@@ -0,0 +1,748 @@
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
26+ (something, everywhere, everywhereM, everything, everywhereBut,
27+ mkT, mkM, mkQ, extM, extQ)
28+
29+import Language.PureScript.Values
30+import Language.PureScript.Types
31+import Language.PureScript.Kinds
32+import Language.PureScript.Names
33+import Language.PureScript.TypeChecker.Monad
34+import Language.PureScript.TypeChecker.Kinds
35+import Language.PureScript.TypeChecker.Synonyms
36+import Language.PureScript.Pretty
37+import Language.PureScript.Unknown
38+
39+import Control.Monad.State
40+import Control.Monad.Error
41+
42+import Control.Applicative
43+import Control.Arrow (Arrow(..), Kleisli(..), (***), (&&&), second)
44+import qualified Control.Category as C
45+
46+import qualified Data.Map as M
47+
48+instance Unifiable Type where
49+ unknown = TUnknown
50+ isUnknown (TUnknown u) = Just u
51+ isUnknown _ = Nothing
52+ (~~) = unifyTypes
53+ apply s (TUnknown u) = runSubstitution s u
54+ apply s (SaturatedTypeSynonym name tys) = SaturatedTypeSynonym name $ map (apply s) tys
55+ apply s (ForAll idents ty) = ForAll idents $ apply s ty
56+ apply s (Array t) = Array (apply s t)
57+ apply s (Object r) = Object (apply s r)
58+ apply s (Function args ret) = Function (map (apply s) args) (apply s ret)
59+ apply s (TypeApp t1 t2) = TypeApp (apply s t1) (apply s t2)
60+ apply _ t = t
61+ unknowns (TUnknown (Unknown u)) = [u]
62+ unknowns (SaturatedTypeSynonym _ tys) = concatMap unknowns tys
63+ unknowns (ForAll idents ty) = unknowns ty
64+ unknowns (Array t) = unknowns t
65+ unknowns (Object r) = unknowns r
66+ unknowns (Function args ret) = concatMap unknowns args ++ unknowns ret
67+ unknowns (TypeApp t1 t2) = unknowns t1 ++ unknowns t2
68+ unknowns _ = []
69+
70+instance Unifiable Row where
71+ unknown = RUnknown
72+ isUnknown (RUnknown u) = Just u
73+ isUnknown _ = Nothing
74+ r1 ~~ r2 =
75+ let
76+ (s1, r1') = rowToList r1
77+ (s2, r2') = rowToList r2
78+ int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
79+ sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
80+ sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
81+ in do
82+ forM_ int (uncurry (~~))
83+ unifyRows sd1 r1' sd2 r2'
84+ where
85+ unifyRows :: [(String, Type)] -> Row -> [(String, Type)] -> Row -> Subst Check ()
86+ unifyRows [] (RUnknown u) sd r = replace u (rowFromList (sd, r))
87+ unifyRows sd r [] (RUnknown u) = replace u (rowFromList (sd, r))
88+ unifyRows ns@((name, ty):row) r others u@(RUnknown un) = do
89+ occursCheck un ty
90+ forM row $ \(_, ty) -> occursCheck un ty
91+ u' <- fresh
92+ u ~~ RCons name ty u'
93+ unifyRows row r others u'
94+ unifyRows [] REmpty [] REmpty = return ()
95+ unifyRows [] (RowVar v1) [] (RowVar v2) | v1 == v2 = return ()
96+ unifyRows [] (RSkolem s1) [] (RSkolem s2) | s1 == s2 = return ()
97+ unifyRows sd1 r1 sd2 r2 = throwError $ "Cannot unify " ++ prettyPrintRow (rowFromList (sd1, r1)) ++ " with " ++ prettyPrintRow (rowFromList (sd2, r2)) ++ "."
98+ apply s (RUnknown u) = runSubstitution s u
99+ apply s (RCons name ty r) = RCons name (apply s ty) (apply s r)
100+ apply _ r = r
101+ unknowns (RUnknown (Unknown u)) = [u]
102+ unknowns (RCons _ ty r) = unknowns ty ++ unknowns r
103+ unknowns _ = []
104+
105+unifyTypes :: Type -> Type -> Subst Check ()
106+unifyTypes t1 t2 = rethrow (\e -> "Error unifying type " ++ prettyPrintType t1 ++ " with type " ++ prettyPrintType t2 ++ ":\n" ++ e) $ do
107+ unifyTypes' t1 t2
108+ where
109+ unifyTypes' (TUnknown u1) (TUnknown u2) | u1 == u2 = return ()
110+ unifyTypes' (TUnknown u) t = replace u t
111+ unifyTypes' t (TUnknown u) = replace u t
112+ unifyTypes' (SaturatedTypeSynonym name1 args1) (SaturatedTypeSynonym name2 args2)
113+ | name1 == name2 = zipWithM_ unifyTypes args1 args2
114+ unifyTypes' (SaturatedTypeSynonym name args) ty = do
115+ ty1 <- expandTypeSynonym name args
116+ ty1 `unifyTypes` ty
117+ unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
118+ unifyTypes' (ForAll ident1 ty1) (ForAll ident2 ty2) = do
119+ sk <- skolemize ident1 ty1
120+ replaced <- replaceVarWithUnknown ident2 ty2
121+ sk `unifyTypes` replaced
122+ unifyTypes' (ForAll ident ty1) ty2 = do
123+ sk <- skolemize ident ty1
124+ sk `unifyTypes` ty2
125+ unifyTypes' ty f@(ForAll _ _) = f `unifyTypes` ty
126+ unifyTypes' Number Number = return ()
127+ unifyTypes' String String = return ()
128+ unifyTypes' Boolean Boolean = return ()
129+ unifyTypes' (Array s) (Array t) = s `unifyTypes` t
130+ unifyTypes' (Object row1) (Object row2) = row1 ~~ row2
131+ unifyTypes' (Function args1 ret1) (Function args2 ret2) = do
132+ guardWith "Function applied to incorrect number of args" $ length args1 == length args2
133+ zipWithM_ unifyTypes args1 args2
134+ ret1 `unifyTypes` ret2
135+ unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
136+ unifyTypes' (TypeConstructor c1) (TypeConstructor c2) = do
137+ modulePath <- checkModulePath `fmap` lift get
138+ guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (qualify modulePath c1 == qualify modulePath c2)
139+ unifyTypes' (TypeApp t1 t2) (TypeApp t3 t4) = do
140+ t1 `unifyTypes` t3
141+ t2 `unifyTypes` t4
142+ unifyTypes' (Skolem s1) (Skolem s2) | s1 == s2 = return ()
143+ unifyTypes' t1 t2 = throwError $ "Cannot unify " ++ prettyPrintType t1 ++ " with " ++ prettyPrintType t2 ++ "."
144+
145+isFunction :: Value -> Bool
146+isFunction (Abs _ _) = True
147+isFunction (TypedValue untyped _) = isFunction untyped
148+isFunction _ = False
149+
150+typeOf :: Maybe Ident -> Value -> Check Type
151+typeOf name val = do
152+ (ty, sub, checks) <- runSubst $ case name of
153+ Just ident | isFunction val ->
154+ case val of
155+ TypedValue val ty -> do
156+ kind <- lift $ kindOf ty
157+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
158+ ty' <- lift $ replaceAllTypeSynonyms ty
159+ check (M.singleton ident ty) val ty'
160+ return ty'
161+ _ -> do
162+ me <- fresh
163+ ty <- infer (M.singleton ident me) val
164+ ty ~~ me
165+ return ty
166+ _ -> infer M.empty val
167+ escapeCheck checks ty sub
168+ skolemEscapeCheck ty
169+ return $ varIfUnknown $ desaturateAllTypeSynonyms $ setifyAll ty
170+
171+escapeCheck :: [AnyUnifiable] -> Type -> Substitution -> Check ()
172+escapeCheck checks ty sub =
173+ let
174+ visibleUnknowns = nub $ unknowns ty
175+ in
176+ forM_ checks $ \check -> case check of
177+ AnyUnifiable t -> do
178+ let unsolvedUnknowns = nub . unknowns $ apply sub t
179+ guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
180+
181+skolemEscapeCheck :: Type -> Check ()
182+skolemEscapeCheck ty =
183+ case something (extQ (mkQ Nothing findSkolems) findRSkolems) ty of
184+ Nothing -> return ()
185+ Just _ -> throwError "Skolem variables cannot escape. Consider adding a type signature."
186+ where
187+ findSkolems (Skolem _) = return ()
188+ findSkolems _ = mzero
189+ findRSkolems (RSkolem _) = return ()
190+ findRSkolems _ = mzero
191+
192+setify :: Row -> Row
193+setify = rowFromList . first (M.toList . M.fromList) . rowToList
194+
195+setifyAll :: (D.Data d) => d -> d
196+setifyAll = everywhere (mkT setify)
197+
198+varIfUnknown :: Type -> Type
199+varIfUnknown ty = mkForAll (sort . map ((:) 'u' . show) . nub $ unknowns ty) ty
200+
201+replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
202+replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
203+
204+replaceTypeVars :: (D.Data d) => String -> Type -> d -> d
205+replaceTypeVars name t = everywhereBut (mkQ False isShadowed) (mkT replace)
206+ where
207+ replace (TypeVar v) | v == name = t
208+ replace t = t
209+ isShadowed (ForAll v _) | v == name = True
210+ isShadowed _ = False
211+
212+replaceRowVars :: (D.Data d) => String -> Row -> d -> d
213+replaceRowVars name r = everywhere (mkT replace)
214+ where
215+ replace (RowVar v) | v == name = r
216+ replace t = t
217+
218+replaceAllVarsWithUnknowns :: Type -> Subst Check Type
219+replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
220+replaceAllVarsWithUnknowns ty = return ty
221+
222+replaceVarWithUnknown :: String -> Type -> Subst Check Type
223+replaceVarWithUnknown ident ty = do
224+ tu <- fresh
225+ ru <- fresh
226+ return $ replaceRowVars ident ru . replaceTypeVars ident tu $ ty
227+
228+replaceAllTypeSynonyms :: (D.Data d) => d -> Check d
229+replaceAllTypeSynonyms d = do
230+ env <- getEnv
231+ let syns = map (\((path, name), (args, _)) -> (Qualified path name, length args)) . M.toList $ typeSynonyms env
232+ either throwError return $ saturateAllTypeSynonyms syns d
233+
234+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
235+desaturateAllTypeSynonyms = everywhere (mkT replace)
236+ where
237+ replace (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
238+ replace t = t
239+
240+expandAllTypeSynonyms :: Type -> Subst Check Type
241+expandAllTypeSynonyms (SaturatedTypeSynonym name args) = expandTypeSynonym name args >>= expandAllTypeSynonyms
242+expandAllTypeSynonyms ty = return ty
243+
244+expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Check Type
245+expandTypeSynonym name args = do
246+ env <- lift getEnv
247+ modulePath <- checkModulePath `fmap` lift get
248+ case M.lookup (qualify modulePath name) (typeSynonyms env) of
249+ Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
250+ Nothing -> error "Type synonym was not defined"
251+
252+ensureNoDuplicateProperties :: [(String, Value)] -> Check ()
253+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
254+
255+infer :: M.Map Ident Type -> Value -> Subst Check Type
256+infer m val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ do
257+ ty <- infer' m val
258+ escapeCheckLater ty
259+ return ty
260+
261+infer' _ (NumericLiteral _) = return Number
262+infer' _ (StringLiteral _) = return String
263+infer' _ (BooleanLiteral _) = return Boolean
264+infer' m (ArrayLiteral vals) = do
265+ ts <- mapM (infer m) vals
266+ arr <- fresh
267+ forM_ ts $ \t -> arr ~~ Array t
268+ return arr
269+infer' m (Unary op val) = do
270+ t <- infer m val
271+ inferUnary op t
272+infer' m (Binary op left right) = do
273+ t1 <- infer m left
274+ t2 <- infer m right
275+ inferBinary op t1 t2
276+infer' m (ObjectLiteral ps) = do
277+ lift $ ensureNoDuplicateProperties ps
278+ ts <- mapM (infer m . snd) ps
279+ let fields = zipWith (\(name, _) t -> (name, t)) ps ts
280+ return $ Object $ rowFromList (fields, REmpty)
281+infer' m (ObjectUpdate o ps) = do
282+ lift $ ensureNoDuplicateProperties ps
283+ row <- fresh
284+ newTys <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer m . snd) ps
285+ oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
286+ check m o $ Object $ rowFromList (oldTys, row)
287+ return $ Object $ rowFromList (newTys, row)
288+infer' m (Indexer index val) = do
289+ el <- fresh
290+ check m index Number
291+ check m val (Array el)
292+ return el
293+infer' m (Accessor prop val) = do
294+ obj <- infer m val
295+ propTy <- inferProperty obj prop
296+ case propTy of
297+ Nothing -> do
298+ field <- fresh
299+ rest <- fresh
300+ obj `subsumes` Object (RCons prop field rest)
301+ return field
302+ Just ty -> return ty
303+infer' m (Abs args ret) = do
304+ ts <- replicateM (length args) fresh
305+ let m' = m `M.union` M.fromList (zip args ts)
306+ body <- infer m' ret
307+ return $ Function ts body
308+infer' m app@(App _ _) = do
309+ let (f, argss) = unfoldApplication app
310+ ft <- infer m f
311+ ret <- fresh
312+ checkFunctionApplications m ft argss ret
313+ return ret
314+infer' m (Var var@(Qualified mp name)) = do
315+ case mp of
316+ ModulePath [] ->
317+ case M.lookup name m of
318+ Just ty -> lift $ replaceAllTypeSynonyms ty
319+ Nothing -> lookupGlobal
320+ _ -> lookupGlobal
321+ where
322+ lookupGlobal = do
323+ env <- lift getEnv
324+ modulePath <- checkModulePath `fmap` lift get
325+ case M.lookup (qualify modulePath var) (names env) of
326+ Nothing -> throwError $ show var ++ " is undefined"
327+ Just (ty, _) -> lift $ replaceAllTypeSynonyms ty
328+infer' m (Block ss) = do
329+ ret <- fresh
330+ (allCodePathsReturn, _) <- checkBlock m M.empty ret ss
331+ guardWith "Block is missing a return statement" allCodePathsReturn
332+ return ret
333+infer' m (Constructor c) = do
334+ env <- lift getEnv
335+ modulePath <- checkModulePath `fmap` lift get
336+ case M.lookup (qualify modulePath c) (dataConstructors env) of
337+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
338+ Just ty -> lift $ replaceAllTypeSynonyms ty
339+infer' m (Case val binders) = do
340+ t1 <- infer m val
341+ ret <- fresh
342+ checkBinders m t1 ret binders
343+ return ret
344+infer' m (IfThenElse cond th el) = do
345+ check m cond Boolean
346+ t2 <- infer m th
347+ t3 <- infer m el
348+ t2 ~~ t3
349+ return t2
350+infer' m (TypedValue val ty) = do
351+ kind <- lift $ kindOf ty
352+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
353+ ty' <- lift $ replaceAllTypeSynonyms ty
354+ check m val ty'
355+ return ty'
356+
357+inferProperty :: Type -> String -> Subst Check (Maybe Type)
358+inferProperty (Object row) prop = do
359+ let (props, _) = rowToList row
360+ return $ lookup prop props
361+inferProperty (SaturatedTypeSynonym name args) prop = do
362+ replaced <- expandTypeSynonym name args
363+ inferProperty replaced prop
364+inferProperty (ForAll ident ty) prop = do
365+ replaced <- replaceVarWithUnknown ident ty
366+ inferProperty replaced prop
367+inferProperty _ prop = return Nothing
368+
369+inferUnary :: UnaryOperator -> Type -> Subst Check Type
370+inferUnary op val =
371+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
372+ (valTy, resTy) -> do
373+ val ~~ valTy
374+ return resTy
375+
376+checkUnary :: M.Map Ident Type -> UnaryOperator -> Value -> Type -> Subst Check ()
377+checkUnary m op val res =
378+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
379+ (valTy, resTy) -> do
380+ res ~~ resTy
381+ check m val valTy
382+
383+unaryOps :: [(UnaryOperator, (Type, Type))]
384+unaryOps = [ (Negate, (Number, Number))
385+ , (Not, (Boolean, Boolean))
386+ , (BitwiseNot, (Number, Number))
387+ ]
388+
389+inferBinary :: BinaryOperator -> Type -> Type -> Subst Check Type
390+inferBinary op left right | isEqualityTest op = do
391+ left ~~ right
392+ return Boolean
393+inferBinary op left right =
394+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
395+ (valTy, resTy) -> do
396+ left ~~ valTy
397+ right ~~ valTy
398+ return resTy
399+
400+checkBinary :: M.Map Ident Type -> BinaryOperator -> Value -> Value -> Type -> Subst Check ()
401+checkBinary m op left right res | isEqualityTest op = do
402+ res ~~ Boolean
403+ t1 <- infer m left
404+ t2 <- infer m right
405+ t1 ~~ t2
406+checkBinary m op left right res =
407+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
408+ (valTy, resTy) -> do
409+ res ~~ resTy
410+ check m left valTy
411+ check m right valTy
412+
413+isEqualityTest :: BinaryOperator -> Bool
414+isEqualityTest EqualTo = True
415+isEqualityTest NotEqualTo = True
416+isEqualityTest _ = False
417+
418+binaryOps :: [(BinaryOperator, (Type, Type))]
419+binaryOps = [ (Add, (Number, Number))
420+ , (Subtract, (Number, Number))
421+ , (Multiply, (Number, Number))
422+ , (Divide, (Number, Number))
423+ , (Modulus, (Number, Number))
424+ , (BitwiseAnd, (Number, Number))
425+ , (BitwiseOr, (Number, Number))
426+ , (BitwiseXor, (Number, Number))
427+ , (ShiftRight, (Number, Number))
428+ , (ZeroFillShiftRight, (Number, Number))
429+ , (And, (Boolean, Boolean))
430+ , (Or, (Boolean, Boolean))
431+ , (Concat, (String, String))
432+ , (Modulus, (Number, Number))
433+ , (LessThan, (Number, Boolean))
434+ , (LessThanOrEqualTo, (Number, Boolean))
435+ , (GreaterThan, (Number, Boolean))
436+ , (GreaterThanOrEqualTo, (Number, Boolean))
437+ ]
438+
439+inferBinder :: Type -> Binder -> Subst Check (M.Map Ident Type)
440+inferBinder _ NullBinder = return M.empty
441+inferBinder val (StringBinder _) = val ~~ String >> return M.empty
442+inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
443+inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
444+inferBinder val (VarBinder name) = return $ M.singleton name val
445+inferBinder val (NullaryBinder ctor) = do
446+ env <- lift getEnv
447+ modulePath <- checkModulePath `fmap` lift get
448+ case M.lookup (qualify modulePath ctor) (dataConstructors env) of
449+ Just ty -> do
450+ ty `subsumes` val
451+ return M.empty
452+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
453+inferBinder val (UnaryBinder ctor binder) = 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+ Function [obj] ret <- replaceAllVarsWithUnknowns ty
459+ val `subsumes` ret
460+ inferBinder obj binder
461+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
462+inferBinder val (ObjectBinder props) = do
463+ row <- fresh
464+ rest <- fresh
465+ m1 <- inferRowProperties row rest props
466+ val ~~ Object row
467+ return m1
468+ where
469+ inferRowProperties :: Row -> Row -> [(String, Binder)] -> Subst Check (M.Map Ident Type)
470+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
471+ inferRowProperties nrow row ((name, binder):binders) = do
472+ propTy <- fresh
473+ m1 <- inferBinder propTy binder
474+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
475+ return $ m1 `M.union` m2
476+inferBinder val (ArrayBinder binders rest) = do
477+ el <- fresh
478+ m1 <- M.unions <$> mapM (inferBinder el) binders
479+ val ~~ Array el
480+ case rest of
481+ Nothing -> return m1
482+ Just binder -> do
483+ m2 <- inferBinder val binder
484+ return $ m1 `M.union` m2
485+inferBinder val (NamedBinder name binder) = do
486+ m <- inferBinder val binder
487+ return $ M.insert name val m
488+
489+inferGuardedBinder :: M.Map Ident Type -> Type -> Binder -> Subst Check (M.Map Ident Type)
490+inferGuardedBinder m val (GuardedBinder cond binder) = do
491+ m1 <- inferBinder val binder
492+ check (m1 `M.union` m) cond Boolean
493+ return m1
494+inferGuardedBinder m val b = inferBinder val b
495+
496+checkBinders :: M.Map Ident Type -> Type -> Type -> [(Binder, Value)] -> Subst Check ()
497+checkBinders _ _ _ [] = return ()
498+checkBinders m nval ret ((binder, val):bs) = do
499+ m1 <- inferGuardedBinder m nval binder
500+ check (m1 `M.union` m) val ret
501+ checkBinders m nval ret bs
502+
503+assignVariable :: Ident -> M.Map Ident Type -> Subst Check ()
504+assignVariable name m =
505+ case M.lookup name m of
506+ Nothing -> return ()
507+ Just _ -> throwError $ "Variable with name " ++ show name ++ " already exists."
508+
509+checkStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> Statement -> Subst Check (Bool, M.Map Ident Type)
510+checkStatement m mass ret (VariableIntroduction name val) = do
511+ assignVariable name (m `M.union` mass)
512+ t <- infer m val
513+ return (False, M.insert name t mass)
514+checkStatement m mass ret (Assignment ident val) = do
515+ t <- infer m val
516+ case M.lookup ident mass of
517+ Nothing -> throwError $ "No local variable with name " ++ show ident
518+ Just ty -> do t ~~ ty
519+ return (False, mass)
520+checkStatement m mass ret (While val inner) = do
521+ check m val Boolean
522+ (allCodePathsReturn, _) <- checkBlock m mass ret inner
523+ return (allCodePathsReturn, mass)
524+checkStatement m mass ret (If ifst) = do
525+ allCodePathsReturn <- checkIfStatement m mass ret ifst
526+ return (allCodePathsReturn, mass)
527+checkStatement m mass ret (For ident start end inner) = do
528+ assignVariable ident (m `M.union` mass)
529+ check (m `M.union` mass) start Number
530+ check (m `M.union` mass) end Number
531+ let mass1 = M.insert ident Number mass
532+ (allCodePathsReturn, _) <- checkBlock (m `M.union` mass1) mass1 ret inner
533+ return (allCodePathsReturn, mass)
534+checkStatement m mass ret (ForEach ident vals inner) = do
535+ assignVariable ident (m `M.union` mass)
536+ val <- fresh
537+ check (m `M.union` mass) vals (Array val)
538+ let mass1 = M.insert ident val mass
539+ (allCodePathsReturn, _) <- checkBlock (m `M.union` mass1) mass1 ret inner
540+ guardWith "Cannot return from within a foreach block" $ not allCodePathsReturn
541+ return (False, mass)
542+checkStatement m mass ret (Return val) = do
543+ check (m `M.union` mass) val ret
544+ return (True, mass)
545+
546+checkIfStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> IfStatement -> Subst Check Bool
547+checkIfStatement m mass ret (IfStatement val thens Nothing) = do
548+ check m val Boolean
549+ _ <- checkBlock m mass ret thens
550+ return False
551+checkIfStatement m mass ret (IfStatement val thens (Just elses)) = do
552+ check m val Boolean
553+ (allCodePathsReturn1, _) <- checkBlock m mass ret thens
554+ allCodePathsReturn2 <- checkElseStatement m mass ret elses
555+ return $ allCodePathsReturn1 && allCodePathsReturn2
556+
557+checkElseStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> ElseStatement -> Subst Check Bool
558+checkElseStatement m mass ret (Else elses) = fst <$> checkBlock m mass ret elses
559+checkElseStatement m mass ret (ElseIf ifst) = checkIfStatement m mass ret ifst
560+
561+checkBlock :: M.Map Ident Type -> M.Map Ident Type -> Type -> [Statement] -> Subst Check (Bool, M.Map Ident Type)
562+checkBlock _ mass _ [] = return (False, mass)
563+checkBlock m mass ret (s:ss) = do
564+ (b1, mass1) <- checkStatement (m `M.union` mass) mass ret s
565+ case (b1, ss) of
566+ (True, []) -> return (True, mass1)
567+ (True, _) -> throwError "Unreachable code"
568+ (False, ss) -> do
569+ (b2, mass2) <- checkBlock m mass1 ret ss
570+ return (b2, mass2)
571+
572+skolemize :: String -> Type -> Subst Check Type
573+skolemize ident ty = do
574+ tsk <- Skolem <$> fresh'
575+ rsk <- RSkolem <$> fresh'
576+ return $ replaceRowVars ident rsk $ replaceTypeVars ident tsk ty
577+
578+check :: M.Map Ident Type -> Value -> Type -> Subst Check ()
579+check m val ty = rethrow errorMessage $ check' m val ty
580+ where
581+ errorMessage msg =
582+ "Error checking type of term " ++
583+ prettyPrintValue val ++
584+ " against type " ++
585+ prettyPrintType ty ++
586+ ":\n" ++
587+ msg
588+
589+check' :: M.Map Ident Type -> Value -> Type -> Subst Check ()
590+check' m val (ForAll idents ty) = do
591+ sk <- skolemize idents ty
592+ check m val sk
593+check' m val u@(TUnknown _) = do
594+ ty <- infer m val
595+ -- Don't unify an unknown with an inferred polytype
596+ ty' <- replaceAllVarsWithUnknowns ty
597+ ty' ~~ u
598+check' m (NumericLiteral _) Number = return ()
599+check' m (StringLiteral _) String = return ()
600+check' m (BooleanLiteral _) Boolean = return ()
601+check' m (Unary op val) ty = checkUnary m op val ty
602+check' m (Binary op left right) ty = checkBinary m op left right ty
603+check' m (ArrayLiteral vals) (Array ty) = forM_ vals (\val -> check m val ty)
604+check' m (Indexer index vals) ty = check m index Number >> check m vals (Array ty)
605+check' m (Abs args ret) (Function argTys retTy) = do
606+ guardWith "Incorrect number of function arguments" (length args == length argTys)
607+ let bindings = M.fromList (zip args argTys)
608+ check (bindings `M.union` m) ret retTy
609+check' m app@(App _ _) ret = do
610+ let (f, argss) = unfoldApplication app
611+ ft <- infer m f
612+ checkFunctionApplications m ft argss ret
613+check' m v@(Var var@(Qualified mp name)) ty = do
614+ case mp of
615+ ModulePath [] ->
616+ case M.lookup name m of
617+ Just ty1 -> do
618+ repl <- lift $ replaceAllTypeSynonyms ty1
619+ repl `subsumes` ty
620+ Nothing -> lookupGlobal
621+ _ -> lookupGlobal
622+ where
623+ lookupGlobal = do
624+ env <- lift getEnv
625+ modulePath <- checkModulePath `fmap` lift get
626+ case M.lookup (qualify modulePath var) (names env) of
627+ Nothing -> throwError $ show var ++ " is undefined"
628+ Just (ty1, _) -> do
629+ repl <- lift $ replaceAllTypeSynonyms ty1
630+ repl `subsumes` ty
631+check' m (TypedValue val ty1) ty2 = do
632+ kind <- lift $ kindOf ty1
633+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
634+ ty1 `subsumes` ty2
635+ check m val ty1
636+check' m (Case val binders) ret = do
637+ t1 <- infer m val
638+ checkBinders m t1 ret binders
639+check' m (IfThenElse cond th el) ty = do
640+ check m cond Boolean
641+ check m th ty
642+ check m el ty
643+check' m (ObjectLiteral ps) (Object row) = do
644+ lift $ ensureNoDuplicateProperties ps
645+ checkProperties m ps row False
646+check' m (ObjectUpdate obj ps) (Object row) = do
647+ lift $ ensureNoDuplicateProperties ps
648+ us <- zip (map fst ps) <$> replicateM (length ps) fresh
649+ let (propsToCheck, rest) = rowToList row
650+ propsToRemove = map fst ps
651+ remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
652+ check m obj (Object (rowFromList (us ++ remainingProps, rest)))
653+ checkProperties m ps row True
654+check' m (Accessor prop val) ty = do
655+ rest <- fresh
656+ check m val (Object (RCons prop ty rest))
657+check' m (Block ss) ret = do
658+ (allCodePathsReturn, _) <- checkBlock m M.empty ret ss
659+ guardWith "Block is missing a return statement" allCodePathsReturn
660+check' m (Constructor c) ty = do
661+ env <- lift getEnv
662+ modulePath <- checkModulePath `fmap` lift get
663+ case M.lookup (qualify modulePath c) (dataConstructors env) of
664+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
665+ Just ty1 -> do
666+ repl <- lift $ replaceAllTypeSynonyms ty1
667+ repl `subsumes` ty
668+check' m val (SaturatedTypeSynonym name args) = do
669+ ty <- expandTypeSynonym name args
670+ check m val ty
671+check' _ val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
672+
673+checkProperties :: M.Map Ident Type -> [(String, Value)] -> Row -> Bool -> Subst Check ()
674+checkProperties m ps row lax = let (ts, r') = rowToList row in go ps ts r' where
675+ go [] [] REmpty = return ()
676+ go [] [] u@(RUnknown _) = u ~~ REmpty
677+ go [] [] (RSkolem _) | lax = return ()
678+ go [] ((p, _): _) _ | lax = return ()
679+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
680+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
681+ go ((p,v):ps) [] u@(RUnknown _) = do
682+ ty <- infer m v
683+ rest <- fresh
684+ u ~~ RCons p ty rest
685+ go ps [] rest
686+ go ((p,v):ps) ts r =
687+ case lookup p ts of
688+ Nothing -> do
689+ ty <- infer m v
690+ rest <- fresh
691+ r ~~ RCons p ty rest
692+ go ps ts rest
693+ Just ty -> do
694+ check m v ty
695+ go ps (delete (p, ty) ts) r
696+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
697+
698+unfoldApplication :: Value -> (Value, [[Value]])
699+unfoldApplication = go []
700+ where
701+ go argss (App f args) = go (args:argss) f
702+ go argss f = (f, argss)
703+
704+checkFunctionApplications :: M.Map Ident Type -> Type -> [[Value]] -> Type -> Subst Check ()
705+checkFunctionApplications _ _ [] _ = error "Nullary function application"
706+checkFunctionApplications m fnTy [args] ret = checkFunctionApplication m fnTy args ret
707+checkFunctionApplications m fnTy (args:argss) ret = do
708+ f <- fresh
709+ checkFunctionApplication m fnTy args f
710+ checkFunctionApplications m f argss ret
711+
712+checkFunctionApplication :: M.Map Ident Type -> Type -> [Value] -> Type -> Subst Check ()
713+checkFunctionApplication m fnTy args ret = rethrow errorMessage $ checkFunctionApplication' m fnTy args ret
714+ where
715+ errorMessage msg = "Error applying function of type "
716+ ++ prettyPrintType fnTy
717+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
718+ ++ ", expecting value of type "
719+ ++ prettyPrintType ret ++ ":\n" ++ msg
720+
721+checkFunctionApplication' :: M.Map Ident Type -> Type -> [Value] -> Type -> Subst Check ()
722+checkFunctionApplication' m (Function argTys retTy) args ret = do
723+ guardWith "Incorrect number of function arguments" (length args == length argTys)
724+ zipWithM (check m) args argTys
725+ retTy `subsumes` ret
726+checkFunctionApplication' m (ForAll ident ty) args ret = do
727+ replaced <- replaceVarWithUnknown ident ty
728+ checkFunctionApplication m replaced args ret
729+checkFunctionApplication' m u@(TUnknown _) args ret = do
730+ tyArgs <- mapM (\arg -> infer m arg >>= replaceAllVarsWithUnknowns) args
731+ u ~~ Function tyArgs ret
732+checkFunctionApplication' m (SaturatedTypeSynonym name tyArgs) args ret = do
733+ ty <- expandTypeSynonym name tyArgs
734+ checkFunctionApplication' m ty args ret
735+checkFunctionApplication' _ fnTy args ret = throwError $ "Cannot apply function of type "
736+ ++ prettyPrintType fnTy
737+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
738+ ++ ". Expecting value of type " ++ prettyPrintType ret ++ "."
739+
740+subsumes :: Type -> Type -> Subst Check ()
741+subsumes (ForAll ident ty1) ty2 = do
742+ replaced <- replaceVarWithUnknown ident ty1
743+ replaced `subsumes` ty2
744+subsumes (Function args1 ret1) (Function args2 ret2) = do
745+ zipWithM subsumes args2 args1
746+ ret1 `subsumes` ret2
747+subsumes ty1 ty2 = ty1 ~~ ty2
748+