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, isPrimTyCon,
119 isUnboxedTupleTyCon, isUnLiftedTyCon,
120 isFunTyCon, isNewTyCon, isClosedNewTyCon,
121 newTyConRep, newTyConRhs,
122 isAlgTyCon, isSuperKindTyCon,
123 tcExpandTyCon_maybe, coreExpandTyCon_maybe,
124 tyConKind, PrimRep(..), tyConPrimRep, tyConUnique
128 import StaticFlags ( opt_DictsStrict )
129 import Util ( mapAccumL, seqList, snocView, thenCmp, isEqual, all2 )
131 import UniqSet ( sizeUniqSet ) -- Should come via VarSet
132 import Maybe ( isJust )
135 import TyCon ( isRecursiveTyCon, tyConArity, isCoercionTyCon )
136 import Util ( lengthIs )
141 %************************************************************************
145 %************************************************************************
147 In Core, we "look through" non-recursive newtypes and PredTypes.
150 {-# INLINE coreView #-}
151 coreView :: Type -> Maybe Type
152 -- Strips off the *top layer only* of a type to give
153 -- its underlying representation type.
154 -- Returns Nothing if there is nothing to look through.
156 -- In the case of newtypes, it returns
157 -- *either* a vanilla TyConApp (recursive newtype, or non-saturated)
158 -- *or* the newtype representation (otherwise), meaning the
159 -- type written in the RHS of the newtype decl,
160 -- which may itself be a newtype
162 -- Example: newtype R = MkR S
164 -- newtype T = MkT (T -> T)
165 -- expandNewTcApp on R gives Just S
167 -- on T gives Nothing (no expansion)
169 -- By being non-recursive and inlined, this case analysis gets efficiently
170 -- joined onto the case analysis that the caller is already doing
171 coreView (NoteTy _ ty) = Just ty
173 | isEqPred p = Nothing
174 | otherwise = Just (predTypeRep p)
175 coreView (TyConApp tc tys) | Just (tenv, rhs, tys') <- coreExpandTyCon_maybe tc tys
176 = Just (mkAppTys (substTy (mkTopTvSubst tenv) rhs) tys')
177 -- Its important to use mkAppTys, rather than (foldl AppTy),
178 -- because the function part might well return a
179 -- partially-applied type constructor; indeed, usually will!
180 coreView ty = Nothing
184 -----------------------------------------------
185 {-# INLINE tcView #-}
186 tcView :: Type -> Maybe Type
187 -- Same, but for the type checker, which just looks through synonyms
188 tcView (NoteTy _ ty) = Just ty
189 tcView (TyConApp tc tys) | Just (tenv, rhs, tys') <- tcExpandTyCon_maybe tc tys
190 = Just (mkAppTys (substTy (mkTopTvSubst tenv) rhs) tys')
193 -----------------------------------------------
194 {-# INLINE kindView #-}
195 kindView :: Kind -> Maybe Kind
196 -- C.f. coreView, tcView
197 -- For the moment, we don't even handle synonyms in kinds
198 kindView (NoteTy _ k) = Just k
199 kindView other = Nothing
203 %************************************************************************
205 \subsection{Constructor-specific functions}
207 %************************************************************************
210 ---------------------------------------------------------------------
214 mkTyVarTy :: TyVar -> Type
217 mkTyVarTys :: [TyVar] -> [Type]
218 mkTyVarTys = map mkTyVarTy -- a common use of mkTyVarTy
220 getTyVar :: String -> Type -> TyVar
221 getTyVar msg ty = case getTyVar_maybe ty of
223 Nothing -> panic ("getTyVar: " ++ msg)
225 isTyVarTy :: Type -> Bool
226 isTyVarTy ty = isJust (getTyVar_maybe ty)
228 getTyVar_maybe :: Type -> Maybe TyVar
229 getTyVar_maybe ty | Just ty' <- coreView ty = getTyVar_maybe ty'
230 getTyVar_maybe (TyVarTy tv) = Just tv
231 getTyVar_maybe other = Nothing
236 ---------------------------------------------------------------------
239 We need to be pretty careful with AppTy to make sure we obey the
240 invariant that a TyConApp is always visibly so. mkAppTy maintains the
244 mkAppTy orig_ty1 orig_ty2
247 mk_app (NoteTy _ ty1) = mk_app ty1
248 mk_app (TyConApp tc tys) = mkTyConApp tc (tys ++ [orig_ty2])
249 mk_app ty1 = AppTy orig_ty1 orig_ty2
250 -- Note that the TyConApp could be an
251 -- under-saturated type synonym. GHC allows that; e.g.
252 -- type Foo k = k a -> k a
254 -- foo :: Foo Id -> Foo Id
256 -- Here Id is partially applied in the type sig for Foo,
257 -- but once the type synonyms are expanded all is well
259 mkAppTys :: Type -> [Type] -> Type
260 mkAppTys orig_ty1 [] = orig_ty1
261 -- This check for an empty list of type arguments
262 -- avoids the needless loss of a type synonym constructor.
263 -- For example: mkAppTys Rational []
264 -- returns to (Ratio Integer), which has needlessly lost
265 -- the Rational part.
266 mkAppTys orig_ty1 orig_tys2
269 mk_app (NoteTy _ ty1) = mk_app ty1
270 mk_app (TyConApp tc tys) = mkTyConApp tc (tys ++ orig_tys2)
271 -- mkTyConApp: see notes with mkAppTy
272 mk_app ty1 = foldl AppTy orig_ty1 orig_tys2
275 splitAppTy_maybe :: Type -> Maybe (Type, Type)
276 splitAppTy_maybe ty | Just ty' <- coreView ty
277 = splitAppTy_maybe ty'
278 splitAppTy_maybe ty = repSplitAppTy_maybe ty
281 repSplitAppTy_maybe :: Type -> Maybe (Type,Type)
282 -- Does the AppTy split, but assumes that any view stuff is already done
283 repSplitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [ty1], ty2)
284 repSplitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2)
285 repSplitAppTy_maybe (TyConApp tc tys) = case snocView tys of
286 Just (tys', ty') -> Just (TyConApp tc tys', ty')
288 repSplitAppTy_maybe other = Nothing
290 splitAppTy :: Type -> (Type, Type)
291 splitAppTy ty = case splitAppTy_maybe ty of
293 Nothing -> panic "splitAppTy"
296 splitAppTys :: Type -> (Type, [Type])
297 splitAppTys ty = split ty ty []
299 split orig_ty ty args | Just ty' <- coreView ty = split orig_ty ty' args
300 split orig_ty (AppTy ty arg) args = split ty ty (arg:args)
301 split orig_ty (TyConApp tc tc_args) args = (TyConApp tc [], tc_args ++ args)
302 split orig_ty (FunTy ty1 ty2) args = ASSERT( null args )
303 (TyConApp funTyCon [], [ty1,ty2])
304 split orig_ty ty args = (orig_ty, args)
309 ---------------------------------------------------------------------
314 mkFunTy :: Type -> Type -> Type
315 mkFunTy (PredTy (EqPred ty1 ty2)) res = mkForAllTy (mkWildCoVar (PredTy (EqPred ty1 ty2))) res
316 mkFunTy arg res = FunTy arg res
318 mkFunTys :: [Type] -> Type -> Type
319 mkFunTys tys ty = foldr mkFunTy ty tys
321 isFunTy :: Type -> Bool
322 isFunTy ty = isJust (splitFunTy_maybe ty)
324 splitFunTy :: Type -> (Type, Type)
325 splitFunTy ty | Just ty' <- coreView ty = splitFunTy ty'
326 splitFunTy (FunTy arg res) = (arg, res)
327 splitFunTy other = pprPanic "splitFunTy" (ppr other)
329 splitFunTy_maybe :: Type -> Maybe (Type, Type)
330 splitFunTy_maybe ty | Just ty' <- coreView ty = splitFunTy_maybe ty'
331 splitFunTy_maybe (FunTy arg res) = Just (arg, res)
332 splitFunTy_maybe other = Nothing
334 splitFunTys :: Type -> ([Type], Type)
335 splitFunTys ty = split [] ty ty
337 split args orig_ty ty | Just ty' <- coreView ty = split args orig_ty ty'
338 split args orig_ty (FunTy arg res) = split (arg:args) res res
339 split args orig_ty ty = (reverse args, orig_ty)
341 splitFunTysN :: Int -> Type -> ([Type], Type)
342 -- Split off exactly n arg tys
343 splitFunTysN 0 ty = ([], ty)
344 splitFunTysN n ty = case splitFunTy ty of { (arg, res) ->
345 case splitFunTysN (n-1) res of { (args, res) ->
348 zipFunTys :: Outputable a => [a] -> Type -> ([(a,Type)], Type)
349 zipFunTys orig_xs orig_ty = split [] orig_xs orig_ty orig_ty
351 split acc [] nty ty = (reverse acc, nty)
353 | Just ty' <- coreView ty = split acc xs nty ty'
354 split acc (x:xs) nty (FunTy arg res) = split ((x,arg):acc) xs res res
355 split acc (x:xs) nty ty = pprPanic "zipFunTys" (ppr orig_xs <+> ppr orig_ty)
357 funResultTy :: Type -> Type
358 funResultTy ty | Just ty' <- coreView ty = funResultTy ty'
359 funResultTy (FunTy arg res) = res
360 funResultTy ty = pprPanic "funResultTy" (ppr ty)
362 funArgTy :: Type -> Type
363 funArgTy ty | Just ty' <- coreView ty = funArgTy ty'
364 funArgTy (FunTy arg res) = arg
365 funArgTy ty = pprPanic "funArgTy" (ppr ty)
369 ---------------------------------------------------------------------
372 @mkTyConApp@ is a key function, because it builds a TyConApp, FunTy or PredTy,
376 mkTyConApp :: TyCon -> [Type] -> Type
378 | isFunTyCon tycon, [ty1,ty2] <- tys
384 mkTyConTy :: TyCon -> Type
385 mkTyConTy tycon = mkTyConApp tycon []
387 -- splitTyConApp "looks through" synonyms, because they don't
388 -- mean a distinct type, but all other type-constructor applications
389 -- including functions are returned as Just ..
391 tyConAppTyCon :: Type -> TyCon
392 tyConAppTyCon ty = fst (splitTyConApp ty)
394 tyConAppArgs :: Type -> [Type]
395 tyConAppArgs ty = snd (splitTyConApp ty)
397 splitTyConApp :: Type -> (TyCon, [Type])
398 splitTyConApp ty = case splitTyConApp_maybe ty of
400 Nothing -> pprPanic "splitTyConApp" (ppr ty)
402 splitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
403 splitTyConApp_maybe ty | Just ty' <- coreView ty = splitTyConApp_maybe ty'
404 splitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
405 splitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
406 splitTyConApp_maybe other = Nothing
408 -- Sometimes we do NOT want to look throught a newtype. When case matching
409 -- on a newtype we want a convenient way to access the arguments of a newty
410 -- constructor so as to properly form a coercion.
411 splitNewTyConApp :: Type -> (TyCon, [Type])
412 splitNewTyConApp ty = case splitNewTyConApp_maybe ty of
414 Nothing -> pprPanic "splitNewTyConApp" (ppr ty)
415 splitNewTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
416 splitNewTyConApp_maybe ty | Just ty' <- tcView ty = splitNewTyConApp_maybe ty'
417 splitNewTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
418 splitNewTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
419 splitNewTyConApp_maybe other = Nothing
421 -- get instantiated newtype rhs, the arguments had better saturate
423 newTyConInstRhs :: TyCon -> [Type] -> Type
424 newTyConInstRhs tycon tys =
425 let (tvs, ty) = newTyConRhs tycon in substTyWith tvs tys ty
430 ---------------------------------------------------------------------
434 Notes on type synonyms
435 ~~~~~~~~~~~~~~~~~~~~~~
436 The various "split" functions (splitFunTy, splitRhoTy, splitForAllTy) try
437 to return type synonyms whereever possible. Thus
442 splitFunTys (a -> Foo a) = ([a], Foo a)
445 The reason is that we then get better (shorter) type signatures in
446 interfaces. Notably this plays a role in tcTySigs in TcBinds.lhs.
451 repType looks through
455 (d) usage annotations
456 (e) all newtypes, including recursive ones, but not newtype families
457 It's useful in the back end.
460 repType :: Type -> Type
461 -- Only applied to types of kind *; hence tycons are saturated
462 repType ty | Just ty' <- coreView ty = repType ty'
463 repType (ForAllTy _ ty) = repType ty
464 repType (TyConApp tc tys)
465 | isClosedNewTyCon tc = -- Recursive newtypes are opaque to coreView
466 -- but we must expand them here. Sure to
467 -- be saturated because repType is only applied
468 -- to types of kind *
469 ASSERT( {- isRecursiveTyCon tc && -} tys `lengthIs` tyConArity tc )
470 repType (new_type_rep tc tys)
473 -- new_type_rep doesn't ask any questions:
474 -- it just expands newtype, whether recursive or not
475 new_type_rep new_tycon tys = ASSERT( tys `lengthIs` tyConArity new_tycon )
476 case newTyConRep new_tycon of
477 (tvs, rep_ty) -> substTyWith tvs tys rep_ty
479 -- ToDo: this could be moved to the code generator, using splitTyConApp instead
480 -- of inspecting the type directly.
481 typePrimRep :: Type -> PrimRep
482 typePrimRep ty = case repType ty of
483 TyConApp tc _ -> tyConPrimRep tc
485 AppTy _ _ -> PtrRep -- See note below
487 other -> pprPanic "typePrimRep" (ppr ty)
488 -- Types of the form 'f a' must be of kind *, not *#, so
489 -- we are guaranteed that they are represented by pointers.
490 -- The reason is that f must have kind *->*, not *->*#, because
491 -- (we claim) there is no way to constrain f's kind any other
497 ---------------------------------------------------------------------
502 mkForAllTy :: TyVar -> Type -> Type
504 = mkForAllTys [tyvar] ty
506 mkForAllTys :: [TyVar] -> Type -> Type
507 mkForAllTys tyvars ty = foldr ForAllTy ty tyvars
509 isForAllTy :: Type -> Bool
510 isForAllTy (NoteTy _ ty) = isForAllTy ty
511 isForAllTy (ForAllTy _ _) = True
512 isForAllTy other_ty = False
514 splitForAllTy_maybe :: Type -> Maybe (TyVar, Type)
515 splitForAllTy_maybe ty = splitFAT_m ty
517 splitFAT_m ty | Just ty' <- coreView ty = splitFAT_m ty'
518 splitFAT_m (ForAllTy tyvar ty) = Just(tyvar, ty)
519 splitFAT_m _ = Nothing
521 splitForAllTys :: Type -> ([TyVar], Type)
522 splitForAllTys ty = split ty ty []
524 split orig_ty ty tvs | Just ty' <- coreView ty = split orig_ty ty' tvs
525 split orig_ty (ForAllTy tv ty) tvs = split ty ty (tv:tvs)
526 split orig_ty t tvs = (reverse tvs, orig_ty)
528 dropForAlls :: Type -> Type
529 dropForAlls ty = snd (splitForAllTys ty)
532 -- (mkPiType now in CoreUtils)
536 Instantiate a for-all type with one or more type arguments.
537 Used when we have a polymorphic function applied to type args:
539 Then we use (applyTys type-of-f [t1,t2]) to compute the type of
543 applyTy :: Type -> Type -> Type
544 applyTy ty arg | Just ty' <- coreView ty = applyTy ty' arg
545 applyTy (ForAllTy tv ty) arg = substTyWith [tv] [arg] ty
546 applyTy other arg = panic "applyTy"
548 applyTys :: Type -> [Type] -> Type
549 -- This function is interesting because
550 -- a) the function may have more for-alls than there are args
551 -- b) less obviously, it may have fewer for-alls
552 -- For case (b) think of
553 -- applyTys (forall a.a) [forall b.b, Int]
554 -- This really can happen, via dressing up polymorphic types with newtype
555 -- clothing. Here's an example:
556 -- newtype R = R (forall a. a->a)
557 -- foo = case undefined :: R of
560 applyTys orig_fun_ty [] = orig_fun_ty
561 applyTys orig_fun_ty arg_tys
562 | n_tvs == n_args -- The vastly common case
563 = substTyWith tvs arg_tys rho_ty
564 | n_tvs > n_args -- Too many for-alls
565 = substTyWith (take n_args tvs) arg_tys
566 (mkForAllTys (drop n_args tvs) rho_ty)
567 | otherwise -- Too many type args
568 = ASSERT2( n_tvs > 0, ppr orig_fun_ty ) -- Zero case gives infnite loop!
569 applyTys (substTyWith tvs (take n_tvs arg_tys) rho_ty)
572 (tvs, rho_ty) = splitForAllTys orig_fun_ty
574 n_args = length arg_tys
578 %************************************************************************
580 \subsection{Source types}
582 %************************************************************************
584 A "source type" is a type that is a separate type as far as the type checker is
585 concerned, but which has low-level representation as far as the back end is concerned.
587 Source types are always lifted.
589 The key function is predTypeRep which gives the representation of a source type:
592 mkPredTy :: PredType -> Type
593 mkPredTy pred = PredTy pred
595 mkPredTys :: ThetaType -> [Type]
596 mkPredTys preds = map PredTy preds
598 predTypeRep :: PredType -> Type
599 -- Convert a PredType to its "representation type";
600 -- the post-type-checking type used by all the Core passes of GHC.
601 -- Unwraps only the outermost level; for example, the result might
602 -- be a newtype application
603 predTypeRep (IParam _ ty) = ty
604 predTypeRep (ClassP clas tys) = mkTyConApp (classTyCon clas) tys
605 -- Result might be a newtype application, but the consumer will
606 -- look through that too if necessary
607 predTypeRep (EqPred ty1 ty2) = pprPanic "predTypeRep" (ppr (EqPred ty1 ty2))
611 %************************************************************************
615 %************************************************************************
618 splitRecNewType_maybe :: Type -> Maybe Type
619 -- Sometimes we want to look through a recursive newtype, and that's what happens here
620 -- It only strips *one layer* off, so the caller will usually call itself recursively
621 -- Only applied to types of kind *, hence the newtype is always saturated
622 splitRecNewType_maybe ty | Just ty' <- coreView ty = splitRecNewType_maybe ty'
623 splitRecNewType_maybe (TyConApp tc tys)
624 | isClosedNewTyCon tc
625 = ASSERT( tys `lengthIs` tyConArity tc ) -- splitRecNewType_maybe only be applied
626 -- to *types* (of kind *)
627 ASSERT( isRecursiveTyCon tc ) -- Guaranteed by coreView
628 case newTyConRhs tc of
629 (tvs, rep_ty) -> ASSERT( length tvs == length tys )
630 Just (substTyWith tvs tys rep_ty)
632 splitRecNewType_maybe other = Nothing
639 %************************************************************************
641 \subsection{Kinds and free variables}
643 %************************************************************************
645 ---------------------------------------------------------------------
646 Finding the kind of a type
647 ~~~~~~~~~~~~~~~~~~~~~~~~~~
649 typeKind :: Type -> Kind
650 typeKind (TyConApp tycon tys) = ASSERT( not (isCoercionTyCon tycon) )
651 -- We should be looking for the coercion kind,
653 foldr (\_ k -> kindFunResult k) (tyConKind tycon) tys
654 typeKind (NoteTy _ ty) = typeKind ty
655 typeKind (PredTy pred) = predKind pred
656 typeKind (AppTy fun arg) = kindFunResult (typeKind fun)
657 typeKind (ForAllTy tv ty) = typeKind ty
658 typeKind (TyVarTy tyvar) = tyVarKind tyvar
659 typeKind (FunTy arg res)
660 -- Hack alert. The kind of (Int -> Int#) is liftedTypeKind (*),
661 -- not unliftedTypKind (#)
662 -- The only things that can be after a function arrow are
663 -- (a) types (of kind openTypeKind or its sub-kinds)
664 -- (b) kinds (of super-kind TY) (e.g. * -> (* -> *))
665 | isTySuperKind k = k
666 | otherwise = ASSERT( isSubOpenTypeKind k) liftedTypeKind
670 predKind :: PredType -> Kind
671 predKind (EqPred {}) = coSuperKind -- A coercion kind!
672 predKind (ClassP {}) = liftedTypeKind -- Class and implicitPredicates are
673 predKind (IParam {}) = liftedTypeKind -- always represented by lifted types
677 ---------------------------------------------------------------------
678 Free variables of a type
679 ~~~~~~~~~~~~~~~~~~~~~~~~
681 tyVarsOfType :: Type -> TyVarSet
682 -- NB: for type synonyms tyVarsOfType does *not* expand the synonym
683 tyVarsOfType (TyVarTy tv) = unitVarSet tv
684 tyVarsOfType (TyConApp tycon tys) = tyVarsOfTypes tys
685 tyVarsOfType (NoteTy (FTVNote tvs) ty2) = tvs
686 tyVarsOfType (PredTy sty) = tyVarsOfPred sty
687 tyVarsOfType (FunTy arg res) = tyVarsOfType arg `unionVarSet` tyVarsOfType res
688 tyVarsOfType (AppTy fun arg) = tyVarsOfType fun `unionVarSet` tyVarsOfType arg
689 tyVarsOfType (ForAllTy tyvar ty) = delVarSet (tyVarsOfType ty) tyvar
691 tyVarsOfTypes :: [Type] -> TyVarSet
692 tyVarsOfTypes tys = foldr (unionVarSet.tyVarsOfType) emptyVarSet tys
694 tyVarsOfPred :: PredType -> TyVarSet
695 tyVarsOfPred (IParam _ ty) = tyVarsOfType ty
696 tyVarsOfPred (ClassP _ tys) = tyVarsOfTypes tys
697 tyVarsOfPred (EqPred ty1 ty2) = tyVarsOfType ty1 `unionVarSet` tyVarsOfType ty2
699 tyVarsOfTheta :: ThetaType -> TyVarSet
700 tyVarsOfTheta = foldr (unionVarSet . tyVarsOfPred) emptyVarSet
702 -- Add a Note with the free tyvars to the top of the type
703 addFreeTyVars :: Type -> Type
704 addFreeTyVars ty@(NoteTy (FTVNote _) _) = ty
705 addFreeTyVars ty = NoteTy (FTVNote (tyVarsOfType ty)) ty
709 %************************************************************************
711 \subsection{TidyType}
713 %************************************************************************
715 tidyTy tidies up a type for printing in an error message, or in
718 It doesn't change the uniques at all, just the print names.
721 tidyTyVarBndr :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
722 tidyTyVarBndr (tidy_env, subst) tyvar
723 = case tidyOccName tidy_env (getOccName name) of
724 (tidy', occ') -> ((tidy', subst'), tyvar')
726 subst' = extendVarEnv subst tyvar tyvar'
727 tyvar' = setTyVarName tyvar name'
728 name' = tidyNameOcc name occ'
730 name = tyVarName tyvar
732 tidyFreeTyVars :: TidyEnv -> TyVarSet -> TidyEnv
733 -- Add the free tyvars to the env in tidy form,
734 -- so that we can tidy the type they are free in
735 tidyFreeTyVars env tyvars = fst (tidyOpenTyVars env (varSetElems tyvars))
737 tidyOpenTyVars :: TidyEnv -> [TyVar] -> (TidyEnv, [TyVar])
738 tidyOpenTyVars env tyvars = mapAccumL tidyOpenTyVar env tyvars
740 tidyOpenTyVar :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
741 -- Treat a new tyvar as a binder, and give it a fresh tidy name
742 tidyOpenTyVar env@(tidy_env, subst) tyvar
743 = case lookupVarEnv subst tyvar of
744 Just tyvar' -> (env, tyvar') -- Already substituted
745 Nothing -> tidyTyVarBndr env tyvar -- Treat it as a binder
747 tidyType :: TidyEnv -> Type -> Type
748 tidyType env@(tidy_env, subst) ty
751 go (TyVarTy tv) = case lookupVarEnv subst tv of
752 Nothing -> TyVarTy tv
753 Just tv' -> TyVarTy tv'
754 go (TyConApp tycon tys) = let args = map go tys
755 in args `seqList` TyConApp tycon args
756 go (NoteTy note ty) = (NoteTy $! (go_note note)) $! (go ty)
757 go (PredTy sty) = PredTy (tidyPred env sty)
758 go (AppTy fun arg) = (AppTy $! (go fun)) $! (go arg)
759 go (FunTy fun arg) = (FunTy $! (go fun)) $! (go arg)
760 go (ForAllTy tv ty) = ForAllTy tvp $! (tidyType envp ty)
762 (envp, tvp) = tidyTyVarBndr env tv
764 go_note note@(FTVNote ftvs) = note -- No need to tidy the free tyvars
766 tidyTypes env tys = map (tidyType env) tys
768 tidyPred :: TidyEnv -> PredType -> PredType
769 tidyPred env (IParam n ty) = IParam n (tidyType env ty)
770 tidyPred env (ClassP clas tys) = ClassP clas (tidyTypes env tys)
771 tidyPred env (EqPred ty1 ty2) = EqPred (tidyType env ty1) (tidyType env ty2)
775 @tidyOpenType@ grabs the free type variables, tidies them
776 and then uses @tidyType@ to work over the type itself
779 tidyOpenType :: TidyEnv -> Type -> (TidyEnv, Type)
781 = (env', tidyType env' ty)
783 env' = tidyFreeTyVars env (tyVarsOfType ty)
785 tidyOpenTypes :: TidyEnv -> [Type] -> (TidyEnv, [Type])
786 tidyOpenTypes env tys = mapAccumL tidyOpenType env tys
788 tidyTopType :: Type -> Type
789 tidyTopType ty = tidyType emptyTidyEnv ty
794 tidyKind :: TidyEnv -> Kind -> (TidyEnv, Kind)
795 tidyKind env k = tidyOpenType env k
800 %************************************************************************
802 \subsection{Liftedness}
804 %************************************************************************
807 isUnLiftedType :: Type -> Bool
808 -- isUnLiftedType returns True for forall'd unlifted types:
809 -- x :: forall a. Int#
810 -- I found bindings like these were getting floated to the top level.
811 -- They are pretty bogus types, mind you. It would be better never to
814 isUnLiftedType ty | Just ty' <- coreView ty = isUnLiftedType ty'
815 isUnLiftedType (ForAllTy tv ty) = isUnLiftedType ty
816 isUnLiftedType (TyConApp tc _) = isUnLiftedTyCon tc
817 isUnLiftedType other = False
819 isUnboxedTupleType :: Type -> Bool
820 isUnboxedTupleType ty = case splitTyConApp_maybe ty of
821 Just (tc, ty_args) -> isUnboxedTupleTyCon tc
824 -- Should only be applied to *types*; hence the assert
825 isAlgType :: Type -> Bool
826 isAlgType ty = case splitTyConApp_maybe ty of
827 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
832 @isStrictType@ computes whether an argument (or let RHS) should
833 be computed strictly or lazily, based only on its type.
834 Works just like isUnLiftedType, except that it has a special case
835 for dictionaries. Since it takes account of ClassP, you might think
836 this function should be in TcType, but isStrictType is used by DataCon,
837 which is below TcType in the hierarchy, so it's convenient to put it here.
840 isStrictType (PredTy pred) = isStrictPred pred
841 isStrictType ty | Just ty' <- coreView ty = isStrictType ty'
842 isStrictType (ForAllTy tv ty) = isStrictType ty
843 isStrictType (TyConApp tc _) = isUnLiftedTyCon tc
844 isStrictType other = False
846 isStrictPred (ClassP clas _) = opt_DictsStrict && not (isNewTyCon (classTyCon clas))
847 isStrictPred other = False
848 -- We may be strict in dictionary types, but only if it
849 -- has more than one component.
850 -- [Being strict in a single-component dictionary risks
851 -- poking the dictionary component, which is wrong.]
855 isPrimitiveType :: Type -> Bool
856 -- Returns types that are opaque to Haskell.
857 -- Most of these are unlifted, but now that we interact with .NET, we
858 -- may have primtive (foreign-imported) types that are lifted
859 isPrimitiveType ty = case splitTyConApp_maybe ty of
860 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
866 %************************************************************************
868 \subsection{Sequencing on types
870 %************************************************************************
873 seqType :: Type -> ()
874 seqType (TyVarTy tv) = tv `seq` ()
875 seqType (AppTy t1 t2) = seqType t1 `seq` seqType t2
876 seqType (FunTy t1 t2) = seqType t1 `seq` seqType t2
877 seqType (NoteTy note t2) = seqNote note `seq` seqType t2
878 seqType (PredTy p) = seqPred p
879 seqType (TyConApp tc tys) = tc `seq` seqTypes tys
880 seqType (ForAllTy tv ty) = tv `seq` seqType ty
882 seqTypes :: [Type] -> ()
884 seqTypes (ty:tys) = seqType ty `seq` seqTypes tys
886 seqNote :: TyNote -> ()
887 seqNote (FTVNote set) = sizeUniqSet set `seq` ()
889 seqPred :: PredType -> ()
890 seqPred (ClassP c tys) = c `seq` seqTypes tys
891 seqPred (IParam n ty) = n `seq` seqType ty
892 seqPred (EqPred ty1 ty2) = seqType ty1 `seq` seqType ty2
896 %************************************************************************
898 Equality for Core types
899 (We don't use instances so that we know where it happens)
901 %************************************************************************
903 Note that eqType works right even for partial applications of newtypes.
904 See Note [Newtype eta] in TyCon.lhs
907 coreEqType :: Type -> Type -> Bool
911 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfType t1 `unionVarSet` tyVarsOfType t2))
913 eq env (TyVarTy tv1) (TyVarTy tv2) = rnOccL env tv1 == rnOccR env tv2
914 eq env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = eq (rnBndr2 env tv1 tv2) t1 t2
915 eq env (AppTy s1 t1) (AppTy s2 t2) = eq env s1 s2 && eq env t1 t2
916 eq env (FunTy s1 t1) (FunTy s2 t2) = eq env s1 s2 && eq env t1 t2
917 eq env (TyConApp tc1 tys1) (TyConApp tc2 tys2)
918 | tc1 == tc2, all2 (eq env) tys1 tys2 = True
919 -- The lengths should be equal because
920 -- the two types have the same kind
921 -- NB: if the type constructors differ that does not
922 -- necessarily mean that the types aren't equal
923 -- (synonyms, newtypes)
924 -- Even if the type constructors are the same, but the arguments
925 -- differ, the two types could be the same (e.g. if the arg is just
926 -- ignored in the RHS). In both these cases we fall through to an
927 -- attempt to expand one side or the other.
929 -- Now deal with newtypes, synonyms, pred-tys
930 eq env t1 t2 | Just t1' <- coreView t1 = eq env t1' t2
931 | Just t2' <- coreView t2 = eq env t1 t2'
933 -- Fall through case; not equal!
938 %************************************************************************
940 Comparision for source types
941 (We don't use instances so that we know where it happens)
943 %************************************************************************
947 do *not* look through newtypes, PredTypes
950 tcEqType :: Type -> Type -> Bool
951 tcEqType t1 t2 = isEqual $ cmpType t1 t2
953 tcEqTypes :: [Type] -> [Type] -> Bool
954 tcEqTypes tys1 tys2 = isEqual $ cmpTypes tys1 tys2
956 tcCmpType :: Type -> Type -> Ordering
957 tcCmpType t1 t2 = cmpType t1 t2
959 tcCmpTypes :: [Type] -> [Type] -> Ordering
960 tcCmpTypes tys1 tys2 = cmpTypes tys1 tys2
962 tcEqPred :: PredType -> PredType -> Bool
963 tcEqPred p1 p2 = isEqual $ cmpPred p1 p2
965 tcCmpPred :: PredType -> PredType -> Ordering
966 tcCmpPred p1 p2 = cmpPred p1 p2
968 tcEqTypeX :: RnEnv2 -> Type -> Type -> Bool
969 tcEqTypeX env t1 t2 = isEqual $ cmpTypeX env t1 t2
972 Now here comes the real worker
975 cmpType :: Type -> Type -> Ordering
976 cmpType t1 t2 = cmpTypeX rn_env t1 t2
978 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfType t1 `unionVarSet` tyVarsOfType t2))
980 cmpTypes :: [Type] -> [Type] -> Ordering
981 cmpTypes ts1 ts2 = cmpTypesX rn_env ts1 ts2
983 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfTypes ts1 `unionVarSet` tyVarsOfTypes ts2))
985 cmpPred :: PredType -> PredType -> Ordering
986 cmpPred p1 p2 = cmpPredX rn_env p1 p2
988 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfPred p1 `unionVarSet` tyVarsOfPred p2))
990 cmpTypeX :: RnEnv2 -> Type -> Type -> Ordering -- Main workhorse
991 cmpTypeX env t1 t2 | Just t1' <- tcView t1 = cmpTypeX env t1' t2
992 | Just t2' <- tcView t2 = cmpTypeX env t1 t2'
994 cmpTypeX env (TyVarTy tv1) (TyVarTy tv2) = rnOccL env tv1 `compare` rnOccR env tv2
995 cmpTypeX env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = cmpTypeX (rnBndr2 env tv1 tv2) t1 t2
996 cmpTypeX env (AppTy s1 t1) (AppTy s2 t2) = cmpTypeX env s1 s2 `thenCmp` cmpTypeX env t1 t2
997 cmpTypeX env (FunTy s1 t1) (FunTy s2 t2) = cmpTypeX env s1 s2 `thenCmp` cmpTypeX env t1 t2
998 cmpTypeX env (PredTy p1) (PredTy p2) = cmpPredX env p1 p2
999 cmpTypeX env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` cmpTypesX env tys1 tys2
1000 cmpTypeX env t1 (NoteTy _ t2) = cmpTypeX env t1 t2
1002 -- Deal with the rest: TyVarTy < AppTy < FunTy < TyConApp < ForAllTy < PredTy
1003 cmpTypeX env (AppTy _ _) (TyVarTy _) = GT
1005 cmpTypeX env (FunTy _ _) (TyVarTy _) = GT
1006 cmpTypeX env (FunTy _ _) (AppTy _ _) = GT
1008 cmpTypeX env (TyConApp _ _) (TyVarTy _) = GT
1009 cmpTypeX env (TyConApp _ _) (AppTy _ _) = GT
1010 cmpTypeX env (TyConApp _ _) (FunTy _ _) = GT
1012 cmpTypeX env (ForAllTy _ _) (TyVarTy _) = GT
1013 cmpTypeX env (ForAllTy _ _) (AppTy _ _) = GT
1014 cmpTypeX env (ForAllTy _ _) (FunTy _ _) = GT
1015 cmpTypeX env (ForAllTy _ _) (TyConApp _ _) = GT
1017 cmpTypeX env (PredTy _) t2 = GT
1019 cmpTypeX env _ _ = LT
1022 cmpTypesX :: RnEnv2 -> [Type] -> [Type] -> Ordering
1023 cmpTypesX env [] [] = EQ
1024 cmpTypesX env (t1:tys1) (t2:tys2) = cmpTypeX env t1 t2 `thenCmp` cmpTypesX env tys1 tys2
1025 cmpTypesX env [] tys = LT
1026 cmpTypesX env ty [] = GT
1029 cmpPredX :: RnEnv2 -> PredType -> PredType -> Ordering
1030 cmpPredX env (IParam n1 ty1) (IParam n2 ty2) = (n1 `compare` n2) `thenCmp` cmpTypeX env ty1 ty2
1031 -- Compare types as well as names for implicit parameters
1032 -- This comparison is used exclusively (I think) for the
1033 -- finite map built in TcSimplify
1034 cmpPredX env (ClassP c1 tys1) (ClassP c2 tys2) = (c1 `compare` c2) `thenCmp` cmpTypesX env tys1 tys2
1035 cmpPredX env (EqPred ty1 ty2) (EqPred ty1' ty2') = (cmpTypeX env ty1 ty1') `thenCmp` (cmpTypeX env ty2 ty2')
1037 -- Constructor order: IParam < ClassP < EqPred
1038 cmpPredX env (IParam {}) _ = LT
1039 cmpPredX env (ClassP {}) (IParam {}) = GT
1040 cmpPredX env (ClassP {}) (EqPred {}) = LT
1041 cmpPredX env (EqPred {}) _ = GT
1044 PredTypes are used as a FM key in TcSimplify,
1045 so we take the easy path and make them an instance of Ord
1048 instance Eq PredType where { (==) = tcEqPred }
1049 instance Ord PredType where { compare = tcCmpPred }
1053 %************************************************************************
1057 %************************************************************************
1061 = TvSubst InScopeSet -- The in-scope type variables
1062 TvSubstEnv -- The substitution itself
1063 -- See Note [Apply Once]
1065 {- ----------------------------------------------------------
1068 We use TvSubsts to instantiate things, and we might instantiate
1072 So the substition might go [a->b, b->a]. A similar situation arises in Core
1073 when we find a beta redex like
1074 (/\ a /\ b -> e) b a
1075 Then we also end up with a substition that permutes type variables. Other
1076 variations happen to; for example [a -> (a, b)].
1078 ***************************************************
1079 *** So a TvSubst must be applied precisely once ***
1080 ***************************************************
1082 A TvSubst is not idempotent, but, unlike the non-idempotent substitution
1083 we use during unifications, it must not be repeatedly applied.
1084 -------------------------------------------------------------- -}
1087 type TvSubstEnv = TyVarEnv Type
1088 -- A TvSubstEnv is used both inside a TvSubst (with the apply-once
1089 -- invariant discussed in Note [Apply Once]), and also independently
1090 -- in the middle of matching, and unification (see Types.Unify)
1091 -- So you have to look at the context to know if it's idempotent or
1092 -- apply-once or whatever
1093 emptyTvSubstEnv :: TvSubstEnv
1094 emptyTvSubstEnv = emptyVarEnv
1096 composeTvSubst :: InScopeSet -> TvSubstEnv -> TvSubstEnv -> TvSubstEnv
1097 -- (compose env1 env2)(x) is env1(env2(x)); i.e. apply env2 then env1
1098 -- It assumes that both are idempotent
1099 -- Typically, env1 is the refinement to a base substitution env2
1100 composeTvSubst in_scope env1 env2
1101 = env1 `plusVarEnv` mapVarEnv (substTy subst1) env2
1102 -- First apply env1 to the range of env2
1103 -- Then combine the two, making sure that env1 loses if
1104 -- both bind the same variable; that's why env1 is the
1105 -- *left* argument to plusVarEnv, because the right arg wins
1107 subst1 = TvSubst in_scope env1
1109 emptyTvSubst = TvSubst emptyInScopeSet emptyVarEnv
1111 isEmptyTvSubst :: TvSubst -> Bool
1112 isEmptyTvSubst (TvSubst _ env) = isEmptyVarEnv env
1114 mkTvSubst :: InScopeSet -> TvSubstEnv -> TvSubst
1117 getTvSubstEnv :: TvSubst -> TvSubstEnv
1118 getTvSubstEnv (TvSubst _ env) = env
1120 getTvInScope :: TvSubst -> InScopeSet
1121 getTvInScope (TvSubst in_scope _) = in_scope
1123 isInScope :: Var -> TvSubst -> Bool
1124 isInScope v (TvSubst in_scope _) = v `elemInScopeSet` in_scope
1126 notElemTvSubst :: TyVar -> TvSubst -> Bool
1127 notElemTvSubst tv (TvSubst _ env) = not (tv `elemVarEnv` env)
1129 setTvSubstEnv :: TvSubst -> TvSubstEnv -> TvSubst
1130 setTvSubstEnv (TvSubst in_scope _) env = TvSubst in_scope env
1132 extendTvInScope :: TvSubst -> [Var] -> TvSubst
1133 extendTvInScope (TvSubst in_scope env) vars = TvSubst (extendInScopeSetList in_scope vars) env
1135 extendTvSubst :: TvSubst -> TyVar -> Type -> TvSubst
1136 extendTvSubst (TvSubst in_scope env) tv ty = TvSubst in_scope (extendVarEnv env tv ty)
1138 extendTvSubstList :: TvSubst -> [TyVar] -> [Type] -> TvSubst
1139 extendTvSubstList (TvSubst in_scope env) tvs tys
1140 = TvSubst in_scope (extendVarEnvList env (tvs `zip` tys))
1142 -- mkOpenTvSubst and zipOpenTvSubst generate the in-scope set from
1143 -- the types given; but it's just a thunk so with a bit of luck
1144 -- it'll never be evaluated
1146 mkOpenTvSubst :: TvSubstEnv -> TvSubst
1147 mkOpenTvSubst env = TvSubst (mkInScopeSet (tyVarsOfTypes (varEnvElts env))) env
1149 zipOpenTvSubst :: [TyVar] -> [Type] -> TvSubst
1150 zipOpenTvSubst tyvars tys
1152 | length tyvars /= length tys
1153 = pprTrace "zipOpenTvSubst" (ppr tyvars $$ ppr tys) emptyTvSubst
1156 = TvSubst (mkInScopeSet (tyVarsOfTypes tys)) (zipTyEnv tyvars tys)
1158 -- mkTopTvSubst is called when doing top-level substitutions.
1159 -- Here we expect that the free vars of the range of the
1160 -- substitution will be empty.
1161 mkTopTvSubst :: [(TyVar, Type)] -> TvSubst
1162 mkTopTvSubst prs = TvSubst emptyInScopeSet (mkVarEnv prs)
1164 zipTopTvSubst :: [TyVar] -> [Type] -> TvSubst
1165 zipTopTvSubst tyvars tys
1167 | length tyvars /= length tys
1168 = pprTrace "zipOpenTvSubst" (ppr tyvars $$ ppr tys) emptyTvSubst
1171 = TvSubst emptyInScopeSet (zipTyEnv tyvars tys)
1173 zipTyEnv :: [TyVar] -> [Type] -> TvSubstEnv
1176 | length tyvars /= length tys
1177 = pprTrace "mkTopTvSubst" (ppr tyvars $$ ppr tys) emptyVarEnv
1180 = zip_ty_env tyvars tys emptyVarEnv
1182 -- Later substitutions in the list over-ride earlier ones,
1183 -- but there should be no loops
1184 zip_ty_env [] [] env = env
1185 zip_ty_env (tv:tvs) (ty:tys) env = zip_ty_env tvs tys (extendVarEnv env tv ty)
1186 -- There used to be a special case for when
1188 -- (a not-uncommon case) in which case the substitution was dropped.
1189 -- But the type-tidier changes the print-name of a type variable without
1190 -- changing the unique, and that led to a bug. Why? Pre-tidying, we had
1191 -- a type {Foo t}, where Foo is a one-method class. So Foo is really a newtype.
1192 -- And it happened that t was the type variable of the class. Post-tiding,
1193 -- it got turned into {Foo t2}. The ext-core printer expanded this using
1194 -- sourceTypeRep, but that said "Oh, t == t2" because they have the same unique,
1195 -- and so generated a rep type mentioning t not t2.
1197 -- Simplest fix is to nuke the "optimisation"
1198 zip_ty_env tvs tys env = pprTrace "Var/Type length mismatch: " (ppr tvs $$ ppr tys) env
1199 -- zip_ty_env _ _ env = env
1201 instance Outputable TvSubst where
1202 ppr (TvSubst ins env)
1203 = brackets $ sep[ ptext SLIT("TvSubst"),
1204 nest 2 (ptext SLIT("In scope:") <+> ppr ins),
1205 nest 2 (ptext SLIT("Env:") <+> ppr env) ]
1208 %************************************************************************
1210 Performing type substitutions
1212 %************************************************************************
1215 substTyWith :: [TyVar] -> [Type] -> Type -> Type
1216 substTyWith tvs tys = ASSERT( length tvs == length tys )
1217 substTy (zipOpenTvSubst tvs tys)
1219 substTy :: TvSubst -> Type -> Type
1220 substTy subst ty | isEmptyTvSubst subst = ty
1221 | otherwise = subst_ty subst ty
1223 substTys :: TvSubst -> [Type] -> [Type]
1224 substTys subst tys | isEmptyTvSubst subst = tys
1225 | otherwise = map (subst_ty subst) tys
1227 substTheta :: TvSubst -> ThetaType -> ThetaType
1228 substTheta subst theta
1229 | isEmptyTvSubst subst = theta
1230 | otherwise = map (substPred subst) theta
1232 substPred :: TvSubst -> PredType -> PredType
1233 substPred subst (IParam n ty) = IParam n (subst_ty subst ty)
1234 substPred subst (ClassP clas tys) = ClassP clas (map (subst_ty subst) tys)
1235 substPred subst (EqPred ty1 ty2) = EqPred (subst_ty subst ty1) (subst_ty subst ty2)
1237 deShadowTy :: TyVarSet -> Type -> Type -- Remove any nested binders mentioning tvs
1239 = subst_ty (mkTvSubst in_scope emptyTvSubstEnv) ty
1241 in_scope = mkInScopeSet tvs
1243 subst_ty :: TvSubst -> Type -> Type
1244 -- subst_ty is the main workhorse for type substitution
1246 -- Note that the in_scope set is poked only if we hit a forall
1247 -- so it may often never be fully computed
1251 go (TyVarTy tv) = substTyVar subst tv
1252 go (TyConApp tc tys) = let args = map go tys
1253 in args `seqList` TyConApp tc args
1255 go (PredTy p) = PredTy $! (substPred subst p)
1257 go (NoteTy (FTVNote _) ty2) = go ty2 -- Discard the free tyvar note
1259 go (FunTy arg res) = (FunTy $! (go arg)) $! (go res)
1260 go (AppTy fun arg) = mkAppTy (go fun) $! (go arg)
1261 -- The mkAppTy smart constructor is important
1262 -- we might be replacing (a Int), represented with App
1263 -- by [Int], represented with TyConApp
1264 go (ForAllTy tv ty) = case substTyVarBndr subst tv of
1265 (subst', tv') -> ForAllTy tv' $! (subst_ty subst' ty)
1267 substTyVar :: TvSubst -> TyVar -> Type
1268 substTyVar subst@(TvSubst in_scope env) tv
1269 = case lookupTyVar subst tv of {
1270 Nothing -> TyVarTy tv;
1271 Just ty -> ty -- See Note [Apply Once]
1274 lookupTyVar :: TvSubst -> TyVar -> Maybe Type
1275 lookupTyVar (TvSubst in_scope env) tv = lookupVarEnv env tv
1277 substTyVarBndr :: TvSubst -> TyVar -> (TvSubst, TyVar)
1278 substTyVarBndr subst@(TvSubst in_scope env) old_var
1279 = (TvSubst (in_scope `extendInScopeSet` new_var) new_env, new_var)
1282 new_env | no_change = delVarEnv env old_var
1283 | otherwise = extendVarEnv env old_var (TyVarTy new_var)
1285 no_change = new_var == old_var && not is_co_var
1286 -- no_change means that the new_var is identical in
1287 -- all respects to the old_var (same unique, same kind)
1289 -- In that case we don't need to extend the substitution
1290 -- to map old to new. But instead we must zap any
1291 -- current substitution for the variable. For example:
1292 -- (\x.e) with id_subst = [x |-> e']
1293 -- Here we must simply zap the substitution for x
1295 new_var = uniqAway in_scope subst_old_var
1296 -- The uniqAway part makes sure the new variable is not already in scope
1298 subst_old_var -- subst_old_var is old_var with the substitution applied to its kind
1299 -- It's only worth doing the substitution for coercions,
1300 -- becuase only they can have free type variables
1301 | is_co_var = setTyVarKind old_var (substTy subst kind)
1302 | otherwise = old_var
1303 kind = tyVarKind old_var
1304 is_co_var = isCoercionKind kind
1307 ----------------------------------------------------
1312 There's a little subtyping at the kind level:
1321 where * [LiftedTypeKind] means boxed type
1322 # [UnliftedTypeKind] means unboxed type
1323 (#) [UbxTupleKind] means unboxed tuple
1324 ?? [ArgTypeKind] is the lub of *,#
1325 ? [OpenTypeKind] means any type at all
1329 error :: forall a:?. String -> a
1330 (->) :: ?? -> ? -> *
1331 (\(x::t) -> ...) Here t::?? (i.e. not unboxed tuple)
1334 type KindVar = TyVar -- invariant: KindVar will always be a
1335 -- TcTyVar with details MetaTv TauTv ...
1336 -- kind var constructors and functions are in TcType
1338 type SimpleKind = Kind
1343 During kind inference, a kind variable unifies only with
1345 sk ::= * | sk1 -> sk2
1347 data T a = MkT a (T Int#)
1348 fails. We give T the kind (k -> *), and the kind variable k won't unify
1349 with # (the kind of Int#).
1353 When creating a fresh internal type variable, we give it a kind to express
1354 constraints on it. E.g. in (\x->e) we make up a fresh type variable for x,
1357 During unification we only bind an internal type variable to a type
1358 whose kind is lower in the sub-kind hierarchy than the kind of the tyvar.
1360 When unifying two internal type variables, we collect their kind constraints by
1361 finding the GLB of the two. Since the partial order is a tree, they only
1362 have a glb if one is a sub-kind of the other. In that case, we bind the
1363 less-informative one to the more informative one. Neat, eh?
1370 %************************************************************************
1372 Functions over Kinds
1374 %************************************************************************
1377 kindFunResult :: Kind -> Kind
1378 kindFunResult k = funResultTy k
1380 splitKindFunTys :: Kind -> ([Kind],Kind)
1381 splitKindFunTys k = splitFunTys k
1383 splitKindFunTysN :: Int -> Kind -> ([Kind],Kind)
1384 splitKindFunTysN k = splitFunTysN k
1386 isUbxTupleKind, isOpenTypeKind, isArgTypeKind, isUnliftedTypeKind :: Kind -> Bool
1388 isOpenTypeKindCon tc = tyConUnique tc == openTypeKindTyConKey
1390 isOpenTypeKind (TyConApp tc _) = isOpenTypeKindCon tc
1391 isOpenTypeKind other = False
1393 isUbxTupleKindCon tc = tyConUnique tc == ubxTupleKindTyConKey
1395 isUbxTupleKind (TyConApp tc _) = isUbxTupleKindCon tc
1396 isUbxTupleKind other = False
1398 isArgTypeKindCon tc = tyConUnique tc == argTypeKindTyConKey
1400 isArgTypeKind (TyConApp tc _) = isArgTypeKindCon tc
1401 isArgTypeKind other = False
1403 isUnliftedTypeKindCon tc = tyConUnique tc == unliftedTypeKindTyConKey
1405 isUnliftedTypeKind (TyConApp tc _) = isUnliftedTypeKindCon tc
1406 isUnliftedTypeKind other = False
1408 isSubOpenTypeKind :: Kind -> Bool
1409 -- True of any sub-kind of OpenTypeKind (i.e. anything except arrow)
1410 isSubOpenTypeKind (FunTy k1 k2) = ASSERT2 ( isKind k1, text "isSubOpenTypeKind" <+> ppr k1 <+> text "::" <+> ppr (typeKind k1) )
1411 ASSERT2 ( isKind k2, text "isSubOpenTypeKind" <+> ppr k2 <+> text "::" <+> ppr (typeKind k2) )
1413 isSubOpenTypeKind (TyConApp kc []) = ASSERT( isKind (TyConApp kc []) ) True
1414 isSubOpenTypeKind other = ASSERT( isKind other ) False
1415 -- This is a conservative answer
1416 -- It matters in the call to isSubKind in
1417 -- checkExpectedKind.
1419 isSubArgTypeKindCon kc
1420 | isUnliftedTypeKindCon kc = True
1421 | isLiftedTypeKindCon kc = True
1422 | isArgTypeKindCon kc = True
1425 isSubArgTypeKind :: Kind -> Bool
1426 -- True of any sub-kind of ArgTypeKind
1427 isSubArgTypeKind (TyConApp kc []) = isSubArgTypeKindCon kc
1428 isSubArgTypeKind other = False
1430 isSuperKind :: Type -> Bool
1431 isSuperKind (TyConApp (skc) []) = isSuperKindTyCon skc
1432 isSuperKind other = False
1434 isKind :: Kind -> Bool
1435 isKind k = isSuperKind (typeKind k)
1439 isSubKind :: Kind -> Kind -> Bool
1440 -- (k1 `isSubKind` k2) checks that k1 <: k2
1441 isSubKind (TyConApp kc1 []) (TyConApp kc2 []) = kc1 `isSubKindCon` kc2
1442 isSubKind (FunTy a1 r1) (FunTy a2 r2) = (a2 `isSubKind` a1) && (r1 `isSubKind` r2)
1443 isSubKind (PredTy (EqPred ty1 ty2)) (PredTy (EqPred ty1' ty2'))
1444 = ty1 `tcEqType` ty1' && ty2 `tcEqType` ty2'
1445 isSubKind k1 k2 = False
1447 eqKind :: Kind -> Kind -> Bool
1450 isSubKindCon :: TyCon -> TyCon -> Bool
1451 -- (kc1 `isSubKindCon` kc2) checks that kc1 <: kc2
1452 isSubKindCon kc1 kc2
1453 | isLiftedTypeKindCon kc1 && isLiftedTypeKindCon kc2 = True
1454 | isUnliftedTypeKindCon kc1 && isUnliftedTypeKindCon kc2 = True
1455 | isUbxTupleKindCon kc1 && isUbxTupleKindCon kc2 = True
1456 | isOpenTypeKindCon kc2 = True
1457 -- we already know kc1 is not a fun, its a TyCon
1458 | isArgTypeKindCon kc2 && isSubArgTypeKindCon kc1 = True
1461 defaultKind :: Kind -> Kind
1462 -- Used when generalising: default kind '?' and '??' to '*'
1464 -- When we generalise, we make generic type variables whose kind is
1465 -- simple (* or *->* etc). So generic type variables (other than
1466 -- built-in constants like 'error') always have simple kinds. This is important;
1469 -- We want f to get type
1470 -- f :: forall (a::*). a -> Bool
1472 -- f :: forall (a::??). a -> Bool
1473 -- because that would allow a call like (f 3#) as well as (f True),
1474 --and the calling conventions differ. This defaulting is done in TcMType.zonkTcTyVarBndr.
1476 | isSubOpenTypeKind k = liftedTypeKind
1477 | isSubArgTypeKind k = liftedTypeKind
1480 isCoercionKind :: Kind -> Bool
1481 -- All coercions are of form (ty1 :=: ty2)
1482 -- This function is here rather than in Coercion,
1483 -- because it's used by substTy
1484 isCoercionKind k | Just k' <- kindView k = isCoercionKind k'
1485 isCoercionKind (PredTy (EqPred {})) = True
1486 isCoercionKind other = False
1488 isEqPred :: PredType -> Bool
1489 isEqPred (EqPred _ _) = True
1490 isEqPred other = False