@@ -1,754 +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 (everything, mkT, something, everywhere, mkQ)
26−
27−import Language.PureScript.Values
28−import Language.PureScript.Types
29−import Language.PureScript.Kinds
30−import Language.PureScript.Names
31−import Language.PureScript.TypeChecker.Monad
32−import Language.PureScript.TypeChecker.Kinds
33−import Language.PureScript.TypeChecker.Synonyms
34−import Language.PureScript.Pretty
35−import Language.PureScript.Unknown
36−
37−import Control.Monad.State
38−import Control.Monad.Error
39−import Control.Monad.Reader
40−
41−import Control.Applicative
42−import Control.Arrow (Arrow(..))
43−
44−import qualified Data.Map as M
45−import Data.Function (on)
46−
47−instance Unifiable Type where
48− unknown = TUnknown
49− isUnknown (TUnknown u) = Just u
50− isUnknown _ = Nothing
51− (~~) = unifyTypes
52− apply s (TUnknown u) = runSubstitution s u
53− apply s (SaturatedTypeSynonym name tys) = SaturatedTypeSynonym name $ map (apply s) tys
54− apply s (ForAll idents ty) = ForAll idents $ apply s ty
55− apply s (Array t) = Array (apply s t)
56− apply s (Object r) = Object (apply s r)
57− apply s (Function args ret) = Function (map (apply s) args) (apply s ret)
58− apply s (TypeApp t1 t2) = TypeApp (apply s t1) (apply s t2)
59− apply s (RCons name ty r) = RCons name (apply s ty) (apply s r)
60− apply _ t = t
61− unknowns (TUnknown (Unknown u)) = [u]
62− unknowns (SaturatedTypeSynonym _ tys) = concatMap unknowns tys
63− unknowns (ForAll _ ty) = unknowns ty
64− unknowns (Array t) = unknowns t
65− unknowns (Object r) = unknowns r
66− unknowns (Function args ret) = concatMap unknowns args ++ unknowns ret
67− unknowns (TypeApp t1 t2) = unknowns t1 ++ unknowns t2
68− unknowns (RCons _ ty r) = unknowns ty ++ unknowns r
69− unknowns _ = []
70−
71−unifyTypes :: Type -> Type -> Subst ()
72−unifyTypes t1 t2 = rethrow (\e -> "Error unifying type " ++ prettyPrintType t1 ++ " with type " ++ prettyPrintType t2 ++ ":\n" ++ e) $ do
73− unifyTypes' t1 t2
74− where
75− unifyTypes' (TUnknown u1) (TUnknown u2) | u1 == u2 = return ()
76− unifyTypes' (TUnknown u) t = replace u t
77− unifyTypes' t (TUnknown u) = replace u t
78− unifyTypes' (SaturatedTypeSynonym name args) ty = do
79− ty1 <- expandTypeSynonym name args
80− ty1 `unifyTypes` ty
81− unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
82− unifyTypes' (ForAll ident1 ty1) (ForAll ident2 ty2) = do
83− sk <- skolemize ident1 ty1
84− replaced <- replaceVarWithUnknown ident2 ty2
85− sk `unifyTypes` replaced
86− unifyTypes' (ForAll ident ty1) ty2 = do
87− sk <- skolemize ident ty1
88− sk `unifyTypes` ty2
89− unifyTypes' ty f@(ForAll _ _) = f `unifyTypes` ty
90− unifyTypes' Number Number = return ()
91− unifyTypes' String String = return ()
92− unifyTypes' Boolean Boolean = return ()
93− unifyTypes' (Array s) (Array t) = s `unifyTypes` t
94− unifyTypes' (Object row1) (Object row2) = row1 ~~ row2
95− unifyTypes' (Function args1 ret1) (Function args2 ret2) = do
96− guardWith "Function applied to incorrect number of args" $ length args1 == length args2
97− zipWithM_ unifyTypes args1 args2
98− ret1 `unifyTypes` ret2
99− unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
100− unifyTypes' (TypeConstructor c1) (TypeConstructor c2) = do
101− env <- getEnv
102− moduleName <- substCurrentModule `fmap` ask
103− guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (typeConstructorsAreEqual env moduleName c1 c2)
104− unifyTypes' (TypeApp t3 t4) (TypeApp t5 t6) = do
105− t3 `unifyTypes` t5
106− t4 `unifyTypes` t6
107− unifyTypes' (Skolem s1) (Skolem s2) | s1 == s2 = return ()
108− unifyTypes' r1@(RCons _ _ _) r2 = unifyRows r1 r2
109− unifyTypes' r1 r2@(RCons _ _ _) = unifyRows r1 r2
110− unifyTypes' r1@REmpty r2 = unifyRows r1 r2
111− unifyTypes' r1 r2@REmpty = unifyRows r1 r2
112− unifyTypes' t3 t4 = throwError $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
113−
114−unifyRows :: Type -> Type -> Subst ()
115−unifyRows r1 r2 =
116− let
117− (s1, r1') = rowToList r1
118− (s2, r2') = rowToList r2
119− int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
120− sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
121− sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
122− in do
123− forM_ int (uncurry (~~))
124− unifyRows' sd1 r1' sd2 r2'
125− where
126− unifyRows' :: [(String, Type)] -> Type -> [(String, Type)] -> Type -> Subst ()
127− unifyRows' [] (TUnknown u) sd r = replace u (rowFromList (sd, r))
128− unifyRows' sd r [] (TUnknown u) = replace u (rowFromList (sd, r))
129− unifyRows' ((name, ty):row) r others u@(TUnknown un) = do
130− occursCheck un ty
131− forM_ row $ \(_, t) -> occursCheck un t
132− u' <- fresh
133− u ~~ RCons name ty u'
134− unifyRows' row r others u'
135− unifyRows' [] REmpty [] REmpty = return ()
136− unifyRows' [] (TypeVar v1) [] (TypeVar v2) | v1 == v2 = return ()
137− unifyRows' [] (Skolem s1) [] (Skolem s2) | s1 == s2 = return ()
138− unifyRows' sd3 r3 sd4 r4 = throwError $ "Cannot unify " ++ prettyPrintRow (rowFromList (sd3, r3)) ++ " with " ++ prettyPrintRow (rowFromList (sd4, r4)) ++ "."
139−
140−typeConstructorsAreEqual :: Environment -> ModuleName -> Qualified ProperName -> Qualified ProperName -> Bool
141−typeConstructorsAreEqual env moduleName = (==) `on` canonicalizeType moduleName env
142−
143−typesOf :: ModuleName -> [(Ident, Value)] -> Check [(Ident, (Value, Type))]
144−typesOf moduleName vals = do
145− tys <- fmap (\(tys, s) -> map (\(ident, (val, ty)) -> (ident, (overTypes (apply s) val, apply s ty))) tys)
146− . runSubst (SubstContext moduleName) $ do
147− let es = map isTyped vals
148− typed = filter (isJust . snd . snd) es
149− untyped = filter (isNothing . snd . snd) es
150− typedDict = map (\(ident, (_, Just ty)) -> (ident, ty)) typed
151− untypedNames <- replicateM (length untyped) fresh
152− let untypedDict = zip (map fst untyped) untypedNames
153− dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ typedDict ++ untypedDict)
154− forM es $ \e -> do
155− triple@(_, (val, ty)) <- case e of
156− (ident, (val, Just ty)) -> do
157− kind <- liftCheck $ kindOf moduleName ty
158− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
159− ty' <- replaceAllTypeSynonyms ty
160− val' <- bindNames dict $ check val ty'
161− return (ident, (val', ty'))
162− (ident, (val, Nothing)) -> do
163− TypedValue val' ty <- bindNames dict $ infer val
164− ty ~~ fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
165− return (ident, (val', ty))
166− when (moduleName == ModuleName (ProperName "Main") && fst e == Ident "main") $ do
167− [eff, a] <- replicateM 2 fresh
168− ty ~~ TypeApp (TypeApp (TypeConstructor (Qualified (Just (ModuleName (ProperName "Eff"))) (ProperName "Eff"))) eff) a
169− escapeCheck val ty
170− return triple
171− forM_ tys $ skolemEscapeCheck . snd . snd
172− return $ map (\(ident, (val, ty)) -> ( ident, ( overTypes (desaturateAllTypeSynonyms . setifyAll) val
173− , varIfUnknown . desaturateAllTypeSynonyms . setifyAll $ ty))) tys
174−
175−isTyped :: (Ident, Value) -> (Ident, (Value, Maybe Type))
176−isTyped (name, TypedValue value ty) = (name, (value, Just ty))
177−isTyped (name, value) = (name, (value, Nothing))
178−
179−overTypes :: (Type -> Type) -> Value -> Value
180−overTypes f = everywhere (mkT f)
181−
182−escapeCheck :: Value -> Type -> Subst ()
183−escapeCheck value ty = do
184− subst <- substSubst <$> getSubstState
185− let visibleUnknowns = nub $ unknowns $ apply subst ty
186− let allUnknowns = findAllTypes value
187− forM_ allUnknowns $ \t -> do
188− let unsolvedUnknowns = nub . unknowns $ apply subst t
189− guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
190−
191−findAllTypes :: Value -> [Type]
192−findAllTypes = everything (++) (mkQ [] go)
193− where
194− go (TypedValue _ ty) = [ty]
195− go _ = []
196−
197−skolemEscapeCheck :: Type -> Check ()
198−skolemEscapeCheck ty =
199− case something (mkQ Nothing findSkolems) ty of
200− Nothing -> return ()
201− Just _ -> throwError $ "Skolem variables cannot escape. Consider adding a type signature." ++ show ty
202− where
203− findSkolems (Skolem _) = return ()
204− findSkolems _ = mzero
205−
206−setify :: Type -> Type
207−setify = rowFromList . first (M.toList . M.fromList) . rowToList
208−
209−setifyAll :: (D.Data d) => d -> d
210−setifyAll = everywhere (mkT setify)
211−
212−varIfUnknown :: Type -> Type
213−varIfUnknown ty =
214− let unks = nub $ unknowns ty
215− toName = (:) 't' . show
216− ty' = everywhere (mkT typeToVar) $ ty
217− typeToVar :: Type -> Type
218− typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
219− typeToVar t = t
220− in mkForAll (sort . map toName $ unks) ty'
221−
222−replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
223−replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
224−
225−replaceAllVarsWithUnknowns :: Type -> Subst Type
226−replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
227−replaceAllVarsWithUnknowns ty = return ty
228−
229−replaceVarWithUnknown :: String -> Type -> Subst Type
230−replaceVarWithUnknown ident ty = do
231− tu <- fresh
232− return $ replaceTypeVars ident tu $ ty
233−
234−replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadReader SubstContext m, MonadError String m) => (D.Data d) => d -> m d
235−replaceAllTypeSynonyms d = do
236− env <- getEnv
237− moduleName <- substCurrentModule <$> ask
238− let syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
239− either throwError return $ saturateAllTypeSynonyms env moduleName syns d
240−
241−desaturateAllTypeSynonyms :: (D.Data d) => d -> d
242−desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
243− where
244− replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
245− replaceSaturatedTypeSynonym t = t
246−
247−expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Type
248−expandTypeSynonym name args = do
249− env <- getEnv
250− moduleName <- substCurrentModule `fmap` ask
251− case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
252− Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
253− Nothing -> error "Type synonym was not defined"
254−
255−ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
256−ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
257−
258−infer :: Value -> Subst Value
259−infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ infer' val
260−
261−infer' :: Value -> Subst Value
262−infer' v@(NumericLiteral _) = return $ TypedValue v Number
263−infer' v@(StringLiteral _) = return $ TypedValue v String
264−infer' v@(BooleanLiteral _) = return $ TypedValue v Boolean
265−infer' (ArrayLiteral vals) = do
266− ts <- mapM infer vals
267− els <- fresh
268− forM_ ts $ \(TypedValue _ t) -> els ~~ Array t
269− return $ TypedValue (ArrayLiteral ts) els
270−infer' (Unary op val) = do
271− v <- infer val
272− inferUnary op v
273−infer' (Binary op left right) = do
274− v1 <- infer left
275− v2 <- infer right
276− inferBinary op v1 v2
277−infer' (ObjectLiteral ps) = do
278− ensureNoDuplicateProperties ps
279− ts <- mapM (infer . snd) ps
280− let fields = zipWith (\name (TypedValue _ t) -> (name, t)) (map fst ps) ts
281− ty = Object $ rowFromList (fields, REmpty)
282− return $ TypedValue (ObjectLiteral (zip (map fst ps) ts)) ty
283−infer' (ObjectUpdate o ps) = do
284− ensureNoDuplicateProperties ps
285− row <- fresh
286− newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
287− let newTys = map (\(name, TypedValue _ ty) -> (name, ty)) newVals
288− oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
289− o' <- check o $ Object $ rowFromList (oldTys, row)
290− return $ TypedValue (ObjectUpdate o' newVals) $ Object $ rowFromList (newTys, row)
291−infer' (Indexer index val) = do
292− el <- fresh
293− index' <- check index Number
294− val' <- check val (Array el)
295− return $ TypedValue (Indexer (TypedValue index' Number) (TypedValue val' (Array el))) el
296−infer' (Accessor prop val) = do
297− typed@(TypedValue _ objTy) <- infer val
298− propTy <- inferProperty objTy prop
299− case propTy of
300− Nothing -> do
301− field <- fresh
302− rest <- fresh
303− objTy `subsumes` Object (RCons prop field rest)
304− return $ TypedValue (Accessor prop typed) field
305− Just ty -> return $ TypedValue (Accessor prop typed) ty
306−infer' (Abs args ret) = do
307− ts <- replicateM (length args) fresh
308− moduleName <- substCurrentModule <$> ask
309− bindLocalVariables moduleName (zip args ts) $ do
310− body@(TypedValue _ bodyTy) <- infer' ret
311− return $ TypedValue (Abs args body) $ Function ts bodyTy
312−infer' (App f args) = do
313− f'@(TypedValue _ ft) <- infer f
314− ret <- fresh
315− app <- checkFunctionApplication f' ft args ret
316− return $ TypedValue app ret
317−infer' (Var var) = do
318− moduleName <- substCurrentModule <$> ask
319− ty <- lookupVariable moduleName var
320− ty' <- replaceAllTypeSynonyms ty
321− case ty' of
322− ConstrainedType constraints _ -> return $ TypedValue (App (Var var) [TypeClassDictionary constraints]) ty'
323− _ -> return $ TypedValue (Var var) ty'
324−infer' (Block ss) = do
325− ret <- fresh
326− (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
327− guardWith "Block is missing a return statement" allCodePathsReturn
328− return $ TypedValue (Block ss') ret
329−infer' v@(Constructor c) = do
330− env <- getEnv
331− moduleName <- substCurrentModule `fmap` ask
332− case M.lookup (qualify moduleName c) (dataConstructors env) of
333− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
334− Just (ty, _) -> do ty' <- replaceAllTypeSynonyms ty
335− return $ TypedValue v ty'
336−infer' (Case vals binders) = do
337− ts <- mapM infer vals
338− ret <- fresh
339− binders' <- checkBinders (map (\(TypedValue _ t) -> t) ts) ret binders
340− return $ TypedValue (Case ts binders') ret
341−infer' (IfThenElse cond th el) = do
342− cond' <- check cond Boolean
343− v2@(TypedValue _ t2) <- infer th
344− v3@(TypedValue _ t3) <- infer el
345− t2 ~~ t3
346− return $ TypedValue (IfThenElse cond' v2 v3) t2
347−infer' (TypedValue val ty) = do
348− moduleName <- substCurrentModule <$> ask
349− kind <- liftCheck $ kindOf moduleName ty
350− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
351− ty' <- replaceAllTypeSynonyms ty
352− val' <- check val ty'
353− return $ TypedValue val' ty
354−infer' _ = error "Invalid argument to infer"
355−
356−inferProperty :: Type -> String -> Subst (Maybe Type)
357−inferProperty (Object row) prop = do
358− let (props, _) = rowToList row
359− return $ lookup prop props
360−inferProperty (SaturatedTypeSynonym name args) prop = do
361− replaced <- expandTypeSynonym name args
362− inferProperty replaced prop
363−inferProperty (ForAll ident ty) prop = do
364− replaced <- replaceVarWithUnknown ident ty
365− inferProperty replaced prop
366−inferProperty _ _ = return Nothing
367−
368−inferUnary :: UnaryOperator -> Value -> Subst Value
369−inferUnary op (TypedValue val valTy) =
370− case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
371− (valTy', resTy) -> do
372− valTy' ~~ valTy
373− return $ TypedValue (Unary op val) resTy
374−inferUnary _ _ = error "Invalid arguments to inferUnary"
375−
376−checkUnary :: UnaryOperator -> Value -> Type -> Subst Value
377−checkUnary op val res =
378− case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
379− (valTy, resTy) -> do
380− res ~~ resTy
381− val' <- check val valTy
382− return $ Unary op val'
383−
384−unaryOps :: [(UnaryOperator, (Type, Type))]
385−unaryOps = [ (Negate, (Number, Number))
386− , (Not, (Boolean, Boolean))
387− , (BitwiseNot, (Number, Number))
388− ]
389−
390−inferBinary :: BinaryOperator -> Value -> Value -> Subst Value
391−inferBinary op left@(TypedValue _ leftTy) right@(TypedValue _ rightTy) | isEqualityTest op = do
392− leftTy ~~ rightTy
393− return $ TypedValue (Binary op left right) Boolean
394−inferBinary op left@(TypedValue _ leftTy) right@(TypedValue _ rightTy) =
395− case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
396− (valTy, resTy) -> do
397− leftTy ~~ valTy
398− rightTy ~~ valTy
399− return $ TypedValue (Binary op left right) resTy
400−inferBinary _ _ _ = error "Invalid arguments to inferBinary"
401−
402−checkBinary :: BinaryOperator -> Value -> Value -> Type -> Subst Value
403−checkBinary op left right res | isEqualityTest op = do
404− res ~~ Boolean
405− left'@(TypedValue _ t1) <- infer left
406− right'@(TypedValue _ t2) <- infer right
407− t1 ~~ t2
408− return $ Binary op left' right'
409−checkBinary op left right res =
410− case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
411− (valTy, resTy) -> do
412− res ~~ resTy
413− left' <- check left valTy
414− right' <- check right valTy
415− return $ Binary op left' right'
416−
417−isEqualityTest :: BinaryOperator -> Bool
418−isEqualityTest EqualTo = True
419−isEqualityTest NotEqualTo = True
420−isEqualityTest _ = False
421−
422−binaryOps :: [(BinaryOperator, (Type, Type))]
423−binaryOps = [ (Add, (Number, Number))
424− , (Subtract, (Number, Number))
425− , (Multiply, (Number, Number))
426− , (Divide, (Number, Number))
427− , (Modulus, (Number, Number))
428− , (BitwiseAnd, (Number, Number))
429− , (BitwiseOr, (Number, Number))
430− , (BitwiseXor, (Number, Number))
431− , (ShiftRight, (Number, Number))
432− , (ZeroFillShiftRight, (Number, Number))
433− , (And, (Boolean, Boolean))
434− , (Or, (Boolean, Boolean))
435− , (Concat, (String, String))
436− , (Modulus, (Number, Number))
437− , (LessThan, (Number, Boolean))
438− , (LessThanOrEqualTo, (Number, Boolean))
439− , (GreaterThan, (Number, Boolean))
440− , (GreaterThanOrEqualTo, (Number, Boolean))
441− ]
442−
443−inferBinder :: Type -> Binder -> Subst (M.Map Ident Type)
444−inferBinder _ NullBinder = return M.empty
445−inferBinder val (StringBinder _) = val ~~ String >> return M.empty
446−inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
447−inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
448−inferBinder val (VarBinder name) = return $ M.singleton name val
449−inferBinder val (NullaryBinder ctor) = do
450− env <- getEnv
451− moduleName <- substCurrentModule <$> ask
452− case M.lookup (qualify moduleName ctor) (dataConstructors env) of
453− Just (ty, _) -> do
454− ty `subsumes` val
455− return M.empty
456− _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
457−inferBinder val (UnaryBinder ctor binder) = do
458− env <- getEnv
459− moduleName <- substCurrentModule <$> ask
460− case M.lookup (qualify moduleName ctor) (dataConstructors env) of
461− Just (ty, _) -> do
462− fn <- replaceAllVarsWithUnknowns ty
463− case fn of
464− Function [obj] ret -> do
465− val `subsumes` ret
466− inferBinder obj binder
467− _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
468− _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
469−inferBinder val (ObjectBinder props) = do
470− row <- fresh
471− rest <- fresh
472− m1 <- inferRowProperties row rest props
473− val ~~ Object row
474− return m1
475− where
476− inferRowProperties :: Type -> Type -> [(String, Binder)] -> Subst (M.Map Ident Type)
477− inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
478− inferRowProperties nrow row ((name, binder):binders) = do
479− propTy <- fresh
480− m1 <- inferBinder propTy binder
481− m2 <- inferRowProperties nrow (RCons name propTy row) binders
482− return $ m1 `M.union` m2
483−inferBinder val (ArrayBinder binders) = do
484− el <- fresh
485− m1 <- M.unions <$> mapM (inferBinder el) binders
486− val ~~ Array el
487− return m1
488−inferBinder val (ConsBinder headBinder tailBinder) = do
489− el <- fresh
490− m1 <- inferBinder el headBinder
491− m2 <- inferBinder val tailBinder
492− val ~~ Array el
493− return $ m1 `M.union` m2
494−inferBinder val (NamedBinder name binder) = do
495− m <- inferBinder val binder
496− return $ M.insert name val m
497−
498−checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> Subst [([Binder], Maybe Guard, Value)]
499−checkBinders _ _ [] = return []
500−checkBinders nvals ret ((binders, grd, val):bs) = do
501− moduleName <- substCurrentModule <$> ask
502− m1 <- M.unions <$> zipWithM inferBinder nvals binders
503− r <- bindLocalVariables moduleName (M.toList m1) $ do
504− val' <- check val ret
505− case grd of
506− Nothing -> return (binders, Nothing, val')
507− Just g -> do
508− g' <- check g Boolean
509− return (binders, Just g', val')
510− rs <- checkBinders nvals ret bs
511− return $ r : rs
512−
513−assignVariable :: Ident -> Subst ()
514−assignVariable name = do
515− env <- checkEnv <$> get
516− moduleName <- substCurrentModule <$> ask
517− case M.lookup (moduleName, name) (names env) of
518− Just (_, LocalVariable) -> throwError $ "Variable with name " ++ show name ++ " already exists."
519− _ -> return ()
520−
521−checkStatement :: M.Map Ident Type -> Type -> Statement -> Subst (Bool, M.Map Ident Type, Statement)
522−checkStatement mass _ (VariableIntroduction name val) = do
523− assignVariable name
524− val'@(TypedValue _ t) <- infer val
525− return (False, M.insert name t mass, VariableIntroduction name val')
526−checkStatement mass _ (Assignment ident val) = do
527− val'@(TypedValue _ t) <- infer val
528− case M.lookup ident mass of
529− Nothing -> throwError $ "No local variable with name " ++ show ident
530− Just ty -> do t ~~ ty
531− return (False, mass, Assignment ident val')
532−checkStatement mass ret (While val inner) = do
533− val' <- check val Boolean
534− (allCodePathsReturn, _, inner') <- checkBlock mass ret inner
535− return (allCodePathsReturn, mass, While val' inner')
536−checkStatement mass ret (If ifst) = do
537− (allCodePathsReturn, ifst') <- checkIfStatement mass ret ifst
538− return (allCodePathsReturn, mass, If ifst')
539−checkStatement mass ret (For ident start end inner) = do
540− moduleName <- substCurrentModule <$> ask
541− assignVariable ident
542− start' <- check start Number
543− end' <- check end Number
544− (allCodePathsReturn, _, inner') <- bindLocalVariables moduleName [(ident, Number)] $ checkBlock mass ret inner
545− return (allCodePathsReturn, mass, For ident start' end' inner')
546−checkStatement mass ret (Return val) = do
547− val' <- check val ret
548− return (True, mass, Return val')
549−
550−checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> Subst (Bool, IfStatement)
551−checkIfStatement mass ret (IfStatement val thens Nothing) = do
552− val' <- check val Boolean
553− (_, _, thens') <- checkBlock mass ret thens
554− return (False, IfStatement val' thens' Nothing)
555−checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
556− val' <- check val Boolean
557− (allCodePathsReturn1, _, thens') <- checkBlock mass ret thens
558− (allCodePathsReturn2, elses') <- checkElseStatement mass ret elses
559− return (allCodePathsReturn1 && allCodePathsReturn2, IfStatement val' thens' (Just elses'))
560−
561−checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> Subst (Bool, ElseStatement)
562−checkElseStatement mass ret (Else elses) = do
563− (allCodePathsReturn, _, elses') <- checkBlock mass ret elses
564− return (allCodePathsReturn, Else elses')
565−checkElseStatement mass ret (ElseIf ifst) = (id *** ElseIf) <$> checkIfStatement mass ret ifst
566−
567−checkBlock :: M.Map Ident Type -> Type -> [Statement] -> Subst (Bool, M.Map Ident Type, [Statement])
568−checkBlock mass _ [] = return (False, mass, [])
569−checkBlock mass ret (s:ss) = do
570− moduleName <- substCurrentModule <$> ask
571− (b1, mass1, s') <- checkStatement mass ret s
572− bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
573− (True, []) -> return (True, mass1, [s'])
574− (True, _) -> throwError "Unreachable code"
575− (False, ss') -> do
576− (b, m, ss'') <- checkBlock mass1 ret ss'
577− return (b, m, s':ss'')
578−
579−skolemize :: String -> Type -> Subst Type
580−skolemize ident ty = do
581− tsk <- Skolem <$> fresh'
582− return $ replaceTypeVars ident tsk ty
583−
584−check :: Value -> Type -> Subst Value
585−check val ty = rethrow errorMessage $ check' val ty
586− where
587− errorMessage msg =
588− "Error checking type of term " ++
589− prettyPrintValue val ++
590− " against type " ++
591− prettyPrintType ty ++
592− ":\n" ++
593− msg
594−
595−check' :: Value -> Type -> Subst Value
596−check' val (ForAll idents ty) = do
597− sk <- skolemize idents ty
598− check val sk
599−check' val (ConstrainedType constraints ty) = do
600− val' <- check val ty
601− return $ Abs (map (\_ -> Ident "__dict") constraints) val'
602−check' val u@(TUnknown _) = do
603− val'@(TypedValue _ ty) <- infer val
604− -- Don't unify an unknown with an inferred polytype
605− ty' <- replaceAllVarsWithUnknowns ty
606− ty' ~~ u
607− return val'
608−check' v@(NumericLiteral _) Number = return v
609−check' v@(StringLiteral _) String = return v
610−check' v@(BooleanLiteral _) Boolean = return v
611−check' (Unary op val) ty = checkUnary op val ty
612−check' (Binary op left right) ty = checkBinary op left right ty
613−check' (ArrayLiteral vals) (Array ty) = ArrayLiteral <$> forM vals (\val -> check val ty)
614−check' (Indexer index vals) ty = do
615− index' <- check index Number
616− vals' <- check vals (Array ty)
617− return $ Indexer index' vals'
618−check' (Abs args ret) (Function argTys retTy) = do
619− moduleName <- substCurrentModule <$> ask
620− guardWith "Incorrect number of function arguments" (length args == length argTys)
621− ret' <- bindLocalVariables moduleName (zip args argTys) $ check ret retTy
622− return $ Abs args ret'
623−check' (App f args) ret = do
624− f'@(TypedValue _ ft) <- infer f
625− app <- checkFunctionApplication f' ft args ret
626− return $ app
627−check' (Var var) ty = do
628− moduleName <- substCurrentModule <$> ask
629− ty1 <- lookupVariable moduleName var
630− repl <- replaceAllTypeSynonyms ty1
631− repl `subsumes` ty
632− return $ Var var
633−check' (TypedValue val ty1) ty2 = do
634− moduleName <- substCurrentModule <$> ask
635− kind <- liftCheck $ kindOf moduleName ty1
636− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
637− ty1 `subsumes` ty2
638− val' <- check val ty1
639− return $ TypedValue val' ty1
640−check' (Case vals binders) ret = do
641− vals' <- mapM infer vals
642− let ts = map (\(TypedValue _ t) -> t) vals'
643− binders' <- checkBinders ts ret binders
644− return $ Case vals' binders'
645−check' (IfThenElse cond th el) ty = do
646− cond' <- check cond Boolean
647− th' <- check th ty
648− el' <- check el ty
649− return $ IfThenElse cond' th' el'
650−check' (ObjectLiteral ps) (Object row) = do
651− ensureNoDuplicateProperties ps
652− ps' <- checkProperties ps row False
653− return $ ObjectLiteral ps'
654−check' (ObjectUpdate obj ps) (Object row) = do
655− ensureNoDuplicateProperties ps
656− us <- zip (map fst ps) <$> replicateM (length ps) fresh
657− let (propsToCheck, rest) = rowToList row
658− propsToRemove = map fst ps
659− remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
660− obj' <- check obj (Object (rowFromList (us ++ remainingProps, rest)))
661− ps' <- checkProperties ps row True
662− return $ ObjectUpdate obj' ps'
663−check' (Accessor prop val) ty = do
664− rest <- fresh
665− val' <- check val (Object (RCons prop ty rest))
666− return $ Accessor prop val'
667−check' (Block ss) ret = do
668− (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
669− guardWith "Block is missing a return statement" allCodePathsReturn
670− return $ Block ss'
671−check' (Constructor c) ty = do
672− env <- getEnv
673− moduleName <- substCurrentModule <$> ask
674− case M.lookup (qualify moduleName c) (dataConstructors env) of
675− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
676− Just (ty1, _) -> do
677− repl <- replaceAllTypeSynonyms ty1
678− repl `subsumes` ty
679− return $ Constructor c
680−check' val (SaturatedTypeSynonym name args) = do
681− ty <- expandTypeSynonym name args
682− check val ty
683−check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
684−
685−checkProperties :: [(String, Value)] -> Type -> Bool -> Subst [(String, Value)]
686−checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
687− go [] [] REmpty = return []
688− go [] [] u@(TUnknown _) = do u ~~ REmpty
689− return []
690− go [] [] (Skolem _) | lax = return []
691− go [] ((p, _): _) _ | lax = return []
692− | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
693− go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
694− go ((p,v):ps') [] u@(TUnknown _) = do
695− v'@(TypedValue _ ty) <- infer v
696− rest <- fresh
697− u ~~ RCons p ty rest
698− ps'' <- go ps' [] rest
699− return $ (p, v') : ps''
700− go ((p,v):ps') ts r =
701− case lookup p ts of
702− Nothing -> do
703− v'@(TypedValue _ ty) <- infer v
704− rest <- fresh
705− r ~~ RCons p ty rest
706− ps'' <- go ps' ts rest
707− return $ (p, v') : ps''
708− Just ty -> do
709− v' <- check v ty
710− ps'' <- go ps' (delete (p, ty) ts) r
711− return $ (p, v') : ps''
712− go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
713−
714−checkFunctionApplication :: Value -> Type -> [Value] -> Type -> Subst Value
715−checkFunctionApplication fn fnTy args ret = rethrow errorMessage $ checkFunctionApplication' fn fnTy args ret
716− where
717− errorMessage msg = "Error applying function of type "
718− ++ prettyPrintType fnTy
719− ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
720− ++ ":\n" ++ msg
721−
722−checkFunctionApplication' :: Value -> Type -> [Value] -> Type -> Subst Value
723−checkFunctionApplication' fn (Function argTys retTy) args ret = do
724− guardWith "Incorrect number of function arguments" (length args == length argTys)
725− args' <- zipWithM check args argTys
726− retTy `subsumes` ret
727− return $ App fn args'
728−checkFunctionApplication' fn (ForAll ident ty) args ret = do
729− replaced <- replaceVarWithUnknown ident ty
730− checkFunctionApplication fn replaced args ret
731−checkFunctionApplication' fn u@(TUnknown _) args ret = do
732− args' <- mapM (\arg -> infer arg >>= \(TypedValue v t) -> TypedValue v <$> replaceAllVarsWithUnknowns t) args
733− let tys = map (\(TypedValue _ t) -> t) args'
734− u ~~ Function tys ret
735− return $ App fn args'
736−checkFunctionApplication' fn (SaturatedTypeSynonym name tyArgs) args ret = do
737− ty <- expandTypeSynonym name tyArgs
738− checkFunctionApplication fn ty args ret
739−checkFunctionApplication' fn (ConstrainedType constraints fnTy) args ret = do
740− checkFunctionApplication' (App fn [TypeClassDictionary constraints]) fnTy args ret
741−checkFunctionApplication' _ fnTy args ret = throwError $ "Applying a function of type "
742− ++ prettyPrintType fnTy
743− ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
744− ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
745−
746−subsumes :: Type -> Type -> Subst ()
747−subsumes (ForAll ident ty1) ty2 = do
748− replaced <- replaceVarWithUnknown ident ty1
749− replaced `subsumes` ty2
750−subsumes (Function args1 ret1) (Function args2 ret2) = do
751− zipWithM_ subsumes args2 args1
752− ret1 `subsumes` ret2
753−subsumes ty1 ty2 = ty1 ~~ ty2
754−