@@ -1,992 +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−{-
24− The following functions represent the corresponding type checking judgements:
25−
26− infer
27− Synthesize a type for a value
28−
29− check
30− Check a value has a given type
31−
32− checkProperties
33− Check an object with a given type contains specified properties
34−
35− checkFunctionApplication
36− Check a function of a given type returns a value of another type when applied to its arguments
37−
38− subsumes
39− Check a type subsumes another type
40−-}
41−
42−import Data.List
43−import Data.Maybe (maybeToList, isNothing, isJust, fromMaybe)
44−import qualified Data.Data as D
45−import Data.Generics
46− (mkM, everywhereM, everything, mkT, something, everywhere, mkQ)
47−
48−import Language.PureScript.Values
49−import Language.PureScript.Types
50−import Language.PureScript.Kinds
51−import Language.PureScript.Names
52−import Language.PureScript.TypeChecker.Monad
53−import Language.PureScript.TypeChecker.Kinds
54−import Language.PureScript.TypeChecker.Synonyms
55−import Language.PureScript.Pretty
56−import Language.PureScript.Unknown
57−
58−import Control.Monad.State
59−import Control.Monad.Error
60−import Control.Monad.Reader
61−
62−import Control.Applicative
63−import Control.Arrow (Arrow(..))
64−
65−import qualified Data.Map as M
66−import Data.Function (on)
67−
68−instance Unifiable Type where
69− unknown = TUnknown
70− isUnknown (TUnknown u) = Just u
71− isUnknown _ = Nothing
72− (~~) = unifyTypes
73− apply s (TUnknown u) = runSubstitution s u
74− apply s (SaturatedTypeSynonym name tys) = SaturatedTypeSynonym name $ map (apply s) tys
75− apply s (ForAll idents ty) = ForAll idents $ apply s ty
76− apply s (Object r) = Object (apply s r)
77− apply s (Function args ret) = Function (map (apply s) args) (apply s ret)
78− apply s (TypeApp t1 t2) = TypeApp (apply s t1) (apply s t2)
79− apply s (RCons name ty r) = RCons name (apply s ty) (apply s r)
80− apply _ t = t
81− unknowns (TUnknown (Unknown u)) = [u]
82− unknowns (SaturatedTypeSynonym _ tys) = concatMap unknowns tys
83− unknowns (ForAll _ ty) = unknowns ty
84− unknowns (Object r) = unknowns r
85− unknowns (Function args ret) = concatMap unknowns args ++ unknowns ret
86− unknowns (TypeApp t1 t2) = unknowns t1 ++ unknowns t2
87− unknowns (RCons _ ty r) = unknowns ty ++ unknowns r
88− unknowns _ = []
89−
90−-- |
91−-- Unify two types, updating the current substitution
92−--
93−unifyTypes :: Type -> Type -> Subst ()
94−unifyTypes t1 t2 = rethrow (\e -> "Error unifying type " ++ prettyPrintType t1 ++ " with type " ++ prettyPrintType t2 ++ ":\n" ++ e) $ do
95− unifyTypes' t1 t2
96− where
97− unifyTypes' (TUnknown u1) (TUnknown u2) | u1 == u2 = return ()
98− unifyTypes' (TUnknown u) t = replace u t
99− unifyTypes' t (TUnknown u) = replace u t
100− unifyTypes' (SaturatedTypeSynonym name args) ty = do
101− ty1 <- expandTypeSynonym name args
102− ty1 `unifyTypes` ty
103− unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
104− unifyTypes' (ForAll ident1 ty1) (ForAll ident2 ty2) = do
105− sk <- skolemize ident1 ty1
106− replaced <- replaceVarWithUnknown ident2 ty2
107− sk `unifyTypes` replaced
108− unifyTypes' (ForAll ident ty1) ty2 = do
109− sk <- skolemize ident ty1
110− sk `unifyTypes` ty2
111− unifyTypes' ty f@(ForAll _ _) = f `unifyTypes` ty
112− unifyTypes' Number Number = return ()
113− unifyTypes' String String = return ()
114− unifyTypes' Boolean Boolean = return ()
115− unifyTypes' Array Array = return ()
116− unifyTypes' (Object row1) (Object row2) = row1 ~~ row2
117− unifyTypes' (Function args1 ret1) (Function args2 ret2) = do
118− guardWith "Function applied to incorrect number of args" $ length args1 == length args2
119− zipWithM_ unifyTypes args1 args2
120− ret1 `unifyTypes` ret2
121− unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
122− unifyTypes' (TypeConstructor c1) (TypeConstructor c2) = do
123− env <- getEnv
124− moduleName <- substCurrentModule `fmap` ask
125− guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (typeConstructorsAreEqual env moduleName c1 c2)
126− unifyTypes' (TypeApp t3 t4) (TypeApp t5 t6) = do
127− t3 `unifyTypes` t5
128− t4 `unifyTypes` t6
129− unifyTypes' (Skolem s1) (Skolem s2) | s1 == s2 = return ()
130− unifyTypes' r1@(RCons _ _ _) r2 = unifyRows r1 r2
131− unifyTypes' r1 r2@(RCons _ _ _) = unifyRows r1 r2
132− unifyTypes' r1@REmpty r2 = unifyRows r1 r2
133− unifyTypes' r1 r2@REmpty = unifyRows r1 r2
134− unifyTypes' t3 t4 = throwError $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
135−
136−-- |
137−-- Unify two rows, updating the current substitution
138−--
139−-- Common labels are first identified, and unified. Remaining labels and types are unified with a
140−-- trailing row unification variable, if appropriate, otherwise leftover labels result in a unification
141−-- error.
142−--
143−unifyRows :: Type -> Type -> Subst ()
144−unifyRows r1 r2 =
145− let
146− (s1, r1') = rowToList r1
147− (s2, r2') = rowToList r2
148− int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
149− sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
150− sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
151− in do
152− forM_ int (uncurry (~~))
153− unifyRows' sd1 r1' sd2 r2'
154− where
155− unifyRows' :: [(String, Type)] -> Type -> [(String, Type)] -> Type -> Subst ()
156− unifyRows' [] (TUnknown u) sd r = replace u (rowFromList (sd, r))
157− unifyRows' sd r [] (TUnknown u) = replace u (rowFromList (sd, r))
158− unifyRows' ((name, ty):row) r others u@(TUnknown un) = do
159− occursCheck un ty
160− forM_ row $ \(_, t) -> occursCheck un t
161− u' <- fresh
162− u ~~ RCons name ty u'
163− unifyRows' row r others u'
164− unifyRows' [] REmpty [] REmpty = return ()
165− unifyRows' [] (TypeVar v1) [] (TypeVar v2) | v1 == v2 = return ()
166− unifyRows' [] (Skolem s1) [] (Skolem s2) | s1 == s2 = return ()
167− unifyRows' sd3 r3 sd4 r4 = throwError $ "Cannot unify " ++ prettyPrintRow (rowFromList (sd3, r3)) ++ " with " ++ prettyPrintRow (rowFromList (sd4, r4)) ++ "."
168−
169−-- |
170−-- Ensure type constructors are equal after canonicalization
171−--
172−typeConstructorsAreEqual :: Environment -> ModuleName -> Qualified ProperName -> Qualified ProperName -> Bool
173−typeConstructorsAreEqual env moduleName = (==) `on` canonicalizeType moduleName env
174−
175−-- |
176−-- Infer the types of multiple mutually-recursive values, and return elaborated values including
177−-- type class dictionaries and type annotations.
178−--
179−typesOf :: ModuleName -> [(Ident, Value)] -> Check [(Ident, (Value, Type))]
180−typesOf moduleName vals = do
181− tys <- fmap (\(tys, s) -> map (\(ident, (val, ty)) -> (ident, (overTypes (apply s) val, apply s ty))) tys)
182− . runSubst (SubstContext moduleName) $ do
183− let es = map isTyped vals
184− typed = filter (isJust . snd . snd) es
185− untyped = filter (isNothing . snd . snd) es
186− typedDict = map (\(ident, (_, Just ty)) -> (ident, ty)) typed
187− untypedNames <- replicateM (length untyped) fresh
188− let untypedDict = zip (map fst untyped) untypedNames
189− dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ (map (id *** fst) typedDict) ++ untypedDict)
190− forM es $ \e -> do
191− triple@(_, (val, ty)) <- case e of
192− (ident, (val, Just (ty, checkType))) -> do
193− kind <- liftCheck $ kindOf moduleName ty
194− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
195− ty' <- replaceAllTypeSynonyms ty
196− val' <- bindNames dict $ if checkType then check val ty' else return val
197− return (ident, (val', ty'))
198− (ident, (val, Nothing)) -> do
199− TypedValue _ val' ty <- bindNames dict $ infer val
200− ty ~~ fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
201− return (ident, (val', ty))
202− when (moduleName == ModuleName (ProperName "Main") && fst e == Ident "main") $ do
203− [eff, a] <- replicateM 2 fresh
204− ty ~~ TypeApp (TypeApp (TypeConstructor (Qualified (Just (ModuleName (ProperName "Eff"))) (ProperName "Eff"))) eff) a
205− escapeCheck val ty
206− return triple
207− forM_ tys $ skolemEscapeCheck . snd . snd
208− forM tys $ \(ident, (val, ty)) -> do
209− val' <- replaceTypeClassDictionaries moduleName val
210− return (ident, (overTypes (desaturateAllTypeSynonyms . setifyAll) $ val'
211− , varIfUnknown . desaturateAllTypeSynonyms . setifyAll $ ty))
212−
213−-- |
214−-- Check if a value contains a type annotation
215−--
216−isTyped :: (Ident, Value) -> (Ident, (Value, Maybe (Type, Bool)))
217−isTyped (name, TypedValue checkType value ty) = (name, (value, Just (ty, checkType)))
218−isTyped (name, value) = (name, (value, Nothing))
219−
220−-- |
221−-- Map a function over type annotations appearing inside a value
222−--
223−overTypes :: (Type -> Type) -> Value -> Value
224−overTypes f = everywhere (mkT f)
225−
226−-- |
227−-- Replace type class dictionary placeholders with inferred type class dictionaries
228−--
229−replaceTypeClassDictionaries :: ModuleName -> Value -> Check Value
230−replaceTypeClassDictionaries mn = everywhereM (mkM go)
231− where
232− go (TypeClassDictionary constraint dicts) = entails mn dicts constraint
233− go other = return other
234−
235−-- |
236−-- Check that the current set of type class dictionaries entail the specified type class goal, and, if so,
237−-- return a type class dictionary reference.
238−--
239−entails :: ModuleName -> [TypeClassDictionaryInScope] -> (Qualified ProperName, Type) -> Check Value
240−entails moduleName context goal@(className, ty) = do
241− env <- getEnv
242− case go env goal of
243− [] -> throwError $ "No " ++ show className ++ " instance found for " ++ prettyPrintType ty
244− (dict : _) -> return dict
245− where
246− go env (className', ty') =
247− [ mkDictionary (canonicalizeDictionary tcd) args
248− | tcd <- context
249− , filterModule tcd
250− , typeConstructorsAreEqual env moduleName className' (tcdClassName tcd)
251− , subst <- maybeToList $ typeHeadsAreEqual moduleName env ty' (tcdInstanceType tcd)
252− , args <- solveSubgoals env subst (tcdDependencies tcd) ]
253− solveSubgoals _ _ Nothing = return Nothing
254− solveSubgoals env subst (Just subgoals) = do
255− dict <- mapM (go env) (replaceAllTypeVars subst subgoals)
256− return $ Just dict
257− mkDictionary fnName args = maybe id (flip App) args $ (Var fnName)
258− filterModule (TypeClassDictionaryInScope { tcdName = Qualified (Just mn) _ }) | mn == moduleName = True
259− filterModule (TypeClassDictionaryInScope { tcdName = Qualified Nothing _ }) = True
260− filterModule _ = False
261− canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDRegular, tcdName = nm }) = nm
262− canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDAlias nm }) = nm
263−
264−-- |
265−-- Check whether the type heads of two types are equal (for the purposes of type class dictionary lookup),
266−-- and return a substitution from type variables to types which makes the type heads unify.
267−--
268−typeHeadsAreEqual :: ModuleName -> Environment -> Type -> Type -> Maybe [(String, Type)]
269−typeHeadsAreEqual _ _ String String = Just []
270−typeHeadsAreEqual _ _ Number Number = Just []
271−typeHeadsAreEqual _ _ Boolean Boolean = Just []
272−typeHeadsAreEqual _ _ (Skolem s1) (Skolem s2) | s1 == s2 = Just []
273−typeHeadsAreEqual _ _ Array Array = Just []
274−typeHeadsAreEqual m e (TypeConstructor c1) (TypeConstructor c2) | typeConstructorsAreEqual e m c1 c2 = Just []
275−typeHeadsAreEqual m e (TypeApp h1 (TypeVar v)) (TypeApp h2 arg) = (:) (v, arg) <$> typeHeadsAreEqual m e h1 h2
276−typeHeadsAreEqual m e t1@(TypeApp _ _) t2@(TypeApp _ (TypeVar _)) = typeHeadsAreEqual m e t2 t1
277−typeHeadsAreEqual _ _ _ _ = Nothing
278−
279−-- |
280−-- Ensure unsolved unification variables do not escape
281−--
282−escapeCheck :: Value -> Type -> Subst ()
283−escapeCheck value ty = do
284− subst <- substSubst <$> getSubstState
285− let visibleUnknowns = nub $ unknowns $ apply subst ty
286− let allUnknowns = findAllTypes value
287− forM_ allUnknowns $ \t -> do
288− let unsolvedUnknowns = nub . unknowns $ apply subst t
289− guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
290−
291−-- |
292−-- Find all type annotations occuring inside a value
293−--
294−findAllTypes :: Value -> [Type]
295−findAllTypes = everything (++) (mkQ [] go)
296− where
297− go (TypedValue _ _ ty) = [ty]
298− go _ = []
299−
300−-- |
301−-- Ensure skolem variables do not escape their scope
302−--
303−skolemEscapeCheck :: Type -> Check ()
304−skolemEscapeCheck ty =
305− case something (mkQ Nothing findSkolems) ty of
306− Nothing -> return ()
307− Just _ -> throwError $ "Skolem variables cannot escape. Consider adding a type signature." ++ show ty
308− where
309− findSkolems (Skolem _) = return ()
310− findSkolems _ = mzero
311−
312−-- |
313−-- Ensure a row contains no duplicate labels
314−--
315−setify :: Type -> Type
316−setify = rowFromList . first (M.toList . M.fromList) . rowToList
317−
318−-- |
319−-- \"Setify\" all rows occuring inside a value
320−--
321−setifyAll :: (D.Data d) => d -> d
322−setifyAll = everywhere (mkT setify)
323−
324−-- |
325−-- Replace outermost unsolved unification variables with named type variables
326−--
327−varIfUnknown :: Type -> Type
328−varIfUnknown ty =
329− let unks = nub $ unknowns ty
330− toName = (:) 't' . show
331− ty' = everywhere (mkT typeToVar) $ ty
332− typeToVar :: Type -> Type
333− typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
334− typeToVar t = t
335− in mkForAll (sort . map toName $ unks) ty'
336−
337−-- |
338−-- Replace named type variables with types
339−--
340−replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
341−replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
342−
343−-- |
344−-- Replace named type variables with new unification variables
345−--
346−replaceAllVarsWithUnknowns :: Type -> Subst Type
347−replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
348−replaceAllVarsWithUnknowns ty = return ty
349−
350−-- |
351−-- Replace a single type variable with a new unification variable
352−--
353−replaceVarWithUnknown :: String -> Type -> Subst Type
354−replaceVarWithUnknown ident ty = do
355− tu <- fresh
356− return $ replaceTypeVars ident tu $ ty
357−
358−-- |
359−-- Replace fully applied type synonyms with the @SaturatedTypeSynonym@ data constructor, which helps generate
360−-- better error messages during unification.
361−--
362−replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadReader SubstContext m, MonadError String m) => (D.Data d) => d -> m d
363−replaceAllTypeSynonyms d = do
364− env <- getEnv
365− moduleName <- substCurrentModule <$> ask
366− let syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
367− either throwError return $ saturateAllTypeSynonyms env moduleName syns d
368−
369−-- |
370−-- \"Desaturate\" @SaturatedTypeSynonym@s
371−--
372−desaturateAllTypeSynonyms :: (D.Data d) => d -> d
373−desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
374− where
375− replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
376− replaceSaturatedTypeSynonym t = t
377−
378−-- |
379−-- Replace a type synonym and its arguments with the aliased type
380−--
381−expandTypeSynonym :: Qualified ProperName -> [Type] -> Subst Type
382−expandTypeSynonym name args = do
383− env <- getEnv
384− moduleName <- substCurrentModule `fmap` ask
385− case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
386− Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
387− Nothing -> error "Type synonym was not defined"
388−
389−-- |
390−-- Ensure a set of property names and value does not contain duplicate labels
391−--
392−ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
393−ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
394−
395−-- |
396−-- Infer a type for a value, rethrowing any error to provide a more useful error message
397−--
398−infer :: Value -> Subst Value
399−infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ infer' val
400−
401−-- |
402−-- Infer a type for a value
403−--
404−infer' :: Value -> Subst Value
405−infer' v@(NumericLiteral _) = return $ TypedValue True v Number
406−infer' v@(StringLiteral _) = return $ TypedValue True v String
407−infer' v@(BooleanLiteral _) = return $ TypedValue True v Boolean
408−infer' (ArrayLiteral vals) = do
409− ts <- mapM infer vals
410− els <- fresh
411− forM_ ts $ \(TypedValue _ _ t) -> els ~~ TypeApp Array t
412− return $ TypedValue True (ArrayLiteral ts) els
413−infer' (Unary op val) = do
414− v <- infer val
415− inferUnary op v
416−infer' (Binary op left right) = do
417− v1 <- infer left
418− v2 <- infer right
419− inferBinary op v1 v2
420−infer' (ObjectLiteral ps) = do
421− ensureNoDuplicateProperties ps
422− ts <- mapM (infer . snd) ps
423− let fields = zipWith (\name (TypedValue _ _ t) -> (name, t)) (map fst ps) ts
424− ty = Object $ rowFromList (fields, REmpty)
425− return $ TypedValue True (ObjectLiteral (zip (map fst ps) ts)) ty
426−infer' (ObjectUpdate o ps) = do
427− ensureNoDuplicateProperties ps
428− row <- fresh
429− newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
430− let newTys = map (\(name, TypedValue _ _ ty) -> (name, ty)) newVals
431− oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
432− o' <- check o $ Object $ rowFromList (oldTys, row)
433− return $ TypedValue True (ObjectUpdate o' newVals) $ Object $ rowFromList (newTys, row)
434−infer' (Indexer index val) = do
435− el <- fresh
436− index' <- check index Number
437− val' <- check val (TypeApp Array el)
438− return $ TypedValue True (Indexer (TypedValue True index' Number) (TypedValue True val' (TypeApp Array el))) el
439−infer' (Accessor prop val) = do
440− typed@(TypedValue _ _ objTy) <- infer val
441− propTy <- inferProperty objTy prop
442− case propTy of
443− Nothing -> do
444− field <- fresh
445− rest <- fresh
446− objTy `subsumes` Object (RCons prop field rest)
447− return $ TypedValue True (Accessor prop typed) field
448− Just ty -> return $ TypedValue True (Accessor prop typed) ty
449−infer' (Abs args ret) = do
450− ts <- replicateM (length args) fresh
451− moduleName <- substCurrentModule <$> ask
452− bindLocalVariables moduleName (zip args ts) $ do
453− body@(TypedValue _ _ bodyTy) <- infer' ret
454− return $ TypedValue True (Abs args body) $ Function ts bodyTy
455−infer' (App f args) = do
456− f'@(TypedValue _ _ ft) <- infer f
457− ret <- fresh
458− app <- checkFunctionApplication f' ft args ret
459− return $ TypedValue True app ret
460−infer' (Var var) = do
461− moduleName <- substCurrentModule <$> ask
462− ty <- lookupVariable moduleName var
463− ty' <- replaceAllTypeSynonyms ty
464− case ty' of
465− ConstrainedType constraints _ -> do
466− env <- getEnv
467− dicts <- getTypeClassDictionaries
468− return $ TypedValue True (App (Var var) (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) ty'
469− _ -> return $ TypedValue True (Var var) ty'
470−infer' (Block ss) = do
471− ret <- fresh
472− (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
473− guardWith "Block is missing a return statement" allCodePathsReturn
474− return $ TypedValue True (Block ss') ret
475−infer' v@(Constructor c) = do
476− env <- getEnv
477− moduleName <- substCurrentModule `fmap` ask
478− case M.lookup (qualify moduleName c) (dataConstructors env) of
479− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
480− Just (ty, _) -> do ty' <- replaceAllTypeSynonyms ty
481− return $ TypedValue True v ty'
482−infer' (Case vals binders) = do
483− ts <- mapM infer vals
484− ret <- fresh
485− binders' <- checkBinders (map (\(TypedValue _ _ t) -> t) ts) ret binders
486− return $ TypedValue True (Case ts binders') ret
487−infer' (IfThenElse cond th el) = do
488− cond' <- check cond Boolean
489− v2@(TypedValue _ _ t2) <- infer th
490− v3@(TypedValue _ _ t3) <- infer el
491− t2 ~~ t3
492− return $ TypedValue True (IfThenElse cond' v2 v3) t2
493−infer' (TypedValue checkType val ty) = do
494− moduleName <- substCurrentModule <$> ask
495− kind <- liftCheck $ kindOf moduleName ty
496− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
497− ty' <- replaceAllTypeSynonyms ty
498− val' <- if checkType then check val ty' else return val
499− return $ TypedValue True val' ty
500−infer' _ = error "Invalid argument to infer"
501−
502−-- |
503−-- Infer the type of a property inside a record with a given type
504−--
505−inferProperty :: Type -> String -> Subst (Maybe Type)
506−inferProperty (Object row) prop = do
507− let (props, _) = rowToList row
508− return $ lookup prop props
509−inferProperty (SaturatedTypeSynonym name args) prop = do
510− replaced <- expandTypeSynonym name args
511− inferProperty replaced prop
512−inferProperty (ForAll ident ty) prop = do
513− replaced <- replaceVarWithUnknown ident ty
514− inferProperty replaced prop
515−inferProperty _ _ = return Nothing
516−
517−-- |
518−-- Infer the type of a unary operator application
519−--
520−inferUnary :: UnaryOperator -> Value -> Subst Value
521−inferUnary op (TypedValue _ val valTy) =
522− case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
523− (valTy', resTy) -> do
524− valTy' ~~ valTy
525− return $ TypedValue True (Unary op val) resTy
526−inferUnary _ _ = error "Invalid arguments to inferUnary"
527−
528−-- |
529−-- Check the type of a unary operator application
530−--
531−checkUnary :: UnaryOperator -> Value -> Type -> Subst Value
532−checkUnary op val res =
533− case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
534− (valTy, resTy) -> do
535− res ~~ resTy
536− val' <- check val valTy
537− return $ Unary op val'
538−
539−-- |
540−-- Built-in unary operators
541−--
542−unaryOps :: [(UnaryOperator, (Type, Type))]
543−unaryOps = [ (Negate, (Number, Number))
544− , (Not, (Boolean, Boolean))
545− , (BitwiseNot, (Number, Number))
546− ]
547−
548−-- |
549−-- Infer the type of a binary operator application
550−--
551−inferBinary :: BinaryOperator -> Value -> Value -> Subst Value
552−inferBinary op left@(TypedValue _ _ leftTy) right@(TypedValue _ _ rightTy) | isEqualityTest op = do
553− leftTy ~~ rightTy
554− return $ TypedValue True (Binary op left right) Boolean
555−inferBinary op left@(TypedValue _ _ leftTy) right@(TypedValue _ _ rightTy) =
556− case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
557− (valTy, resTy) -> do
558− leftTy ~~ valTy
559− rightTy ~~ valTy
560− return $ TypedValue True (Binary op left right) resTy
561−inferBinary _ _ _ = error "Invalid arguments to inferBinary"
562−
563−-- |
564−-- Check the type of a binary operator application
565−--
566−checkBinary :: BinaryOperator -> Value -> Value -> Type -> Subst Value
567−checkBinary op left right res | isEqualityTest op = do
568− res ~~ Boolean
569− left'@(TypedValue _ _ t1) <- infer left
570− right'@(TypedValue _ _ t2) <- infer right
571− t1 ~~ t2
572− return $ Binary op left' right'
573−checkBinary op left right res =
574− case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
575− (valTy, resTy) -> do
576− res ~~ resTy
577− left' <- check left valTy
578− right' <- check right valTy
579− return $ Binary op left' right'
580−
581−-- |
582−-- Check if a @BinaryOperator@ is an equality test
583−--
584−isEqualityTest :: BinaryOperator -> Bool
585−isEqualityTest EqualTo = True
586−isEqualityTest NotEqualTo = True
587−isEqualityTest _ = False
588−
589−-- |
590−-- Built-in binary operators
591−--
592−binaryOps :: [(BinaryOperator, (Type, Type))]
593−binaryOps = [ (Add, (Number, Number))
594− , (Subtract, (Number, Number))
595− , (Multiply, (Number, Number))
596− , (Divide, (Number, Number))
597− , (Modulus, (Number, Number))
598− , (BitwiseAnd, (Number, Number))
599− , (BitwiseOr, (Number, Number))
600− , (BitwiseXor, (Number, Number))
601− , (ShiftRight, (Number, Number))
602− , (ZeroFillShiftRight, (Number, Number))
603− , (And, (Boolean, Boolean))
604− , (Or, (Boolean, Boolean))
605− , (Concat, (String, String))
606− , (Modulus, (Number, Number))
607− , (LessThan, (Number, Boolean))
608− , (LessThanOrEqualTo, (Number, Boolean))
609− , (GreaterThan, (Number, Boolean))
610− , (GreaterThanOrEqualTo, (Number, Boolean))
611− ]
612−
613−-- |
614−-- Infer the types of variables brought into scope by a binder
615−--
616−inferBinder :: Type -> Binder -> Subst (M.Map Ident Type)
617−inferBinder _ NullBinder = return M.empty
618−inferBinder val (StringBinder _) = val ~~ String >> return M.empty
619−inferBinder val (NumberBinder _) = val ~~ Number >> return M.empty
620−inferBinder val (BooleanBinder _) = val ~~ Boolean >> return M.empty
621−inferBinder val (VarBinder name) = return $ M.singleton name val
622−inferBinder val (NullaryBinder ctor) = do
623− env <- getEnv
624− moduleName <- substCurrentModule <$> ask
625− case M.lookup (qualify moduleName ctor) (dataConstructors env) of
626− Just (ty, _) -> do
627− ty `subsumes` val
628− return M.empty
629− _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
630−inferBinder val (UnaryBinder ctor binder) = do
631− env <- getEnv
632− moduleName <- substCurrentModule <$> ask
633− case M.lookup (qualify moduleName ctor) (dataConstructors env) of
634− Just (ty, _) -> do
635− fn <- replaceAllVarsWithUnknowns ty
636− case fn of
637− Function [obj] ret -> do
638− val `subsumes` ret
639− inferBinder obj binder
640− _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
641− _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
642−inferBinder val (ObjectBinder props) = do
643− row <- fresh
644− rest <- fresh
645− m1 <- inferRowProperties row rest props
646− val ~~ Object row
647− return m1
648− where
649− inferRowProperties :: Type -> Type -> [(String, Binder)] -> Subst (M.Map Ident Type)
650− inferRowProperties nrow row [] = nrow ~~ row >> return M.empty
651− inferRowProperties nrow row ((name, binder):binders) = do
652− propTy <- fresh
653− m1 <- inferBinder propTy binder
654− m2 <- inferRowProperties nrow (RCons name propTy row) binders
655− return $ m1 `M.union` m2
656−inferBinder val (ArrayBinder binders) = do
657− el <- fresh
658− m1 <- M.unions <$> mapM (inferBinder el) binders
659− val ~~ TypeApp Array el
660− return m1
661−inferBinder val (ConsBinder headBinder tailBinder) = do
662− el <- fresh
663− m1 <- inferBinder el headBinder
664− m2 <- inferBinder val tailBinder
665− val ~~ TypeApp Array el
666− return $ m1 `M.union` m2
667−inferBinder val (NamedBinder name binder) = do
668− m <- inferBinder val binder
669− return $ M.insert name val m
670−
671−-- |
672−-- Check the types of the return values in a set of binders in a case statement
673−--
674−checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> Subst [([Binder], Maybe Guard, Value)]
675−checkBinders _ _ [] = return []
676−checkBinders nvals ret ((binders, grd, val):bs) = do
677− moduleName <- substCurrentModule <$> ask
678− m1 <- M.unions <$> zipWithM inferBinder nvals binders
679− r <- bindLocalVariables moduleName (M.toList m1) $ do
680− val' <- check val ret
681− case grd of
682− Nothing -> return (binders, Nothing, val')
683− Just g -> do
684− g' <- check g Boolean
685− return (binders, Just g', val')
686− rs <- checkBinders nvals ret bs
687− return $ r : rs
688−
689−-- |
690−-- Check that a local variable name is not already used
691−--
692−assignVariable :: Ident -> Subst ()
693−assignVariable name = do
694− env <- checkEnv <$> get
695− moduleName <- substCurrentModule <$> ask
696− case M.lookup (moduleName, name) (names env) of
697− Just _ -> throwError $ "Variable with name " ++ show name ++ " already exists."
698− _ -> return ()
699−
700−-- |
701−-- Check the type of the return values of a statement, returning whether or not the statement returns on
702−-- all code paths
703−--
704−checkStatement :: M.Map Ident Type -> Type -> Statement -> Subst (Bool, M.Map Ident Type, Statement)
705−checkStatement mass _ (VariableIntroduction name val) = do
706− assignVariable name
707− val'@(TypedValue _ _ t) <- infer val
708− return (False, M.insert name t mass, VariableIntroduction name val')
709−checkStatement mass _ (Assignment ident val) = do
710− val'@(TypedValue _ _ t) <- infer val
711− case M.lookup ident mass of
712− Nothing -> throwError $ "No local variable with name " ++ show ident
713− Just ty -> do t ~~ ty
714− return (False, mass, Assignment ident val')
715−checkStatement mass ret (While val inner) = do
716− val' <- check val Boolean
717− (allCodePathsReturn, _, inner') <- checkBlock mass ret inner
718− return (allCodePathsReturn, mass, While val' inner')
719−checkStatement mass ret (If ifst) = do
720− (allCodePathsReturn, ifst') <- checkIfStatement mass ret ifst
721− return (allCodePathsReturn, mass, If ifst')
722−checkStatement mass ret (For ident start end inner) = do
723− moduleName <- substCurrentModule <$> ask
724− assignVariable ident
725− start' <- check start Number
726− end' <- check end Number
727− (allCodePathsReturn, _, inner') <- bindLocalVariables moduleName [(ident, Number)] $ checkBlock mass ret inner
728− return (allCodePathsReturn, mass, For ident start' end' inner')
729−checkStatement mass ret (Return val) = do
730− val' <- check val ret
731− return (True, mass, Return val')
732−
733−-- |
734−-- Check the type of an if-then-else statement
735−--
736−checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> Subst (Bool, IfStatement)
737−checkIfStatement mass ret (IfStatement val thens Nothing) = do
738− val' <- check val Boolean
739− (_, _, thens') <- checkBlock mass ret thens
740− return (False, IfStatement val' thens' Nothing)
741−checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
742− val' <- check val Boolean
743− (allCodePathsReturn1, _, thens') <- checkBlock mass ret thens
744− (allCodePathsReturn2, elses') <- checkElseStatement mass ret elses
745− return (allCodePathsReturn1 && allCodePathsReturn2, IfStatement val' thens' (Just elses'))
746−
747−-- |
748−-- Check the type of an else statement
749−--
750−checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> Subst (Bool, ElseStatement)
751−checkElseStatement mass ret (Else elses) = do
752− (allCodePathsReturn, _, elses') <- checkBlock mass ret elses
753− return (allCodePathsReturn, Else elses')
754−checkElseStatement mass ret (ElseIf ifst) = (id *** ElseIf) <$> checkIfStatement mass ret ifst
755−
756−-- |
757−-- Check the type of the return value of a block of statements
758−--
759−checkBlock :: M.Map Ident Type -> Type -> [Statement] -> Subst (Bool, M.Map Ident Type, [Statement])
760−checkBlock mass _ [] = return (False, mass, [])
761−checkBlock mass ret (s:ss) = do
762− moduleName <- substCurrentModule <$> ask
763− (b1, mass1, s') <- checkStatement mass ret s
764− bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
765− (True, []) -> return (True, mass1, [s'])
766− (True, _) -> throwError "Unreachable code"
767− (False, ss') -> do
768− (b, m, ss'') <- checkBlock mass1 ret ss'
769− return (b, m, s':ss'')
770−
771−-- |
772−-- Skolemize a type variable by replacing its instances with fresh skolem constants
773−--
774−skolemize :: String -> Type -> Subst Type
775−skolemize ident ty = do
776− tsk <- Skolem <$> fresh'
777− return $ replaceTypeVars ident tsk ty
778−
779−-- |
780−-- Check the type of a value, rethrowing errors to provide a better error message
781−--
782−check :: Value -> Type -> Subst Value
783−check val ty = rethrow errorMessage $ check' val ty
784− where
785− errorMessage msg =
786− "Error checking type of term " ++
787− prettyPrintValue val ++
788− " against type " ++
789− prettyPrintType ty ++
790− ":\n" ++
791− msg
792−
793−-- |
794−-- Check the type of a value
795−--
796−check' :: Value -> Type -> Subst Value
797−check' val (ForAll idents ty) = do
798− sk <- skolemize idents ty
799− check val sk
800−check' val (ConstrainedType constraints ty) = do
801− env <- getEnv
802− moduleName <- substCurrentModule <$> ask
803− dictNames <- flip mapM constraints $ \(Qualified _ (ProperName className), _) -> do
804− n <- liftCheck freshDictionaryName
805− return $ Ident $ "__dict_" ++ className ++ "_" ++ show n
806− val' <- withTypeClassDictionaries (zipWith (\name (className, instanceTy) ->
807− TypeClassDictionaryInScope name className instanceTy Nothing TCDRegular) (map (Qualified Nothing) dictNames)
808− (qualifyAllUnqualifiedNames moduleName env constraints)) $
809− check val ty
810− return $ Abs dictNames val'
811−check' val u@(TUnknown _) = do
812− val'@(TypedValue _ _ ty) <- infer val
813− -- Don't unify an unknown with an inferred polytype
814− ty' <- replaceAllVarsWithUnknowns ty
815− ty' ~~ u
816− return val'
817−check' v@(NumericLiteral _) Number = return v
818−check' v@(StringLiteral _) String = return v
819−check' v@(BooleanLiteral _) Boolean = return v
820−check' (Unary op val) ty = checkUnary op val ty
821−check' (Binary op left right) ty = checkBinary op left right ty
822−check' (ArrayLiteral vals) (TypeApp Array ty) = ArrayLiteral <$> forM vals (\val -> check val ty)
823−check' (Indexer index vals) ty = do
824− index' <- check index Number
825− vals' <- check vals (TypeApp Array ty)
826− return $ Indexer index' vals'
827−check' (Abs args ret) (Function argTys retTy) = do
828− moduleName <- substCurrentModule <$> ask
829− guardWith "Incorrect number of function arguments" (length args == length argTys)
830− ret' <- bindLocalVariables moduleName (zip args argTys) $ check ret retTy
831− return $ Abs args ret'
832−check' (App f args) ret = do
833− f'@(TypedValue _ _ ft) <- infer f
834− app <- checkFunctionApplication f' ft args ret
835− return $ app
836−check' (Var var) ty = do
837− moduleName <- substCurrentModule <$> ask
838− ty1 <- lookupVariable moduleName var
839− repl <- replaceAllTypeSynonyms ty1
840− repl `subsumes` ty
841− return $ Var var
842−check' (TypedValue checkType val ty1) ty2 = do
843− moduleName <- substCurrentModule <$> ask
844− kind <- liftCheck $ kindOf moduleName ty1
845− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
846− ty1 `subsumes` ty2
847− val' <- if checkType then check val ty1 else return val
848− return $ TypedValue True val' ty1
849−check' (Case vals binders) ret = do
850− vals' <- mapM infer vals
851− let ts = map (\(TypedValue _ _ t) -> t) vals'
852− binders' <- checkBinders ts ret binders
853− return $ Case vals' binders'
854−check' (IfThenElse cond th el) ty = do
855− cond' <- check cond Boolean
856− th' <- check th ty
857− el' <- check el ty
858− return $ IfThenElse cond' th' el'
859−check' (ObjectLiteral ps) (Object row) = do
860− ensureNoDuplicateProperties ps
861− ps' <- checkProperties ps row False
862− return $ ObjectLiteral ps'
863−check' (ObjectUpdate obj ps) (Object row) = do
864− ensureNoDuplicateProperties ps
865− us <- zip (map fst ps) <$> replicateM (length ps) fresh
866− let (propsToCheck, rest) = rowToList row
867− propsToRemove = map fst ps
868− remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
869− obj' <- check obj (Object (rowFromList (us ++ remainingProps, rest)))
870− ps' <- checkProperties ps row True
871− return $ ObjectUpdate obj' ps'
872−check' (Accessor prop val) ty = do
873− rest <- fresh
874− val' <- check val (Object (RCons prop ty rest))
875− return $ Accessor prop val'
876−check' (Block ss) ret = do
877− (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
878− guardWith "Block is missing a return statement" allCodePathsReturn
879− return $ Block ss'
880−check' (Constructor c) ty = do
881− env <- getEnv
882− moduleName <- substCurrentModule <$> ask
883− case M.lookup (qualify moduleName c) (dataConstructors env) of
884− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
885− Just (ty1, _) -> do
886− repl <- replaceAllTypeSynonyms ty1
887− repl `subsumes` ty
888− return $ Constructor c
889−check' val (SaturatedTypeSynonym name args) = do
890− ty <- expandTypeSynonym name args
891− check val ty
892−check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
893−
894−-- |
895−-- Check the type of a collection of named record fields
896−--
897−-- The @lax@ parameter controls whether or not every record member has to be provided. For object updates, this is not the case.
898−--
899−checkProperties :: [(String, Value)] -> Type -> Bool -> Subst [(String, Value)]
900−checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
901− go [] [] REmpty = return []
902− go [] [] u@(TUnknown _) = do u ~~ REmpty
903− return []
904− go [] [] (Skolem _) | lax = return []
905− go [] ((p, _): _) _ | lax = return []
906− | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
907− go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
908− go ((p,v):ps') [] u@(TUnknown _) = do
909− v'@(TypedValue _ _ ty) <- infer v
910− rest <- fresh
911− u ~~ RCons p ty rest
912− ps'' <- go ps' [] rest
913− return $ (p, v') : ps''
914− go ((p,v):ps') ts r =
915− case lookup p ts of
916− Nothing -> do
917− v'@(TypedValue _ _ ty) <- infer v
918− rest <- fresh
919− r ~~ RCons p ty rest
920− ps'' <- go ps' ts rest
921− return $ (p, v') : ps''
922− Just ty -> do
923− v' <- check v ty
924− ps'' <- go ps' (delete (p, ty) ts) r
925− return $ (p, v') : ps''
926− go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
927−
928−-- |
929−-- Check the type of a function application, rethrowing errors to provide a better error message
930−--
931−checkFunctionApplication :: Value -> Type -> [Value] -> Type -> Subst Value
932−checkFunctionApplication fn fnTy args ret = rethrow errorMessage $ checkFunctionApplication' fn fnTy args ret
933− where
934− errorMessage msg = "Error applying function of type "
935− ++ prettyPrintType fnTy
936− ++ " to arguments " ++ intercalate ", " (map prettyPrintValue args)
937− ++ ":\n" ++ msg
938−
939−-- |
940−-- Check the type of a function application
941−--
942−checkFunctionApplication' :: Value -> Type -> [Value] -> Type -> Subst Value
943−checkFunctionApplication' fn (Function argTys retTy) args ret = do
944− guardWith "Incorrect number of function arguments" (length args == length argTys)
945− args' <- zipWithM check args argTys
946− retTy `subsumes` ret
947− return $ App fn args'
948−checkFunctionApplication' fn (ForAll ident ty) args ret = do
949− replaced <- replaceVarWithUnknown ident ty
950− checkFunctionApplication fn replaced args ret
951−checkFunctionApplication' fn u@(TUnknown _) args ret = do
952− args' <- mapM (\arg -> infer arg >>= \(TypedValue _ v t) -> TypedValue True v <$> replaceAllVarsWithUnknowns t) args
953− let tys = map (\(TypedValue _ _ t) -> t) args'
954− u ~~ Function tys ret
955− return $ App fn args'
956−checkFunctionApplication' fn (SaturatedTypeSynonym name tyArgs) args ret = do
957− ty <- expandTypeSynonym name tyArgs
958− checkFunctionApplication fn ty args ret
959−checkFunctionApplication' fn (ConstrainedType constraints fnTy) args ret = do
960− env <- getEnv
961− dicts <- getTypeClassDictionaries
962− moduleName <- substCurrentModule <$> ask
963− checkFunctionApplication' (App fn (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) fnTy args ret
964−checkFunctionApplication' _ fnTy args ret = throwError $ "Applying a function of type "
965− ++ prettyPrintType fnTy
966− ++ " to argument(s) " ++ intercalate ", " (map prettyPrintValue args)
967− ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
968−
969−-- |
970−-- Check whether one type subsumes another, rethrowing errors to provide a better error message
971−--
972−subsumes :: Type -> Type -> Subst ()
973−subsumes ty1 ty2 = rethrow errorMessage $ subsumes' ty1 ty2
974− where
975− errorMessage msg = "Error checking that type "
976− ++ prettyPrintType ty1
977− ++ " subsumes type "
978− ++ prettyPrintType ty2
979− ++ ":\n" ++ msg
980−
981−-- |
982−-- Check whether one type subsumes another
983−--
984−subsumes' :: Type -> Type -> Subst ()
985−subsumes' (ForAll ident ty1) ty2 = do
986− replaced <- replaceVarWithUnknown ident ty1
987− replaced `subsumes` ty2
988−subsumes' (Function args1 ret1) (Function args2 ret2) = do
989− zipWithM_ subsumes args2 args1
990− ret1 `subsumes` ret2
991−subsumes' ty1 ty2 = ty1 ~~ ty2
992−