2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
4 \section[Id]{@Ids@: Value and constructor identifiers}
7 #include "HsVersions.h"
11 GenId(..), -- *naughtily* used in some places (e.g., TcHsSyn)
12 SYN_IE(Id), IdDetails,
14 SYN_IE(ConTag), fIRST_TAG,
15 SYN_IE(DataCon), SYN_IE(DictFun), SYN_IE(DictVar),
37 -- DESTRUCTION (excluding pragmatic info)
53 recordSelectorFieldLabel,
59 cmpId_withSpecDataCon,
66 isConstMethodId_maybe,
69 isDefaultMethodId_maybe,
76 isSuperDictSelId_maybe,
83 unfoldingUnfriendlyId,
89 -- PRINTING and RENUMBERING
100 -- UNFOLDING, ARITY, UPDATE, AND STRICTNESS STUFF (etc)
117 SYN_IE(IdEnv), SYN_IE(GenIdSet), SYN_IE(IdSet),
138 modifyIdEnv_Directly,
148 IMPORT_DELOOPER(IdLoop) -- for paranoia checking
149 IMPORT_DELOOPER(TyLoop) -- for paranoia checking
152 import Class ( classOpString, SYN_IE(Class), GenClass, SYN_IE(ClassOp), GenClassOp )
154 import Maybes ( maybeToBool )
155 import Name ( nameUnique, mkLocalName, mkSysLocalName, isLocalName,
156 mkCompoundName, mkInstDeclName,
157 isLocallyDefinedName, occNameString, modAndOcc,
158 isLocallyDefined, changeUnique, isWiredInName,
159 nameString, getOccString, setNameVisibility,
160 isExported, ExportFlag(..), DefnInfo, Provenance,
163 import PrelMods ( pREL_TUP, pREL_BASE )
164 import Lex ( mkTupNameStr )
165 import FieldLabel ( fieldLabelName, FieldLabel(..){-instances-} )
166 import PragmaInfo ( PragmaInfo(..) )
167 import PprEnv -- ( SYN_IE(NmbrM), NmbrEnv(..) )
168 import PprType ( getTypeString, specMaybeTysSuffix,
174 import MatchEnv ( MatchEnv )
175 import SrcLoc ( mkBuiltinSrcLoc )
176 import TysWiredIn ( tupleTyCon )
177 import TyCon ( TyCon, tyConDataCons )
178 import Type ( mkSigmaTy, mkTyVarTys, mkFunTys, mkDictTy,
179 applyTyCon, instantiateTy, mkForAllTys,
180 tyVarsOfType, applyTypeEnvToTy, typePrimRep,
181 GenType, SYN_IE(ThetaType), SYN_IE(TauType), SYN_IE(Type)
183 import TyVar ( alphaTyVars, isEmptyTyVarSet, SYN_IE(TyVarEnv) )
184 import Usage ( SYN_IE(UVar) )
186 import UniqSet -- practically all of it
187 import Unique ( getBuiltinUniques, pprUnique, showUnique,
189 Unique{-instance Ord3-}
191 import Util ( mapAccumL, nOfThem, zipEqual, assoc,
192 panic, panic#, pprPanic, assertPanic
196 Here are the @Id@ and @IdDetails@ datatypes; also see the notes that
199 Every @Id@ has a @Unique@, to uniquify it and for fast comparison, a
200 @Type@, and an @IdInfo@ (non-essential info about it, e.g.,
201 strictness). The essential info about different kinds of @Ids@ is
204 ToDo: possibly cache other stuff in the single-constructor @Id@ type.
208 Unique -- Key for fast comparison
210 ty -- Id's type; used all the time;
211 IdDetails -- Stuff about individual kinds of Ids.
212 PragmaInfo -- Properties of this Id requested by programmer
213 -- eg specialise-me, inline-me
214 IdInfo -- Properties of this Id deduced by compiler
218 data StrictnessMark = MarkedStrict | NotMarkedStrict
222 ---------------- Local values
224 = LocalId Bool -- Local name; mentioned by the user
225 -- True <=> no free type vars
227 | SysLocalId Bool -- Local name; made up by the compiler
230 | PrimitiveId PrimOp -- The Id for a primitive operation
232 | SpecPragmaId -- Local name; introduced by the compiler
233 (Maybe Id) -- for explicit specid in pragma
234 Bool -- as for LocalId
236 ---------------- Global values
238 | ImportedId -- Global name (Imported or Implicit); Id imported from an interface
240 ---------------- Data constructors
243 [StrictnessMark] -- Strict args; length = arity
244 [FieldLabel] -- Field labels for this constructor
246 [TyVar] [(Class,Type)] [Type] TyCon
248 -- forall tyvars . theta_ty =>
249 -- unitype_1 -> ... -> unitype_n -> tycon tyvars
251 | TupleConId Int -- Its arity
253 | RecordSelId FieldLabel
255 ---------------- Things to do with overloading
257 | SuperDictSelId -- Selector for superclass dictionary
258 Class -- The class (input dict)
259 Class -- The superclass (result dict)
261 | MethodSelId Class -- An overloaded class operation, with
262 -- a fully polymorphic type. Its code
263 -- just selects a method from the
264 -- dictionary. The class.
265 ClassOp -- The operation
267 -- NB: The IdInfo for a MethodSelId has all the info about its
268 -- related "constant method Ids", which are just
269 -- specialisations of this general one.
271 | DefaultMethodId -- Default method for a particular class op
272 Class -- same class, <blah-blah> info as MethodSelId
273 ClassOp -- (surprise, surprise)
274 Bool -- True <=> I *know* this default method Id
275 -- is a generated one that just says
276 -- `error "No default method for <op>"'.
279 | DictFunId Class -- A DictFun is uniquely identified
280 Type -- by its class and type; this type has free type vars,
281 -- whose identity is irrelevant. Eg Class = Eq
283 -- The "a" is irrelevant. As it is too painful to
284 -- actually do comparisons that way, we kindly supply
285 -- a Unique for that purpose.
288 | ConstMethodId -- A method which depends only on the type of the
289 -- instance, and not on any further dictionaries etc.
290 Class -- Uniquely identified by:
291 Type -- (class, type, classop) triple
293 Module -- module where instance came from
295 | InstId -- An instance of a dictionary, class operation,
296 -- or overloaded value (Local name)
297 Bool -- as for LocalId
299 | SpecId -- A specialisation of another Id
300 Id -- Id of which this is a specialisation
301 [Maybe Type] -- Types at which it is specialised;
302 -- A "Nothing" says this type ain't relevant.
303 Bool -- True <=> no free type vars; it's not enough
304 -- to know about the unspec version, because
305 -- we may specialise to a type w/ free tyvars
306 -- (i.e., in one of the "Maybe Type" dudes).
308 -- Scheduled for deletion: SLPJ Nov 96
309 -- Nobody seems to depend on knowing this.
310 | WorkerId -- A "worker" for some other Id
311 Id -- Id for which this is a worker
319 DictFunIds are generated from instance decls.
324 instance Foo a => Foo [a] where
327 generates the dict fun id decl
329 dfun.Foo.[*] = \d -> ...
331 The dfun id is uniquely named by the (class, type) pair. Notice, it
332 isn't a (class,tycon) pair any more, because we may get manually or
333 automatically generated specialisations of the instance decl:
335 instance Foo [Int] where
342 The type variables in the name are irrelevant; we print them as stars.
345 Constant method ids are generated from instance decls where
346 there is no context; that is, no dictionaries are needed to
347 construct the method. Example
349 instance Foo Int where
352 Then we get a constant method
357 It is possible, albeit unusual, to have a constant method
358 for an instance decl which has type vars:
360 instance Foo [a] where
364 We get the constant method
368 So a constant method is identified by a class/op/type triple.
369 The type variables in the type are irrelevant.
372 For Ids whose names must be known/deducible in other modules, we have
373 to conjure up their worker's names (and their worker's worker's
374 names... etc) in a known systematic way.
377 %************************************************************************
379 \subsection[Id-documentation]{Documentation}
381 %************************************************************************
385 The @Id@ datatype describes {\em values}. The basic things we want to
386 know: (1)~a value's {\em type} (@idType@ is a very common
387 operation in the compiler); and (2)~what ``flavour'' of value it might
388 be---for example, it can be terribly useful to know that a value is a
392 %----------------------------------------------------------------------
393 \item[@DataConId@:] For the data constructors declared by a @data@
394 declaration. Their type is kept in {\em two} forms---as a regular
395 @Type@ (in the usual place), and also in its constituent pieces (in
396 the ``details''). We are frequently interested in those pieces.
398 %----------------------------------------------------------------------
399 \item[@TupleConId@:] This is just a special shorthand for @DataCons@ for
400 the infinite family of tuples.
402 %----------------------------------------------------------------------
403 \item[@ImportedId@:] These are values defined outside this module.
404 {\em Everything} we want to know about them must be stored here (or in
407 %----------------------------------------------------------------------
408 \item[@MethodSelId@:] A selector from a dictionary; it may select either
409 a method or a dictionary for one of the class's superclasses.
411 %----------------------------------------------------------------------
414 @mkDictFunId [a,b..] theta C T@ is the function derived from the
417 instance theta => C (T a b ..) where
420 It builds function @Id@ which maps dictionaries for theta,
421 to a dictionary for C (T a b ..).
423 *Note* that with the ``Mark Jones optimisation'', the theta may
424 include dictionaries for the immediate superclasses of C at the type
427 %----------------------------------------------------------------------
430 %----------------------------------------------------------------------
433 %----------------------------------------------------------------------
436 %----------------------------------------------------------------------
437 \item[@LocalId@:] A purely-local value, e.g., a function argument,
438 something defined in a @where@ clauses, ... --- but which appears in
439 the original program text.
441 %----------------------------------------------------------------------
442 \item[@SysLocalId@:] Same as a @LocalId@, except does {\em not} appear in
443 the original program text; these are introduced by the compiler in
446 %----------------------------------------------------------------------
447 \item[@SpecPragmaId@:] Introduced by the compiler to record
448 Specialisation pragmas. It is dead code which MUST NOT be removed
449 before specialisation.
454 %----------------------------------------------------------------------
457 @DataCons@ @TupleCons@, @Importeds@, @SuperDictSelIds@,
458 @MethodSelIds@, @DictFunIds@, and @DefaultMethodIds@ have the following
462 They have no free type variables, so if you are making a
463 type-variable substitution you don't need to look inside them.
465 They are constants, so they are not free variables. (When the STG
466 machine makes a closure, it puts all the free variables in the
467 closure; the above are not required.)
469 Note that @InstIds@, @Locals@ and @SysLocals@ {\em may} have the above
470 properties, but they may not.
473 %************************************************************************
475 \subsection[Id-general-funs]{General @Id@-related functions}
477 %************************************************************************
480 isDataCon (Id _ _ _ (DataConId _ _ _ _ _ _ _) _ _) = True
481 isDataCon (Id _ _ _ (TupleConId _) _ _) = True
482 isDataCon (Id _ _ _ (SpecId unspec _ _) _ _) = isDataCon unspec
483 isDataCon other = False
485 isTupleCon (Id _ _ _ (TupleConId _) _ _) = True
486 isTupleCon (Id _ _ _ (SpecId unspec _ _) _ _) = isTupleCon unspec
487 isTupleCon other = False
490 isSpecId_maybe (Id _ _ _ (SpecId unspec ty_maybes _) _ _)
491 = ASSERT(not (maybeToBool (isSpecId_maybe unspec)))
492 Just (unspec, ty_maybes)
493 isSpecId_maybe other_id
496 isSpecPragmaId_maybe (Id _ _ _ (SpecPragmaId specid _) _ _)
498 isSpecPragmaId_maybe other_id
503 @toplevelishId@ tells whether an @Id@ {\em may} be defined in a nested
504 @let(rec)@ (returns @False@), or whether it is {\em sure} to be
505 defined at top level (returns @True@). This is used to decide whether
506 the @Id@ is a candidate free variable. NB: you are only {\em sure}
507 about something if it returns @True@!
510 toplevelishId :: Id -> Bool
511 idHasNoFreeTyVars :: Id -> Bool
513 toplevelishId (Id _ _ _ details _ _)
516 chk (DataConId _ _ _ _ _ _ _) = True
517 chk (TupleConId _) = True
518 chk (RecordSelId _) = True
519 chk ImportedId = True
520 chk (SuperDictSelId _ _) = True
521 chk (MethodSelId _ _) = True
522 chk (DefaultMethodId _ _ _) = True
523 chk (DictFunId _ _) = True
524 chk (ConstMethodId _ _ _ _) = True
525 chk (SpecId unspec _ _) = toplevelishId unspec
526 -- depends what the unspecialised thing is
527 chk (WorkerId unwrkr) = toplevelishId unwrkr
528 chk (InstId _) = False -- these are local
529 chk (LocalId _) = False
530 chk (SysLocalId _) = False
531 chk (SpecPragmaId _ _) = False
532 chk (PrimitiveId _) = True
534 idHasNoFreeTyVars (Id _ _ _ details _ info)
537 chk (DataConId _ _ _ _ _ _ _) = True
538 chk (TupleConId _) = True
539 chk (RecordSelId _) = True
540 chk ImportedId = True
541 chk (SuperDictSelId _ _) = True
542 chk (MethodSelId _ _) = True
543 chk (DefaultMethodId _ _ _) = True
544 chk (DictFunId _ _) = True
545 chk (ConstMethodId _ _ _ _) = True
546 chk (WorkerId unwrkr) = idHasNoFreeTyVars unwrkr
547 chk (SpecId _ _ no_free_tvs) = no_free_tvs
548 chk (InstId no_free_tvs) = no_free_tvs
549 chk (LocalId no_free_tvs) = no_free_tvs
550 chk (SysLocalId no_free_tvs) = no_free_tvs
551 chk (SpecPragmaId _ no_free_tvs) = no_free_tvs
552 chk (PrimitiveId _) = True
554 -- omitIfaceSigForId tells whether an Id's info is implied by other declarations,
555 -- so we don't need to put its signature in an interface file, even if it's mentioned
556 -- in some other interface unfolding.
562 omitIfaceSigForId (Id _ name _ details _ _)
568 ImportedId -> True -- Never put imports in interface file
569 (PrimitiveId _) -> True -- Ditto, for primitives
571 -- This group is Ids that are implied by their type or class decl;
572 -- remember that all type and class decls appear in the interface file.
573 -- The dfun id must *not* be omitted, because it carries version info for
575 (DataConId _ _ _ _ _ _ _) -> True
576 (TupleConId _) -> True
577 (RecordSelId _) -> True
578 (SuperDictSelId _ _) -> True
579 (MethodSelId _ _) -> True
581 other -> False -- Don't omit!
582 -- NB DefaultMethodIds are not omitted
586 isImportedId (Id _ _ _ ImportedId _ _) = True
587 isImportedId other = False
589 isBottomingId (Id _ _ _ _ _ info) = bottomIsGuaranteed (strictnessInfo info)
591 isSysLocalId (Id _ _ _ (SysLocalId _) _ _) = True
592 isSysLocalId other = False
594 isSpecPragmaId (Id _ _ _ (SpecPragmaId _ _) _ _) = True
595 isSpecPragmaId other = False
597 isMethodSelId_maybe (Id _ _ _ (MethodSelId cls op) _ _) = Just (cls,op)
598 isMethodSelId_maybe _ = Nothing
600 isDefaultMethodId (Id _ _ _ (DefaultMethodId _ _ _) _ _) = True
601 isDefaultMethodId other = False
603 isDefaultMethodId_maybe (Id _ _ _ (DefaultMethodId cls clsop err) _ _)
604 = Just (cls, clsop, err)
605 isDefaultMethodId_maybe other = Nothing
607 isDictFunId (Id _ _ _ (DictFunId _ _) _ _) = True
608 isDictFunId other = False
610 isConstMethodId (Id _ _ _ (ConstMethodId _ _ _ _) _ _) = True
611 isConstMethodId other = False
613 isConstMethodId_maybe (Id _ _ _ (ConstMethodId cls ty clsop _) _ _)
614 = Just (cls, ty, clsop)
615 isConstMethodId_maybe other = Nothing
617 isSuperDictSelId_maybe (Id _ _ _ (SuperDictSelId c sc) _ _) = Just (c, sc)
618 isSuperDictSelId_maybe other_id = Nothing
620 isWorkerId (Id _ _ _ (WorkerId _) _ _) = True
621 isWorkerId other = False
623 isWrapperId id = workerExists (getIdStrictness id)
625 isPrimitiveId_maybe (Id _ _ _ (PrimitiveId primop) _ _) = Just primop
626 isPrimitiveId_maybe other = Nothing
629 Tell them who my wrapper function is.
632 myWrapperMaybe :: Id -> Maybe Id
634 myWrapperMaybe (Id _ _ _ (WorkerId my_wrapper) _ _) = Just my_wrapper
635 myWrapperMaybe other_id = Nothing
640 unfoldingUnfriendlyId -- return True iff it is definitely a bad
641 :: Id -- idea to export an unfolding that
642 -> Bool -- mentions this Id. Reason: it cannot
643 -- possibly be seen in another module.
645 unfoldingUnfriendlyId id = not (externallyVisibleId id)
648 @externallyVisibleId@: is it true that another module might be
649 able to ``see'' this Id in a code generation sense. That
650 is, another .o file might refer to this Id.
652 In tidyCorePgm (SimplCore.lhs) we carefully set each top level thing's
653 local-ness precisely so that the test here would be easy
656 externallyVisibleId :: Id -> Bool
657 externallyVisibleId id@(Id _ name _ _ _ _) = not (isLocalName name)
658 -- not local => global => externally visible
661 CLAIM (not ASSERTed) for @applyTypeEnvToId@ and @applySubstToId@:
662 `Top-levelish Ids'' cannot have any free type variables, so applying
663 the type-env cannot have any effect. (NB: checked in CoreLint?)
665 The special casing is in @applyTypeEnvToId@, not @apply_to_Id@, as the
666 former ``should be'' the usual crunch point.
669 type TypeEnv = TyVarEnv Type
671 applyTypeEnvToId :: TypeEnv -> Id -> Id
673 applyTypeEnvToId type_env id@(Id _ _ ty _ _ _)
674 | idHasNoFreeTyVars id
677 = apply_to_Id ( \ ty ->
678 applyTypeEnvToTy type_env ty
683 apply_to_Id :: (Type -> Type) -> Id -> Id
685 apply_to_Id ty_fn (Id u n ty details prag info)
689 Id u n new_ty (apply_to_details details) prag (apply_to_IdInfo ty_fn info)
691 apply_to_details (SpecId unspec ty_maybes no_ftvs)
693 new_unspec = apply_to_Id ty_fn unspec
694 new_maybes = map apply_to_maybe ty_maybes
696 SpecId new_unspec new_maybes (no_free_tvs ty)
697 -- ToDo: gratuitous recalc no_ftvs???? (also InstId)
699 apply_to_maybe Nothing = Nothing
700 apply_to_maybe (Just ty) = Just (ty_fn ty)
702 apply_to_details (WorkerId unwrkr)
704 new_unwrkr = apply_to_Id ty_fn unwrkr
708 apply_to_details other = other
711 Sadly, I don't think the one using the magic typechecker substitution
712 can be done with @apply_to_Id@. Here we go....
714 Strictness is very important here. We can't leave behind thunks
715 with pointers to the substitution: it {\em must} be single-threaded.
719 applySubstToId :: Subst -> Id -> (Subst, Id)
721 applySubstToId subst id@(Id u n ty info details)
722 -- *cannot* have a "idHasNoFreeTyVars" get-out clause
723 -- because, in the typechecker, we are still
724 -- *concocting* the types.
725 = case (applySubstToTy subst ty) of { (s2, new_ty) ->
726 case (applySubstToIdInfo s2 info) of { (s3, new_info) ->
727 case (apply_to_details s3 new_ty details) of { (s4, new_details) ->
728 (s4, Id u n new_ty new_info new_details) }}}
730 apply_to_details subst _ (InstId inst no_ftvs)
731 = case (applySubstToInst subst inst) of { (s2, new_inst) ->
732 (s2, InstId new_inst no_ftvs{-ToDo:right???-}) }
734 apply_to_details subst new_ty (SpecId unspec ty_maybes _)
735 = case (applySubstToId subst unspec) of { (s2, new_unspec) ->
736 case (mapAccumL apply_to_maybe s2 ty_maybes) of { (s3, new_maybes) ->
737 (s3, SpecId new_unspec new_maybes (no_free_tvs new_ty)) }}
738 -- NB: recalc no_ftvs (I think it's necessary (?) WDP 95/04)
740 apply_to_maybe subst Nothing = (subst, Nothing)
741 apply_to_maybe subst (Just ty)
742 = case (applySubstToTy subst ty) of { (s2, new_ty) ->
745 apply_to_details subst _ (WorkerId unwrkr)
746 = case (applySubstToId subst unwrkr) of { (s2, new_unwrkr) ->
747 (s2, WorkerId new_unwrkr) }
749 apply_to_details subst _ other = (subst, other)
753 %************************************************************************
755 \subsection[Id-type-funs]{Type-related @Id@ functions}
757 %************************************************************************
760 idType :: GenId ty -> ty
762 idType (Id _ _ ty _ _ _) = ty
767 getMentionedTyConsAndClassesFromId :: Id -> (Bag TyCon, Bag Class)
769 getMentionedTyConsAndClassesFromId id
770 = getMentionedTyConsAndClassesFromType (idType id)
775 idPrimRep i = typePrimRep (idType i)
778 %************************************************************************
780 \subsection[Id-overloading]{Functions related to overloading}
782 %************************************************************************
785 mkSuperDictSelId u clas sc ty
786 = addStandardIdInfo $
787 Id u name ty details NoPragmaInfo noIdInfo
789 name = mkCompoundName name_fn u (getName clas)
790 details = SuperDictSelId clas sc
791 name_fn clas_str = SLIT("scsel_") _APPEND_ clas_str _APPEND_ mod _APPEND_ occNameString occ
792 (mod,occ) = modAndOcc sc
794 -- For method selectors the clean thing to do is
795 -- to give the method selector the same name as the class op itself.
796 mkMethodSelId op_name rec_c op ty
797 = addStandardIdInfo $
798 Id (uniqueOf op_name) op_name ty (MethodSelId rec_c op) NoPragmaInfo noIdInfo
800 mkDefaultMethodId dm_name rec_c op gen ty
801 = Id (uniqueOf dm_name) dm_name ty (DefaultMethodId rec_c op gen) NoPragmaInfo noIdInfo
803 mkDictFunId dfun_name full_ty clas ity
804 = Id (nameUnique dfun_name) dfun_name full_ty details NoPragmaInfo noIdInfo
806 details = DictFunId clas ity
808 mkConstMethodId uniq clas op ity full_ty from_here locn mod info
809 = Id uniq name full_ty details NoPragmaInfo info
811 name = mkInstDeclName uniq mod (VarOcc occ_name) locn from_here
812 details = ConstMethodId clas ity op mod
813 occ_name = classOpString op _APPEND_
814 SLIT("_cm_") _APPEND_ renum_type_string full_ty ity
816 mkWorkerId u unwrkr ty info
817 = Id u name ty details NoPragmaInfo info
819 name = mkCompoundName name_fn u (getName unwrkr)
820 details = WorkerId unwrkr
821 name_fn wkr_str = SLIT("$w") _APPEND_ wkr_str
824 = Id u (changeUnique name u) ty (InstId (no_free_tvs ty)) NoPragmaInfo noIdInfo
827 getConstMethodId clas op ty
828 = -- constant-method info is hidden in the IdInfo of
829 -- the class-op id (as mentioned up above).
831 sel_id = getMethodSelId clas op
833 case (lookupConstMethodId (getIdSpecialisation sel_id) ty) of
835 Nothing -> pprError "ERROR: getConstMethodId:" (ppAboves [
836 ppCat [ppr PprDebug ty, ppr PprDebug ops, ppr PprDebug op_ids,
837 ppr PprDebug sel_id],
838 ppStr "(This can arise if an interface pragma refers to an instance",
839 ppStr "but there is no imported interface which *defines* that instance.",
840 ppStr "The info above, however ugly, should indicate what else you need to import."
845 renum_type_string full_ty ity
847 nmbrType full_ty `thenNmbr` \ _ -> -- so all the tyvars get added to renumbering...
848 nmbrType ity `thenNmbr` \ rn_ity ->
849 returnNmbr (getTypeString rn_ity)
853 %************************************************************************
855 \subsection[local-funs]{@LocalId@-related functions}
857 %************************************************************************
860 mkImported n ty info = Id (nameUnique n) n ty ImportedId NoPragmaInfo info
862 mkPrimitiveId n ty primop
863 = addStandardIdInfo $
864 Id (nameUnique n) n ty (PrimitiveId primop) NoPragmaInfo noIdInfo
870 type MyTy a b = GenType (GenTyVar a) b
871 type MyId a b = GenId (MyTy a b)
873 no_free_tvs ty = isEmptyTyVarSet (tyVarsOfType ty)
875 -- SysLocal: for an Id being created by the compiler out of thin air...
876 -- UserLocal: an Id with a name the user might recognize...
877 mkSysLocal :: FAST_STRING -> Unique -> MyTy a b -> SrcLoc -> MyId a b
878 mkUserLocal :: OccName -> Unique -> MyTy a b -> SrcLoc -> MyId a b
880 mkSysLocal str uniq ty loc
881 = Id uniq (mkSysLocalName uniq str loc) ty (SysLocalId (no_free_tvs ty)) NoPragmaInfo noIdInfo
883 mkUserLocal occ uniq ty loc
884 = Id uniq (mkLocalName uniq occ loc) ty (LocalId (no_free_tvs ty)) NoPragmaInfo noIdInfo
886 mkUserId :: Name -> MyTy a b -> PragmaInfo -> MyId a b
887 mkUserId name ty pragma_info
888 = Id (nameUnique name) name ty (LocalId (no_free_tvs ty)) pragma_info noIdInfo
895 -- for a SpecPragmaId being created by the compiler out of thin air...
896 mkSpecPragmaId :: OccName -> Unique -> Type -> Maybe Id -> SrcLoc -> Id
897 mkSpecPragmaId str uniq ty specid loc
898 = Id uniq (mkShortName str loc) ty noIdInfo (SpecPragmaId specid (no_free_tvs ty))
901 mkSpecId u unspec ty_maybes ty info
902 = ASSERT(not (maybeToBool (isSpecId_maybe unspec)))
903 Id u n ty info (SpecId unspec ty_maybes (no_free_tvs ty))
905 -- Specialised version of constructor: only used in STG and code generation
906 -- Note: The specialsied Id has the same unique as the unspeced Id
908 mkSameSpecCon ty_maybes unspec@(Id u n ty info details)
909 = ASSERT(isDataCon unspec)
910 ASSERT(not (maybeToBool (isSpecId_maybe unspec)))
911 Id u n new_ty info (SpecId unspec ty_maybes (no_free_tvs new_ty))
913 new_ty = specialiseTy ty ty_maybes 0
915 localiseId :: Id -> Id
916 localiseId id@(Id u n ty info details)
917 = Id u (mkShortName name loc) ty info (LocalId (no_free_tvs ty))
923 -- See notes with setNameVisibility (Name.lhs)
924 setIdVisibility :: Module -> Id -> Id
925 setIdVisibility mod (Id uniq name ty details prag info)
926 = Id uniq (setNameVisibility mod name) ty details prag info
928 mkIdWithNewUniq :: Id -> Unique -> Id
929 mkIdWithNewUniq (Id _ n ty details prag info) u
930 = Id u (changeUnique n u) ty details prag info
933 Make some local @Ids@ for a template @CoreExpr@. These have bogus
934 @Uniques@, but that's OK because the templates are supposed to be
935 instantiated before use.
937 mkTemplateLocals :: [Type] -> [Id]
939 = zipWith (\ u -> \ ty -> mkSysLocal SLIT("tpl") u ty mkBuiltinSrcLoc)
940 (getBuiltinUniques (length tys))
945 getIdInfo :: GenId ty -> IdInfo
946 getPragmaInfo :: GenId ty -> PragmaInfo
948 getIdInfo (Id _ _ _ _ _ info) = info
949 getPragmaInfo (Id _ _ _ _ info _) = info
951 replaceIdInfo :: Id -> IdInfo -> Id
953 replaceIdInfo (Id u n ty details pinfo _) info = Id u n ty details pinfo info
956 selectIdInfoForSpecId :: Id -> IdInfo
957 selectIdInfoForSpecId unspec
958 = ASSERT(not (maybeToBool (isSpecId_maybe unspec)))
959 noIdInfo `addUnfoldInfo` getIdUnfolding unspec
963 %************************************************************************
965 \subsection[Id-arities]{Arity-related functions}
967 %************************************************************************
969 For locally-defined Ids, the code generator maintains its own notion
970 of their arities; so it should not be asking... (but other things
971 besides the code-generator need arity info!)
974 getIdArity :: Id -> ArityInfo
975 getIdArity id@(Id _ _ _ _ _ id_info)
976 = --ASSERT( not (isDataCon id))
979 dataConArity, dataConNumFields :: DataCon -> Int
981 dataConArity id@(Id _ _ _ _ _ id_info)
982 = ASSERT(isDataCon id)
983 case arityInfo id_info of
985 other -> pprPanic "dataConArity:Nothing:" (pprId PprDebug id)
988 = ASSERT(isDataCon id)
989 case (dataConSig id) of { (_, _, arg_tys, _) ->
992 isNullaryDataCon con = dataConNumFields con == 0 -- function of convenience
994 addIdArity :: Id -> ArityInfo -> Id
995 addIdArity (Id u n ty details pinfo info) arity
996 = Id u n ty details pinfo (info `addArityInfo` arity)
999 %************************************************************************
1001 \subsection[constructor-funs]{@DataCon@-related functions (incl.~tuples)}
1003 %************************************************************************
1007 -> [StrictnessMark] -> [FieldLabel]
1008 -> [TyVar] -> ThetaType -> [TauType] -> TyCon
1010 -- can get the tag and all the pieces of the type from the Type
1012 mkDataCon n stricts fields tvs ctxt args_tys tycon
1013 = ASSERT(length stricts == length args_tys)
1014 addStandardIdInfo data_con
1016 -- NB: data_con self-recursion; should be OK as tags are not
1017 -- looked at until late in the game.
1022 (DataConId data_con_tag stricts fields tvs ctxt args_tys tycon)
1023 IWantToBeINLINEd -- Always inline constructors if possible
1026 data_con_tag = assoc "mkDataCon" (data_con_family `zip` [fIRST_TAG..]) data_con
1027 data_con_family = tyConDataCons tycon
1030 = mkSigmaTy tvs ctxt
1031 (mkFunTys args_tys (applyTyCon tycon (mkTyVarTys tvs)))
1034 mkTupleCon :: Arity -> Name -> Type -> Id
1035 mkTupleCon arity name ty
1036 = addStandardIdInfo tuple_id
1038 tuple_id = Id (nameUnique name) name ty
1040 IWantToBeINLINEd -- Always inline constructors if possible
1044 fIRST_TAG = 1 -- Tags allocated from here for real constructors
1048 dataConTag :: DataCon -> ConTag -- will panic if not a DataCon
1049 dataConTag (Id _ _ _ (DataConId tag _ _ _ _ _ _) _ _) = tag
1050 dataConTag (Id _ _ _ (TupleConId _) _ _) = fIRST_TAG
1051 dataConTag (Id _ _ _ (SpecId unspec _ _) _ _) = dataConTag unspec
1053 dataConTyCon :: DataCon -> TyCon -- will panic if not a DataCon
1054 dataConTyCon (Id _ _ _ (DataConId _ _ _ _ _ _ tycon) _ _) = tycon
1055 dataConTyCon (Id _ _ _ (TupleConId a) _ _) = tupleTyCon a
1057 dataConSig :: DataCon -> ([TyVar], ThetaType, [TauType], TyCon)
1058 -- will panic if not a DataCon
1060 dataConSig (Id _ _ _ (DataConId _ _ _ tyvars theta_ty arg_tys tycon) _ _)
1061 = (tyvars, theta_ty, arg_tys, tycon)
1063 dataConSig (Id _ _ _ (TupleConId arity) _ _)
1064 = (tyvars, [], tyvar_tys, tupleTyCon arity)
1066 tyvars = take arity alphaTyVars
1067 tyvar_tys = mkTyVarTys tyvars
1070 -- dataConRepType returns the type of the representation of a contructor
1071 -- This may differ from the type of the contructor Id itself for two reasons:
1072 -- a) the constructor Id may be overloaded, but the dictionary isn't stored
1073 -- b) the constructor may store an unboxed version of a strict field.
1074 -- Here's an example illustrating both:
1075 -- data Ord a => T a = MkT Int! a
1077 -- T :: Ord a => Int -> a -> T a
1078 -- but the rep type is
1079 -- Trep :: Int# -> a -> T a
1080 -- Actually, the unboxed part isn't implemented yet!
1082 dataConRepType :: GenId (GenType tv u) -> GenType tv u
1084 = mkForAllTys tyvars tau
1086 (tyvars, theta, tau) = splitSigmaTy (idType con)
1088 dataConFieldLabels :: DataCon -> [FieldLabel]
1089 dataConFieldLabels (Id _ _ _ (DataConId _ _ fields _ _ _ _) _ _) = fields
1090 dataConFieldLabels (Id _ _ _ (TupleConId _) _ _) = []
1092 dataConStrictMarks :: DataCon -> [StrictnessMark]
1093 dataConStrictMarks (Id _ _ _ (DataConId _ stricts _ _ _ _ _) _ _) = stricts
1094 dataConStrictMarks (Id _ _ _ (TupleConId arity) _ _)
1095 = nOfThem arity NotMarkedStrict
1097 dataConRawArgTys :: DataCon -> [TauType] -- a function of convenience
1098 dataConRawArgTys con = case (dataConSig con) of { (_,_, arg_tys,_) -> arg_tys }
1100 dataConArgTys :: DataCon
1101 -> [Type] -- Instantiated at these types
1102 -> [Type] -- Needs arguments of these types
1103 dataConArgTys con_id inst_tys
1104 = map (instantiateTy tenv) arg_tys
1106 (tyvars, _, arg_tys, _) = dataConSig con_id
1107 tenv = zipEqual "dataConArgTys" tyvars inst_tys
1111 mkRecordSelId field_label selector_ty
1112 = addStandardIdInfo $ -- Record selectors have a standard unfolding
1113 Id (nameUnique name)
1116 (RecordSelId field_label)
1120 name = fieldLabelName field_label
1122 recordSelectorFieldLabel :: Id -> FieldLabel
1123 recordSelectorFieldLabel (Id _ _ _ (RecordSelId lbl) _ _) = lbl
1125 isRecordSelector (Id _ _ _ (RecordSelId lbl) _ _) = True
1126 isRecordSelector other = False
1130 Data type declarations are of the form:
1132 data Foo a b = C1 ... | C2 ... | ... | Cn ...
1134 For each constructor @Ci@, we want to generate a curried function; so, e.g., for
1135 @C1 x y z@, we want a function binding:
1137 fun_C1 = /\ a -> /\ b -> \ [x, y, z] -> Con C1 [a, b] [x, y, z]
1139 Notice the ``big lambdas'' and type arguments to @Con@---we are producing
1140 2nd-order polymorphic lambda calculus with explicit types.
1142 %************************************************************************
1144 \subsection[unfolding-Ids]{Functions related to @Ids@' unfoldings}
1146 %************************************************************************
1149 getIdUnfolding :: Id -> Unfolding
1151 getIdUnfolding (Id _ _ _ _ _ info) = unfoldInfo info
1153 addIdUnfolding :: Id -> Unfolding -> Id
1154 addIdUnfolding id@(Id u n ty details prag info) unfolding
1155 = Id u n ty details prag (info `addUnfoldInfo` unfolding)
1158 The inline pragma tells us to be very keen to inline this Id, but it's still
1159 OK not to if optimisation is switched off.
1162 idWantsToBeINLINEd :: Id -> Bool
1164 idWantsToBeINLINEd (Id _ _ _ _ IWantToBeINLINEd _) = True
1165 idWantsToBeINLINEd _ = False
1167 addInlinePragma :: Id -> Id
1168 addInlinePragma (Id u sn ty details _ info)
1169 = Id u sn ty details IWantToBeINLINEd info
1173 The predicate @idMustBeINLINEd@ says that this Id absolutely must be inlined.
1174 It's only true for primitives, because we don't want to make a closure for each of them.
1177 idMustBeINLINEd (Id _ _ _ (PrimitiveId primop) _ _) = True
1178 idMustBeINLINEd other = False
1182 %************************************************************************
1184 \subsection[IdInfo-funs]{Functions related to @Ids@' @IdInfos@}
1186 %************************************************************************
1189 getIdDemandInfo :: Id -> DemandInfo
1190 getIdDemandInfo (Id _ _ _ _ _ info) = demandInfo info
1192 addIdDemandInfo :: Id -> DemandInfo -> Id
1193 addIdDemandInfo (Id u n ty details prags info) demand_info
1194 = Id u n ty details prags (info `addDemandInfo` demand_info)
1198 getIdUpdateInfo :: Id -> UpdateInfo
1199 getIdUpdateInfo (Id _ _ _ _ _ info) = updateInfo info
1201 addIdUpdateInfo :: Id -> UpdateInfo -> Id
1202 addIdUpdateInfo (Id u n ty details prags info) upd_info
1203 = Id u n ty details prags (info `addUpdateInfo` upd_info)
1208 getIdArgUsageInfo :: Id -> ArgUsageInfo
1209 getIdArgUsageInfo (Id u n ty info details) = argUsageInfo info
1211 addIdArgUsageInfo :: Id -> ArgUsageInfo -> Id
1212 addIdArgUsageInfo (Id u n ty info details) au_info
1213 = Id u n ty (info `addArgusageInfo` au_info) details
1219 getIdFBTypeInfo :: Id -> FBTypeInfo
1220 getIdFBTypeInfo (Id u n ty info details) = fbTypeInfo info
1222 addIdFBTypeInfo :: Id -> FBTypeInfo -> Id
1223 addIdFBTypeInfo (Id u n ty info details) upd_info
1224 = Id u n ty (info `addFBTypeInfo` upd_info) details
1229 getIdSpecialisation :: Id -> SpecEnv
1230 getIdSpecialisation (Id _ _ _ _ _ info) = specInfo info
1232 addIdSpecialisation :: Id -> SpecEnv -> Id
1233 addIdSpecialisation (Id u n ty details prags info) spec_info
1234 = Id u n ty details prags (info `addSpecInfo` spec_info)
1237 Strictness: we snaffle the info out of the IdInfo.
1240 getIdStrictness :: Id -> StrictnessInfo Id
1242 getIdStrictness (Id _ _ _ _ _ info) = strictnessInfo info
1244 addIdStrictness :: Id -> StrictnessInfo Id -> Id
1245 addIdStrictness (Id u n ty details prags info) strict_info
1246 = Id u n ty details prags (info `addStrictnessInfo` strict_info)
1249 %************************************************************************
1251 \subsection[Id-comparison]{Comparison functions for @Id@s}
1253 %************************************************************************
1255 Comparison: equality and ordering---this stuff gets {\em hammered}.
1258 cmpId (Id u1 _ _ _ _ _) (Id u2 _ _ _ _ _) = cmp u1 u2
1259 -- short and very sweet
1263 instance Ord3 (GenId ty) where
1266 instance Eq (GenId ty) where
1267 a == b = case (a `cmp` b) of { EQ_ -> True; _ -> False }
1268 a /= b = case (a `cmp` b) of { EQ_ -> False; _ -> True }
1270 instance Ord (GenId ty) where
1271 a <= b = case (a `cmp` b) of { LT_ -> True; EQ_ -> True; GT__ -> False }
1272 a < b = case (a `cmp` b) of { LT_ -> True; EQ_ -> False; GT__ -> False }
1273 a >= b = case (a `cmp` b) of { LT_ -> False; EQ_ -> True; GT__ -> True }
1274 a > b = case (a `cmp` b) of { LT_ -> False; EQ_ -> False; GT__ -> True }
1275 _tagCmp a b = case (a `cmp` b) of { LT_ -> _LT; EQ_ -> _EQ; GT__ -> _GT }
1278 @cmpId_withSpecDataCon@ ensures that any spectys are taken into
1279 account when comparing two data constructors. We need to do this
1280 because a specialised data constructor has the same Unique as its
1281 unspecialised counterpart.
1284 cmpId_withSpecDataCon :: Id -> Id -> TAG_
1286 cmpId_withSpecDataCon id1 id2
1287 | eq_ids && isDataCon id1 && isDataCon id2
1288 = cmpEqDataCon id1 id2
1293 cmp_ids = cmpId id1 id2
1294 eq_ids = case cmp_ids of { EQ_ -> True; other -> False }
1296 cmpEqDataCon (Id _ _ _ (SpecId _ mtys1 _) _ _) (Id _ _ _ (SpecId _ mtys2 _) _ _)
1297 = panic# "Id.cmpEqDataCon:cmpUniTypeMaybeList mtys1 mtys2"
1299 cmpEqDataCon _ (Id _ _ _ (SpecId _ _ _) _ _) = LT_
1300 cmpEqDataCon (Id _ _ _ (SpecId _ _ _) _ _) _ = GT_
1301 cmpEqDataCon _ _ = EQ_
1304 %************************************************************************
1306 \subsection[Id-other-instances]{Other instance declarations for @Id@s}
1308 %************************************************************************
1311 instance Outputable ty => Outputable (GenId ty) where
1312 ppr sty id = pprId sty id
1314 -- and a SPECIALIZEd one:
1315 instance Outputable {-Id, i.e.:-}(GenId Type) where
1316 ppr sty id = pprId sty id
1318 showId :: PprStyle -> Id -> String
1319 showId sty id = ppShow 80 (pprId sty id)
1322 Default printing code (not used for interfaces):
1324 pprId :: Outputable ty => PprStyle -> GenId ty -> Pretty
1326 pprId sty (Id u n _ _ _ _) = ppr sty n
1327 -- WDP 96/05/06: We can re-elaborate this as we go along...
1331 idUnique (Id u _ _ _ _ _) = u
1333 instance Uniquable (GenId ty) where
1336 instance NamedThing (GenId ty) where
1337 getName this_id@(Id u n _ details _ _) = n
1340 Note: The code generator doesn't carry a @UniqueSupply@, so it uses
1341 the @Uniques@ out of local @Ids@ given to it.
1343 %************************************************************************
1345 \subsection{@IdEnv@s and @IdSet@s}
1347 %************************************************************************
1350 type IdEnv elt = UniqFM elt
1352 nullIdEnv :: IdEnv a
1354 mkIdEnv :: [(GenId ty, a)] -> IdEnv a
1355 unitIdEnv :: GenId ty -> a -> IdEnv a
1356 addOneToIdEnv :: IdEnv a -> GenId ty -> a -> IdEnv a
1357 growIdEnv :: IdEnv a -> IdEnv a -> IdEnv a
1358 growIdEnvList :: IdEnv a -> [(GenId ty, a)] -> IdEnv a
1360 delManyFromIdEnv :: IdEnv a -> [GenId ty] -> IdEnv a
1361 delOneFromIdEnv :: IdEnv a -> GenId ty -> IdEnv a
1362 combineIdEnvs :: (a -> a -> a) -> IdEnv a -> IdEnv a -> IdEnv a
1363 mapIdEnv :: (a -> b) -> IdEnv a -> IdEnv b
1364 modifyIdEnv :: (a -> a) -> IdEnv a -> GenId ty -> IdEnv a
1365 rngIdEnv :: IdEnv a -> [a]
1367 isNullIdEnv :: IdEnv a -> Bool
1368 lookupIdEnv :: IdEnv a -> GenId ty -> Maybe a
1369 lookupNoFailIdEnv :: IdEnv a -> GenId ty -> a
1373 addOneToIdEnv = addToUFM
1374 combineIdEnvs = plusUFM_C
1375 delManyFromIdEnv = delListFromUFM
1376 delOneFromIdEnv = delFromUFM
1378 lookupIdEnv = lookupUFM
1381 nullIdEnv = emptyUFM
1385 growIdEnvList env pairs = plusUFM env (listToUFM pairs)
1386 isNullIdEnv env = sizeUFM env == 0
1387 lookupNoFailIdEnv env id = case (lookupIdEnv env id) of { Just xx -> xx }
1389 -- modifyIdEnv: Look up a thing in the IdEnv, then mash it with the
1390 -- modify function, and put it back.
1392 modifyIdEnv mangle_fn env key
1393 = case (lookupIdEnv env key) of
1395 Just xx -> addOneToIdEnv env key (mangle_fn xx)
1397 modifyIdEnv_Directly mangle_fn env key
1398 = case (lookupUFM_Directly env key) of
1400 Just xx -> addToUFM_Directly env key (mangle_fn xx)
1404 type GenIdSet ty = UniqSet (GenId ty)
1405 type IdSet = UniqSet (GenId Type)
1407 emptyIdSet :: GenIdSet ty
1408 intersectIdSets :: GenIdSet ty -> GenIdSet ty -> GenIdSet ty
1409 unionIdSets :: GenIdSet ty -> GenIdSet ty -> GenIdSet ty
1410 unionManyIdSets :: [GenIdSet ty] -> GenIdSet ty
1411 idSetToList :: GenIdSet ty -> [GenId ty]
1412 unitIdSet :: GenId ty -> GenIdSet ty
1413 addOneToIdSet :: GenIdSet ty -> GenId ty -> GenIdSet ty
1414 elementOfIdSet :: GenId ty -> GenIdSet ty -> Bool
1415 minusIdSet :: GenIdSet ty -> GenIdSet ty -> GenIdSet ty
1416 isEmptyIdSet :: GenIdSet ty -> Bool
1417 mkIdSet :: [GenId ty] -> GenIdSet ty
1419 emptyIdSet = emptyUniqSet
1420 unitIdSet = unitUniqSet
1421 addOneToIdSet = addOneToUniqSet
1422 intersectIdSets = intersectUniqSets
1423 unionIdSets = unionUniqSets
1424 unionManyIdSets = unionManyUniqSets
1425 idSetToList = uniqSetToList
1426 elementOfIdSet = elementOfUniqSet
1427 minusIdSet = minusUniqSet
1428 isEmptyIdSet = isEmptyUniqSet
1433 addId, nmbrId, nmbrDataCon :: Id -> NmbrM Id
1435 addId id@(Id u n ty det prag info) nenv@(NmbrEnv ui ut uu idenv tvenv uvenv)
1436 = case (lookupUFM_Directly idenv u) of
1437 Just xx -> trace "addId: already in map!" $
1440 if toplevelishId id then
1441 trace "addId: can't add toplevelish!" $
1443 else -- alloc a new unique for this guy
1444 -- and add an entry in the idenv
1445 -- NB: *** KNOT-TYING ***
1447 nenv_plus_id = NmbrEnv (incrUnique ui) ut uu
1448 (addToUFM_Directly idenv u new_id)
1451 (nenv2, new_ty) = nmbrType ty nenv_plus_id
1452 (nenv3, new_det) = nmbr_details det nenv2
1454 new_id = Id ui n new_ty new_det prag info
1458 nmbrId id@(Id u n ty det prag info) nenv@(NmbrEnv ui ut uu idenv tvenv uvenv)
1459 = case (lookupUFM_Directly idenv u) of
1460 Just xx -> (nenv, xx)
1462 if not (toplevelishId id) then
1463 trace "nmbrId: lookup failed" $
1467 (nenv2, new_ty) = nmbrType ty nenv
1468 (nenv3, new_det) = nmbr_details det nenv2
1470 new_id = Id u n new_ty new_det prag info
1474 -- used when renumbering TyCons to produce data decls...
1475 nmbrDataCon id@(Id _ _ _ (TupleConId _) _ _) nenv
1476 = (nenv, id) -- nothing to do for tuples
1478 nmbrDataCon id@(Id u n ty (DataConId tag marks fields tvs theta arg_tys tc) prag info) nenv@(NmbrEnv ui ut uu idenv tvenv uvenv)
1479 = case (lookupUFM_Directly idenv u) of
1480 Just xx -> trace "nmbrDataCon: in env???\n" (nenv, xx)
1483 (nenv2, new_fields) = (mapNmbr nmbrField fields) nenv
1484 (nenv3, new_arg_tys) = (mapNmbr nmbrType arg_tys) nenv2
1486 new_det = DataConId tag marks new_fields (bottom "tvs") (bottom "theta") new_arg_tys tc
1487 new_id = Id u n (bottom "ty") new_det prag info
1491 bottom msg = panic ("nmbrDataCon"++msg)
1494 nmbr_details :: IdDetails -> NmbrM IdDetails
1496 nmbr_details (DataConId tag marks fields tvs theta arg_tys tc)
1497 = mapNmbr nmbrTyVar tvs `thenNmbr` \ new_tvs ->
1498 mapNmbr nmbrField fields `thenNmbr` \ new_fields ->
1499 mapNmbr nmbr_theta theta `thenNmbr` \ new_theta ->
1500 mapNmbr nmbrType arg_tys `thenNmbr` \ new_arg_tys ->
1501 returnNmbr (DataConId tag marks new_fields new_tvs new_theta new_arg_tys tc)
1504 = --nmbrClass c `thenNmbr` \ new_c ->
1505 nmbrType t `thenNmbr` \ new_t ->
1506 returnNmbr (c, new_t)
1508 -- ToDo:add more cases as needed
1509 nmbr_details other_details = returnNmbr other_details
1512 nmbrField (FieldLabel n ty tag)
1513 = nmbrType ty `thenNmbr` \ new_ty ->
1514 returnNmbr (FieldLabel n new_ty tag)