@@ -1,1004 +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− (everythingWithContext, mkM, everywhereM, everything, mkT,
49− something, everywhere, mkQ)
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
60−import Control.Monad.State
61−import Control.Monad.Error
62−import Control.Monad.Reader
63−import Control.Monad.Unify
65−import Control.Applicative
66−import Control.Arrow (Arrow(..))
68−import qualified Data.Map as M
69−import Data.Function (on)
70−import Debug.Trace (trace)
72−instance Partial Type where
74− isUnknown (TUnknown u) = Just u
75− isUnknown _ = Nothing
77−instance Unifiable Check Type where
81−-- Unify two types, updating the current substitution
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
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
93− unifyTypes' ty s@(SaturatedTypeSynonym _ _) = s `unifyTypes` ty
94− unifyTypes' (ForAll ident1 ty1 sc1) (ForAll ident2 ty2 sc2) =
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
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
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
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 ++ "."
125−-- Unify two rows, updating the current substitution
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
131−unifyRows :: Type -> Type -> UnifyT Type Check ()
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 ]
140− forM_ int (uncurry (=?=))
141− unifyRows' sd1 r1' sd2 r2'
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
148− forM_ row $ \(_, t) -> occursCheck un t
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)) ++ "."
158−-- Ensure type constructors are equal after canonicalization
160−typeConstructorsAreEqual :: Environment -> ModuleName -> Qualified ProperName -> Qualified ProperName -> Bool
161−typeConstructorsAreEqual env moduleName = (==) `on` canonicalizeType moduleName env
164−-- Infer the types of multiple mutually-recursive values, and return elaborated values including
165−-- type class dictionaries and type annotations.
167−typesOf :: ModuleName -> [(Ident, Value)] -> Check [(Ident, (Value, Type))]
168−typesOf moduleName vals = do
169− tys <- fmap tidyUp . liftUnify $ do
171− -- Map each declaration to a name/value pair, with an optional type, if the declaration is typed
172− es = map isTyped vals
173− -- Filter the typed and untyped declarations
174− typed = filter (isJust . snd . snd) es
175− untyped = filter (isNothing . snd . snd) es
176− -- Make a map of names to typed declarations
177− typedDict = map (\(ident, (_, Just (ty, _))) -> (ident, ty)) typed
178− -- Create fresh unification variables for the types of untyped declarations
179− untypedNames <- replicateM (length untyped) fresh
181− -- Make a map of names to the unification variables of untyped declarations
182− untypedDict = zip (map fst untyped) untypedNames
183− -- Create the dictionary of all name/type pairs, which will be added to the environment during type checking
184− dict = M.fromList (map (\(ident, ty) -> ((moduleName, ident), (ty, LocalVariable))) $ typedDict ++ untypedDict)
185− forM es $ \e@(_, (val, _)) -> do
186− -- If the declaration is a function, it has access to other values in the binding group.
187− -- If not, the generated code might fail at runtime since those values might be undefined.
188− let dict' = if isFunction val then dict else M.empty
189− triple@(_, (val, ty)) <- case e of
190− -- Typed declarations
191− (ident, (val, Just (ty, checkType))) -> do
193− kind <- liftCheck $ kindOf moduleName ty
194− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
195− -- Check the type with the new names in scope
196− ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
197− val' <- bindNames dict' $ if checkType
198− then TypedValue True <$> check val ty' <*> pure ty'
199− else return (TypedValue False val ty')
200− return (ident, (val', ty'))
201− -- Untyped declarations
202− (ident, (val, Nothing)) -> do
203− -- Infer the type with the new names in scope
204− TypedValue _ val' ty <- bindNames dict' $ infer val
205− ty =?= fromMaybe (error "name not found in dictionary") (lookup ident untypedDict)
206− return (ident, (TypedValue True val' ty, ty))
207− -- If run-main is enabled, need to check that Main.main has type Eff eff a for some eff, a
208− when (moduleName == ModuleName (ProperName "Main") && fst e == Ident "main") $ do
209− [eff, a] <- replicateM 2 fresh
210− ty =?= TypeApp (TypeApp (TypeConstructor (Qualified (Just (ModuleName (ProperName "Eff"))) (ProperName "Eff"))) eff) a
211− -- Make sure unification variables do not escape
214− forM tys $ \(ident, (val, ty)) -> rethrow (("Error in " ++ show ident ++ ": \n") ++) $ do
215− -- Replace type class dictionary placeholders with actual dictionaries
216− val' <- replaceTypeClassDictionaries moduleName val
217− -- Check skolem variables did not escape their scope
218− skolemEscapeCheck val'
220− return $ (ident, (overTypes (desaturateAllTypeSynonyms . setifyAll) $ val'
221− , varIfUnknown . desaturateAllTypeSynonyms . setifyAll $ ty))
223− -- Apply the substitution that was returned from runUnify to both types and (type-annotated) values
224− tidyUp (ts, sub) = map (\(i, (val, ty)) -> (i, (overTypes (sub $?) val, sub $? ty))) ts
227−-- Check if a value introduces a function
229−isFunction :: Value -> Bool
230−isFunction (Abs _ _) = True
231−isFunction (TypedValue _ val _) = isFunction val
235−-- Check if a value contains a type annotation
237−isTyped :: (Ident, Value) -> (Ident, (Value, Maybe (Type, Bool)))
238−isTyped (name, TypedValue checkType value ty) = (name, (value, Just (ty, checkType)))
239−isTyped (name, value) = (name, (value, Nothing))
242−-- Map a function over type annotations appearing inside a value
244−overTypes :: (Type -> Type) -> Value -> Value
245−overTypes f = everywhere (mkT f)
248−-- Replace type class dictionary placeholders with inferred type class dictionaries
250−replaceTypeClassDictionaries :: ModuleName -> Value -> Check Value
251−replaceTypeClassDictionaries mn = everywhereM (mkM go)
253− go (TypeClassDictionary constraint dicts) = entails mn dicts constraint
254− go other = return other
257−-- Check that the current set of type class dictionaries entail the specified type class goal, and, if so,
258−-- return a type class dictionary reference.
260−entails :: ModuleName -> [TypeClassDictionaryInScope] -> (Qualified ProperName, Type) -> Check Value
261−entails moduleName context goal@(className, ty) = do
264− [] -> throwError $ "No " ++ show className ++ " instance found for " ++ prettyPrintType ty
265− (dict : _) -> return dict
267− go env (className', ty') =
268− [ mkDictionary (canonicalizeDictionary tcd) args
270− -- Choose type class dictionaries in scope in the current module
272− -- Make sure the type class name matches the one we are trying to satisfy
273− , typeConstructorsAreEqual env moduleName className' (tcdClassName tcd)
274− -- Make sure the type unifies with the type in the type instance definition
275− , subst <- maybeToList $ typeHeadsAreEqual moduleName env ty' (tcdInstanceType tcd)
276− -- Solve any necessary subgoals
277− , args <- solveSubgoals env subst (tcdDependencies tcd) ]
278− -- Create dictionaries for subgoals which still need to be solved by calling go recursively
279− -- E.g. the goal (Show a, Show b) => Show (Either a b) can be satisfied if the current type
280− -- unifies with Either a b, and we can satisfy the subgoals Show a and Show b recursively.
281− solveSubgoals :: Environment -> [(String, Type)] -> Maybe [(Qualified ProperName, Type)] -> [Maybe [Value]]
282− solveSubgoals _ _ Nothing = return Nothing
283− solveSubgoals env subst (Just subgoals) = do
284− dict <- mapM (go env) (replaceAllTypeVars subst subgoals)
286− -- Make a dictionary from subgoal dictionaries by applying the correct function
287− mkDictionary :: Qualified Ident -> Maybe [Value] -> Value
288− mkDictionary fnName Nothing = Var fnName
289− mkDictionary fnName (Just dicts) = foldl App (Var fnName) dicts
290− -- Filter out type dictionaries which are in scope in the current module
291− filterModule :: TypeClassDictionaryInScope -> Bool
292− filterModule (TypeClassDictionaryInScope { tcdName = Qualified (Just mn) _ }) | mn == moduleName = True
293− filterModule (TypeClassDictionaryInScope { tcdName = Qualified Nothing _ }) = True
294− filterModule _ = False
295− -- Resolve a type class dictionary in scope to an actual value by following any (TCDAlias) pointers
296− -- which originated from module imports
297− canonicalizeDictionary :: TypeClassDictionaryInScope -> Qualified Ident
298− canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDRegular, tcdName = nm }) = nm
299− canonicalizeDictionary (TypeClassDictionaryInScope { tcdType = TCDAlias nm }) = nm
302−-- Check whether the type heads of two types are equal (for the purposes of type class dictionary lookup),
303−-- and return a substitution from type variables to types which makes the type heads unify.
305−typeHeadsAreEqual :: ModuleName -> Environment -> Type -> Type -> Maybe [(String, Type)]
306−typeHeadsAreEqual _ _ (Skolem s1 _) (Skolem s2 _) | s1 == s2 = Just []
307−typeHeadsAreEqual _ _ (TypeVar v) t = Just [(v, t)]
308−typeHeadsAreEqual _ _ t (TypeVar v) = Just [(v, t)]
309−typeHeadsAreEqual m e (TypeConstructor c1) (TypeConstructor c2) | typeConstructorsAreEqual e m c1 c2 = Just []
310−typeHeadsAreEqual m e (TypeApp h1 (TypeVar v)) (TypeApp h2 arg) = (:) (v, arg) <$> typeHeadsAreEqual m e h1 h2
311−typeHeadsAreEqual m e t1@(TypeApp _ _) t2@(TypeApp _ (TypeVar _)) = typeHeadsAreEqual m e t2 t1
312−typeHeadsAreEqual _ _ _ _ = Nothing
315−-- Ensure unsolved unification variables do not escape
317−escapeCheck :: Value -> Type -> UnifyT Type Check ()
318−escapeCheck value ty = do
319− subst <- unifyCurrentSubstitution <$> UnifyT get
320− let visibleUnknowns = nub $ unknowns $ subst $? ty
321− let allUnknowns = findAllTypes value
322− forM_ allUnknowns $ \t -> do
323− let unsolvedUnknowns = nub . unknowns $ subst $? t
324− guardWith "Escape check fails" $ null $ unsolvedUnknowns \\ visibleUnknowns
327−-- Find all type annotations occuring inside a value
329−findAllTypes :: Value -> [Type]
330−findAllTypes = everything (++) (mkQ [] go)
332− go (TypedValue _ _ ty) = [ty]
336−-- Ensure skolem variables do not escape their scope
338−skolemEscapeCheck :: Value -> Check ()
339−skolemEscapeCheck (TypedValue False _ _) = return ()
340−skolemEscapeCheck root@(TypedValue _ _ _) =
341− -- Every skolem variable is created when a ForAll type is skolemized.
342− -- This determines the scope of that skolem variable, which is copied from the SkolemScope
343− -- field of the ForAll constructor.
344− -- We traverse the tree top-down, and collect any SkolemScopes introduced by ForAlls.
345− -- If a Skolem is encountered whose SkolemScope is not in the current list, we have found
346− -- an escaped skolem variable.
347− case everythingWithContext [] (++) (mkQ ((,) []) go) root of
349− ((binding, val) : _) -> throwError $ "Rigid/skolem type variable bound by " ++ maybe "<unknown>" prettyPrintValue binding ++ " has escaped at " ++ prettyPrintValue val
351− go :: Value -> [(SkolemScope, Value)] -> ([(Maybe Value, Value)], [(SkolemScope, Value)])
352− go val@(TypedValue _ _ (ForAll _ _ (Just sco))) scos = ([], (sco, val) : scos)
353− go val@(TypedValue _ _ ty) scos = case collectSkolems ty \\ map fst scos of
354− (sco : _) -> ([(findBindingScope sco, val)], scos)
357− collectSkolems :: Type -> [SkolemScope]
358− collectSkolems = nub . everything (++) (mkQ [] collect)
360− collect (Skolem _ scope) = [scope]
362− go _ scos = ([], scos)
363− findBindingScope :: SkolemScope -> Maybe Value
364− findBindingScope sco = something (mkQ Nothing go) root
366− go val@(TypedValue _ _ (ForAll _ _ (Just sco'))) | sco == sco' = Just val
368−skolemEscapeCheck val = throwError $ "Untyped value passed to skolemEscapeCheck: " ++ prettyPrintValue val
371−-- Ensure a row contains no duplicate labels
373−setify :: Type -> Type
374−setify = rowFromList . first (M.toList . M.fromList) . rowToList
377−-- \"Setify\" all rows occuring inside a value
379−setifyAll :: (D.Data d) => d -> d
380−setifyAll = everywhere (mkT setify)
383−-- Replace outermost unsolved unification variables with named type variables
385−varIfUnknown :: Type -> Type
387− let unks = nub $ unknowns ty
388− toName = (:) 't' . show
389− ty' = everywhere (mkT typeToVar) $ ty
390− typeToVar :: Type -> Type
391− typeToVar (TUnknown (Unknown u)) = TypeVar (toName u)
393− in mkForAll (sort . map (toName . runUnknown) $ unks) ty'
396−-- Replace named type variables with types
398−replaceAllTypeVars :: (D.Data d) => [(String, Type)] -> d -> d
399−replaceAllTypeVars = foldl' (\f (name, ty) -> replaceTypeVars name ty . f) id
402−-- Remove any ForAlls and ConstrainedType constructors in a type by introducing new unknowns
403−-- or TypeClassDictionary values.
405−-- This is necessary during type checking to avoid unifying a polymorphic type with a
406−-- unification variable.
408−instantiatePolyTypeWithUnknowns :: Value -> Type -> UnifyT Type Check (Value, Type)
409−instantiatePolyTypeWithUnknowns val (ForAll ident ty _) = do
410− ty' <- replaceVarWithUnknown ident ty
411− instantiatePolyTypeWithUnknowns val ty'
412−instantiatePolyTypeWithUnknowns val (ConstrainedType constraints ty) = do
414− Just moduleName <- checkCurrentModule <$> get
415− dicts <- getTypeClassDictionaries
416− (_, ty') <- instantiatePolyTypeWithUnknowns (error "Types under a constraint cannot themselves be constrained") ty
417− return (foldl App val (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints)), ty')
418−instantiatePolyTypeWithUnknowns val ty = return (val, ty)
421−-- Replace a single type variable with a new unification variable
423−replaceVarWithUnknown :: String -> Type -> UnifyT Type Check Type
424−replaceVarWithUnknown ident ty = do
426− return $ replaceTypeVars ident tu $ ty
429−-- Replace fully applied type synonyms with the @SaturatedTypeSynonym@ data constructor, which helps generate
430−-- better error messages during unification.
432−replaceAllTypeSynonyms :: (Functor m, MonadState CheckState m, MonadError String m) => (D.Data d) => d -> m d
433−replaceAllTypeSynonyms d = do
435− Just moduleName <- checkCurrentModule <$> get
436− let syns = map (\((path, name), (args, _)) -> ((path, name), length args)) . M.toList $ typeSynonyms env
437− either throwError return $ saturateAllTypeSynonyms env moduleName syns d
440−-- \"Desaturate\" @SaturatedTypeSynonym@s
442−desaturateAllTypeSynonyms :: (D.Data d) => d -> d
443−desaturateAllTypeSynonyms = everywhere (mkT replaceSaturatedTypeSynonym)
445− replaceSaturatedTypeSynonym (SaturatedTypeSynonym name args) = foldl TypeApp (TypeConstructor name) args
446− replaceSaturatedTypeSynonym t = t
449−-- Replace a type synonym and its arguments with the aliased type
451−expandTypeSynonym :: Qualified ProperName -> [Type] -> UnifyT Type Check Type
452−expandTypeSynonym name args = do
454− Just moduleName <- checkCurrentModule <$> get
455− case M.lookup (canonicalizeType moduleName env name) (typeSynonyms env) of
456− Just (synArgs, body) -> return $ replaceAllTypeVars (zip synArgs args) body
457− Nothing -> error "Type synonym was not defined"
460−-- Ensure a set of property names and value does not contain duplicate labels
462−ensureNoDuplicateProperties :: (MonadError String m) => [(String, Value)] -> m ()
463−ensureNoDuplicateProperties ps = guardWith "Duplicate property names" $ length (nub . map fst $ ps) == length ps
466−-- Infer a type for a value, rethrowing any error to provide a more useful error message
468−infer :: Value -> UnifyT Type Check Value
469−infer val = rethrow (\e -> "Error inferring type of term " ++ prettyPrintValue val ++ ":\n" ++ e) $ infer' val
472−-- Infer a type for a value
474−infer' :: Value -> UnifyT Type Check Value
475−infer' v@(NumericLiteral _) = return $ TypedValue True v tyNumber
476−infer' v@(StringLiteral _) = return $ TypedValue True v tyString
477−infer' v@(BooleanLiteral _) = return $ TypedValue True v tyBoolean
478−infer' (ArrayLiteral vals) = do
479− ts <- mapM infer vals
481− forM_ ts $ \(TypedValue _ _ t) -> els =?= TypeApp tyArray t
482− return $ TypedValue True (ArrayLiteral ts) els
483−infer' (ObjectLiteral ps) = do
484− ensureNoDuplicateProperties ps
485− ts <- mapM (infer . snd) ps
486− let fields = zipWith (\name (TypedValue _ _ t) -> (name, t)) (map fst ps) ts
487− ty = Object $ rowFromList (fields, REmpty)
488− return $ TypedValue True (ObjectLiteral (zip (map fst ps) ts)) ty
489−infer' (ObjectUpdate o ps) = do
490− ensureNoDuplicateProperties ps
492− newVals <- zipWith (\(name, _) t -> (name, t)) ps <$> mapM (infer . snd) ps
493− let newTys = map (\(name, TypedValue _ _ ty) -> (name, ty)) newVals
494− oldTys <- zip (map fst ps) <$> replicateM (length ps) fresh
495− let oldTy = Object $ rowFromList (oldTys, row)
496− o' <- TypedValue True <$> check o oldTy <*> pure oldTy
497− return $ TypedValue True (ObjectUpdate o' newVals) $ Object $ rowFromList (newTys, row)
498−infer' (Accessor prop val) = do
499− typed@(TypedValue _ _ objTy) <- infer val
500− propTy <- inferProperty objTy prop
505− _ <- subsumes Nothing objTy (Object (RCons prop field rest))
506− return $ TypedValue True (Accessor prop typed) field
507− Just ty -> return $ TypedValue True (Accessor prop typed) ty
508−infer' (Abs arg ret) = do
510− Just moduleName <- checkCurrentModule <$> get
511− bindLocalVariables moduleName [(arg, ty)] $ do
512− body@(TypedValue _ _ bodyTy) <- infer' ret
513− return $ TypedValue True (Abs arg body) $ function ty bodyTy
514−infer' (App f arg) = do
515− f'@(TypedValue _ _ ft) <- infer f
516− (ret, app) <- checkFunctionApplication f' ft arg
517− return $ TypedValue True app ret
518−infer' (Var var) = do
519− Just moduleName <- checkCurrentModule <$> get
520− ty <- introduceSkolemScope <=< replaceAllTypeSynonyms <=< lookupVariable moduleName $ var
522− ConstrainedType constraints ty' -> do
524− dicts <- getTypeClassDictionaries
525− return $ TypedValue True (foldl App (Var var) (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) ty'
526− _ -> return $ TypedValue True (Var var) ty
527−infer' (Block ss) = do
529− (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
530− guardWith "Block is missing a return statement" allCodePathsReturn
531− return $ TypedValue True (Block ss') ret
532−infer' v@(Constructor c) = do
534− Just moduleName <- checkCurrentModule <$> get
535− case M.lookup (qualify moduleName c) (dataConstructors env) of
536− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
537− Just (ty, _) -> do ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
538− return $ TypedValue True v ty'
539−infer' (Case vals binders) = do
540− ts <- mapM infer vals
542− binders' <- checkBinders (map (\(TypedValue _ _ t) -> t) ts) ret binders
543− return $ TypedValue True (Case ts binders') ret
544−infer' (IfThenElse cond th el) = do
545− cond' <- check cond tyBoolean
546− v2@(TypedValue _ _ t2) <- infer th
547− v3@(TypedValue _ _ t3) <- infer el
549− return $ TypedValue True (IfThenElse cond' v2 v3) t2
550−infer' (TypedValue checkType val ty) = do
551− Just moduleName <- checkCurrentModule <$> get
552− kind <- liftCheck $ kindOf moduleName ty
553− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
554− ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
555− val' <- if checkType then check val ty' else return val
556− return $ TypedValue True val' ty'
557−infer' _ = error "Invalid argument to infer"
560−-- Infer the type of a property inside a record with a given type
562−inferProperty :: Type -> String -> UnifyT Type Check (Maybe Type)
563−inferProperty (Object row) prop = do
564− let (props, _) = rowToList row
565− return $ lookup prop props
566−inferProperty (SaturatedTypeSynonym name args) prop = do
567− replaced <- introduceSkolemScope <=< expandTypeSynonym name $ args
568− inferProperty replaced prop
569−inferProperty (ForAll ident ty _) prop = do
570− replaced <- replaceVarWithUnknown ident ty
571− inferProperty replaced prop
572−inferProperty _ _ = return Nothing
575−-- Infer the types of variables brought into scope by a binder
577−inferBinder :: Type -> Binder -> UnifyT Type Check (M.Map Ident Type)
578−inferBinder _ NullBinder = return M.empty
579−inferBinder val (StringBinder _) = val =?= tyString >> return M.empty
580−inferBinder val (NumberBinder _) = val =?= tyNumber >> return M.empty
581−inferBinder val (BooleanBinder _) = val =?= tyBoolean >> return M.empty
582−inferBinder val (VarBinder name) = return $ M.singleton name val
583−inferBinder val (NullaryBinder ctor) = do
585− Just moduleName <- checkCurrentModule <$> get
586− case M.lookup (qualify moduleName ctor) (dataConstructors env) of
588− _ <- subsumes Nothing ty val
590− _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
591−inferBinder val (UnaryBinder ctor binder) = do
593− Just moduleName <- checkCurrentModule <$> get
594− case M.lookup (qualify moduleName ctor) (dataConstructors env) of
596− (_, fn) <- instantiatePolyTypeWithUnknowns (error "Data constructor types cannot contains constraints") ty
598− TypeApp (TypeApp t obj) ret | t == tyFunction -> do
599− _ <- subsumes Nothing val ret
600− inferBinder obj binder
601− _ -> throwError $ "Constructor " ++ show ctor ++ " is not a unary constructor"
602− _ -> throwError $ "Constructor " ++ show ctor ++ " is not defined"
603−inferBinder val (ObjectBinder props) = do
606− m1 <- inferRowProperties row rest props
610− inferRowProperties :: Type -> Type -> [(String, Binder)] -> UnifyT Type Check (M.Map Ident Type)
611− inferRowProperties nrow row [] = nrow =?= row >> return M.empty
612− inferRowProperties nrow row ((name, binder):binders) = do
614− m1 <- inferBinder propTy binder
615− m2 <- inferRowProperties nrow (RCons name propTy row) binders
616− return $ m1 `M.union` m2
617−inferBinder val (ArrayBinder binders) = do
619− m1 <- M.unions <$> mapM (inferBinder el) binders
620− val =?= TypeApp tyArray el
622−inferBinder val (ConsBinder headBinder tailBinder) = do
624− m1 <- inferBinder el headBinder
625− m2 <- inferBinder val tailBinder
626− val =?= TypeApp tyArray el
627− return $ m1 `M.union` m2
628−inferBinder val (NamedBinder name binder) = do
629− m <- inferBinder val binder
630− return $ M.insert name val m
633−-- Check the types of the return values in a set of binders in a case statement
635−checkBinders :: [Type] -> Type -> [([Binder], Maybe Guard, Value)] -> UnifyT Type Check [([Binder], Maybe Guard, Value)]
636−checkBinders _ _ [] = return []
637−checkBinders nvals ret ((binders, grd, val):bs) = do
638− Just moduleName <- checkCurrentModule <$> get
639− m1 <- M.unions <$> zipWithM inferBinder nvals binders
640− r <- bindLocalVariables moduleName (M.toList m1) $ do
641− val' <- TypedValue True <$> check val ret <*> pure ret
643− Nothing -> return (binders, Nothing, val')
645− g' <- check g tyBoolean
646− return (binders, Just g', val')
647− rs <- checkBinders nvals ret bs
651−-- Check that a local variable name is not already used
653−assignVariable :: Ident -> UnifyT Type Check ()
654−assignVariable name = do
655− env <- checkEnv <$> get
656− Just moduleName <- checkCurrentModule <$> get
657− case M.lookup (moduleName, name) (names env) of
658− Just _ -> UnifyT . lift . throwError $ "Variable with name " ++ show name ++ " already exists."
662−-- Check the type of the return values of a statement, returning whether or not the statement returns on
665−checkStatement :: M.Map Ident Type -> Type -> Statement -> UnifyT Type Check (Bool, M.Map Ident Type, Statement)
666−checkStatement mass _ (VariableIntroduction name val) = do
668− val'@(TypedValue _ _ t) <- infer val
669− return (False, M.insert name t mass, VariableIntroduction name val')
670−checkStatement mass _ (Assignment ident val) = do
671− val'@(TypedValue _ _ t) <- infer val
672− case M.lookup ident mass of
673− Nothing -> throwError $ "No local variable with name " ++ show ident
674− Just ty -> do t =?= ty
675− return (False, mass, Assignment ident val')
676−checkStatement mass ret (While val inner) = do
677− val' <- check val tyBoolean
678− (allCodePathsReturn, _, inner') <- checkBlock mass ret inner
679− return (allCodePathsReturn, mass, While val' inner')
680−checkStatement mass ret (If ifst) = do
681− (allCodePathsReturn, ifst') <- checkIfStatement mass ret ifst
682− return (allCodePathsReturn, mass, If ifst')
683−checkStatement mass ret (For ident start end inner) = do
684− Just moduleName <- checkCurrentModule <$> get
685− assignVariable ident
686− start' <- check start tyNumber
687− end' <- check end tyNumber
688− (allCodePathsReturn, _, inner') <- bindLocalVariables moduleName [(ident, tyNumber)] $ checkBlock mass ret inner
689− return (allCodePathsReturn, mass, For ident start' end' inner')
690−checkStatement mass ret (Return val) = do
691− val' <- check val ret
692− return (True, mass, Return (TypedValue True val' ret))
695−-- Check the type of an if-then-else statement
697−checkIfStatement :: M.Map Ident Type -> Type -> IfStatement -> UnifyT Type Check (Bool, IfStatement)
698−checkIfStatement mass ret (IfStatement val thens Nothing) = do
699− val' <- check val tyBoolean
700− (_, _, thens') <- checkBlock mass ret thens
701− return (False, IfStatement val' thens' Nothing)
702−checkIfStatement mass ret (IfStatement val thens (Just elses)) = do
703− val' <- check val tyBoolean
704− (allCodePathsReturn1, _, thens') <- checkBlock mass ret thens
705− (allCodePathsReturn2, elses') <- checkElseStatement mass ret elses
706− return (allCodePathsReturn1 && allCodePathsReturn2, IfStatement val' thens' (Just elses'))
709−-- Check the type of an else statement
711−checkElseStatement :: M.Map Ident Type -> Type -> ElseStatement -> UnifyT Type Check (Bool, ElseStatement)
712−checkElseStatement mass ret (Else elses) = do
713− (allCodePathsReturn, _, elses') <- checkBlock mass ret elses
714− return (allCodePathsReturn, Else elses')
715−checkElseStatement mass ret (ElseIf ifst) = (id *** ElseIf) <$> checkIfStatement mass ret ifst
718−-- Check the type of the return value of a block of statements
720−checkBlock :: M.Map Ident Type -> Type -> [Statement] -> UnifyT Type Check (Bool, M.Map Ident Type, [Statement])
721−checkBlock mass _ [] = return (False, mass, [])
722−checkBlock mass ret (s:ss) = do
723− Just moduleName <- checkCurrentModule <$> get
724− (b1, mass1, s') <- checkStatement mass ret s
725− bindLocalVariables moduleName (M.toList mass1) $ case (b1, ss) of
726− (True, []) -> return (True, mass1, [s'])
727− (True, _) -> throwError "Unreachable code"
729− (b, m, ss'') <- checkBlock mass1 ret ss'
730− return (b, m, s':ss'')
733−-- Generate a new skolem constant
735−newSkolemConstant :: UnifyT Type Check Int
736−newSkolemConstant = runUnknown <$> fresh'
739−-- Generate a new skolem scope
741−newSkolemScope :: UnifyT Type Check SkolemScope
742−newSkolemScope = SkolemScope . runUnknown <$> fresh'
745−-- Skolemize a type variable by replacing its instances with fresh skolem constants
747−skolemize :: (D.Data d) => String -> Int -> SkolemScope -> d -> d
748−skolemize ident sko scope d = replaceTypeVars ident (Skolem sko scope) d
751−-- Introduce skolem scope at every occurence of a ForAll
753−introduceSkolemScope :: Type -> UnifyT Type Check Type
754−introduceSkolemScope = everywhereM (mkM go)
756− go (ForAll ident ty Nothing) = ForAll ident ty <$> (Just <$> newSkolemScope)
757− go other = return other
760−-- Check the type of a value, rethrowing errors to provide a better error message
762−check :: Value -> Type -> UnifyT Type Check Value
763−check val ty = rethrow errorMessage $ check' val ty
766− "Error checking type of term " ++
767− prettyPrintValue val ++
769− prettyPrintType ty ++
774−-- Check the type of a value
776−check' :: Value -> Type -> UnifyT Type Check Value
777−check' val t@(ForAll ident ty _) = do
778− scope <- newSkolemScope
779− sko <- newSkolemConstant
780− let sk = skolemize ident sko scope ty
781− val' <- check val sk
782− return $ TypedValue True val' (ForAll ident ty (Just scope))
783−check' val t@(ConstrainedType constraints ty) = do
785− Just moduleName <- checkCurrentModule <$> get
786− dictNames <- flip mapM constraints $ \(Qualified _ (ProperName className), _) -> do
787− n <- liftCheck freshDictionaryName
788− return $ Ident $ "__dict_" ++ className ++ "_" ++ show n
789− val' <- withTypeClassDictionaries (zipWith (\name (className, instanceTy) ->
790− TypeClassDictionaryInScope name className instanceTy Nothing TCDRegular) (map (Qualified Nothing) dictNames)
791− (qualifyAllUnqualifiedNames moduleName env constraints)) $
793− return $ TypedValue True (foldr Abs val' dictNames) t
794−check' val t@(SaturatedTypeSynonym name args) = do
795− ty <- introduceSkolemScope <=< expandTypeSynonym name $ args
796− val' <- check val ty
797− return $ TypedValue True val' ty
798−check' val u@(TUnknown _) = do
799− val'@(TypedValue _ _ ty) <- infer val
800− -- Don't unify an unknown with an inferred polytype
801− (val'', ty') <- instantiatePolyTypeWithUnknowns val' ty
803− return $ TypedValue True val'' ty'
804−check' v@(NumericLiteral _) t | t == tyNumber =
805− return $ TypedValue True v t
806−check' v@(StringLiteral _) t | t == tyString =
807− return $ TypedValue True v t
808−check' v@(BooleanLiteral _) t | t == tyBoolean =
809− return $ TypedValue True v t
810−check' (ArrayLiteral vals) t@(TypeApp a ty) | a == tyArray = do
811− arr <- ArrayLiteral <$> forM vals (\val -> check val ty)
812− return $ TypedValue True arr t
813−check' (Abs arg ret) ty@(TypeApp (TypeApp t argTy) retTy) | t == tyFunction = do
814− Just moduleName <- checkCurrentModule <$> get
815− ret' <- bindLocalVariables moduleName [(arg, argTy)] $ check ret retTy
816− return $ TypedValue True (Abs arg ret') ty
817−check' (App f arg) ret = do
818− f'@(TypedValue _ _ ft) <- infer f
819− (ret', app) <- checkFunctionApplication f' ft arg
820− subsumes Nothing ret' ret
821− return $ TypedValue True app ret
822−check' v@(Var var) ty = do
823− Just moduleName <- checkCurrentModule <$> get
824− repl <- introduceSkolemScope <=< replaceAllTypeSynonyms <=< lookupVariable moduleName $ var
825− ty' <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty
826− v' <- subsumes (Just v) repl ty'
828− Nothing -> throwError "Unable to check type subsumption"
829− Just v'' -> return $ TypedValue True v'' ty'
830−check' (TypedValue checkType val ty1) ty2 = do
831− Just moduleName <- checkCurrentModule <$> get
832− kind <- liftCheck $ kindOf moduleName ty1
833− guardWith ("Expected type of kind *, was " ++ prettyPrintKind kind) $ kind == Star
834− val' <- subsumes (Just val) ty1 ty2
836− Nothing -> throwError "Unable to check type subsumption"
838− val''' <- if checkType then check val'' ty1 else return val''
839− return $ TypedValue checkType (TypedValue True val''' ty1) ty2
840−check' (Case vals binders) ret = do
841− vals' <- mapM infer vals
842− let ts = map (\(TypedValue _ _ t) -> t) vals'
843− binders' <- checkBinders ts ret binders
844− return $ TypedValue True (Case vals' binders') ret
845−check' (IfThenElse cond th el) ty = do
846− cond' <- check cond tyBoolean
849− return $ TypedValue True (IfThenElse cond' th' el') ty
850−check' (ObjectLiteral ps) t@(Object row) = do
851− ensureNoDuplicateProperties ps
852− ps' <- checkProperties ps row False
853− return $ TypedValue True (ObjectLiteral ps') t
854−check' (ObjectUpdate obj ps) t@(Object row) = do
855− ensureNoDuplicateProperties ps
856− us <- zip (map fst ps) <$> replicateM (length ps) fresh
857− let (propsToCheck, rest) = rowToList row
858− propsToRemove = map fst ps
859− remainingProps = filter (\(p, _) -> p `notElem` propsToRemove) propsToCheck
860− obj' <- check obj (Object (rowFromList (us ++ remainingProps, rest)))
861− ps' <- checkProperties ps row True
862− return $ TypedValue True (ObjectUpdate obj' ps') t
863−check' (Accessor prop val) ty = do
865− val' <- check val (Object (RCons prop ty rest))
866− return $ TypedValue True (Accessor prop val') ty
867−check' (Block ss) ret = do
868− (allCodePathsReturn, _, ss') <- checkBlock M.empty ret ss
869− guardWith "Block is missing a return statement" allCodePathsReturn
870− return $ TypedValue True (Block ss') ret
871−check' (Constructor c) ty = do
873− Just moduleName <- checkCurrentModule <$> get
874− case M.lookup (qualify moduleName c) (dataConstructors env) of
875− Nothing -> throwError $ "Constructor " ++ show c ++ " is undefined"
877− repl <- introduceSkolemScope <=< replaceAllTypeSynonyms $ ty1
878− _ <- subsumes Nothing repl ty
879− return $ TypedValue True (Constructor c) ty
880−check' val ty = throwError $ prettyPrintValue val ++ " does not have type " ++ prettyPrintType ty
883−-- Check the type of a collection of named record fields
885−-- The @lax@ parameter controls whether or not every record member has to be provided. For object updates, this is not the case.
887−checkProperties :: [(String, Value)] -> Type -> Bool -> UnifyT Type Check [(String, Value)]
888−checkProperties ps row lax = let (ts, r') = rowToList row in go ps ts r' where
889− go [] [] REmpty = return []
890− go [] [] u@(TUnknown _) = do u =?= REmpty
892− go [] [] (Skolem _ _) | lax = return []
893− go [] ((p, _): _) _ | lax = return []
894− | otherwise = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have property " ++ p
895− go ((p,_):_) [] REmpty = throwError $ "Property " ++ p ++ " is not present in closed object type " ++ prettyPrintRow row
896− go ((p,v):ps') [] u@(TUnknown _) = do
897− v'@(TypedValue _ _ ty) <- infer v
899− u =?= RCons p ty rest
900− ps'' <- go ps' [] rest
901− return $ (p, v') : ps''
902− go ((p,v):ps') ts r =
905− v'@(TypedValue _ _ ty) <- infer v
907− r =?= RCons p ty rest
908− ps'' <- go ps' ts rest
909− return $ (p, v') : ps''
912− ps'' <- go ps' (delete (p, ty) ts) r
913− return $ (p, v') : ps''
914− go _ _ _ = throwError $ prettyPrintValue (ObjectLiteral ps) ++ " does not have type " ++ prettyPrintType (Object row)
917−-- Check the type of a function application, rethrowing errors to provide a better error message
919−checkFunctionApplication :: Value -> Type -> Value -> UnifyT Type Check (Type, Value)
920−checkFunctionApplication fn fnTy arg = rethrow errorMessage $ checkFunctionApplication' fn fnTy arg
922− errorMessage msg = "Error applying function of type "
923− ++ prettyPrintType fnTy
924− ++ " to argument " ++ prettyPrintValue arg
928−-- Check the type of a function application
930−checkFunctionApplication' :: Value -> Type -> Value -> UnifyT Type Check (Type, Value)
931−checkFunctionApplication' fn (TypeApp (TypeApp tyFunction' argTy) retTy) arg = do
932− tyFunction' =?= tyFunction
933− arg' <- check arg argTy
934− return (retTy, App fn arg')
935−checkFunctionApplication' fn (ForAll ident ty _) arg = do
936− replaced <- replaceVarWithUnknown ident ty
937− checkFunctionApplication fn replaced arg
938−checkFunctionApplication' fn u@(TUnknown _) arg = do
940− TypedValue _ v t <- infer arg
941− (v', t') <- instantiatePolyTypeWithUnknowns arg t
942− return $ TypedValue True v' t'
943− let ty = (\(TypedValue _ _ t) -> t) arg'
945− u =?= function ty ret
946− return (ret, App fn arg')
947−checkFunctionApplication' fn (SaturatedTypeSynonym name tyArgs) arg = do
948− ty <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
949− checkFunctionApplication fn ty arg
950−checkFunctionApplication' fn (ConstrainedType constraints fnTy) arg = do
952− dicts <- getTypeClassDictionaries
953− Just moduleName <- checkCurrentModule <$> get
954− checkFunctionApplication' (foldl App fn (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))) fnTy arg
955−checkFunctionApplication' _ fnTy arg = throwError $ "Cannot apply a function of type "
956− ++ prettyPrintType fnTy
957− ++ " to argument " ++ prettyPrintValue arg
960−-- Check whether one type subsumes another, rethrowing errors to provide a better error message
962−subsumes :: Maybe Value -> Type -> Type -> UnifyT Type Check (Maybe Value)
963−subsumes val ty1 ty2 = rethrow errorMessage $ subsumes' val ty1 ty2
965− errorMessage msg = "Error checking that type "
966− ++ prettyPrintType ty1
967− ++ " subsumes type "
968− ++ prettyPrintType ty2
972−-- Check whether one type subsumes another
974−subsumes' :: Maybe Value -> Type -> Type -> UnifyT Type Check (Maybe Value)
975−subsumes' val (ForAll ident ty1 _) ty2 = do
976− replaced <- replaceVarWithUnknown ident ty1
977− subsumes val replaced ty2
978−subsumes' val ty1 (ForAll ident ty2 sco) =
981− sko <- newSkolemConstant
982− let sk = skolemize ident sko sco' ty2
984− Nothing -> throwError "Skolem variable scope is unspecified"
985−subsumes' val (TypeApp (TypeApp f1 arg1) ret1) (TypeApp (TypeApp f2 arg2) ret2) | f1 == tyFunction && f2 == tyFunction = do
986− subsumes Nothing arg2 arg1
987− subsumes Nothing ret1 ret2
989−subsumes' val (SaturatedTypeSynonym name tyArgs) ty2 = do
990− ty1 <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
991− subsumes val ty1 ty2
992−subsumes' val ty1 (SaturatedTypeSynonym name tyArgs) = do
993− ty2 <- introduceSkolemScope <=< expandTypeSynonym name $ tyArgs
994− subsumes val ty1 ty2
995−subsumes' (Just val) (ConstrainedType constraints ty1) ty2 = do
997− dicts <- getTypeClassDictionaries
998− Just moduleName <- checkCurrentModule <$> get
999− _ <- subsumes' Nothing ty1 ty2
1000− return . Just $ foldl App val (map (flip TypeClassDictionary dicts) (qualifyAllUnqualifiedNames moduleName env constraints))
1001−subsumes' val ty1 ty2 = do