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 ( boolTy, charTy, mkListTy )
40 import PrelNames ( pREL_ERR, pREL_GHC )
41 import PrelRules ( primOpRule )
42 import Rules ( addRule )
43 import Type ( Type, ClassContext, mkDictTy, mkDictTys, mkTyConApp, mkTyVarTys,
44 mkFunTys, mkFunTy, mkSigmaTy, classesToPreds,
45 isUnLiftedType, mkForAllTys, mkTyVarTy, tyVarsOfType, tyVarsOfTypes,
46 splitSigmaTy, splitFunTy_maybe,
47 splitFunTys, splitForAllTys, unUsgTy,
50 import Module ( Module )
51 import CoreUtils ( exprType, mkInlineMe )
52 import CoreUnfold ( mkTopUnfolding, mkCompulsoryUnfolding, mkOtherCon )
53 import Literal ( Literal(..) )
54 import TyCon ( TyCon, isNewTyCon, tyConTyVars, tyConDataCons, isDataTyCon,
55 tyConTheta, isProductTyCon, isUnboxedTupleTyCon )
56 import Class ( Class, classBigSig, classTyCon, classTyVars, classSelIds )
57 import Var ( Id, TyVar )
58 import VarSet ( isEmptyVarSet )
59 import Name ( mkDerivedName, mkWiredInIdName, mkLocalName,
60 mkWorkerOcc, mkSuperDictSelOcc, mkCCallName,
63 import OccName ( mkSrcVarOcc )
64 import PrimOp ( PrimOp(DataToTagOp, CCallOp),
65 primOpSig, mkPrimOpIdName,
68 import Demand ( wwStrict, wwPrim, mkStrictnessInfo )
69 import DataCon ( DataCon, StrictnessMark(..),
70 dataConFieldLabels, dataConRepArity, dataConTyCon,
71 dataConArgTys, dataConRepType, dataConRepStrictness,
72 dataConInstOrigArgTys,
73 dataConName, dataConTheta,
74 dataConSig, dataConStrictMarks, dataConId,
75 maybeMarkedUnboxed, splitProductType_maybe
77 import Id ( idType, mkId,
78 mkVanillaId, mkTemplateLocals,
79 mkTemplateLocal, setInlinePragma, idCprInfo
81 import IdInfo ( IdInfo, vanillaIdInfo, mkIdInfo,
82 exactArity, setUnfoldingInfo, setCafInfo, setCprInfo,
83 setArityInfo, setInlinePragInfo, setSpecInfo,
84 mkStrictnessInfo, setStrictnessInfo,
85 IdFlavour(..), InlinePragInfo(..), CafInfo(..), StrictnessInfo(..), CprInfo(..)
87 import FieldLabel ( FieldLabel, FieldLabelTag, mkFieldLabel, fieldLabelName,
88 firstFieldLabelTag, allFieldLabelTags, fieldLabelType
93 import Maybe ( isJust )
96 import UnicodeUtil ( stringToUtf8 )
101 %************************************************************************
103 \subsection{Wired in Ids}
105 %************************************************************************
109 = [ -- These error-y things are wired in because we don't yet have
110 -- a way to express in an interface file that the result type variable
111 -- is 'open'; that is can be unified with an unboxed type
113 -- [The interface file format now carry such information, but there's
114 -- no way yet of expressing at the definition site for these error-reporting
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 {- I nuked this because map (:) xs would create a
262 new local lambda for the (:) in core-to-stg.
263 There isn't a defn for the worker!
265 | null dict_args && all not_marked_strict strict_marks
266 = Var work_id -- The common case. Not only is this efficient,
267 -- but it also ensures that the wrapper is replaced
268 -- by the worker even when there are no args.
272 -- This is really important in rule matching,
273 -- which is a bit sad. (We could match on the wrappers,
274 -- but that makes it less likely that rules will match
275 -- when we bring bits of unfoldings together
279 = mkLams all_tyvars $ mkLams dict_args $
280 mkLams ex_dict_args $ mkLams id_args $
281 foldr mk_case con_app
282 (zip (ex_dict_args++id_args) strict_marks) i3 []
284 con_app i rep_ids = mkApps (Var work_id)
285 (map varToCoreExpr (all_tyvars ++ reverse rep_ids))
287 (tyvars, theta, ex_tyvars, ex_theta, orig_arg_tys, tycon) = dataConSig data_con
288 all_tyvars = tyvars ++ ex_tyvars
290 dict_tys = mkDictTys theta
291 ex_dict_tys = mkDictTys ex_theta
292 all_arg_tys = dict_tys ++ ex_dict_tys ++ orig_arg_tys
293 result_ty = mkTyConApp tycon (mkTyVarTys tyvars)
295 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
299 (dict_args, i1) = mkLocals 1 dict_tys
300 (ex_dict_args,i2) = mkLocals i1 ex_dict_tys
301 (id_args,i3) = mkLocals i2 orig_arg_tys
303 (id_arg1:_) = id_args -- Used for newtype only
305 strict_marks = dataConStrictMarks data_con
306 not_marked_strict NotMarkedStrict = True
307 not_marked_strict other = False
311 :: (Id, StrictnessMark) -- arg, strictness
312 -> (Int -> [Id] -> CoreExpr) -- body
313 -> Int -- next rep arg id
314 -> [Id] -- rep args so far
316 mk_case (arg,strict) body i rep_args
318 NotMarkedStrict -> body i (arg:rep_args)
320 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
322 Case (Var arg) arg [(DEFAULT,[], body i (arg:rep_args))]
324 MarkedUnboxed con tys ->
325 Case (Var arg) arg [(DataAlt con, con_args,
326 body i' (reverse con_args++rep_args))]
328 (con_args,i') = mkLocals i tys
332 %************************************************************************
334 \subsection{Record selectors}
336 %************************************************************************
338 We're going to build a record selector unfolding that looks like this:
340 data T a b c = T1 { ..., op :: a, ...}
341 | T2 { ..., op :: a, ...}
344 sel = /\ a b c -> \ d -> case d of
349 Similarly for newtypes
351 newtype N a = MkN { unN :: a->a }
354 unN n = coerce (a->a) n
356 We need to take a little care if the field has a polymorphic type:
358 data R = R { f :: forall a. a->a }
362 f :: forall a. R -> a -> a
363 f = /\ a \ r = case r of
366 (not f :: R -> forall a. a->a, which gives the type inference mechanism
367 problems at call sites)
369 Similarly for newtypes
371 newtype N = MkN { unN :: forall a. a->a }
373 unN :: forall a. N -> a -> a
374 unN = /\a -> \n:N -> coerce (a->a) n
377 mkRecordSelId tycon field_label unpack_id unpackUtf8_id
378 -- Assumes that all fields with the same field label have the same type
380 -- Annoyingly, we have to pass in the unpackCString# Id, because
381 -- we can't conjure it up out of thin air
384 sel_id = mkId (fieldLabelName field_label) selector_ty info
386 field_ty = fieldLabelType field_label
387 data_cons = tyConDataCons tycon
388 tyvars = tyConTyVars tycon -- These scope over the types in
389 -- the FieldLabels of constructors of this type
390 tycon_theta = tyConTheta tycon -- The context on the data decl
391 -- eg data (Eq a, Ord b) => T a b = ...
392 (field_tyvars,field_tau) = splitForAllTys field_ty
394 data_ty = mkTyConApp tycon tyvar_tys
395 tyvar_tys = mkTyVarTys tyvars
397 -- Very tiresomely, the selectors are (unnecessarily!) overloaded over
398 -- just the dictionaries in the types of the constructors that contain
399 -- the relevant field. Urgh.
400 -- NB: this code relies on the fact that DataCons are quantified over
401 -- the identical type variables as their parent TyCon
402 dict_tys = [mkDictTy cls tys | (cls, tys) <- tycon_theta, needed_dict (cls, tys)]
403 needed_dict pred = or [ pred `elem` (dataConTheta dc)
404 | (DataAlt dc, _, _) <- the_alts]
407 selector_ty = mkForAllTys tyvars $ mkForAllTys field_tyvars $
408 mkFunTys dict_tys $ mkFunTy data_ty field_tau
410 info = mkIdInfo (RecordSelId field_label)
411 `setArityInfo` exactArity (1 + length dict_tys)
412 `setUnfoldingInfo` unfolding
413 `setCafInfo` NoCafRefs
414 -- ToDo: consider adding further IdInfo
416 unfolding = mkTopUnfolding sel_rhs
419 (data_id:dict_ids) = mkTemplateLocals (data_ty:dict_tys)
420 alts = map mk_maybe_alt data_cons
421 the_alts = catMaybes alts
422 default_alt | all isJust alts = [] -- No default needed
423 | otherwise = [(DEFAULT, [], error_expr)]
425 sel_rhs = mkLams tyvars $ mkLams field_tyvars $
426 mkLams dict_ids $ Lam data_id $
429 sel_body | isNewTyCon tycon = Note (Coerce (unUsgTy field_tau) (unUsgTy data_ty)) (Var data_id)
430 | otherwise = Case (Var data_id) data_id (the_alts ++ default_alt)
432 mk_maybe_alt data_con
433 = case maybe_the_arg_id of
435 Just the_arg_id -> Just (DataAlt data_con, real_args, expr)
437 body = mkVarApps (Var the_arg_id) field_tyvars
438 strict_marks = dataConStrictMarks data_con
439 (expr, real_args) = rebuildConArgs data_con arg_ids strict_marks body
442 arg_ids = mkTemplateLocals (dataConInstOrigArgTys data_con tyvar_tys)
443 -- The first one will shadow data_id, but who cares
444 maybe_the_arg_id = assocMaybe (field_lbls `zip` arg_ids) field_label
445 field_lbls = dataConFieldLabels data_con
447 error_expr = mkApps (Var rEC_SEL_ERROR_ID) [Type (unUsgTy field_tau), err_string]
448 -- preserves invariant that type args are *not* usage-annotated on top. KSW 1999-04.
450 | all safeChar full_msg
451 = App (Var unpack_id) (Lit (MachStr (_PK_ full_msg)))
453 = App (Var unpackUtf8_id) (Lit (MachStr (_PK_ (stringToUtf8 (map ord full_msg)))))
455 safeChar c = c >= '\1' && c <= '\xFF'
456 -- TODO: Putting this Unicode stuff here is ugly. Find a better
457 -- generic place to make string literals. This logic is repeated
459 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
462 -- this rather ugly function converts the unpacked data con arguments back into
463 -- their packed form. It is almost the same as the version in DsUtils, except that
464 -- we use template locals here rather than newDsId (ToDo: merge these).
467 :: DataCon -- the con we're matching on
468 -> [Id] -- the source-level args
469 -> [StrictnessMark] -- the strictness annotations (per-arg)
470 -> CoreExpr -- the body
471 -> Int -- template local
474 rebuildConArgs con [] stricts body i = (body, [])
475 rebuildConArgs con (arg:args) stricts body i | isTyVar arg
476 = let (body', args') = rebuildConArgs con args stricts body i
478 rebuildConArgs con (arg:args) (str:stricts) body i
479 = case maybeMarkedUnboxed str of
480 Just (pack_con1, _) ->
481 case splitProductType_maybe (idType arg) of
482 Just (_, tycon_args, pack_con, con_arg_tys) ->
483 ASSERT( pack_con == pack_con1 )
484 let unpacked_args = zipWith mkTemplateLocal [i..] con_arg_tys
485 (body', real_args) = rebuildConArgs con args stricts body
486 (i + length con_arg_tys)
489 Let (NonRec arg (mkConApp pack_con
490 (map Type tycon_args ++
491 map Var unpacked_args))) body',
492 unpacked_args ++ real_args
495 _ -> let (body', args') = rebuildConArgs con args stricts body i
496 in (body', arg:args')
500 %************************************************************************
502 \subsection{Dictionary selectors}
504 %************************************************************************
506 Selecting a field for a dictionary. If there is just one field, then
507 there's nothing to do.
509 ToDo: unify with mkRecordSelId.
512 mkDictSelId :: Name -> Class -> Id
513 mkDictSelId name clas
517 sel_id = mkId name ty info
518 field_lbl = mkFieldLabel name tycon ty tag
519 tag = assoc "MkId.mkDictSelId" (classSelIds clas `zip` allFieldLabelTags) sel_id
521 info = mkIdInfo (RecordSelId field_lbl)
522 `setArityInfo` exactArity 1
523 `setUnfoldingInfo` unfolding
524 `setCafInfo` NoCafRefs
526 -- We no longer use 'must-inline' on record selectors. They'll
527 -- inline like crazy if they scrutinise a constructor
529 unfolding = mkTopUnfolding rhs
531 tyvars = classTyVars clas
533 tycon = classTyCon clas
534 [data_con] = tyConDataCons tycon
535 tyvar_tys = mkTyVarTys tyvars
536 arg_tys = dataConArgTys data_con tyvar_tys
537 the_arg_id = arg_ids !! (tag - firstFieldLabelTag)
539 dict_ty = mkDictTy clas tyvar_tys
540 (dict_id:arg_ids) = mkTemplateLocals (dict_ty : arg_tys)
542 rhs | isNewTyCon tycon = mkLams tyvars $ Lam dict_id $
543 Note (Coerce (head arg_tys) dict_ty) (Var dict_id)
544 | otherwise = mkLams tyvars $ Lam dict_id $
545 Case (Var dict_id) dict_id
546 [(DataAlt data_con, arg_ids, Var the_arg_id)]
550 %************************************************************************
552 \subsection{Primitive operations
554 %************************************************************************
557 mkPrimOpId :: PrimOp -> Id
561 (tyvars,arg_tys,res_ty, arity, strict_info) = primOpSig prim_op
562 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
563 name = mkPrimOpIdName prim_op id
564 id = mkId name ty info
566 info = mkIdInfo (PrimOpId prim_op)
568 `setArityInfo` exactArity arity
569 `setStrictnessInfo` strict_info
571 rules = addRule id emptyCoreRules (primOpRule prim_op)
574 -- For each ccall we manufacture a separate CCallOpId, giving it
575 -- a fresh unique, a type that is correct for this particular ccall,
576 -- and a CCall structure that gives the correct details about calling
579 -- The *name* of this Id is a local name whose OccName gives the full
580 -- details of the ccall, type and all. This means that the interface
581 -- file reader can reconstruct a suitable Id
583 mkCCallOpId :: Unique -> CCall -> Type -> Id
584 mkCCallOpId uniq ccall ty
585 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
586 -- A CCallOpId should have no free type variables;
587 -- when doing substitutions won't substitute over it
590 occ_str = showSDocIface (braces (pprCCallOp ccall <+> ppr ty))
591 -- The "occurrence name" of a ccall is the full info about the
592 -- ccall; it is encoded, but may have embedded spaces etc!
594 name = mkCCallName uniq occ_str
595 prim_op = CCallOp ccall
597 info = mkIdInfo (PrimOpId prim_op)
598 `setArityInfo` exactArity arity
599 `setStrictnessInfo` strict_info
601 (_, tau) = splitForAllTys ty
602 (arg_tys, _) = splitFunTys tau
603 arity = length arg_tys
604 strict_info = mkStrictnessInfo (take arity (repeat wwPrim), False)
608 %************************************************************************
610 \subsection{DictFuns}
612 %************************************************************************
615 mkDictFunId :: Name -- Name to use for the dict fun;
622 mkDictFunId dfun_name clas inst_tyvars inst_tys inst_decl_theta
623 = mkVanillaId dfun_name dfun_ty
625 dfun_theta = classesToPreds inst_decl_theta
627 {- 1 dec 99: disable the Mark Jones optimisation for the sake
628 of compatibility with Hugs.
629 See `types/InstEnv' for a discussion related to this.
631 (class_tyvars, sc_theta, _, _) = classBigSig clas
632 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
633 sc_theta' = substClasses (mkTopTyVarSubst class_tyvars inst_tys) sc_theta
634 dfun_theta = case inst_decl_theta of
635 [] -> [] -- If inst_decl_theta is empty, then we don't
636 -- want to have any dict arguments, so that we can
637 -- expose the constant methods.
639 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
640 -- Otherwise we pass the superclass dictionaries to
641 -- the dictionary function; the Mark Jones optimisation.
643 -- NOTE the "nub". I got caught by this one:
644 -- class Monad m => MonadT t m where ...
645 -- instance Monad m => MonadT (EnvT env) m where ...
646 -- Here, the inst_decl_theta has (Monad m); but so
647 -- does the sc_theta'!
649 -- NOTE the "not_const". I got caught by this one too:
650 -- class Foo a => Baz a b where ...
651 -- instance Wob b => Baz T b where..
652 -- Now sc_theta' has Foo T
654 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
658 %************************************************************************
660 \subsection{Un-definable}
662 %************************************************************************
664 These two can't be defined in Haskell.
666 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
667 just gets expanded into a type coercion wherever it occurs. Hence we
668 add it as a built-in Id with an unfolding here.
670 The type variables we use here are "open" type variables: this means
671 they can unify with both unlifted and lifted types. Hence we provide
672 another gun with which to shoot yourself in the foot.
676 = pcMiscPrelId unsafeCoerceIdKey pREL_GHC SLIT("unsafeCoerce#") ty info
679 `setUnfoldingInfo` mkCompulsoryUnfolding rhs
682 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
683 (mkFunTy openAlphaTy openBetaTy)
684 [x] = mkTemplateLocals [openAlphaTy]
685 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
686 Note (Coerce openBetaTy openAlphaTy) (Var x)
690 @getTag#@ is another function which can't be defined in Haskell. It needs to
691 evaluate its argument and call the dataToTag# primitive.
695 = pcMiscPrelId getTagIdKey pREL_GHC SLIT("getTag#") ty info
698 `setUnfoldingInfo` mkCompulsoryUnfolding rhs
699 -- We don't provide a defn for this; you must inline it
701 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy intPrimTy)
702 [x,y] = mkTemplateLocals [alphaTy,alphaTy]
703 rhs = mkLams [alphaTyVar,x] $
704 Case (Var x) y [ (DEFAULT, [], mkApps (Var dataToTagId) [Type alphaTy, Var y]) ]
706 dataToTagId = mkPrimOpId DataToTagOp
709 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
710 nasty as-is, change it back to a literal (@Literal@).
713 realWorldPrimId -- :: State# RealWorld
714 = pcMiscPrelId realWorldPrimIdKey pREL_GHC SLIT("realWorld#")
716 (noCafIdInfo `setUnfoldingInfo` mkOtherCon [])
717 -- The mkOtherCon makes it look that realWorld# is evaluated
718 -- which in turn makes Simplify.interestingArg return True,
719 -- which in turn makes INLINE things applied to realWorld# likely
724 %************************************************************************
726 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
728 %************************************************************************
730 GHC randomly injects these into the code.
732 @patError@ is just a version of @error@ for pattern-matching
733 failures. It knows various ``codes'' which expand to longer
734 strings---this saves space!
736 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
737 well shouldn't be yanked on, but if one is, then you will get a
738 friendly message from @absentErr@ (rather than a totally random
741 @parError@ is a special version of @error@ which the compiler does
742 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
743 templates, but we don't ever expect to generate code for it.
747 = pc_bottoming_Id errorIdKey pREL_ERR SLIT("error") errorTy
749 = generic_ERROR_ID patErrorIdKey SLIT("patError")
751 = generic_ERROR_ID recSelErrIdKey SLIT("recSelError")
753 = generic_ERROR_ID recConErrorIdKey SLIT("recConError")
755 = generic_ERROR_ID recUpdErrorIdKey SLIT("recUpdError")
757 = generic_ERROR_ID irrefutPatErrorIdKey SLIT("irrefutPatError")
758 nON_EXHAUSTIVE_GUARDS_ERROR_ID
759 = generic_ERROR_ID nonExhaustiveGuardsErrorIdKey SLIT("nonExhaustiveGuardsError")
760 nO_METHOD_BINDING_ERROR_ID
761 = generic_ERROR_ID noMethodBindingErrorIdKey SLIT("noMethodBindingError")
764 = pc_bottoming_Id absentErrorIdKey pREL_ERR SLIT("absentErr")
765 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy)
768 = pcMiscPrelId parErrorIdKey pREL_ERR SLIT("parError")
769 (mkSigmaTy [openAlphaTyVar] [] openAlphaTy) noCafIdInfo
774 %************************************************************************
776 \subsection{Utilities}
778 %************************************************************************
781 pcMiscPrelId :: Unique{-IdKey-} -> Module -> FAST_STRING -> Type -> IdInfo -> Id
782 pcMiscPrelId key mod str ty info
784 name = mkWiredInIdName key mod (mkSrcVarOcc str) imp
785 imp = mkId name ty info -- the usual case...
788 -- We lie and say the thing is imported; otherwise, we get into
789 -- a mess with dependency analysis; e.g., core2stg may heave in
790 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
791 -- being compiled, then it's just a matter of luck if the definition
792 -- will be in "the right place" to be in scope.
794 pc_bottoming_Id key mod name ty
795 = pcMiscPrelId key mod name ty bottoming_info
797 bottoming_info = noCafIdInfo
798 `setStrictnessInfo` mkStrictnessInfo ([wwStrict], True)
800 -- these "bottom" out, no matter what their arguments
802 generic_ERROR_ID u n = pc_bottoming_Id u pREL_ERR n errorTy
805 noCafIdInfo = vanillaIdInfo `setCafInfo` NoCafRefs
807 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
808 openAlphaTy = mkTyVarTy openAlphaTyVar
809 openBetaTy = mkTyVarTy openBetaTyVar
812 errorTy = mkUsgTy UsMany $
813 mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkUsgTy UsOnce (mkListTy charTy)]
814 (mkUsgTy UsMany openAlphaTy))
815 -- Notice the openAlphaTyVar. It says that "error" can be applied
816 -- to unboxed as well as boxed types. This is OK because it never
817 -- returns, so the return type is irrelevant.