@@ -0,0 +1,778 @@
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+ (extT, something, everywhere, everywhereM, everything,
27+ everywhereBut, 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 =
200+ let unks = nub $ unknowns ty
201+ toName = (:) 't' . show
202+ ty' = everywhere (mkT rowToVar) . everywhere (mkT typeToVar) $ ty
203+ typeToVar :: Type -> Type
204+ typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
205+ typeToVar t = t
206+ rowToVar :: Row -> Row
207+ rowToVar (RUnknown (Unknown u)) = RowVar (toName u)
208+ rowToVar t = t
209+ in mkForAll (sort . map toName $ unks) ty'
210+
211+replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
212+replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
213+
214+replaceTypeVars :: (D.Data d) => String -> Type -> d -> d
215+replaceTypeVars name t = everywhereBut (mkQ False isShadowed) (mkT replace)
216+ where
217+ replace (TypeVar v) | v == name = t
218+ replace t = t
219+ isShadowed (ForAll v _) | v == name = True
220+ isShadowed _ = False
221+
222+replaceRowVars :: (D.Data d) => String -> Row -> d -> d
223+replaceRowVars name r = everywhere (mkT replace)
224+ where
225+ replace (RowVar v) | v == name = r
226+ replace t = t
227+
228+replaceAllVarsWithUnknowns :: Type -> Subst Check Type
229+replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
230+replaceAllVarsWithUnknowns ty = return ty
231+
232+replaceVarWithUnknown :: String -> Type -> Subst Check Type
233+replaceVarWithUnknown ident ty = do
234+ tu <- fresh
235+ ru <- fresh
236+ return $ replaceRowVars ident ru . replaceTypeVars ident tu $ ty
237+
238+replaceAllTypeSynonyms :: (D.Data d) => d -> Check d
239+replaceAllTypeSynonyms d = do
240+ env <- getEnv
241+ let syns = map (\((path, name), (args, _)) -> (Qualified path name, length args)) . M.toList $ typeSynonyms env
242+ either throwError return $ saturateAllTypeSynonyms syns d
243+
244+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
245+desaturateAllTypeSynonyms = everywhere (mkT replace)
246+ where
247+ replace (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
248+ replace t = t
249+
250+expandAllTypeSynonyms :: Type -> Subst Check Type
251+expandAllTypeSynonyms (SaturatedTypeSynonym name args) = expandTypeSynonym name args >>= expandAllTypeSynonyms
252+expandAllTypeSynonyms ty = return ty
253+
254+expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Check Type
255+expandTypeSynonym name args = do
256+ env <- lift getEnv
257+ modulePath <- checkModulePath `fmap` lift get
258+ case M.lookup (qualify modulePath name) (typeSynonyms env) of
259+ Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
260+ Nothing -> error "Type synonym was not defined"
261+
262+ensureNoDuplicateProperties :: [(String, Value)] -> Check ()
263+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
264+
265+infer :: M.Map Ident Type -> Value -> Subst Check Type
266+infer m val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ do
267+ ty <- infer' m val
268+ escapeCheckLater ty
269+ return ty
270+
271+infer' _ (NumericLiteral _) = return Number
272+infer' _ (StringLiteral _) = return String
273+infer' _ (BooleanLiteral _) = return Boolean
274+infer' m (ArrayLiteral vals) = do
275+ ts <- mapM (infer m) vals
276+ arr <- fresh
277+ forM_ ts $ \t -> arr ~~ Array t
278+ return arr
279+infer' m (Unary op val) = do
280+ t <- infer m val
281+ inferUnary op t
282+infer' m (Binary op left right) = do
283+ t1 <- infer m left
284+ t2 <- infer m right
285+ inferBinary op t1 t2
286+infer' m (ObjectLiteral ps) = do
287+ lift $ ensureNoDuplicateProperties ps
288+ ts <- mapM (infer m . snd) ps
289+ let fields = zipWith (\(name, _) t -> (name, t)) ps ts
290+ return $ Object $ rowFromList (fields, REmpty)
291+infer' m (ObjectUpdate o ps) = do
292+ lift $ ensureNoDuplicateProperties ps
293+ row <- fresh
294+ newTys <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer m . snd) ps
295+ oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
296+ check m o $ Object $ rowFromList (oldTys, row)
297+ return $ Object $ rowFromList (newTys, row)
298+infer' m (Indexer index val) = do
299+ el <- fresh
300+ check m index Number
301+ check m val (Array el)
302+ return el
303+infer' m (Accessor prop val) = do
304+ obj <- infer m val
305+ propTy <- inferProperty obj prop
306+ case propTy of
307+ Nothing -> do
308+ field <- fresh
309+ rest <- fresh
310+ obj `subsumes` Object (RCons prop field rest)
311+ return field
312+ Just ty -> return ty
313+infer' m (Abs args ret) = do
314+ ts <- replicateM (length args) fresh
315+ let m' = m `M.union` M.fromList (zip args ts)
316+ body <- infer m' ret
317+ return $ Function ts body
318+infer' m app@(App _ _) = do
319+ let (f, argss) = unfoldApplication app
320+ ft <- infer m f
321+ ret <- fresh
322+ checkFunctionApplications m ft argss ret
323+ return ret
324+infer' m (Var var@(Qualified mp name)) = do
325+ case mp of
326+ ModulePath [] ->
327+ case M.lookup name m of
328+ Just ty -> lift $ replaceAllTypeSynonyms ty
329+ Nothing -> lookupGlobal
330+ _ -> lookupGlobal
331+ where
332+ lookupGlobal = do
333+ env <- lift getEnv
334+ modulePath <- checkModulePath `fmap` lift get
335+ case M.lookup (qualify modulePath var) (names env) of
336+ Nothing -> throwError $ show var ++ " is undefined"
337+ Just (ty, _) -> lift $ replaceAllTypeSynonyms ty
338+infer' m (Block ss) = do
339+ ret <- fresh
340+ (allCodePathsReturn, _) <- checkBlock m M.empty ret ss
341+ guardWith "Block is missing a return statement" allCodePathsReturn
342+ return ret
343+infer' m (Constructor c) = do
344+ env <- lift getEnv
345+ modulePath <- checkModulePath `fmap` lift get
346+ case M.lookup (qualify modulePath c) (dataConstructors env) of
347+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
348+ Just ty -> lift $ replaceAllTypeSynonyms ty
349+infer' m (Case val binders) = do
350+ t1 <- infer m val
351+ ret <- fresh
352+ checkBinders m t1 ret binders
353+ return ret
354+infer' m (IfThenElse cond th el) = do
355+ check m cond Boolean
356+ t2 <- infer m th
357+ t3 <- infer m el
358+ t2 ~~ t3
359+ return t2
360+infer' m (TypedValue val ty) = do
361+ kind <- lift $ kindOf ty
362+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
363+ ty' <- lift $ replaceAllTypeSynonyms ty
364+ check m val ty'
365+ return ty'
366+
367+inferProperty :: Type -> String -> Subst Check (Maybe Type)
368+inferProperty (Object row) prop = do
369+ let (props, _) = rowToList row
370+ return $ lookup prop props
371+inferProperty (SaturatedTypeSynonym name args) prop = do
372+ replaced <- expandTypeSynonym name args
373+ inferProperty replaced prop
374+inferProperty (ForAll ident ty) prop = do
375+ replaced <- replaceVarWithUnknown ident ty
376+ inferProperty replaced prop
377+inferProperty _ prop = return Nothing
378+
379+inferUnary :: UnaryOperator -> Type -> Subst Check Type
380+inferUnary op val =
381+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
382+ (valTy, resTy) -> do
383+ val ~~ valTy
384+ return resTy
385+
386+checkUnary :: M.Map Ident Type -> UnaryOperator -> Value -> Type -> Subst Check ()
387+checkUnary m op val res =
388+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
389+ (valTy, resTy) -> do
390+ res ~~ resTy
391+ check m val valTy
392+
393+unaryOps :: [(UnaryOperator, (Type, Type))]
394+unaryOps = [ (Negate, (Number, Number))
395+ , (Not, (Boolean, Boolean))
396+ , (BitwiseNot, (Number, Number))
397+ ]
398+
399+inferBinary :: BinaryOperator -> Type -> Type -> Subst Check Type
400+inferBinary op left right | isEqualityTest op = do
401+ left ~~ right
402+ return Boolean
403+inferBinary op left right =
404+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
405+ (valTy, resTy) -> do
406+ left ~~ valTy
407+ right ~~ valTy
408+ return resTy
409+
410+checkBinary :: M.Map Ident Type -> BinaryOperator -> Value -> Value -> Type -> Subst Check ()
411+checkBinary m op left right res | isEqualityTest op = do
412+ res ~~ Boolean
413+ t1 <- infer m left
414+ t2 <- infer m right
415+ t1 ~~ t2
416+checkBinary m op left right res =
417+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
418+ (valTy, resTy) -> do
419+ res ~~ resTy
420+ check m left valTy
421+ check m right valTy
422+
423+isEqualityTest :: BinaryOperator -> Bool
424+isEqualityTest EqualTo = True
425+isEqualityTest NotEqualTo = True
426+isEqualityTest _ = False
427+
428+binaryOps :: [(BinaryOperator, (Type, Type))]
429+binaryOps = [ (Add, (Number, Number))
430+ , (Subtract, (Number, Number))
431+ , (Multiply, (Number, Number))
432+ , (Divide, (Number, Number))
433+ , (Modulus, (Number, Number))
434+ , (BitwiseAnd, (Number, Number))
435+ , (BitwiseOr, (Number, Number))
436+ , (BitwiseXor, (Number, Number))
437+ , (ShiftRight, (Number, Number))
438+ , (ZeroFillShiftRight, (Number, Number))
439+ , (And, (Boolean, Boolean))
440+ , (Or, (Boolean, Boolean))
441+ , (Concat, (String, String))
442+ , (Modulus, (Number, Number))
443+ , (LessThan, (Number, Boolean))
444+ , (LessThanOrEqualTo, (Number, Boolean))
445+ , (GreaterThan, (Number, Boolean))
446+ , (GreaterThanOrEqualTo, (Number, Boolean))
447+ ]
448+
449+inferBinder :: Type -> Binder -> Subst Check (M.Map Ident Type)
450+inferBinder _ NullBinder = return M.empty
451+inferBinder val (StringBinder _) = val ~~ String >> return M.empty
452+inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
453+inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
454+inferBinder val (VarBinder name) = return $ M.singleton name val
455+inferBinder val (NullaryBinder ctor) = do
456+ env <- lift getEnv
457+ modulePath <- checkModulePath `fmap` lift get
458+ case M.lookup (qualify modulePath ctor) (dataConstructors env) of
459+ Just ty -> do
460+ ty `subsumes` val
461+ return M.empty
462+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
463+inferBinder val (UnaryBinder ctor binder) = 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+ Function [obj] ret <- replaceAllVarsWithUnknowns ty
469+ val `subsumes` ret
470+ inferBinder obj binder
471+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
472+inferBinder val (ObjectBinder props) = do
473+ row <- fresh
474+ rest <- fresh
475+ m1 <- inferRowProperties row rest props
476+ val ~~ Object row
477+ return m1
478+ where
479+ inferRowProperties :: Row -> Row -> [(String, Binder)] -> Subst Check (M.Map Ident Type)
480+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
481+ inferRowProperties nrow row ((name, binder):binders) = do
482+ propTy <- fresh
483+ m1 <- inferBinder propTy binder
484+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
485+ return $ m1 `M.union` m2
486+inferBinder val (ArrayBinder binders rest) = do
487+ el <- fresh
488+ m1 <- M.unions <$> mapM (inferBinder el) binders
489+ val ~~ Array el
490+ case rest of
491+ Nothing -> return m1
492+ Just binder -> do
493+ m2 <- inferBinder val binder
494+ return $ m1 `M.union` m2
495+inferBinder val (NamedBinder name binder) = do
496+ m <- inferBinder val binder
497+ return $ M.insert name val m
498+
499+inferGuardedBinder :: M.Map Ident Type -> Type -> Binder -> Subst Check (M.Map Ident Type)
500+inferGuardedBinder m val (GuardedBinder cond binder) = do
501+ m1 <- inferBinder val binder
502+ check (m1 `M.union` m) cond Boolean
503+ return m1
504+inferGuardedBinder m val b = inferBinder val b
505+
506+checkBinders :: M.Map Ident Type -> Type -> Type -> [(Binder, Value)] -> Subst Check ()
507+checkBinders _ _ _ [] = return ()
508+checkBinders m nval ret ((binder, val):bs) = do
509+ m1 <- inferGuardedBinder m nval binder
510+ check (m1 `M.union` m) val ret
511+ checkBinders m nval ret bs
512+
513+assignVariable :: Ident -> M.Map Ident Type -> Subst Check ()
514+assignVariable name m =
515+ case M.lookup name m of
516+ Nothing -> return ()
517+ Just _ -> throwError $ "Variable with name " ++ show name ++ " already exists."
518+
519+checkStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> Statement -> Subst Check (Bool, M.Map Ident Type)
520+checkStatement m mass ret (VariableIntroduction name val) = do
521+ assignVariable name (m `M.union` mass)
522+ t <- infer m val
523+ return (False, M.insert name t mass)
524+checkStatement m mass ret (Assignment ident val) = do
525+ t <- infer m val
526+ case M.lookup ident mass of
527+ Nothing -> throwError $ "No local variable with name " ++ show ident
528+ Just ty -> do t ~~ ty
529+ return (False, mass)
530+checkStatement m mass ret (While val inner) = do
531+ check m val Boolean
532+ (allCodePathsReturn, _) <- checkBlock m mass ret inner
533+ return (allCodePathsReturn, mass)
534+checkStatement m mass ret (If ifst) = do
535+ allCodePathsReturn <- checkIfStatement m mass ret ifst
536+ return (allCodePathsReturn, mass)
537+checkStatement m mass ret (For ident start end inner) = do
538+ assignVariable ident (m `M.union` mass)
539+ check (m `M.union` mass) start Number
540+ check (m `M.union` mass) end Number
541+ let mass1 = M.insert ident Number mass
542+ (allCodePathsReturn, _) <- checkBlock (m `M.union` mass1) mass1 ret inner
543+ return (allCodePathsReturn, mass)
544+checkStatement m mass ret (ForEach ident vals inner) = do
545+ assignVariable ident (m `M.union` mass)
546+ val <- fresh
547+ check (m `M.union` mass) vals (Array val)
548+ let mass1 = M.insert ident val mass
549+ (allCodePathsReturn, _) <- checkBlock (m `M.union` mass1) mass1 ret inner
550+ guardWith "Cannot return from within a foreach block" $ not allCodePathsReturn
551+ return (False, mass)
552+checkStatement m mass ret (Return val) = do
553+ check (m `M.union` mass) val ret
554+ return (True, mass)
555+
556+checkIfStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> IfStatement -> Subst Check Bool
557+checkIfStatement m mass ret (IfStatement val thens Nothing) = do
558+ check m val Boolean
559+ _ <- checkBlock m mass ret thens
560+ return False
561+checkIfStatement m mass ret (IfStatement val thens (Just elses)) = do
562+ check m val Boolean
563+ (allCodePathsReturn1, _) <- checkBlock m mass ret thens
564+ allCodePathsReturn2 <- checkElseStatement m mass ret elses
565+ return $ allCodePathsReturn1 && allCodePathsReturn2
566+
567+checkElseStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> ElseStatement -> Subst Check Bool
568+checkElseStatement m mass ret (Else elses) = fst <$> checkBlock m mass ret elses
569+checkElseStatement m mass ret (ElseIf ifst) = checkIfStatement m mass ret ifst
570+
571+checkBlock :: M.Map Ident Type -> M.Map Ident Type -> Type -> [Statement] -> Subst Check (Bool, M.Map Ident Type)
572+checkBlock _ mass _ [] = return (False, mass)
573+checkBlock m mass ret (s:ss) = do
574+ (b1, mass1) <- checkStatement (m `M.union` mass) mass ret s
575+ case (b1, ss) of
576+ (True, []) -> return (True, mass1)
577+ (True, _) -> throwError "Unreachable code"
578+ (False, ss) -> do
579+ (b2, mass2) <- checkBlock m mass1 ret ss
580+ return (b2, mass2)
581+
582+skolemize :: String -> Type -> Subst Check Type
583+skolemize ident ty = do
584+ tsk <- Skolem <$> fresh'
585+ rsk <- RSkolem <$> fresh'
586+ return $ replaceRowVars ident rsk $ replaceTypeVars ident tsk ty
587+
588+check :: M.Map Ident Type -> Value -> Type -> Subst Check ()
589+check m val ty = rethrow errorMessage $ check' m val ty
590+ where
591+ errorMessage msg =
592+ "Error checking type of term " ++
593+ prettyPrintValue val ++
594+ " against type " ++
595+ prettyPrintType ty ++
596+ ":\n" ++
597+ msg
598+
599+check' :: M.Map Ident Type -> Value -> Type -> Subst Check ()
600+check' m val (ForAll idents ty) = do
601+ sk <- skolemize idents ty
602+ check m val sk
603+check' m val u@(TUnknown _) = do
604+ ty <- infer m val
605+ -- Don't unify an unknown with an inferred polytype
606+ ty' <- replaceAllVarsWithUnknowns ty
607+ ty' ~~ u
608+check' m (NumericLiteral _) Number = return ()
609+check' m (StringLiteral _) String = return ()
610+check' m (BooleanLiteral _) Boolean = return ()
611+check' m (Unary op val) ty = checkUnary m op val ty
612+check' m (Binary op left right) ty = checkBinary m op left right ty
613+check' m (ArrayLiteral vals) (Array ty) = forM_ vals (\val -> check m val ty)
614+check' m (Indexer index vals) ty = check m index Number >> check m vals (Array ty)
615+check' m (Abs args ret) (Function argTys retTy) = do
616+ guardWith "Incorrect number of function arguments" (length args == length argTys)
617+ let bindings = M.fromList (zip args argTys)
618+ check (bindings `M.union` m) ret retTy
619+check' m app@(App _ _) ret = do
620+ let (f, argss) = unfoldApplication app
621+ ft <- infer m f
622+ checkFunctionApplications m ft argss ret
623+check' m v@(Var var@(Qualified mp name)) ty = do
624+ case mp of
625+ ModulePath [] ->
626+ case M.lookup name m of
627+ Just ty1 -> do
628+ repl <- lift $ replaceAllTypeSynonyms ty1
629+ repl `subsumes` ty
630+ Nothing -> lookupGlobal
631+ _ -> lookupGlobal
632+ where
633+ lookupGlobal = do
634+ env <- lift getEnv
635+ modulePath <- checkModulePath `fmap` lift get
636+ case M.lookup (qualify modulePath var) (names env) of
637+ Nothing -> throwError $ show var ++ " is undefined"
638+ Just (ty1, _) -> do
639+ repl <- lift $ replaceAllTypeSynonyms ty1
640+ repl `subsumes` ty
641+check' m (TypedValue val ty1) ty2 = do
642+ kind <- lift $ kindOf ty1
643+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
644+ ty1 `subsumes` ty2
645+ check m val ty1
646+check' m (Case val binders) ret = do
647+ t1 <- infer m val
648+ checkBinders m t1 ret binders
649+check' m (IfThenElse cond th el) ty = do
650+ check m cond Boolean
651+ check m th ty
652+ check m el ty
653+check' m (ObjectLiteral ps) (Object row) = do
654+ lift $ ensureNoDuplicateProperties ps
655+ checkProperties m ps row False
656+check' m (ObjectUpdate obj ps) (Object row) = do
657+ lift $ ensureNoDuplicateProperties ps
658+ us <- zip (map fst ps) <$> replicateM (length ps) fresh
659+ let (propsToCheck, rest) = rowToList row
660+ propsToRemove = map fst ps
661+ remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
662+ check m obj (Object (rowFromList (us ++ remainingProps, rest)))
663+ checkProperties m ps row True
664+check' m (Accessor prop val) ty = do
665+ rest <- fresh
666+ check m val (Object (RCons prop ty rest))
667+check' m (Block ss) ret = do
668+ (allCodePathsReturn, _) <- checkBlock m M.empty ret ss
669+ guardWith "Block is missing a return statement" allCodePathsReturn
670+check' m (Constructor c) ty = do
671+ env <- lift getEnv
672+ modulePath <- checkModulePath `fmap` lift get
673+ case M.lookup (qualify modulePath c) (dataConstructors env) of
674+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
675+ Just ty1 -> do
676+ repl <- lift $ replaceAllTypeSynonyms ty1
677+ repl `subsumes` ty
678+check' m val (SaturatedTypeSynonym name args) = do
679+ ty <- expandTypeSynonym name args
680+ check m val ty
681+check' _ val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
682+
683+checkProperties :: M.Map Ident Type -> [(String, Value)] -> Row -> Bool -> Subst Check ()
684+checkProperties m ps row lax = let (ts, r') = rowToList row in go ps ts r' where
685+ go [] [] REmpty = return ()
686+ go [] [] u@(RUnknown _) = u ~~ REmpty
687+ go [] [] (RSkolem _) | lax = return ()
688+ go [] ((p, _): _) _ | lax = return ()
689+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
690+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
691+ go ((p,v):ps) [] u@(RUnknown _) = do
692+ ty <- infer m v
693+ rest <- fresh
694+ u ~~ RCons p ty rest
695+ go ps [] rest
696+ go ((p,v):ps) ts r =
697+ case lookup p ts of
698+ Nothing -> do
699+ ty <- infer m v
700+ rest <- fresh
701+ r ~~ RCons p ty rest
702+ go ps ts rest
703+ Just ty -> do
704+ check m v ty
705+ go ps (delete (p, ty) ts) r
706+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
707+
708+unfoldApplication :: Value -> (Value, [[Value]])
709+unfoldApplication = go []
710+ where
711+ go argss (App f args) = go (args:argss) f
712+ go argss f = (f, argss)
713+
714+checkFunctionApplications :: M.Map Ident Type -> Type -> [[Value]] -> Type -> Subst Check ()
715+checkFunctionApplications _ _ [] _ = error "Nullary function application"
716+checkFunctionApplications m fnTy [args] ret = checkFunctionApplication m fnTy args ret
717+checkFunctionApplications m fnTy (args:argss) ret = do
718+ argTys <- mapM (infer m) args
719+ f <- inferFunctionApplication m fnTy argTys
720+ checkFunctionApplications m f argss ret
721+
722+checkFunctionApplication :: M.Map Ident Type -> Type -> [Value] -> Type -> Subst Check ()
723+checkFunctionApplication m fnTy args ret = rethrow errorMessage $ checkFunctionApplication' m fnTy args ret
724+ where
725+ errorMessage msg = "Error applying function of type "
726+ ++ prettyPrintType fnTy
727+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
728+ ++ ", expecting value of type "
729+ ++ prettyPrintType ret ++ ":\n" ++ msg
730+
731+inferFunctionApplication :: M.Map Ident Type -> Type -> [Type] -> Subst Check Type
732+inferFunctionApplication m (Function argTys retTy) args = do
733+ guardWith "Incorrect number of function arguments" (length args == length argTys)
734+ zipWithM subsumes args argTys
735+ return retTy
736+inferFunctionApplication m (ForAll ident ty) args = do
737+ replaced <- replaceVarWithUnknown ident ty
738+ inferFunctionApplication m replaced args
739+inferFunctionApplication m u@(TUnknown _) args = do
740+ ret <- fresh
741+ args' <- mapM replaceAllVarsWithUnknowns args
742+ u ~~ Function args' ret
743+ return ret
744+inferFunctionApplication m (SaturatedTypeSynonym name tyArgs) args = do
745+ ty <- expandTypeSynonym name tyArgs
746+ inferFunctionApplication m ty args
747+inferFunctionApplication _ fnTy args = throwError $ "Cannot apply function of type "
748+ ++ prettyPrintType fnTy
749+ ++ " to argument(s) of type(s) " ++ intercalate ", " (map prettyPrintType args)
750+
751+checkFunctionApplication' :: M.Map Ident Type -> Type -> [Value] -> Type -> Subst Check ()
752+checkFunctionApplication' m (Function argTys retTy) args ret = do
753+ guardWith "Incorrect number of function arguments" (length args == length argTys)
754+ zipWithM (check m) args argTys
755+ retTy `subsumes` ret
756+checkFunctionApplication' m (ForAll ident ty) args ret = do
757+ replaced <- replaceVarWithUnknown ident ty
758+ checkFunctionApplication m replaced args ret
759+checkFunctionApplication' m u@(TUnknown _) args ret = do
760+ tyArgs <- mapM (\arg -> infer m arg >>= replaceAllVarsWithUnknowns) args
761+ u ~~ Function tyArgs ret
762+checkFunctionApplication' m (SaturatedTypeSynonym name tyArgs) args ret = do
763+ ty <- expandTypeSynonym name tyArgs
764+ checkFunctionApplication' m ty args ret
765+checkFunctionApplication' _ fnTy args ret = throwError $ "Applying a function of type "
766+ ++ prettyPrintType fnTy
767+ ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
768+ ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
769+
770+subsumes :: Type -> Type -> Subst Check ()
771+subsumes (ForAll ident ty1) ty2 = do
772+ replaced <- replaceVarWithUnknown ident ty1
773+ replaced `subsumes` ty2
774+subsumes (Function args1 ret1) (Function args2 ret2) = do
775+ zipWithM subsumes args2 args1
776+ ret1 `subsumes` ret2
777+subsumes ty1 ty2 = ty1 ~~ ty2
778+