2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1998
6 Type - public interface
10 -- re-exports from TypeRep
11 TyThing(..), Type, PredType(..), ThetaType,
15 Kind, SimpleKind, KindVar,
16 kindFunResult, splitKindFunTys, splitKindFunTysN,
18 liftedTypeKindTyCon, openTypeKindTyCon, unliftedTypeKindTyCon,
19 argTypeKindTyCon, ubxTupleKindTyCon,
21 liftedTypeKind, unliftedTypeKind, openTypeKind,
22 argTypeKind, ubxTupleKind,
24 tySuperKind, coSuperKind,
26 isLiftedTypeKind, isUnliftedTypeKind, isOpenTypeKind,
27 isUbxTupleKind, isArgTypeKind, isKind, isTySuperKind,
28 isCoSuperKind, isSuperKind, isCoercionKind, isEqPred,
29 mkArrowKind, mkArrowKinds,
31 isSubArgTypeKind, isSubOpenTypeKind, isSubKind, defaultKind, eqKind,
34 -- Re-exports from TyCon
37 mkTyVarTy, mkTyVarTys, getTyVar, getTyVar_maybe, isTyVarTy,
39 mkAppTy, mkAppTys, splitAppTy, splitAppTys,
40 splitAppTy_maybe, repSplitAppTy_maybe,
42 mkFunTy, mkFunTys, splitFunTy, splitFunTy_maybe,
43 splitFunTys, splitFunTysN,
44 funResultTy, funArgTy, zipFunTys, isFunTy,
46 mkTyConApp, mkTyConTy,
47 tyConAppTyCon, tyConAppArgs,
48 splitTyConApp_maybe, splitTyConApp,
49 splitNewTyConApp_maybe, splitNewTyConApp,
51 repType, repType', typePrimRep, coreView, tcView, kindView,
53 mkForAllTy, mkForAllTys, splitForAllTy_maybe, splitForAllTys,
54 applyTy, applyTys, isForAllTy, dropForAlls,
57 predTypeRep, mkPredTy, mkPredTys, pprSourceTyCon,
60 splitRecNewType_maybe, newTyConInstRhs,
63 isUnLiftedType, isUnboxedTupleType, isAlgType, isPrimitiveType,
64 isStrictType, isStrictPred,
67 tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tyVarsOfTheta,
68 typeKind, addFreeTyVars,
70 -- Tidying up for printing
72 tidyOpenType, tidyOpenTypes,
73 tidyTyVarBndr, tidyFreeTyVars,
74 tidyOpenTyVar, tidyOpenTyVars,
75 tidyTopType, tidyPred,
79 coreEqType, tcEqType, tcEqTypes, tcCmpType, tcCmpTypes,
80 tcEqPred, tcCmpPred, tcEqTypeX,
86 TvSubstEnv, emptyTvSubstEnv, -- Representation widely visible
87 TvSubst(..), emptyTvSubst, -- Representation visible to a few friends
88 mkTvSubst, mkOpenTvSubst, zipOpenTvSubst, zipTopTvSubst, mkTopTvSubst, notElemTvSubst,
89 getTvSubstEnv, setTvSubstEnv, getTvInScope, extendTvInScope,
90 extendTvSubst, extendTvSubstList, isInScope, composeTvSubst, zipTyEnv,
93 -- Performing substitution on types
94 substTy, substTys, substTyWith, substTheta,
95 substPred, substTyVar, substTyVars, substTyVarBndr, deShadowTy, lookupTyVar,
98 pprType, pprParendType, pprTypeApp, pprTyThingCategory, pprForAll,
99 pprPred, pprTheta, pprThetaArrow, pprClassPred, pprKind, pprParendKind
102 #include "HsVersions.h"
104 -- We import the representation and primitive functions from TypeRep.
105 -- Many things are reexported, but not the representation!
125 import Data.Maybe ( isJust )
129 %************************************************************************
133 %************************************************************************
135 In Core, we "look through" non-recursive newtypes and PredTypes.
138 {-# INLINE coreView #-}
139 coreView :: Type -> Maybe Type
140 -- Strips off the *top layer only* of a type to give
141 -- its underlying representation type.
142 -- Returns Nothing if there is nothing to look through.
144 -- In the case of newtypes, it returns
145 -- *either* a vanilla TyConApp (recursive newtype, or non-saturated)
146 -- *or* the newtype representation (otherwise), meaning the
147 -- type written in the RHS of the newtype decl,
148 -- which may itself be a newtype
150 -- Example: newtype R = MkR S
152 -- newtype T = MkT (T -> T)
153 -- expandNewTcApp on R gives Just S
155 -- on T gives Nothing (no expansion)
157 -- By being non-recursive and inlined, this case analysis gets efficiently
158 -- joined onto the case analysis that the caller is already doing
159 coreView (NoteTy _ ty) = Just ty
161 | isEqPred p = Nothing
162 | otherwise = Just (predTypeRep p)
163 coreView (TyConApp tc tys) | Just (tenv, rhs, tys') <- coreExpandTyCon_maybe tc tys
164 = Just (mkAppTys (substTy (mkTopTvSubst tenv) rhs) tys')
165 -- Its important to use mkAppTys, rather than (foldl AppTy),
166 -- because the function part might well return a
167 -- partially-applied type constructor; indeed, usually will!
168 coreView ty = Nothing
172 -----------------------------------------------
173 {-# INLINE tcView #-}
174 tcView :: Type -> Maybe Type
175 -- Same, but for the type checker, which just looks through synonyms
176 tcView (NoteTy _ ty) = Just ty
177 tcView (TyConApp tc tys) | Just (tenv, rhs, tys') <- tcExpandTyCon_maybe tc tys
178 = Just (mkAppTys (substTy (mkTopTvSubst tenv) rhs) tys')
181 -----------------------------------------------
182 {-# INLINE kindView #-}
183 kindView :: Kind -> Maybe Kind
184 -- C.f. coreView, tcView
185 -- For the moment, we don't even handle synonyms in kinds
186 kindView (NoteTy _ k) = Just k
187 kindView other = Nothing
191 %************************************************************************
193 \subsection{Constructor-specific functions}
195 %************************************************************************
198 ---------------------------------------------------------------------
202 mkTyVarTy :: TyVar -> Type
205 mkTyVarTys :: [TyVar] -> [Type]
206 mkTyVarTys = map mkTyVarTy -- a common use of mkTyVarTy
208 getTyVar :: String -> Type -> TyVar
209 getTyVar msg ty = case getTyVar_maybe ty of
211 Nothing -> panic ("getTyVar: " ++ msg)
213 isTyVarTy :: Type -> Bool
214 isTyVarTy ty = isJust (getTyVar_maybe ty)
216 getTyVar_maybe :: Type -> Maybe TyVar
217 getTyVar_maybe ty | Just ty' <- coreView ty = getTyVar_maybe ty'
218 getTyVar_maybe (TyVarTy tv) = Just tv
219 getTyVar_maybe other = Nothing
224 ---------------------------------------------------------------------
227 We need to be pretty careful with AppTy to make sure we obey the
228 invariant that a TyConApp is always visibly so. mkAppTy maintains the
232 mkAppTy orig_ty1 orig_ty2
235 mk_app (NoteTy _ ty1) = mk_app ty1
236 mk_app (TyConApp tc tys) = mkTyConApp tc (tys ++ [orig_ty2])
237 mk_app ty1 = AppTy orig_ty1 orig_ty2
238 -- Note that the TyConApp could be an
239 -- under-saturated type synonym. GHC allows that; e.g.
240 -- type Foo k = k a -> k a
242 -- foo :: Foo Id -> Foo Id
244 -- Here Id is partially applied in the type sig for Foo,
245 -- but once the type synonyms are expanded all is well
247 mkAppTys :: Type -> [Type] -> Type
248 mkAppTys orig_ty1 [] = orig_ty1
249 -- This check for an empty list of type arguments
250 -- avoids the needless loss of a type synonym constructor.
251 -- For example: mkAppTys Rational []
252 -- returns to (Ratio Integer), which has needlessly lost
253 -- the Rational part.
254 mkAppTys orig_ty1 orig_tys2
257 mk_app (NoteTy _ ty1) = mk_app ty1
258 mk_app (TyConApp tc tys) = mkTyConApp tc (tys ++ orig_tys2)
259 -- mkTyConApp: see notes with mkAppTy
260 mk_app ty1 = foldl AppTy orig_ty1 orig_tys2
263 splitAppTy_maybe :: Type -> Maybe (Type, Type)
264 splitAppTy_maybe ty | Just ty' <- coreView ty
265 = splitAppTy_maybe ty'
266 splitAppTy_maybe ty = repSplitAppTy_maybe ty
269 repSplitAppTy_maybe :: Type -> Maybe (Type,Type)
270 -- Does the AppTy split, but assumes that any view stuff is already done
271 repSplitAppTy_maybe (FunTy ty1 ty2) = Just (TyConApp funTyCon [ty1], ty2)
272 repSplitAppTy_maybe (AppTy ty1 ty2) = Just (ty1, ty2)
273 repSplitAppTy_maybe (TyConApp tc tys) = case snocView tys of
274 Just (tys', ty') -> Just (TyConApp tc tys', ty')
276 repSplitAppTy_maybe other = Nothing
278 splitAppTy :: Type -> (Type, Type)
279 splitAppTy ty = case splitAppTy_maybe ty of
281 Nothing -> panic "splitAppTy"
284 splitAppTys :: Type -> (Type, [Type])
285 splitAppTys ty = split ty ty []
287 split orig_ty ty args | Just ty' <- coreView ty = split orig_ty ty' args
288 split orig_ty (AppTy ty arg) args = split ty ty (arg:args)
289 split orig_ty (TyConApp tc tc_args) args = (TyConApp tc [], tc_args ++ args)
290 split orig_ty (FunTy ty1 ty2) args = ASSERT( null args )
291 (TyConApp funTyCon [], [ty1,ty2])
292 split orig_ty ty args = (orig_ty, args)
297 ---------------------------------------------------------------------
302 mkFunTy :: Type -> Type -> Type
303 mkFunTy (PredTy (EqPred ty1 ty2)) res = mkForAllTy (mkWildCoVar (PredTy (EqPred ty1 ty2))) res
304 mkFunTy arg res = FunTy arg res
306 mkFunTys :: [Type] -> Type -> Type
307 mkFunTys tys ty = foldr mkFunTy ty tys
309 isFunTy :: Type -> Bool
310 isFunTy ty = isJust (splitFunTy_maybe ty)
312 splitFunTy :: Type -> (Type, Type)
313 splitFunTy ty | Just ty' <- coreView ty = splitFunTy ty'
314 splitFunTy (FunTy arg res) = (arg, res)
315 splitFunTy other = pprPanic "splitFunTy" (ppr other)
317 splitFunTy_maybe :: Type -> Maybe (Type, Type)
318 splitFunTy_maybe ty | Just ty' <- coreView ty = splitFunTy_maybe ty'
319 splitFunTy_maybe (FunTy arg res) = Just (arg, res)
320 splitFunTy_maybe other = Nothing
322 splitFunTys :: Type -> ([Type], Type)
323 splitFunTys ty = split [] ty ty
325 split args orig_ty ty | Just ty' <- coreView ty = split args orig_ty ty'
326 split args orig_ty (FunTy arg res) = split (arg:args) res res
327 split args orig_ty ty = (reverse args, orig_ty)
329 splitFunTysN :: Int -> Type -> ([Type], Type)
330 -- Split off exactly n arg tys
331 splitFunTysN 0 ty = ([], ty)
332 splitFunTysN n ty = case splitFunTy ty of { (arg, res) ->
333 case splitFunTysN (n-1) res of { (args, res) ->
336 zipFunTys :: Outputable a => [a] -> Type -> ([(a,Type)], Type)
337 zipFunTys orig_xs orig_ty = split [] orig_xs orig_ty orig_ty
339 split acc [] nty ty = (reverse acc, nty)
341 | Just ty' <- coreView ty = split acc xs nty ty'
342 split acc (x:xs) nty (FunTy arg res) = split ((x,arg):acc) xs res res
343 split acc (x:xs) nty ty = pprPanic "zipFunTys" (ppr orig_xs <+> ppr orig_ty)
345 funResultTy :: Type -> Type
346 funResultTy ty | Just ty' <- coreView ty = funResultTy ty'
347 funResultTy (FunTy arg res) = res
348 funResultTy ty = pprPanic "funResultTy" (ppr ty)
350 funArgTy :: Type -> Type
351 funArgTy ty | Just ty' <- coreView ty = funArgTy ty'
352 funArgTy (FunTy arg res) = arg
353 funArgTy ty = pprPanic "funArgTy" (ppr ty)
357 ---------------------------------------------------------------------
360 @mkTyConApp@ is a key function, because it builds a TyConApp, FunTy or PredTy,
364 mkTyConApp :: TyCon -> [Type] -> Type
366 | isFunTyCon tycon, [ty1,ty2] <- tys
372 mkTyConTy :: TyCon -> Type
373 mkTyConTy tycon = mkTyConApp tycon []
375 -- splitTyConApp "looks through" synonyms, because they don't
376 -- mean a distinct type, but all other type-constructor applications
377 -- including functions are returned as Just ..
379 tyConAppTyCon :: Type -> TyCon
380 tyConAppTyCon ty = fst (splitTyConApp ty)
382 tyConAppArgs :: Type -> [Type]
383 tyConAppArgs ty = snd (splitTyConApp ty)
385 splitTyConApp :: Type -> (TyCon, [Type])
386 splitTyConApp ty = case splitTyConApp_maybe ty of
388 Nothing -> pprPanic "splitTyConApp" (ppr ty)
390 splitTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
391 splitTyConApp_maybe ty | Just ty' <- coreView ty = splitTyConApp_maybe ty'
392 splitTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
393 splitTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
394 splitTyConApp_maybe other = Nothing
396 -- Sometimes we do NOT want to look throught a newtype. When case matching
397 -- on a newtype we want a convenient way to access the arguments of a newty
398 -- constructor so as to properly form a coercion.
399 splitNewTyConApp :: Type -> (TyCon, [Type])
400 splitNewTyConApp ty = case splitNewTyConApp_maybe ty of
402 Nothing -> pprPanic "splitNewTyConApp" (ppr ty)
403 splitNewTyConApp_maybe :: Type -> Maybe (TyCon, [Type])
404 splitNewTyConApp_maybe ty | Just ty' <- tcView ty = splitNewTyConApp_maybe ty'
405 splitNewTyConApp_maybe (TyConApp tc tys) = Just (tc, tys)
406 splitNewTyConApp_maybe (FunTy arg res) = Just (funTyCon, [arg,res])
407 splitNewTyConApp_maybe other = Nothing
409 -- get instantiated newtype rhs, the arguments had better saturate
411 newTyConInstRhs :: TyCon -> [Type] -> Type
412 newTyConInstRhs tycon tys =
413 let (tvs, ty) = newTyConRhs tycon in substTyWith tvs tys ty
417 ---------------------------------------------------------------------
421 Notes on type synonyms
422 ~~~~~~~~~~~~~~~~~~~~~~
423 The various "split" functions (splitFunTy, splitRhoTy, splitForAllTy) try
424 to return type synonyms whereever possible. Thus
429 splitFunTys (a -> Foo a) = ([a], Foo a)
432 The reason is that we then get better (shorter) type signatures in
433 interfaces. Notably this plays a role in tcTySigs in TcBinds.lhs.
438 repType looks through
442 (d) usage annotations
443 (e) all newtypes, including recursive ones, but not newtype families
444 It's useful in the back end.
447 repType :: Type -> Type
448 -- Only applied to types of kind *; hence tycons are saturated
449 repType ty | Just ty' <- coreView ty = repType ty'
450 repType (ForAllTy _ ty) = repType ty
451 repType (TyConApp tc tys)
452 | isClosedNewTyCon tc = -- Recursive newtypes are opaque to coreView
453 -- but we must expand them here. Sure to
454 -- be saturated because repType is only applied
455 -- to types of kind *
456 ASSERT( {- isRecursiveTyCon tc && -} tys `lengthIs` tyConArity tc )
457 repType (new_type_rep tc tys)
460 -- repType' aims to be a more thorough version of repType
461 -- For now it simply looks through the TyConApp args too
462 repType' ty -- | pprTrace "repType'" (ppr ty $$ ppr (go1 ty)) False = undefined
466 go (TyConApp tc tys) = mkTyConApp tc (map repType' 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))
606 -- Pretty prints a tycon, using the family instance in case of a
607 -- representation tycon. For example
608 -- e.g. data T [a] = ...
609 -- In that case we want to print `T [a]', where T is the family TyCon
611 | Just (repTyCon, tys) <- tyConFamInst_maybe tycon
612 = ppr $ repTyCon `TyConApp` tys -- can't be FunTyCon
618 %************************************************************************
622 %************************************************************************
625 splitRecNewType_maybe :: Type -> Maybe Type
626 -- Sometimes we want to look through a recursive newtype, and that's what happens here
627 -- It only strips *one layer* off, so the caller will usually call itself recursively
628 -- Only applied to types of kind *, hence the newtype is always saturated
629 splitRecNewType_maybe ty | Just ty' <- coreView ty = splitRecNewType_maybe ty'
630 splitRecNewType_maybe (TyConApp tc tys)
631 | isClosedNewTyCon tc
632 = ASSERT( tys `lengthIs` tyConArity tc ) -- splitRecNewType_maybe only be applied
633 -- to *types* (of kind *)
634 ASSERT( isRecursiveTyCon tc ) -- Guaranteed by coreView
635 case newTyConRhs tc of
636 (tvs, rep_ty) -> ASSERT( length tvs == length tys )
637 Just (substTyWith tvs tys rep_ty)
639 splitRecNewType_maybe other = Nothing
646 %************************************************************************
648 \subsection{Kinds and free variables}
650 %************************************************************************
652 ---------------------------------------------------------------------
653 Finding the kind of a type
654 ~~~~~~~~~~~~~~~~~~~~~~~~~~
656 typeKind :: Type -> Kind
657 typeKind (TyConApp tycon tys) = ASSERT( not (isCoercionTyCon tycon) )
658 -- We should be looking for the coercion kind,
660 foldr (\_ k -> kindFunResult k) (tyConKind tycon) tys
661 typeKind (NoteTy _ ty) = typeKind ty
662 typeKind (PredTy pred) = predKind pred
663 typeKind (AppTy fun arg) = kindFunResult (typeKind fun)
664 typeKind (ForAllTy tv ty) = typeKind ty
665 typeKind (TyVarTy tyvar) = tyVarKind tyvar
666 typeKind (FunTy arg res)
667 -- Hack alert. The kind of (Int -> Int#) is liftedTypeKind (*),
668 -- not unliftedTypKind (#)
669 -- The only things that can be after a function arrow are
670 -- (a) types (of kind openTypeKind or its sub-kinds)
671 -- (b) kinds (of super-kind TY) (e.g. * -> (* -> *))
672 | isTySuperKind k = k
673 | otherwise = ASSERT( isSubOpenTypeKind k) liftedTypeKind
677 predKind :: PredType -> Kind
678 predKind (EqPred {}) = coSuperKind -- A coercion kind!
679 predKind (ClassP {}) = liftedTypeKind -- Class and implicitPredicates are
680 predKind (IParam {}) = liftedTypeKind -- always represented by lifted types
684 ---------------------------------------------------------------------
685 Free variables of a type
686 ~~~~~~~~~~~~~~~~~~~~~~~~
688 tyVarsOfType :: Type -> TyVarSet
689 -- NB: for type synonyms tyVarsOfType does *not* expand the synonym
690 tyVarsOfType (TyVarTy tv) = unitVarSet tv
691 tyVarsOfType (TyConApp tycon tys) = tyVarsOfTypes tys
692 tyVarsOfType (NoteTy (FTVNote tvs) ty2) = tvs
693 tyVarsOfType (PredTy sty) = tyVarsOfPred sty
694 tyVarsOfType (FunTy arg res) = tyVarsOfType arg `unionVarSet` tyVarsOfType res
695 tyVarsOfType (AppTy fun arg) = tyVarsOfType fun `unionVarSet` tyVarsOfType arg
696 tyVarsOfType (ForAllTy tyvar ty) = delVarSet (tyVarsOfType ty) tyvar
698 tyVarsOfTypes :: [Type] -> TyVarSet
699 tyVarsOfTypes tys = foldr (unionVarSet.tyVarsOfType) emptyVarSet tys
701 tyVarsOfPred :: PredType -> TyVarSet
702 tyVarsOfPred (IParam _ ty) = tyVarsOfType ty
703 tyVarsOfPred (ClassP _ tys) = tyVarsOfTypes tys
704 tyVarsOfPred (EqPred ty1 ty2) = tyVarsOfType ty1 `unionVarSet` tyVarsOfType ty2
706 tyVarsOfTheta :: ThetaType -> TyVarSet
707 tyVarsOfTheta = foldr (unionVarSet . tyVarsOfPred) emptyVarSet
709 -- Add a Note with the free tyvars to the top of the type
710 addFreeTyVars :: Type -> Type
711 addFreeTyVars ty@(NoteTy (FTVNote _) _) = ty
712 addFreeTyVars ty = NoteTy (FTVNote (tyVarsOfType ty)) ty
716 %************************************************************************
718 \subsection{TidyType}
720 %************************************************************************
722 tidyTy tidies up a type for printing in an error message, or in
725 It doesn't change the uniques at all, just the print names.
728 tidyTyVarBndr :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
729 tidyTyVarBndr env@(tidy_env, subst) tyvar
730 = case tidyOccName tidy_env (getOccName name) of
731 (tidy', occ') -> ((tidy', subst'), tyvar'')
733 subst' = extendVarEnv subst tyvar tyvar''
734 tyvar' = setTyVarName tyvar name'
735 name' = tidyNameOcc name occ'
736 -- Don't forget to tidy the kind for coercions!
737 tyvar'' | isCoVar tyvar = setTyVarKind tyvar' kind'
739 kind' = tidyType env (tyVarKind tyvar)
741 name = tyVarName tyvar
743 tidyFreeTyVars :: TidyEnv -> TyVarSet -> TidyEnv
744 -- Add the free tyvars to the env in tidy form,
745 -- so that we can tidy the type they are free in
746 tidyFreeTyVars env tyvars = fst (tidyOpenTyVars env (varSetElems tyvars))
748 tidyOpenTyVars :: TidyEnv -> [TyVar] -> (TidyEnv, [TyVar])
749 tidyOpenTyVars env tyvars = mapAccumL tidyOpenTyVar env tyvars
751 tidyOpenTyVar :: TidyEnv -> TyVar -> (TidyEnv, TyVar)
752 -- Treat a new tyvar as a binder, and give it a fresh tidy name
753 tidyOpenTyVar env@(tidy_env, subst) tyvar
754 = case lookupVarEnv subst tyvar of
755 Just tyvar' -> (env, tyvar') -- Already substituted
756 Nothing -> tidyTyVarBndr env tyvar -- Treat it as a binder
758 tidyType :: TidyEnv -> Type -> Type
759 tidyType env@(tidy_env, subst) ty
762 go (TyVarTy tv) = case lookupVarEnv subst tv of
763 Nothing -> TyVarTy tv
764 Just tv' -> TyVarTy tv'
765 go (TyConApp tycon tys) = let args = map go tys
766 in args `seqList` TyConApp tycon args
767 go (NoteTy note ty) = (NoteTy $! (go_note note)) $! (go ty)
768 go (PredTy sty) = PredTy (tidyPred env sty)
769 go (AppTy fun arg) = (AppTy $! (go fun)) $! (go arg)
770 go (FunTy fun arg) = (FunTy $! (go fun)) $! (go arg)
771 go (ForAllTy tv ty) = ForAllTy tvp $! (tidyType envp ty)
773 (envp, tvp) = tidyTyVarBndr env tv
775 go_note note@(FTVNote ftvs) = note -- No need to tidy the free tyvars
777 tidyTypes env tys = map (tidyType env) tys
779 tidyPred :: TidyEnv -> PredType -> PredType
780 tidyPred env (IParam n ty) = IParam n (tidyType env ty)
781 tidyPred env (ClassP clas tys) = ClassP clas (tidyTypes env tys)
782 tidyPred env (EqPred ty1 ty2) = EqPred (tidyType env ty1) (tidyType env ty2)
786 @tidyOpenType@ grabs the free type variables, tidies them
787 and then uses @tidyType@ to work over the type itself
790 tidyOpenType :: TidyEnv -> Type -> (TidyEnv, Type)
792 = (env', tidyType env' ty)
794 env' = tidyFreeTyVars env (tyVarsOfType ty)
796 tidyOpenTypes :: TidyEnv -> [Type] -> (TidyEnv, [Type])
797 tidyOpenTypes env tys = mapAccumL tidyOpenType env tys
799 tidyTopType :: Type -> Type
800 tidyTopType ty = tidyType emptyTidyEnv ty
805 tidyKind :: TidyEnv -> Kind -> (TidyEnv, Kind)
806 tidyKind env k = tidyOpenType env k
811 %************************************************************************
813 \subsection{Liftedness}
815 %************************************************************************
818 isUnLiftedType :: Type -> Bool
819 -- isUnLiftedType returns True for forall'd unlifted types:
820 -- x :: forall a. Int#
821 -- I found bindings like these were getting floated to the top level.
822 -- They are pretty bogus types, mind you. It would be better never to
825 isUnLiftedType ty | Just ty' <- coreView ty = isUnLiftedType ty'
826 isUnLiftedType (ForAllTy tv ty) = isUnLiftedType ty
827 isUnLiftedType (TyConApp tc _) = isUnLiftedTyCon tc
828 isUnLiftedType other = False
830 isUnboxedTupleType :: Type -> Bool
831 isUnboxedTupleType ty = case splitTyConApp_maybe ty of
832 Just (tc, ty_args) -> isUnboxedTupleTyCon tc
835 -- Should only be applied to *types*; hence the assert
836 isAlgType :: Type -> Bool
837 isAlgType ty = case splitTyConApp_maybe ty of
838 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
843 @isStrictType@ computes whether an argument (or let RHS) should
844 be computed strictly or lazily, based only on its type.
845 Works just like isUnLiftedType, except that it has a special case
846 for dictionaries. Since it takes account of ClassP, you might think
847 this function should be in TcType, but isStrictType is used by DataCon,
848 which is below TcType in the hierarchy, so it's convenient to put it here.
851 isStrictType (PredTy pred) = isStrictPred pred
852 isStrictType ty | Just ty' <- coreView ty = isStrictType ty'
853 isStrictType (ForAllTy tv ty) = isStrictType ty
854 isStrictType (TyConApp tc _) = isUnLiftedTyCon tc
855 isStrictType other = False
857 isStrictPred (ClassP clas _) = opt_DictsStrict && not (isNewTyCon (classTyCon clas))
858 isStrictPred other = False
859 -- We may be strict in dictionary types, but only if it
860 -- has more than one component.
861 -- [Being strict in a single-component dictionary risks
862 -- poking the dictionary component, which is wrong.]
866 isPrimitiveType :: Type -> Bool
867 -- Returns types that are opaque to Haskell.
868 -- Most of these are unlifted, but now that we interact with .NET, we
869 -- may have primtive (foreign-imported) types that are lifted
870 isPrimitiveType ty = case splitTyConApp_maybe ty of
871 Just (tc, ty_args) -> ASSERT( ty_args `lengthIs` tyConArity tc )
877 %************************************************************************
879 \subsection{Sequencing on types
881 %************************************************************************
884 seqType :: Type -> ()
885 seqType (TyVarTy tv) = tv `seq` ()
886 seqType (AppTy t1 t2) = seqType t1 `seq` seqType t2
887 seqType (FunTy t1 t2) = seqType t1 `seq` seqType t2
888 seqType (NoteTy note t2) = seqNote note `seq` seqType t2
889 seqType (PredTy p) = seqPred p
890 seqType (TyConApp tc tys) = tc `seq` seqTypes tys
891 seqType (ForAllTy tv ty) = tv `seq` seqType ty
893 seqTypes :: [Type] -> ()
895 seqTypes (ty:tys) = seqType ty `seq` seqTypes tys
897 seqNote :: TyNote -> ()
898 seqNote (FTVNote set) = sizeUniqSet set `seq` ()
900 seqPred :: PredType -> ()
901 seqPred (ClassP c tys) = c `seq` seqTypes tys
902 seqPred (IParam n ty) = n `seq` seqType ty
903 seqPred (EqPred ty1 ty2) = seqType ty1 `seq` seqType ty2
907 %************************************************************************
909 Equality for Core types
910 (We don't use instances so that we know where it happens)
912 %************************************************************************
914 Note that eqType works right even for partial applications of newtypes.
915 See Note [Newtype eta] in TyCon.lhs
918 coreEqType :: Type -> Type -> Bool
922 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfType t1 `unionVarSet` tyVarsOfType t2))
924 eq env (TyVarTy tv1) (TyVarTy tv2) = rnOccL env tv1 == rnOccR env tv2
925 eq env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = eq (rnBndr2 env tv1 tv2) t1 t2
926 eq env (AppTy s1 t1) (AppTy s2 t2) = eq env s1 s2 && eq env t1 t2
927 eq env (FunTy s1 t1) (FunTy s2 t2) = eq env s1 s2 && eq env t1 t2
928 eq env (TyConApp tc1 tys1) (TyConApp tc2 tys2)
929 | tc1 == tc2, all2 (eq env) tys1 tys2 = True
930 -- The lengths should be equal because
931 -- the two types have the same kind
932 -- NB: if the type constructors differ that does not
933 -- necessarily mean that the types aren't equal
934 -- (synonyms, newtypes)
935 -- Even if the type constructors are the same, but the arguments
936 -- differ, the two types could be the same (e.g. if the arg is just
937 -- ignored in the RHS). In both these cases we fall through to an
938 -- attempt to expand one side or the other.
940 -- Now deal with newtypes, synonyms, pred-tys
941 eq env t1 t2 | Just t1' <- coreView t1 = eq env t1' t2
942 | Just t2' <- coreView t2 = eq env t1 t2'
944 -- Fall through case; not equal!
949 %************************************************************************
951 Comparision for source types
952 (We don't use instances so that we know where it happens)
954 %************************************************************************
958 do *not* look through newtypes, PredTypes
961 tcEqType :: Type -> Type -> Bool
962 tcEqType t1 t2 = isEqual $ cmpType t1 t2
964 tcEqTypes :: [Type] -> [Type] -> Bool
965 tcEqTypes tys1 tys2 = isEqual $ cmpTypes tys1 tys2
967 tcCmpType :: Type -> Type -> Ordering
968 tcCmpType t1 t2 = cmpType t1 t2
970 tcCmpTypes :: [Type] -> [Type] -> Ordering
971 tcCmpTypes tys1 tys2 = cmpTypes tys1 tys2
973 tcEqPred :: PredType -> PredType -> Bool
974 tcEqPred p1 p2 = isEqual $ cmpPred p1 p2
976 tcCmpPred :: PredType -> PredType -> Ordering
977 tcCmpPred p1 p2 = cmpPred p1 p2
979 tcEqTypeX :: RnEnv2 -> Type -> Type -> Bool
980 tcEqTypeX env t1 t2 = isEqual $ cmpTypeX env t1 t2
983 Now here comes the real worker
986 cmpType :: Type -> Type -> Ordering
987 cmpType t1 t2 = cmpTypeX rn_env t1 t2
989 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfType t1 `unionVarSet` tyVarsOfType t2))
991 cmpTypes :: [Type] -> [Type] -> Ordering
992 cmpTypes ts1 ts2 = cmpTypesX rn_env ts1 ts2
994 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfTypes ts1 `unionVarSet` tyVarsOfTypes ts2))
996 cmpPred :: PredType -> PredType -> Ordering
997 cmpPred p1 p2 = cmpPredX rn_env p1 p2
999 rn_env = mkRnEnv2 (mkInScopeSet (tyVarsOfPred p1 `unionVarSet` tyVarsOfPred p2))
1001 cmpTypeX :: RnEnv2 -> Type -> Type -> Ordering -- Main workhorse
1002 cmpTypeX env t1 t2 | Just t1' <- tcView t1 = cmpTypeX env t1' t2
1003 | Just t2' <- tcView t2 = cmpTypeX env t1 t2'
1005 cmpTypeX env (TyVarTy tv1) (TyVarTy tv2) = rnOccL env tv1 `compare` rnOccR env tv2
1006 cmpTypeX env (ForAllTy tv1 t1) (ForAllTy tv2 t2) = cmpTypeX (rnBndr2 env tv1 tv2) t1 t2
1007 cmpTypeX env (AppTy s1 t1) (AppTy s2 t2) = cmpTypeX env s1 s2 `thenCmp` cmpTypeX env t1 t2
1008 cmpTypeX env (FunTy s1 t1) (FunTy s2 t2) = cmpTypeX env s1 s2 `thenCmp` cmpTypeX env t1 t2
1009 cmpTypeX env (PredTy p1) (PredTy p2) = cmpPredX env p1 p2
1010 cmpTypeX env (TyConApp tc1 tys1) (TyConApp tc2 tys2) = (tc1 `compare` tc2) `thenCmp` cmpTypesX env tys1 tys2
1011 cmpTypeX env t1 (NoteTy _ t2) = cmpTypeX env t1 t2
1013 -- Deal with the rest: TyVarTy < AppTy < FunTy < TyConApp < ForAllTy < PredTy
1014 cmpTypeX env (AppTy _ _) (TyVarTy _) = GT
1016 cmpTypeX env (FunTy _ _) (TyVarTy _) = GT
1017 cmpTypeX env (FunTy _ _) (AppTy _ _) = GT
1019 cmpTypeX env (TyConApp _ _) (TyVarTy _) = GT
1020 cmpTypeX env (TyConApp _ _) (AppTy _ _) = GT
1021 cmpTypeX env (TyConApp _ _) (FunTy _ _) = GT
1023 cmpTypeX env (ForAllTy _ _) (TyVarTy _) = GT
1024 cmpTypeX env (ForAllTy _ _) (AppTy _ _) = GT
1025 cmpTypeX env (ForAllTy _ _) (FunTy _ _) = GT
1026 cmpTypeX env (ForAllTy _ _) (TyConApp _ _) = GT
1028 cmpTypeX env (PredTy _) t2 = GT
1030 cmpTypeX env _ _ = LT
1033 cmpTypesX :: RnEnv2 -> [Type] -> [Type] -> Ordering
1034 cmpTypesX env [] [] = EQ
1035 cmpTypesX env (t1:tys1) (t2:tys2) = cmpTypeX env t1 t2 `thenCmp` cmpTypesX env tys1 tys2
1036 cmpTypesX env [] tys = LT
1037 cmpTypesX env ty [] = GT
1040 cmpPredX :: RnEnv2 -> PredType -> PredType -> Ordering
1041 cmpPredX env (IParam n1 ty1) (IParam n2 ty2) = (n1 `compare` n2) `thenCmp` cmpTypeX env ty1 ty2
1042 -- Compare names only for implicit parameters
1043 -- This comparison is used exclusively (I believe)
1044 -- for the Avails finite map built in TcSimplify
1045 -- If the types differ we keep them distinct so that we see
1046 -- a distinct pair to run improvement on
1047 cmpPredX env (ClassP c1 tys1) (ClassP c2 tys2) = (c1 `compare` c2) `thenCmp` (cmpTypesX env tys1 tys2)
1048 cmpPredX env (EqPred ty1 ty2) (EqPred ty1' ty2') = (cmpTypeX env ty1 ty1') `thenCmp` (cmpTypeX env ty2 ty2')
1050 -- Constructor order: IParam < ClassP < EqPred
1051 cmpPredX env (IParam {}) _ = LT
1052 cmpPredX env (ClassP {}) (IParam {}) = GT
1053 cmpPredX env (ClassP {}) (EqPred {}) = LT
1054 cmpPredX env (EqPred {}) _ = GT
1057 PredTypes are used as a FM key in TcSimplify,
1058 so we take the easy path and make them an instance of Ord
1061 instance Eq PredType where { (==) = tcEqPred }
1062 instance Ord PredType where { compare = tcCmpPred }
1066 %************************************************************************
1070 %************************************************************************
1074 = TvSubst InScopeSet -- The in-scope type variables
1075 TvSubstEnv -- The substitution itself
1076 -- See Note [Apply Once]
1077 -- and Note [Extending the TvSubstEnv]
1079 {- ----------------------------------------------------------
1083 We use TvSubsts to instantiate things, and we might instantiate
1087 So the substition might go [a->b, b->a]. A similar situation arises in Core
1088 when we find a beta redex like
1089 (/\ a /\ b -> e) b a
1090 Then we also end up with a substition that permutes type variables. Other
1091 variations happen to; for example [a -> (a, b)].
1093 ***************************************************
1094 *** So a TvSubst must be applied precisely once ***
1095 ***************************************************
1097 A TvSubst is not idempotent, but, unlike the non-idempotent substitution
1098 we use during unifications, it must not be repeatedly applied.
1100 Note [Extending the TvSubst]
1101 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1102 The following invariant should hold of a TvSubst
1104 The in-scope set is needed *only* to
1105 guide the generation of fresh uniques
1107 In particular, the *kind* of the type variables in
1108 the in-scope set is not relevant
1110 This invariant allows a short-cut when the TvSubstEnv is empty:
1111 if the TvSubstEnv is empty --- i.e. (isEmptyTvSubt subst) holds ---
1112 then (substTy subst ty) does nothing.
1114 For example, consider:
1115 (/\a. /\b:(a~Int). ...b..) Int
1116 We substitute Int for 'a'. The Unique of 'b' does not change, but
1117 nevertheless we add 'b' to the TvSubstEnv, because b's type does change
1119 This invariant has several crucial consequences:
1121 * In substTyVarBndr, we need extend the TvSubstEnv
1122 - if the unique has changed
1123 - or if the kind has changed
1125 * In substTyVar, we do not need to consult the in-scope set;
1126 the TvSubstEnv is enough
1128 * In substTy, substTheta, we can short-circuit when the TvSubstEnv is empty
1131 -------------------------------------------------------------- -}
1134 type TvSubstEnv = TyVarEnv Type
1135 -- A TvSubstEnv is used both inside a TvSubst (with the apply-once
1136 -- invariant discussed in Note [Apply Once]), and also independently
1137 -- in the middle of matching, and unification (see Types.Unify)
1138 -- So you have to look at the context to know if it's idempotent or
1139 -- apply-once or whatever
1140 emptyTvSubstEnv :: TvSubstEnv
1141 emptyTvSubstEnv = emptyVarEnv
1143 composeTvSubst :: InScopeSet -> TvSubstEnv -> TvSubstEnv -> TvSubstEnv
1144 -- (compose env1 env2)(x) is env1(env2(x)); i.e. apply env2 then env1
1145 -- It assumes that both are idempotent
1146 -- Typically, env1 is the refinement to a base substitution env2
1147 composeTvSubst in_scope env1 env2
1148 = env1 `plusVarEnv` mapVarEnv (substTy subst1) env2
1149 -- First apply env1 to the range of env2
1150 -- Then combine the two, making sure that env1 loses if
1151 -- both bind the same variable; that's why env1 is the
1152 -- *left* argument to plusVarEnv, because the right arg wins
1154 subst1 = TvSubst in_scope env1
1156 emptyTvSubst = TvSubst emptyInScopeSet emptyVarEnv
1158 isEmptyTvSubst :: TvSubst -> Bool
1159 -- See Note [Extending the TvSubstEnv]
1160 isEmptyTvSubst (TvSubst _ env) = isEmptyVarEnv env
1162 mkTvSubst :: InScopeSet -> TvSubstEnv -> TvSubst
1165 getTvSubstEnv :: TvSubst -> TvSubstEnv
1166 getTvSubstEnv (TvSubst _ env) = env
1168 getTvInScope :: TvSubst -> InScopeSet
1169 getTvInScope (TvSubst in_scope _) = in_scope
1171 isInScope :: Var -> TvSubst -> Bool
1172 isInScope v (TvSubst in_scope _) = v `elemInScopeSet` in_scope
1174 notElemTvSubst :: TyVar -> TvSubst -> Bool
1175 notElemTvSubst tv (TvSubst _ env) = not (tv `elemVarEnv` env)
1177 setTvSubstEnv :: TvSubst -> TvSubstEnv -> TvSubst
1178 setTvSubstEnv (TvSubst in_scope _) env = TvSubst in_scope env
1180 extendTvInScope :: TvSubst -> [Var] -> TvSubst
1181 extendTvInScope (TvSubst in_scope env) vars = TvSubst (extendInScopeSetList in_scope vars) env
1183 extendTvSubst :: TvSubst -> TyVar -> Type -> TvSubst
1184 extendTvSubst (TvSubst in_scope env) tv ty = TvSubst in_scope (extendVarEnv env tv ty)
1186 extendTvSubstList :: TvSubst -> [TyVar] -> [Type] -> TvSubst
1187 extendTvSubstList (TvSubst in_scope env) tvs tys
1188 = TvSubst in_scope (extendVarEnvList env (tvs `zip` tys))
1190 -- mkOpenTvSubst and zipOpenTvSubst generate the in-scope set from
1191 -- the types given; but it's just a thunk so with a bit of luck
1192 -- it'll never be evaluated
1194 mkOpenTvSubst :: TvSubstEnv -> TvSubst
1195 mkOpenTvSubst env = TvSubst (mkInScopeSet (tyVarsOfTypes (varEnvElts env))) env
1197 zipOpenTvSubst :: [TyVar] -> [Type] -> TvSubst
1198 zipOpenTvSubst tyvars tys
1200 | length tyvars /= length tys
1201 = pprTrace "zipOpenTvSubst" (ppr tyvars $$ ppr tys) emptyTvSubst
1204 = TvSubst (mkInScopeSet (tyVarsOfTypes tys)) (zipTyEnv tyvars tys)
1206 -- mkTopTvSubst is called when doing top-level substitutions.
1207 -- Here we expect that the free vars of the range of the
1208 -- substitution will be empty.
1209 mkTopTvSubst :: [(TyVar, Type)] -> TvSubst
1210 mkTopTvSubst prs = TvSubst emptyInScopeSet (mkVarEnv prs)
1212 zipTopTvSubst :: [TyVar] -> [Type] -> TvSubst
1213 zipTopTvSubst tyvars tys
1215 | length tyvars /= length tys
1216 = pprTrace "zipTopTvSubst" (ppr tyvars $$ ppr tys) emptyTvSubst
1219 = TvSubst emptyInScopeSet (zipTyEnv tyvars tys)
1221 zipTyEnv :: [TyVar] -> [Type] -> TvSubstEnv
1224 | length tyvars /= length tys
1225 = pprTrace "mkTopTvSubst" (ppr tyvars $$ ppr tys) emptyVarEnv
1228 = zip_ty_env tyvars tys emptyVarEnv
1230 -- Later substitutions in the list over-ride earlier ones,
1231 -- but there should be no loops
1232 zip_ty_env [] [] env = env
1233 zip_ty_env (tv:tvs) (ty:tys) env = zip_ty_env tvs tys (extendVarEnv env tv ty)
1234 -- There used to be a special case for when
1236 -- (a not-uncommon case) in which case the substitution was dropped.
1237 -- But the type-tidier changes the print-name of a type variable without
1238 -- changing the unique, and that led to a bug. Why? Pre-tidying, we had
1239 -- a type {Foo t}, where Foo is a one-method class. So Foo is really a newtype.
1240 -- And it happened that t was the type variable of the class. Post-tiding,
1241 -- it got turned into {Foo t2}. The ext-core printer expanded this using
1242 -- sourceTypeRep, but that said "Oh, t == t2" because they have the same unique,
1243 -- and so generated a rep type mentioning t not t2.
1245 -- Simplest fix is to nuke the "optimisation"
1246 zip_ty_env tvs tys env = pprTrace "Var/Type length mismatch: " (ppr tvs $$ ppr tys) env
1247 -- zip_ty_env _ _ env = env
1249 instance Outputable TvSubst where
1250 ppr (TvSubst ins env)
1251 = brackets $ sep[ ptext SLIT("TvSubst"),
1252 nest 2 (ptext SLIT("In scope:") <+> ppr ins),
1253 nest 2 (ptext SLIT("Env:") <+> ppr env) ]
1256 %************************************************************************
1258 Performing type substitutions
1260 %************************************************************************
1263 substTyWith :: [TyVar] -> [Type] -> Type -> Type
1264 substTyWith tvs tys = ASSERT( length tvs == length tys )
1265 substTy (zipOpenTvSubst tvs tys)
1267 substTy :: TvSubst -> Type -> Type
1268 substTy subst ty | isEmptyTvSubst subst = ty
1269 | otherwise = subst_ty subst ty
1271 substTys :: TvSubst -> [Type] -> [Type]
1272 substTys subst tys | isEmptyTvSubst subst = tys
1273 | otherwise = map (subst_ty subst) tys
1275 substTheta :: TvSubst -> ThetaType -> ThetaType
1276 substTheta subst theta
1277 | isEmptyTvSubst subst = theta
1278 | otherwise = map (substPred subst) theta
1280 substPred :: TvSubst -> PredType -> PredType
1281 substPred subst (IParam n ty) = IParam n (subst_ty subst ty)
1282 substPred subst (ClassP clas tys) = ClassP clas (map (subst_ty subst) tys)
1283 substPred subst (EqPred ty1 ty2) = EqPred (subst_ty subst ty1) (subst_ty subst ty2)
1285 deShadowTy :: TyVarSet -> Type -> Type -- Remove any nested binders mentioning tvs
1287 = subst_ty (mkTvSubst in_scope emptyTvSubstEnv) ty
1289 in_scope = mkInScopeSet tvs
1291 subst_ty :: TvSubst -> Type -> Type
1292 -- subst_ty is the main workhorse for type substitution
1294 -- Note that the in_scope set is poked only if we hit a forall
1295 -- so it may often never be fully computed
1299 go (TyVarTy tv) = substTyVar subst tv
1300 go (TyConApp tc tys) = let args = map go tys
1301 in args `seqList` TyConApp tc args
1303 go (PredTy p) = PredTy $! (substPred subst p)
1305 go (NoteTy (FTVNote _) ty2) = go ty2 -- Discard the free tyvar note
1307 go (FunTy arg res) = (FunTy $! (go arg)) $! (go res)
1308 go (AppTy fun arg) = mkAppTy (go fun) $! (go arg)
1309 -- The mkAppTy smart constructor is important
1310 -- we might be replacing (a Int), represented with App
1311 -- by [Int], represented with TyConApp
1312 go (ForAllTy tv ty) = case substTyVarBndr subst tv of
1313 (subst', tv') -> ForAllTy tv' $! (subst_ty subst' ty)
1315 substTyVar :: TvSubst -> TyVar -> Type
1316 substTyVar subst@(TvSubst in_scope env) tv
1317 = case lookupTyVar subst tv of {
1318 Nothing -> TyVarTy tv;
1319 Just ty -> ty -- See Note [Apply Once]
1322 substTyVars :: TvSubst -> [TyVar] -> [Type]
1323 substTyVars subst tvs = map (substTyVar subst) tvs
1325 lookupTyVar :: TvSubst -> TyVar -> Maybe Type
1326 -- See Note [Extending the TvSubst]
1327 lookupTyVar (TvSubst in_scope env) tv = lookupVarEnv env tv
1329 substTyVarBndr :: TvSubst -> TyVar -> (TvSubst, TyVar)
1330 substTyVarBndr subst@(TvSubst in_scope env) old_var
1331 = (TvSubst (in_scope `extendInScopeSet` new_var) new_env, new_var)
1333 is_co_var = isCoVar old_var
1335 new_env | no_change = delVarEnv env old_var
1336 | otherwise = extendVarEnv env old_var (TyVarTy new_var)
1338 no_change = new_var == old_var && not is_co_var
1339 -- no_change means that the new_var is identical in
1340 -- all respects to the old_var (same unique, same kind)
1341 -- See Note [Extending the TvSubst]
1343 -- In that case we don't need to extend the substitution
1344 -- to map old to new. But instead we must zap any
1345 -- current substitution for the variable. For example:
1346 -- (\x.e) with id_subst = [x |-> e']
1347 -- Here we must simply zap the substitution for x
1349 new_var = uniqAway in_scope subst_old_var
1350 -- The uniqAway part makes sure the new variable is not already in scope
1352 subst_old_var -- subst_old_var is old_var with the substitution applied to its kind
1353 -- It's only worth doing the substitution for coercions,
1354 -- becuase only they can have free type variables
1355 | is_co_var = setTyVarKind old_var (substTy subst (tyVarKind old_var))
1356 | otherwise = old_var
1359 ----------------------------------------------------
1364 There's a little subtyping at the kind level:
1373 where * [LiftedTypeKind] means boxed type
1374 # [UnliftedTypeKind] means unboxed type
1375 (#) [UbxTupleKind] means unboxed tuple
1376 ?? [ArgTypeKind] is the lub of *,#
1377 ? [OpenTypeKind] means any type at all
1381 error :: forall a:?. String -> a
1382 (->) :: ?? -> ? -> *
1383 (\(x::t) -> ...) Here t::?? (i.e. not unboxed tuple)
1386 type KindVar = TyVar -- invariant: KindVar will always be a
1387 -- TcTyVar with details MetaTv TauTv ...
1388 -- kind var constructors and functions are in TcType
1390 type SimpleKind = Kind
1395 During kind inference, a kind variable unifies only with
1397 sk ::= * | sk1 -> sk2
1399 data T a = MkT a (T Int#)
1400 fails. We give T the kind (k -> *), and the kind variable k won't unify
1401 with # (the kind of Int#).
1405 When creating a fresh internal type variable, we give it a kind to express
1406 constraints on it. E.g. in (\x->e) we make up a fresh type variable for x,
1409 During unification we only bind an internal type variable to a type
1410 whose kind is lower in the sub-kind hierarchy than the kind of the tyvar.
1412 When unifying two internal type variables, we collect their kind constraints by
1413 finding the GLB of the two. Since the partial order is a tree, they only
1414 have a glb if one is a sub-kind of the other. In that case, we bind the
1415 less-informative one to the more informative one. Neat, eh?
1422 %************************************************************************
1424 Functions over Kinds
1426 %************************************************************************
1429 kindFunResult :: Kind -> Kind
1430 kindFunResult k = funResultTy k
1432 splitKindFunTys :: Kind -> ([Kind],Kind)
1433 splitKindFunTys k = splitFunTys k
1435 splitKindFunTysN :: Int -> Kind -> ([Kind],Kind)
1436 splitKindFunTysN k = splitFunTysN k
1438 isUbxTupleKind, isOpenTypeKind, isArgTypeKind, isUnliftedTypeKind :: Kind -> Bool
1440 isOpenTypeKindCon tc = tyConUnique tc == openTypeKindTyConKey
1442 isOpenTypeKind (TyConApp tc _) = isOpenTypeKindCon tc
1443 isOpenTypeKind other = False
1445 isUbxTupleKindCon tc = tyConUnique tc == ubxTupleKindTyConKey
1447 isUbxTupleKind (TyConApp tc _) = isUbxTupleKindCon tc
1448 isUbxTupleKind other = False
1450 isArgTypeKindCon tc = tyConUnique tc == argTypeKindTyConKey
1452 isArgTypeKind (TyConApp tc _) = isArgTypeKindCon tc
1453 isArgTypeKind other = False
1455 isUnliftedTypeKindCon tc = tyConUnique tc == unliftedTypeKindTyConKey
1457 isUnliftedTypeKind (TyConApp tc _) = isUnliftedTypeKindCon tc
1458 isUnliftedTypeKind other = False
1460 isSubOpenTypeKind :: Kind -> Bool
1461 -- True of any sub-kind of OpenTypeKind (i.e. anything except arrow)
1462 isSubOpenTypeKind (FunTy k1 k2) = ASSERT2 ( isKind k1, text "isSubOpenTypeKind" <+> ppr k1 <+> text "::" <+> ppr (typeKind k1) )
1463 ASSERT2 ( isKind k2, text "isSubOpenTypeKind" <+> ppr k2 <+> text "::" <+> ppr (typeKind k2) )
1465 isSubOpenTypeKind (TyConApp kc []) = ASSERT( isKind (TyConApp kc []) ) True
1466 isSubOpenTypeKind other = ASSERT( isKind other ) False
1467 -- This is a conservative answer
1468 -- It matters in the call to isSubKind in
1469 -- checkExpectedKind.
1471 isSubArgTypeKindCon kc
1472 | isUnliftedTypeKindCon kc = True
1473 | isLiftedTypeKindCon kc = True
1474 | isArgTypeKindCon kc = True
1477 isSubArgTypeKind :: Kind -> Bool
1478 -- True of any sub-kind of ArgTypeKind
1479 isSubArgTypeKind (TyConApp kc []) = isSubArgTypeKindCon kc
1480 isSubArgTypeKind other = False
1482 isSuperKind :: Type -> Bool
1483 isSuperKind (TyConApp (skc) []) = isSuperKindTyCon skc
1484 isSuperKind other = False
1486 isKind :: Kind -> Bool
1487 isKind k = isSuperKind (typeKind k)
1491 isSubKind :: Kind -> Kind -> Bool
1492 -- (k1 `isSubKind` k2) checks that k1 <: k2
1493 isSubKind (TyConApp kc1 []) (TyConApp kc2 []) = kc1 `isSubKindCon` kc2
1494 isSubKind (FunTy a1 r1) (FunTy a2 r2) = (a2 `isSubKind` a1) && (r1 `isSubKind` r2)
1495 isSubKind (PredTy (EqPred ty1 ty2)) (PredTy (EqPred ty1' ty2'))
1496 = ty1 `tcEqType` ty1' && ty2 `tcEqType` ty2'
1497 isSubKind k1 k2 = False
1499 eqKind :: Kind -> Kind -> Bool
1502 isSubKindCon :: TyCon -> TyCon -> Bool
1503 -- (kc1 `isSubKindCon` kc2) checks that kc1 <: kc2
1504 isSubKindCon kc1 kc2
1505 | isLiftedTypeKindCon kc1 && isLiftedTypeKindCon kc2 = True
1506 | isUnliftedTypeKindCon kc1 && isUnliftedTypeKindCon kc2 = True
1507 | isUbxTupleKindCon kc1 && isUbxTupleKindCon kc2 = True
1508 | isOpenTypeKindCon kc2 = True
1509 -- we already know kc1 is not a fun, its a TyCon
1510 | isArgTypeKindCon kc2 && isSubArgTypeKindCon kc1 = True
1513 defaultKind :: Kind -> Kind
1514 -- Used when generalising: default kind '?' and '??' to '*'
1516 -- When we generalise, we make generic type variables whose kind is
1517 -- simple (* or *->* etc). So generic type variables (other than
1518 -- built-in constants like 'error') always have simple kinds. This is important;
1521 -- We want f to get type
1522 -- f :: forall (a::*). a -> Bool
1524 -- f :: forall (a::??). a -> Bool
1525 -- because that would allow a call like (f 3#) as well as (f True),
1526 --and the calling conventions differ. This defaulting is done in TcMType.zonkTcTyVarBndr.
1528 | isSubOpenTypeKind k = liftedTypeKind
1529 | isSubArgTypeKind k = liftedTypeKind
1532 isEqPred :: PredType -> Bool
1533 isEqPred (EqPred _ _) = True
1534 isEqPred other = False