@@ -0,0 +1,805 @@
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 -> [TypeClassDictionaryInScope] -> (Qualified ProperName, Type) -> Check Value
192+entails moduleName context goal@(className, ty) = do
193+ env <- getEnv
194+ case go env goal of
195+ [] -> throwError $ "No " ++ show className ++ " instance found for " ++ prettyPrintType ty
196+ (dict : _) -> return dict
197+ where
198+ go env (className', ty') =
199+ [ mkDictionary (tcdName tcd) args
200+ | tcd <- context
201+ , qualify moduleName className' == qualify moduleName (tcdClassName tcd)
202+ , subst <- maybeToList $ typeHeadsAreEqual moduleName env ty' (tcdInstanceType tcd)
203+ , args <- solveSubgoals env subst (tcdDependencies tcd) ]
204+ solveSubgoals _ _ Nothing = [Nothing]
205+ solveSubgoals env subst (Just subgoals) = do
206+ dict <- mapM (go env) (replaceAllTypeVars subst subgoals)
207+ return $ Just dict
208+ mkDictionary fnName Nothing = Var (Qualified Nothing fnName)
209+ mkDictionary fnName (Just args) = App (Var (Qualified Nothing fnName)) args
210+
211+typeHeadsAreEqual :: ModuleName -> Environment -> Type -> Type -> Maybe [(String, Type)]
212+typeHeadsAreEqual _ _ String String = Just []
213+typeHeadsAreEqual _ _ Number Number = Just []
214+typeHeadsAreEqual _ _ Boolean Boolean = Just []
215+typeHeadsAreEqual _ _ (Skolem s1) (Skolem s2) | s1 == s2 = Just []
216+typeHeadsAreEqual m e (Array ty1) (Array ty2) = typeHeadsAreEqual m e ty1 ty2
217+typeHeadsAreEqual m e (TypeConstructor c1) (TypeConstructor c2) | typeConstructorsAreEqual e m c1 c2 = Just []
218+typeHeadsAreEqual m e (TypeApp h1 (TypeVar v)) (TypeApp h2 arg) = (:) (v, arg) <$> typeHeadsAreEqual m e h1 h2
219+typeHeadsAreEqual m e t1@(TypeApp _ _) t2@(TypeApp _ (TypeVar _)) = typeHeadsAreEqual m e t2 t1
220+typeHeadsAreEqual _ _ _ _ = Nothing
221+
222+escapeCheck :: Value -> Type -> Subst ()
223+escapeCheck value ty = do
224+ subst <- substSubst <$> getSubstState
225+ let visibleUnknowns = nub $ unknowns $ apply subst ty
226+ let allUnknowns = findAllTypes value
227+ forM_ allUnknowns $ \t -> do
228+ let unsolvedUnknowns = nub . unknowns $ apply subst t
229+ guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
230+
231+findAllTypes :: Value -> [Type]
232+findAllTypes = everything (++) (mkQ [] go)
233+ where
234+ go (TypedValue _ ty) = [ty]
235+ go _ = []
236+
237+skolemEscapeCheck :: Type -> Check ()
238+skolemEscapeCheck ty =
239+ case something (mkQ Nothing findSkolems) ty of
240+ Nothing -> return ()
241+ Just _ -> throwError $ "Skolem variables cannot escape. Consider adding a type signature." ++ show ty
242+ where
243+ findSkolems (Skolem _) = return ()
244+ findSkolems _ = mzero
245+
246+setify :: Type -> Type
247+setify = rowFromList . first (M.toList . M.fromList) . rowToList
248+
249+setifyAll :: (D.Data d) => d -> d
250+setifyAll = everywhere (mkT setify)
251+
252+varIfUnknown :: Type -> Type
253+varIfUnknown ty =
254+ let unks = nub $ unknowns ty
255+ toName = (:) 't' . show
256+ ty' = everywhere (mkT typeToVar) $ ty
257+ typeToVar :: Type -> Type
258+ typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
259+ typeToVar t = t
260+ in mkForAll (sort . map toName $ unks) ty'
261+
262+replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
263+replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
264+
265+replaceAllVarsWithUnknowns :: Type -> Subst Type
266+replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
267+replaceAllVarsWithUnknowns ty = return ty
268+
269+replaceVarWithUnknown :: String -> Type -> Subst Type
270+replaceVarWithUnknown ident ty = do
271+ tu <- fresh
272+ return $ replaceTypeVars ident tu $ ty
273+
274+replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadReader SubstContext m, MonadError String m) => (D.Data d) => d -> m d
275+replaceAllTypeSynonyms d = do
276+ env <- getEnv
277+ moduleName <- substCurrentModule <$> ask
278+ let syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
279+ either throwError return $ saturateAllTypeSynonyms env moduleName syns d
280+
281+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
282+desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
283+ where
284+ replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
285+ replaceSaturatedTypeSynonym t = t
286+
287+expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Type
288+expandTypeSynonym name args = do
289+ env <- getEnv
290+ moduleName <- substCurrentModule `fmap` ask
291+ case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
292+ Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
293+ Nothing -> error "Type synonym was not defined"
294+
295+ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
296+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
297+
298+infer :: Value -> Subst Value
299+infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ infer' val
300+
301+infer' :: Value -> Subst Value
302+infer' v@(NumericLiteral _) = return $ TypedValue v Number
303+infer' v@(StringLiteral _) = return $ TypedValue v String
304+infer' v@(BooleanLiteral _) = return $ TypedValue v Boolean
305+infer' (ArrayLiteral vals) = do
306+ ts <- mapM infer vals
307+ els <- fresh
308+ forM_ ts $ \(TypedValue _ t) -> els ~~ Array t
309+ return $ TypedValue (ArrayLiteral ts) els
310+infer' (Unary op val) = do
311+ v <- infer val
312+ inferUnary op v
313+infer' (Binary op left right) = do
314+ v1 <- infer left
315+ v2 <- infer right
316+ inferBinary op v1 v2
317+infer' (ObjectLiteral ps) = do
318+ ensureNoDuplicateProperties ps
319+ ts <- mapM (infer . snd) ps
320+ let fields = zipWith (\name (TypedValue _ t) -> (name, t)) (map fst ps) ts
321+ ty = Object $ rowFromList (fields, REmpty)
322+ return $ TypedValue (ObjectLiteral (zip (map fst ps) ts)) ty
323+infer' (ObjectUpdate o ps) = do
324+ ensureNoDuplicateProperties ps
325+ row <- fresh
326+ newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
327+ let newTys = map (\(name, TypedValue _ ty) -> (name, ty)) newVals
328+ oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
329+ o' <- check o $ Object $ rowFromList (oldTys, row)
330+ return $ TypedValue (ObjectUpdate o' newVals) $ Object $ rowFromList (newTys, row)
331+infer' (Indexer index val) = do
332+ el <- fresh
333+ index' <- check index Number
334+ val' <- check val (Array el)
335+ return $ TypedValue (Indexer (TypedValue index' Number) (TypedValue val' (Array el))) el
336+infer' (Accessor prop val) = do
337+ typed@(TypedValue _ objTy) <- infer val
338+ propTy <- inferProperty objTy prop
339+ case propTy of
340+ Nothing -> do
341+ field <- fresh
342+ rest <- fresh
343+ objTy `subsumes` Object (RCons prop field rest)
344+ return $ TypedValue (Accessor prop typed) field
345+ Just ty -> return $ TypedValue (Accessor prop typed) ty
346+infer' (Abs args ret) = do
347+ ts <- replicateM (length args) fresh
348+ moduleName <- substCurrentModule <$> ask
349+ bindLocalVariables moduleName (zip args ts) $ do
350+ body@(TypedValue _ bodyTy) <- infer' ret
351+ return $ TypedValue (Abs args body) $ Function ts bodyTy
352+infer' (App f args) = do
353+ f'@(TypedValue _ ft) <- infer f
354+ ret <- fresh
355+ app <- checkFunctionApplication f' ft args ret
356+ return $ TypedValue app ret
357+infer' (Var var) = do
358+ moduleName <- substCurrentModule <$> ask
359+ ty <- lookupVariable moduleName var
360+ ty' <- replaceAllTypeSynonyms ty
361+ case ty' of
362+ ConstrainedType constraints _ -> do
363+ env <- getEnv
364+ dicts <- getTypeClassDictionaries
365+ return $ TypedValue (App (Var var) (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) ty'
366+ _ -> return $ TypedValue (Var var) ty'
367+infer' (Block ss) = do
368+ ret <- fresh
369+ (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
370+ guardWith "Block is missing a return statement" allCodePathsReturn
371+ return $ TypedValue (Block ss') ret
372+infer' v@(Constructor c) = do
373+ env <- getEnv
374+ moduleName <- substCurrentModule `fmap` ask
375+ case M.lookup (qualify moduleName c) (dataConstructors env) of
376+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
377+ Just (ty, _) -> do ty' <- replaceAllTypeSynonyms ty
378+ return $ TypedValue v ty'
379+infer' (Case vals binders) = do
380+ ts <- mapM infer vals
381+ ret <- fresh
382+ binders' <- checkBinders (map (\(TypedValue _ t) -> t) ts) ret binders
383+ return $ TypedValue (Case ts binders') ret
384+infer' (IfThenElse cond th el) = do
385+ cond' <- check cond Boolean
386+ v2@(TypedValue _ t2) <- infer th
387+ v3@(TypedValue _ t3) <- infer el
388+ t2 ~~ t3
389+ return $ TypedValue (IfThenElse cond' v2 v3) t2
390+infer' (TypedValue val ty) = do
391+ moduleName <- substCurrentModule <$> ask
392+ kind <- liftCheck $ kindOf moduleName ty
393+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
394+ ty' <- replaceAllTypeSynonyms ty
395+ val' <- check val ty'
396+ return $ TypedValue val' ty
397+infer' _ = error "Invalid argument to infer"
398+
399+inferProperty :: Type -> String -> Subst (Maybe Type)
400+inferProperty (Object row) prop = do
401+ let (props, _) = rowToList row
402+ return $ lookup prop props
403+inferProperty (SaturatedTypeSynonym name args) prop = do
404+ replaced <- expandTypeSynonym name args
405+ inferProperty replaced prop
406+inferProperty (ForAll ident ty) prop = do
407+ replaced <- replaceVarWithUnknown ident ty
408+ inferProperty replaced prop
409+inferProperty _ _ = return Nothing
410+
411+inferUnary :: UnaryOperator -> Value -> Subst Value
412+inferUnary op (TypedValue val valTy) =
413+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
414+ (valTy', resTy) -> do
415+ valTy' ~~ valTy
416+ return $ TypedValue (Unary op val) resTy
417+inferUnary _ _ = error "Invalid arguments to inferUnary"
418+
419+checkUnary :: UnaryOperator -> Value -> Type -> Subst Value
420+checkUnary op val res =
421+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
422+ (valTy, resTy) -> do
423+ res ~~ resTy
424+ val' <- check val valTy
425+ return $ Unary op val'
426+
427+unaryOps :: [(UnaryOperator, (Type, Type))]
428+unaryOps = [ (Negate, (Number, Number))
429+ , (Not, (Boolean, Boolean))
430+ , (BitwiseNot, (Number, Number))
431+ ]
432+
433+inferBinary :: BinaryOperator -> Value -> Value -> Subst Value
434+inferBinary op left@(TypedValue _ leftTy) right@(TypedValue _ rightTy) | isEqualityTest op = do
435+ leftTy ~~ rightTy
436+ return $ TypedValue (Binary op left right) Boolean
437+inferBinary op left@(TypedValue _ leftTy) right@(TypedValue _ rightTy) =
438+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
439+ (valTy, resTy) -> do
440+ leftTy ~~ valTy
441+ rightTy ~~ valTy
442+ return $ TypedValue (Binary op left right) resTy
443+inferBinary _ _ _ = error "Invalid arguments to inferBinary"
444+
445+checkBinary :: BinaryOperator -> Value -> Value -> Type -> Subst Value
446+checkBinary op left right res | isEqualityTest op = do
447+ res ~~ Boolean
448+ left'@(TypedValue _ t1) <- infer left
449+ right'@(TypedValue _ t2) <- infer right
450+ t1 ~~ t2
451+ return $ Binary op left' right'
452+checkBinary op left right res =
453+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
454+ (valTy, resTy) -> do
455+ res ~~ resTy
456+ left' <- check left valTy
457+ right' <- check right valTy
458+ return $ Binary op left' right'
459+
460+isEqualityTest :: BinaryOperator -> Bool
461+isEqualityTest EqualTo = True
462+isEqualityTest NotEqualTo = True
463+isEqualityTest _ = False
464+
465+binaryOps :: [(BinaryOperator, (Type, Type))]
466+binaryOps = [ (Add, (Number, Number))
467+ , (Subtract, (Number, Number))
468+ , (Multiply, (Number, Number))
469+ , (Divide, (Number, Number))
470+ , (Modulus, (Number, Number))
471+ , (BitwiseAnd, (Number, Number))
472+ , (BitwiseOr, (Number, Number))
473+ , (BitwiseXor, (Number, Number))
474+ , (ShiftRight, (Number, Number))
475+ , (ZeroFillShiftRight, (Number, Number))
476+ , (And, (Boolean, Boolean))
477+ , (Or, (Boolean, Boolean))
478+ , (Concat, (String, String))
479+ , (Modulus, (Number, Number))
480+ , (LessThan, (Number, Boolean))
481+ , (LessThanOrEqualTo, (Number, Boolean))
482+ , (GreaterThan, (Number, Boolean))
483+ , (GreaterThanOrEqualTo, (Number, Boolean))
484+ ]
485+
486+inferBinder :: Type -> Binder -> Subst (M.Map Ident Type)
487+inferBinder _ NullBinder = return M.empty
488+inferBinder val (StringBinder _) = val ~~ String >> return M.empty
489+inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
490+inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
491+inferBinder val (VarBinder name) = return $ M.singleton name val
492+inferBinder val (NullaryBinder ctor) = do
493+ env <- getEnv
494+ moduleName <- substCurrentModule <$> ask
495+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
496+ Just (ty, _) -> do
497+ ty `subsumes` val
498+ return M.empty
499+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
500+inferBinder val (UnaryBinder ctor binder) = do
501+ env <- getEnv
502+ moduleName <- substCurrentModule <$> ask
503+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
504+ Just (ty, _) -> do
505+ fn <- replaceAllVarsWithUnknowns ty
506+ case fn of
507+ Function [obj] ret -> do
508+ val `subsumes` ret
509+ inferBinder obj binder
510+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
511+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
512+inferBinder val (ObjectBinder props) = do
513+ row <- fresh
514+ rest <- fresh
515+ m1 <- inferRowProperties row rest props
516+ val ~~ Object row
517+ return m1
518+ where
519+ inferRowProperties :: Type -> Type -> [(String, Binder)] -> Subst (M.Map Ident Type)
520+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
521+ inferRowProperties nrow row ((name, binder):binders) = do
522+ propTy <- fresh
523+ m1 <- inferBinder propTy binder
524+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
525+ return $ m1 `M.union` m2
526+inferBinder val (ArrayBinder binders) = do
527+ el <- fresh
528+ m1 <- M.unions <$> mapM (inferBinder el) binders
529+ val ~~ Array el
530+ return m1
531+inferBinder val (ConsBinder headBinder tailBinder) = do
532+ el <- fresh
533+ m1 <- inferBinder el headBinder
534+ m2 <- inferBinder val tailBinder
535+ val ~~ Array el
536+ return $ m1 `M.union` m2
537+inferBinder val (NamedBinder name binder) = do
538+ m <- inferBinder val binder
539+ return $ M.insert name val m
540+
541+checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> Subst [([Binder], Maybe Guard, Value)]
542+checkBinders _ _ [] = return []
543+checkBinders nvals ret ((binders, grd, val):bs) = do
544+ moduleName <- substCurrentModule <$> ask
545+ m1 <- M.unions <$> zipWithM inferBinder nvals binders
546+ r <- bindLocalVariables moduleName (M.toList m1) $ do
547+ val' <- check val ret
548+ case grd of
549+ Nothing -> return (binders, Nothing, val')
550+ Just g -> do
551+ g' <- check g Boolean
552+ return (binders, Just g', val')
553+ rs <- checkBinders nvals ret bs
554+ return $ r : rs
555+
556+assignVariable :: Ident -> Subst ()
557+assignVariable name = do
558+ env <- checkEnv <$> get
559+ moduleName <- substCurrentModule <$> ask
560+ case M.lookup (moduleName, name) (names env) of
561+ Just (_, LocalVariable) -> throwError $ "Variable with name " ++ show name ++ " already exists."
562+ _ -> return ()
563+
564+checkStatement :: M.Map Ident Type -> Type -> Statement -> Subst (Bool, M.Map Ident Type, Statement)
565+checkStatement mass _ (VariableIntroduction name val) = do
566+ assignVariable name
567+ val'@(TypedValue _ t) <- infer val
568+ return (False, M.insert name t mass, VariableIntroduction name val')
569+checkStatement mass _ (Assignment ident val) = do
570+ val'@(TypedValue _ t) <- infer val
571+ case M.lookup ident mass of
572+ Nothing -> throwError $ "No local variable with name " ++ show ident
573+ Just ty -> do t ~~ ty
574+ return (False, mass, Assignment ident val')
575+checkStatement mass ret (While val inner) = do
576+ val' <- check val Boolean
577+ (allCodePathsReturn, _, inner') <- checkBlock mass ret inner
578+ return (allCodePathsReturn, mass, While val' inner')
579+checkStatement mass ret (If ifst) = do
580+ (allCodePathsReturn, ifst') <- checkIfStatement mass ret ifst
581+ return (allCodePathsReturn, mass, If ifst')
582+checkStatement mass ret (For ident start end inner) = do
583+ moduleName <- substCurrentModule <$> ask
584+ assignVariable ident
585+ start' <- check start Number
586+ end' <- check end Number
587+ (allCodePathsReturn, _, inner') <- bindLocalVariables moduleName [(ident, Number)] $ checkBlock mass ret inner
588+ return (allCodePathsReturn, mass, For ident start' end' inner')
589+checkStatement mass ret (Return val) = do
590+ val' <- check val ret
591+ return (True, mass, Return val')
592+
593+checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> Subst (Bool, IfStatement)
594+checkIfStatement mass ret (IfStatement val thens Nothing) = do
595+ val' <- check val Boolean
596+ (_, _, thens') <- checkBlock mass ret thens
597+ return (False, IfStatement val' thens' Nothing)
598+checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
599+ val' <- check val Boolean
600+ (allCodePathsReturn1, _, thens') <- checkBlock mass ret thens
601+ (allCodePathsReturn2, elses') <- checkElseStatement mass ret elses
602+ return (allCodePathsReturn1 && allCodePathsReturn2, IfStatement val' thens' (Just elses'))
603+
604+checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> Subst (Bool, ElseStatement)
605+checkElseStatement mass ret (Else elses) = do
606+ (allCodePathsReturn, _, elses') <- checkBlock mass ret elses
607+ return (allCodePathsReturn, Else elses')
608+checkElseStatement mass ret (ElseIf ifst) = (id *** ElseIf) <$> checkIfStatement mass ret ifst
609+
610+checkBlock :: M.Map Ident Type -> Type -> [Statement] -> Subst (Bool, M.Map Ident Type, [Statement])
611+checkBlock mass _ [] = return (False, mass, [])
612+checkBlock mass ret (s:ss) = do
613+ moduleName <- substCurrentModule <$> ask
614+ (b1, mass1, s') <- checkStatement mass ret s
615+ bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
616+ (True, []) -> return (True, mass1, [s'])
617+ (True, _) -> throwError "Unreachable code"
618+ (False, ss') -> do
619+ (b, m, ss'') <- checkBlock mass1 ret ss'
620+ return (b, m, s':ss'')
621+
622+skolemize :: String -> Type -> Subst Type
623+skolemize ident ty = do
624+ tsk <- Skolem <$> fresh'
625+ return $ replaceTypeVars ident tsk ty
626+
627+check :: Value -> Type -> Subst Value
628+check val ty = rethrow errorMessage $ check' val ty
629+ where
630+ errorMessage msg =
631+ "Error checking type of term " ++
632+ prettyPrintValue val ++
633+ " against type " ++
634+ prettyPrintType ty ++
635+ ":\n" ++
636+ msg
637+
638+check' :: Value -> Type -> Subst Value
639+check' val (ForAll idents ty) = do
640+ sk <- skolemize idents ty
641+ check val sk
642+check' val (ConstrainedType constraints ty) = do
643+ env <- getEnv
644+ moduleName <- substCurrentModule <$> ask
645+ dictNames <- flip mapM constraints $ \(Qualified _ (ProperName className), _) -> do
646+ n <- liftCheck freshDictionaryName
647+ return $ Ident $ "__dict_" ++ className ++ "_" ++ show n
648+ val' <- withTypeClassDictionaries (zipWith (\name (className, instanceTy) -> TypeClassDictionaryInScope name className instanceTy Nothing) dictNames (qualifyAllUnqualifiedNames moduleName env constraints)) $ check val ty
649+ return $ Abs dictNames val'
650+check' val u@(TUnknown _) = do
651+ val'@(TypedValue _ ty) <- infer val
652+ -- Don't unify an unknown with an inferred polytype
653+ ty' <- replaceAllVarsWithUnknowns ty
654+ ty' ~~ u
655+ return val'
656+check' v@(NumericLiteral _) Number = return v
657+check' v@(StringLiteral _) String = return v
658+check' v@(BooleanLiteral _) Boolean = return v
659+check' (Unary op val) ty = checkUnary op val ty
660+check' (Binary op left right) ty = checkBinary op left right ty
661+check' (ArrayLiteral vals) (Array ty) = ArrayLiteral <$> forM vals (\val -> check val ty)
662+check' (Indexer index vals) ty = do
663+ index' <- check index Number
664+ vals' <- check vals (Array ty)
665+ return $ Indexer index' vals'
666+check' (Abs args ret) (Function argTys retTy) = do
667+ moduleName <- substCurrentModule <$> ask
668+ guardWith "Incorrect number of function arguments" (length args == length argTys)
669+ ret' <- bindLocalVariables moduleName (zip args argTys) $ check ret retTy
670+ return $ Abs args ret'
671+check' (App f args) ret = do
672+ f'@(TypedValue _ ft) <- infer f
673+ app <- checkFunctionApplication f' ft args ret
674+ return $ app
675+check' (Var var) ty = do
676+ moduleName <- substCurrentModule <$> ask
677+ ty1 <- lookupVariable moduleName var
678+ repl <- replaceAllTypeSynonyms ty1
679+ repl `subsumes` ty
680+ return $ Var var
681+check' (TypedValue val ty1) ty2 = do
682+ moduleName <- substCurrentModule <$> ask
683+ kind <- liftCheck $ kindOf moduleName ty1
684+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
685+ ty1 `subsumes` ty2
686+ val' <- check val ty1
687+ return $ TypedValue val' ty1
688+check' (Case vals binders) ret = do
689+ vals' <- mapM infer vals
690+ let ts = map (\(TypedValue _ t) -> t) vals'
691+ binders' <- checkBinders ts ret binders
692+ return $ Case vals' binders'
693+check' (IfThenElse cond th el) ty = do
694+ cond' <- check cond Boolean
695+ th' <- check th ty
696+ el' <- check el ty
697+ return $ IfThenElse cond' th' el'
698+check' (ObjectLiteral ps) (Object row) = do
699+ ensureNoDuplicateProperties ps
700+ ps' <- checkProperties ps row False
701+ return $ ObjectLiteral ps'
702+check' (ObjectUpdate obj ps) (Object row) = do
703+ ensureNoDuplicateProperties ps
704+ us <- zip (map fst ps) <$> replicateM (length ps) fresh
705+ let (propsToCheck, rest) = rowToList row
706+ propsToRemove = map fst ps
707+ remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
708+ obj' <- check obj (Object (rowFromList (us ++ remainingProps, rest)))
709+ ps' <- checkProperties ps row True
710+ return $ ObjectUpdate obj' ps'
711+check' (Accessor prop val) ty = do
712+ rest <- fresh
713+ val' <- check val (Object (RCons prop ty rest))
714+ return $ Accessor prop val'
715+check' (Block ss) ret = do
716+ (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
717+ guardWith "Block is missing a return statement" allCodePathsReturn
718+ return $ Block ss'
719+check' (Constructor c) ty = do
720+ env <- getEnv
721+ moduleName <- substCurrentModule <$> ask
722+ case M.lookup (qualify moduleName c) (dataConstructors env) of
723+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
724+ Just (ty1, _) -> do
725+ repl <- replaceAllTypeSynonyms ty1
726+ repl `subsumes` ty
727+ return $ Constructor c
728+check' val (SaturatedTypeSynonym name args) = do
729+ ty <- expandTypeSynonym name args
730+ check val ty
731+check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
732+
733+checkProperties :: [(String, Value)] -> Type -> Bool -> Subst [(String, Value)]
734+checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
735+ go [] [] REmpty = return []
736+ go [] [] u@(TUnknown _) = do u ~~ REmpty
737+ return []
738+ go [] [] (Skolem _) | lax = return []
739+ go [] ((p, _): _) _ | lax = return []
740+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
741+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
742+ go ((p,v):ps') [] u@(TUnknown _) = do
743+ v'@(TypedValue _ ty) <- infer v
744+ rest <- fresh
745+ u ~~ RCons p ty rest
746+ ps'' <- go ps' [] rest
747+ return $ (p, v') : ps''
748+ go ((p,v):ps') ts r =
749+ case lookup p ts of
750+ Nothing -> do
751+ v'@(TypedValue _ ty) <- infer v
752+ rest <- fresh
753+ r ~~ RCons p ty rest
754+ ps'' <- go ps' ts rest
755+ return $ (p, v') : ps''
756+ Just ty -> do
757+ v' <- check v ty
758+ ps'' <- go ps' (delete (p, ty) ts) r
759+ return $ (p, v') : ps''
760+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
761+
762+checkFunctionApplication :: Value -> Type -> [Value] -> Type -> Subst Value
763+checkFunctionApplication fn fnTy args ret = rethrow errorMessage $ checkFunctionApplication' fn fnTy args ret
764+ where
765+ errorMessage msg = "Error applying function of type "
766+ ++ prettyPrintType fnTy
767+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
768+ ++ ":\n" ++ msg
769+
770+checkFunctionApplication' :: Value -> Type -> [Value] -> Type -> Subst Value
771+checkFunctionApplication' fn (Function argTys retTy) args ret = do
772+ guardWith "Incorrect number of function arguments" (length args == length argTys)
773+ args' <- zipWithM check args argTys
774+ retTy `subsumes` ret
775+ return $ App fn args'
776+checkFunctionApplication' fn (ForAll ident ty) args ret = do
777+ replaced <- replaceVarWithUnknown ident ty
778+ checkFunctionApplication fn replaced args ret
779+checkFunctionApplication' fn u@(TUnknown _) args ret = do
780+ args' <- mapM (\arg -> infer arg >>= \(TypedValue v t) -> TypedValue v <$> replaceAllVarsWithUnknowns t) args
781+ let tys = map (\(TypedValue _ t) -> t) args'
782+ u ~~ Function tys ret
783+ return $ App fn args'
784+checkFunctionApplication' fn (SaturatedTypeSynonym name tyArgs) args ret = do
785+ ty <- expandTypeSynonym name tyArgs
786+ checkFunctionApplication fn ty args ret
787+checkFunctionApplication' fn (ConstrainedType constraints fnTy) args ret = do
788+ env <- getEnv
789+ dicts <- getTypeClassDictionaries
790+ moduleName <- substCurrentModule <$> ask
791+ checkFunctionApplication' (App fn (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) fnTy args ret
792+checkFunctionApplication' _ fnTy args ret = throwError $ "Applying a function of type "
793+ ++ prettyPrintType fnTy
794+ ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
795+ ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
796+
797+subsumes :: Type -> Type -> Subst ()
798+subsumes (ForAll ident ty1) ty2 = do
799+ replaced <- replaceVarWithUnknown ident ty1
800+ replaced `subsumes` ty2
801+subsumes (Function args1 ret1) (Function args2 ret2) = do
802+ zipWithM_ subsumes args2 args1
803+ ret1 `subsumes` ret2
804+subsumes ty1 ty2 = ty1 ~~ ty2
805+