@@ -1,770 +0,0 @@
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−