonyms env) of
254+ Just (synArgs, body) -> do
255+ let m = M.fromList $ zip synArgs args
256+ return $ replaceTypeVars m body
257+ Nothing -> error "Type synonym was not defined"
258+
259+ensureNoDuplicateProperties :: [(String, Value)] -> Check ()
260+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
261+
262+infer :: M.Map Ident Type -> Value -> Subst Check Type
263+infer m val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ do
264+ ty <- infer' m val
265+ escapeCheckLater ty
266+ return ty
267+
268+infer' _ (NumericLiteral _) = return Number
269+infer' _ (StringLiteral _) = return String
270+infer' _ (BooleanLiteral _) = return Boolean
271+infer' m (ArrayLiteral vals) = do
272+ ts <- mapM (infer m) vals
273+ arr <- fresh
274+ forM_ ts $ \t -> arr ~~ Array t
275+ return arr
276+infer' m (Unary op val) = do
277+ t <- infer m val
278+ inferUnary op t
279+infer' m (Binary op left right) = do
280+ t1 <- infer m left
281+ t2 <- infer m right
282+ inferBinary op t1 t2
283+infer' m (ObjectLiteral ps) = do
284+ lift $ ensureNoDuplicateProperties ps
285+ ts <- mapM (infer m . snd) ps
286+ let fields = zipWith (\(name, _) t -> (name, t)) ps ts
287+ return $ Object $ typesToRow fields
288+infer' m (ObjectUpdate o ps) = do
289+ lift $ ensureNoDuplicateProperties ps
290+ obj <- infer m o
291+ row <- fresh
292+ ts <- mapM (infer m . snd) ps
293+ let tys = zipWith (\(name, _) t -> (name, t)) ps ts
294+ obj ~~ Object (rowFromList (tys, row))
295+ return obj
296+infer' m (Indexer index val) = do
297+ el <- fresh
298+ check m index Number
299+ check m val (Array el)
300+ return el
301+infer' m (Accessor prop val) = do
302+ obj <- infer m val
303+ propTy <- inferProperty obj prop
304+ case propTy of
305+ Nothing -> do
306+ field <- fresh
307+ rest <- fresh
308+ obj `subsumes` Object (RCons prop field rest)
309+ return field
310+ Just ty -> return ty
311+infer' m (Abs args ret) = do
312+ ts <- replicateM (length args) fresh
313+ let m' = m `M.union` M.fromList (zip args ts)
314+ body <- infer m' ret
315+ return $ Function ts body
316+infer' m app@(App _ _) = do
317+ let (f, argss) = unfoldApplication app
318+ ft <- infer m f
319+ ret <- fresh
320+ checkFunctionApplications m ft argss ret
321+ return ret
322+infer' m (Var var@(Qualified mp name)) = do
323+ case mp of
324+ ModulePath [] ->
325+ case M.lookup name m of
326+ Just ty -> lift $ replaceAllTypeSynonyms ty
327+ Nothing -> lookupGlobal
328+ _ -> lookupGlobal
329+ where
330+ lookupGlobal = do
331+ env <- lift getEnv
332+ modulePath <- checkModulePath `fmap` lift get
333+ case M.lookup (qualify modulePath var) (names env) of
334+ Nothing -> throwError $ show var ++ " is undefined"
335+ Just (ty, _) -> lift $ replaceAllTypeSynonyms ty
336+infer' m (Block ss) = do
337+ ret <- fresh
338+ (allCodePathsReturn, _) <- checkBlock m M.empty ret ss
339+ guardWith "Block is missing a return statement" allCodePathsReturn
340+ return ret
341+infer' m (Constructor c) = do
342+ env <- lift getEnv
343+ modulePath <- checkModulePath `fmap` lift get
344+ case M.lookup (qualify modulePath c) (dataConstructors env) of
345+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
346+ Just ty -> lift $ replaceAllTypeSynonyms ty
347+infer' m (Case val binders) = do
348+ t1 <- infer m val
349+ ret <- fresh
350+ checkBinders m t1 ret binders
351+ return ret
352+infer' m (IfThenElse cond th el) = do
353+ check m cond Boolean
354+ t2 <- infer m th
355+ t3 <- infer m el
356+ t2 ~~ t3
357+ return t2
358+infer' m (TypedValue val ty) = do
359+ kind <- lift $ kindOf ty
360+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
361+ ty' <- lift $ replaceAllTypeSynonyms ty
362+ check m val ty'
363+ return ty'
364+
365+inferProperty :: Type -> String -> Subst Check (Maybe Type)
366+inferProperty (Object row) prop = do
367+ let (props, _) = rowToList row
368+ return $ lookup prop props
369+inferProperty (SaturatedTypeSynonym name args) prop = do
370+ replaced <- expandTypeSynonym name args
371+ inferProperty replaced prop
372+inferProperty (ForAll ident ty) prop = do
373+ replaced <- replaceVarsWithUnknowns [ident] ty
374+ inferProperty replaced prop
375+inferProperty _ prop = return Nothing
376+
377+inferUnary :: UnaryOperator -> Type -> Subst Check Type
378+inferUnary op val =
379+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
380+ (valTy, resTy) -> do
381+ val ~~ valTy
382+ return resTy
383+
384+checkUnary :: M.Map Ident Type -> UnaryOperator -> Value -> Type -> Subst Check ()
385+checkUnary m op val res =
386+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
387+ (valTy, resTy) -> do
388+ res ~~ resTy
389+ check m val valTy
390+
391+unaryOps :: [(UnaryOperator, (Type, Type))]
392+unaryOps = [ (Negate, (Number, Number))
393+ , (Not, (Boolean, Boolean))
394+ , (BitwiseNot, (Number, Number))
395+ ]
396+
397+inferBinary :: BinaryOperator -> Type -> Type -> Subst Check Type
398+inferBinary op left right | isEqualityTest op = do
399+ left ~~ right
400+ return Boolean
401+inferBinary op left right =
402+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
403+ (valTy, resTy) -> do
404+ left ~~ valTy
405+ right ~~ valTy
406+ return resTy
407+
408+checkBinary :: M.Map Ident Type -> BinaryOperator -> Value -> Value -> Type -> Subst Check ()
409+checkBinary m op left right res | isEqualityTest op = do
410+ res ~~ Boolean
411+ t1 <- infer m left
412+ t2 <- infer m right
413+ t1 ~~ t2
414+checkBinary m op left right res =
415+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
416+ (valTy, resTy) -> do
417+ res ~~ resTy
418+ check m left valTy
419+ check m right valTy
420+
421+isEqualityTest :: BinaryOperator -> Bool
422+isEqualityTest EqualTo = True
423+isEqualityTest NotEqualTo = True
424+isEqualityTest _ = False
425+
426+binaryOps :: [(BinaryOperator, (Type, Type))]
427+binaryOps = [ (Add, (Number, Number))
428+ , (Subtract, (Number, Number))
429+ , (Multiply, (Number, Number))
430+ , (Divide, (Number, Number))
431+ , (Modulus, (Number, Number))
432+ , (BitwiseAnd, (Number, Number))
433+ , (BitwiseOr, (Number, Number))
434+ , (BitwiseXor, (Number, Number))
435+ , (ShiftRight, (Number, Number))
436+ , (ZeroFillShiftRight, (Number, Number))
437+ , (And, (Boolean, Boolean))
438+ , (Or, (Boolean, Boolean))
439+ , (Concat, (String, String))
440+ , (Modulus, (Number, Number))
441+ , (LessThan, (Number, Boolean))
442+ , (LessThanOrEqualTo, (Number, Boolean))
443+ , (GreaterThan, (Number, Boolean))
444+ , (GreaterThanOrEqualTo, (Number, Boolean))
445+ ]
446+
447+inferBinder :: Type -> Binder -> Subst Check (M.Map Ident Type)
448+inferBinder _ NullBinder = return M.empty
449+inferBinder val (StringBinder _) = val ~~ String >> return M.empty
450+inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
451+inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
452+inferBinder val (VarBinder name) = return $ M.singleton name val
453+inferBinder val (NullaryBinder ctor) = do
454+ env <- lift getEnv
455+ modulePath <- checkModulePath `fmap` lift get
456+ case M.lookup (qualify modulePath ctor) (dataConstructors env) of
457+ Just ty -> do
458+ ty `subsumes` val
459+ return M.empty
460+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
461+inferBinder val (UnaryBinder ctor binder) = 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+ obj <- fresh
467+ ty `subsumes` (Function [obj] val)
468+ inferBinder obj binder
469+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
470+inferBinder val (ObjectBinder props) = do
471+ row <- fresh
472+ rest <- fresh
473+ m1 <- inferRowProperties row rest props
474+ val ~~ Object row
475+ return m1
476+ where
477+ inferRowProperties :: Row -> Row -> [(String, Binder)] -> Subst Check (M.Map Ident Type)
478+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
479+ inferRowProperties nrow row ((name, binder):binders) = do
480+ propTy <- fresh
481+ m1 <- inferBinder propTy binder
482+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
483+ return $ m1 `M.union` m2
484+inferBinder val (ArrayBinder binders rest) = do
485+ el <- fresh
486+ m1 <- M.unions <$> mapM (inferBinder el) binders
487+ val ~~ Array el
488+ case rest of
489+ Nothing -> return m1
490+ Just binder -> do
491+ m2 <- inferBinder val binder
492+ return $ m1 `M.union` m2
493+inferBinder val (NamedBinder name binder) = do
494+ m <- inferBinder val binder
495+ return $ M.insert name val m
496+
497+inferGuardedBinder :: M.Map Ident Type -> Type -> Binder -> Subst Check (M.Map Ident Type)
498+inferGuardedBinder m val (GuardedBinder cond binder) = do
499+ m1 <- inferBinder val binder
500+ ty <- infer (m `M.union` m1) cond
501+ ty ~~ Boolean
502+ return m1
503+inferGuardedBinder m val b = inferBinder val b
504+
505+checkBinders :: M.Map Ident Type -> Type -> Type -> [(Binder, Value)] -> Subst Check ()
506+checkBinders _ _ _ [] = return ()
507+checkBinders m nval ret ((binder, val):bs) = do
508+ m1 <- inferGuardedBinder m nval binder
509+ check (m `M.union` m1) val ret
510+ checkBinders m nval ret bs
511+
512+assignVariable :: Ident -> M.Map Ident Type -> Subst Check ()
513+assignVariable name m =
514+ case M.lookup name m of
515+ Nothing -> return ()
516+ Just _ -> throwError $ "Variable with name " ++ show name ++ " already exists."
517+
518+checkStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> Statement -> Subst Check (Bool, M.Map Ident Type)
519+checkStatement m mass ret (VariableIntroduction name val) = do
520+ assignVariable name (m `M.union` mass)
521+ t <- infer m val
522+ return (False, M.insert name t mass)
523+checkStatement m mass ret (Assignment ident val) = do
524+ t <- infer m val
525+ case M.lookup ident mass of
526+ Nothing -> throwError $ "No local variable with name " ++ show ident
527+ Just ty -> do t ~~ ty
528+ return (False, mass)
529+checkStatement m mass ret (While val inner) = do
530+ check m val Boolean
531+ (allCodePathsReturn, _) <- checkBlock m mass ret inner
532+ return (allCodePathsReturn, mass)
533+checkStatement m mass ret (If ifst) = do
534+ allCodePathsReturn <- checkIfStatement m mass ret ifst
535+ return (allCodePathsReturn, mass)
536+checkStatement m mass ret (For ident start end inner) = do
537+ assignVariable ident (m `M.union` mass)
538+ check (m `M.union` mass) start Number
539+ check (m `M.union` mass) end Number
540+ let mass1 = M.insert ident Number mass
541+ (allCodePathsReturn, _) <- checkBlock (m `M.union` mass1) mass1 ret inner
542+ return (allCodePathsReturn, mass)
543+checkStatement m mass ret (ForEach ident vals inner) = do
544+ assignVariable ident (m `M.union` mass)
545+ val <- fresh
546+ check (m `M.union` mass) vals (Array val)
547+ let mass1 = M.insert ident val mass
548+ (allCodePathsReturn, _) <- checkBlock (m `M.union` mass1) mass1 ret inner
549+ guardWith "Cannot return from within a foreach block" $ not allCodePathsReturn
550+ return (False, mass)
551+checkStatement m mass ret (Return val) = do
552+ check (m `M.union` mass) val ret
553+ return (True, mass)
554+
555+checkIfStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> IfStatement -> Subst Check Bool
556+checkIfStatement m mass ret (IfStatement val thens Nothing) = do
557+ check m val Boolean
558+ _ <- checkBlock m mass ret thens
559+ return False
560+checkIfStatement m mass ret (IfStatement val thens (Just elses)) = do
561+ check m val Boolean
562+ (allCodePathsReturn1, _) <- checkBlock m mass ret thens
563+ allCodePathsReturn2 <- checkElseStatement m mass ret elses
564+ return $ allCodePathsReturn1 && allCodePathsReturn2
565+
566+checkElseStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> ElseStatement -> Subst Check Bool
567+checkElseStatement m mass ret (Else elses) = fst <$> checkBlock m mass ret elses
568+checkElseStatement m mass ret (ElseIf ifst) = checkIfStatement m mass ret ifst
569+
570+checkBlock :: M.Map Ident Type -> M.Map Ident Type -> Type -> [Statement] -> Subst Check (Bool, M.Map Ident Type)
571+checkBlock _ mass _ [] = return (False, mass)
572+checkBlock m mass ret (s:ss) = do
573+ (b1, mass1) <- checkStatement (m `M.union` mass) mass ret s
574+ case (b1, ss) of
575+ (True, []) -> return (True, mass1)
576+ (True, _) -> throwError "Unreachable code"
577+ (False, ss) -> do
578+ (b2, mass2) <- checkBlock m mass1 ret ss
579+ return (b2, mass2)
580+
581+skolemize :: String -> Type -> Subst Check Type
582+skolemize ident ty = do
583+ tsk <- Skolem <$> fresh'
584+ rsk <- RSkolem <$> fresh'
585+ return $ replaceRowVars (M.singleton ident rsk) $ replaceTypeVars (M.singleton ident tsk) ty
586+
587+check :: M.Map Ident Type -> Value -> Type -> Subst Check ()
588+check m val ty = rethrow errorMessage $ check' m val ty
589+ where
590+ errorMessage msg =
591+ "Error checking type of term " ++
592+ prettyPrintValue val ++
593+ " against type " ++
594+ prettyPrintType ty ++
595+ ":\n" ++
596+ msg
597+
598+check' :: M.Map Ident Type -> Value -> Type -> Subst Check ()
599+check' m val (ForAll idents ty) = do
600+ sk <- skolemize idents ty
601+ check m val sk
602+check' m val u@(TUnknown _) = do
603+ ty <- infer m val
604+ -- Don't unify an unknown with an inferred polytype
605+ ty' <- replaceAllVarsWithUnknowns ty
606+ ty' ~~ u
607+check' m (NumericLiteral _) Number = return ()
608+check' m (StringLiteral _) String = return ()
609+check' m (BooleanLiteral _) Boolean = return ()
610+check' m (Unary op val) ty = checkUnary m op val ty
611+check' m (Binary op left right) ty = checkBinary m op left right ty
612+check' m (ArrayLiteral vals) (Array ty) = forM_ vals (\val -> check m val ty)
613+check' m (Indexer index vals) ty = check m index Number >> check m vals (Array ty)
614+check' m (Abs args ret) (Function argTys retTy) = do
615+ guardWith "Incorrect number of function arguments" (length args == length argTys)
616+ let bindings = M.fromList (zip args argTys)
617+ check (bindings `M.union` m) ret retTy
618+check' m app@(App _ _) ret = do
619+ let (f, argss) = unfoldApplication app
620+ ft <- infer m f
621+ checkFunctionApplications m ft argss ret
622+check' m v@(Var var@(Qualified mp name)) ty = do
623+ case mp of
624+ ModulePath [] ->
625+ case M.lookup name m of
626+ Just ty1 -> do
627+ repl <- lift $ replaceAllTypeSynonyms ty1
628+ repl `subsumes` ty
629+ Nothing -> lookupGlobal
630+ _ -> lookupGlobal
631+ where
632+ lookupGlobal = do
633+ env <- lift getEnv
634+ modulePath <- checkModulePath `fmap` lift get
635+ case M.lookup (qualify modulePath var) (names env) of
636+ Nothing -> throwError $ show var ++ " is undefined"
637+ Just (ty1, _) -> do
638+ repl <- lift $ replaceAllTypeSynonyms ty1
639+ repl `subsumes` ty
640+check' m (TypedValue val ty1) ty2 = do
641+ kind <- lift $ kindOf ty1
642+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
643+ ty1 `subsumes` ty2
644+ check m val ty1
645+check' m (Case val binders) ret = do
646+ t1 <- infer m val
647+ checkBinders m t1 ret binders
648+check' m (IfThenElse cond th el) ty = do
649+ check m cond Boolean
650+ check m th ty
651+ check m el ty
652+check' m (ObjectLiteral ps) (Object row) = do
653+ lift $ ensureNoDuplicateProperties ps
654+ checkProperties m ps row False
655+check' m (ObjectUpdate obj ps) objTy@(Object row) = do
656+ lift $ ensureNoDuplicateProperties ps
657+ check m obj objTy
658+ checkProperties m ps row True
659+check' m (Accessor prop val) ty = do
660+ rest <- fresh
661+ check m val (Object (RCons prop ty rest))
662+check' m (Block ss) ret = do
663+ (allCodePathsReturn, _) <- checkBlock m M.empty ret ss
664+ guardWith "Block is missing a return statement" allCodePathsReturn
665+check' m (Constructor c) ty = do
666+ env <- lift getEnv
667+ modulePath <- checkModulePath `fmap` lift get
668+ case M.lookup (qualify modulePath c) (dataConstructors env) of
669+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
670+ Just ty1 -> do
671+ repl <- lift $ replaceAllTypeSynonyms ty1
672+ repl `subsumes` ty
673+check' m val (SaturatedTypeSynonym name args) = do
674+ ty <- expandTypeSynonym name args
675+ check m val ty
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+unfoldApplication :: Value -> (Value, [[Value]])
704+unfoldApplication = go []
705+ where
706+ go argss (App f args) = go (args:argss) f
707+ go argss f = (f, argss)
708+
709+checkFunctionApplications :: M.Map Ident Type -> Type -> [[Value]] -> Type -> Subst Check ()
710+checkFunctionApplications _ _ [] _ = error "Nullary function application"
711+checkFunctionApplications m fnTy [args] ret = checkFunctionApplication m fnTy args ret
712+checkFunctionApplications m fnTy (args:argss) ret = do
713+ f <- fresh
714+ checkFunctionApplication m fnTy args f
715+ checkFunctionApplications m f argss ret
716+
717+checkFunctionApplication :: M.Map Ident Type -> Type -> [Value] -> Type -> Subst Check ()
718+checkFunctionApplication m fnTy args ret = rethrow errorMessage $ checkFunctionApplication' m fnTy args ret
719+ where
720+ errorMessage msg = "Error applying function of type "
721+ ++ prettyPrintType fnTy
722+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
723+ ++ ", expecting value of type "
724+ ++ prettyPrintType ret ++ ":\n" ++ msg
725+
726+checkFunctionApplication' :: M.Map Ident Type -> Type -> [Value] -> Type -> Subst Check ()
727+checkFunctionApplication' m (Function argTys retTy) args ret = do
728+ guardWith "Incorrect number of function arguments" (length args == length argTys)
729+ zipWithM (check m) args argTys
730+ retTy `subsumes` ret
731+checkFunctionApplication' m (ForAll ident ty) args ret = do
732+ replaced <- replaceVarsWithUnknowns [ident] ty
733+ checkFunctionApplication m replaced args ret
734+checkFunctionApplication' m u@(TUnknown _) args ret = do
735+ tyArgs <- mapM (\arg -> infer m arg >>= replaceAllVarsWithUnknowns) args
736+ u ~~ Function tyArgs ret
737+checkFunctionApplication' m (SaturatedTypeSynonym name tyArgs) args ret = do
738+ ty <- expandTypeSynonym name tyArgs
739+ checkFunctionApplication' m ty args ret
740+checkFunctionApplication' _ fnTy args ret = throwError $ "Cannot apply function of type "
741+ ++ prettyPrintType fnTy
742+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
743+ ++ ". Expecting value of type " ++ prettyPrintType ret ++ "."
744+
745+subsumes :: Type -> Type -> Subst Check ()
746+subsumes (ForAll ident ty1) ty2 = do
747+ replaced <- replaceVarsWithUnknowns [ident] ty1
748+ replaced `subsumes` ty2
749+subsumes (Function args1 ret1) (Function args2 ret2) = do
750+ zipWithM subsumes args2 args1
751+ ret1 `subsumes` ret2
752+subsumes ty1 ty2 = ty1 ~~ ty2
753+