@@ -1,1151 +0,0 @@
1−-----------------------------------------------------------------------------
2−--
3−-- Module : Language.PureScript.TypeChecker.Types
4−-- Copyright : (c) Phil Freeman 2013
5−-- License : MIT
6−--
7−-- Maintainer : Phil Freeman <paf31@cantab.net>
8−-- Stability : experimental
9−-- Portability :
10−--
11−-- |
12−-- This module implements the type checker
13−--
14−-----------------------------------------------------------------------------
15−
16−{-# OPTIONS_GHC -fno-warn-orphans #-}
17−{-# LANGUAGE FlexibleInstances #-}
18−{-# LANGUAGE FlexibleContexts #-}
19−{-# LANGUAGE MultiParamTypeClasses #-}
20−
21−module Language.PureScript.TypeChecker.Types (
22− typesOf
23−) where
24−
25−{-
26− The following functions represent the corresponding type checking judgements:
27−
28− infer
29− Synthesize a type for a value
30−
31− check
32− Check a value has a given type
33−
34− checkProperties
35− Check an object with a given type contains specified properties
36−
37− checkFunctionApplication
38− Check a function of a given type returns a value of another type when applied to its arguments
39−
40− subsumes
41− Check a type subsumes another type
42−-}
43−
44−import Data.List
45−import Data.Maybe (maybeToList, fromMaybe)
46−import Data.Function (on)
47−import Data.Ord (comparing)
48−import Data.Monoid
49−import Data.Either (lefts, rights)
50−
51−import Language.PureScript.Declarations
52−import Language.PureScript.Types
53−import Language.PureScript.Kinds
54−import Language.PureScript.Names
55−import Language.PureScript.TypeClassDictionaries
56−import Language.PureScript.TypeChecker.Monad
57−import Language.PureScript.TypeChecker.Kinds
58−import Language.PureScript.TypeChecker.Synonyms
59−import Language.PureScript.Pretty
60−import Language.PureScript.Environment
61−import Language.PureScript.Errors
62−import qualified Language.PureScript.Constants as C
63−
64−import Control.Monad.State
65−import Control.Monad.Error
66−import Control.Monad.Unify
67−
68−import Control.Applicative
69−import Control.Arrow (Arrow(..))
70−
71−import qualified Data.Map as M
72−import qualified Data.HashMap.Strict as H
73−
74−instance Partial Type where
75− unknown = TUnknown
76− isUnknown (TUnknown u) = Just u
77− isUnknown _ = Nothing
78− unknowns = everythingOnTypes (++) go
79− where
80− go (TUnknown u) = [u]
81− go _ = []
82− ($?) sub = everywhereOnTypes go
83− where
84− go t@(TUnknown u) = case H.lookup u (runSubstitution sub) of
85− Nothing -> t
86− Just t' -> t'
87− go other = other
88−
89−instance Unifiable Check Type where
90− (=?=) = unifyTypes
91−
92−-- |
93−-- Unify two types, updating the current substitution
94−--
95−unifyTypes :: Type -> Type -> UnifyT Type Check ()
96−unifyTypes t1 t2 = rethrow (mkErrorStack ("Error unifying type " ++ prettyPrintType t1 ++ " with type " ++ prettyPrintType t2) Nothing <>) $
97− unifyTypes' t1 t2
98− where
99− unifyTypes' (TUnknown u1) (TUnknown u2) | u1 == u2 = return ()
100− unifyTypes' (TUnknown u) t = u =:= t
101− unifyTypes' t (TUnknown u) = u =:= t
102− unifyTypes' (SaturatedTypeSynonym name args) ty = do
103− ty1 <- introduceSkolemScope <=< expandTypeSynonym name $ args
104− ty1 `unifyTypes` ty
105− unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
106− unifyTypes' (ForAll ident1 ty1 sc1) (ForAll ident2 ty2 sc2) =
107− case (sc1, sc2) of
108− (Just sc1', Just sc2') -> do
109− sko <- newSkolemConstant
110− let sk1 = skolemize ident1 sko sc1' ty1
111− let sk2 = skolemize ident2 sko sc2' ty2
112− sk1 `unifyTypes` sk2
113− _ -> error "Skolemized type variable was not given a scope"
114− unifyTypes' (ForAll ident ty1 (Just sc)) ty2 = do
115− sko <- newSkolemConstant
116− let sk = skolemize ident sko sc ty1
117− sk `unifyTypes` ty2
118− unifyTypes' ForAll{} _ = throwError . strMsg $ "Skolem variable scope is unspecified"
119− unifyTypes' ty f@ForAll{} = f `unifyTypes` ty
120− unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
121− unifyTypes' (TypeConstructor c1) (TypeConstructor c2) =
122− guardWith (strMsg ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".")) (c1 == c2)
123− unifyTypes' (TypeApp t3 t4) (TypeApp t5 t6) = do
124− t3 `unifyTypes` t5
125− t4 `unifyTypes` t6
126− unifyTypes' (Skolem _ s1 _) (Skolem _ s2 _) | s1 == s2 = return ()
127− unifyTypes' r1@RCons{} r2 = unifyRows r1 r2
128− unifyTypes' r1 r2@RCons{} = unifyRows r1 r2
129− unifyTypes' r1@REmpty r2 = unifyRows r1 r2
130− unifyTypes' r1 r2@REmpty = unifyRows r1 r2
131− unifyTypes' t@(ConstrainedType _ _) _ = throwError . strMsg $ "Attempted to unify a constrained type " ++ prettyPrintType t ++ " with another type."
132− unifyTypes' t3 t4@(ConstrainedType _ _) = unifyTypes' t4 t3
133− unifyTypes' t3 t4 = throwError . strMsg $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
134−
135−-- |
136−-- Unify two rows, updating the current substitution
137−--
138−-- Common labels are first identified, and unified. Remaining labels and types are unified with a
139−-- trailing row unification variable, if appropriate, otherwise leftover labels result in a unification
140−-- error.
141−--
142−unifyRows :: Type -> Type -> UnifyT Type Check ()
143−unifyRows r1 r2 =
144− let
145− (s1, r1') = rowToList r1
146− (s2, r2') = rowToList r2
147− int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
148− sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
149− sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
150− in do
151− forM_ int (uncurry (=?=))
152− unifyRows' sd1 r1' sd2 r2'
153− where
154− unifyRows' :: [(String, Type)] -> Type -> [(String, Type)] -> Type -> UnifyT Type Check ()
155− unifyRows' [] (TUnknown u) sd r = u =:= rowFromList (sd, r)
156− unifyRows' sd r [] (TUnknown u) = u =:= rowFromList (sd, r)
157− unifyRows' ((name, ty):row) r others u@(TUnknown un) = do
158− occursCheck un ty
159− forM_ row $ \(_, t) -> occursCheck un t
160− u' <- fresh
161− u =?= RCons name ty u'
162− unifyRows' row r others u'
163− unifyRows' [] REmpty [] REmpty = return ()
164− unifyRows' [] (TypeVar v1) [] (TypeVar v2) | v1 == v2 = return ()
165− unifyRows' [] (Skolem _ s1 _) [] (Skolem _ s2 _) | s1 == s2 = return ()
166− unifyRows' sd3 r3 sd4 r4 = throwError . strMsg $ "Cannot unify (" ++ prettyPrintRow (rowFromList (sd3, r3)) ++ ") with (" ++ prettyPrintRow (rowFromList (sd4, r4)) ++ ")"
167−
168−-- |
169−-- Infer the types of multiple mutually-recursive values, and return elaborated values including
170−-- type class dictionaries and type annotations.
171−--
172−typesOf :: Maybe ModuleName -> ModuleName -> [(Ident, Expr)] -> Check [(Ident, (Expr, Type))]
173−typesOf mainModuleName moduleName vals = do
174− tys <- fmap tidyUp . liftUnify $ do
175− (untyped, typed, dict, untypedDict) <- typeDictionaryForBindingGroup moduleName vals
176− ds1 <- parU typed $ \e -> do
177− triple@(_, (_, ty)) <- checkTypedBindingGroupElement moduleName e dict
178− checkMain (fst e) ty
179− return triple
180− ds2 <- forM untyped $ \e -> do
181− triple@(_, (_, ty)) <- typeForBindingGroupElement e dict untypedDict
182− checkMain (fst e) ty
183− return triple
184− return $ ds1 ++ ds2
185−
186− forM tys $ \(ident, (val, ty)) -> do
187− -- Replace type class dictionary placeholders with actual dictionaries
188− val' <- replaceTypeClassDictionaries moduleName val
189− -- Check skolem variables did not escape their scope
190− skolemEscapeCheck val'
191− -- Remove type synonyms placeholders, remove duplicate row fields, and replace
192− -- top-level unification variables with named type variables.
193− let val'' = overTypes (desaturateAllTypeSynonyms . setifyAll) val'
194− ty' = varIfUnknown . desaturateAllTypeSynonyms . setifyAll $ ty
195− return (ident, (val'', ty'))
196− where
197− -- Apply the substitution that was returned from runUnify to both types and (type-annotated) values
198− tidyUp (ts, sub) = map (\(i, (val, ty)) -> (i, (overTypes (sub $?) val, sub $? ty))) ts
199− -- If --main is enabled, need to check that `main` has type Eff eff a for some eff, a
200− checkMain nm ty = when (Just moduleName == mainModuleName && nm == Ident C.main) $ do
201− [eff, a] <- replicateM 2 fresh
202− ty =?= TypeApp (TypeApp (TypeConstructor (Qualified (Just (ModuleName [ProperName "Control", ProperName "Monad", ProperName "Eff"])) (ProperName "Eff"))) eff) a
203−
204−type TypeData = M.Map (ModuleName, Ident) (Type, NameKind, NameVisibility)
205−
206−type UntypedData = [(Ident, Type)]
207−
208−typeDictionaryForBindingGroup :: ModuleName -> [(Ident, Expr)] -> UnifyT Type Check ([(Ident, Expr)], [(Ident, (Expr, Type, Bool))], TypeData, UntypedData)
209−typeDictionaryForBindingGroup moduleName vals = do
210− let
211− -- Map each declaration to a name/value pair, with an optional type, if the declaration is typed
212− es = map isTyped vals
213− -- Filter the typed and untyped declarations
214− untyped = lefts es
215− typed = rights es
216− -- Make a map of names to typed declarations
217− typedDict = map (\(ident, (_, ty, _)) -> (ident, ty)) typed
218−
219− -- Create fresh unification variables for the types of untyped declarations
220− untypedNames <- replicateM (length untyped) fresh
221−
222− let
223− -- Make a map of names to the unification variables of untyped declarations
224− untypedDict = zip (map fst untyped) untypedNames
225− -- Create the dictionary of all name/type pairs, which will be added to the environment during type checking
226− dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable, Undefined))) $ typedDict ++ untypedDict)
227− return (untyped, typed, dict, untypedDict)
228−
229−checkTypedBindingGroupElement :: ModuleName -> (Ident, (Expr, Type, Bool)) -> TypeData -> UnifyT Type Check (Ident, (Expr, Type))
230−checkTypedBindingGroupElement moduleName (ident, (val', ty, checkType)) dict = do
231− -- Kind check
232− kind <- liftCheck $ kindOf moduleName ty
233− guardWith (strMsg $ "Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
234− -- Check the type with the new names in scope
235− ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
236− val'' <- if checkType
237− then bindNames dict $ TypedValue True <$> check val' ty' <*> pure ty'
238− else return (TypedValue False val' ty')
239− return (ident, (val'', ty'))
240−
241−typeForBindingGroupElement :: (Ident, Expr) -> TypeData -> UntypedData -> UnifyT Type Check (Ident, (Expr, Type))
242−typeForBindingGroupElement (ident, val) dict untypedDict = do
243− -- Infer the type with the new names in scope
244− TypedValue _ val' ty <- bindNames dict $ infer val
245− ty =?= fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
246− return (ident, (TypedValue True val' ty, ty))
247−
248−-- |
249−-- Check if a value contains a type annotation
250−--
251−isTyped :: (Ident, Expr) -> (Either (Ident, Expr) (Ident, (Expr, Type, Bool)))
252−isTyped (name, TypedValue checkType value ty) = Right (name, (value, ty, checkType))
253−isTyped (name, value) = Left (name, value)
254−
255−-- |
256−-- Map a function over type annotations appearing inside a value
257−--
258−overTypes :: (Type -> Type) -> Expr -> Expr
259−overTypes f = let (_, f', _) = everywhereOnValues id g id in f'
260− where
261− g :: Expr -> Expr
262− g (TypedValue checkTy val t) = TypedValue checkTy val (f t)
263− g (TypeClassDictionary b (nm, tys) sco) = TypeClassDictionary b (nm, map f tys) sco
264− g other = other
265−
266−-- |
267−-- Replace type class dictionary placeholders with inferred type class dictionaries
268−--
269−replaceTypeClassDictionaries :: ModuleName -> Expr -> Check Expr
270−replaceTypeClassDictionaries mn =
271− let (_, f, _) = everywhereOnValuesTopDownM return go return
272− in f
273− where
274− go (TypeClassDictionary trySuperclasses constraint dicts) = do
275− env <- getEnv
276− entails env mn dicts constraint trySuperclasses
277− go other = return other
278−
279−-- |
280−-- A simplified representation of expressions which are used to represent type
281−-- class dictionaries at runtime, which can be compared for equality
282−--
283−data DictionaryValue
284− -- |
285− -- A dictionary which is brought into scope by a local constraint
286− --
287− = LocalDictionaryValue (Qualified Ident)
288− -- |
289− -- A dictionary which is brought into scope by an instance declaration
290− --
291− | GlobalDictionaryValue (Qualified Ident)
292− -- |
293− -- A dictionary which depends on other dictionaries
294− --
295− | DependentDictionaryValue (Qualified Ident) [DictionaryValue]
296− -- |
297− -- A subclass dictionary
298− --
299− | SubclassDictionaryValue DictionaryValue (Qualified ProperName) Integer
300− deriving (Show, Ord, Eq)
301−
302−-- |
303−-- Check that the current set of type class dictionaries entail the specified type class goal, and, if so,
304−-- return a type class dictionary reference.
305−--
306−entails :: Environment -> ModuleName -> [TypeClassDictionaryInScope] -> (Qualified ProperName, [Type]) -> Bool -> Check Expr
307−entails env moduleName context = solve (sortedNubBy canonicalizeDictionary (filter filterModule context))
308− where
309− sortedNubBy :: (Ord k) => (v -> k) -> [v] -> [v]
310− sortedNubBy f vs = M.elems (M.fromList (map (f &&& id) vs))
311−
312− -- Filter out type dictionaries which are in scope in the current module
313− filterModule :: TypeClassDictionaryInScope -> Bool
314− filterModule (TypeClassDictionaryInScope { tcdName = Qualified (Just mn) _ }) | mn == moduleName = True
315− filterModule (TypeClassDictionaryInScope { tcdName = Qualified Nothing _ }) = True
316− filterModule _ = False
317−
318− solve context' (className, tys) trySuperclasses =
319− let
320− dicts = go trySuperclasses className tys
321− in case sortedNubBy dictTrace (chooseSimplestDictionaries dicts) of
322− [] -> throwError . strMsg $ "No instance found for " ++ show className ++ " " ++ unwords (map prettyPrintTypeAtom tys)
323− [_] -> return $ dictionaryValueToValue $ head dicts
324− _ -> throwError . strMsg $ "Overlapping instances found for " ++ show className ++ " " ++ unwords (map prettyPrintTypeAtom tys)
325− where
326− go trySuperclasses' className' tys' =
327− -- Look for regular type instances
328− [ mkDictionary (canonicalizeDictionary tcd) args
329− | tcd <- context'
330− -- Make sure the type class name matches the one we are trying to satisfy
331− , className' == tcdClassName tcd
332− -- Make sure the type unifies with the type in the type instance definition
333− , subst <- maybeToList . (>>= verifySubstitution) . fmap concat $ zipWithM (typeHeadsAreEqual moduleName env) tys' (tcdInstanceTypes tcd)
334− -- Solve any necessary subgoals
335− , args <- solveSubgoals subst (tcdDependencies tcd) ] ++
336−
337− -- Look for implementations via superclasses
338− [ SubclassDictionaryValue suDict superclass index
339− | trySuperclasses'
340− , (subclassName, (args, _, implies)) <- M.toList (typeClasses env)
341− -- Try each superclass
342− , (index, (superclass, suTyArgs)) <- zip [0..] implies
343− -- Make sure the type class name matches the superclass name
344− , className' == superclass
345− -- Make sure the types unify with the types in the superclass implication
346− , subst <- maybeToList . (>>= verifySubstitution) . fmap concat $ zipWithM (typeHeadsAreEqual moduleName env) tys' suTyArgs
347− -- Finally, satisfy the subclass constraint
348− , args' <- maybeToList $ mapM (flip lookup subst) args
349− , suDict <- go True subclassName args' ]
350−
351− -- Create dictionaries for subgoals which still need to be solved by calling go recursively
352− -- E.g. the goal (Show a, Show b) => Show (Either a b) can be satisfied if the current type
353− -- unifies with Either a b, and we can satisfy the subgoals Show a and Show b recursively.
354− solveSubgoals :: [(String, Type)] -> Maybe [(Qualified ProperName, [Type])] -> [Maybe [DictionaryValue]]
355− solveSubgoals _ Nothing = return Nothing
356− solveSubgoals subst (Just subgoals) = do
357− dict <- mapM (uncurry (go True) . second (map (replaceAllTypeVars subst))) subgoals
358− return $ Just dict
359− -- Make a dictionary from subgoal dictionaries by applying the correct function
360− mkDictionary :: Qualified Ident -> Maybe [DictionaryValue] -> DictionaryValue
361− mkDictionary fnName Nothing = LocalDictionaryValue fnName
362− mkDictionary fnName (Just []) = GlobalDictionaryValue fnName
363− mkDictionary fnName (Just dicts) = DependentDictionaryValue fnName dicts
364− -- Turn a DictionaryValue into a Expr
365− dictionaryValueToValue :: DictionaryValue -> Expr
366− dictionaryValueToValue (LocalDictionaryValue fnName) = Var fnName
367− dictionaryValueToValue (GlobalDictionaryValue fnName) = App (Var fnName) valUndefined
368− dictionaryValueToValue (DependentDictionaryValue fnName dicts) = foldl App (Var fnName) (map dictionaryValueToValue dicts)
369− dictionaryValueToValue (SubclassDictionaryValue dict superclassName index) =
370− App (Accessor (C.__superclass_ ++ show superclassName ++ "_" ++ show index)
371− (dictionaryValueToValue dict))
372− valUndefined
373− -- Ensure that a substitution is valid
374− verifySubstitution :: [(String, Type)] -> Maybe [(String, Type)]
375− verifySubstitution subst = do
376− let grps = groupBy ((==) `on` fst) subst
377− guard (all (pairwise (unifiesWith env) . map snd) grps)
378− return $ map head grps
379− -- Choose the simplest DictionaryValues from a list of candidates
380− -- The reason for this function is as follows:
381− -- When considering overlapping instances, we don't want to consider the same dictionary
382− -- to be an overlap of itself when obtained as a superclass of another class.
383− -- Observing that we probably don't want to select a superclass instance when an instance
384− -- is available directly, and that there is no way for a superclass instance to actually
385− -- introduce an overlap that wouldn't have been there already, we simply remove dictionaries
386− -- obtained as superclass instances if there are simpler instances available.
387− chooseSimplestDictionaries :: [DictionaryValue] -> [DictionaryValue]
388− chooseSimplestDictionaries ds = case filter isSimpleDictionaryValue ds of
389− [] -> ds
390− simple -> simple
391− isSimpleDictionaryValue SubclassDictionaryValue{} = False
392− isSimpleDictionaryValue (DependentDictionaryValue _ ds) = all isSimpleDictionaryValue ds
393− isSimpleDictionaryValue _ = True
394− -- |
395− -- Get the "trace" of a DictionaryValue - that is, remove all SubclassDictionaryValue
396− -- data constructors
397− --
398− dictTrace :: DictionaryValue -> DictionaryValue
399− dictTrace (DependentDictionaryValue fnName dicts) = DependentDictionaryValue fnName $ map dictTrace dicts
400− dictTrace (SubclassDictionaryValue dict _ _) = dictTrace dict
401− dictTrace other = other
402−
403− valUndefined :: Expr
404− valUndefined = Var (Qualified (Just (ModuleName [ProperName C.prim])) (Ident C.undefined))
405−
406−-- |
407−-- Check all values in a list pairwise match a predicate
408−--
409−pairwise :: (a -> a -> Bool) -> [a] -> Bool
410−pairwise _ [] = True
411−pairwise _ [_] = True
412−pairwise p (x : xs) = all (p x) xs && pairwise p xs
413−
414−-- |
415−-- Check that two types unify
416−--
417−unifiesWith :: Environment -> Type -> Type -> Bool
418−unifiesWith _ (TUnknown u1) (TUnknown u2) | u1 == u2 = True
419−unifiesWith _ (Skolem _ s1 _) (Skolem _ s2 _) | s1 == s2 = True
420−unifiesWith _ (TypeVar v1) (TypeVar v2) | v1 == v2 = True
421−unifiesWith _ (TypeConstructor c1) (TypeConstructor c2) | c1 == c2 = True
422−unifiesWith e (TypeApp h1 t1) (TypeApp h2 t2) = unifiesWith e h1 h2 && unifiesWith e t1 t2
423−unifiesWith e (SaturatedTypeSynonym name args) t2 =
424− case expandTypeSynonym' e name args of
425− Left _ -> False
426− Right t1 -> unifiesWith e t1 t2
427−unifiesWith e t1 t2@(SaturatedTypeSynonym _ _) = unifiesWith e t2 t1
428−unifiesWith _ _ _ = False
429−
430−-- |
431−-- Check whether the type heads of two types are equal (for the purposes of type class dictionary lookup),
432−-- and return a substitution from type variables to types which makes the type heads unify.
433−--
434−typeHeadsAreEqual :: ModuleName -> Environment -> Type -> Type -> Maybe [(String, Type)]
435−typeHeadsAreEqual _ _ (Skolem _ s1 _) (Skolem _ s2 _) | s1 == s2 = Just []
436−typeHeadsAreEqual _ _ t (TypeVar v) = Just [(v, t)]
437−typeHeadsAreEqual _ _ (TypeConstructor c1) (TypeConstructor c2) | c1 == c2 = Just []
438−typeHeadsAreEqual m e (TypeApp h1 t1) (TypeApp h2 t2) = (++) <$> typeHeadsAreEqual m e h1 h2 <*> typeHeadsAreEqual m e t1 t2
439−typeHeadsAreEqual m e (SaturatedTypeSynonym name args) t2 = case expandTypeSynonym' e name args of
440− Left _ -> Nothing
441− Right t1 -> typeHeadsAreEqual m e t1 t2
442−typeHeadsAreEqual _ _ _ _ = Nothing
443−
444−-- |
445−-- Ensure skolem variables do not escape their scope
446−--
447−skolemEscapeCheck :: Expr -> Check ()
448−skolemEscapeCheck (TypedValue False _ _) = return ()
449−skolemEscapeCheck root@TypedValue{} =
450− -- Every skolem variable is created when a ForAll type is skolemized.
451− -- This determines the scope of that skolem variable, which is copied from the SkolemScope
452− -- field of the ForAll constructor.
453− -- We traverse the tree top-down, and collect any SkolemScopes introduced by ForAlls.
454− -- If a Skolem is encountered whose SkolemScope is not in the current list, we have found
455− -- an escaped skolem variable.
456− let (_, f, _, _, _) = everythingWithContextOnValues [] [] (++) def go def def def
457− in case f root of
458− [] -> return ()
459− ((binding, val) : _) -> throwError $ mkErrorStack ("Rigid/skolem type variable " ++ maybe "" (("bound by " ++) . prettyPrintValue) binding ++ " has escaped.") (Just (ExprError val))
460− where
461− def s _ = (s, [])
462−
463− go :: [(SkolemScope, Expr)] -> Expr -> ([(SkolemScope, Expr)], [(Maybe Expr, Expr)])
464− go scos val@(TypedValue _ _ (ForAll _ _ (Just sco))) = ((sco, val) : scos, [])
465− go scos val@(TypedValue _ _ ty) = case collectSkolems ty \\ map fst scos of
466− (sco : _) -> (scos, [(findBindingScope sco, val)])
467− _ -> (scos, [])
468− where
469− collectSkolems :: Type -> [SkolemScope]
470− collectSkolems = nub . everythingOnTypes (++) collect
471− where
472− collect (Skolem _ _ scope) = [scope]
473− collect _ = []
474− go scos _ = (scos, [])
475− findBindingScope :: SkolemScope -> Maybe Expr
476− findBindingScope sco =
477− let (_, f, _, _, _) = everythingOnValues mappend (const mempty) go' (const mempty) (const mempty) (const mempty)
478− in getFirst $ f root
479− where
480− go' val@(TypedValue _ _ (ForAll _ _ (Just sco'))) | sco == sco' = First (Just val)
481− go' _ = mempty
482−skolemEscapeCheck val = throwError $ mkErrorStack "Untyped value passed to skolemEscapeCheck" (Just (ExprError val))
483−
484−-- |
485−-- Ensure a row contains no duplicate labels
486−--
487−setify :: Type -> Type
488−setify = rowFromList . first (M.toList . M.fromList) . rowToList
489−
490−-- |
491−-- \"Setify\" all rows occuring inside a value
492−--
493−setifyAll :: Type -> Type
494−setifyAll = everywhereOnTypes setify
495−
496−-- |
497−-- Replace outermost unsolved unification variables with named type variables
498−--
499−varIfUnknown :: Type -> Type
500−varIfUnknown ty =
501− let unks = nub $ unknowns ty
502− toName = (:) 't' . show
503− ty' = everywhereOnTypes typeToVar ty
504− typeToVar :: Type -> Type
505− typeToVar (TUnknown u) = TypeVar (toName u)
506− typeToVar t = t
507− in mkForAll (sort . map toName $ unks) ty'
508−
509−-- |
510−-- Remove any ForAlls and ConstrainedType constructors in a type by introducing new unknowns
511−-- or TypeClassDictionary values.
512−--
513−-- This is necessary during type checking to avoid unifying a polymorphic type with a
514−-- unification variable.
515−--
516−instantiatePolyTypeWithUnknowns :: Expr -> Type -> UnifyT Type Check (Expr, Type)
517−instantiatePolyTypeWithUnknowns val (ForAll ident ty _) = do
518− ty' <- replaceVarWithUnknown ident ty
519− instantiatePolyTypeWithUnknowns val ty'
520−instantiatePolyTypeWithUnknowns val (ConstrainedType constraints ty) = do
521− dicts <- getTypeClassDictionaries
522− (_, ty') <- instantiatePolyTypeWithUnknowns (error "Types under a constraint cannot themselves be constrained") ty
523− return (foldl App val (map (flip (TypeClassDictionary True) dicts) constraints), ty')
524−instantiatePolyTypeWithUnknowns val ty = return (val, ty)
525−
526−-- |
527−-- Replace a single type variable with a new unification variable
528−--
529−replaceVarWithUnknown :: String -> Type -> UnifyT Type Check Type
530−replaceVarWithUnknown ident ty = do
531− tu <- fresh
532− return $ replaceTypeVars ident tu ty
533−
534−-- |
535−-- Replace fully applied type synonyms with the @SaturatedTypeSynonym@ data constructor, which helps generate
536−-- better error messages during unification.
537−--
538−replaceAllTypeSynonyms' :: Environment -> Type -> Either String Type
539−replaceAllTypeSynonyms' env d =
540− let
541− syns = map (\(name, (args, _)) -> (name, length args)) . M.toList $ typeSynonyms env
542− in
543− saturateAllTypeSynonyms syns d
544−
545−replaceAllTypeSynonyms :: (Error e, Functor m, Monad m, MonadState CheckState m, MonadError e m) => Type -> m Type
546−replaceAllTypeSynonyms d = do
547− env <- getEnv
548− either (throwError . strMsg) return $ replaceAllTypeSynonyms' env d
549−
550−-- |
551−-- \"Desaturate\" @SaturatedTypeSynonym@s
552−--
553−desaturateAllTypeSynonyms :: Type -> Type
554−desaturateAllTypeSynonyms = everywhereOnTypes replaceSaturatedTypeSynonym
555− where
556− replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
557− replaceSaturatedTypeSynonym t = t
558−
559−-- |
560−-- Replace a type synonym and its arguments with the aliased type
561−--
562−expandTypeSynonym' :: Environment -> Qualified ProperName -> [Type] -> Either String Type
563−expandTypeSynonym' env name args =
564− case M.lookup name (typeSynonyms env) of
565− Just (synArgs, body) -> do
566− let repl = replaceAllTypeVars (zip synArgs args) body
567− replaceAllTypeSynonyms' env repl
568− Nothing -> error "Type synonym was not defined"
569−
570−expandTypeSynonym :: (Error e, Functor m, Monad m, MonadState CheckState m, MonadError e m) => Qualified ProperName -> [Type] -> m Type
571−expandTypeSynonym name args = do
572− env <- getEnv
573− either (throwError . strMsg) return $ expandTypeSynonym' env name args
574−
575−expandAllTypeSynonyms :: (Error e, Functor m, Applicative m, Monad m, MonadState CheckState m, MonadError e m) => Type -> m Type
576−expandAllTypeSynonyms = everywhereOnTypesTopDownM go
577− where
578− go (SaturatedTypeSynonym name args) = expandTypeSynonym name args
579− go other = return other
580−
581−-- |
582−-- Ensure a set of property names and value does not contain duplicate labels
583−--
584−ensureNoDuplicateProperties :: (Error e, MonadError e m) => [(String, Expr)] -> m ()
585−ensureNoDuplicateProperties ps = guardWith (strMsg "Duplicate property names") $ length (nub . map fst $ ps) == length ps
586−
587−-- |
588−-- Infer a type for a value, rethrowing any error to provide a more useful error message
589−--
590−infer :: Expr -> UnifyT Type Check Expr
591−infer val = rethrow (mkErrorStack "Error inferring type of value" (Just (ExprError val)) <>) $ infer' val
592−
593−-- |
594−-- Infer a type for a value
595−--
596−infer' :: Expr -> UnifyT Type Check Expr
597−infer' v@(NumericLiteral _) = return $ TypedValue True v tyNumber
598−infer' v@(StringLiteral _) = return $ TypedValue True v tyString
599−infer' v@(BooleanLiteral _) = return $ TypedValue True v tyBoolean
600−infer' (ArrayLiteral vals) = do
601− ts <- mapM infer vals
602− els <- fresh
603− forM_ ts $ \(TypedValue _ _ t) -> els =?= t
604− return $ TypedValue True (ArrayLiteral ts) (TypeApp tyArray els)
605−infer' (ObjectLiteral ps) = do
606− ensureNoDuplicateProperties ps
607− ts <- mapM (infer . snd) ps
608− let fields = zipWith (\name (TypedValue _ _ t) -> (name, t)) (map fst ps) ts
609− ty = TypeApp tyObject $ rowFromList (fields, REmpty)
610− return $ TypedValue True (ObjectLiteral (zip (map fst ps) ts)) ty
611−infer' (ObjectUpdate o ps) = do
612− ensureNoDuplicateProperties ps
613− row <- fresh
614− newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
615− let newTys = map (\(name, TypedValue _ _ ty) -> (name, ty)) newVals
616− oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
617− let oldTy = TypeApp tyObject $ rowFromList (oldTys, row)
618− o' <- TypedValue True <$> check o oldTy <*> pure oldTy
619− return $ TypedValue True (ObjectUpdate o' newVals) $ TypeApp tyObject $ rowFromList (newTys, row)
620−infer' (Accessor prop val) = do
621− typed@(TypedValue _ _ objTy) <- infer val
622− propTy <- inferProperty objTy prop
623− case propTy of
624− Nothing -> do
625− field <- fresh
626− rest <- fresh
627− _ <- subsumes Nothing objTy (TypeApp tyObject (RCons prop field rest))
628− return $ TypedValue True (Accessor prop typed) field
629− Just ty -> return $ TypedValue True (Accessor prop typed) ty
630−infer' (Abs (Left arg) ret) = do
631− ty <- fresh
632− Just moduleName <- checkCurrentModule <$> get
633− makeBindingGroupVisible $ bindLocalVariables moduleName [(arg, ty, Defined)] $ do
634− body@(TypedValue _ _ bodyTy) <- infer' ret
635− return $ TypedValue True (Abs (Left arg) body) $ function ty bodyTy
636−infer' (Abs (Right _) _) = error "Binder was not desugared"
637−infer' (App f arg) = do
638− f'@(TypedValue _ _ ft) <- infer f
639− (ret, app) <- checkFunctionApplication f' ft arg Nothing
640− return $ TypedValue True app ret
641−infer' (Var var) = do
642− Just moduleName <- checkCurrentModule <$> get
643− checkVisibility moduleName var
644− ty <- introduceSkolemScope <=< replaceAllTypeSynonyms <=< lookupVariable moduleName $ var
645− case ty of
646− ConstrainedType constraints ty' -> do
647− dicts <- getTypeClassDictionaries
648− return $ TypedValue True (foldl App (Var var) (map (flip (TypeClassDictionary True) dicts) constraints)) ty'
649− _ -> return $ TypedValue True (Var var) ty
650−infer' v@(Constructor c) = do
651− env <- getEnv
652− case M.lookup c (dataConstructors env) of
653− Nothing -> throwError . strMsg $ "Constructor " ++ show c ++ " is undefined"
654− Just (_, _, ty) -> do ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
655− return $ TypedValue True v ty'
656−infer' (Case vals binders) = do
657− ts <- mapM infer vals
658− ret <- fresh
659− binders' <- checkBinders (map (\(TypedValue _ _ t) -> t) ts) ret binders
660− return $ TypedValue True (Case ts binders') ret
661−infer' (IfThenElse cond th el) = do
662− cond' <- check cond tyBoolean
663− v2@(TypedValue _ _ t2) <- infer th
664− v3@(TypedValue _ _ t3) <- infer el
665− (v2', v3', t) <- meet v2 v3 t2 t3
666− return $ TypedValue True (IfThenElse cond' v2' v3') t
667−infer' (Let ds val) = do
668− (ds', val'@(TypedValue _ _ valTy)) <- inferLetBinding [] ds val infer
669− return $ TypedValue True (Let ds' val') valTy
670−infer' (SuperClassDictionary className tys) = do
671− dicts <- getTypeClassDictionaries
672− return $ TypeClassDictionary False (className, tys) dicts
673−infer' (TypedValue checkType val ty) = do
674− Just moduleName <- checkCurrentModule <$> get
675− kind <- liftCheck $ kindOf moduleName ty
676− guardWith (strMsg $ "Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
677− ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
678− val' <- if checkType then check val ty' else return val
679− return $ TypedValue True val' ty'
680−infer' (PositionedValue pos val) = rethrowWithPosition pos $ infer' val
681−infer' _ = error "Invalid argument to infer"
682−
683−inferLetBinding :: [Declaration] -> [Declaration] -> Expr -> (Expr -> UnifyT Type Check Expr) -> UnifyT Type Check ([Declaration], Expr)
684−inferLetBinding seen [] ret j = (,) seen <$> makeBindingGroupVisible (j ret)
685−inferLetBinding seen (ValueDeclaration ident nameKind [] Nothing tv@(TypedValue checkType val ty) : rest) ret j = do
686− Just moduleName <- checkCurrentModule <$> get
687− kind <- liftCheck $ kindOf moduleName ty
688− guardWith (strMsg $ "Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
689− let dict = M.singleton (moduleName, ident) (ty, nameKind, Undefined)
690− ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
691− TypedValue _ val' ty'' <- if checkType then bindNames dict (check val ty') else return tv
692− bindNames (M.singleton (moduleName, ident) (ty'', nameKind, Defined)) $ inferLetBinding (seen ++ [ValueDeclaration ident nameKind [] Nothing (TypedValue checkType val' ty'')]) rest ret j
693−inferLetBinding seen (ValueDeclaration ident nameKind [] Nothing val : rest) ret j = do
694− valTy <- fresh
695− Just moduleName <- checkCurrentModule <$> get
696− let dict = M.singleton (moduleName, ident) (valTy, nameKind, Undefined)
697− TypedValue _ val' valTy' <- bindNames dict $ infer val
698− valTy =?= valTy'
699− bindNames (M.singleton (moduleName, ident) (valTy', nameKind, Defined)) $ inferLetBinding (seen ++ [ValueDeclaration ident nameKind [] Nothing val']) rest ret j
700−inferLetBinding seen (BindingGroupDeclaration ds : rest) ret j = do
701− Just moduleName <- checkCurrentModule <$> get
702− (untyped, typed, dict, untypedDict) <- typeDictionaryForBindingGroup moduleName (map (\(i, _, v) -> (i, v)) ds)
703− ds1' <- parU typed $ \e -> checkTypedBindingGroupElement moduleName e dict
704− ds2' <- forM untyped $ \e -> typeForBindingGroupElement e dict untypedDict
705− let ds' = [(ident, LocalVariable, val') | (ident, (val', _)) <- ds1' ++ ds2']
706− makeBindingGroupVisible $ bindNames dict $ inferLetBinding (seen ++ [BindingGroupDeclaration ds']) rest ret j
707−inferLetBinding seen (PositionedDeclaration pos d : ds) ret j = rethrowWithPosition pos $ do
708− ((d' : ds'), val') <- inferLetBinding seen (d : ds) ret j
709− return (PositionedDeclaration pos d' : ds', val')
710−inferLetBinding _ _ _ _ = error "Invalid argument to inferLetBinding"
711−
712−-- |
713−-- Infer the type of a property inside a record with a given type
714−--
715−inferProperty :: Type -> String -> UnifyT Type Check (Maybe Type)
716−inferProperty (TypeApp obj row) prop | obj == tyObject = do
717− let (props, _) = rowToList row
718− return $ lookup prop props
719−inferProperty (SaturatedTypeSynonym name args) prop = do
720− replaced <- introduceSkolemScope <=< expandTypeSynonym name $ args
721− inferProperty replaced prop
722−inferProperty (ForAll ident ty _) prop = do
723− replaced <- replaceVarWithUnknown ident ty
724− inferProperty replaced prop
725−inferProperty _ _ = return Nothing
726−
727−-- |
728−-- Infer the types of variables brought into scope by a binder
729−--
730−inferBinder :: Type -> Binder -> UnifyT Type Check (M.Map Ident Type)
731−inferBinder _ NullBinder = return M.empty
732−inferBinder val (StringBinder _) = val =?= tyString >> return M.empty
733−inferBinder val (NumberBinder _) = val =?= tyNumber >> return M.empty
734−inferBinder val (BooleanBinder _) = val =?= tyBoolean >> return M.empty
735−inferBinder val (VarBinder name) = return $ M.singleton name val
736−inferBinder val (ConstructorBinder ctor binders) = do
737− env <- getEnv
738− case M.lookup ctor (dataConstructors env) of
739− Just (_, _, ty) -> do
740− (_, fn) <- instantiatePolyTypeWithUnknowns (error "Data constructor types cannot contain constraints") ty
741− fn' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ fn
742− go binders fn'
743− where
744− go [] ty' = do
745− _ <- subsumes Nothing val ty'
746− return M.empty
747− go (binder : binders') (TypeApp (TypeApp t obj) ret) | t == tyFunction =
748− M.union <$> inferBinder obj binder <*> go binders' ret
749− go _ _ = throwError . strMsg $ "Wrong number of arguments to constructor " ++ show ctor
750− _ -> throwError . strMsg $ "Constructor " ++ show ctor ++ " is not defined"
751−inferBinder val (ObjectBinder props) = do
752− row <- fresh
753− rest <- fresh
754− m1 <- inferRowProperties row rest props
755− val =?= TypeApp tyObject row
756− return m1
757− where
758− inferRowProperties :: Type -> Type -> [(String, Binder)] -> UnifyT Type Check (M.Map Ident Type)
759− inferRowProperties nrow row [] = nrow =?= row >> return M.empty
760− inferRowProperties nrow row ((name, binder):binders) = do
761− propTy <- fresh
762− m1 <- inferBinder propTy binder
763− m2 <- inferRowProperties nrow (RCons name propTy row) binders
764− return $ m1 `M.union` m2
765−inferBinder val (ArrayBinder binders) = do
766− el <- fresh
767− m1 <- M.unions <$> mapM (inferBinder el) binders
768− val =?= TypeApp tyArray el
769− return m1
770−inferBinder val (ConsBinder headBinder tailBinder) = do
771− el <- fresh
772− m1 <- inferBinder el headBinder
773− m2 <- inferBinder val tailBinder
774− val =?= TypeApp tyArray el
775− return $ m1 `M.union` m2
776−inferBinder val (NamedBinder name binder) = do
777− m <- inferBinder val binder
778− return $ M.insert name val m
779−inferBinder val (PositionedBinder pos binder) =
780− rethrowWithPosition pos $ inferBinder val binder
781−
782−-- |
783−-- Check the types of the return values in a set of binders in a case statement
784−--
785−checkBinders :: [Type] -> Type -> [CaseAlternative] -> UnifyT Type Check [CaseAlternative]
786−checkBinders _ _ [] = return []
787−checkBinders nvals ret (CaseAlternative binders grd val : bs) = do
788− guardWith (strMsg "Overlapping binders in case statement") $
789− let ns = concatMap binderNames binders in length (nub ns) == length ns
790− Just moduleName <- checkCurrentModule <$> get
791− m1 <- M.unions <$> zipWithM inferBinder nvals binders
792− r <- bindLocalVariables moduleName [ (name, ty, Defined) | (name, ty) <- M.toList m1 ] $ do
793− val' <- TypedValue True <$> check val ret <*> pure ret
794− case grd of
795− Nothing -> return $ CaseAlternative binders Nothing val'
796− Just g -> do
797− g' <- check g tyBoolean
798− return $ CaseAlternative binders (Just g') val'
799− rs <- checkBinders nvals ret bs
800− return $ r : rs
801−
802−-- |
803−-- Generate a new skolem constant
804−--
805−newSkolemConstant :: UnifyT Type Check Int
806−newSkolemConstant = fresh'
807−
808−-- |
809−-- Generate a new skolem scope
810−--
811−newSkolemScope :: UnifyT Type Check SkolemScope
812−newSkolemScope = SkolemScope <$> fresh'
813−
814−-- |
815−-- Skolemize a type variable by replacing its instances with fresh skolem constants
816−--
817−skolemize :: String -> Int -> SkolemScope -> Type -> Type
818−skolemize ident sko scope = replaceTypeVars ident (Skolem ident sko scope)
819−
820−-- |
821−-- This function has one purpose - to skolemize type variables appearing in a
822−-- SuperClassDictionary placeholder. These type variables are somewhat unique since they are the
823−-- only example of scoped type variables.
824−--
825−skolemizeTypesInValue :: String -> Int -> SkolemScope -> Expr -> Expr
826−skolemizeTypesInValue ident sko scope = let (_, f, _) = everywhereOnValues id go id in f
827− where
828− go (SuperClassDictionary c ts) = SuperClassDictionary c (map (skolemize ident sko scope) ts)
829− go other = other
830−
831−-- |
832−-- Introduce skolem scope at every occurence of a ForAll
833−--
834−introduceSkolemScope :: Type -> UnifyT Type Check Type
835−introduceSkolemScope = everywhereOnTypesM go
836− where
837− go (ForAll ident ty Nothing) = ForAll ident ty <$> (Just <$> newSkolemScope)
838− go other = return other
839−
840−-- |
841−-- Check the type of a value, rethrowing errors to provide a better error message
842−--
843−check :: Expr -> Type -> UnifyT Type Check Expr
844−check val ty = rethrow (mkErrorStack errorMessage (Just (ExprError val)) <>) $ check' val ty
845− where
846− errorMessage =
847− "Error checking type of term " ++
848− prettyPrintValue val ++
849− " against type " ++
850− prettyPrintType ty
851−
852−-- |
853−-- Check the type of a value
854−--
855−check' :: Expr -> Type -> UnifyT Type Check Expr
856−check' val (ForAll ident ty _) = do
857− scope <- newSkolemScope
858− sko <- newSkolemConstant
859− let sk = skolemize ident sko scope ty
860− let skVal = skolemizeTypesInValue ident sko scope val
861− val' <- check skVal sk
862− return $ TypedValue True val' (ForAll ident ty (Just scope))
863−check' val t@(ConstrainedType constraints ty) = do
864− dictNames <- forM constraints $ \(Qualified _ (ProperName className), _) -> do
865− n <- liftCheck freshDictionaryName
866− return $ Ident $ "__dict_" ++ className ++ "_" ++ show n
867− val' <- makeBindingGroupVisible $ withTypeClassDictionaries (zipWith (\name (className, instanceTy) ->
868− TypeClassDictionaryInScope name className instanceTy Nothing TCDRegular False) (map (Qualified Nothing) dictNames)
869− constraints) $ check val ty
870− return $ TypedValue True (foldr (Abs . Left) val' dictNames) t
871−check' val (SaturatedTypeSynonym name args) = do
872− ty <- introduceSkolemScope <=< expandTypeSynonym name $ args
873− check val ty
874−check' val u@(TUnknown _) = do
875− val'@(TypedValue _ _ ty) <- infer val
876− -- Don't unify an unknown with an inferred polytype
877− (val'', ty') <- instantiatePolyTypeWithUnknowns val' ty
878− ty' =?= u
879− return $ TypedValue True val'' ty'
880−check' v@(NumericLiteral _) t | t == tyNumber =
881− return $ TypedValue True v t
882−check' v@(StringLiteral _) t | t == tyString =
883− return $ TypedValue True v t
884−check' v@(BooleanLiteral _) t | t == tyBoolean =
885− return $ TypedValue True v t
886−check' (ArrayLiteral vals) t@(TypeApp a ty) = do
887− a =?= tyArray
888− array <- ArrayLiteral <$> forM vals (`check` ty)
889− return $ TypedValue True array t
890−check' (Abs (Left arg) ret) ty@(TypeApp (TypeApp t argTy) retTy) | t == tyFunction = do
891− Just moduleName <- checkCurrentModule <$> get
892− ret' <- makeBindingGroupVisible $ bindLocalVariables moduleName [(arg, argTy, Defined)] $ check ret retTy
893− return $ TypedValue True (Abs (Left arg) ret') ty
894−check' (Abs (Right _) _) _ = error "Binder was not desugared"
895−check' (App f arg) ret = do
896− f'@(TypedValue _ _ ft) <- infer f
897− (_, app) <- checkFunctionApplication f' ft arg (Just ret)
898− return $ TypedValue True app ret
899−check' v@(Var var) ty = do
900− Just moduleName <- checkCurrentModule <$> get
901− checkVisibility moduleName var
902− repl <- introduceSkolemScope <=< replaceAllTypeSynonyms <=< lookupVariable moduleName $ var
903− ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
904− v' <- subsumes (Just v) repl ty'
905− case v' of
906− Nothing -> throwError . strMsg $ "Unable to check type subsumption"
907− Just v'' -> return $ TypedValue True v'' ty'
908−check' (SuperClassDictionary className tys) _ = do
909− {-
910− -- Here, we replace a placeholder for a superclass dictionary with a regular
911− -- TypeClassDictionary placeholder. The reason we do this is that it is necessary to have the
912− -- correct super instance dictionaries in scope, and these are not available when the type class
913− -- declaration gets desugared.
914− --
915− -- Note also that the first argument to TypeClassDictionary is False, meaning we _do not_ want
916− -- to consider superclass instances when searching for this dictionary - doing so might lead
917− -- to traversing a cycle in the instance graph.
918− -}
919− dicts <- getTypeClassDictionaries
920− return $ TypeClassDictionary False (className, tys) dicts
921−check' (TypedValue checkType val ty1) ty2 = do
922− Just moduleName <- checkCurrentModule <$> get
923− kind <- liftCheck $ kindOf moduleName ty1
924− guardWith (strMsg $ "Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
925− ty1' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty1
926− ty2' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty2
927− val' <- subsumes (Just val) ty1' ty2'
928− case val' of
929− Nothing -> throwError . strMsg $ "Unable to check type subsumption"
930− Just val'' -> do
931− val''' <- if checkType then check val'' ty2' else return val''
932− return $ TypedValue checkType (TypedValue True val''' ty1') ty2'
933−check' (Case vals binders) ret = do
934− vals' <- mapM infer vals
935− let ts = map (\(TypedValue _ _ t) -> t) vals'
936− binders' <- checkBinders ts ret binders
937− return $ TypedValue True (Case vals' binders') ret
938−check' (IfThenElse cond th el) ty = do
939− cond' <- check cond tyBoolean
940− th' <- check th ty
941− el' <- check el ty
942− return $ TypedValue True (IfThenElse cond' th' el') ty
943−check' (ObjectLiteral ps) t@(TypeApp obj row) | obj == tyObject = do
944− ensureNoDuplicateProperties ps
945− ps' <- checkProperties ps row False
946− return $ TypedValue True (ObjectLiteral ps') t
947−check' (TypeClassDictionaryConstructorApp name ps) t = do
948− ps' <- check' ps t
949− return $ TypedValue True (TypeClassDictionaryConstructorApp name ps') t
950−check' (ObjectUpdate obj ps) t@(TypeApp o row) | o == tyObject = do
951− ensureNoDuplicateProperties ps
952− us <- zip (map fst ps) <$> replicateM (length ps) fresh
953− let (propsToCheck, rest) = rowToList row
954− propsToRemove = map fst ps
955− remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
956− obj' <- check obj (TypeApp tyObject (rowFromList (us ++ remainingProps, rest)))
957− ps' <- checkProperties ps row True
958− return $ TypedValue True (ObjectUpdate obj' ps') t
959−check' (Accessor prop val) ty = do
960− rest <- fresh
961− val' <- check val (TypeApp tyObject (RCons prop ty rest))
962− return $ TypedValue True (Accessor prop val') ty
963−check' (Constructor c) ty = do
964− env <- getEnv
965− case M.lookup c (dataConstructors env) of
966− Nothing -> throwError . strMsg $ "Constructor " ++ show c ++ " is undefined"
967− Just (_, _, ty1) -> do
968− repl <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty1
969− _ <- subsumes Nothing repl ty
970− return $ TypedValue True (Constructor c) ty
971−check' (Let ds val) ty = do
972− (ds', val') <- inferLetBinding [] ds val (flip check ty)
973− return $ TypedValue True (Let ds' val') ty
974−check' val ty | containsTypeSynonyms ty = do
975− ty' <- introduceSkolemScope <=< expandAllTypeSynonyms $ ty
976− check val ty'
977−check' (PositionedValue pos val) ty =
978− rethrowWithPosition pos $ check val ty
979−check' val ty = throwError $ mkErrorStack ("Expr does not have type " ++ prettyPrintType ty) (Just (ExprError val))
980−
981−containsTypeSynonyms :: Type -> Bool
982−containsTypeSynonyms = everythingOnTypes (||) go where
983− go (SaturatedTypeSynonym _ _) = True
984− go _ = False
985−
986−-- |
987−-- Check the type of a collection of named record fields
988−--
989−-- The @lax@ parameter controls whether or not every record member has to be provided. For object updates, this is not the case.
990−--
991−checkProperties :: [(String, Expr)] -> Type -> Bool -> UnifyT Type Check [(String, Expr)]
992−checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
993− go [] [] REmpty = return []
994− go [] [] u@(TUnknown _) = do u =?= REmpty
995− return []
996− go [] [] (Skolem _ _ _) | lax = return []
997− go [] ((p, _): _) _ | lax = return []
998− | otherwise = throwError $ mkErrorStack ("Object does not have property " ++ p) (Just (ExprError (ObjectLiteral ps)))
999− go ((p,_):_) [] REmpty = throwError $ mkErrorStack ("Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row) (Just (ExprError (ObjectLiteral ps)))
1000− go ((p,v):ps') [] u@(TUnknown _) = do
1001− v'@(TypedValue _ _ ty) <- infer v
1002− rest <- fresh
1003− u =?= RCons p ty rest
1004− ps'' <- go ps' [] rest
1005− return $ (p, v') : ps''
1006− go ((p,v):ps') ts r =
1007− case lookup p ts of
1008− Nothing -> do
1009− v'@(TypedValue _ _ ty) <- infer v
1010− rest <- fresh
1011− r =?= RCons p ty rest
1012− ps'' <- go ps' ts rest
1013− return $ (p, v') : ps''
1014− Just ty -> do
1015− v' <- check v ty
1016− ps'' <- go ps' (delete (p, ty) ts) r
1017− return $ (p, v') : ps''
1018− go _ _ _ = throwError $ mkErrorStack ("Object does not have type " ++ prettyPrintType (TypeApp tyObject row)) (Just (ExprError (ObjectLiteral ps)))
1019−
1020−-- |
1021−-- Check the type of a function application, rethrowing errors to provide a better error message
1022−--
1023−checkFunctionApplication :: Expr -> Type -> Expr -> Maybe Type -> UnifyT Type Check (Type, Expr)
1024−checkFunctionApplication fn fnTy arg ret = rethrow (mkErrorStack errorMessage (Just (ExprError fn)) <>) $ do
1025− subst <- unifyCurrentSubstitution <$> UnifyT get
1026− checkFunctionApplication' fn (subst $? fnTy) arg (($?) subst <$> ret)
1027− where
1028− errorMessage = "Error applying function of type "
1029− ++ prettyPrintType fnTy
1030− ++ " to argument " ++ prettyPrintValue arg
1031−
1032−-- |
1033−-- Check the type of a function application
1034−--
1035−checkFunctionApplication' :: Expr -> Type -> Expr -> Maybe Type -> UnifyT Type Check (Type, Expr)
1036−checkFunctionApplication' fn (TypeApp (TypeApp tyFunction' argTy) retTy) arg ret = do
1037− tyFunction' =?= tyFunction
1038− arg' <- check arg argTy
1039− case ret of
1040− Nothing -> return (retTy, App fn arg')
1041− Just ret' -> do
1042− Just app' <- subsumes (Just (App fn arg')) retTy ret'
1043− return (retTy, app')
1044−checkFunctionApplication' fn (ForAll ident ty _) arg ret = do
1045− replaced <- replaceVarWithUnknown ident ty
1046− checkFunctionApplication fn replaced arg ret
1047−checkFunctionApplication' fn u@(TUnknown _) arg ret = do
1048− arg' <- do
1049− TypedValue _ arg' t <- infer arg
1050− (arg'', t') <- instantiatePolyTypeWithUnknowns arg' t
1051− return $ TypedValue True arg'' t'
1052− let ty = (\(TypedValue _ _ t) -> t) arg'
1053− ret' <- maybe fresh return ret
1054− u =?= function ty ret'
1055− return (ret', App fn arg')
1056−checkFunctionApplication' fn (SaturatedTypeSynonym name tyArgs) arg ret = do
1057− ty <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
1058− checkFunctionApplication fn ty arg ret
1059−checkFunctionApplication' fn (ConstrainedType constraints fnTy) arg ret = do
1060− dicts <- getTypeClassDictionaries
1061− checkFunctionApplication' (foldl App fn (map (flip (TypeClassDictionary True) dicts) constraints)) fnTy arg ret
1062−checkFunctionApplication' fn fnTy dict@(TypeClassDictionary _ _ _) _ =
1063− return (fnTy, App fn dict)
1064−checkFunctionApplication' _ fnTy arg _ = throwError . strMsg $ "Cannot apply a function of type "
1065− ++ prettyPrintType fnTy
1066− ++ " to argument " ++ prettyPrintValue arg
1067−
1068−-- |
1069−-- Check whether one type subsumes another, rethrowing errors to provide a better error message
1070−--
1071−subsumes :: Maybe Expr -> Type -> Type -> UnifyT Type Check (Maybe Expr)
1072−subsumes val ty1 ty2 = rethrow (mkErrorStack errorMessage (ExprError <$> val) <>) $ subsumes' val ty1 ty2
1073− where
1074− errorMessage = "Error checking that type "
1075− ++ prettyPrintType ty1
1076− ++ " subsumes type "
1077− ++ prettyPrintType ty2
1078−
1079−-- |
1080−-- Check whether one type subsumes another
1081−--
1082−subsumes' :: Maybe Expr -> Type -> Type -> UnifyT Type Check (Maybe Expr)
1083−subsumes' val (ForAll ident ty1 _) ty2 = do
1084− replaced <- replaceVarWithUnknown ident ty1
1085− subsumes val replaced ty2
1086−subsumes' val ty1 (ForAll ident ty2 sco) =
1087− case sco of
1088− Just sco' -> do
1089− sko <- newSkolemConstant
1090− let sk = skolemize ident sko sco' ty2
1091− subsumes val ty1 sk
1092− Nothing -> throwError . strMsg $ "Skolem variable scope is unspecified"
1093−subsumes' val (TypeApp (TypeApp f1 arg1) ret1) (TypeApp (TypeApp f2 arg2) ret2) | f1 == tyFunction && f2 == tyFunction = do
1094− _ <- subsumes Nothing arg2 arg1
1095− _ <- subsumes Nothing ret1 ret2
1096− return val
1097−subsumes' val (SaturatedTypeSynonym name tyArgs) ty2 = do
1098− ty1 <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
1099− subsumes val ty1 ty2
1100−subsumes' val ty1 (SaturatedTypeSynonym name tyArgs) = do
1101− ty2 <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
1102− subsumes val ty1 ty2
1103−subsumes' (Just val) (ConstrainedType constraints ty1) ty2 = do
1104− dicts <- getTypeClassDictionaries
1105− subsumes' (Just $ foldl App val (map (flip (TypeClassDictionary True) dicts) constraints)) ty1 ty2
1106−subsumes' val (TypeApp f1 r1) (TypeApp f2 r2) | f1 == tyObject && f2 == tyObject = do
1107− let
1108− (ts1, r1') = rowToList r1
1109− (ts2, r2') = rowToList r2
1110− ts1' = sortBy (comparing fst) ts1
1111− ts2' = sortBy (comparing fst) ts2
1112− go ts1' ts2' r1' r2'
1113− return val
1114− where
1115− go [] ts2 r1' r2' = r1' =?= rowFromList (ts2, r2')
1116− go ts1 [] r1' r2' = r2' =?= rowFromList (ts1, r1')
1117− go ((p1, ty1) : ts1) ((p2, ty2) : ts2) r1' r2'
1118− | p1 == p2 = do _ <- subsumes Nothing ty1 ty2
1119− go ts1 ts2 r1' r2'
1120− | p1 < p2 = do rest <- fresh
1121− r2' =?= RCons p1 ty1 rest
1122− go ts1 ((p2, ty2) : ts2) r1' rest
1123− | otherwise = do rest <- fresh
1124− r1' =?= RCons p2 ty2 rest
1125− go ((p1, ty1) : ts1) ts2 rest r2'
1126−subsumes' val ty1 ty2@(TypeApp obj _) | obj == tyObject = subsumes val ty2 ty1
1127−subsumes' val ty1 ty2 = do
1128− ty1 =?= ty2
1129− return val
1130−
1131−-- |
1132−-- Compute the meet of two types, i.e. the most general type which both types subsume.
1133−-- TODO: handle constrained types
1134−--
1135−meet :: Expr -> Expr -> Type -> Type -> UnifyT Type Check (Expr, Expr, Type)
1136−meet e1 e2 (ForAll ident t1 _) t2 = do
1137− t1' <- replaceVarWithUnknown ident t1
1138− meet e1 e2 t1' t2
1139−meet e1 e2 t1 (ForAll ident t2 _) = do
1140− t2' <- replaceVarWithUnknown ident t2
1141− meet e1 e2 t1 t2'
1142−meet e1 e2 t1 t2 = do
1143− t1 =?= t2
1144− return (e1, e2, t1)
1145−
1146−
1147−
1148−
1149−
1150−
1151−