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