@@ -1,791 +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 (maybeToList, isNothing, isJust, fromMaybe)
24−import qualified Data.Data as D
25−import Data.Generics
26− (mkM, everywhereM, everything, mkT, something, everywhere, mkQ)
27−
28−import Language.PureScript.Values
29−import Language.PureScript.Types
30−import Language.PureScript.Kinds
31−import Language.PureScript.Names
32−import Language.PureScript.TypeChecker.Monad
33−import Language.PureScript.TypeChecker.Kinds
34−import Language.PureScript.TypeChecker.Synonyms
35−import Language.PureScript.Pretty
36−import Language.PureScript.Unknown
37−
38−import Control.Monad.State
39−import Control.Monad.Error
40−import Control.Monad.Reader
41−
42−import Control.Applicative
43−import Control.Arrow (Arrow(..))
44−
45−import qualified Data.Map as M
46−import Data.Function (on)
47−
48−instance Unifiable Type where
49− unknown = TUnknown
50− isUnknown (TUnknown u) = Just u
51− isUnknown _ = Nothing
52− (~~) = unifyTypes
53− apply s (TUnknown u) = runSubstitution s u
54− apply s (SaturatedTypeSynonym name tys) = SaturatedTypeSynonym name $ map (apply s) tys
55− apply s (ForAll idents ty) = ForAll idents $ apply s ty
56− apply s (Array t) = Array (apply s t)
57− apply s (Object r) = Object (apply s r)
58− apply s (Function args ret) = Function (map (apply s) args) (apply s ret)
59− apply s (TypeApp t1 t2) = TypeApp (apply s t1) (apply s t2)
60− apply s (RCons name ty r) = RCons name (apply s ty) (apply s r)
61− apply _ t = t
62− unknowns (TUnknown (Unknown u)) = [u]
63− unknowns (SaturatedTypeSynonym _ tys) = concatMap unknowns tys
64− unknowns (ForAll _ ty) = unknowns ty
65− unknowns (Array t) = unknowns t
66− unknowns (Object r) = unknowns r
67− unknowns (Function args ret) = concatMap unknowns args ++ unknowns ret
68− unknowns (TypeApp t1 t2) = unknowns t1 ++ unknowns t2
69− unknowns (RCons _ ty r) = unknowns ty ++ unknowns r
70− unknowns _ = []
71−
72−unifyTypes :: Type -> Type -> Subst ()
73−unifyTypes t1 t2 = rethrow (\e -> "Error unifying type " ++ prettyPrintType t1 ++ " with type " ++ prettyPrintType t2 ++ ":\n" ++ e) $ do
74− unifyTypes' t1 t2
75− where
76− unifyTypes' (TUnknown u1) (TUnknown u2) | u1 == u2 = return ()
77− unifyTypes' (TUnknown u) t = replace u t
78− unifyTypes' t (TUnknown u) = replace u t
79− unifyTypes' (SaturatedTypeSynonym name args) ty = do
80− ty1 <- expandTypeSynonym name args
81− ty1 `unifyTypes` ty
82− unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
83− unifyTypes' (ForAll ident1 ty1) (ForAll ident2 ty2) = do
84− sk <- skolemize ident1 ty1
85− replaced <- replaceVarWithUnknown ident2 ty2
86− sk `unifyTypes` replaced
87− unifyTypes' (ForAll ident ty1) ty2 = do
88− sk <- skolemize ident ty1
89− sk `unifyTypes` ty2
90− unifyTypes' ty f@(ForAll _ _) = f `unifyTypes` ty
91− unifyTypes' Number Number = return ()
92− unifyTypes' String String = return ()
93− unifyTypes' Boolean Boolean = return ()
94− unifyTypes' (Array s) (Array t) = s `unifyTypes` t
95− unifyTypes' (Object row1) (Object row2) = row1 ~~ row2
96− unifyTypes' (Function args1 ret1) (Function args2 ret2) = do
97− guardWith "Function applied to incorrect number of args" $ length args1 == length args2
98− zipWithM_ unifyTypes args1 args2
99− ret1 `unifyTypes` ret2
100− unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
101− unifyTypes' (TypeConstructor c1) (TypeConstructor c2) = do
102− env <- getEnv
103− moduleName <- substCurrentModule `fmap` ask
104− guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (typeConstructorsAreEqual env moduleName c1 c2)
105− unifyTypes' (TypeApp t3 t4) (TypeApp t5 t6) = do
106− t3 `unifyTypes` t5
107− t4 `unifyTypes` t6
108− unifyTypes' (Skolem s1) (Skolem s2) | s1 == s2 = return ()
109− unifyTypes' r1@(RCons _ _ _) r2 = unifyRows r1 r2
110− unifyTypes' r1 r2@(RCons _ _ _) = unifyRows r1 r2
111− unifyTypes' r1@REmpty r2 = unifyRows r1 r2
112− unifyTypes' r1 r2@REmpty = unifyRows r1 r2
113− unifyTypes' t3 t4 = throwError $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
114−
115−unifyRows :: Type -> Type -> Subst ()
116−unifyRows r1 r2 =
117− let
118− (s1, r1') = rowToList r1
119− (s2, r2') = rowToList r2
120− int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
121− sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
122− sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
123− in do
124− forM_ int (uncurry (~~))
125− unifyRows' sd1 r1' sd2 r2'
126− where
127− unifyRows' :: [(String, Type)] -> Type -> [(String, Type)] -> Type -> Subst ()
128− unifyRows' [] (TUnknown u) sd r = replace u (rowFromList (sd, r))
129− unifyRows' sd r [] (TUnknown u) = replace u (rowFromList (sd, r))
130− unifyRows' ((name, ty):row) r others u@(TUnknown un) = do
131− occursCheck un ty
132− forM_ row $ \(_, t) -> occursCheck un t
133− u' <- fresh
134− u ~~ RCons name ty u'
135− unifyRows' row r others u'
136− unifyRows' [] REmpty [] REmpty = return ()
137− unifyRows' [] (TypeVar v1) [] (TypeVar v2) | v1 == v2 = return ()
138− unifyRows' [] (Skolem s1) [] (Skolem s2) | s1 == s2 = return ()
139− unifyRows' sd3 r3 sd4 r4 = throwError $ "Cannot unify " ++ prettyPrintRow (rowFromList (sd3, r3)) ++ " with " ++ prettyPrintRow (rowFromList (sd4, r4)) ++ "."
140−
141−typeConstructorsAreEqual :: Environment -> ModuleName -> Qualified ProperName -> Qualified ProperName -> Bool
142−typeConstructorsAreEqual env moduleName = (==) `on` canonicalizeType moduleName env
143−
144−typesOf :: ModuleName -> [(Ident, Value)] -> Check [(Ident, (Value, Type))]
145−typesOf moduleName vals = do
146− tys <- fmap (\(tys, s) -> map (\(ident, (val, ty)) -> (ident, (overTypes (apply s) val, apply s ty))) tys)
147− . runSubst (SubstContext moduleName) $ do
148− let es = map isTyped vals
149− typed = filter (isJust . snd . snd) es
150− untyped = filter (isNothing . snd . snd) es
151− typedDict = map (\(ident, (_, Just ty)) -> (ident, ty)) typed
152− untypedNames <- replicateM (length untyped) fresh
153− let untypedDict = zip (map fst untyped) untypedNames
154− dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ typedDict ++ untypedDict)
155− forM es $ \e -> do
156− triple@(_, (val, ty)) <- case e of
157− (ident, (val, Just ty)) -> do
158− kind <- liftCheck $ kindOf moduleName ty
159− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
160− ty' <- replaceAllTypeSynonyms ty
161− val' <- bindNames dict $ check val ty'
162− return (ident, (val', ty'))
163− (ident, (val, Nothing)) -> do
164− TypedValue val' ty <- bindNames dict $ infer val
165− ty ~~ fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
166− return (ident, (val', ty))
167− when (moduleName == ModuleName (ProperName "Main") && fst e == Ident "main") $ do
168− [eff, a] <- replicateM 2 fresh
169− ty ~~ TypeApp (TypeApp (TypeConstructor (Qualified (Just (ModuleName (ProperName "Eff"))) (ProperName "Eff"))) eff) a
170− escapeCheck val ty
171− return triple
172− forM_ tys $ skolemEscapeCheck . snd . snd
173− forM tys $ \(ident, (val, ty)) -> do
174− val' <- replaceTypeClassDictionaries 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)] -> (Qualified ProperName, Type) -> Check Value
192−entails context goal =
193− case go goal of
194− [] -> throwError $ "No type class instance for " ++ show goal ++ " in context " ++ show context
195− (dict : _) -> return dict
196− where
197− go (className, ty) = [ App (Var (Qualified Nothing fnName)) args
198− | (fnName, subgoals, className', ty') <- context
199− , className == className'
200− , subst <- maybeToList $ typeHeadsAreEqual ty ty'
201− , args <- forM (replaceAllTypeVars subst subgoals) go ]
202− typeHeadsAreEqual :: Type -> Type -> Maybe [(String, Type)]
203− typeHeadsAreEqual String String = Just []
204− typeHeadsAreEqual Number Number = Just []
205− typeHeadsAreEqual Boolean Boolean = Just []
206− typeHeadsAreEqual (Skolem s1) (Skolem s2) | s1 == s2 = Just []
207− typeHeadsAreEqual (Array ty1) (Array ty2) = typeHeadsAreEqual ty1 ty2
208− typeHeadsAreEqual (TypeConstructor c1) (TypeConstructor c2) | c1 == c2 = Just []
209− typeHeadsAreEqual (TypeApp h1 (TypeVar v)) (TypeApp h2 arg) = do
210− m <- typeHeadsAreEqual h1 h2
211− return $ (v, arg) : m
212− typeHeadsAreEqual t1@(TypeApp _ _) t2@(TypeApp _ (TypeVar _)) = typeHeadsAreEqual t2 t1
213− typeHeadsAreEqual _ _ = Nothing
214−
215−escapeCheck :: Value -> Type -> Subst ()
216−escapeCheck value ty = do
217− subst <- substSubst <$> getSubstState
218− let visibleUnknowns = nub $ unknowns $ apply subst ty
219− let allUnknowns = findAllTypes value
220− forM_ allUnknowns $ \t -> do
221− let unsolvedUnknowns = nub . unknowns $ apply subst t
222− guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
223−
224−findAllTypes :: Value -> [Type]
225−findAllTypes = everything (++) (mkQ [] go)
226− where
227− go (TypedValue _ ty) = [ty]
228− go _ = []
229−
230−skolemEscapeCheck :: Type -> Check ()
231−skolemEscapeCheck ty =
232− case something (mkQ Nothing findSkolems) ty of
233− Nothing -> return ()
234− Just _ -> throwError $ "Skolem variables cannot escape. Consider adding a type signature." ++ show ty
235− where
236− findSkolems (Skolem _) = return ()
237− findSkolems _ = mzero
238−
239−setify :: Type -> Type
240−setify = rowFromList . first (M.toList . M.fromList) . rowToList
241−
242−setifyAll :: (D.Data d) => d -> d
243−setifyAll = everywhere (mkT setify)
244−
245−varIfUnknown :: Type -> Type
246−varIfUnknown ty =
247− let unks = nub $ unknowns ty
248− toName = (:) 't' . show
249− ty' = everywhere (mkT typeToVar) $ ty
250− typeToVar :: Type -> Type
251− typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
252− typeToVar t = t
253− in mkForAll (sort . map toName $ unks) ty'
254−
255−replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
256−replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
257−
258−replaceAllVarsWithUnknowns :: Type -> Subst Type
259−replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
260−replaceAllVarsWithUnknowns ty = return ty
261−
262−replaceVarWithUnknown :: String -> Type -> Subst Type
263−replaceVarWithUnknown ident ty = do
264− tu <- fresh
265− return $ replaceTypeVars ident tu $ ty
266−
267−replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadReader SubstContext m, MonadError String m) => (D.Data d) => d -> m d
268−replaceAllTypeSynonyms d = do
269− env <- getEnv
270− moduleName <- substCurrentModule <$> ask
271− let syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
272− either throwError return $ saturateAllTypeSynonyms env moduleName syns d
273−
274−desaturateAllTypeSynonyms :: (D.Data d) => d -> d
275−desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
276− where
277− replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
278− replaceSaturatedTypeSynonym t = t
279−
280−expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Type
281−expandTypeSynonym name args = do
282− env <- getEnv
283− moduleName <- substCurrentModule `fmap` ask
284− case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
285− Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
286− Nothing -> error "Type synonym was not defined"
287−
288−ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
289−ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
290−
291−infer :: Value -> Subst Value
292−infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ infer' val
293−
294−infer' :: Value -> Subst Value
295−infer' v@(NumericLiteral _) = return $ TypedValue v Number
296−infer' v@(StringLiteral _) = return $ TypedValue v String
297−infer' v@(BooleanLiteral _) = return $ TypedValue v Boolean
298−infer' (ArrayLiteral vals) = do
299− ts <- mapM infer vals
300− els <- fresh
301− forM_ ts $ \(TypedValue _ t) -> els ~~ Array t
302− return $ TypedValue (ArrayLiteral ts) els
303−infer' (Unary op val) = do
304− v <- infer val
305− inferUnary op v
306−infer' (Binary op left right) = do
307− v1 <- infer left
308− v2 <- infer right
309− inferBinary op v1 v2
310−infer' (ObjectLiteral ps) = do
311− ensureNoDuplicateProperties ps
312− ts <- mapM (infer . snd) ps
313− let fields = zipWith (\name (TypedValue _ t) -> (name, t)) (map fst ps) ts
314− ty = Object $ rowFromList (fields, REmpty)
315− return $ TypedValue (ObjectLiteral (zip (map fst ps) ts)) ty
316−infer' (ObjectUpdate o ps) = do
317− ensureNoDuplicateProperties ps
318− row <- fresh
319− newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
320− let newTys = map (\(name, TypedValue _ ty) -> (name, ty)) newVals
321− oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
322− o' <- check o $ Object $ rowFromList (oldTys, row)
323− return $ TypedValue (ObjectUpdate o' newVals) $ Object $ rowFromList (newTys, row)
324−infer' (Indexer index val) = do
325− el <- fresh
326− index' <- check index Number
327− val' <- check val (Array el)
328− return $ TypedValue (Indexer (TypedValue index' Number) (TypedValue val' (Array el))) el
329−infer' (Accessor prop val) = do
330− typed@(TypedValue _ objTy) <- infer val
331− propTy <- inferProperty objTy prop
332− case propTy of
333− Nothing -> do
334− field <- fresh
335− rest <- fresh
336− objTy `subsumes` Object (RCons prop field rest)
337− return $ TypedValue (Accessor prop typed) field
338− Just ty -> return $ TypedValue (Accessor prop typed) ty
339−infer' (Abs args ret) = do
340− ts <- replicateM (length args) fresh
341− moduleName <- substCurrentModule <$> ask
342− bindLocalVariables moduleName (zip args ts) $ do
343− body@(TypedValue _ bodyTy) <- infer' ret
344− return $ TypedValue (Abs args body) $ Function ts bodyTy
345−infer' (App f args) = do
346− f'@(TypedValue _ ft) <- infer f
347− ret <- fresh
348− app <- checkFunctionApplication f' ft args ret
349− return $ TypedValue app ret
350−infer' (Var var) = do
351− moduleName <- substCurrentModule <$> ask
352− ty <- lookupVariable moduleName var
353− ty' <- replaceAllTypeSynonyms ty
354− case ty' of
355− ConstrainedType constraints _ -> do
356− dicts <- getTypeClassDictionaries
357− return $ TypedValue (App (Var var) (map (flip TypeClassDictionary dicts) constraints)) ty'
358− _ -> return $ TypedValue (Var var) ty'
359−infer' (Block ss) = do
360− ret <- fresh
361− (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
362− guardWith "Block is missing a return statement" allCodePathsReturn
363− return $ TypedValue (Block ss') ret
364−infer' v@(Constructor c) = do
365− env <- getEnv
366− moduleName <- substCurrentModule `fmap` ask
367− case M.lookup (qualify moduleName c) (dataConstructors env) of
368− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
369− Just (ty, _) -> do ty' <- replaceAllTypeSynonyms ty
370− return $ TypedValue v ty'
371−infer' (Case vals binders) = do
372− ts <- mapM infer vals
373− ret <- fresh
374− binders' <- checkBinders (map (\(TypedValue _ t) -> t) ts) ret binders
375− return $ TypedValue (Case ts binders') ret
376−infer' (IfThenElse cond th el) = do
377− cond' <- check cond Boolean
378− v2@(TypedValue _ t2) <- infer th
379− v3@(TypedValue _ t3) <- infer el
380− t2 ~~ t3
381− return $ TypedValue (IfThenElse cond' v2 v3) t2
382−infer' (TypedValue val ty) = do
383− moduleName <- substCurrentModule <$> ask
384− kind <- liftCheck $ kindOf moduleName ty
385− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
386− ty' <- replaceAllTypeSynonyms ty
387− val' <- check val ty'
388− return $ TypedValue val' ty
389−infer' _ = error "Invalid argument to infer"
390−
391−inferProperty :: Type -> String -> Subst (Maybe Type)
392−inferProperty (Object row) prop = do
393− let (props, _) = rowToList row
394− return $ lookup prop props
395−inferProperty (SaturatedTypeSynonym name args) prop = do
396− replaced <- expandTypeSynonym name args
397− inferProperty replaced prop
398−inferProperty (ForAll ident ty) prop = do
399− replaced <- replaceVarWithUnknown ident ty
400− inferProperty replaced prop
401−inferProperty _ _ = return Nothing
402−
403−inferUnary :: UnaryOperator -> Value -> Subst Value
404−inferUnary op (TypedValue val valTy) =
405− case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
406− (valTy', resTy) -> do
407− valTy' ~~ valTy
408− return $ TypedValue (Unary op val) resTy
409−inferUnary _ _ = error "Invalid arguments to inferUnary"
410−
411−checkUnary :: UnaryOperator -> Value -> Type -> Subst Value
412−checkUnary op val res =
413− case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
414− (valTy, resTy) -> do
415− res ~~ resTy
416− val' <- check val valTy
417− return $ Unary op val'
418−
419−unaryOps :: [(UnaryOperator, (Type, Type))]
420−unaryOps = [ (Negate, (Number, Number))
421− , (Not, (Boolean, Boolean))
422− , (BitwiseNot, (Number, Number))
423− ]
424−
425−inferBinary :: BinaryOperator -> Value -> Value -> Subst Value
426−inferBinary op left@(TypedValue _ leftTy) right@(TypedValue _ rightTy) | isEqualityTest op = do
427− leftTy ~~ rightTy
428− return $ TypedValue (Binary op left right) Boolean
429−inferBinary op left@(TypedValue _ leftTy) right@(TypedValue _ rightTy) =
430− case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
431− (valTy, resTy) -> do
432− leftTy ~~ valTy
433− rightTy ~~ valTy
434− return $ TypedValue (Binary op left right) resTy
435−inferBinary _ _ _ = error "Invalid arguments to inferBinary"
436−
437−checkBinary :: BinaryOperator -> Value -> Value -> Type -> Subst Value
438−checkBinary op left right res | isEqualityTest op = do
439− res ~~ Boolean
440− left'@(TypedValue _ t1) <- infer left
441− right'@(TypedValue _ t2) <- infer right
442− t1 ~~ t2
443− return $ Binary op left' right'
444−checkBinary op left right res =
445− case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
446− (valTy, resTy) -> do
447− res ~~ resTy
448− left' <- check left valTy
449− right' <- check right valTy
450− return $ Binary op left' right'
451−
452−isEqualityTest :: BinaryOperator -> Bool
453−isEqualityTest EqualTo = True
454−isEqualityTest NotEqualTo = True
455−isEqualityTest _ = False
456−
457−binaryOps :: [(BinaryOperator, (Type, Type))]
458−binaryOps = [ (Add, (Number, Number))
459− , (Subtract, (Number, Number))
460− , (Multiply, (Number, Number))
461− , (Divide, (Number, Number))
462− , (Modulus, (Number, Number))
463− , (BitwiseAnd, (Number, Number))
464− , (BitwiseOr, (Number, Number))
465− , (BitwiseXor, (Number, Number))
466− , (ShiftRight, (Number, Number))
467− , (ZeroFillShiftRight, (Number, Number))
468− , (And, (Boolean, Boolean))
469− , (Or, (Boolean, Boolean))
470− , (Concat, (String, String))
471− , (Modulus, (Number, Number))
472− , (LessThan, (Number, Boolean))
473− , (LessThanOrEqualTo, (Number, Boolean))
474− , (GreaterThan, (Number, Boolean))
475− , (GreaterThanOrEqualTo, (Number, Boolean))
476− ]
477−
478−inferBinder :: Type -> Binder -> Subst (M.Map Ident Type)
479−inferBinder _ NullBinder = return M.empty
480−inferBinder val (StringBinder _) = val ~~ String >> return M.empty
481−inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
482−inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
483−inferBinder val (VarBinder name) = return $ M.singleton name val
484−inferBinder val (NullaryBinder ctor) = do
485− env <- getEnv
486− moduleName <- substCurrentModule <$> ask
487− case M.lookup (qualify moduleName ctor) (dataConstructors env) of
488− Just (ty, _) -> do
489− ty `subsumes` val
490− return M.empty
491− _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
492−inferBinder val (UnaryBinder ctor binder) = do
493− env <- getEnv
494− moduleName <- substCurrentModule <$> ask
495− case M.lookup (qualify moduleName ctor) (dataConstructors env) of
496− Just (ty, _) -> do
497− fn <- replaceAllVarsWithUnknowns ty
498− case fn of
499− Function [obj] ret -> do
500− val `subsumes` ret
501− inferBinder obj binder
502− _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
503− _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
504−inferBinder val (ObjectBinder props) = do
505− row <- fresh
506− rest <- fresh
507− m1 <- inferRowProperties row rest props
508− val ~~ Object row
509− return m1
510− where
511− inferRowProperties :: Type -> Type -> [(String, Binder)] -> Subst (M.Map Ident Type)
512− inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
513− inferRowProperties nrow row ((name, binder):binders) = do
514− propTy <- fresh
515− m1 <- inferBinder propTy binder
516− m2 <- inferRowProperties nrow (RCons name propTy row) binders
517− return $ m1 `M.union` m2
518−inferBinder val (ArrayBinder binders) = do
519− el <- fresh
520− m1 <- M.unions <$> mapM (inferBinder el) binders
521− val ~~ Array el
522− return m1
523−inferBinder val (ConsBinder headBinder tailBinder) = do
524− el <- fresh
525− m1 <- inferBinder el headBinder
526− m2 <- inferBinder val tailBinder
527− val ~~ Array el
528− return $ m1 `M.union` m2
529−inferBinder val (NamedBinder name binder) = do
530− m <- inferBinder val binder
531− return $ M.insert name val m
532−
533−checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> Subst [([Binder], Maybe Guard, Value)]
534−checkBinders _ _ [] = return []
535−checkBinders nvals ret ((binders, grd, val):bs) = do
536− moduleName <- substCurrentModule <$> ask
537− m1 <- M.unions <$> zipWithM inferBinder nvals binders
538− r <- bindLocalVariables moduleName (M.toList m1) $ do
539− val' <- check val ret
540− case grd of
541− Nothing -> return (binders, Nothing, val')
542− Just g -> do
543− g' <- check g Boolean
544− return (binders, Just g', val')
545− rs <- checkBinders nvals ret bs
546− return $ r : rs
547−
548−assignVariable :: Ident -> Subst ()
549−assignVariable name = do
550− env <- checkEnv <$> get
551− moduleName <- substCurrentModule <$> ask
552− case M.lookup (moduleName, name) (names env) of
553− Just (_, LocalVariable) -> throwError $ "Variable with name " ++ show name ++ " already exists."
554− _ -> return ()
555−
556−checkStatement :: M.Map Ident Type -> Type -> Statement -> Subst (Bool, M.Map Ident Type, Statement)
557−checkStatement mass _ (VariableIntroduction name val) = do
558− assignVariable name
559− val'@(TypedValue _ t) <- infer val
560− return (False, M.insert name t mass, VariableIntroduction name val')
561−checkStatement mass _ (Assignment ident val) = do
562− val'@(TypedValue _ t) <- infer val
563− case M.lookup ident mass of
564− Nothing -> throwError $ "No local variable with name " ++ show ident
565− Just ty -> do t ~~ ty
566− return (False, mass, Assignment ident val')
567−checkStatement mass ret (While val inner) = do
568− val' <- check val Boolean
569− (allCodePathsReturn, _, inner') <- checkBlock mass ret inner
570− return (allCodePathsReturn, mass, While val' inner')
571−checkStatement mass ret (If ifst) = do
572− (allCodePathsReturn, ifst') <- checkIfStatement mass ret ifst
573− return (allCodePathsReturn, mass, If ifst')
574−checkStatement mass ret (For ident start end inner) = do
575− moduleName <- substCurrentModule <$> ask
576− assignVariable ident
577− start' <- check start Number
578− end' <- check end Number
579− (allCodePathsReturn, _, inner') <- bindLocalVariables moduleName [(ident, Number)] $ checkBlock mass ret inner
580− return (allCodePathsReturn, mass, For ident start' end' inner')
581−checkStatement mass ret (Return val) = do
582− val' <- check val ret
583− return (True, mass, Return val')
584−
585−checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> Subst (Bool, IfStatement)
586−checkIfStatement mass ret (IfStatement val thens Nothing) = do
587− val' <- check val Boolean
588− (_, _, thens') <- checkBlock mass ret thens
589− return (False, IfStatement val' thens' Nothing)
590−checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
591− val' <- check val Boolean
592− (allCodePathsReturn1, _, thens') <- checkBlock mass ret thens
593− (allCodePathsReturn2, elses') <- checkElseStatement mass ret elses
594− return (allCodePathsReturn1 && allCodePathsReturn2, IfStatement val' thens' (Just elses'))
595−
596−checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> Subst (Bool, ElseStatement)
597−checkElseStatement mass ret (Else elses) = do
598− (allCodePathsReturn, _, elses') <- checkBlock mass ret elses
599− return (allCodePathsReturn, Else elses')
600−checkElseStatement mass ret (ElseIf ifst) = (id *** ElseIf) <$> checkIfStatement mass ret ifst
601−
602−checkBlock :: M.Map Ident Type -> Type -> [Statement] -> Subst (Bool, M.Map Ident Type, [Statement])
603−checkBlock mass _ [] = return (False, mass, [])
604−checkBlock mass ret (s:ss) = do
605− moduleName <- substCurrentModule <$> ask
606− (b1, mass1, s') <- checkStatement mass ret s
607− bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
608− (True, []) -> return (True, mass1, [s'])
609− (True, _) -> throwError "Unreachable code"
610− (False, ss') -> do
611− (b, m, ss'') <- checkBlock mass1 ret ss'
612− return (b, m, s':ss'')
613−
614−skolemize :: String -> Type -> Subst Type
615−skolemize ident ty = do
616− tsk <- Skolem <$> fresh'
617− return $ replaceTypeVars ident tsk ty
618−
619−check :: Value -> Type -> Subst Value
620−check val ty = rethrow errorMessage $ check' val ty
621− where
622− errorMessage msg =
623− "Error checking type of term " ++
624− prettyPrintValue val ++
625− " against type " ++
626− prettyPrintType ty ++
627− ":\n" ++
628− msg
629−
630−check' :: Value -> Type -> Subst Value
631−check' val (ForAll idents ty) = do
632− sk <- skolemize idents ty
633− check val sk
634−check' val (ConstrainedType constraints ty) = do
635− let dictName = Ident "__dict" -- TODO
636− val' <- withTypeClassDictionaries (map (\(className, instanceTy) -> (dictName, [], className, instanceTy)) constraints) $ check val ty
637− return $ Abs (map (\_ -> dictName) constraints) val'
638−check' val u@(TUnknown _) = do
639− val'@(TypedValue _ ty) <- infer val
640− -- Don't unify an unknown with an inferred polytype
641− ty' <- replaceAllVarsWithUnknowns ty
642− ty' ~~ u
643− return val'
644−check' v@(NumericLiteral _) Number = return v
645−check' v@(StringLiteral _) String = return v
646−check' v@(BooleanLiteral _) Boolean = return v
647−check' (Unary op val) ty = checkUnary op val ty
648−check' (Binary op left right) ty = checkBinary op left right ty
649−check' (ArrayLiteral vals) (Array ty) = ArrayLiteral <$> forM vals (\val -> check val ty)
650−check' (Indexer index vals) ty = do
651− index' <- check index Number
652− vals' <- check vals (Array ty)
653− return $ Indexer index' vals'
654−check' (Abs args ret) (Function argTys retTy) = do
655− moduleName <- substCurrentModule <$> ask
656− guardWith "Incorrect number of function arguments" (length args == length argTys)
657− ret' <- bindLocalVariables moduleName (zip args argTys) $ check ret retTy
658− return $ Abs args ret'
659−check' (App f args) ret = do
660− f'@(TypedValue _ ft) <- infer f
661− app <- checkFunctionApplication f' ft args ret
662− return $ app
663−check' (Var var) ty = do
664− moduleName <- substCurrentModule <$> ask
665− ty1 <- lookupVariable moduleName var
666− repl <- replaceAllTypeSynonyms ty1
667− repl `subsumes` ty
668− return $ Var var
669−check' (TypedValue val ty1) ty2 = do
670− moduleName <- substCurrentModule <$> ask
671− kind <- liftCheck $ kindOf moduleName ty1
672− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
673− ty1 `subsumes` ty2
674− val' <- check val ty1
675− return $ TypedValue val' ty1
676−check' (Case vals binders) ret = do
677− vals' <- mapM infer vals
678− let ts = map (\(TypedValue _ t) -> t) vals'
679− binders' <- checkBinders ts ret binders
680− return $ Case vals' binders'
681−check' (IfThenElse cond th el) ty = do
682− cond' <- check cond Boolean
683− th' <- check th ty
684− el' <- check el ty
685− return $ IfThenElse cond' th' el'
686−check' (ObjectLiteral ps) (Object row) = do
687− ensureNoDuplicateProperties ps
688− ps' <- checkProperties ps row False
689− return $ ObjectLiteral ps'
690−check' (ObjectUpdate obj ps) (Object row) = do
691− ensureNoDuplicateProperties ps
692− us <- zip (map fst ps) <$> replicateM (length ps) fresh
693− let (propsToCheck, rest) = rowToList row
694− propsToRemove = map fst ps
695− remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
696− obj' <- check obj (Object (rowFromList (us ++ remainingProps, rest)))
697− ps' <- checkProperties ps row True
698− return $ ObjectUpdate obj' ps'
699−check' (Accessor prop val) ty = do
700− rest <- fresh
701− val' <- check val (Object (RCons prop ty rest))
702− return $ Accessor prop val'
703−check' (Block ss) ret = do
704− (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
705− guardWith "Block is missing a return statement" allCodePathsReturn
706− return $ Block ss'
707−check' (Constructor c) ty = do
708− env <- getEnv
709− moduleName <- substCurrentModule <$> ask
710− case M.lookup (qualify moduleName c) (dataConstructors env) of
711− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
712− Just (ty1, _) -> do
713− repl <- replaceAllTypeSynonyms ty1
714− repl `subsumes` ty
715− return $ Constructor c
716−check' val (SaturatedTypeSynonym name args) = do
717− ty <- expandTypeSynonym name args
718− check val ty
719−check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
720−
721−checkProperties :: [(String, Value)] -> Type -> Bool -> Subst [(String, Value)]
722−checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
723− go [] [] REmpty = return []
724− go [] [] u@(TUnknown _) = do u ~~ REmpty
725− return []
726− go [] [] (Skolem _) | lax = return []
727− go [] ((p, _): _) _ | lax = return []
728− | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
729− go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
730− go ((p,v):ps') [] u@(TUnknown _) = do
731− v'@(TypedValue _ ty) <- infer v
732− rest <- fresh
733− u ~~ RCons p ty rest
734− ps'' <- go ps' [] rest
735− return $ (p, v') : ps''
736− go ((p,v):ps') ts r =
737− case lookup p ts of
738− Nothing -> do
739− v'@(TypedValue _ ty) <- infer v
740− rest <- fresh
741− r ~~ RCons p ty rest
742− ps'' <- go ps' ts rest
743− return $ (p, v') : ps''
744− Just ty -> do
745− v' <- check v ty
746− ps'' <- go ps' (delete (p, ty) ts) r
747− return $ (p, v') : ps''
748− go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
749−
750−checkFunctionApplication :: Value -> Type -> [Value] -> Type -> Subst Value
751−checkFunctionApplication fn fnTy args ret = rethrow errorMessage $ checkFunctionApplication' fn fnTy args ret
752− where
753− errorMessage msg = "Error applying function of type "
754− ++ prettyPrintType fnTy
755− ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
756− ++ ":\n" ++ msg
757−
758−checkFunctionApplication' :: Value -> Type -> [Value] -> Type -> Subst Value
759−checkFunctionApplication' fn (Function argTys retTy) args ret = do
760− guardWith "Incorrect number of function arguments" (length args == length argTys)
761− args' <- zipWithM check args argTys
762− retTy `subsumes` ret
763− return $ App fn args'
764−checkFunctionApplication' fn (ForAll ident ty) args ret = do
765− replaced <- replaceVarWithUnknown ident ty
766− checkFunctionApplication fn replaced args ret
767−checkFunctionApplication' fn u@(TUnknown _) args ret = do
768− args' <- mapM (\arg -> infer arg >>= \(TypedValue v t) -> TypedValue v <$> replaceAllVarsWithUnknowns t) args
769− let tys = map (\(TypedValue _ t) -> t) args'
770− u ~~ Function tys ret
771− return $ App fn args'
772−checkFunctionApplication' fn (SaturatedTypeSynonym name tyArgs) args ret = do
773− ty <- expandTypeSynonym name tyArgs
774− checkFunctionApplication fn ty args ret
775−checkFunctionApplication' fn (ConstrainedType constraints fnTy) args ret = do
776− dicts <- getTypeClassDictionaries
777− checkFunctionApplication' (App fn (map (flip TypeClassDictionary dicts) constraints)) fnTy args ret
778−checkFunctionApplication' _ fnTy args ret = throwError $ "Applying a function of type "
779− ++ prettyPrintType fnTy
780− ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
781− ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
782−
783−subsumes :: Type -> Type -> Subst ()
784−subsumes (ForAll ident ty1) ty2 = do
785− replaced <- replaceVarWithUnknown ident ty1
786− replaced `subsumes` ty2
787−subsumes (Function args1 ret1) (Function args2 ret2) = do
788− zipWithM_ subsumes args2 args1
789− ret1 `subsumes` ret2
790−subsumes ty1 ty2 = ty1 ~~ ty2
791−