@@ -0,0 +1,794 @@
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 (maybeToList, isNothing, isJust, fromMaybe)
24+import qualified Data.Data as D
25+import Data.Generics
26+ (mkM, everywhereM, everything, 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 [(Ident, (Value, Type))]
145+typesOf moduleName vals = do
146+ tys <- fmap (\(tys, s) -> map (\(ident, (val, ty)) -> (ident, (overTypes (apply s) val, apply s ty))) tys)
147+ . runSubst (SubstContext moduleName) $ do
148+ let es = map isTyped vals
149+ typed = filter (isJust . snd . snd) es
150+ untyped = filter (isNothing . snd . snd) es
151+ typedDict = map (\(ident, (_, Just ty)) -> (ident, ty)) typed
152+ untypedNames <- replicateM (length untyped) fresh
153+ let untypedDict = zip (map fst untyped) untypedNames
154+ dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ typedDict ++ untypedDict)
155+ forM es $ \e -> do
156+ triple@(_, (val, ty)) <- case e of
157+ (ident, (val, Just ty)) -> do
158+ kind <- liftCheck $ kindOf moduleName ty
159+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
160+ ty' <- replaceAllTypeSynonyms ty
161+ val' <- bindNames dict $ check val ty'
162+ return (ident, (val', ty'))
163+ (ident, (val, Nothing)) -> do
164+ TypedValue val' ty <- bindNames dict $ infer val
165+ ty ~~ fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
166+ return (ident, (val', ty))
167+ when (moduleName == ModuleName (ProperName "Main") && fst e == Ident "main") $ do
168+ [eff, a] <- replicateM 2 fresh
169+ ty ~~ TypeApp (TypeApp (TypeConstructor (Qualified (Just (ModuleName (ProperName "Eff"))) (ProperName "Eff"))) eff) a
170+ escapeCheck val ty
171+ return triple
172+ forM_ tys $ skolemEscapeCheck . snd . snd
173+ forM tys $ \(ident, (val, ty)) -> do
174+ val' <- replaceTypeClassDictionaries moduleName val
175+ return (ident, (overTypes (desaturateAllTypeSynonyms . setifyAll) $ val'
176+ , varIfUnknown . desaturateAllTypeSynonyms . setifyAll $ ty))
177+
178+isTyped :: (Ident, Value) -> (Ident, (Value, Maybe Type))
179+isTyped (name, TypedValue value ty) = (name, (value, Just ty))
180+isTyped (name, value) = (name, (value, Nothing))
181+
182+overTypes :: (Type -> Type) -> Value -> Value
183+overTypes f = everywhere (mkT f)
184+
185+replaceTypeClassDictionaries :: ModuleName -> Value -> Check Value
186+replaceTypeClassDictionaries mn = everywhereM (mkM go)
187+ where
188+ go (TypeClassDictionary constraint dicts) = entails mn dicts constraint
189+ go other = return other
190+
191+entails :: ModuleName -> [(Ident, [(Qualified ProperName, Type)], Qualified ProperName, Type)] -> (Qualified ProperName, Type) -> Check Value
192+entails moduleName context goal = do
193+ env <- getEnv
194+ case go env goal of
195+ [] -> throwError $ "No type class instance for " ++ show goal ++ " in context " ++ show context
196+ (dict : _) -> return dict
197+ where
198+ go env (className, ty) =
199+ [ App (Var (Qualified Nothing fnName)) args
200+ | (fnName, subgoals, className', ty') <- context
201+ , className == className'
202+ , subst <- maybeToList $ typeHeadsAreEqual moduleName env ty ty'
203+ , args <- forM (replaceAllTypeVars subst subgoals) (go env) ]
204+
205+typeHeadsAreEqual :: ModuleName -> Environment -> Type -> Type -> Maybe [(String, Type)]
206+typeHeadsAreEqual _ _ String String = Just []
207+typeHeadsAreEqual _ _ Number Number = Just []
208+typeHeadsAreEqual _ _ Boolean Boolean = Just []
209+typeHeadsAreEqual _ _ (Skolem s1) (Skolem s2) | s1 == s2 = Just []
210+typeHeadsAreEqual m e (Array ty1) (Array ty2) = typeHeadsAreEqual m e ty1 ty2
211+typeHeadsAreEqual m e (TypeConstructor c1) (TypeConstructor c2) | typeConstructorsAreEqual e m c1 c2 = Just []
212+typeHeadsAreEqual m e (TypeApp h1 (TypeVar v)) (TypeApp h2 arg) = (:) (v, arg) <$> typeHeadsAreEqual m e h1 h2
213+typeHeadsAreEqual m e t1@(TypeApp _ _) t2@(TypeApp _ (TypeVar _)) = typeHeadsAreEqual m e t2 t1
214+typeHeadsAreEqual _ _ _ _ = Nothing
215+
216+escapeCheck :: Value -> Type -> Subst ()
217+escapeCheck value ty = do
218+ subst <- substSubst <$> getSubstState
219+ let visibleUnknowns = nub $ unknowns $ apply subst ty
220+ let allUnknowns = findAllTypes value
221+ forM_ allUnknowns $ \t -> do
222+ let unsolvedUnknowns = nub . unknowns $ apply subst t
223+ guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
224+
225+findAllTypes :: Value -> [Type]
226+findAllTypes = everything (++) (mkQ [] go)
227+ where
228+ go (TypedValue _ ty) = [ty]
229+ go _ = []
230+
231+skolemEscapeCheck :: Type -> Check ()
232+skolemEscapeCheck ty =
233+ case something (mkQ Nothing findSkolems) ty of
234+ Nothing -> return ()
235+ Just _ -> throwError $ "Skolem variables cannot escape. Consider adding a type signature." ++ show ty
236+ where
237+ findSkolems (Skolem _) = return ()
238+ findSkolems _ = mzero
239+
240+setify :: Type -> Type
241+setify = rowFromList . first (M.toList . M.fromList) . rowToList
242+
243+setifyAll :: (D.Data d) => d -> d
244+setifyAll = everywhere (mkT setify)
245+
246+varIfUnknown :: Type -> Type
247+varIfUnknown ty =
248+ let unks = nub $ unknowns ty
249+ toName = (:) 't' . show
250+ ty' = everywhere (mkT typeToVar) $ ty
251+ typeToVar :: Type -> Type
252+ typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
253+ typeToVar t = t
254+ in mkForAll (sort . map toName $ unks) ty'
255+
256+replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
257+replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
258+
259+replaceAllVarsWithUnknowns :: Type -> Subst Type
260+replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
261+replaceAllVarsWithUnknowns ty = return ty
262+
263+replaceVarWithUnknown :: String -> Type -> Subst Type
264+replaceVarWithUnknown ident ty = do
265+ tu <- fresh
266+ return $ replaceTypeVars ident tu $ ty
267+
268+replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadReader SubstContext m, MonadError String m) => (D.Data d) => d -> m d
269+replaceAllTypeSynonyms d = do
270+ env <- getEnv
271+ moduleName <- substCurrentModule <$> ask
272+ let syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
273+ either throwError return $ saturateAllTypeSynonyms env moduleName syns d
274+
275+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
276+desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
277+ where
278+ replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
279+ replaceSaturatedTypeSynonym t = t
280+
281+expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Type
282+expandTypeSynonym name args = do
283+ env <- getEnv
284+ moduleName <- substCurrentModule `fmap` ask
285+ case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
286+ Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
287+ Nothing -> error "Type synonym was not defined"
288+
289+ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
290+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
291+
292+infer :: Value -> Subst Value
293+infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ infer' val
294+
295+infer' :: Value -> Subst Value
296+infer' v@(NumericLiteral _) = return $ TypedValue v Number
297+infer' v@(StringLiteral _) = return $ TypedValue v String
298+infer' v@(BooleanLiteral _) = return $ TypedValue v Boolean
299+infer' (ArrayLiteral vals) = do
300+ ts <- mapM infer vals
301+ els <- fresh
302+ forM_ ts $ \(TypedValue _ t) -> els ~~ Array t
303+ return $ TypedValue (ArrayLiteral ts) els
304+infer' (Unary op val) = do
305+ v <- infer val
306+ inferUnary op v
307+infer' (Binary op left right) = do
308+ v1 <- infer left
309+ v2 <- infer right
310+ inferBinary op v1 v2
311+infer' (ObjectLiteral ps) = do
312+ ensureNoDuplicateProperties ps
313+ ts <- mapM (infer . snd) ps
314+ let fields = zipWith (\name (TypedValue _ t) -> (name, t)) (map fst ps) ts
315+ ty = Object $ rowFromList (fields, REmpty)
316+ return $ TypedValue (ObjectLiteral (zip (map fst ps) ts)) ty
317+infer' (ObjectUpdate o ps) = do
318+ ensureNoDuplicateProperties ps
319+ row <- fresh
320+ newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
321+ let newTys = map (\(name, TypedValue _ ty) -> (name, ty)) newVals
322+ oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
323+ o' <- check o $ Object $ rowFromList (oldTys, row)
324+ return $ TypedValue (ObjectUpdate o' newVals) $ Object $ rowFromList (newTys, row)
325+infer' (Indexer index val) = do
326+ el <- fresh
327+ index' <- check index Number
328+ val' <- check val (Array el)
329+ return $ TypedValue (Indexer (TypedValue index' Number) (TypedValue val' (Array el))) el
330+infer' (Accessor prop val) = do
331+ typed@(TypedValue _ objTy) <- infer val
332+ propTy <- inferProperty objTy prop
333+ case propTy of
334+ Nothing -> do
335+ field <- fresh
336+ rest <- fresh
337+ objTy `subsumes` Object (RCons prop field rest)
338+ return $ TypedValue (Accessor prop typed) field
339+ Just ty -> return $ TypedValue (Accessor prop typed) ty
340+infer' (Abs args ret) = do
341+ ts <- replicateM (length args) fresh
342+ moduleName <- substCurrentModule <$> ask
343+ bindLocalVariables moduleName (zip args ts) $ do
344+ body@(TypedValue _ bodyTy) <- infer' ret
345+ return $ TypedValue (Abs args body) $ Function ts bodyTy
346+infer' (App f args) = do
347+ f'@(TypedValue _ ft) <- infer f
348+ ret <- fresh
349+ app <- checkFunctionApplication f' ft args ret
350+ return $ TypedValue app ret
351+infer' (Var var) = do
352+ moduleName <- substCurrentModule <$> ask
353+ ty <- lookupVariable moduleName var
354+ ty' <- replaceAllTypeSynonyms ty
355+ case ty' of
356+ ConstrainedType constraints _ -> do
357+ dicts <- getTypeClassDictionaries
358+ return $ TypedValue (App (Var var) (map (flip TypeClassDictionary dicts) constraints)) ty'
359+ _ -> return $ TypedValue (Var var) ty'
360+infer' (Block ss) = do
361+ ret <- fresh
362+ (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
363+ guardWith "Block is missing a return statement" allCodePathsReturn
364+ return $ TypedValue (Block ss') ret
365+infer' v@(Constructor c) = do
366+ env <- getEnv
367+ moduleName <- substCurrentModule `fmap` ask
368+ case M.lookup (qualify moduleName c) (dataConstructors env) of
369+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
370+ Just (ty, _) -> do ty' <- replaceAllTypeSynonyms ty
371+ return $ TypedValue v ty'
372+infer' (Case vals binders) = do
373+ ts <- mapM infer vals
374+ ret <- fresh
375+ binders' <- checkBinders (map (\(TypedValue _ t) -> t) ts) ret binders
376+ return $ TypedValue (Case ts binders') ret
377+infer' (IfThenElse cond th el) = do
378+ cond' <- check cond Boolean
379+ v2@(TypedValue _ t2) <- infer th
380+ v3@(TypedValue _ t3) <- infer el
381+ t2 ~~ t3
382+ return $ TypedValue (IfThenElse cond' v2 v3) t2
383+infer' (TypedValue val ty) = do
384+ moduleName <- substCurrentModule <$> ask
385+ kind <- liftCheck $ kindOf moduleName ty
386+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
387+ ty' <- replaceAllTypeSynonyms ty
388+ val' <- check val ty'
389+ return $ TypedValue val' ty
390+infer' _ = error "Invalid argument to infer"
391+
392+inferProperty :: Type -> String -> Subst (Maybe Type)
393+inferProperty (Object row) prop = do
394+ let (props, _) = rowToList row
395+ return $ lookup prop props
396+inferProperty (SaturatedTypeSynonym name args) prop = do
397+ replaced <- expandTypeSynonym name args
398+ inferProperty replaced prop
399+inferProperty (ForAll ident ty) prop = do
400+ replaced <- replaceVarWithUnknown ident ty
401+ inferProperty replaced prop
402+inferProperty _ _ = return Nothing
403+
404+inferUnary :: UnaryOperator -> Value -> Subst Value
405+inferUnary op (TypedValue val valTy) =
406+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
407+ (valTy', resTy) -> do
408+ valTy' ~~ valTy
409+ return $ TypedValue (Unary op val) resTy
410+inferUnary _ _ = error "Invalid arguments to inferUnary"
411+
412+checkUnary :: UnaryOperator -> Value -> Type -> Subst Value
413+checkUnary op val res =
414+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
415+ (valTy, resTy) -> do
416+ res ~~ resTy
417+ val' <- check val valTy
418+ return $ Unary op val'
419+
420+unaryOps :: [(UnaryOperator, (Type, Type))]
421+unaryOps = [ (Negate, (Number, Number))
422+ , (Not, (Boolean, Boolean))
423+ , (BitwiseNot, (Number, Number))
424+ ]
425+
426+inferBinary :: BinaryOperator -> Value -> Value -> Subst Value
427+inferBinary op left@(TypedValue _ leftTy) right@(TypedValue _ rightTy) | isEqualityTest op = do
428+ leftTy ~~ rightTy
429+ return $ TypedValue (Binary op left right) Boolean
430+inferBinary op left@(TypedValue _ leftTy) right@(TypedValue _ rightTy) =
431+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
432+ (valTy, resTy) -> do
433+ leftTy ~~ valTy
434+ rightTy ~~ valTy
435+ return $ TypedValue (Binary op left right) resTy
436+inferBinary _ _ _ = error "Invalid arguments to inferBinary"
437+
438+checkBinary :: BinaryOperator -> Value -> Value -> Type -> Subst Value
439+checkBinary op left right res | isEqualityTest op = do
440+ res ~~ Boolean
441+ left'@(TypedValue _ t1) <- infer left
442+ right'@(TypedValue _ t2) <- infer right
443+ t1 ~~ t2
444+ return $ Binary op left' right'
445+checkBinary op left right res =
446+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
447+ (valTy, resTy) -> do
448+ res ~~ resTy
449+ left' <- check left valTy
450+ right' <- check right valTy
451+ return $ Binary op left' right'
452+
453+isEqualityTest :: BinaryOperator -> Bool
454+isEqualityTest EqualTo = True
455+isEqualityTest NotEqualTo = True
456+isEqualityTest _ = False
457+
458+binaryOps :: [(BinaryOperator, (Type, Type))]
459+binaryOps = [ (Add, (Number, Number))
460+ , (Subtract, (Number, Number))
461+ , (Multiply, (Number, Number))
462+ , (Divide, (Number, Number))
463+ , (Modulus, (Number, Number))
464+ , (BitwiseAnd, (Number, Number))
465+ , (BitwiseOr, (Number, Number))
466+ , (BitwiseXor, (Number, Number))
467+ , (ShiftRight, (Number, Number))
468+ , (ZeroFillShiftRight, (Number, Number))
469+ , (And, (Boolean, Boolean))
470+ , (Or, (Boolean, Boolean))
471+ , (Concat, (String, String))
472+ , (Modulus, (Number, Number))
473+ , (LessThan, (Number, Boolean))
474+ , (LessThanOrEqualTo, (Number, Boolean))
475+ , (GreaterThan, (Number, Boolean))
476+ , (GreaterThanOrEqualTo, (Number, Boolean))
477+ ]
478+
479+inferBinder :: Type -> Binder -> Subst (M.Map Ident Type)
480+inferBinder _ NullBinder = return M.empty
481+inferBinder val (StringBinder _) = val ~~ String >> return M.empty
482+inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
483+inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
484+inferBinder val (VarBinder name) = return $ M.singleton name val
485+inferBinder val (NullaryBinder ctor) = do
486+ env <- getEnv
487+ moduleName <- substCurrentModule <$> ask
488+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
489+ Just (ty, _) -> do
490+ ty `subsumes` val
491+ return M.empty
492+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
493+inferBinder val (UnaryBinder ctor binder) = do
494+ env <- getEnv
495+ moduleName <- substCurrentModule <$> ask
496+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
497+ Just (ty, _) -> do
498+ fn <- replaceAllVarsWithUnknowns ty
499+ case fn of
500+ Function [obj] ret -> do
501+ val `subsumes` ret
502+ inferBinder obj binder
503+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
504+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
505+inferBinder val (ObjectBinder props) = do
506+ row <- fresh
507+ rest <- fresh
508+ m1 <- inferRowProperties row rest props
509+ val ~~ Object row
510+ return m1
511+ where
512+ inferRowProperties :: Type -> Type -> [(String, Binder)] -> Subst (M.Map Ident Type)
513+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
514+ inferRowProperties nrow row ((name, binder):binders) = do
515+ propTy <- fresh
516+ m1 <- inferBinder propTy binder
517+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
518+ return $ m1 `M.union` m2
519+inferBinder val (ArrayBinder binders) = do
520+ el <- fresh
521+ m1 <- M.unions <$> mapM (inferBinder el) binders
522+ val ~~ Array el
523+ return m1
524+inferBinder val (ConsBinder headBinder tailBinder) = do
525+ el <- fresh
526+ m1 <- inferBinder el headBinder
527+ m2 <- inferBinder val tailBinder
528+ val ~~ Array el
529+ return $ m1 `M.union` m2
530+inferBinder val (NamedBinder name binder) = do
531+ m <- inferBinder val binder
532+ return $ M.insert name val m
533+
534+checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> Subst [([Binder], Maybe Guard, Value)]
535+checkBinders _ _ [] = return []
536+checkBinders nvals ret ((binders, grd, val):bs) = do
537+ moduleName <- substCurrentModule <$> ask
538+ m1 <- M.unions <$> zipWithM inferBinder nvals binders
539+ r <- bindLocalVariables moduleName (M.toList m1) $ do
540+ val' <- check val ret
541+ case grd of
542+ Nothing -> return (binders, Nothing, val')
543+ Just g -> do
544+ g' <- check g Boolean
545+ return (binders, Just g', val')
546+ rs <- checkBinders nvals ret bs
547+ return $ r : rs
548+
549+assignVariable :: Ident -> Subst ()
550+assignVariable name = do
551+ env <- checkEnv <$> get
552+ moduleName <- substCurrentModule <$> ask
553+ case M.lookup (moduleName, name) (names env) of
554+ Just (_, LocalVariable) -> throwError $ "Variable with name " ++ show name ++ " already exists."
555+ _ -> return ()
556+
557+checkStatement :: M.Map Ident Type -> Type -> Statement -> Subst (Bool, M.Map Ident Type, Statement)
558+checkStatement mass _ (VariableIntroduction name val) = do
559+ assignVariable name
560+ val'@(TypedValue _ t) <- infer val
561+ return (False, M.insert name t mass, VariableIntroduction name val')
562+checkStatement mass _ (Assignment ident val) = do
563+ val'@(TypedValue _ t) <- infer val
564+ case M.lookup ident mass of
565+ Nothing -> throwError $ "No local variable with name " ++ show ident
566+ Just ty -> do t ~~ ty
567+ return (False, mass, Assignment ident val')
568+checkStatement mass ret (While val inner) = do
569+ val' <- check val Boolean
570+ (allCodePathsReturn, _, inner') <- checkBlock mass ret inner
571+ return (allCodePathsReturn, mass, While val' inner')
572+checkStatement mass ret (If ifst) = do
573+ (allCodePathsReturn, ifst') <- checkIfStatement mass ret ifst
574+ return (allCodePathsReturn, mass, If ifst')
575+checkStatement mass ret (For ident start end inner) = do
576+ moduleName <- substCurrentModule <$> ask
577+ assignVariable ident
578+ start' <- check start Number
579+ end' <- check end Number
580+ (allCodePathsReturn, _, inner') <- bindLocalVariables moduleName [(ident, Number)] $ checkBlock mass ret inner
581+ return (allCodePathsReturn, mass, For ident start' end' inner')
582+checkStatement mass ret (Return val) = do
583+ val' <- check val ret
584+ return (True, mass, Return val')
585+
586+checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> Subst (Bool, IfStatement)
587+checkIfStatement mass ret (IfStatement val thens Nothing) = do
588+ val' <- check val Boolean
589+ (_, _, thens') <- checkBlock mass ret thens
590+ return (False, IfStatement val' thens' Nothing)
591+checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
592+ val' <- check val Boolean
593+ (allCodePathsReturn1, _, thens') <- checkBlock mass ret thens
594+ (allCodePathsReturn2, elses') <- checkElseStatement mass ret elses
595+ return (allCodePathsReturn1 && allCodePathsReturn2, IfStatement val' thens' (Just elses'))
596+
597+checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> Subst (Bool, ElseStatement)
598+checkElseStatement mass ret (Else elses) = do
599+ (allCodePathsReturn, _, elses') <- checkBlock mass ret elses
600+ return (allCodePathsReturn, Else elses')
601+checkElseStatement mass ret (ElseIf ifst) = (id *** ElseIf) <$> checkIfStatement mass ret ifst
602+
603+checkBlock :: M.Map Ident Type -> Type -> [Statement] -> Subst (Bool, M.Map Ident Type, [Statement])
604+checkBlock mass _ [] = return (False, mass, [])
605+checkBlock mass ret (s:ss) = do
606+ moduleName <- substCurrentModule <$> ask
607+ (b1, mass1, s') <- checkStatement mass ret s
608+ bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
609+ (True, []) -> return (True, mass1, [s'])
610+ (True, _) -> throwError "Unreachable code"
611+ (False, ss') -> do
612+ (b, m, ss'') <- checkBlock mass1 ret ss'
613+ return (b, m, s':ss'')
614+
615+skolemize :: String -> Type -> Subst Type
616+skolemize ident ty = do
617+ tsk <- Skolem <$> fresh'
618+ return $ replaceTypeVars ident tsk ty
619+
620+check :: Value -> Type -> Subst Value
621+check val ty = rethrow errorMessage $ check' val ty
622+ where
623+ errorMessage msg =
624+ "Error checking type of term " ++
625+ prettyPrintValue val ++
626+ " against type " ++
627+ prettyPrintType ty ++
628+ ":\n" ++
629+ msg
630+
631+check' :: Value -> Type -> Subst Value
632+check' val (ForAll idents ty) = do
633+ sk <- skolemize idents ty
634+ check val sk
635+check' val (ConstrainedType constraints ty) = do
636+ dictNames <- flip mapM constraints $ \(Qualified _ (ProperName className), _) -> do
637+ n <- liftCheck freshDictionaryName
638+ return $ Ident $ "__dict_" ++ className ++ "_" ++ show n
639+ val' <- withTypeClassDictionaries (zipWith (\name (className, instanceTy) -> (name, [], className, instanceTy)) dictNames constraints) $ check val ty
640+ return $ Abs dictNames val'
641+check' val u@(TUnknown _) = do
642+ val'@(TypedValue _ ty) <- infer val
643+ -- Don't unify an unknown with an inferred polytype
644+ ty' <- replaceAllVarsWithUnknowns ty
645+ ty' ~~ u
646+ return val'
647+check' v@(NumericLiteral _) Number = return v
648+check' v@(StringLiteral _) String = return v
649+check' v@(BooleanLiteral _) Boolean = return v
650+check' (Unary op val) ty = checkUnary op val ty
651+check' (Binary op left right) ty = checkBinary op left right ty
652+check' (ArrayLiteral vals) (Array ty) = ArrayLiteral <$> forM vals (\val -> check val ty)
653+check' (Indexer index vals) ty = do
654+ index' <- check index Number
655+ vals' <- check vals (Array ty)
656+ return $ Indexer index' vals'
657+check' (Abs args ret) (Function argTys retTy) = do
658+ moduleName <- substCurrentModule <$> ask
659+ guardWith "Incorrect number of function arguments" (length args == length argTys)
660+ ret' <- bindLocalVariables moduleName (zip args argTys) $ check ret retTy
661+ return $ Abs args ret'
662+check' (App f args) ret = do
663+ f'@(TypedValue _ ft) <- infer f
664+ app <- checkFunctionApplication f' ft args ret
665+ return $ app
666+check' (Var var) ty = do
667+ moduleName <- substCurrentModule <$> ask
668+ ty1 <- lookupVariable moduleName var
669+ repl <- replaceAllTypeSynonyms ty1
670+ repl `subsumes` ty
671+ return $ Var var
672+check' (TypedValue val ty1) ty2 = do
673+ moduleName <- substCurrentModule <$> ask
674+ kind <- liftCheck $ kindOf moduleName ty1
675+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
676+ ty1 `subsumes` ty2
677+ val' <- check val ty1
678+ return $ TypedValue val' ty1
679+check' (Case vals binders) ret = do
680+ vals' <- mapM infer vals
681+ let ts = map (\(TypedValue _ t) -> t) vals'
682+ binders' <- checkBinders ts ret binders
683+ return $ Case vals' binders'
684+check' (IfThenElse cond th el) ty = do
685+ cond' <- check cond Boolean
686+ th' <- check th ty
687+ el' <- check el ty
688+ return $ IfThenElse cond' th' el'
689+check' (ObjectLiteral ps) (Object row) = do
690+ ensureNoDuplicateProperties ps
691+ ps' <- checkProperties ps row False
692+ return $ ObjectLiteral ps'
693+check' (ObjectUpdate obj ps) (Object row) = do
694+ ensureNoDuplicateProperties ps
695+ us <- zip (map fst ps) <$> replicateM (length ps) fresh
696+ let (propsToCheck, rest) = rowToList row
697+ propsToRemove = map fst ps
698+ remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
699+ obj' <- check obj (Object (rowFromList (us ++ remainingProps, rest)))
700+ ps' <- checkProperties ps row True
701+ return $ ObjectUpdate obj' ps'
702+check' (Accessor prop val) ty = do
703+ rest <- fresh
704+ val' <- check val (Object (RCons prop ty rest))
705+ return $ Accessor prop val'
706+check' (Block ss) ret = do
707+ (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
708+ guardWith "Block is missing a return statement" allCodePathsReturn
709+ return $ Block ss'
710+check' (Constructor c) ty = do
711+ env <- getEnv
712+ moduleName <- substCurrentModule <$> ask
713+ case M.lookup (qualify moduleName c) (dataConstructors env) of
714+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
715+ Just (ty1, _) -> do
716+ repl <- replaceAllTypeSynonyms ty1
717+ repl `subsumes` ty
718+ return $ Constructor c
719+check' val (SaturatedTypeSynonym name args) = do
720+ ty <- expandTypeSynonym name args
721+ check val ty
722+check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
723+
724+checkProperties :: [(String, Value)] -> Type -> Bool -> Subst [(String, Value)]
725+checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
726+ go [] [] REmpty = return []
727+ go [] [] u@(TUnknown _) = do u ~~ REmpty
728+ return []
729+ go [] [] (Skolem _) | lax = return []
730+ go [] ((p, _): _) _ | lax = return []
731+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
732+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
733+ go ((p,v):ps') [] u@(TUnknown _) = do
734+ v'@(TypedValue _ ty) <- infer v
735+ rest <- fresh
736+ u ~~ RCons p ty rest
737+ ps'' <- go ps' [] rest
738+ return $ (p, v') : ps''
739+ go ((p,v):ps') ts r =
740+ case lookup p ts of
741+ Nothing -> do
742+ v'@(TypedValue _ ty) <- infer v
743+ rest <- fresh
744+ r ~~ RCons p ty rest
745+ ps'' <- go ps' ts rest
746+ return $ (p, v') : ps''
747+ Just ty -> do
748+ v' <- check v ty
749+ ps'' <- go ps' (delete (p, ty) ts) r
750+ return $ (p, v') : ps''
751+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
752+
753+checkFunctionApplication :: Value -> Type -> [Value] -> Type -> Subst Value
754+checkFunctionApplication fn fnTy args ret = rethrow errorMessage $ checkFunctionApplication' fn fnTy args ret
755+ where
756+ errorMessage msg = "Error applying function of type "
757+ ++ prettyPrintType fnTy
758+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
759+ ++ ":\n" ++ msg
760+
761+checkFunctionApplication' :: Value -> Type -> [Value] -> Type -> Subst Value
762+checkFunctionApplication' fn (Function argTys retTy) args ret = do
763+ guardWith "Incorrect number of function arguments" (length args == length argTys)
764+ args' <- zipWithM check args argTys
765+ retTy `subsumes` ret
766+ return $ App fn args'
767+checkFunctionApplication' fn (ForAll ident ty) args ret = do
768+ replaced <- replaceVarWithUnknown ident ty
769+ checkFunctionApplication fn replaced args ret
770+checkFunctionApplication' fn u@(TUnknown _) args ret = do
771+ args' <- mapM (\arg -> infer arg >>= \(TypedValue v t) -> TypedValue v <$> replaceAllVarsWithUnknowns t) args
772+ let tys = map (\(TypedValue _ t) -> t) args'
773+ u ~~ Function tys ret
774+ return $ App fn args'
775+checkFunctionApplication' fn (SaturatedTypeSynonym name tyArgs) args ret = do
776+ ty <- expandTypeSynonym name tyArgs
777+ checkFunctionApplication fn ty args ret
778+checkFunctionApplication' fn (ConstrainedType constraints fnTy) args ret = do
779+ dicts <- getTypeClassDictionaries
780+ checkFunctionApplication' (App fn (map (flip TypeClassDictionary dicts) constraints)) fnTy args ret
781+checkFunctionApplication' _ fnTy args ret = throwError $ "Applying a function of type "
782+ ++ prettyPrintType fnTy
783+ ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
784+ ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
785+
786+subsumes :: Type -> Type -> Subst ()
787+subsumes (ForAll ident ty1) ty2 = do
788+ replaced <- replaceVarWithUnknown ident ty1
789+ replaced `subsumes` ty2
790+subsumes (Function args1 ret1) (Function args2 ret2) = do
791+ zipWithM_ subsumes args2 args1
792+ ret1 `subsumes` ret2
793+subsumes ty1 ty2 = ty1 ~~ ty2
794+