@@ -0,0 +1,783 @@
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+{-# OPTIONS_GHC -fno-warn-orphans #-}
16+{-# LANGUAGE DeriveDataTypeable, FlexibleContexts #-}
17+
18+module Language.PureScript.TypeChecker.Types (
19+ typesOf
20+) where
21+
22+import Data.List
23+import Data.Maybe (fromMaybe)
24+import Data.Either (lefts, rights)
25+import qualified Data.Data as D
26+import Data.Generics
27+ (mkT, something, everywhere, everywhereBut, mkQ, 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+import Control.Monad.Reader
42+
43+import Control.Applicative
44+import Control.Arrow (Arrow(..))
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 _ 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 ()
86+ unifyRows [] (RUnknown u) sd r = replace u (rowFromList (sd, r))
87+ unifyRows sd r [] (RUnknown u) = replace u (rowFromList (sd, r))
88+ unifyRows ((name, ty):row) r others u@(RUnknown un) = do
89+ occursCheck un ty
90+ forM row $ \(_, t) -> occursCheck un t
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 sd3 r3 sd4 r4 = throwError $ "Cannot unify " ++ prettyPrintRow (rowFromList (sd3, r3)) ++ " with " ++ prettyPrintRow (rowFromList (sd4, r4)) ++ "."
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 ()
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+ env <- getEnv
138+ moduleName <- substCurrentModule `fmap` ask
139+ guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (typeConstructorsAreEqual env moduleName c1 c2)
140+ unifyTypes' (TypeApp t3 t4) (TypeApp t5 t6) = do
141+ t3 `unifyTypes` t5
142+ t4 `unifyTypes` t6
143+ unifyTypes' (Skolem s1) (Skolem s2) | s1 == s2 = return ()
144+ unifyTypes' t3 t4 = throwError $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
145+
146+typeConstructorsAreEqual :: Environment -> ModuleName -> Qualified ProperName -> Qualified ProperName -> Bool
147+typeConstructorsAreEqual env moduleName c1 c2 =
148+ let
149+ c1' = qualify moduleName c1
150+ c2' = qualify moduleName c2
151+ in
152+ canonicalize env c1' == canonicalize env c2'
153+ where
154+ canonicalize :: Environment -> (ModuleName, ProperName) -> (ModuleName, ProperName)
155+ canonicalize _ key = case key `M.lookup` types env of
156+ Just (_, DataAlias mn' pn') -> (mn', pn')
157+ _ -> key
158+
159+typesOf :: ModuleName -> [(Ident, Value)] -> Check [Type]
160+typesOf moduleName vals = do
161+ (tys, sub, checks) <- runSubst (SubstContext moduleName) $ do
162+ let es = map isTyped vals
163+ typed = lefts es
164+ untyped = rights es
165+ typedDict = map (\(ident, ty, _) -> (ident, ty)) typed
166+ untypedNames <- replicateM (length untyped) fresh
167+ let untypedDict = zip (map fst untyped) untypedNames
168+ dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ typedDict ++ untypedDict)
169+ tys <- forM es $ \e -> case e of
170+ Left (_, ty, val) -> do
171+ kind <- liftCheck $ kindOf moduleName ty
172+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
173+ ty' <- replaceAllTypeSynonyms ty
174+ bindNames dict $ check val ty'
175+ return ty'
176+ Right (ident, val) -> do
177+ ty <- bindNames dict $ infer val
178+ ty ~~ fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
179+ return ty
180+ return tys
181+ forM tys $ flip (escapeCheck checks) sub
182+ forM tys $ skolemEscapeCheck
183+ return $ map (varIfUnknown . desaturateAllTypeSynonyms . setifyAll) tys
184+
185+isTyped :: (Ident, Value) -> Either (Ident, Type, Value) (Ident, Value)
186+isTyped (name, TypedValue value ty) = Left (name, ty, value)
187+isTyped (name, value) = Right (name, value)
188+
189+escapeCheck :: [AnyUnifiable] -> Type -> Substitution -> Check ()
190+escapeCheck checks ty sub =
191+ let
192+ visibleUnknowns = nub $ unknowns ty
193+ in
194+ forM_ checks $ \c -> case c of
195+ AnyUnifiable t -> do
196+ let unsolvedUnknowns = nub . unknowns $ apply sub t
197+ guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
198+
199+skolemEscapeCheck :: Type -> Check ()
200+skolemEscapeCheck ty =
201+ case something (extQ (mkQ Nothing findSkolems) findRSkolems) ty of
202+ Nothing -> return ()
203+ Just _ -> throwError "Skolem variables cannot escape. Consider adding a type signature."
204+ where
205+ findSkolems (Skolem _) = return ()
206+ findSkolems _ = mzero
207+ findRSkolems (RSkolem _) = return ()
208+ findRSkolems _ = mzero
209+
210+setify :: Row -> Row
211+setify = rowFromList . first (M.toList . M.fromList) . rowToList
212+
213+setifyAll :: (D.Data d) => d -> d
214+setifyAll = everywhere (mkT setify)
215+
216+varIfUnknown :: Type -> Type
217+varIfUnknown ty =
218+ let unks = nub $ unknowns ty
219+ toName = (:) 't' . show
220+ ty' = everywhere (mkT rowToVar) . everywhere (mkT typeToVar) $ ty
221+ typeToVar :: Type -> Type
222+ typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
223+ typeToVar t = t
224+ rowToVar :: Row -> Row
225+ rowToVar (RUnknown (Unknown u)) = RowVar (toName u)
226+ rowToVar t = t
227+ in mkForAll (sort . map toName $ unks) ty'
228+
229+replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
230+replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
231+
232+replaceTypeVars :: (D.Data d) => String -> Type -> d -> d
233+replaceTypeVars name t = everywhereBut (mkQ False isShadowed) (mkT replaceTypeVar)
234+ where
235+ replaceTypeVar (TypeVar v) | v == name = t
236+ replaceTypeVar other = other
237+ isShadowed (ForAll v _) | v == name = True
238+ isShadowed _ = False
239+
240+replaceRowVars :: (D.Data d) => String -> Row -> d -> d
241+replaceRowVars name r = everywhere (mkT replaceRowVar)
242+ where
243+ replaceRowVar (RowVar v) | v == name = r
244+ replaceRowVar other = other
245+
246+replaceAllVarsWithUnknowns :: Type -> Subst Type
247+replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
248+replaceAllVarsWithUnknowns ty = return ty
249+
250+replaceVarWithUnknown :: String -> Type -> Subst Type
251+replaceVarWithUnknown ident ty = do
252+ tu <- fresh
253+ ru <- fresh
254+ return $ replaceRowVars ident ru . replaceTypeVars ident tu $ ty
255+
256+replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadReader SubstContext m, MonadError String m) => (D.Data d) => d -> m d
257+replaceAllTypeSynonyms d = do
258+ env <- getEnv
259+ moduleName <- substCurrentModule <$> ask
260+ let syns = map (\((path, name), (args, _)) -> (Qualified (Just path) name, length args)) . M.toList $ typeSynonyms env
261+ either throwError return $ saturateAllTypeSynonyms moduleName syns d
262+
263+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
264+desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
265+ where
266+ replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
267+ replaceSaturatedTypeSynonym t = t
268+
269+expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Type
270+expandTypeSynonym name args = do
271+ env <- getEnv
272+ moduleName <- substCurrentModule `fmap` ask
273+ case M.lookup (qualify moduleName name) (typeSynonyms env) of
274+ Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
275+ Nothing -> error "Type synonym was not defined"
276+
277+ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
278+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
279+
280+infer :: Value -> Subst Type
281+infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ do
282+ ty <- infer' val
283+ escapeCheckLater ty
284+ return ty
285+
286+infer' :: Value -> Subst Type
287+infer' (NumericLiteral _) = return Number
288+infer' (StringLiteral _) = return String
289+infer' (BooleanLiteral _) = return Boolean
290+infer' (ArrayLiteral vals) = do
291+ ts <- mapM (infer) vals
292+ els <- fresh
293+ forM_ ts $ \t -> els ~~ Array t
294+ return els
295+infer' (Unary op val) = do
296+ t <- infer val
297+ inferUnary op t
298+infer' (Binary op left right) = do
299+ t1 <- infer left
300+ t2 <- infer right
301+ inferBinary op t1 t2
302+infer' (ObjectLiteral ps) = do
303+ ensureNoDuplicateProperties ps
304+ ts <- mapM (infer . snd) ps
305+ let fields = zipWith (\(name, _) t -> (name, t)) ps ts
306+ return $ Object $ rowFromList (fields, REmpty)
307+infer' (ObjectUpdate o ps) = do
308+ ensureNoDuplicateProperties ps
309+ row <- fresh
310+ newTys <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
311+ oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
312+ check o $ Object $ rowFromList (oldTys, row)
313+ return $ Object $ rowFromList (newTys, row)
314+infer' (Indexer index val) = do
315+ el <- fresh
316+ check index Number
317+ check val (Array el)
318+ return el
319+infer' (Accessor prop val) = do
320+ obj <- infer val
321+ propTy <- inferProperty obj prop
322+ case propTy of
323+ Nothing -> do
324+ field <- fresh
325+ rest <- fresh
326+ obj `subsumes` Object (RCons prop field rest)
327+ return field
328+ Just ty -> return ty
329+infer' (Abs args ret) = do
330+ ts <- replicateM (length args) fresh
331+ moduleName <- substCurrentModule <$> ask
332+ bindLocalVariables moduleName (zip args ts) $ do
333+ body <- infer' ret
334+ return $ Function ts body
335+infer' app@(App _ _) = do
336+ let (f, argss) = unfoldApplication app
337+ ft <- infer f
338+ ret <- fresh
339+ checkFunctionApplications ft argss ret
340+ return ret
341+infer' (Var var) = do
342+ moduleName <- substCurrentModule <$> ask
343+ ty <- lookupVariable moduleName var
344+ replaceAllTypeSynonyms ty
345+infer' (Block ss) = do
346+ ret <- fresh
347+ (allCodePathsReturn, _) <- checkBlock M.empty ret ss
348+ guardWith "Block is missing a return statement" allCodePathsReturn
349+ return ret
350+infer' (Constructor c) = do
351+ env <- getEnv
352+ moduleName <- substCurrentModule `fmap` ask
353+ case M.lookup (qualify moduleName c) (dataConstructors env) of
354+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
355+ Just ty -> replaceAllTypeSynonyms ty
356+infer' (Case vals binders) = do
357+ ts <- mapM infer vals
358+ ret <- fresh
359+ checkBinders ts ret binders
360+ return ret
361+infer' (IfThenElse cond th el) = do
362+ check cond Boolean
363+ t2 <- infer th
364+ t3 <- infer el
365+ t2 ~~ t3
366+ return t2
367+infer' (TypedValue val ty) = do
368+ moduleName <- substCurrentModule <$> ask
369+ kind <- liftCheck $ kindOf moduleName ty
370+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
371+ ty' <- replaceAllTypeSynonyms ty
372+ check val ty'
373+ return ty'
374+infer' _ = error "Invalid argument to infer"
375+
376+inferProperty :: Type -> String -> Subst (Maybe Type)
377+inferProperty (Object row) prop = do
378+ let (props, _) = rowToList row
379+ return $ lookup prop props
380+inferProperty (SaturatedTypeSynonym name args) prop = do
381+ replaced <- expandTypeSynonym name args
382+ inferProperty replaced prop
383+inferProperty (ForAll ident ty) prop = do
384+ replaced <- replaceVarWithUnknown ident ty
385+ inferProperty replaced prop
386+inferProperty _ _ = return Nothing
387+
388+inferUnary :: UnaryOperator -> Type -> Subst Type
389+inferUnary op val =
390+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
391+ (valTy, resTy) -> do
392+ val ~~ valTy
393+ return resTy
394+
395+checkUnary :: UnaryOperator -> Value -> Type -> Subst ()
396+checkUnary op val res =
397+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
398+ (valTy, resTy) -> do
399+ res ~~ resTy
400+ check val valTy
401+
402+unaryOps :: [(UnaryOperator, (Type, Type))]
403+unaryOps = [ (Negate, (Number, Number))
404+ , (Not, (Boolean, Boolean))
405+ , (BitwiseNot, (Number, Number))
406+ ]
407+
408+inferBinary :: BinaryOperator -> Type -> Type -> Subst Type
409+inferBinary op left right | isEqualityTest op = do
410+ left ~~ right
411+ return Boolean
412+inferBinary op left right =
413+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
414+ (valTy, resTy) -> do
415+ left ~~ valTy
416+ right ~~ valTy
417+ return resTy
418+
419+checkBinary :: BinaryOperator -> Value -> Value -> Type -> Subst ()
420+checkBinary op left right res | isEqualityTest op = do
421+ res ~~ Boolean
422+ t1 <- infer left
423+ t2 <- infer right
424+ t1 ~~ t2
425+checkBinary op left right res =
426+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
427+ (valTy, resTy) -> do
428+ res ~~ resTy
429+ check left valTy
430+ check right valTy
431+
432+isEqualityTest :: BinaryOperator -> Bool
433+isEqualityTest EqualTo = True
434+isEqualityTest NotEqualTo = True
435+isEqualityTest _ = False
436+
437+binaryOps :: [(BinaryOperator, (Type, Type))]
438+binaryOps = [ (Add, (Number, Number))
439+ , (Subtract, (Number, Number))
440+ , (Multiply, (Number, Number))
441+ , (Divide, (Number, Number))
442+ , (Modulus, (Number, Number))
443+ , (BitwiseAnd, (Number, Number))
444+ , (BitwiseOr, (Number, Number))
445+ , (BitwiseXor, (Number, Number))
446+ , (ShiftRight, (Number, Number))
447+ , (ZeroFillShiftRight, (Number, Number))
448+ , (And, (Boolean, Boolean))
449+ , (Or, (Boolean, Boolean))
450+ , (Concat, (String, String))
451+ , (Modulus, (Number, Number))
452+ , (LessThan, (Number, Boolean))
453+ , (LessThanOrEqualTo, (Number, Boolean))
454+ , (GreaterThan, (Number, Boolean))
455+ , (GreaterThanOrEqualTo, (Number, Boolean))
456+ ]
457+
458+inferBinder :: Type -> Binder -> Subst (M.Map Ident Type)
459+inferBinder _ NullBinder = return M.empty
460+inferBinder val (StringBinder _) = val ~~ String >> return M.empty
461+inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
462+inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
463+inferBinder val (VarBinder name) = return $ M.singleton name val
464+inferBinder val (NullaryBinder ctor) = do
465+ env <- getEnv
466+ moduleName <- substCurrentModule <$> ask
467+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
468+ Just ty -> do
469+ ty `subsumes` val
470+ return M.empty
471+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
472+inferBinder val (UnaryBinder ctor binder) = do
473+ env <- getEnv
474+ moduleName <- substCurrentModule <$> ask
475+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
476+ Just ty -> do
477+ fn <- replaceAllVarsWithUnknowns ty
478+ case fn of
479+ Function [obj] ret -> do
480+ val `subsumes` ret
481+ inferBinder obj binder
482+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
483+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
484+inferBinder val (ObjectBinder props) = do
485+ row <- fresh
486+ rest <- fresh
487+ m1 <- inferRowProperties row rest props
488+ val ~~ Object row
489+ return m1
490+ where
491+ inferRowProperties :: Row -> Row -> [(String, Binder)] -> Subst (M.Map Ident Type)
492+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
493+ inferRowProperties nrow row ((name, binder):binders) = do
494+ propTy <- fresh
495+ m1 <- inferBinder propTy binder
496+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
497+ return $ m1 `M.union` m2
498+inferBinder val (ArrayBinder binders) = do
499+ el <- fresh
500+ m1 <- M.unions <$> mapM (inferBinder el) binders
501+ val ~~ Array el
502+ return m1
503+inferBinder val (ConsBinder headBinder tailBinder) = do
504+ el <- fresh
505+ m1 <- inferBinder el headBinder
506+ m2 <- inferBinder val tailBinder
507+ val ~~ Array el
508+ return $ m1 `M.union` m2
509+inferBinder val (NamedBinder name binder) = do
510+ m <- inferBinder val binder
511+ return $ M.insert name val m
512+
513+checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> Subst ()
514+checkBinders _ _ [] = return ()
515+checkBinders nvals ret ((binders, grd, val):bs) = do
516+ moduleName <- substCurrentModule <$> ask
517+ m1 <- M.unions <$> zipWithM inferBinder nvals binders
518+ bindLocalVariables moduleName (M.toList m1) $ do
519+ check val ret
520+ case grd of
521+ Nothing -> return ()
522+ Just g -> check g Boolean
523+ checkBinders nvals ret bs
524+
525+assignVariable :: Ident -> Subst ()
526+assignVariable name = do
527+ env <- checkEnv <$> get
528+ moduleName <- substCurrentModule <$> ask
529+ case M.lookup (moduleName, name) (names env) of
530+ Just (_, LocalVariable) -> throwError $ "Variable with name " ++ show name ++ " already exists."
531+ _ -> return ()
532+
533+checkStatement :: M.Map Ident Type -> Type -> Statement -> Subst (Bool, M.Map Ident Type)
534+checkStatement mass _ (VariableIntroduction name val) = do
535+ assignVariable name
536+ t <- infer val
537+ return (False, M.insert name t mass)
538+checkStatement mass _ (Assignment ident val) = do
539+ t <- infer val
540+ case M.lookup ident mass of
541+ Nothing -> throwError $ "No local variable with name " ++ show ident
542+ Just ty -> do t ~~ ty
543+ return (False, mass)
544+checkStatement mass ret (While val inner) = do
545+ check val Boolean
546+ (allCodePathsReturn, _) <- checkBlock mass ret inner
547+ return (allCodePathsReturn, mass)
548+checkStatement mass ret (If ifst) = do
549+ allCodePathsReturn <- checkIfStatement mass ret ifst
550+ return (allCodePathsReturn, mass)
551+checkStatement mass ret (For ident start end inner) = do
552+ moduleName <- substCurrentModule <$> ask
553+ assignVariable ident
554+ check start Number
555+ check end Number
556+ (allCodePathsReturn, _) <- bindLocalVariables moduleName [(ident, Number)] $ checkBlock mass ret inner
557+ return (allCodePathsReturn, mass)
558+checkStatement mass ret (ForEach ident vals inner) = do
559+ moduleName <- substCurrentModule <$> ask
560+ assignVariable ident
561+ val <- fresh
562+ check vals (Array val)
563+ (allCodePathsReturn, _) <- bindLocalVariables moduleName [(ident, val)] $ checkBlock mass ret inner
564+ guardWith "Cannot return from within a foreach block" $ not allCodePathsReturn
565+ return (False, mass)
566+checkStatement mass _ (ValueStatement val) = do
567+ check val unit
568+ return (False, mass)
569+checkStatement mass ret (Return val) = do
570+ check val ret
571+ return (True, mass)
572+
573+checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> Subst Bool
574+checkIfStatement mass ret (IfStatement val thens Nothing) = do
575+ check val Boolean
576+ _ <- checkBlock mass ret thens
577+ return False
578+checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
579+ check val Boolean
580+ (allCodePathsReturn1, _) <- checkBlock mass ret thens
581+ allCodePathsReturn2 <- checkElseStatement mass ret elses
582+ return $ allCodePathsReturn1 && allCodePathsReturn2
583+
584+checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> Subst Bool
585+checkElseStatement mass ret (Else elses) = fst <$> checkBlock mass ret elses
586+checkElseStatement mass ret (ElseIf ifst) = checkIfStatement mass ret ifst
587+
588+checkBlock :: M.Map Ident Type -> Type -> [Statement] -> Subst (Bool, M.Map Ident Type)
589+checkBlock mass _ [] = return (False, mass)
590+checkBlock mass ret (s:ss) = do
591+ moduleName <- substCurrentModule <$> ask
592+ (b1, mass1) <- checkStatement mass ret s
593+ bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
594+ (True, []) -> return (True, mass1)
595+ (True, _) -> throwError "Unreachable code"
596+ (False, ss') -> checkBlock mass1 ret ss'
597+
598+skolemize :: String -> Type -> Subst Type
599+skolemize ident ty = do
600+ tsk <- Skolem <$> fresh'
601+ rsk <- RSkolem <$> fresh'
602+ return $ replaceRowVars ident rsk $ replaceTypeVars ident tsk ty
603+
604+check :: Value -> Type -> Subst ()
605+check val ty = rethrow errorMessage $ check' val ty
606+ where
607+ errorMessage msg =
608+ "Error checking type of term " ++
609+ prettyPrintValue val ++
610+ " against type " ++
611+ prettyPrintType ty ++
612+ ":\n" ++
613+ msg
614+
615+check' :: Value -> Type -> Subst ()
616+check' val (ForAll idents ty) = do
617+ sk <- skolemize idents ty
618+ check val sk
619+check' val u@(TUnknown _) = do
620+ ty <- infer val
621+ -- Don't unify an unknown with an inferred polytype
622+ ty' <- replaceAllVarsWithUnknowns ty
623+ ty' ~~ u
624+check' (NumericLiteral _) Number = return ()
625+check' (StringLiteral _) String = return ()
626+check' (BooleanLiteral _) Boolean = return ()
627+check' (Unary op val) ty = checkUnary op val ty
628+check' (Binary op left right) ty = checkBinary op left right ty
629+check' (ArrayLiteral vals) (Array ty) = forM_ vals (\val -> check val ty)
630+check' (Indexer index vals) ty = check index Number >> check vals (Array ty)
631+check' (Abs args ret) (Function argTys retTy) = do
632+ moduleName <- substCurrentModule <$> ask
633+ guardWith "Incorrect number of function arguments" (length args == length argTys)
634+ bindLocalVariables moduleName (zip args argTys) $ check ret retTy
635+check' app@(App _ _) ret = do
636+ let (f, argss) = unfoldApplication app
637+ ft <- infer f
638+ checkFunctionApplications ft argss ret
639+check' (Var var) ty = do
640+ moduleName <- substCurrentModule <$> ask
641+ ty1 <- lookupVariable moduleName var
642+ repl <- replaceAllTypeSynonyms ty1
643+ repl `subsumes` ty
644+check' (TypedValue val ty1) ty2 = do
645+ moduleName <- substCurrentModule <$> ask
646+ kind <- liftCheck $ kindOf moduleName ty1
647+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
648+ ty1 `subsumes` ty2
649+ check val ty1
650+check' (Case vals binders) ret = do
651+ ts <- mapM infer vals
652+ checkBinders ts ret binders
653+check' (IfThenElse cond th el) ty = do
654+ check cond Boolean
655+ check th ty
656+ check el ty
657+check' (ObjectLiteral ps) (Object row) = do
658+ ensureNoDuplicateProperties ps
659+ checkProperties ps row False
660+check' (ObjectUpdate obj ps) (Object row) = do
661+ ensureNoDuplicateProperties ps
662+ us <- zip (map fst ps) <$> replicateM (length ps) fresh
663+ let (propsToCheck, rest) = rowToList row
664+ propsToRemove = map fst ps
665+ remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
666+ check obj (Object (rowFromList (us ++ remainingProps, rest)))
667+ checkProperties ps row True
668+check' (Accessor prop val) ty = do
669+ rest <- fresh
670+ check val (Object (RCons prop ty rest))
671+check' (Block ss) ret = do
672+ (allCodePathsReturn, _) <- checkBlock M.empty ret ss
673+ guardWith "Block is missing a return statement" allCodePathsReturn
674+check' (Constructor c) ty = do
675+ env <- getEnv
676+ moduleName <- substCurrentModule <$> ask
677+ case M.lookup (qualify moduleName c) (dataConstructors env) of
678+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
679+ Just ty1 -> do
680+ repl <- replaceAllTypeSynonyms ty1
681+ repl `subsumes` ty
682+check' val (SaturatedTypeSynonym name args) = do
683+ ty <- expandTypeSynonym name args
684+ check val ty
685+check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
686+
687+checkProperties :: [(String, Value)] -> Row -> Bool -> Subst ()
688+checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
689+ go [] [] REmpty = return ()
690+ go [] [] u@(RUnknown _) = u ~~ REmpty
691+ go [] [] (RSkolem _) | lax = return ()
692+ go [] ((p, _): _) _ | lax = return ()
693+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
694+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
695+ go ((p,v):ps') [] u@(RUnknown _) = do
696+ ty <- infer v
697+ rest <- fresh
698+ u ~~ RCons p ty rest
699+ go ps' [] rest
700+ go ((p,v):ps') ts r =
701+ case lookup p ts of
702+ Nothing -> do
703+ ty <- infer v
704+ rest <- fresh
705+ r ~~ RCons p ty rest
706+ go ps' ts rest
707+ Just ty -> do
708+ check v ty
709+ go ps' (delete (p, ty) ts) r
710+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
711+
712+unfoldApplication :: Value -> (Value, [[Value]])
713+unfoldApplication = go []
714+ where
715+ go argss (App f args) = go (args:argss) f
716+ go argss f = (f, argss)
717+
718+checkFunctionApplications :: Type -> [[Value]] -> Type -> Subst ()
719+checkFunctionApplications _ [] _ = error "Nullary function application"
720+checkFunctionApplications fnTy [args] ret = checkFunctionApplication fnTy args ret
721+checkFunctionApplications fnTy (args:argss) ret = do
722+ argTys <- mapM (infer) args
723+ f <- inferFunctionApplication fnTy argTys
724+ checkFunctionApplications f argss ret
725+
726+checkFunctionApplication :: Type -> [Value] -> Type -> Subst ()
727+checkFunctionApplication fnTy args ret = rethrow errorMessage $ checkFunctionApplication' fnTy args ret
728+ where
729+ errorMessage msg = "Error applying function of type "
730+ ++ prettyPrintType fnTy
731+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
732+ ++ ", expecting value of type "
733+ ++ prettyPrintType ret ++ ":\n" ++ msg
734+
735+inferFunctionApplication :: Type -> [Type] -> Subst Type
736+inferFunctionApplication (Function argTys retTy) args = do
737+ guardWith "Incorrect number of function arguments" (length args == length argTys)
738+ zipWithM subsumes args argTys
739+ return retTy
740+inferFunctionApplication (ForAll ident ty) args = do
741+ replaced <- replaceVarWithUnknown ident ty
742+ inferFunctionApplication replaced args
743+inferFunctionApplication u@(TUnknown _) args = do
744+
745+ ret <- fresh
746+ args' <- mapM replaceAllVarsWithUnknowns args
747+ u ~~ Function args' ret
748+ return ret
749+inferFunctionApplication (SaturatedTypeSynonym name tyArgs) args = do
750+ ty <- expandTypeSynonym name tyArgs
751+ inferFunctionApplication ty args
752+inferFunctionApplication fnTy args = throwError $ "Cannot apply function of type "
753+ ++ prettyPrintType fnTy
754+ ++ " to argument(s) of type(s) " ++ intercalate ", " (map prettyPrintType args)
755+
756+checkFunctionApplication' :: Type -> [Value] -> Type -> Subst ()
757+checkFunctionApplication' (Function argTys retTy) args ret = do
758+ guardWith "Incorrect number of function arguments" (length args == length argTys)
759+ zipWithM (check) args argTys
760+ retTy `subsumes` ret
761+checkFunctionApplication' (ForAll ident ty) args ret = do
762+ replaced <- replaceVarWithUnknown ident ty
763+ checkFunctionApplication replaced args ret
764+checkFunctionApplication' u@(TUnknown _) args ret = do
765+ tyArgs <- mapM (\arg -> infer arg >>= replaceAllVarsWithUnknowns) args
766+ u ~~ Function tyArgs ret
767+checkFunctionApplication' (SaturatedTypeSynonym name tyArgs) args ret = do
768+ ty <- expandTypeSynonym name tyArgs
769+ checkFunctionApplication' ty args ret
770+checkFunctionApplication' fnTy args ret = throwError $ "Applying a function of type "
771+ ++ prettyPrintType fnTy
772+ ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
773+ ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
774+
775+subsumes :: Type -> Type -> Subst ()
776+subsumes (ForAll ident ty1) ty2 = do
777+ replaced <- replaceVarWithUnknown ident ty1
778+ replaced `subsumes` ty2
779+subsumes (Function args1 ret1) (Function args2 ret2) = do
780+ zipWithM subsumes args2 args1
781+ ret1 `subsumes` ret2
782+subsumes ty1 ty2 = ty1 ~~ ty2
783+