@@ -0,0 +1,754 @@
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 [(Ident, (Value, Type))]
144+typesOf moduleName vals = do
145+ tys <- fmap (\(tys, s) -> map (\(ident, (val, ty)) -> (ident, (overTypes (apply s) val, apply s ty))) tys)
146+ . 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+ forM es $ \e -> do
155+ triple@(_, (val, ty)) <- case e of
156+ (ident, (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+ val' <- bindNames dict $ check val ty'
161+ return (ident, (val', ty'))
162+ (ident, (val, Nothing)) -> do
163+ TypedValue val' ty <- bindNames dict $ infer val
164+ ty ~~ fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
165+ return (ident, (val', 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+ escapeCheck val ty
170+ return triple
171+ forM_ tys $ skolemEscapeCheck . snd . snd
172+ return $ map (\(ident, (val, ty)) -> ( ident, ( overTypes (desaturateAllTypeSynonyms . setifyAll) val
173+ , varIfUnknown . desaturateAllTypeSynonyms . setifyAll $ ty))) 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+overTypes :: (Type -> Type) -> Value -> Value
180+overTypes f = everywhere (mkT f)
181+
182+escapeCheck :: Value -> Type -> Subst ()
183+escapeCheck value ty = do
184+ subst <- substSubst <$> getSubstState
185+ let visibleUnknowns = nub $ unknowns $ apply subst ty
186+ let allUnknowns = findAllTypes value
187+ forM_ allUnknowns $ \t -> do
188+ let unsolvedUnknowns = nub . unknowns $ apply subst t
189+ guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
190+
191+findAllTypes :: Value -> [Type]
192+findAllTypes = everything (++) (mkQ [] go)
193+ where
194+ go (TypedValue _ ty) = [ty]
195+ go _ = []
196+
197+skolemEscapeCheck :: Type -> Check ()
198+skolemEscapeCheck ty =
199+ case something (mkQ Nothing findSkolems) ty of
200+ Nothing -> return ()
201+ Just _ -> throwError $ "Skolem variables cannot escape. Consider adding a type signature." ++ show ty
202+ where
203+ findSkolems (Skolem _) = return ()
204+ findSkolems _ = mzero
205+
206+setify :: Type -> Type
207+setify = rowFromList . first (M.toList . M.fromList) . rowToList
208+
209+setifyAll :: (D.Data d) => d -> d
210+setifyAll = everywhere (mkT setify)
211+
212+varIfUnknown :: Type -> Type
213+varIfUnknown ty =
214+ let unks = nub $ unknowns ty
215+ toName = (:) 't' . show
216+ ty' = everywhere (mkT typeToVar) $ ty
217+ typeToVar :: Type -> Type
218+ typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
219+ typeToVar t = t
220+ in mkForAll (sort . map toName $ unks) ty'
221+
222+replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
223+replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
224+
225+replaceAllVarsWithUnknowns :: Type -> Subst Type
226+replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
227+replaceAllVarsWithUnknowns ty = return ty
228+
229+replaceVarWithUnknown :: String -> Type -> Subst Type
230+replaceVarWithUnknown ident ty = do
231+ tu <- fresh
232+ return $ replaceTypeVars ident tu $ ty
233+
234+replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadReader SubstContext m, MonadError String m) => (D.Data d) => d -> m d
235+replaceAllTypeSynonyms d = do
236+ env <- getEnv
237+ moduleName <- substCurrentModule <$> ask
238+ let syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
239+ either throwError return $ saturateAllTypeSynonyms env moduleName syns d
240+
241+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
242+desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
243+ where
244+ replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
245+ replaceSaturatedTypeSynonym t = t
246+
247+expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Type
248+expandTypeSynonym name args = do
249+ env <- getEnv
250+ moduleName <- substCurrentModule `fmap` ask
251+ case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
252+ Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
253+ Nothing -> error "Type synonym was not defined"
254+
255+ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
256+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
257+
258+infer :: Value -> Subst Value
259+infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ infer' val
260+
261+infer' :: Value -> Subst Value
262+infer' v@(NumericLiteral _) = return $ TypedValue v Number
263+infer' v@(StringLiteral _) = return $ TypedValue v String
264+infer' v@(BooleanLiteral _) = return $ TypedValue v Boolean
265+infer' (ArrayLiteral vals) = do
266+ ts <- mapM infer vals
267+ els <- fresh
268+ forM_ ts $ \(TypedValue _ t) -> els ~~ Array t
269+ return $ TypedValue (ArrayLiteral ts) els
270+infer' (Unary op val) = do
271+ v <- infer val
272+ inferUnary op v
273+infer' (Binary op left right) = do
274+ v1 <- infer left
275+ v2 <- infer right
276+ inferBinary op v1 v2
277+infer' (ObjectLiteral ps) = do
278+ ensureNoDuplicateProperties ps
279+ ts <- mapM (infer . snd) ps
280+ let fields = zipWith (\name (TypedValue _ t) -> (name, t)) (map fst ps) ts
281+ ty = Object $ rowFromList (fields, REmpty)
282+ return $ TypedValue (ObjectLiteral (zip (map fst ps) ts)) ty
283+infer' (ObjectUpdate o ps) = do
284+ ensureNoDuplicateProperties ps
285+ row <- fresh
286+ newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
287+ let newTys = map (\(name, TypedValue _ ty) -> (name, ty)) newVals
288+ oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
289+ o' <- check o $ Object $ rowFromList (oldTys, row)
290+ return $ TypedValue (ObjectUpdate o' newVals) $ Object $ rowFromList (newTys, row)
291+infer' (Indexer index val) = do
292+ el <- fresh
293+ index' <- check index Number
294+ val' <- check val (Array el)
295+ return $ TypedValue (Indexer (TypedValue index' Number) (TypedValue val' (Array el))) el
296+infer' (Accessor prop val) = do
297+ typed@(TypedValue _ objTy) <- infer val
298+ propTy <- inferProperty objTy prop
299+ case propTy of
300+ Nothing -> do
301+ field <- fresh
302+ rest <- fresh
303+ objTy `subsumes` Object (RCons prop field rest)
304+ return $ TypedValue (Accessor prop typed) field
305+ Just ty -> return $ TypedValue (Accessor prop typed) ty
306+infer' (Abs args ret) = do
307+ ts <- replicateM (length args) fresh
308+ moduleName <- substCurrentModule <$> ask
309+ bindLocalVariables moduleName (zip args ts) $ do
310+ body@(TypedValue _ bodyTy) <- infer' ret
311+ return $ TypedValue (Abs args body) $ Function ts bodyTy
312+infer' (App f args) = do
313+ f'@(TypedValue _ ft) <- infer f
314+ ret <- fresh
315+ app <- checkFunctionApplication f' ft args ret
316+ return $ TypedValue app ret
317+infer' (Var var) = do
318+ moduleName <- substCurrentModule <$> ask
319+ ty <- lookupVariable moduleName var
320+ ty' <- replaceAllTypeSynonyms ty
321+ case ty' of
322+ ConstrainedType constraints _ -> return $ TypedValue (App (Var var) [TypeClassDictionary constraints]) ty'
323+ _ -> return $ TypedValue (Var var) ty'
324+infer' (Block ss) = do
325+ ret <- fresh
326+ (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
327+ guardWith "Block is missing a return statement" allCodePathsReturn
328+ return $ TypedValue (Block ss') ret
329+infer' v@(Constructor c) = do
330+ env <- getEnv
331+ moduleName <- substCurrentModule `fmap` ask
332+ case M.lookup (qualify moduleName c) (dataConstructors env) of
333+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
334+ Just (ty, _) -> do ty' <- replaceAllTypeSynonyms ty
335+ return $ TypedValue v ty'
336+infer' (Case vals binders) = do
337+ ts <- mapM infer vals
338+ ret <- fresh
339+ binders' <- checkBinders (map (\(TypedValue _ t) -> t) ts) ret binders
340+ return $ TypedValue (Case ts binders') ret
341+infer' (IfThenElse cond th el) = do
342+ cond' <- check cond Boolean
343+ v2@(TypedValue _ t2) <- infer th
344+ v3@(TypedValue _ t3) <- infer el
345+ t2 ~~ t3
346+ return $ TypedValue (IfThenElse cond' v2 v3) t2
347+infer' (TypedValue val ty) = do
348+ moduleName <- substCurrentModule <$> ask
349+ kind <- liftCheck $ kindOf moduleName ty
350+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
351+ ty' <- replaceAllTypeSynonyms ty
352+ val' <- check val ty'
353+ return $ TypedValue val' ty
354+infer' _ = error "Invalid argument to infer"
355+
356+inferProperty :: Type -> String -> Subst (Maybe Type)
357+inferProperty (Object row) prop = do
358+ let (props, _) = rowToList row
359+ return $ lookup prop props
360+inferProperty (SaturatedTypeSynonym name args) prop = do
361+ replaced <- expandTypeSynonym name args
362+ inferProperty replaced prop
363+inferProperty (ForAll ident ty) prop = do
364+ replaced <- replaceVarWithUnknown ident ty
365+ inferProperty replaced prop
366+inferProperty _ _ = return Nothing
367+
368+inferUnary :: UnaryOperator -> Value -> Subst Value
369+inferUnary op (TypedValue val valTy) =
370+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
371+ (valTy', resTy) -> do
372+ valTy' ~~ valTy
373+ return $ TypedValue (Unary op val) resTy
374+inferUnary _ _ = error "Invalid arguments to inferUnary"
375+
376+checkUnary :: UnaryOperator -> Value -> Type -> Subst Value
377+checkUnary op val res =
378+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
379+ (valTy, resTy) -> do
380+ res ~~ resTy
381+ val' <- check val valTy
382+ return $ Unary op val'
383+
384+unaryOps :: [(UnaryOperator, (Type, Type))]
385+unaryOps = [ (Negate, (Number, Number))
386+ , (Not, (Boolean, Boolean))
387+ , (BitwiseNot, (Number, Number))
388+ ]
389+
390+inferBinary :: BinaryOperator -> Value -> Value -> Subst Value
391+inferBinary op left@(TypedValue _ leftTy) right@(TypedValue _ rightTy) | isEqualityTest op = do
392+ leftTy ~~ rightTy
393+ return $ TypedValue (Binary op left right) Boolean
394+inferBinary op left@(TypedValue _ leftTy) right@(TypedValue _ rightTy) =
395+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
396+ (valTy, resTy) -> do
397+ leftTy ~~ valTy
398+ rightTy ~~ valTy
399+ return $ TypedValue (Binary op left right) resTy
400+inferBinary _ _ _ = error "Invalid arguments to inferBinary"
401+
402+checkBinary :: BinaryOperator -> Value -> Value -> Type -> Subst Value
403+checkBinary op left right res | isEqualityTest op = do
404+ res ~~ Boolean
405+ left'@(TypedValue _ t1) <- infer left
406+ right'@(TypedValue _ t2) <- infer right
407+ t1 ~~ t2
408+ return $ Binary op left' right'
409+checkBinary op left right res =
410+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
411+ (valTy, resTy) -> do
412+ res ~~ resTy
413+ left' <- check left valTy
414+ right' <- check right valTy
415+ return $ Binary op left' right'
416+
417+isEqualityTest :: BinaryOperator -> Bool
418+isEqualityTest EqualTo = True
419+isEqualityTest NotEqualTo = True
420+isEqualityTest _ = False
421+
422+binaryOps :: [(BinaryOperator, (Type, Type))]
423+binaryOps = [ (Add, (Number, Number))
424+ , (Subtract, (Number, Number))
425+ , (Multiply, (Number, Number))
426+ , (Divide, (Number, Number))
427+ , (Modulus, (Number, Number))
428+ , (BitwiseAnd, (Number, Number))
429+ , (BitwiseOr, (Number, Number))
430+ , (BitwiseXor, (Number, Number))
431+ , (ShiftRight, (Number, Number))
432+ , (ZeroFillShiftRight, (Number, Number))
433+ , (And, (Boolean, Boolean))
434+ , (Or, (Boolean, Boolean))
435+ , (Concat, (String, String))
436+ , (Modulus, (Number, Number))
437+ , (LessThan, (Number, Boolean))
438+ , (LessThanOrEqualTo, (Number, Boolean))
439+ , (GreaterThan, (Number, Boolean))
440+ , (GreaterThanOrEqualTo, (Number, Boolean))
441+ ]
442+
443+inferBinder :: Type -> Binder -> Subst (M.Map Ident Type)
444+inferBinder _ NullBinder = return M.empty
445+inferBinder val (StringBinder _) = val ~~ String >> return M.empty
446+inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
447+inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
448+inferBinder val (VarBinder name) = return $ M.singleton name val
449+inferBinder val (NullaryBinder ctor) = do
450+ env <- getEnv
451+ moduleName <- substCurrentModule <$> ask
452+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
453+ Just (ty, _) -> do
454+ ty `subsumes` val
455+ return M.empty
456+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
457+inferBinder val (UnaryBinder ctor binder) = do
458+ env <- getEnv
459+ moduleName <- substCurrentModule <$> ask
460+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
461+ Just (ty, _) -> do
462+ fn <- replaceAllVarsWithUnknowns ty
463+ case fn of
464+ Function [obj] ret -> do
465+ val `subsumes` ret
466+ inferBinder obj binder
467+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
468+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
469+inferBinder val (ObjectBinder props) = do
470+ row <- fresh
471+ rest <- fresh
472+ m1 <- inferRowProperties row rest props
473+ val ~~ Object row
474+ return m1
475+ where
476+ inferRowProperties :: Type -> Type -> [(String, Binder)] -> Subst (M.Map Ident Type)
477+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
478+ inferRowProperties nrow row ((name, binder):binders) = do
479+ propTy <- fresh
480+ m1 <- inferBinder propTy binder
481+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
482+ return $ m1 `M.union` m2
483+inferBinder val (ArrayBinder binders) = do
484+ el <- fresh
485+ m1 <- M.unions <$> mapM (inferBinder el) binders
486+ val ~~ Array el
487+ return m1
488+inferBinder val (ConsBinder headBinder tailBinder) = do
489+ el <- fresh
490+ m1 <- inferBinder el headBinder
491+ m2 <- inferBinder val tailBinder
492+ val ~~ Array el
493+ return $ m1 `M.union` m2
494+inferBinder val (NamedBinder name binder) = do
495+ m <- inferBinder val binder
496+ return $ M.insert name val m
497+
498+checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> Subst [([Binder], Maybe Guard, Value)]
499+checkBinders _ _ [] = return []
500+checkBinders nvals ret ((binders, grd, val):bs) = do
501+ moduleName <- substCurrentModule <$> ask
502+ m1 <- M.unions <$> zipWithM inferBinder nvals binders
503+ r <- bindLocalVariables moduleName (M.toList m1) $ do
504+ val' <- check val ret
505+ case grd of
506+ Nothing -> return (binders, Nothing, val')
507+ Just g -> do
508+ g' <- check g Boolean
509+ return (binders, Just g', val')
510+ rs <- checkBinders nvals ret bs
511+ return $ r : rs
512+
513+assignVariable :: Ident -> Subst ()
514+assignVariable name = do
515+ env <- checkEnv <$> get
516+ moduleName <- substCurrentModule <$> ask
517+ case M.lookup (moduleName, name) (names env) of
518+ Just (_, LocalVariable) -> throwError $ "Variable with name " ++ show name ++ " already exists."
519+ _ -> return ()
520+
521+checkStatement :: M.Map Ident Type -> Type -> Statement -> Subst (Bool, M.Map Ident Type, Statement)
522+checkStatement mass _ (VariableIntroduction name val) = do
523+ assignVariable name
524+ val'@(TypedValue _ t) <- infer val
525+ return (False, M.insert name t mass, VariableIntroduction name val')
526+checkStatement mass _ (Assignment ident val) = do
527+ val'@(TypedValue _ t) <- infer val
528+ case M.lookup ident mass of
529+ Nothing -> throwError $ "No local variable with name " ++ show ident
530+ Just ty -> do t ~~ ty
531+ return (False, mass, Assignment ident val')
532+checkStatement mass ret (While val inner) = do
533+ val' <- check val Boolean
534+ (allCodePathsReturn, _, inner') <- checkBlock mass ret inner
535+ return (allCodePathsReturn, mass, While val' inner')
536+checkStatement mass ret (If ifst) = do
537+ (allCodePathsReturn, ifst') <- checkIfStatement mass ret ifst
538+ return (allCodePathsReturn, mass, If ifst')
539+checkStatement mass ret (For ident start end inner) = do
540+ moduleName <- substCurrentModule <$> ask
541+ assignVariable ident
542+ start' <- check start Number
543+ end' <- check end Number
544+ (allCodePathsReturn, _, inner') <- bindLocalVariables moduleName [(ident, Number)] $ checkBlock mass ret inner
545+ return (allCodePathsReturn, mass, For ident start' end' inner')
546+checkStatement mass ret (Return val) = do
547+ val' <- check val ret
548+ return (True, mass, Return val')
549+
550+checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> Subst (Bool, IfStatement)
551+checkIfStatement mass ret (IfStatement val thens Nothing) = do
552+ val' <- check val Boolean
553+ (_, _, thens') <- checkBlock mass ret thens
554+ return (False, IfStatement val' thens' Nothing)
555+checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
556+ val' <- check val Boolean
557+ (allCodePathsReturn1, _, thens') <- checkBlock mass ret thens
558+ (allCodePathsReturn2, elses') <- checkElseStatement mass ret elses
559+ return (allCodePathsReturn1 && allCodePathsReturn2, IfStatement val' thens' (Just elses'))
560+
561+checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> Subst (Bool, ElseStatement)
562+checkElseStatement mass ret (Else elses) = do
563+ (allCodePathsReturn, _, elses') <- checkBlock mass ret elses
564+ return (allCodePathsReturn, Else elses')
565+checkElseStatement mass ret (ElseIf ifst) = (id *** ElseIf) <$> checkIfStatement mass ret ifst
566+
567+checkBlock :: M.Map Ident Type -> Type -> [Statement] -> Subst (Bool, M.Map Ident Type, [Statement])
568+checkBlock mass _ [] = return (False, mass, [])
569+checkBlock mass ret (s:ss) = do
570+ moduleName <- substCurrentModule <$> ask
571+ (b1, mass1, s') <- checkStatement mass ret s
572+ bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
573+ (True, []) -> return (True, mass1, [s'])
574+ (True, _) -> throwError "Unreachable code"
575+ (False, ss') -> do
576+ (b, m, ss'') <- checkBlock mass1 ret ss'
577+ return (b, m, s':ss'')
578+
579+skolemize :: String -> Type -> Subst Type
580+skolemize ident ty = do
581+ tsk <- Skolem <$> fresh'
582+ return $ replaceTypeVars ident tsk ty
583+
584+check :: Value -> Type -> Subst Value
585+check val ty = rethrow errorMessage $ check' val ty
586+ where
587+ errorMessage msg =
588+ "Error checking type of term " ++
589+ prettyPrintValue val ++
590+ " against type " ++
591+ prettyPrintType ty ++
592+ ":\n" ++
593+ msg
594+
595+check' :: Value -> Type -> Subst Value
596+check' val (ForAll idents ty) = do
597+ sk <- skolemize idents ty
598+ check val sk
599+check' val (ConstrainedType constraints ty) = do
600+ val' <- check val ty
601+ return $ Abs (map (\_ -> Ident "__dict") constraints) val'
602+check' val u@(TUnknown _) = do
603+ val'@(TypedValue _ ty) <- infer val
604+ -- Don't unify an unknown with an inferred polytype
605+ ty' <- replaceAllVarsWithUnknowns ty
606+ ty' ~~ u
607+ return val'
608+check' v@(NumericLiteral _) Number = return v
609+check' v@(StringLiteral _) String = return v
610+check' v@(BooleanLiteral _) Boolean = return v
611+check' (Unary op val) ty = checkUnary op val ty
612+check' (Binary op left right) ty = checkBinary op left right ty
613+check' (ArrayLiteral vals) (Array ty) = ArrayLiteral <$> forM vals (\val -> check val ty)
614+check' (Indexer index vals) ty = do
615+ index' <- check index Number
616+ vals' <- check vals (Array ty)
617+ return $ Indexer index' vals'
618+check' (Abs args ret) (Function argTys retTy) = do
619+ moduleName <- substCurrentModule <$> ask
620+ guardWith "Incorrect number of function arguments" (length args == length argTys)
621+ ret' <- bindLocalVariables moduleName (zip args argTys) $ check ret retTy
622+ return $ Abs args ret'
623+check' (App f args) ret = do
624+ f'@(TypedValue _ ft) <- infer f
625+ app <- checkFunctionApplication f' ft args ret
626+ return $ app
627+check' (Var var) ty = do
628+ moduleName <- substCurrentModule <$> ask
629+ ty1 <- lookupVariable moduleName var
630+ repl <- replaceAllTypeSynonyms ty1
631+ repl `subsumes` ty
632+ return $ Var var
633+check' (TypedValue val ty1) ty2 = do
634+ moduleName <- substCurrentModule <$> ask
635+ kind <- liftCheck $ kindOf moduleName ty1
636+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
637+ ty1 `subsumes` ty2
638+ val' <- check val ty1
639+ return $ TypedValue val' ty1
640+check' (Case vals binders) ret = do
641+ vals' <- mapM infer vals
642+ let ts = map (\(TypedValue _ t) -> t) vals'
643+ binders' <- checkBinders ts ret binders
644+ return $ Case vals' binders'
645+check' (IfThenElse cond th el) ty = do
646+ cond' <- check cond Boolean
647+ th' <- check th ty
648+ el' <- check el ty
649+ return $ IfThenElse cond' th' el'
650+check' (ObjectLiteral ps) (Object row) = do
651+ ensureNoDuplicateProperties ps
652+ ps' <- checkProperties ps row False
653+ return $ ObjectLiteral ps'
654+check' (ObjectUpdate obj ps) (Object row) = do
655+ ensureNoDuplicateProperties ps
656+ us <- zip (map fst ps) <$> replicateM (length ps) fresh
657+ let (propsToCheck, rest) = rowToList row
658+ propsToRemove = map fst ps
659+ remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
660+ obj' <- check obj (Object (rowFromList (us ++ remainingProps, rest)))
661+ ps' <- checkProperties ps row True
662+ return $ ObjectUpdate obj' ps'
663+check' (Accessor prop val) ty = do
664+ rest <- fresh
665+ val' <- check val (Object (RCons prop ty rest))
666+ return $ Accessor prop val'
667+check' (Block ss) ret = do
668+ (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
669+ guardWith "Block is missing a return statement" allCodePathsReturn
670+ return $ Block ss'
671+check' (Constructor c) ty = do
672+ env <- getEnv
673+ moduleName <- substCurrentModule <$> ask
674+ case M.lookup (qualify moduleName c) (dataConstructors env) of
675+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
676+ Just (ty1, _) -> do
677+ repl <- replaceAllTypeSynonyms ty1
678+ repl `subsumes` ty
679+ return $ Constructor c
680+check' val (SaturatedTypeSynonym name args) = do
681+ ty <- expandTypeSynonym name args
682+ check val ty
683+check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
684+
685+checkProperties :: [(String, Value)] -> Type -> Bool -> Subst [(String, Value)]
686+checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
687+ go [] [] REmpty = return []
688+ go [] [] u@(TUnknown _) = do u ~~ REmpty
689+ return []
690+ go [] [] (Skolem _) | lax = return []
691+ go [] ((p, _): _) _ | lax = return []
692+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
693+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
694+ go ((p,v):ps') [] u@(TUnknown _) = do
695+ v'@(TypedValue _ ty) <- infer v
696+ rest <- fresh
697+ u ~~ RCons p ty rest
698+ ps'' <- go ps' [] rest
699+ return $ (p, v') : ps''
700+ go ((p,v):ps') ts r =
701+ case lookup p ts of
702+ Nothing -> do
703+ v'@(TypedValue _ ty) <- infer v
704+ rest <- fresh
705+ r ~~ RCons p ty rest
706+ ps'' <- go ps' ts rest
707+ return $ (p, v') : ps''
708+ Just ty -> do
709+ v' <- check v ty
710+ ps'' <- go ps' (delete (p, ty) ts) r
711+ return $ (p, v') : ps''
712+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
713+
714+checkFunctionApplication :: Value -> Type -> [Value] -> Type -> Subst Value
715+checkFunctionApplication fn fnTy args ret = rethrow errorMessage $ checkFunctionApplication' fn fnTy args ret
716+ where
717+ errorMessage msg = "Error applying function of type "
718+ ++ prettyPrintType fnTy
719+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
720+ ++ ":\n" ++ msg
721+
722+checkFunctionApplication' :: Value -> Type -> [Value] -> Type -> Subst Value
723+checkFunctionApplication' fn (Function argTys retTy) args ret = do
724+ guardWith "Incorrect number of function arguments" (length args == length argTys)
725+ args' <- zipWithM check args argTys
726+ retTy `subsumes` ret
727+ return $ App fn args'
728+checkFunctionApplication' fn (ForAll ident ty) args ret = do
729+ replaced <- replaceVarWithUnknown ident ty
730+ checkFunctionApplication fn replaced args ret
731+checkFunctionApplication' fn u@(TUnknown _) args ret = do
732+ args' <- mapM (\arg -> infer arg >>= \(TypedValue v t) -> TypedValue v <$> replaceAllVarsWithUnknowns t) args
733+ let tys = map (\(TypedValue _ t) -> t) args'
734+ u ~~ Function tys ret
735+ return $ App fn args'
736+checkFunctionApplication' fn (SaturatedTypeSynonym name tyArgs) args ret = do
737+ ty <- expandTypeSynonym name tyArgs
738+ checkFunctionApplication fn ty args ret
739+checkFunctionApplication' fn (ConstrainedType constraints fnTy) args ret = do
740+ checkFunctionApplication' (App fn [TypeClassDictionary constraints]) fnTy args ret
741+checkFunctionApplication' _ fnTy args ret = throwError $ "Applying a function of type "
742+ ++ prettyPrintType fnTy
743+ ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
744+ ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
745+
746+subsumes :: Type -> Type -> Subst ()
747+subsumes (ForAll ident ty1) ty2 = do
748+ replaced <- replaceVarWithUnknown ident ty1
749+ replaced `subsumes` ty2
750+subsumes (Function args1 ret1) (Function args2 ret2) = do
751+ zipWithM_ subsumes args2 args1
752+ ret1 `subsumes` ret2
753+subsumes ty1 ty2 = ty1 ~~ ty2
754+