@@ -0,0 +1,745 @@
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+import Data.Function (on)
48+
49+instance Unifiable Type where
50+ unknown = TUnknown
51+ isUnknown (TUnknown u) = Just u
52+ isUnknown _ = Nothing
53+ (~~) = unifyTypes
54+ apply s (TUnknown u) = runSubstitution s u
55+ apply s (SaturatedTypeSynonym name tys) = SaturatedTypeSynonym name $ map (apply s) tys
56+ apply s (ForAll idents ty) = ForAll idents $ apply s ty
57+ apply s (Array t) = Array (apply s t)
58+ apply s (Object r) = Object (apply s r)
59+ apply s (Function args ret) = Function (map (apply s) args) (apply s ret)
60+ apply s (TypeApp t1 t2) = TypeApp (apply s t1) (apply s t2)
61+ apply s (RCons name ty r) = RCons name (apply s ty) (apply s r)
62+ apply _ t = t
63+ unknowns (TUnknown (Unknown u)) = [u]
64+ unknowns (SaturatedTypeSynonym _ tys) = concatMap unknowns tys
65+ unknowns (ForAll _ ty) = unknowns ty
66+ unknowns (Array t) = unknowns t
67+ unknowns (Object r) = unknowns r
68+ unknowns (Function args ret) = concatMap unknowns args ++ unknowns ret
69+ unknowns (TypeApp t1 t2) = unknowns t1 ++ unknowns t2
70+ unknowns (RCons _ ty r) = unknowns ty ++ unknowns r
71+ unknowns _ = []
72+
73+unifyTypes :: Type -> Type -> Subst ()
74+unifyTypes t1 t2 = rethrow (\e -> "Error unifying type " ++ prettyPrintType t1 ++ " with type " ++ prettyPrintType t2 ++ ":\n" ++ e) $ do
75+ unifyTypes' t1 t2
76+ where
77+ unifyTypes' (TUnknown u1) (TUnknown u2) | u1 == u2 = return ()
78+ unifyTypes' (TUnknown u) t = replace u t
79+ unifyTypes' t (TUnknown u) = replace u t
80+ unifyTypes' (SaturatedTypeSynonym name args) ty = do
81+ ty1 <- expandTypeSynonym name args
82+ ty1 `unifyTypes` ty
83+ unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
84+ unifyTypes' (ForAll ident1 ty1) (ForAll ident2 ty2) = do
85+ sk <- skolemize ident1 ty1
86+ replaced <- replaceVarWithUnknown ident2 ty2
87+ sk `unifyTypes` replaced
88+ unifyTypes' (ForAll ident ty1) ty2 = do
89+ sk <- skolemize ident ty1
90+ sk `unifyTypes` ty2
91+ unifyTypes' ty f@(ForAll _ _) = f `unifyTypes` ty
92+ unifyTypes' Number Number = return ()
93+ unifyTypes' String String = return ()
94+ unifyTypes' Boolean Boolean = return ()
95+ unifyTypes' (Array s) (Array t) = s `unifyTypes` t
96+ unifyTypes' (Object row1) (Object row2) = row1 ~~ row2
97+ unifyTypes' (Function args1 ret1) (Function args2 ret2) = do
98+ guardWith "Function applied to incorrect number of args" $ length args1 == length args2
99+ zipWithM_ unifyTypes args1 args2
100+ ret1 `unifyTypes` ret2
101+ unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
102+ unifyTypes' (TypeConstructor c1) (TypeConstructor c2) = do
103+ env <- getEnv
104+ moduleName <- substCurrentModule `fmap` ask
105+ guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (typeConstructorsAreEqual env moduleName c1 c2)
106+ unifyTypes' (TypeApp t3 t4) (TypeApp t5 t6) = do
107+ t3 `unifyTypes` t5
108+ t4 `unifyTypes` t6
109+ unifyTypes' (Skolem s1) (Skolem s2) | s1 == s2 = return ()
110+ unifyTypes' r1@(RCons _ _ _) r2 = unifyRows r1 r2
111+ unifyTypes' r1 r2@(RCons _ _ _) = unifyRows r1 r2
112+ unifyTypes' r1@REmpty r2 = unifyRows r1 r2
113+ unifyTypes' r1 r2@REmpty = unifyRows r1 r2
114+ unifyTypes' t3 t4 = throwError $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
115+
116+unifyRows :: Type -> Type -> Subst ()
117+unifyRows r1 r2 =
118+ let
119+ (s1, r1') = rowToList r1
120+ (s2, r2') = rowToList r2
121+ int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
122+ sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
123+ sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
124+ in do
125+ forM_ int (uncurry (~~))
126+ unifyRows' sd1 r1' sd2 r2'
127+ where
128+ unifyRows' :: [(String, Type)] -> Type -> [(String, Type)] -> Type -> Subst ()
129+ unifyRows' [] (TUnknown u) sd r = replace u (rowFromList (sd, r))
130+ unifyRows' sd r [] (TUnknown u) = replace u (rowFromList (sd, r))
131+ unifyRows' ((name, ty):row) r others u@(TUnknown un) = do
132+ occursCheck un ty
133+ forM row $ \(_, t) -> occursCheck un t
134+ u' <- fresh
135+ u ~~ RCons name ty u'
136+ unifyRows' row r others u'
137+ unifyRows' [] REmpty [] REmpty = return ()
138+ unifyRows' [] (TypeVar v1) [] (TypeVar v2) | v1 == v2 = return ()
139+ unifyRows' [] (Skolem s1) [] (Skolem s2) | s1 == s2 = return ()
140+ unifyRows' sd3 r3 sd4 r4 = throwError $ "Cannot unify " ++ prettyPrintRow (rowFromList (sd3, r3)) ++ " with " ++ prettyPrintRow (rowFromList (sd4, r4)) ++ "."
141+
142+typeConstructorsAreEqual :: Environment -> ModuleName -> Qualified ProperName -> Qualified ProperName -> Bool
143+typeConstructorsAreEqual env moduleName = (==) `on` canonicalizeType moduleName env
144+
145+typesOf :: ModuleName -> [(Ident, Value)] -> Check [Type]
146+typesOf moduleName vals = do
147+ (tys, sub, checks) <- runSubst (SubstContext moduleName) $ do
148+ let es = map isTyped vals
149+ typed = lefts es
150+ untyped = rights es
151+ typedDict = map (\(ident, ty, _) -> (ident, ty)) typed
152+ untypedNames <- replicateM (length untyped) fresh
153+ let untypedDict = zip (map fst untyped) untypedNames
154+ dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ typedDict ++ untypedDict)
155+ tys <- forM es $ \e -> case e of
156+ Left (_, ty, val) -> 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+ Right (ident, val) -> do
163+ ty <- bindNames dict $ infer val
164+ ty ~~ fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
165+ return ty
166+ return tys
167+ forM tys $ flip (escapeCheck checks) sub
168+ forM tys $ skolemEscapeCheck
169+ return $ map (varIfUnknown . desaturateAllTypeSynonyms . setifyAll) tys
170+
171+isTyped :: (Ident, Value) -> Either (Ident, Type, Value) (Ident, Value)
172+isTyped (name, TypedValue value ty) = Left (name, ty, value)
173+isTyped (name, value) = Right (name, value)
174+
175+escapeCheck :: [AnyUnifiable] -> Type -> Substitution -> Check ()
176+escapeCheck checks ty sub =
177+ let
178+ visibleUnknowns = nub $ unknowns ty
179+ in
180+ forM_ checks $ \c -> case c of
181+ AnyUnifiable t -> do
182+ let unsolvedUnknowns = nub . unknowns $ apply sub t
183+ guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
184+
185+skolemEscapeCheck :: Type -> Check ()
186+skolemEscapeCheck ty =
187+ case something (mkQ Nothing findSkolems) ty of
188+ Nothing -> return ()
189+ Just _ -> throwError "Skolem variables cannot escape. Consider adding a type signature."
190+ where
191+ findSkolems (Skolem _) = return ()
192+ findSkolems _ = mzero
193+
194+setify :: Type -> Type
195+setify = rowFromList . first (M.toList . M.fromList) . rowToList
196+
197+setifyAll :: (D.Data d) => d -> d
198+setifyAll = everywhere (mkT setify)
199+
200+varIfUnknown :: Type -> Type
201+varIfUnknown ty =
202+ let unks = nub $ unknowns ty
203+ toName = (:) 't' . show
204+ ty' = everywhere (mkT typeToVar) $ ty
205+ typeToVar :: Type -> Type
206+ typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
207+ typeToVar t = t
208+ in mkForAll (sort . map toName $ unks) ty'
209+
210+replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
211+replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
212+
213+replaceTypeVars :: (D.Data d) => String -> Type -> d -> d
214+replaceTypeVars name t = everywhereBut (mkQ False isShadowed) (mkT replaceTypeVar)
215+ where
216+ replaceTypeVar (TypeVar v) | v == name = t
217+ replaceTypeVar other = other
218+ isShadowed (ForAll v _) | v == name = True
219+ isShadowed _ = False
220+
221+replaceAllVarsWithUnknowns :: Type -> Subst Type
222+replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
223+replaceAllVarsWithUnknowns ty = return ty
224+
225+replaceVarWithUnknown :: String -> Type -> Subst Type
226+replaceVarWithUnknown ident ty = do
227+ tu <- fresh
228+ return $ replaceTypeVars ident tu $ ty
229+
230+replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadReader SubstContext m, MonadError String m) => (D.Data d) => d -> m d
231+replaceAllTypeSynonyms d = do
232+ env <- getEnv
233+ moduleName <- substCurrentModule <$> ask
234+ let syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
235+ either throwError return $ saturateAllTypeSynonyms env moduleName syns d
236+
237+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
238+desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
239+ where
240+ replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
241+ replaceSaturatedTypeSynonym t = t
242+
243+expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Type
244+expandTypeSynonym name args = do
245+ env <- getEnv
246+ moduleName <- substCurrentModule `fmap` ask
247+ case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
248+ Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
249+ Nothing -> error "Type synonym was not defined"
250+
251+ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
252+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
253+
254+infer :: Value -> Subst Type
255+infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ do
256+ ty <- infer' val
257+ escapeCheckLater ty
258+ return ty
259+
260+infer' :: Value -> Subst Type
261+infer' (NumericLiteral _) = return Number
262+infer' (StringLiteral _) = return String
263+infer' (BooleanLiteral _) = return Boolean
264+infer' (ArrayLiteral vals) = do
265+ ts <- mapM (infer) vals
266+ els <- fresh
267+ forM_ ts $ \t -> els ~~ Array t
268+ return els
269+infer' (Unary op val) = do
270+ t <- infer val
271+ inferUnary op t
272+infer' (Binary op left right) = do
273+ t1 <- infer left
274+ t2 <- infer right
275+ inferBinary op t1 t2
276+infer' (ObjectLiteral ps) = do
277+ ensureNoDuplicateProperties ps
278+ ts <- mapM (infer . snd) ps
279+ let fields = zipWith (\(name, _) t -> (name, t)) ps ts
280+ return $ Object $ rowFromList (fields, REmpty)
281+infer' (ObjectUpdate o ps) = do
282+ ensureNoDuplicateProperties ps
283+ row <- fresh
284+ newTys <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
285+ oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
286+ check o $ Object $ rowFromList (oldTys, row)
287+ return $ Object $ rowFromList (newTys, row)
288+infer' (Indexer index val) = do
289+ el <- fresh
290+ check index Number
291+ check val (Array el)
292+ return el
293+infer' (Accessor prop val) = do
294+ obj <- infer val
295+ propTy <- inferProperty obj prop
296+ case propTy of
297+ Nothing -> do
298+ field <- fresh
299+ rest <- fresh
300+ obj `subsumes` Object (RCons prop field rest)
301+ return field
302+ Just ty -> return ty
303+infer' (Abs args ret) = do
304+ ts <- replicateM (length args) fresh
305+ moduleName <- substCurrentModule <$> ask
306+ bindLocalVariables moduleName (zip args ts) $ do
307+ body <- infer' ret
308+ return $ Function ts body
309+infer' app@(App _ _) = do
310+ let (f, argss) = unfoldApplication app
311+ ft <- infer f
312+ ret <- fresh
313+ checkFunctionApplications ft argss ret
314+ return ret
315+infer' (Var var) = do
316+ moduleName <- substCurrentModule <$> ask
317+ ty <- lookupVariable moduleName var
318+ replaceAllTypeSynonyms ty
319+infer' (Block ss) = do
320+ ret <- fresh
321+ (allCodePathsReturn, _) <- checkBlock M.empty ret ss
322+ guardWith "Block is missing a return statement" allCodePathsReturn
323+ return ret
324+infer' (Constructor c) = do
325+ env <- getEnv
326+ moduleName <- substCurrentModule `fmap` ask
327+ case M.lookup (qualify moduleName c) (dataConstructors env) of
328+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
329+ Just (ty, _) -> replaceAllTypeSynonyms ty
330+infer' (Case vals binders) = do
331+ ts <- mapM infer vals
332+ ret <- fresh
333+ checkBinders ts ret binders
334+ return ret
335+infer' (IfThenElse cond th el) = do
336+ check cond Boolean
337+ t2 <- infer th
338+ t3 <- infer el
339+ t2 ~~ t3
340+ return t2
341+infer' (TypedValue val ty) = do
342+ moduleName <- substCurrentModule <$> ask
343+ kind <- liftCheck $ kindOf moduleName ty
344+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
345+ ty' <- replaceAllTypeSynonyms ty
346+ check val ty'
347+ return ty'
348+infer' _ = error "Invalid argument to infer"
349+
350+inferProperty :: Type -> String -> Subst (Maybe Type)
351+inferProperty (Object row) prop = do
352+ let (props, _) = rowToList row
353+ return $ lookup prop props
354+inferProperty (SaturatedTypeSynonym name args) prop = do
355+ replaced <- expandTypeSynonym name args
356+ inferProperty replaced prop
357+inferProperty (ForAll ident ty) prop = do
358+ replaced <- replaceVarWithUnknown ident ty
359+ inferProperty replaced prop
360+inferProperty _ _ = return Nothing
361+
362+inferUnary :: UnaryOperator -> Type -> Subst Type
363+inferUnary op val =
364+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
365+ (valTy, resTy) -> do
366+ val ~~ valTy
367+ return resTy
368+
369+checkUnary :: UnaryOperator -> Value -> Type -> Subst ()
370+checkUnary op val res =
371+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
372+ (valTy, resTy) -> do
373+ res ~~ resTy
374+ check val valTy
375+
376+unaryOps :: [(UnaryOperator, (Type, Type))]
377+unaryOps = [ (Negate, (Number, Number))
378+ , (Not, (Boolean, Boolean))
379+ , (BitwiseNot, (Number, Number))
380+ ]
381+
382+inferBinary :: BinaryOperator -> Type -> Type -> Subst Type
383+inferBinary op left right | isEqualityTest op = do
384+ left ~~ right
385+ return Boolean
386+inferBinary op left right =
387+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
388+ (valTy, resTy) -> do
389+ left ~~ valTy
390+ right ~~ valTy
391+ return resTy
392+
393+checkBinary :: BinaryOperator -> Value -> Value -> Type -> Subst ()
394+checkBinary op left right res | isEqualityTest op = do
395+ res ~~ Boolean
396+ t1 <- infer left
397+ t2 <- infer right
398+ t1 ~~ t2
399+checkBinary op left right res =
400+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
401+ (valTy, resTy) -> do
402+ res ~~ resTy
403+ check left valTy
404+ check right valTy
405+
406+isEqualityTest :: BinaryOperator -> Bool
407+isEqualityTest EqualTo = True
408+isEqualityTest NotEqualTo = True
409+isEqualityTest _ = False
410+
411+binaryOps :: [(BinaryOperator, (Type, Type))]
412+binaryOps = [ (Add, (Number, Number))
413+ , (Subtract, (Number, Number))
414+ , (Multiply, (Number, Number))
415+ , (Divide, (Number, Number))
416+ , (Modulus, (Number, Number))
417+ , (BitwiseAnd, (Number, Number))
418+ , (BitwiseOr, (Number, Number))
419+ , (BitwiseXor, (Number, Number))
420+ , (ShiftRight, (Number, Number))
421+ , (ZeroFillShiftRight, (Number, Number))
422+ , (And, (Boolean, Boolean))
423+ , (Or, (Boolean, Boolean))
424+ , (Concat, (String, String))
425+ , (Modulus, (Number, Number))
426+ , (LessThan, (Number, Boolean))
427+ , (LessThanOrEqualTo, (Number, Boolean))
428+ , (GreaterThan, (Number, Boolean))
429+ , (GreaterThanOrEqualTo, (Number, Boolean))
430+ ]
431+
432+inferBinder :: Type -> Binder -> Subst (M.Map Ident Type)
433+inferBinder _ NullBinder = return M.empty
434+inferBinder val (StringBinder _) = val ~~ String >> return M.empty
435+inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
436+inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
437+inferBinder val (VarBinder name) = return $ M.singleton name val
438+inferBinder val (NullaryBinder ctor) = do
439+ env <- getEnv
440+ moduleName <- substCurrentModule <$> ask
441+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
442+ Just (ty, _) -> do
443+ ty `subsumes` val
444+ return M.empty
445+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
446+inferBinder val (UnaryBinder ctor binder) = do
447+ env <- getEnv
448+ moduleName <- substCurrentModule <$> ask
449+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
450+ Just (ty, _) -> do
451+ fn <- replaceAllVarsWithUnknowns ty
452+ case fn of
453+ Function [obj] ret -> do
454+ val `subsumes` ret
455+ inferBinder obj binder
456+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
457+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
458+inferBinder val (ObjectBinder props) = do
459+ row <- fresh
460+ rest <- fresh
461+ m1 <- inferRowProperties row rest props
462+ val ~~ Object row
463+ return m1
464+ where
465+ inferRowProperties :: Type -> Type -> [(String, Binder)] -> Subst (M.Map Ident Type)
466+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
467+ inferRowProperties nrow row ((name, binder):binders) = do
468+ propTy <- fresh
469+ m1 <- inferBinder propTy binder
470+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
471+ return $ m1 `M.union` m2
472+inferBinder val (ArrayBinder binders) = do
473+ el <- fresh
474+ m1 <- M.unions <$> mapM (inferBinder el) binders
475+ val ~~ Array el
476+ return m1
477+inferBinder val (ConsBinder headBinder tailBinder) = do
478+ el <- fresh
479+ m1 <- inferBinder el headBinder
480+ m2 <- inferBinder val tailBinder
481+ val ~~ Array el
482+ return $ m1 `M.union` m2
483+inferBinder val (NamedBinder name binder) = do
484+ m <- inferBinder val binder
485+ return $ M.insert name val m
486+
487+checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> Subst ()
488+checkBinders _ _ [] = return ()
489+checkBinders nvals ret ((binders, grd, val):bs) = do
490+ moduleName <- substCurrentModule <$> ask
491+ m1 <- M.unions <$> zipWithM inferBinder nvals binders
492+ bindLocalVariables moduleName (M.toList m1) $ do
493+ check val ret
494+ case grd of
495+ Nothing -> return ()
496+ Just g -> check g Boolean
497+ checkBinders nvals ret bs
498+
499+assignVariable :: Ident -> Subst ()
500+assignVariable name = do
501+ env <- checkEnv <$> get
502+ moduleName <- substCurrentModule <$> ask
503+ case M.lookup (moduleName, name) (names env) of
504+ Just (_, LocalVariable) -> throwError $ "Variable with name " ++ show name ++ " already exists."
505+ _ -> return ()
506+
507+checkStatement :: M.Map Ident Type -> Type -> Statement -> Subst (Bool, M.Map Ident Type)
508+checkStatement mass _ (VariableIntroduction name val) = do
509+ assignVariable name
510+ t <- infer val
511+ return (False, M.insert name t mass)
512+checkStatement mass _ (Assignment ident val) = do
513+ t <- infer val
514+ case M.lookup ident mass of
515+ Nothing -> throwError $ "No local variable with name " ++ show ident
516+ Just ty -> do t ~~ ty
517+ return (False, mass)
518+checkStatement mass ret (While val inner) = do
519+ check val Boolean
520+ (allCodePathsReturn, _) <- checkBlock mass ret inner
521+ return (allCodePathsReturn, mass)
522+checkStatement mass ret (If ifst) = do
523+ allCodePathsReturn <- checkIfStatement mass ret ifst
524+ return (allCodePathsReturn, mass)
525+checkStatement mass ret (For ident start end inner) = do
526+ moduleName <- substCurrentModule <$> ask
527+ assignVariable ident
528+ check start Number
529+ check end Number
530+ (allCodePathsReturn, _) <- bindLocalVariables moduleName [(ident, Number)] $ checkBlock mass ret inner
531+ return (allCodePathsReturn, mass)
532+checkStatement mass ret (Return val) = do
533+ check val ret
534+ return (True, mass)
535+
536+checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> Subst Bool
537+checkIfStatement mass ret (IfStatement val thens Nothing) = do
538+ check val Boolean
539+ _ <- checkBlock mass ret thens
540+ return False
541+checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
542+ check val Boolean
543+ (allCodePathsReturn1, _) <- checkBlock mass ret thens
544+ allCodePathsReturn2 <- checkElseStatement mass ret elses
545+ return $ allCodePathsReturn1 && allCodePathsReturn2
546+
547+checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> Subst Bool
548+checkElseStatement mass ret (Else elses) = fst <$> checkBlock mass ret elses
549+checkElseStatement mass ret (ElseIf ifst) = checkIfStatement mass ret ifst
550+
551+checkBlock :: M.Map Ident Type -> Type -> [Statement] -> Subst (Bool, M.Map Ident Type)
552+checkBlock mass _ [] = return (False, mass)
553+checkBlock mass ret (s:ss) = do
554+ moduleName <- substCurrentModule <$> ask
555+ (b1, mass1) <- checkStatement mass ret s
556+ bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
557+ (True, []) -> return (True, mass1)
558+ (True, _) -> throwError "Unreachable code"
559+ (False, ss') -> checkBlock mass1 ret ss'
560+
561+skolemize :: String -> Type -> Subst Type
562+skolemize ident ty = do
563+ tsk <- Skolem <$> fresh'
564+ return $ replaceTypeVars ident tsk ty
565+
566+check :: Value -> Type -> Subst ()
567+check val ty = rethrow errorMessage $ check' val ty
568+ where
569+ errorMessage msg =
570+ "Error checking type of term " ++
571+ prettyPrintValue val ++
572+ " against type " ++
573+ prettyPrintType ty ++
574+ ":\n" ++
575+ msg
576+
577+check' :: Value -> Type -> Subst ()
578+check' val (ForAll idents ty) = do
579+ sk <- skolemize idents ty
580+ check val sk
581+check' val u@(TUnknown _) = do
582+ ty <- infer val
583+ -- Don't unify an unknown with an inferred polytype
584+ ty' <- replaceAllVarsWithUnknowns ty
585+ ty' ~~ u
586+check' (NumericLiteral _) Number = return ()
587+check' (StringLiteral _) String = return ()
588+check' (BooleanLiteral _) Boolean = return ()
589+check' (Unary op val) ty = checkUnary op val ty
590+check' (Binary op left right) ty = checkBinary op left right ty
591+check' (ArrayLiteral vals) (Array ty) = forM_ vals (\val -> check val ty)
592+check' (Indexer index vals) ty = check index Number >> check vals (Array ty)
593+check' (Abs args ret) (Function argTys retTy) = do
594+ moduleName <- substCurrentModule <$> ask
595+ guardWith "Incorrect number of function arguments" (length args == length argTys)
596+ bindLocalVariables moduleName (zip args argTys) $ check ret retTy
597+check' app@(App _ _) ret = do
598+ let (f, argss) = unfoldApplication app
599+ ft <- infer f
600+ checkFunctionApplications ft argss ret
601+check' (Var var) ty = do
602+ moduleName <- substCurrentModule <$> ask
603+ ty1 <- lookupVariable moduleName var
604+ repl <- replaceAllTypeSynonyms ty1
605+ repl `subsumes` ty
606+check' (TypedValue val ty1) ty2 = do
607+ moduleName <- substCurrentModule <$> ask
608+ kind <- liftCheck $ kindOf moduleName ty1
609+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
610+ ty1 `subsumes` ty2
611+ check val ty1
612+check' (Case vals binders) ret = do
613+ ts <- mapM infer vals
614+ checkBinders ts ret binders
615+check' (IfThenElse cond th el) ty = do
616+ check cond Boolean
617+ check th ty
618+ check el ty
619+check' (ObjectLiteral ps) (Object row) = do
620+ ensureNoDuplicateProperties ps
621+ checkProperties ps row False
622+check' (ObjectUpdate obj ps) (Object row) = do
623+ ensureNoDuplicateProperties ps
624+ us <- zip (map fst ps) <$> replicateM (length ps) fresh
625+ let (propsToCheck, rest) = rowToList row
626+ propsToRemove = map fst ps
627+ remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
628+ check obj (Object (rowFromList (us ++ remainingProps, rest)))
629+ checkProperties ps row True
630+check' (Accessor prop val) ty = do
631+ rest <- fresh
632+ check val (Object (RCons prop ty rest))
633+check' (Block ss) ret = do
634+ (allCodePathsReturn, _) <- checkBlock M.empty ret ss
635+ guardWith "Block is missing a return statement" allCodePathsReturn
636+check' (Constructor c) ty = do
637+ env <- getEnv
638+ moduleName <- substCurrentModule <$> ask
639+ case M.lookup (qualify moduleName c) (dataConstructors env) of
640+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
641+ Just (ty1, _) -> do
642+ repl <- replaceAllTypeSynonyms ty1
643+ repl `subsumes` ty
644+check' val (SaturatedTypeSynonym name args) = do
645+ ty <- expandTypeSynonym name args
646+ check val ty
647+check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
648+
649+checkProperties :: [(String, Value)] -> Type -> Bool -> Subst ()
650+checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
651+ go [] [] REmpty = return ()
652+ go [] [] u@(TUnknown _) = u ~~ REmpty
653+ go [] [] (Skolem _) | lax = return ()
654+ go [] ((p, _): _) _ | lax = return ()
655+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
656+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
657+ go ((p,v):ps') [] u@(TUnknown _) = do
658+ ty <- infer v
659+ rest <- fresh
660+ u ~~ RCons p ty rest
661+ go ps' [] rest
662+ go ((p,v):ps') ts r =
663+ case lookup p ts of
664+ Nothing -> do
665+ ty <- infer v
666+ rest <- fresh
667+ r ~~ RCons p ty rest
668+ go ps' ts rest
669+ Just ty -> do
670+ check v ty
671+ go ps' (delete (p, ty) ts) r
672+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
673+
674+unfoldApplication :: Value -> (Value, [[Value]])
675+unfoldApplication = go []
676+ where
677+ go argss (App f args) = go (args:argss) f
678+ go argss f = (f, argss)
679+
680+checkFunctionApplications :: Type -> [[Value]] -> Type -> Subst ()
681+checkFunctionApplications _ [] _ = error "Nullary function application"
682+checkFunctionApplications fnTy [args] ret = checkFunctionApplication fnTy args ret
683+checkFunctionApplications fnTy (args:argss) ret = do
684+ argTys <- mapM (infer) args
685+ f <- inferFunctionApplication fnTy argTys
686+ checkFunctionApplications f argss ret
687+
688+checkFunctionApplication :: Type -> [Value] -> Type -> Subst ()
689+checkFunctionApplication fnTy args ret = rethrow errorMessage $ checkFunctionApplication' fnTy args ret
690+ where
691+ errorMessage msg = "Error applying function of type "
692+ ++ prettyPrintType fnTy
693+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
694+ ++ ", expecting value of type "
695+ ++ prettyPrintType ret ++ ":\n" ++ msg
696+
697+inferFunctionApplication :: Type -> [Type] -> Subst Type
698+inferFunctionApplication (Function argTys retTy) args = do
699+ guardWith "Incorrect number of function arguments" (length args == length argTys)
700+ zipWithM subsumes args argTys
701+ return retTy
702+inferFunctionApplication (ForAll ident ty) args = do
703+ replaced <- replaceVarWithUnknown ident ty
704+ inferFunctionApplication replaced args
705+inferFunctionApplication u@(TUnknown _) args = do
706+
707+ ret <- fresh
708+ args' <- mapM replaceAllVarsWithUnknowns args
709+ u ~~ Function args' ret
710+ return ret
711+inferFunctionApplication (SaturatedTypeSynonym name tyArgs) args = do
712+ ty <- expandTypeSynonym name tyArgs
713+ inferFunctionApplication ty args
714+inferFunctionApplication fnTy args = throwError $ "Cannot apply function of type "
715+ ++ prettyPrintType fnTy
716+ ++ " to argument(s) of type(s) " ++ intercalate ", " (map prettyPrintType args)
717+
718+checkFunctionApplication' :: Type -> [Value] -> Type -> Subst ()
719+checkFunctionApplication' (Function argTys retTy) args ret = do
720+ guardWith "Incorrect number of function arguments" (length args == length argTys)
721+ zipWithM (check) args argTys
722+ retTy `subsumes` ret
723+checkFunctionApplication' (ForAll ident ty) args ret = do
724+ replaced <- replaceVarWithUnknown ident ty
725+ checkFunctionApplication replaced args ret
726+checkFunctionApplication' u@(TUnknown _) args ret = do
727+ tyArgs <- mapM (\arg -> infer arg >>= replaceAllVarsWithUnknowns) args
728+ u ~~ Function tyArgs ret
729+checkFunctionApplication' (SaturatedTypeSynonym name tyArgs) args ret = do
730+ ty <- expandTypeSynonym name tyArgs
731+ checkFunctionApplication' ty args ret
732+checkFunctionApplication' fnTy args ret = throwError $ "Applying a function of type "
733+ ++ prettyPrintType fnTy
734+ ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
735+ ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
736+
737+subsumes :: Type -> Type -> Subst ()
738+subsumes (ForAll ident ty1) ty2 = do
739+ replaced <- replaceVarWithUnknown ident ty1
740+ replaced `subsumes` ty2
741+subsumes (Function args1 ret1) (Function args2 ret2) = do
742+ zipWithM subsumes args2 args1
743+ ret1 `subsumes` ret2
744+subsumes ty1 ty2 = ty1 ~~ ty2
745+