@@ -1,942 +0,0 @@
1−-----------------------------------------------------------------------------
2−--
3−-- Module : Language.PureScript.TypeChecker.Types
4−-- Copyright : (c) Phil Freeman 2013
5−-- License : MIT
6−--
7−-- Maintainer : Phil Freeman <paf31@cantab.net>
8−-- Stability : experimental
9−-- Portability :
10−--
11−-- |
12−-- This module implements the type checker
13−--
14−-----------------------------------------------------------------------------
15−
16−{-# OPTIONS_GHC -fno-warn-orphans #-}
17−{-# LANGUAGE DeriveDataTypeable #-}
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, isNothing, isJust, fromMaybe)
46−import qualified Data.Data as D
47−import Data.Generics
48− (everythingWithContext, mkM, everywhereM, everything, mkT,
49− something, everywhere, mkQ)
50−
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−
60−import Control.Monad.State
61−import Control.Monad.Error
62−import Control.Monad.Reader
63−import Control.Monad.Unify
64−
65−import Control.Applicative
66−import Control.Arrow (Arrow(..))
67−
68−import qualified Data.Map as M
69−import Data.Function (on)
70−import Debug.Trace (trace)
71−
72−instance Partial Type where
73− unknown = TUnknown
74− isUnknown (TUnknown u) = Just u
75− isUnknown _ = Nothing
76−
77−instance Unifiable Check Type where
78− (=?=) = unifyTypes
79−
80−-- |
81−-- Unify two types, updating the current substitution
82−--
83−unifyTypes :: Type -> Type -> UnifyT Type Check ()
84−unifyTypes t1 t2 = rethrow (\e -> "Error unifying type " ++ prettyPrintType t1 ++ " with type " ++ prettyPrintType t2 ++ ":\n" ++ e) $ do
85− unifyTypes' t1 t2
86− where
87− unifyTypes' (TUnknown u1) (TUnknown u2) | u1 == u2 = return ()
88− unifyTypes' (TUnknown u) t = u =:= t
89− unifyTypes' t (TUnknown u) = u =:= t
90− unifyTypes' (SaturatedTypeSynonym name args) ty = do
91− ty1 <- introduceSkolemScope <=< expandTypeSynonym name $ args
92− ty1 `unifyTypes` ty
93− unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
94− unifyTypes' (ForAll ident1 ty1 sc1) (ForAll ident2 ty2 sc2) =
95− case (sc1, sc2) of
96− (Just sc1', Just sc2') -> do
97− sko <- newSkolemConstant
98− let sk1 = skolemize ident1 sko sc1' ty1
99− let sk2 = skolemize ident2 sko sc2' ty2
100− sk1 `unifyTypes` sk2
101− _ -> throwError (prettyPrintType ty1)
102− unifyTypes' (ForAll ident ty1 (Just sc)) ty2 = do
103− sko <- newSkolemConstant
104− let sk = skolemize ident sko sc ty1
105− sk `unifyTypes` ty2
106− unifyTypes' (ForAll _ _ _) _ = throwError "Skolem variable scope is unspecified"
107− unifyTypes' ty f@(ForAll _ _ _) = f `unifyTypes` ty
108− unifyTypes' (Object row1) (Object row2) = row1 =?= row2
109− unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
110− unifyTypes' (TypeConstructor c1) (TypeConstructor c2) = do
111− env <- getEnv
112− Just moduleName <- checkCurrentModule <$> get
113− guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (typeConstructorsAreEqual env moduleName c1 c2)
114− unifyTypes' (TypeApp t3 t4) (TypeApp t5 t6) = do
115− t3 `unifyTypes` t5
116− t4 `unifyTypes` t6
117− unifyTypes' (Skolem s1 _) (Skolem s2 _) | s1 == s2 = return ()
118− unifyTypes' r1@(RCons _ _ _) r2 = unifyRows r1 r2
119− unifyTypes' r1 r2@(RCons _ _ _) = unifyRows r1 r2
120− unifyTypes' r1@REmpty r2 = unifyRows r1 r2
121− unifyTypes' r1 r2@REmpty = unifyRows r1 r2
122− unifyTypes' t3 t4 = throwError $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
123−
124−-- |
125−-- Unify two rows, updating the current substitution
126−--
127−-- Common labels are first identified, and unified. Remaining labels and types are unified with a
128−-- trailing row unification variable, if appropriate, otherwise leftover labels result in a unification
129−-- error.
130−--
131−unifyRows :: Type -> Type -> UnifyT Type Check ()
132−unifyRows r1 r2 =
133− let
134− (s1, r1') = rowToList r1
135− (s2, r2') = rowToList r2
136− int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
137− sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
138− sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
139− in do
140− forM_ int (uncurry (=?=))
141− unifyRows' sd1 r1' sd2 r2'
142− where
143− unifyRows' :: [(String, Type)] -> Type -> [(String, Type)] -> Type -> UnifyT Type Check ()
144− unifyRows' [] (TUnknown u) sd r = u =:= rowFromList (sd, r)
145− unifyRows' sd r [] (TUnknown u) = u =:= rowFromList (sd, r)
146− unifyRows' ((name, ty):row) r others u@(TUnknown un) = do
147− occursCheck un ty
148− forM_ row $ \(_, t) -> occursCheck un t
149− u' <- fresh
150− u =?= RCons name ty u'
151− unifyRows' row r others u'
152− unifyRows' [] REmpty [] REmpty = return ()
153− unifyRows' [] (TypeVar v1) [] (TypeVar v2) | v1 == v2 = return ()
154− unifyRows' [] (Skolem s1 _) [] (Skolem s2 _) | s1 == s2 = return ()
155− unifyRows' sd3 r3 sd4 r4 = throwError $ "Cannot unify " ++ prettyPrintRow (rowFromList (sd3, r3)) ++ " with " ++ prettyPrintRow (rowFromList (sd4, r4)) ++ "."
156−
157−-- |
158−-- Ensure type constructors are equal after canonicalization
159−--
160−typeConstructorsAreEqual :: Environment -> ModuleName -> Qualified ProperName -> Qualified ProperName -> Bool
161−typeConstructorsAreEqual env moduleName = (==) `on` canonicalizeType moduleName env
162−
163−-- |
164−-- Infer the types of multiple mutually-recursive values, and return elaborated values including
165−-- type class dictionaries and type annotations.
166−--
167−typesOf :: ModuleName -> [(Ident, Value)] -> Check [(Ident, (Value, Type))]
168−typesOf moduleName vals = do
169− tys <- fmap tidyUp . liftUnify $ do
170− let es = map isTyped vals
171− typed = filter (isJust . snd . snd) es
172− untyped = filter (isNothing . snd . snd) es
173− typedDict = map (\(ident, (_, Just ty)) -> (ident, ty)) typed
174− untypedNames <- replicateM (length untyped) fresh
175− let untypedDict = zip (map fst untyped) untypedNames
176− dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ (map (id *** fst) typedDict) ++ untypedDict)
177− forM es $ \e -> do
178− triple@(_, (val, ty)) <- case e of
179− (ident, (val, Just (ty, checkType))) -> do
180− kind <- liftCheck $ kindOf moduleName ty
181− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
182− ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
183− val' <- bindNames dict $ if checkType
184− then TypedValue True <$> check val ty' <*> pure ty'
185− else return (TypedValue False val ty')
186− return (ident, (val', ty'))
187− (ident, (val, Nothing)) -> do
188− TypedValue _ val' ty <- bindNames dict $ infer val
189− ty =?= fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
190− return (ident, (TypedValue True val' ty, ty))
191− when (moduleName == ModuleName (ProperName "Main") && fst e == Ident "main") $ do
192− [eff, a] <- replicateM 2 fresh
193− ty =?= TypeApp (TypeApp (TypeConstructor (Qualified (Just (ModuleName (ProperName "Eff"))) (ProperName "Eff"))) eff) a
194− escapeCheck val ty
195− return triple
196− forM tys $ \(ident, (val, ty)) -> do
197− val' <- replaceTypeClassDictionaries moduleName val
198− rethrow (("Error in " ++ show ident ++ ": \n") ++) $ skolemEscapeCheck val'
199− return $ (ident, (overTypes (desaturateAllTypeSynonyms . setifyAll) $ val'
200− , varIfUnknown . desaturateAllTypeSynonyms . setifyAll $ ty))
201− where
202− tidyUp (ts, sub) = map (\(i, (val, ty)) -> (i, (overTypes (sub $?) val, sub $? ty))) ts
203−
204−-- |
205−-- Check if a value contains a type annotation
206−--
207−isTyped :: (Ident, Value) -> (Ident, (Value, Maybe (Type, Bool)))
208−isTyped (name, TypedValue checkType value ty) = (name, (value, Just (ty, checkType)))
209−isTyped (name, value) = (name, (value, Nothing))
210−
211−-- |
212−-- Map a function over type annotations appearing inside a value
213−--
214−overTypes :: (Type -> Type) -> Value -> Value
215−overTypes f = everywhere (mkT f)
216−
217−-- |
218−-- Replace type class dictionary placeholders with inferred type class dictionaries
219−--
220−replaceTypeClassDictionaries :: ModuleName -> Value -> Check Value
221−replaceTypeClassDictionaries mn = everywhereM (mkM go)
222− where
223− go (TypeClassDictionary constraint dicts) = entails mn dicts constraint
224− go other = return other
225−
226−-- |
227−-- Check that the current set of type class dictionaries entail the specified type class goal, and, if so,
228−-- return a type class dictionary reference.
229−--
230−entails :: ModuleName -> [TypeClassDictionaryInScope] -> (Qualified ProperName, Type) -> Check Value
231−entails moduleName context goal@(className, ty) = do
232− env <- getEnv
233− case go env goal of
234− [] -> throwError $ "No " ++ show className ++ " instance found for " ++ prettyPrintType ty
235− (dict : _) -> return dict
236− where
237− go env (className', ty') =
238− [ mkDictionary (canonicalizeDictionary tcd) args
239− | tcd <- context
240− , filterModule tcd
241− , typeConstructorsAreEqual env moduleName className' (tcdClassName tcd)
242− , subst <- maybeToList $ typeHeadsAreEqual moduleName env ty' (tcdInstanceType tcd)
243− , args <- solveSubgoals env subst (tcdDependencies tcd) ]
244− solveSubgoals :: Environment -> [(String, Type)] -> Maybe [(Qualified ProperName, Type)] -> [Maybe [Value]]
245− solveSubgoals _ _ Nothing = return Nothing
246− solveSubgoals env subst (Just subgoals) = do
247− dict <- mapM (go env) (replaceAllTypeVars subst subgoals)
248− return $ Just dict
249− mkDictionary :: Qualified Ident -> Maybe [Value] -> Value
250− mkDictionary fnName Nothing = Var fnName
251− mkDictionary fnName (Just dicts) = foldl App (Var fnName) dicts
252− filterModule :: TypeClassDictionaryInScope -> Bool
253− filterModule (TypeClassDictionaryInScope { tcdName = Qualified (Just mn) _ }) | mn == moduleName = True
254− filterModule (TypeClassDictionaryInScope { tcdName = Qualified Nothing _ }) = True
255− filterModule _ = False
256− canonicalizeDictionary :: TypeClassDictionaryInScope -> Qualified Ident
257− canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDRegular, tcdName = nm }) = nm
258− canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDAlias nm }) = nm
259−
260−-- |
261−-- Check whether the type heads of two types are equal (for the purposes of type class dictionary lookup),
262−-- and return a substitution from type variables to types which makes the type heads unify.
263−--
264−typeHeadsAreEqual :: ModuleName -> Environment -> Type -> Type -> Maybe [(String, Type)]
265−typeHeadsAreEqual _ _ (Skolem s1 _) (Skolem s2 _) | s1 == s2 = Just []
266−typeHeadsAreEqual m e (TypeConstructor c1) (TypeConstructor c2) | typeConstructorsAreEqual e m c1 c2 = Just []
267−typeHeadsAreEqual m e (TypeApp h1 (TypeVar v)) (TypeApp h2 arg) = (:) (v, arg) <$> typeHeadsAreEqual m e h1 h2
268−typeHeadsAreEqual m e t1@(TypeApp _ _) t2@(TypeApp _ (TypeVar _)) = typeHeadsAreEqual m e t2 t1
269−typeHeadsAreEqual _ _ _ _ = Nothing
270−
271−-- |
272−-- Ensure unsolved unification variables do not escape
273−--
274−escapeCheck :: Value -> Type -> UnifyT Type Check ()
275−escapeCheck value ty = do
276− subst <- unifyCurrentSubstitution <$> UnifyT get
277− let visibleUnknowns = nub $ unknowns $ subst $? ty
278− let allUnknowns = findAllTypes value
279− forM_ allUnknowns $ \t -> do
280− let unsolvedUnknowns = nub . unknowns $ subst $? t
281− guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
282−
283−-- |
284−-- Find all type annotations occuring inside a value
285−--
286−findAllTypes :: Value -> [Type]
287−findAllTypes = everything (++) (mkQ [] go)
288− where
289− go (TypedValue _ _ ty) = [ty]
290− go _ = []
291−
292−-- |
293−-- Ensure skolem variables do not escape their scope
294−--
295−skolemEscapeCheck :: Value -> Check ()
296−skolemEscapeCheck (TypedValue False _ _) = return ()
297−skolemEscapeCheck root@(TypedValue _ _ _) =
298− case everythingWithContext [] (++) (mkQ ((,) []) go) root of
299− [] -> return ()
300− ((binding, val) : _) -> throwError $ "Rigid/skolem type variable bound by " ++ maybe "<unknown>" prettyPrintValue binding ++ " has escaped at " ++ prettyPrintValue val
301− where
302− go :: Value -> [(SkolemScope, Value)] -> ([(Maybe Value, Value)], [(SkolemScope, Value)])
303− go val@(TypedValue _ _ (ForAll _ _ (Just sco))) scos = ([], (sco, val) : scos)
304− go val@(TypedValue _ _ ty) scos = case collectSkolems ty \\ map fst scos of
305− (sco : _) -> ([(findBindingScope sco, val)], scos)
306− _ -> ([], scos)
307− where
308− collectSkolems :: Type -> [SkolemScope]
309− collectSkolems = nub . everything (++) (mkQ [] collect)
310− where
311− collect (Skolem _ scope) = [scope]
312− collect _ = []
313− go _ scos = ([], scos)
314− findBindingScope :: SkolemScope -> Maybe Value
315− findBindingScope sco = something (mkQ Nothing go) root
316− where
317− go val@(TypedValue _ _ (ForAll _ _ (Just sco'))) | sco == sco' = Just val
318− go _ = Nothing
319−skolemEscapeCheck val = throwError $ "Untyped value passed to skolemEscapeCheck: " ++ prettyPrintValue val
320−
321−-- |
322−-- Ensure a row contains no duplicate labels
323−--
324−setify :: Type -> Type
325−setify = rowFromList . first (M.toList . M.fromList) . rowToList
326−
327−-- |
328−-- \"Setify\" all rows occuring inside a value
329−--
330−setifyAll :: (D.Data d) => d -> d
331−setifyAll = everywhere (mkT setify)
332−
333−-- |
334−-- Replace outermost unsolved unification variables with named type variables
335−--
336−varIfUnknown :: Type -> Type
337−varIfUnknown ty =
338− let unks = nub $ unknowns ty
339− toName = (:) 't' . show
340− ty' = everywhere (mkT typeToVar) $ ty
341− typeToVar :: Type -> Type
342− typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
343− typeToVar t = t
344− in mkForAll (sort . map (toName . runUnknown) $ unks) ty'
345−
346−-- |
347−-- Replace named type variables with types
348−--
349−replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
350−replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
351−
352−-- |
353−-- Replace named type variables with new unification variables
354−--
355−replaceAllVarsWithUnknowns :: Type -> UnifyT Type Check Type
356−replaceAllVarsWithUnknowns (ForAll ident ty _) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
357−replaceAllVarsWithUnknowns ty = return ty
358−
359−-- |
360−-- Replace a single type variable with a new unification variable
361−--
362−replaceVarWithUnknown :: String -> Type -> UnifyT Type Check Type
363−replaceVarWithUnknown ident ty = do
364− tu <- fresh
365− return $ replaceTypeVars ident tu $ ty
366−
367−-- |
368−-- Replace fully applied type synonyms with the @SaturatedTypeSynonym@ data constructor, which helps generate
369−-- better error messages during unification.
370−--
371−replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadError String m) => (D.Data d) => d -> m d
372−replaceAllTypeSynonyms d = do
373− env <- getEnv
374− Just moduleName <- checkCurrentModule <$> get
375− let syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
376− either throwError return $ saturateAllTypeSynonyms env moduleName syns d
377−
378−-- |
379−-- \"Desaturate\" @SaturatedTypeSynonym@s
380−--
381−desaturateAllTypeSynonyms :: (D.Data d) => d -> d
382−desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
383− where
384− replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
385− replaceSaturatedTypeSynonym t = t
386−
387−-- |
388−-- Replace a type synonym and its arguments with the aliased type
389−--
390−expandTypeSynonym :: Qualified ProperName -> [Type] -> UnifyT Type Check Type
391−expandTypeSynonym name args = do
392− env <- getEnv
393− Just moduleName <- checkCurrentModule <$> get
394− case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
395− Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
396− Nothing -> error "Type synonym was not defined"
397−
398−-- |
399−-- Ensure a set of property names and value does not contain duplicate labels
400−--
401−ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
402−ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
403−
404−-- |
405−-- Infer a type for a value, rethrowing any error to provide a more useful error message
406−--
407−infer :: Value -> UnifyT Type Check Value
408−infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ infer' val
409−
410−-- |
411−-- Infer a type for a value
412−--
413−infer' :: Value -> UnifyT Type Check Value
414−infer' v@(NumericLiteral _) = return $ TypedValue True v tyNumber
415−infer' v@(StringLiteral _) = return $ TypedValue True v tyString
416−infer' v@(BooleanLiteral _) = return $ TypedValue True v tyBoolean
417−infer' (ArrayLiteral vals) = do
418− ts <- mapM infer vals
419− els <- fresh
420− forM_ ts $ \(TypedValue _ _ t) -> els =?= TypeApp tyArray t
421− return $ TypedValue True (ArrayLiteral ts) els
422−infer' (ObjectLiteral ps) = do
423− ensureNoDuplicateProperties ps
424− ts <- mapM (infer . snd) ps
425− let fields = zipWith (\name (TypedValue _ _ t) -> (name, t)) (map fst ps) ts
426− ty = Object $ rowFromList (fields, REmpty)
427− return $ TypedValue True (ObjectLiteral (zip (map fst ps) ts)) ty
428−infer' (ObjectUpdate o ps) = do
429− ensureNoDuplicateProperties ps
430− row <- fresh
431− newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
432− let newTys = map (\(name, TypedValue _ _ ty) -> (name, ty)) newVals
433− oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
434− let oldTy = Object $ rowFromList (oldTys, row)
435− o' <- TypedValue True <$> check o oldTy <*> pure oldTy
436− return $ TypedValue True (ObjectUpdate o' newVals) $ Object $ rowFromList (newTys, row)
437−infer' (Accessor prop val) = do
438− typed@(TypedValue _ _ objTy) <- infer val
439− propTy <- inferProperty objTy prop
440− case propTy of
441− Nothing -> do
442− field <- fresh
443− rest <- fresh
444− _ <- subsumes Nothing objTy (Object (RCons prop field rest))
445− return $ TypedValue True (Accessor prop typed) field
446− Just ty -> return $ TypedValue True (Accessor prop typed) ty
447−infer' (Abs arg ret) = do
448− ty <- fresh
449− Just moduleName <- checkCurrentModule <$> get
450− bindLocalVariables moduleName [(arg, ty)] $ do
451− body@(TypedValue _ _ bodyTy) <- infer' ret
452− return $ TypedValue True (Abs arg body) $ function ty bodyTy
453−infer' (App f arg) = do
454− f'@(TypedValue _ _ ft) <- infer f
455− (ret, app) <- checkFunctionApplication f' ft arg
456− return $ TypedValue True app ret
457−infer' (Var var) = do
458− Just moduleName <- checkCurrentModule <$> get
459− ty <- introduceSkolemScope <=< replaceAllTypeSynonyms <=< lookupVariable moduleName $ var
460− case ty of
461− ConstrainedType constraints _ -> do
462− env <- getEnv
463− dicts <- getTypeClassDictionaries
464− return $ TypedValue True (foldl App (Var var) (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) ty
465− _ -> return $ TypedValue True (Var var) ty
466−infer' (Block ss) = do
467− ret <- fresh
468− (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
469− guardWith "Block is missing a return statement" allCodePathsReturn
470− return $ TypedValue True (Block ss') ret
471−infer' v@(Constructor c) = do
472− env <- getEnv
473− Just moduleName <- checkCurrentModule <$> get
474− case M.lookup (qualify moduleName c) (dataConstructors env) of
475− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
476− Just (ty, _) -> do ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
477− return $ TypedValue True v ty'
478−infer' (Case vals binders) = do
479− ts <- mapM infer vals
480− ret <- fresh
481− binders' <- checkBinders (map (\(TypedValue _ _ t) -> t) ts) ret binders
482− return $ TypedValue True (Case ts binders') ret
483−infer' (IfThenElse cond th el) = do
484− cond' <- check cond tyBoolean
485− v2@(TypedValue _ _ t2) <- infer th
486− v3@(TypedValue _ _ t3) <- infer el
487− t2 =?= t3
488− return $ TypedValue True (IfThenElse cond' v2 v3) t2
489−infer' (TypedValue checkType val ty) = do
490− Just moduleName <- checkCurrentModule <$> get
491− kind <- liftCheck $ kindOf moduleName ty
492− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
493− ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
494− val' <- if checkType then check val ty' else return val
495− return $ TypedValue True val' ty'
496−infer' _ = error "Invalid argument to infer"
497−
498−-- |
499−-- Infer the type of a property inside a record with a given type
500−--
501−inferProperty :: Type -> String -> UnifyT Type Check (Maybe Type)
502−inferProperty (Object row) prop = do
503− let (props, _) = rowToList row
504− return $ lookup prop props
505−inferProperty (SaturatedTypeSynonym name args) prop = do
506− replaced <- introduceSkolemScope <=< expandTypeSynonym name $ args
507− inferProperty replaced prop
508−inferProperty (ForAll ident ty _) prop = do
509− replaced <- replaceVarWithUnknown ident ty
510− inferProperty replaced prop
511−inferProperty _ _ = return Nothing
512−
513−-- |
514−-- Infer the types of variables brought into scope by a binder
515−--
516−inferBinder :: Type -> Binder -> UnifyT Type Check (M.Map Ident Type)
517−inferBinder _ NullBinder = return M.empty
518−inferBinder val (StringBinder _) = val =?= tyString >> return M.empty
519−inferBinder val (NumberBinder _) = val =?= tyNumber >> return M.empty
520−inferBinder val (BooleanBinder _) = val =?= tyBoolean >> return M.empty
521−inferBinder val (VarBinder name) = return $ M.singleton name val
522−inferBinder val (NullaryBinder ctor) = do
523− env <- getEnv
524− Just moduleName <- checkCurrentModule <$> get
525− case M.lookup (qualify moduleName ctor) (dataConstructors env) of
526− Just (ty, _) -> do
527− _ <- subsumes Nothing ty val
528− return M.empty
529− _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
530−inferBinder val (UnaryBinder ctor binder) = do
531− env <- getEnv
532− Just moduleName <- checkCurrentModule <$> get
533− case M.lookup (qualify moduleName ctor) (dataConstructors env) of
534− Just (ty, _) -> do
535− fn <- replaceAllVarsWithUnknowns ty
536− case fn of
537− TypeApp (TypeApp t obj) ret | t == tyFunction -> do
538− _ <- subsumes Nothing val ret
539− inferBinder obj binder
540− _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
541− _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
542−inferBinder val (ObjectBinder props) = do
543− row <- fresh
544− rest <- fresh
545− m1 <- inferRowProperties row rest props
546− val =?= Object row
547− return m1
548− where
549− inferRowProperties :: Type -> Type -> [(String, Binder)] -> UnifyT Type Check (M.Map Ident Type)
550− inferRowProperties nrow row [] = nrow =?= row >> return M.empty
551− inferRowProperties nrow row ((name, binder):binders) = do
552− propTy <- fresh
553− m1 <- inferBinder propTy binder
554− m2 <- inferRowProperties nrow (RCons name propTy row) binders
555− return $ m1 `M.union` m2
556−inferBinder val (ArrayBinder binders) = do
557− el <- fresh
558− m1 <- M.unions <$> mapM (inferBinder el) binders
559− val =?= TypeApp tyArray el
560− return m1
561−inferBinder val (ConsBinder headBinder tailBinder) = do
562− el <- fresh
563− m1 <- inferBinder el headBinder
564− m2 <- inferBinder val tailBinder
565− val =?= TypeApp tyArray el
566− return $ m1 `M.union` m2
567−inferBinder val (NamedBinder name binder) = do
568− m <- inferBinder val binder
569− return $ M.insert name val m
570−
571−-- |
572−-- Check the types of the return values in a set of binders in a case statement
573−--
574−checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> UnifyT Type Check [([Binder], Maybe Guard, Value)]
575−checkBinders _ _ [] = return []
576−checkBinders nvals ret ((binders, grd, val):bs) = do
577− Just moduleName <- checkCurrentModule <$> get
578− m1 <- M.unions <$> zipWithM inferBinder nvals binders
579− r <- bindLocalVariables moduleName (M.toList m1) $ do
580− val' <- TypedValue True <$> check val ret <*> pure ret
581− case grd of
582− Nothing -> return (binders, Nothing, val')
583− Just g -> do
584− g' <- check g tyBoolean
585− return (binders, Just g', val')
586− rs <- checkBinders nvals ret bs
587− return $ r : rs
588−
589−-- |
590−-- Check that a local variable name is not already used
591−--
592−assignVariable :: Ident -> UnifyT Type Check ()
593−assignVariable name = do
594− env <- checkEnv <$> get
595− Just moduleName <- checkCurrentModule <$> get
596− case M.lookup (moduleName, name) (names env) of
597− Just _ -> UnifyT . lift . throwError $ "Variable with name " ++ show name ++ " already exists."
598− _ -> return ()
599−
600−-- |
601−-- Check the type of the return values of a statement, returning whether or not the statement returns on
602−-- all code paths
603−--
604−checkStatement :: M.Map Ident Type -> Type -> Statement -> UnifyT Type Check (Bool, M.Map Ident Type, Statement)
605−checkStatement mass _ (VariableIntroduction name val) = do
606− assignVariable name
607− val'@(TypedValue _ _ t) <- infer val
608− return (False, M.insert name t mass, VariableIntroduction name val')
609−checkStatement mass _ (Assignment ident val) = do
610− val'@(TypedValue _ _ t) <- infer val
611− case M.lookup ident mass of
612− Nothing -> throwError $ "No local variable with name " ++ show ident
613− Just ty -> do t =?= ty
614− return (False, mass, Assignment ident val')
615−checkStatement mass ret (While val inner) = do
616− val' <- check val tyBoolean
617− (allCodePathsReturn, _, inner') <- checkBlock mass ret inner
618− return (allCodePathsReturn, mass, While val' inner')
619−checkStatement mass ret (If ifst) = do
620− (allCodePathsReturn, ifst') <- checkIfStatement mass ret ifst
621− return (allCodePathsReturn, mass, If ifst')
622−checkStatement mass ret (For ident start end inner) = do
623− Just moduleName <- checkCurrentModule <$> get
624− assignVariable ident
625− start' <- check start tyNumber
626− end' <- check end tyNumber
627− (allCodePathsReturn, _, inner') <- bindLocalVariables moduleName [(ident, tyNumber)] $ checkBlock mass ret inner
628− return (allCodePathsReturn, mass, For ident start' end' inner')
629−checkStatement mass ret (Return val) = do
630− val' <- check val ret
631− return (True, mass, Return (TypedValue True val' ret))
632−
633−-- |
634−-- Check the type of an if-then-else statement
635−--
636−checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> UnifyT Type Check (Bool, IfStatement)
637−checkIfStatement mass ret (IfStatement val thens Nothing) = do
638− val' <- check val tyBoolean
639− (_, _, thens') <- checkBlock mass ret thens
640− return (False, IfStatement val' thens' Nothing)
641−checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
642− val' <- check val tyBoolean
643− (allCodePathsReturn1, _, thens') <- checkBlock mass ret thens
644− (allCodePathsReturn2, elses') <- checkElseStatement mass ret elses
645− return (allCodePathsReturn1 && allCodePathsReturn2, IfStatement val' thens' (Just elses'))
646−
647−-- |
648−-- Check the type of an else statement
649−--
650−checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> UnifyT Type Check (Bool, ElseStatement)
651−checkElseStatement mass ret (Else elses) = do
652− (allCodePathsReturn, _, elses') <- checkBlock mass ret elses
653− return (allCodePathsReturn, Else elses')
654−checkElseStatement mass ret (ElseIf ifst) = (id *** ElseIf) <$> checkIfStatement mass ret ifst
655−
656−-- |
657−-- Check the type of the return value of a block of statements
658−--
659−checkBlock :: M.Map Ident Type -> Type -> [Statement] -> UnifyT Type Check (Bool, M.Map Ident Type, [Statement])
660−checkBlock mass _ [] = return (False, mass, [])
661−checkBlock mass ret (s:ss) = do
662− Just moduleName <- checkCurrentModule <$> get
663− (b1, mass1, s') <- checkStatement mass ret s
664− bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
665− (True, []) -> return (True, mass1, [s'])
666− (True, _) -> throwError "Unreachable code"
667− (False, ss') -> do
668− (b, m, ss'') <- checkBlock mass1 ret ss'
669− return (b, m, s':ss'')
670−
671−-- |
672−-- Generate a new skolem constant
673−--
674−newSkolemConstant :: UnifyT Type Check Int
675−newSkolemConstant = runUnknown <$> fresh'
676−
677−-- |
678−-- Generate a new skolem scope
679−--
680−newSkolemScope :: UnifyT Type Check SkolemScope
681−newSkolemScope = SkolemScope . runUnknown <$> fresh'
682−
683−-- |
684−-- Skolemize a type variable by replacing its instances with fresh skolem constants
685−--
686−skolemize :: (D.Data d) => String -> Int -> SkolemScope -> d -> d
687−skolemize ident sko scope d = replaceTypeVars ident (Skolem sko scope) d
688−
689−-- |
690−-- Introduce skolem scope at every occurence of a ForAll
691−--
692−introduceSkolemScope :: Type -> UnifyT Type Check Type
693−introduceSkolemScope = everywhereM (mkM go)
694− where
695− go (ForAll ident ty Nothing) = ForAll ident ty <$> (Just <$> newSkolemScope)
696− go other = return other
697−
698−-- |
699−-- Check the type of a value, rethrowing errors to provide a better error message
700−--
701−check :: Value -> Type -> UnifyT Type Check Value
702−check val ty = rethrow errorMessage $ check' val ty
703− where
704− errorMessage msg =
705− "Error checking type of term " ++
706− prettyPrintValue val ++
707− " against type " ++
708− prettyPrintType ty ++
709− ":\n" ++
710− msg
711−
712−-- |
713−-- Check the type of a value
714−--
715−check' :: Value -> Type -> UnifyT Type Check Value
716−check' val t@(ForAll ident ty _) = do
717− scope <- newSkolemScope
718− sko <- newSkolemConstant
719− let sk = skolemize ident sko scope ty
720− val' <- check val sk
721− return $ TypedValue True val' (ForAll ident ty (Just scope))
722−check' val t@(ConstrainedType constraints ty) = do
723− env <- getEnv
724− Just moduleName <- checkCurrentModule <$> get
725− dictNames <- flip mapM constraints $ \(Qualified _ (ProperName className), _) -> do
726− n <- liftCheck freshDictionaryName
727− return $ Ident $ "__dict_" ++ className ++ "_" ++ show n
728− val' <- withTypeClassDictionaries (zipWith (\name (className, instanceTy) ->
729− TypeClassDictionaryInScope name className instanceTy Nothing TCDRegular) (map (Qualified Nothing) dictNames)
730− (qualifyAllUnqualifiedNames moduleName env constraints)) $
731− check val ty
732− return $ TypedValue True (foldr Abs val' dictNames) t
733−check' val t@(SaturatedTypeSynonym name args) = do
734− ty <- introduceSkolemScope <=< expandTypeSynonym name $ args
735− val' <- check val ty
736− return $ TypedValue True val' ty
737−check' val u@(TUnknown _) = do
738− val'@(TypedValue _ _ ty) <- infer val
739− -- Don't unify an unknown with an inferred polytype
740− ty' <- replaceAllVarsWithUnknowns ty
741− ty' =?= u
742− return $ TypedValue True val' ty'
743−check' v@(NumericLiteral _) t | t == tyNumber =
744− return $ TypedValue True v t
745−check' v@(StringLiteral _) t | t == tyString =
746− return $ TypedValue True v t
747−check' v@(BooleanLiteral _) t | t == tyBoolean =
748− return $ TypedValue True v t
749−check' (ArrayLiteral vals) t@(TypeApp a ty) | a == tyArray = do
750− arr <- ArrayLiteral <$> forM vals (\val -> check val ty)
751− return $ TypedValue True arr t
752−check' (Abs arg ret) ty@(TypeApp (TypeApp t argTy) retTy) | t == tyFunction = do
753− Just moduleName <- checkCurrentModule <$> get
754− ret' <- bindLocalVariables moduleName [(arg, argTy)] $ check ret retTy
755− return $ TypedValue True (Abs arg ret') ty
756−check' (App f arg) ret = do
757− f'@(TypedValue _ _ ft) <- infer f
758− (ret', app) <- checkFunctionApplication f' ft arg
759− subsumes Nothing ret' ret
760− return $ TypedValue True app ret
761−check' v@(Var var) ty = do
762− Just moduleName <- checkCurrentModule <$> get
763− repl <- introduceSkolemScope <=< replaceAllTypeSynonyms <=< lookupVariable moduleName $ var
764− ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
765− v' <- subsumes (Just v) repl ty'
766− case v' of
767− Nothing -> throwError "Unable to check type subsumption"
768− Just v'' -> return $ TypedValue True v'' ty'
769−check' (TypedValue checkType val ty1) ty2 = do
770− Just moduleName <- checkCurrentModule <$> get
771− kind <- liftCheck $ kindOf moduleName ty1
772− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
773− val' <- subsumes (Just val) ty1 ty2
774− case val' of
775− Nothing -> throwError "Unable to check type subsumption"
776− Just val'' -> do
777− val''' <- if checkType then check val'' ty1 else return val''
778− return $ TypedValue checkType (TypedValue True val''' ty1) ty2
779−check' (Case vals binders) ret = do
780− vals' <- mapM infer vals
781− let ts = map (\(TypedValue _ _ t) -> t) vals'
782− binders' <- checkBinders ts ret binders
783− return $ TypedValue True (Case vals' binders') ret
784−check' (IfThenElse cond th el) ty = do
785− cond' <- check cond tyBoolean
786− th' <- check th ty
787− el' <- check el ty
788− return $ TypedValue True (IfThenElse cond' th' el') ty
789−check' (ObjectLiteral ps) t@(Object row) = do
790− ensureNoDuplicateProperties ps
791− ps' <- checkProperties ps row False
792− return $ TypedValue True (ObjectLiteral ps') t
793−check' (ObjectUpdate obj ps) t@(Object row) = do
794− ensureNoDuplicateProperties ps
795− us <- zip (map fst ps) <$> replicateM (length ps) fresh
796− let (propsToCheck, rest) = rowToList row
797− propsToRemove = map fst ps
798− remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
799− obj' <- check obj (Object (rowFromList (us ++ remainingProps, rest)))
800− ps' <- checkProperties ps row True
801− return $ TypedValue True (ObjectUpdate obj' ps') t
802−check' (Accessor prop val) ty = do
803− rest <- fresh
804− val' <- check val (Object (RCons prop ty rest))
805− return $ TypedValue True (Accessor prop val') ty
806−check' (Block ss) ret = do
807− (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
808− guardWith "Block is missing a return statement" allCodePathsReturn
809− return $ TypedValue True (Block ss') ret
810−check' (Constructor c) ty = do
811− env <- getEnv
812− Just moduleName <- checkCurrentModule <$> get
813− case M.lookup (qualify moduleName c) (dataConstructors env) of
814− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
815− Just (ty1, _) -> do
816− repl <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty1
817− _ <- subsumes Nothing repl ty
818− return $ TypedValue True (Constructor c) ty
819−check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
820−
821−-- |
822−-- Check the type of a collection of named record fields
823−--
824−-- The @lax@ parameter controls whether or not every record member has to be provided. For object updates, this is not the case.
825−--
826−checkProperties :: [(String, Value)] -> Type -> Bool -> UnifyT Type Check [(String, Value)]
827−checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
828− go [] [] REmpty = return []
829− go [] [] u@(TUnknown _) = do u =?= REmpty
830− return []
831− go [] [] (Skolem _ _) | lax = return []
832− go [] ((p, _): _) _ | lax = return []
833− | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
834− go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
835− go ((p,v):ps') [] u@(TUnknown _) = do
836− v'@(TypedValue _ _ ty) <- infer v
837− rest <- fresh
838− u =?= RCons p ty rest
839− ps'' <- go ps' [] rest
840− return $ (p, v') : ps''
841− go ((p,v):ps') ts r =
842− case lookup p ts of
843− Nothing -> do
844− v'@(TypedValue _ _ ty) <- infer v
845− rest <- fresh
846− r =?= RCons p ty rest
847− ps'' <- go ps' ts rest
848− return $ (p, v') : ps''
849− Just ty -> do
850− v' <- check v ty
851− ps'' <- go ps' (delete (p, ty) ts) r
852− return $ (p, v') : ps''
853− go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
854−
855−-- |
856−-- Check the type of a function application, rethrowing errors to provide a better error message
857−--
858−checkFunctionApplication :: Value -> Type -> Value -> UnifyT Type Check (Type, Value)
859−checkFunctionApplication fn fnTy arg = rethrow errorMessage $ checkFunctionApplication' fn fnTy arg
860− where
861− errorMessage msg = "Error applying function of type "
862− ++ prettyPrintType fnTy
863− ++ " to argument " ++ prettyPrintValue arg
864− ++ ":\n" ++ msg
865−
866−-- |
867−-- Check the type of a function application
868−--
869−checkFunctionApplication' :: Value -> Type -> Value -> UnifyT Type Check (Type, Value)
870−checkFunctionApplication' fn (TypeApp (TypeApp tyFunction' argTy) retTy) arg = do
871− tyFunction' =?= tyFunction
872− arg' <- check arg argTy
873− return (retTy, App fn arg')
874−checkFunctionApplication' fn (ForAll ident ty _) arg = do
875− replaced <- replaceVarWithUnknown ident ty
876− checkFunctionApplication fn replaced arg
877−checkFunctionApplication' fn u@(TUnknown _) arg = do
878− arg' <- do
879− TypedValue _ v t <- infer arg
880− TypedValue True v <$> replaceAllVarsWithUnknowns t
881− let ty = (\(TypedValue _ _ t) -> t) arg'
882− ret <- fresh
883− u =?= function ty ret
884− return (ret, App fn arg')
885−checkFunctionApplication' fn (SaturatedTypeSynonym name tyArgs) arg = do
886− ty <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
887− checkFunctionApplication fn ty arg
888−checkFunctionApplication' fn (ConstrainedType constraints fnTy) arg = do
889− env <- getEnv
890− dicts <- getTypeClassDictionaries
891− Just moduleName <- checkCurrentModule <$> get
892− checkFunctionApplication' (foldl App fn (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) fnTy arg
893−checkFunctionApplication' _ fnTy arg = throwError $ "Cannot apply a function of type "
894− ++ prettyPrintType fnTy
895− ++ " to argument " ++ prettyPrintValue arg
896−
897−-- |
898−-- Check whether one type subsumes another, rethrowing errors to provide a better error message
899−--
900−subsumes :: Maybe Value -> Type -> Type -> UnifyT Type Check (Maybe Value)
901−subsumes val ty1 ty2 = rethrow errorMessage $ subsumes' val ty1 ty2
902− where
903− errorMessage msg = "Error checking that type "
904− ++ prettyPrintType ty1
905− ++ " subsumes type "
906− ++ prettyPrintType ty2
907− ++ ":\n" ++ msg
908−
909−-- |
910−-- Check whether one type subsumes another
911−--
912−subsumes' :: Maybe Value -> Type -> Type -> UnifyT Type Check (Maybe Value)
913−subsumes' val (ForAll ident ty1 _) ty2 = do
914− replaced <- replaceVarWithUnknown ident ty1
915− subsumes val replaced ty2
916−subsumes' val ty1 (ForAll ident ty2 sco) =
917− case sco of
918− Just sco' -> do
919− sko <- newSkolemConstant
920− let sk = skolemize ident sko sco' ty2
921− subsumes val ty1 sk
922− Nothing -> throwError "Skolem variable scope is unspecified"
923−subsumes' val (TypeApp (TypeApp f1 arg1) ret1) (TypeApp (TypeApp f2 arg2) ret2) | f1 == tyFunction && f2 == tyFunction = do
924− subsumes Nothing arg2 arg1
925− subsumes Nothing ret1 ret2
926− return val
927−subsumes' val (SaturatedTypeSynonym name tyArgs) ty2 = do
928− ty1 <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
929− subsumes val ty1 ty2
930−subsumes' val ty1 (SaturatedTypeSynonym name tyArgs) = do
931− ty2 <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
932− subsumes val ty1 ty2
933−subsumes' (Just val) (ConstrainedType constraints ty1) ty2 = do
934− env <- getEnv
935− dicts <- getTypeClassDictionaries
936− Just moduleName <- checkCurrentModule <$> get
937− _ <- subsumes' Nothing ty1 ty2
938− return . Just $ foldl App val (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))
939−subsumes' val ty1 ty2 = do
940− ty1 =?= ty2
941− return val
942−