@@ -0,0 +1,743 @@
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 (everything, mkT, something, everywhere, mkQ)
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+import Control.Monad.Reader
40+
41+import Control.Applicative
42+import Control.Arrow (Arrow(..))
43+
44+import qualified Data.Map as M
45+import Data.Function (on)
46+
47+instance Unifiable Type where
48+ unknown = TUnknown
49+ isUnknown (TUnknown u) = Just u
50+ isUnknown _ = Nothing
51+ (~~) = unifyTypes
52+ apply s (TUnknown u) = runSubstitution s u
53+ apply s (SaturatedTypeSynonym name tys) = SaturatedTypeSynonym name $ map (apply s) tys
54+ apply s (ForAll idents ty) = ForAll idents $ apply s ty
55+ apply s (Array t) = Array (apply s t)
56+ apply s (Object r) = Object (apply s r)
57+ apply s (Function args ret) = Function (map (apply s) args) (apply s ret)
58+ apply s (TypeApp t1 t2) = TypeApp (apply s t1) (apply s t2)
59+ apply s (RCons name ty r) = RCons name (apply s ty) (apply s r)
60+ apply _ t = t
61+ unknowns (TUnknown (Unknown u)) = [u]
62+ unknowns (SaturatedTypeSynonym _ tys) = concatMap unknowns tys
63+ unknowns (ForAll _ ty) = unknowns ty
64+ unknowns (Array t) = unknowns t
65+ unknowns (Object r) = unknowns r
66+ unknowns (Function args ret) = concatMap unknowns args ++ unknowns ret
67+ unknowns (TypeApp t1 t2) = unknowns t1 ++ unknowns t2
68+ unknowns (RCons _ ty r) = unknowns ty ++ unknowns r
69+ unknowns _ = []
70+
71+unifyTypes :: Type -> Type -> Subst ()
72+unifyTypes t1 t2 = rethrow (\e -> "Error unifying type " ++ prettyPrintType t1 ++ " with type " ++ prettyPrintType t2 ++ ":\n" ++ e) $ do
73+ unifyTypes' t1 t2
74+ where
75+ unifyTypes' (TUnknown u1) (TUnknown u2) | u1 == u2 = return ()
76+ unifyTypes' (TUnknown u) t = replace u t
77+ unifyTypes' t (TUnknown u) = replace u t
78+ unifyTypes' (SaturatedTypeSynonym name args) ty = do
79+ ty1 <- expandTypeSynonym name args
80+ ty1 `unifyTypes` ty
81+ unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
82+ unifyTypes' (ForAll ident1 ty1) (ForAll ident2 ty2) = do
83+ sk <- skolemize ident1 ty1
84+ replaced <- replaceVarWithUnknown ident2 ty2
85+ sk `unifyTypes` replaced
86+ unifyTypes' (ForAll ident ty1) ty2 = do
87+ sk <- skolemize ident ty1
88+ sk `unifyTypes` ty2
89+ unifyTypes' ty f@(ForAll _ _) = f `unifyTypes` ty
90+ unifyTypes' Number Number = return ()
91+ unifyTypes' String String = return ()
92+ unifyTypes' Boolean Boolean = return ()
93+ unifyTypes' (Array s) (Array t) = s `unifyTypes` t
94+ unifyTypes' (Object row1) (Object row2) = row1 ~~ row2
95+ unifyTypes' (Function args1 ret1) (Function args2 ret2) = do
96+ guardWith "Function applied to incorrect number of args" $ length args1 == length args2
97+ zipWithM_ unifyTypes args1 args2
98+ ret1 `unifyTypes` ret2
99+ unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
100+ unifyTypes' (TypeConstructor c1) (TypeConstructor c2) = do
101+ env <- getEnv
102+ moduleName <- substCurrentModule `fmap` ask
103+ guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (typeConstructorsAreEqual env moduleName c1 c2)
104+ unifyTypes' (TypeApp t3 t4) (TypeApp t5 t6) = do
105+ t3 `unifyTypes` t5
106+ t4 `unifyTypes` t6
107+ unifyTypes' (Skolem s1) (Skolem s2) | s1 == s2 = return ()
108+ unifyTypes' r1@(RCons _ _ _) r2 = unifyRows r1 r2
109+ unifyTypes' r1 r2@(RCons _ _ _) = unifyRows r1 r2
110+ unifyTypes' r1@REmpty r2 = unifyRows r1 r2
111+ unifyTypes' r1 r2@REmpty = unifyRows r1 r2
112+ unifyTypes' t3 t4 = throwError $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
113+
114+unifyRows :: Type -> Type -> Subst ()
115+unifyRows r1 r2 =
116+ let
117+ (s1, r1') = rowToList r1
118+ (s2, r2') = rowToList r2
119+ int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
120+ sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
121+ sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
122+ in do
123+ forM_ int (uncurry (~~))
124+ unifyRows' sd1 r1' sd2 r2'
125+ where
126+ unifyRows' :: [(String, Type)] -> Type -> [(String, Type)] -> Type -> Subst ()
127+ unifyRows' [] (TUnknown u) sd r = replace u (rowFromList (sd, r))
128+ unifyRows' sd r [] (TUnknown u) = replace u (rowFromList (sd, r))
129+ unifyRows' ((name, ty):row) r others u@(TUnknown un) = do
130+ occursCheck un ty
131+ forM_ row $ \(_, t) -> occursCheck un t
132+ u' <- fresh
133+ u ~~ RCons name ty u'
134+ unifyRows' row r others u'
135+ unifyRows' [] REmpty [] REmpty = return ()
136+ unifyRows' [] (TypeVar v1) [] (TypeVar v2) | v1 == v2 = return ()
137+ unifyRows' [] (Skolem s1) [] (Skolem s2) | s1 == s2 = return ()
138+ unifyRows' sd3 r3 sd4 r4 = throwError $ "Cannot unify " ++ prettyPrintRow (rowFromList (sd3, r3)) ++ " with " ++ prettyPrintRow (rowFromList (sd4, r4)) ++ "."
139+
140+typeConstructorsAreEqual :: Environment -> ModuleName -> Qualified ProperName -> Qualified ProperName -> Bool
141+typeConstructorsAreEqual env moduleName = (==) `on` canonicalizeType moduleName env
142+
143+typesOf :: ModuleName -> [(Ident, Value)] -> Check [Type]
144+typesOf moduleName vals = do
145+ (tys, _) <- runSubst (SubstContext moduleName) $ do
146+ let es = map isTyped vals
147+ typed = filter (isJust . snd . snd) es
148+ untyped = filter (isNothing . snd . snd) es
149+ typedDict = map (\(ident, (_, Just ty)) -> (ident, ty)) typed
150+ untypedNames <- replicateM (length untyped) fresh
151+ let untypedDict = zip (map fst untyped) untypedNames
152+ dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ typedDict ++ untypedDict)
153+ tys <- forM es $ \e -> do
154+ (val, ty) <- case e of
155+ (_, (val, Just ty)) -> do
156+ kind <- liftCheck $ kindOf moduleName ty
157+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
158+ ty' <- replaceAllTypeSynonyms ty
159+ val' <- bindNames dict $ check val ty'
160+ return (val', ty')
161+ (ident, (val, Nothing)) -> do
162+ TypedValue val' ty <- bindNames dict $ infer val
163+ ty ~~ fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
164+ return (val', ty)
165+ when (moduleName == ModuleName (ProperName "Main") && fst e == Ident "main") $ do
166+ [eff, a] <- replicateM 2 fresh
167+ ty ~~ TypeApp (TypeApp (TypeConstructor (Qualified (Just (ModuleName (ProperName "Eff"))) (ProperName "Eff"))) eff) a
168+ escapeCheck val ty
169+ return ty
170+ return tys
171+ forM_ tys $ skolemEscapeCheck
172+ return $ map (varIfUnknown . desaturateAllTypeSynonyms . setifyAll) tys
173+
174+isTyped :: (Ident, Value) -> (Ident, (Value, Maybe Type))
175+isTyped (name, TypedValue value ty) = (name, (value, Just ty))
176+isTyped (name, value) = (name, (value, Nothing))
177+
178+escapeCheck :: Value -> Type -> Subst ()
179+escapeCheck value ty = do
180+ subst <- substSubst <$> getSubstState
181+ let visibleUnknowns = nub $ unknowns $ apply subst ty
182+ let allUnknowns = findAllTypes value
183+ forM_ allUnknowns $ \t -> do
184+ let unsolvedUnknowns = nub . unknowns $ apply subst t
185+ guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
186+
187+findAllTypes :: Value -> [Type]
188+findAllTypes = everything (++) (mkQ [] go)
189+ where
190+ go (TypedValue _ ty) = [ty]
191+ go _ = []
192+
193+skolemEscapeCheck :: Type -> Check ()
194+skolemEscapeCheck ty =
195+ case something (mkQ Nothing findSkolems) ty of
196+ Nothing -> return ()
197+ Just _ -> throwError $ "Skolem variables cannot escape. Consider adding a type signature." ++ show ty
198+ where
199+ findSkolems (Skolem _) = return ()
200+ findSkolems _ = mzero
201+
202+setify :: Type -> Type
203+setify = rowFromList . first (M.toList . M.fromList) . rowToList
204+
205+setifyAll :: (D.Data d) => d -> d
206+setifyAll = everywhere (mkT setify)
207+
208+varIfUnknown :: Type -> Type
209+varIfUnknown ty =
210+ let unks = nub $ unknowns ty
211+ toName = (:) 't' . show
212+ ty' = everywhere (mkT typeToVar) $ ty
213+ typeToVar :: Type -> Type
214+ typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
215+ typeToVar t = t
216+ in mkForAll (sort . map toName $ unks) ty'
217+
218+replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
219+replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
220+
221+replaceAllVarsWithUnknowns :: Type -> Subst Type
222+replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
223+replaceAllVarsWithUnknowns ty = return ty
224+
225+replaceVarWithUnknown :: String -> Type -> Subst Type
226+replaceVarWithUnknown ident ty = do
227+ tu <- fresh
228+ return $ replaceTypeVars ident tu $ ty
229+
230+replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadReader SubstContext m, MonadError String m) => (D.Data d) => d -> m d
231+replaceAllTypeSynonyms d = do
232+ env <- getEnv
233+ moduleName <- substCurrentModule <$> ask
234+ let syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
235+ either throwError return $ saturateAllTypeSynonyms env moduleName syns d
236+
237+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
238+desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
239+ where
240+ replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
241+ replaceSaturatedTypeSynonym t = t
242+
243+expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Type
244+expandTypeSynonym name args = do
245+ env <- getEnv
246+ moduleName <- substCurrentModule `fmap` ask
247+ case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
248+ Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
249+ Nothing -> error "Type synonym was not defined"
250+
251+ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
252+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
253+
254+infer :: Value -> Subst Value
255+infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ infer' val
256+
257+infer' :: Value -> Subst Value
258+infer' v@(NumericLiteral _) = return $ TypedValue v Number
259+infer' v@(StringLiteral _) = return $ TypedValue v String
260+infer' v@(BooleanLiteral _) = return $ TypedValue v Boolean
261+infer' (ArrayLiteral vals) = do
262+ ts <- mapM infer vals
263+ els <- fresh
264+ forM_ ts $ \(TypedValue _ t) -> els ~~ Array t
265+ return $ TypedValue (ArrayLiteral ts) els
266+infer' (Unary op val) = do
267+ v <- infer val
268+ inferUnary op v
269+infer' (Binary op left right) = do
270+ v1 <- infer left
271+ v2 <- infer right
272+ inferBinary op v1 v2
273+infer' (ObjectLiteral ps) = do
274+ ensureNoDuplicateProperties ps
275+ ts <- mapM (infer . snd) ps
276+ let fields = zipWith (\name (TypedValue _ t) -> (name, t)) (map fst ps) ts
277+ ty = Object $ rowFromList (fields, REmpty)
278+ return $ TypedValue (ObjectLiteral (zip (map fst ps) ts)) ty
279+infer' (ObjectUpdate o ps) = do
280+ ensureNoDuplicateProperties ps
281+ row <- fresh
282+ newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
283+ let newTys = map (\(name, TypedValue _ ty) -> (name, ty)) newVals
284+ oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
285+ o' <- check o $ Object $ rowFromList (oldTys, row)
286+ return $ TypedValue (ObjectUpdate o' newVals) $ Object $ rowFromList (newTys, row)
287+infer' (Indexer index val) = do
288+ el <- fresh
289+ index' <- check index Number
290+ val' <- check val (Array el)
291+ return $ TypedValue (Indexer (TypedValue index' Number) (TypedValue val' (Array el))) el
292+infer' (Accessor prop val) = do
293+ typed@(TypedValue _ objTy) <- infer val
294+ propTy <- inferProperty objTy prop
295+ case propTy of
296+ Nothing -> do
297+ field <- fresh
298+ rest <- fresh
299+ objTy `subsumes` Object (RCons prop field rest)
300+ return $ TypedValue (Accessor prop typed) field
301+ Just ty -> return $ TypedValue (Accessor prop typed) ty
302+infer' (Abs args ret) = do
303+ ts <- replicateM (length args) fresh
304+ moduleName <- substCurrentModule <$> ask
305+ bindLocalVariables moduleName (zip args ts) $ do
306+ (TypedValue body bodyTy) <- infer' ret
307+ return $ TypedValue (Abs args body) $ Function ts bodyTy
308+infer' (App f args) = do
309+ (TypedValue f' ft) <- infer f
310+ ret <- fresh
311+ args' <- checkFunctionApplication ft args ret
312+ return $ TypedValue (App f' args') ret
313+infer' (Var var) = do
314+ moduleName <- substCurrentModule <$> ask
315+ ty <- lookupVariable moduleName var
316+ ty' <- replaceAllTypeSynonyms ty
317+ return $ TypedValue (Var var) ty'
318+infer' (Block ss) = do
319+ ret <- fresh
320+ (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
321+ guardWith "Block is missing a return statement" allCodePathsReturn
322+ return $ TypedValue (Block ss') ret
323+infer' v@(Constructor c) = do
324+ env <- getEnv
325+ moduleName <- substCurrentModule `fmap` ask
326+ case M.lookup (qualify moduleName c) (dataConstructors env) of
327+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
328+ Just (ty, _) -> do ty' <- replaceAllTypeSynonyms ty
329+ return $ TypedValue v ty'
330+infer' (Case vals binders) = do
331+ ts <- mapM infer vals
332+ ret <- fresh
333+ binders' <- checkBinders (map (\(TypedValue _ t) -> t) ts) ret binders
334+ return $ TypedValue (Case ts binders') ret
335+infer' (IfThenElse cond th el) = do
336+ cond' <- check cond Boolean
337+ v2@(TypedValue _ t2) <- infer th
338+ v3@(TypedValue _ t3) <- infer el
339+ t2 ~~ t3
340+ return $ TypedValue (IfThenElse cond' v2 v3) t2
341+infer' (TypedValue val ty) = do
342+ moduleName <- substCurrentModule <$> ask
343+ kind <- liftCheck $ kindOf moduleName ty
344+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
345+ ty' <- replaceAllTypeSynonyms ty
346+ check val ty'
347+infer' _ = error "Invalid argument to infer"
348+
349+inferProperty :: Type -> String -> Subst (Maybe Type)
350+inferProperty (Object row) prop = do
351+ let (props, _) = rowToList row
352+ return $ lookup prop props
353+inferProperty (SaturatedTypeSynonym name args) prop = do
354+ replaced <- expandTypeSynonym name args
355+ inferProperty replaced prop
356+inferProperty (ForAll ident ty) prop = do
357+ replaced <- replaceVarWithUnknown ident ty
358+ inferProperty replaced prop
359+inferProperty _ _ = return Nothing
360+
361+inferUnary :: UnaryOperator -> Value -> Subst Value
362+inferUnary op (TypedValue val valTy) =
363+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
364+ (valTy', resTy) -> do
365+ valTy' ~~ valTy
366+ return $ TypedValue (Unary op val) resTy
367+inferUnary _ _ = error "Invalid arguments to inferUnary"
368+
369+checkUnary :: UnaryOperator -> Value -> Type -> Subst Value
370+checkUnary op val res =
371+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
372+ (valTy, resTy) -> do
373+ res ~~ resTy
374+ val' <- check val valTy
375+ return $ Unary op val'
376+
377+unaryOps :: [(UnaryOperator, (Type, Type))]
378+unaryOps = [ (Negate, (Number, Number))
379+ , (Not, (Boolean, Boolean))
380+ , (BitwiseNot, (Number, Number))
381+ ]
382+
383+inferBinary :: BinaryOperator -> Value -> Value -> Subst Value
384+inferBinary op left@(TypedValue _ leftTy) right@(TypedValue _ rightTy) | isEqualityTest op = do
385+ leftTy ~~ rightTy
386+ return $ TypedValue (Binary op left right) Boolean
387+inferBinary op left@(TypedValue _ leftTy) right@(TypedValue _ rightTy) =
388+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
389+ (valTy, resTy) -> do
390+ leftTy ~~ valTy
391+ rightTy ~~ valTy
392+ return $ TypedValue (Binary op left right) resTy
393+inferBinary _ _ _ = error "Invalid arguments to inferBinary"
394+
395+checkBinary :: BinaryOperator -> Value -> Value -> Type -> Subst Value
396+checkBinary op left right res | isEqualityTest op = do
397+ res ~~ Boolean
398+ left'@(TypedValue _ t1) <- infer left
399+ right'@(TypedValue _ t2) <- infer right
400+ t1 ~~ t2
401+ return $ Binary op left' right'
402+checkBinary op left right res =
403+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
404+ (valTy, resTy) -> do
405+ res ~~ resTy
406+ left' <- check left valTy
407+ right' <- check right valTy
408+ return $ Binary op left' right'
409+
410+isEqualityTest :: BinaryOperator -> Bool
411+isEqualityTest EqualTo = True
412+isEqualityTest NotEqualTo = True
413+isEqualityTest _ = False
414+
415+binaryOps :: [(BinaryOperator, (Type, Type))]
416+binaryOps = [ (Add, (Number, Number))
417+ , (Subtract, (Number, Number))
418+ , (Multiply, (Number, Number))
419+ , (Divide, (Number, Number))
420+ , (Modulus, (Number, Number))
421+ , (BitwiseAnd, (Number, Number))
422+ , (BitwiseOr, (Number, Number))
423+ , (BitwiseXor, (Number, Number))
424+ , (ShiftRight, (Number, Number))
425+ , (ZeroFillShiftRight, (Number, Number))
426+ , (And, (Boolean, Boolean))
427+ , (Or, (Boolean, Boolean))
428+ , (Concat, (String, String))
429+ , (Modulus, (Number, Number))
430+ , (LessThan, (Number, Boolean))
431+ , (LessThanOrEqualTo, (Number, Boolean))
432+ , (GreaterThan, (Number, Boolean))
433+ , (GreaterThanOrEqualTo, (Number, Boolean))
434+ ]
435+
436+inferBinder :: Type -> Binder -> Subst (M.Map Ident Type)
437+inferBinder _ NullBinder = return M.empty
438+inferBinder val (StringBinder _) = val ~~ String >> return M.empty
439+inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
440+inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
441+inferBinder val (VarBinder name) = return $ M.singleton name val
442+inferBinder val (NullaryBinder ctor) = do
443+ env <- getEnv
444+ moduleName <- substCurrentModule <$> ask
445+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
446+ Just (ty, _) -> do
447+ ty `subsumes` val
448+ return M.empty
449+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
450+inferBinder val (UnaryBinder ctor binder) = do
451+ env <- getEnv
452+ moduleName <- substCurrentModule <$> ask
453+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
454+ Just (ty, _) -> do
455+ fn <- replaceAllVarsWithUnknowns ty
456+ case fn of
457+ Function [obj] ret -> do
458+ val `subsumes` ret
459+ inferBinder obj binder
460+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
461+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
462+inferBinder val (ObjectBinder props) = do
463+ row <- fresh
464+ rest <- fresh
465+ m1 <- inferRowProperties row rest props
466+ val ~~ Object row
467+ return m1
468+ where
469+ inferRowProperties :: Type -> Type -> [(String, Binder)] -> Subst (M.Map Ident Type)
470+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
471+ inferRowProperties nrow row ((name, binder):binders) = do
472+ propTy <- fresh
473+ m1 <- inferBinder propTy binder
474+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
475+ return $ m1 `M.union` m2
476+inferBinder val (ArrayBinder binders) = do
477+ el <- fresh
478+ m1 <- M.unions <$> mapM (inferBinder el) binders
479+ val ~~ Array el
480+ return m1
481+inferBinder val (ConsBinder headBinder tailBinder) = do
482+ el <- fresh
483+ m1 <- inferBinder el headBinder
484+ m2 <- inferBinder val tailBinder
485+ val ~~ Array el
486+ return $ m1 `M.union` m2
487+inferBinder val (NamedBinder name binder) = do
488+ m <- inferBinder val binder
489+ return $ M.insert name val m
490+
491+checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> Subst [([Binder], Maybe Guard, Value)]
492+checkBinders _ _ [] = return []
493+checkBinders nvals ret ((binders, grd, val):bs) = do
494+ moduleName <- substCurrentModule <$> ask
495+ m1 <- M.unions <$> zipWithM inferBinder nvals binders
496+ r <- bindLocalVariables moduleName (M.toList m1) $ do
497+ val' <- check val ret
498+ case grd of
499+ Nothing -> return (binders, Nothing, val')
500+ Just g -> do
501+ g' <- check g Boolean
502+ return (binders, Just g', val')
503+ rs <- checkBinders nvals ret bs
504+ return $ r : rs
505+
506+assignVariable :: Ident -> Subst ()
507+assignVariable name = do
508+ env <- checkEnv <$> get
509+ moduleName <- substCurrentModule <$> ask
510+ case M.lookup (moduleName, name) (names env) of
511+ Just (_, LocalVariable) -> throwError $ "Variable with name " ++ show name ++ " already exists."
512+ _ -> return ()
513+
514+checkStatement :: M.Map Ident Type -> Type -> Statement -> Subst (Bool, M.Map Ident Type, Statement)
515+checkStatement mass _ (VariableIntroduction name val) = do
516+ assignVariable name
517+ val'@(TypedValue _ t) <- infer val
518+ return (False, M.insert name t mass, VariableIntroduction name val')
519+checkStatement mass _ (Assignment ident val) = do
520+ val'@(TypedValue _ t) <- infer val
521+ case M.lookup ident mass of
522+ Nothing -> throwError $ "No local variable with name " ++ show ident
523+ Just ty -> do t ~~ ty
524+ return (False, mass, Assignment ident val')
525+checkStatement mass ret (While val inner) = do
526+ val' <- check val Boolean
527+ (allCodePathsReturn, _, inner') <- checkBlock mass ret inner
528+ return (allCodePathsReturn, mass, While val' inner')
529+checkStatement mass ret (If ifst) = do
530+ (allCodePathsReturn, ifst') <- checkIfStatement mass ret ifst
531+ return (allCodePathsReturn, mass, If ifst')
532+checkStatement mass ret (For ident start end inner) = do
533+ moduleName <- substCurrentModule <$> ask
534+ assignVariable ident
535+ start' <- check start Number
536+ end' <- check end Number
537+ (allCodePathsReturn, _, inner') <- bindLocalVariables moduleName [(ident, Number)] $ checkBlock mass ret inner
538+ return (allCodePathsReturn, mass, For ident start' end' inner')
539+checkStatement mass ret (Return val) = do
540+ val' <- check val ret
541+ return (True, mass, Return val')
542+
543+checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> Subst (Bool, IfStatement)
544+checkIfStatement mass ret (IfStatement val thens Nothing) = do
545+ val' <- check val Boolean
546+ (_, _, thens') <- checkBlock mass ret thens
547+ return (False, IfStatement val' thens' Nothing)
548+checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
549+ val' <- check val Boolean
550+ (allCodePathsReturn1, _, thens') <- checkBlock mass ret thens
551+ (allCodePathsReturn2, elses') <- checkElseStatement mass ret elses
552+ return (allCodePathsReturn1 && allCodePathsReturn2, IfStatement val' thens' (Just elses'))
553+
554+checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> Subst (Bool, ElseStatement)
555+checkElseStatement mass ret (Else elses) = do
556+ (allCodePathsReturn, _, elses') <- checkBlock mass ret elses
557+ return (allCodePathsReturn, Else elses')
558+checkElseStatement mass ret (ElseIf ifst) = (id *** ElseIf) <$> checkIfStatement mass ret ifst
559+
560+checkBlock :: M.Map Ident Type -> Type -> [Statement] -> Subst (Bool, M.Map Ident Type, [Statement])
561+checkBlock mass _ [] = return (False, mass, [])
562+checkBlock mass ret (s:ss) = do
563+ moduleName <- substCurrentModule <$> ask
564+ (b1, mass1, s') <- checkStatement mass ret s
565+ bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
566+ (True, []) -> return (True, mass1, [s'])
567+ (True, _) -> throwError "Unreachable code"
568+ (False, ss') -> do
569+ (b, m, ss'') <- checkBlock mass1 ret ss'
570+ return (b, m, s':ss'')
571+
572+skolemize :: String -> Type -> Subst Type
573+skolemize ident ty = do
574+ tsk <- Skolem <$> fresh'
575+ return $ replaceTypeVars ident tsk ty
576+
577+check :: Value -> Type -> Subst Value
578+check val ty = rethrow errorMessage $ check' val ty
579+ where
580+ errorMessage msg =
581+ "Error checking type of term " ++
582+ prettyPrintValue val ++
583+ " against type " ++
584+ prettyPrintType ty ++
585+ ":\n" ++
586+ msg
587+
588+check' :: Value -> Type -> Subst Value
589+check' val (ForAll idents ty) = do
590+ sk <- skolemize idents ty
591+ check val sk
592+check' val u@(TUnknown _) = do
593+ val'@(TypedValue _ ty) <- infer val
594+ -- Don't unify an unknown with an inferred polytype
595+ ty' <- replaceAllVarsWithUnknowns ty
596+ ty' ~~ u
597+ return val'
598+check' v@(NumericLiteral _) Number = return v
599+check' v@(StringLiteral _) String = return v
600+check' v@(BooleanLiteral _) Boolean = return v
601+check' (Unary op val) ty = checkUnary op val ty
602+check' (Binary op left right) ty = checkBinary op left right ty
603+check' (ArrayLiteral vals) (Array ty) = ArrayLiteral <$> forM vals (\val -> check val ty)
604+check' (Indexer index vals) ty = do
605+ index' <- check index Number
606+ vals' <- check vals (Array ty)
607+ return $ Indexer index' vals'
608+check' (Abs args ret) (Function argTys retTy) = do
609+ moduleName <- substCurrentModule <$> ask
610+ guardWith "Incorrect number of function arguments" (length args == length argTys)
611+ ret' <- bindLocalVariables moduleName (zip args argTys) $ check ret retTy
612+ return $ Abs args ret'
613+check' (App f args) ret = do
614+ f'@(TypedValue _ ft) <- infer f
615+ args' <- checkFunctionApplication ft args ret
616+ return $ App f' args'
617+check' (Var var) ty = do
618+ moduleName <- substCurrentModule <$> ask
619+ ty1 <- lookupVariable moduleName var
620+ repl <- replaceAllTypeSynonyms ty1
621+ repl `subsumes` ty
622+ return $ Var var
623+check' (TypedValue val ty1) ty2 = do
624+ moduleName <- substCurrentModule <$> ask
625+ kind <- liftCheck $ kindOf moduleName ty1
626+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
627+ ty1 `subsumes` ty2
628+ val' <- check val ty1
629+ return $ TypedValue val' ty1
630+check' (Case vals binders) ret = do
631+ vals' <- mapM infer vals
632+ let ts = map (\(TypedValue _ t) -> t) vals'
633+ binders' <- checkBinders ts ret binders
634+ return $ Case vals' binders'
635+check' (IfThenElse cond th el) ty = do
636+ cond' <- check cond Boolean
637+ th' <- check th ty
638+ el' <- check el ty
639+ return $ IfThenElse cond' th' el'
640+check' (ObjectLiteral ps) (Object row) = do
641+ ensureNoDuplicateProperties ps
642+ ps' <- checkProperties ps row False
643+ return $ ObjectLiteral ps'
644+check' (ObjectUpdate obj ps) (Object row) = do
645+ ensureNoDuplicateProperties ps
646+ us <- zip (map fst ps) <$> replicateM (length ps) fresh
647+ let (propsToCheck, rest) = rowToList row
648+ propsToRemove = map fst ps
649+ remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
650+ obj' <- check obj (Object (rowFromList (us ++ remainingProps, rest)))
651+ ps' <- checkProperties ps row True
652+ return $ ObjectUpdate obj' ps'
653+check' (Accessor prop val) ty = do
654+ rest <- fresh
655+ val' <- check val (Object (RCons prop ty rest))
656+ return $ Accessor prop val'
657+check' (Block ss) ret = do
658+ (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
659+ guardWith "Block is missing a return statement" allCodePathsReturn
660+ return $ Block ss'
661+check' (Constructor c) ty = do
662+ env <- getEnv
663+ moduleName <- substCurrentModule <$> ask
664+ case M.lookup (qualify moduleName c) (dataConstructors env) of
665+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
666+ Just (ty1, _) -> do
667+ repl <- replaceAllTypeSynonyms ty1
668+ repl `subsumes` ty
669+ return $ Constructor c
670+check' val (SaturatedTypeSynonym name args) = do
671+ ty <- expandTypeSynonym name args
672+ check val ty
673+check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
674+
675+checkProperties :: [(String, Value)] -> Type -> Bool -> Subst [(String, Value)]
676+checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
677+ go [] [] REmpty = return []
678+ go [] [] u@(TUnknown _) = do u ~~ REmpty
679+ return []
680+ go [] [] (Skolem _) | lax = return []
681+ go [] ((p, _): _) _ | lax = return []
682+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
683+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
684+ go ((p,v):ps') [] u@(TUnknown _) = do
685+ v'@(TypedValue _ ty) <- infer v
686+ rest <- fresh
687+ u ~~ RCons p ty rest
688+ ps'' <- go ps' [] rest
689+ return $ (p, v') : ps''
690+ go ((p,v):ps') ts r =
691+ case lookup p ts of
692+ Nothing -> do
693+ v'@(TypedValue _ ty) <- infer v
694+ rest <- fresh
695+ r ~~ RCons p ty rest
696+ ps'' <- go ps' ts rest
697+ return $ (p, v') : ps''
698+ Just ty -> do
699+ v' <- check v ty
700+ ps'' <- go ps' (delete (p, ty) ts) r
701+ return $ (p, v') : ps''
702+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
703+
704+checkFunctionApplication :: Type -> [Value] -> Type -> Subst [Value]
705+checkFunctionApplication fnTy args ret = rethrow errorMessage $ checkFunctionApplication' fnTy args ret
706+ where
707+ errorMessage msg = "Error applying function of type "
708+ ++ prettyPrintType fnTy
709+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
710+ ++ ", expecting value of type "
711+ ++ prettyPrintType ret ++ ":\n" ++ msg
712+
713+checkFunctionApplication' :: Type -> [Value] -> Type -> Subst [Value]
714+checkFunctionApplication' (Function argTys retTy) args ret = do
715+ guardWith "Incorrect number of function arguments" (length args == length argTys)
716+ args' <- zipWithM check args argTys
717+ retTy `subsumes` ret
718+ return args'
719+checkFunctionApplication' (ForAll ident ty) args ret = do
720+ replaced <- replaceVarWithUnknown ident ty
721+ checkFunctionApplication replaced args ret
722+checkFunctionApplication' u@(TUnknown _) args ret = do
723+ args' <- mapM (\arg -> infer arg >>= \(TypedValue v t) -> TypedValue v <$> replaceAllVarsWithUnknowns t) args
724+ let tys = map (\(TypedValue _ t) -> t) args'
725+ u ~~ Function tys ret
726+ return args'
727+checkFunctionApplication' (SaturatedTypeSynonym name tyArgs) args ret = do
728+ ty <- expandTypeSynonym name tyArgs
729+ checkFunctionApplication' ty args ret
730+checkFunctionApplication' fnTy args ret = throwError $ "Applying a function of type "
731+ ++ prettyPrintType fnTy
732+ ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
733+ ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
734+
735+subsumes :: Type -> Type -> Subst ()
736+subsumes (ForAll ident ty1) ty2 = do
737+ replaced <- replaceVarWithUnknown ident ty1
738+ replaced `subsumes` ty2
739+subsumes (Function args1 ret1) (Function args2 ret2) = do
740+ zipWithM_ subsumes args2 args1
741+ ret1 `subsumes` ret2
742+subsumes ty1 ty2 = ty1 ~~ ty2
743+