@@ -1,973 +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−-- This module implements the type checker
13−--
14−-----------------------------------------------------------------------------
15−
16−{-# OPTIONS_GHC -fno-warn-orphans #-}
17−{-# LANGUAGE DeriveDataTypeable, FlexibleContexts #-}
18−
19−module Language.PureScript.TypeChecker.Types (
20− typesOf
21−) where
22−
23−import Data.List
24−import Data.Maybe (maybeToList, isNothing, isJust, fromMaybe)
25−import qualified Data.Data as D
26−import Data.Generics
27− (mkM, everywhereM, everything, mkT, something, everywhere, mkQ)
28−
29−import Language.PureScript.Values
30−import Language.PureScript.Types
31−import Language.PureScript.Kinds
32−import Language.PureScript.Names
33−import Language.PureScript.TypeChecker.Monad
34−import Language.PureScript.TypeChecker.Kinds
35−import Language.PureScript.TypeChecker.Synonyms
36−import Language.PureScript.Pretty
37−import Language.PureScript.Unknown
38−
39−import Control.Monad.State
40−import Control.Monad.Error
41−import Control.Monad.Reader
42−
43−import Control.Applicative
44−import Control.Arrow (Arrow(..))
45−
46−import qualified Data.Map as M
47−import Data.Function (on)
48−
49−instance Unifiable Type where
50− unknown = TUnknown
51− isUnknown (TUnknown u) = Just u
52− isUnknown _ = Nothing
53− (~~) = unifyTypes
54− apply s (TUnknown u) = runSubstitution s u
55− apply s (SaturatedTypeSynonym name tys) = SaturatedTypeSynonym name $ map (apply s) tys
56− apply s (ForAll idents ty) = ForAll idents $ apply s ty
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 (Object r) = unknowns r
66− unknowns (Function args ret) = concatMap unknowns args ++ unknowns ret
67− unknowns (TypeApp t1 t2) = unknowns t1 ++ unknowns t2
68− unknowns (RCons _ ty r) = unknowns ty ++ unknowns r
69− unknowns _ = []
70−
71−-- |
72−-- Unify two types, updating the current substitution
73−--
74−unifyTypes :: Type -> Type -> Subst ()
75−unifyTypes t1 t2 = rethrow (\e -> "Error unifying type " ++ prettyPrintType t1 ++ " with type " ++ prettyPrintType t2 ++ ":\n" ++ e) $ do
76− unifyTypes' t1 t2
77− where
78− unifyTypes' (TUnknown u1) (TUnknown u2) | u1 == u2 = return ()
79− unifyTypes' (TUnknown u) t = replace u t
80− unifyTypes' t (TUnknown u) = replace u t
81− unifyTypes' (SaturatedTypeSynonym name args) ty = do
82− ty1 <- expandTypeSynonym name args
83− ty1 `unifyTypes` ty
84− unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
85− unifyTypes' (ForAll ident1 ty1) (ForAll ident2 ty2) = do
86− sk <- skolemize ident1 ty1
87− replaced <- replaceVarWithUnknown ident2 ty2
88− sk `unifyTypes` replaced
89− unifyTypes' (ForAll ident ty1) ty2 = do
90− sk <- skolemize ident ty1
91− sk `unifyTypes` ty2
92− unifyTypes' ty f@(ForAll _ _) = f `unifyTypes` ty
93− unifyTypes' Number Number = return ()
94− unifyTypes' String String = return ()
95− unifyTypes' Boolean Boolean = return ()
96− unifyTypes' Array Array = return ()
97− unifyTypes' (Object row1) (Object row2) = row1 ~~ row2
98− unifyTypes' (Function args1 ret1) (Function args2 ret2) = do
99− guardWith "Function applied to incorrect number of args" $ length args1 == length args2
100− zipWithM_ unifyTypes args1 args2
101− ret1 `unifyTypes` ret2
102− unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
103− unifyTypes' (TypeConstructor c1) (TypeConstructor c2) = do
104− env <- getEnv
105− moduleName <- substCurrentModule `fmap` ask
106− guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (typeConstructorsAreEqual env moduleName c1 c2)
107− unifyTypes' (TypeApp t3 t4) (TypeApp t5 t6) = do
108− t3 `unifyTypes` t5
109− t4 `unifyTypes` t6
110− unifyTypes' (Skolem s1) (Skolem s2) | s1 == s2 = return ()
111− unifyTypes' r1@(RCons _ _ _) r2 = unifyRows r1 r2
112− unifyTypes' r1 r2@(RCons _ _ _) = unifyRows r1 r2
113− unifyTypes' r1@REmpty r2 = unifyRows r1 r2
114− unifyTypes' r1 r2@REmpty = unifyRows r1 r2
115− unifyTypes' t3 t4 = throwError $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
116−
117−-- |
118−-- Unify two rows, updating the current substitution
119−--
120−-- Common labels are first identified, and unified. Remaining labels and types are unified with a
121−-- trailing row unification variable, if appropriate, otherwise leftover labels result in a unification
122−-- error.
123−--
124−unifyRows :: Type -> Type -> Subst ()
125−unifyRows r1 r2 =
126− let
127− (s1, r1') = rowToList r1
128− (s2, r2') = rowToList r2
129− int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
130− sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
131− sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
132− in do
133− forM_ int (uncurry (~~))
134− unifyRows' sd1 r1' sd2 r2'
135− where
136− unifyRows' :: [(String, Type)] -> Type -> [(String, Type)] -> Type -> Subst ()
137− unifyRows' [] (TUnknown u) sd r = replace u (rowFromList (sd, r))
138− unifyRows' sd r [] (TUnknown u) = replace u (rowFromList (sd, r))
139− unifyRows' ((name, ty):row) r others u@(TUnknown un) = do
140− occursCheck un ty
141− forM_ row $ \(_, t) -> occursCheck un t
142− u' <- fresh
143− u ~~ RCons name ty u'
144− unifyRows' row r others u'
145− unifyRows' [] REmpty [] REmpty = return ()
146− unifyRows' [] (TypeVar v1) [] (TypeVar v2) | v1 == v2 = return ()
147− unifyRows' [] (Skolem s1) [] (Skolem s2) | s1 == s2 = return ()
148− unifyRows' sd3 r3 sd4 r4 = throwError $ "Cannot unify " ++ prettyPrintRow (rowFromList (sd3, r3)) ++ " with " ++ prettyPrintRow (rowFromList (sd4, r4)) ++ "."
149−
150−-- |
151−-- Ensure type constructors are equal after canonicalization
152−--
153−typeConstructorsAreEqual :: Environment -> ModuleName -> Qualified ProperName -> Qualified ProperName -> Bool
154−typeConstructorsAreEqual env moduleName = (==) `on` canonicalizeType moduleName env
155−
156−-- |
157−-- Infer the types of multiple mutually-recursive values, and return elaborated values including
158−-- type class dictionaries and type annotations.
159−--
160−typesOf :: ModuleName -> [(Ident, Value)] -> Check [(Ident, (Value, Type))]
161−typesOf moduleName vals = do
162− tys <- fmap (\(tys, s) -> map (\(ident, (val, ty)) -> (ident, (overTypes (apply s) val, apply s ty))) tys)
163− . runSubst (SubstContext moduleName) $ do
164− let es = map isTyped vals
165− typed = filter (isJust . snd . snd) es
166− untyped = filter (isNothing . snd . snd) es
167− typedDict = map (\(ident, (_, Just ty)) -> (ident, ty)) typed
168− untypedNames <- replicateM (length untyped) fresh
169− let untypedDict = zip (map fst untyped) untypedNames
170− dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ (map (id *** fst) typedDict) ++ untypedDict)
171− forM es $ \e -> do
172− triple@(_, (val, ty)) <- case e of
173− (ident, (val, Just (ty, checkType))) -> do
174− kind <- liftCheck $ kindOf moduleName ty
175− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
176− ty' <- replaceAllTypeSynonyms ty
177− val' <- bindNames dict $ if checkType then check val ty' else return val
178− return (ident, (val', ty'))
179− (ident, (val, Nothing)) -> do
180− TypedValue _ val' ty <- bindNames dict $ infer val
181− ty ~~ fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
182− return (ident, (val', ty))
183− when (moduleName == ModuleName (ProperName "Main") && fst e == Ident "main") $ do
184− [eff, a] <- replicateM 2 fresh
185− ty ~~ TypeApp (TypeApp (TypeConstructor (Qualified (Just (ModuleName (ProperName "Eff"))) (ProperName "Eff"))) eff) a
186− escapeCheck val ty
187− return triple
188− forM_ tys $ skolemEscapeCheck . snd . snd
189− forM tys $ \(ident, (val, ty)) -> do
190− val' <- replaceTypeClassDictionaries moduleName val
191− return (ident, (overTypes (desaturateAllTypeSynonyms . setifyAll) $ val'
192− , varIfUnknown . desaturateAllTypeSynonyms . setifyAll $ ty))
193−
194−-- |
195−-- Check if a value contains a type annotation
196−--
197−isTyped :: (Ident, Value) -> (Ident, (Value, Maybe (Type, Bool)))
198−isTyped (name, TypedValue checkType value ty) = (name, (value, Just (ty, checkType)))
199−isTyped (name, value) = (name, (value, Nothing))
200−
201−-- |
202−-- Map a function over type annotations appearing inside a value
203−--
204−overTypes :: (Type -> Type) -> Value -> Value
205−overTypes f = everywhere (mkT f)
206−
207−-- |
208−-- Replace type class dictionary placeholders with inferred type class dictionaries
209−--
210−replaceTypeClassDictionaries :: ModuleName -> Value -> Check Value
211−replaceTypeClassDictionaries mn = everywhereM (mkM go)
212− where
213− go (TypeClassDictionary constraint dicts) = entails mn dicts constraint
214− go other = return other
215−
216−-- |
217−-- Check that the current set of type class dictionaries entail the specified type class goal, and, if so,
218−-- return a type class dictionary reference.
219−--
220−entails :: ModuleName -> [TypeClassDictionaryInScope] -> (Qualified ProperName, Type) -> Check Value
221−entails moduleName context goal@(className, ty) = do
222− env <- getEnv
223− case go env goal of
224− [] -> throwError $ "No " ++ show className ++ " instance found for " ++ prettyPrintType ty
225− (dict : _) -> return dict
226− where
227− go env (className', ty') =
228− [ mkDictionary (canonicalizeDictionary tcd) args
229− | tcd <- context
230− , filterModule tcd
231− , typeConstructorsAreEqual env moduleName className' (tcdClassName tcd)
232− , subst <- maybeToList $ typeHeadsAreEqual moduleName env ty' (tcdInstanceType tcd)
233− , args <- solveSubgoals env subst (tcdDependencies tcd) ]
234− solveSubgoals _ _ Nothing = return Nothing
235− solveSubgoals env subst (Just subgoals) = do
236− dict <- mapM (go env) (replaceAllTypeVars subst subgoals)
237− return $ Just dict
238− mkDictionary fnName args = maybe id (flip App) args $ (Var fnName)
239− filterModule (TypeClassDictionaryInScope { tcdName = Qualified (Just mn) _ }) | mn == moduleName = True
240− filterModule (TypeClassDictionaryInScope { tcdName = Qualified Nothing _ }) = True
241− filterModule _ = False
242− canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDRegular, tcdName = nm }) = nm
243− canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDAlias nm }) = nm
244−
245−-- |
246−-- Check whether the type heads of two types are equal (for the purposes of type class dictionary lookup),
247−-- and return a substitution from type variables to types which makes the type heads unify.
248−--
249−typeHeadsAreEqual :: ModuleName -> Environment -> Type -> Type -> Maybe [(String, Type)]
250−typeHeadsAreEqual _ _ String String = Just []
251−typeHeadsAreEqual _ _ Number Number = Just []
252−typeHeadsAreEqual _ _ Boolean Boolean = Just []
253−typeHeadsAreEqual _ _ (Skolem s1) (Skolem s2) | s1 == s2 = Just []
254−typeHeadsAreEqual _ _ Array Array = Just []
255−typeHeadsAreEqual m e (TypeConstructor c1) (TypeConstructor c2) | typeConstructorsAreEqual e m c1 c2 = Just []
256−typeHeadsAreEqual m e (TypeApp h1 (TypeVar v)) (TypeApp h2 arg) = (:) (v, arg) <$> typeHeadsAreEqual m e h1 h2
257−typeHeadsAreEqual m e t1@(TypeApp _ _) t2@(TypeApp _ (TypeVar _)) = typeHeadsAreEqual m e t2 t1
258−typeHeadsAreEqual _ _ _ _ = Nothing
259−
260−-- |
261−-- Ensure unsolved unification variables do not escape
262−--
263−escapeCheck :: Value -> Type -> Subst ()
264−escapeCheck value ty = do
265− subst <- substSubst <$> getSubstState
266− let visibleUnknowns = nub $ unknowns $ apply subst ty
267− let allUnknowns = findAllTypes value
268− forM_ allUnknowns $ \t -> do
269− let unsolvedUnknowns = nub . unknowns $ apply subst t
270− guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
271−
272−-- |
273−-- Find all type annotations occuring inside a value
274−--
275−findAllTypes :: Value -> [Type]
276−findAllTypes = everything (++) (mkQ [] go)
277− where
278− go (TypedValue _ _ ty) = [ty]
279− go _ = []
280−
281−-- |
282−-- Ensure skolem variables do not escape their scope
283−--
284−skolemEscapeCheck :: Type -> Check ()
285−skolemEscapeCheck ty =
286− case something (mkQ Nothing findSkolems) ty of
287− Nothing -> return ()
288− Just _ -> throwError $ "Skolem variables cannot escape. Consider adding a type signature." ++ show ty
289− where
290− findSkolems (Skolem _) = return ()
291− findSkolems _ = mzero
292−
293−-- |
294−-- Ensure a row contains no duplicate labels
295−--
296−setify :: Type -> Type
297−setify = rowFromList . first (M.toList . M.fromList) . rowToList
298−
299−-- |
300−-- \"Setify\" all rows occuring inside a value
301−--
302−setifyAll :: (D.Data d) => d -> d
303−setifyAll = everywhere (mkT setify)
304−
305−-- |
306−-- Replace outermost unsolved unification variables with named type variables
307−--
308−varIfUnknown :: Type -> Type
309−varIfUnknown ty =
310− let unks = nub $ unknowns ty
311− toName = (:) 't' . show
312− ty' = everywhere (mkT typeToVar) $ ty
313− typeToVar :: Type -> Type
314− typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
315− typeToVar t = t
316− in mkForAll (sort . map toName $ unks) ty'
317−
318−-- |
319−-- Replace named type variables with types
320−--
321−replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
322−replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
323−
324−-- |
325−-- Replace named type variables with new unification variables
326−--
327−replaceAllVarsWithUnknowns :: Type -> Subst Type
328−replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
329−replaceAllVarsWithUnknowns ty = return ty
330−
331−-- |
332−-- Replace a single type variable with a new unification variable
333−--
334−replaceVarWithUnknown :: String -> Type -> Subst Type
335−replaceVarWithUnknown ident ty = do
336− tu <- fresh
337− return $ replaceTypeVars ident tu $ ty
338−
339−-- |
340−-- Replace fully applied type synonyms with the @SaturatedTypeSynonym@ data constructor, which helps generate
341−-- better error messages during unification.
342−--
343−replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadReader SubstContext m, MonadError String m) => (D.Data d) => d -> m d
344−replaceAllTypeSynonyms d = do
345− env <- getEnv
346− moduleName <- substCurrentModule <$> ask
347− let syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
348− either throwError return $ saturateAllTypeSynonyms env moduleName syns d
349−
350−-- |
351−-- \"Desaturate\" @SaturatedTypeSynonym@s
352−--
353−desaturateAllTypeSynonyms :: (D.Data d) => d -> d
354−desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
355− where
356− replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
357− replaceSaturatedTypeSynonym t = t
358−
359−-- |
360−-- Replace a type synonym and its arguments with the aliased type
361−--
362−expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Type
363−expandTypeSynonym name args = do
364− env <- getEnv
365− moduleName <- substCurrentModule `fmap` ask
366− case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
367− Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
368− Nothing -> error "Type synonym was not defined"
369−
370−-- |
371−-- Ensure a set of property names and value does not contain duplicate labels
372−--
373−ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
374−ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
375−
376−-- |
377−-- Infer a type for a value, rethrowing any error to provide a more useful error message
378−--
379−infer :: Value -> Subst Value
380−infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ infer' val
381−
382−-- |
383−-- Infer a type for a value
384−--
385−infer' :: Value -> Subst Value
386−infer' v@(NumericLiteral _) = return $ TypedValue True v Number
387−infer' v@(StringLiteral _) = return $ TypedValue True v String
388−infer' v@(BooleanLiteral _) = return $ TypedValue True v Boolean
389−infer' (ArrayLiteral vals) = do
390− ts <- mapM infer vals
391− els <- fresh
392− forM_ ts $ \(TypedValue _ _ t) -> els ~~ TypeApp Array t
393− return $ TypedValue True (ArrayLiteral ts) els
394−infer' (Unary op val) = do
395− v <- infer val
396− inferUnary op v
397−infer' (Binary op left right) = do
398− v1 <- infer left
399− v2 <- infer right
400− inferBinary op v1 v2
401−infer' (ObjectLiteral ps) = do
402− ensureNoDuplicateProperties ps
403− ts <- mapM (infer . snd) ps
404− let fields = zipWith (\name (TypedValue _ _ t) -> (name, t)) (map fst ps) ts
405− ty = Object $ rowFromList (fields, REmpty)
406− return $ TypedValue True (ObjectLiteral (zip (map fst ps) ts)) ty
407−infer' (ObjectUpdate o ps) = do
408− ensureNoDuplicateProperties ps
409− row <- fresh
410− newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
411− let newTys = map (\(name, TypedValue _ _ ty) -> (name, ty)) newVals
412− oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
413− o' <- check o $ Object $ rowFromList (oldTys, row)
414− return $ TypedValue True (ObjectUpdate o' newVals) $ Object $ rowFromList (newTys, row)
415−infer' (Indexer index val) = do
416− el <- fresh
417− index' <- check index Number
418− val' <- check val (TypeApp Array el)
419− return $ TypedValue True (Indexer (TypedValue True index' Number) (TypedValue True val' (TypeApp Array el))) el
420−infer' (Accessor prop val) = do
421− typed@(TypedValue _ _ objTy) <- infer val
422− propTy <- inferProperty objTy prop
423− case propTy of
424− Nothing -> do
425− field <- fresh
426− rest <- fresh
427− objTy `subsumes` Object (RCons prop field rest)
428− return $ TypedValue True (Accessor prop typed) field
429− Just ty -> return $ TypedValue True (Accessor prop typed) ty
430−infer' (Abs args ret) = do
431− ts <- replicateM (length args) fresh
432− moduleName <- substCurrentModule <$> ask
433− bindLocalVariables moduleName (zip args ts) $ do
434− body@(TypedValue _ _ bodyTy) <- infer' ret
435− return $ TypedValue True (Abs args body) $ Function ts bodyTy
436−infer' (App f args) = do
437− f'@(TypedValue _ _ ft) <- infer f
438− ret <- fresh
439− app <- checkFunctionApplication f' ft args ret
440− return $ TypedValue True app ret
441−infer' (Var var) = do
442− moduleName <- substCurrentModule <$> ask
443− ty <- lookupVariable moduleName var
444− ty' <- replaceAllTypeSynonyms ty
445− case ty' of
446− ConstrainedType constraints _ -> do
447− env <- getEnv
448− dicts <- getTypeClassDictionaries
449− return $ TypedValue True (App (Var var) (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) ty'
450− _ -> return $ TypedValue True (Var var) ty'
451−infer' (Block ss) = do
452− ret <- fresh
453− (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
454− guardWith "Block is missing a return statement" allCodePathsReturn
455− return $ TypedValue True (Block ss') ret
456−infer' v@(Constructor c) = do
457− env <- getEnv
458− moduleName <- substCurrentModule `fmap` ask
459− case M.lookup (qualify moduleName c) (dataConstructors env) of
460− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
461− Just (ty, _) -> do ty' <- replaceAllTypeSynonyms ty
462− return $ TypedValue True v ty'
463−infer' (Case vals binders) = do
464− ts <- mapM infer vals
465− ret <- fresh
466− binders' <- checkBinders (map (\(TypedValue _ _ t) -> t) ts) ret binders
467− return $ TypedValue True (Case ts binders') ret
468−infer' (IfThenElse cond th el) = do
469− cond' <- check cond Boolean
470− v2@(TypedValue _ _ t2) <- infer th
471− v3@(TypedValue _ _ t3) <- infer el
472− t2 ~~ t3
473− return $ TypedValue True (IfThenElse cond' v2 v3) t2
474−infer' (TypedValue checkType val ty) = do
475− moduleName <- substCurrentModule <$> ask
476− kind <- liftCheck $ kindOf moduleName ty
477− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
478− ty' <- replaceAllTypeSynonyms ty
479− val' <- if checkType then check val ty' else return val
480− return $ TypedValue True val' ty
481−infer' _ = error "Invalid argument to infer"
482−
483−-- |
484−-- Infer the type of a property inside a record with a given type
485−--
486−inferProperty :: Type -> String -> Subst (Maybe Type)
487−inferProperty (Object row) prop = do
488− let (props, _) = rowToList row
489− return $ lookup prop props
490−inferProperty (SaturatedTypeSynonym name args) prop = do
491− replaced <- expandTypeSynonym name args
492− inferProperty replaced prop
493−inferProperty (ForAll ident ty) prop = do
494− replaced <- replaceVarWithUnknown ident ty
495− inferProperty replaced prop
496−inferProperty _ _ = return Nothing
497−
498−-- |
499−-- Infer the type of a unary operator application
500−--
501−inferUnary :: UnaryOperator -> Value -> Subst Value
502−inferUnary op (TypedValue _ val valTy) =
503− case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
504− (valTy', resTy) -> do
505− valTy' ~~ valTy
506− return $ TypedValue True (Unary op val) resTy
507−inferUnary _ _ = error "Invalid arguments to inferUnary"
508−
509−-- |
510−-- Check the type of a unary operator application
511−--
512−checkUnary :: UnaryOperator -> Value -> Type -> Subst Value
513−checkUnary op val res =
514− case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
515− (valTy, resTy) -> do
516− res ~~ resTy
517− val' <- check val valTy
518− return $ Unary op val'
519−
520−-- |
521−-- Built-in unary operators
522−--
523−unaryOps :: [(UnaryOperator, (Type, Type))]
524−unaryOps = [ (Negate, (Number, Number))
525− , (Not, (Boolean, Boolean))
526− , (BitwiseNot, (Number, Number))
527− ]
528−
529−-- |
530−-- Infer the type of a binary operator application
531−--
532−inferBinary :: BinaryOperator -> Value -> Value -> Subst Value
533−inferBinary op left@(TypedValue _ _ leftTy) right@(TypedValue _ _ rightTy) | isEqualityTest op = do
534− leftTy ~~ rightTy
535− return $ TypedValue True (Binary op left right) Boolean
536−inferBinary op left@(TypedValue _ _ leftTy) right@(TypedValue _ _ rightTy) =
537− case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
538− (valTy, resTy) -> do
539− leftTy ~~ valTy
540− rightTy ~~ valTy
541− return $ TypedValue True (Binary op left right) resTy
542−inferBinary _ _ _ = error "Invalid arguments to inferBinary"
543−
544−-- |
545−-- Check the type of a binary operator application
546−--
547−checkBinary :: BinaryOperator -> Value -> Value -> Type -> Subst Value
548−checkBinary op left right res | isEqualityTest op = do
549− res ~~ Boolean
550− left'@(TypedValue _ _ t1) <- infer left
551− right'@(TypedValue _ _ t2) <- infer right
552− t1 ~~ t2
553− return $ Binary op left' right'
554−checkBinary op left right res =
555− case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
556− (valTy, resTy) -> do
557− res ~~ resTy
558− left' <- check left valTy
559− right' <- check right valTy
560− return $ Binary op left' right'
561−
562−-- |
563−-- Check if a @BinaryOperator@ is an equality test
564−--
565−isEqualityTest :: BinaryOperator -> Bool
566−isEqualityTest EqualTo = True
567−isEqualityTest NotEqualTo = True
568−isEqualityTest _ = False
569−
570−-- |
571−-- Built-in binary operators
572−--
573−binaryOps :: [(BinaryOperator, (Type, Type))]
574−binaryOps = [ (Add, (Number, Number))
575− , (Subtract, (Number, Number))
576− , (Multiply, (Number, Number))
577− , (Divide, (Number, Number))
578− , (Modulus, (Number, Number))
579− , (BitwiseAnd, (Number, Number))
580− , (BitwiseOr, (Number, Number))
581− , (BitwiseXor, (Number, Number))
582− , (ShiftRight, (Number, Number))
583− , (ZeroFillShiftRight, (Number, Number))
584− , (And, (Boolean, Boolean))
585− , (Or, (Boolean, Boolean))
586− , (Concat, (String, String))
587− , (Modulus, (Number, Number))
588− , (LessThan, (Number, Boolean))
589− , (LessThanOrEqualTo, (Number, Boolean))
590− , (GreaterThan, (Number, Boolean))
591− , (GreaterThanOrEqualTo, (Number, Boolean))
592− ]
593−
594−-- |
595−-- Infer the types of variables brought into scope by a binder
596−--
597−inferBinder :: Type -> Binder -> Subst (M.Map Ident Type)
598−inferBinder _ NullBinder = return M.empty
599−inferBinder val (StringBinder _) = val ~~ String >> return M.empty
600−inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
601−inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
602−inferBinder val (VarBinder name) = return $ M.singleton name val
603−inferBinder val (NullaryBinder ctor) = do
604− env <- getEnv
605− moduleName <- substCurrentModule <$> ask
606− case M.lookup (qualify moduleName ctor) (dataConstructors env) of
607− Just (ty, _) -> do
608− ty `subsumes` val
609− return M.empty
610− _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
611−inferBinder val (UnaryBinder ctor binder) = do
612− env <- getEnv
613− moduleName <- substCurrentModule <$> ask
614− case M.lookup (qualify moduleName ctor) (dataConstructors env) of
615− Just (ty, _) -> do
616− fn <- replaceAllVarsWithUnknowns ty
617− case fn of
618− Function [obj] ret -> do
619− val `subsumes` ret
620− inferBinder obj binder
621− _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
622− _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
623−inferBinder val (ObjectBinder props) = do
624− row <- fresh
625− rest <- fresh
626− m1 <- inferRowProperties row rest props
627− val ~~ Object row
628− return m1
629− where
630− inferRowProperties :: Type -> Type -> [(String, Binder)] -> Subst (M.Map Ident Type)
631− inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
632− inferRowProperties nrow row ((name, binder):binders) = do
633− propTy <- fresh
634− m1 <- inferBinder propTy binder
635− m2 <- inferRowProperties nrow (RCons name propTy row) binders
636− return $ m1 `M.union` m2
637−inferBinder val (ArrayBinder binders) = do
638− el <- fresh
639− m1 <- M.unions <$> mapM (inferBinder el) binders
640− val ~~ TypeApp Array el
641− return m1
642−inferBinder val (ConsBinder headBinder tailBinder) = do
643− el <- fresh
644− m1 <- inferBinder el headBinder
645− m2 <- inferBinder val tailBinder
646− val ~~ TypeApp Array el
647− return $ m1 `M.union` m2
648−inferBinder val (NamedBinder name binder) = do
649− m <- inferBinder val binder
650− return $ M.insert name val m
651−
652−-- |
653−-- Check the types of the return values in a set of binders in a case statement
654−--
655−checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> Subst [([Binder], Maybe Guard, Value)]
656−checkBinders _ _ [] = return []
657−checkBinders nvals ret ((binders, grd, val):bs) = do
658− moduleName <- substCurrentModule <$> ask
659− m1 <- M.unions <$> zipWithM inferBinder nvals binders
660− r <- bindLocalVariables moduleName (M.toList m1) $ do
661− val' <- check val ret
662− case grd of
663− Nothing -> return (binders, Nothing, val')
664− Just g -> do
665− g' <- check g Boolean
666− return (binders, Just g', val')
667− rs <- checkBinders nvals ret bs
668− return $ r : rs
669−
670−-- |
671−-- Check that a local variable name is not already used
672−--
673−assignVariable :: Ident -> Subst ()
674−assignVariable name = do
675− env <- checkEnv <$> get
676− moduleName <- substCurrentModule <$> ask
677− case M.lookup (moduleName, name) (names env) of
678− Just (_, LocalVariable) -> throwError $ "Variable with name " ++ show name ++ " already exists."
679− _ -> return ()
680−
681−-- |
682−-- Check the type of the return values of a statement, returning whether or not the statement returns on
683−-- all code paths
684−--
685−checkStatement :: M.Map Ident Type -> Type -> Statement -> Subst (Bool, M.Map Ident Type, Statement)
686−checkStatement mass _ (VariableIntroduction name val) = do
687− assignVariable name
688− val'@(TypedValue _ _ t) <- infer val
689− return (False, M.insert name t mass, VariableIntroduction name val')
690−checkStatement mass _ (Assignment ident val) = do
691− val'@(TypedValue _ _ t) <- infer val
692− case M.lookup ident mass of
693− Nothing -> throwError $ "No local variable with name " ++ show ident
694− Just ty -> do t ~~ ty
695− return (False, mass, Assignment ident val')
696−checkStatement mass ret (While val inner) = do
697− val' <- check val Boolean
698− (allCodePathsReturn, _, inner') <- checkBlock mass ret inner
699− return (allCodePathsReturn, mass, While val' inner')
700−checkStatement mass ret (If ifst) = do
701− (allCodePathsReturn, ifst') <- checkIfStatement mass ret ifst
702− return (allCodePathsReturn, mass, If ifst')
703−checkStatement mass ret (For ident start end inner) = do
704− moduleName <- substCurrentModule <$> ask
705− assignVariable ident
706− start' <- check start Number
707− end' <- check end Number
708− (allCodePathsReturn, _, inner') <- bindLocalVariables moduleName [(ident, Number)] $ checkBlock mass ret inner
709− return (allCodePathsReturn, mass, For ident start' end' inner')
710−checkStatement mass ret (Return val) = do
711− val' <- check val ret
712− return (True, mass, Return val')
713−
714−-- |
715−-- Check the type of an if-then-else statement
716−--
717−checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> Subst (Bool, IfStatement)
718−checkIfStatement mass ret (IfStatement val thens Nothing) = do
719− val' <- check val Boolean
720− (_, _, thens') <- checkBlock mass ret thens
721− return (False, IfStatement val' thens' Nothing)
722−checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
723− val' <- check val Boolean
724− (allCodePathsReturn1, _, thens') <- checkBlock mass ret thens
725− (allCodePathsReturn2, elses') <- checkElseStatement mass ret elses
726− return (allCodePathsReturn1 && allCodePathsReturn2, IfStatement val' thens' (Just elses'))
727−
728−-- |
729−-- Check the type of an else statement
730−--
731−checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> Subst (Bool, ElseStatement)
732−checkElseStatement mass ret (Else elses) = do
733− (allCodePathsReturn, _, elses') <- checkBlock mass ret elses
734− return (allCodePathsReturn, Else elses')
735−checkElseStatement mass ret (ElseIf ifst) = (id *** ElseIf) <$> checkIfStatement mass ret ifst
736−
737−-- |
738−-- Check the type of the return value of a block of statements
739−--
740−checkBlock :: M.Map Ident Type -> Type -> [Statement] -> Subst (Bool, M.Map Ident Type, [Statement])
741−checkBlock mass _ [] = return (False, mass, [])
742−checkBlock mass ret (s:ss) = do
743− moduleName <- substCurrentModule <$> ask
744− (b1, mass1, s') <- checkStatement mass ret s
745− bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
746− (True, []) -> return (True, mass1, [s'])
747− (True, _) -> throwError "Unreachable code"
748− (False, ss') -> do
749− (b, m, ss'') <- checkBlock mass1 ret ss'
750− return (b, m, s':ss'')
751−
752−-- |
753−-- Skolemize a type variable by replacing its instances with fresh skolem constants
754−--
755−skolemize :: String -> Type -> Subst Type
756−skolemize ident ty = do
757− tsk <- Skolem <$> fresh'
758− return $ replaceTypeVars ident tsk ty
759−
760−-- |
761−-- Check the type of a value, rethrowing errors to provide a better error message
762−--
763−check :: Value -> Type -> Subst Value
764−check val ty = rethrow errorMessage $ check' val ty
765− where
766− errorMessage msg =
767− "Error checking type of term " ++
768− prettyPrintValue val ++
769− " against type " ++
770− prettyPrintType ty ++
771− ":\n" ++
772− msg
773−
774−-- |
775−-- Check the type of a value
776−--
777−check' :: Value -> Type -> Subst Value
778−check' val (ForAll idents ty) = do
779− sk <- skolemize idents ty
780− check val sk
781−check' val (ConstrainedType constraints ty) = do
782− env <- getEnv
783− moduleName <- substCurrentModule <$> ask
784− dictNames <- flip mapM constraints $ \(Qualified _ (ProperName className), _) -> do
785− n <- liftCheck freshDictionaryName
786− return $ Ident $ "__dict_" ++ className ++ "_" ++ show n
787− val' <- withTypeClassDictionaries (zipWith (\name (className, instanceTy) ->
788− TypeClassDictionaryInScope name className instanceTy Nothing TCDRegular) (map (Qualified Nothing) dictNames)
789− (qualifyAllUnqualifiedNames moduleName env constraints)) $
790− check val ty
791− return $ Abs dictNames val'
792−check' val u@(TUnknown _) = do
793− val'@(TypedValue _ _ ty) <- infer val
794− -- Don't unify an unknown with an inferred polytype
795− ty' <- replaceAllVarsWithUnknowns ty
796− ty' ~~ u
797− return val'
798−check' v@(NumericLiteral _) Number = return v
799−check' v@(StringLiteral _) String = return v
800−check' v@(BooleanLiteral _) Boolean = return v
801−check' (Unary op val) ty = checkUnary op val ty
802−check' (Binary op left right) ty = checkBinary op left right ty
803−check' (ArrayLiteral vals) (TypeApp Array ty) = ArrayLiteral <$> forM vals (\val -> check val ty)
804−check' (Indexer index vals) ty = do
805− index' <- check index Number
806− vals' <- check vals (TypeApp Array ty)
807− return $ Indexer index' vals'
808−check' (Abs args ret) (Function argTys retTy) = do
809− moduleName <- substCurrentModule <$> ask
810− guardWith "Incorrect number of function arguments" (length args == length argTys)
811− ret' <- bindLocalVariables moduleName (zip args argTys) $ check ret retTy
812− return $ Abs args ret'
813−check' (App f args) ret = do
814− f'@(TypedValue _ _ ft) <- infer f
815− app <- checkFunctionApplication f' ft args ret
816− return $ app
817−check' (Var var) ty = do
818− moduleName <- substCurrentModule <$> ask
819− ty1 <- lookupVariable moduleName var
820− repl <- replaceAllTypeSynonyms ty1
821− repl `subsumes` ty
822− return $ Var var
823−check' (TypedValue checkType val ty1) ty2 = do
824− moduleName <- substCurrentModule <$> ask
825− kind <- liftCheck $ kindOf moduleName ty1
826− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
827− ty1 `subsumes` ty2
828− val' <- if checkType then check val ty1 else return val
829− return $ TypedValue True val' ty1
830−check' (Case vals binders) ret = do
831− vals' <- mapM infer vals
832− let ts = map (\(TypedValue _ _ t) -> t) vals'
833− binders' <- checkBinders ts ret binders
834− return $ Case vals' binders'
835−check' (IfThenElse cond th el) ty = do
836− cond' <- check cond Boolean
837− th' <- check th ty
838− el' <- check el ty
839− return $ IfThenElse cond' th' el'
840−check' (ObjectLiteral ps) (Object row) = do
841− ensureNoDuplicateProperties ps
842− ps' <- checkProperties ps row False
843− return $ ObjectLiteral ps'
844−check' (ObjectUpdate obj ps) (Object row) = do
845− ensureNoDuplicateProperties ps
846− us <- zip (map fst ps) <$> replicateM (length ps) fresh
847− let (propsToCheck, rest) = rowToList row
848− propsToRemove = map fst ps
849− remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
850− obj' <- check obj (Object (rowFromList (us ++ remainingProps, rest)))
851− ps' <- checkProperties ps row True
852− return $ ObjectUpdate obj' ps'
853−check' (Accessor prop val) ty = do
854− rest <- fresh
855− val' <- check val (Object (RCons prop ty rest))
856− return $ Accessor prop val'
857−check' (Block ss) ret = do
858− (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
859− guardWith "Block is missing a return statement" allCodePathsReturn
860− return $ Block ss'
861−check' (Constructor c) ty = do
862− env <- getEnv
863− moduleName <- substCurrentModule <$> ask
864− case M.lookup (qualify moduleName c) (dataConstructors env) of
865− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
866− Just (ty1, _) -> do
867− repl <- replaceAllTypeSynonyms ty1
868− repl `subsumes` ty
869− return $ Constructor c
870−check' val (SaturatedTypeSynonym name args) = do
871− ty <- expandTypeSynonym name args
872− check val ty
873−check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
874−
875−-- |
876−-- Check the type of a collection of named record fields
877−--
878−-- The @lax@ parameter controls whether or not every record member has to be provided. For object updates, this is not the case.
879−--
880−checkProperties :: [(String, Value)] -> Type -> Bool -> Subst [(String, Value)]
881−checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
882− go [] [] REmpty = return []
883− go [] [] u@(TUnknown _) = do u ~~ REmpty
884− return []
885− go [] [] (Skolem _) | lax = return []
886− go [] ((p, _): _) _ | lax = return []
887− | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
888− go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
889− go ((p,v):ps') [] u@(TUnknown _) = do
890− v'@(TypedValue _ _ ty) <- infer v
891− rest <- fresh
892− u ~~ RCons p ty rest
893− ps'' <- go ps' [] rest
894− return $ (p, v') : ps''
895− go ((p,v):ps') ts r =
896− case lookup p ts of
897− Nothing -> do
898− v'@(TypedValue _ _ ty) <- infer v
899− rest <- fresh
900− r ~~ RCons p ty rest
901− ps'' <- go ps' ts rest
902− return $ (p, v') : ps''
903− Just ty -> do
904− v' <- check v ty
905− ps'' <- go ps' (delete (p, ty) ts) r
906− return $ (p, v') : ps''
907− go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
908−
909−-- |
910−-- Check the type of a function application, rethrowing errors to provide a better error message
911−--
912−checkFunctionApplication :: Value -> Type -> [Value] -> Type -> Subst Value
913−checkFunctionApplication fn fnTy args ret = rethrow errorMessage $ checkFunctionApplication' fn fnTy args ret
914− where
915− errorMessage msg = "Error applying function of type "
916− ++ prettyPrintType fnTy
917− ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
918− ++ ":\n" ++ msg
919−
920−-- |
921−-- Check the type of a function application
922−--
923−checkFunctionApplication' :: Value -> Type -> [Value] -> Type -> Subst Value
924−checkFunctionApplication' fn (Function argTys retTy) args ret = do
925− guardWith "Incorrect number of function arguments" (length args == length argTys)
926− args' <- zipWithM check args argTys
927− retTy `subsumes` ret
928− return $ App fn args'
929−checkFunctionApplication' fn (ForAll ident ty) args ret = do
930− replaced <- replaceVarWithUnknown ident ty
931− checkFunctionApplication fn replaced args ret
932−checkFunctionApplication' fn u@(TUnknown _) args ret = do
933− args' <- mapM (\arg -> infer arg >>= \(TypedValue _ v t) -> TypedValue True v <$> replaceAllVarsWithUnknowns t) args
934− let tys = map (\(TypedValue _ _ t) -> t) args'
935− u ~~ Function tys ret
936− return $ App fn args'
937−checkFunctionApplication' fn (SaturatedTypeSynonym name tyArgs) args ret = do
938− ty <- expandTypeSynonym name tyArgs
939− checkFunctionApplication fn ty args ret
940−checkFunctionApplication' fn (ConstrainedType constraints fnTy) args ret = do
941− env <- getEnv
942− dicts <- getTypeClassDictionaries
943− moduleName <- substCurrentModule <$> ask
944− checkFunctionApplication' (App fn (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) fnTy args ret
945−checkFunctionApplication' _ fnTy args ret = throwError $ "Applying a function of type "
946− ++ prettyPrintType fnTy
947− ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
948− ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
949−
950−-- |
951−-- Check whether one type subsumes another, rethrowing errors to provide a better error message
952−--
953−subsumes :: Type -> Type -> Subst ()
954−subsumes ty1 ty2 = rethrow errorMessage $ subsumes' ty1 ty2
955− where
956− errorMessage msg = "Error checking that type "
957− ++ prettyPrintType ty1
958− ++ " subsumes type "
959− ++ prettyPrintType ty2
960− ++ ":\n" ++ msg
961−
962−-- |
963−-- Check whether one type subsumes another
964−--
965−subsumes' :: Type -> Type -> Subst ()
966−subsumes' (ForAll ident ty1) ty2 = do
967− replaced <- replaceVarWithUnknown ident ty1
968− replaced `subsumes` ty2
969−subsumes' (Function args1 ret1) (Function args2 ret2) = do
970− zipWithM_ subsumes args2 args1
971− ret1 `subsumes` ret2
972−subsumes' ty1 ty2 = ty1 ~~ ty2
973−