@@ -0,0 +1,763 @@
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 <- replaceVarsWithUnknowns [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) = replaceVarsWithUnknowns [ident] ty >>= replaceAllVarsWithUnknowns
220+replaceAllVarsWithUnknowns ty = return ty
221+
222+replaceVarsWithUnknowns :: [String] -> Type -> Subst Check Type
223+replaceVarsWithUnknowns idents = flip evalStateT M.empty . everywhereM (flip extM f $ mkM g)
224+ where
225+ f :: Type -> StateT (M.Map String Int) (Subst Check) Type
226+ f (TypeVar var) | var `elem` idents = do
227+ m <- get
228+ n <- lift fresh'
229+ case M.lookup var m of
230+ Nothing -> do
231+ put (M.insert var n m)
232+ return $ TUnknown (Unknown n)
233+ Just u -> return $ TUnknown (Unknown u)
234+ f t = return t
235+ g :: Row -> StateT (M.Map String Int) (Subst Check) Row
236+ g (RowVar var) | var `elem` idents = do
237+ m <- get
238+ n <- lift fresh'
239+ case M.lookup var m of
240+ Nothing -> do
241+ put (M.insert var n m)
242+ return $ RUnknown (Unknown n)
243+ Just u -> return $ RUnknown (Unknown u)
244+ g r = return r
245+
246+replaceAllTypeSynonyms :: (D.Data d) => d -> Check d
247+replaceAllTypeSynonyms d = do
248+ env <- getEnv
249+ let syns = map (\((path, name), (args, _)) -> (Qualified path name, length args)) . M.toList $ typeSynonyms env
250+ either throwError return $ saturateAllTypeSynonyms syns d
251+
252+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
253+desaturateAllTypeSynonyms = everywhere (mkT replace)
254+ where
255+ replace (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
256+ replace t = t
257+
258+expandAllTypeSynonyms :: Type -> Subst Check Type
259+expandAllTypeSynonyms (SaturatedTypeSynonym name args) = expandTypeSynonym name args >>= expandAllTypeSynonyms
260+expandAllTypeSynonyms ty = return ty
261+
262+expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Check Type
263+expandTypeSynonym name args = do
264+ env <- lift getEnv
265+ modulePath <- checkModulePath `fmap` lift get
266+ case M.lookup (qualify modulePath name) (typeSynonyms env) of
267+ Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
268+ Nothing -> error "Type synonym was not defined"
269+
270+ensureNoDuplicateProperties :: [(String, Value)] -> Check ()
271+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
272+
273+infer :: M.Map Ident Type -> Value -> Subst Check Type
274+infer m val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ do
275+ ty <- infer' m val
276+ escapeCheckLater ty
277+ return ty
278+
279+infer' _ (NumericLiteral _) = return Number
280+infer' _ (StringLiteral _) = return String
281+infer' _ (BooleanLiteral _) = return Boolean
282+infer' m (ArrayLiteral vals) = do
283+ ts <- mapM (infer m) vals
284+ arr <- fresh
285+ forM_ ts $ \t -> arr ~~ Array t
286+ return arr
287+infer' m (Unary op val) = do
288+ t <- infer m val
289+ inferUnary op t
290+infer' m (Binary op left right) = do
291+ t1 <- infer m left
292+ t2 <- infer m right
293+ inferBinary op t1 t2
294+infer' m (ObjectLiteral ps) = do
295+ lift $ ensureNoDuplicateProperties ps
296+ ts <- mapM (infer m . snd) ps
297+ let fields = zipWith (\(name, _) t -> (name, t)) ps ts
298+ return $ Object $ typesToRow fields
299+infer' m (ObjectUpdate o ps) = do
300+ lift $ ensureNoDuplicateProperties ps
301+ obj <- infer m o
302+ row <- fresh
303+ ts <- mapM (infer m . snd) ps
304+ let tys = zipWith (\(name, _) t -> (name, t)) ps ts
305+ obj ~~ Object (rowFromList (tys, row))
306+ return obj
307+infer' m (Indexer index val) = do
308+ el <- fresh
309+ check m index Number
310+ check m val (Array el)
311+ return el
312+infer' m (Accessor prop val) = do
313+ obj <- infer m val
314+ propTy <- inferProperty obj prop
315+ case propTy of
316+ Nothing -> do
317+ field <- fresh
318+ rest <- fresh
319+ obj `subsumes` Object (RCons prop field rest)
320+ return field
321+ Just ty -> return ty
322+infer' m (Abs args ret) = do
323+ ts <- replicateM (length args) fresh
324+ let m' = m `M.union` M.fromList (zip args ts)
325+ body <- infer m' ret
326+ return $ Function ts body
327+infer' m app@(App _ _) = do
328+ let (f, argss) = unfoldApplication app
329+ ft <- infer m f
330+ ret <- fresh
331+ checkFunctionApplications m ft argss ret
332+ return ret
333+infer' m (Var var@(Qualified mp name)) = do
334+ case mp of
335+ ModulePath [] ->
336+ case M.lookup name m of
337+ Just ty -> lift $ replaceAllTypeSynonyms ty
338+ Nothing -> lookupGlobal
339+ _ -> lookupGlobal
340+ where
341+ lookupGlobal = do
342+ env <- lift getEnv
343+ modulePath <- checkModulePath `fmap` lift get
344+ case M.lookup (qualify modulePath var) (names env) of
345+ Nothing -> throwError $ show var ++ " is undefined"
346+ Just (ty, _) -> lift $ replaceAllTypeSynonyms ty
347+infer' m (Block ss) = do
348+ ret <- fresh
349+ (allCodePathsReturn, _) <- checkBlock m M.empty ret ss
350+ guardWith "Block is missing a return statement" allCodePathsReturn
351+ return ret
352+infer' m (Constructor c) = do
353+ env <- lift getEnv
354+ modulePath <- checkModulePath `fmap` lift get
355+ case M.lookup (qualify modulePath c) (dataConstructors env) of
356+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
357+ Just ty -> lift $ replaceAllTypeSynonyms ty
358+infer' m (Case val binders) = do
359+ t1 <- infer m val
360+ ret <- fresh
361+ checkBinders m t1 ret binders
362+ return ret
363+infer' m (IfThenElse cond th el) = do
364+ check m cond Boolean
365+ t2 <- infer m th
366+ t3 <- infer m el
367+ t2 ~~ t3
368+ return t2
369+infer' m (TypedValue val ty) = do
370+ kind <- lift $ kindOf ty
371+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
372+ ty' <- lift $ replaceAllTypeSynonyms ty
373+ check m val ty'
374+ return ty'
375+
376+inferProperty :: Type -> String -> Subst Check (Maybe Type)
377+inferProperty (Object row) prop = do
378+ let (props, _) = rowToList row
379+ return $ lookup prop props
380+inferProperty (SaturatedTypeSynonym name args) prop = do
381+ replaced <- expandTypeSynonym name args
382+ inferProperty replaced prop
383+inferProperty (ForAll ident ty) prop = do
384+ replaced <- replaceVarsWithUnknowns [ident] ty
385+ inferProperty replaced prop
386+inferProperty _ prop = return Nothing
387+
388+inferUnary :: UnaryOperator -> Type -> Subst Check Type
389+inferUnary op val =
390+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
391+ (valTy, resTy) -> do
392+ val ~~ valTy
393+ return resTy
394+
395+checkUnary :: M.Map Ident Type -> UnaryOperator -> Value -> Type -> Subst Check ()
396+checkUnary m op val res =
397+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
398+ (valTy, resTy) -> do
399+ res ~~ resTy
400+ check m val valTy
401+
402+unaryOps :: [(UnaryOperator, (Type, Type))]
403+unaryOps = [ (Negate, (Number, Number))
404+ , (Not, (Boolean, Boolean))
405+ , (BitwiseNot, (Number, Number))
406+ ]
407+
408+inferBinary :: BinaryOperator -> Type -> Type -> Subst Check Type
409+inferBinary op left right | isEqualityTest op = do
410+ left ~~ right
411+ return Boolean
412+inferBinary op left right =
413+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
414+ (valTy, resTy) -> do
415+ left ~~ valTy
416+ right ~~ valTy
417+ return resTy
418+
419+checkBinary :: M.Map Ident Type -> BinaryOperator -> Value -> Value -> Type -> Subst Check ()
420+checkBinary m op left right res | isEqualityTest op = do
421+ res ~~ Boolean
422+ t1 <- infer m left
423+ t2 <- infer m right
424+ t1 ~~ t2
425+checkBinary m op left right res =
426+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
427+ (valTy, resTy) -> do
428+ res ~~ resTy
429+ check m left valTy
430+ check m right valTy
431+
432+isEqualityTest :: BinaryOperator -> Bool
433+isEqualityTest EqualTo = True
434+isEqualityTest NotEqualTo = True
435+isEqualityTest _ = False
436+
437+binaryOps :: [(BinaryOperator, (Type, Type))]
438+binaryOps = [ (Add, (Number, Number))
439+ , (Subtract, (Number, Number))
440+ , (Multiply, (Number, Number))
441+ , (Divide, (Number, Number))
442+ , (Modulus, (Number, Number))
443+ , (BitwiseAnd, (Number, Number))
444+ , (BitwiseOr, (Number, Number))
445+ , (BitwiseXor, (Number, Number))
446+ , (ShiftRight, (Number, Number))
447+ , (ZeroFillShiftRight, (Number, Number))
448+ , (And, (Boolean, Boolean))
449+ , (Or, (Boolean, Boolean))
450+ , (Concat, (String, String))
451+ , (Modulus, (Number, Number))
452+ , (LessThan, (Number, Boolean))
453+ , (LessThanOrEqualTo, (Number, Boolean))
454+ , (GreaterThan, (Number, Boolean))
455+ , (GreaterThanOrEqualTo, (Number, Boolean))
456+ ]
457+
458+inferBinder :: Type -> Binder -> Subst Check (M.Map Ident Type)
459+inferBinder _ NullBinder = return M.empty
460+inferBinder val (StringBinder _) = val ~~ String >> return M.empty
461+inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
462+inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
463+inferBinder val (VarBinder name) = return $ M.singleton name val
464+inferBinder val (NullaryBinder ctor) = do
465+ env <- lift getEnv
466+ modulePath <- checkModulePath `fmap` lift get
467+ case M.lookup (qualify modulePath ctor) (dataConstructors env) of
468+ Just ty -> do
469+ ty `subsumes` val
470+ return M.empty
471+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
472+inferBinder val (UnaryBinder ctor binder) = do
473+ env <- lift getEnv
474+ modulePath <- checkModulePath `fmap` lift get
475+ case M.lookup (qualify modulePath ctor) (dataConstructors env) of
476+ Just ty -> do
477+ Function [obj] ret <- replaceAllVarsWithUnknowns ty
478+ val `subsumes` ret
479+ inferBinder obj binder
480+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
481+inferBinder val (ObjectBinder props) = do
482+ row <- fresh
483+ rest <- fresh
484+ m1 <- inferRowProperties row rest props
485+ val ~~ Object row
486+ return m1
487+ where
488+ inferRowProperties :: Row -> Row -> [(String, Binder)] -> Subst Check (M.Map Ident Type)
489+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
490+ inferRowProperties nrow row ((name, binder):binders) = do
491+ propTy <- fresh
492+ m1 <- inferBinder propTy binder
493+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
494+ return $ m1 `M.union` m2
495+inferBinder val (ArrayBinder binders rest) = do
496+ el <- fresh
497+ m1 <- M.unions <$> mapM (inferBinder el) binders
498+ val ~~ Array el
499+ case rest of
500+ Nothing -> return m1
501+ Just binder -> do
502+ m2 <- inferBinder val binder
503+ return $ m1 `M.union` m2
504+inferBinder val (NamedBinder name binder) = do
505+ m <- inferBinder val binder
506+ return $ M.insert name val m
507+
508+inferGuardedBinder :: M.Map Ident Type -> Type -> Binder -> Subst Check (M.Map Ident Type)
509+inferGuardedBinder m val (GuardedBinder cond binder) = do
510+ m1 <- inferBinder val binder
511+ check (m1 `M.union` m) cond Boolean
512+ return m1
513+inferGuardedBinder m val b = inferBinder val b
514+
515+checkBinders :: M.Map Ident Type -> Type -> Type -> [(Binder, Value)] -> Subst Check ()
516+checkBinders _ _ _ [] = return ()
517+checkBinders m nval ret ((binder, val):bs) = do
518+ m1 <- inferGuardedBinder m nval binder
519+ check (m1 `M.union` m) val ret
520+ checkBinders m nval ret bs
521+
522+assignVariable :: Ident -> M.Map Ident Type -> Subst Check ()
523+assignVariable name m =
524+ case M.lookup name m of
525+ Nothing -> return ()
526+ Just _ -> throwError $ "Variable with name " ++ show name ++ " already exists."
527+
528+checkStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> Statement -> Subst Check (Bool, M.Map Ident Type)
529+checkStatement m mass ret (VariableIntroduction name val) = do
530+ assignVariable name (m `M.union` mass)
531+ t <- infer m val
532+ return (False, M.insert name t mass)
533+checkStatement m mass ret (Assignment ident val) = do
534+ t <- infer m val
535+ case M.lookup ident mass of
536+ Nothing -> throwError $ "No local variable with name " ++ show ident
537+ Just ty -> do t ~~ ty
538+ return (False, mass)
539+checkStatement m mass ret (While val inner) = do
540+ check m val Boolean
541+ (allCodePathsReturn, _) <- checkBlock m mass ret inner
542+ return (allCodePathsReturn, mass)
543+checkStatement m mass ret (If ifst) = do
544+ allCodePathsReturn <- checkIfStatement m mass ret ifst
545+ return (allCodePathsReturn, mass)
546+checkStatement m mass ret (For ident start end inner) = do
547+ assignVariable ident (m `M.union` mass)
548+ check (m `M.union` mass) start Number
549+ check (m `M.union` mass) end Number
550+ let mass1 = M.insert ident Number mass
551+ (allCodePathsReturn, _) <- checkBlock (m `M.union` mass1) mass1 ret inner
552+ return (allCodePathsReturn, mass)
553+checkStatement m mass ret (ForEach ident vals inner) = do
554+ assignVariable ident (m `M.union` mass)
555+ val <- fresh
556+ check (m `M.union` mass) vals (Array val)
557+ let mass1 = M.insert ident val mass
558+ (allCodePathsReturn, _) <- checkBlock (m `M.union` mass1) mass1 ret inner
559+ guardWith "Cannot return from within a foreach block" $ not allCodePathsReturn
560+ return (False, mass)
561+checkStatement m mass ret (Return val) = do
562+ check (m `M.union` mass) val ret
563+ return (True, mass)
564+
565+checkIfStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> IfStatement -> Subst Check Bool
566+checkIfStatement m mass ret (IfStatement val thens Nothing) = do
567+ check m val Boolean
568+ _ <- checkBlock m mass ret thens
569+ return False
570+checkIfStatement m mass ret (IfStatement val thens (Just elses)) = do
571+ check m val Boolean
572+ (allCodePathsReturn1, _) <- checkBlock m mass ret thens
573+ allCodePathsReturn2 <- checkElseStatement m mass ret elses
574+ return $ allCodePathsReturn1 && allCodePathsReturn2
575+
576+checkElseStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> ElseStatement -> Subst Check Bool
577+checkElseStatement m mass ret (Else elses) = fst <$> checkBlock m mass ret elses
578+checkElseStatement m mass ret (ElseIf ifst) = checkIfStatement m mass ret ifst
579+
580+checkBlock :: M.Map Ident Type -> M.Map Ident Type -> Type -> [Statement] -> Subst Check (Bool, M.Map Ident Type)
581+checkBlock _ mass _ [] = return (False, mass)
582+checkBlock m mass ret (s:ss) = do
583+ (b1, mass1) <- checkStatement (m `M.union` mass) mass ret s
584+ case (b1, ss) of
585+ (True, []) -> return (True, mass1)
586+ (True, _) -> throwError "Unreachable code"
587+ (False, ss) -> do
588+ (b2, mass2) <- checkBlock m mass1 ret ss
589+ return (b2, mass2)
590+
591+skolemize :: String -> Type -> Subst Check Type
592+skolemize ident ty = do
593+ tsk <- Skolem <$> fresh'
594+ rsk <- RSkolem <$> fresh'
595+ return $ replaceRowVars ident rsk $ replaceTypeVars ident tsk ty
596+
597+check :: M.Map Ident Type -> Value -> Type -> Subst Check ()
598+check m val ty = rethrow errorMessage $ check' m val ty
599+ where
600+ errorMessage msg =
601+ "Error checking type of term " ++
602+ prettyPrintValue val ++
603+ " against type " ++
604+ prettyPrintType ty ++
605+ ":\n" ++
606+ msg
607+
608+check' :: M.Map Ident Type -> Value -> Type -> Subst Check ()
609+check' m val (ForAll idents ty) = do
610+ sk <- skolemize idents ty
611+ check m val sk
612+check' m val u@(TUnknown _) = do
613+ ty <- infer m val
614+ -- Don't unify an unknown with an inferred polytype
615+ ty' <- replaceAllVarsWithUnknowns ty
616+ ty' ~~ u
617+check' m (NumericLiteral _) Number = return ()
618+check' m (StringLiteral _) String = return ()
619+check' m (BooleanLiteral _) Boolean = return ()
620+check' m (Unary op val) ty = checkUnary m op val ty
621+check' m (Binary op left right) ty = checkBinary m op left right ty
622+check' m (ArrayLiteral vals) (Array ty) = forM_ vals (\val -> check m val ty)
623+check' m (Indexer index vals) ty = check m index Number >> check m vals (Array ty)
624+check' m (Abs args ret) (Function argTys retTy) = do
625+ guardWith "Incorrect number of function arguments" (length args == length argTys)
626+ let bindings = M.fromList (zip args argTys)
627+ check (bindings `M.union` m) ret retTy
628+check' m app@(App _ _) ret = do
629+ let (f, argss) = unfoldApplication app
630+ ft <- infer m f
631+ checkFunctionApplications m ft argss ret
632+check' m v@(Var var@(Qualified mp name)) ty = do
633+ case mp of
634+ ModulePath [] ->
635+ case M.lookup name m of
636+ Just ty1 -> do
637+ repl <- lift $ replaceAllTypeSynonyms ty1
638+ repl `subsumes` ty
639+ Nothing -> lookupGlobal
640+ _ -> lookupGlobal
641+ where
642+ lookupGlobal = do
643+ env <- lift getEnv
644+ modulePath <- checkModulePath `fmap` lift get
645+ case M.lookup (qualify modulePath var) (names env) of
646+ Nothing -> throwError $ show var ++ " is undefined"
647+ Just (ty1, _) -> do
648+ repl <- lift $ replaceAllTypeSynonyms ty1
649+ repl `subsumes` ty
650+check' m (TypedValue val ty1) ty2 = do
651+ kind <- lift $ kindOf ty1
652+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
653+ ty1 `subsumes` ty2
654+ check m val ty1
655+check' m (Case val binders) ret = do
656+ t1 <- infer m val
657+ checkBinders m t1 ret binders
658+check' m (IfThenElse cond th el) ty = do
659+ check m cond Boolean
660+ check m th ty
661+ check m el ty
662+check' m (ObjectLiteral ps) (Object row) = do
663+ lift $ ensureNoDuplicateProperties ps
664+ checkProperties m ps row False
665+check' m (ObjectUpdate obj ps) objTy@(Object row) = do
666+ lift $ ensureNoDuplicateProperties ps
667+ check m obj objTy
668+ checkProperties m ps row True
669+check' m (Accessor prop val) ty = do
670+ rest <- fresh
671+ check m val (Object (RCons prop ty rest))
672+check' m (Block ss) ret = do
673+ (allCodePathsReturn, _) <- checkBlock m M.empty ret ss
674+ guardWith "Block is missing a return statement" allCodePathsReturn
675+check' m (Constructor c) ty = do
676+ env <- lift getEnv
677+ modulePath <- checkModulePath `fmap` lift get
678+ case M.lookup (qualify modulePath c) (dataConstructors env) of
679+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
680+ Just ty1 -> do
681+ repl <- lift $ replaceAllTypeSynonyms ty1
682+ repl `subsumes` ty
683+check' m val (SaturatedTypeSynonym name args) = do
684+ ty <- expandTypeSynonym name args
685+ check m val ty
686+check' _ val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
687+
688+checkProperties :: M.Map Ident Type -> [(String, Value)] -> Row -> Bool -> Subst Check ()
689+checkProperties m ps row lax = let (ts, r') = rowToList row in go ps ts r' where
690+ go [] [] REmpty = return ()
691+ go [] [] u@(RUnknown _) = u ~~ REmpty
692+ go [] [] (RSkolem _) | lax = return ()
693+ go [] ((p, _): _) _ | lax = return ()
694+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
695+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
696+ go ((p,v):ps) [] u@(RUnknown _) = do
697+ ty <- infer m v
698+ rest <- fresh
699+ u ~~ RCons p ty rest
700+ go ps [] rest
701+ go ((p,v):ps) ts r =
702+ case lookup p ts of
703+ Nothing -> do
704+ ty <- infer m v
705+ rest <- fresh
706+ r ~~ RCons p ty rest
707+ go ps ts rest
708+ Just ty -> do
709+ check m v ty
710+ go ps (delete (p, ty) ts) r
711+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
712+
713+unfoldApplication :: Value -> (Value, [[Value]])
714+unfoldApplication = go []
715+ where
716+ go argss (App f args) = go (args:argss) f
717+ go argss f = (f, argss)
718+
719+checkFunctionApplications :: M.Map Ident Type -> Type -> [[Value]] -> Type -> Subst Check ()
720+checkFunctionApplications _ _ [] _ = error "Nullary function application"
721+checkFunctionApplications m fnTy [args] ret = checkFunctionApplication m fnTy args ret
722+checkFunctionApplications m fnTy (args:argss) ret = do
723+ f <- fresh
724+ checkFunctionApplication m fnTy args f
725+ checkFunctionApplications m f argss ret
726+
727+checkFunctionApplication :: M.Map Ident Type -> Type -> [Value] -> Type -> Subst Check ()
728+checkFunctionApplication m fnTy args ret = rethrow errorMessage $ checkFunctionApplication' m fnTy args ret
729+ where
730+ errorMessage msg = "Error applying function of type "
731+ ++ prettyPrintType fnTy
732+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
733+ ++ ", expecting value of type "
734+ ++ prettyPrintType ret ++ ":\n" ++ msg
735+
736+checkFunctionApplication' :: M.Map Ident Type -> Type -> [Value] -> Type -> Subst Check ()
737+checkFunctionApplication' m (Function argTys retTy) args ret = do
738+ guardWith "Incorrect number of function arguments" (length args == length argTys)
739+ zipWithM (check m) args argTys
740+ retTy `subsumes` ret
741+checkFunctionApplication' m (ForAll ident ty) args ret = do
742+ replaced <- replaceVarsWithUnknowns [ident] ty
743+ checkFunctionApplication m replaced args ret
744+checkFunctionApplication' m u@(TUnknown _) args ret = do
745+ tyArgs <- mapM (\arg -> infer m arg >>= replaceAllVarsWithUnknowns) args
746+ u ~~ Function tyArgs ret
747+checkFunctionApplication' m (SaturatedTypeSynonym name tyArgs) args ret = do
748+ ty <- expandTypeSynonym name tyArgs
749+ checkFunctionApplication' m ty args ret
750+checkFunctionApplication' _ fnTy args ret = throwError $ "Cannot apply function of type "
751+ ++ prettyPrintType fnTy
752+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
753+ ++ ". Expecting value of type " ++ prettyPrintType ret ++ "."
754+
755+subsumes :: Type -> Type -> Subst Check ()
756+subsumes (ForAll ident ty1) ty2 = do
757+ replaced <- replaceVarsWithUnknowns [ident] ty1
758+ replaced `subsumes` ty2
759+subsumes (Function args1 ret1) (Function args2 ret2) = do
760+ zipWithM subsumes args2 args1
761+ ret1 `subsumes` ret2
762+subsumes ty1 ty2 = ty1 ~~ ty2
763+