@@ -1,757 +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, 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−
41−import Control.Applicative
42−import Control.Arrow (Arrow(..))
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 _ 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 ()
84− unifyRows [] (RUnknown u) sd r = replace u (rowFromList (sd, r))
85− unifyRows sd r [] (RUnknown u) = replace u (rowFromList (sd, r))
86− unifyRows ((name, ty):row) r others u@(RUnknown un) = do
87− occursCheck un ty
88− forM row $ \(_, t) -> occursCheck un t
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 sd3 r3 sd4 r4 = throwError $ "Cannot unify " ++ prettyPrintRow (rowFromList (sd3, r3)) ++ " with " ++ prettyPrintRow (rowFromList (sd4, r4)) ++ "."
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 ()
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 <- replaceVarWithUnknown 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` get
136− guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (qualify modulePath c1 == qualify modulePath c2)
137− unifyTypes' (TypeApp t3 t4) (TypeApp t5 t6) = do
138− t3 `unifyTypes` t5
139− t4 `unifyTypes` t6
140− unifyTypes' (Skolem s1) (Skolem s2) | s1 == s2 = return ()
141− unifyTypes' t3 t4 = throwError $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
142−
143−typesOf :: [(Ident, Value)] -> Check [Type]
144−typesOf vals = do
145− (tys, sub, checks) <- runSubst $ do
146− modulePath <- checkModulePath <$> get
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) -> ((modulePath, ident), (ty, LocalVariable))) $ typedDict ++ untypedDict)
154− tys <- forM es $ \e -> case e of
155− Left (_, ty, val) -> do
156− kind <- liftCheck $ kindOf 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 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− modulePath <- checkModulePath `fmap` get
257− case M.lookup (qualify modulePath 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− bindLocalVariables (zip args ts) $ do
316− body <- infer' ret
317− return $ Function ts body
318−infer' app@(App _ _) = do
319− let (f, argss) = unfoldApplication app
320− ft <- infer f
321− ret <- fresh
322− checkFunctionApplications ft argss ret
323− return ret
324−infer' (Var var) = do
325− ty <- lookupVariable var
326− replaceAllTypeSynonyms ty
327−infer' (Block ss) = do
328− ret <- fresh
329− (allCodePathsReturn, _) <- checkBlock M.empty ret ss
330− guardWith "Block is missing a return statement" allCodePathsReturn
331− return ret
332−infer' (Constructor c) = do
333− env <- getEnv
334− modulePath <- checkModulePath `fmap` get
335− case M.lookup (qualify modulePath c) (dataConstructors env) of
336− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
337− Just ty -> replaceAllTypeSynonyms ty
338−infer' (Case vals binders) = do
339− ts <- mapM infer vals
340− ret <- fresh
341− checkBinders ts ret binders
342− return ret
343−infer' (IfThenElse cond th el) = do
344− check cond Boolean
345− t2 <- infer th
346− t3 <- infer el
347− t2 ~~ t3
348− return t2
349−infer' (TypedValue val ty) = do
350− kind <- liftCheck $ kindOf ty
351− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
352− ty' <- replaceAllTypeSynonyms ty
353− check val ty'
354− return ty'
355−infer' _ = error "Invalid argument to infer"
356−
357−inferProperty :: Type -> String -> Subst (Maybe Type)
358−inferProperty (Object row) prop = do
359− let (props, _) = rowToList row
360− return $ lookup prop props
361−inferProperty (SaturatedTypeSynonym name args) prop = do
362− replaced <- expandTypeSynonym name args
363− inferProperty replaced prop
364−inferProperty (ForAll ident ty) prop = do
365− replaced <- replaceVarWithUnknown ident ty
366− inferProperty replaced prop
367−inferProperty _ _ = return Nothing
368−
369−inferUnary :: UnaryOperator -> Type -> Subst Type
370−inferUnary op val =
371− case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
372− (valTy, resTy) -> do
373− val ~~ valTy
374− return resTy
375−
376−checkUnary :: UnaryOperator -> Value -> Type -> Subst ()
377−checkUnary op val res =
378− case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
379− (valTy, resTy) -> do
380− res ~~ resTy
381− check val valTy
382−
383−unaryOps :: [(UnaryOperator, (Type, Type))]
384−unaryOps = [ (Negate, (Number, Number))
385− , (Not, (Boolean, Boolean))
386− , (BitwiseNot, (Number, Number))
387− ]
388−
389−inferBinary :: BinaryOperator -> Type -> Type -> Subst Type
390−inferBinary op left right | isEqualityTest op = do
391− left ~~ right
392− return Boolean
393−inferBinary op left right =
394− case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
395− (valTy, resTy) -> do
396− left ~~ valTy
397− right ~~ valTy
398− return resTy
399−
400−checkBinary :: BinaryOperator -> Value -> Value -> Type -> Subst ()
401−checkBinary op left right res | isEqualityTest op = do
402− res ~~ Boolean
403− t1 <- infer left
404− t2 <- infer right
405− t1 ~~ t2
406−checkBinary op left right res =
407− case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
408− (valTy, resTy) -> do
409− res ~~ resTy
410− check left valTy
411− check right valTy
412−
413−isEqualityTest :: BinaryOperator -> Bool
414−isEqualityTest EqualTo = True
415−isEqualityTest NotEqualTo = True
416−isEqualityTest _ = False
417−
418−binaryOps :: [(BinaryOperator, (Type, Type))]
419−binaryOps = [ (Add, (Number, Number))
420− , (Subtract, (Number, Number))
421− , (Multiply, (Number, Number))
422− , (Divide, (Number, Number))
423− , (Modulus, (Number, Number))
424− , (BitwiseAnd, (Number, Number))
425− , (BitwiseOr, (Number, Number))
426− , (BitwiseXor, (Number, Number))
427− , (ShiftRight, (Number, Number))
428− , (ZeroFillShiftRight, (Number, Number))
429− , (And, (Boolean, Boolean))
430− , (Or, (Boolean, Boolean))
431− , (Concat, (String, String))
432− , (Modulus, (Number, Number))
433− , (LessThan, (Number, Boolean))
434− , (LessThanOrEqualTo, (Number, Boolean))
435− , (GreaterThan, (Number, Boolean))
436− , (GreaterThanOrEqualTo, (Number, Boolean))
437− ]
438−
439−inferBinder :: Type -> Binder -> Subst (M.Map Ident Type)
440−inferBinder _ NullBinder = return M.empty
441−inferBinder val (StringBinder _) = val ~~ String >> return M.empty
442−inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
443−inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
444−inferBinder val (VarBinder name) = return $ M.singleton name val
445−inferBinder val (NullaryBinder ctor) = do
446− env <- getEnv
447− modulePath <- checkModulePath <$> get
448− case M.lookup (qualify modulePath ctor) (dataConstructors env) of
449− Just ty -> do
450− ty `subsumes` val
451− return M.empty
452− _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
453−inferBinder val (UnaryBinder ctor binder) = do
454− env <- getEnv
455− modulePath <- checkModulePath <$> get
456− case M.lookup (qualify modulePath ctor) (dataConstructors env) of
457− Just ty -> do
458− fn <- replaceAllVarsWithUnknowns ty
459− case fn of
460− Function [obj] ret -> do
461− val `subsumes` ret
462− inferBinder obj binder
463− _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
464− _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
465−inferBinder val (ObjectBinder props) = do
466− row <- fresh
467− rest <- fresh
468− m1 <- inferRowProperties row rest props
469− val ~~ Object row
470− return m1
471− where
472− inferRowProperties :: Row -> Row -> [(String, Binder)] -> Subst (M.Map Ident Type)
473− inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
474− inferRowProperties nrow row ((name, binder):binders) = do
475− propTy <- fresh
476− m1 <- inferBinder propTy binder
477− m2 <- inferRowProperties nrow (RCons name propTy row) binders
478− return $ m1 `M.union` m2
479−inferBinder val (ArrayBinder binders) = do
480− el <- fresh
481− m1 <- M.unions <$> mapM (inferBinder el) binders
482− val ~~ Array el
483− return m1
484−inferBinder val (ConsBinder headBinder tailBinder) = do
485− el <- fresh
486− m1 <- inferBinder el headBinder
487− m2 <- inferBinder val tailBinder
488− val ~~ Array el
489− return $ m1 `M.union` m2
490−inferBinder val (NamedBinder name binder) = do
491− m <- inferBinder val binder
492− return $ M.insert name val m
493−
494−checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> Subst ()
495−checkBinders _ _ [] = return ()
496−checkBinders nvals ret ((binders, grd, val):bs) = do
497− m1 <- M.unions <$> zipWithM inferBinder nvals binders
498− bindLocalVariables (M.toList m1) $ do
499− check val ret
500− case grd of
501− Nothing -> return ()
502− Just g -> check g Boolean
503− checkBinders nvals ret bs
504−
505−assignVariable :: Ident -> Subst ()
506−assignVariable name = do
507− env <- checkEnv <$> get
508− modulePath <- checkModulePath <$> get
509− case M.lookup (modulePath, name) (names env) of
510− Just (_, LocalVariable) -> throwError $ "Variable with name " ++ show name ++ " already exists."
511− _ -> return ()
512−
513−checkStatement :: M.Map Ident Type -> Type -> Statement -> Subst (Bool, M.Map Ident Type)
514−checkStatement mass _ (VariableIntroduction name val) = do
515− assignVariable name
516− t <- infer val
517− return (False, M.insert name t mass)
518−checkStatement mass _ (Assignment ident val) = do
519− t <- infer val
520− case M.lookup ident mass of
521− Nothing -> throwError $ "No local variable with name " ++ show ident
522− Just ty -> do t ~~ ty
523− return (False, mass)
524−checkStatement mass ret (While val inner) = do
525− check val Boolean
526− (allCodePathsReturn, _) <- checkBlock mass ret inner
527− return (allCodePathsReturn, mass)
528−checkStatement mass ret (If ifst) = do
529− allCodePathsReturn <- checkIfStatement mass ret ifst
530− return (allCodePathsReturn, mass)
531−checkStatement mass ret (For ident start end inner) = do
532− assignVariable ident
533− check start Number
534− check end Number
535− (allCodePathsReturn, _) <- bindLocalVariables [(ident, Number)] $ checkBlock mass ret inner
536− return (allCodePathsReturn, mass)
537−checkStatement mass ret (ForEach ident vals inner) = do
538− assignVariable ident
539− val <- fresh
540− check vals (Array val)
541− (allCodePathsReturn, _) <- bindLocalVariables [(ident, val)] $ checkBlock mass ret inner
542− guardWith "Cannot return from within a foreach block" $ not allCodePathsReturn
543− return (False, mass)
544−checkStatement mass _ (ValueStatement val) = do
545− check val unit
546− return (False, mass)
547−checkStatement mass ret (Return val) = do
548− check val ret
549− return (True, mass)
550−
551−checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> Subst Bool
552−checkIfStatement mass ret (IfStatement val thens Nothing) = do
553− check val Boolean
554− _ <- checkBlock mass ret thens
555− return False
556−checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
557− check val Boolean
558− (allCodePathsReturn1, _) <- checkBlock mass ret thens
559− allCodePathsReturn2 <- checkElseStatement mass ret elses
560− return $ allCodePathsReturn1 && allCodePathsReturn2
561−
562−checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> Subst Bool
563−checkElseStatement mass ret (Else elses) = fst <$> checkBlock mass ret elses
564−checkElseStatement mass ret (ElseIf ifst) = checkIfStatement mass ret ifst
565−
566−checkBlock :: M.Map Ident Type -> Type -> [Statement] -> Subst (Bool, M.Map Ident Type)
567−checkBlock mass _ [] = return (False, mass)
568−checkBlock mass ret (s:ss) = do
569− (b1, mass1) <- checkStatement mass ret s
570− bindLocalVariables (M.toList mass1) $ case (b1, ss) of
571− (True, []) -> return (True, mass1)
572− (True, _) -> throwError "Unreachable code"
573− (False, ss') -> checkBlock mass1 ret ss'
574−
575−skolemize :: String -> Type -> Subst Type
576−skolemize ident ty = do
577− tsk <- Skolem <$> fresh'
578− rsk <- RSkolem <$> fresh'
579− return $ replaceRowVars ident rsk $ replaceTypeVars ident tsk ty
580−
581−check :: Value -> Type -> Subst ()
582−check val ty = rethrow errorMessage $ check' val ty
583− where
584− errorMessage msg =
585− "Error checking type of term " ++
586− prettyPrintValue val ++
587− " against type " ++
588− prettyPrintType ty ++
589− ":\n" ++
590− msg
591−
592−check' :: Value -> Type -> Subst ()
593−check' val (ForAll idents ty) = do
594− sk <- skolemize idents ty
595− check val sk
596−check' val u@(TUnknown _) = do
597− ty <- infer val
598− -- Don't unify an unknown with an inferred polytype
599− ty' <- replaceAllVarsWithUnknowns ty
600− ty' ~~ u
601−check' (NumericLiteral _) Number = return ()
602−check' (StringLiteral _) String = return ()
603−check' (BooleanLiteral _) Boolean = return ()
604−check' (Unary op val) ty = checkUnary op val ty
605−check' (Binary op left right) ty = checkBinary op left right ty
606−check' (ArrayLiteral vals) (Array ty) = forM_ vals (\val -> check val ty)
607−check' (Indexer index vals) ty = check index Number >> check vals (Array ty)
608−check' (Abs args ret) (Function argTys retTy) = do
609− guardWith "Incorrect number of function arguments" (length args == length argTys)
610− bindLocalVariables (zip args argTys) $ check ret retTy
611−check' app@(App _ _) ret = do
612− let (f, argss) = unfoldApplication app
613− ft <- infer f
614− checkFunctionApplications ft argss ret
615−check' (Var var) ty = do
616− ty1 <- lookupVariable var
617− repl <- replaceAllTypeSynonyms ty1
618− repl `subsumes` ty
619−check' (TypedValue val ty1) ty2 = do
620− kind <- liftCheck $ kindOf ty1
621− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
622− ty1 `subsumes` ty2
623− check val ty1
624−check' (Case vals binders) ret = do
625− ts <- mapM infer vals
626− checkBinders ts ret binders
627−check' (IfThenElse cond th el) ty = do
628− check cond Boolean
629− check th ty
630− check el ty
631−check' (ObjectLiteral ps) (Object row) = do
632− ensureNoDuplicateProperties ps
633− checkProperties ps row False
634−check' (ObjectUpdate obj ps) (Object row) = do
635− ensureNoDuplicateProperties ps
636− us <- zip (map fst ps) <$> replicateM (length ps) fresh
637− let (propsToCheck, rest) = rowToList row
638− propsToRemove = map fst ps
639− remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
640− check obj (Object (rowFromList (us ++ remainingProps, rest)))
641− checkProperties ps row True
642−check' (Accessor prop val) ty = do
643− rest <- fresh
644− check val (Object (RCons prop ty rest))
645−check' (Block ss) ret = do
646− (allCodePathsReturn, _) <- checkBlock M.empty ret ss
647− guardWith "Block is missing a return statement" allCodePathsReturn
648−check' (Constructor c) ty = do
649− env <- getEnv
650− modulePath <- checkModulePath <$> get
651− case M.lookup (qualify modulePath c) (dataConstructors env) of
652− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
653− Just ty1 -> do
654− repl <- replaceAllTypeSynonyms ty1
655− repl `subsumes` ty
656−check' val (SaturatedTypeSynonym name args) = do
657− ty <- expandTypeSynonym name args
658− check val ty
659−check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
660−
661−checkProperties :: [(String, Value)] -> Row -> Bool -> Subst ()
662−checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
663− go [] [] REmpty = return ()
664− go [] [] u@(RUnknown _) = u ~~ REmpty
665− go [] [] (RSkolem _) | lax = return ()
666− go [] ((p, _): _) _ | lax = return ()
667− | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
668− go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
669− go ((p,v):ps') [] u@(RUnknown _) = do
670− ty <- infer v
671− rest <- fresh
672− u ~~ RCons p ty rest
673− go ps' [] rest
674− go ((p,v):ps') ts r =
675− case lookup p ts of
676− Nothing -> do
677− ty <- infer v
678− rest <- fresh
679− r ~~ RCons p ty rest
680− go ps' ts rest
681− Just ty -> do
682− check v ty
683− go ps' (delete (p, ty) ts) r
684− go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
685−
686−unfoldApplication :: Value -> (Value, [[Value]])
687−unfoldApplication = go []
688− where
689− go argss (App f args) = go (args:argss) f
690− go argss f = (f, argss)
691−
692−checkFunctionApplications :: Type -> [[Value]] -> Type -> Subst ()
693−checkFunctionApplications _ [] _ = error "Nullary function application"
694−checkFunctionApplications fnTy [args] ret = checkFunctionApplication fnTy args ret
695−checkFunctionApplications fnTy (args:argss) ret = do
696− argTys <- mapM (infer) args
697− f <- inferFunctionApplication fnTy argTys
698− checkFunctionApplications f argss ret
699−
700−checkFunctionApplication :: Type -> [Value] -> Type -> Subst ()
701−checkFunctionApplication fnTy args ret = rethrow errorMessage $ checkFunctionApplication' fnTy args ret
702− where
703− errorMessage msg = "Error applying function of type "
704− ++ prettyPrintType fnTy
705− ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
706− ++ ", expecting value of type "
707− ++ prettyPrintType ret ++ ":\n" ++ msg
708−
709−inferFunctionApplication :: Type -> [Type] -> Subst Type
710−inferFunctionApplication (Function argTys retTy) args = do
711− guardWith "Incorrect number of function arguments" (length args == length argTys)
712− zipWithM subsumes args argTys
713− return retTy
714−inferFunctionApplication (ForAll ident ty) args = do
715− replaced <- replaceVarWithUnknown ident ty
716− inferFunctionApplication replaced args
717−inferFunctionApplication u@(TUnknown _) args = do
718−
719− ret <- fresh
720− args' <- mapM replaceAllVarsWithUnknowns args
721− u ~~ Function args' ret
722− return ret
723−inferFunctionApplication (SaturatedTypeSynonym name tyArgs) args = do
724− ty <- expandTypeSynonym name tyArgs
725− inferFunctionApplication ty args
726−inferFunctionApplication fnTy args = throwError $ "Cannot apply function of type "
727− ++ prettyPrintType fnTy
728− ++ " to argument(s) of type(s) " ++ intercalate ", " (map prettyPrintType args)
729−
730−checkFunctionApplication' :: Type -> [Value] -> Type -> Subst ()
731−checkFunctionApplication' (Function argTys retTy) args ret = do
732− guardWith "Incorrect number of function arguments" (length args == length argTys)
733− zipWithM (check) args argTys
734− retTy `subsumes` ret
735−checkFunctionApplication' (ForAll ident ty) args ret = do
736− replaced <- replaceVarWithUnknown ident ty
737− checkFunctionApplication replaced args ret
738−checkFunctionApplication' u@(TUnknown _) args ret = do
739− tyArgs <- mapM (\arg -> infer arg >>= replaceAllVarsWithUnknowns) args
740− u ~~ Function tyArgs ret
741−checkFunctionApplication' (SaturatedTypeSynonym name tyArgs) args ret = do
742− ty <- expandTypeSynonym name tyArgs
743− checkFunctionApplication' ty args ret
744−checkFunctionApplication' fnTy args ret = throwError $ "Applying a function of type "
745− ++ prettyPrintType fnTy
746− ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
747− ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
748−
749−subsumes :: Type -> Type -> Subst ()
750−subsumes (ForAll ident ty1) ty2 = do
751− replaced <- replaceVarWithUnknown ident ty1
752− replaced `subsumes` ty2
753−subsumes (Function args1 ret1) (Function args2 ret2) = do
754− zipWithM subsumes args2 args1
755− ret1 `subsumes` ret2
756−subsumes ty1 ty2 = ty1 ~~ ty2
757−