@@ -0,0 +1,782 @@
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, FlexibleContexts #-}
16+
17+module Language.PureScript.TypeChecker.Types (
18+ typesOf
19+) where
20+
21+import Data.List
22+import Data.Maybe (fromMaybe)
23+import Data.Either (lefts, rights)
24+import qualified Data.Data as D
25+import Data.Generics
26+ (mkT, something, everywhere, everywhereBut, mkQ, extQ)
27+
28+import Language.PureScript.Values
29+import Language.PureScript.Types
30+import Language.PureScript.Kinds
31+import Language.PureScript.Names
32+import Language.PureScript.TypeChecker.Monad
33+import Language.PureScript.TypeChecker.Kinds
34+import Language.PureScript.TypeChecker.Synonyms
35+import Language.PureScript.Pretty
36+import Language.PureScript.Unknown
37+
38+import Control.Monad.State
39+import Control.Monad.Error
40+import Control.Monad.Reader
41+
42+import Control.Applicative
43+import Control.Arrow (Arrow(..))
44+
45+import qualified Data.Map as M
46+
47+instance Unifiable Type where
48+ unknown = TUnknown
49+ isUnknown (TUnknown u) = Just u
50+ isUnknown _ = Nothing
51+ (~~) = unifyTypes
52+ apply s (TUnknown u) = runSubstitution s u
53+ apply s (SaturatedTypeSynonym name tys) = SaturatedTypeSynonym name $ map (apply s) tys
54+ apply s (ForAll idents ty) = ForAll idents $ apply s ty
55+ apply s (Array t) = Array (apply s t)
56+ apply s (Object r) = Object (apply s r)
57+ apply s (Function args ret) = Function (map (apply s) args) (apply s ret)
58+ apply s (TypeApp t1 t2) = TypeApp (apply s t1) (apply s t2)
59+ apply _ t = t
60+ unknowns (TUnknown (Unknown u)) = [u]
61+ unknowns (SaturatedTypeSynonym _ tys) = concatMap unknowns tys
62+ unknowns (ForAll _ ty) = unknowns ty
63+ unknowns (Array t) = unknowns t
64+ unknowns (Object r) = unknowns r
65+ unknowns (Function args ret) = concatMap unknowns args ++ unknowns ret
66+ unknowns (TypeApp t1 t2) = unknowns t1 ++ unknowns t2
67+ unknowns _ = []
68+
69+instance Unifiable Row where
70+ unknown = RUnknown
71+ isUnknown (RUnknown u) = Just u
72+ isUnknown _ = Nothing
73+ r1 ~~ r2 =
74+ let
75+ (s1, r1') = rowToList r1
76+ (s2, r2') = rowToList r2
77+ int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
78+ sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
79+ sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
80+ in do
81+ forM_ int (uncurry (~~))
82+ unifyRows sd1 r1' sd2 r2'
83+ where
84+ unifyRows :: [(String, Type)] -> Row -> [(String, Type)] -> Row -> Subst ()
85+ unifyRows [] (RUnknown u) sd r = replace u (rowFromList (sd, r))
86+ unifyRows sd r [] (RUnknown u) = replace u (rowFromList (sd, r))
87+ unifyRows ((name, ty):row) r others u@(RUnknown un) = do
88+ occursCheck un ty
89+ forM row $ \(_, t) -> occursCheck un t
90+ u' <- fresh
91+ u ~~ RCons name ty u'
92+ unifyRows row r others u'
93+ unifyRows [] REmpty [] REmpty = return ()
94+ unifyRows [] (RowVar v1) [] (RowVar v2) | v1 == v2 = return ()
95+ unifyRows [] (RSkolem s1) [] (RSkolem s2) | s1 == s2 = return ()
96+ unifyRows sd3 r3 sd4 r4 = throwError $ "Cannot unify " ++ prettyPrintRow (rowFromList (sd3, r3)) ++ " with " ++ prettyPrintRow (rowFromList (sd4, r4)) ++ "."
97+ apply s (RUnknown u) = runSubstitution s u
98+ apply s (RCons name ty r) = RCons name (apply s ty) (apply s r)
99+ apply _ r = r
100+ unknowns (RUnknown (Unknown u)) = [u]
101+ unknowns (RCons _ ty r) = unknowns ty ++ unknowns r
102+ unknowns _ = []
103+
104+unifyTypes :: Type -> Type -> Subst ()
105+unifyTypes t1 t2 = rethrow (\e -> "Error unifying type " ++ prettyPrintType t1 ++ " with type " ++ prettyPrintType t2 ++ ":\n" ++ e) $ do
106+ unifyTypes' t1 t2
107+ where
108+ unifyTypes' (TUnknown u1) (TUnknown u2) | u1 == u2 = return ()
109+ unifyTypes' (TUnknown u) t = replace u t
110+ unifyTypes' t (TUnknown u) = replace u t
111+ unifyTypes' (SaturatedTypeSynonym name1 args1) (SaturatedTypeSynonym name2 args2)
112+ | name1 == name2 = zipWithM_ unifyTypes args1 args2
113+ unifyTypes' (SaturatedTypeSynonym name args) ty = do
114+ ty1 <- expandTypeSynonym name args
115+ ty1 `unifyTypes` ty
116+ unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
117+ unifyTypes' (ForAll ident1 ty1) (ForAll ident2 ty2) = do
118+ sk <- skolemize ident1 ty1
119+ replaced <- replaceVarWithUnknown ident2 ty2
120+ sk `unifyTypes` replaced
121+ unifyTypes' (ForAll ident ty1) ty2 = do
122+ sk <- skolemize ident ty1
123+ sk `unifyTypes` ty2
124+ unifyTypes' ty f@(ForAll _ _) = f `unifyTypes` ty
125+ unifyTypes' Number Number = return ()
126+ unifyTypes' String String = return ()
127+ unifyTypes' Boolean Boolean = return ()
128+ unifyTypes' (Array s) (Array t) = s `unifyTypes` t
129+ unifyTypes' (Object row1) (Object row2) = row1 ~~ row2
130+ unifyTypes' (Function args1 ret1) (Function args2 ret2) = do
131+ guardWith "Function applied to incorrect number of args" $ length args1 == length args2
132+ zipWithM_ unifyTypes args1 args2
133+ ret1 `unifyTypes` ret2
134+ unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
135+ unifyTypes' (TypeConstructor c1) (TypeConstructor c2) = do
136+ env <- getEnv
137+ moduleName <- substCurrentModule `fmap` ask
138+ guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (typeConstructorsAreEqual env moduleName c1 c2)
139+ unifyTypes' (TypeApp t3 t4) (TypeApp t5 t6) = do
140+ t3 `unifyTypes` t5
141+ t4 `unifyTypes` t6
142+ unifyTypes' (Skolem s1) (Skolem s2) | s1 == s2 = return ()
143+ unifyTypes' t3 t4 = throwError $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
144+
145+typeConstructorsAreEqual :: Environment -> ModuleName -> Qualified ProperName -> Qualified ProperName -> Bool
146+typeConstructorsAreEqual env moduleName c1 c2 =
147+ let
148+ c1' = qualify moduleName c1
149+ c2' = qualify moduleName c2
150+ in
151+ canonicalize env c1' == canonicalize env c2'
152+ where
153+ canonicalize :: Environment -> (ModuleName, ProperName) -> (ModuleName, ProperName)
154+ canonicalize _ key = case key `M.lookup` types env of
155+ Just (_, DataAlias mn' pn') -> (mn', pn')
156+ _ -> key
157+
158+typesOf :: ModuleName -> [(Ident, Value)] -> Check [Type]
159+typesOf moduleName vals = do
160+ (tys, sub, checks) <- runSubst (SubstContext moduleName) $ do
161+ let es = map isTyped vals
162+ typed = lefts es
163+ untyped = rights es
164+ typedDict = map (\(ident, ty, _) -> (ident, ty)) typed
165+ untypedNames <- replicateM (length untyped) fresh
166+ let untypedDict = zip (map fst untyped) untypedNames
167+ dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ typedDict ++ untypedDict)
168+ tys <- forM es $ \e -> case e of
169+ Left (_, ty, val) -> do
170+ kind <- liftCheck $ kindOf moduleName ty
171+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
172+ ty' <- replaceAllTypeSynonyms ty
173+ bindNames dict $ check val ty'
174+ return ty'
175+ Right (ident, val) -> do
176+ ty <- bindNames dict $ infer val
177+ ty ~~ fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
178+ return ty
179+ return tys
180+ forM tys $ flip (escapeCheck checks) sub
181+ forM tys $ skolemEscapeCheck
182+ return $ map (varIfUnknown . desaturateAllTypeSynonyms . setifyAll) tys
183+
184+isTyped :: (Ident, Value) -> Either (Ident, Type, Value) (Ident, Value)
185+isTyped (name, TypedValue value ty) = Left (name, ty, value)
186+isTyped (name, value) = Right (name, value)
187+
188+escapeCheck :: [AnyUnifiable] -> Type -> Substitution -> Check ()
189+escapeCheck checks ty sub =
190+ let
191+ visibleUnknowns = nub $ unknowns ty
192+ in
193+ forM_ checks $ \c -> case c of
194+ AnyUnifiable t -> do
195+ let unsolvedUnknowns = nub . unknowns $ apply sub t
196+ guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
197+
198+skolemEscapeCheck :: Type -> Check ()
199+skolemEscapeCheck ty =
200+ case something (extQ (mkQ Nothing findSkolems) findRSkolems) ty of
201+ Nothing -> return ()
202+ Just _ -> throwError "Skolem variables cannot escape. Consider adding a type signature."
203+ where
204+ findSkolems (Skolem _) = return ()
205+ findSkolems _ = mzero
206+ findRSkolems (RSkolem _) = return ()
207+ findRSkolems _ = mzero
208+
209+setify :: Row -> Row
210+setify = rowFromList . first (M.toList . M.fromList) . rowToList
211+
212+setifyAll :: (D.Data d) => d -> d
213+setifyAll = everywhere (mkT setify)
214+
215+varIfUnknown :: Type -> Type
216+varIfUnknown ty =
217+ let unks = nub $ unknowns ty
218+ toName = (:) 't' . show
219+ ty' = everywhere (mkT rowToVar) . everywhere (mkT typeToVar) $ ty
220+ typeToVar :: Type -> Type
221+ typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
222+ typeToVar t = t
223+ rowToVar :: Row -> Row
224+ rowToVar (RUnknown (Unknown u)) = RowVar (toName u)
225+ rowToVar t = t
226+ in mkForAll (sort . map toName $ unks) ty'
227+
228+replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
229+replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
230+
231+replaceTypeVars :: (D.Data d) => String -> Type -> d -> d
232+replaceTypeVars name t = everywhereBut (mkQ False isShadowed) (mkT replaceTypeVar)
233+ where
234+ replaceTypeVar (TypeVar v) | v == name = t
235+ replaceTypeVar other = other
236+ isShadowed (ForAll v _) | v == name = True
237+ isShadowed _ = False
238+
239+replaceRowVars :: (D.Data d) => String -> Row -> d -> d
240+replaceRowVars name r = everywhere (mkT replaceRowVar)
241+ where
242+ replaceRowVar (RowVar v) | v == name = r
243+ replaceRowVar other = other
244+
245+replaceAllVarsWithUnknowns :: Type -> Subst Type
246+replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
247+replaceAllVarsWithUnknowns ty = return ty
248+
249+replaceVarWithUnknown :: String -> Type -> Subst Type
250+replaceVarWithUnknown ident ty = do
251+ tu <- fresh
252+ ru <- fresh
253+ return $ replaceRowVars ident ru . replaceTypeVars ident tu $ ty
254+
255+replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadReader SubstContext m, MonadError String m) => (D.Data d) => d -> m d
256+replaceAllTypeSynonyms d = do
257+ env <- getEnv
258+ moduleName <- substCurrentModule <$> ask
259+ let syns = map (\((path, name), (args, _)) -> (Qualified (Just path) name, length args)) . M.toList $ typeSynonyms env
260+ either throwError return $ saturateAllTypeSynonyms moduleName syns d
261+
262+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
263+desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
264+ where
265+ replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
266+ replaceSaturatedTypeSynonym t = t
267+
268+expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Type
269+expandTypeSynonym name args = do
270+ env <- getEnv
271+ moduleName <- substCurrentModule `fmap` ask
272+ case M.lookup (qualify moduleName name) (typeSynonyms env) of
273+ Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
274+ Nothing -> error "Type synonym was not defined"
275+
276+ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
277+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
278+
279+infer :: Value -> Subst Type
280+infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ do
281+ ty <- infer' val
282+ escapeCheckLater ty
283+ return ty
284+
285+infer' :: Value -> Subst Type
286+infer' (NumericLiteral _) = return Number
287+infer' (StringLiteral _) = return String
288+infer' (BooleanLiteral _) = return Boolean
289+infer' (ArrayLiteral vals) = do
290+ ts <- mapM (infer) vals
291+ els <- fresh
292+ forM_ ts $ \t -> els ~~ Array t
293+ return els
294+infer' (Unary op val) = do
295+ t <- infer val
296+ inferUnary op t
297+infer' (Binary op left right) = do
298+ t1 <- infer left
299+ t2 <- infer right
300+ inferBinary op t1 t2
301+infer' (ObjectLiteral ps) = do
302+ ensureNoDuplicateProperties ps
303+ ts <- mapM (infer . snd) ps
304+ let fields = zipWith (\(name, _) t -> (name, t)) ps ts
305+ return $ Object $ rowFromList (fields, REmpty)
306+infer' (ObjectUpdate o ps) = do
307+ ensureNoDuplicateProperties ps
308+ row <- fresh
309+ newTys <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
310+ oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
311+ check o $ Object $ rowFromList (oldTys, row)
312+ return $ Object $ rowFromList (newTys, row)
313+infer' (Indexer index val) = do
314+ el <- fresh
315+ check index Number
316+ check val (Array el)
317+ return el
318+infer' (Accessor prop val) = do
319+ obj <- infer val
320+ propTy <- inferProperty obj prop
321+ case propTy of
322+ Nothing -> do
323+ field <- fresh
324+ rest <- fresh
325+ obj `subsumes` Object (RCons prop field rest)
326+ return field
327+ Just ty -> return ty
328+infer' (Abs args ret) = do
329+ ts <- replicateM (length args) fresh
330+ moduleName <- substCurrentModule <$> ask
331+ bindLocalVariables moduleName (zip args ts) $ do
332+ body <- infer' ret
333+ return $ Function ts body
334+infer' app@(App _ _) = do
335+ let (f, argss) = unfoldApplication app
336+ ft <- infer f
337+ ret <- fresh
338+ checkFunctionApplications ft argss ret
339+ return ret
340+infer' (Var var) = do
341+ moduleName <- substCurrentModule <$> ask
342+ ty <- lookupVariable moduleName var
343+ replaceAllTypeSynonyms ty
344+infer' (Block ss) = do
345+ ret <- fresh
346+ (allCodePathsReturn, _) <- checkBlock M.empty ret ss
347+ guardWith "Block is missing a return statement" allCodePathsReturn
348+ return ret
349+infer' (Constructor c) = do
350+ env <- getEnv
351+ moduleName <- substCurrentModule `fmap` ask
352+ case M.lookup (qualify moduleName c) (dataConstructors env) of
353+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
354+ Just ty -> replaceAllTypeSynonyms ty
355+infer' (Case vals binders) = do
356+ ts <- mapM infer vals
357+ ret <- fresh
358+ checkBinders ts ret binders
359+ return ret
360+infer' (IfThenElse cond th el) = do
361+ check cond Boolean
362+ t2 <- infer th
363+ t3 <- infer el
364+ t2 ~~ t3
365+ return t2
366+infer' (TypedValue val ty) = do
367+ moduleName <- substCurrentModule <$> ask
368+ kind <- liftCheck $ kindOf moduleName ty
369+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
370+ ty' <- replaceAllTypeSynonyms ty
371+ check val ty'
372+ return ty'
373+infer' _ = error "Invalid argument to infer"
374+
375+inferProperty :: Type -> String -> Subst (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 <- replaceVarWithUnknown ident ty
384+ inferProperty replaced prop
385+inferProperty _ _ = return Nothing
386+
387+inferUnary :: UnaryOperator -> Type -> Subst 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 :: UnaryOperator -> Value -> Type -> Subst ()
395+checkUnary op val res =
396+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
397+ (valTy, resTy) -> do
398+ res ~~ resTy
399+ check 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 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 :: BinaryOperator -> Value -> Value -> Type -> Subst ()
419+checkBinary op left right res | isEqualityTest op = do
420+ res ~~ Boolean
421+ t1 <- infer left
422+ t2 <- infer right
423+ t1 ~~ t2
424+checkBinary op left right res =
425+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
426+ (valTy, resTy) -> do
427+ res ~~ resTy
428+ check left valTy
429+ check 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 (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 <- getEnv
465+ moduleName <- substCurrentModule <$> ask
466+ case M.lookup (qualify moduleName 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 <- getEnv
473+ moduleName <- substCurrentModule <$> ask
474+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
475+ Just ty -> do
476+ fn <- replaceAllVarsWithUnknowns ty
477+ case fn of
478+ Function [obj] ret -> do
479+ val `subsumes` ret
480+ inferBinder obj binder
481+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
482+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
483+inferBinder val (ObjectBinder props) = do
484+ row <- fresh
485+ rest <- fresh
486+ m1 <- inferRowProperties row rest props
487+ val ~~ Object row
488+ return m1
489+ where
490+ inferRowProperties :: Row -> Row -> [(String, Binder)] -> Subst (M.Map Ident Type)
491+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
492+ inferRowProperties nrow row ((name, binder):binders) = do
493+ propTy <- fresh
494+ m1 <- inferBinder propTy binder
495+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
496+ return $ m1 `M.union` m2
497+inferBinder val (ArrayBinder binders) = do
498+ el <- fresh
499+ m1 <- M.unions <$> mapM (inferBinder el) binders
500+ val ~~ Array el
501+ return m1
502+inferBinder val (ConsBinder headBinder tailBinder) = do
503+ el <- fresh
504+ m1 <- inferBinder el headBinder
505+ m2 <- inferBinder val tailBinder
506+ val ~~ Array el
507+ return $ m1 `M.union` m2
508+inferBinder val (NamedBinder name binder) = do
509+ m <- inferBinder val binder
510+ return $ M.insert name val m
511+
512+checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> Subst ()
513+checkBinders _ _ [] = return ()
514+checkBinders nvals ret ((binders, grd, val):bs) = do
515+ moduleName <- substCurrentModule <$> ask
516+ m1 <- M.unions <$> zipWithM inferBinder nvals binders
517+ bindLocalVariables moduleName (M.toList m1) $ do
518+ check val ret
519+ case grd of
520+ Nothing -> return ()
521+ Just g -> check g Boolean
522+ checkBinders nvals ret bs
523+
524+assignVariable :: Ident -> Subst ()
525+assignVariable name = do
526+ env <- checkEnv <$> get
527+ moduleName <- substCurrentModule <$> ask
528+ case M.lookup (moduleName, name) (names env) of
529+ Just (_, LocalVariable) -> throwError $ "Variable with name " ++ show name ++ " already exists."
530+ _ -> return ()
531+
532+checkStatement :: M.Map Ident Type -> Type -> Statement -> Subst (Bool, M.Map Ident Type)
533+checkStatement mass _ (VariableIntroduction name val) = do
534+ assignVariable name
535+ t <- infer val
536+ return (False, M.insert name t mass)
537+checkStatement mass _ (Assignment ident val) = do
538+ t <- infer val
539+ case M.lookup ident mass of
540+ Nothing -> throwError $ "No local variable with name " ++ show ident
541+ Just ty -> do t ~~ ty
542+ return (False, mass)
543+checkStatement mass ret (While val inner) = do
544+ check val Boolean
545+ (allCodePathsReturn, _) <- checkBlock mass ret inner
546+ return (allCodePathsReturn, mass)
547+checkStatement mass ret (If ifst) = do
548+ allCodePathsReturn <- checkIfStatement mass ret ifst
549+ return (allCodePathsReturn, mass)
550+checkStatement mass ret (For ident start end inner) = do
551+ moduleName <- substCurrentModule <$> ask
552+ assignVariable ident
553+ check start Number
554+ check end Number
555+ (allCodePathsReturn, _) <- bindLocalVariables moduleName [(ident, Number)] $ checkBlock mass ret inner
556+ return (allCodePathsReturn, mass)
557+checkStatement mass ret (ForEach ident vals inner) = do
558+ moduleName <- substCurrentModule <$> ask
559+ assignVariable ident
560+ val <- fresh
561+ check vals (Array val)
562+ (allCodePathsReturn, _) <- bindLocalVariables moduleName [(ident, val)] $ checkBlock mass ret inner
563+ guardWith "Cannot return from within a foreach block" $ not allCodePathsReturn
564+ return (False, mass)
565+checkStatement mass _ (ValueStatement val) = do
566+ check val unit
567+ return (False, mass)
568+checkStatement mass ret (Return val) = do
569+ check val ret
570+ return (True, mass)
571+
572+checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> Subst Bool
573+checkIfStatement mass ret (IfStatement val thens Nothing) = do
574+ check val Boolean
575+ _ <- checkBlock mass ret thens
576+ return False
577+checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
578+ check val Boolean
579+ (allCodePathsReturn1, _) <- checkBlock mass ret thens
580+ allCodePathsReturn2 <- checkElseStatement mass ret elses
581+ return $ allCodePathsReturn1 && allCodePathsReturn2
582+
583+checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> Subst Bool
584+checkElseStatement mass ret (Else elses) = fst <$> checkBlock mass ret elses
585+checkElseStatement mass ret (ElseIf ifst) = checkIfStatement mass ret ifst
586+
587+checkBlock :: M.Map Ident Type -> Type -> [Statement] -> Subst (Bool, M.Map Ident Type)
588+checkBlock mass _ [] = return (False, mass)
589+checkBlock mass ret (s:ss) = do
590+ moduleName <- substCurrentModule <$> ask
591+ (b1, mass1) <- checkStatement mass ret s
592+ bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
593+ (True, []) -> return (True, mass1)
594+ (True, _) -> throwError "Unreachable code"
595+ (False, ss') -> checkBlock mass1 ret ss'
596+
597+skolemize :: String -> Type -> Subst Type
598+skolemize ident ty = do
599+ tsk <- Skolem <$> fresh'
600+ rsk <- RSkolem <$> fresh'
601+ return $ replaceRowVars ident rsk $ replaceTypeVars ident tsk ty
602+
603+check :: Value -> Type -> Subst ()
604+check val ty = rethrow errorMessage $ check' val ty
605+ where
606+ errorMessage msg =
607+ "Error checking type of term " ++
608+ prettyPrintValue val ++
609+ " against type " ++
610+ prettyPrintType ty ++
611+ ":\n" ++
612+ msg
613+
614+check' :: Value -> Type -> Subst ()
615+check' val (ForAll idents ty) = do
616+ sk <- skolemize idents ty
617+ check val sk
618+check' val u@(TUnknown _) = do
619+ ty <- infer val
620+ -- Don't unify an unknown with an inferred polytype
621+ ty' <- replaceAllVarsWithUnknowns ty
622+ ty' ~~ u
623+check' (NumericLiteral _) Number = return ()
624+check' (StringLiteral _) String = return ()
625+check' (BooleanLiteral _) Boolean = return ()
626+check' (Unary op val) ty = checkUnary op val ty
627+check' (Binary op left right) ty = checkBinary op left right ty
628+check' (ArrayLiteral vals) (Array ty) = forM_ vals (\val -> check val ty)
629+check' (Indexer index vals) ty = check index Number >> check vals (Array ty)
630+check' (Abs args ret) (Function argTys retTy) = do
631+ moduleName <- substCurrentModule <$> ask
632+ guardWith "Incorrect number of function arguments" (length args == length argTys)
633+ bindLocalVariables moduleName (zip args argTys) $ check ret retTy
634+check' app@(App _ _) ret = do
635+ let (f, argss) = unfoldApplication app
636+ ft <- infer f
637+ checkFunctionApplications ft argss ret
638+check' (Var var) ty = do
639+ moduleName <- substCurrentModule <$> ask
640+ ty1 <- lookupVariable moduleName var
641+ repl <- replaceAllTypeSynonyms ty1
642+ repl `subsumes` ty
643+check' (TypedValue val ty1) ty2 = do
644+ moduleName <- substCurrentModule <$> ask
645+ kind <- liftCheck $ kindOf moduleName ty1
646+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
647+ ty1 `subsumes` ty2
648+ check val ty1
649+check' (Case vals binders) ret = do
650+ ts <- mapM infer vals
651+ checkBinders ts ret binders
652+check' (IfThenElse cond th el) ty = do
653+ check cond Boolean
654+ check th ty
655+ check el ty
656+check' (ObjectLiteral ps) (Object row) = do
657+ ensureNoDuplicateProperties ps
658+ checkProperties ps row False
659+check' (ObjectUpdate obj ps) (Object row) = do
660+ ensureNoDuplicateProperties ps
661+ us <- zip (map fst ps) <$> replicateM (length ps) fresh
662+ let (propsToCheck, rest) = rowToList row
663+ propsToRemove = map fst ps
664+ remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
665+ check obj (Object (rowFromList (us ++ remainingProps, rest)))
666+ checkProperties ps row True
667+check' (Accessor prop val) ty = do
668+ rest <- fresh
669+ check val (Object (RCons prop ty rest))
670+check' (Block ss) ret = do
671+ (allCodePathsReturn, _) <- checkBlock M.empty ret ss
672+ guardWith "Block is missing a return statement" allCodePathsReturn
673+check' (Constructor c) ty = do
674+ env <- getEnv
675+ moduleName <- substCurrentModule <$> ask
676+ case M.lookup (qualify moduleName c) (dataConstructors env) of
677+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
678+ Just ty1 -> do
679+ repl <- replaceAllTypeSynonyms ty1
680+ repl `subsumes` ty
681+check' val (SaturatedTypeSynonym name args) = do
682+ ty <- expandTypeSynonym name args
683+ check val ty
684+check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
685+
686+checkProperties :: [(String, Value)] -> Row -> Bool -> Subst ()
687+checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
688+ go [] [] REmpty = return ()
689+ go [] [] u@(RUnknown _) = u ~~ REmpty
690+ go [] [] (RSkolem _) | lax = return ()
691+ go [] ((p, _): _) _ | lax = return ()
692+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
693+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
694+ go ((p,v):ps') [] u@(RUnknown _) = do
695+ ty <- infer v
696+ rest <- fresh
697+ u ~~ RCons p ty rest
698+ go ps' [] rest
699+ go ((p,v):ps') ts r =
700+ case lookup p ts of
701+ Nothing -> do
702+ ty <- infer v
703+ rest <- fresh
704+ r ~~ RCons p ty rest
705+ go ps' ts rest
706+ Just ty -> do
707+ check v ty
708+ go ps' (delete (p, ty) ts) r
709+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
710+
711+unfoldApplication :: Value -> (Value, [[Value]])
712+unfoldApplication = go []
713+ where
714+ go argss (App f args) = go (args:argss) f
715+ go argss f = (f, argss)
716+
717+checkFunctionApplications :: Type -> [[Value]] -> Type -> Subst ()
718+checkFunctionApplications _ [] _ = error "Nullary function application"
719+checkFunctionApplications fnTy [args] ret = checkFunctionApplication fnTy args ret
720+checkFunctionApplications fnTy (args:argss) ret = do
721+ argTys <- mapM (infer) args
722+ f <- inferFunctionApplication fnTy argTys
723+ checkFunctionApplications f argss ret
724+
725+checkFunctionApplication :: Type -> [Value] -> Type -> Subst ()
726+checkFunctionApplication fnTy args ret = rethrow errorMessage $ checkFunctionApplication' fnTy args ret
727+ where
728+ errorMessage msg = "Error applying function of type "
729+ ++ prettyPrintType fnTy
730+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
731+ ++ ", expecting value of type "
732+ ++ prettyPrintType ret ++ ":\n" ++ msg
733+
734+inferFunctionApplication :: Type -> [Type] -> Subst Type
735+inferFunctionApplication (Function argTys retTy) args = do
736+ guardWith "Incorrect number of function arguments" (length args == length argTys)
737+ zipWithM subsumes args argTys
738+ return retTy
739+inferFunctionApplication (ForAll ident ty) args = do
740+ replaced <- replaceVarWithUnknown ident ty
741+ inferFunctionApplication replaced args
742+inferFunctionApplication u@(TUnknown _) args = do
743+
744+ ret <- fresh
745+ args' <- mapM replaceAllVarsWithUnknowns args
746+ u ~~ Function args' ret
747+ return ret
748+inferFunctionApplication (SaturatedTypeSynonym name tyArgs) args = do
749+ ty <- expandTypeSynonym name tyArgs
750+ inferFunctionApplication ty args
751+inferFunctionApplication fnTy args = throwError $ "Cannot apply function of type "
752+ ++ prettyPrintType fnTy
753+ ++ " to argument(s) of type(s) " ++ intercalate ", " (map prettyPrintType args)
754+
755+checkFunctionApplication' :: Type -> [Value] -> Type -> Subst ()
756+checkFunctionApplication' (Function argTys retTy) args ret = do
757+ guardWith "Incorrect number of function arguments" (length args == length argTys)
758+ zipWithM (check) args argTys
759+ retTy `subsumes` ret
760+checkFunctionApplication' (ForAll ident ty) args ret = do
761+ replaced <- replaceVarWithUnknown ident ty
762+ checkFunctionApplication replaced args ret
763+checkFunctionApplication' u@(TUnknown _) args ret = do
764+ tyArgs <- mapM (\arg -> infer arg >>= replaceAllVarsWithUnknowns) args
765+ u ~~ Function tyArgs ret
766+checkFunctionApplication' (SaturatedTypeSynonym name tyArgs) args ret = do
767+ ty <- expandTypeSynonym name tyArgs
768+ checkFunctionApplication' ty args ret
769+checkFunctionApplication' fnTy args ret = throwError $ "Applying a function of type "
770+ ++ prettyPrintType fnTy
771+ ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
772+ ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
773+
774+subsumes :: Type -> Type -> Subst ()
775+subsumes (ForAll ident ty1) ty2 = do
776+ replaced <- replaceVarWithUnknown ident ty1
777+ replaced `subsumes` ty2
778+subsumes (Function args1 ret1) (Function args2 ret2) = do
779+ zipWithM subsumes args2 args1
780+ ret1 `subsumes` ret2
781+subsumes ty1 ty2 = ty1 ~~ ty2
782+