@@ -0,0 +1,811 @@
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 (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 (Object r) = unknowns r
65+ unknowns (Function args ret) = concatMap unknowns args ++ unknowns ret
66+ unknowns (TypeApp t1 t2) = unknowns t1 ++ unknowns t2
67+ unknowns (RCons _ ty r) = unknowns ty ++ unknowns r
68+ unknowns _ = []
69+
70+unifyTypes :: Type -> Type -> Subst ()
71+unifyTypes t1 t2 = rethrow (\e -> "Error unifying type " ++ prettyPrintType t1 ++ " with type " ++ prettyPrintType t2 ++ ":\n" ++ e) $ do
72+ unifyTypes' t1 t2
73+ where
74+ unifyTypes' (TUnknown u1) (TUnknown u2) | u1 == u2 = return ()
75+ unifyTypes' (TUnknown u) t = replace u t
76+ unifyTypes' t (TUnknown u) = replace u t
77+ unifyTypes' (SaturatedTypeSynonym name args) ty = do
78+ ty1 <- expandTypeSynonym name args
79+ ty1 `unifyTypes` ty
80+ unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
81+ unifyTypes' (ForAll ident1 ty1) (ForAll ident2 ty2) = do
82+ sk <- skolemize ident1 ty1
83+ replaced <- replaceVarWithUnknown ident2 ty2
84+ sk `unifyTypes` replaced
85+ unifyTypes' (ForAll ident ty1) ty2 = do
86+ sk <- skolemize ident ty1
87+ sk `unifyTypes` ty2
88+ unifyTypes' ty f@(ForAll _ _) = f `unifyTypes` ty
89+ unifyTypes' Number Number = return ()
90+ unifyTypes' String String = return ()
91+ unifyTypes' Boolean Boolean = return ()
92+ unifyTypes' Array Array = return ()
93+ unifyTypes' (Object row1) (Object row2) = row1 ~~ row2
94+ unifyTypes' (Function args1 ret1) (Function args2 ret2) = do
95+ guardWith "Function applied to incorrect number of args" $ length args1 == length args2
96+ zipWithM_ unifyTypes args1 args2
97+ ret1 `unifyTypes` ret2
98+ unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
99+ unifyTypes' (TypeConstructor c1) (TypeConstructor c2) = do
100+ env <- getEnv
101+ moduleName <- substCurrentModule `fmap` ask
102+ guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (typeConstructorsAreEqual env moduleName c1 c2)
103+ unifyTypes' (TypeApp t3 t4) (TypeApp t5 t6) = do
104+ t3 `unifyTypes` t5
105+ t4 `unifyTypes` t6
106+ unifyTypes' (Skolem s1) (Skolem s2) | s1 == s2 = return ()
107+ unifyTypes' r1@(RCons _ _ _) r2 = unifyRows r1 r2
108+ unifyTypes' r1 r2@(RCons _ _ _) = unifyRows r1 r2
109+ unifyTypes' r1@REmpty r2 = unifyRows r1 r2
110+ unifyTypes' r1 r2@REmpty = unifyRows r1 r2
111+ unifyTypes' t3 t4 = throwError $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
112+
113+unifyRows :: Type -> Type -> Subst ()
114+unifyRows r1 r2 =
115+ let
116+ (s1, r1') = rowToList r1
117+ (s2, r2') = rowToList r2
118+ int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
119+ sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
120+ sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
121+ in do
122+ forM_ int (uncurry (~~))
123+ unifyRows' sd1 r1' sd2 r2'
124+ where
125+ unifyRows' :: [(String, Type)] -> Type -> [(String, Type)] -> Type -> Subst ()
126+ unifyRows' [] (TUnknown u) sd r = replace u (rowFromList (sd, r))
127+ unifyRows' sd r [] (TUnknown u) = replace u (rowFromList (sd, r))
128+ unifyRows' ((name, ty):row) r others u@(TUnknown un) = do
129+ occursCheck un ty
130+ forM_ row $ \(_, t) -> occursCheck un t
131+ u' <- fresh
132+ u ~~ RCons name ty u'
133+ unifyRows' row r others u'
134+ unifyRows' [] REmpty [] REmpty = return ()
135+ unifyRows' [] (TypeVar v1) [] (TypeVar v2) | v1 == v2 = return ()
136+ unifyRows' [] (Skolem s1) [] (Skolem s2) | s1 == s2 = return ()
137+ unifyRows' sd3 r3 sd4 r4 = throwError $ "Cannot unify " ++ prettyPrintRow (rowFromList (sd3, r3)) ++ " with " ++ prettyPrintRow (rowFromList (sd4, r4)) ++ "."
138+
139+typeConstructorsAreEqual :: Environment -> ModuleName -> Qualified ProperName -> Qualified ProperName -> Bool
140+typeConstructorsAreEqual env moduleName = (==) `on` canonicalizeType moduleName env
141+
142+typesOf :: ModuleName -> [(Ident, Value)] -> Check [(Ident, (Value, Type))]
143+typesOf moduleName vals = do
144+ tys <- fmap (\(tys, s) -> map (\(ident, (val, ty)) -> (ident, (overTypes (apply s) val, apply s ty))) tys)
145+ . runSubst (SubstContext moduleName) $ do
146+ let es = map isTyped vals
147+ typed = filter (isJust . snd . snd) es
148+ untyped = filter (isNothing . snd . snd) es
149+ typedDict = map (\(ident, (_, Just ty)) -> (ident, ty)) typed
150+ untypedNames <- replicateM (length untyped) fresh
151+ let untypedDict = zip (map fst untyped) untypedNames
152+ dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ (map (id *** fst) typedDict) ++ untypedDict)
153+ forM es $ \e -> do
154+ triple@(_, (val, ty)) <- case e of
155+ (ident, (val, Just (ty, checkType))) -> do
156+ kind <- liftCheck $ kindOf moduleName ty
157+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
158+ ty' <- replaceAllTypeSynonyms ty
159+ val' <- bindNames dict $ if checkType then check val ty' else return val
160+ return (ident, (val', ty'))
161+ (ident, (val, Nothing)) -> do
162+ TypedValue _ val' ty <- bindNames dict $ infer val
163+ ty ~~ fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
164+ return (ident, (val', ty))
165+ when (moduleName == ModuleName (ProperName "Main") && fst e == Ident "main") $ do
166+ [eff, a] <- replicateM 2 fresh
167+ ty ~~ TypeApp (TypeApp (TypeConstructor (Qualified (Just (ModuleName (ProperName "Eff"))) (ProperName "Eff"))) eff) a
168+ escapeCheck val ty
169+ return triple
170+ forM_ tys $ skolemEscapeCheck . snd . snd
171+ forM tys $ \(ident, (val, ty)) -> do
172+ val' <- replaceTypeClassDictionaries moduleName val
173+ return (ident, (overTypes (desaturateAllTypeSynonyms . setifyAll) $ val'
174+ , varIfUnknown . desaturateAllTypeSynonyms . setifyAll $ ty))
175+
176+isTyped :: (Ident, Value) -> (Ident, (Value, Maybe (Type, Bool)))
177+isTyped (name, TypedValue checkType value ty) = (name, (value, Just (ty, checkType)))
178+isTyped (name, value) = (name, (value, Nothing))
179+
180+overTypes :: (Type -> Type) -> Value -> Value
181+overTypes f = everywhere (mkT f)
182+
183+replaceTypeClassDictionaries :: ModuleName -> Value -> Check Value
184+replaceTypeClassDictionaries mn = everywhereM (mkM go)
185+ where
186+ go (TypeClassDictionary constraint dicts) = entails mn dicts constraint
187+ go other = return other
188+
189+entails :: ModuleName -> [TypeClassDictionaryInScope] -> (Qualified ProperName, Type) -> Check Value
190+entails moduleName context goal@(className, ty) = do
191+ env <- getEnv
192+ case go env goal of
193+ [] -> throwError $ "No " ++ show className ++ " instance found for " ++ prettyPrintType ty
194+ (dict : _) -> return dict
195+ where
196+ go env (className', ty') =
197+ [ mkDictionary (canonicalizeDictionary tcd) args
198+ | tcd <- context
199+ , filterModule tcd
200+ , typeConstructorsAreEqual env moduleName className' (tcdClassName tcd)
201+ , subst <- maybeToList $ typeHeadsAreEqual moduleName env ty' (tcdInstanceType tcd)
202+ , args <- solveSubgoals env subst (tcdDependencies tcd) ]
203+ solveSubgoals _ _ Nothing = return Nothing
204+ solveSubgoals env subst (Just subgoals) = do
205+ dict <- mapM (go env) (replaceAllTypeVars subst subgoals)
206+ return $ Just dict
207+ mkDictionary fnName args = maybe id (flip App) args $ (Var fnName)
208+ filterModule (TypeClassDictionaryInScope { tcdName = Qualified (Just mn) _ }) | mn == moduleName = True
209+ filterModule (TypeClassDictionaryInScope { tcdName = Qualified Nothing _ }) = True
210+ filterModule _ = False
211+ canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDRegular, tcdName = nm }) = nm
212+ canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDAlias nm }) = nm
213+
214+typeHeadsAreEqual :: ModuleName -> Environment -> Type -> Type -> Maybe [(String, Type)]
215+typeHeadsAreEqual _ _ String String = Just []
216+typeHeadsAreEqual _ _ Number Number = Just []
217+typeHeadsAreEqual _ _ Boolean Boolean = Just []
218+typeHeadsAreEqual _ _ (Skolem s1) (Skolem s2) | s1 == s2 = Just []
219+typeHeadsAreEqual _ _ Array Array = Just []
220+typeHeadsAreEqual m e (TypeConstructor c1) (TypeConstructor c2) | typeConstructorsAreEqual e m c1 c2 = Just []
221+typeHeadsAreEqual m e (TypeApp h1 (TypeVar v)) (TypeApp h2 arg) = (:) (v, arg) <$> typeHeadsAreEqual m e h1 h2
222+typeHeadsAreEqual m e t1@(TypeApp _ _) t2@(TypeApp _ (TypeVar _)) = typeHeadsAreEqual m e t2 t1
223+typeHeadsAreEqual _ _ _ _ = Nothing
224+
225+escapeCheck :: Value -> Type -> Subst ()
226+escapeCheck value ty = do
227+ subst <- substSubst <$> getSubstState
228+ let visibleUnknowns = nub $ unknowns $ apply subst ty
229+ let allUnknowns = findAllTypes value
230+ forM_ allUnknowns $ \t -> do
231+ let unsolvedUnknowns = nub . unknowns $ apply subst t
232+ guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
233+
234+findAllTypes :: Value -> [Type]
235+findAllTypes = everything (++) (mkQ [] go)
236+ where
237+ go (TypedValue _ _ ty) = [ty]
238+ go _ = []
239+
240+skolemEscapeCheck :: Type -> Check ()
241+skolemEscapeCheck ty =
242+ case something (mkQ Nothing findSkolems) ty of
243+ Nothing -> return ()
244+ Just _ -> throwError $ "Skolem variables cannot escape. Consider adding a type signature." ++ show ty
245+ where
246+ findSkolems (Skolem _) = return ()
247+ findSkolems _ = mzero
248+
249+setify :: Type -> Type
250+setify = rowFromList . first (M.toList . M.fromList) . rowToList
251+
252+setifyAll :: (D.Data d) => d -> d
253+setifyAll = everywhere (mkT setify)
254+
255+varIfUnknown :: Type -> Type
256+varIfUnknown ty =
257+ let unks = nub $ unknowns ty
258+ toName = (:) 't' . show
259+ ty' = everywhere (mkT typeToVar) $ ty
260+ typeToVar :: Type -> Type
261+ typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
262+ typeToVar t = t
263+ in mkForAll (sort . map toName $ unks) ty'
264+
265+replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
266+replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
267+
268+replaceAllVarsWithUnknowns :: Type -> Subst Type
269+replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
270+replaceAllVarsWithUnknowns ty = return ty
271+
272+replaceVarWithUnknown :: String -> Type -> Subst Type
273+replaceVarWithUnknown ident ty = do
274+ tu <- fresh
275+ return $ replaceTypeVars ident tu $ ty
276+
277+replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadReader SubstContext m, MonadError String m) => (D.Data d) => d -> m d
278+replaceAllTypeSynonyms d = do
279+ env <- getEnv
280+ moduleName <- substCurrentModule <$> ask
281+ let syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
282+ either throwError return $ saturateAllTypeSynonyms env moduleName syns d
283+
284+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
285+desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
286+ where
287+ replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
288+ replaceSaturatedTypeSynonym t = t
289+
290+expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Type
291+expandTypeSynonym name args = do
292+ env <- getEnv
293+ moduleName <- substCurrentModule `fmap` ask
294+ case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
295+ Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
296+ Nothing -> error "Type synonym was not defined"
297+
298+ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
299+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
300+
301+infer :: Value -> Subst Value
302+infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ infer' val
303+
304+infer' :: Value -> Subst Value
305+infer' v@(NumericLiteral _) = return $ TypedValue True v Number
306+infer' v@(StringLiteral _) = return $ TypedValue True v String
307+infer' v@(BooleanLiteral _) = return $ TypedValue True v Boolean
308+infer' (ArrayLiteral vals) = do
309+ ts <- mapM infer vals
310+ els <- fresh
311+ forM_ ts $ \(TypedValue _ _ t) -> els ~~ TypeApp Array t
312+ return $ TypedValue True (ArrayLiteral ts) els
313+infer' (Unary op val) = do
314+ v <- infer val
315+ inferUnary op v
316+infer' (Binary op left right) = do
317+ v1 <- infer left
318+ v2 <- infer right
319+ inferBinary op v1 v2
320+infer' (ObjectLiteral ps) = do
321+ ensureNoDuplicateProperties ps
322+ ts <- mapM (infer . snd) ps
323+ let fields = zipWith (\name (TypedValue _ _ t) -> (name, t)) (map fst ps) ts
324+ ty = Object $ rowFromList (fields, REmpty)
325+ return $ TypedValue True (ObjectLiteral (zip (map fst ps) ts)) ty
326+infer' (ObjectUpdate o ps) = do
327+ ensureNoDuplicateProperties ps
328+ row <- fresh
329+ newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
330+ let newTys = map (\(name, TypedValue _ _ ty) -> (name, ty)) newVals
331+ oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
332+ o' <- check o $ Object $ rowFromList (oldTys, row)
333+ return $ TypedValue True (ObjectUpdate o' newVals) $ Object $ rowFromList (newTys, row)
334+infer' (Indexer index val) = do
335+ el <- fresh
336+ index' <- check index Number
337+ val' <- check val (TypeApp Array el)
338+ return $ TypedValue True (Indexer (TypedValue True index' Number) (TypedValue True val' (TypeApp Array el))) el
339+infer' (Accessor prop val) = do
340+ typed@(TypedValue _ _ objTy) <- infer val
341+ propTy <- inferProperty objTy prop
342+ case propTy of
343+ Nothing -> do
344+ field <- fresh
345+ rest <- fresh
346+ objTy `subsumes` Object (RCons prop field rest)
347+ return $ TypedValue True (Accessor prop typed) field
348+ Just ty -> return $ TypedValue True (Accessor prop typed) ty
349+infer' (Abs args ret) = do
350+ ts <- replicateM (length args) fresh
351+ moduleName <- substCurrentModule <$> ask
352+ bindLocalVariables moduleName (zip args ts) $ do
353+ body@(TypedValue _ _ bodyTy) <- infer' ret
354+ return $ TypedValue True (Abs args body) $ Function ts bodyTy
355+infer' (App f args) = do
356+ f'@(TypedValue _ _ ft) <- infer f
357+ ret <- fresh
358+ app <- checkFunctionApplication f' ft args ret
359+ return $ TypedValue True app ret
360+infer' (Var var) = do
361+ moduleName <- substCurrentModule <$> ask
362+ ty <- lookupVariable moduleName var
363+ ty' <- replaceAllTypeSynonyms ty
364+ case ty' of
365+ ConstrainedType constraints _ -> do
366+ env <- getEnv
367+ dicts <- getTypeClassDictionaries
368+ return $ TypedValue True (App (Var var) (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) ty'
369+ _ -> return $ TypedValue True (Var var) ty'
370+infer' (Block ss) = do
371+ ret <- fresh
372+ (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
373+ guardWith "Block is missing a return statement" allCodePathsReturn
374+ return $ TypedValue True (Block ss') ret
375+infer' v@(Constructor c) = do
376+ env <- getEnv
377+ moduleName <- substCurrentModule `fmap` ask
378+ case M.lookup (qualify moduleName c) (dataConstructors env) of
379+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
380+ Just (ty, _) -> do ty' <- replaceAllTypeSynonyms ty
381+ return $ TypedValue True v ty'
382+infer' (Case vals binders) = do
383+ ts <- mapM infer vals
384+ ret <- fresh
385+ binders' <- checkBinders (map (\(TypedValue _ _ t) -> t) ts) ret binders
386+ return $ TypedValue True (Case ts binders') ret
387+infer' (IfThenElse cond th el) = do
388+ cond' <- check cond Boolean
389+ v2@(TypedValue _ _ t2) <- infer th
390+ v3@(TypedValue _ _ t3) <- infer el
391+ t2 ~~ t3
392+ return $ TypedValue True (IfThenElse cond' v2 v3) t2
393+infer' (TypedValue checkType val ty) = do
394+ moduleName <- substCurrentModule <$> ask
395+ kind <- liftCheck $ kindOf moduleName ty
396+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
397+ ty' <- replaceAllTypeSynonyms ty
398+ val' <- if checkType then check val ty' else return val
399+ return $ TypedValue True val' ty
400+infer' _ = error "Invalid argument to infer"
401+
402+inferProperty :: Type -> String -> Subst (Maybe Type)
403+inferProperty (Object row) prop = do
404+ let (props, _) = rowToList row
405+ return $ lookup prop props
406+inferProperty (SaturatedTypeSynonym name args) prop = do
407+ replaced <- expandTypeSynonym name args
408+ inferProperty replaced prop
409+inferProperty (ForAll ident ty) prop = do
410+ replaced <- replaceVarWithUnknown ident ty
411+ inferProperty replaced prop
412+inferProperty _ _ = return Nothing
413+
414+inferUnary :: UnaryOperator -> Value -> Subst Value
415+inferUnary op (TypedValue _ val valTy) =
416+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
417+ (valTy', resTy) -> do
418+ valTy' ~~ valTy
419+ return $ TypedValue True (Unary op val) resTy
420+inferUnary _ _ = error "Invalid arguments to inferUnary"
421+
422+checkUnary :: UnaryOperator -> Value -> Type -> Subst Value
423+checkUnary op val res =
424+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
425+ (valTy, resTy) -> do
426+ res ~~ resTy
427+ val' <- check val valTy
428+ return $ Unary op val'
429+
430+unaryOps :: [(UnaryOperator, (Type, Type))]
431+unaryOps = [ (Negate, (Number, Number))
432+ , (Not, (Boolean, Boolean))
433+ , (BitwiseNot, (Number, Number))
434+ ]
435+
436+inferBinary :: BinaryOperator -> Value -> Value -> Subst Value
437+inferBinary op left@(TypedValue _ _ leftTy) right@(TypedValue _ _ rightTy) | isEqualityTest op = do
438+ leftTy ~~ rightTy
439+ return $ TypedValue True (Binary op left right) Boolean
440+inferBinary op left@(TypedValue _ _ leftTy) right@(TypedValue _ _ rightTy) =
441+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
442+ (valTy, resTy) -> do
443+ leftTy ~~ valTy
444+ rightTy ~~ valTy
445+ return $ TypedValue True (Binary op left right) resTy
446+inferBinary _ _ _ = error "Invalid arguments to inferBinary"
447+
448+checkBinary :: BinaryOperator -> Value -> Value -> Type -> Subst Value
449+checkBinary op left right res | isEqualityTest op = do
450+ res ~~ Boolean
451+ left'@(TypedValue _ _ t1) <- infer left
452+ right'@(TypedValue _ _ t2) <- infer right
453+ t1 ~~ t2
454+ return $ Binary op left' right'
455+checkBinary op left right res =
456+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
457+ (valTy, resTy) -> do
458+ res ~~ resTy
459+ left' <- check left valTy
460+ right' <- check right valTy
461+ return $ Binary op left' right'
462+
463+isEqualityTest :: BinaryOperator -> Bool
464+isEqualityTest EqualTo = True
465+isEqualityTest NotEqualTo = True
466+isEqualityTest _ = False
467+
468+binaryOps :: [(BinaryOperator, (Type, Type))]
469+binaryOps = [ (Add, (Number, Number))
470+ , (Subtract, (Number, Number))
471+ , (Multiply, (Number, Number))
472+ , (Divide, (Number, Number))
473+ , (Modulus, (Number, Number))
474+ , (BitwiseAnd, (Number, Number))
475+ , (BitwiseOr, (Number, Number))
476+ , (BitwiseXor, (Number, Number))
477+ , (ShiftRight, (Number, Number))
478+ , (ZeroFillShiftRight, (Number, Number))
479+ , (And, (Boolean, Boolean))
480+ , (Or, (Boolean, Boolean))
481+ , (Concat, (String, String))
482+ , (Modulus, (Number, Number))
483+ , (LessThan, (Number, Boolean))
484+ , (LessThanOrEqualTo, (Number, Boolean))
485+ , (GreaterThan, (Number, Boolean))
486+ , (GreaterThanOrEqualTo, (Number, Boolean))
487+ ]
488+
489+inferBinder :: Type -> Binder -> Subst (M.Map Ident Type)
490+inferBinder _ NullBinder = return M.empty
491+inferBinder val (StringBinder _) = val ~~ String >> return M.empty
492+inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
493+inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
494+inferBinder val (VarBinder name) = return $ M.singleton name val
495+inferBinder val (NullaryBinder ctor) = do
496+ env <- getEnv
497+ moduleName <- substCurrentModule <$> ask
498+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
499+ Just (ty, _) -> do
500+ ty `subsumes` val
501+ return M.empty
502+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
503+inferBinder val (UnaryBinder ctor binder) = do
504+ env <- getEnv
505+ moduleName <- substCurrentModule <$> ask
506+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
507+ Just (ty, _) -> do
508+ fn <- replaceAllVarsWithUnknowns ty
509+ case fn of
510+ Function [obj] ret -> do
511+ val `subsumes` ret
512+ inferBinder obj binder
513+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
514+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
515+inferBinder val (ObjectBinder props) = do
516+ row <- fresh
517+ rest <- fresh
518+ m1 <- inferRowProperties row rest props
519+ val ~~ Object row
520+ return m1
521+ where
522+ inferRowProperties :: Type -> Type -> [(String, Binder)] -> Subst (M.Map Ident Type)
523+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
524+ inferRowProperties nrow row ((name, binder):binders) = do
525+ propTy <- fresh
526+ m1 <- inferBinder propTy binder
527+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
528+ return $ m1 `M.union` m2
529+inferBinder val (ArrayBinder binders) = do
530+ el <- fresh
531+ m1 <- M.unions <$> mapM (inferBinder el) binders
532+ val ~~ TypeApp Array el
533+ return m1
534+inferBinder val (ConsBinder headBinder tailBinder) = do
535+ el <- fresh
536+ m1 <- inferBinder el headBinder
537+ m2 <- inferBinder val tailBinder
538+ val ~~ TypeApp Array el
539+ return $ m1 `M.union` m2
540+inferBinder val (NamedBinder name binder) = do
541+ m <- inferBinder val binder
542+ return $ M.insert name val m
543+
544+checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> Subst [([Binder], Maybe Guard, Value)]
545+checkBinders _ _ [] = return []
546+checkBinders nvals ret ((binders, grd, val):bs) = do
547+ moduleName <- substCurrentModule <$> ask
548+ m1 <- M.unions <$> zipWithM inferBinder nvals binders
549+ r <- bindLocalVariables moduleName (M.toList m1) $ do
550+ val' <- check val ret
551+ case grd of
552+ Nothing -> return (binders, Nothing, val')
553+ Just g -> do
554+ g' <- check g Boolean
555+ return (binders, Just g', val')
556+ rs <- checkBinders nvals ret bs
557+ return $ r : rs
558+
559+assignVariable :: Ident -> Subst ()
560+assignVariable name = do
561+ env <- checkEnv <$> get
562+ moduleName <- substCurrentModule <$> ask
563+ case M.lookup (moduleName, name) (names env) of
564+ Just (_, LocalVariable) -> throwError $ "Variable with name " ++ show name ++ " already exists."
565+ _ -> return ()
566+
567+checkStatement :: M.Map Ident Type -> Type -> Statement -> Subst (Bool, M.Map Ident Type, Statement)
568+checkStatement mass _ (VariableIntroduction name val) = do
569+ assignVariable name
570+ val'@(TypedValue _ _ t) <- infer val
571+ return (False, M.insert name t mass, VariableIntroduction name val')
572+checkStatement mass _ (Assignment ident val) = do
573+ val'@(TypedValue _ _ t) <- infer val
574+ case M.lookup ident mass of
575+ Nothing -> throwError $ "No local variable with name " ++ show ident
576+ Just ty -> do t ~~ ty
577+ return (False, mass, Assignment ident val')
578+checkStatement mass ret (While val inner) = do
579+ val' <- check val Boolean
580+ (allCodePathsReturn, _, inner') <- checkBlock mass ret inner
581+ return (allCodePathsReturn, mass, While val' inner')
582+checkStatement mass ret (If ifst) = do
583+ (allCodePathsReturn, ifst') <- checkIfStatement mass ret ifst
584+ return (allCodePathsReturn, mass, If ifst')
585+checkStatement mass ret (For ident start end inner) = do
586+ moduleName <- substCurrentModule <$> ask
587+ assignVariable ident
588+ start' <- check start Number
589+ end' <- check end Number
590+ (allCodePathsReturn, _, inner') <- bindLocalVariables moduleName [(ident, Number)] $ checkBlock mass ret inner
591+ return (allCodePathsReturn, mass, For ident start' end' inner')
592+checkStatement mass ret (Return val) = do
593+ val' <- check val ret
594+ return (True, mass, Return val')
595+
596+checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> Subst (Bool, IfStatement)
597+checkIfStatement mass ret (IfStatement val thens Nothing) = do
598+ val' <- check val Boolean
599+ (_, _, thens') <- checkBlock mass ret thens
600+ return (False, IfStatement val' thens' Nothing)
601+checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
602+ val' <- check val Boolean
603+ (allCodePathsReturn1, _, thens') <- checkBlock mass ret thens
604+ (allCodePathsReturn2, elses') <- checkElseStatement mass ret elses
605+ return (allCodePathsReturn1 && allCodePathsReturn2, IfStatement val' thens' (Just elses'))
606+
607+checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> Subst (Bool, ElseStatement)
608+checkElseStatement mass ret (Else elses) = do
609+ (allCodePathsReturn, _, elses') <- checkBlock mass ret elses
610+ return (allCodePathsReturn, Else elses')
611+checkElseStatement mass ret (ElseIf ifst) = (id *** ElseIf) <$> checkIfStatement mass ret ifst
612+
613+checkBlock :: M.Map Ident Type -> Type -> [Statement] -> Subst (Bool, M.Map Ident Type, [Statement])
614+checkBlock mass _ [] = return (False, mass, [])
615+checkBlock mass ret (s:ss) = do
616+ moduleName <- substCurrentModule <$> ask
617+ (b1, mass1, s') <- checkStatement mass ret s
618+ bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
619+ (True, []) -> return (True, mass1, [s'])
620+ (True, _) -> throwError "Unreachable code"
621+ (False, ss') -> do
622+ (b, m, ss'') <- checkBlock mass1 ret ss'
623+ return (b, m, s':ss'')
624+
625+skolemize :: String -> Type -> Subst Type
626+skolemize ident ty = do
627+ tsk <- Skolem <$> fresh'
628+ return $ replaceTypeVars ident tsk ty
629+
630+check :: Value -> Type -> Subst Value
631+check val ty = rethrow errorMessage $ check' val ty
632+ where
633+ errorMessage msg =
634+ "Error checking type of term " ++
635+ prettyPrintValue val ++
636+ " against type " ++
637+ prettyPrintType ty ++
638+ ":\n" ++
639+ msg
640+
641+check' :: Value -> Type -> Subst Value
642+check' val (ForAll idents ty) = do
643+ sk <- skolemize idents ty
644+ check val sk
645+check' val (ConstrainedType constraints ty) = do
646+ env <- getEnv
647+ moduleName <- substCurrentModule <$> ask
648+ dictNames <- flip mapM constraints $ \(Qualified _ (ProperName className), _) -> do
649+ n <- liftCheck freshDictionaryName
650+ return $ Ident $ "__dict_" ++ className ++ "_" ++ show n
651+ val' <- withTypeClassDictionaries (zipWith (\name (className, instanceTy) ->
652+ TypeClassDictionaryInScope name className instanceTy Nothing TCDRegular) (map (Qualified Nothing) dictNames)
653+ (qualifyAllUnqualifiedNames moduleName env constraints)) $
654+ check val ty
655+ return $ Abs dictNames val'
656+check' val u@(TUnknown _) = do
657+ val'@(TypedValue _ _ ty) <- infer val
658+ -- Don't unify an unknown with an inferred polytype
659+ ty' <- replaceAllVarsWithUnknowns ty
660+ ty' ~~ u
661+ return val'
662+check' v@(NumericLiteral _) Number = return v
663+check' v@(StringLiteral _) String = return v
664+check' v@(BooleanLiteral _) Boolean = return v
665+check' (Unary op val) ty = checkUnary op val ty
666+check' (Binary op left right) ty = checkBinary op left right ty
667+check' (ArrayLiteral vals) (TypeApp Array ty) = ArrayLiteral <$> forM vals (\val -> check val ty)
668+check' (Indexer index vals) ty = do
669+ index' <- check index Number
670+ vals' <- check vals (TypeApp Array ty)
671+ return $ Indexer index' vals'
672+check' (Abs args ret) (Function argTys retTy) = do
673+ moduleName <- substCurrentModule <$> ask
674+ guardWith "Incorrect number of function arguments" (length args == length argTys)
675+ ret' <- bindLocalVariables moduleName (zip args argTys) $ check ret retTy
676+ return $ Abs args ret'
677+check' (App f args) ret = do
678+ f'@(TypedValue _ _ ft) <- infer f
679+ app <- checkFunctionApplication f' ft args ret
680+ return $ app
681+check' (Var var) ty = do
682+ moduleName <- substCurrentModule <$> ask
683+ ty1 <- lookupVariable moduleName var
684+ repl <- replaceAllTypeSynonyms ty1
685+ repl `subsumes` ty
686+ return $ Var var
687+check' (TypedValue checkType val ty1) ty2 = do
688+ moduleName <- substCurrentModule <$> ask
689+ kind <- liftCheck $ kindOf moduleName ty1
690+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
691+ ty1 `subsumes` ty2
692+ val' <- if checkType then check val ty1 else return val
693+ return $ TypedValue True val' ty1
694+check' (Case vals binders) ret = do
695+ vals' <- mapM infer vals
696+ let ts = map (\(TypedValue _ _ t) -> t) vals'
697+ binders' <- checkBinders ts ret binders
698+ return $ Case vals' binders'
699+check' (IfThenElse cond th el) ty = do
700+ cond' <- check cond Boolean
701+ th' <- check th ty
702+ el' <- check el ty
703+ return $ IfThenElse cond' th' el'
704+check' (ObjectLiteral ps) (Object row) = do
705+ ensureNoDuplicateProperties ps
706+ ps' <- checkProperties ps row False
707+ return $ ObjectLiteral ps'
708+check' (ObjectUpdate obj ps) (Object row) = do
709+ ensureNoDuplicateProperties ps
710+ us <- zip (map fst ps) <$> replicateM (length ps) fresh
711+ let (propsToCheck, rest) = rowToList row
712+ propsToRemove = map fst ps
713+ remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
714+ obj' <- check obj (Object (rowFromList (us ++ remainingProps, rest)))
715+ ps' <- checkProperties ps row True
716+ return $ ObjectUpdate obj' ps'
717+check' (Accessor prop val) ty = do
718+ rest <- fresh
719+ val' <- check val (Object (RCons prop ty rest))
720+ return $ Accessor prop val'
721+check' (Block ss) ret = do
722+ (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
723+ guardWith "Block is missing a return statement" allCodePathsReturn
724+ return $ Block ss'
725+check' (Constructor c) ty = do
726+ env <- getEnv
727+ moduleName <- substCurrentModule <$> ask
728+ case M.lookup (qualify moduleName c) (dataConstructors env) of
729+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
730+ Just (ty1, _) -> do
731+ repl <- replaceAllTypeSynonyms ty1
732+ repl `subsumes` ty
733+ return $ Constructor c
734+check' val (SaturatedTypeSynonym name args) = do
735+ ty <- expandTypeSynonym name args
736+ check val ty
737+check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
738+
739+checkProperties :: [(String, Value)] -> Type -> Bool -> Subst [(String, Value)]
740+checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
741+ go [] [] REmpty = return []
742+ go [] [] u@(TUnknown _) = do u ~~ REmpty
743+ return []
744+ go [] [] (Skolem _) | lax = return []
745+ go [] ((p, _): _) _ | lax = return []
746+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
747+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
748+ go ((p,v):ps') [] u@(TUnknown _) = do
749+ v'@(TypedValue _ _ ty) <- infer v
750+ rest <- fresh
751+ u ~~ RCons p ty rest
752+ ps'' <- go ps' [] rest
753+ return $ (p, v') : ps''
754+ go ((p,v):ps') ts r =
755+ case lookup p ts of
756+ Nothing -> do
757+ v'@(TypedValue _ _ ty) <- infer v
758+ rest <- fresh
759+ r ~~ RCons p ty rest
760+ ps'' <- go ps' ts rest
761+ return $ (p, v') : ps''
762+ Just ty -> do
763+ v' <- check v ty
764+ ps'' <- go ps' (delete (p, ty) ts) r
765+ return $ (p, v') : ps''
766+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
767+
768+checkFunctionApplication :: Value -> Type -> [Value] -> Type -> Subst Value
769+checkFunctionApplication fn fnTy args ret = rethrow errorMessage $ checkFunctionApplication' fn fnTy args ret
770+ where
771+ errorMessage msg = "Error applying function of type "
772+ ++ prettyPrintType fnTy
773+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
774+ ++ ":\n" ++ msg
775+
776+checkFunctionApplication' :: Value -> Type -> [Value] -> Type -> Subst Value
777+checkFunctionApplication' fn (Function argTys retTy) args ret = do
778+ guardWith "Incorrect number of function arguments" (length args == length argTys)
779+ args' <- zipWithM check args argTys
780+ retTy `subsumes` ret
781+ return $ App fn args'
782+checkFunctionApplication' fn (ForAll ident ty) args ret = do
783+ replaced <- replaceVarWithUnknown ident ty
784+ checkFunctionApplication fn replaced args ret
785+checkFunctionApplication' fn u@(TUnknown _) args ret = do
786+ args' <- mapM (\arg -> infer arg >>= \(TypedValue _ v t) -> TypedValue True v <$> replaceAllVarsWithUnknowns t) args
787+ let tys = map (\(TypedValue _ _ t) -> t) args'
788+ u ~~ Function tys ret
789+ return $ App fn args'
790+checkFunctionApplication' fn (SaturatedTypeSynonym name tyArgs) args ret = do
791+ ty <- expandTypeSynonym name tyArgs
792+ checkFunctionApplication fn ty args ret
793+checkFunctionApplication' fn (ConstrainedType constraints fnTy) args ret = do
794+ env <- getEnv
795+ dicts <- getTypeClassDictionaries
796+ moduleName <- substCurrentModule <$> ask
797+ checkFunctionApplication' (App fn (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) fnTy args ret
798+checkFunctionApplication' _ fnTy args ret = throwError $ "Applying a function of type "
799+ ++ prettyPrintType fnTy
800+ ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
801+ ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
802+
803+subsumes :: Type -> Type -> Subst ()
804+subsumes (ForAll ident ty1) ty2 = do
805+ replaced <- replaceVarWithUnknown ident ty1
806+ replaced `subsumes` ty2
807+subsumes (Function args1 ret1) (Function args2 ret2) = do
808+ zipWithM_ subsumes args2 args1
809+ ret1 `subsumes` ret2
810+subsumes ty1 ty2 = ty1 ~~ ty2
811+