@@ -0,0 +1,962 @@
1+-----------------------------------------------------------------------------
3+-- Module : Language.PureScript.TypeChecker.Types
4+-- Copyright : (c) Phil Freeman 2013
7+-- Maintainer : Phil Freeman <paf31@cantab.net>
8+-- Stability : experimental
12+-- This module implements the type checker
14+-----------------------------------------------------------------------------
16+{-# OPTIONS_GHC -fno-warn-orphans #-}
17+{-# LANGUAGE DeriveDataTypeable #-}
18+{-# LANGUAGE FlexibleContexts #-}
19+{-# LANGUAGE MultiParamTypeClasses #-}
21+module Language.PureScript.TypeChecker.Types (
26+ The following functions represent the corresponding type checking judgements:
29+ Synthesize a type for a value
32+ Check a value has a given type
35+ Check an object with a given type contains specified properties
37+ checkFunctionApplication
38+ Check a function of a given type returns a value of another type when applied to its arguments
41+ Check a type subsumes another type
45+import Data.Maybe (maybeToList, isNothing, isJust, fromMaybe)
46+import qualified Data.Data as D
48+ (everythingWithContext, mkM, everywhereM, everything, mkT,
49+ something, everywhere, mkQ)
50+import Data.Generics.Extras
52+import Language.PureScript.Values
53+import Language.PureScript.Types
54+import Language.PureScript.Kinds
55+import Language.PureScript.Names
56+import Language.PureScript.TypeChecker.Monad
57+import Language.PureScript.TypeChecker.Kinds
58+import Language.PureScript.TypeChecker.Synonyms
59+import Language.PureScript.Pretty
61+import Control.Monad.State
62+import Control.Monad.Error
63+import Control.Monad.Reader
64+import Control.Monad.Unify
66+import Control.Applicative
67+import Control.Arrow (Arrow(..))
69+import qualified Data.Map as M
70+import Data.Function (on)
71+import Data.Ord (comparing)
73+instance Partial Type where
75+ isUnknown (TUnknown u) = Just u
76+ isUnknown _ = Nothing
78+instance Unifiable Check Type where
82+-- Unify two types, updating the current substitution
84+unifyTypes :: Type -> Type -> UnifyT Type Check ()
85+unifyTypes t1 t2 = rethrow (\e -> "Error unifying type " ++ prettyPrintType t1 ++ " with type " ++ prettyPrintType t2 ++ ":\n" ++ e) $ do
88+ unifyTypes' (TUnknown u1) (TUnknown u2) | u1 == u2 = return ()
89+ unifyTypes' (TUnknown u) t = u =:= t
90+ unifyTypes' t (TUnknown u) = u =:= t
91+ unifyTypes' (SaturatedTypeSynonym name args) ty = do
92+ ty1 <- introduceSkolemScope <=< expandTypeSynonym name $ args
94+ unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
95+ unifyTypes' (ForAll ident1 ty1 sc1) (ForAll ident2 ty2 sc2) =
97+ (Just sc1', Just sc2') -> do
98+ sko <- newSkolemConstant
99+ let sk1 = skolemize ident1 sko sc1' ty1
100+ let sk2 = skolemize ident2 sko sc2' ty2
101+ sk1 `unifyTypes` sk2
102+ _ -> throwError (prettyPrintType ty1)
103+ unifyTypes' (ForAll ident ty1 (Just sc)) ty2 = do
104+ sko <- newSkolemConstant
105+ let sk = skolemize ident sko sc ty1
107+ unifyTypes' (ForAll _ _ _) _ = throwError "Skolem variable scope is unspecified"
108+ unifyTypes' ty f@(ForAll _ _ _) = f `unifyTypes` ty
109+ unifyTypes' (Object row1) (Object row2) = row1 =?= row2
110+ unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
111+ unifyTypes' (TypeConstructor c1) (TypeConstructor c2) = do
113+ Just moduleName <- checkCurrentModule <$> get
114+ guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (typeConstructorsAreEqual env moduleName c1 c2)
115+ unifyTypes' (TypeApp t3 t4) (TypeApp t5 t6) = do
118+ unifyTypes' (Skolem s1 _) (Skolem s2 _) | s1 == s2 = return ()
119+ unifyTypes' r1@(RCons _ _ _) r2 = unifyRows r1 r2
120+ unifyTypes' r1 r2@(RCons _ _ _) = unifyRows r1 r2
121+ unifyTypes' r1@REmpty r2 = unifyRows r1 r2
122+ unifyTypes' r1 r2@REmpty = unifyRows r1 r2
123+ unifyTypes' t3 t4 = throwError $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
126+-- Unify two rows, updating the current substitution
128+-- Common labels are first identified, and unified. Remaining labels and types are unified with a
129+-- trailing row unification variable, if appropriate, otherwise leftover labels result in a unification
132+unifyRows :: Type -> Type -> UnifyT Type Check ()
135+ (s1, r1') = rowToList r1
136+ (s2, r2') = rowToList r2
137+ int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
138+ sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
139+ sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
141+ forM_ int (uncurry (=?=))
142+ unifyRows' sd1 r1' sd2 r2'
144+ unifyRows' :: [(String, Type)] -> Type -> [(String, Type)] -> Type -> UnifyT Type Check ()
145+ unifyRows' [] (TUnknown u) sd r = u =:= rowFromList (sd, r)
146+ unifyRows' sd r [] (TUnknown u) = u =:= rowFromList (sd, r)
147+ unifyRows' ((name, ty):row) r others u@(TUnknown un) = do
149+ forM_ row $ \(_, t) -> occursCheck un t
151+ u =?= RCons name ty u'
152+ unifyRows' row r others u'
153+ unifyRows' [] REmpty [] REmpty = return ()
154+ unifyRows' [] (TypeVar v1) [] (TypeVar v2) | v1 == v2 = return ()
155+ unifyRows' [] (Skolem s1 _) [] (Skolem s2 _) | s1 == s2 = return ()
156+ unifyRows' sd3 r3 sd4 r4 = throwError $ "Cannot unify (" ++ prettyPrintRow (rowFromList (sd3, r3)) ++ ") with (" ++ prettyPrintRow (rowFromList (sd4, r4)) ++ ")."
159+-- Ensure type constructors are equal after canonicalization
161+typeConstructorsAreEqual :: Environment -> ModuleName -> Qualified ProperName -> Qualified ProperName -> Bool
162+typeConstructorsAreEqual env moduleName = (==) `on` canonicalizeType moduleName env
165+-- Infer the types of multiple mutually-recursive values, and return elaborated values including
166+-- type class dictionaries and type annotations.
168+typesOf :: Maybe ModuleName -> ModuleName -> [(Ident, Value)] -> Check [(Ident, (Value, Type))]
169+typesOf mainModuleName moduleName vals = do
170+ tys <- fmap tidyUp . liftUnify $ do
172+ -- Map each declaration to a name/value pair, with an optional type, if the declaration is typed
173+ es = map isTyped vals
174+ -- Filter the typed and untyped declarations
175+ typed = filter (isJust . snd . snd) es
176+ untyped = filter (isNothing . snd . snd) es
177+ -- Make a map of names to typed declarations
178+ typedDict = map (\(ident, (_, Just (ty, _))) -> (ident, ty)) typed
179+ -- Create fresh unification variables for the types of untyped declarations
180+ untypedNames <- replicateM (length untyped) fresh
182+ -- Make a map of names to the unification variables of untyped declarations
183+ untypedDict = zip (map fst untyped) untypedNames
184+ -- Create the dictionary of all name/type pairs, which will be added to the environment during type checking
185+ dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ typedDict ++ untypedDict)
186+ forM es $ \e@(_, (val, _)) -> do
187+ -- If the declaration is a function, it has access to other values in the binding group.
188+ -- If not, the generated code might fail at runtime since those values might be undefined.
189+ let dict' = if isFunction val then dict else M.empty
190+ triple@(_, (val, ty)) <- case e of
191+ -- Typed declarations
192+ (ident, (val, Just (ty, checkType))) -> do
194+ kind <- liftCheck $ kindOf moduleName ty
195+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
196+ -- Check the type with the new names in scope
197+ ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
198+ val' <- bindNames dict' $ if checkType
199+ then TypedValue True <$> check val ty' <*> pure ty'
200+ else return (TypedValue False val ty')
201+ return (ident, (val', ty'))
202+ -- Untyped declarations
203+ (ident, (val, Nothing)) -> do
204+ -- Infer the type with the new names in scope
205+ TypedValue _ val' ty <- bindNames dict' $ infer val
206+ ty =?= fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
207+ return (ident, (TypedValue True val' ty, ty))
208+ -- If --main is enabled, need to check that `main` has type Eff eff a for some eff, a
209+ when (Just moduleName == mainModuleName && fst e == Ident "main") $ do
210+ [eff, a] <- replicateM 2 fresh
211+ ty =?= TypeApp (TypeApp (TypeConstructor (Qualified (Just (ModuleName [ProperName "Control", ProperName "Monad", ProperName "Eff"])) (ProperName "Eff"))) eff) a
212+ -- Make sure unification variables do not escape
215+ forM tys $ \(ident, (val, ty)) -> do
216+ -- Replace type class dictionary placeholders with actual dictionaries
217+ val' <- replaceTypeClassDictionaries moduleName val
218+ -- Check skolem variables did not escape their scope
219+ skolemEscapeCheck val'
220+ -- Remove type synonyms placeholders, remove duplicate row fields, and replace
221+ -- top-level unification variables with named type variables.
222+ let val'' = overTypes (desaturateAllTypeSynonyms . setifyAll) val'
223+ ty' = varIfUnknown . desaturateAllTypeSynonyms . setifyAll $ ty
224+ return $ (ident, (val'', ty'))
226+ -- Apply the substitution that was returned from runUnify to both types and (type-annotated) values
227+ tidyUp (ts, sub) = map (\(i, (val, ty)) -> (i, (overTypes (sub $?) val, sub $? ty))) ts
230+-- Check if a value introduces a function
232+isFunction :: Value -> Bool
233+isFunction (Abs _ _) = True
234+isFunction (TypedValue _ val _) = isFunction val
238+-- Check if a value contains a type annotation
240+isTyped :: (Ident, Value) -> (Ident, (Value, Maybe (Type, Bool)))
241+isTyped (name, TypedValue checkType value ty) = (name, (value, Just (ty, checkType)))
242+isTyped (name, value) = (name, (value, Nothing))
245+-- Map a function over type annotations appearing inside a value
247+overTypes :: (Type -> Type) -> Value -> Value
248+overTypes f = everywhere (mkT f)
251+-- Replace type class dictionary placeholders with inferred type class dictionaries
253+replaceTypeClassDictionaries :: ModuleName -> Value -> Check Value
254+replaceTypeClassDictionaries mn = everywhereM' (mkM go)
256+ go (TypeClassDictionary constraint dicts) = entails mn dicts constraint
257+ go other = return other
260+-- Check that the current set of type class dictionaries entail the specified type class goal, and, if so,
261+-- return a type class dictionary reference.
263+entails :: ModuleName -> [TypeClassDictionaryInScope] -> (Qualified ProperName, [Type]) -> Check Value
264+entails moduleName context goal@(className, tys) = do
267+ [] -> throwError $ "No " ++ show className ++ " instance found for " ++ intercalate ", " (map prettyPrintType tys)
268+ (dict : _) -> return dict
270+ go env (className', tys') =
271+ [ mkDictionary (canonicalizeDictionary tcd) args
273+ -- Choose type class dictionaries in scope in the current module
275+ -- Make sure the type class name matches the one we are trying to satisfy
276+ , typeConstructorsAreEqual env moduleName className' (tcdClassName tcd)
277+ -- Make sure the type unifies with the type in the type instance definition
278+ , subst <- maybeToList . (>>= verifySubstitution) . fmap concat $ zipWithM (typeHeadsAreEqual moduleName env) tys' (tcdInstanceTypes tcd)
279+ -- Solve any necessary subgoals
280+ , args <- solveSubgoals env subst (tcdDependencies tcd) ]
281+ -- Create dictionaries for subgoals which still need to be solved by calling go recursively
282+ -- E.g. the goal (Show a, Show b) => Show (Either a b) can be satisfied if the current type
283+ -- unifies with Either a b, and we can satisfy the subgoals Show a and Show b recursively.
284+ solveSubgoals :: Environment -> [(String, Type)] -> Maybe [(Qualified ProperName, [Type])] -> [Maybe [Value]]
285+ solveSubgoals _ _ Nothing = return Nothing
286+ solveSubgoals env subst (Just subgoals) = do
287+ dict <- mapM (go env) (map (id *** map (replaceAllTypeVars subst)) subgoals)
289+ -- Make a dictionary from subgoal dictionaries by applying the correct function
290+ mkDictionary :: Qualified Ident -> Maybe [Value] -> Value
291+ mkDictionary fnName Nothing = Var fnName
292+ mkDictionary fnName (Just []) = App (Var fnName) (ObjectLiteral [])
293+ mkDictionary fnName (Just dicts) = foldl App (Var fnName) dicts
294+ -- Filter out type dictionaries which are in scope in the current module
295+ filterModule :: TypeClassDictionaryInScope -> Bool
296+ filterModule (TypeClassDictionaryInScope { tcdName = Qualified (Just mn) _ }) | mn == moduleName = True
297+ filterModule (TypeClassDictionaryInScope { tcdName = Qualified Nothing _ }) = True
298+ filterModule _ = False
299+ -- Resolve a type class dictionary in scope to an actual value by following any (TCDAlias) pointers
300+ -- which originated from module imports
301+ canonicalizeDictionary :: TypeClassDictionaryInScope -> Qualified Ident
302+ canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDRegular, tcdName = nm }) = nm
303+ canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDAlias nm }) = nm
304+ -- Ensure that a substitution is valid
305+ verifySubstitution :: [(String, Type)] -> Maybe [(String, Type)]
306+ verifySubstitution subst = do
307+ let grps = groupBy ((==) `on` fst) subst
308+ guard (all ((==) 1 . length . nubBy ((==) `on` snd)) grps)
309+ return $ map head grps
312+-- Check whether the type heads of two types are equal (for the purposes of type class dictionary lookup),
313+-- and return a substitution from type variables to types which makes the type heads unify.
315+typeHeadsAreEqual :: ModuleName -> Environment -> Type -> Type -> Maybe [(String, Type)]
316+typeHeadsAreEqual _ _ (Skolem s1 _) (Skolem s2 _) | s1 == s2 = Just []
317+typeHeadsAreEqual _ _ (TypeVar v) t = Just [(v, t)]
318+typeHeadsAreEqual _ _ t (TypeVar v) = Just [(v, t)]
319+typeHeadsAreEqual m e (TypeConstructor c1) (TypeConstructor c2) | typeConstructorsAreEqual e m c1 c2 = Just []
320+typeHeadsAreEqual m e (TypeApp h1 (TypeVar v)) (TypeApp h2 arg) = (:) (v, arg) <$> typeHeadsAreEqual m e h1 h2
321+typeHeadsAreEqual m e t1@(TypeApp _ _) t2@(TypeApp _ (TypeVar _)) = typeHeadsAreEqual m e t2 t1
322+typeHeadsAreEqual m e (SaturatedTypeSynonym name args) t2 = case expandTypeSynonym' e m name args of
324+ Right t1 -> typeHeadsAreEqual m e t1 t2
325+typeHeadsAreEqual _ _ _ _ = Nothing
328+-- Ensure unsolved unification variables do not escape
330+escapeCheck :: Value -> Type -> UnifyT Type Check ()
331+escapeCheck value ty = do
332+ subst <- unifyCurrentSubstitution <$> UnifyT get
333+ let visibleUnknowns = nub $ unknowns $ subst $? ty
334+ let allUnknowns = findAllTypes value
335+ forM_ allUnknowns $ \t -> do
336+ let unsolvedUnknowns = nub . unknowns $ subst $? t
337+ guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
340+-- Find all type annotations occuring inside a value
342+findAllTypes :: Value -> [Type]
343+findAllTypes = everything (++) (mkQ [] go)
345+ go (TypedValue _ _ ty) = [ty]
349+-- Ensure skolem variables do not escape their scope
351+skolemEscapeCheck :: Value -> Check ()
352+skolemEscapeCheck (TypedValue False _ _) = return ()
353+skolemEscapeCheck root@(TypedValue _ _ _) =
354+ -- Every skolem variable is created when a ForAll type is skolemized.
355+ -- This determines the scope of that skolem variable, which is copied from the SkolemScope
356+ -- field of the ForAll constructor.
357+ -- We traverse the tree top-down, and collect any SkolemScopes introduced by ForAlls.
358+ -- If a Skolem is encountered whose SkolemScope is not in the current list, we have found
359+ -- an escaped skolem variable.
360+ case everythingWithContext [] (++) (mkQ ((,) []) go) root of
362+ ((binding, val) : _) -> throwError $ "Rigid/skolem type variable bound by " ++ maybe "<unknown>" prettyPrintValue binding ++ " has escaped at " ++ prettyPrintValue val
364+ go :: Value -> [(SkolemScope, Value)] -> ([(Maybe Value, Value)], [(SkolemScope, Value)])
365+ go val@(TypedValue _ _ (ForAll _ _ (Just sco))) scos = ([], (sco, val) : scos)
366+ go val@(TypedValue _ _ ty) scos = case collectSkolems ty \\ map fst scos of
367+ (sco : _) -> ([(findBindingScope sco, val)], scos)
370+ collectSkolems :: Type -> [SkolemScope]
371+ collectSkolems = nub . everything (++) (mkQ [] collect)
373+ collect (Skolem _ scope) = [scope]
375+ go _ scos = ([], scos)
376+ findBindingScope :: SkolemScope -> Maybe Value
377+ findBindingScope sco = something (mkQ Nothing go) root
379+ go val@(TypedValue _ _ (ForAll _ _ (Just sco'))) | sco == sco' = Just val
381+skolemEscapeCheck val = throwError $ "Untyped value passed to skolemEscapeCheck: " ++ prettyPrintValue val
384+-- Ensure a row contains no duplicate labels
386+setify :: Type -> Type
387+setify = rowFromList . first (M.toList . M.fromList) . rowToList
390+-- \"Setify\" all rows occuring inside a value
392+setifyAll :: (D.Data d) => d -> d
393+setifyAll = everywhere (mkT setify)
396+-- Replace outermost unsolved unification variables with named type variables
398+varIfUnknown :: Type -> Type
400+ let unks = nub $ unknowns ty
401+ toName = (:) 't' . show
402+ ty' = everywhere (mkT typeToVar) $ ty
403+ typeToVar :: Type -> Type
404+ typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
406+ in mkForAll (sort . map (toName . runUnknown) $ unks) ty'
409+-- Remove any ForAlls and ConstrainedType constructors in a type by introducing new unknowns
410+-- or TypeClassDictionary values.
412+-- This is necessary during type checking to avoid unifying a polymorphic type with a
413+-- unification variable.
415+instantiatePolyTypeWithUnknowns :: Value -> Type -> UnifyT Type Check (Value, Type)
416+instantiatePolyTypeWithUnknowns val (ForAll ident ty _) = do
417+ ty' <- replaceVarWithUnknown ident ty
418+ instantiatePolyTypeWithUnknowns val ty'
419+instantiatePolyTypeWithUnknowns val (ConstrainedType constraints ty) = do
421+ Just moduleName <- checkCurrentModule <$> get
422+ dicts <- getTypeClassDictionaries
423+ (_, ty') <- instantiatePolyTypeWithUnknowns (error "Types under a constraint cannot themselves be constrained") ty
424+ return (foldl App val (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints)), ty')
425+instantiatePolyTypeWithUnknowns val ty = return (val, ty)
428+-- Replace a single type variable with a new unification variable
430+replaceVarWithUnknown :: String -> Type -> UnifyT Type Check Type
431+replaceVarWithUnknown ident ty = do
433+ return $ replaceTypeVars ident tu $ ty
436+-- Replace fully applied type synonyms with the @SaturatedTypeSynonym@ data constructor, which helps generate
437+-- better error messages during unification.
439+replaceAllTypeSynonyms' :: (D.Data d) => Environment -> ModuleName -> d -> Either String d
440+replaceAllTypeSynonyms' env moduleName d =
442+ syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
444+ saturateAllTypeSynonyms env moduleName syns d
446+replaceAllTypeSynonyms :: (Functor m, Monad m, MonadState CheckState m, MonadError String m) => (D.Data d) => d -> m d
447+replaceAllTypeSynonyms d = do
449+ Just moduleName <- checkCurrentModule <$> get
450+ either throwError return $ replaceAllTypeSynonyms' env moduleName d
453+-- \"Desaturate\" @SaturatedTypeSynonym@s
455+desaturateAllTypeSynonyms :: (D.Data d) => d -> d
456+desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
458+ replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
459+ replaceSaturatedTypeSynonym t = t
462+-- Replace a type synonym and its arguments with the aliased type
464+expandTypeSynonym' :: Environment -> ModuleName -> Qualified ProperName -> [Type] -> Either String Type
465+expandTypeSynonym' env moduleName name args =
466+ case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
467+ Just (synArgs, body) -> do
468+ let repl = replaceAllTypeVars (zip synArgs args) body
469+ replaceAllTypeSynonyms' env moduleName repl
470+ Nothing -> error "Type synonym was not defined"
472+expandTypeSynonym :: (Functor m, Monad m, MonadState CheckState m, MonadError String m) => Qualified ProperName -> [Type] -> m Type
473+expandTypeSynonym name args = do
475+ Just moduleName <- checkCurrentModule <$> get
476+ either throwError return $ expandTypeSynonym' env moduleName name args
479+-- Ensure a set of property names and value does not contain duplicate labels
481+ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
482+ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
485+-- Infer a type for a value, rethrowing any error to provide a more useful error message
487+infer :: Value -> UnifyT Type Check Value
488+infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ infer' val
491+-- Infer a type for a value
493+infer' :: Value -> UnifyT Type Check Value
494+infer' v@(NumericLiteral _) = return $ TypedValue True v tyNumber
495+infer' v@(StringLiteral _) = return $ TypedValue True v tyString
496+infer' v@(BooleanLiteral _) = return $ TypedValue True v tyBoolean
497+infer' (ArrayLiteral vals) = do
498+ ts <- mapM infer vals
500+ forM_ ts $ \(TypedValue _ _ t) -> els =?= TypeApp tyArray t
501+ return $ TypedValue True (ArrayLiteral ts) els
502+infer' (ObjectLiteral ps) = do
503+ ensureNoDuplicateProperties ps
504+ ts <- mapM (infer . snd) ps
505+ let fields = zipWith (\name (TypedValue _ _ t) -> (name, t)) (map fst ps) ts
506+ ty = Object $ rowFromList (fields, REmpty)
507+ return $ TypedValue True (ObjectLiteral (zip (map fst ps) ts)) ty
508+infer' (ObjectUpdate o ps) = do
509+ ensureNoDuplicateProperties ps
511+ newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
512+ let newTys = map (\(name, TypedValue _ _ ty) -> (name, ty)) newVals
513+ oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
514+ let oldTy = Object $ rowFromList (oldTys, row)
515+ o' <- TypedValue True <$> check o oldTy <*> pure oldTy
516+ return $ TypedValue True (ObjectUpdate o' newVals) $ Object $ rowFromList (newTys, row)
517+infer' (Accessor prop val) = do
518+ typed@(TypedValue _ _ objTy) <- infer val
519+ propTy <- inferProperty objTy prop
524+ _ <- subsumes Nothing objTy (Object (RCons prop field rest))
525+ return $ TypedValue True (Accessor prop typed) field
526+ Just ty -> return $ TypedValue True (Accessor prop typed) ty
527+infer' (Abs (Left arg) ret) = do
529+ Just moduleName <- checkCurrentModule <$> get
530+ bindLocalVariables moduleName [(arg, ty)] $ do
531+ body@(TypedValue _ _ bodyTy) <- infer' ret
532+ return $ TypedValue True (Abs (Left arg) body) $ function ty bodyTy
533+infer' (Abs (Right _) _) = error "Binder was not desugared"
534+infer' (App f arg) = do
535+ f'@(TypedValue _ _ ft) <- infer f
536+ (ret, app) <- checkFunctionApplication f' ft arg
537+ return $ TypedValue True app ret
538+infer' (Var var) = do
539+ Just moduleName <- checkCurrentModule <$> get
540+ ty <- introduceSkolemScope <=< replaceAllTypeSynonyms <=< lookupVariable moduleName $ var
542+ ConstrainedType constraints ty' -> do
544+ dicts <- getTypeClassDictionaries
545+ return $ TypedValue True (foldl App (Var var) (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) ty'
546+ _ -> return $ TypedValue True (Var var) ty
547+infer' v@(Constructor c) = do
549+ Just moduleName <- checkCurrentModule <$> get
550+ case M.lookup (qualify moduleName c) (dataConstructors env) of
551+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
552+ Just (ty, _) -> do ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
553+ return $ TypedValue True v ty'
554+infer' (Case vals binders) = do
555+ ts <- mapM infer vals
557+ binders' <- checkBinders (map (\(TypedValue _ _ t) -> t) ts) ret binders
558+ return $ TypedValue True (Case ts binders') ret
559+infer' (IfThenElse cond th el) = do
560+ cond' <- check cond tyBoolean
561+ v2@(TypedValue _ _ t2) <- infer th
562+ v3@(TypedValue _ _ t3) <- infer el
564+ return $ TypedValue True (IfThenElse cond' v2 v3) t2
565+infer' (TypedValue checkType val ty) = do
566+ Just moduleName <- checkCurrentModule <$> get
567+ kind <- liftCheck $ kindOf moduleName ty
568+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
569+ ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
570+ val' <- if checkType then check val ty' else return val
571+ return $ TypedValue True val' ty'
572+infer' _ = error "Invalid argument to infer"
575+-- Infer the type of a property inside a record with a given type
577+inferProperty :: Type -> String -> UnifyT Type Check (Maybe Type)
578+inferProperty (Object row) prop = do
579+ let (props, _) = rowToList row
580+ return $ lookup prop props
581+inferProperty (SaturatedTypeSynonym name args) prop = do
582+ replaced <- introduceSkolemScope <=< expandTypeSynonym name $ args
583+ inferProperty replaced prop
584+inferProperty (ForAll ident ty _) prop = do
585+ replaced <- replaceVarWithUnknown ident ty
586+ inferProperty replaced prop
587+inferProperty _ _ = return Nothing
590+-- Infer the types of variables brought into scope by a binder
592+inferBinder :: Type -> Binder -> UnifyT Type Check (M.Map Ident Type)
593+inferBinder _ NullBinder = return M.empty
594+inferBinder val (StringBinder _) = val =?= tyString >> return M.empty
595+inferBinder val (NumberBinder _) = val =?= tyNumber >> return M.empty
596+inferBinder val (BooleanBinder _) = val =?= tyBoolean >> return M.empty
597+inferBinder val (VarBinder name) = return $ M.singleton name val
598+inferBinder val (ConstructorBinder ctor binders) = do
600+ Just moduleName <- checkCurrentModule <$> get
601+ case M.lookup (qualify moduleName ctor) (dataConstructors env) of
603+ (_, fn) <- instantiatePolyTypeWithUnknowns (error "Data constructor types cannot contains constraints") ty
607+ subsumes Nothing val ty
609+ go (binder : binders) (TypeApp (TypeApp t obj) ret) | t == tyFunction =
610+ M.union <$> inferBinder obj binder <*> go binders ret
611+ go _ _ = throwError $ "Wrong number of arguments to constructor " ++ show ctor
612+ _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
613+inferBinder val (ObjectBinder props) = do
616+ m1 <- inferRowProperties row rest props
620+ inferRowProperties :: Type -> Type -> [(String, Binder)] -> UnifyT Type Check (M.Map Ident Type)
621+ inferRowProperties nrow row [] = nrow =?= row >> return M.empty
622+ inferRowProperties nrow row ((name, binder):binders) = do
624+ m1 <- inferBinder propTy binder
625+ m2 <- inferRowProperties nrow (RCons name propTy row) binders
626+ return $ m1 `M.union` m2
627+inferBinder val (ArrayBinder binders) = do
629+ m1 <- M.unions <$> mapM (inferBinder el) binders
630+ val =?= TypeApp tyArray el
632+inferBinder val (ConsBinder headBinder tailBinder) = do
634+ m1 <- inferBinder el headBinder
635+ m2 <- inferBinder val tailBinder
636+ val =?= TypeApp tyArray el
637+ return $ m1 `M.union` m2
638+inferBinder val (NamedBinder name binder) = do
639+ m <- inferBinder val binder
640+ return $ M.insert name val m
643+-- Check the types of the return values in a set of binders in a case statement
645+checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> UnifyT Type Check [([Binder], Maybe Guard, Value)]
646+checkBinders _ _ [] = return []
647+checkBinders nvals ret ((binders, grd, val):bs) = do
648+ Just moduleName <- checkCurrentModule <$> get
649+ m1 <- M.unions <$> zipWithM inferBinder nvals binders
650+ r <- bindLocalVariables moduleName (M.toList m1) $ do
651+ val' <- TypedValue True <$> check val ret <*> pure ret
653+ Nothing -> return (binders, Nothing, val')
655+ g' <- check g tyBoolean
656+ return (binders, Just g', val')
657+ rs <- checkBinders nvals ret bs
661+-- Check that a local variable name is not already used
663+assignVariable :: Ident -> UnifyT Type Check ()
664+assignVariable name = do
665+ env <- checkEnv <$> get
666+ Just moduleName <- checkCurrentModule <$> get
667+ case M.lookup (moduleName, name) (names env) of
668+ Just _ -> UnifyT . lift . throwError $ "Variable with name " ++ show name ++ " already exists."
672+-- Generate a new skolem constant
674+newSkolemConstant :: UnifyT Type Check Int
675+newSkolemConstant = runUnknown <$> fresh'
678+-- Generate a new skolem scope
680+newSkolemScope :: UnifyT Type Check SkolemScope
681+newSkolemScope = SkolemScope . runUnknown <$> fresh'
684+-- Skolemize a type variable by replacing its instances with fresh skolem constants
686+skolemize :: String -> Int -> SkolemScope -> Type -> Type
687+skolemize ident sko scope = replaceTypeVars ident (Skolem sko scope)
690+-- Introduce skolem scope at every occurence of a ForAll
692+introduceSkolemScope :: Type -> UnifyT Type Check Type
693+introduceSkolemScope = everywhereM (mkM go)
695+ go (ForAll ident ty Nothing) = ForAll ident ty <$> (Just <$> newSkolemScope)
696+ go other = return other
699+-- Check the type of a value, rethrowing errors to provide a better error message
701+check :: Value -> Type -> UnifyT Type Check Value
702+check val ty = rethrow errorMessage $ check' val ty
705+ "Error checking type of term " ++
706+ prettyPrintValue val ++
708+ prettyPrintType ty ++
713+-- Check the type of a value
715+check' :: Value -> Type -> UnifyT Type Check Value
716+check' val t@(ForAll ident ty _) = do
717+ scope <- newSkolemScope
718+ sko <- newSkolemConstant
719+ let sk = skolemize ident sko scope ty
720+ val' <- check val sk
721+ return $ TypedValue True val' (ForAll ident ty (Just scope))
722+check' val t@(ConstrainedType constraints ty) = do
724+ Just moduleName <- checkCurrentModule <$> get
725+ dictNames <- flip mapM constraints $ \(Qualified _ (ProperName className), _) -> do
726+ n <- liftCheck freshDictionaryName
727+ return $ Ident $ "__dict_" ++ className ++ "_" ++ show n
728+ val' <- withTypeClassDictionaries (zipWith (\name (className, instanceTy) ->
729+ TypeClassDictionaryInScope name className instanceTy Nothing TCDRegular) (map (Qualified Nothing) dictNames)
730+ (qualifyAllUnqualifiedNames moduleName env constraints)) $
732+ return $ TypedValue True (foldr Abs val' (map Left dictNames)) t
733+check' val t@(SaturatedTypeSynonym name args) = do
734+ ty <- introduceSkolemScope <=< expandTypeSynonym name $ args
735+ val' <- check val ty
736+ return $ TypedValue True val' ty
737+check' val u@(TUnknown _) = do
738+ val'@(TypedValue _ _ ty) <- infer val
739+ -- Don't unify an unknown with an inferred polytype
740+ (val'', ty') <- instantiatePolyTypeWithUnknowns val' ty
742+ return $ TypedValue True val'' ty'
743+check' v@(NumericLiteral _) t | t == tyNumber =
744+ return $ TypedValue True v t
745+check' v@(StringLiteral _) t | t == tyString =
746+ return $ TypedValue True v t
747+check' v@(BooleanLiteral _) t | t == tyBoolean =
748+ return $ TypedValue True v t
749+check' (ArrayLiteral vals) t@(TypeApp a ty) | a == tyArray = do
750+ arr <- ArrayLiteral <$> forM vals (\val -> check val ty)
751+ return $ TypedValue True arr t
752+check' (Abs (Left arg) ret) ty@(TypeApp (TypeApp t argTy) retTy) | t == tyFunction = do
753+ Just moduleName <- checkCurrentModule <$> get
754+ ret' <- bindLocalVariables moduleName [(arg, argTy)] $ check ret retTy
755+ return $ TypedValue True (Abs (Left arg) ret') ty
756+check' (Abs (Right _) _) _ = error "Binder was not desugared"
757+check' (App f arg) ret = do
758+ f'@(TypedValue _ _ ft) <- infer f
759+ (ret', app) <- checkFunctionApplication f' ft arg
760+ subsumes Nothing ret' ret
761+ return $ TypedValue True app ret
762+check' v@(Var var) ty = do
763+ Just moduleName <- checkCurrentModule <$> get
764+ repl <- introduceSkolemScope <=< replaceAllTypeSynonyms <=< lookupVariable moduleName $ var
765+ ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
766+ v' <- subsumes (Just v) repl ty'
768+ Nothing -> throwError "Unable to check type subsumption"
769+ Just v'' -> return $ TypedValue True v'' ty'
770+check' (TypedValue checkType val ty1) ty2 = do
771+ Just moduleName <- checkCurrentModule <$> get
772+ kind <- liftCheck $ kindOf moduleName ty1
773+ guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
774+ ty1' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty1
775+ val' <- subsumes (Just val) ty1' ty2
777+ Nothing -> throwError "Unable to check type subsumption"
779+ val''' <- if checkType then check val'' ty1 else return val''
780+ return $ TypedValue checkType (TypedValue True val''' ty1) ty2
781+check' (Case vals binders) ret = do
782+ vals' <- mapM infer vals
783+ let ts = map (\(TypedValue _ _ t) -> t) vals'
784+ binders' <- checkBinders ts ret binders
785+ return $ TypedValue True (Case vals' binders') ret
786+check' (IfThenElse cond th el) ty = do
787+ cond' <- check cond tyBoolean
790+ return $ TypedValue True (IfThenElse cond' th' el') ty
791+check' (ObjectLiteral ps) t@(Object row) = do
792+ ensureNoDuplicateProperties ps
793+ ps' <- checkProperties ps row False
794+ return $ TypedValue True (ObjectLiteral ps') t
795+check' (ObjectUpdate obj ps) t@(Object row) = do
796+ ensureNoDuplicateProperties ps
797+ us <- zip (map fst ps) <$> replicateM (length ps) fresh
798+ let (propsToCheck, rest) = rowToList row
799+ propsToRemove = map fst ps
800+ remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
801+ obj' <- check obj (Object (rowFromList (us ++ remainingProps, rest)))
802+ ps' <- checkProperties ps row True
803+ return $ TypedValue True (ObjectUpdate obj' ps') t
804+check' (Accessor prop val) ty = do
806+ val' <- check val (Object (RCons prop ty rest))
807+ return $ TypedValue True (Accessor prop val') ty
808+check' (Constructor c) ty = do
810+ Just moduleName <- checkCurrentModule <$> get
811+ case M.lookup (qualify moduleName c) (dataConstructors env) of
812+ Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
814+ repl <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty1
815+ _ <- subsumes Nothing repl ty
816+ return $ TypedValue True (Constructor c) ty
817+check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
820+-- Check the type of a collection of named record fields
822+-- The @lax@ parameter controls whether or not every record member has to be provided. For object updates, this is not the case.
824+checkProperties :: [(String, Value)] -> Type -> Bool -> UnifyT Type Check [(String, Value)]
825+checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
826+ go [] [] REmpty = return []
827+ go [] [] u@(TUnknown _) = do u =?= REmpty
829+ go [] [] (Skolem _ _) | lax = return []
830+ go [] ((p, _): _) _ | lax = return []
831+ | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
832+ go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
833+ go ((p,v):ps') [] u@(TUnknown _) = do
834+ v'@(TypedValue _ _ ty) <- infer v
836+ u =?= RCons p ty rest
837+ ps'' <- go ps' [] rest
838+ return $ (p, v') : ps''
839+ go ((p,v):ps') ts r =
842+ v'@(TypedValue _ _ ty) <- infer v
844+ r =?= RCons p ty rest
845+ ps'' <- go ps' ts rest
846+ return $ (p, v') : ps''
849+ ps'' <- go ps' (delete (p, ty) ts) r
850+ return $ (p, v') : ps''
851+ go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
854+-- Check the type of a function application, rethrowing errors to provide a better error message
856+checkFunctionApplication :: Value -> Type -> Value -> UnifyT Type Check (Type, Value)
857+checkFunctionApplication fn fnTy arg = rethrow errorMessage $ checkFunctionApplication' fn fnTy arg
859+ errorMessage msg = "Error applying function of type "
860+ ++ prettyPrintType fnTy
861+ ++ " to argument " ++ prettyPrintValue arg
865+-- Check the type of a function application
867+checkFunctionApplication' :: Value -> Type -> Value -> UnifyT Type Check (Type, Value)
868+checkFunctionApplication' fn (TypeApp (TypeApp tyFunction' argTy) retTy) arg = do
869+ tyFunction' =?= tyFunction
870+ arg' <- check arg argTy
871+ return (retTy, App fn arg')
872+checkFunctionApplication' fn (ForAll ident ty _) arg = do
873+ replaced <- replaceVarWithUnknown ident ty
874+ checkFunctionApplication fn replaced arg
875+checkFunctionApplication' fn u@(TUnknown _) arg = do
877+ TypedValue _ arg' t <- infer arg
878+ (arg'', t') <- instantiatePolyTypeWithUnknowns arg' t
879+ return $ TypedValue True arg'' t'
880+ let ty = (\(TypedValue _ _ t) -> t) arg'
882+ u =?= function ty ret
883+ return (ret, App fn arg')
884+checkFunctionApplication' fn (SaturatedTypeSynonym name tyArgs) arg = do
885+ ty <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
886+ checkFunctionApplication fn ty arg
887+checkFunctionApplication' fn (ConstrainedType constraints fnTy) arg = do
889+ dicts <- getTypeClassDictionaries
890+ Just moduleName <- checkCurrentModule <$> get
891+ checkFunctionApplication' (foldl App fn (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) fnTy arg
892+checkFunctionApplication' _ fnTy arg = throwError $ "Cannot apply a function of type "
893+ ++ prettyPrintType fnTy
894+ ++ " to argument " ++ prettyPrintValue arg
897+-- Check whether one type subsumes another, rethrowing errors to provide a better error message
899+subsumes :: Maybe Value -> Type -> Type -> UnifyT Type Check (Maybe Value)
900+subsumes val ty1 ty2 = rethrow errorMessage $ subsumes' val ty1 ty2
902+ errorMessage msg = "Error checking that type "
903+ ++ prettyPrintType ty1
904+ ++ " subsumes type "
905+ ++ prettyPrintType ty2
909+-- Check whether one type subsumes another
911+subsumes' :: Maybe Value -> Type -> Type -> UnifyT Type Check (Maybe Value)
912+subsumes' val (ForAll ident ty1 _) ty2 = do
913+ replaced <- replaceVarWithUnknown ident ty1
914+ subsumes val replaced ty2
915+subsumes' val ty1 (ForAll ident ty2 sco) =
918+ sko <- newSkolemConstant
919+ let sk = skolemize ident sko sco' ty2
921+ Nothing -> throwError "Skolem variable scope is unspecified"
922+subsumes' val (TypeApp (TypeApp f1 arg1) ret1) (TypeApp (TypeApp f2 arg2) ret2) | f1 == tyFunction && f2 == tyFunction = do
923+ subsumes Nothing arg2 arg1
924+ subsumes Nothing ret1 ret2
926+subsumes' val (SaturatedTypeSynonym name tyArgs) ty2 = do
927+ ty1 <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
928+ subsumes val ty1 ty2
929+subsumes' val ty1 (SaturatedTypeSynonym name tyArgs) = do
930+ ty2 <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
931+ subsumes val ty1 ty2
932+subsumes' (Just val) (ConstrainedType constraints ty1) ty2 = do
934+ dicts <- getTypeClassDictionaries
935+ Just moduleName <- checkCurrentModule <$> get
936+ _ <- subsumes' Nothing ty1 ty2
937+ return . Just $ foldl App val (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))
938+subsumes' val (Object r1) (Object r2) = do
940+ (ts1, r1') = rowToList r1
941+ (ts2, r2') = rowToList r2
942+ ts1' = sortBy (comparing fst) ts1
943+ ts2' = sortBy (comparing fst) ts2
944+ go ts1' ts2' r1' r2'
947+ go [] ts2 r1 r2 = r1 =?= rowFromList (ts2, r2)
948+ go ts1 [] r1 r2 = r2 =?= rowFromList (ts1, r1)
949+ go ((p1, ty1) : ts1) ((p2, ty2) : ts2) r1 r2
950+ | p1 == p2 = do subsumes Nothing ty1 ty2
952+ | p1 < p2 = do rest <- fresh
953+ r2 =?= RCons p1 ty1 rest
954+ go ts1 ((p2, ty2) : ts2) r1 rest
955+ | p1 > p2 = do rest <- fresh
956+ r1 =?= RCons p2 ty2 rest
957+ go ((p1, ty1) : ts1) ts2 rest r2
958+subsumes' val ty1 ty2@(Object _) = subsumes val ty2 ty1
959+subsumes' val ty1 ty2 = do