@@ -0,0 +1,815 @@
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))) $ (map (id *** fst) typedDict) ++ untypedDict)
155+ forM es $ \e -> do
156+ triple@(_, (val, ty)) <- case e of
157+ (ident, (val, Just (ty, checkType))) -> 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 $ if checkType then check val ty' else return val
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 moduleName val
175+ return (ident, (overTypes (desaturateAllTypeSynonyms . setifyAll) $ val'
176+ , varIfUnknown . desaturateAllTypeSynonyms . setifyAll $ ty))
177+
178+isTyped :: (Ident, Value) -> (Ident, (Value, Maybe (Type, Bool)))
179+isTyped (name, TypedValue checkType value ty) = (name, (value, Just (ty, checkType)))
180+isTyped (name, value) = (name, (value, Nothing))
181+
182+overTypes :: (Type -> Type) -> Value -> Value
183+overTypes f = everywhere (mkT f)
184+
185+replaceTypeClassDictionaries :: ModuleName -> Value -> Check Value
186+replaceTypeClassDictionaries mn = everywhereM (mkM go)
187+ where
188+ go (TypeClassDictionary constraint dicts) = entails mn dicts constraint
189+ go other = return other
190+
191+entails :: ModuleName -> [TypeClassDictionaryInScope] -> (Qualified ProperName, Type) -> Check Value
192+entails moduleName context goal@(className, ty) = do
193+ env <- getEnv
194+ case go env goal of
195+ [] -> throwError $ "No " ++ show className ++ " instance found for " ++ prettyPrintType ty
196+ (dict : _) -> return dict
197+ where
198+ go env (className', ty') =
199+ [ mkDictionary (canonicalizeDictionary tcd) args
200+ | tcd <- context
201+ , filterModule tcd
202+ , typeConstructorsAreEqual env moduleName className' (tcdClassName tcd)
203+ , subst <- maybeToList $ typeHeadsAreEqual moduleName env ty' (tcdInstanceType tcd)
204+ , args <- solveSubgoals env subst (tcdDependencies tcd) ]
205+ solveSubgoals _ _ Nothing = return Nothing
206+ solveSubgoals env subst (Just subgoals) = do
207+ dict <- mapM (go env) (replaceAllTypeVars subst subgoals)
208+ return $ Just dict
209+ mkDictionary fnName args = maybe id (flip App) args $ (Var fnName)
210+ filterModule (TypeClassDictionaryInScope { tcdName = Qualified (Just mn) _ }) | mn == moduleName = True
211+ filterModule (TypeClassDictionaryInScope { tcdName = Qualified Nothing _ }) = True
212+ filterModule _ = False
213+ canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDRegular, tcdName = nm }) = nm
214+ canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDAlias nm }) = nm
215+
216+typeHeadsAreEqual :: ModuleName -> Environment -> Type -> Type -> Maybe [(String, Type)]
217+typeHeadsAreEqual _ _ String String = Just []
218+typeHeadsAreEqual _ _ Number Number = Just []
219+typeHeadsAreEqual _ _ Boolean Boolean = Just []
220+typeHeadsAreEqual _ _ (Skolem s1) (Skolem s2) | s1 == s2 = Just []
221+typeHeadsAreEqual _ _ (Array (TypeVar v)) (Array ty) = Just [(v, ty)]
222+typeHeadsAreEqual _ _ (Array ty) (Array (TypeVar v)) = Just [(v, ty)]
223+typeHeadsAreEqual m e (Array ty1) (Array ty2) = typeHeadsAreEqual m e ty1 ty2
224+typeHeadsAreEqual m e (TypeConstructor c1) (TypeConstructor c2) | typeConstructorsAreEqual e m c1 c2 = Just []
225+typeHeadsAreEqual m e (TypeApp h1 (TypeVar v)) (TypeApp h2 arg) = (:) (v, arg) <$> typeHeadsAreEqual m e h1 h2
226+typeHeadsAreEqual m e t1@(TypeApp _ _) t2@(TypeApp _ (TypeVar _)) = typeHeadsAreEqual m e t2 t1
227+typeHeadsAreEqual _ _ _ _ = Nothing
228+
229+escapeCheck :: Value -> Type -> Subst ()
230+escapeCheck value ty = do
231+ subst <- substSubst <$> getSubstState
232+ let visibleUnknowns = nub $ unknowns $ apply subst ty
233+ let allUnknowns = findAllTypes value
234+ forM_ allUnknowns $ \t -> do
235+ let unsolvedUnknowns = nub . unknowns $ apply subst t
236+ guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
237+
238+findAllTypes :: Value -> [Type]
239+findAllTypes = everything (++) (mkQ [] go)
240+ where
241+ go (TypedValue _ _ ty) = [ty]
242+ go _ = []
243+
244+skolemEscapeCheck :: Type -> Check ()
245+skolemEscapeCheck ty =
246+ case something (mkQ Nothing findSkolems) ty of
247+ Nothing -> return ()
248+ Just _ -> throwError $ "Skolem variables cannot escape. Consider adding a type signature." ++ show ty
249+ where
250+ findSkolems (Skolem _) = return ()
251+ findSkolems _ = mzero
252+
253+setify :: Type -> Type
254+setify = rowFromList . first (M.toList . M.fromList) . rowToList
255+
256+setifyAll :: (D.Data d) => d -> d
257+setifyAll = everywhere (mkT setify)
258+
259+varIfUnknown :: Type -> Type
260+varIfUnknown ty =
261+ let unks = nub $ unknowns ty
262+ toName = (:) 't' . show
263+ ty' = everywhere (mkT typeToVar) $ ty
264+ typeToVar :: Type -> Type
265+ typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
266+ typeToVar t = t
267+ in mkForAll (sort . map toName $ unks) ty'
268+
269+replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
270+replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
271+
272+replaceAllVarsWithUnknowns :: Type -> Subst Type
273+replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
274+replaceAllVarsWithUnknowns ty = return ty
275+
276+replaceVarWithUnknown :: String -> Type -> Subst Type
277+replaceVarWithUnknown ident ty = do
278+ tu <- fresh
279+ return $ replaceTypeVars ident tu $ ty
280+
281+replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadReader SubstContext m, MonadError String m) => (D.Data d) => d -> m d
282+replaceAllTypeSynonyms d = do
283+ env <- getEnv
284+ moduleName <- substCurrentModule <$> ask
285+ let syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
286+ either throwError return $ saturateAllTypeSynonyms env moduleName syns d
287+
288+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
289+desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
290+ where
291+ replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
292+ replaceSaturatedTypeSynonym t = t
293+
294+expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Type
295+expandTypeSynonym name args = do
296+ env <- getEnv
297+ moduleName <- substCurrentModule `fmap` ask
298+ case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
299+ Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
300+ Nothing -> error "Type synonym was not defined"
301+
302+ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
303+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
304+
305+infer :: Value -> Subst Value
306+infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ infer' val
307+
308+infer' :: Value -> Subst Value
309+infer' v@(NumericLiteral _) = return $ TypedValue True v Number
310+infer' v@(StringLiteral _) = return $ TypedValue True v String
311+infer' v@(BooleanLiteral _) = return $ TypedValue True v Boolean
312+infer' (ArrayLiteral vals) = do
313+ ts <- mapM infer vals
314+ els <- fresh
315+ forM_ ts $ \(TypedValue _ _ t) -> els ~~ Array t
316+ return $ TypedValue True (ArrayLiteral ts) els
317+infer' (Unary op val) = do
318+ v <- infer val
319+ inferUnary op v
320+infer' (Binary op left right) = do
321+ v1 <- infer left
322+ v2 <- infer right
323+ inferBinary op v1 v2
324+infer' (ObjectLiteral ps) = do
325+ ensureNoDuplicateProperties ps
326+ ts <- mapM (infer . snd) ps
327+ let fields = zipWith (\name (TypedValue _ _ t) -> (name, t)) (map fst ps) ts
328+ ty = Object $ rowFromList (fields, REmpty)
329+ return $ TypedValue True (ObjectLiteral (zip (map fst ps) ts)) ty
330+infer' (ObjectUpdate o ps) = do
331+ ensureNoDuplicateProperties ps
332+ row <- fresh
333+ newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
334+ let newTys = map (\(name, TypedValue _ _ ty) -> (name, ty)) newVals
335+ oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
336+ o' <- check o $ Object $ rowFromList (oldTys, row)
337+ return $ TypedValue True (ObjectUpdate o' newVals) $ Object $ rowFromList (newTys, row)
338+infer' (Indexer index val) = do
339+ el <- fresh
340+ index' <- check index Number
341+ val' <- check val (Array el)
342+ return $ TypedValue True (Indexer (TypedValue True index' Number) (TypedValue True val' (Array el))) el
343+infer' (Accessor prop val) = do
344+ typed@(TypedValue _ _ objTy) <- infer val
345+ propTy <- inferProperty objTy prop
346+ case propTy of
347+ Nothing -> do
348+ field <- fresh
349+ rest <- fresh
350+ objTy `subsumes` Object (RCons prop field rest)
351+ return $ TypedValue True (Accessor prop typed) field
352+ Just ty -> return $ TypedValue True (Accessor prop typed) ty
353+infer' (Abs args ret) = do
354+ ts <- replicateM (length args) fresh
355+ moduleName <- substCurrentModule <$> ask
356+ bindLocalVariables moduleName (zip args ts) $ do
357+ body@(TypedValue _ _ bodyTy) <- infer' ret
358+ return $ TypedValue True (Abs args body) $ Function ts bodyTy
359+infer' (App f args) = do
360+ f'@(TypedValue _ _ ft) <- infer f
361+ ret <- fresh
362+ app <- checkFunctionApplication f' ft args ret
363+ return $ TypedValue True app ret
364+infer' (Var var) = do
365+ moduleName <- substCurrentModule <$> ask
366+ ty <- lookupVariable moduleName var
367+ ty' <- replaceAllTypeSynonyms ty
368+ case ty' of
369+ ConstrainedType constraints _ -> do
370+ env <- getEnv
371+ dicts <- getTypeClassDictionaries
372+ return $ TypedValue True (App (Var var) (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) ty'
373+ _ -> return $ TypedValue True (Var var) ty'
374+infer' (Block ss) = do
375+ ret <- fresh
376+ (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
377+ guardWith "Block is missing a return statement" allCodePathsReturn
378+ return $ TypedValue True (Block ss') ret
379+infer' v@(Constructor c) = do
380+ env <- getEnv
381+ moduleName <- substCurrentModule `fmap` ask
382+ case M.lookup (qualify moduleName c) (dataConstructors env) of
383+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
384+ Just (ty, _) -> do ty' <- replaceAllTypeSynonyms ty
385+ return $ TypedValue True v ty'
386+infer' (Case vals binders) = do
387+ ts <- mapM infer vals
388+ ret <- fresh
389+ binders' <- checkBinders (map (\(TypedValue _ _ t) -> t) ts) ret binders
390+ return $ TypedValue True (Case ts binders') ret
391+infer' (IfThenElse cond th el) = do
392+ cond' <- check cond Boolean
393+ v2@(TypedValue _ _ t2) <- infer th
394+ v3@(TypedValue _ _ t3) <- infer el
395+ t2 ~~ t3
396+ return $ TypedValue True (IfThenElse cond' v2 v3) t2
397+infer' (TypedValue checkType val ty) = do
398+ moduleName <- substCurrentModule <$> ask
399+ kind <- liftCheck $ kindOf moduleName ty
400+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
401+ ty' <- replaceAllTypeSynonyms ty
402+ val' <- if checkType then check val ty' else return val
403+ return $ TypedValue True val' ty
404+infer' _ = error "Invalid argument to infer"
405+
406+inferProperty :: Type -> String -> Subst (Maybe Type)
407+inferProperty (Object row) prop = do
408+ let (props, _) = rowToList row
409+ return $ lookup prop props
410+inferProperty (SaturatedTypeSynonym name args) prop = do
411+ replaced <- expandTypeSynonym name args
412+ inferProperty replaced prop
413+inferProperty (ForAll ident ty) prop = do
414+ replaced <- replaceVarWithUnknown ident ty
415+ inferProperty replaced prop
416+inferProperty _ _ = return Nothing
417+
418+inferUnary :: UnaryOperator -> Value -> Subst Value
419+inferUnary op (TypedValue _ val valTy) =
420+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
421+ (valTy', resTy) -> do
422+ valTy' ~~ valTy
423+ return $ TypedValue True (Unary op val) resTy
424+inferUnary _ _ = error "Invalid arguments to inferUnary"
425+
426+checkUnary :: UnaryOperator -> Value -> Type -> Subst Value
427+checkUnary op val res =
428+ case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
429+ (valTy, resTy) -> do
430+ res ~~ resTy
431+ val' <- check val valTy
432+ return $ Unary op val'
433+
434+unaryOps :: [(UnaryOperator, (Type, Type))]
435+unaryOps = [ (Negate, (Number, Number))
436+ , (Not, (Boolean, Boolean))
437+ , (BitwiseNot, (Number, Number))
438+ ]
439+
440+inferBinary :: BinaryOperator -> Value -> Value -> Subst Value
441+inferBinary op left@(TypedValue _ _ leftTy) right@(TypedValue _ _ rightTy) | isEqualityTest op = do
442+ leftTy ~~ rightTy
443+ return $ TypedValue True (Binary op left right) Boolean
444+inferBinary op left@(TypedValue _ _ leftTy) right@(TypedValue _ _ rightTy) =
445+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
446+ (valTy, resTy) -> do
447+ leftTy ~~ valTy
448+ rightTy ~~ valTy
449+ return $ TypedValue True (Binary op left right) resTy
450+inferBinary _ _ _ = error "Invalid arguments to inferBinary"
451+
452+checkBinary :: BinaryOperator -> Value -> Value -> Type -> Subst Value
453+checkBinary op left right res | isEqualityTest op = do
454+ res ~~ Boolean
455+ left'@(TypedValue _ _ t1) <- infer left
456+ right'@(TypedValue _ _ t2) <- infer right
457+ t1 ~~ t2
458+ return $ Binary op left' right'
459+checkBinary op left right res =
460+ case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
461+ (valTy, resTy) -> do
462+ res ~~ resTy
463+ left' <- check left valTy
464+ right' <- check right valTy
465+ return $ Binary op left' right'
466+
467+isEqualityTest :: BinaryOperator -> Bool
468+isEqualityTest EqualTo = True
469+isEqualityTest NotEqualTo = True
470+isEqualityTest _ = False
471+
472+binaryOps :: [(BinaryOperator, (Type, Type))]
473+binaryOps = [ (Add, (Number, Number))
474+ , (Subtract, (Number, Number))
475+ , (Multiply, (Number, Number))
476+ , (Divide, (Number, Number))
477+ , (Modulus, (Number, Number))
478+ , (BitwiseAnd, (Number, Number))
479+ , (BitwiseOr, (Number, Number))
480+ , (BitwiseXor, (Number, Number))
481+ , (ShiftRight, (Number, Number))
482+ , (ZeroFillShiftRight, (Number, Number))
483+ , (And, (Boolean, Boolean))
484+ , (Or, (Boolean, Boolean))
485+ , (Concat, (String, String))
486+ , (Modulus, (Number, Number))
487+ , (LessThan, (Number, Boolean))
488+ , (LessThanOrEqualTo, (Number, Boolean))
489+ , (GreaterThan, (Number, Boolean))
490+ , (GreaterThanOrEqualTo, (Number, Boolean))
491+ ]
492+
493+inferBinder :: Type -> Binder -> Subst (M.Map Ident Type)
494+inferBinder _ NullBinder = return M.empty
495+inferBinder val (StringBinder _) = val ~~ String >> return M.empty
496+inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
497+inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
498+inferBinder val (VarBinder name) = return $ M.singleton name val
499+inferBinder val (NullaryBinder ctor) = do
500+ env <- getEnv
501+ moduleName <- substCurrentModule <$> ask
502+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
503+ Just (ty, _) -> do
504+ ty `subsumes` val
505+ return M.empty
506+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
507+inferBinder val (UnaryBinder ctor binder) = do
508+ env <- getEnv
509+ moduleName <- substCurrentModule <$> ask
510+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
511+ Just (ty, _) -> do
512+ fn <- replaceAllVarsWithUnknowns ty
513+ case fn of
514+ Function [obj] ret -> do
515+ val `subsumes` ret
516+ inferBinder obj binder
517+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
518+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
519+inferBinder val (ObjectBinder props) = do
520+ row <- fresh
521+ rest <- fresh
522+ m1 <- inferRowProperties row rest props
523+ val ~~ Object row
524+ return m1
525+ where
526+ inferRowProperties :: Type -> Type -> [(String, Binder)] -> Subst (M.Map Ident Type)
527+ inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
528+ inferRowProperties nrow row ((name, binder):binders) = do
529+ propTy <- fresh
530+ m1 <- inferBinder propTy binder
531+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
532+ return $ m1 `M.union` m2
533+inferBinder val (ArrayBinder binders) = do
534+ el <- fresh
535+ m1 <- M.unions <$> mapM (inferBinder el) binders
536+ val ~~ Array el
537+ return m1
538+inferBinder val (ConsBinder headBinder tailBinder) = do
539+ el <- fresh
540+ m1 <- inferBinder el headBinder
541+ m2 <- inferBinder val tailBinder
542+ val ~~ Array el
543+ return $ m1 `M.union` m2
544+inferBinder val (NamedBinder name binder) = do
545+ m <- inferBinder val binder
546+ return $ M.insert name val m
547+
548+checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> Subst [([Binder], Maybe Guard, Value)]
549+checkBinders _ _ [] = return []
550+checkBinders nvals ret ((binders, grd, val):bs) = do
551+ moduleName <- substCurrentModule <$> ask
552+ m1 <- M.unions <$> zipWithM inferBinder nvals binders
553+ r <- bindLocalVariables moduleName (M.toList m1) $ do
554+ val' <- check val ret
555+ case grd of
556+ Nothing -> return (binders, Nothing, val')
557+ Just g -> do
558+ g' <- check g Boolean
559+ return (binders, Just g', val')
560+ rs <- checkBinders nvals ret bs
561+ return $ r : rs
562+
563+assignVariable :: Ident -> Subst ()
564+assignVariable name = do
565+ env <- checkEnv <$> get
566+ moduleName <- substCurrentModule <$> ask
567+ case M.lookup (moduleName, name) (names env) of
568+ Just (_, LocalVariable) -> throwError $ "Variable with name " ++ show name ++ " already exists."
569+ _ -> return ()
570+
571+checkStatement :: M.Map Ident Type -> Type -> Statement -> Subst (Bool, M.Map Ident Type, Statement)
572+checkStatement mass _ (VariableIntroduction name val) = do
573+ assignVariable name
574+ val'@(TypedValue _ _ t) <- infer val
575+ return (False, M.insert name t mass, VariableIntroduction name val')
576+checkStatement mass _ (Assignment ident val) = do
577+ val'@(TypedValue _ _ t) <- infer val
578+ case M.lookup ident mass of
579+ Nothing -> throwError $ "No local variable with name " ++ show ident
580+ Just ty -> do t ~~ ty
581+ return (False, mass, Assignment ident val')
582+checkStatement mass ret (While val inner) = do
583+ val' <- check val Boolean
584+ (allCodePathsReturn, _, inner') <- checkBlock mass ret inner
585+ return (allCodePathsReturn, mass, While val' inner')
586+checkStatement mass ret (If ifst) = do
587+ (allCodePathsReturn, ifst') <- checkIfStatement mass ret ifst
588+ return (allCodePathsReturn, mass, If ifst')
589+checkStatement mass ret (For ident start end inner) = do
590+ moduleName <- substCurrentModule <$> ask
591+ assignVariable ident
592+ start' <- check start Number
593+ end' <- check end Number
594+ (allCodePathsReturn, _, inner') <- bindLocalVariables moduleName [(ident, Number)] $ checkBlock mass ret inner
595+ return (allCodePathsReturn, mass, For ident start' end' inner')
596+checkStatement mass ret (Return val) = do
597+ val' <- check val ret
598+ return (True, mass, Return val')
599+
600+checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> Subst (Bool, IfStatement)
601+checkIfStatement mass ret (IfStatement val thens Nothing) = do
602+ val' <- check val Boolean
603+ (_, _, thens') <- checkBlock mass ret thens
604+ return (False, IfStatement val' thens' Nothing)
605+checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
606+ val' <- check val Boolean
607+ (allCodePathsReturn1, _, thens') <- checkBlock mass ret thens
608+ (allCodePathsReturn2, elses') <- checkElseStatement mass ret elses
609+ return (allCodePathsReturn1 && allCodePathsReturn2, IfStatement val' thens' (Just elses'))
610+
611+checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> Subst (Bool, ElseStatement)
612+checkElseStatement mass ret (Else elses) = do
613+ (allCodePathsReturn, _, elses') <- checkBlock mass ret elses
614+ return (allCodePathsReturn, Else elses')
615+checkElseStatement mass ret (ElseIf ifst) = (id *** ElseIf) <$> checkIfStatement mass ret ifst
616+
617+checkBlock :: M.Map Ident Type -> Type -> [Statement] -> Subst (Bool, M.Map Ident Type, [Statement])
618+checkBlock mass _ [] = return (False, mass, [])
619+checkBlock mass ret (s:ss) = do
620+ moduleName <- substCurrentModule <$> ask
621+ (b1, mass1, s') <- checkStatement mass ret s
622+ bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
623+ (True, []) -> return (True, mass1, [s'])
624+ (True, _) -> throwError "Unreachable code"
625+ (False, ss') -> do
626+ (b, m, ss'') <- checkBlock mass1 ret ss'
627+ return (b, m, s':ss'')
628+
629+skolemize :: String -> Type -> Subst Type
630+skolemize ident ty = do
631+ tsk <- Skolem <$> fresh'
632+ return $ replaceTypeVars ident tsk ty
633+
634+check :: Value -> Type -> Subst Value
635+check val ty = rethrow errorMessage $ check' val ty
636+ where
637+ errorMessage msg =
638+ "Error checking type of term " ++
639+ prettyPrintValue val ++
640+ " against type " ++
641+ prettyPrintType ty ++
642+ ":\n" ++
643+ msg
644+
645+check' :: Value -> Type -> Subst Value
646+check' val (ForAll idents ty) = do
647+ sk <- skolemize idents ty
648+ check val sk
649+check' val (ConstrainedType constraints ty) = do
650+ env <- getEnv
651+ moduleName <- substCurrentModule <$> ask
652+ dictNames <- flip mapM constraints $ \(Qualified _ (ProperName className), _) -> do
653+ n <- liftCheck freshDictionaryName
654+ return $ Ident $ "__dict_" ++ className ++ "_" ++ show n
655+ val' <- withTypeClassDictionaries (zipWith (\name (className, instanceTy) ->
656+ TypeClassDictionaryInScope name className instanceTy Nothing TCDRegular) (map (Qualified Nothing) dictNames)
657+ (qualifyAllUnqualifiedNames moduleName env constraints)) $
658+ check val ty
659+ return $ Abs dictNames val'
660+check' val u@(TUnknown _) = do
661+ val'@(TypedValue _ _ ty) <- infer val
662+ -- Don't unify an unknown with an inferred polytype
663+ ty' <- replaceAllVarsWithUnknowns ty
664+ ty' ~~ u
665+ return val'
666+check' v@(NumericLiteral _) Number = return v
667+check' v@(StringLiteral _) String = return v
668+check' v@(BooleanLiteral _) Boolean = return v
669+check' (Unary op val) ty = checkUnary op val ty
670+check' (Binary op left right) ty = checkBinary op left right ty
671+check' (ArrayLiteral vals) (Array ty) = ArrayLiteral <$> forM vals (\val -> check val ty)
672+check' (Indexer index vals) ty = do
673+ index' <- check index Number
674+ vals' <- check vals (Array ty)
675+ return $ Indexer index' vals'
676+check' (Abs args ret) (Function argTys retTy) = do
677+ moduleName <- substCurrentModule <$> ask
678+ guardWith "Incorrect number of function arguments" (length args == length argTys)
679+ ret' <- bindLocalVariables moduleName (zip args argTys) $ check ret retTy
680+ return $ Abs args ret'
681+check' (App f args) ret = do
682+ f'@(TypedValue _ _ ft) <- infer f
683+ app <- checkFunctionApplication f' ft args ret
684+ return $ app
685+check' (Var var) ty = do
686+ moduleName <- substCurrentModule <$> ask
687+ ty1 <- lookupVariable moduleName var
688+ repl <- replaceAllTypeSynonyms ty1
689+ repl `subsumes` ty
690+ return $ Var var
691+check' (TypedValue checkType val ty1) ty2 = do
692+ moduleName <- substCurrentModule <$> ask
693+ kind <- liftCheck $ kindOf moduleName ty1
694+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
695+ ty1 `subsumes` ty2
696+ val' <- if checkType then check val ty1 else return val
697+ return $ TypedValue True val' ty1
698+check' (Case vals binders) ret = do
699+ vals' <- mapM infer vals
700+ let ts = map (\(TypedValue _ _ t) -> t) vals'
701+ binders' <- checkBinders ts ret binders
702+ return $ Case vals' binders'
703+check' (IfThenElse cond th el) ty = do
704+ cond' <- check cond Boolean
705+ th' <- check th ty
706+ el' <- check el ty
707+ return $ IfThenElse cond' th' el'
708+check' (ObjectLiteral ps) (Object row) = do
709+ ensureNoDuplicateProperties ps
710+ ps' <- checkProperties ps row False
711+ return $ ObjectLiteral ps'
712+check' (ObjectUpdate obj ps) (Object row) = do
713+ ensureNoDuplicateProperties ps
714+ us <- zip (map fst ps) <$> replicateM (length ps) fresh
715+ let (propsToCheck, rest) = rowToList row
716+ propsToRemove = map fst ps
717+ remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
718+ obj' <- check obj (Object (rowFromList (us ++ remainingProps, rest)))
719+ ps' <- checkProperties ps row True
720+ return $ ObjectUpdate obj' ps'
721+check' (Accessor prop val) ty = do
722+ rest <- fresh
723+ val' <- check val (Object (RCons prop ty rest))
724+ return $ Accessor prop val'
725+check' (Block ss) ret = do
726+ (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
727+ guardWith "Block is missing a return statement" allCodePathsReturn
728+ return $ Block ss'
729+check' (Constructor c) ty = do
730+ env <- getEnv
731+ moduleName <- substCurrentModule <$> ask
732+ case M.lookup (qualify moduleName c) (dataConstructors env) of
733+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
734+ Just (ty1, _) -> do
735+ repl <- replaceAllTypeSynonyms ty1
736+ repl `subsumes` ty
737+ return $ Constructor c
738+check' val (SaturatedTypeSynonym name args) = do
739+ ty <- expandTypeSynonym name args
740+ check val ty
741+check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
742+
743+checkProperties :: [(String, Value)] -> Type -> Bool -> Subst [(String, Value)]
744+checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
745+ go [] [] REmpty = return []
746+ go [] [] u@(TUnknown _) = do u ~~ REmpty
747+ return []
748+ go [] [] (Skolem _) | lax = return []
749+ go [] ((p, _): _) _ | lax = return []
750+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
751+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
752+ go ((p,v):ps') [] u@(TUnknown _) = do
753+ v'@(TypedValue _ _ ty) <- infer v
754+ rest <- fresh
755+ u ~~ RCons p ty rest
756+ ps'' <- go ps' [] rest
757+ return $ (p, v') : ps''
758+ go ((p,v):ps') ts r =
759+ case lookup p ts of
760+ Nothing -> do
761+ v'@(TypedValue _ _ ty) <- infer v
762+ rest <- fresh
763+ r ~~ RCons p ty rest
764+ ps'' <- go ps' ts rest
765+ return $ (p, v') : ps''
766+ Just ty -> do
767+ v' <- check v ty
768+ ps'' <- go ps' (delete (p, ty) ts) r
769+ return $ (p, v') : ps''
770+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
771+
772+checkFunctionApplication :: Value -> Type -> [Value] -> Type -> Subst Value
773+checkFunctionApplication fn fnTy args ret = rethrow errorMessage $ checkFunctionApplication' fn fnTy args ret
774+ where
775+ errorMessage msg = "Error applying function of type "
776+ ++ prettyPrintType fnTy
777+ ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
778+ ++ ":\n" ++ msg
779+
780+checkFunctionApplication' :: Value -> Type -> [Value] -> Type -> Subst Value
781+checkFunctionApplication' fn (Function argTys retTy) args ret = do
782+ guardWith "Incorrect number of function arguments" (length args == length argTys)
783+ args' <- zipWithM check args argTys
784+ retTy `subsumes` ret
785+ return $ App fn args'
786+checkFunctionApplication' fn (ForAll ident ty) args ret = do
787+ replaced <- replaceVarWithUnknown ident ty
788+ checkFunctionApplication fn replaced args ret
789+checkFunctionApplication' fn u@(TUnknown _) args ret = do
790+ args' <- mapM (\arg -> infer arg >>= \(TypedValue _ v t) -> TypedValue True v <$> replaceAllVarsWithUnknowns t) args
791+ let tys = map (\(TypedValue _ _ t) -> t) args'
792+ u ~~ Function tys ret
793+ return $ App fn args'
794+checkFunctionApplication' fn (SaturatedTypeSynonym name tyArgs) args ret = do
795+ ty <- expandTypeSynonym name tyArgs
796+ checkFunctionApplication fn ty args ret
797+checkFunctionApplication' fn (ConstrainedType constraints fnTy) args ret = do
798+ env <- getEnv
799+ dicts <- getTypeClassDictionaries
800+ moduleName <- substCurrentModule <$> ask
801+ checkFunctionApplication' (App fn (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) fnTy args ret
802+checkFunctionApplication' _ fnTy args ret = throwError $ "Applying a function of type "
803+ ++ prettyPrintType fnTy
804+ ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
805+ ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
806+
807+subsumes :: Type -> Type -> Subst ()
808+subsumes (ForAll ident ty1) ty2 = do
809+ replaced <- replaceVarWithUnknown ident ty1
810+ replaced `subsumes` ty2
811+subsumes (Function args1 ret1) (Function args2 ret2) = do
812+ zipWithM_ subsumes args2 args1
813+ ret1 `subsumes` ret2
814+subsumes ty1 ty2 = ty1 ~~ ty2
815+