@@ -0,0 +1,770 @@
1+-----------------------------------------------------------------------------
2+--
3+-- Module : Language.PureScript.TypeChecker.Types
4+-- Copyright : (c) Phil Freeman 2013
5+-- License : MIT
6+--
7+-- Maintainer : Phil Freeman <paf31@cantab.net>
8+-- Stability : experimental
9+-- Portability :
10+--
11+-- |
12+--
13+-----------------------------------------------------------------------------
14+
15+{-# OPTIONS_GHC -fno-warn-orphans #-}
16+{-# LANGUAGE DeriveDataTypeable, FlexibleContexts #-}
17+
18+module Language.PureScript.TypeChecker.Types (
19+ typesOf
20+) where
21+
22+import Data.List
23+import Data.Maybe (isNothing, isJust, fromMaybe)
24+import qualified Data.Data as D
25+import Data.Generics
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 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 :: Value -> Check Value
186+replaceTypeClassDictionaries = everywhereM (mkM go)
187+ where
188+ go (TypeClassDictionary constraint dicts) = entails dicts constraint
189+ go other = return other
190+
191+entails :: [(Ident, Qualified ProperName, Type)] -> (Qualified ProperName, Type) -> Check Value
192+entails _ _ = return $ Var $ Qualified Nothing $ Ident "placeholder" -- TODO
193+
194+escapeCheck :: Value -> Type -> Subst ()
195+escapeCheck value ty = do
196+ subst <- substSubst <$> getSubstState
197+ let visibleUnknowns = nub $ unknowns $ apply subst ty
198+ let allUnknowns = findAllTypes value
199+ forM_ allUnknowns $ \t -> do
200+ let unsolvedUnknowns = nub . unknowns $ apply subst t
201+ guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
202+
203+findAllTypes :: Value -> [Type]
204+findAllTypes = everything (++) (mkQ [] go)
205+ where
206+ go (TypedValue _ ty) = [ty]
207+ go _ = []
208+
209+skolemEscapeCheck :: Type -> Check ()
210+skolemEscapeCheck ty =
211+ case something (mkQ Nothing findSkolems) ty of
212+ Nothing -> return ()
213+ Just _ -> throwError $ "Skolem variables cannot escape. Consider adding a type signature." ++ show ty
214+ where
215+ findSkolems (Skolem _) = return ()
216+ findSkolems _ = mzero
217+
218+setify :: Type -> Type
219+setify = rowFromList . first (M.toList . M.fromList) . rowToList
220+
221+setifyAll :: (D.Data d) => d -> d
222+setifyAll = everywhere (mkT setify)
223+
224+varIfUnknown :: Type -> Type
225+varIfUnknown ty =
226+ let unks = nub $ unknowns ty
227+ toName = (:) 't' . show
228+ ty' = everywhere (mkT typeToVar) $ ty
229+ typeToVar :: Type -> Type
230+ typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
231+ typeToVar t = t
232+ in mkForAll (sort . map toName $ unks) ty'
233+
234+replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
235+replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
236+
237+replaceAllVarsWithUnknowns :: Type -> Subst Type
238+replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
239+replaceAllVarsWithUnknowns ty = return ty
240+
241+replaceVarWithUnknown :: String -> Type -> Subst Type
242+replaceVarWithUnknown ident ty = do
243+ tu <- fresh
244+ return $ replaceTypeVars ident tu $ ty
245+
246+replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadReader SubstContext m, MonadError String m) => (D.Data d) => d -> m d
247+replaceAllTypeSynonyms d = do
248+ env <- getEnv
249+ moduleName <- substCurrentModule <$> ask
250+ let syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
251+ either throwError return $ saturateAllTypeSynonyms env moduleName syns d
252+
253+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
254+desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
255+ where
256+ replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
257+ replaceSaturatedTypeSynonym t = t
258+
259+expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Type
260+expandTypeSynonym name args = do
261+ env <- getEnv
262+ moduleName <- substCurrentModule `fmap` ask
263+ case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
264+ Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
265+ Nothing -> error "Type synonym was not defined"
266+
267+ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
268+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
269+
270+infer :: Value -> Subst Value
271+infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ infer' val
272+
273+infer' :: Value -> Subst Value
274+infer' v@(NumericLiteral _) = return $ TypedValue v Number
275+infer' v@(StringLiteral _) = return $ TypedValue v String
276+infer' v@(BooleanLiteral _) = return $ TypedValue v Boolean
277+infer' (ArrayLiteral vals) = do
278+ ts <- mapM infer vals
279+ els <- fresh
280+ forM_ ts $ \(TypedValue _ t) -> els ~~ Array t
281+ return $ TypedValue (ArrayLiteral ts) els
282+infer' (Unary op val) = do
283+ v <- infer val
284+ inferUnary op v
285+infer' (Binary op left right) = do
286+ v1 <- infer left
287+ v2 <- infer right
288+ inferBinary op v1 v2
289+infer' (ObjectLiteral ps) = do
290+ ensureNoDuplicateProperties ps
291+ ts <- mapM (infer . snd) ps
292+ let fields = zipWith (\name (TypedValue _ t) -> (name, t)) (map fst ps) ts
293+ ty = Object $ rowFromList (fields, REmpty)
294+ return $ TypedValue (ObjectLiteral (zip (map fst ps) ts)) ty
295+infer' (ObjectUpdate o ps) = do
296+ ensureNoDuplicateProperties ps
297+ row <- fresh
298+ newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
299+ let newTys = map (\(name, TypedValue _ ty) -> (name, ty)) newVals
300+ oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
301+ o' <- check o $ Object $ rowFromList (oldTys, row)
302+ return $ TypedValue (ObjectUpdate o' newVals) $ Object $ rowFromList (newTys, row)
303+infer' (Indexer index val) = do
304+ el <- fresh
305+ index' <- check index Number
306+ val' <- check val (Array el)
307+ return $ TypedValue (Indexer (TypedValue index' Number) (TypedValue val' (Array el))) el
308+infer' (Accessor prop val) = do
309+ typed@(TypedValue _ objTy) <- infer val
310+ propTy <- inferProperty objTy prop
311+ case propTy of
312+ Nothing -> do
313+ field <- fresh
314+ rest <- fresh
315+ objTy `subsumes` Object (RCons prop field rest)
316+ return $ TypedValue (Accessor prop typed) field
317+ Just ty -> return $ TypedValue (Accessor prop typed) ty
318+infer' (Abs args ret) = do
319+ ts <- replicateM (length args) fresh
320+ moduleName <- substCurrentModule <$> ask
321+ bindLocalVariables moduleName (zip args ts) $ do
322+ body@(TypedValue _ bodyTy) <- infer' ret
323+ return $ TypedValue (Abs args body) $ Function ts bodyTy
324+infer' (App f args) = do
325+ f'@(TypedValue _ ft) <- infer f
326+ ret <- fresh
327+ app <- checkFunctionApplication f' ft args ret
328+ return $ TypedValue app ret
329+infer' (Var var) = do
330+ moduleName <- substCurrentModule <$> ask
331+ ty <- lookupVariable moduleName var
332+ ty' <- replaceAllTypeSynonyms ty
333+ case ty' of
334+ ConstrainedType constraints _ -> do
335+ dicts <- getTypeClassDictionaries
336+ return $ TypedValue (App (Var var) (map (flip TypeClassDictionary dicts) constraints)) ty'
337+ _ -> return $ TypedValue (Var var) ty'
338+infer' (Block ss) = do
339+ ret <- fresh
340+ (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
341+ guardWith "Block is missing a return statement" allCodePathsReturn
342+ return $ TypedValue (Block ss') ret
343+infer' v@(Constructor c) = do
344+ env <- getEnv
345+ moduleName <- substCurrentModule `fmap` ask
346+ case M.lookup (qualify moduleName c) (dataConstructors env) of
347+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
348+ Just (ty, _) -> do ty' <- replaceAllTypeSynonyms ty
349+ return $ TypedValue v ty'
350+infer' (Case vals binders) = do
351+ ts <- mapM infer vals
352+ ret <- fresh
353+ binders' <- checkBinders (map (\(TypedValue _ t) -> t) ts) ret binders
354+ return $ TypedValue (Case ts binders') ret
355+infer' (IfThenElse cond th el) = do
356+ cond' <- check cond Boolean
357+ v2@(TypedValue _ t2) <- infer th
358+ v3@(TypedValue _ t3) <- infer el
359+ t2 ~~ t3
360+ return $ TypedValue (IfThenElse cond' v2 v3) t2
361+infer' (TypedValue val ty) = do
362+ moduleName <- substCurrentModule <$> ask
363+ kind <- liftCheck $ kindOf moduleName ty
364+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
365+ ty' <- replaceAllTypeSynonyms ty
366+ val' <- check val ty'
367+ return $ TypedValue val' ty
368+infer' _ = error "Invalid argument to infer"
369+
370+inferProperty :: Type -> String -> Subst (Maybe Type)
371+inferProperty (Object row) prop = do
372+ let (props, _) = rowToList row
373+ return $ lookup prop props
374+inferProperty (SaturatedTypeSynonym name args) prop = do
375+ replaced <- expandTypeSynonym name args
376+ inferProperty replaced prop
377+inferProperty (ForAll ident ty) prop = do
378+ replaced <- replaceVarWithUnknown ident ty
379+ inferProperty replaced prop
380+inferProperty _ _ = return Nothing
381+
382+inferUnary :: UnaryOperator -> Value -> Subst Value
383+inferUnary op (TypedValue val valTy) =
384+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
385+ (valTy', resTy) -> do
386+ valTy' ~~ valTy
387+ return $ TypedValue (Unary op val) resTy
388+inferUnary _ _ = error "Invalid arguments to inferUnary"
389+
390+checkUnary :: UnaryOperator -> Value -> Type -> Subst Value
391+checkUnary op val res =
392+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
393+ (valTy, resTy) -> do
394+ res ~~ resTy
395+ val' <- check val valTy
396+ return $ Unary op val'
397+
398+unaryOps :: [(UnaryOperator, (Type, Type))]
399+unaryOps = [ (Negate, (Number, Number))
400+ , (Not, (Boolean, Boolean))
401+ , (BitwiseNot, (Number, Number))
402+ ]
403+
404+inferBinary :: BinaryOperator -> Value -> Value -> Subst Value
405+inferBinary op left@(TypedValue _ leftTy) right@(TypedValue _ rightTy) | isEqualityTest op = do
406+ leftTy ~~ rightTy
407+ return $ TypedValue (Binary op left right) Boolean
408+inferBinary op left@(TypedValue _ leftTy) right@(TypedValue _ rightTy) =
409+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
410+ (valTy, resTy) -> do
411+ leftTy ~~ valTy
412+ rightTy ~~ valTy
413+ return $ TypedValue (Binary op left right) resTy
414+inferBinary _ _ _ = error "Invalid arguments to inferBinary"
415+
416+checkBinary :: BinaryOperator -> Value -> Value -> Type -> Subst Value
417+checkBinary op left right res | isEqualityTest op = do
418+ res ~~ Boolean
419+ left'@(TypedValue _ t1) <- infer left
420+ right'@(TypedValue _ t2) <- infer right
421+ t1 ~~ t2
422+ return $ Binary op left' right'
423+checkBinary op left right res =
424+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
425+ (valTy, resTy) -> do
426+ res ~~ resTy
427+ left' <- check left valTy
428+ right' <- check right valTy
429+ return $ Binary op left' right'
430+
431+isEqualityTest :: BinaryOperator -> Bool
432+isEqualityTest EqualTo = True
433+isEqualityTest NotEqualTo = True
434+isEqualityTest _ = False
435+
436+binaryOps :: [(BinaryOperator, (Type, Type))]
437+binaryOps = [ (Add, (Number, Number))
438+ , (Subtract, (Number, Number))
439+ , (Multiply, (Number, Number))
440+ , (Divide, (Number, Number))
441+ , (Modulus, (Number, Number))
442+ , (BitwiseAnd, (Number, Number))
443+ , (BitwiseOr, (Number, Number))
444+ , (BitwiseXor, (Number, Number))
445+ , (ShiftRight, (Number, Number))
446+ , (ZeroFillShiftRight, (Number, Number))
447+ , (And, (Boolean, Boolean))
448+ , (Or, (Boolean, Boolean))
449+ , (Concat, (String, String))
450+ , (Modulus, (Number, Number))
451+ , (LessThan, (Number, Boolean))
452+ , (LessThanOrEqualTo, (Number, Boolean))
453+ , (GreaterThan, (Number, Boolean))
454+ , (GreaterThanOrEqualTo, (Number, Boolean))
455+ ]
456+
457+inferBinder :: Type -> Binder -> Subst (M.Map Ident Type)
458+inferBinder _ NullBinder = return M.empty
459+inferBinder val (StringBinder _) = val ~~ String >> return M.empty
460+inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
461+inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
462+inferBinder val (VarBinder name) = return $ M.singleton name val
463+inferBinder val (NullaryBinder ctor) = do
464+ env <- getEnv
465+ moduleName <- substCurrentModule <$> ask
466+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
467+ Just (ty, _) -> do
468+ ty `subsumes` val
469+ return M.empty
470+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
471+inferBinder val (UnaryBinder ctor binder) = do
472+ env <- getEnv
473+ moduleName <- substCurrentModule <$> ask
474+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
475+ Just (ty, _) -> do
476+ fn <- replaceAllVarsWithUnknowns ty
477+ case fn of
478+ Function [obj] ret -> do
479+ val `subsumes` ret
480+ inferBinder obj binder
481+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
482+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
483+inferBinder val (ObjectBinder props) = do
484+ row <- fresh
485+ rest <- fresh
486+ m1 <- inferRowProperties row rest props
487+ val ~~ Object row
488+ return m1
489+ where
490+ inferRowProperties :: Type -> Type -> [(String, Binder)] -> Subst (M.Map Ident Type)
491+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
492+ inferRowProperties nrow row ((name, binder):binders) = do
493+ propTy <- fresh
494+ m1 <- inferBinder propTy binder
495+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
496+ return $ m1 `M.union` m2
497+inferBinder val (ArrayBinder binders) = do
498+ el <- fresh
499+ m1 <- M.unions <$> mapM (inferBinder el) binders
500+ val ~~ Array el
501+ return m1
502+inferBinder val (ConsBinder headBinder tailBinder) = do
503+ el <- fresh
504+ m1 <- inferBinder el headBinder
505+ m2 <- inferBinder val tailBinder
506+ val ~~ Array el
507+ return $ m1 `M.union` m2
508+inferBinder val (NamedBinder name binder) = do
509+ m <- inferBinder val binder
510+ return $ M.insert name val m
511+
512+checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> Subst [([Binder], Maybe Guard, Value)]
513+checkBinders _ _ [] = return []
514+checkBinders nvals ret ((binders, grd, val):bs) = do
515+ moduleName <- substCurrentModule <$> ask
516+ m1 <- M.unions <$> zipWithM inferBinder nvals binders
517+ r <- bindLocalVariables moduleName (M.toList m1) $ do
518+ val' <- check val ret
519+ case grd of
520+ Nothing -> return (binders, Nothing, val')
521+ Just g -> do
522+ g' <- check g Boolean
523+ return (binders, Just g', val')
524+ rs <- checkBinders nvals ret bs
525+ return $ r : rs
526+
527+assignVariable :: Ident -> Subst ()
528+assignVariable name = do
529+ env <- checkEnv <$> get
530+ moduleName <- substCurrentModule <$> ask
531+ case M.lookup (moduleName, name) (names env) of
532+ Just (_, LocalVariable) -> throwError $ "Variable with name " ++ show name ++ " already exists."
533+ _ -> return ()
534+
535+checkStatement :: M.Map Ident Type -> Type -> Statement -> Subst (Bool, M.Map Ident Type, Statement)
536+checkStatement mass _ (VariableIntroduction name val) = do
537+ assignVariable name
538+ val'@(TypedValue _ t) <- infer val
539+ return (False, M.insert name t mass, VariableIntroduction name val')
540+checkStatement mass _ (Assignment ident val) = do
541+ val'@(TypedValue _ t) <- infer val
542+ case M.lookup ident mass of
543+ Nothing -> throwError $ "No local variable with name " ++ show ident
544+ Just ty -> do t ~~ ty
545+ return (False, mass, Assignment ident val')
546+checkStatement mass ret (While val inner) = do
547+ val' <- check val Boolean
548+ (allCodePathsReturn, _, inner') <- checkBlock mass ret inner
549+ return (allCodePathsReturn, mass, While val' inner')
550+checkStatement mass ret (If ifst) = do
551+ (allCodePathsReturn, ifst') <- checkIfStatement mass ret ifst
552+ return (allCodePathsReturn, mass, If ifst')
553+checkStatement mass ret (For ident start end inner) = do
554+ moduleName <- substCurrentModule <$> ask
555+ assignVariable ident
556+ start' <- check start Number
557+ end' <- check end Number
558+ (allCodePathsReturn, _, inner') <- bindLocalVariables moduleName [(ident, Number)] $ checkBlock mass ret inner
559+ return (allCodePathsReturn, mass, For ident start' end' inner')
560+checkStatement mass ret (Return val) = do
561+ val' <- check val ret
562+ return (True, mass, Return val')
563+
564+checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> Subst (Bool, IfStatement)
565+checkIfStatement mass ret (IfStatement val thens Nothing) = do
566+ val' <- check val Boolean
567+ (_, _, thens') <- checkBlock mass ret thens
568+ return (False, IfStatement val' thens' Nothing)
569+checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
570+ val' <- check val Boolean
571+ (allCodePathsReturn1, _, thens') <- checkBlock mass ret thens
572+ (allCodePathsReturn2, elses') <- checkElseStatement mass ret elses
573+ return (allCodePathsReturn1 && allCodePathsReturn2, IfStatement val' thens' (Just elses'))
574+
575+checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> Subst (Bool, ElseStatement)
576+checkElseStatement mass ret (Else elses) = do
577+ (allCodePathsReturn, _, elses') <- checkBlock mass ret elses
578+ return (allCodePathsReturn, Else elses')
579+checkElseStatement mass ret (ElseIf ifst) = (id *** ElseIf) <$> checkIfStatement mass ret ifst
580+
581+checkBlock :: M.Map Ident Type -> Type -> [Statement] -> Subst (Bool, M.Map Ident Type, [Statement])
582+checkBlock mass _ [] = return (False, mass, [])
583+checkBlock mass ret (s:ss) = do
584+ moduleName <- substCurrentModule <$> ask
585+ (b1, mass1, s') <- checkStatement mass ret s
586+ bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
587+ (True, []) -> return (True, mass1, [s'])
588+ (True, _) -> throwError "Unreachable code"
589+ (False, ss') -> do
590+ (b, m, ss'') <- checkBlock mass1 ret ss'
591+ return (b, m, s':ss'')
592+
593+skolemize :: String -> Type -> Subst Type
594+skolemize ident ty = do
595+ tsk <- Skolem <$> fresh'
596+ return $ replaceTypeVars ident tsk ty
597+
598+check :: Value -> Type -> Subst Value
599+check val ty = rethrow errorMessage $ check' val ty
600+ where
601+ errorMessage msg =
602+ "Error checking type of term " ++
603+ prettyPrintValue val ++
604+ " against type " ++
605+ prettyPrintType ty ++
606+ ":\n" ++
607+ msg
608+
609+check' :: Value -> Type -> Subst Value
610+check' val (ForAll idents ty) = do
611+ sk <- skolemize idents ty
612+ check val sk
613+check' val (ConstrainedType constraints ty) = do
614+ let dictName = Ident "__dict" -- TODO
615+ val' <- withTypeClassDictionaries (map (\(className, instanceTy) -> (dictName, className, instanceTy)) constraints) $ check val ty
616+ return $ Abs (map (\_ -> dictName) constraints) val'
617+check' val u@(TUnknown _) = do
618+ val'@(TypedValue _ ty) <- infer val
619+ -- Don't unify an unknown with an inferred polytype
620+ ty' <- replaceAllVarsWithUnknowns ty
621+ ty' ~~ u
622+ return val'
623+check' v@(NumericLiteral _) Number = return v
624+check' v@(StringLiteral _) String = return v
625+check' v@(BooleanLiteral _) Boolean = return v
626+check' (Unary op val) ty = checkUnary op val ty
627+check' (Binary op left right) ty = checkBinary op left right ty
628+check' (ArrayLiteral vals) (Array ty) = ArrayLiteral <$> forM vals (\val -> check val ty)
629+check' (Indexer index vals) ty = do
630+ index' <- check index Number
631+ vals' <- check vals (Array ty)
632+ return $ Indexer index' vals'
633+check' (Abs args ret) (Function argTys retTy) = do
634+ moduleName <- substCurrentModule <$> ask
635+ guardWith "Incorrect number of function arguments" (length args == length argTys)
636+ ret' <- bindLocalVariables moduleName (zip args argTys) $ check ret retTy
637+ return $ Abs args ret'
638+check' (App f args) ret = do
639+ f'@(TypedValue _ ft) <- infer f
640+ app <- checkFunctionApplication f' ft args ret
641+ return $ app
642+check' (Var var) ty = do
643+ moduleName <- substCurrentModule <$> ask
644+ ty1 <- lookupVariable moduleName var
645+ repl <- replaceAllTypeSynonyms ty1
646+ repl `subsumes` ty
647+ return $ Var var
648+check' (TypedValue val ty1) ty2 = do
649+ moduleName <- substCurrentModule <$> ask
650+ kind <- liftCheck $ kindOf moduleName ty1
651+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
652+ ty1 `subsumes` ty2
653+ val' <- check val ty1
654+ return $ TypedValue val' ty1
655+check' (Case vals binders) ret = do
656+ vals' <- mapM infer vals
657+ let ts = map (\(TypedValue _ t) -> t) vals'
658+ binders' <- checkBinders ts ret binders
659+ return $ Case vals' binders'
660+check' (IfThenElse cond th el) ty = do
661+ cond' <- check cond Boolean
662+ th' <- check th ty
663+ el' <- check el ty
664+ return $ IfThenElse cond' th' el'
665+check' (ObjectLiteral ps) (Object row) = do
666+ ensureNoDuplicateProperties ps
667+ ps' <- checkProperties ps row False
668+ return $ ObjectLiteral ps'
669+check' (ObjectUpdate obj ps) (Object row) = do
670+ ensureNoDuplicateProperties ps
671+ us <- zip (map fst ps) <$> replicateM (length ps) fresh
672+ let (propsToCheck, rest) = rowToList row
673+ propsToRemove = map fst ps
674+ remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
675+ obj' <- check obj (Object (rowFromList (us ++ remainingProps, rest)))
676+ ps' <- checkProperties ps row True
677+ return $ ObjectUpdate obj' ps'
678+check' (Accessor prop val) ty = do
679+ rest <- fresh
680+ val' <- check val (Object (RCons prop ty rest))
681+ return $ Accessor prop val'
682+check' (Block ss) ret = do
683+ (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
684+ guardWith "Block is missing a return statement" allCodePathsReturn
685+ return $ Block ss'
686+check' (Constructor c) ty = do
687+ env <- getEnv
688+ moduleName <- substCurrentModule <$> ask
689+ case M.lookup (qualify moduleName c) (dataConstructors env) of
690+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
691+ Just (ty1, _) -> do
692+ repl <- replaceAllTypeSynonyms ty1
693+ repl `subsumes` ty
694+ return $ Constructor c
695+check' val (SaturatedTypeSynonym name args) = do
696+ ty <- expandTypeSynonym name args
697+ check val ty
698+check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
699+
700+checkProperties :: [(String, Value)] -> Type -> Bool -> Subst [(String, Value)]
701+checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
702+ go [] [] REmpty = return []
703+ go [] [] u@(TUnknown _) = do u ~~ REmpty
704+ return []
705+ go [] [] (Skolem _) | lax = return []
706+ go [] ((p, _): _) _ | lax = return []
707+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
708+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
709+ go ((p,v):ps') [] u@(TUnknown _) = do
710+ v'@(TypedValue _ ty) <- infer v
711+ rest <- fresh
712+ u ~~ RCons p ty rest
713+ ps'' <- go ps' [] rest
714+ return $ (p, v') : ps''
715+ go ((p,v):ps') ts r =
716+ case lookup p ts of
717+ Nothing -> do
718+ v'@(TypedValue _ ty) <- infer v
719+ rest <- fresh
720+ r ~~ RCons p ty rest
721+ ps'' <- go ps' ts rest
722+ return $ (p, v') : ps''
723+ Just ty -> do
724+ v' <- check v ty
725+ ps'' <- go ps' (delete (p, ty) ts) r
726+ return $ (p, v') : ps''
727+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
728+
729+checkFunctionApplication :: Value -> Type -> [Value] -> Type -> Subst Value
730+checkFunctionApplication fn fnTy args ret = rethrow errorMessage $ checkFunctionApplication' fn fnTy args ret
731+ where
732+ errorMessage msg = "Error applying function of type "
733+ ++ prettyPrintType fnTy
734+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
735+ ++ ":\n" ++ msg
736+
737+checkFunctionApplication' :: Value -> Type -> [Value] -> Type -> Subst Value
738+checkFunctionApplication' fn (Function argTys retTy) args ret = do
739+ guardWith "Incorrect number of function arguments" (length args == length argTys)
740+ args' <- zipWithM check args argTys
741+ retTy `subsumes` ret
742+ return $ App fn args'
743+checkFunctionApplication' fn (ForAll ident ty) args ret = do
744+ replaced <- replaceVarWithUnknown ident ty
745+ checkFunctionApplication fn replaced args ret
746+checkFunctionApplication' fn u@(TUnknown _) args ret = do
747+ args' <- mapM (\arg -> infer arg >>= \(TypedValue v t) -> TypedValue v <$> replaceAllVarsWithUnknowns t) args
748+ let tys = map (\(TypedValue _ t) -> t) args'
749+ u ~~ Function tys ret
750+ return $ App fn args'
751+checkFunctionApplication' fn (SaturatedTypeSynonym name tyArgs) args ret = do
752+ ty <- expandTypeSynonym name tyArgs
753+ checkFunctionApplication fn ty args ret
754+checkFunctionApplication' fn (ConstrainedType constraints fnTy) args ret = do
755+ dicts <- getTypeClassDictionaries
756+ checkFunctionApplication' (App fn (map (flip TypeClassDictionary dicts) constraints)) fnTy args ret
757+checkFunctionApplication' _ fnTy args ret = throwError $ "Applying a function of type "
758+ ++ prettyPrintType fnTy
759+ ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
760+ ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
761+
762+subsumes :: Type -> Type -> Subst ()
763+subsumes (ForAll ident ty1) ty2 = do
764+ replaced <- replaceVarWithUnknown ident ty1
765+ replaced `subsumes` ty2
766+subsumes (Function args1 ret1) (Function args2 ret2) = do
767+ zipWithM_ subsumes args2 args1
768+ ret1 `subsumes` ret2
769+subsumes ty1 ty2 = ty1 ~~ ty2
770+