@@ -0,0 +1,756 @@
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)
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 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 name1 args1) (SaturatedTypeSynonym name2 args2)
80+ | name1 == name2 = zipWithM_ unifyTypes args1 args2
81+ unifyTypes' (SaturatedTypeSynonym name args) ty = do
82+ ty1 <- expandTypeSynonym name args
83+ ty1 `unifyTypes` ty
84+ unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
85+ unifyTypes' (ForAll ident1 ty1) (ForAll ident2 ty2) = do
86+ sk <- skolemize ident1 ty1
87+ replaced <- replaceVarWithUnknown ident2 ty2
88+ sk `unifyTypes` replaced
89+ unifyTypes' (ForAll ident ty1) ty2 = do
90+ sk <- skolemize ident ty1
91+ sk `unifyTypes` ty2
92+ unifyTypes' ty f@(ForAll _ _) = f `unifyTypes` ty
93+ unifyTypes' Number Number = return ()
94+ unifyTypes' String String = return ()
95+ unifyTypes' Boolean Boolean = return ()
96+ unifyTypes' (Array s) (Array t) = s `unifyTypes` t
97+ unifyTypes' (Object row1) (Object row2) = row1 ~~ row2
98+ unifyTypes' (Function args1 ret1) (Function args2 ret2) = do
99+ guardWith "Function applied to incorrect number of args" $ length args1 == length args2
100+ zipWithM_ unifyTypes args1 args2
101+ ret1 `unifyTypes` ret2
102+ unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
103+ unifyTypes' (TypeConstructor c1) (TypeConstructor c2) = do
104+ env <- getEnv
105+ moduleName <- substCurrentModule `fmap` ask
106+ guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (typeConstructorsAreEqual env moduleName c1 c2)
107+ unifyTypes' (TypeApp t3 t4) (TypeApp t5 t6) = do
108+ t3 `unifyTypes` t5
109+ t4 `unifyTypes` t6
110+ unifyTypes' (Skolem s1) (Skolem s2) | s1 == s2 = return ()
111+ unifyTypes' r1@(RCons _ _ _) r2 = unifyRows r1 r2
112+ unifyTypes' r1 r2@(RCons _ _ _) = unifyRows r1 r2
113+ unifyTypes' r1@REmpty r2 = unifyRows r1 r2
114+ unifyTypes' r1 r2@REmpty = unifyRows r1 r2
115+ unifyTypes' t3 t4 = throwError $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
116+
117+unifyRows :: Type -> Type -> Subst ()
118+unifyRows r1 r2 =
119+ let
120+ (s1, r1') = rowToList r1
121+ (s2, r2') = rowToList r2
122+ int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
123+ sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
124+ sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
125+ in do
126+ forM_ int (uncurry (~~))
127+ unifyRows' sd1 r1' sd2 r2'
128+ where
129+ unifyRows' :: [(String, Type)] -> Type -> [(String, Type)] -> Type -> Subst ()
130+ unifyRows' [] (TUnknown u) sd r = replace u (rowFromList (sd, r))
131+ unifyRows' sd r [] (TUnknown u) = replace u (rowFromList (sd, r))
132+ unifyRows' ((name, ty):row) r others u@(TUnknown un) = do
133+ occursCheck un ty
134+ forM row $ \(_, t) -> occursCheck un t
135+ u' <- fresh
136+ u ~~ RCons name ty u'
137+ unifyRows' row r others u'
138+ unifyRows' [] REmpty [] REmpty = return ()
139+ unifyRows' [] (TypeVar v1) [] (TypeVar v2) | v1 == v2 = return ()
140+ unifyRows' [] (Skolem s1) [] (Skolem s2) | s1 == s2 = return ()
141+ unifyRows' sd3 r3 sd4 r4 = throwError $ "Cannot unify " ++ prettyPrintRow (rowFromList (sd3, r3)) ++ " with " ++ prettyPrintRow (rowFromList (sd4, r4)) ++ "."
142+
143+typeConstructorsAreEqual :: Environment -> ModuleName -> Qualified ProperName -> Qualified ProperName -> Bool
144+typeConstructorsAreEqual env moduleName c1 c2 =
145+ let
146+ c1' = qualify moduleName c1
147+ c2' = qualify moduleName c2
148+ in
149+ canonicalize env c1' == canonicalize env c2'
150+ where
151+ canonicalize :: Environment -> (ModuleName, ProperName) -> (ModuleName, ProperName)
152+ canonicalize _ key = case key `M.lookup` types env of
153+ Just (_, DataAlias mn' pn') -> (mn', pn')
154+ _ -> key
155+
156+typesOf :: ModuleName -> [(Ident, Value)] -> Check [Type]
157+typesOf moduleName vals = do
158+ (tys, sub, checks) <- runSubst (SubstContext moduleName) $ do
159+ let es = map isTyped vals
160+ typed = lefts es
161+ untyped = rights es
162+ typedDict = map (\(ident, ty, _) -> (ident, ty)) typed
163+ untypedNames <- replicateM (length untyped) fresh
164+ let untypedDict = zip (map fst untyped) untypedNames
165+ dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ typedDict ++ untypedDict)
166+ tys <- forM es $ \e -> case e of
167+ Left (_, ty, val) -> do
168+ kind <- liftCheck $ kindOf moduleName ty
169+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
170+ ty' <- replaceAllTypeSynonyms ty
171+ bindNames dict $ check val ty'
172+ return ty'
173+ Right (ident, val) -> do
174+ ty <- bindNames dict $ infer val
175+ ty ~~ fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
176+ return ty
177+ return tys
178+ forM tys $ flip (escapeCheck checks) sub
179+ forM tys $ skolemEscapeCheck
180+ return $ map (varIfUnknown . desaturateAllTypeSynonyms . setifyAll) tys
181+
182+isTyped :: (Ident, Value) -> Either (Ident, Type, Value) (Ident, Value)
183+isTyped (name, TypedValue value ty) = Left (name, ty, value)
184+isTyped (name, value) = Right (name, value)
185+
186+escapeCheck :: [AnyUnifiable] -> Type -> Substitution -> Check ()
187+escapeCheck checks ty sub =
188+ let
189+ visibleUnknowns = nub $ unknowns ty
190+ in
191+ forM_ checks $ \c -> case c of
192+ AnyUnifiable t -> do
193+ let unsolvedUnknowns = nub . unknowns $ apply sub t
194+ guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
195+
196+skolemEscapeCheck :: Type -> Check ()
197+skolemEscapeCheck ty =
198+ case something (mkQ Nothing findSkolems) ty of
199+ Nothing -> return ()
200+ Just _ -> throwError "Skolem variables cannot escape. Consider adding a type signature."
201+ where
202+ findSkolems (Skolem _) = return ()
203+ findSkolems _ = mzero
204+
205+setify :: Type -> Type
206+setify = rowFromList . first (M.toList . M.fromList) . rowToList
207+
208+setifyAll :: (D.Data d) => d -> d
209+setifyAll = everywhere (mkT setify)
210+
211+varIfUnknown :: Type -> Type
212+varIfUnknown ty =
213+ let unks = nub $ unknowns ty
214+ toName = (:) 't' . show
215+ ty' = everywhere (mkT typeToVar) $ ty
216+ typeToVar :: Type -> Type
217+ typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
218+ typeToVar t = t
219+ in mkForAll (sort . map toName $ unks) ty'
220+
221+replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
222+replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
223+
224+replaceTypeVars :: (D.Data d) => String -> Type -> d -> d
225+replaceTypeVars name t = everywhereBut (mkQ False isShadowed) (mkT replaceTypeVar)
226+ where
227+ replaceTypeVar (TypeVar v) | v == name = t
228+ replaceTypeVar other = other
229+ isShadowed (ForAll v _) | v == name = True
230+ isShadowed _ = False
231+
232+replaceAllVarsWithUnknowns :: Type -> Subst Type
233+replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
234+replaceAllVarsWithUnknowns ty = return ty
235+
236+replaceVarWithUnknown :: String -> Type -> Subst Type
237+replaceVarWithUnknown ident ty = do
238+ tu <- fresh
239+ return $ replaceTypeVars ident tu $ ty
240+
241+replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadReader SubstContext m, MonadError String m) => (D.Data d) => d -> m d
242+replaceAllTypeSynonyms d = do
243+ env <- getEnv
244+ moduleName <- substCurrentModule <$> ask
245+ let syns = map (\((path, name), (args, _)) -> (Qualified (Just path) name, length args)) . M.toList $ typeSynonyms env
246+ either throwError return $ saturateAllTypeSynonyms moduleName syns d
247+
248+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
249+desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
250+ where
251+ replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
252+ replaceSaturatedTypeSynonym t = t
253+
254+expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Type
255+expandTypeSynonym name args = do
256+ env <- getEnv
257+ moduleName <- substCurrentModule `fmap` ask
258+ case M.lookup (qualify moduleName name) (typeSynonyms env) of
259+ Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
260+ Nothing -> error "Type synonym was not defined"
261+
262+ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
263+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
264+
265+infer :: Value -> Subst Type
266+infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ do
267+ ty <- infer' val
268+ escapeCheckLater ty
269+ return ty
270+
271+infer' :: Value -> Subst Type
272+infer' (NumericLiteral _) = return Number
273+infer' (StringLiteral _) = return String
274+infer' (BooleanLiteral _) = return Boolean
275+infer' (ArrayLiteral vals) = do
276+ ts <- mapM (infer) vals
277+ els <- fresh
278+ forM_ ts $ \t -> els ~~ Array t
279+ return els
280+infer' (Unary op val) = do
281+ t <- infer val
282+ inferUnary op t
283+infer' (Binary op left right) = do
284+ t1 <- infer left
285+ t2 <- infer right
286+ inferBinary op t1 t2
287+infer' (ObjectLiteral ps) = do
288+ ensureNoDuplicateProperties ps
289+ ts <- mapM (infer . snd) ps
290+ let fields = zipWith (\(name, _) t -> (name, t)) ps ts
291+ return $ Object $ rowFromList (fields, REmpty)
292+infer' (ObjectUpdate o ps) = do
293+ ensureNoDuplicateProperties ps
294+ row <- fresh
295+ newTys <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
296+ oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
297+ check o $ Object $ rowFromList (oldTys, row)
298+ return $ Object $ rowFromList (newTys, row)
299+infer' (Indexer index val) = do
300+ el <- fresh
301+ check index Number
302+ check val (Array el)
303+ return el
304+infer' (Accessor prop val) = do
305+ obj <- infer val
306+ propTy <- inferProperty obj prop
307+ case propTy of
308+ Nothing -> do
309+ field <- fresh
310+ rest <- fresh
311+ obj `subsumes` Object (RCons prop field rest)
312+ return field
313+ Just ty -> return ty
314+infer' (Abs args ret) = do
315+ ts <- replicateM (length args) fresh
316+ moduleName <- substCurrentModule <$> ask
317+ bindLocalVariables moduleName (zip args ts) $ do
318+ body <- infer' ret
319+ return $ Function ts body
320+infer' app@(App _ _) = do
321+ let (f, argss) = unfoldApplication app
322+ ft <- infer f
323+ ret <- fresh
324+ checkFunctionApplications ft argss ret
325+ return ret
326+infer' (Var var) = do
327+ moduleName <- substCurrentModule <$> ask
328+ ty <- lookupVariable moduleName var
329+ replaceAllTypeSynonyms ty
330+infer' (Block ss) = do
331+ ret <- fresh
332+ (allCodePathsReturn, _) <- checkBlock M.empty ret ss
333+ guardWith "Block is missing a return statement" allCodePathsReturn
334+ return ret
335+infer' (Constructor c) = do
336+ env <- getEnv
337+ moduleName <- substCurrentModule `fmap` ask
338+ case M.lookup (qualify moduleName c) (dataConstructors env) of
339+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
340+ Just ty -> replaceAllTypeSynonyms ty
341+infer' (Case vals binders) = do
342+ ts <- mapM infer vals
343+ ret <- fresh
344+ checkBinders ts ret binders
345+ return ret
346+infer' (IfThenElse cond th el) = do
347+ check cond Boolean
348+ t2 <- infer th
349+ t3 <- infer el
350+ t2 ~~ t3
351+ return t2
352+infer' (TypedValue val ty) = do
353+ moduleName <- substCurrentModule <$> ask
354+ kind <- liftCheck $ kindOf moduleName ty
355+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
356+ ty' <- replaceAllTypeSynonyms ty
357+ check val ty'
358+ return ty'
359+infer' _ = error "Invalid argument to infer"
360+
361+inferProperty :: Type -> String -> Subst (Maybe Type)
362+inferProperty (Object row) prop = do
363+ let (props, _) = rowToList row
364+ return $ lookup prop props
365+inferProperty (SaturatedTypeSynonym name args) prop = do
366+ replaced <- expandTypeSynonym name args
367+ inferProperty replaced prop
368+inferProperty (ForAll ident ty) prop = do
369+ replaced <- replaceVarWithUnknown ident ty
370+ inferProperty replaced prop
371+inferProperty _ _ = return Nothing
372+
373+inferUnary :: UnaryOperator -> Type -> Subst Type
374+inferUnary op val =
375+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
376+ (valTy, resTy) -> do
377+ val ~~ valTy
378+ return resTy
379+
380+checkUnary :: UnaryOperator -> Value -> Type -> Subst ()
381+checkUnary op val res =
382+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
383+ (valTy, resTy) -> do
384+ res ~~ resTy
385+ check val valTy
386+
387+unaryOps :: [(UnaryOperator, (Type, Type))]
388+unaryOps = [ (Negate, (Number, Number))
389+ , (Not, (Boolean, Boolean))
390+ , (BitwiseNot, (Number, Number))
391+ ]
392+
393+inferBinary :: BinaryOperator -> Type -> Type -> Subst Type
394+inferBinary op left right | isEqualityTest op = do
395+ left ~~ right
396+ return Boolean
397+inferBinary op left right =
398+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
399+ (valTy, resTy) -> do
400+ left ~~ valTy
401+ right ~~ valTy
402+ return resTy
403+
404+checkBinary :: BinaryOperator -> Value -> Value -> Type -> Subst ()
405+checkBinary op left right res | isEqualityTest op = do
406+ res ~~ Boolean
407+ t1 <- infer left
408+ t2 <- infer right
409+ t1 ~~ t2
410+checkBinary op left right res =
411+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
412+ (valTy, resTy) -> do
413+ res ~~ resTy
414+ check left valTy
415+ check right valTy
416+
417+isEqualityTest :: BinaryOperator -> Bool
418+isEqualityTest EqualTo = True
419+isEqualityTest NotEqualTo = True
420+isEqualityTest _ = False
421+
422+binaryOps :: [(BinaryOperator, (Type, Type))]
423+binaryOps = [ (Add, (Number, Number))
424+ , (Subtract, (Number, Number))
425+ , (Multiply, (Number, Number))
426+ , (Divide, (Number, Number))
427+ , (Modulus, (Number, Number))
428+ , (BitwiseAnd, (Number, Number))
429+ , (BitwiseOr, (Number, Number))
430+ , (BitwiseXor, (Number, Number))
431+ , (ShiftRight, (Number, Number))
432+ , (ZeroFillShiftRight, (Number, Number))
433+ , (And, (Boolean, Boolean))
434+ , (Or, (Boolean, Boolean))
435+ , (Concat, (String, String))
436+ , (Modulus, (Number, Number))
437+ , (LessThan, (Number, Boolean))
438+ , (LessThanOrEqualTo, (Number, Boolean))
439+ , (GreaterThan, (Number, Boolean))
440+ , (GreaterThanOrEqualTo, (Number, Boolean))
441+ ]
442+
443+inferBinder :: Type -> Binder -> Subst (M.Map Ident Type)
444+inferBinder _ NullBinder = return M.empty
445+inferBinder val (StringBinder _) = val ~~ String >> return M.empty
446+inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
447+inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
448+inferBinder val (VarBinder name) = return $ M.singleton name val
449+inferBinder val (NullaryBinder ctor) = do
450+ env <- getEnv
451+ moduleName <- substCurrentModule <$> ask
452+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
453+ Just ty -> do
454+ ty `subsumes` val
455+ return M.empty
456+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
457+inferBinder val (UnaryBinder ctor binder) = do
458+ env <- getEnv
459+ moduleName <- substCurrentModule <$> ask
460+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
461+ Just ty -> do
462+ fn <- replaceAllVarsWithUnknowns ty
463+ case fn of
464+ Function [obj] ret -> do
465+ val `subsumes` ret
466+ inferBinder obj binder
467+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
468+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
469+inferBinder val (ObjectBinder props) = do
470+ row <- fresh
471+ rest <- fresh
472+ m1 <- inferRowProperties row rest props
473+ val ~~ Object row
474+ return m1
475+ where
476+ inferRowProperties :: Type -> Type -> [(String, Binder)] -> Subst (M.Map Ident Type)
477+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
478+ inferRowProperties nrow row ((name, binder):binders) = do
479+ propTy <- fresh
480+ m1 <- inferBinder propTy binder
481+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
482+ return $ m1 `M.union` m2
483+inferBinder val (ArrayBinder binders) = do
484+ el <- fresh
485+ m1 <- M.unions <$> mapM (inferBinder el) binders
486+ val ~~ Array el
487+ return m1
488+inferBinder val (ConsBinder headBinder tailBinder) = do
489+ el <- fresh
490+ m1 <- inferBinder el headBinder
491+ m2 <- inferBinder val tailBinder
492+ val ~~ Array el
493+ return $ m1 `M.union` m2
494+inferBinder val (NamedBinder name binder) = do
495+ m <- inferBinder val binder
496+ return $ M.insert name val m
497+
498+checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> Subst ()
499+checkBinders _ _ [] = return ()
500+checkBinders nvals ret ((binders, grd, val):bs) = do
501+ moduleName <- substCurrentModule <$> ask
502+ m1 <- M.unions <$> zipWithM inferBinder nvals binders
503+ bindLocalVariables moduleName (M.toList m1) $ do
504+ check val ret
505+ case grd of
506+ Nothing -> return ()
507+ Just g -> check g Boolean
508+ checkBinders nvals ret bs
509+
510+assignVariable :: Ident -> Subst ()
511+assignVariable name = do
512+ env <- checkEnv <$> get
513+ moduleName <- substCurrentModule <$> ask
514+ case M.lookup (moduleName, name) (names env) of
515+ Just (_, LocalVariable) -> throwError $ "Variable with name " ++ show name ++ " already exists."
516+ _ -> return ()
517+
518+checkStatement :: M.Map Ident Type -> Type -> Statement -> Subst (Bool, M.Map Ident Type)
519+checkStatement mass _ (VariableIntroduction name val) = do
520+ assignVariable name
521+ t <- infer val
522+ return (False, M.insert name t mass)
523+checkStatement mass _ (Assignment ident val) = do
524+ t <- infer val
525+ case M.lookup ident mass of
526+ Nothing -> throwError $ "No local variable with name " ++ show ident
527+ Just ty -> do t ~~ ty
528+ return (False, mass)
529+checkStatement mass ret (While val inner) = do
530+ check val Boolean
531+ (allCodePathsReturn, _) <- checkBlock mass ret inner
532+ return (allCodePathsReturn, mass)
533+checkStatement mass ret (If ifst) = do
534+ allCodePathsReturn <- checkIfStatement mass ret ifst
535+ return (allCodePathsReturn, mass)
536+checkStatement mass ret (For ident start end inner) = do
537+ moduleName <- substCurrentModule <$> ask
538+ assignVariable ident
539+ check start Number
540+ check end Number
541+ (allCodePathsReturn, _) <- bindLocalVariables moduleName [(ident, Number)] $ checkBlock mass ret inner
542+ return (allCodePathsReturn, mass)
543+checkStatement mass ret (Return val) = do
544+ check val ret
545+ return (True, mass)
546+
547+checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> Subst Bool
548+checkIfStatement mass ret (IfStatement val thens Nothing) = do
549+ check val Boolean
550+ _ <- checkBlock mass ret thens
551+ return False
552+checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
553+ check val Boolean
554+ (allCodePathsReturn1, _) <- checkBlock mass ret thens
555+ allCodePathsReturn2 <- checkElseStatement mass ret elses
556+ return $ allCodePathsReturn1 && allCodePathsReturn2
557+
558+checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> Subst Bool
559+checkElseStatement mass ret (Else elses) = fst <$> checkBlock mass ret elses
560+checkElseStatement mass ret (ElseIf ifst) = checkIfStatement mass ret ifst
561+
562+checkBlock :: M.Map Ident Type -> Type -> [Statement] -> Subst (Bool, M.Map Ident Type)
563+checkBlock mass _ [] = return (False, mass)
564+checkBlock mass ret (s:ss) = do
565+ moduleName <- substCurrentModule <$> ask
566+ (b1, mass1) <- checkStatement mass ret s
567+ bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
568+ (True, []) -> return (True, mass1)
569+ (True, _) -> throwError "Unreachable code"
570+ (False, ss') -> checkBlock mass1 ret ss'
571+
572+skolemize :: String -> Type -> Subst Type
573+skolemize ident ty = do
574+ tsk <- Skolem <$> fresh'
575+ return $ replaceTypeVars ident tsk ty
576+
577+check :: Value -> Type -> Subst ()
578+check val ty = rethrow errorMessage $ check' val ty
579+ where
580+ errorMessage msg =
581+ "Error checking type of term " ++
582+ prettyPrintValue val ++
583+ " against type " ++
584+ prettyPrintType ty ++
585+ ":\n" ++
586+ msg
587+
588+check' :: Value -> Type -> Subst ()
589+check' val (ForAll idents ty) = do
590+ sk <- skolemize idents ty
591+ check val sk
592+check' val u@(TUnknown _) = do
593+ ty <- infer val
594+ -- Don't unify an unknown with an inferred polytype
595+ ty' <- replaceAllVarsWithUnknowns ty
596+ ty' ~~ u
597+check' (NumericLiteral _) Number = return ()
598+check' (StringLiteral _) String = return ()
599+check' (BooleanLiteral _) Boolean = return ()
600+check' (Unary op val) ty = checkUnary op val ty
601+check' (Binary op left right) ty = checkBinary op left right ty
602+check' (ArrayLiteral vals) (Array ty) = forM_ vals (\val -> check val ty)
603+check' (Indexer index vals) ty = check index Number >> check vals (Array ty)
604+check' (Abs args ret) (Function argTys retTy) = do
605+ moduleName <- substCurrentModule <$> ask
606+ guardWith "Incorrect number of function arguments" (length args == length argTys)
607+ bindLocalVariables moduleName (zip args argTys) $ check ret retTy
608+check' app@(App _ _) ret = do
609+ let (f, argss) = unfoldApplication app
610+ ft <- infer f
611+ checkFunctionApplications ft argss ret
612+check' (Var var) ty = do
613+ moduleName <- substCurrentModule <$> ask
614+ ty1 <- lookupVariable moduleName var
615+ repl <- replaceAllTypeSynonyms ty1
616+ repl `subsumes` ty
617+check' (TypedValue val ty1) ty2 = do
618+ moduleName <- substCurrentModule <$> ask
619+ kind <- liftCheck $ kindOf moduleName ty1
620+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
621+ ty1 `subsumes` ty2
622+ check val ty1
623+check' (Case vals binders) ret = do
624+ ts <- mapM infer vals
625+ checkBinders ts ret binders
626+check' (IfThenElse cond th el) ty = do
627+ check cond Boolean
628+ check th ty
629+ check el ty
630+check' (ObjectLiteral ps) (Object row) = do
631+ ensureNoDuplicateProperties ps
632+ checkProperties ps row False
633+check' (ObjectUpdate obj ps) (Object row) = do
634+ ensureNoDuplicateProperties ps
635+ us <- zip (map fst ps) <$> replicateM (length ps) fresh
636+ let (propsToCheck, rest) = rowToList row
637+ propsToRemove = map fst ps
638+ remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
639+ check obj (Object (rowFromList (us ++ remainingProps, rest)))
640+ checkProperties ps row True
641+check' (Accessor prop val) ty = do
642+ rest <- fresh
643+ check val (Object (RCons prop ty rest))
644+check' (Block ss) ret = do
645+ (allCodePathsReturn, _) <- checkBlock M.empty ret ss
646+ guardWith "Block is missing a return statement" allCodePathsReturn
647+check' (Constructor c) ty = do
648+ env <- getEnv
649+ moduleName <- substCurrentModule <$> ask
650+ case M.lookup (qualify moduleName c) (dataConstructors env) of
651+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
652+ Just ty1 -> do
653+ repl <- replaceAllTypeSynonyms ty1
654+ repl `subsumes` ty
655+check' val (SaturatedTypeSynonym name args) = do
656+ ty <- expandTypeSynonym name args
657+ check val ty
658+check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
659+
660+checkProperties :: [(String, Value)] -> Type -> Bool -> Subst ()
661+checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
662+ go [] [] REmpty = return ()
663+ go [] [] u@(TUnknown _) = u ~~ REmpty
664+ go [] [] (Skolem _) | lax = return ()
665+ go [] ((p, _): _) _ | lax = return ()
666+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
667+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
668+ go ((p,v):ps') [] u@(TUnknown _) = do
669+ ty <- infer v
670+ rest <- fresh
671+ u ~~ RCons p ty rest
672+ go ps' [] rest
673+ go ((p,v):ps') ts r =
674+ case lookup p ts of
675+ Nothing -> do
676+ ty <- infer v
677+ rest <- fresh
678+ r ~~ RCons p ty rest
679+ go ps' ts rest
680+ Just ty -> do
681+ check v ty
682+ go ps' (delete (p, ty) ts) r
683+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
684+
685+unfoldApplication :: Value -> (Value, [[Value]])
686+unfoldApplication = go []
687+ where
688+ go argss (App f args) = go (args:argss) f
689+ go argss f = (f, argss)
690+
691+checkFunctionApplications :: Type -> [[Value]] -> Type -> Subst ()
692+checkFunctionApplications _ [] _ = error "Nullary function application"
693+checkFunctionApplications fnTy [args] ret = checkFunctionApplication fnTy args ret
694+checkFunctionApplications fnTy (args:argss) ret = do
695+ argTys <- mapM (infer) args
696+ f <- inferFunctionApplication fnTy argTys
697+ checkFunctionApplications f argss ret
698+
699+checkFunctionApplication :: Type -> [Value] -> Type -> Subst ()
700+checkFunctionApplication fnTy args ret = rethrow errorMessage $ checkFunctionApplication' fnTy args ret
701+ where
702+ errorMessage msg = "Error applying function of type "
703+ ++ prettyPrintType fnTy
704+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
705+ ++ ", expecting value of type "
706+ ++ prettyPrintType ret ++ ":\n" ++ msg
707+
708+inferFunctionApplication :: Type -> [Type] -> Subst Type
709+inferFunctionApplication (Function argTys retTy) args = do
710+ guardWith "Incorrect number of function arguments" (length args == length argTys)
711+ zipWithM subsumes args argTys
712+ return retTy
713+inferFunctionApplication (ForAll ident ty) args = do
714+ replaced <- replaceVarWithUnknown ident ty
715+ inferFunctionApplication replaced args
716+inferFunctionApplication u@(TUnknown _) args = do
717+
718+ ret <- fresh
719+ args' <- mapM replaceAllVarsWithUnknowns args
720+ u ~~ Function args' ret
721+ return ret
722+inferFunctionApplication (SaturatedTypeSynonym name tyArgs) args = do
723+ ty <- expandTypeSynonym name tyArgs
724+ inferFunctionApplication ty args
725+inferFunctionApplication fnTy args = throwError $ "Cannot apply function of type "
726+ ++ prettyPrintType fnTy
727+ ++ " to argument(s) of type(s) " ++ intercalate ", " (map prettyPrintType args)
728+
729+checkFunctionApplication' :: Type -> [Value] -> Type -> Subst ()
730+checkFunctionApplication' (Function argTys retTy) args ret = do
731+ guardWith "Incorrect number of function arguments" (length args == length argTys)
732+ zipWithM (check) args argTys
733+ retTy `subsumes` ret
734+checkFunctionApplication' (ForAll ident ty) args ret = do
735+ replaced <- replaceVarWithUnknown ident ty
736+ checkFunctionApplication replaced args ret
737+checkFunctionApplication' u@(TUnknown _) args ret = do
738+ tyArgs <- mapM (\arg -> infer arg >>= replaceAllVarsWithUnknowns) args
739+ u ~~ Function tyArgs ret
740+checkFunctionApplication' (SaturatedTypeSynonym name tyArgs) args ret = do
741+ ty <- expandTypeSynonym name tyArgs
742+ checkFunctionApplication' ty args ret
743+checkFunctionApplication' fnTy args ret = throwError $ "Applying a function of type "
744+ ++ prettyPrintType fnTy
745+ ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
746+ ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
747+
748+subsumes :: Type -> Type -> Subst ()
749+subsumes (ForAll ident ty1) ty2 = do
750+ replaced <- replaceVarWithUnknown ident ty1
751+ replaced `subsumes` ty2
752+subsumes (Function args1 ret1) (Function args2 ret2) = do
753+ zipWithM subsumes args2 args1
754+ ret1 `subsumes` ret2
755+subsumes ty1 ty2 = ty1 ~~ ty2
756+