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 mkDictFunId, mkDefaultMethodId,
21 mkPrimOpId, mkFCallId,
23 mkReboxingAlt, wrapNewTypeBody, unwrapNewTypeBody,
24 mkUnpackCase, mkProductBox,
26 -- And some particular Ids; see below for why they are wired in
27 wiredInIds, ghcPrimIds,
28 unsafeCoerceId, realWorldPrimId, voidArgId, nullAddrId, seqId,
29 lazyId, lazyIdUnfolding, lazyIdKey,
32 rEC_CON_ERROR_ID, iRREFUT_PAT_ERROR_ID, rUNTIME_ERROR_ID,
33 nON_EXHAUSTIVE_GUARDS_ERROR_ID, nO_METHOD_BINDING_ERROR_ID,
34 pAT_ERROR_ID, eRROR_ID,
39 #include "HsVersions.h"
42 import BasicTypes ( Arity, StrictnessMark(..), isMarkedUnboxed, isMarkedStrict )
43 import Rules ( mkSpecInfo )
44 import TysPrim ( openAlphaTyVars, alphaTyVar, alphaTy,
45 realWorldStatePrimTy, addrPrimTy
47 import TysWiredIn ( charTy, mkListTy )
48 import PrelRules ( primOpRules )
49 import Type ( TyThing(..), mkForAllTy, tyVarsOfTypes,
50 newTyConInstRhs, mkTopTvSubst, substTyVar, substTy,
51 substTys, zipTopTvSubst )
52 import TcGadt ( gadtRefine, refineType, emptyRefinement )
53 import HsBinds ( ExprCoFn(..), isIdCoercion )
54 import Coercion ( mkSymCoercion, mkUnsafeCoercion, isEqPred )
55 import TcType ( Type, ThetaType, mkDictTy, mkPredTys, mkPredTy,
56 mkTyConApp, mkTyVarTys, mkClassPred, isPredTy,
57 mkFunTys, mkFunTy, mkSigmaTy, tcSplitSigmaTy, tcEqType,
58 isUnLiftedType, mkForAllTys, mkTyVarTy, tyVarsOfType,
59 tcSplitFunTys, tcSplitForAllTys, dataConsStupidTheta
61 import CoreUtils ( exprType, dataConOrigInstPat, mkCoerce )
62 import CoreUnfold ( mkTopUnfolding, mkCompulsoryUnfolding )
63 import Literal ( nullAddrLit, mkStringLit )
64 import TyCon ( TyCon, isNewTyCon, tyConTyVars, tyConDataCons,
66 tyConStupidTheta, isProductTyCon, isDataTyCon,
67 isRecursiveTyCon, isFamInstTyCon,
68 tyConFamInst_maybe, tyConFamilyCoercion_maybe,
70 import Class ( Class, classTyCon, classSelIds )
71 import Var ( Id, TyVar, Var, setIdType )
72 import VarSet ( isEmptyVarSet, subVarSet, varSetElems )
73 import Name ( mkFCallName, mkWiredInName, Name, BuiltInSyntax(..))
74 import OccName ( mkOccNameFS, varName )
75 import PrimOp ( PrimOp, primOpSig, primOpOcc, primOpTag )
76 import ForeignCall ( ForeignCall )
77 import DataCon ( DataCon, DataConIds(..), dataConTyCon,
79 dataConFieldLabels, dataConRepArity, dataConResTys,
80 dataConRepArgTys, dataConRepType, dataConFullSig,
81 dataConStrictMarks, dataConExStricts,
82 splitProductType, isVanillaDataCon, dataConFieldType,
85 import Id ( idType, mkGlobalId, mkVanillaGlobal, mkSysLocal,
86 mkTemplateLocals, mkTemplateLocalsNum, mkExportedLocalId,
87 mkTemplateLocal, idName
89 import IdInfo ( IdInfo, noCafIdInfo, setUnfoldingInfo,
90 setArityInfo, setSpecInfo, setCafInfo,
91 setAllStrictnessInfo, vanillaIdInfo,
92 GlobalIdDetails(..), CafInfo(..)
94 import NewDemand ( mkStrictSig, DmdResult(..),
95 mkTopDmdType, topDmd, evalDmd, lazyDmd, retCPR,
96 Demand(..), Demands(..) )
97 import DmdAnal ( dmdAnalTopRhs )
99 import Unique ( mkBuiltinUnique, mkPrimOpIdUnique )
100 import Maybe ( fromJust )
103 import Util ( dropList, isSingleton )
106 import ListSetOps ( assoc, minusList )
109 %************************************************************************
111 \subsection{Wired in Ids}
113 %************************************************************************
117 = [ -- These error-y things are wired in because we don't yet have
118 -- a way to express in an interface file that the result type variable
119 -- is 'open'; that is can be unified with an unboxed type
121 -- [The interface file format now carry such information, but there's
122 -- no way yet of expressing at the definition site for these
123 -- error-reporting functions that they have an 'open'
124 -- result type. -- sof 1/99]
126 eRROR_ID, -- This one isn't used anywhere else in the compiler
127 -- But we still need it in wiredInIds so that when GHC
128 -- compiles a program that mentions 'error' we don't
129 -- import its type from the interface file; we just get
130 -- the Id defined here. Which has an 'open-tyvar' type.
133 iRREFUT_PAT_ERROR_ID,
134 nON_EXHAUSTIVE_GUARDS_ERROR_ID,
135 nO_METHOD_BINDING_ERROR_ID,
142 -- These Ids are exported from GHC.Prim
144 = [ -- These can't be defined in Haskell, but they have
145 -- perfectly reasonable unfoldings in Core
153 %************************************************************************
155 \subsection{Data constructors}
157 %************************************************************************
159 The wrapper for a constructor is an ordinary top-level binding that evaluates
160 any strict args, unboxes any args that are going to be flattened, and calls
163 We're going to build a constructor that looks like:
165 data (Data a, C b) => T a b = T1 !a !Int b
168 \d1::Data a, d2::C b ->
169 \p q r -> case p of { p ->
171 Con T1 [a,b] [p,q,r]}}
175 * d2 is thrown away --- a context in a data decl is used to make sure
176 one *could* construct dictionaries at the site the constructor
177 is used, but the dictionary isn't actually used.
179 * We have to check that we can construct Data dictionaries for
180 the types a and Int. Once we've done that we can throw d1 away too.
182 * We use (case p of q -> ...) to evaluate p, rather than "seq" because
183 all that matters is that the arguments are evaluated. "seq" is
184 very careful to preserve evaluation order, which we don't need
187 You might think that we could simply give constructors some strictness
188 info, like PrimOps, and let CoreToStg do the let-to-case transformation.
189 But we don't do that because in the case of primops and functions strictness
190 is a *property* not a *requirement*. In the case of constructors we need to
191 do something active to evaluate the argument.
193 Making an explicit case expression allows the simplifier to eliminate
194 it in the (common) case where the constructor arg is already evaluated.
196 [Wrappers for data instance tycons]
197 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
198 In the case of data instances, the wrapper also applies the coercion turning
199 the representation type into the family instance type to cast the result of
200 the wrapper. For example, consider the declarations
202 data family Map k :: * -> *
203 data instance Map (a, b) v = MapPair (Map a (Pair b v))
205 The tycon to which the datacon MapPair belongs gets a unique internal name of
206 the form :R123Map, and we call it the representation tycon. In contrast, Map
207 is the family tycon (accessible via tyConFamInst_maybe). The wrapper and work
208 of MapPair get the types
210 $WMapPair :: forall a b v. Map a (Map a b v) -> Map (a, b) v
211 $wMapPair :: forall a b v. Map a (Map a b v) -> :R123Map a b v
213 which implies that the wrapper code will have to apply the coercion moving
214 between representation and family type. It is accessible via
215 tyConFamilyCoercion_maybe and has kind
217 Co123Map a b v :: {Map (a, b) v :=: :R123Map a b v}
219 This coercion is conditionally applied by wrapFamInstBody.
222 mkDataConIds :: Name -> Name -> DataCon -> DataConIds
223 mkDataConIds wrap_name wkr_name data_con
225 = DCIds Nothing nt_work_id -- Newtype, only has a worker
227 | any isMarkedStrict all_strict_marks -- Algebraic, needs wrapper
228 || not (null eq_spec) -- NB: LoadIface.ifaceDeclSubBndrs
229 || isFamInstTyCon tycon -- depends on this test
230 = DCIds (Just alg_wrap_id) wrk_id
232 | otherwise -- Algebraic, no wrapper
233 = DCIds Nothing wrk_id
235 (univ_tvs, ex_tvs, eq_spec,
236 theta, orig_arg_tys) = dataConFullSig data_con
237 tycon = dataConTyCon data_con
239 ----------- Wrapper --------------
240 -- We used to include the stupid theta in the wrapper's args
241 -- but now we don't. Instead the type checker just injects these
242 -- extra constraints where necessary.
243 wrap_tvs = (univ_tvs `minusList` map fst eq_spec) ++ ex_tvs
244 subst = mkTopTvSubst eq_spec
245 famSubst = ASSERT( length (tyConTyVars tycon ) ==
246 length (mkTyVarTys univ_tvs) )
247 zipTopTvSubst (tyConTyVars tycon) (mkTyVarTys univ_tvs)
248 -- substitution mapping the type constructor's type
249 -- arguments to the universals of the data constructor
250 -- (crucial when type checking interfaces)
251 dict_tys = mkPredTys theta
252 result_ty_args = map (substTyVar subst) univ_tvs
253 result_ty = case tyConFamInst_maybe tycon of
254 -- ordinary constructor
255 Nothing -> mkTyConApp tycon result_ty_args
256 -- family instance constructor
259 mkTyConApp familyTyCon ( substTys subst
262 wrap_ty = mkForAllTys wrap_tvs $ mkFunTys dict_tys $
263 mkFunTys orig_arg_tys $ result_ty
264 -- NB: watch out here if you allow user-written equality
265 -- constraints in data constructor signatures
267 ----------- Worker (algebraic data types only) --------------
268 -- The *worker* for the data constructor is the function that
269 -- takes the representation arguments and builds the constructor.
270 wrk_id = mkGlobalId (DataConWorkId data_con) wkr_name
271 (dataConRepType data_con) wkr_info
273 wkr_arity = dataConRepArity data_con
274 wkr_info = noCafIdInfo
275 `setArityInfo` wkr_arity
276 `setAllStrictnessInfo` Just wkr_sig
277 `setUnfoldingInfo` evaldUnfolding -- Record that it's evaluated,
280 wkr_sig = mkStrictSig (mkTopDmdType (replicate wkr_arity topDmd) cpr_info)
281 -- Notice that we do *not* say the worker is strict
282 -- even if the data constructor is declared strict
283 -- e.g. data T = MkT !(Int,Int)
284 -- Why? Because the *wrapper* is strict (and its unfolding has case
285 -- expresssions that do the evals) but the *worker* itself is not.
286 -- If we pretend it is strict then when we see
287 -- case x of y -> $wMkT y
288 -- the simplifier thinks that y is "sure to be evaluated" (because
289 -- $wMkT is strict) and drops the case. No, $wMkT is not strict.
291 -- When the simplifer sees a pattern
292 -- case e of MkT x -> ...
293 -- it uses the dataConRepStrictness of MkT to mark x as evaluated;
294 -- but that's fine... dataConRepStrictness comes from the data con
295 -- not from the worker Id.
297 cpr_info | isProductTyCon tycon &&
300 wkr_arity <= mAX_CPR_SIZE = retCPR
302 -- RetCPR is only true for products that are real data types;
303 -- that is, not unboxed tuples or [non-recursive] newtypes
305 ----------- Workers for newtypes --------------
306 nt_work_id = mkGlobalId (DataConWrapId data_con) wkr_name wrap_ty nt_work_info
307 nt_work_info = noCafIdInfo -- The NoCaf-ness is set by noCafIdInfo
308 `setArityInfo` 1 -- Arity 1
309 `setUnfoldingInfo` newtype_unf
310 newtype_unf = ASSERT( isVanillaDataCon data_con &&
311 isSingleton orig_arg_tys )
312 -- No existentials on a newtype, but it can have a context
313 -- e.g. newtype Eq a => T a = MkT (...)
314 mkCompulsoryUnfolding $
315 mkLams wrap_tvs $ Lam id_arg1 $
316 wrapNewTypeBody tycon result_ty_args
319 id_arg1 = mkTemplateLocal 1 (head orig_arg_tys)
321 ----------- Wrappers for algebraic data types --------------
322 alg_wrap_id = mkGlobalId (DataConWrapId data_con) wrap_name wrap_ty alg_wrap_info
323 alg_wrap_info = noCafIdInfo -- The NoCaf-ness is set by noCafIdInfo
324 `setArityInfo` alg_arity
325 -- It's important to specify the arity, so that partial
326 -- applications are treated as values
327 `setUnfoldingInfo` alg_unf
328 `setAllStrictnessInfo` Just wrap_sig
330 all_strict_marks = dataConExStricts data_con ++ dataConStrictMarks data_con
331 wrap_sig = mkStrictSig (mkTopDmdType arg_dmds cpr_info)
332 arg_dmds = map mk_dmd all_strict_marks
333 mk_dmd str | isMarkedStrict str = evalDmd
334 | otherwise = lazyDmd
335 -- The Cpr info can be important inside INLINE rhss, where the
336 -- wrapper constructor isn't inlined.
337 -- And the argument strictness can be important too; we
338 -- may not inline a contructor when it is partially applied.
340 -- data W = C !Int !Int !Int
341 -- ...(let w = C x in ...(w p q)...)...
342 -- we want to see that w is strict in its two arguments
344 alg_unf = mkTopUnfolding $ Note InlineMe $
346 mkLams dict_args $ mkLams id_args $
347 foldr mk_case con_app
348 (zip (dict_args ++ id_args) all_strict_marks)
351 con_app _ rep_ids = wrapFamInstBody tycon result_ty_args $
352 Var wrk_id `mkTyApps` result_ty_args
354 `mkTyApps` map snd eq_spec
355 `mkVarApps` reverse rep_ids
357 (dict_args,i2) = mkLocals 1 dict_tys
358 (id_args,i3) = mkLocals i2 orig_arg_tys
362 :: (Id, StrictnessMark) -- Arg, strictness
363 -> (Int -> [Id] -> CoreExpr) -- Body
364 -> Int -- Next rep arg id
365 -> [Id] -- Rep args so far, reversed
367 mk_case (arg,strict) body i rep_args
369 NotMarkedStrict -> body i (arg:rep_args)
371 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
373 Case (Var arg) arg result_ty [(DEFAULT,[], body i (arg:rep_args))]
376 -> unboxProduct i (Var arg) (idType arg) the_body
378 the_body i con_args = body i (reverse con_args ++ rep_args)
380 mAX_CPR_SIZE :: Arity
382 -- We do not treat very big tuples as CPR-ish:
383 -- a) for a start we get into trouble because there aren't
384 -- "enough" unboxed tuple types (a tiresome restriction,
386 -- b) more importantly, big unboxed tuples get returned mainly
387 -- on the stack, and are often then allocated in the heap
388 -- by the caller. So doing CPR for them may in fact make
391 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
395 -- If the type constructor is a representation type of a data instance, wrap
396 -- the expression into a cast adjusting the expression type, which is an
397 -- instance of the representation type, to the corresponding instance of the
398 -- family instance type.
400 wrapFamInstBody :: TyCon -> [Type] -> CoreExpr -> CoreExpr
401 wrapFamInstBody tycon args result_expr
402 | Just co_con <- tyConFamilyCoercion_maybe tycon
403 = mkCoerce (mkSymCoercion (mkTyConApp co_con args)) result_expr
407 -- Apply the coercion in the opposite direction.
409 unwrapFamInstBody :: TyCon -> [Type] -> CoreExpr -> CoreExpr
410 unwrapFamInstBody tycon args result_expr
411 | Just co_con <- tyConFamilyCoercion_maybe tycon
412 = mkCoerce (mkTyConApp co_con args) result_expr
419 %************************************************************************
421 \subsection{Record selectors}
423 %************************************************************************
425 We're going to build a record selector unfolding that looks like this:
427 data T a b c = T1 { ..., op :: a, ...}
428 | T2 { ..., op :: a, ...}
431 sel = /\ a b c -> \ d -> case d of
436 Similarly for newtypes
438 newtype N a = MkN { unN :: a->a }
441 unN n = coerce (a->a) n
443 We need to take a little care if the field has a polymorphic type:
445 data R = R { f :: forall a. a->a }
449 f :: forall a. R -> a -> a
450 f = /\ a \ r = case r of
453 (not f :: R -> forall a. a->a, which gives the type inference mechanism
454 problems at call sites)
456 Similarly for (recursive) newtypes
458 newtype N = MkN { unN :: forall a. a->a }
460 unN :: forall b. N -> b -> b
461 unN = /\b -> \n:N -> (coerce (forall a. a->a) n)
464 Note [Naughty record selectors]
465 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
466 A "naughty" field is one for which we can't define a record
467 selector, because an existential type variable would escape. For example:
468 data T = forall a. MkT { x,y::a }
469 We obviously can't define
471 Nevertheless we *do* put a RecordSelId into the type environment
472 so that if the user tries to use 'x' as a selector we can bleat
473 helpfully, rather than saying unhelpfully that 'x' is not in scope.
474 Hence the sel_naughty flag, to identify record selectors that don't really exist.
476 In general, a field is naughty if its type mentions a type variable that
477 isn't in the result type of the constructor.
479 Note [GADT record selectors]
480 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
481 For GADTs, we require that all constructors with a common field 'f' have the same
482 result type (modulo alpha conversion). [Checked in TcTyClsDecls.checkValidTyCon]
485 T1 { f :: a } :: T [a]
486 T2 { f :: a, y :: b } :: T [a]
487 and now the selector takes that type as its argument:
488 f :: forall a. T [a] -> a
492 Note the forall'd tyvars of the selector are just the free tyvars
493 of the result type; there may be other tyvars in the constructor's
494 type (e.g. 'b' in T2).
498 -- Steps for handling "naughty" vs "non-naughty" selectors:
499 -- 1. Determine naughtiness by comparing field type vs result type
500 -- 2. Install naughty ones with selector_ty of type _|_ and fill in mzero for info
501 -- 3. If it's not naughty, do the normal plan.
503 mkRecordSelId :: TyCon -> FieldLabel -> Id
504 mkRecordSelId tycon field_label
505 -- Assumes that all fields with the same field label have the same type
506 | is_naughty = naughty_id
509 is_naughty = not (tyVarsOfType field_ty `subVarSet` res_tv_set)
510 sel_id_details = RecordSelId tycon field_label is_naughty
512 -- Escapist case here for naughty construcotrs
513 -- We give it no IdInfo, and a type of forall a.a (never looked at)
514 naughty_id = mkGlobalId sel_id_details field_label forall_a_a noCafIdInfo
515 forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar)
517 -- Normal case starts here
518 sel_id = mkGlobalId sel_id_details field_label selector_ty info
519 data_cons = tyConDataCons tycon
520 data_cons_w_field = filter has_field data_cons -- Can't be empty!
521 has_field con = field_label `elem` dataConFieldLabels con
523 con1 = head data_cons_w_field
524 res_tys = dataConResTys con1
525 res_tv_set = tyVarsOfTypes res_tys
526 res_tvs = varSetElems res_tv_set
527 data_ty = mkTyConApp tycon res_tys
528 field_ty = dataConFieldType con1 field_label
530 -- *Very* tiresomely, the selectors are (unnecessarily!) overloaded over
531 -- just the dictionaries in the types of the constructors that contain
532 -- the relevant field. [The Report says that pattern matching on a
533 -- constructor gives the same constraints as applying it.] Urgh.
535 -- However, not all data cons have all constraints (because of
536 -- BuildTyCl.mkDataConStupidTheta). So we need to find all the data cons
537 -- involved in the pattern match and take the union of their constraints.
538 stupid_dict_tys = mkPredTys (dataConsStupidTheta data_cons_w_field)
539 n_stupid_dicts = length stupid_dict_tys
541 (field_tyvars,pre_field_theta,field_tau) = tcSplitSigmaTy field_ty
543 field_theta = filter (not . isEqPred) pre_field_theta
544 field_dict_tys = mkPredTys field_theta
545 n_field_dict_tys = length field_dict_tys
546 -- If the field has a universally quantified type we have to
547 -- be a bit careful. Suppose we have
548 -- data R = R { op :: forall a. Foo a => a -> a }
549 -- Then we can't give op the type
550 -- op :: R -> forall a. Foo a => a -> a
551 -- because the typechecker doesn't understand foralls to the
552 -- right of an arrow. The "right" type to give it is
553 -- op :: forall a. Foo a => R -> a -> a
554 -- But then we must generate the right unfolding too:
555 -- op = /\a -> \dfoo -> \ r ->
558 -- Note that this is exactly the type we'd infer from a user defn
562 selector_ty = mkForAllTys res_tvs $ mkForAllTys field_tyvars $
563 mkFunTys stupid_dict_tys $ mkFunTys field_dict_tys $
564 mkFunTy data_ty field_tau
566 arity = 1 + n_stupid_dicts + n_field_dict_tys
568 (strict_sig, rhs_w_str) = dmdAnalTopRhs sel_rhs
569 -- Use the demand analyser to work out strictness.
570 -- With all this unpackery it's not easy!
573 `setCafInfo` caf_info
575 `setUnfoldingInfo` mkTopUnfolding rhs_w_str
576 `setAllStrictnessInfo` Just strict_sig
578 -- Allocate Ids. We do it a funny way round because field_dict_tys is
579 -- almost always empty. Also note that we use max_dict_tys
580 -- rather than n_dict_tys, because the latter gives an infinite loop:
581 -- n_dict tys depends on the_alts, which depens on arg_ids, which depends
582 -- on arity, which depends on n_dict tys. Sigh! Mega sigh!
583 stupid_dict_ids = mkTemplateLocalsNum 1 stupid_dict_tys
584 max_stupid_dicts = length (tyConStupidTheta tycon)
585 field_dict_base = max_stupid_dicts + 1
586 field_dict_ids = mkTemplateLocalsNum field_dict_base field_dict_tys
587 dict_id_base = field_dict_base + n_field_dict_tys
588 data_id = mkTemplateLocal dict_id_base data_ty
589 arg_base = dict_id_base + 1
591 the_alts :: [CoreAlt]
592 the_alts = map mk_alt data_cons_w_field -- Already sorted by data-con
593 no_default = length data_cons == length data_cons_w_field -- No default needed
595 default_alt | no_default = []
596 | otherwise = [(DEFAULT, [], error_expr)]
598 -- The default branch may have CAF refs, because it calls recSelError etc.
599 caf_info | no_default = NoCafRefs
600 | otherwise = MayHaveCafRefs
602 sel_rhs = mkLams res_tvs $ mkLams field_tyvars $
603 mkLams stupid_dict_ids $ mkLams field_dict_ids $
604 Lam data_id $ mk_result sel_body
606 -- NB: A newtype always has a vanilla DataCon; no existentials etc
607 -- res_tys will simply be the dataConUnivTyVars
608 sel_body | isNewTyCon tycon = unwrapNewTypeBody tycon res_tys (Var data_id)
609 | otherwise = Case (Var data_id) data_id field_ty (default_alt ++ the_alts)
611 mk_result poly_result = mkVarApps (mkVarApps poly_result field_tyvars) field_dict_ids
612 -- We pull the field lambdas to the top, so we need to
613 -- apply them in the body. For example:
614 -- data T = MkT { foo :: forall a. a->a }
616 -- foo :: forall a. T -> a -> a
617 -- foo = /\a. \t:T. case t of { MkT f -> f a }
620 = ASSERT2( res_ty `tcEqType` field_ty, ppr data_con $$ ppr res_ty $$ ppr field_ty )
621 mkReboxingAlt rebox_uniqs data_con (ex_tvs ++ co_tvs ++ arg_vs) rhs
623 -- get pattern binders with types appropriately instantiated
624 arg_uniqs = map mkBuiltinUnique [arg_base..]
625 (ex_tvs, co_tvs, arg_vs) = dataConOrigInstPat arg_uniqs data_con res_tys
627 rebox_base = arg_base + length ex_tvs + length co_tvs + length arg_vs
628 rebox_uniqs = map mkBuiltinUnique [rebox_base..]
630 -- data T :: *->* where T1 { fld :: Maybe b } -> T [b]
631 -- Hence T1 :: forall a b. (a=[b]) => b -> T a
632 -- fld :: forall b. T [b] -> Maybe b
633 -- fld = /\b.\(t:T[b]). case t of
634 -- T1 b' (c : [b]=[b']) (x:Maybe b')
635 -- -> x `cast` Maybe (sym (right c))
637 Succeeded refinement = gadtRefine emptyRefinement ex_tvs co_tvs
638 (co_fn, res_ty) = refineType refinement (idType the_arg_id)
639 -- Generate the refinement for b'=b,
640 -- and apply to (Maybe b'), to get (Maybe b)
643 ExprCoFn co -> Cast (Var the_arg_id) co
644 id_co -> ASSERT(isIdCoercion id_co) Var the_arg_id
646 field_vs = filter (not . isPredTy . idType) arg_vs
647 the_arg_id = assoc "mkRecordSelId:mk_alt" (field_lbls `zip` field_vs) field_label
648 field_lbls = dataConFieldLabels data_con
650 error_expr = mkRuntimeErrorApp rEC_SEL_ERROR_ID field_ty full_msg
651 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
653 -- unbox a product type...
654 -- we will recurse into newtypes, casting along the way, and unbox at the
655 -- first product data constructor we find. e.g.
657 -- data PairInt = PairInt Int Int
658 -- newtype S = MkS PairInt
661 -- If we have e = MkT (MkS (PairInt 0 1)) and some body expecting a list of
662 -- ids, we get (modulo int passing)
664 -- case (e `cast` CoT) `cast` CoS of
665 -- PairInt a b -> body [a,b]
667 -- The Ints passed around are just for creating fresh locals
668 unboxProduct :: Int -> CoreExpr -> Type -> (Int -> [Id] -> CoreExpr) -> CoreExpr
669 unboxProduct i arg arg_ty body
672 result = mkUnpackCase the_id arg con_args boxing_con rhs
673 (_tycon, _tycon_args, boxing_con, tys) = deepSplitProductType "unboxProduct" arg_ty
674 ([the_id], i') = mkLocals i [arg_ty]
675 (con_args, i'') = mkLocals i' tys
676 rhs = body i'' con_args
678 mkUnpackCase :: Id -> CoreExpr -> [Id] -> DataCon -> CoreExpr -> CoreExpr
679 -- (mkUnpackCase x e args Con body)
681 -- case (e `cast` ...) of bndr { Con args -> body }
683 -- the type of the bndr passed in is irrelevent
684 mkUnpackCase bndr arg unpk_args boxing_con body
685 = Case cast_arg (setIdType bndr bndr_ty) (exprType body) [(DataAlt boxing_con, unpk_args, body)]
687 (cast_arg, bndr_ty) = go (idType bndr) arg
689 | (tycon, tycon_args, _, _) <- splitProductType "mkUnpackCase" ty
690 , isNewTyCon tycon && not (isRecursiveTyCon tycon)
691 = go (newTyConInstRhs tycon tycon_args)
692 (unwrapNewTypeBody tycon tycon_args arg)
693 | otherwise = (arg, ty)
696 reboxProduct :: [Unique] -- uniques to create new local binders
697 -> Type -- type of product to box
698 -> ([Unique], -- remaining uniques
699 CoreExpr, -- boxed product
700 [Id]) -- Ids being boxed into product
703 (_tycon, _tycon_args, _pack_con, con_arg_tys) = deepSplitProductType "reboxProduct" ty
705 us' = dropList con_arg_tys us
707 arg_ids = zipWith (mkSysLocal FSLIT("rb")) us con_arg_tys
709 bind_rhs = mkProductBox arg_ids ty
712 (us', bind_rhs, arg_ids)
714 mkProductBox :: [Id] -> Type -> CoreExpr
715 mkProductBox arg_ids ty
718 (tycon, tycon_args, pack_con, _con_arg_tys) = splitProductType "mkProductBox" ty
721 | isNewTyCon tycon && not (isRecursiveTyCon tycon)
722 = wrap (mkProductBox arg_ids (newTyConInstRhs tycon tycon_args))
723 | otherwise = mkConApp pack_con (map Type tycon_args ++ map Var arg_ids)
725 wrap expr = wrapNewTypeBody tycon tycon_args expr
728 -- (mkReboxingAlt us con xs rhs) basically constructs the case
729 -- alternative (con, xs, rhs)
730 -- but it does the reboxing necessary to construct the *source*
731 -- arguments, xs, from the representation arguments ys.
733 -- data T = MkT !(Int,Int) Bool
735 -- mkReboxingAlt MkT [x,b] r
736 -- = (DataAlt MkT, [y::Int,z::Int,b], let x = (y,z) in r)
738 -- mkDataAlt should really be in DataCon, but it can't because
739 -- it manipulates CoreSyn.
742 :: [Unique] -- Uniques for the new Ids
744 -> [Var] -- Source-level args, including existential dicts
748 mkReboxingAlt us con args rhs
749 | not (any isMarkedUnboxed stricts)
750 = (DataAlt con, args, rhs)
754 (binds, args') = go args stricts us
756 (DataAlt con, args', mkLets binds rhs)
759 stricts = dataConExStricts con ++ dataConStrictMarks con
761 go [] _stricts _us = ([], [])
763 -- Type variable case
764 go (arg:args) stricts us
766 = let (binds, args') = go args stricts us
767 in (binds, arg:args')
769 -- Term variable case
770 go (arg:args) (str:stricts) us
771 | isMarkedUnboxed str
773 let (binds, unpacked_args') = go args stricts us'
774 (us', bind_rhs, unpacked_args) = reboxProduct us (idType arg)
776 (NonRec arg bind_rhs : binds, unpacked_args ++ unpacked_args')
778 = let (binds, args') = go args stricts us
779 in (binds, arg:args')
783 %************************************************************************
785 \subsection{Dictionary selectors}
787 %************************************************************************
789 Selecting a field for a dictionary. If there is just one field, then
790 there's nothing to do.
792 Dictionary selectors may get nested forall-types. Thus:
795 op :: forall b. Ord b => a -> b -> b
797 Then the top-level type for op is
799 op :: forall a. Foo a =>
803 This is unlike ordinary record selectors, which have all the for-alls
804 at the outside. When dealing with classes it's very convenient to
805 recover the original type signature from the class op selector.
808 mkDictSelId :: Name -> Class -> Id
809 mkDictSelId name clas
810 = mkGlobalId (ClassOpId clas) name sel_ty info
812 sel_ty = mkForAllTys tyvars (mkFunTy (idType dict_id) (idType the_arg_id))
813 -- We can't just say (exprType rhs), because that would give a type
815 -- for a single-op class (after all, the selector is the identity)
816 -- But it's type must expose the representation of the dictionary
817 -- to gat (say) C a -> (a -> a)
821 `setUnfoldingInfo` mkTopUnfolding rhs
822 `setAllStrictnessInfo` Just strict_sig
824 -- We no longer use 'must-inline' on record selectors. They'll
825 -- inline like crazy if they scrutinise a constructor
827 -- The strictness signature is of the form U(AAAVAAAA) -> T
828 -- where the V depends on which item we are selecting
829 -- It's worth giving one, so that absence info etc is generated
830 -- even if the selector isn't inlined
831 strict_sig = mkStrictSig (mkTopDmdType [arg_dmd] TopRes)
832 arg_dmd | isNewTyCon tycon = evalDmd
833 | otherwise = Eval (Prod [ if the_arg_id == id then evalDmd else Abs
836 tycon = classTyCon clas
837 [data_con] = tyConDataCons tycon
838 tyvars = dataConUnivTyVars data_con
839 arg_tys = ASSERT( isVanillaDataCon data_con ) dataConRepArgTys data_con
840 the_arg_id = assoc "MkId.mkDictSelId" (map idName (classSelIds clas) `zip` arg_ids) name
842 pred = mkClassPred clas (mkTyVarTys tyvars)
843 (dict_id:arg_ids) = mkTemplateLocals (mkPredTy pred : arg_tys)
845 rhs = mkLams tyvars (Lam dict_id rhs_body)
846 rhs_body | isNewTyCon tycon = unwrapNewTypeBody tycon (map mkTyVarTy tyvars) (Var dict_id)
847 | otherwise = Case (Var dict_id) dict_id (idType the_arg_id)
848 [(DataAlt data_con, arg_ids, Var the_arg_id)]
850 wrapNewTypeBody :: TyCon -> [Type] -> CoreExpr -> CoreExpr
851 -- The wrapper for the data constructor for a newtype looks like this:
852 -- newtype T a = MkT (a,Int)
853 -- MkT :: forall a. (a,Int) -> T a
854 -- MkT = /\a. \(x:(a,Int)). x `cast` sym (CoT a)
855 -- where CoT is the coercion TyCon assoicated with the newtype
857 -- The call (wrapNewTypeBody T [a] e) returns the
858 -- body of the wrapper, namely
859 -- e `cast` (CoT [a])
861 -- If a coercion constructor is prodivided in the newtype, then we use
862 -- it, otherwise the wrap/unwrap are both no-ops
864 -- If the we are dealing with a newtype instance, we have a second coercion
865 -- identifying the family instance with the constructor of the newtype
866 -- instance. This coercion is applied in any case (ie, composed with the
867 -- coercion constructor of the newtype or applied by itself).
869 wrapNewTypeBody tycon args result_expr
870 = wrapFamInstBody tycon args inner
873 | Just co_con <- newTyConCo_maybe tycon
874 = mkCoerce (mkSymCoercion (mkTyConApp co_con args)) result_expr
878 -- When unwrapping, we do *not* apply any family coercion, because this will
879 -- be done via a CoPat by the type checker. We have to do it this way as
880 -- computing the right type arguments for the coercion requires more than just
881 -- a spliting operation (cf, TcPat.tcConPat).
883 unwrapNewTypeBody :: TyCon -> [Type] -> CoreExpr -> CoreExpr
884 unwrapNewTypeBody tycon args result_expr
885 | Just co_con <- newTyConCo_maybe tycon
886 = mkCoerce (mkTyConApp co_con args) result_expr
894 %************************************************************************
896 \subsection{Primitive operations
898 %************************************************************************
901 mkPrimOpId :: PrimOp -> Id
905 (tyvars,arg_tys,res_ty, arity, strict_sig) = primOpSig prim_op
906 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
907 name = mkWiredInName gHC_PRIM (primOpOcc prim_op)
908 (mkPrimOpIdUnique (primOpTag prim_op))
909 Nothing (AnId id) UserSyntax
910 id = mkGlobalId (PrimOpId prim_op) name ty info
913 `setSpecInfo` mkSpecInfo (primOpRules prim_op name)
915 `setAllStrictnessInfo` Just strict_sig
917 -- For each ccall we manufacture a separate CCallOpId, giving it
918 -- a fresh unique, a type that is correct for this particular ccall,
919 -- and a CCall structure that gives the correct details about calling
922 -- The *name* of this Id is a local name whose OccName gives the full
923 -- details of the ccall, type and all. This means that the interface
924 -- file reader can reconstruct a suitable Id
926 mkFCallId :: Unique -> ForeignCall -> Type -> Id
927 mkFCallId uniq fcall ty
928 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
929 -- A CCallOpId should have no free type variables;
930 -- when doing substitutions won't substitute over it
931 mkGlobalId (FCallId fcall) name ty info
933 occ_str = showSDoc (braces (ppr fcall <+> ppr ty))
934 -- The "occurrence name" of a ccall is the full info about the
935 -- ccall; it is encoded, but may have embedded spaces etc!
937 name = mkFCallName uniq occ_str
941 `setAllStrictnessInfo` Just strict_sig
943 (_, tau) = tcSplitForAllTys ty
944 (arg_tys, _) = tcSplitFunTys tau
945 arity = length arg_tys
946 strict_sig = mkStrictSig (mkTopDmdType (replicate arity evalDmd) TopRes)
950 %************************************************************************
952 \subsection{DictFuns and default methods}
954 %************************************************************************
956 Important notes about dict funs and default methods
957 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
958 Dict funs and default methods are *not* ImplicitIds. Their definition
959 involves user-written code, so we can't figure out their strictness etc
960 based on fixed info, as we can for constructors and record selectors (say).
962 We build them as LocalIds, but with External Names. This ensures that
963 they are taken to account by free-variable finding and dependency
964 analysis (e.g. CoreFVs.exprFreeVars).
966 Why shouldn't they be bound as GlobalIds? Because, in particular, if
967 they are globals, the specialiser floats dict uses above their defns,
968 which prevents good simplifications happening. Also the strictness
969 analyser treats a occurrence of a GlobalId as imported and assumes it
970 contains strictness in its IdInfo, which isn't true if the thing is
971 bound in the same module as the occurrence.
973 It's OK for dfuns to be LocalIds, because we form the instance-env to
974 pass on to the next module (md_insts) in CoreTidy, afer tidying
975 and globalising the top-level Ids.
977 BUT make sure they are *exported* LocalIds (mkExportedLocalId) so
978 that they aren't discarded by the occurrence analyser.
981 mkDefaultMethodId dm_name ty = mkExportedLocalId dm_name ty
983 mkDictFunId :: Name -- Name to use for the dict fun;
990 mkDictFunId dfun_name inst_tyvars dfun_theta clas inst_tys
991 = mkExportedLocalId dfun_name dfun_ty
993 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
995 {- 1 dec 99: disable the Mark Jones optimisation for the sake
996 of compatibility with Hugs.
997 See `types/InstEnv' for a discussion related to this.
999 (class_tyvars, sc_theta, _, _) = classBigSig clas
1000 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
1001 sc_theta' = substClasses (zipTopTvSubst class_tyvars inst_tys) sc_theta
1002 dfun_theta = case inst_decl_theta of
1003 [] -> [] -- If inst_decl_theta is empty, then we don't
1004 -- want to have any dict arguments, so that we can
1005 -- expose the constant methods.
1007 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
1008 -- Otherwise we pass the superclass dictionaries to
1009 -- the dictionary function; the Mark Jones optimisation.
1011 -- NOTE the "nub". I got caught by this one:
1012 -- class Monad m => MonadT t m where ...
1013 -- instance Monad m => MonadT (EnvT env) m where ...
1014 -- Here, the inst_decl_theta has (Monad m); but so
1015 -- does the sc_theta'!
1017 -- NOTE the "not_const". I got caught by this one too:
1018 -- class Foo a => Baz a b where ...
1019 -- instance Wob b => Baz T b where..
1020 -- Now sc_theta' has Foo T
1025 %************************************************************************
1027 \subsection{Un-definable}
1029 %************************************************************************
1031 These Ids can't be defined in Haskell. They could be defined in
1032 unfoldings in the wired-in GHC.Prim interface file, but we'd have to
1033 ensure that they were definitely, definitely inlined, because there is
1034 no curried identifier for them. That's what mkCompulsoryUnfolding
1035 does. If we had a way to get a compulsory unfolding from an interface
1036 file, we could do that, but we don't right now.
1038 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
1039 just gets expanded into a type coercion wherever it occurs. Hence we
1040 add it as a built-in Id with an unfolding here.
1042 The type variables we use here are "open" type variables: this means
1043 they can unify with both unlifted and lifted types. Hence we provide
1044 another gun with which to shoot yourself in the foot.
1047 mkWiredInIdName mod fs uniq id
1048 = mkWiredInName mod (mkOccNameFS varName fs) uniq Nothing (AnId id) UserSyntax
1050 unsafeCoerceName = mkWiredInIdName gHC_PRIM FSLIT("unsafeCoerce#") unsafeCoerceIdKey unsafeCoerceId
1051 nullAddrName = mkWiredInIdName gHC_PRIM FSLIT("nullAddr#") nullAddrIdKey nullAddrId
1052 seqName = mkWiredInIdName gHC_PRIM FSLIT("seq") seqIdKey seqId
1053 realWorldName = mkWiredInIdName gHC_PRIM FSLIT("realWorld#") realWorldPrimIdKey realWorldPrimId
1054 lazyIdName = mkWiredInIdName gHC_BASE FSLIT("lazy") lazyIdKey lazyId
1056 errorName = mkWiredInIdName gHC_ERR FSLIT("error") errorIdKey eRROR_ID
1057 recSelErrorName = mkWiredInIdName gHC_ERR FSLIT("recSelError") recSelErrorIdKey rEC_SEL_ERROR_ID
1058 runtimeErrorName = mkWiredInIdName gHC_ERR FSLIT("runtimeError") runtimeErrorIdKey rUNTIME_ERROR_ID
1059 irrefutPatErrorName = mkWiredInIdName gHC_ERR FSLIT("irrefutPatError") irrefutPatErrorIdKey iRREFUT_PAT_ERROR_ID
1060 recConErrorName = mkWiredInIdName gHC_ERR FSLIT("recConError") recConErrorIdKey rEC_CON_ERROR_ID
1061 patErrorName = mkWiredInIdName gHC_ERR FSLIT("patError") patErrorIdKey pAT_ERROR_ID
1062 noMethodBindingErrorName = mkWiredInIdName gHC_ERR FSLIT("noMethodBindingError")
1063 noMethodBindingErrorIdKey nO_METHOD_BINDING_ERROR_ID
1064 nonExhaustiveGuardsErrorName
1065 = mkWiredInIdName gHC_ERR FSLIT("nonExhaustiveGuardsError")
1066 nonExhaustiveGuardsErrorIdKey nON_EXHAUSTIVE_GUARDS_ERROR_ID
1070 -- unsafeCoerce# :: forall a b. a -> b
1072 = pcMiscPrelId unsafeCoerceName ty info
1074 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
1077 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
1078 (mkFunTy openAlphaTy openBetaTy)
1079 [x] = mkTemplateLocals [openAlphaTy]
1080 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
1081 -- Note (Coerce openBetaTy openAlphaTy) (Var x)
1082 Cast (Var x) (mkUnsafeCoercion openAlphaTy openBetaTy)
1084 -- nullAddr# :: Addr#
1085 -- The reason is is here is because we don't provide
1086 -- a way to write this literal in Haskell.
1088 = pcMiscPrelId nullAddrName addrPrimTy info
1090 info = noCafIdInfo `setUnfoldingInfo`
1091 mkCompulsoryUnfolding (Lit nullAddrLit)
1094 = pcMiscPrelId seqName ty info
1096 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
1099 ty = mkForAllTys [alphaTyVar,openBetaTyVar]
1100 (mkFunTy alphaTy (mkFunTy openBetaTy openBetaTy))
1101 [x,y] = mkTemplateLocals [alphaTy, openBetaTy]
1102 rhs = mkLams [alphaTyVar,openBetaTyVar,x,y] (Case (Var x) x openBetaTy [(DEFAULT, [], Var y)])
1104 -- lazy :: forall a?. a? -> a? (i.e. works for unboxed types too)
1105 -- Used to lazify pseq: pseq a b = a `seq` lazy b
1107 -- Also, no strictness: by being a built-in Id, all the info about lazyId comes from here,
1108 -- not from GHC.Base.hi. This is important, because the strictness
1109 -- analyser will spot it as strict!
1111 -- Also no unfolding in lazyId: it gets "inlined" by a HACK in the worker/wrapper pass
1112 -- (see WorkWrap.wwExpr)
1113 -- We could use inline phases to do this, but that would be vulnerable to changes in
1114 -- phase numbering....we must inline precisely after strictness analysis.
1116 = pcMiscPrelId lazyIdName ty info
1119 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy alphaTy)
1121 lazyIdUnfolding :: CoreExpr -- Used to expand 'lazyId' after strictness anal
1122 lazyIdUnfolding = mkLams [openAlphaTyVar,x] (Var x)
1124 [x] = mkTemplateLocals [openAlphaTy]
1127 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
1128 nasty as-is, change it back to a literal (@Literal@).
1130 voidArgId is a Local Id used simply as an argument in functions
1131 where we just want an arg to avoid having a thunk of unlifted type.
1133 x = \ void :: State# RealWorld -> (# p, q #)
1135 This comes up in strictness analysis
1138 realWorldPrimId -- :: State# RealWorld
1139 = pcMiscPrelId realWorldName realWorldStatePrimTy
1140 (noCafIdInfo `setUnfoldingInfo` evaldUnfolding)
1141 -- The evaldUnfolding makes it look that realWorld# is evaluated
1142 -- which in turn makes Simplify.interestingArg return True,
1143 -- which in turn makes INLINE things applied to realWorld# likely
1146 voidArgId -- :: State# RealWorld
1147 = mkSysLocal FSLIT("void") voidArgIdKey realWorldStatePrimTy
1151 %************************************************************************
1153 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
1155 %************************************************************************
1157 GHC randomly injects these into the code.
1159 @patError@ is just a version of @error@ for pattern-matching
1160 failures. It knows various ``codes'' which expand to longer
1161 strings---this saves space!
1163 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
1164 well shouldn't be yanked on, but if one is, then you will get a
1165 friendly message from @absentErr@ (rather than a totally random
1168 @parError@ is a special version of @error@ which the compiler does
1169 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
1170 templates, but we don't ever expect to generate code for it.
1174 :: Id -- Should be of type (forall a. Addr# -> a)
1175 -- where Addr# points to a UTF8 encoded string
1176 -> Type -- The type to instantiate 'a'
1177 -> String -- The string to print
1180 mkRuntimeErrorApp err_id res_ty err_msg
1181 = mkApps (Var err_id) [Type res_ty, err_string]
1183 err_string = Lit (mkStringLit err_msg)
1185 rEC_SEL_ERROR_ID = mkRuntimeErrorId recSelErrorName
1186 rUNTIME_ERROR_ID = mkRuntimeErrorId runtimeErrorName
1187 iRREFUT_PAT_ERROR_ID = mkRuntimeErrorId irrefutPatErrorName
1188 rEC_CON_ERROR_ID = mkRuntimeErrorId recConErrorName
1189 pAT_ERROR_ID = mkRuntimeErrorId patErrorName
1190 nO_METHOD_BINDING_ERROR_ID = mkRuntimeErrorId noMethodBindingErrorName
1191 nON_EXHAUSTIVE_GUARDS_ERROR_ID = mkRuntimeErrorId nonExhaustiveGuardsErrorName
1193 -- The runtime error Ids take a UTF8-encoded string as argument
1194 mkRuntimeErrorId name = pc_bottoming_Id name runtimeErrorTy
1195 runtimeErrorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTy addrPrimTy openAlphaTy)
1199 eRROR_ID = pc_bottoming_Id errorName errorTy
1202 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy] openAlphaTy)
1203 -- Notice the openAlphaTyVar. It says that "error" can be applied
1204 -- to unboxed as well as boxed types. This is OK because it never
1205 -- returns, so the return type is irrelevant.
1209 %************************************************************************
1211 \subsection{Utilities}
1213 %************************************************************************
1216 pcMiscPrelId :: Name -> Type -> IdInfo -> Id
1217 pcMiscPrelId name ty info
1218 = mkVanillaGlobal name ty info
1219 -- We lie and say the thing is imported; otherwise, we get into
1220 -- a mess with dependency analysis; e.g., core2stg may heave in
1221 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
1222 -- being compiled, then it's just a matter of luck if the definition
1223 -- will be in "the right place" to be in scope.
1225 pc_bottoming_Id name ty
1226 = pcMiscPrelId name ty bottoming_info
1228 bottoming_info = vanillaIdInfo `setAllStrictnessInfo` Just strict_sig
1229 -- Do *not* mark them as NoCafRefs, because they can indeed have
1230 -- CAF refs. For example, pAT_ERROR_ID calls GHC.Err.untangle,
1231 -- which has some CAFs
1232 -- In due course we may arrange that these error-y things are
1233 -- regarded by the GC as permanently live, in which case we
1234 -- can give them NoCaf info. As it is, any function that calls
1235 -- any pc_bottoming_Id will itself have CafRefs, which bloats
1238 strict_sig = mkStrictSig (mkTopDmdType [evalDmd] BotRes)
1239 -- These "bottom" out, no matter what their arguments
1241 (openAlphaTyVar:openBetaTyVar:_) = openAlphaTyVars
1242 openAlphaTy = mkTyVarTy openAlphaTyVar
1243 openBetaTy = mkTyVarTy openBetaTyVar