@@ -1,994 +0,0 @@
1−-----------------------------------------------------------------------------
3−-- Module : Language.PureScript.TypeChecker.Types
4−-- Copyright : (c) Phil Freeman 2013
7−-- Maintainer : Phil Freeman <paf31@cantab.net>
8−-- Stability : experimental
12−-- This module implements the type checker
14−-----------------------------------------------------------------------------
16−{-# OPTIONS_GHC -fno-warn-orphans #-}
17−{-# LANGUAGE DeriveDataTypeable #-}
18−{-# LANGUAGE FlexibleContexts #-}
19−{-# LANGUAGE MultiParamTypeClasses #-}
21−module Language.PureScript.TypeChecker.Types (
26− The following functions represent the corresponding type checking judgements:
29− Synthesize a type for a value
32− Check a value has a given type
35− Check an object with a given type contains specified properties
37− checkFunctionApplication
38− Check a function of a given type returns a value of another type when applied to its arguments
41− Check a type subsumes another type
45−import Data.Maybe (maybeToList, isNothing, isJust, fromMaybe)
46−import qualified Data.Data as D
48− (mkM, everywhereM, everything, mkT, something, everywhere, mkQ)
50−import Language.PureScript.Values
51−import Language.PureScript.Types
52−import Language.PureScript.Kinds
53−import Language.PureScript.Names
54−import Language.PureScript.TypeChecker.Monad
55−import Language.PureScript.TypeChecker.Kinds
56−import Language.PureScript.TypeChecker.Synonyms
57−import Language.PureScript.Pretty
59−import Control.Monad.State
60−import Control.Monad.Error
61−import Control.Monad.Reader
62−import Control.Monad.Unify
64−import Control.Applicative
65−import Control.Arrow (Arrow(..))
67−import qualified Data.Map as M
68−import Data.Function (on)
70−instance Unifiable Check Type where
72− isUnknown (TUnknown u) = Just u
73− isUnknown _ = Nothing
77−-- Unify two types, updating the current substitution
79−unifyTypes :: Type -> Type -> UnifyT Check ()
80−unifyTypes t1 t2 = rethrow (\e -> "Error unifying type " ++ prettyPrintType t1 ++ " with type " ++ prettyPrintType t2 ++ ":\n" ++ e) $ do
83− unifyTypes' (TUnknown u1) (TUnknown u2) | u1 == u2 = return ()
84− unifyTypes' (TUnknown u) t = replace u t
85− unifyTypes' t (TUnknown u) = replace u t
86− unifyTypes' (SaturatedTypeSynonym name args) ty = do
87− ty1 <- expandTypeSynonym name args
89− unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
90− unifyTypes' (ForAll ident1 ty1) (ForAll ident2 ty2) = do
91− sk <- skolemize ident1 ty1
92− replaced <- replaceVarWithUnknown ident2 ty2
93− sk `unifyTypes` replaced
94− unifyTypes' (ForAll ident ty1) ty2 = do
95− sk <- skolemize ident ty1
97− unifyTypes' ty f@(ForAll _ _) = f `unifyTypes` ty
98− unifyTypes' Number Number = return ()
99− unifyTypes' String String = return ()
100− unifyTypes' Boolean Boolean = return ()
101− unifyTypes' Array Array = return ()
102− unifyTypes' Function Function = return ()
103− unifyTypes' (Object row1) (Object row2) = row1 ?= row2
104− unifyTypes' (TypeVar v1) (TypeVar v2) | v1 == v2 = return ()
105− unifyTypes' (TypeConstructor c1) (TypeConstructor c2) = do
107− Just moduleName <- checkCurrentModule <$> get
108− guardWith ("Cannot unify " ++ show c1 ++ " with " ++ show c2 ++ ".") (typeConstructorsAreEqual env moduleName c1 c2)
109− unifyTypes' (TypeApp t3 t4) (TypeApp t5 t6) = do
112− unifyTypes' (Skolem s1) (Skolem s2) | s1 == s2 = return ()
113− unifyTypes' r1@(RCons _ _ _) r2 = unifyRows r1 r2
114− unifyTypes' r1 r2@(RCons _ _ _) = unifyRows r1 r2
115− unifyTypes' r1@REmpty r2 = unifyRows r1 r2
116− unifyTypes' r1 r2@REmpty = unifyRows r1 r2
117− unifyTypes' t3 t4 = throwError $ "Cannot unify " ++ prettyPrintType t3 ++ " with " ++ prettyPrintType t4 ++ "."
120−-- Unify two rows, updating the current substitution
122−-- Common labels are first identified, and unified. Remaining labels and types are unified with a
123−-- trailing row unification variable, if appropriate, otherwise leftover labels result in a unification
126−unifyRows :: Type -> Type -> UnifyT Check ()
129− (s1, r1') = rowToList r1
130− (s2, r2') = rowToList r2
131− int = [ (t1, t2) | (name, t1) <- s1, (name', t2) <- s2, name == name' ]
132− sd1 = [ (name, t1) | (name, t1) <- s1, name `notElem` map fst s2 ]
133− sd2 = [ (name, t2) | (name, t2) <- s2, name `notElem` map fst s1 ]
135− forM_ int (uncurry (?=))
136− unifyRows' sd1 r1' sd2 r2'
138− unifyRows' :: [(String, Type)] -> Type -> [(String, Type)] -> Type -> UnifyT Check ()
139− unifyRows' [] (TUnknown u) sd r = replace u (rowFromList (sd, r))
140− unifyRows' sd r [] (TUnknown u) = replace u (rowFromList (sd, r))
141− unifyRows' ((name, ty):row) r others u@(TUnknown un) = do
143− forM_ row $ \(_, t) -> occursCheck un t
145− u ?= RCons name ty u'
146− unifyRows' row r others u'
147− unifyRows' [] REmpty [] REmpty = return ()
148− unifyRows' [] (TypeVar v1) [] (TypeVar v2) | v1 == v2 = return ()
149− unifyRows' [] (Skolem s1) [] (Skolem s2) | s1 == s2 = return ()
150− unifyRows' sd3 r3 sd4 r4 = throwError $ "Cannot unify " ++ prettyPrintRow (rowFromList (sd3, r3)) ++ " with " ++ prettyPrintRow (rowFromList (sd4, r4)) ++ "."
153−-- Ensure type constructors are equal after canonicalization
155−typeConstructorsAreEqual :: Environment -> ModuleName -> Qualified ProperName -> Qualified ProperName -> Bool
156−typeConstructorsAreEqual env moduleName = (==) `on` canonicalizeType moduleName env
159−-- Infer the types of multiple mutually-recursive values, and return elaborated values including
160−-- type class dictionaries and type annotations.
162−typesOf :: ModuleName -> [(Ident, Value)] -> Check [(Ident, (Value, Type))]
163−typesOf moduleName vals = do
164− tys <- liftUnify $ do
165− let es = map isTyped vals
166− typed = filter (isJust . snd . snd) es
167− untyped = filter (isNothing . snd . snd) es
168− typedDict = map (\(ident, (_, Just ty)) -> (ident, ty)) typed
169− untypedNames <- replicateM (length untyped) fresh
170− let untypedDict = zip (map fst untyped) untypedNames
171− dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ (map (id *** fst) typedDict) ++ untypedDict)
173− triple@(_, (val, ty)) <- case e of
174− (ident, (val, Just (ty, checkType))) -> do
175− kind <- liftCheck $ kindOf moduleName ty
176− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
177− ty' <- replaceAllTypeSynonyms ty
178− val' <- bindNames dict $ if checkType then check val ty' else return val
179− return (ident, (val', ty'))
180− (ident, (val, Nothing)) -> do
181− TypedValue _ val' ty <- bindNames dict $ infer val
182− ty ?= fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
183− return (ident, (val', ty))
184− when (moduleName == ModuleName (ProperName "Main") && fst e == Ident "main") $ do
185− [eff, a] <- replicateM 2 fresh
186− ty ?= TypeApp (TypeApp (TypeConstructor (Qualified (Just (ModuleName (ProperName "Eff"))) (ProperName "Eff"))) eff) a
189− forM_ tys $ skolemEscapeCheck . snd . snd
190− forM tys $ \(ident, (val, ty)) -> do
191− val' <- replaceTypeClassDictionaries moduleName val
192− return (ident, (overTypes (desaturateAllTypeSynonyms . setifyAll) $ val'
193− , varIfUnknown . desaturateAllTypeSynonyms . setifyAll $ ty))
196−-- Check if a value contains a type annotation
198−isTyped :: (Ident, Value) -> (Ident, (Value, Maybe (Type, Bool)))
199−isTyped (name, TypedValue checkType value ty) = (name, (value, Just (ty, checkType)))
200−isTyped (name, value) = (name, (value, Nothing))
203−-- Map a function over type annotations appearing inside a value
205−overTypes :: (Type -> Type) -> Value -> Value
206−overTypes f = everywhere (mkT f)
209−-- Replace type class dictionary placeholders with inferred type class dictionaries
211−replaceTypeClassDictionaries :: ModuleName -> Value -> Check Value
212−replaceTypeClassDictionaries mn = everywhereM (mkM go)
214− go (TypeClassDictionary constraint dicts) = entails mn dicts constraint
215− go other = return other
218−-- Check that the current set of type class dictionaries entail the specified type class goal, and, if so,
219−-- return a type class dictionary reference.
221−entails :: ModuleName -> [TypeClassDictionaryInScope] -> (Qualified ProperName, Type) -> Check Value
222−entails moduleName context goal@(className, ty) = do
225− [] -> throwError $ "No " ++ show className ++ " instance found for " ++ prettyPrintType ty
226− (dict : _) -> return dict
228− go env (className', ty') =
229− [ mkDictionary (canonicalizeDictionary tcd) args
232− , typeConstructorsAreEqual env moduleName className' (tcdClassName tcd)
233− , subst <- maybeToList $ typeHeadsAreEqual moduleName env ty' (tcdInstanceType tcd)
234− , args <- solveSubgoals env subst (tcdDependencies tcd) ]
235− solveSubgoals :: Environment -> [(String, Type)] -> Maybe [(Qualified ProperName, Type)] -> [Maybe [Value]]
236− solveSubgoals _ _ Nothing = return Nothing
237− solveSubgoals env subst (Just subgoals) = do
238− dict <- mapM (go env) (replaceAllTypeVars subst subgoals)
240− mkDictionary :: Qualified Ident -> Maybe [Value] -> Value
241− mkDictionary fnName Nothing = Var fnName
242− mkDictionary fnName (Just dicts) = foldr (flip App) (Var fnName) dicts
243− filterModule :: TypeClassDictionaryInScope -> Bool
244− filterModule (TypeClassDictionaryInScope { tcdName = Qualified (Just mn) _ }) | mn == moduleName = True
245− filterModule (TypeClassDictionaryInScope { tcdName = Qualified Nothing _ }) = True
246− filterModule _ = False
247− canonicalizeDictionary :: TypeClassDictionaryInScope -> Qualified Ident
248− canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDRegular, tcdName = nm }) = nm
249− canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDAlias nm }) = nm
252−-- Check whether the type heads of two types are equal (for the purposes of type class dictionary lookup),
253−-- and return a substitution from type variables to types which makes the type heads unify.
255−typeHeadsAreEqual :: ModuleName -> Environment -> Type -> Type -> Maybe [(String, Type)]
256−typeHeadsAreEqual _ _ String String = Just []
257−typeHeadsAreEqual _ _ Number Number = Just []
258−typeHeadsAreEqual _ _ Boolean Boolean = Just []
259−typeHeadsAreEqual _ _ (Skolem s1) (Skolem s2) | s1 == s2 = Just []
260−typeHeadsAreEqual _ _ Array Array = Just []
261−typeHeadsAreEqual _ _ Function Function = Just []
262−typeHeadsAreEqual m e (TypeConstructor c1) (TypeConstructor c2) | typeConstructorsAreEqual e m c1 c2 = Just []
263−typeHeadsAreEqual m e (TypeApp h1 (TypeVar v)) (TypeApp h2 arg) = (:) (v, arg) <$> typeHeadsAreEqual m e h1 h2
264−typeHeadsAreEqual m e t1@(TypeApp _ _) t2@(TypeApp _ (TypeVar _)) = typeHeadsAreEqual m e t2 t1
265−typeHeadsAreEqual _ _ _ _ = Nothing
268−-- Ensure unsolved unification variables do not escape
270−escapeCheck :: Value -> Type -> UnifyT Check ()
271−escapeCheck value ty = do
272− subst <- unifyCurrentSubstitution <$> UnifyT get
273− let visibleUnknowns = nub $ unknowns $ runSubstitution subst ty
274− let allUnknowns = findAllTypes value
275− forM_ allUnknowns $ \t -> do
276− let unsolvedUnknowns = nub . unknowns $ runSubstitution subst t
277− guardWith ("Escape check fails" ++ show ( runSubstitution subst ty, runSubstitution subst t)) $ null $ unsolvedUnknowns \\ visibleUnknowns
280−-- Find all type annotations occuring inside a value
282−findAllTypes :: Value -> [Type]
283−findAllTypes = everything (++) (mkQ [] go)
285− go (TypedValue _ _ ty) = [ty]
289−-- Ensure skolem variables do not escape their scope
291−skolemEscapeCheck :: Type -> Check ()
292−skolemEscapeCheck ty =
293− case something (mkQ Nothing findSkolems) ty of
294− Nothing -> return ()
295− Just _ -> throwError $ "Skolem variables cannot escape. Consider adding a type signature."
297− findSkolems (Skolem _) = return ()
298− findSkolems _ = mzero
301−-- Ensure a row contains no duplicate labels
303−setify :: Type -> Type
304−setify = rowFromList . first (M.toList . M.fromList) . rowToList
307−-- \"Setify\" all rows occuring inside a value
309−setifyAll :: (D.Data d) => d -> d
310−setifyAll = everywhere (mkT setify)
313−-- Replace outermost unsolved unification variables with named type variables
315−varIfUnknown :: Type -> Type
317− let unks = nub $ unknowns ty
318− toName = (:) 't' . show
319− ty' = everywhere (mkT typeToVar) $ ty
320− typeToVar :: Type -> Type
321− typeToVar (TUnknown (TypedUnknown (Unknown u))) = TypeVar (toName u)
323− in mkForAll (sort . map (toName . runUnknown) $ unks) ty'
326−-- Replace named type variables with types
328−replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
329−replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
332−-- Replace named type variables with new unification variables
334−replaceAllVarsWithUnknowns :: Type -> UnifyT Check Type
335−replaceAllVarsWithUnknowns (ForAll ident ty) = replaceVarWithUnknown ident ty >>= replaceAllVarsWithUnknowns
336−replaceAllVarsWithUnknowns ty = return ty
339−-- Replace a single type variable with a new unification variable
341−replaceVarWithUnknown :: String -> Type -> UnifyT Check Type
342−replaceVarWithUnknown ident ty = do
344− return $ replaceTypeVars ident tu $ ty
347−-- Replace fully applied type synonyms with the @SaturatedTypeSynonym@ data constructor, which helps generate
348−-- better error messages during unification.
350−replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadError String m) => (D.Data d) => d -> m d
351−replaceAllTypeSynonyms d = do
353− Just moduleName <- checkCurrentModule <$> get
354− let syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
355− either throwError return $ saturateAllTypeSynonyms env moduleName syns d
358−-- \"Desaturate\" @SaturatedTypeSynonym@s
360−desaturateAllTypeSynonyms :: (D.Data d) => d -> d
361−desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
363− replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
364− replaceSaturatedTypeSynonym t = t
367−-- Replace a type synonym and its arguments with the aliased type
369−expandTypeSynonym :: Qualified ProperName -> [Type] -> UnifyT Check Type
370−expandTypeSynonym name args = do
372− Just moduleName <- checkCurrentModule <$> get
373− case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
374− Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
375− Nothing -> error "Type synonym was not defined"
378−-- Ensure a set of property names and value does not contain duplicate labels
380−ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
381−ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
384−-- Infer a type for a value, rethrowing any error to provide a more useful error message
386−infer :: Value -> UnifyT Check Value
387−infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ infer' val
390−-- Infer a type for a value
392−infer' :: Value -> UnifyT Check Value
393−infer' v@(NumericLiteral _) = return $ TypedValue True v Number
394−infer' v@(StringLiteral _) = return $ TypedValue True v String
395−infer' v@(BooleanLiteral _) = return $ TypedValue True v Boolean
396−infer' (ArrayLiteral vals) = do
397− ts <- mapM infer vals
399− forM_ ts $ \(TypedValue _ _ t) -> els ?= TypeApp Array t
400− return $ TypedValue True (ArrayLiteral ts) els
401−infer' (Unary op val) = do
404−infer' (Binary op left right) = do
407− inferBinary op v1 v2
408−infer' (ObjectLiteral ps) = do
409− ensureNoDuplicateProperties ps
410− ts <- mapM (infer . snd) ps
411− let fields = zipWith (\name (TypedValue _ _ t) -> (name, t)) (map fst ps) ts
412− ty = Object $ rowFromList (fields, REmpty)
413− return $ TypedValue True (ObjectLiteral (zip (map fst ps) ts)) ty
414−infer' (ObjectUpdate o ps) = do
415− ensureNoDuplicateProperties ps
417− newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
418− let newTys = map (\(name, TypedValue _ _ ty) -> (name, ty)) newVals
419− oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
420− o' <- check o $ Object $ rowFromList (oldTys, row)
421− return $ TypedValue True (ObjectUpdate o' newVals) $ Object $ rowFromList (newTys, row)
422−infer' (Indexer index val) = do
424− index' <- check index Number
425− val' <- check val (TypeApp Array el)
426− return $ TypedValue True (Indexer (TypedValue True index' Number) (TypedValue True val' (TypeApp Array el))) el
427−infer' (Accessor prop val) = do
428− typed@(TypedValue _ _ objTy) <- infer val
429− propTy <- inferProperty objTy prop
434− _ <- subsumes Nothing objTy (Object (RCons prop field rest))
435− return $ TypedValue True (Accessor prop typed) field
436− Just ty -> return $ TypedValue True (Accessor prop typed) ty
437−infer' (Abs arg ret) = do
439− Just moduleName <- checkCurrentModule <$> get
440− bindLocalVariables moduleName [(arg, ty)] $ do
441− body@(TypedValue _ _ bodyTy) <- infer' ret
442− return $ TypedValue True (Abs arg body) $ function ty bodyTy
443−infer' (App f arg) = do
444− f'@(TypedValue _ _ ft) <- infer f
446− app <- checkFunctionApplication f' ft arg ret
447− return $ TypedValue True app ret
448−infer' (Var var) = do
449− Just moduleName <- checkCurrentModule <$> get
450− ty <- lookupVariable moduleName var
451− ty' <- replaceAllTypeSynonyms ty
453− ConstrainedType constraints _ -> do
455− dicts <- getTypeClassDictionaries
456− return $ TypedValue True (foldl App (Var var) (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) ty'
457− _ -> return $ TypedValue True (Var var) ty'
458−infer' (Block ss) = do
460− (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
461− guardWith "Block is missing a return statement" allCodePathsReturn
462− return $ TypedValue True (Block ss') ret
463−infer' v@(Constructor c) = do
465− Just moduleName <- checkCurrentModule <$> get
466− case M.lookup (qualify moduleName c) (dataConstructors env) of
467− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
468− Just (ty, _) -> do ty' <- replaceAllTypeSynonyms ty
469− return $ TypedValue True v ty'
470−infer' (Case vals binders) = do
471− ts <- mapM infer vals
473− binders' <- checkBinders (map (\(TypedValue _ _ t) -> t) ts) ret binders
474− return $ TypedValue True (Case ts binders') ret
475−infer' (IfThenElse cond th el) = do
476− cond' <- check cond Boolean
477− v2@(TypedValue _ _ t2) <- infer th
478− v3@(TypedValue _ _ t3) <- infer el
480− return $ TypedValue True (IfThenElse cond' v2 v3) t2
481−infer' (TypedValue checkType val ty) = do
482− Just moduleName <- checkCurrentModule <$> get
483− kind <- liftCheck $ kindOf moduleName ty
484− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
485− ty' <- replaceAllTypeSynonyms ty
486− val' <- if checkType then check val ty' else return val
487− return $ TypedValue True val' ty
488−infer' _ = error "Invalid argument to infer"
491−-- Infer the type of a property inside a record with a given type
493−inferProperty :: Type -> String -> UnifyT Check (Maybe Type)
494−inferProperty (Object row) prop = do
495− let (props, _) = rowToList row
496− return $ lookup prop props
497−inferProperty (SaturatedTypeSynonym name args) prop = do
498− replaced <- expandTypeSynonym name args
499− inferProperty replaced prop
500−inferProperty (ForAll ident ty) prop = do
501− replaced <- replaceVarWithUnknown ident ty
502− inferProperty replaced prop
503−inferProperty _ _ = return Nothing
506−-- Infer the type of a unary operator application
508−inferUnary :: UnaryOperator -> Value -> UnifyT Check Value
509−inferUnary op (TypedValue _ val valTy) =
510− case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
511− (valTy', resTy) -> do
513− return $ TypedValue True (Unary op val) resTy
514−inferUnary _ _ = error "Invalid arguments to inferUnary"
517−-- Check the type of a unary operator application
519−checkUnary :: UnaryOperator -> Value -> Type -> UnifyT Check Value
520−checkUnary op val res =
521− case fromMaybe (error "Invalid operator") $ lookup op unaryOps of
522− (valTy, resTy) -> do
524− val' <- check val valTy
525− return $ Unary op val'
528−-- Built-in unary operators
530−unaryOps :: [(UnaryOperator, (Type, Type))]
531−unaryOps = [ (Negate, (Number, Number))
532− , (Not, (Boolean, Boolean))
533− , (BitwiseNot, (Number, Number))
537−-- Infer the type of a binary operator application
539−inferBinary :: BinaryOperator -> Value -> Value -> UnifyT Check Value
540−inferBinary op left@(TypedValue _ _ leftTy) right@(TypedValue _ _ rightTy) | isEqualityTest op = do
542− return $ TypedValue True (Binary op left right) Boolean
543−inferBinary op left@(TypedValue _ _ leftTy) right@(TypedValue _ _ rightTy) =
544− case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
545− (valTy, resTy) -> do
548− return $ TypedValue True (Binary op left right) resTy
549−inferBinary _ _ _ = error "Invalid arguments to inferBinary"
552−-- Check the type of a binary operator application
554−checkBinary :: BinaryOperator -> Value -> Value -> Type -> UnifyT Check Value
555−checkBinary op left right res | isEqualityTest op = do
557− left'@(TypedValue _ _ t1) <- infer left
558− right'@(TypedValue _ _ t2) <- infer right
560− return $ Binary op left' right'
561−checkBinary op left right res =
562− case fromMaybe (error "Invalid operator") $ lookup op binaryOps of
563− (valTy, resTy) -> do
565− left' <- check left valTy
566− right' <- check right valTy
567− return $ Binary op left' right'
570−-- Check if a @BinaryOperator@ is an equality test
572−isEqualityTest :: BinaryOperator -> Bool
573−isEqualityTest EqualTo = True
574−isEqualityTest NotEqualTo = True
575−isEqualityTest _ = False
578−-- Built-in binary operators
580−binaryOps :: [(BinaryOperator, (Type, Type))]
581−binaryOps = [ (Add, (Number, Number))
582− , (Subtract, (Number, Number))
583− , (Multiply, (Number, Number))
584− , (Divide, (Number, Number))
585− , (Modulus, (Number, Number))
586− , (BitwiseAnd, (Number, Number))
587− , (BitwiseOr, (Number, Number))
588− , (BitwiseXor, (Number, Number))
589− , (ShiftRight, (Number, Number))
590− , (ZeroFillShiftRight, (Number, Number))
591− , (And, (Boolean, Boolean))
592− , (Or, (Boolean, Boolean))
593− , (Concat, (String, String))
594− , (Modulus, (Number, Number))
595− , (LessThan, (Number, Boolean))
596− , (LessThanOrEqualTo, (Number, Boolean))
597− , (GreaterThan, (Number, Boolean))
598− , (GreaterThanOrEqualTo, (Number, Boolean))
602−-- Infer the types of variables brought into scope by a binder
604−inferBinder :: Type -> Binder -> UnifyT Check (M.Map Ident Type)
605−inferBinder _ NullBinder = return M.empty
606−inferBinder val (StringBinder _) = val ?= String >> return M.empty
607−inferBinder val (NumberBinder _) = val ?= Number >> return M.empty
608−inferBinder val (BooleanBinder _) = val ?= Boolean >> return M.empty
609−inferBinder val (VarBinder name) = return $ M.singleton name val
610−inferBinder val (NullaryBinder ctor) = do
612− Just moduleName <- checkCurrentModule <$> get
613− case M.lookup (qualify moduleName ctor) (dataConstructors env) of
615− _ <- subsumes Nothing ty val
617− _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
618−inferBinder val (UnaryBinder ctor binder) = do
620− Just moduleName <- checkCurrentModule <$> get
621− case M.lookup (qualify moduleName ctor) (dataConstructors env) of
623− fn <- replaceAllVarsWithUnknowns ty
625− TypeApp (TypeApp Function obj) ret -> do
626− _ <- subsumes Nothing val ret
627− inferBinder obj binder
628− _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
629− _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
630−inferBinder val (ObjectBinder props) = do
633− m1 <- inferRowProperties row rest props
637− inferRowProperties :: Type -> Type -> [(String, Binder)] -> UnifyT Check (M.Map Ident Type)
638− inferRowProperties nrow row [] = nrow ?= row >> return M.empty
639− inferRowProperties nrow row ((name, binder):binders) = do
641− m1 <- inferBinder propTy binder
642− m2 <- inferRowProperties nrow (RCons name propTy row) binders
643− return $ m1 `M.union` m2
644−inferBinder val (ArrayBinder binders) = do
646− m1 <- M.unions <$> mapM (inferBinder el) binders
647− val ?= TypeApp Array el
649−inferBinder val (ConsBinder headBinder tailBinder) = do
651− m1 <- inferBinder el headBinder
652− m2 <- inferBinder val tailBinder
653− val ?= TypeApp Array el
654− return $ m1 `M.union` m2
655−inferBinder val (NamedBinder name binder) = do
656− m <- inferBinder val binder
657− return $ M.insert name val m
660−-- Check the types of the return values in a set of binders in a case statement
662−checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> UnifyT Check [([Binder], Maybe Guard, Value)]
663−checkBinders _ _ [] = return []
664−checkBinders nvals ret ((binders, grd, val):bs) = do
665− Just moduleName <- checkCurrentModule <$> get
666− m1 <- M.unions <$> zipWithM inferBinder nvals binders
667− r <- bindLocalVariables moduleName (M.toList m1) $ do
668− val' <- check val ret
670− Nothing -> return (binders, Nothing, val')
672− g' <- check g Boolean
673− return (binders, Just g', val')
674− rs <- checkBinders nvals ret bs
678−-- Check that a local variable name is not already used
680−assignVariable :: Ident -> UnifyT Check ()
681−assignVariable name = do
682− env <- checkEnv <$> get
683− Just moduleName <- checkCurrentModule <$> get
684− case M.lookup (moduleName, name) (names env) of
685− Just _ -> UnifyT . lift . throwError $ "Variable with name " ++ show name ++ " already exists."
689−-- Check the type of the return values of a statement, returning whether or not the statement returns on
692−checkStatement :: M.Map Ident Type -> Type -> Statement -> UnifyT Check (Bool, M.Map Ident Type, Statement)
693−checkStatement mass _ (VariableIntroduction name val) = do
695− val'@(TypedValue _ _ t) <- infer val
696− return (False, M.insert name t mass, VariableIntroduction name val')
697−checkStatement mass _ (Assignment ident val) = do
698− val'@(TypedValue _ _ t) <- infer val
699− case M.lookup ident mass of
700− Nothing -> throwError $ "No local variable with name " ++ show ident
701− Just ty -> do t ?= ty
702− return (False, mass, Assignment ident val')
703−checkStatement mass ret (While val inner) = do
704− val' <- check val Boolean
705− (allCodePathsReturn, _, inner') <- checkBlock mass ret inner
706− return (allCodePathsReturn, mass, While val' inner')
707−checkStatement mass ret (If ifst) = do
708− (allCodePathsReturn, ifst') <- checkIfStatement mass ret ifst
709− return (allCodePathsReturn, mass, If ifst')
710−checkStatement mass ret (For ident start end inner) = do
711− Just moduleName <- checkCurrentModule <$> get
712− assignVariable ident
713− start' <- check start Number
714− end' <- check end Number
715− (allCodePathsReturn, _, inner') <- bindLocalVariables moduleName [(ident, Number)] $ checkBlock mass ret inner
716− return (allCodePathsReturn, mass, For ident start' end' inner')
717−checkStatement mass ret (Return val) = do
718− val' <- check val ret
719− return (True, mass, Return val')
722−-- Check the type of an if-then-else statement
724−checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> UnifyT Check (Bool, IfStatement)
725−checkIfStatement mass ret (IfStatement val thens Nothing) = do
726− val' <- check val Boolean
727− (_, _, thens') <- checkBlock mass ret thens
728− return (False, IfStatement val' thens' Nothing)
729−checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
730− val' <- check val Boolean
731− (allCodePathsReturn1, _, thens') <- checkBlock mass ret thens
732− (allCodePathsReturn2, elses') <- checkElseStatement mass ret elses
733− return (allCodePathsReturn1 && allCodePathsReturn2, IfStatement val' thens' (Just elses'))
736−-- Check the type of an else statement
738−checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> UnifyT Check (Bool, ElseStatement)
739−checkElseStatement mass ret (Else elses) = do
740− (allCodePathsReturn, _, elses') <- checkBlock mass ret elses
741− return (allCodePathsReturn, Else elses')
742−checkElseStatement mass ret (ElseIf ifst) = (id *** ElseIf) <$> checkIfStatement mass ret ifst
745−-- Check the type of the return value of a block of statements
747−checkBlock :: M.Map Ident Type -> Type -> [Statement] -> UnifyT Check (Bool, M.Map Ident Type, [Statement])
748−checkBlock mass _ [] = return (False, mass, [])
749−checkBlock mass ret (s:ss) = do
750− Just moduleName <- checkCurrentModule <$> get
751− (b1, mass1, s') <- checkStatement mass ret s
752− bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
753− (True, []) -> return (True, mass1, [s'])
754− (True, _) -> throwError "Unreachable code"
756− (b, m, ss'') <- checkBlock mass1 ret ss'
757− return (b, m, s':ss'')
760−-- Skolemize a type variable by replacing its instances with fresh skolem constants
762−skolemize :: String -> Type -> UnifyT Check Type
763−skolemize ident ty = do
764− tsk <- Skolem . runUnknown <$> fresh'
765− return $ replaceTypeVars ident tsk ty
768−-- Check the type of a value, rethrowing errors to provide a better error message
770−check :: Value -> Type -> UnifyT Check Value
771−check val ty = rethrow errorMessage $ check' val ty
774− "Error checking type of term " ++
775− prettyPrintValue val ++
777− prettyPrintType ty ++
782−-- Check the type of a value
784−check' :: Value -> Type -> UnifyT Check Value
785−check' val (ForAll idents ty) = do
786− sk <- skolemize idents ty
788−check' val (ConstrainedType constraints ty) = do
790− Just moduleName <- checkCurrentModule <$> get
791− dictNames <- flip mapM constraints $ \(Qualified _ (ProperName className), _) -> do
792− n <- liftCheck freshDictionaryName
793− return $ Ident $ "__dict_" ++ className ++ "_" ++ show n
794− val' <- withTypeClassDictionaries (zipWith (\name (className, instanceTy) ->
795− TypeClassDictionaryInScope name className instanceTy Nothing TCDRegular) (map (Qualified Nothing) dictNames)
796− (qualifyAllUnqualifiedNames moduleName env constraints)) $
798− return $ foldr Abs val' dictNames
799−check' val u@(TUnknown _) = do
800− val'@(TypedValue _ _ ty) <- infer val
801− -- Don't unify an unknown with an inferred polytype
802− ty' <- replaceAllVarsWithUnknowns ty
805−check' v@(NumericLiteral _) Number = return v
806−check' v@(StringLiteral _) String = return v
807−check' v@(BooleanLiteral _) Boolean = return v
808−check' (Unary op val) ty = checkUnary op val ty
809−check' (Binary op left right) ty = checkBinary op left right ty
810−check' (ArrayLiteral vals) (TypeApp Array ty) = ArrayLiteral <$> forM vals (\val -> check val ty)
811−check' (Indexer index vals) ty = do
812− index' <- check index Number
813− vals' <- check vals (TypeApp Array ty)
814− return $ Indexer index' vals'
815−check' (Abs arg ret) (TypeApp (TypeApp Function argTy) retTy) = do
816− Just moduleName <- checkCurrentModule <$> get
817− ret' <- bindLocalVariables moduleName [(arg, argTy)] $ check ret retTy
818− return $ Abs arg ret'
819−check' (App f arg) ret = do
820− f'@(TypedValue _ _ ft) <- infer f
821− app <- checkFunctionApplication f' ft arg ret
823−check' v@(Var var) ty = do
824− Just moduleName <- checkCurrentModule <$> get
825− ty1 <- lookupVariable moduleName var
826− repl <- replaceAllTypeSynonyms ty1
827− v' <- subsumes (Just v) repl ty
829− Nothing -> throwError "Unable to check type subsumption"
830− Just v'' -> return v''
831−check' (TypedValue checkType val ty1) ty2 = do
832− Just moduleName <- checkCurrentModule <$> get
833− kind <- liftCheck $ kindOf moduleName ty1
834− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
835− val' <- subsumes (Just val) ty1 ty2
837− Nothing -> throwError "Unable to check type subsumption"
839− val''' <- if checkType then check val'' ty1 else return val''
840− return $ TypedValue True val''' ty1
841−check' (Case vals binders) ret = do
842− vals' <- mapM infer vals
843− let ts = map (\(TypedValue _ _ t) -> t) vals'
844− binders' <- checkBinders ts ret binders
845− return $ Case vals' binders'
846−check' (IfThenElse cond th el) ty = do
847− cond' <- check cond Boolean
850− return $ IfThenElse cond' th' el'
851−check' (ObjectLiteral ps) (Object row) = do
852− ensureNoDuplicateProperties ps
853− ps' <- checkProperties ps row False
854− return $ ObjectLiteral ps'
855−check' (ObjectUpdate obj ps) (Object row) = do
856− ensureNoDuplicateProperties ps
857− us <- zip (map fst ps) <$> replicateM (length ps) fresh
858− let (propsToCheck, rest) = rowToList row
859− propsToRemove = map fst ps
860− remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
861− obj' <- check obj (Object (rowFromList (us ++ remainingProps, rest)))
862− ps' <- checkProperties ps row True
863− return $ ObjectUpdate obj' ps'
864−check' (Accessor prop val) ty = do
866− val' <- check val (Object (RCons prop ty rest))
867− return $ Accessor prop val'
868−check' (Block ss) ret = do
869− (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
870− guardWith "Block is missing a return statement" allCodePathsReturn
872−check' (Constructor c) ty = do
874− Just moduleName <- checkCurrentModule <$> get
875− case M.lookup (qualify moduleName c) (dataConstructors env) of
876− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
878− repl <- replaceAllTypeSynonyms ty1
879− _ <- subsumes Nothing repl ty
880− return $ Constructor c
881−check' val (SaturatedTypeSynonym name args) = do
882− ty <- expandTypeSynonym name args
884−check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
887−-- Check the type of a collection of named record fields
889−-- The @lax@ parameter controls whether or not every record member has to be provided. For object updates, this is not the case.
891−checkProperties :: [(String, Value)] -> Type -> Bool -> UnifyT Check [(String, Value)]
892−checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
893− go [] [] REmpty = return []
894− go [] [] u@(TUnknown _) = do u ?= REmpty
896− go [] [] (Skolem _) | lax = return []
897− go [] ((p, _): _) _ | lax = return []
898− | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
899− go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
900− go ((p,v):ps') [] u@(TUnknown _) = do
901− v'@(TypedValue _ _ ty) <- infer v
903− u ?= RCons p ty rest
904− ps'' <- go ps' [] rest
905− return $ (p, v') : ps''
906− go ((p,v):ps') ts r =
909− v'@(TypedValue _ _ ty) <- infer v
911− r ?= RCons p ty rest
912− ps'' <- go ps' ts rest
913− return $ (p, v') : ps''
916− ps'' <- go ps' (delete (p, ty) ts) r
917− return $ (p, v') : ps''
918− go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
921−-- Check the type of a function application, rethrowing errors to provide a better error message
923−checkFunctionApplication :: Value -> Type -> Value -> Type -> UnifyT Check Value
924−checkFunctionApplication fn fnTy arg ret = rethrow errorMessage $ checkFunctionApplication' fn fnTy arg ret
926− errorMessage msg = "Error applying function of type "
927− ++ prettyPrintType fnTy
928− ++ " to argument " ++ prettyPrintValue arg
932−-- Check the type of a function application
934−checkFunctionApplication' :: Value -> Type -> Value -> Type -> UnifyT Check Value
935−checkFunctionApplication' fn (TypeApp (TypeApp Function argTy) retTy) arg ret = do
936− arg' <- check arg argTy
937− _ <- subsumes Nothing retTy ret
938− return $ App fn arg'
939−checkFunctionApplication' fn (ForAll ident ty) arg ret = do
940− replaced <- replaceVarWithUnknown ident ty
941− checkFunctionApplication fn replaced arg ret
942−checkFunctionApplication' fn u@(TUnknown _) arg ret = do
944− TypedValue _ v t <- infer arg
945− TypedValue True v <$> replaceAllVarsWithUnknowns t
946− let ty = (\(TypedValue _ _ t) -> t) arg'
947− u ?= function ty ret
948− return $ App fn arg'
949−checkFunctionApplication' fn (SaturatedTypeSynonym name tyArgs) arg ret = do
950− ty <- expandTypeSynonym name tyArgs
951− checkFunctionApplication fn ty arg ret
952−checkFunctionApplication' fn (ConstrainedType constraints fnTy) arg ret = do
954− dicts <- getTypeClassDictionaries
955− Just moduleName <- checkCurrentModule <$> get
956− checkFunctionApplication' (foldl App fn (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) fnTy arg ret
957−checkFunctionApplication' _ fnTy arg ret = throwError $ "Applying a function of type "
958− ++ prettyPrintType fnTy
959− ++ " to argument(s) " ++ prettyPrintValue arg
960− ++ " does not yield a value of type " ++ prettyPrintType ret ++ "."
963−-- Check whether one type subsumes another, rethrowing errors to provide a better error message
965−subsumes :: Maybe Value -> Type -> Type -> UnifyT Check (Maybe Value)
966−subsumes val ty1 ty2 = rethrow errorMessage $ subsumes' val ty1 ty2
968− errorMessage msg = "Error checking that type "
969− ++ prettyPrintType ty1
970− ++ " subsumes type "
971− ++ prettyPrintType ty2
975−-- Check whether one type subsumes another
977−subsumes' :: Maybe Value -> Type -> Type -> UnifyT Check (Maybe Value)
978−subsumes' val (ForAll ident ty1) ty2 = do
979− replaced <- replaceVarWithUnknown ident ty1
980− subsumes val replaced ty2
981−subsumes' val (TypeApp (TypeApp Function arg1) ret1) (TypeApp (TypeApp Function arg2) ret2) = do
982− subsumes Nothing arg2 arg1
983− subsumes Nothing ret1 ret2
985−subsumes' (Just val) (ConstrainedType constraints ty1) ty2 = do
987− dicts <- getTypeClassDictionaries
988− Just moduleName <- checkCurrentModule <$> get
989− _ <- subsumes' Nothing ty1 ty2
990− return . Just $ foldl App val (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))
991−subsumes' val ty1 ty2 = do