@@ -1,926 +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 FlexibleContexts #-}
18−{-# LANGUAGE MultiParamTypeClasses #-}
20−module Language.PureScript.TypeChecker.Types (
25− The following functions represent the corresponding type checking judgements:
28− Synthesize a type for a value
31− Check a value has a given type
34− Check an object with a given type contains specified properties
36− checkFunctionApplication
37− Check a function of a given type returns a value of another type when applied to its arguments
40− Check a type subsumes another type
44−import Data.Maybe (maybeToList, isNothing, isJust, fromMaybe)
45−import qualified Data.Data as D
47− (everythingWithContext, mkM, everywhereM, everything, mkT,
48− something, everywhere, mkQ)
49−import Data.Generics.Extras
51−import Language.PureScript.Values
52−import Language.PureScript.Types
53−import Language.PureScript.Kinds
54−import Language.PureScript.Names
55−import Language.PureScript.TypeChecker.Monad
56−import Language.PureScript.TypeChecker.Kinds
57−import Language.PureScript.TypeChecker.Synonyms
58−import Language.PureScript.Pretty
59−import Language.PureScript.Prim
60−import qualified Language.PureScript.Constants as C
62−import Control.Monad.State
63−import Control.Monad.Error
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) $
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) =
112− guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (c1 == c2)
113− unifyTypes' (TypeApp t3 t4) (TypeApp t5 t6) = do
116− unifyTypes' (Skolem s1 _) (Skolem s2 _) | s1 == s2 = return ()
117− unifyTypes' r1@RCons{} r2 = unifyRows r1 r2
118− unifyTypes' r1 r2@RCons{} = unifyRows r1 r2
119− unifyTypes' r1@REmpty r2 = unifyRows r1 r2
120− unifyTypes' r1 r2@REmpty = unifyRows r1 r2
121− unifyTypes' t3 t4 = throwError $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
124−-- Unify two rows, updating the current substitution
126−-- Common labels are first identified, and unified. Remaining labels and types are unified with a
127−-- trailing row unification variable, if appropriate, otherwise leftover labels result in a unification
130−unifyRows :: Type -> Type -> UnifyT Type Check ()
133− (s1, r1') = rowToList r1
134− (s2, r2') = rowToList r2
135− int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
136− sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
137− sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
139− forM_ int (uncurry (=?=))
140− unifyRows' sd1 r1' sd2 r2'
142− unifyRows' :: [(String, Type)] -> Type -> [(String, Type)] -> Type -> UnifyT Type Check ()
143− unifyRows' [] (TUnknown u) sd r = u =:= rowFromList (sd, r)
144− unifyRows' sd r [] (TUnknown u) = u =:= rowFromList (sd, r)
145− unifyRows' ((name, ty):row) r others u@(TUnknown un) = do
147− forM_ row $ \(_, t) -> occursCheck un t
149− u =?= RCons name ty u'
150− unifyRows' row r others u'
151− unifyRows' [] REmpty [] REmpty = return ()
152− unifyRows' [] (TypeVar v1) [] (TypeVar v2) | v1 == v2 = return ()
153− unifyRows' [] (Skolem s1 _) [] (Skolem s2 _) | s1 == s2 = return ()
154− unifyRows' sd3 r3 sd4 r4 = throwError $ "Cannot unify (" ++ prettyPrintRow (rowFromList (sd3, r3)) ++ ") with (" ++ prettyPrintRow (rowFromList (sd4, r4)) ++ ")."
157−-- Infer the types of multiple mutually-recursive values, and return elaborated values including
158−-- type class dictionaries and type annotations.
160−typesOf :: Maybe ModuleName -> ModuleName -> [(Ident, Value)] -> Check [(Ident, (Value, Type))]
161−typesOf mainModuleName moduleName vals = do
162− tys <- fmap tidyUp . liftUnify $ do
164− -- Map each declaration to a name/value pair, with an optional type, if the declaration is typed
165− es = map isTyped vals
166− -- Filter the typed and untyped declarations
167− typed = filter (isJust . snd . snd) es
168− untyped = filter (isNothing . snd . snd) es
169− -- Make a map of names to typed declarations
170− typedDict = map (\(ident, (_, Just (ty, _))) -> (ident, ty)) typed
171− -- Create fresh unification variables for the types of untyped declarations
172− untypedNames <- replicateM (length untyped) fresh
174− -- Make a map of names to the unification variables of untyped declarations
175− untypedDict = zip (map fst untyped) untypedNames
176− -- Create the dictionary of all name/type pairs, which will be added to the environment during type checking
177− dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ typedDict ++ untypedDict)
178− forM es $ \e@(_, (val, _)) -> do
179− -- If the declaration is a function, it has access to other values in the binding group.
180− -- If not, the generated code might fail at runtime since those values might be undefined.
181− let dict' = if isFunction val then dict else M.empty
182− triple@(_, (val', ty)) <- case e of
183− -- Typed declarations
184− (ident, (val', Just (ty, checkType))) -> do
186− kind <- liftCheck $ kindOf moduleName ty
187− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
188− -- Check the type with the new names in scope
189− ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
190− val'' <- bindNames dict' $ if checkType
191− then TypedValue True <$> check val' ty' <*> pure ty'
192− else return (TypedValue False val' ty')
193− return (ident, (val'', ty'))
194− -- Untyped declarations
195− (ident, (val', Nothing)) -> do
196− -- Infer the type with the new names in scope
197− TypedValue _ val'' ty <- bindNames dict' $ infer val'
198− ty =?= fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
199− return (ident, (TypedValue True val'' ty, ty))
200− -- If --main is enabled, need to check that `main` has type Eff eff a for some eff, a
201− when (Just moduleName == mainModuleName && fst e == Ident C.main) $ do
202− [eff, a] <- replicateM 2 fresh
203− ty =?= TypeApp (TypeApp (TypeConstructor (Qualified (Just (ModuleName [ProperName "Control", ProperName "Monad", ProperName "Eff"])) (ProperName "Eff"))) eff) a
204− -- Make sure unification variables do not escape
207− forM tys $ \(ident, (val, ty)) -> do
208− -- Replace type class dictionary placeholders with actual dictionaries
209− val' <- replaceTypeClassDictionaries moduleName val
210− -- Check skolem variables did not escape their scope
211− skolemEscapeCheck val'
212− -- Remove type synonyms placeholders, remove duplicate row fields, and replace
213− -- top-level unification variables with named type variables.
214− let val'' = overTypes (desaturateAllTypeSynonyms . setifyAll) val'
215− ty' = varIfUnknown . desaturateAllTypeSynonyms . setifyAll $ ty
216− return (ident, (val'', ty'))
218− -- Apply the substitution that was returned from runUnify to both types and (type-annotated) values
219− tidyUp (ts, sub) = map (\(i, (val, ty)) -> (i, (overTypes (sub $?) val, sub $? ty))) ts
222−-- Check if a value introduces a function
224−isFunction :: Value -> Bool
225−isFunction (Abs _ _) = True
226−isFunction (TypedValue _ val _) = isFunction val
230−-- Check if a value contains a type annotation
232−isTyped :: (Ident, Value) -> (Ident, (Value, Maybe (Type, Bool)))
233−isTyped (name, TypedValue checkType value ty) = (name, (value, Just (ty, checkType)))
234−isTyped (name, value) = (name, (value, Nothing))
237−-- Map a function over type annotations appearing inside a value
239−overTypes :: (Type -> Type) -> Value -> Value
240−overTypes f = everywhere (mkT f)
243−-- Replace type class dictionary placeholders with inferred type class dictionaries
245−replaceTypeClassDictionaries :: ModuleName -> Value -> Check Value
246−replaceTypeClassDictionaries mn = everywhereM' (mkM go)
248− go (TypeClassDictionary constraint dicts) = entails mn dicts constraint
249− go other = return other
252−-- Check that the current set of type class dictionaries entail the specified type class goal, and, if so,
253−-- return a type class dictionary reference.
255−entails :: ModuleName -> [TypeClassDictionaryInScope] -> (Qualified ProperName, [Type]) -> Check Value
256−entails moduleName context goal@(className, tys) = do
259− [] -> throwError $ "No " ++ show className ++ " instance found for " ++ intercalate ", " (map prettyPrintType tys)
260− (dict : _) -> return dict
262− go env (className', tys') =
263− [ mkDictionary (canonicalizeDictionary tcd) args
265− -- Choose type class dictionaries in scope in the current module
267− -- Make sure the type class name matches the one we are trying to satisfy
268− , className' == tcdClassName tcd
269− -- Make sure the type unifies with the type in the type instance definition
270− , subst <- maybeToList . (>>= verifySubstitution) . fmap concat $ zipWithM (typeHeadsAreEqual moduleName env) tys' (tcdInstanceTypes tcd)
271− -- Solve any necessary subgoals
272− , args <- solveSubgoals env subst (tcdDependencies tcd) ]
273− -- Create dictionaries for subgoals which still need to be solved by calling go recursively
274− -- E.g. the goal (Show a, Show b) => Show (Either a b) can be satisfied if the current type
275− -- unifies with Either a b, and we can satisfy the subgoals Show a and Show b recursively.
276− solveSubgoals :: Environment -> [(String, Type)] -> Maybe [(Qualified ProperName, [Type])] -> [Maybe [Value]]
277− solveSubgoals _ _ Nothing = return Nothing
278− solveSubgoals env subst (Just subgoals) = do
279− dict <- mapM (go env . second (map (replaceAllTypeVars subst))) subgoals
281− -- Make a dictionary from subgoal dictionaries by applying the correct function
282− mkDictionary :: Qualified Ident -> Maybe [Value] -> Value
283− mkDictionary fnName Nothing = Var fnName
284− mkDictionary fnName (Just []) = App (Var fnName) (ObjectLiteral [])
285− mkDictionary fnName (Just dicts) = foldl App (Var fnName) dicts
286− -- Filter out type dictionaries which are in scope in the current module
287− filterModule :: TypeClassDictionaryInScope -> Bool
288− filterModule (TypeClassDictionaryInScope { tcdName = Qualified (Just mn) _ }) | mn == moduleName = True
289− filterModule (TypeClassDictionaryInScope { tcdName = Qualified Nothing _ }) = True
290− filterModule _ = False
291− canonicalizeDictionary :: TypeClassDictionaryInScope -> Qualified Ident
292− canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDRegular, tcdName = nm }) = nm
293− canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDAlias nm }) = nm
294− -- Ensure that a substitution is valid
295− verifySubstitution :: [(String, Type)] -> Maybe [(String, Type)]
296− verifySubstitution subst = do
297− let grps = groupBy ((==) `on` fst) subst
298− guard (all ((==) 1 . length . nubBy ((==) `on` snd)) grps)
299− return $ map head grps
302−-- Check whether the type heads of two types are equal (for the purposes of type class dictionary lookup),
303−-- and return a substitution from type variables to types which makes the type heads unify.
305−typeHeadsAreEqual :: ModuleName -> Environment -> Type -> Type -> Maybe [(String, Type)]
306−typeHeadsAreEqual _ _ (Skolem s1 _) (Skolem s2 _) | s1 == s2 = Just []
307−typeHeadsAreEqual _ _ (TypeVar v) t = Just [(v, t)]
308−typeHeadsAreEqual _ _ t (TypeVar v) = Just [(v, t)]
309−typeHeadsAreEqual _ _ (TypeConstructor c1) (TypeConstructor c2) | c1 == c2 = Just []
310−typeHeadsAreEqual m e (TypeApp h1 (TypeVar v)) (TypeApp h2 arg) = (:) (v, arg) <$> typeHeadsAreEqual m e h1 h2
311−typeHeadsAreEqual m e t1@(TypeApp _ _) t2@(TypeApp _ (TypeVar _)) = typeHeadsAreEqual m e t2 t1
312−typeHeadsAreEqual m e (SaturatedTypeSynonym name args) t2 = case expandTypeSynonym' e name args of
314− Right t1 -> typeHeadsAreEqual m e t1 t2
315−typeHeadsAreEqual _ _ _ _ = Nothing
318−-- Ensure unsolved unification variables do not escape
320−escapeCheck :: Value -> Type -> UnifyT Type Check ()
321−escapeCheck value ty = do
322− subst <- unifyCurrentSubstitution <$> UnifyT get
323− let visibleUnknowns = nub $ unknowns $ subst $? ty
324− let allUnknowns = findAllTypes value
325− forM_ allUnknowns $ \t -> do
326− let unsolvedUnknowns = nub . unknowns $ subst $? t
327− guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
330−-- Find all type annotations occuring inside a value
332−findAllTypes :: Value -> [Type]
333−findAllTypes = everything (++) (mkQ [] go)
335− go (TypedValue _ _ ty) = [ty]
339−-- Ensure skolem variables do not escape their scope
341−skolemEscapeCheck :: Value -> Check ()
342−skolemEscapeCheck (TypedValue False _ _) = return ()
343−skolemEscapeCheck root@TypedValue{} =
344− -- Every skolem variable is created when a ForAll type is skolemized.
345− -- This determines the scope of that skolem variable, which is copied from the SkolemScope
346− -- field of the ForAll constructor.
347− -- We traverse the tree top-down, and collect any SkolemScopes introduced by ForAlls.
348− -- If a Skolem is encountered whose SkolemScope is not in the current list, we have found
349− -- an escaped skolem variable.
350− case everythingWithContext [] (++) (mkQ ((,) []) go) root of
352− ((binding, val) : _) -> throwError $ "Rigid/skolem type variable bound by " ++ maybe "<unknown>" prettyPrintValue binding ++ " has escaped at " ++ prettyPrintValue val
354− go :: Value -> [(SkolemScope, Value)] -> ([(Maybe Value, Value)], [(SkolemScope, Value)])
355− go val@(TypedValue _ _ (ForAll _ _ (Just sco))) scos = ([], (sco, val) : scos)
356− go val@(TypedValue _ _ ty) scos = case collectSkolems ty \\ map fst scos of
357− (sco : _) -> ([(findBindingScope sco, val)], scos)
360− collectSkolems :: Type -> [SkolemScope]
361− collectSkolems = nub . everything (++) (mkQ [] collect)
363− collect (Skolem _ scope) = [scope]
365− go _ scos = ([], scos)
366− findBindingScope :: SkolemScope -> Maybe Value
367− findBindingScope sco = something (mkQ Nothing go') root
369− go' val@(TypedValue _ _ (ForAll _ _ (Just sco'))) | sco == sco' = Just val
371−skolemEscapeCheck val = throwError $ "Untyped value passed to skolemEscapeCheck: " ++ prettyPrintValue val
374−-- Ensure a row contains no duplicate labels
376−setify :: Type -> Type
377−setify = rowFromList . first (M.toList . M.fromList) . rowToList
380−-- \"Setify\" all rows occuring inside a value
382−setifyAll :: (D.Data d) => d -> d
383−setifyAll = everywhere (mkT setify)
386−-- Replace outermost unsolved unification variables with named type variables
388−varIfUnknown :: Type -> Type
390− let unks = nub $ unknowns ty
391− toName = (:) 't' . show
392− ty' = everywhere (mkT typeToVar) ty
393− typeToVar :: Type -> Type
394− typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
396− in mkForAll (sort . map (toName . runUnknown) $ unks) ty'
399−-- Remove any ForAlls and ConstrainedType constructors in a type by introducing new unknowns
400−-- or TypeClassDictionary values.
402−-- This is necessary during type checking to avoid unifying a polymorphic type with a
403−-- unification variable.
405−instantiatePolyTypeWithUnknowns :: Value -> Type -> UnifyT Type Check (Value, Type)
406−instantiatePolyTypeWithUnknowns val (ForAll ident ty _) = do
407− ty' <- replaceVarWithUnknown ident ty
408− instantiatePolyTypeWithUnknowns val ty'
409−instantiatePolyTypeWithUnknowns val (ConstrainedType constraints ty) = do
410− dicts <- getTypeClassDictionaries
411− (_, ty') <- instantiatePolyTypeWithUnknowns (error "Types under a constraint cannot themselves be constrained") ty
412− return (foldl App val (map (flip TypeClassDictionary dicts) constraints), ty')
413−instantiatePolyTypeWithUnknowns val ty = return (val, ty)
416−-- Replace a single type variable with a new unification variable
418−replaceVarWithUnknown :: String -> Type -> UnifyT Type Check Type
419−replaceVarWithUnknown ident ty = do
421− return $ replaceTypeVars ident tu ty
424−-- Replace fully applied type synonyms with the @SaturatedTypeSynonym@ data constructor, which helps generate
425−-- better error messages during unification.
427−replaceAllTypeSynonyms' :: (D.Data d) => Environment -> d -> Either String d
428−replaceAllTypeSynonyms' env d =
430− syns = map (\(name, (args, _)) -> (name, length args)) . M.toList $ typeSynonyms env
432− saturateAllTypeSynonyms syns d
434−replaceAllTypeSynonyms :: (Functor m, Monad m, MonadState CheckState m, MonadError String m) => (D.Data d) => d -> m d
435−replaceAllTypeSynonyms d = do
437− either throwError return $ replaceAllTypeSynonyms' env d
440−-- \"Desaturate\" @SaturatedTypeSynonym@s
442−desaturateAllTypeSynonyms :: (D.Data d) => d -> d
443−desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
445− replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
446− replaceSaturatedTypeSynonym t = t
449−-- Replace a type synonym and its arguments with the aliased type
451−expandTypeSynonym' :: Environment -> Qualified ProperName -> [Type] -> Either String Type
452−expandTypeSynonym' env name args =
453− case M.lookup name (typeSynonyms env) of
454− Just (synArgs, body) -> do
455− let repl = replaceAllTypeVars (zip synArgs args) body
456− replaceAllTypeSynonyms' env repl
457− Nothing -> error "Type synonym was not defined"
459−expandTypeSynonym :: (Functor m, Monad m, MonadState CheckState m, MonadError String m) => Qualified ProperName -> [Type] -> m Type
460−expandTypeSynonym name args = do
462− either throwError return $ expandTypeSynonym' env name args
465−-- Ensure a set of property names and value does not contain duplicate labels
467−ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
468−ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
471−-- Infer a type for a value, rethrowing any error to provide a more useful error message
473−infer :: Value -> UnifyT Type Check Value
474−infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ infer' val
477−-- Infer a type for a value
479−infer' :: Value -> UnifyT Type Check Value
480−infer' v@(NumericLiteral _) = return $ TypedValue True v tyNumber
481−infer' v@(StringLiteral _) = return $ TypedValue True v tyString
482−infer' v@(BooleanLiteral _) = return $ TypedValue True v tyBoolean
483−infer' (ArrayLiteral vals) = do
484− ts <- mapM infer vals
486− forM_ ts $ \(TypedValue _ _ t) -> els =?= TypeApp tyArray t
487− return $ TypedValue True (ArrayLiteral ts) els
488−infer' (ObjectLiteral ps) = do
489− ensureNoDuplicateProperties ps
490− ts <- mapM (infer . snd) ps
491− let fields = zipWith (\name (TypedValue _ _ t) -> (name, t)) (map fst ps) ts
492− ty = Object $ rowFromList (fields, REmpty)
493− return $ TypedValue True (ObjectLiteral (zip (map fst ps) ts)) ty
494−infer' (ObjectUpdate o ps) = do
495− ensureNoDuplicateProperties ps
497− newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
498− let newTys = map (\(name, TypedValue _ _ ty) -> (name, ty)) newVals
499− oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
500− let oldTy = Object $ rowFromList (oldTys, row)
501− o' <- TypedValue True <$> check o oldTy <*> pure oldTy
502− return $ TypedValue True (ObjectUpdate o' newVals) $ Object $ rowFromList (newTys, row)
503−infer' (Accessor prop val) = do
504− typed@(TypedValue _ _ objTy) <- infer val
505− propTy <- inferProperty objTy prop
510− _ <- subsumes Nothing objTy (Object (RCons prop field rest))
511− return $ TypedValue True (Accessor prop typed) field
512− Just ty -> return $ TypedValue True (Accessor prop typed) ty
513−infer' (Abs (Left arg) ret) = do
515− Just moduleName <- checkCurrentModule <$> get
516− bindLocalVariables moduleName [(arg, ty)] $ do
517− body@(TypedValue _ _ bodyTy) <- infer' ret
518− return $ TypedValue True (Abs (Left arg) body) $ function ty bodyTy
519−infer' (Abs (Right _) _) = error "Binder was not desugared"
520−infer' (App f arg) = do
521− f'@(TypedValue _ _ ft) <- infer f
522− (ret, app) <- checkFunctionApplication f' ft arg
523− return $ TypedValue True app ret
524−infer' (Var var) = do
525− Just moduleName <- checkCurrentModule <$> get
526− ty <- introduceSkolemScope <=< replaceAllTypeSynonyms <=< lookupVariable moduleName $ var
528− ConstrainedType constraints ty' -> do
529− dicts <- getTypeClassDictionaries
530− return $ TypedValue True (foldl App (Var var) (map (flip TypeClassDictionary dicts) constraints)) ty'
531− _ -> return $ TypedValue True (Var var) ty
532−infer' v@(Constructor c) = do
534− case M.lookup c (dataConstructors env) of
535− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
536− Just (_, ty) -> do ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
537− return $ TypedValue True v ty'
538−infer' (Case vals binders) = do
539− ts <- mapM infer vals
541− binders' <- checkBinders (map (\(TypedValue _ _ t) -> t) ts) ret binders
542− return $ TypedValue True (Case ts binders') ret
543−infer' (IfThenElse cond th el) = do
544− cond' <- check cond tyBoolean
545− v2@(TypedValue _ _ t2) <- infer th
546− v3@(TypedValue _ _ t3) <- infer el
548− return $ TypedValue True (IfThenElse cond' v2 v3) t2
549−infer' (TypedValue checkType val ty) = do
550− Just moduleName <- checkCurrentModule <$> get
551− kind <- liftCheck $ kindOf moduleName ty
552− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
553− ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
554− val' <- if checkType then check val ty' else return val
555− return $ TypedValue True val' ty'
556−infer' _ = error "Invalid argument to infer"
559−-- Infer the type of a property inside a record with a given type
561−inferProperty :: Type -> String -> UnifyT Type Check (Maybe Type)
562−inferProperty (Object row) prop = do
563− let (props, _) = rowToList row
564− return $ lookup prop props
565−inferProperty (SaturatedTypeSynonym name args) prop = do
566− replaced <- introduceSkolemScope <=< expandTypeSynonym name $ args
567− inferProperty replaced prop
568−inferProperty (ForAll ident ty _) prop = do
569− replaced <- replaceVarWithUnknown ident ty
570− inferProperty replaced prop
571−inferProperty _ _ = return Nothing
574−-- Infer the types of variables brought into scope by a binder
576−inferBinder :: Type -> Binder -> UnifyT Type Check (M.Map Ident Type)
577−inferBinder _ NullBinder = return M.empty
578−inferBinder val (StringBinder _) = val =?= tyString >> return M.empty
579−inferBinder val (NumberBinder _) = val =?= tyNumber >> return M.empty
580−inferBinder val (BooleanBinder _) = val =?= tyBoolean >> return M.empty
581−inferBinder val (VarBinder name) = return $ M.singleton name val
582−inferBinder val (ConstructorBinder ctor binders) = do
584− case M.lookup ctor (dataConstructors env) of
586− (_, fn) <- instantiatePolyTypeWithUnknowns (error "Data constructor types cannot contains constraints") ty
590− _ <- subsumes Nothing val ty'
592− go (binder : binders') (TypeApp (TypeApp t obj) ret) | t == tyFunction =
593− M.union <$> inferBinder obj binder <*> go binders' ret
594− go _ _ = throwError $ "Wrong number of arguments to constructor " ++ show ctor
595− _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
596−inferBinder val (ObjectBinder props) = do
599− m1 <- inferRowProperties row rest props
603− inferRowProperties :: Type -> Type -> [(String, Binder)] -> UnifyT Type Check (M.Map Ident Type)
604− inferRowProperties nrow row [] = nrow =?= row >> return M.empty
605− inferRowProperties nrow row ((name, binder):binders) = do
607− m1 <- inferBinder propTy binder
608− m2 <- inferRowProperties nrow (RCons name propTy row) binders
609− return $ m1 `M.union` m2
610−inferBinder val (ArrayBinder binders) = do
612− m1 <- M.unions <$> mapM (inferBinder el) binders
613− val =?= TypeApp tyArray el
615−inferBinder val (ConsBinder headBinder tailBinder) = do
617− m1 <- inferBinder el headBinder
618− m2 <- inferBinder val tailBinder
619− val =?= TypeApp tyArray el
620− return $ m1 `M.union` m2
621−inferBinder val (NamedBinder name binder) = do
622− m <- inferBinder val binder
623− return $ M.insert name val m
626−-- Check the types of the return values in a set of binders in a case statement
628−checkBinders :: [Type] -> Type -> [CaseAlternative] -> UnifyT Type Check [CaseAlternative]
629−checkBinders _ _ [] = return []
630−checkBinders nvals ret (CaseAlternative binders grd val : bs) = do
631− Just moduleName <- checkCurrentModule <$> get
632− m1 <- M.unions <$> zipWithM inferBinder nvals binders
633− r <- bindLocalVariables moduleName (M.toList m1) $ do
634− val' <- TypedValue True <$> check val ret <*> pure ret
636− Nothing -> return $ CaseAlternative binders Nothing val'
638− g' <- check g tyBoolean
639− return $ CaseAlternative binders (Just g') val'
640− rs <- checkBinders nvals ret bs
644−-- Generate a new skolem constant
646−newSkolemConstant :: UnifyT Type Check Int
647−newSkolemConstant = runUnknown <$> fresh'
650−-- Generate a new skolem scope
652−newSkolemScope :: UnifyT Type Check SkolemScope
653−newSkolemScope = SkolemScope . runUnknown <$> fresh'
656−-- Skolemize a type variable by replacing its instances with fresh skolem constants
658−skolemize :: String -> Int -> SkolemScope -> Type -> Type
659−skolemize ident sko scope = replaceTypeVars ident (Skolem sko scope)
662−-- Introduce skolem scope at every occurence of a ForAll
664−introduceSkolemScope :: Type -> UnifyT Type Check Type
665−introduceSkolemScope = everywhereM (mkM go)
667− go (ForAll ident ty Nothing) = ForAll ident ty <$> (Just <$> newSkolemScope)
668− go other = return other
671−-- Check the type of a value, rethrowing errors to provide a better error message
673−check :: Value -> Type -> UnifyT Type Check Value
674−check val ty = rethrow errorMessage $ check' val ty
677− "Error checking type of term " ++
678− prettyPrintValue val ++
680− prettyPrintType ty ++
685−-- Check the type of a value
687−check' :: Value -> Type -> UnifyT Type Check Value
688−check' val (ForAll ident ty _) = do
689− scope <- newSkolemScope
690− sko <- newSkolemConstant
691− let sk = skolemize ident sko scope ty
692− val' <- check val sk
693− return $ TypedValue True val' (ForAll ident ty (Just scope))
694−check' val t@(ConstrainedType constraints ty) = do
695− dictNames <- forM constraints $ \(Qualified _ (ProperName className), _) -> do
696− n <- liftCheck freshDictionaryName
697− return $ Ident $ "__dict_" ++ className ++ "_" ++ show n
698− val' <- withTypeClassDictionaries (zipWith (\name (className, instanceTy) ->
699− TypeClassDictionaryInScope name className instanceTy Nothing TCDRegular) (map (Qualified Nothing) dictNames)
700− constraints) $ check val ty
701− return $ TypedValue True (foldr (Abs . Left) val' dictNames) t
702−check' val (SaturatedTypeSynonym name args) = do
703− ty <- introduceSkolemScope <=< expandTypeSynonym name $ args
704− val' <- check val ty
705− return $ TypedValue True val' ty
706−check' val u@(TUnknown _) = do
707− val'@(TypedValue _ _ ty) <- infer val
708− -- Don't unify an unknown with an inferred polytype
709− (val'', ty') <- instantiatePolyTypeWithUnknowns val' ty
711− return $ TypedValue True val'' ty'
712−check' v@(NumericLiteral _) t | t == tyNumber =
713− return $ TypedValue True v t
714−check' v@(StringLiteral _) t | t == tyString =
715− return $ TypedValue True v t
716−check' v@(BooleanLiteral _) t | t == tyBoolean =
717− return $ TypedValue True v t
718−check' (ArrayLiteral vals) t@(TypeApp a ty) | a == tyArray = do
719− array <- ArrayLiteral <$> forM vals (`check` ty)
720− return $ TypedValue True array t
721−check' (Abs (Left arg) ret) ty@(TypeApp (TypeApp t argTy) retTy) | t == tyFunction = do
722− Just moduleName <- checkCurrentModule <$> get
723− ret' <- bindLocalVariables moduleName [(arg, argTy)] $ check ret retTy
724− return $ TypedValue True (Abs (Left arg) ret') ty
725−check' (Abs (Right _) _) _ = error "Binder was not desugared"
726−check' (App f arg) ret = do
727− f'@(TypedValue _ _ ft) <- infer f
728− (ret', app) <- checkFunctionApplication f' ft arg
729− _ <- subsumes Nothing ret' ret
730− return $ TypedValue True app ret
731−check' v@(Var var) ty = do
732− Just moduleName <- checkCurrentModule <$> get
733− repl <- introduceSkolemScope <=< replaceAllTypeSynonyms <=< lookupVariable moduleName $ var
734− ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
735− v' <- subsumes (Just v) repl ty'
737− Nothing -> throwError "Unable to check type subsumption"
738− Just v'' -> return $ TypedValue True v'' ty'
739−check' (TypedValue checkType val ty1) ty2 = do
740− Just moduleName <- checkCurrentModule <$> get
741− kind <- liftCheck $ kindOf moduleName ty1
742− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
743− ty1' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty1
744− val' <- subsumes (Just val) ty1' ty2
746− Nothing -> throwError "Unable to check type subsumption"
748− val''' <- if checkType then check val'' ty1 else return val''
749− return $ TypedValue checkType (TypedValue True val''' ty1) ty2
750−check' (Case vals binders) ret = do
751− vals' <- mapM infer vals
752− let ts = map (\(TypedValue _ _ t) -> t) vals'
753− binders' <- checkBinders ts ret binders
754− return $ TypedValue True (Case vals' binders') ret
755−check' (IfThenElse cond th el) ty = do
756− cond' <- check cond tyBoolean
759− return $ TypedValue True (IfThenElse cond' th' el') ty
760−check' (ObjectLiteral ps) t@(Object row) = do
761− ensureNoDuplicateProperties ps
762− ps' <- checkProperties ps row False
763− return $ TypedValue True (ObjectLiteral ps') t
764−check' (ObjectUpdate obj ps) t@(Object row) = do
765− ensureNoDuplicateProperties ps
766− us <- zip (map fst ps) <$> replicateM (length ps) fresh
767− let (propsToCheck, rest) = rowToList row
768− propsToRemove = map fst ps
769− remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
770− obj' <- check obj (Object (rowFromList (us ++ remainingProps, rest)))
771− ps' <- checkProperties ps row True
772− return $ TypedValue True (ObjectUpdate obj' ps') t
773−check' (Accessor prop val) ty = do
775− val' <- check val (Object (RCons prop ty rest))
776− return $ TypedValue True (Accessor prop val') ty
777−check' (Constructor c) ty = do
779− case M.lookup c (dataConstructors env) of
780− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
782− repl <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty1
783− _ <- subsumes Nothing repl ty
784− return $ TypedValue True (Constructor c) ty
785−check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
788−-- Check the type of a collection of named record fields
790−-- The @lax@ parameter controls whether or not every record member has to be provided. For object updates, this is not the case.
792−checkProperties :: [(String, Value)] -> Type -> Bool -> UnifyT Type Check [(String, Value)]
793−checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
794− go [] [] REmpty = return []
795− go [] [] u@(TUnknown _) = do u =?= REmpty
797− go [] [] (Skolem _ _) | lax = return []
798− go [] ((p, _): _) _ | lax = return []
799− | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
800− go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
801− go ((p,v):ps') [] u@(TUnknown _) = do
802− v'@(TypedValue _ _ ty) <- infer v
804− u =?= RCons p ty rest
805− ps'' <- go ps' [] rest
806− return $ (p, v') : ps''
807− go ((p,v):ps') ts r =
810− v'@(TypedValue _ _ ty) <- infer v
812− r =?= RCons p ty rest
813− ps'' <- go ps' ts rest
814− return $ (p, v') : ps''
817− ps'' <- go ps' (delete (p, ty) ts) r
818− return $ (p, v') : ps''
819− go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
822−-- Check the type of a function application, rethrowing errors to provide a better error message
824−checkFunctionApplication :: Value -> Type -> Value -> UnifyT Type Check (Type, Value)
825−checkFunctionApplication fn fnTy arg = rethrow errorMessage $ checkFunctionApplication' fn fnTy arg
827− errorMessage msg = "Error applying function of type "
828− ++ prettyPrintType fnTy
829− ++ " to argument " ++ prettyPrintValue arg
833−-- Check the type of a function application
835−checkFunctionApplication' :: Value -> Type -> Value -> UnifyT Type Check (Type, Value)
836−checkFunctionApplication' fn (TypeApp (TypeApp tyFunction' argTy) retTy) arg = do
837− tyFunction' =?= tyFunction
838− arg' <- check arg argTy
839− return (retTy, App fn arg')
840−checkFunctionApplication' fn (ForAll ident ty _) arg = do
841− replaced <- replaceVarWithUnknown ident ty
842− checkFunctionApplication fn replaced arg
843−checkFunctionApplication' fn u@(TUnknown _) arg = do
845− TypedValue _ arg' t <- infer arg
846− (arg'', t') <- instantiatePolyTypeWithUnknowns arg' t
847− return $ TypedValue True arg'' t'
848− let ty = (\(TypedValue _ _ t) -> t) arg'
850− u =?= function ty ret
851− return (ret, App fn arg')
852−checkFunctionApplication' fn (SaturatedTypeSynonym name tyArgs) arg = do
853− ty <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
854− checkFunctionApplication fn ty arg
855−checkFunctionApplication' fn (ConstrainedType constraints fnTy) arg = do
856− dicts <- getTypeClassDictionaries
857− checkFunctionApplication' (foldl App fn (map (flip TypeClassDictionary dicts) constraints)) fnTy arg
858−checkFunctionApplication' _ fnTy arg = throwError $ "Cannot apply a function of type "
859− ++ prettyPrintType fnTy
860− ++ " to argument " ++ prettyPrintValue arg
863−-- Check whether one type subsumes another, rethrowing errors to provide a better error message
865−subsumes :: Maybe Value -> Type -> Type -> UnifyT Type Check (Maybe Value)
866−subsumes val ty1 ty2 = rethrow errorMessage $ subsumes' val ty1 ty2
868− errorMessage msg = "Error checking that type "
869− ++ prettyPrintType ty1
870− ++ " subsumes type "
871− ++ prettyPrintType ty2
875−-- Check whether one type subsumes another
877−subsumes' :: Maybe Value -> Type -> Type -> UnifyT Type Check (Maybe Value)
878−subsumes' val (ForAll ident ty1 _) ty2 = do
879− replaced <- replaceVarWithUnknown ident ty1
880− subsumes val replaced ty2
881−subsumes' val ty1 (ForAll ident ty2 sco) =
884− sko <- newSkolemConstant
885− let sk = skolemize ident sko sco' ty2
887− Nothing -> throwError "Skolem variable scope is unspecified"
888−subsumes' val (TypeApp (TypeApp f1 arg1) ret1) (TypeApp (TypeApp f2 arg2) ret2) | f1 == tyFunction && f2 == tyFunction = do
889− _ <- subsumes Nothing arg2 arg1
890− _ <- subsumes Nothing ret1 ret2
892−subsumes' val (SaturatedTypeSynonym name tyArgs) ty2 = do
893− ty1 <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
894− subsumes val ty1 ty2
895−subsumes' val ty1 (SaturatedTypeSynonym name tyArgs) = do
896− ty2 <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
897− subsumes val ty1 ty2
898−subsumes' (Just val) (ConstrainedType constraints ty1) ty2 = do
899− dicts <- getTypeClassDictionaries
900− _ <- subsumes' Nothing ty1 ty2
901− return . Just $ foldl App val (map (flip TypeClassDictionary dicts) constraints)
902−subsumes' val (Object r1) (Object r2) = do
904− (ts1, r1') = rowToList r1
905− (ts2, r2') = rowToList r2
906− ts1' = sortBy (comparing fst) ts1
907− ts2' = sortBy (comparing fst) ts2
908− go ts1' ts2' r1' r2'
911− go [] ts2 r1' r2' = r1' =?= rowFromList (ts2, r2')
912− go ts1 [] r1' r2' = r2' =?= rowFromList (ts1, r1')
913− go ((p1, ty1) : ts1) ((p2, ty2) : ts2) r1' r2'
914− | p1 == p2 = do _ <- subsumes Nothing ty1 ty2
916− | p1 < p2 = do rest <- fresh
917− r2' =?= RCons p1 ty1 rest
918− go ts1 ((p2, ty2) : ts2) r1' rest
919− | otherwise = do rest <- fresh
920− r1' =?= RCons p2 ty2 rest
921− go ((p1, ty1) : ts1) ts2 rest r2'
922−subsumes' val ty1 ty2@(Object _) = subsumes val ty2 ty1
923−subsumes' val ty1 ty2 = do