@@ -1,750 +0,0 @@
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 #-}
16−
17−module Language.PureScript.TypeChecker.Types (
18− typeOf
19−) where
20−
21−import Data.List
22−import Data.Maybe (isJust, fromMaybe)
23−import Data.Function
24−import qualified Data.Data as D
25−import Data.Generics (everywhere, everywhereM, everything, everywhereBut, mkT, mkM, mkQ, extM, extQ)
26−
27−import Language.PureScript.Values
28−import Language.PureScript.Types
29−import Language.PureScript.Kinds
30−import Language.PureScript.Names
31−import Language.PureScript.TypeChecker.Monad
32−import Language.PureScript.TypeChecker.Kinds
33−import Language.PureScript.TypeChecker.Synonyms
34−import Language.PureScript.Pretty
35−import Language.PureScript.Unknown
36−
37−import Control.Monad.State
38−import Control.Monad.Error
39−
40−import Control.Applicative
41−import Control.Arrow (Arrow(..), Kleisli(..), (***), (&&&), second)
42−import qualified Control.Category as C
43−
44−import qualified Data.Map as M
45−
46−instance Unifiable Type where
47− unknown = TUnknown
48− isUnknown (TUnknown u) = Just u
49− isUnknown _ = Nothing
50− (~~) = unifyTypes
51− apply s (TUnknown u) = runSubstitution s u
52− apply s (SaturatedTypeSynonym name tys) = SaturatedTypeSynonym name $ map (apply s) tys
53− apply s (ForAll idents ty) = ForAll idents $ apply s ty
54− apply s (Array t) = Array (apply s t)
55− apply s (Object r) = Object (apply s r)
56− apply s (Function args ret) = Function (map (apply s) args) (apply s ret)
57− apply s (TypeApp t1 t2) = TypeApp (apply s t1) (apply s t2)
58− apply _ t = t
59− unknowns (TUnknown (Unknown u)) = [u]
60− unknowns (SaturatedTypeSynonym _ tys) = concatMap unknowns tys
61− unknowns (ForAll idents ty) = unknowns ty
62− unknowns (Array t) = unknowns t
63− unknowns (Object r) = unknowns r
64− unknowns (Function args ret) = concatMap unknowns args ++ unknowns ret
65− unknowns (TypeApp t1 t2) = unknowns t1 ++ unknowns t2
66− unknowns _ = []
67−
68−instance Unifiable Row where
69− unknown = RUnknown
70− isUnknown (RUnknown u) = Just u
71− isUnknown _ = Nothing
72− r1 ~~ r2 =
73− let
74− (s1, r1') = rowToList r1
75− (s2, r2') = rowToList r2
76− int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
77− sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
78− sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
79− in do
80− forM_ int (uncurry (~~))
81− unifyRows sd1 r1' sd2 r2'
82− where
83− unifyRows :: [(String, Type)] -> Row -> [(String, Type)] -> Row -> Subst Check ()
84− unifyRows [] (RUnknown u) sd r = replace u (rowFromList (sd, r))
85− unifyRows sd r [] (RUnknown u) = replace u (rowFromList (sd, r))
86− unifyRows ns@((name, ty):row) r others u@(RUnknown un) = do
87− occursCheck un ty
88− forM row $ \(_, ty) -> occursCheck un ty
89− u' <- fresh
90− u ~~ RCons name ty u'
91− unifyRows row r others u'
92− unifyRows [] REmpty [] REmpty = return ()
93− unifyRows [] (RowVar v1) [] (RowVar v2) | v1 == v2 = return ()
94− unifyRows [] (RSkolem s1) [] (RSkolem s2) | s1 == s2 = return ()
95− unifyRows sd1 r1 sd2 r2 = throwError $ "Cannot unify " ++ prettyPrintRow (rowFromList (sd1, r1)) ++ " with " ++ prettyPrintRow (rowFromList (sd2, r2)) ++ "."
96− apply s (RUnknown u) = runSubstitution s u
97− apply s (RCons name ty r) = RCons name (apply s ty) (apply s r)
98− apply _ r = r
99− unknowns (RUnknown (Unknown u)) = [u]
100− unknowns (RCons _ ty r) = unknowns ty ++ unknowns r
101− unknowns _ = []
102−
103−unifyTypes :: Type -> Type -> Subst Check ()
104−unifyTypes t1 t2 = rethrow (\e -> "Error unifying type " ++ prettyPrintType t1 ++ " with type " ++ prettyPrintType t2 ++ ":\n" ++ e) $ do
105− unifyTypes' t1 t2
106− where
107− unifyTypes' (TUnknown u1) (TUnknown u2) | u1 == u2 = return ()
108− unifyTypes' (TUnknown u) t = replace u t
109− unifyTypes' t (TUnknown u) = replace u t
110− unifyTypes' (SaturatedTypeSynonym name1 args1) (SaturatedTypeSynonym name2 args2)
111− | name1 == name2 = zipWithM_ unifyTypes args1 args2
112− unifyTypes' (SaturatedTypeSynonym name args) ty = do
113− ty1 <- expandTypeSynonym name args
114− ty1 `unifyTypes` ty
115− unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
116− unifyTypes' (ForAll ident1 ty1) (ForAll ident2 ty2) = do
117− sk <- skolemize ident1 ty1
118− replaced <- replaceVarsWithUnknowns [ident2] ty2
119− sk `unifyTypes` replaced
120− unifyTypes' (ForAll ident ty1) ty2 = do
121− sk <- skolemize ident ty1
122− sk `unifyTypes` ty2
123− unifyTypes' ty f@(ForAll _ _) = f `unifyTypes` ty
124− unifyTypes' Number Number = return ()
125− unifyTypes' String String = return ()
126− unifyTypes' Boolean Boolean = return ()
127− unifyTypes' (Array s) (Array t) = s `unifyTypes` t
128− unifyTypes' (Object row1) (Object row2) = row1 ~~ row2
129− unifyTypes' (Function args1 ret1) (Function args2 ret2) = do
130− guardWith "Function applied to incorrect number of args" $ length args1 == length args2
131− zipWithM_ unifyTypes args1 args2
132− ret1 `unifyTypes` ret2
133− unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
134− unifyTypes' (TypeConstructor c1) (TypeConstructor c2) = do
135− modulePath <- checkModulePath `fmap` lift get
136− guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (qualify modulePath c1 == qualify modulePath c2)
137− unifyTypes' (TypeApp t1 t2) (TypeApp t3 t4) = do
138− t1 `unifyTypes` t3
139− t2 `unifyTypes` t4
140− unifyTypes' (Skolem s1) (Skolem s2) | s1 == s2 = return ()
141− unifyTypes' t1 t2 = throwError $ "Cannot unify " ++ prettyPrintType t1 ++ " with " ++ prettyPrintType t2 ++ "."
142−
143−isFunction :: Value -> Bool
144−isFunction (Abs _ _) = True
145−isFunction (TypedValue untyped _) = isFunction untyped
146−isFunction _ = False
147−
148−-- TODO: check skolems don't escape
149−typeOf :: Maybe Ident -> Value -> Check Type
150−typeOf name val = do
151− (ty, sub, checks) <- runSubst $ case name of
152− Just ident | isFunction val ->
153− case val of
154− TypedValue val ty -> do
155− kind <- lift $ kindOf ty
156− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
157− ty' <- lift $ replaceAllTypeSynonyms ty
158− check (M.singleton ident ty) val ty'
159− return ty'
160− _ -> do
161− me <- fresh
162− ty <- infer (M.singleton ident me) val
163− ty ~~ me
164− return ty
165− _ -> infer M.empty val
166− escapeCheck checks ty sub
167− return $ varIfUnknown $ desaturateAllTypeSynonyms $ setifyAll ty
168−
169−escapeCheck :: [AnyUnifiable] -> Type -> Substitution -> Check ()
170−escapeCheck checks ty sub =
171− let
172− visibleUnknowns = nub $ unknowns ty
173− in
174− forM_ checks $ \check -> case check of
175− AnyUnifiable t -> do
176− let unsolvedUnknowns = nub . unknowns $ apply sub t
177− guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
178−
179−setify :: Row -> Row
180−setify = rowFromList . first (M.toList . M.fromList) . rowToList
181−
182−setifyAll :: (D.Data d) => d -> d
183−setifyAll = everywhere (mkT setify)
184−
185−varIfUnknown :: Type -> Type
186−varIfUnknown ty = mkForAll (sort . map ((:) 'u' . show) . nub $ unknowns ty) ty
187−
188−replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
189−replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
190−
191−replaceTypeVars :: (D.Data d) => String -> Type -> d -> d
192−replaceTypeVars name t = everywhereBut (mkQ False isShadowed) (mkT replace)
193− where
194− replace (TypeVar v) | v == name = t
195− replace t = t
196− isShadowed (ForAll v _) | v == name = True
197− isShadowed _ = False
198−
199−replaceRowVars :: (D.Data d) => String -> Row -> d -> d
200−replaceRowVars name r = everywhere (mkT replace)
201− where
202− replace (RowVar v) | v == name = r
203− replace t = t
204−
205−replaceAllVarsWithUnknowns :: Type -> Subst Check Type
206−replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarsWithUnknowns [ident] ty >>= replaceAllVarsWithUnknowns
207−replaceAllVarsWithUnknowns ty = return ty
208−
209−replaceVarsWithUnknowns :: [String] -> Type -> Subst Check Type
210−replaceVarsWithUnknowns idents = flip evalStateT M.empty . everywhereM (flip extM f $ mkM g)
211− where
212− f :: Type -> StateT (M.Map String Int) (Subst Check) Type
213− f (TypeVar var) | var `elem` idents = do
214− m <- get
215− n <- lift fresh'
216− case M.lookup var m of
217− Nothing -> do
218− put (M.insert var n m)
219− return $ TUnknown (Unknown n)
220− Just u -> return $ TUnknown (Unknown u)
221− f t = return t
222− g :: Row -> StateT (M.Map String Int) (Subst Check) Row
223− g (RowVar var) | var `elem` idents = do
224− m <- get
225− n <- lift fresh'
226− case M.lookup var m of
227− Nothing -> do
228− put (M.insert var n m)
229− return $ RUnknown (Unknown n)
230− Just u -> return $ RUnknown (Unknown u)
231− g r = return r
232−
233−replaceAllTypeSynonyms :: (D.Data d) => d -> Check d
234−replaceAllTypeSynonyms d = do
235− env <- getEnv
236− let syns = map (\((path, name), (args, _)) -> (Qualified path name, length args)) . M.toList $ typeSynonyms env
237− either throwError return $ saturateAllTypeSynonyms syns d
238−
239−desaturateAllTypeSynonyms :: (D.Data d) => d -> d
240−desaturateAllTypeSynonyms = everywhere (mkT replace)
241− where
242− replace (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
243− replace t = t
244−
245−expandAllTypeSynonyms :: Type -> Subst Check Type
246−expandAllTypeSynonyms (SaturatedTypeSynonym name args) = expandTypeSynonym name args >>= expandAllTypeSynonyms
247−expandAllTypeSynonyms ty = return ty
248−
249−expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Check Type
250−expandTypeSynonym name args = do
251− env <- lift getEnv
252− modulePath <- checkModulePath `fmap` lift get
253− case M.lookup (qualify modulePath name) (typeSynonyms env) of
254− Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
255− Nothing -> error "Type synonym was not defined"
256−
257−ensureNoDuplicateProperties :: [(String, Value)] -> Check ()
258−ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
259−
260−infer :: M.Map Ident Type -> Value -> Subst Check Type
261−infer m val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ do
262− ty <- infer' m val
263− escapeCheckLater ty
264− return ty
265−
266−infer' _ (NumericLiteral _) = return Number
267−infer' _ (StringLiteral _) = return String
268−infer' _ (BooleanLiteral _) = return Boolean
269−infer' m (ArrayLiteral vals) = do
270− ts <- mapM (infer m) vals
271− arr <- fresh
272− forM_ ts $ \t -> arr ~~ Array t
273− return arr
274−infer' m (Unary op val) = do
275− t <- infer m val
276− inferUnary op t
277−infer' m (Binary op left right) = do
278− t1 <- infer m left
279− t2 <- infer m right
280− inferBinary op t1 t2
281−infer' m (ObjectLiteral ps) = do
282− lift $ ensureNoDuplicateProperties ps
283− ts <- mapM (infer m . snd) ps
284− let fields = zipWith (\(name, _) t -> (name, t)) ps ts
285− return $ Object $ typesToRow fields
286−infer' m (ObjectUpdate o ps) = do
287− lift $ ensureNoDuplicateProperties ps
288− obj <- infer m o
289− row <- fresh
290− ts <- mapM (infer m . snd) ps
291− let tys = zipWith (\(name, _) t -> (name, t)) ps ts
292− obj ~~ Object (rowFromList (tys, row))
293− return obj
294−infer' m (Indexer index val) = do
295− el <- fresh
296− check m index Number
297− check m val (Array el)
298− return el
299−infer' m (Accessor prop val) = do
300− obj <- infer m val
301− propTy <- inferProperty obj prop
302− case propTy of
303− Nothing -> do
304− field <- fresh
305− rest <- fresh
306− obj `subsumes` Object (RCons prop field rest)
307− return field
308− Just ty -> return ty
309−infer' m (Abs args ret) = do
310− ts <- replicateM (length args) fresh
311− let m' = m `M.union` M.fromList (zip args ts)
312− body <- infer m' ret
313− return $ Function ts body
314−infer' m app@(App _ _) = do
315− let (f, argss) = unfoldApplication app
316− ft <- infer m f
317− ret <- fresh
318− checkFunctionApplications m ft argss ret
319− return ret
320−infer' m (Var var@(Qualified mp name)) = do
321− case mp of
322− ModulePath [] ->
323− case M.lookup name m of
324− Just ty -> lift $ replaceAllTypeSynonyms ty
325− Nothing -> lookupGlobal
326− _ -> lookupGlobal
327− where
328− lookupGlobal = do
329− env <- lift getEnv
330− modulePath <- checkModulePath `fmap` lift get
331− case M.lookup (qualify modulePath var) (names env) of
332− Nothing -> throwError $ show var ++ " is undefined"
333− Just (ty, _) -> lift $ replaceAllTypeSynonyms ty
334−infer' m (Block ss) = do
335− ret <- fresh
336− (allCodePathsReturn, _) <- checkBlock m M.empty ret ss
337− guardWith "Block is missing a return statement" allCodePathsReturn
338− return ret
339−infer' m (Constructor c) = do
340− env <- lift getEnv
341− modulePath <- checkModulePath `fmap` lift get
342− case M.lookup (qualify modulePath c) (dataConstructors env) of
343− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
344− Just ty -> lift $ replaceAllTypeSynonyms ty
345−infer' m (Case val binders) = do
346− t1 <- infer m val
347− ret <- fresh
348− checkBinders m t1 ret binders
349− return ret
350−infer' m (IfThenElse cond th el) = do
351− check m cond Boolean
352− t2 <- infer m th
353− t3 <- infer m el
354− t2 ~~ t3
355− return t2
356−infer' m (TypedValue val ty) = do
357− kind <- lift $ kindOf ty
358− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
359− ty' <- lift $ replaceAllTypeSynonyms ty
360− check m val ty'
361− return ty'
362−
363−inferProperty :: Type -> String -> Subst Check (Maybe Type)
364−inferProperty (Object row) prop = do
365− let (props, _) = rowToList row
366− return $ lookup prop props
367−inferProperty (SaturatedTypeSynonym name args) prop = do
368− replaced <- expandTypeSynonym name args
369− inferProperty replaced prop
370−inferProperty (ForAll ident ty) prop = do
371− replaced <- replaceVarsWithUnknowns [ident] ty
372− inferProperty replaced prop
373−inferProperty _ prop = return Nothing
374−
375−inferUnary :: UnaryOperator -> Type -> Subst Check Type
376−inferUnary op val =
377− case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
378− (valTy, resTy) -> do
379− val ~~ valTy
380− return resTy
381−
382−checkUnary :: M.Map Ident Type -> UnaryOperator -> Value -> Type -> Subst Check ()
383−checkUnary m op val res =
384− case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
385− (valTy, resTy) -> do
386− res ~~ resTy
387− check m val valTy
388−
389−unaryOps :: [(UnaryOperator, (Type, Type))]
390−unaryOps = [ (Negate, (Number, Number))
391− , (Not, (Boolean, Boolean))
392− , (BitwiseNot, (Number, Number))
393− ]
394−
395−inferBinary :: BinaryOperator -> Type -> Type -> Subst Check Type
396−inferBinary op left right | isEqualityTest op = do
397− left ~~ right
398− return Boolean
399−inferBinary op left right =
400− case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
401− (valTy, resTy) -> do
402− left ~~ valTy
403− right ~~ valTy
404− return resTy
405−
406−checkBinary :: M.Map Ident Type -> BinaryOperator -> Value -> Value -> Type -> Subst Check ()
407−checkBinary m op left right res | isEqualityTest op = do
408− res ~~ Boolean
409− t1 <- infer m left
410− t2 <- infer m right
411− t1 ~~ t2
412−checkBinary m op left right res =
413− case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
414− (valTy, resTy) -> do
415− res ~~ resTy
416− check m left valTy
417− check m right valTy
418−
419−isEqualityTest :: BinaryOperator -> Bool
420−isEqualityTest EqualTo = True
421−isEqualityTest NotEqualTo = True
422−isEqualityTest _ = False
423−
424−binaryOps :: [(BinaryOperator, (Type, Type))]
425−binaryOps = [ (Add, (Number, Number))
426− , (Subtract, (Number, Number))
427− , (Multiply, (Number, Number))
428− , (Divide, (Number, Number))
429− , (Modulus, (Number, Number))
430− , (BitwiseAnd, (Number, Number))
431− , (BitwiseOr, (Number, Number))
432− , (BitwiseXor, (Number, Number))
433− , (ShiftRight, (Number, Number))
434− , (ZeroFillShiftRight, (Number, Number))
435− , (And, (Boolean, Boolean))
436− , (Or, (Boolean, Boolean))
437− , (Concat, (String, String))
438− , (Modulus, (Number, Number))
439− , (LessThan, (Number, Boolean))
440− , (LessThanOrEqualTo, (Number, Boolean))
441− , (GreaterThan, (Number, Boolean))
442− , (GreaterThanOrEqualTo, (Number, Boolean))
443− ]
444−
445−inferBinder :: Type -> Binder -> Subst Check (M.Map Ident Type)
446−inferBinder _ NullBinder = return M.empty
447−inferBinder val (StringBinder _) = val ~~ String >> return M.empty
448−inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
449−inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
450−inferBinder val (VarBinder name) = return $ M.singleton name val
451−inferBinder val (NullaryBinder ctor) = do
452− env <- lift getEnv
453− modulePath <- checkModulePath `fmap` lift get
454− case M.lookup (qualify modulePath ctor) (dataConstructors env) of
455− Just ty -> do
456− ty `subsumes` val
457− return M.empty
458− _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
459−inferBinder val (UnaryBinder ctor binder) = do
460− env <- lift getEnv
461− modulePath <- checkModulePath `fmap` lift get
462− case M.lookup (qualify modulePath ctor) (dataConstructors env) of
463− Just ty -> do
464− obj <- fresh
465− ty `subsumes` (Function [obj] val)
466− inferBinder obj binder
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 Check (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 rest) = do
483− el <- fresh
484− m1 <- M.unions <$> mapM (inferBinder el) binders
485− val ~~ Array el
486− case rest of
487− Nothing -> return m1
488− Just binder -> do
489− m2 <- inferBinder val binder
490− return $ m1 `M.union` m2
491−inferBinder val (NamedBinder name binder) = do
492− m <- inferBinder val binder
493− return $ M.insert name val m
494−
495−inferGuardedBinder :: M.Map Ident Type -> Type -> Binder -> Subst Check (M.Map Ident Type)
496−inferGuardedBinder m val (GuardedBinder cond binder) = do
497− m1 <- inferBinder val binder
498− check (m1 `M.union` m) cond Boolean
499− return m1
500−inferGuardedBinder m val b = inferBinder val b
501−
502−checkBinders :: M.Map Ident Type -> Type -> Type -> [(Binder, Value)] -> Subst Check ()
503−checkBinders _ _ _ [] = return ()
504−checkBinders m nval ret ((binder, val):bs) = do
505− m1 <- inferGuardedBinder m nval binder
506− check (m1 `M.union` m) val ret
507− checkBinders m nval ret bs
508−
509−assignVariable :: Ident -> M.Map Ident Type -> Subst Check ()
510−assignVariable name m =
511− case M.lookup name m of
512− Nothing -> return ()
513− Just _ -> throwError $ "Variable with name " ++ show name ++ " already exists."
514−
515−checkStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> Statement -> Subst Check (Bool, M.Map Ident Type)
516−checkStatement m mass ret (VariableIntroduction name val) = do
517− assignVariable name (m `M.union` mass)
518− t <- infer m val
519− return (False, M.insert name t mass)
520−checkStatement m mass ret (Assignment ident val) = do
521− t <- infer m val
522− case M.lookup ident mass of
523− Nothing -> throwError $ "No local variable with name " ++ show ident
524− Just ty -> do t ~~ ty
525− return (False, mass)
526−checkStatement m mass ret (While val inner) = do
527− check m val Boolean
528− (allCodePathsReturn, _) <- checkBlock m mass ret inner
529− return (allCodePathsReturn, mass)
530−checkStatement m mass ret (If ifst) = do
531− allCodePathsReturn <- checkIfStatement m mass ret ifst
532− return (allCodePathsReturn, mass)
533−checkStatement m mass ret (For ident start end inner) = do
534− assignVariable ident (m `M.union` mass)
535− check (m `M.union` mass) start Number
536− check (m `M.union` mass) end Number
537− let mass1 = M.insert ident Number mass
538− (allCodePathsReturn, _) <- checkBlock (m `M.union` mass1) mass1 ret inner
539− return (allCodePathsReturn, mass)
540−checkStatement m mass ret (ForEach ident vals inner) = do
541− assignVariable ident (m `M.union` mass)
542− val <- fresh
543− check (m `M.union` mass) vals (Array val)
544− let mass1 = M.insert ident val mass
545− (allCodePathsReturn, _) <- checkBlock (m `M.union` mass1) mass1 ret inner
546− guardWith "Cannot return from within a foreach block" $ not allCodePathsReturn
547− return (False, mass)
548−checkStatement m mass ret (Return val) = do
549− check (m `M.union` mass) val ret
550− return (True, mass)
551−
552−checkIfStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> IfStatement -> Subst Check Bool
553−checkIfStatement m mass ret (IfStatement val thens Nothing) = do
554− check m val Boolean
555− _ <- checkBlock m mass ret thens
556− return False
557−checkIfStatement m mass ret (IfStatement val thens (Just elses)) = do
558− check m val Boolean
559− (allCodePathsReturn1, _) <- checkBlock m mass ret thens
560− allCodePathsReturn2 <- checkElseStatement m mass ret elses
561− return $ allCodePathsReturn1 && allCodePathsReturn2
562−
563−checkElseStatement :: M.Map Ident Type -> M.Map Ident Type -> Type -> ElseStatement -> Subst Check Bool
564−checkElseStatement m mass ret (Else elses) = fst <$> checkBlock m mass ret elses
565−checkElseStatement m mass ret (ElseIf ifst) = checkIfStatement m mass ret ifst
566−
567−checkBlock :: M.Map Ident Type -> M.Map Ident Type -> Type -> [Statement] -> Subst Check (Bool, M.Map Ident Type)
568−checkBlock _ mass _ [] = return (False, mass)
569−checkBlock m mass ret (s:ss) = do
570− (b1, mass1) <- checkStatement (m `M.union` mass) mass ret s
571− case (b1, ss) of
572− (True, []) -> return (True, mass1)
573− (True, _) -> throwError "Unreachable code"
574− (False, ss) -> do
575− (b2, mass2) <- checkBlock m mass1 ret ss
576− return (b2, mass2)
577−
578−skolemize :: String -> Type -> Subst Check Type
579−skolemize ident ty = do
580− tsk <- Skolem <$> fresh'
581− rsk <- RSkolem <$> fresh'
582− return $ replaceRowVars ident rsk $ replaceTypeVars ident tsk ty
583−
584−check :: M.Map Ident Type -> Value -> Type -> Subst Check ()
585−check m val ty = rethrow errorMessage $ check' m val ty
586− where
587− errorMessage msg =
588− "Error checking type of term " ++
589− prettyPrintValue val ++
590− " against type " ++
591− prettyPrintType ty ++
592− ":\n" ++
593− msg
594−
595−check' :: M.Map Ident Type -> Value -> Type -> Subst Check ()
596−check' m val (ForAll idents ty) = do
597− sk <- skolemize idents ty
598− check m val sk
599−check' m val u@(TUnknown _) = do
600− ty <- infer m val
601− -- Don't unify an unknown with an inferred polytype
602− ty' <- replaceAllVarsWithUnknowns ty
603− ty' ~~ u
604−check' m (NumericLiteral _) Number = return ()
605−check' m (StringLiteral _) String = return ()
606−check' m (BooleanLiteral _) Boolean = return ()
607−check' m (Unary op val) ty = checkUnary m op val ty
608−check' m (Binary op left right) ty = checkBinary m op left right ty
609−check' m (ArrayLiteral vals) (Array ty) = forM_ vals (\val -> check m val ty)
610−check' m (Indexer index vals) ty = check m index Number >> check m vals (Array ty)
611−check' m (Abs args ret) (Function argTys retTy) = do
612− guardWith "Incorrect number of function arguments" (length args == length argTys)
613− let bindings = M.fromList (zip args argTys)
614− check (bindings `M.union` m) ret retTy
615−check' m app@(App _ _) ret = do
616− let (f, argss) = unfoldApplication app
617− ft <- infer m f
618− checkFunctionApplications m ft argss ret
619−check' m v@(Var var@(Qualified mp name)) ty = do
620− case mp of
621− ModulePath [] ->
622− case M.lookup name m of
623− Just ty1 -> do
624− repl <- lift $ replaceAllTypeSynonyms ty1
625− repl `subsumes` ty
626− Nothing -> lookupGlobal
627− _ -> lookupGlobal
628− where
629− lookupGlobal = do
630− env <- lift getEnv
631− modulePath <- checkModulePath `fmap` lift get
632− case M.lookup (qualify modulePath var) (names env) of
633− Nothing -> throwError $ show var ++ " is undefined"
634− Just (ty1, _) -> do
635− repl <- lift $ replaceAllTypeSynonyms ty1
636− repl `subsumes` ty
637−check' m (TypedValue val ty1) ty2 = do
638− kind <- lift $ kindOf ty1
639− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
640− ty1 `subsumes` ty2
641− check m val ty1
642−check' m (Case val binders) ret = do
643− t1 <- infer m val
644− checkBinders m t1 ret binders
645−check' m (IfThenElse cond th el) ty = do
646− check m cond Boolean
647− check m th ty
648− check m el ty
649−check' m (ObjectLiteral ps) (Object row) = do
650− lift $ ensureNoDuplicateProperties ps
651− checkProperties m ps row False
652−check' m (ObjectUpdate obj ps) objTy@(Object row) = do
653− lift $ ensureNoDuplicateProperties ps
654− check m obj objTy
655− checkProperties m ps row True
656−check' m (Accessor prop val) ty = do
657− rest <- fresh
658− check m val (Object (RCons prop ty rest))
659−check' m (Block ss) ret = do
660− (allCodePathsReturn, _) <- checkBlock m M.empty ret ss
661− guardWith "Block is missing a return statement" allCodePathsReturn
662−check' m (Constructor c) ty = do
663− env <- lift getEnv
664− modulePath <- checkModulePath `fmap` lift get
665− case M.lookup (qualify modulePath c) (dataConstructors env) of
666− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
667− Just ty1 -> do
668− repl <- lift $ replaceAllTypeSynonyms ty1
669− repl `subsumes` ty
670−check' m val (SaturatedTypeSynonym name args) = do
671− ty <- expandTypeSynonym name args
672− check m val ty
673−check' _ val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
674−
675−checkProperties :: M.Map Ident Type -> [(String, Value)] -> Row -> Bool -> Subst Check ()
676−checkProperties m ps row lax = let (ts, r') = rowToList row in go ps ts r' where
677− go [] [] REmpty = return ()
678− go [] [] u@(RUnknown _) = u ~~ REmpty
679− go [] [] (RSkolem _) | lax = return ()
680− go [] ((p, _): _) _ | lax = return ()
681− | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
682− go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
683− go ((p,v):ps) [] u@(RUnknown _) = do
684− ty <- infer m v
685− rest <- fresh
686− u ~~ RCons p ty rest
687− go ps [] rest
688− go ((p,v):ps) ts r =
689− case lookup p ts of
690− Nothing -> do
691− ty <- infer m v
692− rest <- fresh
693− r ~~ RCons p ty rest
694− go ps ts rest
695− Just ty -> do
696− check m v ty
697− go ps (delete (p, ty) ts) r
698− go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
699−
700−unfoldApplication :: Value -> (Value, [[Value]])
701−unfoldApplication = go []
702− where
703− go argss (App f args) = go (args:argss) f
704− go argss f = (f, argss)
705−
706−checkFunctionApplications :: M.Map Ident Type -> Type -> [[Value]] -> Type -> Subst Check ()
707−checkFunctionApplications _ _ [] _ = error "Nullary function application"
708−checkFunctionApplications m fnTy [args] ret = checkFunctionApplication m fnTy args ret
709−checkFunctionApplications m fnTy (args:argss) ret = do
710− f <- fresh
711− checkFunctionApplication m fnTy args f
712− checkFunctionApplications m f argss ret
713−
714−checkFunctionApplication :: M.Map Ident Type -> Type -> [Value] -> Type -> Subst Check ()
715−checkFunctionApplication m fnTy args ret = rethrow errorMessage $ checkFunctionApplication' m fnTy args ret
716− where
717− errorMessage msg = "Error applying function of type "
718− ++ prettyPrintType fnTy
719− ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
720− ++ ", expecting value of type "
721− ++ prettyPrintType ret ++ ":\n" ++ msg
722−
723−checkFunctionApplication' :: M.Map Ident Type -> Type -> [Value] -> Type -> Subst Check ()
724−checkFunctionApplication' m (Function argTys retTy) args ret = do
725− guardWith "Incorrect number of function arguments" (length args == length argTys)
726− zipWithM (check m) args argTys
727− retTy `subsumes` ret
728−checkFunctionApplication' m (ForAll ident ty) args ret = do
729− replaced <- replaceVarsWithUnknowns [ident] ty
730− checkFunctionApplication m replaced args ret
731−checkFunctionApplication' m u@(TUnknown _) args ret = do
732− tyArgs <- mapM (\arg -> infer m arg >>= replaceAllVarsWithUnknowns) args
733− u ~~ Function tyArgs ret
734−checkFunctionApplication' m (SaturatedTypeSynonym name tyArgs) args ret = do
735− ty <- expandTypeSynonym name tyArgs
736− checkFunctionApplication' m ty args ret
737−checkFunctionApplication' _ fnTy args ret = throwError $ "Cannot apply function of type "
738− ++ prettyPrintType fnTy
739− ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
740− ++ ". Expecting value of type " ++ prettyPrintType ret ++ "."
741−
742−subsumes :: Type -> Type -> Subst Check ()
743−subsumes (ForAll ident ty1) ty2 = do
744− replaced <- replaceVarsWithUnknowns [ident] ty1
745− replaced `subsumes` ty2
746−subsumes (Function args1 ret1) (Function args2 ret2) = do
747− zipWithM subsumes args2 args1
748− ret1 `subsumes` ret2
749−subsumes ty1 ty2 = ty1 ~~ ty2
750−