@@ -0,0 +1,753 @@
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 (isNothing, isJust, fromMaybe)
24+import qualified Data.Data as D
25+import Data.Generics
26+ (mkT, something, everywhere, mkQ)
27+
28+import Language.PureScript.Values
29+import Language.PureScript.Types
30+import Language.PureScript.Kinds
31+import Language.PureScript.Names
32+import Language.PureScript.TypeChecker.Monad
33+import Language.PureScript.TypeChecker.Kinds
34+import Language.PureScript.TypeChecker.Synonyms
35+import Language.PureScript.Pretty
36+import Language.PureScript.Unknown
37+
38+import Control.Monad.State
39+import Control.Monad.Error
40+import Control.Monad.Reader
41+
42+import Control.Applicative
43+import Control.Arrow (Arrow(..))
44+
45+import qualified Data.Map as M
46+import Data.Function (on)
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 name args) ty = do
80+ ty1 <- expandTypeSynonym name args
81+ ty1 `unifyTypes` ty
82+ unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
83+ unifyTypes' (ForAll ident1 ty1) (ForAll ident2 ty2) = do
84+ sk <- skolemize ident1 ty1
85+ replaced <- replaceVarWithUnknown ident2 ty2
86+ sk `unifyTypes` replaced
87+ unifyTypes' (ForAll ident ty1) ty2 = do
88+ sk <- skolemize ident ty1
89+ sk `unifyTypes` ty2
90+ unifyTypes' ty f@(ForAll _ _) = f `unifyTypes` ty
91+ unifyTypes' Number Number = return ()
92+ unifyTypes' String String = return ()
93+ unifyTypes' Boolean Boolean = return ()
94+ unifyTypes' (Array s) (Array t) = s `unifyTypes` t
95+ unifyTypes' (Object row1) (Object row2) = row1 ~~ row2
96+ unifyTypes' (Function args1 ret1) (Function args2 ret2) = do
97+ guardWith "Function applied to incorrect number of args" $ length args1 == length args2
98+ zipWithM_ unifyTypes args1 args2
99+ ret1 `unifyTypes` ret2
100+ unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
101+ unifyTypes' (TypeConstructor c1) (TypeConstructor c2) = do
102+ env <- getEnv
103+ moduleName <- substCurrentModule `fmap` ask
104+ guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (typeConstructorsAreEqual env moduleName c1 c2)
105+ unifyTypes' (TypeApp t3 t4) (TypeApp t5 t6) = do
106+ t3 `unifyTypes` t5
107+ t4 `unifyTypes` t6
108+ unifyTypes' (Skolem s1) (Skolem s2) | s1 == s2 = return ()
109+ unifyTypes' r1@(RCons _ _ _) r2 = unifyRows r1 r2
110+ unifyTypes' r1 r2@(RCons _ _ _) = unifyRows r1 r2
111+ unifyTypes' r1@REmpty r2 = unifyRows r1 r2
112+ unifyTypes' r1 r2@REmpty = unifyRows r1 r2
113+ unifyTypes' t3 t4 = throwError $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
114+
115+unifyRows :: Type -> Type -> Subst ()
116+unifyRows r1 r2 =
117+ let
118+ (s1, r1') = rowToList r1
119+ (s2, r2') = rowToList r2
120+ int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
121+ sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
122+ sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
123+ in do
124+ forM_ int (uncurry (~~))
125+ unifyRows' sd1 r1' sd2 r2'
126+ where
127+ unifyRows' :: [(String, Type)] -> Type -> [(String, Type)] -> Type -> Subst ()
128+ unifyRows' [] (TUnknown u) sd r = replace u (rowFromList (sd, r))
129+ unifyRows' sd r [] (TUnknown u) = replace u (rowFromList (sd, r))
130+ unifyRows' ((name, ty):row) r others u@(TUnknown un) = do
131+ occursCheck un ty
132+ forM row $ \(_, t) -> occursCheck un t
133+ u' <- fresh
134+ u ~~ RCons name ty u'
135+ unifyRows' row r others u'
136+ unifyRows' [] REmpty [] REmpty = return ()
137+ unifyRows' [] (TypeVar v1) [] (TypeVar v2) | v1 == v2 = return ()
138+ unifyRows' [] (Skolem s1) [] (Skolem s2) | s1 == s2 = return ()
139+ unifyRows' sd3 r3 sd4 r4 = throwError $ "Cannot unify " ++ prettyPrintRow (rowFromList (sd3, r3)) ++ " with " ++ prettyPrintRow (rowFromList (sd4, r4)) ++ "."
140+
141+typeConstructorsAreEqual :: Environment -> ModuleName -> Qualified ProperName -> Qualified ProperName -> Bool
142+typeConstructorsAreEqual env moduleName = (==) `on` canonicalizeType moduleName env
143+
144+typesOf :: ModuleName -> [(Ident, Value)] -> Check [Type]
145+typesOf moduleName vals = do
146+ (tys, sub) <- runSubst (SubstContext moduleName) $ do
147+ let es = map isTyped vals
148+ typed = filter (isJust . snd . snd) es
149+ untyped = filter (isNothing . snd . snd) es
150+ typedDict = map (\(ident, (_, Just ty)) -> (ident, ty)) typed
151+ untypedNames <- replicateM (length untyped) fresh
152+ let untypedDict = zip (map fst untyped) untypedNames
153+ dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ typedDict ++ untypedDict)
154+ tys <- forM es $ \e -> do
155+ ty <- case e of
156+ (_, (val, Just ty)) -> 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+ (ident, (val, Nothing)) -> do
163+ TypedValue _ ty <- bindNames dict $ infer val
164+ ty ~~ fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
165+ return ty
166+ when (moduleName == ModuleName (ProperName "Main") && fst e == Ident "main") $ do
167+ [eff, a] <- replicateM 2 fresh
168+ ty ~~ TypeApp (TypeApp (TypeConstructor (Qualified (Just (ModuleName (ProperName "Eff"))) (ProperName "Eff"))) eff) a
169+ return ty
170+ return tys
171+ --forM tys $ flip (escapeCheck checks) sub
172+ forM tys $ skolemEscapeCheck
173+ return $ map (varIfUnknown . desaturateAllTypeSynonyms . setifyAll) tys
174+
175+isTyped :: (Ident, Value) -> (Ident, (Value, Maybe Type))
176+isTyped (name, TypedValue value ty) = (name, (value, Just ty))
177+isTyped (name, value) = (name, (value, Nothing))
178+
179+{-escapeCheck :: [AnyUnifiable] -> Type -> Substitution -> Check ()
180+escapeCheck checks ty sub =
181+ let
182+ visibleUnknowns = nub $ unknowns ty
183+ in
184+ forM_ checks $ \c -> case c of
185+ AnyUnifiable t -> do
186+ let unsolvedUnknowns = nub . unknowns $ apply sub t
187+ guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
188+-}
189+
190+skolemEscapeCheck :: Type -> Check ()
191+skolemEscapeCheck ty =
192+ case something (mkQ Nothing findSkolems) ty of
193+ Nothing -> return ()
194+ Just _ -> throwError "Skolem variables cannot escape. Consider adding a type signature."
195+ where
196+ findSkolems (Skolem _) = return ()
197+ findSkolems _ = mzero
198+
199+setify :: Type -> Type
200+setify = rowFromList . first (M.toList . M.fromList) . rowToList
201+
202+setifyAll :: (D.Data d) => d -> d
203+setifyAll = everywhere (mkT setify)
204+
205+varIfUnknown :: Type -> Type
206+varIfUnknown ty =
207+ let unks = nub $ unknowns ty
208+ toName = (:) 't' . show
209+ ty' = everywhere (mkT typeToVar) $ ty
210+ typeToVar :: Type -> Type
211+ typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
212+ typeToVar t = t
213+ in mkForAll (sort . map toName $ unks) ty'
214+
215+replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
216+replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
217+
218+replaceAllVarsWithUnknowns :: Type -> Subst Type
219+replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
220+replaceAllVarsWithUnknowns ty = return ty
221+
222+replaceVarWithUnknown :: String -> Type -> Subst Type
223+replaceVarWithUnknown ident ty = do
224+ tu <- fresh
225+ return $ replaceTypeVars ident tu $ ty
226+
227+replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadReader SubstContext m, MonadError String m) => (D.Data d) => d -> m d
228+replaceAllTypeSynonyms d = do
229+ env <- getEnv
230+ moduleName <- substCurrentModule <$> ask
231+ let syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
232+ either throwError return $ saturateAllTypeSynonyms env moduleName syns d
233+
234+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
235+desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
236+ where
237+ replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
238+ replaceSaturatedTypeSynonym t = t
239+
240+expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Type
241+expandTypeSynonym name args = do
242+ env <- getEnv
243+ moduleName <- substCurrentModule `fmap` ask
244+ case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
245+ Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
246+ Nothing -> error "Type synonym was not defined"
247+
248+ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
249+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
250+
251+infer :: Value -> Subst Value
252+infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ infer' val
253+
254+infer' :: Value -> Subst Value
255+infer' v@(NumericLiteral _) = return $ TypedValue v Number
256+infer' v@(StringLiteral _) = return $ TypedValue v String
257+infer' v@(BooleanLiteral _) = return $ TypedValue v Boolean
258+infer' (ArrayLiteral vals) = do
259+ ts <- mapM infer vals
260+ els <- fresh
261+ forM_ ts $ \(TypedValue _ t) -> els ~~ Array t
262+ return $ TypedValue (ArrayLiteral ts) els
263+infer' (Unary op val) = do
264+ v <- infer val
265+ inferUnary op v
266+infer' (Binary op left right) = do
267+ v1 <- infer left
268+ v2 <- infer right
269+ inferBinary op v1 v2
270+infer' (ObjectLiteral ps) = do
271+ ensureNoDuplicateProperties ps
272+ ts <- mapM (infer . snd) ps
273+ let fields = zipWith (\name (TypedValue _ t) -> (name, t)) (map fst ps) ts
274+ ty = Object $ rowFromList (fields, REmpty)
275+ return $ TypedValue (ObjectLiteral (zip (map fst ps) ts)) ty
276+infer' (ObjectUpdate o ps) = do
277+ ensureNoDuplicateProperties ps
278+ row <- fresh
279+ newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
280+ let newTys = map (\(name, TypedValue _ ty) -> (name, ty)) newVals
281+ oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
282+ o' <- check o $ Object $ rowFromList (oldTys, row)
283+ return $ TypedValue (ObjectUpdate o' newVals) $ Object $ rowFromList (newTys, row)
284+infer' (Indexer index val) = do
285+ el <- fresh
286+ check index Number
287+ check val (Array el)
288+ return $ TypedValue (Indexer (TypedValue index Number) (TypedValue val (Array el))) el
289+infer' (Accessor prop val) = do
290+ typed@(TypedValue _ objTy) <- infer val
291+ propTy <- inferProperty objTy prop
292+ case propTy of
293+ Nothing -> do
294+ field <- fresh
295+ rest <- fresh
296+ objTy `subsumes` Object (RCons prop field rest)
297+ return $ TypedValue (Accessor prop typed) field
298+ Just ty -> return $ TypedValue (Accessor prop typed) ty
299+infer' (Abs args ret) = do
300+ ts <- replicateM (length args) fresh
301+ moduleName <- substCurrentModule <$> ask
302+ bindLocalVariables moduleName (zip args ts) $ do
303+ (TypedValue body bodyTy) <- infer' ret
304+ return $ TypedValue (Abs args body) $ Function ts bodyTy
305+infer' (App f args) = do
306+ (TypedValue f' ft) <- infer f
307+ ret <- fresh
308+ args' <- checkFunctionApplication ft args ret
309+ return $ TypedValue (App f' args') ret
310+infer' (Var var) = do
311+ moduleName <- substCurrentModule <$> ask
312+ ty <- lookupVariable moduleName var
313+ ty' <- replaceAllTypeSynonyms ty
314+ return $ TypedValue (Var var) ty'
315+infer' (Block ss) = do
316+ ret <- fresh
317+ (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
318+ guardWith "Block is missing a return statement" allCodePathsReturn
319+ return $ TypedValue (Block ss') ret
320+infer' v@(Constructor c) = do
321+ env <- getEnv
322+ moduleName <- substCurrentModule `fmap` ask
323+ case M.lookup (qualify moduleName c) (dataConstructors env) of
324+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
325+ Just (ty, _) -> do ty' <- replaceAllTypeSynonyms ty
326+ return $ TypedValue v ty'
327+infer' (Case vals binders) = do
328+ ts <- mapM infer vals
329+ ret <- fresh
330+ binders' <- checkBinders (map (\(TypedValue _ t) -> t) ts) ret binders
331+ return $ TypedValue (Case ts binders') ret
332+infer' (IfThenElse cond th el) = do
333+ check cond Boolean
334+ TypedValue v2 t2 <- infer th
335+ TypedValue v3 t3 <- infer el
336+ t2 ~~ t3
337+ return $ TypedValue (IfThenElse cond v2 v3) t2
338+infer' (TypedValue val ty) = do
339+ moduleName <- substCurrentModule <$> ask
340+ kind <- liftCheck $ kindOf moduleName ty
341+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
342+ ty' <- replaceAllTypeSynonyms ty
343+ check val ty'
344+infer' _ = error "Invalid argument to infer"
345+
346+inferProperty :: Type -> String -> Subst (Maybe Type)
347+inferProperty (Object row) prop = do
348+ let (props, _) = rowToList row
349+ return $ lookup prop props
350+inferProperty (SaturatedTypeSynonym name args) prop = do
351+ replaced <- expandTypeSynonym name args
352+ inferProperty replaced prop
353+inferProperty (ForAll ident ty) prop = do
354+ replaced <- replaceVarWithUnknown ident ty
355+ inferProperty replaced prop
356+inferProperty _ _ = return Nothing
357+
358+inferUnary :: UnaryOperator -> Value -> Subst Value
359+inferUnary op (TypedValue val valTy) =
360+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
361+ (valTy', resTy) -> do
362+ valTy' ~~ valTy
363+ return $ TypedValue (Unary op val) resTy
364+inferUnary _ _ = error "Invalid arguments to inferUnary"
365+
366+checkUnary :: UnaryOperator -> Value -> Type -> Subst Value
367+checkUnary op val res =
368+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
369+ (valTy, resTy) -> do
370+ res ~~ resTy
371+ check val valTy
372+
373+unaryOps :: [(UnaryOperator, (Type, Type))]
374+unaryOps = [ (Negate, (Number, Number))
375+ , (Not, (Boolean, Boolean))
376+ , (BitwiseNot, (Number, Number))
377+ ]
378+
379+inferBinary :: BinaryOperator -> Value -> Value -> Subst Value
380+inferBinary op left@(TypedValue _ leftTy) right@(TypedValue _ rightTy) | isEqualityTest op = do
381+ leftTy ~~ rightTy
382+ return $ TypedValue (Binary op left right) Boolean
383+inferBinary op left@(TypedValue _ leftTy) right@(TypedValue _ rightTy) =
384+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
385+ (valTy, resTy) -> do
386+ leftTy ~~ valTy
387+ rightTy ~~ valTy
388+ return $ TypedValue (Binary op left right) resTy
389+inferBinary _ _ _ = error "Invalid arguments to inferBinary"
390+
391+checkBinary :: BinaryOperator -> Value -> Value -> Type -> Subst Value
392+checkBinary op left right res | isEqualityTest op = do
393+ res ~~ Boolean
394+ TypedValue v1 t1 <- infer left
395+ TypedValue v2 t2 <- infer right
396+ t1 ~~ t2
397+ return $ TypedValue (Binary op v1 v2) $ res
398+checkBinary op left right res =
399+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
400+ (valTy, resTy) -> do
401+ res ~~ resTy
402+ v1 <- check left valTy
403+ v2 <- check right valTy
404+ return $ TypedValue (Binary op v1 v2) $ res
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 [([Binder], Maybe Guard, Value)]
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+ r <- bindLocalVariables moduleName (M.toList m1) $ do
493+ val' <- check val ret
494+ case grd of
495+ Nothing -> return (binders, Nothing, val')
496+ Just g -> do
497+ g' <- check g Boolean
498+ return (binders, Just g', val')
499+ rs <- checkBinders nvals ret bs
500+ return $ r : rs
501+
502+assignVariable :: Ident -> Subst ()
503+assignVariable name = do
504+ env <- checkEnv <$> get
505+ moduleName <- substCurrentModule <$> ask
506+ case M.lookup (moduleName, name) (names env) of
507+ Just (_, LocalVariable) -> throwError $ "Variable with name " ++ show name ++ " already exists."
508+ _ -> return ()
509+
510+checkStatement :: M.Map Ident Type -> Type -> Statement -> Subst (Bool, M.Map Ident Type, Statement)
511+checkStatement mass _ (VariableIntroduction name val) = do
512+ assignVariable name
513+ val'@(TypedValue _ t) <- infer val
514+ return (False, M.insert name t mass, VariableIntroduction name val')
515+checkStatement mass _ (Assignment ident val) = do
516+ val'@(TypedValue _ t) <- infer val
517+ case M.lookup ident mass of
518+ Nothing -> throwError $ "No local variable with name " ++ show ident
519+ Just ty -> do t ~~ ty
520+ return (False, mass, Assignment ident val')
521+checkStatement mass ret (While val inner) = do
522+ val' <- check val Boolean
523+ (allCodePathsReturn, _, inner') <- checkBlock mass ret inner
524+ return (allCodePathsReturn, mass, While val' inner')
525+checkStatement mass ret (If ifst) = do
526+ (allCodePathsReturn, ifst') <- checkIfStatement mass ret ifst
527+ return (allCodePathsReturn, mass, If ifst')
528+checkStatement mass ret (For ident start end inner) = do
529+ moduleName <- substCurrentModule <$> ask
530+ assignVariable ident
531+ start' <- check start Number
532+ end' <- check end Number
533+ (allCodePathsReturn, _, inner') <- bindLocalVariables moduleName [(ident, Number)] $ checkBlock mass ret inner
534+ return (allCodePathsReturn, mass, For ident start' end' inner')
535+checkStatement mass ret (Return val) = do
536+ val' <- check val ret
537+ return (True, mass, Return val')
538+
539+checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> Subst (Bool, IfStatement)
540+checkIfStatement mass ret (IfStatement val thens Nothing) = do
541+ val' <- check val Boolean
542+ (_, _, thens') <- checkBlock mass ret thens
543+ return (False, IfStatement val' thens' Nothing)
544+checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
545+ val' <- check val Boolean
546+ (allCodePathsReturn1, _, thens') <- checkBlock mass ret thens
547+ (allCodePathsReturn2, elses') <- checkElseStatement mass ret elses
548+ return (allCodePathsReturn1 && allCodePathsReturn2, IfStatement val' thens' (Just elses'))
549+
550+checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> Subst (Bool, ElseStatement)
551+checkElseStatement mass ret (Else elses) = do
552+ (allCodePathsReturn, _, elses') <- checkBlock mass ret elses
553+ return (allCodePathsReturn, Else elses')
554+checkElseStatement mass ret (ElseIf ifst) = (id *** ElseIf) <$> checkIfStatement mass ret ifst
555+
556+checkBlock :: M.Map Ident Type -> Type -> [Statement] -> Subst (Bool, M.Map Ident Type, [Statement])
557+checkBlock mass _ [] = return (False, mass, [])
558+checkBlock mass ret (s:ss) = do
559+ moduleName <- substCurrentModule <$> ask
560+ (b1, mass1, s') <- checkStatement mass ret s
561+ bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
562+ (True, []) -> return (True, mass1, [s'])
563+ (True, _) -> throwError "Unreachable code"
564+ (False, ss') -> do
565+ (b, m, ss'') <- checkBlock mass1 ret ss'
566+ return (b, m, s':ss'')
567+
568+skolemize :: String -> Type -> Subst Type
569+skolemize ident ty = do
570+ tsk <- Skolem <$> fresh'
571+ return $ replaceTypeVars ident tsk ty
572+
573+check :: Value -> Type -> Subst Value
574+check val ty = rethrow errorMessage $ check' val ty
575+ where
576+ errorMessage msg =
577+ "Error checking type of term " ++
578+ prettyPrintValue val ++
579+ " against type " ++
580+ prettyPrintType ty ++
581+ ":\n" ++
582+ msg
583+
584+check' :: Value -> Type -> Subst Value
585+check' val (ForAll idents ty) = do
586+ sk <- skolemize idents ty
587+ check val sk
588+check' val u@(TUnknown _) = do
589+ val'@(TypedValue _ ty) <- infer val
590+ -- Don't unify an unknown with an inferred polytype
591+ ty' <- replaceAllVarsWithUnknowns ty
592+ ty' ~~ u
593+ return val'
594+check' v@(NumericLiteral _) Number = return $ TypedValue v Number
595+check' v@(StringLiteral _) String = return $ TypedValue v String
596+check' v@(BooleanLiteral _) Boolean = return $ TypedValue v Boolean
597+check' (Unary op val) ty = checkUnary op val ty
598+check' (Binary op left right) ty = checkBinary op left right ty
599+check' (ArrayLiteral vals) (Array ty) = TypedValue <$> (ArrayLiteral <$> forM vals (\val -> check val ty)) <*> pure (Array ty)
600+check' (Indexer index vals) ty = check index Number >> check vals (Array ty)
601+check' (Abs args ret) (Function argTys retTy) = do
602+ moduleName <- substCurrentModule <$> ask
603+ guardWith "Incorrect number of function arguments" (length args == length argTys)
604+ bindLocalVariables moduleName (zip args argTys) $ check ret retTy
605+check' (App f args) ret = do
606+ f'@(TypedValue _ ft) <- infer f
607+ args' <- checkFunctionApplication ft args ret
608+ return $ TypedValue (App f' args') ret
609+check' (Var var) ty = do
610+ moduleName <- substCurrentModule <$> ask
611+ ty1 <- lookupVariable moduleName var
612+ repl <- replaceAllTypeSynonyms ty1
613+ repl `subsumes` ty
614+ return $ TypedValue (Var var) ty
615+check' v@(TypedValue val ty1) ty2 = do
616+ moduleName <- substCurrentModule <$> ask
617+ kind <- liftCheck $ kindOf moduleName ty1
618+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
619+ ty1 `subsumes` ty2
620+ check val ty1
621+ return v
622+check' (Case vals binders) ret = do
623+ vals' <- mapM infer vals
624+ let ts = map (\(TypedValue _ t) -> t) vals'
625+ binders' <- checkBinders ts ret binders
626+ return $ TypedValue (Case vals' binders') ret
627+check' (IfThenElse cond th el) ty = do
628+ check cond Boolean
629+ check th ty
630+ check el ty
631+check' (ObjectLiteral ps) t@(Object row) = do
632+ ensureNoDuplicateProperties ps
633+ ps' <- checkProperties ps row False
634+ return $ TypedValue (ObjectLiteral ps') t
635+check' (ObjectUpdate obj ps) t@(Object row) = do
636+ ensureNoDuplicateProperties ps
637+ us <- zip (map fst ps) <$> replicateM (length ps) fresh
638+ let (propsToCheck, rest) = rowToList row
639+ propsToRemove = map fst ps
640+ remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
641+ obj' <- check obj (Object (rowFromList (us ++ remainingProps, rest)))
642+ ps' <- checkProperties ps row True
643+ return $ TypedValue (ObjectUpdate obj' ps') t
644+check' (Accessor prop val) ty = do
645+ rest <- fresh
646+ check val (Object (RCons prop ty rest))
647+check' (Block ss) ret = do
648+ (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
649+ guardWith "Block is missing a return statement" allCodePathsReturn
650+ return $ TypedValue (Block ss') ret
651+check' (Constructor c) ty = do
652+ env <- getEnv
653+ moduleName <- substCurrentModule <$> ask
654+ case M.lookup (qualify moduleName c) (dataConstructors env) of
655+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
656+ Just (ty1, _) -> do
657+ repl <- replaceAllTypeSynonyms ty1
658+ repl `subsumes` ty
659+ return $ TypedValue (Constructor c) ty
660+check' val (SaturatedTypeSynonym name args) = do
661+ ty <- expandTypeSynonym name args
662+ check val ty
663+check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
664+
665+checkProperties :: [(String, Value)] -> Type -> Bool -> Subst [(String, Value)]
666+checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
667+ go [] [] REmpty = return []
668+ go [] [] u@(TUnknown _) = do u ~~ REmpty
669+ return []
670+ go [] [] (Skolem _) | lax = return []
671+ go [] ((p, _): _) _ | lax = return []
672+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
673+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
674+ go ((p,v):ps') [] u@(TUnknown _) = do
675+ v'@(TypedValue _ ty) <- infer v
676+ rest <- fresh
677+ u ~~ RCons p ty rest
678+ ps'' <- go ps' [] rest
679+ return $ (p, v') : ps''
680+ go ((p,v):ps') ts r =
681+ case lookup p ts of
682+ Nothing -> do
683+ v'@(TypedValue _ ty) <- infer v
684+ rest <- fresh
685+ r ~~ RCons p ty rest
686+ ps'' <- go ps' ts rest
687+ return $ (p, v') : ps''
688+ Just ty -> do
689+ v' <- check v ty
690+ ps'' <- go ps' (delete (p, ty) ts) r
691+ return $ (p, v') : ps''
692+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
693+
694+checkFunctionApplication :: Type -> [Value] -> Type -> Subst [Value]
695+checkFunctionApplication fnTy args ret = rethrow errorMessage $ checkFunctionApplication' fnTy args ret
696+ where
697+ errorMessage msg = "Error applying function of type "
698+ ++ prettyPrintType fnTy
699+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
700+ ++ ", expecting value of type "
701+ ++ prettyPrintType ret ++ ":\n" ++ msg
702+
703+inferFunctionApplication :: Type -> [Type] -> Subst Type
704+inferFunctionApplication (Function argTys retTy) args = do
705+ guardWith "Incorrect number of function arguments" (length args == length argTys)
706+ zipWithM subsumes args argTys
707+ return retTy
708+inferFunctionApplication (ForAll ident ty) args = do
709+ replaced <- replaceVarWithUnknown ident ty
710+ inferFunctionApplication replaced args
711+inferFunctionApplication u@(TUnknown _) args = do
712+ ret <- fresh
713+ args' <- mapM replaceAllVarsWithUnknowns args
714+ u ~~ Function args' ret
715+ return ret
716+inferFunctionApplication (SaturatedTypeSynonym name tyArgs) args = do
717+ ty <- expandTypeSynonym name tyArgs
718+ inferFunctionApplication ty args
719+inferFunctionApplication fnTy args = throwError $ "Cannot apply function of type "
720+ ++ prettyPrintType fnTy
721+ ++ " to argument(s) of type(s) " ++ intercalate ", " (map prettyPrintType args)
722+
723+checkFunctionApplication' :: Type -> [Value] -> Type -> Subst [Value]
724+checkFunctionApplication' (Function argTys retTy) args ret = do
725+ guardWith "Incorrect number of function arguments" (length args == length argTys)
726+ args' <- zipWithM check args argTys
727+ retTy `subsumes` ret
728+ return args'
729+checkFunctionApplication' (ForAll ident ty) args ret = do
730+ replaced <- replaceVarWithUnknown ident ty
731+ checkFunctionApplication replaced args ret
732+checkFunctionApplication' u@(TUnknown _) args ret = do
733+ args' <- mapM (\arg -> infer arg >>= \(TypedValue v t) -> TypedValue v <$> replaceAllVarsWithUnknowns t) args
734+ let tys = map (\(TypedValue _ t) -> t) args'
735+ u ~~ Function tys ret
736+ return args'
737+checkFunctionApplication' (SaturatedTypeSynonym name tyArgs) args ret = do
738+ ty <- expandTypeSynonym name tyArgs
739+ checkFunctionApplication' ty args ret
740+checkFunctionApplication' fnTy args ret = throwError $ "Applying a function of type "
741+ ++ prettyPrintType fnTy
742+ ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
743+ ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
744+
745+subsumes :: Type -> Type -> Subst ()
746+subsumes (ForAll ident ty1) ty2 = do
747+ replaced <- replaceVarWithUnknown ident ty1
748+ replaced `subsumes` ty2
749+subsumes (Function args1 ret1) (Function args2 ret2) = do
750+ zipWithM subsumes args2 args1
751+ ret1 `subsumes` ret2
752+subsumes ty1 ty2 = ty1 ~~ ty2
753+