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,
60 splitRecNewType_maybe, newTyConInstRhs,
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 %************************************************************************
637 %************************************************************************
640 splitRecNewType_maybe :: Type -> Maybe Type
641 -- Sometimes we want to look through a recursive newtype, and that's what happens here
642 -- It only strips *one layer* off, so the caller will usually call itself recursively
643 -- Only applied to types of kind *, hence the newtype is always saturated
644 splitRecNewType_maybe ty | Just ty' <- coreView ty = splitRecNewType_maybe ty'
645 splitRecNewType_maybe (TyConApp tc tys)
646 | isClosedNewTyCon tc
647 = ASSERT( tys `lengthIs` tyConArity tc ) -- splitRecNewType_maybe only be applied
648 -- to *types* (of kind *)
649 ASSERT( isRecursiveTyCon tc ) -- Guaranteed by coreView
650 case newTyConRhs tc of
651 (tvs, rep_ty) -> ASSERT( length tvs == length tys )
652 Just (substTyWith tvs tys rep_ty)
654 splitRecNewType_maybe other = Nothing
658 %************************************************************************
660 \subsection{Kinds and free variables}
662 %************************************************************************
664 ---------------------------------------------------------------------
665 Finding the kind of a type
666 ~~~~~~~~~~~~~~~~~~~~~~~~~~
668 typeKind :: Type -> Kind
669 typeKind (TyConApp tycon tys) = ASSERT( not (isCoercionTyCon tycon) )
670 -- We should be looking for the coercion kind,
672 foldr (\_ k -> kindFunResult k) (tyConKind tycon) tys
673 typeKind (NoteTy _ ty) = typeKind ty
674 typeKind (PredTy pred) = predKind pred
675 typeKind (AppTy fun arg) = kindFunResult (typeKind fun)
676 typeKind (ForAllTy tv ty) = typeKind ty
677 typeKind (TyVarTy tyvar) = tyVarKind tyvar
678 typeKind (FunTy arg res)
679 -- Hack alert. The kind of (Int -> Int#) is liftedTypeKind (*),
680 -- not unliftedTypKind (#)
681 -- The only things that can be after a function arrow are
682 -- (a) types (of kind openTypeKind or its sub-kinds)
683 -- (b) kinds (of super-kind TY) (e.g. * -> (* -> *))
684 | isTySuperKind k = k
685 | otherwise = ASSERT( isSubOpenTypeKind k) liftedTypeKind
689 predKind :: PredType -> Kind
690 predKind (EqPred {}) = coSuperKind -- A coercion kind!
691 predKind (ClassP {}) = liftedTypeKind -- Class and implicitPredicates are
692 predKind (IParam {}) = liftedTypeKind -- always represented by lifted types
696 ---------------------------------------------------------------------
697 Free variables of a type
698 ~~~~~~~~~~~~~~~~~~~~~~~~
700 tyVarsOfType :: Type -> TyVarSet
701 -- NB: for type synonyms tyVarsOfType does *not* expand the synonym
702 tyVarsOfType (TyVarTy tv) = unitVarSet tv
703 tyVarsOfType (TyConApp tycon tys) = tyVarsOfTypes tys
704 tyVarsOfType (NoteTy (FTVNote tvs) ty2) = tvs
705 tyVarsOfType (PredTy sty) = tyVarsOfPred sty
706 tyVarsOfType (FunTy arg res) = tyVarsOfType arg `unionVarSet` tyVarsOfType res
707 tyVarsOfType (AppTy fun arg) = tyVarsOfType fun `unionVarSet` tyVarsOfType arg
708 tyVarsOfType (ForAllTy tyvar ty) = delVarSet (tyVarsOfType ty) tyvar
710 tyVarsOfTypes :: [Type] -> TyVarSet
711 tyVarsOfTypes tys = foldr (unionVarSet.tyVarsOfType) emptyVarSet tys
713 tyVarsOfPred :: PredType -> TyVarSet
714 tyVarsOfPred (IParam _ ty) = tyVarsOfType ty
715 tyVarsOfPred (ClassP _ tys) = tyVarsOfTypes tys
716 tyVarsOfPred (EqPred ty1 ty2) = tyVarsOfType ty1 `unionVarSet` tyVarsOfType ty2
718 tyVarsOfTheta :: ThetaType -> TyVarSet
719 tyVarsOfTheta = foldr (unionVarSet . tyVarsOfPred) emptyVarSet
721 -- Add a Note with the free tyvars to the top of the type
722 addFreeTyVars :: Type -> Type
723 addFreeTyVars ty@(NoteTy (FTVNote _) _) = ty
724 addFreeTyVars ty = NoteTy (FTVNote (tyVarsOfType ty)) ty
728 %************************************************************************
730 \subsection{TidyType}
732 %************************************************************************
734 tidyTy tidies up a type for printing in an error message, or in
737 It doesn't change the uniques at all, just the print names.
740 tidyTyVarBndr :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
741 tidyTyVarBndr env@(tidy_env, subst) tyvar
742 = case tidyOccName tidy_env (getOccName name) of
743 (tidy', occ') -> ((tidy', subst'), tyvar'')
745 subst' = extendVarEnv subst tyvar tyvar''
746 tyvar' = setTyVarName tyvar name'
747 name' = tidyNameOcc name occ'
748 -- Don't forget to tidy the kind for coercions!
749 tyvar'' | isCoVar tyvar = setTyVarKind tyvar' kind'
751 kind' = tidyType env (tyVarKind tyvar)
753 name = tyVarName tyvar
755 tidyFreeTyVars :: TidyEnv -> TyVarSet -> TidyEnv
756 -- Add the free tyvars to the env in tidy form,
757 -- so that we can tidy the type they are free in
758 tidyFreeTyVars env tyvars = fst (tidyOpenTyVars env (varSetElems tyvars))
760 tidyOpenTyVars :: TidyEnv -> [TyVar] -> (TidyEnv, [TyVar])
761 tidyOpenTyVars env tyvars = mapAccumL tidyOpenTyVar env tyvars
763 tidyOpenTyVar :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
764 -- Treat a new tyvar as a binder, and give it a fresh tidy name
765 tidyOpenTyVar env@(tidy_env, subst) tyvar
766 = case lookupVarEnv subst tyvar of
767 Just tyvar' -> (env, tyvar') -- Already substituted
768 Nothing -> tidyTyVarBndr env tyvar -- Treat it as a binder
770 tidyType :: TidyEnv -> Type -> Type
771 tidyType env@(tidy_env, subst) ty
774 go (TyVarTy tv) = case lookupVarEnv subst tv of
775 Nothing -> TyVarTy tv
776 Just tv' -> TyVarTy tv'
777 go (TyConApp tycon tys) = let args = map go tys
778 in args `seqList` TyConApp tycon args
779 go (NoteTy note ty) = (NoteTy $! (go_note note)) $! (go ty)
780 go (PredTy sty) = PredTy (tidyPred env sty)
781 go (AppTy fun arg) = (AppTy $! (go fun)) $! (go arg)
782 go (FunTy fun arg) = (FunTy $! (go fun)) $! (go arg)
783 go (ForAllTy tv ty) = ForAllTy tvp $! (tidyType envp ty)
785 (envp, tvp) = tidyTyVarBndr env tv
787 go_note note@(FTVNote ftvs) = note -- No need to tidy the free tyvars
789 tidyTypes env tys = map (tidyType env) tys
791 tidyPred :: TidyEnv -> PredType -> PredType
792 tidyPred env (IParam n ty) = IParam n (tidyType env ty)
793 tidyPred env (ClassP clas tys) = ClassP clas (tidyTypes env tys)
794 tidyPred env (EqPred ty1 ty2) = EqPred (tidyType env ty1) (tidyType env ty2)
798 @tidyOpenType@ grabs the free type variables, tidies them
799 and then uses @tidyType@ to work over the type itself
802 tidyOpenType :: TidyEnv -> Type -> (TidyEnv, Type)
804 = (env', tidyType env' ty)
806 env' = tidyFreeTyVars env (tyVarsOfType ty)
808 tidyOpenTypes :: TidyEnv -> [Type] -> (TidyEnv, [Type])
809 tidyOpenTypes env tys = mapAccumL tidyOpenType env tys
811 tidyTopType :: Type -> Type
812 tidyTopType ty = tidyType emptyTidyEnv ty
817 tidyKind :: TidyEnv -> Kind -> (TidyEnv, Kind)
818 tidyKind env k = tidyOpenType env k
823 %************************************************************************
825 \subsection{Liftedness}
827 %************************************************************************
830 isUnLiftedType :: Type -> Bool
831 -- isUnLiftedType returns True for forall'd unlifted types:
832 -- x :: forall a. Int#
833 -- I found bindings like these were getting floated to the top level.
834 -- They are pretty bogus types, mind you. It would be better never to
837 isUnLiftedType ty | Just ty' <- coreView ty = isUnLiftedType ty'
838 isUnLiftedType (ForAllTy tv ty) = isUnLiftedType ty
839 isUnLiftedType (TyConApp tc _) = isUnLiftedTyCon tc
840 isUnLiftedType other = False
842 isUnboxedTupleType :: Type -> Bool
843 isUnboxedTupleType ty = case splitTyConApp_maybe ty of
844 Just (tc, ty_args) -> isUnboxedTupleTyCon tc
847 -- Should only be applied to *types*; hence the assert
848 isAlgType :: Type -> Bool
849 isAlgType ty = case splitTyConApp_maybe ty of
850 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
855 @isStrictType@ computes whether an argument (or let RHS) should
856 be computed strictly or lazily, based only on its type.
857 Works just like isUnLiftedType, except that it has a special case
858 for dictionaries. Since it takes account of ClassP, you might think
859 this function should be in TcType, but isStrictType is used by DataCon,
860 which is below TcType in the hierarchy, so it's convenient to put it here.
863 isStrictType (PredTy pred) = isStrictPred pred
864 isStrictType ty | Just ty' <- coreView ty = isStrictType ty'
865 isStrictType (ForAllTy tv ty) = isStrictType ty
866 isStrictType (TyConApp tc _) = isUnLiftedTyCon tc
867 isStrictType other = False
869 isStrictPred (ClassP clas _) = opt_DictsStrict && not (isNewTyCon (classTyCon clas))
870 isStrictPred other = False
871 -- We may be strict in dictionary types, but only if it
872 -- has more than one component.
873 -- [Being strict in a single-component dictionary risks
874 -- poking the dictionary component, which is wrong.]
878 isPrimitiveType :: Type -> Bool
879 -- Returns types that are opaque to Haskell.
880 -- Most of these are unlifted, but now that we interact with .NET, we
881 -- may have primtive (foreign-imported) types that are lifted
882 isPrimitiveType ty = case splitTyConApp_maybe ty of
883 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
889 %************************************************************************
891 \subsection{Sequencing on types
893 %************************************************************************
896 seqType :: Type -> ()
897 seqType (TyVarTy tv) = tv `seq` ()
898 seqType (AppTy t1 t2) = seqType t1 `seq` seqType t2
899 seqType (FunTy t1 t2) = seqType t1 `seq` seqType t2
900 seqType (NoteTy note t2) = seqNote note `seq` seqType t2
901 seqType (PredTy p) = seqPred p
902 seqType (TyConApp tc tys) = tc `seq` seqTypes tys
903 seqType (ForAllTy tv ty) = tv `seq` seqType ty
905 seqTypes :: [Type] -> ()
907 seqTypes (ty:tys) = seqType ty `seq` seqTypes tys
909 seqNote :: TyNote -> ()
910 seqNote (FTVNote set) = sizeUniqSet set `seq` ()
912 seqPred :: PredType -> ()
913 seqPred (ClassP c tys) = c `seq` seqTypes tys
914 seqPred (IParam n ty) = n `seq` seqType ty
915 seqPred (EqPred ty1 ty2) = seqType ty1 `seq` seqType ty2
919 %************************************************************************
921 Equality for Core types
922 (We don't use instances so that we know where it happens)
924 %************************************************************************
926 Note that eqType works right even for partial applications of newtypes.
927 See Note [Newtype eta] in TyCon.lhs
930 coreEqType :: Type -> Type -> Bool
934 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfType t1 `unionVarSet` tyVarsOfType t2))
936 eq env (TyVarTy tv1) (TyVarTy tv2) = rnOccL env tv1 == rnOccR env tv2
937 eq env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = eq (rnBndr2 env tv1 tv2) t1 t2
938 eq env (AppTy s1 t1) (AppTy s2 t2) = eq env s1 s2 && eq env t1 t2
939 eq env (FunTy s1 t1) (FunTy s2 t2) = eq env s1 s2 && eq env t1 t2
940 eq env (TyConApp tc1 tys1) (TyConApp tc2 tys2)
941 | tc1 == tc2, all2 (eq env) tys1 tys2 = True
942 -- The lengths should be equal because
943 -- the two types have the same kind
944 -- NB: if the type constructors differ that does not
945 -- necessarily mean that the types aren't equal
946 -- (synonyms, newtypes)
947 -- Even if the type constructors are the same, but the arguments
948 -- differ, the two types could be the same (e.g. if the arg is just
949 -- ignored in the RHS). In both these cases we fall through to an
950 -- attempt to expand one side or the other.
952 -- Now deal with newtypes, synonyms, pred-tys
953 eq env t1 t2 | Just t1' <- coreView t1 = eq env t1' t2
954 | Just t2' <- coreView t2 = eq env t1 t2'
956 -- Fall through case; not equal!
961 %************************************************************************
963 Comparision for source types
964 (We don't use instances so that we know where it happens)
966 %************************************************************************
970 do *not* look through newtypes, PredTypes
973 tcEqType :: Type -> Type -> Bool
974 tcEqType t1 t2 = isEqual $ cmpType t1 t2
976 tcEqTypes :: [Type] -> [Type] -> Bool
977 tcEqTypes tys1 tys2 = isEqual $ cmpTypes tys1 tys2
979 tcCmpType :: Type -> Type -> Ordering
980 tcCmpType t1 t2 = cmpType t1 t2
982 tcCmpTypes :: [Type] -> [Type] -> Ordering
983 tcCmpTypes tys1 tys2 = cmpTypes tys1 tys2
985 tcEqPred :: PredType -> PredType -> Bool
986 tcEqPred p1 p2 = isEqual $ cmpPred p1 p2
988 tcCmpPred :: PredType -> PredType -> Ordering
989 tcCmpPred p1 p2 = cmpPred p1 p2
991 tcEqTypeX :: RnEnv2 -> Type -> Type -> Bool
992 tcEqTypeX env t1 t2 = isEqual $ cmpTypeX env t1 t2
995 Now here comes the real worker
998 cmpType :: Type -> Type -> Ordering
999 cmpType t1 t2 = cmpTypeX rn_env t1 t2
1001 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfType t1 `unionVarSet` tyVarsOfType t2))
1003 cmpTypes :: [Type] -> [Type] -> Ordering
1004 cmpTypes ts1 ts2 = cmpTypesX rn_env ts1 ts2
1006 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfTypes ts1 `unionVarSet` tyVarsOfTypes ts2))
1008 cmpPred :: PredType -> PredType -> Ordering
1009 cmpPred p1 p2 = cmpPredX rn_env p1 p2
1011 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfPred p1 `unionVarSet` tyVarsOfPred p2))
1013 cmpTypeX :: RnEnv2 -> Type -> Type -> Ordering -- Main workhorse
1014 cmpTypeX env t1 t2 | Just t1' <- tcView t1 = cmpTypeX env t1' t2
1015 | Just t2' <- tcView t2 = cmpTypeX env t1 t2'
1017 cmpTypeX env (TyVarTy tv1) (TyVarTy tv2) = rnOccL env tv1 `compare` rnOccR env tv2
1018 cmpTypeX env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = cmpTypeX (rnBndr2 env tv1 tv2) t1 t2
1019 cmpTypeX env (AppTy s1 t1) (AppTy s2 t2) = cmpTypeX env s1 s2 `thenCmp` cmpTypeX env t1 t2
1020 cmpTypeX env (FunTy s1 t1) (FunTy s2 t2) = cmpTypeX env s1 s2 `thenCmp` cmpTypeX env t1 t2
1021 cmpTypeX env (PredTy p1) (PredTy p2) = cmpPredX env p1 p2
1022 cmpTypeX env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` cmpTypesX env tys1 tys2
1023 cmpTypeX env t1 (NoteTy _ t2) = cmpTypeX env t1 t2
1025 -- Deal with the rest: TyVarTy < AppTy < FunTy < TyConApp < ForAllTy < PredTy
1026 cmpTypeX env (AppTy _ _) (TyVarTy _) = GT
1028 cmpTypeX env (FunTy _ _) (TyVarTy _) = GT
1029 cmpTypeX env (FunTy _ _) (AppTy _ _) = GT
1031 cmpTypeX env (TyConApp _ _) (TyVarTy _) = GT
1032 cmpTypeX env (TyConApp _ _) (AppTy _ _) = GT
1033 cmpTypeX env (TyConApp _ _) (FunTy _ _) = GT
1035 cmpTypeX env (ForAllTy _ _) (TyVarTy _) = GT
1036 cmpTypeX env (ForAllTy _ _) (AppTy _ _) = GT
1037 cmpTypeX env (ForAllTy _ _) (FunTy _ _) = GT
1038 cmpTypeX env (ForAllTy _ _) (TyConApp _ _) = GT
1040 cmpTypeX env (PredTy _) t2 = GT
1042 cmpTypeX env _ _ = LT
1045 cmpTypesX :: RnEnv2 -> [Type] -> [Type] -> Ordering
1046 cmpTypesX env [] [] = EQ
1047 cmpTypesX env (t1:tys1) (t2:tys2) = cmpTypeX env t1 t2 `thenCmp` cmpTypesX env tys1 tys2
1048 cmpTypesX env [] tys = LT
1049 cmpTypesX env ty [] = GT
1052 cmpPredX :: RnEnv2 -> PredType -> PredType -> Ordering
1053 cmpPredX env (IParam n1 ty1) (IParam n2 ty2) = (n1 `compare` n2) `thenCmp` cmpTypeX env ty1 ty2
1054 -- Compare names only for implicit parameters
1055 -- This comparison is used exclusively (I believe)
1056 -- for the Avails finite map built in TcSimplify
1057 -- If the types differ we keep them distinct so that we see
1058 -- a distinct pair to run improvement on
1059 cmpPredX env (ClassP c1 tys1) (ClassP c2 tys2) = (c1 `compare` c2) `thenCmp` (cmpTypesX env tys1 tys2)
1060 cmpPredX env (EqPred ty1 ty2) (EqPred ty1' ty2') = (cmpTypeX env ty1 ty1') `thenCmp` (cmpTypeX env ty2 ty2')
1062 -- Constructor order: IParam < ClassP < EqPred
1063 cmpPredX env (IParam {}) _ = LT
1064 cmpPredX env (ClassP {}) (IParam {}) = GT
1065 cmpPredX env (ClassP {}) (EqPred {}) = LT
1066 cmpPredX env (EqPred {}) _ = GT
1069 PredTypes are used as a FM key in TcSimplify,
1070 so we take the easy path and make them an instance of Ord
1073 instance Eq PredType where { (==) = tcEqPred }
1074 instance Ord PredType where { compare = tcCmpPred }
1078 %************************************************************************
1082 %************************************************************************
1086 = TvSubst InScopeSet -- The in-scope type variables
1087 TvSubstEnv -- The substitution itself
1088 -- See Note [Apply Once]
1089 -- and Note [Extending the TvSubstEnv]
1091 {- ----------------------------------------------------------
1095 We use TvSubsts to instantiate things, and we might instantiate
1099 So the substition might go [a->b, b->a]. A similar situation arises in Core
1100 when we find a beta redex like
1101 (/\ a /\ b -> e) b a
1102 Then we also end up with a substition that permutes type variables. Other
1103 variations happen to; for example [a -> (a, b)].
1105 ***************************************************
1106 *** So a TvSubst must be applied precisely once ***
1107 ***************************************************
1109 A TvSubst is not idempotent, but, unlike the non-idempotent substitution
1110 we use during unifications, it must not be repeatedly applied.
1112 Note [Extending the TvSubst]
1113 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1114 The following invariant should hold of a TvSubst
1116 The in-scope set is needed *only* to
1117 guide the generation of fresh uniques
1119 In particular, the *kind* of the type variables in
1120 the in-scope set is not relevant
1122 This invariant allows a short-cut when the TvSubstEnv is empty:
1123 if the TvSubstEnv is empty --- i.e. (isEmptyTvSubt subst) holds ---
1124 then (substTy subst ty) does nothing.
1126 For example, consider:
1127 (/\a. /\b:(a~Int). ...b..) Int
1128 We substitute Int for 'a'. The Unique of 'b' does not change, but
1129 nevertheless we add 'b' to the TvSubstEnv, because b's type does change
1131 This invariant has several crucial consequences:
1133 * In substTyVarBndr, we need extend the TvSubstEnv
1134 - if the unique has changed
1135 - or if the kind has changed
1137 * In substTyVar, we do not need to consult the in-scope set;
1138 the TvSubstEnv is enough
1140 * In substTy, substTheta, we can short-circuit when the TvSubstEnv is empty
1143 -------------------------------------------------------------- -}
1146 type TvSubstEnv = TyVarEnv Type
1147 -- A TvSubstEnv is used both inside a TvSubst (with the apply-once
1148 -- invariant discussed in Note [Apply Once]), and also independently
1149 -- in the middle of matching, and unification (see Types.Unify)
1150 -- So you have to look at the context to know if it's idempotent or
1151 -- apply-once or whatever
1152 emptyTvSubstEnv :: TvSubstEnv
1153 emptyTvSubstEnv = emptyVarEnv
1155 composeTvSubst :: InScopeSet -> TvSubstEnv -> TvSubstEnv -> TvSubstEnv
1156 -- (compose env1 env2)(x) is env1(env2(x)); i.e. apply env2 then env1
1157 -- It assumes that both are idempotent
1158 -- Typically, env1 is the refinement to a base substitution env2
1159 composeTvSubst in_scope env1 env2
1160 = env1 `plusVarEnv` mapVarEnv (substTy subst1) env2
1161 -- First apply env1 to the range of env2
1162 -- Then combine the two, making sure that env1 loses if
1163 -- both bind the same variable; that's why env1 is the
1164 -- *left* argument to plusVarEnv, because the right arg wins
1166 subst1 = TvSubst in_scope env1
1168 emptyTvSubst = TvSubst emptyInScopeSet emptyVarEnv
1170 isEmptyTvSubst :: TvSubst -> Bool
1171 -- See Note [Extending the TvSubstEnv]
1172 isEmptyTvSubst (TvSubst _ env) = isEmptyVarEnv env
1174 mkTvSubst :: InScopeSet -> TvSubstEnv -> TvSubst
1177 getTvSubstEnv :: TvSubst -> TvSubstEnv
1178 getTvSubstEnv (TvSubst _ env) = env
1180 getTvInScope :: TvSubst -> InScopeSet
1181 getTvInScope (TvSubst in_scope _) = in_scope
1183 isInScope :: Var -> TvSubst -> Bool
1184 isInScope v (TvSubst in_scope _) = v `elemInScopeSet` in_scope
1186 notElemTvSubst :: TyVar -> TvSubst -> Bool
1187 notElemTvSubst tv (TvSubst _ env) = not (tv `elemVarEnv` env)
1189 setTvSubstEnv :: TvSubst -> TvSubstEnv -> TvSubst
1190 setTvSubstEnv (TvSubst in_scope _) env = TvSubst in_scope env
1192 extendTvInScope :: TvSubst -> [Var] -> TvSubst
1193 extendTvInScope (TvSubst in_scope env) vars = TvSubst (extendInScopeSetList in_scope vars) env
1195 extendTvSubst :: TvSubst -> TyVar -> Type -> TvSubst
1196 extendTvSubst (TvSubst in_scope env) tv ty = TvSubst in_scope (extendVarEnv env tv ty)
1198 extendTvSubstList :: TvSubst -> [TyVar] -> [Type] -> TvSubst
1199 extendTvSubstList (TvSubst in_scope env) tvs tys
1200 = TvSubst in_scope (extendVarEnvList env (tvs `zip` tys))
1202 -- mkOpenTvSubst and zipOpenTvSubst generate the in-scope set from
1203 -- the types given; but it's just a thunk so with a bit of luck
1204 -- it'll never be evaluated
1206 mkOpenTvSubst :: TvSubstEnv -> TvSubst
1207 mkOpenTvSubst env = TvSubst (mkInScopeSet (tyVarsOfTypes (varEnvElts env))) env
1209 zipOpenTvSubst :: [TyVar] -> [Type] -> TvSubst
1210 zipOpenTvSubst tyvars tys
1212 | length tyvars /= length tys
1213 = pprTrace "zipOpenTvSubst" (ppr tyvars $$ ppr tys) emptyTvSubst
1216 = TvSubst (mkInScopeSet (tyVarsOfTypes tys)) (zipTyEnv tyvars tys)
1218 -- mkTopTvSubst is called when doing top-level substitutions.
1219 -- Here we expect that the free vars of the range of the
1220 -- substitution will be empty.
1221 mkTopTvSubst :: [(TyVar, Type)] -> TvSubst
1222 mkTopTvSubst prs = TvSubst emptyInScopeSet (mkVarEnv prs)
1224 zipTopTvSubst :: [TyVar] -> [Type] -> TvSubst
1225 zipTopTvSubst tyvars tys
1227 | length tyvars /= length tys
1228 = pprTrace "zipTopTvSubst" (ppr tyvars $$ ppr tys) emptyTvSubst
1231 = TvSubst emptyInScopeSet (zipTyEnv tyvars tys)
1233 zipTyEnv :: [TyVar] -> [Type] -> TvSubstEnv
1236 | length tyvars /= length tys
1237 = pprTrace "mkTopTvSubst" (ppr tyvars $$ ppr tys) emptyVarEnv
1240 = zip_ty_env tyvars tys emptyVarEnv
1242 -- Later substitutions in the list over-ride earlier ones,
1243 -- but there should be no loops
1244 zip_ty_env [] [] env = env
1245 zip_ty_env (tv:tvs) (ty:tys) env = zip_ty_env tvs tys (extendVarEnv env tv ty)
1246 -- There used to be a special case for when
1248 -- (a not-uncommon case) in which case the substitution was dropped.
1249 -- But the type-tidier changes the print-name of a type variable without
1250 -- changing the unique, and that led to a bug. Why? Pre-tidying, we had
1251 -- a type {Foo t}, where Foo is a one-method class. So Foo is really a newtype.
1252 -- And it happened that t was the type variable of the class. Post-tiding,
1253 -- it got turned into {Foo t2}. The ext-core printer expanded this using
1254 -- sourceTypeRep, but that said "Oh, t == t2" because they have the same unique,
1255 -- and so generated a rep type mentioning t not t2.
1257 -- Simplest fix is to nuke the "optimisation"
1258 zip_ty_env tvs tys env = pprTrace "Var/Type length mismatch: " (ppr tvs $$ ppr tys) env
1259 -- zip_ty_env _ _ env = env
1261 instance Outputable TvSubst where
1262 ppr (TvSubst ins env)
1263 = brackets $ sep[ ptext SLIT("TvSubst"),
1264 nest 2 (ptext SLIT("In scope:") <+> ppr ins),
1265 nest 2 (ptext SLIT("Env:") <+> ppr env) ]
1268 %************************************************************************
1270 Performing type substitutions
1272 %************************************************************************
1275 substTyWith :: [TyVar] -> [Type] -> Type -> Type
1276 substTyWith tvs tys = ASSERT( length tvs == length tys )
1277 substTy (zipOpenTvSubst tvs tys)
1279 substTy :: TvSubst -> Type -> Type
1280 substTy subst ty | isEmptyTvSubst subst = ty
1281 | otherwise = subst_ty subst ty
1283 substTys :: TvSubst -> [Type] -> [Type]
1284 substTys subst tys | isEmptyTvSubst subst = tys
1285 | otherwise = map (subst_ty subst) tys
1287 substTheta :: TvSubst -> ThetaType -> ThetaType
1288 substTheta subst theta
1289 | isEmptyTvSubst subst = theta
1290 | otherwise = map (substPred subst) theta
1292 substPred :: TvSubst -> PredType -> PredType
1293 substPred subst (IParam n ty) = IParam n (subst_ty subst ty)
1294 substPred subst (ClassP clas tys) = ClassP clas (map (subst_ty subst) tys)
1295 substPred subst (EqPred ty1 ty2) = EqPred (subst_ty subst ty1) (subst_ty subst ty2)
1297 deShadowTy :: TyVarSet -> Type -> Type -- Remove any nested binders mentioning tvs
1299 = subst_ty (mkTvSubst in_scope emptyTvSubstEnv) ty
1301 in_scope = mkInScopeSet tvs
1303 subst_ty :: TvSubst -> Type -> Type
1304 -- subst_ty is the main workhorse for type substitution
1306 -- Note that the in_scope set is poked only if we hit a forall
1307 -- so it may often never be fully computed
1311 go (TyVarTy tv) = substTyVar subst tv
1312 go (TyConApp tc tys) = let args = map go tys
1313 in args `seqList` TyConApp tc args
1315 go (PredTy p) = PredTy $! (substPred subst p)
1317 go (NoteTy (FTVNote _) ty2) = go ty2 -- Discard the free tyvar note
1319 go (FunTy arg res) = (FunTy $! (go arg)) $! (go res)
1320 go (AppTy fun arg) = mkAppTy (go fun) $! (go arg)
1321 -- The mkAppTy smart constructor is important
1322 -- we might be replacing (a Int), represented with App
1323 -- by [Int], represented with TyConApp
1324 go (ForAllTy tv ty) = case substTyVarBndr subst tv of
1325 (subst', tv') -> ForAllTy tv' $! (subst_ty subst' ty)
1327 substTyVar :: TvSubst -> TyVar -> Type
1328 substTyVar subst@(TvSubst in_scope env) tv
1329 = case lookupTyVar subst tv of {
1330 Nothing -> TyVarTy tv;
1331 Just ty -> ty -- See Note [Apply Once]
1334 substTyVars :: TvSubst -> [TyVar] -> [Type]
1335 substTyVars subst tvs = map (substTyVar subst) tvs
1337 lookupTyVar :: TvSubst -> TyVar -> Maybe Type
1338 -- See Note [Extending the TvSubst]
1339 lookupTyVar (TvSubst in_scope env) tv = lookupVarEnv env tv
1341 substTyVarBndr :: TvSubst -> TyVar -> (TvSubst, TyVar)
1342 substTyVarBndr subst@(TvSubst in_scope env) old_var
1343 = (TvSubst (in_scope `extendInScopeSet` new_var) new_env, new_var)
1345 is_co_var = isCoVar old_var
1347 new_env | no_change = delVarEnv env old_var
1348 | otherwise = extendVarEnv env old_var (TyVarTy new_var)
1350 no_change = new_var == old_var && not is_co_var
1351 -- no_change means that the new_var is identical in
1352 -- all respects to the old_var (same unique, same kind)
1353 -- See Note [Extending the TvSubst]
1355 -- In that case we don't need to extend the substitution
1356 -- to map old to new. But instead we must zap any
1357 -- current substitution for the variable. For example:
1358 -- (\x.e) with id_subst = [x |-> e']
1359 -- Here we must simply zap the substitution for x
1361 new_var = uniqAway in_scope subst_old_var
1362 -- The uniqAway part makes sure the new variable is not already in scope
1364 subst_old_var -- subst_old_var is old_var with the substitution applied to its kind
1365 -- It's only worth doing the substitution for coercions,
1366 -- becuase only they can have free type variables
1367 | is_co_var = setTyVarKind old_var (substTy subst (tyVarKind old_var))
1368 | otherwise = old_var
1371 ----------------------------------------------------
1376 There's a little subtyping at the kind level:
1385 where * [LiftedTypeKind] means boxed type
1386 # [UnliftedTypeKind] means unboxed type
1387 (#) [UbxTupleKind] means unboxed tuple
1388 ?? [ArgTypeKind] is the lub of *,#
1389 ? [OpenTypeKind] means any type at all
1393 error :: forall a:?. String -> a
1394 (->) :: ?? -> ? -> *
1395 (\(x::t) -> ...) Here t::?? (i.e. not unboxed tuple)
1398 type KindVar = TyVar -- invariant: KindVar will always be a
1399 -- TcTyVar with details MetaTv TauTv ...
1400 -- kind var constructors and functions are in TcType
1402 type SimpleKind = Kind
1407 During kind inference, a kind variable unifies only with
1409 sk ::= * | sk1 -> sk2
1411 data T a = MkT a (T Int#)
1412 fails. We give T the kind (k -> *), and the kind variable k won't unify
1413 with # (the kind of Int#).
1417 When creating a fresh internal type variable, we give it a kind to express
1418 constraints on it. E.g. in (\x->e) we make up a fresh type variable for x,
1421 During unification we only bind an internal type variable to a type
1422 whose kind is lower in the sub-kind hierarchy than the kind of the tyvar.
1424 When unifying two internal type variables, we collect their kind constraints by
1425 finding the GLB of the two. Since the partial order is a tree, they only
1426 have a glb if one is a sub-kind of the other. In that case, we bind the
1427 less-informative one to the more informative one. Neat, eh?
1434 %************************************************************************
1436 Functions over Kinds
1438 %************************************************************************
1441 kindFunResult :: Kind -> Kind
1442 kindFunResult k = funResultTy k
1444 splitKindFunTys :: Kind -> ([Kind],Kind)
1445 splitKindFunTys k = splitFunTys k
1447 splitKindFunTysN :: Int -> Kind -> ([Kind],Kind)
1448 splitKindFunTysN k = splitFunTysN k
1450 isUbxTupleKind, isOpenTypeKind, isArgTypeKind, isUnliftedTypeKind :: Kind -> Bool
1452 isOpenTypeKindCon tc = tyConUnique tc == openTypeKindTyConKey
1454 isOpenTypeKind (TyConApp tc _) = isOpenTypeKindCon tc
1455 isOpenTypeKind other = False
1457 isUbxTupleKindCon tc = tyConUnique tc == ubxTupleKindTyConKey
1459 isUbxTupleKind (TyConApp tc _) = isUbxTupleKindCon tc
1460 isUbxTupleKind other = False
1462 isArgTypeKindCon tc = tyConUnique tc == argTypeKindTyConKey
1464 isArgTypeKind (TyConApp tc _) = isArgTypeKindCon tc
1465 isArgTypeKind other = False
1467 isUnliftedTypeKindCon tc = tyConUnique tc == unliftedTypeKindTyConKey
1469 isUnliftedTypeKind (TyConApp tc _) = isUnliftedTypeKindCon tc
1470 isUnliftedTypeKind other = False
1472 isSubOpenTypeKind :: Kind -> Bool
1473 -- True of any sub-kind of OpenTypeKind (i.e. anything except arrow)
1474 isSubOpenTypeKind (FunTy k1 k2) = ASSERT2 ( isKind k1, text "isSubOpenTypeKind" <+> ppr k1 <+> text "::" <+> ppr (typeKind k1) )
1475 ASSERT2 ( isKind k2, text "isSubOpenTypeKind" <+> ppr k2 <+> text "::" <+> ppr (typeKind k2) )
1477 isSubOpenTypeKind (TyConApp kc []) = ASSERT( isKind (TyConApp kc []) ) True
1478 isSubOpenTypeKind other = ASSERT( isKind other ) False
1479 -- This is a conservative answer
1480 -- It matters in the call to isSubKind in
1481 -- checkExpectedKind.
1483 isSubArgTypeKindCon kc
1484 | isUnliftedTypeKindCon kc = True
1485 | isLiftedTypeKindCon kc = True
1486 | isArgTypeKindCon kc = True
1489 isSubArgTypeKind :: Kind -> Bool
1490 -- True of any sub-kind of ArgTypeKind
1491 isSubArgTypeKind (TyConApp kc []) = isSubArgTypeKindCon kc
1492 isSubArgTypeKind other = False
1494 isSuperKind :: Type -> Bool
1495 isSuperKind (TyConApp (skc) []) = isSuperKindTyCon skc
1496 isSuperKind other = False
1498 isKind :: Kind -> Bool
1499 isKind k = isSuperKind (typeKind k)
1503 isSubKind :: Kind -> Kind -> Bool
1504 -- (k1 `isSubKind` k2) checks that k1 <: k2
1505 isSubKind (TyConApp kc1 []) (TyConApp kc2 []) = kc1 `isSubKindCon` kc2
1506 isSubKind (FunTy a1 r1) (FunTy a2 r2) = (a2 `isSubKind` a1) && (r1 `isSubKind` r2)
1507 isSubKind (PredTy (EqPred ty1 ty2)) (PredTy (EqPred ty1' ty2'))
1508 = ty1 `tcEqType` ty1' && ty2 `tcEqType` ty2'
1509 isSubKind k1 k2 = False
1511 eqKind :: Kind -> Kind -> Bool
1514 isSubKindCon :: TyCon -> TyCon -> Bool
1515 -- (kc1 `isSubKindCon` kc2) checks that kc1 <: kc2
1516 isSubKindCon kc1 kc2
1517 | isLiftedTypeKindCon kc1 && isLiftedTypeKindCon kc2 = True
1518 | isUnliftedTypeKindCon kc1 && isUnliftedTypeKindCon kc2 = True
1519 | isUbxTupleKindCon kc1 && isUbxTupleKindCon kc2 = True
1520 | isOpenTypeKindCon kc2 = True
1521 -- we already know kc1 is not a fun, its a TyCon
1522 | isArgTypeKindCon kc2 && isSubArgTypeKindCon kc1 = True
1525 defaultKind :: Kind -> Kind
1526 -- Used when generalising: default kind '?' and '??' to '*'
1528 -- When we generalise, we make generic type variables whose kind is
1529 -- simple (* or *->* etc). So generic type variables (other than
1530 -- built-in constants like 'error') always have simple kinds. This is important;
1533 -- We want f to get type
1534 -- f :: forall (a::*). a -> Bool
1536 -- f :: forall (a::??). a -> Bool
1537 -- because that would allow a call like (f 3#) as well as (f True),
1538 --and the calling conventions differ. This defaulting is done in TcMType.zonkTcTyVarBndr.
1540 | isSubOpenTypeKind k = liftedTypeKind
1541 | isSubArgTypeKind k = liftedTypeKind
1544 isEqPred :: PredType -> Bool
1545 isEqPred (EqPred _ _) = True
1546 isEqPred other = False