@@ -0,0 +1,806 @@
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))) $ (map (id *** fst) typedDict) ++ untypedDict)
155+ forM es $ \e -> do
156+ triple@(_, (val, ty)) <- case e of
157+ (ident, (val, Just (ty, checkType))) -> 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 $ if checkType then check val ty' else return val
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, Bool)))
179+isTyped (name, TypedValue checkType value ty) = (name, (value, Just (ty, checkType)))
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 " ++ show context
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 (TypeVar v)) (Array ty) = Just [(v, ty)]
217+typeHeadsAreEqual m e (Array ty) (Array (TypeVar v)) = Just [(v, ty)]
218+typeHeadsAreEqual m e (TypeConstructor c1) (TypeConstructor c2) | typeConstructorsAreEqual e m c1 c2 = Just []
219+typeHeadsAreEqual m e (TypeApp h1 (TypeVar v)) (TypeApp h2 arg) = (:) (v, arg) <$> typeHeadsAreEqual m e h1 h2
220+typeHeadsAreEqual m e t1@(TypeApp _ _) t2@(TypeApp _ (TypeVar _)) = typeHeadsAreEqual m e t2 t1
221+typeHeadsAreEqual _ _ _ _ = Nothing
222+
223+escapeCheck :: Value -> Type -> Subst ()
224+escapeCheck value ty = do
225+ subst <- substSubst <$> getSubstState
226+ let visibleUnknowns = nub $ unknowns $ apply subst ty
227+ let allUnknowns = findAllTypes value
228+ forM_ allUnknowns $ \t -> do
229+ let unsolvedUnknowns = nub . unknowns $ apply subst t
230+ guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
231+
232+findAllTypes :: Value -> [Type]
233+findAllTypes = everything (++) (mkQ [] go)
234+ where
235+ go (TypedValue _ _ ty) = [ty]
236+ go _ = []
237+
238+skolemEscapeCheck :: Type -> Check ()
239+skolemEscapeCheck ty =
240+ case something (mkQ Nothing findSkolems) ty of
241+ Nothing -> return ()
242+ Just _ -> throwError $ "Skolem variables cannot escape. Consider adding a type signature." ++ show ty
243+ where
244+ findSkolems (Skolem _) = return ()
245+ findSkolems _ = mzero
246+
247+setify :: Type -> Type
248+setify = rowFromList . first (M.toList . M.fromList) . rowToList
249+
250+setifyAll :: (D.Data d) => d -> d
251+setifyAll = everywhere (mkT setify)
252+
253+varIfUnknown :: Type -> Type
254+varIfUnknown ty =
255+ let unks = nub $ unknowns ty
256+ toName = (:) 't' . show
257+ ty' = everywhere (mkT typeToVar) $ ty
258+ typeToVar :: Type -> Type
259+ typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
260+ typeToVar t = t
261+ in mkForAll (sort . map toName $ unks) ty'
262+
263+replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
264+replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
265+
266+replaceAllVarsWithUnknowns :: Type -> Subst Type
267+replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
268+replaceAllVarsWithUnknowns ty = return ty
269+
270+replaceVarWithUnknown :: String -> Type -> Subst Type
271+replaceVarWithUnknown ident ty = do
272+ tu <- fresh
273+ return $ replaceTypeVars ident tu $ ty
274+
275+replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadReader SubstContext m, MonadError String m) => (D.Data d) => d -> m d
276+replaceAllTypeSynonyms d = do
277+ env <- getEnv
278+ moduleName <- substCurrentModule <$> ask
279+ let syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
280+ either throwError return $ saturateAllTypeSynonyms env moduleName syns d
281+
282+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
283+desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
284+ where
285+ replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
286+ replaceSaturatedTypeSynonym t = t
287+
288+expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Type
289+expandTypeSynonym name args = do
290+ env <- getEnv
291+ moduleName <- substCurrentModule `fmap` ask
292+ case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
293+ Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
294+ Nothing -> error "Type synonym was not defined"
295+
296+ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
297+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
298+
299+infer :: Value -> Subst Value
300+infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ infer' val
301+
302+infer' :: Value -> Subst Value
303+infer' v@(NumericLiteral _) = return $ TypedValue True v Number
304+infer' v@(StringLiteral _) = return $ TypedValue True v String
305+infer' v@(BooleanLiteral _) = return $ TypedValue True v Boolean
306+infer' (ArrayLiteral vals) = do
307+ ts <- mapM infer vals
308+ els <- fresh
309+ forM_ ts $ \(TypedValue _ _ t) -> els ~~ Array t
310+ return $ TypedValue True (ArrayLiteral ts) els
311+infer' (Unary op val) = do
312+ v <- infer val
313+ inferUnary op v
314+infer' (Binary op left right) = do
315+ v1 <- infer left
316+ v2 <- infer right
317+ inferBinary op v1 v2
318+infer' (ObjectLiteral ps) = do
319+ ensureNoDuplicateProperties ps
320+ ts <- mapM (infer . snd) ps
321+ let fields = zipWith (\name (TypedValue _ _ t) -> (name, t)) (map fst ps) ts
322+ ty = Object $ rowFromList (fields, REmpty)
323+ return $ TypedValue True (ObjectLiteral (zip (map fst ps) ts)) ty
324+infer' (ObjectUpdate o ps) = do
325+ ensureNoDuplicateProperties ps
326+ row <- fresh
327+ newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
328+ let newTys = map (\(name, TypedValue _ _ ty) -> (name, ty)) newVals
329+ oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
330+ o' <- check o $ Object $ rowFromList (oldTys, row)
331+ return $ TypedValue True (ObjectUpdate o' newVals) $ Object $ rowFromList (newTys, row)
332+infer' (Indexer index val) = do
333+ el <- fresh
334+ index' <- check index Number
335+ val' <- check val (Array el)
336+ return $ TypedValue True (Indexer (TypedValue True index' Number) (TypedValue True val' (Array el))) el
337+infer' (Accessor prop val) = do
338+ typed@(TypedValue _ _ objTy) <- infer val
339+ propTy <- inferProperty objTy prop
340+ case propTy of
341+ Nothing -> do
342+ field <- fresh
343+ rest <- fresh
344+ objTy `subsumes` Object (RCons prop field rest)
345+ return $ TypedValue True (Accessor prop typed) field
346+ Just ty -> return $ TypedValue True (Accessor prop typed) ty
347+infer' (Abs args ret) = do
348+ ts <- replicateM (length args) fresh
349+ moduleName <- substCurrentModule <$> ask
350+ bindLocalVariables moduleName (zip args ts) $ do
351+ body@(TypedValue _ _ bodyTy) <- infer' ret
352+ return $ TypedValue True (Abs args body) $ Function ts bodyTy
353+infer' (App f args) = do
354+ f'@(TypedValue _ _ ft) <- infer f
355+ ret <- fresh
356+ app <- checkFunctionApplication f' ft args ret
357+ return $ TypedValue True app ret
358+infer' (Var var) = do
359+ moduleName <- substCurrentModule <$> ask
360+ ty <- lookupVariable moduleName var
361+ ty' <- replaceAllTypeSynonyms ty
362+ case ty' of
363+ ConstrainedType constraints _ -> do
364+ env <- getEnv
365+ dicts <- getTypeClassDictionaries
366+ return $ TypedValue True (App (Var var) (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) ty'
367+ _ -> return $ TypedValue True (Var var) ty'
368+infer' (Block ss) = do
369+ ret <- fresh
370+ (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
371+ guardWith "Block is missing a return statement" allCodePathsReturn
372+ return $ TypedValue True (Block ss') ret
373+infer' v@(Constructor c) = do
374+ env <- getEnv
375+ moduleName <- substCurrentModule `fmap` ask
376+ case M.lookup (qualify moduleName c) (dataConstructors env) of
377+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
378+ Just (ty, _) -> do ty' <- replaceAllTypeSynonyms ty
379+ return $ TypedValue True v ty'
380+infer' (Case vals binders) = do
381+ ts <- mapM infer vals
382+ ret <- fresh
383+ binders' <- checkBinders (map (\(TypedValue _ _ t) -> t) ts) ret binders
384+ return $ TypedValue True (Case ts binders') ret
385+infer' (IfThenElse cond th el) = do
386+ cond' <- check cond Boolean
387+ v2@(TypedValue _ _ t2) <- infer th
388+ v3@(TypedValue _ _ t3) <- infer el
389+ t2 ~~ t3
390+ return $ TypedValue True (IfThenElse cond' v2 v3) t2
391+infer' (TypedValue checkType val ty) = do
392+ moduleName <- substCurrentModule <$> ask
393+ kind <- liftCheck $ kindOf moduleName ty
394+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
395+ ty' <- replaceAllTypeSynonyms ty
396+ val' <- if checkType then check val ty' else return val
397+ return $ TypedValue True val' ty
398+infer' _ = error "Invalid argument to infer"
399+
400+inferProperty :: Type -> String -> Subst (Maybe Type)
401+inferProperty (Object row) prop = do
402+ let (props, _) = rowToList row
403+ return $ lookup prop props
404+inferProperty (SaturatedTypeSynonym name args) prop = do
405+ replaced <- expandTypeSynonym name args
406+ inferProperty replaced prop
407+inferProperty (ForAll ident ty) prop = do
408+ replaced <- replaceVarWithUnknown ident ty
409+ inferProperty replaced prop
410+inferProperty _ _ = return Nothing
411+
412+inferUnary :: UnaryOperator -> Value -> Subst Value
413+inferUnary op (TypedValue _ val valTy) =
414+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
415+ (valTy', resTy) -> do
416+ valTy' ~~ valTy
417+ return $ TypedValue True (Unary op val) resTy
418+inferUnary _ _ = error "Invalid arguments to inferUnary"
419+
420+checkUnary :: UnaryOperator -> Value -> Type -> Subst Value
421+checkUnary op val res =
422+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
423+ (valTy, resTy) -> do
424+ res ~~ resTy
425+ val' <- check val valTy
426+ return $ Unary op val'
427+
428+unaryOps :: [(UnaryOperator, (Type, Type))]
429+unaryOps = [ (Negate, (Number, Number))
430+ , (Not, (Boolean, Boolean))
431+ , (BitwiseNot, (Number, Number))
432+ ]
433+
434+inferBinary :: BinaryOperator -> Value -> Value -> Subst Value
435+inferBinary op left@(TypedValue _ _ leftTy) right@(TypedValue _ _ rightTy) | isEqualityTest op = do
436+ leftTy ~~ rightTy
437+ return $ TypedValue True (Binary op left right) Boolean
438+inferBinary op left@(TypedValue _ _ leftTy) right@(TypedValue _ _ rightTy) =
439+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
440+ (valTy, resTy) -> do
441+ leftTy ~~ valTy
442+ rightTy ~~ valTy
443+ return $ TypedValue True (Binary op left right) resTy
444+inferBinary _ _ _ = error "Invalid arguments to inferBinary"
445+
446+checkBinary :: BinaryOperator -> Value -> Value -> Type -> Subst Value
447+checkBinary op left right res | isEqualityTest op = do
448+ res ~~ Boolean
449+ left'@(TypedValue _ _ t1) <- infer left
450+ right'@(TypedValue _ _ t2) <- infer right
451+ t1 ~~ t2
452+ return $ Binary op left' right'
453+checkBinary op left right res =
454+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
455+ (valTy, resTy) -> do
456+ res ~~ resTy
457+ left' <- check left valTy
458+ right' <- check right valTy
459+ return $ Binary op left' right'
460+
461+isEqualityTest :: BinaryOperator -> Bool
462+isEqualityTest EqualTo = True
463+isEqualityTest NotEqualTo = True
464+isEqualityTest _ = False
465+
466+binaryOps :: [(BinaryOperator, (Type, Type))]
467+binaryOps = [ (Add, (Number, Number))
468+ , (Subtract, (Number, Number))
469+ , (Multiply, (Number, Number))
470+ , (Divide, (Number, Number))
471+ , (Modulus, (Number, Number))
472+ , (BitwiseAnd, (Number, Number))
473+ , (BitwiseOr, (Number, Number))
474+ , (BitwiseXor, (Number, Number))
475+ , (ShiftRight, (Number, Number))
476+ , (ZeroFillShiftRight, (Number, Number))
477+ , (And, (Boolean, Boolean))
478+ , (Or, (Boolean, Boolean))
479+ , (Concat, (String, String))
480+ , (Modulus, (Number, Number))
481+ , (LessThan, (Number, Boolean))
482+ , (LessThanOrEqualTo, (Number, Boolean))
483+ , (GreaterThan, (Number, Boolean))
484+ , (GreaterThanOrEqualTo, (Number, Boolean))
485+ ]
486+
487+inferBinder :: Type -> Binder -> Subst (M.Map Ident Type)
488+inferBinder _ NullBinder = return M.empty
489+inferBinder val (StringBinder _) = val ~~ String >> return M.empty
490+inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
491+inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
492+inferBinder val (VarBinder name) = return $ M.singleton name val
493+inferBinder val (NullaryBinder ctor) = do
494+ env <- getEnv
495+ moduleName <- substCurrentModule <$> ask
496+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
497+ Just (ty, _) -> do
498+ ty `subsumes` val
499+ return M.empty
500+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
501+inferBinder val (UnaryBinder ctor binder) = do
502+ env <- getEnv
503+ moduleName <- substCurrentModule <$> ask
504+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
505+ Just (ty, _) -> do
506+ fn <- replaceAllVarsWithUnknowns ty
507+ case fn of
508+ Function [obj] ret -> do
509+ val `subsumes` ret
510+ inferBinder obj binder
511+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
512+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
513+inferBinder val (ObjectBinder props) = do
514+ row <- fresh
515+ rest <- fresh
516+ m1 <- inferRowProperties row rest props
517+ val ~~ Object row
518+ return m1
519+ where
520+ inferRowProperties :: Type -> Type -> [(String, Binder)] -> Subst (M.Map Ident Type)
521+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
522+ inferRowProperties nrow row ((name, binder):binders) = do
523+ propTy <- fresh
524+ m1 <- inferBinder propTy binder
525+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
526+ return $ m1 `M.union` m2
527+inferBinder val (ArrayBinder binders) = do
528+ el <- fresh
529+ m1 <- M.unions <$> mapM (inferBinder el) binders
530+ val ~~ Array el
531+ return m1
532+inferBinder val (ConsBinder headBinder tailBinder) = do
533+ el <- fresh
534+ m1 <- inferBinder el headBinder
535+ m2 <- inferBinder val tailBinder
536+ val ~~ Array el
537+ return $ m1 `M.union` m2
538+inferBinder val (NamedBinder name binder) = do
539+ m <- inferBinder val binder
540+ return $ M.insert name val m
541+
542+checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> Subst [([Binder], Maybe Guard, Value)]
543+checkBinders _ _ [] = return []
544+checkBinders nvals ret ((binders, grd, val):bs) = do
545+ moduleName <- substCurrentModule <$> ask
546+ m1 <- M.unions <$> zipWithM inferBinder nvals binders
547+ r <- bindLocalVariables moduleName (M.toList m1) $ do
548+ val' <- check val ret
549+ case grd of
550+ Nothing -> return (binders, Nothing, val')
551+ Just g -> do
552+ g' <- check g Boolean
553+ return (binders, Just g', val')
554+ rs <- checkBinders nvals ret bs
555+ return $ r : rs
556+
557+assignVariable :: Ident -> Subst ()
558+assignVariable name = do
559+ env <- checkEnv <$> get
560+ moduleName <- substCurrentModule <$> ask
561+ case M.lookup (moduleName, name) (names env) of
562+ Just (_, LocalVariable) -> throwError $ "Variable with name " ++ show name ++ " already exists."
563+ _ -> return ()
564+
565+checkStatement :: M.Map Ident Type -> Type -> Statement -> Subst (Bool, M.Map Ident Type, Statement)
566+checkStatement mass _ (VariableIntroduction name val) = do
567+ assignVariable name
568+ val'@(TypedValue _ _ t) <- infer val
569+ return (False, M.insert name t mass, VariableIntroduction name val')
570+checkStatement mass _ (Assignment ident val) = do
571+ val'@(TypedValue _ _ t) <- infer val
572+ case M.lookup ident mass of
573+ Nothing -> throwError $ "No local variable with name " ++ show ident
574+ Just ty -> do t ~~ ty
575+ return (False, mass, Assignment ident val')
576+checkStatement mass ret (While val inner) = do
577+ val' <- check val Boolean
578+ (allCodePathsReturn, _, inner') <- checkBlock mass ret inner
579+ return (allCodePathsReturn, mass, While val' inner')
580+checkStatement mass ret (If ifst) = do
581+ (allCodePathsReturn, ifst') <- checkIfStatement mass ret ifst
582+ return (allCodePathsReturn, mass, If ifst')
583+checkStatement mass ret (For ident start end inner) = do
584+ moduleName <- substCurrentModule <$> ask
585+ assignVariable ident
586+ start' <- check start Number
587+ end' <- check end Number
588+ (allCodePathsReturn, _, inner') <- bindLocalVariables moduleName [(ident, Number)] $ checkBlock mass ret inner
589+ return (allCodePathsReturn, mass, For ident start' end' inner')
590+checkStatement mass ret (Return val) = do
591+ val' <- check val ret
592+ return (True, mass, Return val')
593+
594+checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> Subst (Bool, IfStatement)
595+checkIfStatement mass ret (IfStatement val thens Nothing) = do
596+ val' <- check val Boolean
597+ (_, _, thens') <- checkBlock mass ret thens
598+ return (False, IfStatement val' thens' Nothing)
599+checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
600+ val' <- check val Boolean
601+ (allCodePathsReturn1, _, thens') <- checkBlock mass ret thens
602+ (allCodePathsReturn2, elses') <- checkElseStatement mass ret elses
603+ return (allCodePathsReturn1 && allCodePathsReturn2, IfStatement val' thens' (Just elses'))
604+
605+checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> Subst (Bool, ElseStatement)
606+checkElseStatement mass ret (Else elses) = do
607+ (allCodePathsReturn, _, elses') <- checkBlock mass ret elses
608+ return (allCodePathsReturn, Else elses')
609+checkElseStatement mass ret (ElseIf ifst) = (id *** ElseIf) <$> checkIfStatement mass ret ifst
610+
611+checkBlock :: M.Map Ident Type -> Type -> [Statement] -> Subst (Bool, M.Map Ident Type, [Statement])
612+checkBlock mass _ [] = return (False, mass, [])
613+checkBlock mass ret (s:ss) = do
614+ moduleName <- substCurrentModule <$> ask
615+ (b1, mass1, s') <- checkStatement mass ret s
616+ bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
617+ (True, []) -> return (True, mass1, [s'])
618+ (True, _) -> throwError "Unreachable code"
619+ (False, ss') -> do
620+ (b, m, ss'') <- checkBlock mass1 ret ss'
621+ return (b, m, s':ss'')
622+
623+skolemize :: String -> Type -> Subst Type
624+skolemize ident ty = do
625+ tsk <- Skolem <$> fresh'
626+ return $ replaceTypeVars ident tsk ty
627+
628+check :: Value -> Type -> Subst Value
629+check val ty = rethrow errorMessage $ check' val ty
630+ where
631+ errorMessage msg =
632+ "Error checking type of term " ++
633+ prettyPrintValue val ++
634+ " against type " ++
635+ prettyPrintType ty ++
636+ ":\n" ++
637+ msg
638+
639+check' :: Value -> Type -> Subst Value
640+check' val (ForAll idents ty) = do
641+ sk <- skolemize idents ty
642+ check val sk
643+check' val (ConstrainedType constraints ty) = do
644+ env <- getEnv
645+ moduleName <- substCurrentModule <$> ask
646+ dictNames <- flip mapM constraints $ \(Qualified _ (ProperName className), _) -> do
647+ n <- liftCheck freshDictionaryName
648+ return $ Ident $ "__dict_" ++ className ++ "_" ++ show n
649+ val' <- withTypeClassDictionaries (zipWith (\name (className, instanceTy) -> TypeClassDictionaryInScope name className instanceTy Nothing) dictNames (qualifyAllUnqualifiedNames moduleName env constraints)) $ check val ty
650+ return $ Abs dictNames val'
651+check' val u@(TUnknown _) = do
652+ val'@(TypedValue _ _ ty) <- infer val
653+ -- Don't unify an unknown with an inferred polytype
654+ ty' <- replaceAllVarsWithUnknowns ty
655+ ty' ~~ u
656+ return val'
657+check' v@(NumericLiteral _) Number = return v
658+check' v@(StringLiteral _) String = return v
659+check' v@(BooleanLiteral _) Boolean = return v
660+check' (Unary op val) ty = checkUnary op val ty
661+check' (Binary op left right) ty = checkBinary op left right ty
662+check' (ArrayLiteral vals) (Array ty) = ArrayLiteral <$> forM vals (\val -> check val ty)
663+check' (Indexer index vals) ty = do
664+ index' <- check index Number
665+ vals' <- check vals (Array ty)
666+ return $ Indexer index' vals'
667+check' (Abs args ret) (Function argTys retTy) = do
668+ moduleName <- substCurrentModule <$> ask
669+ guardWith "Incorrect number of function arguments" (length args == length argTys)
670+ ret' <- bindLocalVariables moduleName (zip args argTys) $ check ret retTy
671+ return $ Abs args ret'
672+check' (App f args) ret = do
673+ f'@(TypedValue _ _ ft) <- infer f
674+ app <- checkFunctionApplication f' ft args ret
675+ return $ app
676+check' (Var var) ty = do
677+ moduleName <- substCurrentModule <$> ask
678+ ty1 <- lookupVariable moduleName var
679+ repl <- replaceAllTypeSynonyms ty1
680+ repl `subsumes` ty
681+ return $ Var var
682+check' (TypedValue checkType val ty1) ty2 = do
683+ moduleName <- substCurrentModule <$> ask
684+ kind <- liftCheck $ kindOf moduleName ty1
685+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
686+ ty1 `subsumes` ty2
687+ val' <- if checkType then check val ty1 else return val
688+ return $ TypedValue True val' ty1
689+check' (Case vals binders) ret = do
690+ vals' <- mapM infer vals
691+ let ts = map (\(TypedValue _ _ t) -> t) vals'
692+ binders' <- checkBinders ts ret binders
693+ return $ Case vals' binders'
694+check' (IfThenElse cond th el) ty = do
695+ cond' <- check cond Boolean
696+ th' <- check th ty
697+ el' <- check el ty
698+ return $ IfThenElse cond' th' el'
699+check' (ObjectLiteral ps) (Object row) = do
700+ ensureNoDuplicateProperties ps
701+ ps' <- checkProperties ps row False
702+ return $ ObjectLiteral ps'
703+check' (ObjectUpdate obj ps) (Object row) = do
704+ ensureNoDuplicateProperties ps
705+ us <- zip (map fst ps) <$> replicateM (length ps) fresh
706+ let (propsToCheck, rest) = rowToList row
707+ propsToRemove = map fst ps
708+ remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
709+ obj' <- check obj (Object (rowFromList (us ++ remainingProps, rest)))
710+ ps' <- checkProperties ps row True
711+ return $ ObjectUpdate obj' ps'
712+check' (Accessor prop val) ty = do
713+ rest <- fresh
714+ val' <- check val (Object (RCons prop ty rest))
715+ return $ Accessor prop val'
716+check' (Block ss) ret = do
717+ (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
718+ guardWith "Block is missing a return statement" allCodePathsReturn
719+ return $ Block ss'
720+check' (Constructor c) ty = do
721+ env <- getEnv
722+ moduleName <- substCurrentModule <$> ask
723+ case M.lookup (qualify moduleName c) (dataConstructors env) of
724+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
725+ Just (ty1, _) -> do
726+ repl <- replaceAllTypeSynonyms ty1
727+ repl `subsumes` ty
728+ return $ Constructor c
729+check' val (SaturatedTypeSynonym name args) = do
730+ ty <- expandTypeSynonym name args
731+ check val ty
732+check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
733+
734+checkProperties :: [(String, Value)] -> Type -> Bool -> Subst [(String, Value)]
735+checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
736+ go [] [] REmpty = return []
737+ go [] [] u@(TUnknown _) = do u ~~ REmpty
738+ return []
739+ go [] [] (Skolem _) | lax = return []
740+ go [] ((p, _): _) _ | lax = return []
741+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
742+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
743+ go ((p,v):ps') [] u@(TUnknown _) = do
744+ v'@(TypedValue _ _ ty) <- infer v
745+ rest <- fresh
746+ u ~~ RCons p ty rest
747+ ps'' <- go ps' [] rest
748+ return $ (p, v') : ps''
749+ go ((p,v):ps') ts r =
750+ case lookup p ts of
751+ Nothing -> do
752+ v'@(TypedValue _ _ ty) <- infer v
753+ rest <- fresh
754+ r ~~ RCons p ty rest
755+ ps'' <- go ps' ts rest
756+ return $ (p, v') : ps''
757+ Just ty -> do
758+ v' <- check v ty
759+ ps'' <- go ps' (delete (p, ty) ts) r
760+ return $ (p, v') : ps''
761+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
762+
763+checkFunctionApplication :: Value -> Type -> [Value] -> Type -> Subst Value
764+checkFunctionApplication fn fnTy args ret = rethrow errorMessage $ checkFunctionApplication' fn fnTy args ret
765+ where
766+ errorMessage msg = "Error applying function of type "
767+ ++ prettyPrintType fnTy
768+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
769+ ++ ":\n" ++ msg
770+
771+checkFunctionApplication' :: Value -> Type -> [Value] -> Type -> Subst Value
772+checkFunctionApplication' fn (Function argTys retTy) args ret = do
773+ guardWith "Incorrect number of function arguments" (length args == length argTys)
774+ args' <- zipWithM check args argTys
775+ retTy `subsumes` ret
776+ return $ App fn args'
777+checkFunctionApplication' fn (ForAll ident ty) args ret = do
778+ replaced <- replaceVarWithUnknown ident ty
779+ checkFunctionApplication fn replaced args ret
780+checkFunctionApplication' fn u@(TUnknown _) args ret = do
781+ args' <- mapM (\arg -> infer arg >>= \(TypedValue _ v t) -> TypedValue True v <$> replaceAllVarsWithUnknowns t) args
782+ let tys = map (\(TypedValue _ _ t) -> t) args'
783+ u ~~ Function tys ret
784+ return $ App fn args'
785+checkFunctionApplication' fn (SaturatedTypeSynonym name tyArgs) args ret = do
786+ ty <- expandTypeSynonym name tyArgs
787+ checkFunctionApplication fn ty args ret
788+checkFunctionApplication' fn (ConstrainedType constraints fnTy) args ret = do
789+ env <- getEnv
790+ dicts <- getTypeClassDictionaries
791+ moduleName <- substCurrentModule <$> ask
792+ checkFunctionApplication' (App fn (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) fnTy args ret
793+checkFunctionApplication' _ fnTy args ret = throwError $ "Applying a function of type "
794+ ++ prettyPrintType fnTy
795+ ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
796+ ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
797+
798+subsumes :: Type -> Type -> Subst ()
799+subsumes (ForAll ident ty1) ty2 = do
800+ replaced <- replaceVarWithUnknown ident ty1
801+ replaced `subsumes` ty2
802+subsumes (Function args1 ret1) (Function args2 ret2) = do
803+ zipWithM_ subsumes args2 args1
804+ ret1 `subsumes` ret2
805+subsumes ty1 ty2 = ty1 ~~ ty2
806+