2 % (c) The University of Glasgow 2006
3 % (c) The AQUA Project, Glasgow University, 1998
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
15 {-# OPTIONS -fno-warn-missing-signatures #-}
16 -- The above warning supression flag is a temporary kludge.
17 -- While working on this module you are encouraged to remove it and fix
18 -- any warnings in the module. See
19 -- <http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings>
23 mkDictFunId, mkDefaultMethodId,
28 mkPrimOpId, mkFCallId, mkTickBoxOpId, mkBreakPointOpId,
30 mkReboxingAlt, wrapNewTypeBody, unwrapNewTypeBody,
31 wrapFamInstBody, unwrapFamInstScrut,
32 mkUnpackCase, mkProductBox,
34 -- And some particular Ids; see below for why they are wired in
35 wiredInIds, ghcPrimIds,
36 unsafeCoerceId, realWorldPrimId, voidArgId, nullAddrId, seqId,
37 lazyId, lazyIdUnfolding, lazyIdKey,
40 rEC_CON_ERROR_ID, iRREFUT_PAT_ERROR_ID, rUNTIME_ERROR_ID,
41 nON_EXHAUSTIVE_GUARDS_ERROR_ID, nO_METHOD_BINDING_ERROR_ID,
42 pAT_ERROR_ID, eRROR_ID,
47 #include "HsVersions.h"
70 import Var ( Var, TyVar, mkCoVar)
78 import BasicTypes hiding ( SuccessFlag(..) )
86 %************************************************************************
88 \subsection{Wired in Ids}
90 %************************************************************************
95 = [ -- These error-y things are wired in because we don't yet have
96 -- a way to express in an interface file that the result type variable
97 -- is 'open'; that is can be unified with an unboxed type
99 -- [The interface file format now carry such information, but there's
100 -- no way yet of expressing at the definition site for these
101 -- error-reporting functions that they have an 'open'
102 -- result type. -- sof 1/99]
104 eRROR_ID, -- This one isn't used anywhere else in the compiler
105 -- But we still need it in wiredInIds so that when GHC
106 -- compiles a program that mentions 'error' we don't
107 -- import its type from the interface file; we just get
108 -- the Id defined here. Which has an 'open-tyvar' type.
111 iRREFUT_PAT_ERROR_ID,
112 nON_EXHAUSTIVE_GUARDS_ERROR_ID,
113 nO_METHOD_BINDING_ERROR_ID,
120 -- These Ids are exported from GHC.Prim
123 = [ -- These can't be defined in Haskell, but they have
124 -- perfectly reasonable unfoldings in Core
132 %************************************************************************
134 \subsection{Data constructors}
136 %************************************************************************
138 The wrapper for a constructor is an ordinary top-level binding that evaluates
139 any strict args, unboxes any args that are going to be flattened, and calls
142 We're going to build a constructor that looks like:
144 data (Data a, C b) => T a b = T1 !a !Int b
147 \d1::Data a, d2::C b ->
148 \p q r -> case p of { p ->
150 Con T1 [a,b] [p,q,r]}}
154 * d2 is thrown away --- a context in a data decl is used to make sure
155 one *could* construct dictionaries at the site the constructor
156 is used, but the dictionary isn't actually used.
158 * We have to check that we can construct Data dictionaries for
159 the types a and Int. Once we've done that we can throw d1 away too.
161 * We use (case p of q -> ...) to evaluate p, rather than "seq" because
162 all that matters is that the arguments are evaluated. "seq" is
163 very careful to preserve evaluation order, which we don't need
166 You might think that we could simply give constructors some strictness
167 info, like PrimOps, and let CoreToStg do the let-to-case transformation.
168 But we don't do that because in the case of primops and functions strictness
169 is a *property* not a *requirement*. In the case of constructors we need to
170 do something active to evaluate the argument.
172 Making an explicit case expression allows the simplifier to eliminate
173 it in the (common) case where the constructor arg is already evaluated.
175 Note [Wrappers for data instance tycons]
176 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
177 In the case of data instances, the wrapper also applies the coercion turning
178 the representation type into the family instance type to cast the result of
179 the wrapper. For example, consider the declarations
181 data family Map k :: * -> *
182 data instance Map (a, b) v = MapPair (Map a (Pair b v))
184 The tycon to which the datacon MapPair belongs gets a unique internal
185 name of the form :R123Map, and we call it the representation tycon.
186 In contrast, Map is the family tycon (accessible via
187 tyConFamInst_maybe). A coercion allows you to move between
188 representation and family type. It is accessible from :R123Map via
189 tyConFamilyCoercion_maybe and has kind
191 Co123Map a b v :: {Map (a, b) v ~ :R123Map a b v}
193 The wrapper and worker of MapPair get the types
196 $WMapPair :: forall a b v. Map a (Map a b v) -> Map (a, b) v
197 $WMapPair a b v = MapPair a b v `cast` sym (Co123Map a b v)
200 MapPair :: forall a b v. Map a (Map a b v) -> :R123Map a b v
202 This coercion is conditionally applied by wrapFamInstBody.
204 It's a bit more complicated if the data instance is a GADT as well!
206 data instance T [a] where
207 T1 :: forall b. b -> T [Maybe b]
209 Co7T a :: T [a] ~ :R7T a
214 $WT1 :: forall b. b -> T [Maybe b]
215 $WT1 b v = T1 (Maybe b) b (Maybe b) v
216 `cast` sym (Co7T (Maybe b))
219 T1 :: forall c b. (c ~ Maybe b) => b -> :R7T c
222 mkDataConIds :: Name -> Name -> DataCon -> DataConIds
223 mkDataConIds wrap_name wkr_name data_con
224 | isNewTyCon tycon -- Newtype, only has a worker
225 = DCIds Nothing nt_work_id
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 eq_theta, dict_theta, orig_arg_tys, res_ty) = dataConFullSig data_con
237 tycon = dataConTyCon data_con -- The representation TyCon (not family)
239 ----------- Worker (algebraic data types only) --------------
240 -- The *worker* for the data constructor is the function that
241 -- takes the representation arguments and builds the constructor.
242 wrk_id = mkGlobalId (DataConWorkId data_con) wkr_name
243 (dataConRepType data_con) wkr_info
245 wkr_arity = dataConRepArity data_con
246 wkr_info = noCafIdInfo
247 `setArityInfo` wkr_arity
248 `setAllStrictnessInfo` Just wkr_sig
249 `setUnfoldingInfo` evaldUnfolding -- Record that it's evaluated,
252 wkr_sig = mkStrictSig (mkTopDmdType (replicate wkr_arity topDmd) cpr_info)
253 -- Note [Data-con worker strictness]
254 -- Notice that we do *not* say the worker is strict
255 -- even if the data constructor is declared strict
256 -- e.g. data T = MkT !(Int,Int)
257 -- Why? Because the *wrapper* is strict (and its unfolding has case
258 -- expresssions that do the evals) but the *worker* itself is not.
259 -- If we pretend it is strict then when we see
260 -- case x of y -> $wMkT y
261 -- the simplifier thinks that y is "sure to be evaluated" (because
262 -- $wMkT is strict) and drops the case. No, $wMkT is not strict.
264 -- When the simplifer sees a pattern
265 -- case e of MkT x -> ...
266 -- it uses the dataConRepStrictness of MkT to mark x as evaluated;
267 -- but that's fine... dataConRepStrictness comes from the data con
268 -- not from the worker Id.
270 cpr_info | isProductTyCon tycon &&
273 wkr_arity <= mAX_CPR_SIZE = retCPR
275 -- RetCPR is only true for products that are real data types;
276 -- that is, not unboxed tuples or [non-recursive] newtypes
278 ----------- Workers for newtypes --------------
279 nt_work_id = mkGlobalId (DataConWrapId data_con) wkr_name wrap_ty nt_work_info
280 nt_work_info = noCafIdInfo -- The NoCaf-ness is set by noCafIdInfo
281 `setArityInfo` 1 -- Arity 1
282 `setUnfoldingInfo` newtype_unf
283 newtype_unf = -- The assertion below is no longer correct:
284 -- there may be a dict theta rather than a singleton orig_arg_ty
285 -- ASSERT( isVanillaDataCon data_con &&
286 -- isSingleton orig_arg_tys )
288 -- No existentials on a newtype, but it can have a context
289 -- e.g. newtype Eq a => T a = MkT (...)
290 mkCompulsoryUnfolding $
291 mkLams wrap_tvs $ Lam id_arg1 $
292 wrapNewTypeBody tycon res_ty_args
295 id_arg1 = mkTemplateLocal 1
296 (if null orig_arg_tys
297 then ASSERT(not (null $ dataConDictTheta data_con))
298 mkPredTy $ head (dataConDictTheta data_con)
299 else head orig_arg_tys
302 ----------- Wrapper --------------
303 -- We used to include the stupid theta in the wrapper's args
304 -- but now we don't. Instead the type checker just injects these
305 -- extra constraints where necessary.
306 wrap_tvs = (univ_tvs `minusList` map fst eq_spec) ++ ex_tvs
307 res_ty_args = substTyVars (mkTopTvSubst eq_spec) univ_tvs
308 eq_tys = mkPredTys eq_theta
309 dict_tys = mkPredTys dict_theta
310 wrap_ty = mkForAllTys wrap_tvs $ mkFunTys eq_tys $ mkFunTys dict_tys $
311 mkFunTys orig_arg_tys $ res_ty
312 -- NB: watch out here if you allow user-written equality
313 -- constraints in data constructor signatures
315 ----------- Wrappers for algebraic data types --------------
316 alg_wrap_id = mkGlobalId (DataConWrapId data_con) wrap_name wrap_ty alg_wrap_info
317 alg_wrap_info = noCafIdInfo -- The NoCaf-ness is set by noCafIdInfo
318 `setArityInfo` wrap_arity
319 -- It's important to specify the arity, so that partial
320 -- applications are treated as values
321 `setUnfoldingInfo` wrap_unf
322 `setAllStrictnessInfo` Just wrap_sig
324 all_strict_marks = dataConExStricts data_con ++ dataConStrictMarks data_con
325 wrap_sig = mkStrictSig (mkTopDmdType arg_dmds cpr_info)
326 arg_dmds = map mk_dmd all_strict_marks
327 mk_dmd str | isMarkedStrict str = evalDmd
328 | otherwise = lazyDmd
329 -- The Cpr info can be important inside INLINE rhss, where the
330 -- wrapper constructor isn't inlined.
331 -- And the argument strictness can be important too; we
332 -- may not inline a contructor when it is partially applied.
334 -- data W = C !Int !Int !Int
335 -- ...(let w = C x in ...(w p q)...)...
336 -- we want to see that w is strict in its two arguments
338 wrap_unf = mkImplicitUnfolding $ Note InlineMe $
341 mkLams dict_args $ mkLams id_args $
342 foldr mk_case con_app
343 (zip (dict_args ++ id_args) all_strict_marks)
346 con_app _ rep_ids = wrapFamInstBody tycon res_ty_args $
347 Var wrk_id `mkTyApps` res_ty_args
349 -- Equality evidence:
350 `mkTyApps` map snd eq_spec
352 `mkVarApps` reverse rep_ids
354 (dict_args,i2) = mkLocals 1 dict_tys
355 (id_args,i3) = mkLocals i2 orig_arg_tys
357 (eq_args,_) = mkCoVarLocals i3 eq_tys
359 mkCoVarLocals i [] = ([],i)
360 mkCoVarLocals i (x:xs) = let (ys,j) = mkCoVarLocals (i+1) xs
361 y = mkCoVar (mkSysTvName (mkBuiltinUnique i) (fsLit "dc_co")) x
365 :: (Id, StrictnessMark) -- Arg, strictness
366 -> (Int -> [Id] -> CoreExpr) -- Body
367 -> Int -- Next rep arg id
368 -> [Id] -- Rep args so far, reversed
370 mk_case (arg,strict) body i rep_args
372 NotMarkedStrict -> body i (arg:rep_args)
374 | isUnLiftedType (idType arg) -> body i (arg:rep_args)
376 Case (Var arg) arg res_ty [(DEFAULT,[], body i (arg:rep_args))]
379 -> unboxProduct i (Var arg) (idType arg) the_body
381 the_body i con_args = body i (reverse con_args ++ rep_args)
383 mAX_CPR_SIZE :: Arity
385 -- We do not treat very big tuples as CPR-ish:
386 -- a) for a start we get into trouble because there aren't
387 -- "enough" unboxed tuple types (a tiresome restriction,
389 -- b) more importantly, big unboxed tuples get returned mainly
390 -- on the stack, and are often then allocated in the heap
391 -- by the caller. So doing CPR for them may in fact make
394 mkLocals i tys = (zipWith mkTemplateLocal [i..i+n-1] tys, i+n)
400 %************************************************************************
402 \subsection{Record selectors}
404 %************************************************************************
406 We're going to build a record selector unfolding that looks like this:
408 data T a b c = T1 { ..., op :: a, ...}
409 | T2 { ..., op :: a, ...}
412 sel = /\ a b c -> \ d -> case d of
417 Similarly for newtypes
419 newtype N a = MkN { unN :: a->a }
422 unN n = coerce (a->a) n
424 We need to take a little care if the field has a polymorphic type:
426 data R = R { f :: forall a. a->a }
430 f :: forall a. R -> a -> a
431 f = /\ a \ r = case r of
434 (not f :: R -> forall a. a->a, which gives the type inference mechanism
435 problems at call sites)
437 Similarly for (recursive) newtypes
439 newtype N = MkN { unN :: forall a. a->a }
441 unN :: forall b. N -> b -> b
442 unN = /\b -> \n:N -> (coerce (forall a. a->a) n)
445 Note [Naughty record selectors]
446 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
447 A "naughty" field is one for which we can't define a record
448 selector, because an existential type variable would escape. For example:
449 data T = forall a. MkT { x,y::a }
450 We obviously can't define
452 Nevertheless we *do* put a RecordSelId into the type environment
453 so that if the user tries to use 'x' as a selector we can bleat
454 helpfully, rather than saying unhelpfully that 'x' is not in scope.
455 Hence the sel_naughty flag, to identify record selectors that don't really exist.
457 In general, a field is naughty if its type mentions a type variable that
458 isn't in the result type of the constructor.
460 Note [GADT record selectors]
461 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
462 For GADTs, we require that all constructors with a common field 'f' have the same
463 result type (modulo alpha conversion). [Checked in TcTyClsDecls.checkValidTyCon]
466 T1 { f :: Maybe a } :: T [a]
467 T2 { f :: Maybe a, y :: b } :: T [a]
469 and now the selector takes that result type as its argument:
470 f :: forall a. T [a] -> Maybe a
472 Details: the "real" types of T1,T2 are:
473 T1 :: forall r a. (r~[a]) => a -> T r
474 T2 :: forall r a b. (r~[a]) => a -> b -> T r
476 So the selector loooks like this:
477 f :: forall a. T [a] -> Maybe a
480 T1 c (g:[a]~[c]) (v:Maybe c) -> v `cast` Maybe (right (sym g))
481 T2 c d (g:[a]~[c]) (v:Maybe c) (w:d) -> v `cast` Maybe (right (sym g))
483 Note the forall'd tyvars of the selector are just the free tyvars
484 of the result type; there may be other tyvars in the constructor's
485 type (e.g. 'b' in T2).
487 Note the need for casts in the result!
489 Note [Selector running example]
490 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
491 It's OK to combine GADTs and type families. Here's a running example:
493 data instance T [a] where
494 T1 { fld :: b } :: T [Maybe b]
496 The representation type looks like this
498 T1 { fld :: b } :: :R7T (Maybe b)
500 and there's coercion from the family type to the representation type
501 :CoR7T a :: T [a] ~ :R7T a
503 The selector we want for fld looks like this:
505 fld :: forall b. T [Maybe b] -> b
506 fld = /\b. \(d::T [Maybe b]).
507 case d `cast` :CoR7T (Maybe b) of
510 The scrutinee of the case has type :R7T (Maybe b), which can be
511 gotten by appying the eq_spec to the univ_tvs of the data con.
514 mkRecordSelId :: TyCon -> FieldLabel -> Id
515 mkRecordSelId tycon field_label
516 -- Assumes that all fields with the same field label have the same type
519 -- Because this function gets called by implicitTyThings, we need to
520 -- produce the OccName of the Id without doing any suspend type checks.
521 -- (see the note [Tricky iface loop]).
522 -- A suspended type-check is sometimes necessary to compute field_ty,
523 -- so we need to make sure that we suspend anything that depends on field_ty.
525 -- the overall result
526 sel_id = mkGlobalId sel_id_details field_label theType theInfo
528 -- check whether the type is naughty: this thunk does not get forced
529 -- until the type is actually needed
530 field_ty = dataConFieldType con1 field_label
531 is_naughty = not (tyVarsOfType field_ty `subVarSet` data_tv_set)
533 -- it's important that this doesn't force the if
534 (theType, theInfo) = if is_naughty
535 -- Escapist case here for naughty constructors
536 -- We give it no IdInfo, and a type of
537 -- forall a.a (never looked at)
538 then (forall_a_a, noCafIdInfo)
539 -- otherwise do the real case
540 else (selector_ty, info)
542 sel_id_details = RecordSelId { sel_tycon = tycon,
543 sel_label = field_label,
544 sel_naughty = is_naughty }
545 -- For a data type family, the tycon is the *instance* TyCon
548 forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar)
550 -- real case starts here:
551 data_cons = tyConDataCons tycon
552 data_cons_w_field = filter has_field data_cons -- Can't be empty!
553 has_field con = field_label `elem` dataConFieldLabels con
555 con1 = ASSERT( not (null data_cons_w_field) ) head data_cons_w_field
556 (univ_tvs, _, eq_spec, _, _, _, data_ty) = dataConFullSig con1
557 -- For a data type family, the data_ty (and hence selector_ty) mentions
558 -- only the family TyCon, not the instance TyCon
559 data_tv_set = tyVarsOfType data_ty
560 data_tvs = varSetElems data_tv_set
562 -- _Very_ tiresomely, the selectors are (unnecessarily!) overloaded over
563 -- just the dictionaries in the types of the constructors that contain
564 -- the relevant field. [The Report says that pattern matching on a
565 -- constructor gives the same constraints as applying it.] Urgh.
567 -- However, not all data cons have all constraints (because of
568 -- BuildTyCl.mkDataConStupidTheta). So we need to find all the data cons
569 -- involved in the pattern match and take the union of their constraints.
570 stupid_dict_tys = mkPredTys (dataConsStupidTheta data_cons_w_field)
571 n_stupid_dicts = length stupid_dict_tys
573 (field_tyvars,pre_field_theta,field_tau) = tcSplitSigmaTy field_ty
574 field_theta = filter (not . isEqPred) pre_field_theta
575 field_dict_tys = mkPredTys field_theta
576 n_field_dict_tys = length field_dict_tys
577 -- If the field has a universally quantified type we have to
578 -- be a bit careful. Suppose we have
579 -- data R = R { op :: forall a. Foo a => a -> a }
580 -- Then we can't give op the type
581 -- op :: R -> forall a. Foo a => a -> a
582 -- because the typechecker doesn't understand foralls to the
583 -- right of an arrow. The "right" type to give it is
584 -- op :: forall a. Foo a => R -> a -> a
585 -- But then we must generate the right unfolding too:
586 -- op = /\a -> \dfoo -> \ r ->
589 -- Note that this is exactly the type we'd infer from a user defn
593 selector_ty = mkForAllTys data_tvs $ mkForAllTys field_tyvars $
594 mkFunTys stupid_dict_tys $ mkFunTys field_dict_tys $
595 mkFunTy data_ty field_tau
597 arity = 1 + n_stupid_dicts + n_field_dict_tys
599 (strict_sig, rhs_w_str) = dmdAnalTopRhs sel_rhs
600 -- Use the demand analyser to work out strictness.
601 -- With all this unpackery it's not easy!
604 `setCafInfo` caf_info
606 `setUnfoldingInfo` unfolding
607 `setAllStrictnessInfo` Just strict_sig
609 unfolding = mkImplicitUnfolding rhs_w_str
611 -- Allocate Ids. We do it a funny way round because field_dict_tys is
612 -- almost always empty. Also note that we use max_dict_tys
613 -- rather than n_dict_tys, because the latter gives an infinite loop:
614 -- n_dict tys depends on the_alts, which depens on arg_ids, which
615 -- depends on arity, which depends on n_dict tys. Sigh! Mega sigh!
616 stupid_dict_ids = mkTemplateLocalsNum 1 stupid_dict_tys
617 max_stupid_dicts = length (tyConStupidTheta tycon)
618 field_dict_base = max_stupid_dicts + 1
619 field_dict_ids = mkTemplateLocalsNum field_dict_base field_dict_tys
620 dict_id_base = field_dict_base + n_field_dict_tys
621 data_id = mkTemplateLocal dict_id_base data_ty
622 scrut_id = mkTemplateLocal (dict_id_base+1) scrut_ty
623 arg_base = dict_id_base + 2
625 the_alts :: [CoreAlt]
626 the_alts = map mk_alt data_cons_w_field -- Already sorted by data-con
627 no_default = length data_cons == length data_cons_w_field -- No default needed
629 default_alt | no_default = []
630 | otherwise = [(DEFAULT, [], error_expr)]
632 -- The default branch may have CAF refs, because it calls recSelError etc.
633 caf_info | no_default = NoCafRefs
634 | otherwise = MayHaveCafRefs
636 sel_rhs = mkLams data_tvs $ mkLams field_tyvars $
637 mkLams stupid_dict_ids $ mkLams field_dict_ids $
638 Lam data_id $ mk_result sel_body
640 scrut_ty_args = substTyVars (mkTopTvSubst eq_spec) univ_tvs
641 scrut_ty = mkTyConApp tycon scrut_ty_args
642 scrut = unwrapFamInstScrut tycon scrut_ty_args (Var data_id)
643 -- First coerce from the type family to the representation type
645 -- NB: A newtype always has a vanilla DataCon; no existentials etc
646 -- data_tys will simply be the dataConUnivTyVars
647 sel_body | isNewTyCon tycon = unwrapNewTypeBody tycon scrut_ty_args scrut
648 | otherwise = Case scrut scrut_id field_ty (default_alt ++ the_alts)
650 mk_result poly_result = mkVarApps (mkVarApps poly_result field_tyvars) field_dict_ids
651 -- We pull the field lambdas to the top, so we need to
652 -- apply them in the body. For example:
653 -- data T = MkT { foo :: forall a. a->a }
655 -- foo :: forall a. T -> a -> a
656 -- foo = /\a. \t:T. case t of { MkT f -> f a }
659 = mkReboxingAlt rebox_uniqs data_con (ex_tvs ++ co_tvs ++ arg_vs) rhs
661 -- get pattern binders with types appropriately instantiated
662 arg_uniqs = map mkBuiltinUnique [arg_base..]
663 (ex_tvs, co_tvs, arg_vs) = dataConOrigInstPat arg_uniqs data_con
666 rebox_base = arg_base + length ex_tvs + length co_tvs + length arg_vs
667 rebox_uniqs = map mkBuiltinUnique [rebox_base..]
669 -- data T :: *->* where T1 { fld :: Maybe b } -> T [b]
670 -- Hence T1 :: forall a b. (a~[b]) => b -> T a
671 -- fld :: forall b. T [b] -> Maybe b
672 -- fld = /\b.\(t:T[b]). case t of
673 -- T1 b' (c : [b]=[b']) (x:Maybe b')
674 -- -> x `cast` Maybe (sym (right c))
676 -- Generate the cast for the result
677 -- See Note [GADT record selectors] for why a cast is needed
678 in_scope_tvs = ex_tvs ++ co_tvs ++ data_tvs
679 reft = matchRefine in_scope_tvs (map (mkSymCoercion . mkTyVarTy) co_tvs)
680 rhs = case refineType reft (idType the_arg_id) of
681 Nothing -> Var the_arg_id
682 Just (co, data_ty) -> ASSERT2( data_ty `tcEqType` field_ty,
683 ppr data_con $$ ppr data_ty $$ ppr field_ty )
684 Cast (Var the_arg_id) co
686 field_vs = filter (not . isPredTy . idType) arg_vs
687 the_arg_id = assoc "mkRecordSelId:mk_alt"
688 (field_lbls `zip` field_vs) field_label
689 field_lbls = dataConFieldLabels data_con
691 error_expr = mkRuntimeErrorApp rEC_SEL_ERROR_ID field_ty full_msg
692 full_msg = showSDoc (sep [text "No match in record selector", ppr sel_id])
694 -- unbox a product type...
695 -- we will recurse into newtypes, casting along the way, and unbox at the
696 -- first product data constructor we find. e.g.
698 -- data PairInt = PairInt Int Int
699 -- newtype S = MkS PairInt
702 -- If we have e = MkT (MkS (PairInt 0 1)) and some body expecting a list of
703 -- ids, we get (modulo int passing)
705 -- case (e `cast` CoT) `cast` CoS of
706 -- PairInt a b -> body [a,b]
708 -- The Ints passed around are just for creating fresh locals
709 unboxProduct :: Int -> CoreExpr -> Type -> (Int -> [Id] -> CoreExpr) -> CoreExpr
710 unboxProduct i arg arg_ty body
713 result = mkUnpackCase the_id arg con_args boxing_con rhs
714 (_tycon, _tycon_args, boxing_con, tys) = deepSplitProductType "unboxProduct" arg_ty
715 ([the_id], i') = mkLocals i [arg_ty]
716 (con_args, i'') = mkLocals i' tys
717 rhs = body i'' con_args
719 mkUnpackCase :: Id -> CoreExpr -> [Id] -> DataCon -> CoreExpr -> CoreExpr
720 -- (mkUnpackCase x e args Con body)
722 -- case (e `cast` ...) of bndr { Con args -> body }
724 -- the type of the bndr passed in is irrelevent
725 mkUnpackCase bndr arg unpk_args boxing_con body
726 = Case cast_arg (setIdType bndr bndr_ty) (exprType body) [(DataAlt boxing_con, unpk_args, body)]
728 (cast_arg, bndr_ty) = go (idType bndr) arg
730 | (tycon, tycon_args, _, _) <- splitProductType "mkUnpackCase" ty
731 , isNewTyCon tycon && not (isRecursiveTyCon tycon)
732 = go (newTyConInstRhs tycon tycon_args)
733 (unwrapNewTypeBody tycon tycon_args arg)
734 | otherwise = (arg, ty)
737 reboxProduct :: [Unique] -- uniques to create new local binders
738 -> Type -- type of product to box
739 -> ([Unique], -- remaining uniques
740 CoreExpr, -- boxed product
741 [Id]) -- Ids being boxed into product
744 (_tycon, _tycon_args, _pack_con, con_arg_tys) = deepSplitProductType "reboxProduct" ty
746 us' = dropList con_arg_tys us
748 arg_ids = zipWith (mkSysLocal (fsLit "rb")) us con_arg_tys
750 bind_rhs = mkProductBox arg_ids ty
753 (us', bind_rhs, arg_ids)
755 mkProductBox :: [Id] -> Type -> CoreExpr
756 mkProductBox arg_ids ty
759 (tycon, tycon_args, pack_con, _con_arg_tys) = splitProductType "mkProductBox" ty
762 | isNewTyCon tycon && not (isRecursiveTyCon tycon)
763 = wrap (mkProductBox arg_ids (newTyConInstRhs tycon tycon_args))
764 | otherwise = mkConApp pack_con (map Type tycon_args ++ map Var arg_ids)
766 wrap expr = wrapNewTypeBody tycon tycon_args expr
769 -- (mkReboxingAlt us con xs rhs) basically constructs the case
770 -- alternative (con, xs, rhs)
771 -- but it does the reboxing necessary to construct the *source*
772 -- arguments, xs, from the representation arguments ys.
774 -- data T = MkT !(Int,Int) Bool
776 -- mkReboxingAlt MkT [x,b] r
777 -- = (DataAlt MkT, [y::Int,z::Int,b], let x = (y,z) in r)
779 -- mkDataAlt should really be in DataCon, but it can't because
780 -- it manipulates CoreSyn.
783 :: [Unique] -- Uniques for the new Ids
785 -> [Var] -- Source-level args, including existential dicts
789 mkReboxingAlt us con args rhs
790 | not (any isMarkedUnboxed stricts)
791 = (DataAlt con, args, rhs)
795 (binds, args') = go args stricts us
797 (DataAlt con, args', mkLets binds rhs)
800 stricts = dataConExStricts con ++ dataConStrictMarks con
802 go [] _stricts _us = ([], [])
804 -- Type variable case
805 go (arg:args) stricts us
807 = let (binds, args') = go args stricts us
808 in (binds, arg:args')
810 -- Term variable case
811 go (arg:args) (str:stricts) us
812 | isMarkedUnboxed str
814 let (binds, unpacked_args') = go args stricts us'
815 (us', bind_rhs, unpacked_args) = reboxProduct us (idType arg)
817 (NonRec arg bind_rhs : binds, unpacked_args ++ unpacked_args')
819 = let (binds, args') = go args stricts us
820 in (binds, arg:args')
821 go (_ : _) [] _ = panic "mkReboxingAlt"
825 %************************************************************************
827 \subsection{Dictionary selectors}
829 %************************************************************************
831 Selecting a field for a dictionary. If there is just one field, then
832 there's nothing to do.
834 Dictionary selectors may get nested forall-types. Thus:
837 op :: forall b. Ord b => a -> b -> b
839 Then the top-level type for op is
841 op :: forall a. Foo a =>
845 This is unlike ordinary record selectors, which have all the for-alls
846 at the outside. When dealing with classes it's very convenient to
847 recover the original type signature from the class op selector.
850 mkDictSelId :: Bool -- True <=> don't include the unfolding
851 -- Little point on imports without -O, because the
852 -- dictionary itself won't be visible
853 -> Name -> Class -> Id
854 mkDictSelId no_unf name clas
855 = mkGlobalId (ClassOpId clas) name sel_ty info
857 sel_ty = mkForAllTys tyvars (mkFunTy (idType dict_id) (idType the_arg_id))
858 -- We can't just say (exprType rhs), because that would give a type
860 -- for a single-op class (after all, the selector is the identity)
861 -- But it's type must expose the representation of the dictionary
862 -- to get (say) C a -> (a -> a)
866 `setAllStrictnessInfo` Just strict_sig
867 `setUnfoldingInfo` (if no_unf then noUnfolding
868 else mkImplicitUnfolding rhs)
870 -- We no longer use 'must-inline' on record selectors. They'll
871 -- inline like crazy if they scrutinise a constructor
873 -- The strictness signature is of the form U(AAAVAAAA) -> T
874 -- where the V depends on which item we are selecting
875 -- It's worth giving one, so that absence info etc is generated
876 -- even if the selector isn't inlined
877 strict_sig = mkStrictSig (mkTopDmdType [arg_dmd] TopRes)
878 arg_dmd | isNewTyCon tycon = evalDmd
879 | otherwise = Eval (Prod [ if the_arg_id == id then evalDmd else Abs
882 tycon = classTyCon clas
883 [data_con] = tyConDataCons tycon
884 tyvars = dataConUnivTyVars data_con
885 arg_tys = {- ASSERT( isVanillaDataCon data_con ) -} dataConRepArgTys data_con
886 eq_theta = dataConEqTheta data_con
887 the_arg_id = assoc "MkId.mkDictSelId" (map idName (classSelIds clas) `zip` arg_ids) name
889 pred = mkClassPred clas (mkTyVarTys tyvars)
890 dict_id = mkTemplateLocal 1 $ mkPredTy pred
891 (eq_ids,n) = mkCoVarLocals 2 $ mkPredTys eq_theta
892 arg_ids = mkTemplateLocalsNum n arg_tys
894 mkCoVarLocals i [] = ([],i)
895 mkCoVarLocals i (x:xs) = let (ys,j) = mkCoVarLocals (i+1) xs
896 y = mkCoVar (mkSysTvName (mkBuiltinUnique i) (fsLit "dc_co")) x
899 rhs = mkLams tyvars (Lam dict_id rhs_body)
900 rhs_body | isNewTyCon tycon = unwrapNewTypeBody tycon (map mkTyVarTy tyvars) (Var dict_id)
901 | otherwise = Case (Var dict_id) dict_id (idType the_arg_id)
902 [(DataAlt data_con, eq_ids ++ arg_ids, Var the_arg_id)]
906 %************************************************************************
908 Wrapping and unwrapping newtypes and type families
910 %************************************************************************
913 wrapNewTypeBody :: TyCon -> [Type] -> CoreExpr -> CoreExpr
914 -- The wrapper for the data constructor for a newtype looks like this:
915 -- newtype T a = MkT (a,Int)
916 -- MkT :: forall a. (a,Int) -> T a
917 -- MkT = /\a. \(x:(a,Int)). x `cast` sym (CoT a)
918 -- where CoT is the coercion TyCon assoicated with the newtype
920 -- The call (wrapNewTypeBody T [a] e) returns the
921 -- body of the wrapper, namely
922 -- e `cast` (CoT [a])
924 -- If a coercion constructor is provided in the newtype, then we use
925 -- it, otherwise the wrap/unwrap are both no-ops
927 -- If the we are dealing with a newtype *instance*, we have a second coercion
928 -- identifying the family instance with the constructor of the newtype
929 -- instance. This coercion is applied in any case (ie, composed with the
930 -- coercion constructor of the newtype or applied by itself).
932 wrapNewTypeBody tycon args result_expr
933 = wrapFamInstBody tycon args inner
936 | Just co_con <- newTyConCo_maybe tycon
937 = mkCoerce (mkSymCoercion (mkTyConApp co_con args)) result_expr
941 -- When unwrapping, we do *not* apply any family coercion, because this will
942 -- be done via a CoPat by the type checker. We have to do it this way as
943 -- computing the right type arguments for the coercion requires more than just
944 -- a spliting operation (cf, TcPat.tcConPat).
946 unwrapNewTypeBody :: TyCon -> [Type] -> CoreExpr -> CoreExpr
947 unwrapNewTypeBody tycon args result_expr
948 | Just co_con <- newTyConCo_maybe tycon
949 = mkCoerce (mkTyConApp co_con args) result_expr
953 -- If the type constructor is a representation type of a data instance, wrap
954 -- the expression into a cast adjusting the expression type, which is an
955 -- instance of the representation type, to the corresponding instance of the
956 -- family instance type.
957 -- See Note [Wrappers for data instance tycons]
958 wrapFamInstBody :: TyCon -> [Type] -> CoreExpr -> CoreExpr
959 wrapFamInstBody tycon args body
960 | Just co_con <- tyConFamilyCoercion_maybe tycon
961 = mkCoerce (mkSymCoercion (mkTyConApp co_con args)) body
965 unwrapFamInstScrut :: TyCon -> [Type] -> CoreExpr -> CoreExpr
966 unwrapFamInstScrut tycon args scrut
967 | Just co_con <- tyConFamilyCoercion_maybe tycon
968 = mkCoerce (mkTyConApp co_con args) scrut
974 %************************************************************************
976 \subsection{Primitive operations}
978 %************************************************************************
981 mkPrimOpId :: PrimOp -> Id
985 (tyvars,arg_tys,res_ty, arity, strict_sig) = primOpSig prim_op
986 ty = mkForAllTys tyvars (mkFunTys arg_tys res_ty)
987 name = mkWiredInName gHC_PRIM (primOpOcc prim_op)
988 (mkPrimOpIdUnique (primOpTag prim_op))
990 id = mkGlobalId (PrimOpId prim_op) name ty info
993 `setSpecInfo` mkSpecInfo (primOpRules prim_op name)
995 `setAllStrictnessInfo` Just strict_sig
997 -- For each ccall we manufacture a separate CCallOpId, giving it
998 -- a fresh unique, a type that is correct for this particular ccall,
999 -- and a CCall structure that gives the correct details about calling
1002 -- The *name* of this Id is a local name whose OccName gives the full
1003 -- details of the ccall, type and all. This means that the interface
1004 -- file reader can reconstruct a suitable Id
1006 mkFCallId :: Unique -> ForeignCall -> Type -> Id
1007 mkFCallId uniq fcall ty
1008 = ASSERT( isEmptyVarSet (tyVarsOfType ty) )
1009 -- A CCallOpId should have no free type variables;
1010 -- when doing substitutions won't substitute over it
1011 mkGlobalId (FCallId fcall) name ty info
1013 occ_str = showSDoc (braces (ppr fcall <+> ppr ty))
1014 -- The "occurrence name" of a ccall is the full info about the
1015 -- ccall; it is encoded, but may have embedded spaces etc!
1017 name = mkFCallName uniq occ_str
1020 `setArityInfo` arity
1021 `setAllStrictnessInfo` Just strict_sig
1023 (_, tau) = tcSplitForAllTys ty
1024 (arg_tys, _) = tcSplitFunTys tau
1025 arity = length arg_tys
1026 strict_sig = mkStrictSig (mkTopDmdType (replicate arity evalDmd) TopRes)
1028 -- Tick boxes and breakpoints are both represented as TickBoxOpIds,
1029 -- except for the type:
1031 -- a plain HPC tick box has type (State# RealWorld)
1032 -- a breakpoint Id has type forall a.a
1034 -- The breakpoint Id will be applied to a list of arbitrary free variables,
1035 -- which is why it needs a polymorphic type.
1037 mkTickBoxOpId :: Unique -> Module -> TickBoxId -> Id
1038 mkTickBoxOpId uniq mod ix = mkTickBox' uniq mod ix realWorldStatePrimTy
1040 mkBreakPointOpId :: Unique -> Module -> TickBoxId -> Id
1041 mkBreakPointOpId uniq mod ix = mkTickBox' uniq mod ix ty
1042 where ty = mkSigmaTy [openAlphaTyVar] [] openAlphaTy
1044 mkTickBox' uniq mod ix ty = mkGlobalId (TickBoxOpId tickbox) name ty info
1046 tickbox = TickBox mod ix
1047 occ_str = showSDoc (braces (ppr tickbox))
1048 name = mkTickBoxOpName uniq occ_str
1053 %************************************************************************
1055 \subsection{DictFuns and default methods}
1057 %************************************************************************
1059 Important notes about dict funs and default methods
1060 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1061 Dict funs and default methods are *not* ImplicitIds. Their definition
1062 involves user-written code, so we can't figure out their strictness etc
1063 based on fixed info, as we can for constructors and record selectors (say).
1065 We build them as LocalIds, but with External Names. This ensures that
1066 they are taken to account by free-variable finding and dependency
1067 analysis (e.g. CoreFVs.exprFreeVars).
1069 Why shouldn't they be bound as GlobalIds? Because, in particular, if
1070 they are globals, the specialiser floats dict uses above their defns,
1071 which prevents good simplifications happening. Also the strictness
1072 analyser treats a occurrence of a GlobalId as imported and assumes it
1073 contains strictness in its IdInfo, which isn't true if the thing is
1074 bound in the same module as the occurrence.
1076 It's OK for dfuns to be LocalIds, because we form the instance-env to
1077 pass on to the next module (md_insts) in CoreTidy, afer tidying
1078 and globalising the top-level Ids.
1080 BUT make sure they are *exported* LocalIds (mkExportedLocalId) so
1081 that they aren't discarded by the occurrence analyser.
1084 mkDefaultMethodId dm_name ty = mkExportedLocalId dm_name ty
1086 mkDictFunId :: Name -- Name to use for the dict fun;
1093 mkDictFunId dfun_name inst_tyvars dfun_theta clas inst_tys
1094 = mkExportedLocalId dfun_name dfun_ty
1096 dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
1098 {- 1 dec 99: disable the Mark Jones optimisation for the sake
1099 of compatibility with Hugs.
1100 See `types/InstEnv' for a discussion related to this.
1102 (class_tyvars, sc_theta, _, _) = classBigSig clas
1103 not_const (clas, tys) = not (isEmptyVarSet (tyVarsOfTypes tys))
1104 sc_theta' = substClasses (zipTopTvSubst class_tyvars inst_tys) sc_theta
1105 dfun_theta = case inst_decl_theta of
1106 [] -> [] -- If inst_decl_theta is empty, then we don't
1107 -- want to have any dict arguments, so that we can
1108 -- expose the constant methods.
1110 other -> nub (inst_decl_theta ++ filter not_const sc_theta')
1111 -- Otherwise we pass the superclass dictionaries to
1112 -- the dictionary function; the Mark Jones optimisation.
1114 -- NOTE the "nub". I got caught by this one:
1115 -- class Monad m => MonadT t m where ...
1116 -- instance Monad m => MonadT (EnvT env) m where ...
1117 -- Here, the inst_decl_theta has (Monad m); but so
1118 -- does the sc_theta'!
1120 -- NOTE the "not_const". I got caught by this one too:
1121 -- class Foo a => Baz a b where ...
1122 -- instance Wob b => Baz T b where..
1123 -- Now sc_theta' has Foo T
1128 %************************************************************************
1130 \subsection{Un-definable}
1132 %************************************************************************
1134 These Ids can't be defined in Haskell. They could be defined in
1135 unfoldings in the wired-in GHC.Prim interface file, but we'd have to
1136 ensure that they were definitely, definitely inlined, because there is
1137 no curried identifier for them. That's what mkCompulsoryUnfolding
1138 does. If we had a way to get a compulsory unfolding from an interface
1139 file, we could do that, but we don't right now.
1141 unsafeCoerce# isn't so much a PrimOp as a phantom identifier, that
1142 just gets expanded into a type coercion wherever it occurs. Hence we
1143 add it as a built-in Id with an unfolding here.
1145 The type variables we use here are "open" type variables: this means
1146 they can unify with both unlifted and lifted types. Hence we provide
1147 another gun with which to shoot yourself in the foot.
1150 mkWiredInIdName mod fs uniq id
1151 = mkWiredInName mod (mkOccNameFS varName fs) uniq (AnId id) UserSyntax
1153 unsafeCoerceName = mkWiredInIdName gHC_PRIM (fsLit "unsafeCoerce#") unsafeCoerceIdKey unsafeCoerceId
1154 nullAddrName = mkWiredInIdName gHC_PRIM (fsLit "nullAddr#") nullAddrIdKey nullAddrId
1155 seqName = mkWiredInIdName gHC_PRIM (fsLit "seq") seqIdKey seqId
1156 realWorldName = mkWiredInIdName gHC_PRIM (fsLit "realWorld#") realWorldPrimIdKey realWorldPrimId
1157 lazyIdName = mkWiredInIdName gHC_BASE (fsLit "lazy") lazyIdKey lazyId
1159 errorName = mkWiredInIdName gHC_ERR (fsLit "error") errorIdKey eRROR_ID
1160 recSelErrorName = mkWiredInIdName cONTROL_EXCEPTION_BASE (fsLit "recSelError") recSelErrorIdKey rEC_SEL_ERROR_ID
1161 runtimeErrorName = mkWiredInIdName cONTROL_EXCEPTION_BASE (fsLit "runtimeError") runtimeErrorIdKey rUNTIME_ERROR_ID
1162 irrefutPatErrorName = mkWiredInIdName cONTROL_EXCEPTION_BASE (fsLit "irrefutPatError") irrefutPatErrorIdKey iRREFUT_PAT_ERROR_ID
1163 recConErrorName = mkWiredInIdName cONTROL_EXCEPTION_BASE (fsLit "recConError") recConErrorIdKey rEC_CON_ERROR_ID
1164 patErrorName = mkWiredInIdName cONTROL_EXCEPTION_BASE (fsLit "patError") patErrorIdKey pAT_ERROR_ID
1165 noMethodBindingErrorName = mkWiredInIdName cONTROL_EXCEPTION_BASE (fsLit "noMethodBindingError")
1166 noMethodBindingErrorIdKey nO_METHOD_BINDING_ERROR_ID
1167 nonExhaustiveGuardsErrorName
1168 = mkWiredInIdName cONTROL_EXCEPTION_BASE (fsLit "nonExhaustiveGuardsError")
1169 nonExhaustiveGuardsErrorIdKey nON_EXHAUSTIVE_GUARDS_ERROR_ID
1173 ------------------------------------------------
1174 -- unsafeCoerce# :: forall a b. a -> b
1176 = pcMiscPrelId unsafeCoerceName ty info
1178 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
1181 ty = mkForAllTys [openAlphaTyVar,openBetaTyVar]
1182 (mkFunTy openAlphaTy openBetaTy)
1183 [x] = mkTemplateLocals [openAlphaTy]
1184 rhs = mkLams [openAlphaTyVar,openBetaTyVar,x] $
1185 Cast (Var x) (mkUnsafeCoercion openAlphaTy openBetaTy)
1187 ------------------------------------------------
1189 -- nullAddr# :: Addr#
1190 -- The reason is is here is because we don't provide
1191 -- a way to write this literal in Haskell.
1192 nullAddrId = pcMiscPrelId nullAddrName addrPrimTy info
1194 info = noCafIdInfo `setUnfoldingInfo`
1195 mkCompulsoryUnfolding (Lit nullAddrLit)
1197 ------------------------------------------------
1199 -- 'seq' is very special. See notes with
1200 -- See DsUtils.lhs Note [Desugaring seq (1)] and
1201 -- Note [Desugaring seq (2)] and
1202 -- Fixity is set in LoadIface.ghcPrimIface
1203 seqId = pcMiscPrelId seqName ty info
1205 info = noCafIdInfo `setUnfoldingInfo` mkCompulsoryUnfolding rhs
1208 ty = mkForAllTys [alphaTyVar,openBetaTyVar]
1209 (mkFunTy alphaTy (mkFunTy openBetaTy openBetaTy))
1210 [x,y] = mkTemplateLocals [alphaTy, openBetaTy]
1211 rhs = mkLams [alphaTyVar,openBetaTyVar,x,y] (Case (Var x) x openBetaTy [(DEFAULT, [], Var y)])
1213 ------------------------------------------------
1215 -- lazy :: forall a?. a? -> a? (i.e. works for unboxed types too)
1216 -- Used to lazify pseq: pseq a b = a `seq` lazy b
1218 -- Also, no strictness: by being a built-in Id, all the info about lazyId comes from here,
1219 -- not from GHC.Base.hi. This is important, because the strictness
1220 -- analyser will spot it as strict!
1222 -- Also no unfolding in lazyId: it gets "inlined" by a HACK in the worker/wrapperpass
1223 -- (see WorkWrap.wwExpr)
1224 -- We could use inline phases to do this, but that would be vulnerable to changes in
1225 -- phase numbering....we must inline precisely after strictness analysis.
1226 lazyId = pcMiscPrelId lazyIdName ty info
1229 ty = mkForAllTys [alphaTyVar] (mkFunTy alphaTy alphaTy)
1231 lazyIdUnfolding :: CoreExpr -- Used to expand 'lazyId' after strictness anal
1232 lazyIdUnfolding = mkLams [openAlphaTyVar,x] (Var x)
1234 [x] = mkTemplateLocals [openAlphaTy]
1237 @realWorld#@ used to be a magic literal, \tr{void#}. If things get
1238 nasty as-is, change it back to a literal (@Literal@).
1240 voidArgId is a Local Id used simply as an argument in functions
1241 where we just want an arg to avoid having a thunk of unlifted type.
1243 x = \ void :: State# RealWorld -> (# p, q #)
1245 This comes up in strictness analysis
1248 realWorldPrimId -- :: State# RealWorld
1249 = pcMiscPrelId realWorldName realWorldStatePrimTy
1250 (noCafIdInfo `setUnfoldingInfo` evaldUnfolding)
1251 -- The evaldUnfolding makes it look that realWorld# is evaluated
1252 -- which in turn makes Simplify.interestingArg return True,
1253 -- which in turn makes INLINE things applied to realWorld# likely
1257 voidArgId -- :: State# RealWorld
1258 = mkSysLocal (fsLit "void") voidArgIdKey realWorldStatePrimTy
1262 %************************************************************************
1264 \subsection[PrelVals-error-related]{@error@ and friends; @trace@}
1266 %************************************************************************
1268 GHC randomly injects these into the code.
1270 @patError@ is just a version of @error@ for pattern-matching
1271 failures. It knows various ``codes'' which expand to longer
1272 strings---this saves space!
1274 @absentErr@ is a thing we put in for ``absent'' arguments. They jolly
1275 well shouldn't be yanked on, but if one is, then you will get a
1276 friendly message from @absentErr@ (rather than a totally random
1279 @parError@ is a special version of @error@ which the compiler does
1280 not know to be a bottoming Id. It is used in the @_par_@ and @_seq_@
1281 templates, but we don't ever expect to generate code for it.
1285 :: Id -- Should be of type (forall a. Addr# -> a)
1286 -- where Addr# points to a UTF8 encoded string
1287 -> Type -- The type to instantiate 'a'
1288 -> String -- The string to print
1291 mkRuntimeErrorApp err_id res_ty err_msg
1292 = mkApps (Var err_id) [Type res_ty, err_string]
1294 err_string = Lit (mkMachString err_msg)
1296 rEC_SEL_ERROR_ID = mkRuntimeErrorId recSelErrorName
1297 rUNTIME_ERROR_ID = mkRuntimeErrorId runtimeErrorName
1298 iRREFUT_PAT_ERROR_ID = mkRuntimeErrorId irrefutPatErrorName
1299 rEC_CON_ERROR_ID = mkRuntimeErrorId recConErrorName
1300 pAT_ERROR_ID = mkRuntimeErrorId patErrorName
1301 nO_METHOD_BINDING_ERROR_ID = mkRuntimeErrorId noMethodBindingErrorName
1302 nON_EXHAUSTIVE_GUARDS_ERROR_ID = mkRuntimeErrorId nonExhaustiveGuardsErrorName
1304 -- The runtime error Ids take a UTF8-encoded string as argument
1306 mkRuntimeErrorId :: Name -> Id
1307 mkRuntimeErrorId name = pc_bottoming_Id name runtimeErrorTy
1309 runtimeErrorTy :: Type
1310 runtimeErrorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTy addrPrimTy openAlphaTy)
1314 eRROR_ID = pc_bottoming_Id errorName errorTy
1317 errorTy = mkSigmaTy [openAlphaTyVar] [] (mkFunTys [mkListTy charTy] openAlphaTy)
1318 -- Notice the openAlphaTyVar. It says that "error" can be applied
1319 -- to unboxed as well as boxed types. This is OK because it never
1320 -- returns, so the return type is irrelevant.
1324 %************************************************************************
1326 \subsection{Utilities}
1328 %************************************************************************
1331 pcMiscPrelId :: Name -> Type -> IdInfo -> Id
1332 pcMiscPrelId name ty info
1333 = mkVanillaGlobalWithInfo name ty info
1334 -- We lie and say the thing is imported; otherwise, we get into
1335 -- a mess with dependency analysis; e.g., core2stg may heave in
1336 -- random calls to GHCbase.unpackPS__. If GHCbase is the module
1337 -- being compiled, then it's just a matter of luck if the definition
1338 -- will be in "the right place" to be in scope.
1340 pc_bottoming_Id :: Name -> Type -> Id
1341 -- Function of arity 1, which diverges after being given one argument
1342 pc_bottoming_Id name ty
1343 = pcMiscPrelId name ty bottoming_info
1345 bottoming_info = vanillaIdInfo `setAllStrictnessInfo` Just strict_sig
1347 -- Make arity and strictness agree
1349 -- Do *not* mark them as NoCafRefs, because they can indeed have
1350 -- CAF refs. For example, pAT_ERROR_ID calls GHC.Err.untangle,
1351 -- which has some CAFs
1352 -- In due course we may arrange that these error-y things are
1353 -- regarded by the GC as permanently live, in which case we
1354 -- can give them NoCaf info. As it is, any function that calls
1355 -- any pc_bottoming_Id will itself have CafRefs, which bloats
1358 strict_sig = mkStrictSig (mkTopDmdType [evalDmd] BotRes)
1359 -- These "bottom" out, no matter what their arguments