2 % (c) The GRASP/AQUA Project, Glasgow University, 1998
4 \section[Type]{Type - public interface}
9 -- re-exports from TypeRep
10 TyThing(..), Type, PredType(..), ThetaType,
14 Kind, SimpleKind, KindVar,
15 kindFunResult, splitKindFunTys, splitKindFunTysN,
17 liftedTypeKindTyCon, openTypeKindTyCon, unliftedTypeKindTyCon,
18 argTypeKindTyCon, ubxTupleKindTyCon,
20 liftedTypeKind, unliftedTypeKind, openTypeKind,
21 argTypeKind, ubxTupleKind,
23 tySuperKind, coSuperKind,
25 isLiftedTypeKind, isUnliftedTypeKind, isOpenTypeKind,
26 isUbxTupleKind, isArgTypeKind, isKind, isTySuperKind,
27 isCoSuperKind, isSuperKind, isCoercionKind, isEqPred,
28 mkArrowKind, mkArrowKinds,
30 isSubArgTypeKind, isSubOpenTypeKind, isSubKind, defaultKind, eqKind,
33 -- Re-exports from TyCon
36 mkTyVarTy, mkTyVarTys, getTyVar, getTyVar_maybe, isTyVarTy,
38 mkAppTy, mkAppTys, splitAppTy, splitAppTys,
39 splitAppTy_maybe, repSplitAppTy_maybe,
41 mkFunTy, mkFunTys, splitFunTy, splitFunTy_maybe,
42 splitFunTys, splitFunTysN,
43 funResultTy, funArgTy, zipFunTys, isFunTy,
45 mkTyConApp, mkTyConTy,
46 tyConAppTyCon, tyConAppArgs,
47 splitTyConApp_maybe, splitTyConApp,
48 splitNewTyConApp_maybe, splitNewTyConApp,
50 repType, typePrimRep, coreView, tcView, kindView,
52 mkForAllTy, mkForAllTys, splitForAllTy_maybe, splitForAllTys,
53 applyTy, applyTys, isForAllTy, dropForAlls,
56 predTypeRep, mkPredTy, mkPredTys,
59 splitRecNewType_maybe, newTyConInstRhs,
62 isUnLiftedType, isUnboxedTupleType, isAlgType, isPrimitiveType,
63 isStrictType, isStrictPred,
66 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
67 typeKind, addFreeTyVars,
69 -- Tidying up for printing
71 tidyOpenType, tidyOpenTypes,
72 tidyTyVarBndr, tidyFreeTyVars,
73 tidyOpenTyVar, tidyOpenTyVars,
74 tidyTopType, tidyPred,
78 coreEqType, tcEqType, tcEqTypes, tcCmpType, tcCmpTypes,
79 tcEqPred, tcCmpPred, tcEqTypeX,
85 TvSubstEnv, emptyTvSubstEnv, -- Representation widely visible
86 TvSubst(..), emptyTvSubst, -- Representation visible to a few friends
87 mkTvSubst, mkOpenTvSubst, zipOpenTvSubst, zipTopTvSubst, mkTopTvSubst, notElemTvSubst,
88 getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope,
89 extendTvSubst, extendTvSubstList, isInScope, composeTvSubst, zipTyEnv,
91 -- Performing substitution on types
92 substTy, substTys, substTyWith, substTheta,
93 substPred, substTyVar, substTyVarBndr, deShadowTy, lookupTyVar,
96 pprType, pprParendType, pprTyThingCategory,
97 pprPred, pprTheta, pprThetaArrow, pprClassPred, pprKind, pprParendKind
100 #include "HsVersions.h"
102 -- We import the representation and primitive functions from TypeRep.
103 -- Many things are reexported, but not the representation!
108 import Var ( Var, TyVar, tyVarKind, tyVarName,
109 setTyVarName, setTyVarKind, mkWildCoVar )
113 import OccName ( tidyOccName )
114 import Name ( NamedThing(..), tidyNameOcc )
115 import Class ( Class, classTyCon )
116 import PrelNames( openTypeKindTyConKey, unliftedTypeKindTyConKey,
117 ubxTupleKindTyConKey, argTypeKindTyConKey )
118 import TyCon ( TyCon, isRecursiveTyCon, isPrimTyCon,
119 isUnboxedTupleTyCon, isUnLiftedTyCon,
120 isFunTyCon, isNewTyCon, isOpenTyCon, newTyConRep,
122 isAlgTyCon, tyConArity, isSuperKindTyCon,
123 tcExpandTyCon_maybe, coreExpandTyCon_maybe,
124 tyConKind, PrimRep(..), tyConPrimRep, tyConUnique,
125 isCoercionTyCon_maybe, isCoercionTyCon
129 import StaticFlags ( opt_DictsStrict )
130 import Util ( mapAccumL, seqList, lengthIs, snocView, thenCmp, isEqual, all2 )
132 import UniqSet ( sizeUniqSet ) -- Should come via VarSet
133 import Maybe ( isJust )
137 %************************************************************************
141 %************************************************************************
143 In Core, we "look through" non-recursive newtypes and PredTypes.
146 {-# INLINE coreView #-}
147 coreView :: Type -> Maybe Type
148 -- Strips off the *top layer only* of a type to give
149 -- its underlying representation type.
150 -- Returns Nothing if there is nothing to look through.
152 -- In the case of newtypes, it returns
153 -- *either* a vanilla TyConApp (recursive newtype, or non-saturated)
154 -- *or* the newtype representation (otherwise), meaning the
155 -- type written in the RHS of the newtype decl,
156 -- which may itself be a newtype
158 -- Example: newtype R = MkR S
160 -- newtype T = MkT (T -> T)
161 -- expandNewTcApp on R gives Just S
163 -- on T gives Nothing (no expansion)
165 -- By being non-recursive and inlined, this case analysis gets efficiently
166 -- joined onto the case analysis that the caller is already doing
167 coreView (NoteTy _ ty) = Just ty
169 | isEqPred p = Nothing
170 | otherwise = Just (predTypeRep p)
171 coreView (TyConApp tc tys) | Just (tenv, rhs, tys') <- coreExpandTyCon_maybe tc tys
172 = Just (mkAppTys (substTy (mkTopTvSubst tenv) rhs) tys')
173 -- Its important to use mkAppTys, rather than (foldl AppTy),
174 -- because the function part might well return a
175 -- partially-applied type constructor; indeed, usually will!
176 coreView ty = Nothing
180 -----------------------------------------------
181 {-# INLINE tcView #-}
182 tcView :: Type -> Maybe Type
183 -- Same, but for the type checker, which just looks through synonyms
184 tcView (NoteTy _ ty) = Just ty
185 tcView (TyConApp tc tys) | Just (tenv, rhs, tys') <- tcExpandTyCon_maybe tc tys
186 = Just (mkAppTys (substTy (mkTopTvSubst tenv) rhs) tys')
189 -----------------------------------------------
190 {-# INLINE kindView #-}
191 kindView :: Kind -> Maybe Kind
192 -- C.f. coreView, tcView
193 -- For the moment, we don't even handle synonyms in kinds
194 kindView (NoteTy _ k) = Just k
195 kindView other = Nothing
199 %************************************************************************
201 \subsection{Constructor-specific functions}
203 %************************************************************************
206 ---------------------------------------------------------------------
210 mkTyVarTy :: TyVar -> Type
213 mkTyVarTys :: [TyVar] -> [Type]
214 mkTyVarTys = map mkTyVarTy -- a common use of mkTyVarTy
216 getTyVar :: String -> Type -> TyVar
217 getTyVar msg ty = case getTyVar_maybe ty of
219 Nothing -> panic ("getTyVar: " ++ msg)
221 isTyVarTy :: Type -> Bool
222 isTyVarTy ty = isJust (getTyVar_maybe ty)
224 getTyVar_maybe :: Type -> Maybe TyVar
225 getTyVar_maybe ty | Just ty' <- coreView ty = getTyVar_maybe ty'
226 getTyVar_maybe (TyVarTy tv) = Just tv
227 getTyVar_maybe other = Nothing
232 ---------------------------------------------------------------------
235 We need to be pretty careful with AppTy to make sure we obey the
236 invariant that a TyConApp is always visibly so. mkAppTy maintains the
240 mkAppTy orig_ty1 orig_ty2
243 mk_app (NoteTy _ ty1) = mk_app ty1
244 mk_app (TyConApp tc tys) = mkTyConApp tc (tys ++ [orig_ty2])
245 mk_app ty1 = AppTy orig_ty1 orig_ty2
246 -- Note that the TyConApp could be an
247 -- under-saturated type synonym. GHC allows that; e.g.
248 -- type Foo k = k a -> k a
250 -- foo :: Foo Id -> Foo Id
252 -- Here Id is partially applied in the type sig for Foo,
253 -- but once the type synonyms are expanded all is well
255 mkAppTys :: Type -> [Type] -> Type
256 mkAppTys orig_ty1 [] = orig_ty1
257 -- This check for an empty list of type arguments
258 -- avoids the needless loss of a type synonym constructor.
259 -- For example: mkAppTys Rational []
260 -- returns to (Ratio Integer), which has needlessly lost
261 -- the Rational part.
262 mkAppTys orig_ty1 orig_tys2
265 mk_app (NoteTy _ ty1) = mk_app ty1
266 mk_app (TyConApp tc tys) = mkTyConApp tc (tys ++ orig_tys2)
267 -- mkTyConApp: see notes with mkAppTy
268 mk_app ty1 = foldl AppTy orig_ty1 orig_tys2
271 splitAppTy_maybe :: Type -> Maybe (Type, Type)
272 splitAppTy_maybe ty | Just ty' <- coreView ty
273 = splitAppTy_maybe ty'
274 splitAppTy_maybe ty = repSplitAppTy_maybe ty
277 repSplitAppTy_maybe :: Type -> Maybe (Type,Type)
278 -- Does the AppTy split, but assumes that any view stuff is already done
279 repSplitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [ty1], ty2)
280 repSplitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2)
281 repSplitAppTy_maybe (TyConApp tc tys) = case snocView tys of
282 Just (tys', ty') -> Just (TyConApp tc tys', ty')
284 repSplitAppTy_maybe other = Nothing
286 splitAppTy :: Type -> (Type, Type)
287 splitAppTy ty = case splitAppTy_maybe ty of
289 Nothing -> panic "splitAppTy"
292 splitAppTys :: Type -> (Type, [Type])
293 splitAppTys ty = split ty ty []
295 split orig_ty ty args | Just ty' <- coreView ty = split orig_ty ty' args
296 split orig_ty (AppTy ty arg) args = split ty ty (arg:args)
297 split orig_ty (TyConApp tc tc_args) args = (TyConApp tc [], tc_args ++ args)
298 split orig_ty (FunTy ty1 ty2) args = ASSERT( null args )
299 (TyConApp funTyCon [], [ty1,ty2])
300 split orig_ty ty args = (orig_ty, args)
305 ---------------------------------------------------------------------
310 mkFunTy :: Type -> Type -> Type
311 mkFunTy (PredTy (EqPred ty1 ty2)) res = mkForAllTy (mkWildCoVar (PredTy (EqPred ty1 ty2))) res
312 mkFunTy arg res = FunTy arg res
314 mkFunTys :: [Type] -> Type -> Type
315 mkFunTys tys ty = foldr mkFunTy ty tys
317 isFunTy :: Type -> Bool
318 isFunTy ty = isJust (splitFunTy_maybe ty)
320 splitFunTy :: Type -> (Type, Type)
321 splitFunTy ty | Just ty' <- coreView ty = splitFunTy ty'
322 splitFunTy (FunTy arg res) = (arg, res)
323 splitFunTy other = pprPanic "splitFunTy" (ppr other)
325 splitFunTy_maybe :: Type -> Maybe (Type, Type)
326 splitFunTy_maybe ty | Just ty' <- coreView ty = splitFunTy_maybe ty'
327 splitFunTy_maybe (FunTy arg res) = Just (arg, res)
328 splitFunTy_maybe other = Nothing
330 splitFunTys :: Type -> ([Type], Type)
331 splitFunTys ty = split [] ty ty
333 split args orig_ty ty | Just ty' <- coreView ty = split args orig_ty ty'
334 split args orig_ty (FunTy arg res) = split (arg:args) res res
335 split args orig_ty ty = (reverse args, orig_ty)
337 splitFunTysN :: Int -> Type -> ([Type], Type)
338 -- Split off exactly n arg tys
339 splitFunTysN 0 ty = ([], ty)
340 splitFunTysN n ty = case splitFunTy ty of { (arg, res) ->
341 case splitFunTysN (n-1) res of { (args, res) ->
344 zipFunTys :: Outputable a => [a] -> Type -> ([(a,Type)], Type)
345 zipFunTys orig_xs orig_ty = split [] orig_xs orig_ty orig_ty
347 split acc [] nty ty = (reverse acc, nty)
349 | Just ty' <- coreView ty = split acc xs nty ty'
350 split acc (x:xs) nty (FunTy arg res) = split ((x,arg):acc) xs res res
351 split acc (x:xs) nty ty = pprPanic "zipFunTys" (ppr orig_xs <+> ppr orig_ty)
353 funResultTy :: Type -> Type
354 funResultTy ty | Just ty' <- coreView ty = funResultTy ty'
355 funResultTy (FunTy arg res) = res
356 funResultTy ty = pprPanic "funResultTy" (ppr ty)
358 funArgTy :: Type -> Type
359 funArgTy ty | Just ty' <- coreView ty = funArgTy ty'
360 funArgTy (FunTy arg res) = arg
361 funArgTy ty = pprPanic "funArgTy" (ppr ty)
365 ---------------------------------------------------------------------
368 @mkTyConApp@ is a key function, because it builds a TyConApp, FunTy or PredTy,
372 mkTyConApp :: TyCon -> [Type] -> Type
374 | isFunTyCon tycon, [ty1,ty2] <- tys
380 mkTyConTy :: TyCon -> Type
381 mkTyConTy tycon = mkTyConApp tycon []
383 -- splitTyConApp "looks through" synonyms, because they don't
384 -- mean a distinct type, but all other type-constructor applications
385 -- including functions are returned as Just ..
387 tyConAppTyCon :: Type -> TyCon
388 tyConAppTyCon ty = fst (splitTyConApp ty)
390 tyConAppArgs :: Type -> [Type]
391 tyConAppArgs ty = snd (splitTyConApp ty)
393 splitTyConApp :: Type -> (TyCon, [Type])
394 splitTyConApp ty = case splitTyConApp_maybe ty of
396 Nothing -> pprPanic "splitTyConApp" (ppr ty)
398 splitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
399 splitTyConApp_maybe ty | Just ty' <- coreView ty = splitTyConApp_maybe ty'
400 splitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
401 splitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
402 splitTyConApp_maybe other = Nothing
404 -- Sometimes we do NOT want to look throught a newtype. When case matching
405 -- on a newtype we want a convenient way to access the arguments of a newty
406 -- constructor so as to properly form a coercion.
407 splitNewTyConApp :: Type -> (TyCon, [Type])
408 splitNewTyConApp ty = case splitNewTyConApp_maybe ty of
410 Nothing -> pprPanic "splitNewTyConApp" (ppr ty)
411 splitNewTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
412 splitNewTyConApp_maybe ty | Just ty' <- tcView ty = splitNewTyConApp_maybe ty'
413 splitNewTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
414 splitNewTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
415 splitNewTyConApp_maybe other = Nothing
417 -- get instantiated newtype rhs, the arguments had better saturate
419 newTyConInstRhs :: TyCon -> [Type] -> Type
420 newTyConInstRhs tycon tys =
421 let (tvs, ty) = newTyConRhs tycon in substTyWith tvs tys ty
426 ---------------------------------------------------------------------
430 Notes on type synonyms
431 ~~~~~~~~~~~~~~~~~~~~~~
432 The various "split" functions (splitFunTy, splitRhoTy, splitForAllTy) try
433 to return type synonyms whereever possible. Thus
438 splitFunTys (a -> Foo a) = ([a], Foo a)
441 The reason is that we then get better (shorter) type signatures in
442 interfaces. Notably this plays a role in tcTySigs in TcBinds.lhs.
447 repType looks through
451 (d) usage annotations
452 (e) all newtypes, including recursive ones, but not newtype families
453 It's useful in the back end.
456 repType :: Type -> Type
457 -- Only applied to types of kind *; hence tycons are saturated
458 repType ty | Just ty' <- coreView ty = repType ty'
459 repType (ForAllTy _ ty) = repType ty
460 repType (TyConApp tc tys)
462 not (isOpenTyCon tc) = -- Recursive newtypes are opaque to coreView
463 -- but we must expand them here. Sure to
464 -- be saturated because repType is only applied
465 -- to types of kind *
466 ASSERT( {- isRecursiveTyCon tc && -} tys `lengthIs` tyConArity tc )
467 repType (new_type_rep tc tys)
470 -- new_type_rep doesn't ask any questions:
471 -- it just expands newtype, whether recursive or not
472 new_type_rep new_tycon tys = ASSERT( tys `lengthIs` tyConArity new_tycon )
473 case newTyConRep new_tycon of
474 (tvs, rep_ty) -> substTyWith tvs tys rep_ty
476 -- ToDo: this could be moved to the code generator, using splitTyConApp instead
477 -- of inspecting the type directly.
478 typePrimRep :: Type -> PrimRep
479 typePrimRep ty = case repType ty of
480 TyConApp tc _ -> tyConPrimRep tc
482 AppTy _ _ -> PtrRep -- See note below
484 other -> pprPanic "typePrimRep" (ppr ty)
485 -- Types of the form 'f a' must be of kind *, not *#, so
486 -- we are guaranteed that they are represented by pointers.
487 -- The reason is that f must have kind *->*, not *->*#, because
488 -- (we claim) there is no way to constrain f's kind any other
494 ---------------------------------------------------------------------
499 mkForAllTy :: TyVar -> Type -> Type
501 = mkForAllTys [tyvar] ty
503 mkForAllTys :: [TyVar] -> Type -> Type
504 mkForAllTys tyvars ty = foldr ForAllTy ty tyvars
506 isForAllTy :: Type -> Bool
507 isForAllTy (NoteTy _ ty) = isForAllTy ty
508 isForAllTy (ForAllTy _ _) = True
509 isForAllTy other_ty = False
511 splitForAllTy_maybe :: Type -> Maybe (TyVar, Type)
512 splitForAllTy_maybe ty = splitFAT_m ty
514 splitFAT_m ty | Just ty' <- coreView ty = splitFAT_m ty'
515 splitFAT_m (ForAllTy tyvar ty) = Just(tyvar, ty)
516 splitFAT_m _ = Nothing
518 splitForAllTys :: Type -> ([TyVar], Type)
519 splitForAllTys ty = split ty ty []
521 split orig_ty ty tvs | Just ty' <- coreView ty = split orig_ty ty' tvs
522 split orig_ty (ForAllTy tv ty) tvs = split ty ty (tv:tvs)
523 split orig_ty t tvs = (reverse tvs, orig_ty)
525 dropForAlls :: Type -> Type
526 dropForAlls ty = snd (splitForAllTys ty)
529 -- (mkPiType now in CoreUtils)
533 Instantiate a for-all type with one or more type arguments.
534 Used when we have a polymorphic function applied to type args:
536 Then we use (applyTys type-of-f [t1,t2]) to compute the type of
540 applyTy :: Type -> Type -> Type
541 applyTy ty arg | Just ty' <- coreView ty = applyTy ty' arg
542 applyTy (ForAllTy tv ty) arg = substTyWith [tv] [arg] ty
543 applyTy other arg = panic "applyTy"
545 applyTys :: Type -> [Type] -> Type
546 -- This function is interesting because
547 -- a) the function may have more for-alls than there are args
548 -- b) less obviously, it may have fewer for-alls
549 -- For case (b) think of
550 -- applyTys (forall a.a) [forall b.b, Int]
551 -- This really can happen, via dressing up polymorphic types with newtype
552 -- clothing. Here's an example:
553 -- newtype R = R (forall a. a->a)
554 -- foo = case undefined :: R of
557 applyTys orig_fun_ty [] = orig_fun_ty
558 applyTys orig_fun_ty arg_tys
559 | n_tvs == n_args -- The vastly common case
560 = substTyWith tvs arg_tys rho_ty
561 | n_tvs > n_args -- Too many for-alls
562 = substTyWith (take n_args tvs) arg_tys
563 (mkForAllTys (drop n_args tvs) rho_ty)
564 | otherwise -- Too many type args
565 = ASSERT2( n_tvs > 0, ppr orig_fun_ty ) -- Zero case gives infnite loop!
566 applyTys (substTyWith tvs (take n_tvs arg_tys) rho_ty)
569 (tvs, rho_ty) = splitForAllTys orig_fun_ty
571 n_args = length arg_tys
575 %************************************************************************
577 \subsection{Source types}
579 %************************************************************************
581 A "source type" is a type that is a separate type as far as the type checker is
582 concerned, but which has low-level representation as far as the back end is concerned.
584 Source types are always lifted.
586 The key function is predTypeRep which gives the representation of a source type:
589 mkPredTy :: PredType -> Type
590 mkPredTy pred = PredTy pred
592 mkPredTys :: ThetaType -> [Type]
593 mkPredTys preds = map PredTy preds
595 predTypeRep :: PredType -> Type
596 -- Convert a PredType to its "representation type";
597 -- the post-type-checking type used by all the Core passes of GHC.
598 -- Unwraps only the outermost level; for example, the result might
599 -- be a newtype application
600 predTypeRep (IParam _ ty) = ty
601 predTypeRep (ClassP clas tys) = mkTyConApp (classTyCon clas) tys
602 -- Result might be a newtype application, but the consumer will
603 -- look through that too if necessary
604 predTypeRep (EqPred ty1 ty2) = pprPanic "predTypeRep" (ppr (EqPred ty1 ty2))
608 %************************************************************************
612 %************************************************************************
615 splitRecNewType_maybe :: Type -> Maybe Type
616 -- Sometimes we want to look through a recursive newtype, and that's what happens here
617 -- It only strips *one layer* off, so the caller will usually call itself recursively
618 -- Only applied to types of kind *, hence the newtype is always saturated
619 splitRecNewType_maybe ty | Just ty' <- coreView ty = splitRecNewType_maybe ty'
620 splitRecNewType_maybe (TyConApp tc tys)
622 = ASSERT( tys `lengthIs` tyConArity tc ) -- splitRecNewType_maybe only be applied
623 -- to *types* (of kind *)
624 ASSERT( isRecursiveTyCon tc ) -- Guaranteed by coreView
625 case newTyConRhs tc of
626 (tvs, rep_ty) -> ASSERT( length tvs == length tys )
627 Just (substTyWith tvs tys rep_ty)
629 splitRecNewType_maybe other = Nothing
636 %************************************************************************
638 \subsection{Kinds and free variables}
640 %************************************************************************
642 ---------------------------------------------------------------------
643 Finding the kind of a type
644 ~~~~~~~~~~~~~~~~~~~~~~~~~~
646 typeKind :: Type -> Kind
647 typeKind (TyConApp tycon tys) = ASSERT( not (isCoercionTyCon tycon) )
648 -- We should be looking for the coercion kind,
650 foldr (\_ k -> kindFunResult k) (tyConKind tycon) tys
651 typeKind (NoteTy _ ty) = typeKind ty
652 typeKind (PredTy pred) = predKind pred
653 typeKind (AppTy fun arg) = kindFunResult (typeKind fun)
654 typeKind (ForAllTy tv ty) = typeKind ty
655 typeKind (TyVarTy tyvar) = tyVarKind tyvar
656 typeKind (FunTy arg res)
657 -- Hack alert. The kind of (Int -> Int#) is liftedTypeKind (*),
658 -- not unliftedTypKind (#)
659 -- The only things that can be after a function arrow are
660 -- (a) types (of kind openTypeKind or its sub-kinds)
661 -- (b) kinds (of super-kind TY) (e.g. * -> (* -> *))
662 | isTySuperKind k = k
663 | otherwise = ASSERT( isSubOpenTypeKind k) liftedTypeKind
667 predKind :: PredType -> Kind
668 predKind (EqPred {}) = coSuperKind -- A coercion kind!
669 predKind (ClassP {}) = liftedTypeKind -- Class and implicitPredicates are
670 predKind (IParam {}) = liftedTypeKind -- always represented by lifted types
674 ---------------------------------------------------------------------
675 Free variables of a type
676 ~~~~~~~~~~~~~~~~~~~~~~~~
678 tyVarsOfType :: Type -> TyVarSet
679 -- NB: for type synonyms tyVarsOfType does *not* expand the synonym
680 tyVarsOfType (TyVarTy tv) = unitVarSet tv
681 tyVarsOfType (TyConApp tycon tys) = tyVarsOfTypes tys
682 tyVarsOfType (NoteTy (FTVNote tvs) ty2) = tvs
683 tyVarsOfType (PredTy sty) = tyVarsOfPred sty
684 tyVarsOfType (FunTy arg res) = tyVarsOfType arg `unionVarSet` tyVarsOfType res
685 tyVarsOfType (AppTy fun arg) = tyVarsOfType fun `unionVarSet` tyVarsOfType arg
686 tyVarsOfType (ForAllTy tyvar ty) = delVarSet (tyVarsOfType ty) tyvar
688 tyVarsOfTypes :: [Type] -> TyVarSet
689 tyVarsOfTypes tys = foldr (unionVarSet.tyVarsOfType) emptyVarSet tys
691 tyVarsOfPred :: PredType -> TyVarSet
692 tyVarsOfPred (IParam _ ty) = tyVarsOfType ty
693 tyVarsOfPred (ClassP _ tys) = tyVarsOfTypes tys
694 tyVarsOfPred (EqPred ty1 ty2) = tyVarsOfType ty1 `unionVarSet` tyVarsOfType ty2
696 tyVarsOfTheta :: ThetaType -> TyVarSet
697 tyVarsOfTheta = foldr (unionVarSet . tyVarsOfPred) emptyVarSet
699 -- Add a Note with the free tyvars to the top of the type
700 addFreeTyVars :: Type -> Type
701 addFreeTyVars ty@(NoteTy (FTVNote _) _) = ty
702 addFreeTyVars ty = NoteTy (FTVNote (tyVarsOfType ty)) ty
706 %************************************************************************
708 \subsection{TidyType}
710 %************************************************************************
712 tidyTy tidies up a type for printing in an error message, or in
715 It doesn't change the uniques at all, just the print names.
718 tidyTyVarBndr :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
719 tidyTyVarBndr (tidy_env, subst) tyvar
720 = case tidyOccName tidy_env (getOccName name) of
721 (tidy', occ') -> ((tidy', subst'), tyvar')
723 subst' = extendVarEnv subst tyvar tyvar'
724 tyvar' = setTyVarName tyvar name'
725 name' = tidyNameOcc name occ'
727 name = tyVarName tyvar
729 tidyFreeTyVars :: TidyEnv -> TyVarSet -> TidyEnv
730 -- Add the free tyvars to the env in tidy form,
731 -- so that we can tidy the type they are free in
732 tidyFreeTyVars env tyvars = fst (tidyOpenTyVars env (varSetElems tyvars))
734 tidyOpenTyVars :: TidyEnv -> [TyVar] -> (TidyEnv, [TyVar])
735 tidyOpenTyVars env tyvars = mapAccumL tidyOpenTyVar env tyvars
737 tidyOpenTyVar :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
738 -- Treat a new tyvar as a binder, and give it a fresh tidy name
739 tidyOpenTyVar env@(tidy_env, subst) tyvar
740 = case lookupVarEnv subst tyvar of
741 Just tyvar' -> (env, tyvar') -- Already substituted
742 Nothing -> tidyTyVarBndr env tyvar -- Treat it as a binder
744 tidyType :: TidyEnv -> Type -> Type
745 tidyType env@(tidy_env, subst) ty
748 go (TyVarTy tv) = case lookupVarEnv subst tv of
749 Nothing -> TyVarTy tv
750 Just tv' -> TyVarTy tv'
751 go (TyConApp tycon tys) = let args = map go tys
752 in args `seqList` TyConApp tycon args
753 go (NoteTy note ty) = (NoteTy $! (go_note note)) $! (go ty)
754 go (PredTy sty) = PredTy (tidyPred env sty)
755 go (AppTy fun arg) = (AppTy $! (go fun)) $! (go arg)
756 go (FunTy fun arg) = (FunTy $! (go fun)) $! (go arg)
757 go (ForAllTy tv ty) = ForAllTy tvp $! (tidyType envp ty)
759 (envp, tvp) = tidyTyVarBndr env tv
761 go_note note@(FTVNote ftvs) = note -- No need to tidy the free tyvars
763 tidyTypes env tys = map (tidyType env) tys
765 tidyPred :: TidyEnv -> PredType -> PredType
766 tidyPred env (IParam n ty) = IParam n (tidyType env ty)
767 tidyPred env (ClassP clas tys) = ClassP clas (tidyTypes env tys)
768 tidyPred env (EqPred ty1 ty2) = EqPred (tidyType env ty1) (tidyType env ty2)
772 @tidyOpenType@ grabs the free type variables, tidies them
773 and then uses @tidyType@ to work over the type itself
776 tidyOpenType :: TidyEnv -> Type -> (TidyEnv, Type)
778 = (env', tidyType env' ty)
780 env' = tidyFreeTyVars env (tyVarsOfType ty)
782 tidyOpenTypes :: TidyEnv -> [Type] -> (TidyEnv, [Type])
783 tidyOpenTypes env tys = mapAccumL tidyOpenType env tys
785 tidyTopType :: Type -> Type
786 tidyTopType ty = tidyType emptyTidyEnv ty
791 tidyKind :: TidyEnv -> Kind -> (TidyEnv, Kind)
792 tidyKind env k = tidyOpenType env k
797 %************************************************************************
799 \subsection{Liftedness}
801 %************************************************************************
804 isUnLiftedType :: Type -> Bool
805 -- isUnLiftedType returns True for forall'd unlifted types:
806 -- x :: forall a. Int#
807 -- I found bindings like these were getting floated to the top level.
808 -- They are pretty bogus types, mind you. It would be better never to
811 isUnLiftedType ty | Just ty' <- coreView ty = isUnLiftedType ty'
812 isUnLiftedType (ForAllTy tv ty) = isUnLiftedType ty
813 isUnLiftedType (TyConApp tc _) = isUnLiftedTyCon tc
814 isUnLiftedType other = False
816 isUnboxedTupleType :: Type -> Bool
817 isUnboxedTupleType ty = case splitTyConApp_maybe ty of
818 Just (tc, ty_args) -> isUnboxedTupleTyCon tc
821 -- Should only be applied to *types*; hence the assert
822 isAlgType :: Type -> Bool
823 isAlgType ty = case splitTyConApp_maybe ty of
824 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
829 @isStrictType@ computes whether an argument (or let RHS) should
830 be computed strictly or lazily, based only on its type.
831 Works just like isUnLiftedType, except that it has a special case
832 for dictionaries. Since it takes account of ClassP, you might think
833 this function should be in TcType, but isStrictType is used by DataCon,
834 which is below TcType in the hierarchy, so it's convenient to put it here.
837 isStrictType (PredTy pred) = isStrictPred pred
838 isStrictType ty | Just ty' <- coreView ty = isStrictType ty'
839 isStrictType (ForAllTy tv ty) = isStrictType ty
840 isStrictType (TyConApp tc _) = isUnLiftedTyCon tc
841 isStrictType other = False
843 isStrictPred (ClassP clas _) = opt_DictsStrict && not (isNewTyCon (classTyCon clas))
844 isStrictPred other = False
845 -- We may be strict in dictionary types, but only if it
846 -- has more than one component.
847 -- [Being strict in a single-component dictionary risks
848 -- poking the dictionary component, which is wrong.]
852 isPrimitiveType :: Type -> Bool
853 -- Returns types that are opaque to Haskell.
854 -- Most of these are unlifted, but now that we interact with .NET, we
855 -- may have primtive (foreign-imported) types that are lifted
856 isPrimitiveType ty = case splitTyConApp_maybe ty of
857 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
863 %************************************************************************
865 \subsection{Sequencing on types
867 %************************************************************************
870 seqType :: Type -> ()
871 seqType (TyVarTy tv) = tv `seq` ()
872 seqType (AppTy t1 t2) = seqType t1 `seq` seqType t2
873 seqType (FunTy t1 t2) = seqType t1 `seq` seqType t2
874 seqType (NoteTy note t2) = seqNote note `seq` seqType t2
875 seqType (PredTy p) = seqPred p
876 seqType (TyConApp tc tys) = tc `seq` seqTypes tys
877 seqType (ForAllTy tv ty) = tv `seq` seqType ty
879 seqTypes :: [Type] -> ()
881 seqTypes (ty:tys) = seqType ty `seq` seqTypes tys
883 seqNote :: TyNote -> ()
884 seqNote (FTVNote set) = sizeUniqSet set `seq` ()
886 seqPred :: PredType -> ()
887 seqPred (ClassP c tys) = c `seq` seqTypes tys
888 seqPred (IParam n ty) = n `seq` seqType ty
889 seqPred (EqPred ty1 ty2) = seqType ty1 `seq` seqType ty2
893 %************************************************************************
895 Equality for Core types
896 (We don't use instances so that we know where it happens)
898 %************************************************************************
900 Note that eqType works right even for partial applications of newtypes.
901 See Note [Newtype eta] in TyCon.lhs
904 coreEqType :: Type -> Type -> Bool
908 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfType t1 `unionVarSet` tyVarsOfType t2))
910 eq env (TyVarTy tv1) (TyVarTy tv2) = rnOccL env tv1 == rnOccR env tv2
911 eq env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = eq (rnBndr2 env tv1 tv2) t1 t2
912 eq env (AppTy s1 t1) (AppTy s2 t2) = eq env s1 s2 && eq env t1 t2
913 eq env (FunTy s1 t1) (FunTy s2 t2) = eq env s1 s2 && eq env t1 t2
914 eq env (TyConApp tc1 tys1) (TyConApp tc2 tys2)
915 | tc1 == tc2, all2 (eq env) tys1 tys2 = True
916 -- The lengths should be equal because
917 -- the two types have the same kind
918 -- NB: if the type constructors differ that does not
919 -- necessarily mean that the types aren't equal
920 -- (synonyms, newtypes)
921 -- Even if the type constructors are the same, but the arguments
922 -- differ, the two types could be the same (e.g. if the arg is just
923 -- ignored in the RHS). In both these cases we fall through to an
924 -- attempt to expand one side or the other.
926 -- Now deal with newtypes, synonyms, pred-tys
927 eq env t1 t2 | Just t1' <- coreView t1 = eq env t1' t2
928 | Just t2' <- coreView t2 = eq env t1 t2'
930 -- Fall through case; not equal!
935 %************************************************************************
937 Comparision for source types
938 (We don't use instances so that we know where it happens)
940 %************************************************************************
944 do *not* look through newtypes, PredTypes
947 tcEqType :: Type -> Type -> Bool
948 tcEqType t1 t2 = isEqual $ cmpType t1 t2
950 tcEqTypes :: [Type] -> [Type] -> Bool
951 tcEqTypes tys1 tys2 = isEqual $ cmpTypes tys1 tys2
953 tcCmpType :: Type -> Type -> Ordering
954 tcCmpType t1 t2 = cmpType t1 t2
956 tcCmpTypes :: [Type] -> [Type] -> Ordering
957 tcCmpTypes tys1 tys2 = cmpTypes tys1 tys2
959 tcEqPred :: PredType -> PredType -> Bool
960 tcEqPred p1 p2 = isEqual $ cmpPred p1 p2
962 tcCmpPred :: PredType -> PredType -> Ordering
963 tcCmpPred p1 p2 = cmpPred p1 p2
965 tcEqTypeX :: RnEnv2 -> Type -> Type -> Bool
966 tcEqTypeX env t1 t2 = isEqual $ cmpTypeX env t1 t2
969 Now here comes the real worker
972 cmpType :: Type -> Type -> Ordering
973 cmpType t1 t2 = cmpTypeX rn_env t1 t2
975 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfType t1 `unionVarSet` tyVarsOfType t2))
977 cmpTypes :: [Type] -> [Type] -> Ordering
978 cmpTypes ts1 ts2 = cmpTypesX rn_env ts1 ts2
980 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfTypes ts1 `unionVarSet` tyVarsOfTypes ts2))
982 cmpPred :: PredType -> PredType -> Ordering
983 cmpPred p1 p2 = cmpPredX rn_env p1 p2
985 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfPred p1 `unionVarSet` tyVarsOfPred p2))
987 cmpTypeX :: RnEnv2 -> Type -> Type -> Ordering -- Main workhorse
988 cmpTypeX env t1 t2 | Just t1' <- tcView t1 = cmpTypeX env t1' t2
989 | Just t2' <- tcView t2 = cmpTypeX env t1 t2'
991 cmpTypeX env (TyVarTy tv1) (TyVarTy tv2) = rnOccL env tv1 `compare` rnOccR env tv2
992 cmpTypeX env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = cmpTypeX (rnBndr2 env tv1 tv2) t1 t2
993 cmpTypeX env (AppTy s1 t1) (AppTy s2 t2) = cmpTypeX env s1 s2 `thenCmp` cmpTypeX env t1 t2
994 cmpTypeX env (FunTy s1 t1) (FunTy s2 t2) = cmpTypeX env s1 s2 `thenCmp` cmpTypeX env t1 t2
995 cmpTypeX env (PredTy p1) (PredTy p2) = cmpPredX env p1 p2
996 cmpTypeX env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` cmpTypesX env tys1 tys2
997 cmpTypeX env t1 (NoteTy _ t2) = cmpTypeX env t1 t2
999 -- Deal with the rest: TyVarTy < AppTy < FunTy < TyConApp < ForAllTy < PredTy
1000 cmpTypeX env (AppTy _ _) (TyVarTy _) = GT
1002 cmpTypeX env (FunTy _ _) (TyVarTy _) = GT
1003 cmpTypeX env (FunTy _ _) (AppTy _ _) = GT
1005 cmpTypeX env (TyConApp _ _) (TyVarTy _) = GT
1006 cmpTypeX env (TyConApp _ _) (AppTy _ _) = GT
1007 cmpTypeX env (TyConApp _ _) (FunTy _ _) = GT
1009 cmpTypeX env (ForAllTy _ _) (TyVarTy _) = GT
1010 cmpTypeX env (ForAllTy _ _) (AppTy _ _) = GT
1011 cmpTypeX env (ForAllTy _ _) (FunTy _ _) = GT
1012 cmpTypeX env (ForAllTy _ _) (TyConApp _ _) = GT
1014 cmpTypeX env (PredTy _) t2 = GT
1016 cmpTypeX env _ _ = LT
1019 cmpTypesX :: RnEnv2 -> [Type] -> [Type] -> Ordering
1020 cmpTypesX env [] [] = EQ
1021 cmpTypesX env (t1:tys1) (t2:tys2) = cmpTypeX env t1 t2 `thenCmp` cmpTypesX env tys1 tys2
1022 cmpTypesX env [] tys = LT
1023 cmpTypesX env ty [] = GT
1026 cmpPredX :: RnEnv2 -> PredType -> PredType -> Ordering
1027 cmpPredX env (IParam n1 ty1) (IParam n2 ty2) = (n1 `compare` n2) `thenCmp` cmpTypeX env ty1 ty2
1028 -- Compare types as well as names for implicit parameters
1029 -- This comparison is used exclusively (I think) for the
1030 -- finite map built in TcSimplify
1031 cmpPredX env (ClassP c1 tys1) (ClassP c2 tys2) = (c1 `compare` c2) `thenCmp` cmpTypesX env tys1 tys2
1032 cmpPredX env (IParam _ _) (ClassP _ _) = LT
1033 cmpPredX env (ClassP _ _) (IParam _ _) = GT
1034 cmpPredX env (EqPred ty1 ty2) (EqPred ty1' ty2') = (cmpTypeX env ty1 ty1') `thenCmp` (cmpTypeX env ty2 ty2')
1037 PredTypes are used as a FM key in TcSimplify,
1038 so we take the easy path and make them an instance of Ord
1041 instance Eq PredType where { (==) = tcEqPred }
1042 instance Ord PredType where { compare = tcCmpPred }
1046 %************************************************************************
1050 %************************************************************************
1054 = TvSubst InScopeSet -- The in-scope type variables
1055 TvSubstEnv -- The substitution itself
1056 -- See Note [Apply Once]
1058 {- ----------------------------------------------------------
1061 We use TvSubsts to instantiate things, and we might instantiate
1065 So the substition might go [a->b, b->a]. A similar situation arises in Core
1066 when we find a beta redex like
1067 (/\ a /\ b -> e) b a
1068 Then we also end up with a substition that permutes type variables. Other
1069 variations happen to; for example [a -> (a, b)].
1071 ***************************************************
1072 *** So a TvSubst must be applied precisely once ***
1073 ***************************************************
1075 A TvSubst is not idempotent, but, unlike the non-idempotent substitution
1076 we use during unifications, it must not be repeatedly applied.
1077 -------------------------------------------------------------- -}
1080 type TvSubstEnv = TyVarEnv Type
1081 -- A TvSubstEnv is used both inside a TvSubst (with the apply-once
1082 -- invariant discussed in Note [Apply Once]), and also independently
1083 -- in the middle of matching, and unification (see Types.Unify)
1084 -- So you have to look at the context to know if it's idempotent or
1085 -- apply-once or whatever
1086 emptyTvSubstEnv :: TvSubstEnv
1087 emptyTvSubstEnv = emptyVarEnv
1089 composeTvSubst :: InScopeSet -> TvSubstEnv -> TvSubstEnv -> TvSubstEnv
1090 -- (compose env1 env2)(x) is env1(env2(x)); i.e. apply env2 then env1
1091 -- It assumes that both are idempotent
1092 -- Typically, env1 is the refinement to a base substitution env2
1093 composeTvSubst in_scope env1 env2
1094 = env1 `plusVarEnv` mapVarEnv (substTy subst1) env2
1095 -- First apply env1 to the range of env2
1096 -- Then combine the two, making sure that env1 loses if
1097 -- both bind the same variable; that's why env1 is the
1098 -- *left* argument to plusVarEnv, because the right arg wins
1100 subst1 = TvSubst in_scope env1
1102 emptyTvSubst = TvSubst emptyInScopeSet emptyVarEnv
1104 isEmptyTvSubst :: TvSubst -> Bool
1105 isEmptyTvSubst (TvSubst _ env) = isEmptyVarEnv env
1107 mkTvSubst :: InScopeSet -> TvSubstEnv -> TvSubst
1110 getTvSubstEnv :: TvSubst -> TvSubstEnv
1111 getTvSubstEnv (TvSubst _ env) = env
1113 getTvInScope :: TvSubst -> InScopeSet
1114 getTvInScope (TvSubst in_scope _) = in_scope
1116 isInScope :: Var -> TvSubst -> Bool
1117 isInScope v (TvSubst in_scope _) = v `elemInScopeSet` in_scope
1119 notElemTvSubst :: TyVar -> TvSubst -> Bool
1120 notElemTvSubst tv (TvSubst _ env) = not (tv `elemVarEnv` env)
1122 setTvSubstEnv :: TvSubst -> TvSubstEnv -> TvSubst
1123 setTvSubstEnv (TvSubst in_scope _) env = TvSubst in_scope env
1125 extendTvInScope :: TvSubst -> [Var] -> TvSubst
1126 extendTvInScope (TvSubst in_scope env) vars = TvSubst (extendInScopeSetList in_scope vars) env
1128 extendTvSubst :: TvSubst -> TyVar -> Type -> TvSubst
1129 extendTvSubst (TvSubst in_scope env) tv ty = TvSubst in_scope (extendVarEnv env tv ty)
1131 extendTvSubstList :: TvSubst -> [TyVar] -> [Type] -> TvSubst
1132 extendTvSubstList (TvSubst in_scope env) tvs tys
1133 = TvSubst in_scope (extendVarEnvList env (tvs `zip` tys))
1135 -- mkOpenTvSubst and zipOpenTvSubst generate the in-scope set from
1136 -- the types given; but it's just a thunk so with a bit of luck
1137 -- it'll never be evaluated
1139 mkOpenTvSubst :: TvSubstEnv -> TvSubst
1140 mkOpenTvSubst env = TvSubst (mkInScopeSet (tyVarsOfTypes (varEnvElts env))) env
1142 zipOpenTvSubst :: [TyVar] -> [Type] -> TvSubst
1143 zipOpenTvSubst tyvars tys
1145 | length tyvars /= length tys
1146 = pprTrace "zipOpenTvSubst" (ppr tyvars $$ ppr tys) emptyTvSubst
1149 = TvSubst (mkInScopeSet (tyVarsOfTypes tys)) (zipTyEnv tyvars tys)
1151 -- mkTopTvSubst is called when doing top-level substitutions.
1152 -- Here we expect that the free vars of the range of the
1153 -- substitution will be empty.
1154 mkTopTvSubst :: [(TyVar, Type)] -> TvSubst
1155 mkTopTvSubst prs = TvSubst emptyInScopeSet (mkVarEnv prs)
1157 zipTopTvSubst :: [TyVar] -> [Type] -> TvSubst
1158 zipTopTvSubst tyvars tys
1160 | length tyvars /= length tys
1161 = pprTrace "zipOpenTvSubst" (ppr tyvars $$ ppr tys) emptyTvSubst
1164 = TvSubst emptyInScopeSet (zipTyEnv tyvars tys)
1166 zipTyEnv :: [TyVar] -> [Type] -> TvSubstEnv
1169 | length tyvars /= length tys
1170 = pprTrace "mkTopTvSubst" (ppr tyvars $$ ppr tys) emptyVarEnv
1173 = zip_ty_env tyvars tys emptyVarEnv
1175 -- Later substitutions in the list over-ride earlier ones,
1176 -- but there should be no loops
1177 zip_ty_env [] [] env = env
1178 zip_ty_env (tv:tvs) (ty:tys) env = zip_ty_env tvs tys (extendVarEnv env tv ty)
1179 -- There used to be a special case for when
1181 -- (a not-uncommon case) in which case the substitution was dropped.
1182 -- But the type-tidier changes the print-name of a type variable without
1183 -- changing the unique, and that led to a bug. Why? Pre-tidying, we had
1184 -- a type {Foo t}, where Foo is a one-method class. So Foo is really a newtype.
1185 -- And it happened that t was the type variable of the class. Post-tiding,
1186 -- it got turned into {Foo t2}. The ext-core printer expanded this using
1187 -- sourceTypeRep, but that said "Oh, t == t2" because they have the same unique,
1188 -- and so generated a rep type mentioning t not t2.
1190 -- Simplest fix is to nuke the "optimisation"
1191 zip_ty_env tvs tys env = pprTrace "Var/Type length mismatch: " (ppr tvs $$ ppr tys) env
1192 -- zip_ty_env _ _ env = env
1194 instance Outputable TvSubst where
1195 ppr (TvSubst ins env)
1196 = brackets $ sep[ ptext SLIT("TvSubst"),
1197 nest 2 (ptext SLIT("In scope:") <+> ppr ins),
1198 nest 2 (ptext SLIT("Env:") <+> ppr env) ]
1201 %************************************************************************
1203 Performing type substitutions
1205 %************************************************************************
1208 substTyWith :: [TyVar] -> [Type] -> Type -> Type
1209 substTyWith tvs tys = ASSERT( length tvs == length tys )
1210 substTy (zipOpenTvSubst tvs tys)
1212 substTy :: TvSubst -> Type -> Type
1213 substTy subst ty | isEmptyTvSubst subst = ty
1214 | otherwise = subst_ty subst ty
1216 substTys :: TvSubst -> [Type] -> [Type]
1217 substTys subst tys | isEmptyTvSubst subst = tys
1218 | otherwise = map (subst_ty subst) tys
1220 substTheta :: TvSubst -> ThetaType -> ThetaType
1221 substTheta subst theta
1222 | isEmptyTvSubst subst = theta
1223 | otherwise = map (substPred subst) theta
1225 substPred :: TvSubst -> PredType -> PredType
1226 substPred subst (IParam n ty) = IParam n (subst_ty subst ty)
1227 substPred subst (ClassP clas tys) = ClassP clas (map (subst_ty subst) tys)
1228 substPred subst (EqPred ty1 ty2) = EqPred (subst_ty subst ty1) (subst_ty subst ty2)
1230 deShadowTy :: TyVarSet -> Type -> Type -- Remove any nested binders mentioning tvs
1232 = subst_ty (mkTvSubst in_scope emptyTvSubstEnv) ty
1234 in_scope = mkInScopeSet tvs
1236 subst_ty :: TvSubst -> Type -> Type
1237 -- subst_ty is the main workhorse for type substitution
1239 -- Note that the in_scope set is poked only if we hit a forall
1240 -- so it may often never be fully computed
1244 go (TyVarTy tv) = substTyVar subst tv
1245 go (TyConApp tc tys) = let args = map go tys
1246 in args `seqList` TyConApp tc args
1248 go (PredTy p) = PredTy $! (substPred subst p)
1250 go (NoteTy (FTVNote _) ty2) = go ty2 -- Discard the free tyvar note
1252 go (FunTy arg res) = (FunTy $! (go arg)) $! (go res)
1253 go (AppTy fun arg) = mkAppTy (go fun) $! (go arg)
1254 -- The mkAppTy smart constructor is important
1255 -- we might be replacing (a Int), represented with App
1256 -- by [Int], represented with TyConApp
1257 go (ForAllTy tv ty) = case substTyVarBndr subst tv of
1258 (subst', tv') -> ForAllTy tv' $! (subst_ty subst' ty)
1260 substTyVar :: TvSubst -> TyVar -> Type
1261 substTyVar subst@(TvSubst in_scope env) tv
1262 = case lookupTyVar subst tv of {
1263 Nothing -> TyVarTy tv;
1264 Just ty -> ty -- See Note [Apply Once]
1267 lookupTyVar :: TvSubst -> TyVar -> Maybe Type
1268 lookupTyVar (TvSubst in_scope env) tv = lookupVarEnv env tv
1270 substTyVarBndr :: TvSubst -> TyVar -> (TvSubst, TyVar)
1271 substTyVarBndr subst@(TvSubst in_scope env) old_var
1272 = (TvSubst (in_scope `extendInScopeSet` new_var) new_env, new_var)
1275 new_env | no_change = delVarEnv env old_var
1276 | otherwise = extendVarEnv env old_var (TyVarTy new_var)
1278 no_change = new_var == old_var && not is_co_var
1279 -- no_change means that the new_var is identical in
1280 -- all respects to the old_var (same unique, same kind)
1282 -- In that case we don't need to extend the substitution
1283 -- to map old to new. But instead we must zap any
1284 -- current substitution for the variable. For example:
1285 -- (\x.e) with id_subst = [x |-> e']
1286 -- Here we must simply zap the substitution for x
1288 new_var = uniqAway in_scope subst_old_var
1289 -- The uniqAway part makes sure the new variable is not already in scope
1291 subst_old_var -- subst_old_var is old_var with the substitution applied to its kind
1292 -- It's only worth doing the substitution for coercions,
1293 -- becuase only they can have free type variables
1294 | is_co_var = setTyVarKind old_var (substTy subst kind)
1295 | otherwise = old_var
1296 kind = tyVarKind old_var
1297 is_co_var = isCoercionKind kind
1300 ----------------------------------------------------
1305 There's a little subtyping at the kind level:
1314 where * [LiftedTypeKind] means boxed type
1315 # [UnliftedTypeKind] means unboxed type
1316 (#) [UbxTupleKind] means unboxed tuple
1317 ?? [ArgTypeKind] is the lub of *,#
1318 ? [OpenTypeKind] means any type at all
1322 error :: forall a:?. String -> a
1323 (->) :: ?? -> ? -> *
1324 (\(x::t) -> ...) Here t::?? (i.e. not unboxed tuple)
1327 type KindVar = TyVar -- invariant: KindVar will always be a
1328 -- TcTyVar with details MetaTv TauTv ...
1329 -- kind var constructors and functions are in TcType
1331 type SimpleKind = Kind
1336 During kind inference, a kind variable unifies only with
1338 sk ::= * | sk1 -> sk2
1340 data T a = MkT a (T Int#)
1341 fails. We give T the kind (k -> *), and the kind variable k won't unify
1342 with # (the kind of Int#).
1346 When creating a fresh internal type variable, we give it a kind to express
1347 constraints on it. E.g. in (\x->e) we make up a fresh type variable for x,
1350 During unification we only bind an internal type variable to a type
1351 whose kind is lower in the sub-kind hierarchy than the kind of the tyvar.
1353 When unifying two internal type variables, we collect their kind constraints by
1354 finding the GLB of the two. Since the partial order is a tree, they only
1355 have a glb if one is a sub-kind of the other. In that case, we bind the
1356 less-informative one to the more informative one. Neat, eh?
1363 %************************************************************************
1365 Functions over Kinds
1367 %************************************************************************
1370 kindFunResult :: Kind -> Kind
1371 kindFunResult k = funResultTy k
1373 splitKindFunTys :: Kind -> ([Kind],Kind)
1374 splitKindFunTys k = splitFunTys k
1376 splitKindFunTysN :: Int -> Kind -> ([Kind],Kind)
1377 splitKindFunTysN k = splitFunTysN k
1379 isUbxTupleKind, isOpenTypeKind, isArgTypeKind, isUnliftedTypeKind :: Kind -> Bool
1381 isOpenTypeKindCon tc = tyConUnique tc == openTypeKindTyConKey
1383 isOpenTypeKind (TyConApp tc _) = isOpenTypeKindCon tc
1384 isOpenTypeKind other = False
1386 isUbxTupleKindCon tc = tyConUnique tc == ubxTupleKindTyConKey
1388 isUbxTupleKind (TyConApp tc _) = isUbxTupleKindCon tc
1389 isUbxTupleKind other = False
1391 isArgTypeKindCon tc = tyConUnique tc == argTypeKindTyConKey
1393 isArgTypeKind (TyConApp tc _) = isArgTypeKindCon tc
1394 isArgTypeKind other = False
1396 isUnliftedTypeKindCon tc = tyConUnique tc == unliftedTypeKindTyConKey
1398 isUnliftedTypeKind (TyConApp tc _) = isUnliftedTypeKindCon tc
1399 isUnliftedTypeKind other = False
1401 isSubOpenTypeKind :: Kind -> Bool
1402 -- True of any sub-kind of OpenTypeKind (i.e. anything except arrow)
1403 isSubOpenTypeKind (FunTy k1 k2) = ASSERT2 ( isKind k1, text "isSubOpenTypeKind" <+> ppr k1 <+> text "::" <+> ppr (typeKind k1) )
1404 ASSERT2 ( isKind k2, text "isSubOpenTypeKind" <+> ppr k2 <+> text "::" <+> ppr (typeKind k2) )
1406 isSubOpenTypeKind (TyConApp kc []) = ASSERT( isKind (TyConApp kc []) ) True
1407 isSubOpenTypeKind other = ASSERT( isKind other ) False
1408 -- This is a conservative answer
1409 -- It matters in the call to isSubKind in
1410 -- checkExpectedKind.
1412 isSubArgTypeKindCon kc
1413 | isUnliftedTypeKindCon kc = True
1414 | isLiftedTypeKindCon kc = True
1415 | isArgTypeKindCon kc = True
1418 isSubArgTypeKind :: Kind -> Bool
1419 -- True of any sub-kind of ArgTypeKind
1420 isSubArgTypeKind (TyConApp kc []) = isSubArgTypeKindCon kc
1421 isSubArgTypeKind other = False
1423 isSuperKind :: Type -> Bool
1424 isSuperKind (TyConApp (skc) []) = isSuperKindTyCon skc
1425 isSuperKind other = False
1427 isKind :: Kind -> Bool
1428 isKind k = isSuperKind (typeKind k)
1432 isSubKind :: Kind -> Kind -> Bool
1433 -- (k1 `isSubKind` k2) checks that k1 <: k2
1434 isSubKind (TyConApp kc1 []) (TyConApp kc2 []) = kc1 `isSubKindCon` kc1
1435 isSubKind (FunTy a1 r1) (FunTy a2 r2) = (a2 `isSubKind` a1) && (r1 `isSubKind` r2)
1436 isSubKind (PredTy (EqPred ty1 ty2)) (PredTy (EqPred ty1' ty2'))
1437 = ty1 `tcEqType` ty1' && ty2 `tcEqType` ty2'
1438 isSubKind k1 k2 = False
1440 eqKind :: Kind -> Kind -> Bool
1443 isSubKindCon :: TyCon -> TyCon -> Bool
1444 -- (kc1 `isSubKindCon` kc2) checks that kc1 <: kc2
1445 isSubKindCon kc1 kc2
1446 | isLiftedTypeKindCon kc1 && isLiftedTypeKindCon kc2 = True
1447 | isUnliftedTypeKindCon kc1 && isUnliftedTypeKindCon kc2 = True
1448 | isUbxTupleKindCon kc1 && isUbxTupleKindCon kc2 = True
1449 | isOpenTypeKindCon kc2 = True
1450 -- we already know kc1 is not a fun, its a TyCon
1451 | isArgTypeKindCon kc2 && isSubArgTypeKindCon kc1 = True
1454 defaultKind :: Kind -> Kind
1455 -- Used when generalising: default kind '?' and '??' to '*'
1457 -- When we generalise, we make generic type variables whose kind is
1458 -- simple (* or *->* etc). So generic type variables (other than
1459 -- built-in constants like 'error') always have simple kinds. This is important;
1462 -- We want f to get type
1463 -- f :: forall (a::*). a -> Bool
1465 -- f :: forall (a::??). a -> Bool
1466 -- because that would allow a call like (f 3#) as well as (f True),
1467 --and the calling conventions differ. This defaulting is done in TcMType.zonkTcTyVarBndr.
1469 | isSubOpenTypeKind k = liftedTypeKind
1470 | isSubArgTypeKind k = liftedTypeKind
1473 isCoercionKind :: Kind -> Bool
1474 -- All coercions are of form (ty1 :=: ty2)
1475 -- This function is here rather than in Coercion,
1476 -- because it's used by substTy
1477 isCoercionKind k | Just k' <- kindView k = isCoercionKind k'
1478 isCoercionKind (PredTy (EqPred {})) = True
1479 isCoercionKind other = False
1481 isEqPred :: PredType -> Bool
1482 isEqPred (EqPred _ _) = True
1483 isEqPred other = False