@@ -1,985 +0,0 @@
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 FlexibleInstances #-}
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.Declarations
53−import Language.PureScript.Types
54−import Language.PureScript.Kinds
55−import Language.PureScript.Names
56−import Language.PureScript.TypeClassDictionaries
57−import Language.PureScript.TypeChecker.Monad
58−import Language.PureScript.TypeChecker.Kinds
59−import Language.PureScript.TypeChecker.Synonyms
60−import Language.PureScript.Pretty
61−import Language.PureScript.Environment
62−import qualified Language.PureScript.Constants as C
64−import Control.Monad.State
65−import Control.Monad.Error
66−import Control.Monad.Unify
68−import Control.Applicative
69−import Control.Arrow (Arrow(..))
71−import qualified Data.Map as M
72−import Data.Function (on)
73−import Data.Ord (comparing)
74−import Data.Monoid ((<>))
76−instance Partial Type where
78− isUnknown (TUnknown u) = Just u
79− isUnknown _ = Nothing
81−instance Unifiable Check Type where
85−-- Unify two types, updating the current substitution
87−unifyTypes :: Type -> Type -> UnifyT Type Check ()
88−unifyTypes t1 t2 = rethrow (mkUnifyErrorStack ("Error unifying type " ++ prettyPrintType t1 ++ " with type " ++ prettyPrintType t2) Nothing <>) $
91− unifyTypes' (TUnknown u1) (TUnknown u2) | u1 == u2 = return ()
92− unifyTypes' (TUnknown u) t = u =:= t
93− unifyTypes' t (TUnknown u) = u =:= t
94− unifyTypes' (SaturatedTypeSynonym name args) ty = do
95− ty1 <- introduceSkolemScope <=< expandTypeSynonym name $ args
97− unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
98− unifyTypes' (ForAll ident1 ty1 sc1) (ForAll ident2 ty2 sc2) =
100− (Just sc1', Just sc2') -> do
101− sko <- newSkolemConstant
102− let sk1 = skolemize ident1 sko sc1' ty1
103− let sk2 = skolemize ident2 sko sc2' ty2
104− sk1 `unifyTypes` sk2
105− _ -> error "Skolemized type variable was not given a scope"
106− unifyTypes' (ForAll ident ty1 (Just sc)) ty2 = do
107− sko <- newSkolemConstant
108− let sk = skolemize ident sko sc ty1
110− unifyTypes' ForAll{} _ = throwError . strMsg $ "Skolem variable scope is unspecified"
111− unifyTypes' ty f@ForAll{} = f `unifyTypes` ty
112− unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
113− unifyTypes' (TypeConstructor c1) (TypeConstructor c2) =
114− guardWith (strMsg ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".")) (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' t@(ConstrainedType _ _) _ = throwError . strMsg $ "Attempted to unify a constrained type " ++ prettyPrintType t ++ " with another type."
124− unifyTypes' t3 t4@(ConstrainedType _ _) = unifyTypes' t4 t3
125− unifyTypes' t3 t4 = throwError . strMsg $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
128−-- Unify two rows, updating the current substitution
130−-- Common labels are first identified, and unified. Remaining labels and types are unified with a
131−-- trailing row unification variable, if appropriate, otherwise leftover labels result in a unification
134−unifyRows :: Type -> Type -> UnifyT Type Check ()
137− (s1, r1') = rowToList r1
138− (s2, r2') = rowToList r2
139− int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
140− sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
141− sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
143− forM_ int (uncurry (=?=))
144− unifyRows' sd1 r1' sd2 r2'
146− unifyRows' :: [(String, Type)] -> Type -> [(String, Type)] -> Type -> UnifyT Type Check ()
147− unifyRows' [] (TUnknown u) sd r = u =:= rowFromList (sd, r)
148− unifyRows' sd r [] (TUnknown u) = u =:= rowFromList (sd, r)
149− unifyRows' ((name, ty):row) r others u@(TUnknown un) = do
151− forM_ row $ \(_, t) -> occursCheck un t
153− u =?= RCons name ty u'
154− unifyRows' row r others u'
155− unifyRows' [] REmpty [] REmpty = return ()
156− unifyRows' [] (TypeVar v1) [] (TypeVar v2) | v1 == v2 = return ()
157− unifyRows' [] (Skolem s1 _) [] (Skolem s2 _) | s1 == s2 = return ()
158− unifyRows' sd3 r3 sd4 r4 = throwError . strMsg $ "Cannot unify (" ++ prettyPrintRow (rowFromList (sd3, r3)) ++ ") with (" ++ prettyPrintRow (rowFromList (sd4, r4)) ++ ")"
161−-- Infer the types of multiple mutually-recursive values, and return elaborated values including
162−-- type class dictionaries and type annotations.
164−typesOf :: Maybe ModuleName -> ModuleName -> [(Ident, Value)] -> Check [(Ident, (Value, Type))]
165−typesOf mainModuleName moduleName vals = do
166− tys <- fmap tidyUp . liftUnify $ do
167− (es, dict, untypedDict) <- typeDictionaryForBindingGroup moduleName vals
169− triple@(_, (_, ty)) <- typeForBindingGroupElement moduleName e dict untypedDict
170− -- If --main is enabled, need to check that `main` has type Eff eff a for some eff, a
171− when (Just moduleName == mainModuleName && fst e == Ident C.main) $ do
172− [eff, a] <- replicateM 2 fresh
173− ty =?= TypeApp (TypeApp (TypeConstructor (Qualified (Just (ModuleName [ProperName "Control", ProperName "Monad", ProperName "Eff"])) (ProperName "Eff"))) eff) a
176− forM tys $ \(ident, (val, ty)) -> do
177− -- Replace type class dictionary placeholders with actual dictionaries
178− val' <- replaceTypeClassDictionaries moduleName val
179− -- Check skolem variables did not escape their scope
180− skolemEscapeCheck val'
181− -- Remove type synonyms placeholders, remove duplicate row fields, and replace
182− -- top-level unification variables with named type variables.
183− let val'' = overTypes (desaturateAllTypeSynonyms . setifyAll) val'
184− ty' = varIfUnknown . desaturateAllTypeSynonyms . setifyAll $ ty
185− return (ident, (val'', ty'))
187− -- Apply the substitution that was returned from runUnify to both types and (type-annotated) values
188− tidyUp (ts, sub) = map (\(i, (val, ty)) -> (i, (overTypes (sub $?) val, sub $? ty))) ts
190−typeDictionaryForBindingGroup :: ModuleName -> [(Ident, Value)] -> UnifyT Type Check ([(Ident, (Value, Maybe (Type, Bool)))], M.Map (ModuleName, Ident) (Type, NameKind), [(Ident, Type)])
191−typeDictionaryForBindingGroup moduleName vals = do
193− -- Map each declaration to a name/value pair, with an optional type, if the declaration is typed
194− es = map isTyped vals
195− -- Filter the typed and untyped declarations
196− typed = filter (isJust . snd . snd) es
197− untyped = filter (isNothing . snd . snd) es
198− -- Make a map of names to typed declarations
199− typedDict = map (\(ident, (_, Just (ty, _))) -> (ident, ty)) typed
201− -- Create fresh unification variables for the types of untyped declarations
202− untypedNames <- replicateM (length untyped) fresh
205− -- Make a map of names to the unification variables of untyped declarations
206− untypedDict = zip (map fst untyped) untypedNames
207− -- Create the dictionary of all name/type pairs, which will be added to the environment during type checking
208− dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ typedDict ++ untypedDict)
209− return (es, dict, untypedDict)
211−typeForBindingGroupElement :: ModuleName -> (Ident, (Value, Maybe (Type, Bool))) -> M.Map (ModuleName, Ident) (Type, NameKind) -> [(Ident, Type)] -> UnifyT Type Check (Ident, (Value, Type))
212−typeForBindingGroupElement moduleName e@(_, (val, _)) dict untypedDict = do
213− -- If the declaration is a function, it has access to other values in the binding group.
214− -- If not, the generated code might fail at runtime since those values might be undefined.
215− let dict' = if isFunction val then dict else M.empty
217− -- Typed declarations
218− (ident, (val', Just (ty, checkType))) -> do
220− kind <- liftCheck $ kindOf moduleName ty
221− guardWith (strMsg $ "Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
222− -- Check the type with the new names in scope
223− ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
224− val'' <- bindNames dict' $ if checkType
225− then TypedValue True <$> check val' ty' <*> pure ty'
226− else return (TypedValue False val' ty')
227− return (ident, (val'', ty'))
228− -- Untyped declarations
229− (ident, (val', Nothing)) -> do
230− -- Infer the type with the new names in scope
231− TypedValue _ val'' ty <- bindNames dict' $ infer val'
232− ty =?= fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
233− return (ident, (TypedValue True val'' ty, ty))
236−-- Check if a value introduces a function
238−isFunction :: Value -> Bool
239−isFunction (Abs _ _) = True
240−isFunction (TypedValue _ val _) = isFunction val
241−isFunction (PositionedValue _ val) = isFunction val
245−-- Check if a value contains a type annotation
247−isTyped :: (Ident, Value) -> (Ident, (Value, Maybe (Type, Bool)))
248−isTyped (name, TypedValue checkType value ty) = (name, (value, Just (ty, checkType)))
249−isTyped (name, value) = (name, (value, Nothing))
252−-- Map a function over type annotations appearing inside a value
254−overTypes :: (Type -> Type) -> Value -> Value
255−overTypes f = everywhere (mkT f)
258−-- Replace type class dictionary placeholders with inferred type class dictionaries
260−replaceTypeClassDictionaries :: ModuleName -> Value -> Check Value
261−replaceTypeClassDictionaries mn = everywhereM' (mkM go)
263− go (TypeClassDictionary constraint dicts) = do
265− entails env mn dicts constraint
266− go other = return other
269−-- Check that the current set of type class dictionaries entail the specified type class goal, and, if so,
270−-- return a type class dictionary reference.
272−entails :: Environment -> ModuleName -> [TypeClassDictionaryInScope] -> (Qualified ProperName, [Type]) -> Check Value
273−entails env moduleName context goal@(className, tys) = do
275− [] -> throwError . strMsg $ "No " ++ show className ++ " instance found for " ++ intercalate ", " (map prettyPrintType tys)
276− (dict : _) -> return dict
278− go (className', tys') =
279− [ mkDictionary (canonicalizeDictionary tcd) args
281− -- Choose type class dictionaries in scope in the current module
283− -- Make sure the type class name matches the one we are trying to satisfy
284− , className' == tcdClassName tcd
285− -- Make sure the type unifies with the type in the type instance definition
286− , subst <- maybeToList . (>>= verifySubstitution) . fmap concat $ zipWithM (typeHeadsAreEqual moduleName env) tys' (tcdInstanceTypes tcd)
287− -- Solve any necessary subgoals
288− , args <- solveSubgoals subst (tcdDependencies tcd) ]
289− -- Create dictionaries for subgoals which still need to be solved by calling go recursively
290− -- E.g. the goal (Show a, Show b) => Show (Either a b) can be satisfied if the current type
291− -- unifies with Either a b, and we can satisfy the subgoals Show a and Show b recursively.
292− solveSubgoals :: [(String, Type)] -> Maybe [(Qualified ProperName, [Type])] -> [Maybe [Value]]
293− solveSubgoals _ Nothing = return Nothing
294− solveSubgoals subst (Just subgoals) = do
295− dict <- mapM (go . second (map (replaceAllTypeVars subst))) subgoals
297− -- Make a dictionary from subgoal dictionaries by applying the correct function
298− mkDictionary :: Qualified Ident -> Maybe [Value] -> Value
299− mkDictionary fnName Nothing = Var fnName
300− mkDictionary fnName (Just []) = App (Var fnName) (ObjectLiteral [])
301− mkDictionary fnName (Just dicts) = foldl App (Var fnName) dicts
302− -- Filter out type dictionaries which are in scope in the current module
303− filterModule :: TypeClassDictionaryInScope -> Bool
304− filterModule (TypeClassDictionaryInScope { tcdName = Qualified (Just mn) _ }) | mn == moduleName = True
305− filterModule (TypeClassDictionaryInScope { tcdName = Qualified Nothing _ }) = True
306− filterModule _ = False
307− -- Ensure that a substitution is valid
308− verifySubstitution :: [(String, Type)] -> Maybe [(String, Type)]
309− verifySubstitution subst = do
310− let grps = groupBy ((==) `on` fst) subst
311− guard (all (pairwise (unifiesWith env) . map snd) grps)
312− return $ map head grps
315−-- Check all values in a list pairwise match a predicate
317−pairwise :: (a -> a -> Bool) -> [a] -> Bool
319−pairwise _ [_] = True
320−pairwise p (x : xs) = all (p x) xs && pairwise p xs
323−-- Check that two types unify
325−unifiesWith :: Environment -> Type -> Type -> Bool
326−unifiesWith _ (TUnknown _) _ = True
327−unifiesWith _ _ (TUnknown _) = True
328−unifiesWith _ (Skolem s1 _) (Skolem s2 _) | s1 == s2 = True
329−unifiesWith _ (TypeVar v1) (TypeVar v2) | v1 == v2 = True
330−unifiesWith _ (TypeConstructor c1) (TypeConstructor c2) | c1 == c2 = True
331−unifiesWith e (TypeApp h1 t1) (TypeApp h2 t2) = unifiesWith e h1 h2 && unifiesWith e t1 t2
332−unifiesWith e (SaturatedTypeSynonym name args) t2 =
333− case expandTypeSynonym' e name args of
335− Right t1 -> unifiesWith e t1 t2
336−unifiesWith e t1 t2@(SaturatedTypeSynonym _ _) = unifiesWith e t2 t1
337−unifiesWith _ _ _ = False
340−-- Check whether the type heads of two types are equal (for the purposes of type class dictionary lookup),
341−-- and return a substitution from type variables to types which makes the type heads unify.
343−typeHeadsAreEqual :: ModuleName -> Environment -> Type -> Type -> Maybe [(String, Type)]
344−typeHeadsAreEqual _ _ (Skolem s1 _) (Skolem s2 _) | s1 == s2 = Just []
345−typeHeadsAreEqual _ _ t (TypeVar v) = Just [(v, t)]
346−typeHeadsAreEqual _ _ (TypeConstructor c1) (TypeConstructor c2) | c1 == c2 = Just []
347−typeHeadsAreEqual m e (TypeApp h1 t1) (TypeApp h2 t2) = (++) <$> typeHeadsAreEqual m e h1 h2 <*> typeHeadsAreEqual m e t1 t2
348−typeHeadsAreEqual m e (SaturatedTypeSynonym name args) t2 = case expandTypeSynonym' e name args of
350− Right t1 -> typeHeadsAreEqual m e t1 t2
351−typeHeadsAreEqual _ _ _ _ = Nothing
354−-- Ensure skolem variables do not escape their scope
356−skolemEscapeCheck :: Value -> Check ()
357−skolemEscapeCheck (TypedValue False _ _) = return ()
358−skolemEscapeCheck root@TypedValue{} =
359− -- Every skolem variable is created when a ForAll type is skolemized.
360− -- This determines the scope of that skolem variable, which is copied from the SkolemScope
361− -- field of the ForAll constructor.
362− -- We traverse the tree top-down, and collect any SkolemScopes introduced by ForAlls.
363− -- If a Skolem is encountered whose SkolemScope is not in the current list, we have found
364− -- an escaped skolem variable.
365− case everythingWithContext [] (++) (mkQ ((,) []) go) root of
367− ((binding, val) : _) -> throwError $ mkUnifyErrorStack ("Rigid/skolem type variable " ++ maybe "" (("bound by " ++) . prettyPrintValue) binding ++ " has escaped.") (Just (ValueError val))
369− go :: Value -> [(SkolemScope, Value)] -> ([(Maybe Value, Value)], [(SkolemScope, Value)])
370− go val@(TypedValue _ _ (ForAll _ _ (Just sco))) scos = ([], (sco, val) : scos)
371− go val@(TypedValue _ _ ty) scos = case collectSkolems ty \\ map fst scos of
372− (sco : _) -> ([(findBindingScope sco, val)], scos)
375− collectSkolems :: Type -> [SkolemScope]
376− collectSkolems = nub . everything (++) (mkQ [] collect)
378− collect (Skolem _ scope) = [scope]
380− go _ scos = ([], scos)
381− findBindingScope :: SkolemScope -> Maybe Value
382− findBindingScope sco = something (mkQ Nothing go') root
384− go' val@(TypedValue _ _ (ForAll _ _ (Just sco'))) | sco == sco' = Just val
386−skolemEscapeCheck val = throwError $ mkUnifyErrorStack "Untyped value passed to skolemEscapeCheck" (Just (ValueError val))
389−-- Ensure a row contains no duplicate labels
391−setify :: Type -> Type
392−setify = rowFromList . first (M.toList . M.fromList) . rowToList
395−-- \"Setify\" all rows occuring inside a value
397−setifyAll :: (D.Data d) => d -> d
398−setifyAll = everywhere (mkT setify)
401−-- Replace outermost unsolved unification variables with named type variables
403−varIfUnknown :: Type -> Type
405− let unks = nub $ unknowns ty
406− toName = (:) 't' . show
407− ty' = everywhere (mkT typeToVar) ty
408− typeToVar :: Type -> Type
409− typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
411− in mkForAll (sort . map (toName . runUnknown) $ unks) ty'
414−-- Remove any ForAlls and ConstrainedType constructors in a type by introducing new unknowns
415−-- or TypeClassDictionary values.
417−-- This is necessary during type checking to avoid unifying a polymorphic type with a
418−-- unification variable.
420−instantiatePolyTypeWithUnknowns :: Value -> Type -> UnifyT Type Check (Value, Type)
421−instantiatePolyTypeWithUnknowns val (ForAll ident ty _) = do
422− ty' <- replaceVarWithUnknown ident ty
423− instantiatePolyTypeWithUnknowns val ty'
424−instantiatePolyTypeWithUnknowns val (ConstrainedType constraints ty) = do
425− dicts <- getTypeClassDictionaries
426− (_, ty') <- instantiatePolyTypeWithUnknowns (error "Types under a constraint cannot themselves be constrained") ty
427− return (foldl App val (map (flip TypeClassDictionary dicts) constraints), ty')
428−instantiatePolyTypeWithUnknowns val ty = return (val, ty)
431−-- Replace a single type variable with a new unification variable
433−replaceVarWithUnknown :: String -> Type -> UnifyT Type Check Type
434−replaceVarWithUnknown ident ty = do
436− return $ replaceTypeVars ident tu ty
439−-- Replace fully applied type synonyms with the @SaturatedTypeSynonym@ data constructor, which helps generate
440−-- better error messages during unification.
442−replaceAllTypeSynonyms' :: (D.Data d) => Environment -> d -> Either String d
443−replaceAllTypeSynonyms' env d =
445− syns = map (\(name, (args, _)) -> (name, length args)) . M.toList $ typeSynonyms env
447− saturateAllTypeSynonyms syns d
449−replaceAllTypeSynonyms :: (Error e, Functor m, Monad m, MonadState CheckState m, MonadError e m) => (D.Data d) => d -> m d
450−replaceAllTypeSynonyms d = do
452− either (throwError . strMsg) return $ replaceAllTypeSynonyms' env d
455−-- \"Desaturate\" @SaturatedTypeSynonym@s
457−desaturateAllTypeSynonyms :: (D.Data d) => d -> d
458−desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
460− replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
461− replaceSaturatedTypeSynonym t = t
464−-- Replace a type synonym and its arguments with the aliased type
466−expandTypeSynonym' :: Environment -> Qualified ProperName -> [Type] -> Either String Type
467−expandTypeSynonym' env name args =
468− case M.lookup name (typeSynonyms env) of
469− Just (synArgs, body) -> do
470− let repl = replaceAllTypeVars (zip synArgs args) body
471− replaceAllTypeSynonyms' env repl
472− Nothing -> error "Type synonym was not defined"
474−expandTypeSynonym :: (Error e, Functor m, Monad m, MonadState CheckState m, MonadError e m) => Qualified ProperName -> [Type] -> m Type
475−expandTypeSynonym name args = do
477− either (throwError . strMsg) return $ expandTypeSynonym' env name args
479−expandAllTypeSynonyms :: (Error e, Functor m, Monad m, MonadState CheckState m, MonadError e m) => Type -> m Type
480−expandAllTypeSynonyms = everywhereM' (mkM go)
482− go (SaturatedTypeSynonym name args) = expandTypeSynonym name args
483− go other = return other
486−-- Ensure a set of property names and value does not contain duplicate labels
488−ensureNoDuplicateProperties :: (Error e, MonadError e m) => [(String, Value)] -> m ()
489−ensureNoDuplicateProperties ps = guardWith (strMsg "Duplicate property names") $ length (nub . map fst $ ps) == length ps
492−-- Infer a type for a value, rethrowing any error to provide a more useful error message
494−infer :: Value -> UnifyT Type Check Value
495−infer val = rethrow (mkUnifyErrorStack "Error inferring type of value" (Just (ValueError val)) <>) $ infer' val
498−-- Infer a type for a value
500−infer' :: Value -> UnifyT Type Check Value
501−infer' v@(NumericLiteral _) = return $ TypedValue True v tyNumber
502−infer' v@(StringLiteral _) = return $ TypedValue True v tyString
503−infer' v@(BooleanLiteral _) = return $ TypedValue True v tyBoolean
504−infer' (ArrayLiteral vals) = do
505− ts <- mapM infer vals
507− forM_ ts $ \(TypedValue _ _ t) -> els =?= TypeApp tyArray t
508− return $ TypedValue True (ArrayLiteral ts) els
509−infer' (ObjectLiteral ps) = do
510− ensureNoDuplicateProperties ps
511− ts <- mapM (infer . snd) ps
512− let fields = zipWith (\name (TypedValue _ _ t) -> (name, t)) (map fst ps) ts
513− ty = TypeApp tyObject $ rowFromList (fields, REmpty)
514− return $ TypedValue True (ObjectLiteral (zip (map fst ps) ts)) ty
515−infer' (ObjectUpdate o ps) = do
516− ensureNoDuplicateProperties ps
518− newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
519− let newTys = map (\(name, TypedValue _ _ ty) -> (name, ty)) newVals
520− oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
521− let oldTy = TypeApp tyObject $ rowFromList (oldTys, row)
522− o' <- TypedValue True <$> check o oldTy <*> pure oldTy
523− return $ TypedValue True (ObjectUpdate o' newVals) $ TypeApp tyObject $ rowFromList (newTys, row)
524−infer' (Accessor prop val) = do
525− typed@(TypedValue _ _ objTy) <- infer val
526− propTy <- inferProperty objTy prop
531− _ <- subsumes Nothing objTy (TypeApp tyObject (RCons prop field rest))
532− return $ TypedValue True (Accessor prop typed) field
533− Just ty -> return $ TypedValue True (Accessor prop typed) ty
534−infer' (Abs (Left arg) ret) = do
536− Just moduleName <- checkCurrentModule <$> get
537− bindLocalVariables moduleName [(arg, ty)] $ do
538− body@(TypedValue _ _ bodyTy) <- infer' ret
539− return $ TypedValue True (Abs (Left arg) body) $ function ty bodyTy
540−infer' (Abs (Right _) _) = error "Binder was not desugared"
541−infer' (App f arg) = do
542− f'@(TypedValue _ _ ft) <- infer f
543− (ret, app) <- checkFunctionApplication f' ft arg Nothing
544− return $ TypedValue True app ret
545−infer' (Var var) = do
546− Just moduleName <- checkCurrentModule <$> get
547− ty <- introduceSkolemScope <=< replaceAllTypeSynonyms <=< lookupVariable moduleName $ var
549− ConstrainedType constraints ty' -> do
550− dicts <- getTypeClassDictionaries
551− return $ TypedValue True (foldl App (Var var) (map (flip TypeClassDictionary dicts) constraints)) ty'
552− _ -> return $ TypedValue True (Var var) ty
553−infer' v@(Constructor c) = do
555− case M.lookup c (dataConstructors env) of
556− Nothing -> throwError . strMsg $ "Constructor " ++ show c ++ " is undefined"
557− Just (_, ty) -> do ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
558− return $ TypedValue True v ty'
559−infer' (Case vals binders) = do
560− ts <- mapM infer vals
562− binders' <- checkBinders (map (\(TypedValue _ _ t) -> t) ts) ret binders
563− return $ TypedValue True (Case ts binders') ret
564−infer' (IfThenElse cond th el) = do
565− cond' <- check cond tyBoolean
566− v2@(TypedValue _ _ t2) <- infer th
567− v3@(TypedValue _ _ t3) <- infer el
569− return $ TypedValue True (IfThenElse cond' v2 v3) t2
570−infer' (Let ds val) = do
571− (ds', val'@(TypedValue _ _ valTy)) <- inferLetBinding [] ds val infer
572− return $ TypedValue True (Let ds' val') valTy
573−infer' (TypedValue checkType val ty) = do
574− Just moduleName <- checkCurrentModule <$> get
575− kind <- liftCheck $ kindOf moduleName ty
576− guardWith (strMsg $ "Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
577− ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
578− val' <- if checkType then check val ty' else return val
579− return $ TypedValue True val' ty'
580−infer' (PositionedValue pos val) = rethrowWithPosition pos $ infer' val
581−infer' _ = error "Invalid argument to infer"
583−inferLetBinding :: [Declaration] -> [Declaration] -> Value -> (Value -> UnifyT Type Check Value) -> UnifyT Type Check ([Declaration], Value)
584−inferLetBinding seen [] ret j = (,) seen <$> j ret
585−inferLetBinding seen (ValueDeclaration ident nameKind [] Nothing val : rest) ret j = do
587− Just moduleName <- checkCurrentModule <$> get
588− TypedValue _ val' valTy' <- bindNames (M.singleton (moduleName, ident) (valTy, nameKind)) $ infer val
590− bindNames (M.singleton (moduleName, ident) (valTy', nameKind)) $ inferLetBinding (seen ++ [ValueDeclaration ident nameKind [] Nothing val']) rest ret j
591−inferLetBinding seen (BindingGroupDeclaration ds : rest) ret j = do
592− Just moduleName <- checkCurrentModule <$> get
593− (es, dict, untypedDict) <- typeDictionaryForBindingGroup moduleName (map (\(i, _, v) -> (i, v)) ds)
594− ds' <- forM es $ \e -> do
595− (ident, (val', _)) <- typeForBindingGroupElement moduleName e dict untypedDict
596− return $ (ident, LocalVariable, val')
597− bindNames dict $ inferLetBinding (seen ++ [BindingGroupDeclaration ds']) rest ret j
598−inferLetBinding seen (PositionedDeclaration pos d : ds) ret j = do
599− ((d' : ds'), val') <- inferLetBinding seen (d : ds) ret j
600− return (PositionedDeclaration pos d' : ds', val')
601−inferLetBinding _ _ _ _ = error "Invalid argument to inferLetBinding"
604−-- Infer the type of a property inside a record with a given type
606−inferProperty :: Type -> String -> UnifyT Type Check (Maybe Type)
607−inferProperty (TypeApp obj row) prop | obj == tyObject = do
608− let (props, _) = rowToList row
609− return $ lookup prop props
610−inferProperty (SaturatedTypeSynonym name args) prop = do
611− replaced <- introduceSkolemScope <=< expandTypeSynonym name $ args
612− inferProperty replaced prop
613−inferProperty (ForAll ident ty _) prop = do
614− replaced <- replaceVarWithUnknown ident ty
615− inferProperty replaced prop
616−inferProperty _ _ = return Nothing
619−-- Infer the types of variables brought into scope by a binder
621−inferBinder :: Type -> Binder -> UnifyT Type Check (M.Map Ident Type)
622−inferBinder _ NullBinder = return M.empty
623−inferBinder val (StringBinder _) = val =?= tyString >> return M.empty
624−inferBinder val (NumberBinder _) = val =?= tyNumber >> return M.empty
625−inferBinder val (BooleanBinder _) = val =?= tyBoolean >> return M.empty
626−inferBinder val (VarBinder name) = return $ M.singleton name val
627−inferBinder val (ConstructorBinder ctor binders) = do
629− case M.lookup ctor (dataConstructors env) of
631− (_, fn) <- instantiatePolyTypeWithUnknowns (error "Data constructor types cannot contain constraints") ty
632− fn' <- replaceAllTypeSynonyms fn
636− _ <- subsumes Nothing val ty'
638− go (binder : binders') (TypeApp (TypeApp t obj) ret) | t == tyFunction =
639− M.union <$> inferBinder obj binder <*> go binders' ret
640− go _ _ = throwError . strMsg $ "Wrong number of arguments to constructor " ++ show ctor
641− _ -> throwError . strMsg $ "Constructor " ++ show ctor ++ " is not defined"
642−inferBinder val (ObjectBinder props) = do
645− m1 <- inferRowProperties row rest props
646− val =?= TypeApp tyObject row
649− inferRowProperties :: Type -> Type -> [(String, Binder)] -> UnifyT Type Check (M.Map Ident Type)
650− inferRowProperties nrow row [] = nrow =?= row >> return M.empty
651− inferRowProperties nrow row ((name, binder):binders) = do
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
658− m1 <- M.unions <$> mapM (inferBinder el) binders
659− val =?= TypeApp tyArray el
661−inferBinder val (ConsBinder headBinder tailBinder) = do
663− m1 <- inferBinder el headBinder
664− m2 <- inferBinder val tailBinder
665− val =?= TypeApp tyArray 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−inferBinder val (PositionedBinder pos binder) =
671− rethrowWithPosition pos $ inferBinder val binder
674−-- Check the types of the return values in a set of binders in a case statement
676−checkBinders :: [Type] -> Type -> [CaseAlternative] -> UnifyT Type Check [CaseAlternative]
677−checkBinders _ _ [] = return []
678−checkBinders nvals ret (CaseAlternative binders grd val : bs) = do
679− Just moduleName <- checkCurrentModule <$> get
680− m1 <- M.unions <$> zipWithM inferBinder nvals binders
681− r <- bindLocalVariables moduleName (M.toList m1) $ do
682− val' <- TypedValue True <$> check val ret <*> pure ret
684− Nothing -> return $ CaseAlternative binders Nothing val'
686− g' <- check g tyBoolean
687− return $ CaseAlternative binders (Just g') val'
688− rs <- checkBinders nvals ret bs
692−-- Generate a new skolem constant
694−newSkolemConstant :: UnifyT Type Check Int
695−newSkolemConstant = runUnknown <$> fresh'
698−-- Generate a new skolem scope
700−newSkolemScope :: UnifyT Type Check SkolemScope
701−newSkolemScope = SkolemScope . runUnknown <$> fresh'
704−-- Skolemize a type variable by replacing its instances with fresh skolem constants
706−skolemize :: String -> Int -> SkolemScope -> Type -> Type
707−skolemize ident sko scope = replaceTypeVars ident (Skolem sko scope)
710−-- Introduce skolem scope at every occurence of a ForAll
712−introduceSkolemScope :: Type -> UnifyT Type Check Type
713−introduceSkolemScope = everywhereM (mkM go)
715− go (ForAll ident ty Nothing) = ForAll ident ty <$> (Just <$> newSkolemScope)
716− go other = return other
719−-- Check the type of a value, rethrowing errors to provide a better error message
721−check :: Value -> Type -> UnifyT Type Check Value
722−check val ty = rethrow (mkUnifyErrorStack errorMessage (Just (ValueError val)) <>) $ check' val ty
725− "Error checking type of term " ++
726− prettyPrintValue val ++
731−-- Check the type of a value
733−check' :: Value -> Type -> UnifyT Type Check Value
734−check' val (ForAll ident ty _) = do
735− scope <- newSkolemScope
736− sko <- newSkolemConstant
737− let sk = skolemize ident sko scope ty
738− val' <- check val sk
739− return $ TypedValue True val' (ForAll ident ty (Just scope))
740−check' val t@(ConstrainedType constraints ty) = do
741− dictNames <- forM constraints $ \(Qualified _ (ProperName className), _) -> do
742− n <- liftCheck freshDictionaryName
743− return $ Ident $ "__dict_" ++ className ++ "_" ++ show n
744− val' <- withTypeClassDictionaries (zipWith (\name (className, instanceTy) ->
745− TypeClassDictionaryInScope name className instanceTy Nothing TCDRegular) (map (Qualified Nothing) dictNames)
746− constraints) $ check val ty
747− return $ TypedValue True (foldr (Abs . Left) val' dictNames) t
748−check' val (SaturatedTypeSynonym name args) = do
749− ty <- introduceSkolemScope <=< expandTypeSynonym name $ args
751−check' val u@(TUnknown _) = do
752− val'@(TypedValue _ _ ty) <- infer val
753− -- Don't unify an unknown with an inferred polytype
754− (val'', ty') <- instantiatePolyTypeWithUnknowns val' ty
756− return $ TypedValue True val'' ty'
757−check' v@(NumericLiteral _) t | t == tyNumber =
758− return $ TypedValue True v t
759−check' v@(StringLiteral _) t | t == tyString =
760− return $ TypedValue True v t
761−check' v@(BooleanLiteral _) t | t == tyBoolean =
762− return $ TypedValue True v t
763−check' (ArrayLiteral vals) t@(TypeApp a ty) = do
765− array <- ArrayLiteral <$> forM vals (`check` ty)
766− return $ TypedValue True array t
767−check' (Abs (Left arg) ret) ty@(TypeApp (TypeApp t argTy) retTy) | t == tyFunction = do
768− Just moduleName <- checkCurrentModule <$> get
769− ret' <- bindLocalVariables moduleName [(arg, argTy)] $ check ret retTy
770− return $ TypedValue True (Abs (Left arg) ret') ty
771−check' (Abs (Right _) _) _ = error "Binder was not desugared"
772−check' (App f arg) ret = do
773− f'@(TypedValue _ _ ft) <- infer f
774− (_, app) <- checkFunctionApplication f' ft arg (Just ret)
775− return $ TypedValue True app ret
776−check' v@(Var var) ty = do
777− Just moduleName <- checkCurrentModule <$> get
778− repl <- introduceSkolemScope <=< replaceAllTypeSynonyms <=< lookupVariable moduleName $ var
779− ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
780− v' <- subsumes (Just v) repl ty'
782− Nothing -> throwError . strMsg $ "Unable to check type subsumption"
783− Just v'' -> return $ TypedValue True v'' ty'
784−check' (TypedValue checkType val ty1) ty2 = do
785− Just moduleName <- checkCurrentModule <$> get
786− kind <- liftCheck $ kindOf moduleName ty1
787− guardWith (strMsg $ "Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
788− ty1' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty1
789− val' <- subsumes (Just val) ty1' ty2
791− Nothing -> throwError . strMsg $ "Unable to check type subsumption"
793− val''' <- if checkType then check val'' ty1' else return val''
794− return $ TypedValue checkType (TypedValue True val''' ty1) ty2
795−check' (Case vals binders) ret = do
796− vals' <- mapM infer vals
797− let ts = map (\(TypedValue _ _ t) -> t) vals'
798− binders' <- checkBinders ts ret binders
799− return $ TypedValue True (Case vals' binders') ret
800−check' (IfThenElse cond th el) ty = do
801− cond' <- check cond tyBoolean
804− return $ TypedValue True (IfThenElse cond' th' el') ty
805−check' (ObjectLiteral ps) t@(TypeApp obj row) | obj == tyObject = do
806− ensureNoDuplicateProperties ps
807− ps' <- checkProperties ps row False
808− return $ TypedValue True (ObjectLiteral ps') t
809−check' (ObjectUpdate obj ps) t@(TypeApp o row) | o == tyObject = do
810− ensureNoDuplicateProperties ps
811− us <- zip (map fst ps) <$> replicateM (length ps) fresh
812− let (propsToCheck, rest) = rowToList row
813− propsToRemove = map fst ps
814− remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
815− obj' <- check obj (TypeApp tyObject (rowFromList (us ++ remainingProps, rest)))
816− ps' <- checkProperties ps row True
817− return $ TypedValue True (ObjectUpdate obj' ps') t
818−check' (Accessor prop val) ty = do
820− val' <- check val (TypeApp tyObject (RCons prop ty rest))
821− return $ TypedValue True (Accessor prop val') ty
822−check' (Constructor c) ty = do
824− case M.lookup c (dataConstructors env) of
825− Nothing -> throwError . strMsg $ "Constructor " ++ show c ++ " is undefined"
827− repl <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty1
828− _ <- subsumes Nothing repl ty
829− return $ TypedValue True (Constructor c) ty
830−check' (Let ds val) ty = do
831− (ds', val') <- inferLetBinding [] ds val (flip check ty)
832− return $ TypedValue True (Let ds' val') ty
833−check' val ty | containsTypeSynonyms ty = do
834− ty' <- introduceSkolemScope <=< expandAllTypeSynonyms $ ty
836−check' (PositionedValue pos val) ty =
837− rethrowWithPosition pos $ check val ty
838−check' val ty = throwError $ mkUnifyErrorStack ("Value does not have type " ++ prettyPrintType ty) (Just (ValueError val))
840−containsTypeSynonyms :: Type -> Bool
841−containsTypeSynonyms = everything (||) (mkQ False go) where
842− go (SaturatedTypeSynonym _ _) = True
846−-- Check the type of a collection of named record fields
848−-- The @lax@ parameter controls whether or not every record member has to be provided. For object updates, this is not the case.
850−checkProperties :: [(String, Value)] -> Type -> Bool -> UnifyT Type Check [(String, Value)]
851−checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
852− go [] [] REmpty = return []
853− go [] [] u@(TUnknown _) = do u =?= REmpty
855− go [] [] (Skolem _ _) | lax = return []
856− go [] ((p, _): _) _ | lax = return []
857− | otherwise = throwError $ mkUnifyErrorStack ("Object does not have property " ++ p) (Just (ValueError (ObjectLiteral ps)))
858− go ((p,_):_) [] REmpty = throwError $ mkUnifyErrorStack ("Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row) (Just (ValueError (ObjectLiteral ps)))
859− go ((p,v):ps') [] u@(TUnknown _) = do
860− v'@(TypedValue _ _ ty) <- infer v
862− u =?= RCons p ty rest
863− ps'' <- go ps' [] rest
864− return $ (p, v') : ps''
865− go ((p,v):ps') ts r =
868− v'@(TypedValue _ _ ty) <- infer v
870− r =?= RCons p ty rest
871− ps'' <- go ps' ts rest
872− return $ (p, v') : ps''
875− ps'' <- go ps' (delete (p, ty) ts) r
876− return $ (p, v') : ps''
877− go _ _ _ = throwError $ mkUnifyErrorStack ("Object does not have type " ++ prettyPrintType (TypeApp tyObject row)) (Just (ValueError (ObjectLiteral ps)))
880−-- Check the type of a function application, rethrowing errors to provide a better error message
882−checkFunctionApplication :: Value -> Type -> Value -> Maybe Type -> UnifyT Type Check (Type, Value)
883−checkFunctionApplication fn fnTy arg ret = rethrow (mkUnifyErrorStack errorMessage (Just (ValueError fn)) <>) $ checkFunctionApplication' fn fnTy arg ret
885− errorMessage = "Error applying function of type "
886− ++ prettyPrintType fnTy
887− ++ " to argument " ++ prettyPrintValue arg
890−-- Check the type of a function application
892−checkFunctionApplication' :: Value -> Type -> Value -> Maybe Type -> UnifyT Type Check (Type, Value)
893−checkFunctionApplication' fn (TypeApp (TypeApp tyFunction' argTy) retTy) arg ret = do
894− tyFunction' =?= tyFunction
895− _ <- maybe (return Nothing) (subsumes Nothing retTy) ret
896− subst <- unifyCurrentSubstitution <$> UnifyT get
897− arg' <- check arg (subst $? argTy)
898− return (retTy, App fn arg')
899−checkFunctionApplication' fn (ForAll ident ty _) arg ret = do
900− replaced <- replaceVarWithUnknown ident ty
901− checkFunctionApplication fn replaced arg ret
902−checkFunctionApplication' fn u@(TUnknown _) arg ret = do
904− TypedValue _ arg' t <- infer arg
905− (arg'', t') <- instantiatePolyTypeWithUnknowns arg' t
906− return $ TypedValue True arg'' t'
907− let ty = (\(TypedValue _ _ t) -> t) arg'
908− ret' <- maybe fresh return ret
909− u =?= function ty ret'
910− return (ret', App fn arg')
911−checkFunctionApplication' fn (SaturatedTypeSynonym name tyArgs) arg ret = do
912− ty <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
913− checkFunctionApplication fn ty arg ret
914−checkFunctionApplication' fn (ConstrainedType constraints fnTy) arg ret = do
915− dicts <- getTypeClassDictionaries
916− checkFunctionApplication' (foldl App fn (map (flip TypeClassDictionary dicts) constraints)) fnTy arg ret
917−checkFunctionApplication' _ fnTy arg _ = throwError . strMsg $ "Cannot apply a function of type "
918− ++ prettyPrintType fnTy
919− ++ " to argument " ++ prettyPrintValue arg
922−-- Check whether one type subsumes another, rethrowing errors to provide a better error message
924−subsumes :: Maybe Value -> Type -> Type -> UnifyT Type Check (Maybe Value)
925−subsumes val ty1 ty2 = rethrow (mkUnifyErrorStack errorMessage (ValueError <$> val) <>) $ subsumes' val ty1 ty2
927− errorMessage = "Error checking that type "
928− ++ prettyPrintType ty1
929− ++ " subsumes type "
930− ++ prettyPrintType ty2
933−-- Check whether one type subsumes another
935−subsumes' :: Maybe Value -> Type -> Type -> UnifyT Type Check (Maybe Value)
936−subsumes' val (ForAll ident ty1 _) ty2 = do
937− replaced <- replaceVarWithUnknown ident ty1
938− subsumes val replaced ty2
939−subsumes' val ty1 (ForAll ident ty2 sco) =
942− sko <- newSkolemConstant
943− let sk = skolemize ident sko sco' ty2
945− Nothing -> throwError . strMsg $ "Skolem variable scope is unspecified"
946−subsumes' val (TypeApp (TypeApp f1 arg1) ret1) (TypeApp (TypeApp f2 arg2) ret2) | f1 == tyFunction && f2 == tyFunction = do
947− _ <- subsumes Nothing arg2 arg1
948− _ <- subsumes Nothing ret1 ret2
950−subsumes' val (SaturatedTypeSynonym name tyArgs) ty2 = do
951− ty1 <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
952− subsumes val ty1 ty2
953−subsumes' val ty1 (SaturatedTypeSynonym name tyArgs) = do
954− ty2 <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
955− subsumes val ty1 ty2
956−subsumes' (Just val) (ConstrainedType constraints ty1) ty2 = do
957− dicts <- getTypeClassDictionaries
958− _ <- subsumes' Nothing ty1 ty2
959− return . Just $ foldl App val (map (flip TypeClassDictionary dicts) constraints)
960−subsumes' val (TypeApp f1 r1) (TypeApp f2 r2) | f1 == tyObject && f2 == tyObject = do
962− (ts1, r1') = rowToList r1
963− (ts2, r2') = rowToList r2
964− ts1' = sortBy (comparing fst) ts1
965− ts2' = sortBy (comparing fst) ts2
966− go ts1' ts2' r1' r2'
969− go [] ts2 r1' r2' = r1' =?= rowFromList (ts2, r2')
970− go ts1 [] r1' r2' = r2' =?= rowFromList (ts1, r1')
971− go ((p1, ty1) : ts1) ((p2, ty2) : ts2) r1' r2'
972− | p1 == p2 = do _ <- subsumes Nothing ty1 ty2
974− | p1 < p2 = do rest <- fresh
975− r2' =?= RCons p1 ty1 rest
976− go ts1 ((p2, ty2) : ts2) r1' rest
977− | otherwise = do rest <- fresh
978− r1' =?= RCons p2 ty2 rest
979− go ((p1, ty1) : ts1) ts2 rest r2'
980−subsumes' val ty1 ty2@(TypeApp obj _) | obj == tyObject = subsumes val ty2 ty1
981−subsumes' val ty1 ty2 = do