@@ -0,0 +1,749 @@
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 (isNothing, isJust, fromMaybe)
24+import qualified Data.Data as D
25+import Data.Generics
26+ (mkT, something, everywhere, everywhereBut, mkQ)
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+import Data.Function (on)
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 s (RCons name ty r) = RCons name (apply s ty) (apply s r)
61+ apply _ t = t
62+ unknowns (TUnknown (Unknown u)) = [u]
63+ unknowns (SaturatedTypeSynonym _ tys) = concatMap unknowns tys
64+ unknowns (ForAll _ ty) = unknowns ty
65+ unknowns (Array t) = unknowns t
66+ unknowns (Object r) = unknowns r
67+ unknowns (Function args ret) = concatMap unknowns args ++ unknowns ret
68+ unknowns (TypeApp t1 t2) = unknowns t1 ++ unknowns t2
69+ unknowns (RCons _ ty r) = unknowns ty ++ unknowns r
70+ unknowns _ = []
71+
72+unifyTypes :: Type -> Type -> Subst ()
73+unifyTypes t1 t2 = rethrow (\e -> "Error unifying type " ++ prettyPrintType t1 ++ " with type " ++ prettyPrintType t2 ++ ":\n" ++ e) $ do
74+ unifyTypes' t1 t2
75+ where
76+ unifyTypes' (TUnknown u1) (TUnknown u2) | u1 == u2 = return ()
77+ unifyTypes' (TUnknown u) t = replace u t
78+ unifyTypes' t (TUnknown u) = replace u t
79+ unifyTypes' (SaturatedTypeSynonym name args) ty = do
80+ ty1 <- expandTypeSynonym name args
81+ ty1 `unifyTypes` ty
82+ unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
83+ unifyTypes' (ForAll ident1 ty1) (ForAll ident2 ty2) = do
84+ sk <- skolemize ident1 ty1
85+ replaced <- replaceVarWithUnknown ident2 ty2
86+ sk `unifyTypes` replaced
87+ unifyTypes' (ForAll ident ty1) ty2 = do
88+ sk <- skolemize ident ty1
89+ sk `unifyTypes` ty2
90+ unifyTypes' ty f@(ForAll _ _) = f `unifyTypes` ty
91+ unifyTypes' Number Number = return ()
92+ unifyTypes' String String = return ()
93+ unifyTypes' Boolean Boolean = return ()
94+ unifyTypes' (Array s) (Array t) = s `unifyTypes` t
95+ unifyTypes' (Object row1) (Object row2) = row1 ~~ row2
96+ unifyTypes' (Function args1 ret1) (Function args2 ret2) = do
97+ guardWith "Function applied to incorrect number of args" $ length args1 == length args2
98+ zipWithM_ unifyTypes args1 args2
99+ ret1 `unifyTypes` ret2
100+ unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
101+ unifyTypes' (TypeConstructor c1) (TypeConstructor c2) = do
102+ env <- getEnv
103+ moduleName <- substCurrentModule `fmap` ask
104+ guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (typeConstructorsAreEqual env moduleName c1 c2)
105+ unifyTypes' (TypeApp t3 t4) (TypeApp t5 t6) = do
106+ t3 `unifyTypes` t5
107+ t4 `unifyTypes` t6
108+ unifyTypes' (Skolem s1) (Skolem s2) | s1 == s2 = return ()
109+ unifyTypes' r1@(RCons _ _ _) r2 = unifyRows r1 r2
110+ unifyTypes' r1 r2@(RCons _ _ _) = unifyRows r1 r2
111+ unifyTypes' r1@REmpty r2 = unifyRows r1 r2
112+ unifyTypes' r1 r2@REmpty = unifyRows r1 r2
113+ unifyTypes' t3 t4 = throwError $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
114+
115+unifyRows :: Type -> Type -> Subst ()
116+unifyRows r1 r2 =
117+ let
118+ (s1, r1') = rowToList r1
119+ (s2, r2') = rowToList r2
120+ int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
121+ sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
122+ sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
123+ in do
124+ forM_ int (uncurry (~~))
125+ unifyRows' sd1 r1' sd2 r2'
126+ where
127+ unifyRows' :: [(String, Type)] -> Type -> [(String, Type)] -> Type -> Subst ()
128+ unifyRows' [] (TUnknown u) sd r = replace u (rowFromList (sd, r))
129+ unifyRows' sd r [] (TUnknown u) = replace u (rowFromList (sd, r))
130+ unifyRows' ((name, ty):row) r others u@(TUnknown un) = do
131+ occursCheck un ty
132+ forM row $ \(_, t) -> occursCheck un t
133+ u' <- fresh
134+ u ~~ RCons name ty u'
135+ unifyRows' row r others u'
136+ unifyRows' [] REmpty [] REmpty = return ()
137+ unifyRows' [] (TypeVar v1) [] (TypeVar v2) | v1 == v2 = return ()
138+ unifyRows' [] (Skolem s1) [] (Skolem s2) | s1 == s2 = return ()
139+ unifyRows' sd3 r3 sd4 r4 = throwError $ "Cannot unify " ++ prettyPrintRow (rowFromList (sd3, r3)) ++ " with " ++ prettyPrintRow (rowFromList (sd4, r4)) ++ "."
140+
141+typeConstructorsAreEqual :: Environment -> ModuleName -> Qualified ProperName -> Qualified ProperName -> Bool
142+typeConstructorsAreEqual env moduleName = (==) `on` canonicalizeType moduleName env
143+
144+typesOf :: ModuleName -> [(Ident, Value)] -> Check [Type]
145+typesOf moduleName vals = do
146+ (tys, sub, checks) <- runSubst (SubstContext moduleName) $ do
147+ let es = map isTyped vals
148+ typed = filter (isJust . snd . snd) es
149+ untyped = filter (isNothing . snd . snd) es
150+ typedDict = map (\(ident, (_, Just ty)) -> (ident, ty)) typed
151+ untypedNames <- replicateM (length untyped) fresh
152+ let untypedDict = zip (map fst untyped) untypedNames
153+ dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ typedDict ++ untypedDict)
154+ tys <- forM es $ \e -> do
155+ ty <- case e of
156+ (_, (val, Just ty)) -> do
157+ kind <- liftCheck $ kindOf moduleName ty
158+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
159+ ty' <- replaceAllTypeSynonyms ty
160+ bindNames dict $ check val ty'
161+ return ty'
162+ (ident, (val, Nothing)) -> do
163+ ty <- bindNames dict $ infer val
164+ ty ~~ fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
165+ return ty
166+ when (moduleName == ModuleName (ProperName "Main") && fst e == Ident "main") $ do
167+ [eff, a] <- replicateM 2 fresh
168+ ty ~~ TypeApp (TypeApp (TypeConstructor (Qualified (Just (ModuleName (ProperName "Eff"))) (ProperName "Eff"))) eff) a
169+ return ty
170+ return tys
171+ forM tys $ flip (escapeCheck checks) sub
172+ forM tys $ skolemEscapeCheck
173+ return $ map (varIfUnknown . desaturateAllTypeSynonyms . setifyAll) tys
174+
175+isTyped :: (Ident, Value) -> (Ident, (Value, Maybe Type))
176+isTyped (name, TypedValue value ty) = (name, (value, Just ty))
177+isTyped (name, value) = (name, (value, Nothing))
178+
179+escapeCheck :: [AnyUnifiable] -> Type -> Substitution -> Check ()
180+escapeCheck checks ty sub =
181+ let
182+ visibleUnknowns = nub $ unknowns ty
183+ in
184+ forM_ checks $ \c -> case c of
185+ AnyUnifiable t -> do
186+ let unsolvedUnknowns = nub . unknowns $ apply sub t
187+ guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
188+
189+skolemEscapeCheck :: Type -> Check ()
190+skolemEscapeCheck ty =
191+ case something (mkQ Nothing findSkolems) ty of
192+ Nothing -> return ()
193+ Just _ -> throwError "Skolem variables cannot escape. Consider adding a type signature."
194+ where
195+ findSkolems (Skolem _) = return ()
196+ findSkolems _ = mzero
197+
198+setify :: Type -> Type
199+setify = rowFromList . first (M.toList . M.fromList) . rowToList
200+
201+setifyAll :: (D.Data d) => d -> d
202+setifyAll = everywhere (mkT setify)
203+
204+varIfUnknown :: Type -> Type
205+varIfUnknown ty =
206+ let unks = nub $ unknowns ty
207+ toName = (:) 't' . show
208+ ty' = everywhere (mkT typeToVar) $ ty
209+ typeToVar :: Type -> Type
210+ typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
211+ typeToVar t = t
212+ in mkForAll (sort . map toName $ unks) ty'
213+
214+replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
215+replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
216+
217+replaceTypeVars :: (D.Data d) => String -> Type -> d -> d
218+replaceTypeVars name t = everywhereBut (mkQ False isShadowed) (mkT replaceTypeVar)
219+ where
220+ replaceTypeVar (TypeVar v) | v == name = t
221+ replaceTypeVar other = other
222+ isShadowed (ForAll v _) | v == name = True
223+ isShadowed _ = False
224+
225+replaceAllVarsWithUnknowns :: Type -> Subst Type
226+replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
227+replaceAllVarsWithUnknowns ty = return ty
228+
229+replaceVarWithUnknown :: String -> Type -> Subst Type
230+replaceVarWithUnknown ident ty = do
231+ tu <- fresh
232+ return $ replaceTypeVars ident tu $ ty
233+
234+replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadReader SubstContext m, MonadError String m) => (D.Data d) => d -> m d
235+replaceAllTypeSynonyms d = do
236+ env <- getEnv
237+ moduleName <- substCurrentModule <$> ask
238+ let syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
239+ either throwError return $ saturateAllTypeSynonyms env moduleName syns d
240+
241+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
242+desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
243+ where
244+ replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
245+ replaceSaturatedTypeSynonym t = t
246+
247+expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Type
248+expandTypeSynonym name args = do
249+ env <- getEnv
250+ moduleName <- substCurrentModule `fmap` ask
251+ case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
252+ Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
253+ Nothing -> error "Type synonym was not defined"
254+
255+ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
256+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
257+
258+infer :: Value -> Subst Type
259+infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ do
260+ ty <- infer' val
261+ escapeCheckLater ty
262+ return ty
263+
264+infer' :: Value -> Subst Type
265+infer' (NumericLiteral _) = return Number
266+infer' (StringLiteral _) = return String
267+infer' (BooleanLiteral _) = return Boolean
268+infer' (ArrayLiteral vals) = do
269+ ts <- mapM (infer) vals
270+ els <- fresh
271+ forM_ ts $ \t -> els ~~ Array t
272+ return els
273+infer' (Unary op val) = do
274+ t <- infer val
275+ inferUnary op t
276+infer' (Binary op left right) = do
277+ t1 <- infer left
278+ t2 <- infer right
279+ inferBinary op t1 t2
280+infer' (ObjectLiteral ps) = do
281+ ensureNoDuplicateProperties ps
282+ ts <- mapM (infer . snd) ps
283+ let fields = zipWith (\(name, _) t -> (name, t)) ps ts
284+ return $ Object $ rowFromList (fields, REmpty)
285+infer' (ObjectUpdate o ps) = do
286+ ensureNoDuplicateProperties ps
287+ row <- fresh
288+ newTys <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
289+ oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
290+ check o $ Object $ rowFromList (oldTys, row)
291+ return $ Object $ rowFromList (newTys, row)
292+infer' (Indexer index val) = do
293+ el <- fresh
294+ check index Number
295+ check val (Array el)
296+ return el
297+infer' (Accessor prop val) = do
298+ obj <- infer val
299+ propTy <- inferProperty obj prop
300+ case propTy of
301+ Nothing -> do
302+ field <- fresh
303+ rest <- fresh
304+ obj `subsumes` Object (RCons prop field rest)
305+ return field
306+ Just ty -> return ty
307+infer' (Abs args ret) = do
308+ ts <- replicateM (length args) fresh
309+ moduleName <- substCurrentModule <$> ask
310+ bindLocalVariables moduleName (zip args ts) $ do
311+ body <- infer' ret
312+ return $ Function ts body
313+infer' app@(App _ _) = do
314+ let (f, argss) = unfoldApplication app
315+ ft <- infer f
316+ ret <- fresh
317+ checkFunctionApplications ft argss ret
318+ return ret
319+infer' (Var var) = do
320+ moduleName <- substCurrentModule <$> ask
321+ ty <- lookupVariable moduleName var
322+ replaceAllTypeSynonyms ty
323+infer' (Block ss) = do
324+ ret <- fresh
325+ (allCodePathsReturn, _) <- checkBlock M.empty ret ss
326+ guardWith "Block is missing a return statement" allCodePathsReturn
327+ return ret
328+infer' (Constructor c) = do
329+ env <- getEnv
330+ moduleName <- substCurrentModule `fmap` ask
331+ case M.lookup (qualify moduleName c) (dataConstructors env) of
332+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
333+ Just (ty, _) -> replaceAllTypeSynonyms ty
334+infer' (Case vals binders) = do
335+ ts <- mapM infer vals
336+ ret <- fresh
337+ checkBinders ts ret binders
338+ return ret
339+infer' (IfThenElse cond th el) = do
340+ check cond Boolean
341+ t2 <- infer th
342+ t3 <- infer el
343+ t2 ~~ t3
344+ return t2
345+infer' (TypedValue val ty) = do
346+ moduleName <- substCurrentModule <$> ask
347+ kind <- liftCheck $ kindOf moduleName ty
348+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
349+ ty' <- replaceAllTypeSynonyms ty
350+ check val ty'
351+ return ty'
352+infer' _ = error "Invalid argument to infer"
353+
354+inferProperty :: Type -> String -> Subst (Maybe Type)
355+inferProperty (Object row) prop = do
356+ let (props, _) = rowToList row
357+ return $ lookup prop props
358+inferProperty (SaturatedTypeSynonym name args) prop = do
359+ replaced <- expandTypeSynonym name args
360+ inferProperty replaced prop
361+inferProperty (ForAll ident ty) prop = do
362+ replaced <- replaceVarWithUnknown ident ty
363+ inferProperty replaced prop
364+inferProperty _ _ = return Nothing
365+
366+inferUnary :: UnaryOperator -> Type -> Subst Type
367+inferUnary op val =
368+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
369+ (valTy, resTy) -> do
370+ val ~~ valTy
371+ return resTy
372+
373+checkUnary :: UnaryOperator -> Value -> Type -> Subst ()
374+checkUnary op val res =
375+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
376+ (valTy, resTy) -> do
377+ res ~~ resTy
378+ check val valTy
379+
380+unaryOps :: [(UnaryOperator, (Type, Type))]
381+unaryOps = [ (Negate, (Number, Number))
382+ , (Not, (Boolean, Boolean))
383+ , (BitwiseNot, (Number, Number))
384+ ]
385+
386+inferBinary :: BinaryOperator -> Type -> Type -> Subst Type
387+inferBinary op left right | isEqualityTest op = do
388+ left ~~ right
389+ return Boolean
390+inferBinary op left right =
391+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
392+ (valTy, resTy) -> do
393+ left ~~ valTy
394+ right ~~ valTy
395+ return resTy
396+
397+checkBinary :: BinaryOperator -> Value -> Value -> Type -> Subst ()
398+checkBinary op left right res | isEqualityTest op = do
399+ res ~~ Boolean
400+ t1 <- infer left
401+ t2 <- infer right
402+ t1 ~~ t2
403+checkBinary op left right res =
404+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
405+ (valTy, resTy) -> do
406+ res ~~ resTy
407+ check left valTy
408+ check right valTy
409+
410+isEqualityTest :: BinaryOperator -> Bool
411+isEqualityTest EqualTo = True
412+isEqualityTest NotEqualTo = True
413+isEqualityTest _ = False
414+
415+binaryOps :: [(BinaryOperator, (Type, Type))]
416+binaryOps = [ (Add, (Number, Number))
417+ , (Subtract, (Number, Number))
418+ , (Multiply, (Number, Number))
419+ , (Divide, (Number, Number))
420+ , (Modulus, (Number, Number))
421+ , (BitwiseAnd, (Number, Number))
422+ , (BitwiseOr, (Number, Number))
423+ , (BitwiseXor, (Number, Number))
424+ , (ShiftRight, (Number, Number))
425+ , (ZeroFillShiftRight, (Number, Number))
426+ , (And, (Boolean, Boolean))
427+ , (Or, (Boolean, Boolean))
428+ , (Concat, (String, String))
429+ , (Modulus, (Number, Number))
430+ , (LessThan, (Number, Boolean))
431+ , (LessThanOrEqualTo, (Number, Boolean))
432+ , (GreaterThan, (Number, Boolean))
433+ , (GreaterThanOrEqualTo, (Number, Boolean))
434+ ]
435+
436+inferBinder :: Type -> Binder -> Subst (M.Map Ident Type)
437+inferBinder _ NullBinder = return M.empty
438+inferBinder val (StringBinder _) = val ~~ String >> return M.empty
439+inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
440+inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
441+inferBinder val (VarBinder name) = return $ M.singleton name val
442+inferBinder val (NullaryBinder ctor) = do
443+ env <- getEnv
444+ moduleName <- substCurrentModule <$> ask
445+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
446+ Just (ty, _) -> do
447+ ty `subsumes` val
448+ return M.empty
449+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
450+inferBinder val (UnaryBinder ctor binder) = do
451+ env <- getEnv
452+ moduleName <- substCurrentModule <$> ask
453+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
454+ Just (ty, _) -> do
455+ fn <- replaceAllVarsWithUnknowns ty
456+ case fn of
457+ Function [obj] ret -> do
458+ val `subsumes` ret
459+ inferBinder obj binder
460+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
461+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
462+inferBinder val (ObjectBinder props) = do
463+ row <- fresh
464+ rest <- fresh
465+ m1 <- inferRowProperties row rest props
466+ val ~~ Object row
467+ return m1
468+ where
469+ inferRowProperties :: Type -> Type -> [(String, Binder)] -> Subst (M.Map Ident Type)
470+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
471+ inferRowProperties nrow row ((name, binder):binders) = do
472+ propTy <- fresh
473+ m1 <- inferBinder propTy binder
474+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
475+ return $ m1 `M.union` m2
476+inferBinder val (ArrayBinder binders) = do
477+ el <- fresh
478+ m1 <- M.unions <$> mapM (inferBinder el) binders
479+ val ~~ Array el
480+ return m1
481+inferBinder val (ConsBinder headBinder tailBinder) = do
482+ el <- fresh
483+ m1 <- inferBinder el headBinder
484+ m2 <- inferBinder val tailBinder
485+ val ~~ Array el
486+ return $ m1 `M.union` m2
487+inferBinder val (NamedBinder name binder) = do
488+ m <- inferBinder val binder
489+ return $ M.insert name val m
490+
491+checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> Subst ()
492+checkBinders _ _ [] = return ()
493+checkBinders nvals ret ((binders, grd, val):bs) = do
494+ moduleName <- substCurrentModule <$> ask
495+ m1 <- M.unions <$> zipWithM inferBinder nvals binders
496+ bindLocalVariables moduleName (M.toList m1) $ do
497+ check val ret
498+ case grd of
499+ Nothing -> return ()
500+ Just g -> check g Boolean
501+ checkBinders nvals ret bs
502+
503+assignVariable :: Ident -> Subst ()
504+assignVariable name = do
505+ env <- checkEnv <$> get
506+ moduleName <- substCurrentModule <$> ask
507+ case M.lookup (moduleName, name) (names env) of
508+ Just (_, LocalVariable) -> throwError $ "Variable with name " ++ show name ++ " already exists."
509+ _ -> return ()
510+
511+checkStatement :: M.Map Ident Type -> Type -> Statement -> Subst (Bool, M.Map Ident Type)
512+checkStatement mass _ (VariableIntroduction name val) = do
513+ assignVariable name
514+ t <- infer val
515+ return (False, M.insert name t mass)
516+checkStatement mass _ (Assignment ident val) = do
517+ t <- infer val
518+ case M.lookup ident mass of
519+ Nothing -> throwError $ "No local variable with name " ++ show ident
520+ Just ty -> do t ~~ ty
521+ return (False, mass)
522+checkStatement mass ret (While val inner) = do
523+ check val Boolean
524+ (allCodePathsReturn, _) <- checkBlock mass ret inner
525+ return (allCodePathsReturn, mass)
526+checkStatement mass ret (If ifst) = do
527+ allCodePathsReturn <- checkIfStatement mass ret ifst
528+ return (allCodePathsReturn, mass)
529+checkStatement mass ret (For ident start end inner) = do
530+ moduleName <- substCurrentModule <$> ask
531+ assignVariable ident
532+ check start Number
533+ check end Number
534+ (allCodePathsReturn, _) <- bindLocalVariables moduleName [(ident, Number)] $ checkBlock mass ret inner
535+ return (allCodePathsReturn, mass)
536+checkStatement mass ret (Return val) = do
537+ check val ret
538+ return (True, mass)
539+
540+checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> Subst Bool
541+checkIfStatement mass ret (IfStatement val thens Nothing) = do
542+ check val Boolean
543+ _ <- checkBlock mass ret thens
544+ return False
545+checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
546+ check val Boolean
547+ (allCodePathsReturn1, _) <- checkBlock mass ret thens
548+ allCodePathsReturn2 <- checkElseStatement mass ret elses
549+ return $ allCodePathsReturn1 && allCodePathsReturn2
550+
551+checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> Subst Bool
552+checkElseStatement mass ret (Else elses) = fst <$> checkBlock mass ret elses
553+checkElseStatement mass ret (ElseIf ifst) = checkIfStatement mass ret ifst
554+
555+checkBlock :: M.Map Ident Type -> Type -> [Statement] -> Subst (Bool, M.Map Ident Type)
556+checkBlock mass _ [] = return (False, mass)
557+checkBlock mass ret (s:ss) = do
558+ moduleName <- substCurrentModule <$> ask
559+ (b1, mass1) <- checkStatement mass ret s
560+ bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
561+ (True, []) -> return (True, mass1)
562+ (True, _) -> throwError "Unreachable code"
563+ (False, ss') -> checkBlock mass1 ret ss'
564+
565+skolemize :: String -> Type -> Subst Type
566+skolemize ident ty = do
567+ tsk <- Skolem <$> fresh'
568+ return $ replaceTypeVars ident tsk ty
569+
570+check :: Value -> Type -> Subst ()
571+check val ty = rethrow errorMessage $ check' val ty
572+ where
573+ errorMessage msg =
574+ "Error checking type of term " ++
575+ prettyPrintValue val ++
576+ " against type " ++
577+ prettyPrintType ty ++
578+ ":\n" ++
579+ msg
580+
581+check' :: Value -> Type -> Subst ()
582+check' val (ForAll idents ty) = do
583+ sk <- skolemize idents ty
584+ check val sk
585+check' val u@(TUnknown _) = do
586+ ty <- infer val
587+ -- Don't unify an unknown with an inferred polytype
588+ ty' <- replaceAllVarsWithUnknowns ty
589+ ty' ~~ u
590+check' (NumericLiteral _) Number = return ()
591+check' (StringLiteral _) String = return ()
592+check' (BooleanLiteral _) Boolean = return ()
593+check' (Unary op val) ty = checkUnary op val ty
594+check' (Binary op left right) ty = checkBinary op left right ty
595+check' (ArrayLiteral vals) (Array ty) = forM_ vals (\val -> check val ty)
596+check' (Indexer index vals) ty = check index Number >> check vals (Array ty)
597+check' (Abs args ret) (Function argTys retTy) = do
598+ moduleName <- substCurrentModule <$> ask
599+ guardWith "Incorrect number of function arguments" (length args == length argTys)
600+ bindLocalVariables moduleName (zip args argTys) $ check ret retTy
601+check' app@(App _ _) ret = do
602+ let (f, argss) = unfoldApplication app
603+ ft <- infer f
604+ checkFunctionApplications ft argss ret
605+check' (Var var) ty = do
606+ moduleName <- substCurrentModule <$> ask
607+ ty1 <- lookupVariable moduleName var
608+ repl <- replaceAllTypeSynonyms ty1
609+ repl `subsumes` ty
610+check' (TypedValue val ty1) ty2 = do
611+ moduleName <- substCurrentModule <$> ask
612+ kind <- liftCheck $ kindOf moduleName ty1
613+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
614+ ty1 `subsumes` ty2
615+ check val ty1
616+check' (Case vals binders) ret = do
617+ ts <- mapM infer vals
618+ checkBinders ts ret binders
619+check' (IfThenElse cond th el) ty = do
620+ check cond Boolean
621+ check th ty
622+ check el ty
623+check' (ObjectLiteral ps) (Object row) = do
624+ ensureNoDuplicateProperties ps
625+ checkProperties ps row False
626+check' (ObjectUpdate obj ps) (Object row) = do
627+ ensureNoDuplicateProperties ps
628+ us <- zip (map fst ps) <$> replicateM (length ps) fresh
629+ let (propsToCheck, rest) = rowToList row
630+ propsToRemove = map fst ps
631+ remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
632+ check obj (Object (rowFromList (us ++ remainingProps, rest)))
633+ checkProperties ps row True
634+check' (Accessor prop val) ty = do
635+ rest <- fresh
636+ check val (Object (RCons prop ty rest))
637+check' (Block ss) ret = do
638+ (allCodePathsReturn, _) <- checkBlock M.empty ret ss
639+ guardWith "Block is missing a return statement" allCodePathsReturn
640+check' (Constructor c) ty = do
641+ env <- getEnv
642+ moduleName <- substCurrentModule <$> ask
643+ case M.lookup (qualify moduleName c) (dataConstructors env) of
644+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
645+ Just (ty1, _) -> do
646+ repl <- replaceAllTypeSynonyms ty1
647+ repl `subsumes` ty
648+check' val (SaturatedTypeSynonym name args) = do
649+ ty <- expandTypeSynonym name args
650+ check val ty
651+check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
652+
653+checkProperties :: [(String, Value)] -> Type -> Bool -> Subst ()
654+checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
655+ go [] [] REmpty = return ()
656+ go [] [] u@(TUnknown _) = u ~~ REmpty
657+ go [] [] (Skolem _) | lax = return ()
658+ go [] ((p, _): _) _ | lax = return ()
659+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
660+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
661+ go ((p,v):ps') [] u@(TUnknown _) = do
662+ ty <- infer v
663+ rest <- fresh
664+ u ~~ RCons p ty rest
665+ go ps' [] rest
666+ go ((p,v):ps') ts r =
667+ case lookup p ts of
668+ Nothing -> do
669+ ty <- infer v
670+ rest <- fresh
671+ r ~~ RCons p ty rest
672+ go ps' ts rest
673+ Just ty -> do
674+ check v ty
675+ go ps' (delete (p, ty) ts) r
676+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
677+
678+unfoldApplication :: Value -> (Value, [[Value]])
679+unfoldApplication = go []
680+ where
681+ go argss (App f args) = go (args:argss) f
682+ go argss f = (f, argss)
683+
684+checkFunctionApplications :: Type -> [[Value]] -> Type -> Subst ()
685+checkFunctionApplications _ [] _ = error "Nullary function application"
686+checkFunctionApplications fnTy [args] ret = checkFunctionApplication fnTy args ret
687+checkFunctionApplications fnTy (args:argss) ret = do
688+ argTys <- mapM (infer) args
689+ f <- inferFunctionApplication fnTy argTys
690+ checkFunctionApplications f argss ret
691+
692+checkFunctionApplication :: Type -> [Value] -> Type -> Subst ()
693+checkFunctionApplication fnTy args ret = rethrow errorMessage $ checkFunctionApplication' fnTy args ret
694+ where
695+ errorMessage msg = "Error applying function of type "
696+ ++ prettyPrintType fnTy
697+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
698+ ++ ", expecting value of type "
699+ ++ prettyPrintType ret ++ ":\n" ++ msg
700+
701+inferFunctionApplication :: Type -> [Type] -> Subst Type
702+inferFunctionApplication (Function argTys retTy) args = do
703+ guardWith "Incorrect number of function arguments" (length args == length argTys)
704+ zipWithM subsumes args argTys
705+ return retTy
706+inferFunctionApplication (ForAll ident ty) args = do
707+ replaced <- replaceVarWithUnknown ident ty
708+ inferFunctionApplication replaced args
709+inferFunctionApplication u@(TUnknown _) args = do
710+
711+ ret <- fresh
712+ args' <- mapM replaceAllVarsWithUnknowns args
713+ u ~~ Function args' ret
714+ return ret
715+inferFunctionApplication (SaturatedTypeSynonym name tyArgs) args = do
716+ ty <- expandTypeSynonym name tyArgs
717+ inferFunctionApplication ty args
718+inferFunctionApplication fnTy args = throwError $ "Cannot apply function of type "
719+ ++ prettyPrintType fnTy
720+ ++ " to argument(s) of type(s) " ++ intercalate ", " (map prettyPrintType args)
721+
722+checkFunctionApplication' :: Type -> [Value] -> Type -> Subst ()
723+checkFunctionApplication' (Function argTys retTy) args ret = do
724+ guardWith "Incorrect number of function arguments" (length args == length argTys)
725+ zipWithM (check) args argTys
726+ retTy `subsumes` ret
727+checkFunctionApplication' (ForAll ident ty) args ret = do
728+ replaced <- replaceVarWithUnknown ident ty
729+ checkFunctionApplication replaced args ret
730+checkFunctionApplication' u@(TUnknown _) args ret = do
731+ tyArgs <- mapM (\arg -> infer arg >>= replaceAllVarsWithUnknowns) args
732+ u ~~ Function tyArgs ret
733+checkFunctionApplication' (SaturatedTypeSynonym name tyArgs) args ret = do
734+ ty <- expandTypeSynonym name tyArgs
735+ checkFunctionApplication' ty args ret
736+checkFunctionApplication' fnTy args ret = throwError $ "Applying a function of type "
737+ ++ prettyPrintType fnTy
738+ ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
739+ ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
740+
741+subsumes :: Type -> Type -> Subst ()
742+subsumes (ForAll ident ty1) ty2 = do
743+ replaced <- replaceVarWithUnknown ident ty1
744+ replaced `subsumes` ty2
745+subsumes (Function args1 ret1) (Function args2 ret2) = do
746+ zipWithM subsumes args2 args1
747+ ret1 `subsumes` ret2
748+subsumes ty1 ty2 = ty1 ~~ ty2
749+