@@ -0,0 +1,766 @@
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 $ rowFromList (fields, REmpty)
299+infer' m (ObjectUpdate o ps) = do
300+ lift $ ensureNoDuplicateProperties ps
301+ row <- fresh
302+ newTys <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer m . snd) ps
303+ oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
304+ check m o $ Object $ rowFromList (oldTys, row)
305+ return $ Object $ rowFromList (newTys, row)
306+infer' m (Indexer index val) = do
307+ el <- fresh
308+ check m index Number
309+ check m val (Array el)
310+ return el
311+infer' m (Accessor prop val) = do
312+ obj <- infer m val
313+ propTy <- inferProperty obj prop
314+ case propTy of
315+ Nothing -> do
316+ field <- fresh
317+ rest <- fresh
318+ obj `subsumes` Object (RCons prop field rest)
319+ return field
320+ Just ty -> return ty
321+infer' m (Abs args ret) = do
322+ ts <- replicateM (length args) fresh
323+ let m' = m `M.union` M.fromList (zip args ts)
324+ body <- infer m' ret
325+ return $ Function ts body
326+infer' m app@(App _ _) = do
327+ let (f, argss) = unfoldApplication app
328+ ft <- infer m f
329+ ret <- fresh
330+ checkFunctionApplications m ft argss ret
331+ return ret
332+infer' m (Var var@(Qualified mp name)) = do
333+ case mp of
334+ ModulePath [] ->
335+ case M.lookup name m of
336+ Just ty -> lift $ replaceAllTypeSynonyms ty
337+ Nothing -> lookupGlobal
338+ _ -> lookupGlobal
339+ where
340+ lookupGlobal = do
341+ env <- lift getEnv
342+ modulePath <- checkModulePath `fmap` lift get
343+ case M.lookup (qualify modulePath var) (names env) of
344+ Nothing -> throwError $ show var ++ " is undefined"
345+ Just (ty, _) -> lift $ replaceAllTypeSynonyms ty
346+infer' m (Block ss) = do
347+ ret <- fresh
348+ (allCodePathsReturn, _) <- checkBlock m M.empty ret ss
349+ guardWith "Block is missing a return statement" allCodePathsReturn
350+ return ret
351+infer' m (Constructor c) = do
352+ env <- lift getEnv
353+ modulePath <- checkModulePath `fmap` lift get
354+ case M.lookup (qualify modulePath c) (dataConstructors env) of
355+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
356+ Just ty -> lift $ replaceAllTypeSynonyms ty
357+infer' m (Case val binders) = do
358+ t1 <- infer m val
359+ ret <- fresh
360+ checkBinders m t1 ret binders
361+ return ret
362+infer' m (IfThenElse cond th el) = do
363+ check m cond Boolean
364+ t2 <- infer m th
365+ t3 <- infer m el
366+ t2 ~~ t3
367+ return t2
368+infer' m (TypedValue val ty) = do
369+ kind <- lift $ kindOf ty
370+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
371+ ty' <- lift $ replaceAllTypeSynonyms ty
372+ check m val ty'
373+ return ty'
374+
375+inferProperty :: Type -> String -> Subst Check (Maybe Type)
376+inferProperty (Object row) prop = do
377+ let (props, _) = rowToList row
378+ return $ lookup prop props
379+inferProperty (SaturatedTypeSynonym name args) prop = do
380+ replaced <- expandTypeSynonym name args
381+ inferProperty replaced prop
382+inferProperty (ForAll ident ty) prop = do
383+ replaced <- replaceVarsWithUnknowns [ident] ty
384+ inferProperty replaced prop
385+inferProperty _ prop = return Nothing
386+
387+inferUnary :: UnaryOperator -> Type -> Subst Check Type
388+inferUnary op val =
389+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
390+ (valTy, resTy) -> do
391+ val ~~ valTy
392+ return resTy
393+
394+checkUnary :: M.Map Ident Type -> UnaryOperator -> Value -> Type -> Subst Check ()
395+checkUnary m op val res =
396+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
397+ (valTy, resTy) -> do
398+ res ~~ resTy
399+ check m val valTy
400+
401+unaryOps :: [(UnaryOperator, (Type, Type))]
402+unaryOps = [ (Negate, (Number, Number))
403+ , (Not, (Boolean, Boolean))
404+ , (BitwiseNot, (Number, Number))
405+ ]
406+
407+inferBinary :: BinaryOperator -> Type -> Type -> Subst Check Type
408+inferBinary op left right | isEqualityTest op = do
409+ left ~~ right
410+ return Boolean
411+inferBinary op left right =
412+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
413+ (valTy, resTy) -> do
414+ left ~~ valTy
415+ right ~~ valTy
416+ return resTy
417+
418+checkBinary :: M.Map Ident Type -> BinaryOperator -> Value -> Value -> Type -> Subst Check ()
419+checkBinary m op left right res | isEqualityTest op = do
420+ res ~~ Boolean
421+ t1 <- infer m left
422+ t2 <- infer m right
423+ t1 ~~ t2
424+checkBinary m op left right res =
425+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
426+ (valTy, resTy) -> do
427+ res ~~ resTy
428+ check m left valTy
429+ check m right valTy
430+
431+isEqualityTest :: BinaryOperator -> Bool
432+isEqualityTest EqualTo = True
433+isEqualityTest NotEqualTo = True
434+isEqualityTest _ = False
435+
436+binaryOps :: [(BinaryOperator, (Type, Type))]
437+binaryOps = [ (Add, (Number, Number))
438+ , (Subtract, (Number, Number))
439+ , (Multiply, (Number, Number))
440+ , (Divide, (Number, Number))
441+ , (Modulus, (Number, Number))
442+ , (BitwiseAnd, (Number, Number))
443+ , (BitwiseOr, (Number, Number))
444+ , (BitwiseXor, (Number, Number))
445+ , (ShiftRight, (Number, Number))
446+ , (ZeroFillShiftRight, (Number, Number))
447+ , (And, (Boolean, Boolean))
448+ , (Or, (Boolean, Boolean))
449+ , (Concat, (String, String))
450+ , (Modulus, (Number, Number))
451+ , (LessThan, (Number, Boolean))
452+ , (LessThanOrEqualTo, (Number, Boolean))
453+ , (GreaterThan, (Number, Boolean))
454+ , (GreaterThanOrEqualTo, (Number, Boolean))
455+ ]
456+
457+inferBinder :: Type -> Binder -> Subst Check (M.Map Ident Type)
458+inferBinder _ NullBinder = return M.empty
459+inferBinder val (StringBinder _) = val ~~ String >> return M.empty
460+inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
461+inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
462+inferBinder val (VarBinder name) = return $ M.singleton name val
463+inferBinder val (NullaryBinder ctor) = do
464+ env <- lift getEnv
465+ modulePath <- checkModulePath `fmap` lift get
466+ case M.lookup (qualify modulePath ctor) (dataConstructors env) of
467+ Just ty -> do
468+ ty `subsumes` val
469+ return M.empty
470+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
471+inferBinder val (UnaryBinder ctor binder) = do
472+ env <- lift getEnv
473+ modulePath <- checkModulePath `fmap` lift get
474+ case M.lookup (qualify modulePath ctor) (dataConstructors env) of
475+ Just ty -> do
476+ Function [obj] ret <- replaceAllVarsWithUnknowns ty
477+ val `subsumes` ret
478+ inferBinder obj binder
479+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
480+inferBinder val (ObjectBinder props) = do
481+ row <- fresh
482+ rest <- fresh
483+ m1 <- inferRowProperties row rest props
484+ val ~~ Object row
485+ return m1
486+ where
487+ inferRowProperties :: Row -> Row -> [(String, Binder)] -> Subst Check (M.Map Ident Type)
488+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
489+ inferRowProperties nrow row ((name, binder):binders) = do
490+ propTy <- fresh
491+ m1 <- inferBinder propTy binder
492+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
493+ return $ m1 `M.union` m2
494+inferBinder val (ArrayBinder binders rest) = do
495+ el <- fresh
496+ m1 <- M.unions <$> mapM (inferBinder el) binders
497+ val ~~ Array el
498+ case rest of
499+ Nothing -> return m1
500+ Just binder -> do
501+ m2 <- inferBinder val binder
502+ return $ m1 `M.union` m2
503+inferBinder val (NamedBinder name binder) = do
504+ m <- inferBinder val binder
505+ return $ M.insert name val m
506+
507+inferGuardedBinder :: M.Map Ident Type -> Type -> Binder -> Subst Check (M.Map Ident Type)
508+inferGuardedBinder m val (GuardedBinder cond binder) = do
509+ m1 <- inferBinder val binder
510+ check (m1 `M.union` m) cond Boolean
511+ return m1
512+inferGuardedBinder m val b = inferBinder val b
513+
514+checkBinders :: M.Map Ident Type -> Type -> Type -> [(Binder, Value)] -> Subst Check ()
515+checkBinders _ _ _ [] = return ()
516+checkBinders m nval ret ((binder, val):bs) = do
517+ m1 <- inferGuardedBinder m nval binder
518+ check (m1 `M.union` m) val ret
519+ checkBinders m nval ret bs
520+
521+assignVariable :: Ident -> M.Map Ident Type -> Subst Check ()
522+assignVariable name m =
523+ case M.lookup name m of
524+ Nothing -> return ()
525+ Just _ -> throwError $ "Variable with name " ++ show name ++ " already exists."
526+
527+checkStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> Statement -> Subst Check (Bool, M.Map Ident Type)
528+checkStatement m mass ret (VariableIntroduction name val) = do
529+ assignVariable name (m `M.union` mass)
530+ t <- infer m val
531+ return (False, M.insert name t mass)
532+checkStatement m mass ret (Assignment ident val) = do
533+ t <- infer m val
534+ case M.lookup ident mass of
535+ Nothing -> throwError $ "No local variable with name " ++ show ident
536+ Just ty -> do t ~~ ty
537+ return (False, mass)
538+checkStatement m mass ret (While val inner) = do
539+ check m val Boolean
540+ (allCodePathsReturn, _) <- checkBlock m mass ret inner
541+ return (allCodePathsReturn, mass)
542+checkStatement m mass ret (If ifst) = do
543+ allCodePathsReturn <- checkIfStatement m mass ret ifst
544+ return (allCodePathsReturn, mass)
545+checkStatement m mass ret (For ident start end inner) = do
546+ assignVariable ident (m `M.union` mass)
547+ check (m `M.union` mass) start Number
548+ check (m `M.union` mass) end Number
549+ let mass1 = M.insert ident Number mass
550+ (allCodePathsReturn, _) <- checkBlock (m `M.union` mass1) mass1 ret inner
551+ return (allCodePathsReturn, mass)
552+checkStatement m mass ret (ForEach ident vals inner) = do
553+ assignVariable ident (m `M.union` mass)
554+ val <- fresh
555+ check (m `M.union` mass) vals (Array val)
556+ let mass1 = M.insert ident val mass
557+ (allCodePathsReturn, _) <- checkBlock (m `M.union` mass1) mass1 ret inner
558+ guardWith "Cannot return from within a foreach block" $ not allCodePathsReturn
559+ return (False, mass)
560+checkStatement m mass ret (Return val) = do
561+ check (m `M.union` mass) val ret
562+ return (True, mass)
563+
564+checkIfStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> IfStatement -> Subst Check Bool
565+checkIfStatement m mass ret (IfStatement val thens Nothing) = do
566+ check m val Boolean
567+ _ <- checkBlock m mass ret thens
568+ return False
569+checkIfStatement m mass ret (IfStatement val thens (Just elses)) = do
570+ check m val Boolean
571+ (allCodePathsReturn1, _) <- checkBlock m mass ret thens
572+ allCodePathsReturn2 <- checkElseStatement m mass ret elses
573+ return $ allCodePathsReturn1 && allCodePathsReturn2
574+
575+checkElseStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> ElseStatement -> Subst Check Bool
576+checkElseStatement m mass ret (Else elses) = fst <$> checkBlock m mass ret elses
577+checkElseStatement m mass ret (ElseIf ifst) = checkIfStatement m mass ret ifst
578+
579+checkBlock :: M.Map Ident Type -> M.Map Ident Type -> Type -> [Statement] -> Subst Check (Bool, M.Map Ident Type)
580+checkBlock _ mass _ [] = return (False, mass)
581+checkBlock m mass ret (s:ss) = do
582+ (b1, mass1) <- checkStatement (m `M.union` mass) mass ret s
583+ case (b1, ss) of
584+ (True, []) -> return (True, mass1)
585+ (True, _) -> throwError "Unreachable code"
586+ (False, ss) -> do
587+ (b2, mass2) <- checkBlock m mass1 ret ss
588+ return (b2, mass2)
589+
590+skolemize :: String -> Type -> Subst Check Type
591+skolemize ident ty = do
592+ tsk <- Skolem <$> fresh'
593+ rsk <- RSkolem <$> fresh'
594+ return $ replaceRowVars ident rsk $ replaceTypeVars ident tsk ty
595+
596+check :: M.Map Ident Type -> Value -> Type -> Subst Check ()
597+check m val ty = rethrow errorMessage $ check' m val ty
598+ where
599+ errorMessage msg =
600+ "Error checking type of term " ++
601+ prettyPrintValue val ++
602+ " against type " ++
603+ prettyPrintType ty ++
604+ ":\n" ++
605+ msg
606+
607+check' :: M.Map Ident Type -> Value -> Type -> Subst Check ()
608+check' m val (ForAll idents ty) = do
609+ sk <- skolemize idents ty
610+ check m val sk
611+check' m val u@(TUnknown _) = do
612+ ty <- infer m val
613+ -- Don't unify an unknown with an inferred polytype
614+ ty' <- replaceAllVarsWithUnknowns ty
615+ ty' ~~ u
616+check' m (NumericLiteral _) Number = return ()
617+check' m (StringLiteral _) String = return ()
618+check' m (BooleanLiteral _) Boolean = return ()
619+check' m (Unary op val) ty = checkUnary m op val ty
620+check' m (Binary op left right) ty = checkBinary m op left right ty
621+check' m (ArrayLiteral vals) (Array ty) = forM_ vals (\val -> check m val ty)
622+check' m (Indexer index vals) ty = check m index Number >> check m vals (Array ty)
623+check' m (Abs args ret) (Function argTys retTy) = do
624+ guardWith "Incorrect number of function arguments" (length args == length argTys)
625+ let bindings = M.fromList (zip args argTys)
626+ check (bindings `M.union` m) ret retTy
627+check' m app@(App _ _) ret = do
628+ let (f, argss) = unfoldApplication app
629+ ft <- infer m f
630+ checkFunctionApplications m ft argss ret
631+check' m v@(Var var@(Qualified mp name)) ty = do
632+ case mp of
633+ ModulePath [] ->
634+ case M.lookup name m of
635+ Just ty1 -> do
636+ repl <- lift $ replaceAllTypeSynonyms ty1
637+ repl `subsumes` ty
638+ Nothing -> lookupGlobal
639+ _ -> lookupGlobal
640+ where
641+ lookupGlobal = do
642+ env <- lift getEnv
643+ modulePath <- checkModulePath `fmap` lift get
644+ case M.lookup (qualify modulePath var) (names env) of
645+ Nothing -> throwError $ show var ++ " is undefined"
646+ Just (ty1, _) -> do
647+ repl <- lift $ replaceAllTypeSynonyms ty1
648+ repl `subsumes` ty
649+check' m (TypedValue val ty1) ty2 = do
650+ kind <- lift $ kindOf ty1
651+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
652+ ty1 `subsumes` ty2
653+ check m val ty1
654+check' m (Case val binders) ret = do
655+ t1 <- infer m val
656+ checkBinders m t1 ret binders
657+check' m (IfThenElse cond th el) ty = do
658+ check m cond Boolean
659+ check m th ty
660+ check m el ty
661+check' m (ObjectLiteral ps) (Object row) = do
662+ lift $ ensureNoDuplicateProperties ps
663+ checkProperties m ps row False
664+check' m (ObjectUpdate obj ps) (Object row) = do
665+ lift $ ensureNoDuplicateProperties ps
666+ us <- zip (map fst ps) <$> replicateM (length ps) fresh
667+ let (propsToCheck, rest) = rowToList row
668+ propsToRemove = map fst ps
669+ remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
670+ check m obj (Object (rowFromList (us ++ remainingProps, rest)))
671+ checkProperties m ps row True
672+check' m (Accessor prop val) ty = do
673+ rest <- fresh
674+ check m val (Object (RCons prop ty rest))
675+check' m (Block ss) ret = do
676+ (allCodePathsReturn, _) <- checkBlock m M.empty ret ss
677+ guardWith "Block is missing a return statement" allCodePathsReturn
678+check' m (Constructor c) ty = do
679+ env <- lift getEnv
680+ modulePath <- checkModulePath `fmap` lift get
681+ case M.lookup (qualify modulePath c) (dataConstructors env) of
682+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
683+ Just ty1 -> do
684+ repl <- lift $ replaceAllTypeSynonyms ty1
685+ repl `subsumes` ty
686+check' m val (SaturatedTypeSynonym name args) = do
687+ ty <- expandTypeSynonym name args
688+ check m val ty
689+check' _ val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
690+
691+checkProperties :: M.Map Ident Type -> [(String, Value)] -> Row -> Bool -> Subst Check ()
692+checkProperties m ps row lax = let (ts, r') = rowToList row in go ps ts r' where
693+ go [] [] REmpty = return ()
694+ go [] [] u@(RUnknown _) = u ~~ REmpty
695+ go [] [] (RSkolem _) | lax = return ()
696+ go [] ((p, _): _) _ | lax = return ()
697+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
698+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
699+ go ((p,v):ps) [] u@(RUnknown _) = do
700+ ty <- infer m v
701+ rest <- fresh
702+ u ~~ RCons p ty rest
703+ go ps [] rest
704+ go ((p,v):ps) ts r =
705+ case lookup p ts of
706+ Nothing -> do
707+ ty <- infer m v
708+ rest <- fresh
709+ r ~~ RCons p ty rest
710+ go ps ts rest
711+ Just ty -> do
712+ check m v ty
713+ go ps (delete (p, ty) ts) r
714+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
715+
716+unfoldApplication :: Value -> (Value, [[Value]])
717+unfoldApplication = go []
718+ where
719+ go argss (App f args) = go (args:argss) f
720+ go argss f = (f, argss)
721+
722+checkFunctionApplications :: M.Map Ident Type -> Type -> [[Value]] -> Type -> Subst Check ()
723+checkFunctionApplications _ _ [] _ = error "Nullary function application"
724+checkFunctionApplications m fnTy [args] ret = checkFunctionApplication m fnTy args ret
725+checkFunctionApplications m fnTy (args:argss) ret = do
726+ f <- fresh
727+ checkFunctionApplication m fnTy args f
728+ checkFunctionApplications m f argss ret
729+
730+checkFunctionApplication :: M.Map Ident Type -> Type -> [Value] -> Type -> Subst Check ()
731+checkFunctionApplication m fnTy args ret = rethrow errorMessage $ checkFunctionApplication' m fnTy args ret
732+ where
733+ errorMessage msg = "Error applying function of type "
734+ ++ prettyPrintType fnTy
735+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
736+ ++ ", expecting value of type "
737+ ++ prettyPrintType ret ++ ":\n" ++ msg
738+
739+checkFunctionApplication' :: M.Map Ident Type -> Type -> [Value] -> Type -> Subst Check ()
740+checkFunctionApplication' m (Function argTys retTy) args ret = do
741+ guardWith "Incorrect number of function arguments" (length args == length argTys)
742+ zipWithM (check m) args argTys
743+ retTy `subsumes` ret
744+checkFunctionApplication' m (ForAll ident ty) args ret = do
745+ replaced <- replaceVarsWithUnknowns [ident] ty
746+ checkFunctionApplication m replaced args ret
747+checkFunctionApplication' m u@(TUnknown _) args ret = do
748+ tyArgs <- mapM (\arg -> infer m arg >>= replaceAllVarsWithUnknowns) args
749+ u ~~ Function tyArgs ret
750+checkFunctionApplication' m (SaturatedTypeSynonym name tyArgs) args ret = do
751+ ty <- expandTypeSynonym name tyArgs
752+ checkFunctionApplication' m ty args ret
753+checkFunctionApplication' _ fnTy args ret = throwError $ "Cannot apply function of type "
754+ ++ prettyPrintType fnTy
755+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
756+ ++ ". Expecting value of type " ++ prettyPrintType ret ++ "."
757+
758+subsumes :: Type -> Type -> Subst Check ()
759+subsumes (ForAll ident ty1) ty2 = do
760+ replaced <- replaceVarsWithUnknowns [ident] ty1
761+ replaced `subsumes` ty2
762+subsumes (Function args1 ret1) (Function args2 ret2) = do
763+ zipWithM subsumes args2 args1
764+ ret1 `subsumes` ret2
765+subsumes ty1 ty2 = ty1 ~~ ty2
766+