2 % (c) The AQUA Project, Glasgow University, 1998
4 \section[StdIdInfo]{Standard unfoldings}
6 This module contains definitions for the IdInfo for things that
7 have a standard form, namely:
11 * method and superclass selectors
12 * primitive operations
16 mkSpecPragmaId, mkWorkerId,
18 mkDictFunId, mkDefaultMethodId,
21 mkDataConId, mkDataConWrapId,
23 mkPrimOpId, mkCCallOpId,
25 -- And some particular Ids; see below for why they are wired in
27 unsafeCoerceId, realWorldPrimId,
28 eRROR_ID, rEC_SEL_ERROR_ID, pAT_ERROR_ID, rEC_CON_ERROR_ID,
29 rEC_UPD_ERROR_ID, iRREFUT_PAT_ERROR_ID, nON_EXHAUSTIVE_GUARDS_ERROR_ID,
30 nO_METHOD_BINDING_ERROR_ID, aBSENT_ERROR_ID, pAR_ERROR_ID
33 #include "HsVersions.h"
36 import TysPrim ( openAlphaTyVars, alphaTyVar, alphaTy,
37 intPrimTy, realWorldStatePrimTy
39 import TysWiredIn ( charTy, mkListTy )
40 import PrelNames ( pREL_ERR, pREL_GHC )
41 import PrelRules ( primOpRule )
42 import Rules ( addRule )
43 import Type ( Type, ThetaType, mkDictTy, mkDictTys, mkTyConApp, mkTyVarTys,
44 mkFunTys, mkFunTy, mkSigmaTy, splitSigmaTy,
45 isUnLiftedType, mkForAllTys, mkTyVarTy, tyVarsOfType,
46 splitFunTys, splitForAllTys, mkPredTy
48 import Module ( Module )
49 import CoreUtils ( exprType, mkInlineMe )
50 import CoreUnfold ( mkTopUnfolding, mkCompulsoryUnfolding, mkOtherCon )
51 import Literal ( Literal(..) )
52 import TyCon ( TyCon, isNewTyCon, tyConTyVars, tyConDataCons,
53 tyConTheta, isProductTyCon, isDataTyCon )
54 import Class ( Class, classTyCon, classTyVars, classSelIds )
55 import Var ( Id, TyVar )
56 import VarSet ( isEmptyVarSet )
57 import Name ( mkWiredInName, mkLocalName,
58 mkWorkerOcc, mkCCallName,
59 Name, NamedThing(..), getSrcLoc
61 import OccName ( mkVarOcc )
62 import PrimOp ( PrimOp(DataToTagOp, CCallOp),
63 primOpSig, mkPrimOpIdName,
66 import Demand ( wwStrict, wwPrim, mkStrictnessInfo )
67 import DataCon ( DataCon, StrictnessMark(..),
68 dataConFieldLabels, dataConRepArity, dataConTyCon,
69 dataConArgTys, dataConRepType, dataConRepStrictness,
70 dataConInstOrigArgTys,
71 dataConName, dataConTheta,
72 dataConSig, dataConStrictMarks, dataConId,
73 maybeMarkedUnboxed, splitProductType_maybe
75 import Id ( idType, mkId,
76 mkVanillaId, mkTemplateLocals, mkTemplateLocalsNum,
77 mkTemplateLocal, idCprInfo
79 import IdInfo ( IdInfo, constantIdInfo, mkIdInfo,
80 exactArity, setUnfoldingInfo, setCafInfo, setCprInfo,
81 setArityInfo, setSpecInfo, setTyGenInfo,
82 mkStrictnessInfo, setStrictnessInfo,
83 IdFlavour(..), CafInfo(..), CprInfo(..), TyGenInfo(..)
85 import FieldLabel ( mkFieldLabel, fieldLabelName,
86 firstFieldLabelTag, allFieldLabelTags, fieldLabelType
91 import Maybe ( isJust )
93 import ListSetOps ( assoc, assocMaybe )
94 import UnicodeUtil ( stringToUtf8 )
99 %************************************************************************
101 \subsection{Wired in Ids}
103 %************************************************************************
107 = [ -- These error-y things are wired in because we don't yet have
108 -- a way to express in an interface file that the result type variable
109 -- is 'open'; that is can be unified with an unboxed type
111 -- [The interface file format now carry such information, but there's
112 -- no way yet of expressing at the definition site for these
114 -- functions that they have an 'open' result type. -- sof 1/99]
118 , iRREFUT_PAT_ERROR_ID
119 , nON_EXHAUSTIVE_GUARDS_ERROR_ID
120 , nO_METHOD_BINDING_ERROR_ID
126 -- These two can't be defined in Haskell
133 %************************************************************************
135 \subsection{Easy ones}
137 %************************************************************************
140 mkSpecPragmaId occ uniq ty loc
141 = mkId (mkLocalName uniq occ loc) ty (mkIdInfo SpecPragmaId NoCafRefs)
142 -- Maybe a SysLocal? But then we'd lose the location
144 mkDefaultMethodId dm_name rec_c ty
145 = mkId dm_name ty info
147 info = constantIdInfo `setTyGenInfo` TyGenNever
148 -- type is wired-in (see comment at TcClassDcl.tcClassSig), so
149 -- do not generalise it
151 mkWorkerId :: Unique -> Id -> Type -> Id
152 -- A worker gets a local name. CoreTidy will globalise it if necessary.
153 mkWorkerId uniq unwrkr ty
154 = mkVanillaId wkr_name ty
156 wkr_name = mkLocalName uniq (mkWorkerOcc (getOccName unwrkr)) (getSrcLoc unwrkr)
159 %************************************************************************
161 \subsection{Data constructors}
163 %************************************************************************
166 mkDataConId :: Name -> DataCon -> Id
167 -- Makes the *worker* for the data constructor; that is, the function
168 -- that takes the reprsentation arguments and builds the constructor.
169 mkDataConId work_name data_con
170 = mkId work_name (dataConRepType data_con) info
172 info = mkIdInfo (DataConId data_con) NoCafRefs
173 `setArityInfo` exactArity arity
174 `setStrictnessInfo` strict_info
175 `setCprInfo` cpr_info
177 arity = dataConRepArity data_con
179 strict_info = mkStrictnessInfo (dataConRepStrictness data_con, False)
181 tycon = dataConTyCon data_con
182 cpr_info | isProductTyCon tycon &&
184 arity > 0 = ReturnsCPR
185 | otherwise = NoCPRInfo
186 -- ReturnsCPR is only true for products that are real data types;
187 -- that is, not unboxed tuples or newtypes
190 The wrapper for a constructor is an ordinary top-level binding that evaluates
191 any strict args, unboxes any args that are going to be flattened, and calls
194 We're going to build a constructor that looks like:
196 data (Data a, C b) => T a b = T1 !a !Int b
199 \d1::Data a, d2::C b ->
200 \p q r -> case p of { p ->
202 Con T1 [a,b] [p,q,r]}}
206 * d2 is thrown away --- a context in a data decl is used to make sure
207 one *could* construct dictionaries at the site the constructor
208 is used, but the dictionary isn't actually used.
210 * We have to check that we can construct Data dictionaries for
211 the types a and Int. Once we've done that we can throw d1 away too.
213 * We use (case p of q -> ...) to evaluate p, rather than "seq" because
214 all that matters is that the arguments are evaluated. "seq" is
215 very careful to preserve evaluation order, which we don't need
218 You might think that we could simply give constructors some strictness
219 info, like PrimOps, and let CoreToStg do the let-to-case transformation.
220 But we don't do that because in the case of primops and functions strictness
221 is a *property* not a *requirement*. In the case of constructors we need to
222 do something active to evaluate the argument.
224 Making an explicit case expression allows the simplifier to eliminate
225 it in the (common) case where the constructor arg is already evaluated.
228 mkDataConWrapId data_con
231 wrap_id = mkId (dataConName data_con) wrap_ty info
232 work_id = dataConId data_con
234 info = mkIdInfo (DataConWrapId data_con) NoCafRefs
235 `setUnfoldingInfo` mkTopUnfolding (mkInlineMe wrap_rhs)
236 `setCprInfo` cpr_info
237 -- The Cpr info can be important inside INLINE rhss, where the
238 -- wrapper constructor isn't inlined
239 `setArityInfo` exactArity arity
240 -- It's important to specify the arity, so that partial
241 -- applications are treated as values
242 `setTyGenInfo` TyGenNever
243 -- No point generalising its type, since it gets eagerly inlined
246 wrap_ty = mkForAllTys all_tyvars $
250 cpr_info = idCprInfo work_id
252 wrap_rhs | isNewTyCon tycon
253 = ASSERT( null ex_tyvars && null ex_dict_args && length orig_arg_tys == 1 )
254 -- No existentials on a newtype, but it can have a context
255 -- e.g. newtype Eq a => T a = MkT (...)
257 mkLams tyvars $ mkLams dict_args $ Lam id_arg1 $
258 Note (Coerce result_ty (head orig_arg_tys)) (Var id_arg1)
260 | null dict_args && all not_marked_strict strict_marks
261 = Var work_id -- The common case. Not only is this efficient,
262 -- but it also ensures that the wrapper is replaced
263 -- by the worker even when there are no args.
267 -- This is really important in rule matching,
268 -- (We could match on the wrappers,
269 -- but that makes it less likely that rules will match
270 -- when we bring bits of unfoldings together.)
272 -- NB: because of this special case, (map (:) ys) turns into
273 -- (map $w: ys), and thence into (map (\x xs. $w: x xs) ys)
274 -- in core-to-stg. The top-level defn for (:) is never used.
275 -- This is somewhat of a bore, but I'm currently leaving it
276 -- as is, so that there still is a top level curried (:) for
277 -- the interpreter to call.
280 = mkLams all_tyvars $ mkLams dict_args $
281 mkLams ex_dict_args $ mkLams id_args $
282 foldr mk_case con_app
283 (zip (ex_dict_args++id_args) strict_marks) i3 []
285 con_app i rep_ids = mkApps (Var work_id)
286 (map varToCoreExpr (all_tyvars ++ reverse rep_ids))
288 (tyvars, theta, ex_tyvars, ex_theta, orig_arg_tys, tycon) = dataConSig data_con
289 all_tyvars = tyvars ++ ex_tyvars
291 dict_tys = mkDictTys theta
292 ex_dict_tys = mkDictTys ex_theta
293 all_arg_tys = dict_tys ++ ex_dict_tys ++ orig_arg_tys
294 result_ty = mkTyConApp tycon (mkTyVarTys tyvars)
296 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
300 (dict_args, i1) = mkLocals 1 dict_tys
301 (ex_dict_args,i2) = mkLocals i1 ex_dict_tys
302 (id_args,i3) = mkLocals i2 orig_arg_tys
304 (id_arg1:_) = id_args -- Used for newtype only
306 strict_marks = dataConStrictMarks data_con
307 not_marked_strict NotMarkedStrict = True
308 not_marked_strict other = False
312 :: (Id, StrictnessMark) -- arg, strictness
313 -> (Int -> [Id] -> CoreExpr) -- body
314 -> Int -- next rep arg id
315 -> [Id] -- rep args so far
317 mk_case (arg,strict) body i rep_args
319 NotMarkedStrict -> body i (arg:rep_args)
321 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
323 Case (Var arg) arg [(DEFAULT,[], body i (arg:rep_args))]
325 MarkedUnboxed con tys ->
326 Case (Var arg) arg [(DataAlt con, con_args,
327 body i' (reverse con_args++rep_args))]
329 (con_args,i') = mkLocals i tys
333 %************************************************************************
335 \subsection{Record selectors}
337 %************************************************************************
339 We're going to build a record selector unfolding that looks like this:
341 data T a b c = T1 { ..., op :: a, ...}
342 | T2 { ..., op :: a, ...}
345 sel = /\ a b c -> \ d -> case d of
350 Similarly for newtypes
352 newtype N a = MkN { unN :: a->a }
355 unN n = coerce (a->a) n
357 We need to take a little care if the field has a polymorphic type:
359 data R = R { f :: forall a. a->a }
363 f :: forall a. R -> a -> a
364 f = /\ a \ r = case r of
367 (not f :: R -> forall a. a->a, which gives the type inference mechanism
368 problems at call sites)
370 Similarly for newtypes
372 newtype N = MkN { unN :: forall a. a->a }
374 unN :: forall a. N -> a -> a
375 unN = /\a -> \n:N -> coerce (a->a) n
378 mkRecordSelId tycon field_label unpack_id unpackUtf8_id
379 -- Assumes that all fields with the same field label have the same type
381 -- Annoyingly, we have to pass in the unpackCString# Id, because
382 -- we can't conjure it up out of thin air
385 sel_id = mkId (fieldLabelName field_label) selector_ty info
387 field_ty = fieldLabelType field_label
388 data_cons = tyConDataCons tycon
389 tyvars = tyConTyVars tycon -- These scope over the types in
390 -- the FieldLabels of constructors of this type
391 data_ty = mkTyConApp tycon tyvar_tys
392 tyvar_tys = mkTyVarTys tyvars
394 tycon_theta = tyConTheta tycon -- The context on the data decl
395 -- eg data (Eq a, Ord b) => T a b = ...
396 dict_tys = [mkDictTy cls tys | (cls, tys) <- tycon_theta,
397 needed_dict (cls, tys)]
398 needed_dict pred = or [ pred `elem` (dataConTheta dc)
399 | (DataAlt dc, _, _) <- the_alts]
400 n_dict_tys = length dict_tys
402 (field_tyvars,field_theta,field_tau) = splitSigmaTy field_ty
403 field_dict_tys = map mkPredTy field_theta
404 n_field_dict_tys = length field_dict_tys
405 -- If the field has a universally quantified type we have to
406 -- be a bit careful. Suppose we have
407 -- data R = R { op :: forall a => Foo a => a -> a }
408 -- Then we can't give op the type
409 -- op :: R -> forall a. Foo a => a -> a
410 -- because the typechecker doesn't understand foralls to the
411 -- right of an arrow. The "right" type to give it is
412 -- op :: forall a. Foo a => a -> a
413 -- But then we must generat the right unfolding too:
414 -- op = /\a -> \dfoo -> \ r ->
417 -- Note that this is exactly the type we'd infer from a user defn
420 -- Very tiresomely, the selectors are (unnecessarily!) overloaded over
421 -- just the dictionaries in the types of the constructors that contain
422 -- the relevant field. Urgh.
423 -- NB: this code relies on the fact that DataCons are quantified over
424 -- the identical type variables as their parent TyCon
427 selector_ty = mkForAllTys tyvars $ mkForAllTys field_tyvars $
428 mkFunTys dict_tys $ mkFunTys field_dict_tys $
429 mkFunTy data_ty field_tau
431 arity = 1 + n_dict_tys + n_field_dict_tys
432 info = mkIdInfo (RecordSelId field_label) NoCafRefs
433 `setArityInfo` exactArity arity
434 `setUnfoldingInfo` unfolding
435 `setTyGenInfo` TyGenNever
436 -- ToDo: consider adding further IdInfo
438 unfolding = mkTopUnfolding sel_rhs
440 -- Allocate Ids. We do it a funny way round because field_dict_tys is
441 -- almost always empty
442 dict_ids = mkTemplateLocalsNum 1 dict_tys
443 field_dict_ids = mkTemplateLocalsNum (n_dict_tys+1) field_dict_tys
444 data_id = mkTemplateLocal arity data_ty
446 alts = map mk_maybe_alt data_cons
447 the_alts = catMaybes alts
448 default_alt | all isJust alts = [] -- No default needed
449 | otherwise = [(DEFAULT, [], error_expr)]
451 sel_rhs = mkLams tyvars $ mkLams field_tyvars $
452 mkLams dict_ids $ mkLams field_dict_ids $
453 Lam data_id $ sel_body
455 sel_body | isNewTyCon tycon = Note (Coerce field_tau data_ty) (Var data_id)
456 | otherwise = Case (Var data_id) data_id (the_alts ++ default_alt)
458 mk_maybe_alt data_con
459 = case maybe_the_arg_id of
461 Just the_arg_id -> Just (DataAlt data_con, real_args, expr)
463 body = mkVarApps (mkVarApps (Var the_arg_id) field_tyvars) field_dict_ids
464 strict_marks = dataConStrictMarks data_con
465 (expr, real_args) = rebuildConArgs data_con arg_ids strict_marks body
468 arg_ids = mkTemplateLocalsNum (arity+1) (dataConInstOrigArgTys data_con tyvar_tys)
469 -- arity+1 avoids all shadowing
470 maybe_the_arg_id = assocMaybe (field_lbls `zip` arg_ids) field_label
471 field_lbls = dataConFieldLabels data_con
473 error_expr = mkApps (Var rEC_SEL_ERROR_ID) [Type field_tau, err_string]
475 | all safeChar full_msg
476 = App (Var unpack_id) (Lit (MachStr (_PK_ full_msg)))
478 = App (Var unpackUtf8_id) (Lit (MachStr (_PK_ (stringToUtf8 (map ord full_msg)))))
480 safeChar c = c >= '\1' && c <= '\xFF'
481 -- TODO: Putting this Unicode stuff here is ugly. Find a better
482 -- generic place to make string literals. This logic is repeated
484 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
487 -- this rather ugly function converts the unpacked data con arguments back into
488 -- their packed form. It is almost the same as the version in DsUtils, except that
489 -- we use template locals here rather than newDsId (ToDo: merge these).
492 :: DataCon -- the con we're matching on
493 -> [Id] -- the source-level args
494 -> [StrictnessMark] -- the strictness annotations (per-arg)
495 -> CoreExpr -- the body
496 -> Int -- template local
499 rebuildConArgs con [] stricts body i = (body, [])
500 rebuildConArgs con (arg:args) stricts body i | isTyVar arg
501 = let (body', args') = rebuildConArgs con args stricts body i
503 rebuildConArgs con (arg:args) (str:stricts) body i
504 = case maybeMarkedUnboxed str of
505 Just (pack_con1, _) ->
506 case splitProductType_maybe (idType arg) of
507 Just (_, tycon_args, pack_con, con_arg_tys) ->
508 ASSERT( pack_con == pack_con1 )
509 let unpacked_args = zipWith mkTemplateLocal [i..] con_arg_tys
510 (body', real_args) = rebuildConArgs con args stricts body
511 (i + length con_arg_tys)
514 Let (NonRec arg (mkConApp pack_con
515 (map Type tycon_args ++
516 map Var unpacked_args))) body',
517 unpacked_args ++ real_args
520 _ -> let (body', args') = rebuildConArgs con args stricts body i
521 in (body', arg:args')
525 %************************************************************************
527 \subsection{Dictionary selectors}
529 %************************************************************************
531 Selecting a field for a dictionary. If there is just one field, then
532 there's nothing to do.
534 ToDo: unify with mkRecordSelId.
537 mkDictSelId :: Name -> Class -> Id
538 mkDictSelId name clas
542 sel_id = mkId name ty info
543 field_lbl = mkFieldLabel name tycon ty tag
544 tag = assoc "MkId.mkDictSelId" (classSelIds clas `zip` allFieldLabelTags) sel_id
546 info = mkIdInfo (RecordSelId field_lbl) NoCafRefs
547 `setArityInfo` exactArity 1
548 `setUnfoldingInfo` unfolding
549 `setTyGenInfo` TyGenNever
551 -- We no longer use 'must-inline' on record selectors. They'll
552 -- inline like crazy if they scrutinise a constructor
554 unfolding = mkTopUnfolding rhs
556 tyvars = classTyVars clas
558 tycon = classTyCon clas
559 [data_con] = tyConDataCons tycon
560 tyvar_tys = mkTyVarTys tyvars
561 arg_tys = dataConArgTys data_con tyvar_tys
562 the_arg_id = arg_ids !! (tag - firstFieldLabelTag)
564 dict_ty = mkDictTy clas tyvar_tys
565 (dict_id:arg_ids) = mkTemplateLocals (dict_ty : arg_tys)
567 rhs | isNewTyCon tycon = mkLams tyvars $ Lam dict_id $
568 Note (Coerce (head arg_tys) dict_ty) (Var dict_id)
569 | otherwise = mkLams tyvars $ Lam dict_id $
570 Case (Var dict_id) dict_id
571 [(DataAlt data_con, arg_ids, Var the_arg_id)]
575 %************************************************************************
577 \subsection{Primitive operations
579 %************************************************************************
582 mkPrimOpId :: PrimOp -> Id
586 (tyvars,arg_tys,res_ty, arity, strict_info) = primOpSig prim_op
587 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
588 name = mkPrimOpIdName prim_op
589 id = mkId name ty info
591 info = mkIdInfo (PrimOpId prim_op) NoCafRefs
593 `setArityInfo` exactArity arity
594 `setStrictnessInfo` strict_info
596 rules = addRule emptyCoreRules id (primOpRule prim_op)
599 -- For each ccall we manufacture a separate CCallOpId, giving it
600 -- a fresh unique, a type that is correct for this particular ccall,
601 -- and a CCall structure that gives the correct details about calling
604 -- The *name* of this Id is a local name whose OccName gives the full
605 -- details of the ccall, type and all. This means that the interface
606 -- file reader can reconstruct a suitable Id
608 mkCCallOpId :: Unique -> CCall -> Type -> Id
609 mkCCallOpId uniq ccall ty
610 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
611 -- A CCallOpId should have no free type variables;
612 -- when doing substitutions won't substitute over it
615 occ_str = showSDocIface (braces (pprCCallOp ccall <+> ppr ty))
616 -- The "occurrence name" of a ccall is the full info about the
617 -- ccall; it is encoded, but may have embedded spaces etc!
619 name = mkCCallName uniq occ_str
620 prim_op = CCallOp ccall
622 info = mkIdInfo (PrimOpId prim_op) NoCafRefs
623 `setArityInfo` exactArity arity
624 `setStrictnessInfo` strict_info
626 (_, tau) = splitForAllTys ty
627 (arg_tys, _) = splitFunTys tau
628 arity = length arg_tys
629 strict_info = mkStrictnessInfo (take arity (repeat wwPrim), False)
633 %************************************************************************
635 \subsection{DictFuns}
637 %************************************************************************
640 mkDictFunId :: Name -- Name to use for the dict fun;
647 mkDictFunId dfun_name clas inst_tyvars inst_tys dfun_theta
648 = mkId dfun_name dfun_ty info
650 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
651 info = mkIdInfo DictFunId MayHaveCafRefs
652 `setTyGenInfo` TyGenNever
653 -- type is wired-in (see comment at TcClassDcl.tcClassSig), so
654 -- do not generalise it
655 -- An imported dfun may refer to CAFs, so we assume the worst
657 {- 1 dec 99: disable the Mark Jones optimisation for the sake
658 of compatibility with Hugs.
659 See `types/InstEnv' for a discussion related to this.
661 (class_tyvars, sc_theta, _, _) = classBigSig clas
662 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
663 sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys) sc_theta
664 dfun_theta = case inst_decl_theta of
665 [] -> [] -- If inst_decl_theta is empty, then we don't
666 -- want to have any dict arguments, so that we can
667 -- expose the constant methods.
669 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
670 -- Otherwise we pass the superclass dictionaries to
671 -- the dictionary function; the Mark Jones optimisation.
673 -- NOTE the "nub". I got caught by this one:
674 -- class Monad m => MonadT t m where ...
675 -- instance Monad m => MonadT (EnvT env) m where ...
676 -- Here, the inst_decl_theta has (Monad m); but so
677 -- does the sc_theta'!
679 -- NOTE the "not_const". I got caught by this one too:
680 -- class Foo a => Baz a b where ...
681 -- instance Wob b => Baz T b where..
682 -- Now sc_theta' has Foo T
687 %************************************************************************
689 \subsection{Un-definable}
691 %************************************************************************
693 These two can't be defined in Haskell.
695 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
696 just gets expanded into a type coercion wherever it occurs. Hence we
697 add it as a built-in Id with an unfolding here.
699 The type variables we use here are "open" type variables: this means
700 they can unify with both unlifted and lifted types. Hence we provide
701 another gun with which to shoot yourself in the foot.
705 = pcMiscPrelId unsafeCoerceIdKey pREL_GHC SLIT("unsafeCoerce#") ty info
707 info = constantIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
710 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
711 (mkFunTy openAlphaTy openBetaTy)
712 [x] = mkTemplateLocals [openAlphaTy]
713 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
714 Note (Coerce openBetaTy openAlphaTy) (Var x)
718 @getTag#@ is another function which can't be defined in Haskell. It needs to
719 evaluate its argument and call the dataToTag# primitive.
723 = pcMiscPrelId getTagIdKey pREL_GHC SLIT("getTag#") ty info
725 info = constantIdInfo
726 `setUnfoldingInfo` mkCompulsoryUnfolding rhs
727 -- We don't provide a defn for this; you must inline it
729 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy intPrimTy)
730 [x,y] = mkTemplateLocals [alphaTy,alphaTy]
731 rhs = mkLams [alphaTyVar,x] $
732 Case (Var x) y [ (DEFAULT, [], mkApps (Var dataToTagId) [Type alphaTy, Var y]) ]
734 dataToTagId = mkPrimOpId DataToTagOp
737 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
738 nasty as-is, change it back to a literal (@Literal@).
741 realWorldPrimId -- :: State# RealWorld
742 = pcMiscPrelId realWorldPrimIdKey pREL_GHC SLIT("realWorld#")
744 (noCafIdInfo `setUnfoldingInfo` mkOtherCon [])
745 -- The mkOtherCon makes it look that realWorld# is evaluated
746 -- which in turn makes Simplify.interestingArg return True,
747 -- which in turn makes INLINE things applied to realWorld# likely
752 %************************************************************************
754 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
756 %************************************************************************
758 GHC randomly injects these into the code.
760 @patError@ is just a version of @error@ for pattern-matching
761 failures. It knows various ``codes'' which expand to longer
762 strings---this saves space!
764 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
765 well shouldn't be yanked on, but if one is, then you will get a
766 friendly message from @absentErr@ (rather than a totally random
769 @parError@ is a special version of @error@ which the compiler does
770 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
771 templates, but we don't ever expect to generate code for it.
775 = pc_bottoming_Id errorIdKey pREL_ERR SLIT("error") errorTy
777 = generic_ERROR_ID patErrorIdKey SLIT("patError")
779 = generic_ERROR_ID recSelErrIdKey SLIT("recSelError")
781 = generic_ERROR_ID recConErrorIdKey SLIT("recConError")
783 = generic_ERROR_ID recUpdErrorIdKey SLIT("recUpdError")
785 = generic_ERROR_ID irrefutPatErrorIdKey SLIT("irrefutPatError")
786 nON_EXHAUSTIVE_GUARDS_ERROR_ID
787 = generic_ERROR_ID nonExhaustiveGuardsErrorIdKey SLIT("nonExhaustiveGuardsError")
788 nO_METHOD_BINDING_ERROR_ID
789 = generic_ERROR_ID noMethodBindingErrorIdKey SLIT("noMethodBindingError")
792 = pc_bottoming_Id absentErrorIdKey pREL_ERR SLIT("absentErr")
793 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy)
796 = pcMiscPrelId parErrorIdKey pREL_ERR SLIT("parError")
797 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy) noCafIdInfo
802 %************************************************************************
804 \subsection{Utilities}
806 %************************************************************************
809 pcMiscPrelId :: Unique{-IdKey-} -> Module -> FAST_STRING -> Type -> IdInfo -> Id
810 pcMiscPrelId key mod str ty info
812 name = mkWiredInName mod (mkVarOcc str) key
813 imp = mkId name ty info -- the usual case...
816 -- We lie and say the thing is imported; otherwise, we get into
817 -- a mess with dependency analysis; e.g., core2stg may heave in
818 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
819 -- being compiled, then it's just a matter of luck if the definition
820 -- will be in "the right place" to be in scope.
822 pc_bottoming_Id key mod name ty
823 = pcMiscPrelId key mod name ty bottoming_info
825 bottoming_info = noCafIdInfo
826 `setStrictnessInfo` mkStrictnessInfo ([wwStrict], True)
828 -- these "bottom" out, no matter what their arguments
830 generic_ERROR_ID u n = pc_bottoming_Id u pREL_ERR n errorTy
833 noCafIdInfo = constantIdInfo `setCafInfo` NoCafRefs
835 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
836 openAlphaTy = mkTyVarTy openAlphaTyVar
837 openBetaTy = mkTyVarTy openBetaTyVar
840 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy]
842 -- Notice the openAlphaTyVar. It says that "error" can be applied
843 -- to unboxed as well as boxed types. This is OK because it never
844 -- returns, so the return type is irrelevant.