2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1998
6 Type - public interface
10 -- re-exports from TypeRep
11 TyThing(..), Type, PredType(..), ThetaType,
15 Kind, SimpleKind, KindVar,
16 kindFunResult, splitKindFunTys, splitKindFunTysN,
18 liftedTypeKindTyCon, openTypeKindTyCon, unliftedTypeKindTyCon,
19 argTypeKindTyCon, ubxTupleKindTyCon,
21 liftedTypeKind, unliftedTypeKind, openTypeKind,
22 argTypeKind, ubxTupleKind,
24 tySuperKind, coSuperKind,
26 isLiftedTypeKind, isUnliftedTypeKind, isOpenTypeKind,
27 isUbxTupleKind, isArgTypeKind, isKind, isTySuperKind,
28 isCoSuperKind, isSuperKind, isCoercionKind, isEqPred,
29 mkArrowKind, mkArrowKinds,
31 isSubArgTypeKind, isSubOpenTypeKind, isSubKind, defaultKind, eqKind,
34 -- Re-exports from TyCon
37 mkTyVarTy, mkTyVarTys, getTyVar, getTyVar_maybe, isTyVarTy,
39 mkAppTy, mkAppTys, splitAppTy, splitAppTys,
40 splitAppTy_maybe, repSplitAppTy_maybe,
42 mkFunTy, mkFunTys, splitFunTy, splitFunTy_maybe,
43 splitFunTys, splitFunTysN,
44 funResultTy, funArgTy, zipFunTys, isFunTy,
46 mkTyConApp, mkTyConTy,
47 tyConAppTyCon, tyConAppArgs,
48 splitTyConApp_maybe, splitTyConApp,
49 splitNewTyConApp_maybe, splitNewTyConApp,
51 repType, repType', typePrimRep, coreView, tcView, kindView,
53 mkForAllTy, mkForAllTys, splitForAllTy_maybe, splitForAllTys,
54 applyTy, applyTys, isForAllTy, dropForAlls,
57 predTypeRep, mkPredTy, mkPredTys, pprSourceTyCon, mkFamilyTyConApp,
63 isUnLiftedType, isUnboxedTupleType, isAlgType, isPrimitiveType,
64 isStrictType, isStrictPred,
67 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
68 typeKind, addFreeTyVars,
70 -- Tidying up for printing
72 tidyOpenType, tidyOpenTypes,
73 tidyTyVarBndr, tidyFreeTyVars,
74 tidyOpenTyVar, tidyOpenTyVars,
75 tidyTopType, tidyPred,
79 coreEqType, tcEqType, tcEqTypes, tcCmpType, tcCmpTypes,
80 tcEqPred, tcCmpPred, tcEqTypeX,
86 TvSubstEnv, emptyTvSubstEnv, -- Representation widely visible
87 TvSubst(..), emptyTvSubst, -- Representation visible to a few friends
88 mkTvSubst, mkOpenTvSubst, zipOpenTvSubst, zipTopTvSubst, mkTopTvSubst, notElemTvSubst,
89 getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope,
90 extendTvSubst, extendTvSubstList, isInScope, composeTvSubst, zipTyEnv,
93 -- Performing substitution on types
94 substTy, substTys, substTyWith, substTheta,
95 substPred, substTyVar, substTyVars, substTyVarBndr, deShadowTy, lookupTyVar,
98 pprType, pprParendType, pprTypeApp, pprTyThingCategory, pprForAll,
99 pprPred, pprTheta, pprThetaArrow, pprClassPred, pprKind, pprParendKind
102 #include "HsVersions.h"
104 -- We import the representation and primitive functions from TypeRep.
105 -- Many things are reexported, but not the representation!
126 import Data.Maybe ( isJust )
130 %************************************************************************
134 %************************************************************************
136 In Core, we "look through" non-recursive newtypes and PredTypes.
139 {-# INLINE coreView #-}
140 coreView :: Type -> Maybe Type
141 -- Strips off the *top layer only* of a type to give
142 -- its underlying representation type.
143 -- Returns Nothing if there is nothing to look through.
145 -- In the case of newtypes, it returns
146 -- *either* a vanilla TyConApp (recursive newtype, or non-saturated)
147 -- *or* the newtype representation (otherwise), meaning the
148 -- type written in the RHS of the newtype decl,
149 -- which may itself be a newtype
151 -- Example: newtype R = MkR S
153 -- newtype T = MkT (T -> T)
154 -- expandNewTcApp on R gives Just S
156 -- on T gives Nothing (no expansion)
158 -- By being non-recursive and inlined, this case analysis gets efficiently
159 -- joined onto the case analysis that the caller is already doing
160 coreView (NoteTy _ ty) = Just ty
162 | isEqPred p = Nothing
163 | otherwise = Just (predTypeRep p)
164 coreView (TyConApp tc tys) | Just (tenv, rhs, tys') <- coreExpandTyCon_maybe tc tys
165 = Just (mkAppTys (substTy (mkTopTvSubst tenv) rhs) tys')
166 -- Its important to use mkAppTys, rather than (foldl AppTy),
167 -- because the function part might well return a
168 -- partially-applied type constructor; indeed, usually will!
169 coreView ty = Nothing
173 -----------------------------------------------
174 {-# INLINE tcView #-}
175 tcView :: Type -> Maybe Type
176 -- Same, but for the type checker, which just looks through synonyms
177 tcView (NoteTy _ ty) = Just ty
178 tcView (TyConApp tc tys) | Just (tenv, rhs, tys') <- tcExpandTyCon_maybe tc tys
179 = Just (mkAppTys (substTy (mkTopTvSubst tenv) rhs) tys')
182 -----------------------------------------------
183 {-# INLINE kindView #-}
184 kindView :: Kind -> Maybe Kind
185 -- C.f. coreView, tcView
186 -- For the moment, we don't even handle synonyms in kinds
187 kindView (NoteTy _ k) = Just k
188 kindView other = Nothing
192 %************************************************************************
194 \subsection{Constructor-specific functions}
196 %************************************************************************
199 ---------------------------------------------------------------------
203 mkTyVarTy :: TyVar -> Type
206 mkTyVarTys :: [TyVar] -> [Type]
207 mkTyVarTys = map mkTyVarTy -- a common use of mkTyVarTy
209 getTyVar :: String -> Type -> TyVar
210 getTyVar msg ty = case getTyVar_maybe ty of
212 Nothing -> panic ("getTyVar: " ++ msg)
214 isTyVarTy :: Type -> Bool
215 isTyVarTy ty = isJust (getTyVar_maybe ty)
217 getTyVar_maybe :: Type -> Maybe TyVar
218 getTyVar_maybe ty | Just ty' <- coreView ty = getTyVar_maybe ty'
219 getTyVar_maybe (TyVarTy tv) = Just tv
220 getTyVar_maybe other = Nothing
225 ---------------------------------------------------------------------
228 We need to be pretty careful with AppTy to make sure we obey the
229 invariant that a TyConApp is always visibly so. mkAppTy maintains the
233 mkAppTy orig_ty1 orig_ty2
236 mk_app (NoteTy _ ty1) = mk_app ty1
237 mk_app (TyConApp tc tys) = mkTyConApp tc (tys ++ [orig_ty2])
238 mk_app ty1 = AppTy orig_ty1 orig_ty2
239 -- Note that the TyConApp could be an
240 -- under-saturated type synonym. GHC allows that; e.g.
241 -- type Foo k = k a -> k a
243 -- foo :: Foo Id -> Foo Id
245 -- Here Id is partially applied in the type sig for Foo,
246 -- but once the type synonyms are expanded all is well
248 mkAppTys :: Type -> [Type] -> Type
249 mkAppTys orig_ty1 [] = orig_ty1
250 -- This check for an empty list of type arguments
251 -- avoids the needless loss of a type synonym constructor.
252 -- For example: mkAppTys Rational []
253 -- returns to (Ratio Integer), which has needlessly lost
254 -- the Rational part.
255 mkAppTys orig_ty1 orig_tys2
258 mk_app (NoteTy _ ty1) = mk_app ty1
259 mk_app (TyConApp tc tys) = mkTyConApp tc (tys ++ orig_tys2)
260 -- mkTyConApp: see notes with mkAppTy
261 mk_app ty1 = foldl AppTy orig_ty1 orig_tys2
264 splitAppTy_maybe :: Type -> Maybe (Type, Type)
265 splitAppTy_maybe ty | Just ty' <- coreView ty
266 = splitAppTy_maybe ty'
267 splitAppTy_maybe ty = repSplitAppTy_maybe ty
270 repSplitAppTy_maybe :: Type -> Maybe (Type,Type)
271 -- Does the AppTy split, but assumes that any view stuff is already done
272 repSplitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [ty1], ty2)
273 repSplitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2)
274 repSplitAppTy_maybe (TyConApp tc tys) = case snocView tys of
275 Just (tys', ty') -> Just (TyConApp tc tys', ty')
277 repSplitAppTy_maybe other = Nothing
279 splitAppTy :: Type -> (Type, Type)
280 splitAppTy ty = case splitAppTy_maybe ty of
282 Nothing -> panic "splitAppTy"
285 splitAppTys :: Type -> (Type, [Type])
286 splitAppTys ty = split ty ty []
288 split orig_ty ty args | Just ty' <- coreView ty = split orig_ty ty' args
289 split orig_ty (AppTy ty arg) args = split ty ty (arg:args)
290 split orig_ty (TyConApp tc tc_args) args = (TyConApp tc [], tc_args ++ args)
291 split orig_ty (FunTy ty1 ty2) args = ASSERT( null args )
292 (TyConApp funTyCon [], [ty1,ty2])
293 split orig_ty ty args = (orig_ty, args)
298 ---------------------------------------------------------------------
303 mkFunTy :: Type -> Type -> Type
304 mkFunTy (PredTy (EqPred ty1 ty2)) res = mkForAllTy (mkWildCoVar (PredTy (EqPred ty1 ty2))) res
305 mkFunTy arg res = FunTy arg res
307 mkFunTys :: [Type] -> Type -> Type
308 mkFunTys tys ty = foldr mkFunTy ty tys
310 isFunTy :: Type -> Bool
311 isFunTy ty = isJust (splitFunTy_maybe ty)
313 splitFunTy :: Type -> (Type, Type)
314 splitFunTy ty | Just ty' <- coreView ty = splitFunTy ty'
315 splitFunTy (FunTy arg res) = (arg, res)
316 splitFunTy other = pprPanic "splitFunTy" (ppr other)
318 splitFunTy_maybe :: Type -> Maybe (Type, Type)
319 splitFunTy_maybe ty | Just ty' <- coreView ty = splitFunTy_maybe ty'
320 splitFunTy_maybe (FunTy arg res) = Just (arg, res)
321 splitFunTy_maybe other = Nothing
323 splitFunTys :: Type -> ([Type], Type)
324 splitFunTys ty = split [] ty ty
326 split args orig_ty ty | Just ty' <- coreView ty = split args orig_ty ty'
327 split args orig_ty (FunTy arg res) = split (arg:args) res res
328 split args orig_ty ty = (reverse args, orig_ty)
330 splitFunTysN :: Int -> Type -> ([Type], Type)
331 -- Split off exactly n arg tys
332 splitFunTysN 0 ty = ([], ty)
333 splitFunTysN n ty = case splitFunTy ty of { (arg, res) ->
334 case splitFunTysN (n-1) res of { (args, res) ->
337 zipFunTys :: Outputable a => [a] -> Type -> ([(a,Type)], Type)
338 zipFunTys orig_xs orig_ty = split [] orig_xs orig_ty orig_ty
340 split acc [] nty ty = (reverse acc, nty)
342 | Just ty' <- coreView ty = split acc xs nty ty'
343 split acc (x:xs) nty (FunTy arg res) = split ((x,arg):acc) xs res res
344 split acc (x:xs) nty ty = pprPanic "zipFunTys" (ppr orig_xs <+> ppr orig_ty)
346 funResultTy :: Type -> Type
347 funResultTy ty | Just ty' <- coreView ty = funResultTy ty'
348 funResultTy (FunTy arg res) = res
349 funResultTy ty = pprPanic "funResultTy" (ppr ty)
351 funArgTy :: Type -> Type
352 funArgTy ty | Just ty' <- coreView ty = funArgTy ty'
353 funArgTy (FunTy arg res) = arg
354 funArgTy ty = pprPanic "funArgTy" (ppr ty)
358 ---------------------------------------------------------------------
361 @mkTyConApp@ is a key function, because it builds a TyConApp, FunTy or PredTy,
365 mkTyConApp :: TyCon -> [Type] -> Type
367 | isFunTyCon tycon, [ty1,ty2] <- tys
373 mkTyConTy :: TyCon -> Type
374 mkTyConTy tycon = mkTyConApp tycon []
376 -- splitTyConApp "looks through" synonyms, because they don't
377 -- mean a distinct type, but all other type-constructor applications
378 -- including functions are returned as Just ..
380 tyConAppTyCon :: Type -> TyCon
381 tyConAppTyCon ty = fst (splitTyConApp ty)
383 tyConAppArgs :: Type -> [Type]
384 tyConAppArgs ty = snd (splitTyConApp ty)
386 splitTyConApp :: Type -> (TyCon, [Type])
387 splitTyConApp ty = case splitTyConApp_maybe ty of
389 Nothing -> pprPanic "splitTyConApp" (ppr ty)
391 splitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
392 splitTyConApp_maybe ty | Just ty' <- coreView ty = splitTyConApp_maybe ty'
393 splitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
394 splitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
395 splitTyConApp_maybe other = Nothing
397 -- Sometimes we do NOT want to look throught a newtype. When case matching
398 -- on a newtype we want a convenient way to access the arguments of a newty
399 -- constructor so as to properly form a coercion.
400 splitNewTyConApp :: Type -> (TyCon, [Type])
401 splitNewTyConApp ty = case splitNewTyConApp_maybe ty of
403 Nothing -> pprPanic "splitNewTyConApp" (ppr ty)
404 splitNewTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
405 splitNewTyConApp_maybe ty | Just ty' <- tcView ty = splitNewTyConApp_maybe ty'
406 splitNewTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
407 splitNewTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
408 splitNewTyConApp_maybe other = Nothing
410 -- get instantiated newtype rhs, the arguments had better saturate
412 newTyConInstRhs :: TyCon -> [Type] -> Type
413 newTyConInstRhs tycon tys =
414 let (tvs, ty) = newTyConRhs tycon in substTyWith tvs tys ty
418 ---------------------------------------------------------------------
422 Notes on type synonyms
423 ~~~~~~~~~~~~~~~~~~~~~~
424 The various "split" functions (splitFunTy, splitRhoTy, splitForAllTy) try
425 to return type synonyms whereever possible. Thus
430 splitFunTys (a -> Foo a) = ([a], Foo a)
433 The reason is that we then get better (shorter) type signatures in
434 interfaces. Notably this plays a role in tcTySigs in TcBinds.lhs.
439 repType looks through
443 (d) usage annotations
444 (e) all newtypes, including recursive ones, but not newtype families
445 It's useful in the back end.
448 repType :: Type -> Type
449 -- Only applied to types of kind *; hence tycons are saturated
450 repType ty | Just ty' <- coreView ty = repType ty'
451 repType (ForAllTy _ ty) = repType ty
452 repType (TyConApp tc tys)
453 | isClosedNewTyCon tc = -- Recursive newtypes are opaque to coreView
454 -- but we must expand them here. Sure to
455 -- be saturated because repType is only applied
456 -- to types of kind *
457 ASSERT( {- isRecursiveTyCon tc && -} tys `lengthIs` tyConArity tc )
458 repType (new_type_rep tc tys)
461 -- repType' aims to be a more thorough version of repType
462 -- For now it simply looks through the TyConApp args too
463 repType' ty -- | pprTrace "repType'" (ppr ty $$ ppr (go1 ty)) False = undefined
467 go (TyConApp tc tys) = mkTyConApp tc (map repType' tys)
471 -- new_type_rep doesn't ask any questions:
472 -- it just expands newtype, whether recursive or not
473 new_type_rep new_tycon tys = ASSERT( tys `lengthIs` tyConArity new_tycon )
474 case newTyConRep new_tycon of
475 (tvs, rep_ty) -> substTyWith tvs tys rep_ty
477 -- ToDo: this could be moved to the code generator, using splitTyConApp instead
478 -- of inspecting the type directly.
479 typePrimRep :: Type -> PrimRep
480 typePrimRep ty = case repType ty of
481 TyConApp tc _ -> tyConPrimRep tc
483 AppTy _ _ -> PtrRep -- See note below
485 other -> pprPanic "typePrimRep" (ppr ty)
486 -- Types of the form 'f a' must be of kind *, not *#, so
487 -- we are guaranteed that they are represented by pointers.
488 -- The reason is that f must have kind *->*, not *->*#, because
489 -- (we claim) there is no way to constrain f's kind any other
495 ---------------------------------------------------------------------
500 mkForAllTy :: TyVar -> Type -> Type
502 = mkForAllTys [tyvar] ty
504 mkForAllTys :: [TyVar] -> Type -> Type
505 mkForAllTys tyvars ty = foldr ForAllTy ty tyvars
507 isForAllTy :: Type -> Bool
508 isForAllTy (NoteTy _ ty) = isForAllTy ty
509 isForAllTy (ForAllTy _ _) = True
510 isForAllTy other_ty = False
512 splitForAllTy_maybe :: Type -> Maybe (TyVar, Type)
513 splitForAllTy_maybe ty = splitFAT_m ty
515 splitFAT_m ty | Just ty' <- coreView ty = splitFAT_m ty'
516 splitFAT_m (ForAllTy tyvar ty) = Just(tyvar, ty)
517 splitFAT_m _ = Nothing
519 splitForAllTys :: Type -> ([TyVar], Type)
520 splitForAllTys ty = split ty ty []
522 split orig_ty ty tvs | Just ty' <- coreView ty = split orig_ty ty' tvs
523 split orig_ty (ForAllTy tv ty) tvs = split ty ty (tv:tvs)
524 split orig_ty t tvs = (reverse tvs, orig_ty)
526 dropForAlls :: Type -> Type
527 dropForAlls ty = snd (splitForAllTys ty)
530 -- (mkPiType now in CoreUtils)
534 Instantiate a for-all type with one or more type arguments.
535 Used when we have a polymorphic function applied to type args:
537 Then we use (applyTys type-of-f [t1,t2]) to compute the type of
541 applyTy :: Type -> Type -> Type
542 applyTy ty arg | Just ty' <- coreView ty = applyTy ty' arg
543 applyTy (ForAllTy tv ty) arg = substTyWith [tv] [arg] ty
544 applyTy other arg = panic "applyTy"
546 applyTys :: Type -> [Type] -> Type
547 -- This function is interesting because
548 -- a) the function may have more for-alls than there are args
549 -- b) less obviously, it may have fewer for-alls
550 -- For case (b) think of
551 -- applyTys (forall a.a) [forall b.b, Int]
552 -- This really can happen, via dressing up polymorphic types with newtype
553 -- clothing. Here's an example:
554 -- newtype R = R (forall a. a->a)
555 -- foo = case undefined :: R of
558 applyTys orig_fun_ty [] = orig_fun_ty
559 applyTys orig_fun_ty arg_tys
560 | n_tvs == n_args -- The vastly common case
561 = substTyWith tvs arg_tys rho_ty
562 | n_tvs > n_args -- Too many for-alls
563 = substTyWith (take n_args tvs) arg_tys
564 (mkForAllTys (drop n_args tvs) rho_ty)
565 | otherwise -- Too many type args
566 = ASSERT2( n_tvs > 0, ppr orig_fun_ty ) -- Zero case gives infnite loop!
567 applyTys (substTyWith tvs (take n_tvs arg_tys) rho_ty)
570 (tvs, rho_ty) = splitForAllTys orig_fun_ty
572 n_args = length arg_tys
576 %************************************************************************
578 \subsection{Source types}
580 %************************************************************************
582 A "source type" is a type that is a separate type as far as the type checker is
583 concerned, but which has low-level representation as far as the back end is concerned.
585 Source types are always lifted.
587 The key function is predTypeRep which gives the representation of a source type:
590 mkPredTy :: PredType -> Type
591 mkPredTy pred = PredTy pred
593 mkPredTys :: ThetaType -> [Type]
594 mkPredTys preds = map PredTy preds
596 predTypeRep :: PredType -> Type
597 -- Convert a PredType to its "representation type";
598 -- the post-type-checking type used by all the Core passes of GHC.
599 -- Unwraps only the outermost level; for example, the result might
600 -- be a newtype application
601 predTypeRep (IParam _ ty) = ty
602 predTypeRep (ClassP clas tys) = mkTyConApp (classTyCon clas) tys
603 -- Result might be a newtype application, but the consumer will
604 -- look through that too if necessary
605 predTypeRep (EqPred ty1 ty2) = pprPanic "predTypeRep" (ppr (EqPred ty1 ty2))
607 mkFamilyTyConApp :: TyCon -> [Type] -> Type
608 -- Given a family instance TyCon and its arg types, return the
609 -- corresponding family type. E.g.
611 -- data instance T (Maybe b) = MkT b -- Instance tycon :RTL
613 -- mkFamilyTyConApp :RTL Int = T (Maybe Int)
614 mkFamilyTyConApp tc tys
615 | Just (fam_tc, fam_tys) <- tyConFamInst_maybe tc
616 , let fam_subst = zipTopTvSubst (tyConTyVars tc) tys
617 = mkTyConApp fam_tc (substTys fam_subst fam_tys)
621 -- Pretty prints a tycon, using the family instance in case of a
622 -- representation tycon. For example
623 -- e.g. data T [a] = ...
624 -- In that case we want to print `T [a]', where T is the family TyCon
626 | Just (fam_tc, tys) <- tyConFamInst_maybe tycon
627 = ppr $ fam_tc `TyConApp` tys -- can't be FunTyCon
633 %************************************************************************
635 \subsection{Kinds and free variables}
637 %************************************************************************
639 ---------------------------------------------------------------------
640 Finding the kind of a type
641 ~~~~~~~~~~~~~~~~~~~~~~~~~~
643 typeKind :: Type -> Kind
644 typeKind (TyConApp tycon tys) = ASSERT( not (isCoercionTyCon tycon) )
645 -- We should be looking for the coercion kind,
647 foldr (\_ k -> kindFunResult k) (tyConKind tycon) tys
648 typeKind (NoteTy _ ty) = typeKind ty
649 typeKind (PredTy pred) = predKind pred
650 typeKind (AppTy fun arg) = kindFunResult (typeKind fun)
651 typeKind (ForAllTy tv ty) = typeKind ty
652 typeKind (TyVarTy tyvar) = tyVarKind tyvar
653 typeKind (FunTy arg res)
654 -- Hack alert. The kind of (Int -> Int#) is liftedTypeKind (*),
655 -- not unliftedTypKind (#)
656 -- The only things that can be after a function arrow are
657 -- (a) types (of kind openTypeKind or its sub-kinds)
658 -- (b) kinds (of super-kind TY) (e.g. * -> (* -> *))
659 | isTySuperKind k = k
660 | otherwise = ASSERT( isSubOpenTypeKind k) liftedTypeKind
664 predKind :: PredType -> Kind
665 predKind (EqPred {}) = coSuperKind -- A coercion kind!
666 predKind (ClassP {}) = liftedTypeKind -- Class and implicitPredicates are
667 predKind (IParam {}) = liftedTypeKind -- always represented by lifted types
671 ---------------------------------------------------------------------
672 Free variables of a type
673 ~~~~~~~~~~~~~~~~~~~~~~~~
675 tyVarsOfType :: Type -> TyVarSet
676 -- NB: for type synonyms tyVarsOfType does *not* expand the synonym
677 tyVarsOfType (TyVarTy tv) = unitVarSet tv
678 tyVarsOfType (TyConApp tycon tys) = tyVarsOfTypes tys
679 tyVarsOfType (NoteTy (FTVNote tvs) ty2) = tvs
680 tyVarsOfType (PredTy sty) = tyVarsOfPred sty
681 tyVarsOfType (FunTy arg res) = tyVarsOfType arg `unionVarSet` tyVarsOfType res
682 tyVarsOfType (AppTy fun arg) = tyVarsOfType fun `unionVarSet` tyVarsOfType arg
683 tyVarsOfType (ForAllTy tyvar ty) = delVarSet (tyVarsOfType ty) tyvar
685 tyVarsOfTypes :: [Type] -> TyVarSet
686 tyVarsOfTypes tys = foldr (unionVarSet.tyVarsOfType) emptyVarSet tys
688 tyVarsOfPred :: PredType -> TyVarSet
689 tyVarsOfPred (IParam _ ty) = tyVarsOfType ty
690 tyVarsOfPred (ClassP _ tys) = tyVarsOfTypes tys
691 tyVarsOfPred (EqPred ty1 ty2) = tyVarsOfType ty1 `unionVarSet` tyVarsOfType ty2
693 tyVarsOfTheta :: ThetaType -> TyVarSet
694 tyVarsOfTheta = foldr (unionVarSet . tyVarsOfPred) emptyVarSet
696 -- Add a Note with the free tyvars to the top of the type
697 addFreeTyVars :: Type -> Type
698 addFreeTyVars ty@(NoteTy (FTVNote _) _) = ty
699 addFreeTyVars ty = NoteTy (FTVNote (tyVarsOfType ty)) ty
703 %************************************************************************
705 \subsection{TidyType}
707 %************************************************************************
709 tidyTy tidies up a type for printing in an error message, or in
712 It doesn't change the uniques at all, just the print names.
715 tidyTyVarBndr :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
716 tidyTyVarBndr env@(tidy_env, subst) tyvar
717 = case tidyOccName tidy_env (getOccName name) of
718 (tidy', occ') -> ((tidy', subst'), tyvar'')
720 subst' = extendVarEnv subst tyvar tyvar''
721 tyvar' = setTyVarName tyvar name'
722 name' = tidyNameOcc name occ'
723 -- Don't forget to tidy the kind for coercions!
724 tyvar'' | isCoVar tyvar = setTyVarKind tyvar' kind'
726 kind' = tidyType env (tyVarKind tyvar)
728 name = tyVarName tyvar
730 tidyFreeTyVars :: TidyEnv -> TyVarSet -> TidyEnv
731 -- Add the free tyvars to the env in tidy form,
732 -- so that we can tidy the type they are free in
733 tidyFreeTyVars env tyvars = fst (tidyOpenTyVars env (varSetElems tyvars))
735 tidyOpenTyVars :: TidyEnv -> [TyVar] -> (TidyEnv, [TyVar])
736 tidyOpenTyVars env tyvars = mapAccumL tidyOpenTyVar env tyvars
738 tidyOpenTyVar :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
739 -- Treat a new tyvar as a binder, and give it a fresh tidy name
740 tidyOpenTyVar env@(tidy_env, subst) tyvar
741 = case lookupVarEnv subst tyvar of
742 Just tyvar' -> (env, tyvar') -- Already substituted
743 Nothing -> tidyTyVarBndr env tyvar -- Treat it as a binder
745 tidyType :: TidyEnv -> Type -> Type
746 tidyType env@(tidy_env, subst) ty
749 go (TyVarTy tv) = case lookupVarEnv subst tv of
750 Nothing -> TyVarTy tv
751 Just tv' -> TyVarTy tv'
752 go (TyConApp tycon tys) = let args = map go tys
753 in args `seqList` TyConApp tycon args
754 go (NoteTy note ty) = (NoteTy $! (go_note note)) $! (go ty)
755 go (PredTy sty) = PredTy (tidyPred env sty)
756 go (AppTy fun arg) = (AppTy $! (go fun)) $! (go arg)
757 go (FunTy fun arg) = (FunTy $! (go fun)) $! (go arg)
758 go (ForAllTy tv ty) = ForAllTy tvp $! (tidyType envp ty)
760 (envp, tvp) = tidyTyVarBndr env tv
762 go_note note@(FTVNote ftvs) = note -- No need to tidy the free tyvars
764 tidyTypes env tys = map (tidyType env) tys
766 tidyPred :: TidyEnv -> PredType -> PredType
767 tidyPred env (IParam n ty) = IParam n (tidyType env ty)
768 tidyPred env (ClassP clas tys) = ClassP clas (tidyTypes env tys)
769 tidyPred env (EqPred ty1 ty2) = EqPred (tidyType env ty1) (tidyType env ty2)
773 @tidyOpenType@ grabs the free type variables, tidies them
774 and then uses @tidyType@ to work over the type itself
777 tidyOpenType :: TidyEnv -> Type -> (TidyEnv, Type)
779 = (env', tidyType env' ty)
781 env' = tidyFreeTyVars env (tyVarsOfType ty)
783 tidyOpenTypes :: TidyEnv -> [Type] -> (TidyEnv, [Type])
784 tidyOpenTypes env tys = mapAccumL tidyOpenType env tys
786 tidyTopType :: Type -> Type
787 tidyTopType ty = tidyType emptyTidyEnv ty
792 tidyKind :: TidyEnv -> Kind -> (TidyEnv, Kind)
793 tidyKind env k = tidyOpenType env k
798 %************************************************************************
800 \subsection{Liftedness}
802 %************************************************************************
805 isUnLiftedType :: Type -> Bool
806 -- isUnLiftedType returns True for forall'd unlifted types:
807 -- x :: forall a. Int#
808 -- I found bindings like these were getting floated to the top level.
809 -- They are pretty bogus types, mind you. It would be better never to
812 isUnLiftedType ty | Just ty' <- coreView ty = isUnLiftedType ty'
813 isUnLiftedType (ForAllTy tv ty) = isUnLiftedType ty
814 isUnLiftedType (TyConApp tc _) = isUnLiftedTyCon tc
815 isUnLiftedType other = False
817 isUnboxedTupleType :: Type -> Bool
818 isUnboxedTupleType ty = case splitTyConApp_maybe ty of
819 Just (tc, ty_args) -> isUnboxedTupleTyCon tc
822 -- Should only be applied to *types*; hence the assert
823 isAlgType :: Type -> Bool
824 isAlgType ty = case splitTyConApp_maybe ty of
825 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
830 @isStrictType@ computes whether an argument (or let RHS) should
831 be computed strictly or lazily, based only on its type.
832 Works just like isUnLiftedType, except that it has a special case
833 for dictionaries. Since it takes account of ClassP, you might think
834 this function should be in TcType, but isStrictType is used by DataCon,
835 which is below TcType in the hierarchy, so it's convenient to put it here.
838 isStrictType (PredTy pred) = isStrictPred pred
839 isStrictType ty | Just ty' <- coreView ty = isStrictType ty'
840 isStrictType (ForAllTy tv ty) = isStrictType ty
841 isStrictType (TyConApp tc _) = isUnLiftedTyCon tc
842 isStrictType other = False
844 isStrictPred (ClassP clas _) = opt_DictsStrict && not (isNewTyCon (classTyCon clas))
845 isStrictPred other = False
846 -- We may be strict in dictionary types, but only if it
847 -- has more than one component.
848 -- [Being strict in a single-component dictionary risks
849 -- poking the dictionary component, which is wrong.]
853 isPrimitiveType :: Type -> Bool
854 -- Returns types that are opaque to Haskell.
855 -- Most of these are unlifted, but now that we interact with .NET, we
856 -- may have primtive (foreign-imported) types that are lifted
857 isPrimitiveType ty = case splitTyConApp_maybe ty of
858 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
864 %************************************************************************
866 \subsection{Sequencing on types
868 %************************************************************************
871 seqType :: Type -> ()
872 seqType (TyVarTy tv) = tv `seq` ()
873 seqType (AppTy t1 t2) = seqType t1 `seq` seqType t2
874 seqType (FunTy t1 t2) = seqType t1 `seq` seqType t2
875 seqType (NoteTy note t2) = seqNote note `seq` seqType t2
876 seqType (PredTy p) = seqPred p
877 seqType (TyConApp tc tys) = tc `seq` seqTypes tys
878 seqType (ForAllTy tv ty) = tv `seq` seqType ty
880 seqTypes :: [Type] -> ()
882 seqTypes (ty:tys) = seqType ty `seq` seqTypes tys
884 seqNote :: TyNote -> ()
885 seqNote (FTVNote set) = sizeUniqSet set `seq` ()
887 seqPred :: PredType -> ()
888 seqPred (ClassP c tys) = c `seq` seqTypes tys
889 seqPred (IParam n ty) = n `seq` seqType ty
890 seqPred (EqPred ty1 ty2) = seqType ty1 `seq` seqType ty2
894 %************************************************************************
896 Equality for Core types
897 (We don't use instances so that we know where it happens)
899 %************************************************************************
901 Note that eqType works right even for partial applications of newtypes.
902 See Note [Newtype eta] in TyCon.lhs
905 coreEqType :: Type -> Type -> Bool
909 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfType t1 `unionVarSet` tyVarsOfType t2))
911 eq env (TyVarTy tv1) (TyVarTy tv2) = rnOccL env tv1 == rnOccR env tv2
912 eq env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = eq (rnBndr2 env tv1 tv2) t1 t2
913 eq env (AppTy s1 t1) (AppTy s2 t2) = eq env s1 s2 && eq env t1 t2
914 eq env (FunTy s1 t1) (FunTy s2 t2) = eq env s1 s2 && eq env t1 t2
915 eq env (TyConApp tc1 tys1) (TyConApp tc2 tys2)
916 | tc1 == tc2, all2 (eq env) tys1 tys2 = True
917 -- The lengths should be equal because
918 -- the two types have the same kind
919 -- NB: if the type constructors differ that does not
920 -- necessarily mean that the types aren't equal
921 -- (synonyms, newtypes)
922 -- Even if the type constructors are the same, but the arguments
923 -- differ, the two types could be the same (e.g. if the arg is just
924 -- ignored in the RHS). In both these cases we fall through to an
925 -- attempt to expand one side or the other.
927 -- Now deal with newtypes, synonyms, pred-tys
928 eq env t1 t2 | Just t1' <- coreView t1 = eq env t1' t2
929 | Just t2' <- coreView t2 = eq env t1 t2'
931 -- Fall through case; not equal!
936 %************************************************************************
938 Comparision for source types
939 (We don't use instances so that we know where it happens)
941 %************************************************************************
945 do *not* look through newtypes, PredTypes
948 tcEqType :: Type -> Type -> Bool
949 tcEqType t1 t2 = isEqual $ cmpType t1 t2
951 tcEqTypes :: [Type] -> [Type] -> Bool
952 tcEqTypes tys1 tys2 = isEqual $ cmpTypes tys1 tys2
954 tcCmpType :: Type -> Type -> Ordering
955 tcCmpType t1 t2 = cmpType t1 t2
957 tcCmpTypes :: [Type] -> [Type] -> Ordering
958 tcCmpTypes tys1 tys2 = cmpTypes tys1 tys2
960 tcEqPred :: PredType -> PredType -> Bool
961 tcEqPred p1 p2 = isEqual $ cmpPred p1 p2
963 tcCmpPred :: PredType -> PredType -> Ordering
964 tcCmpPred p1 p2 = cmpPred p1 p2
966 tcEqTypeX :: RnEnv2 -> Type -> Type -> Bool
967 tcEqTypeX env t1 t2 = isEqual $ cmpTypeX env t1 t2
970 Now here comes the real worker
973 cmpType :: Type -> Type -> Ordering
974 cmpType t1 t2 = cmpTypeX rn_env t1 t2
976 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfType t1 `unionVarSet` tyVarsOfType t2))
978 cmpTypes :: [Type] -> [Type] -> Ordering
979 cmpTypes ts1 ts2 = cmpTypesX rn_env ts1 ts2
981 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfTypes ts1 `unionVarSet` tyVarsOfTypes ts2))
983 cmpPred :: PredType -> PredType -> Ordering
984 cmpPred p1 p2 = cmpPredX rn_env p1 p2
986 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfPred p1 `unionVarSet` tyVarsOfPred p2))
988 cmpTypeX :: RnEnv2 -> Type -> Type -> Ordering -- Main workhorse
989 cmpTypeX env t1 t2 | Just t1' <- tcView t1 = cmpTypeX env t1' t2
990 | Just t2' <- tcView t2 = cmpTypeX env t1 t2'
992 cmpTypeX env (TyVarTy tv1) (TyVarTy tv2) = rnOccL env tv1 `compare` rnOccR env tv2
993 cmpTypeX env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = cmpTypeX (rnBndr2 env tv1 tv2) t1 t2
994 cmpTypeX env (AppTy s1 t1) (AppTy s2 t2) = cmpTypeX env s1 s2 `thenCmp` cmpTypeX env t1 t2
995 cmpTypeX env (FunTy s1 t1) (FunTy s2 t2) = cmpTypeX env s1 s2 `thenCmp` cmpTypeX env t1 t2
996 cmpTypeX env (PredTy p1) (PredTy p2) = cmpPredX env p1 p2
997 cmpTypeX env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` cmpTypesX env tys1 tys2
998 cmpTypeX env t1 (NoteTy _ t2) = cmpTypeX env t1 t2
1000 -- Deal with the rest: TyVarTy < AppTy < FunTy < TyConApp < ForAllTy < PredTy
1001 cmpTypeX env (AppTy _ _) (TyVarTy _) = GT
1003 cmpTypeX env (FunTy _ _) (TyVarTy _) = GT
1004 cmpTypeX env (FunTy _ _) (AppTy _ _) = GT
1006 cmpTypeX env (TyConApp _ _) (TyVarTy _) = GT
1007 cmpTypeX env (TyConApp _ _) (AppTy _ _) = GT
1008 cmpTypeX env (TyConApp _ _) (FunTy _ _) = GT
1010 cmpTypeX env (ForAllTy _ _) (TyVarTy _) = GT
1011 cmpTypeX env (ForAllTy _ _) (AppTy _ _) = GT
1012 cmpTypeX env (ForAllTy _ _) (FunTy _ _) = GT
1013 cmpTypeX env (ForAllTy _ _) (TyConApp _ _) = GT
1015 cmpTypeX env (PredTy _) t2 = GT
1017 cmpTypeX env _ _ = LT
1020 cmpTypesX :: RnEnv2 -> [Type] -> [Type] -> Ordering
1021 cmpTypesX env [] [] = EQ
1022 cmpTypesX env (t1:tys1) (t2:tys2) = cmpTypeX env t1 t2 `thenCmp` cmpTypesX env tys1 tys2
1023 cmpTypesX env [] tys = LT
1024 cmpTypesX env ty [] = GT
1027 cmpPredX :: RnEnv2 -> PredType -> PredType -> Ordering
1028 cmpPredX env (IParam n1 ty1) (IParam n2 ty2) = (n1 `compare` n2) `thenCmp` cmpTypeX env ty1 ty2
1029 -- Compare names only for implicit parameters
1030 -- This comparison is used exclusively (I believe)
1031 -- for the Avails finite map built in TcSimplify
1032 -- If the types differ we keep them distinct so that we see
1033 -- a distinct pair to run improvement on
1034 cmpPredX env (ClassP c1 tys1) (ClassP c2 tys2) = (c1 `compare` c2) `thenCmp` (cmpTypesX env tys1 tys2)
1035 cmpPredX env (EqPred ty1 ty2) (EqPred ty1' ty2') = (cmpTypeX env ty1 ty1') `thenCmp` (cmpTypeX env ty2 ty2')
1037 -- Constructor order: IParam < ClassP < EqPred
1038 cmpPredX env (IParam {}) _ = LT
1039 cmpPredX env (ClassP {}) (IParam {}) = GT
1040 cmpPredX env (ClassP {}) (EqPred {}) = LT
1041 cmpPredX env (EqPred {}) _ = GT
1044 PredTypes are used as a FM key in TcSimplify,
1045 so we take the easy path and make them an instance of Ord
1048 instance Eq PredType where { (==) = tcEqPred }
1049 instance Ord PredType where { compare = tcCmpPred }
1053 %************************************************************************
1057 %************************************************************************
1061 = TvSubst InScopeSet -- The in-scope type variables
1062 TvSubstEnv -- The substitution itself
1063 -- See Note [Apply Once]
1064 -- and Note [Extending the TvSubstEnv]
1066 {- ----------------------------------------------------------
1070 We use TvSubsts to instantiate things, and we might instantiate
1074 So the substition might go [a->b, b->a]. A similar situation arises in Core
1075 when we find a beta redex like
1076 (/\ a /\ b -> e) b a
1077 Then we also end up with a substition that permutes type variables. Other
1078 variations happen to; for example [a -> (a, b)].
1080 ***************************************************
1081 *** So a TvSubst must be applied precisely once ***
1082 ***************************************************
1084 A TvSubst is not idempotent, but, unlike the non-idempotent substitution
1085 we use during unifications, it must not be repeatedly applied.
1087 Note [Extending the TvSubst]
1088 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1089 The following invariant should hold of a TvSubst
1091 The in-scope set is needed *only* to
1092 guide the generation of fresh uniques
1094 In particular, the *kind* of the type variables in
1095 the in-scope set is not relevant
1097 This invariant allows a short-cut when the TvSubstEnv is empty:
1098 if the TvSubstEnv is empty --- i.e. (isEmptyTvSubt subst) holds ---
1099 then (substTy subst ty) does nothing.
1101 For example, consider:
1102 (/\a. /\b:(a~Int). ...b..) Int
1103 We substitute Int for 'a'. The Unique of 'b' does not change, but
1104 nevertheless we add 'b' to the TvSubstEnv, because b's type does change
1106 This invariant has several crucial consequences:
1108 * In substTyVarBndr, we need extend the TvSubstEnv
1109 - if the unique has changed
1110 - or if the kind has changed
1112 * In substTyVar, we do not need to consult the in-scope set;
1113 the TvSubstEnv is enough
1115 * In substTy, substTheta, we can short-circuit when the TvSubstEnv is empty
1118 -------------------------------------------------------------- -}
1121 type TvSubstEnv = TyVarEnv Type
1122 -- A TvSubstEnv is used both inside a TvSubst (with the apply-once
1123 -- invariant discussed in Note [Apply Once]), and also independently
1124 -- in the middle of matching, and unification (see Types.Unify)
1125 -- So you have to look at the context to know if it's idempotent or
1126 -- apply-once or whatever
1127 emptyTvSubstEnv :: TvSubstEnv
1128 emptyTvSubstEnv = emptyVarEnv
1130 composeTvSubst :: InScopeSet -> TvSubstEnv -> TvSubstEnv -> TvSubstEnv
1131 -- (compose env1 env2)(x) is env1(env2(x)); i.e. apply env2 then env1
1132 -- It assumes that both are idempotent
1133 -- Typically, env1 is the refinement to a base substitution env2
1134 composeTvSubst in_scope env1 env2
1135 = env1 `plusVarEnv` mapVarEnv (substTy subst1) env2
1136 -- First apply env1 to the range of env2
1137 -- Then combine the two, making sure that env1 loses if
1138 -- both bind the same variable; that's why env1 is the
1139 -- *left* argument to plusVarEnv, because the right arg wins
1141 subst1 = TvSubst in_scope env1
1143 emptyTvSubst = TvSubst emptyInScopeSet emptyVarEnv
1145 isEmptyTvSubst :: TvSubst -> Bool
1146 -- See Note [Extending the TvSubstEnv]
1147 isEmptyTvSubst (TvSubst _ env) = isEmptyVarEnv env
1149 mkTvSubst :: InScopeSet -> TvSubstEnv -> TvSubst
1152 getTvSubstEnv :: TvSubst -> TvSubstEnv
1153 getTvSubstEnv (TvSubst _ env) = env
1155 getTvInScope :: TvSubst -> InScopeSet
1156 getTvInScope (TvSubst in_scope _) = in_scope
1158 isInScope :: Var -> TvSubst -> Bool
1159 isInScope v (TvSubst in_scope _) = v `elemInScopeSet` in_scope
1161 notElemTvSubst :: TyVar -> TvSubst -> Bool
1162 notElemTvSubst tv (TvSubst _ env) = not (tv `elemVarEnv` env)
1164 setTvSubstEnv :: TvSubst -> TvSubstEnv -> TvSubst
1165 setTvSubstEnv (TvSubst in_scope _) env = TvSubst in_scope env
1167 extendTvInScope :: TvSubst -> [Var] -> TvSubst
1168 extendTvInScope (TvSubst in_scope env) vars = TvSubst (extendInScopeSetList in_scope vars) env
1170 extendTvSubst :: TvSubst -> TyVar -> Type -> TvSubst
1171 extendTvSubst (TvSubst in_scope env) tv ty = TvSubst in_scope (extendVarEnv env tv ty)
1173 extendTvSubstList :: TvSubst -> [TyVar] -> [Type] -> TvSubst
1174 extendTvSubstList (TvSubst in_scope env) tvs tys
1175 = TvSubst in_scope (extendVarEnvList env (tvs `zip` tys))
1177 -- mkOpenTvSubst and zipOpenTvSubst generate the in-scope set from
1178 -- the types given; but it's just a thunk so with a bit of luck
1179 -- it'll never be evaluated
1181 mkOpenTvSubst :: TvSubstEnv -> TvSubst
1182 mkOpenTvSubst env = TvSubst (mkInScopeSet (tyVarsOfTypes (varEnvElts env))) env
1184 zipOpenTvSubst :: [TyVar] -> [Type] -> TvSubst
1185 zipOpenTvSubst tyvars tys
1187 | length tyvars /= length tys
1188 = pprTrace "zipOpenTvSubst" (ppr tyvars $$ ppr tys) emptyTvSubst
1191 = TvSubst (mkInScopeSet (tyVarsOfTypes tys)) (zipTyEnv tyvars tys)
1193 -- mkTopTvSubst is called when doing top-level substitutions.
1194 -- Here we expect that the free vars of the range of the
1195 -- substitution will be empty.
1196 mkTopTvSubst :: [(TyVar, Type)] -> TvSubst
1197 mkTopTvSubst prs = TvSubst emptyInScopeSet (mkVarEnv prs)
1199 zipTopTvSubst :: [TyVar] -> [Type] -> TvSubst
1200 zipTopTvSubst tyvars tys
1202 | length tyvars /= length tys
1203 = pprTrace "zipTopTvSubst" (ppr tyvars $$ ppr tys) emptyTvSubst
1206 = TvSubst emptyInScopeSet (zipTyEnv tyvars tys)
1208 zipTyEnv :: [TyVar] -> [Type] -> TvSubstEnv
1211 | length tyvars /= length tys
1212 = pprTrace "mkTopTvSubst" (ppr tyvars $$ ppr tys) emptyVarEnv
1215 = zip_ty_env tyvars tys emptyVarEnv
1217 -- Later substitutions in the list over-ride earlier ones,
1218 -- but there should be no loops
1219 zip_ty_env [] [] env = env
1220 zip_ty_env (tv:tvs) (ty:tys) env = zip_ty_env tvs tys (extendVarEnv env tv ty)
1221 -- There used to be a special case for when
1223 -- (a not-uncommon case) in which case the substitution was dropped.
1224 -- But the type-tidier changes the print-name of a type variable without
1225 -- changing the unique, and that led to a bug. Why? Pre-tidying, we had
1226 -- a type {Foo t}, where Foo is a one-method class. So Foo is really a newtype.
1227 -- And it happened that t was the type variable of the class. Post-tiding,
1228 -- it got turned into {Foo t2}. The ext-core printer expanded this using
1229 -- sourceTypeRep, but that said "Oh, t == t2" because they have the same unique,
1230 -- and so generated a rep type mentioning t not t2.
1232 -- Simplest fix is to nuke the "optimisation"
1233 zip_ty_env tvs tys env = pprTrace "Var/Type length mismatch: " (ppr tvs $$ ppr tys) env
1234 -- zip_ty_env _ _ env = env
1236 instance Outputable TvSubst where
1237 ppr (TvSubst ins env)
1238 = brackets $ sep[ ptext SLIT("TvSubst"),
1239 nest 2 (ptext SLIT("In scope:") <+> ppr ins),
1240 nest 2 (ptext SLIT("Env:") <+> ppr env) ]
1243 %************************************************************************
1245 Performing type substitutions
1247 %************************************************************************
1250 substTyWith :: [TyVar] -> [Type] -> Type -> Type
1251 substTyWith tvs tys = ASSERT( length tvs == length tys )
1252 substTy (zipOpenTvSubst tvs tys)
1254 substTy :: TvSubst -> Type -> Type
1255 substTy subst ty | isEmptyTvSubst subst = ty
1256 | otherwise = subst_ty subst ty
1258 substTys :: TvSubst -> [Type] -> [Type]
1259 substTys subst tys | isEmptyTvSubst subst = tys
1260 | otherwise = map (subst_ty subst) tys
1262 substTheta :: TvSubst -> ThetaType -> ThetaType
1263 substTheta subst theta
1264 | isEmptyTvSubst subst = theta
1265 | otherwise = map (substPred subst) theta
1267 substPred :: TvSubst -> PredType -> PredType
1268 substPred subst (IParam n ty) = IParam n (subst_ty subst ty)
1269 substPred subst (ClassP clas tys) = ClassP clas (map (subst_ty subst) tys)
1270 substPred subst (EqPred ty1 ty2) = EqPred (subst_ty subst ty1) (subst_ty subst ty2)
1272 deShadowTy :: TyVarSet -> Type -> Type -- Remove any nested binders mentioning tvs
1274 = subst_ty (mkTvSubst in_scope emptyTvSubstEnv) ty
1276 in_scope = mkInScopeSet tvs
1278 subst_ty :: TvSubst -> Type -> Type
1279 -- subst_ty is the main workhorse for type substitution
1281 -- Note that the in_scope set is poked only if we hit a forall
1282 -- so it may often never be fully computed
1286 go (TyVarTy tv) = substTyVar subst tv
1287 go (TyConApp tc tys) = let args = map go tys
1288 in args `seqList` TyConApp tc args
1290 go (PredTy p) = PredTy $! (substPred subst p)
1292 go (NoteTy (FTVNote _) ty2) = go ty2 -- Discard the free tyvar note
1294 go (FunTy arg res) = (FunTy $! (go arg)) $! (go res)
1295 go (AppTy fun arg) = mkAppTy (go fun) $! (go arg)
1296 -- The mkAppTy smart constructor is important
1297 -- we might be replacing (a Int), represented with App
1298 -- by [Int], represented with TyConApp
1299 go (ForAllTy tv ty) = case substTyVarBndr subst tv of
1300 (subst', tv') -> ForAllTy tv' $! (subst_ty subst' ty)
1302 substTyVar :: TvSubst -> TyVar -> Type
1303 substTyVar subst@(TvSubst in_scope env) tv
1304 = case lookupTyVar subst tv of {
1305 Nothing -> TyVarTy tv;
1306 Just ty -> ty -- See Note [Apply Once]
1309 substTyVars :: TvSubst -> [TyVar] -> [Type]
1310 substTyVars subst tvs = map (substTyVar subst) tvs
1312 lookupTyVar :: TvSubst -> TyVar -> Maybe Type
1313 -- See Note [Extending the TvSubst]
1314 lookupTyVar (TvSubst in_scope env) tv = lookupVarEnv env tv
1316 substTyVarBndr :: TvSubst -> TyVar -> (TvSubst, TyVar)
1317 substTyVarBndr subst@(TvSubst in_scope env) old_var
1318 = (TvSubst (in_scope `extendInScopeSet` new_var) new_env, new_var)
1320 is_co_var = isCoVar old_var
1322 new_env | no_change = delVarEnv env old_var
1323 | otherwise = extendVarEnv env old_var (TyVarTy new_var)
1325 no_change = new_var == old_var && not is_co_var
1326 -- no_change means that the new_var is identical in
1327 -- all respects to the old_var (same unique, same kind)
1328 -- See Note [Extending the TvSubst]
1330 -- In that case we don't need to extend the substitution
1331 -- to map old to new. But instead we must zap any
1332 -- current substitution for the variable. For example:
1333 -- (\x.e) with id_subst = [x |-> e']
1334 -- Here we must simply zap the substitution for x
1336 new_var = uniqAway in_scope subst_old_var
1337 -- The uniqAway part makes sure the new variable is not already in scope
1339 subst_old_var -- subst_old_var is old_var with the substitution applied to its kind
1340 -- It's only worth doing the substitution for coercions,
1341 -- becuase only they can have free type variables
1342 | is_co_var = setTyVarKind old_var (substTy subst (tyVarKind old_var))
1343 | otherwise = old_var
1346 ----------------------------------------------------
1351 There's a little subtyping at the kind level:
1360 where * [LiftedTypeKind] means boxed type
1361 # [UnliftedTypeKind] means unboxed type
1362 (#) [UbxTupleKind] means unboxed tuple
1363 ?? [ArgTypeKind] is the lub of *,#
1364 ? [OpenTypeKind] means any type at all
1368 error :: forall a:?. String -> a
1369 (->) :: ?? -> ? -> *
1370 (\(x::t) -> ...) Here t::?? (i.e. not unboxed tuple)
1373 type KindVar = TyVar -- invariant: KindVar will always be a
1374 -- TcTyVar with details MetaTv TauTv ...
1375 -- kind var constructors and functions are in TcType
1377 type SimpleKind = Kind
1382 During kind inference, a kind variable unifies only with
1384 sk ::= * | sk1 -> sk2
1386 data T a = MkT a (T Int#)
1387 fails. We give T the kind (k -> *), and the kind variable k won't unify
1388 with # (the kind of Int#).
1392 When creating a fresh internal type variable, we give it a kind to express
1393 constraints on it. E.g. in (\x->e) we make up a fresh type variable for x,
1396 During unification we only bind an internal type variable to a type
1397 whose kind is lower in the sub-kind hierarchy than the kind of the tyvar.
1399 When unifying two internal type variables, we collect their kind constraints by
1400 finding the GLB of the two. Since the partial order is a tree, they only
1401 have a glb if one is a sub-kind of the other. In that case, we bind the
1402 less-informative one to the more informative one. Neat, eh?
1409 %************************************************************************
1411 Functions over Kinds
1413 %************************************************************************
1416 kindFunResult :: Kind -> Kind
1417 kindFunResult k = funResultTy k
1419 splitKindFunTys :: Kind -> ([Kind],Kind)
1420 splitKindFunTys k = splitFunTys k
1422 splitKindFunTysN :: Int -> Kind -> ([Kind],Kind)
1423 splitKindFunTysN k = splitFunTysN k
1425 isUbxTupleKind, isOpenTypeKind, isArgTypeKind, isUnliftedTypeKind :: Kind -> Bool
1427 isOpenTypeKindCon tc = tyConUnique tc == openTypeKindTyConKey
1429 isOpenTypeKind (TyConApp tc _) = isOpenTypeKindCon tc
1430 isOpenTypeKind other = False
1432 isUbxTupleKindCon tc = tyConUnique tc == ubxTupleKindTyConKey
1434 isUbxTupleKind (TyConApp tc _) = isUbxTupleKindCon tc
1435 isUbxTupleKind other = False
1437 isArgTypeKindCon tc = tyConUnique tc == argTypeKindTyConKey
1439 isArgTypeKind (TyConApp tc _) = isArgTypeKindCon tc
1440 isArgTypeKind other = False
1442 isUnliftedTypeKindCon tc = tyConUnique tc == unliftedTypeKindTyConKey
1444 isUnliftedTypeKind (TyConApp tc _) = isUnliftedTypeKindCon tc
1445 isUnliftedTypeKind other = False
1447 isSubOpenTypeKind :: Kind -> Bool
1448 -- True of any sub-kind of OpenTypeKind (i.e. anything except arrow)
1449 isSubOpenTypeKind (FunTy k1 k2) = ASSERT2 ( isKind k1, text "isSubOpenTypeKind" <+> ppr k1 <+> text "::" <+> ppr (typeKind k1) )
1450 ASSERT2 ( isKind k2, text "isSubOpenTypeKind" <+> ppr k2 <+> text "::" <+> ppr (typeKind k2) )
1452 isSubOpenTypeKind (TyConApp kc []) = ASSERT( isKind (TyConApp kc []) ) True
1453 isSubOpenTypeKind other = ASSERT( isKind other ) False
1454 -- This is a conservative answer
1455 -- It matters in the call to isSubKind in
1456 -- checkExpectedKind.
1458 isSubArgTypeKindCon kc
1459 | isUnliftedTypeKindCon kc = True
1460 | isLiftedTypeKindCon kc = True
1461 | isArgTypeKindCon kc = True
1464 isSubArgTypeKind :: Kind -> Bool
1465 -- True of any sub-kind of ArgTypeKind
1466 isSubArgTypeKind (TyConApp kc []) = isSubArgTypeKindCon kc
1467 isSubArgTypeKind other = False
1469 isSuperKind :: Type -> Bool
1470 isSuperKind (TyConApp (skc) []) = isSuperKindTyCon skc
1471 isSuperKind other = False
1473 isKind :: Kind -> Bool
1474 isKind k = isSuperKind (typeKind k)
1478 isSubKind :: Kind -> Kind -> Bool
1479 -- (k1 `isSubKind` k2) checks that k1 <: k2
1480 isSubKind (TyConApp kc1 []) (TyConApp kc2 []) = kc1 `isSubKindCon` kc2
1481 isSubKind (FunTy a1 r1) (FunTy a2 r2) = (a2 `isSubKind` a1) && (r1 `isSubKind` r2)
1482 isSubKind (PredTy (EqPred ty1 ty2)) (PredTy (EqPred ty1' ty2'))
1483 = ty1 `tcEqType` ty1' && ty2 `tcEqType` ty2'
1484 isSubKind k1 k2 = False
1486 eqKind :: Kind -> Kind -> Bool
1489 isSubKindCon :: TyCon -> TyCon -> Bool
1490 -- (kc1 `isSubKindCon` kc2) checks that kc1 <: kc2
1491 isSubKindCon kc1 kc2
1492 | isLiftedTypeKindCon kc1 && isLiftedTypeKindCon kc2 = True
1493 | isUnliftedTypeKindCon kc1 && isUnliftedTypeKindCon kc2 = True
1494 | isUbxTupleKindCon kc1 && isUbxTupleKindCon kc2 = True
1495 | isOpenTypeKindCon kc2 = True
1496 -- we already know kc1 is not a fun, its a TyCon
1497 | isArgTypeKindCon kc2 && isSubArgTypeKindCon kc1 = True
1500 defaultKind :: Kind -> Kind
1501 -- Used when generalising: default kind '?' and '??' to '*'
1503 -- When we generalise, we make generic type variables whose kind is
1504 -- simple (* or *->* etc). So generic type variables (other than
1505 -- built-in constants like 'error') always have simple kinds. This is important;
1508 -- We want f to get type
1509 -- f :: forall (a::*). a -> Bool
1511 -- f :: forall (a::??). a -> Bool
1512 -- because that would allow a call like (f 3#) as well as (f True),
1513 --and the calling conventions differ. This defaulting is done in TcMType.zonkTcTyVarBndr.
1515 | isSubOpenTypeKind k = liftedTypeKind
1516 | isSubArgTypeKind k = liftedTypeKind
1519 isEqPred :: PredType -> Bool
1520 isEqPred (EqPred _ _) = True
1521 isEqPred other = False