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,
45 isUnLiftedType, mkForAllTys, mkTyVarTy, tyVarsOfType,
46 splitFunTys, splitForAllTys, unUsgTy,
49 import Module ( Module )
50 import CoreUtils ( exprType, mkInlineMe )
51 import CoreUnfold ( mkTopUnfolding, mkCompulsoryUnfolding, mkOtherCon )
52 import Literal ( Literal(..) )
53 import TyCon ( TyCon, isNewTyCon, tyConTyVars, tyConDataCons,
54 tyConTheta, isProductTyCon, isUnboxedTupleTyCon )
55 import Class ( Class, classTyCon, classTyVars, classSelIds )
56 import Var ( Id, TyVar )
57 import VarSet ( isEmptyVarSet )
58 import Name ( mkDerivedName, mkWiredInName, mkLocalName,
59 mkWorkerOcc, mkCCallName,
62 import OccName ( mkVarOcc )
63 import PrimOp ( PrimOp(DataToTagOp, CCallOp),
64 primOpSig, mkPrimOpIdName,
67 import Demand ( wwStrict, wwPrim, mkStrictnessInfo )
68 import DataCon ( DataCon, StrictnessMark(..),
69 dataConFieldLabels, dataConRepArity, dataConTyCon,
70 dataConArgTys, dataConRepType, dataConRepStrictness,
71 dataConInstOrigArgTys,
72 dataConName, dataConTheta,
73 dataConSig, dataConStrictMarks, dataConId,
74 maybeMarkedUnboxed, splitProductType_maybe
76 import Id ( idType, mkId,
77 mkVanillaId, mkTemplateLocals,
78 mkTemplateLocal, idCprInfo
80 import IdInfo ( IdInfo, vanillaIdInfo, mkIdInfo,
81 exactArity, setUnfoldingInfo, setCafInfo, setCprInfo,
82 setArityInfo, setSpecInfo,
83 mkStrictnessInfo, setStrictnessInfo,
84 IdFlavour(..), CafInfo(..), CprInfo(..)
86 import FieldLabel ( mkFieldLabel, fieldLabelName,
87 firstFieldLabelTag, allFieldLabelTags, fieldLabelType
92 import Maybe ( isJust )
94 import ListSetOps ( assoc, assocMaybe )
95 import UnicodeUtil ( stringToUtf8 )
100 %************************************************************************
102 \subsection{Wired in Ids}
104 %************************************************************************
108 = [ -- These error-y things are wired in because we don't yet have
109 -- a way to express in an interface file that the result type variable
110 -- is 'open'; that is can be unified with an unboxed type
112 -- [The interface file format now carry such information, but there's
113 -- no way yet of expressing at the definition site for these
115 -- functions that they have an 'open' result type. -- sof 1/99]
119 , iRREFUT_PAT_ERROR_ID
120 , nON_EXHAUSTIVE_GUARDS_ERROR_ID
121 , nO_METHOD_BINDING_ERROR_ID
127 -- These two can't be defined in Haskell
134 %************************************************************************
136 \subsection{Easy ones}
138 %************************************************************************
141 mkSpecPragmaId occ uniq ty loc
142 = mkId (mkLocalName uniq occ loc) ty (mkIdInfo SpecPragmaId)
143 -- Maybe a SysLocal? But then we'd lose the location
145 mkDefaultMethodId dm_name rec_c ty
146 = mkVanillaId dm_name ty
148 mkWorkerId uniq unwrkr ty
149 = mkVanillaId (mkDerivedName mkWorkerOcc (getName unwrkr) uniq) ty
152 %************************************************************************
154 \subsection{Data constructors}
156 %************************************************************************
159 mkDataConId :: Name -> DataCon -> Id
160 -- Makes the *worker* for the data constructor; that is, the function
161 -- that takes the reprsentation arguments and builds the constructor.
162 mkDataConId work_name data_con
163 = mkId work_name (dataConRepType data_con) info
165 info = mkIdInfo (DataConId data_con)
166 `setArityInfo` exactArity arity
167 `setStrictnessInfo` strict_info
168 `setCprInfo` cpr_info
170 arity = dataConRepArity data_con
172 strict_info = mkStrictnessInfo (dataConRepStrictness data_con, False)
174 cpr_info | isProductTyCon tycon &&
175 not (isUnboxedTupleTyCon tycon) &&
176 arity > 0 = ReturnsCPR
177 | otherwise = NoCPRInfo
179 tycon = dataConTyCon data_con
180 -- Newtypes don't have a worker at all
182 -- If we are a product with 0 args we must be void(like)
183 -- We can't create an unboxed tuple with 0 args for this
184 -- and since Void has only one, constant value it should
185 -- just mean returning a pointer to a pre-existing cell.
186 -- So we won't really gain from doing anything fancy
187 -- and we treat this case as Top.
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)
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 `setCafInfo` NoCafRefs
243 -- The wrapper Id ends up in STG code as an argument,
244 -- sometimes before its definition, so we want to
245 -- signal that it has no CAFs
247 wrap_ty = mkForAllTys all_tyvars $
251 cpr_info = idCprInfo work_id
253 wrap_rhs | isNewTyCon tycon
254 = ASSERT( null ex_tyvars && null ex_dict_args && length orig_arg_tys == 1 )
255 -- No existentials on a newtype, but it can have a context
256 -- e.g. newtype Eq a => T a = MkT (...)
258 mkLams tyvars $ mkLams dict_args $ Lam id_arg1 $
259 Note (Coerce result_ty (head orig_arg_tys)) (Var id_arg1)
261 | null dict_args && all not_marked_strict strict_marks
262 = Var work_id -- The common case. Not only is this efficient,
263 -- but it also ensures that the wrapper is replaced
264 -- by the worker even when there are no args.
268 -- This is really important in rule matching,
269 -- (We could match on the wrappers,
270 -- but that makes it less likely that rules will match
271 -- when we bring bits of unfoldings together.)
273 -- NB: because of this special case, (map (:) ys) turns into
274 -- (map $w: ys), and thence into (map (\x xs. $w: x xs) ys)
275 -- in core-to-stg. The top-level defn for (:) is never used.
276 -- This is somewhat of a bore, but I'm currently leaving it
277 -- as is, so that there still is a top level curried (:) for
278 -- the interpreter to call.
281 = mkLams all_tyvars $ mkLams dict_args $
282 mkLams ex_dict_args $ mkLams id_args $
283 foldr mk_case con_app
284 (zip (ex_dict_args++id_args) strict_marks) i3 []
286 con_app i rep_ids = mkApps (Var work_id)
287 (map varToCoreExpr (all_tyvars ++ reverse rep_ids))
289 (tyvars, theta, ex_tyvars, ex_theta, orig_arg_tys, tycon) = dataConSig data_con
290 all_tyvars = tyvars ++ ex_tyvars
292 dict_tys = mkDictTys theta
293 ex_dict_tys = mkDictTys ex_theta
294 all_arg_tys = dict_tys ++ ex_dict_tys ++ orig_arg_tys
295 result_ty = mkTyConApp tycon (mkTyVarTys tyvars)
297 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
301 (dict_args, i1) = mkLocals 1 dict_tys
302 (ex_dict_args,i2) = mkLocals i1 ex_dict_tys
303 (id_args,i3) = mkLocals i2 orig_arg_tys
305 (id_arg1:_) = id_args -- Used for newtype only
307 strict_marks = dataConStrictMarks data_con
308 not_marked_strict NotMarkedStrict = True
309 not_marked_strict other = False
313 :: (Id, StrictnessMark) -- arg, strictness
314 -> (Int -> [Id] -> CoreExpr) -- body
315 -> Int -- next rep arg id
316 -> [Id] -- rep args so far
318 mk_case (arg,strict) body i rep_args
320 NotMarkedStrict -> body i (arg:rep_args)
322 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
324 Case (Var arg) arg [(DEFAULT,[], body i (arg:rep_args))]
326 MarkedUnboxed con tys ->
327 Case (Var arg) arg [(DataAlt con, con_args,
328 body i' (reverse con_args++rep_args))]
330 (con_args,i') = mkLocals i tys
334 %************************************************************************
336 \subsection{Record selectors}
338 %************************************************************************
340 We're going to build a record selector unfolding that looks like this:
342 data T a b c = T1 { ..., op :: a, ...}
343 | T2 { ..., op :: a, ...}
346 sel = /\ a b c -> \ d -> case d of
351 Similarly for newtypes
353 newtype N a = MkN { unN :: a->a }
356 unN n = coerce (a->a) n
358 We need to take a little care if the field has a polymorphic type:
360 data R = R { f :: forall a. a->a }
364 f :: forall a. R -> a -> a
365 f = /\ a \ r = case r of
368 (not f :: R -> forall a. a->a, which gives the type inference mechanism
369 problems at call sites)
371 Similarly for newtypes
373 newtype N = MkN { unN :: forall a. a->a }
375 unN :: forall a. N -> a -> a
376 unN = /\a -> \n:N -> coerce (a->a) n
379 mkRecordSelId tycon field_label unpack_id unpackUtf8_id
380 -- Assumes that all fields with the same field label have the same type
382 -- Annoyingly, we have to pass in the unpackCString# Id, because
383 -- we can't conjure it up out of thin air
386 sel_id = mkId (fieldLabelName field_label) selector_ty info
388 field_ty = fieldLabelType field_label
389 data_cons = tyConDataCons tycon
390 tyvars = tyConTyVars tycon -- These scope over the types in
391 -- the FieldLabels of constructors of this type
392 tycon_theta = tyConTheta tycon -- The context on the data decl
393 -- eg data (Eq a, Ord b) => T a b = ...
394 (field_tyvars,field_tau) = splitForAllTys field_ty
396 data_ty = mkTyConApp tycon tyvar_tys
397 tyvar_tys = mkTyVarTys tyvars
399 -- Very tiresomely, the selectors are (unnecessarily!) overloaded over
400 -- just the dictionaries in the types of the constructors that contain
401 -- the relevant field. Urgh.
402 -- NB: this code relies on the fact that DataCons are quantified over
403 -- the identical type variables as their parent TyCon
404 dict_tys = [mkDictTy cls tys | (cls, tys) <- tycon_theta, needed_dict (cls, tys)]
405 needed_dict pred = or [ pred `elem` (dataConTheta dc)
406 | (DataAlt dc, _, _) <- the_alts]
409 selector_ty = mkForAllTys tyvars $ mkForAllTys field_tyvars $
410 mkFunTys dict_tys $ mkFunTy data_ty field_tau
412 info = mkIdInfo (RecordSelId field_label)
413 `setArityInfo` exactArity (1 + length dict_tys)
414 `setUnfoldingInfo` unfolding
415 `setCafInfo` NoCafRefs
416 -- ToDo: consider adding further IdInfo
418 unfolding = mkTopUnfolding sel_rhs
421 (data_id:dict_ids) = mkTemplateLocals (data_ty:dict_tys)
422 alts = map mk_maybe_alt data_cons
423 the_alts = catMaybes alts
424 default_alt | all isJust alts = [] -- No default needed
425 | otherwise = [(DEFAULT, [], error_expr)]
427 sel_rhs = mkLams tyvars $ mkLams field_tyvars $
428 mkLams dict_ids $ Lam data_id $
431 sel_body | isNewTyCon tycon = Note (Coerce (unUsgTy field_tau) (unUsgTy data_ty)) (Var data_id)
432 | otherwise = Case (Var data_id) data_id (the_alts ++ default_alt)
434 mk_maybe_alt data_con
435 = case maybe_the_arg_id of
437 Just the_arg_id -> Just (DataAlt data_con, real_args, expr)
439 body = mkVarApps (Var the_arg_id) field_tyvars
440 strict_marks = dataConStrictMarks data_con
441 (expr, real_args) = rebuildConArgs data_con arg_ids strict_marks body
444 arg_ids = mkTemplateLocals (dataConInstOrigArgTys data_con tyvar_tys)
445 -- The first one will shadow data_id, but who cares
446 maybe_the_arg_id = assocMaybe (field_lbls `zip` arg_ids) field_label
447 field_lbls = dataConFieldLabels data_con
449 error_expr = mkApps (Var rEC_SEL_ERROR_ID) [Type (unUsgTy field_tau), err_string]
450 -- preserves invariant that type args are *not* usage-annotated on top. KSW 1999-04.
452 | all safeChar full_msg
453 = App (Var unpack_id) (Lit (MachStr (_PK_ full_msg)))
455 = App (Var unpackUtf8_id) (Lit (MachStr (_PK_ (stringToUtf8 (map ord full_msg)))))
457 safeChar c = c >= '\1' && c <= '\xFF'
458 -- TODO: Putting this Unicode stuff here is ugly. Find a better
459 -- generic place to make string literals. This logic is repeated
461 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
464 -- this rather ugly function converts the unpacked data con arguments back into
465 -- their packed form. It is almost the same as the version in DsUtils, except that
466 -- we use template locals here rather than newDsId (ToDo: merge these).
469 :: DataCon -- the con we're matching on
470 -> [Id] -- the source-level args
471 -> [StrictnessMark] -- the strictness annotations (per-arg)
472 -> CoreExpr -- the body
473 -> Int -- template local
476 rebuildConArgs con [] stricts body i = (body, [])
477 rebuildConArgs con (arg:args) stricts body i | isTyVar arg
478 = let (body', args') = rebuildConArgs con args stricts body i
480 rebuildConArgs con (arg:args) (str:stricts) body i
481 = case maybeMarkedUnboxed str of
482 Just (pack_con1, _) ->
483 case splitProductType_maybe (idType arg) of
484 Just (_, tycon_args, pack_con, con_arg_tys) ->
485 ASSERT( pack_con == pack_con1 )
486 let unpacked_args = zipWith mkTemplateLocal [i..] con_arg_tys
487 (body', real_args) = rebuildConArgs con args stricts body
488 (i + length con_arg_tys)
491 Let (NonRec arg (mkConApp pack_con
492 (map Type tycon_args ++
493 map Var unpacked_args))) body',
494 unpacked_args ++ real_args
497 _ -> let (body', args') = rebuildConArgs con args stricts body i
498 in (body', arg:args')
502 %************************************************************************
504 \subsection{Dictionary selectors}
506 %************************************************************************
508 Selecting a field for a dictionary. If there is just one field, then
509 there's nothing to do.
511 ToDo: unify with mkRecordSelId.
514 mkDictSelId :: Name -> Class -> Id
515 mkDictSelId name clas
519 sel_id = mkId name ty info
520 field_lbl = mkFieldLabel name tycon ty tag
521 tag = assoc "MkId.mkDictSelId" (classSelIds clas `zip` allFieldLabelTags) sel_id
523 info = mkIdInfo (RecordSelId field_lbl)
524 `setArityInfo` exactArity 1
525 `setUnfoldingInfo` unfolding
526 `setCafInfo` NoCafRefs
528 -- We no longer use 'must-inline' on record selectors. They'll
529 -- inline like crazy if they scrutinise a constructor
531 unfolding = mkTopUnfolding rhs
533 tyvars = classTyVars clas
535 tycon = classTyCon clas
536 [data_con] = tyConDataCons tycon
537 tyvar_tys = mkTyVarTys tyvars
538 arg_tys = dataConArgTys data_con tyvar_tys
539 the_arg_id = arg_ids !! (tag - firstFieldLabelTag)
541 dict_ty = mkDictTy clas tyvar_tys
542 (dict_id:arg_ids) = mkTemplateLocals (dict_ty : arg_tys)
544 rhs | isNewTyCon tycon = mkLams tyvars $ Lam dict_id $
545 Note (Coerce (head arg_tys) dict_ty) (Var dict_id)
546 | otherwise = mkLams tyvars $ Lam dict_id $
547 Case (Var dict_id) dict_id
548 [(DataAlt data_con, arg_ids, Var the_arg_id)]
552 %************************************************************************
554 \subsection{Primitive operations
556 %************************************************************************
559 mkPrimOpId :: PrimOp -> Id
563 (tyvars,arg_tys,res_ty, arity, strict_info) = primOpSig prim_op
564 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
565 name = mkPrimOpIdName prim_op
566 id = mkId name ty info
568 info = mkIdInfo (PrimOpId prim_op)
570 `setArityInfo` exactArity arity
571 `setStrictnessInfo` strict_info
573 rules = addRule emptyCoreRules id (primOpRule prim_op)
576 -- For each ccall we manufacture a separate CCallOpId, giving it
577 -- a fresh unique, a type that is correct for this particular ccall,
578 -- and a CCall structure that gives the correct details about calling
581 -- The *name* of this Id is a local name whose OccName gives the full
582 -- details of the ccall, type and all. This means that the interface
583 -- file reader can reconstruct a suitable Id
585 mkCCallOpId :: Unique -> CCall -> Type -> Id
586 mkCCallOpId uniq ccall ty
587 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
588 -- A CCallOpId should have no free type variables;
589 -- when doing substitutions won't substitute over it
592 occ_str = showSDocIface (braces (pprCCallOp ccall <+> ppr ty))
593 -- The "occurrence name" of a ccall is the full info about the
594 -- ccall; it is encoded, but may have embedded spaces etc!
596 name = mkCCallName uniq occ_str
597 prim_op = CCallOp ccall
599 info = mkIdInfo (PrimOpId prim_op)
600 `setArityInfo` exactArity arity
601 `setStrictnessInfo` strict_info
603 (_, tau) = splitForAllTys ty
604 (arg_tys, _) = splitFunTys tau
605 arity = length arg_tys
606 strict_info = mkStrictnessInfo (take arity (repeat wwPrim), False)
610 %************************************************************************
612 \subsection{DictFuns}
614 %************************************************************************
617 mkDictFunId :: Name -- Name to use for the dict fun;
624 mkDictFunId dfun_name clas inst_tyvars inst_tys dfun_theta
625 = mkVanillaId dfun_name dfun_ty
627 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
629 {- 1 dec 99: disable the Mark Jones optimisation for the sake
630 of compatibility with Hugs.
631 See `types/InstEnv' for a discussion related to this.
633 (class_tyvars, sc_theta, _, _) = classBigSig clas
634 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
635 sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys) sc_theta
636 dfun_theta = case inst_decl_theta of
637 [] -> [] -- If inst_decl_theta is empty, then we don't
638 -- want to have any dict arguments, so that we can
639 -- expose the constant methods.
641 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
642 -- Otherwise we pass the superclass dictionaries to
643 -- the dictionary function; the Mark Jones optimisation.
645 -- NOTE the "nub". I got caught by this one:
646 -- class Monad m => MonadT t m where ...
647 -- instance Monad m => MonadT (EnvT env) m where ...
648 -- Here, the inst_decl_theta has (Monad m); but so
649 -- does the sc_theta'!
651 -- NOTE the "not_const". I got caught by this one too:
652 -- class Foo a => Baz a b where ...
653 -- instance Wob b => Baz T b where..
654 -- Now sc_theta' has Foo T
659 %************************************************************************
661 \subsection{Un-definable}
663 %************************************************************************
665 These two can't be defined in Haskell.
667 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
668 just gets expanded into a type coercion wherever it occurs. Hence we
669 add it as a built-in Id with an unfolding here.
671 The type variables we use here are "open" type variables: this means
672 they can unify with both unlifted and lifted types. Hence we provide
673 another gun with which to shoot yourself in the foot.
677 = pcMiscPrelId unsafeCoerceIdKey pREL_GHC SLIT("unsafeCoerce#") ty info
680 `setUnfoldingInfo` mkCompulsoryUnfolding rhs
683 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
684 (mkFunTy openAlphaTy openBetaTy)
685 [x] = mkTemplateLocals [openAlphaTy]
686 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
687 Note (Coerce openBetaTy openAlphaTy) (Var x)
691 @getTag#@ is another function which can't be defined in Haskell. It needs to
692 evaluate its argument and call the dataToTag# primitive.
696 = pcMiscPrelId getTagIdKey pREL_GHC SLIT("getTag#") ty info
699 `setUnfoldingInfo` mkCompulsoryUnfolding rhs
700 -- We don't provide a defn for this; you must inline it
702 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy intPrimTy)
703 [x,y] = mkTemplateLocals [alphaTy,alphaTy]
704 rhs = mkLams [alphaTyVar,x] $
705 Case (Var x) y [ (DEFAULT, [], mkApps (Var dataToTagId) [Type alphaTy, Var y]) ]
707 dataToTagId = mkPrimOpId DataToTagOp
710 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
711 nasty as-is, change it back to a literal (@Literal@).
714 realWorldPrimId -- :: State# RealWorld
715 = pcMiscPrelId realWorldPrimIdKey pREL_GHC SLIT("realWorld#")
717 (noCafIdInfo `setUnfoldingInfo` mkOtherCon [])
718 -- The mkOtherCon makes it look that realWorld# is evaluated
719 -- which in turn makes Simplify.interestingArg return True,
720 -- which in turn makes INLINE things applied to realWorld# likely
725 %************************************************************************
727 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
729 %************************************************************************
731 GHC randomly injects these into the code.
733 @patError@ is just a version of @error@ for pattern-matching
734 failures. It knows various ``codes'' which expand to longer
735 strings---this saves space!
737 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
738 well shouldn't be yanked on, but if one is, then you will get a
739 friendly message from @absentErr@ (rather than a totally random
742 @parError@ is a special version of @error@ which the compiler does
743 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
744 templates, but we don't ever expect to generate code for it.
748 = pc_bottoming_Id errorIdKey pREL_ERR SLIT("error") errorTy
750 = generic_ERROR_ID patErrorIdKey SLIT("patError")
752 = generic_ERROR_ID recSelErrIdKey SLIT("recSelError")
754 = generic_ERROR_ID recConErrorIdKey SLIT("recConError")
756 = generic_ERROR_ID recUpdErrorIdKey SLIT("recUpdError")
758 = generic_ERROR_ID irrefutPatErrorIdKey SLIT("irrefutPatError")
759 nON_EXHAUSTIVE_GUARDS_ERROR_ID
760 = generic_ERROR_ID nonExhaustiveGuardsErrorIdKey SLIT("nonExhaustiveGuardsError")
761 nO_METHOD_BINDING_ERROR_ID
762 = generic_ERROR_ID noMethodBindingErrorIdKey SLIT("noMethodBindingError")
765 = pc_bottoming_Id absentErrorIdKey pREL_ERR SLIT("absentErr")
766 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy)
769 = pcMiscPrelId parErrorIdKey pREL_ERR SLIT("parError")
770 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy) noCafIdInfo
775 %************************************************************************
777 \subsection{Utilities}
779 %************************************************************************
782 pcMiscPrelId :: Unique{-IdKey-} -> Module -> FAST_STRING -> Type -> IdInfo -> Id
783 pcMiscPrelId key mod str ty info
785 name = mkWiredInName mod (mkVarOcc str) key
786 imp = mkId name ty info -- the usual case...
789 -- We lie and say the thing is imported; otherwise, we get into
790 -- a mess with dependency analysis; e.g., core2stg may heave in
791 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
792 -- being compiled, then it's just a matter of luck if the definition
793 -- will be in "the right place" to be in scope.
795 pc_bottoming_Id key mod name ty
796 = pcMiscPrelId key mod name ty bottoming_info
798 bottoming_info = noCafIdInfo
799 `setStrictnessInfo` mkStrictnessInfo ([wwStrict], True)
801 -- these "bottom" out, no matter what their arguments
803 generic_ERROR_ID u n = pc_bottoming_Id u pREL_ERR n errorTy
806 noCafIdInfo = vanillaIdInfo `setCafInfo` NoCafRefs
808 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
809 openAlphaTy = mkTyVarTy openAlphaTyVar
810 openBetaTy = mkTyVarTy openBetaTyVar
813 errorTy = mkUsgTy UsMany $
814 mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkUsgTy UsOnce (mkListTy charTy)]
815 (mkUsgTy UsMany openAlphaTy))
816 -- Notice the openAlphaTyVar. It says that "error" can be applied
817 -- to unboxed as well as boxed types. This is OK because it never
818 -- returns, so the return type is irrelevant.