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