2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1998
5 \section[DataCon]{@DataCon@: Data Constructors}
9 DataCon, DataConIds(..),
12 dataConRepType, dataConSig, dataConFullSig,
13 dataConName, dataConIdentity, dataConTag, dataConTyCon, dataConUserType,
14 dataConUnivTyVars, dataConExTyVars, dataConAllTyVars, dataConResTys,
15 dataConEqSpec, eqSpecPreds, dataConTheta, dataConStupidTheta,
16 dataConInstArgTys, dataConOrigArgTys,
17 dataConInstOrigArgTys, dataConRepArgTys,
18 dataConFieldLabels, dataConFieldType,
19 dataConStrictMarks, dataConExStricts,
20 dataConSourceArity, dataConRepArity,
22 dataConWorkId, dataConWrapId, dataConWrapId_maybe, dataConImplicitIds,
24 isNullarySrcDataCon, isNullaryRepDataCon, isTupleCon, isUnboxedTupleCon,
25 isVanillaDataCon, classDataCon,
27 splitProductType_maybe, splitProductType, deepSplitProductType,
28 deepSplitProductType_maybe
31 #include "HsVersions.h"
49 Data constructor representation
50 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
51 Consider the following Haskell data type declaration
53 data T = T !Int ![Int]
55 Using the strictness annotations, GHC will represent this as
59 That is, the Int has been unboxed. Furthermore, the Haskell source construction
69 That is, the first argument is unboxed, and the second is evaluated. Finally,
70 pattern matching is translated too:
72 case e of { T a b -> ... }
76 case e of { T a' b -> let a = I# a' in ... }
78 To keep ourselves sane, we name the different versions of the data constructor
79 differently, as follows.
82 Note [Data Constructor Naming]
83 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
84 Each data constructor C has two, and possibly three, Names associated with it:
86 OccName Name space Used for
87 ---------------------------------------------------------------------------
88 * The "source data con" C DataName The DataCon itself
89 * The "real data con" C VarName Its worker Id
90 * The "wrapper data con" $WC VarName Wrapper Id (optional)
92 Each of these three has a distinct Unique. The "source data con" name
93 appears in the output of the renamer, and names the Haskell-source
94 data constructor. The type checker translates it into either the wrapper Id
95 (if it exists) or worker Id (otherwise).
97 The data con has one or two Ids associated with it:
99 The "worker Id", is the actual data constructor.
100 * Every data constructor (newtype or data type) has a worker
102 * The worker is very like a primop, in that it has no binding.
104 * For a *data* type, the worker *is* the data constructor;
107 * For a *newtype*, the worker has a compulsory unfolding which
110 The worker for MkT has unfolding
111 \(x:Int). x `cast` sym CoT
112 Here CoT is the type constructor, witnessing the FC axiom
115 The "wrapper Id", $WC, goes as follows
117 * Its type is exactly what it looks like in the source program.
119 * It is an ordinary function, and it gets a top-level binding
120 like any other function.
122 * The wrapper Id isn't generated for a data type if there is
123 nothing for the wrapper to do. That is, if its defn would be
126 Why might the wrapper have anything to do? Two reasons:
128 * Unboxing strict fields (with -funbox-strict-fields)
129 data T = MkT !(Int,Int)
130 $wMkT :: (Int,Int) -> T
131 $wMkT (x,y) = MkT x y
132 Notice that the worker has two fields where the wapper has
133 just one. That is, the worker has type
134 MkT :: Int -> Int -> T
136 * Equality constraints for GADTs
137 data T a where { MkT :: a -> T [a] }
139 The worker gets a type with explicit equality
141 MkT :: forall a b. (a=[b]) => b -> T a
143 The wrapper has the programmer-specified type:
145 $wMkT a x = MkT [a] a [a] x
146 The third argument is a coerion
151 A note about the stupid context
152 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
153 Data types can have a context:
155 data (Eq a, Ord b) => T a b = T1 a b | T2 a
157 and that makes the constructors have a context too
158 (notice that T2's context is "thinned"):
160 T1 :: (Eq a, Ord b) => a -> b -> T a b
161 T2 :: (Eq a) => a -> T a b
163 Furthermore, this context pops up when pattern matching
164 (though GHC hasn't implemented this, but it is in H98, and
165 I've fixed GHC so that it now does):
169 f :: Eq a => T a b -> a
171 I say the context is "stupid" because the dictionaries passed
172 are immediately discarded -- they do nothing and have no benefit.
173 It's a flaw in the language.
175 Up to now [March 2002] I have put this stupid context into the
176 type of the "wrapper" constructors functions, T1 and T2, but
177 that turned out to be jolly inconvenient for generics, and
178 record update, and other functions that build values of type T
179 (because they don't have suitable dictionaries available).
181 So now I've taken the stupid context out. I simply deal with
182 it separately in the type checker on occurrences of a
183 constructor, either in an expression or in a pattern.
185 [May 2003: actually I think this decision could evasily be
186 reversed now, and probably should be. Generics could be
187 disabled for types with a stupid context; record updates now
188 (H98) needs the context too; etc. It's an unforced change, so
189 I'm leaving it for now --- but it does seem odd that the
190 wrapper doesn't include the stupid context.]
192 [July 04] With the advent of generalised data types, it's less obvious
193 what the "stupid context" is. Consider
194 C :: forall a. Ord a => a -> a -> T (Foo a)
195 Does the C constructor in Core contain the Ord dictionary? Yes, it must:
200 C a (d:Ord a) (p:a) (q:a) -> compare d p q
202 Note that (Foo a) might not be an instance of Ord.
204 %************************************************************************
206 \subsection{Data constructors}
208 %************************************************************************
213 dcName :: Name, -- This is the name of the *source data con*
214 -- (see "Note [Data Constructor Naming]" above)
215 dcUnique :: Unique, -- Cached from Name
220 -- *** As declared by the user
222 -- MkT :: forall x y. (Ord x) => x -> y -> T (x,y)
224 -- *** As represented internally
226 -- MkT :: forall a. forall x y. (a:=:(x,y), Ord x) => x -> y -> T a
228 -- The next six fields express the type of the constructor, in pieces
231 -- dcUnivTyVars = [a]
232 -- dcExTyVars = [x,y]
233 -- dcEqSpec = [a:=:(x,y)]
235 -- dcOrigArgTys = [a,List b]
238 dcVanilla :: Bool, -- True <=> This is a vanilla Haskell 98 data constructor
239 -- Its type is of form
240 -- forall a1..an . t1 -> ... tm -> T a1..an
241 -- No existentials, no coercions, nothing.
242 -- That is: dcExTyVars = dcEqSpec = dcTheta = []
243 -- NB 1: newtypes always have a vanilla data con
244 -- NB 2: a vanilla constructor can still be declared in GADT-style
245 -- syntax, provided its type looks like the above.
246 -- The declaration format is held in the TyCon (algTcGadtSyntax)
248 dcUnivTyVars :: [TyVar], -- Universally-quantified type vars
249 dcExTyVars :: [TyVar], -- Existentially-quantified type vars
250 -- In general, the dcUnivTyVars are NOT NECESSARILY THE SAME AS THE TYVARS
251 -- FOR THE PARENT TyCon. With GADTs the data con might not even have
252 -- the same number of type variables.
253 -- [This is a change (Oct05): previously, vanilla datacons guaranteed to
254 -- have the same type variables as their parent TyCon, but that seems ugly.]
256 -- INVARIANT: the UnivTyVars and ExTyVars all have distinct OccNames
257 -- Reason: less confusing, and easier to generate IfaceSyn
259 dcEqSpec :: [(TyVar,Type)], -- Equalities derived from the result type,
260 -- *as written by the programmer*
261 -- This field allows us to move conveniently between the two ways
262 -- of representing a GADT constructor's type:
263 -- MkT :: forall a b. (a :=: [b]) => b -> T a
264 -- MkT :: forall b. b -> T [b]
265 -- Each equality is of the form (a :=: ty), where 'a' is one of
266 -- the universally quantified type variables
268 dcTheta :: ThetaType, -- The context of the constructor
269 -- In GADT form, this is *exactly* what the programmer writes, even if
270 -- the context constrains only universally quantified variables
271 -- MkT :: forall a. Eq a => a -> T a
272 -- It may contain user-written equality predicates too
274 dcStupidTheta :: ThetaType, -- The context of the data type declaration
275 -- data Eq a => T a = ...
276 -- or, rather, a "thinned" version thereof
277 -- "Thinned", because the Report says
278 -- to eliminate any constraints that don't mention
279 -- tyvars free in the arg types for this constructor
281 -- INVARIANT: the free tyvars of dcStupidTheta are a subset of dcUnivTyVars
282 -- Reason: dcStupidTeta is gotten by thinning the stupid theta from the tycon
284 -- "Stupid", because the dictionaries aren't used for anything.
285 -- Indeed, [as of March 02] they are no longer in the type of
286 -- the wrapper Id, because that makes it harder to use the wrap-id
287 -- to rebuild values after record selection or in generics.
289 dcOrigArgTys :: [Type], -- Original argument types
290 -- (before unboxing and flattening of strict fields)
292 -- Result type of constructor is T t1..tn
293 dcTyCon :: TyCon, -- Result tycon, T
295 -- Now the strictness annotations and field labels of the constructor
296 dcStrictMarks :: [StrictnessMark],
297 -- Strictness annotations as decided by the compiler.
298 -- Does *not* include the existential dictionaries
299 -- length = dataConSourceArity dataCon
301 dcFields :: [FieldLabel],
302 -- Field labels for this constructor, in the
303 -- same order as the argument types;
304 -- length = 0 (if not a record) or dataConSourceArity.
306 -- Constructor representation
307 dcRepArgTys :: [Type], -- Final, representation argument types,
308 -- after unboxing and flattening,
309 -- and *including* existential dictionaries
311 dcRepStrictness :: [StrictnessMark], -- One for each *representation* argument
312 -- See also Note [Data-con worker strictness] in MkId.lhs
314 dcRepType :: Type, -- Type of the constructor
315 -- forall a x y. (a:=:(x,y), Ord x) => x -> y -> MkT a
316 -- (this is *not* of the constructor wrapper Id:
317 -- see Note [Data con representation] below)
318 -- Notice that the existential type parameters come *second*.
319 -- Reason: in a case expression we may find:
320 -- case (e :: T t) of { MkT b (d:Ord b) (x:t) (xs:[b]) -> ... }
321 -- It's convenient to apply the rep-type of MkT to 't', to get
322 -- forall b. Ord b => ...
323 -- and use that to check the pattern. Mind you, this is really only
327 -- Finally, the curried worker function that corresponds to the constructor
328 -- It doesn't have an unfolding; the code generator saturates these Ids
329 -- and allocates a real constructor when it finds one.
331 -- An entirely separate wrapper function is built in TcTyDecls
334 dcInfix :: Bool -- True <=> declared infix
335 -- Used for Template Haskell and 'deriving' only
336 -- The actual fixity is stored elsewhere
340 = DCIds (Maybe Id) Id -- Algebraic data types always have a worker, and
341 -- may or may not have a wrapper, depending on whether
342 -- the wrapper does anything. Newtypes just have a worker
344 -- _Neither_ the worker _nor_ the wrapper take the dcStupidTheta dicts as arguments
346 -- The wrapper takes dcOrigArgTys as its arguments
347 -- The worker takes dcRepArgTys as its arguments
348 -- If the worker is absent, dcRepArgTys is the same as dcOrigArgTys
350 -- The 'Nothing' case of DCIds is important
351 -- Not only is this efficient,
352 -- but it also ensures that the wrapper is replaced
353 -- by the worker (becuase it *is* the worker)
354 -- even when there are no args. E.g. in
356 -- the (:) *is* the worker.
357 -- This is really important in rule matching,
358 -- (We could match on the wrappers,
359 -- but that makes it less likely that rules will match
360 -- when we bring bits of unfoldings together.)
365 fIRST_TAG = 1 -- Tags allocated from here for real constructors
368 Note [Data con representation]
369 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
370 The dcRepType field contains the type of the representation of a contructor
371 This may differ from the type of the contructor *Id* (built
372 by MkId.mkDataConId) for two reasons:
373 a) the constructor Id may be overloaded, but the dictionary isn't stored
374 e.g. data Eq a => T a = MkT a a
376 b) the constructor may store an unboxed version of a strict field.
378 Here's an example illustrating both:
379 data Ord a => T a = MkT Int! a
381 T :: Ord a => Int -> a -> T a
383 Trep :: Int# -> a -> T a
384 Actually, the unboxed part isn't implemented yet!
387 %************************************************************************
389 \subsection{Instances}
391 %************************************************************************
394 instance Eq DataCon where
395 a == b = getUnique a == getUnique b
396 a /= b = getUnique a /= getUnique b
398 instance Ord DataCon where
399 a <= b = getUnique a <= getUnique b
400 a < b = getUnique a < getUnique b
401 a >= b = getUnique a >= getUnique b
402 a > b = getUnique a > getUnique b
403 compare a b = getUnique a `compare` getUnique b
405 instance Uniquable DataCon where
408 instance NamedThing DataCon where
411 instance Outputable DataCon where
412 ppr con = ppr (dataConName con)
414 instance Show DataCon where
415 showsPrec p con = showsPrecSDoc p (ppr con)
419 %************************************************************************
421 \subsection{Construction}
423 %************************************************************************
427 -> Bool -- Declared infix
428 -> [StrictnessMark] -> [FieldLabel]
429 -> [TyVar] -> [TyVar]
430 -> [(TyVar,Type)] -> ThetaType
432 -> ThetaType -> DataConIds
434 -- Can get the tag from the TyCon
436 mkDataCon name declared_infix
437 arg_stricts -- Must match orig_arg_tys 1-1
443 -- Warning: mkDataCon is not a good place to check invariants.
444 -- If the programmer writes the wrong result type in the decl, thus:
445 -- data T a where { MkT :: S }
446 -- then it's possible that the univ_tvs may hit an assertion failure
447 -- if you pull on univ_tvs. This case is checked by checkValidDataCon,
448 -- so the error is detected properly... it's just that asaertions here
449 -- are a little dodgy.
451 = ASSERT( not (any isEqPred theta) )
452 -- We don't currently allow any equality predicates on
453 -- a data constructor (apart from the GADT ones in eq_spec)
456 is_vanilla = null ex_tvs && null eq_spec && null theta
457 con = MkData {dcName = name, dcUnique = nameUnique name,
458 dcVanilla = is_vanilla, dcInfix = declared_infix,
459 dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs,
461 dcStupidTheta = stupid_theta, dcTheta = theta,
462 dcOrigArgTys = orig_arg_tys, dcTyCon = tycon,
463 dcRepArgTys = rep_arg_tys,
464 dcStrictMarks = arg_stricts,
465 dcRepStrictness = rep_arg_stricts,
466 dcFields = fields, dcTag = tag, dcRepType = ty,
469 -- Strictness marks for source-args
470 -- *after unboxing choices*,
471 -- but *including existential dictionaries*
473 -- The 'arg_stricts' passed to mkDataCon are simply those for the
474 -- source-language arguments. We add extra ones for the
475 -- dictionary arguments right here.
476 dict_tys = mkPredTys theta
477 real_arg_tys = dict_tys ++ orig_arg_tys
478 real_stricts = map mk_dict_strict_mark theta ++ arg_stricts
480 -- Representation arguments and demands
481 -- To do: eliminate duplication with MkId
482 (rep_arg_stricts, rep_arg_tys) = computeRep real_stricts real_arg_tys
484 tag = assoc "mkDataCon" (tyConDataCons tycon `zip` [fIRST_TAG..]) con
485 ty = mkForAllTys univ_tvs $ mkForAllTys ex_tvs $
486 mkFunTys (mkPredTys (eqSpecPreds eq_spec)) $
487 -- NB: the dict args are already in rep_arg_tys
488 -- because they might be flattened..
489 -- but the equality predicates are not
490 mkFunTys rep_arg_tys $
491 mkTyConApp tycon (mkTyVarTys univ_tvs)
493 eqSpecPreds :: [(TyVar,Type)] -> ThetaType
494 eqSpecPreds spec = [ mkEqPred (mkTyVarTy tv, ty) | (tv,ty) <- spec ]
496 mk_dict_strict_mark pred | isStrictPred pred = MarkedStrict
497 | otherwise = NotMarkedStrict
501 dataConName :: DataCon -> Name
504 -- generate a name in the format: package:Module.OccName
505 -- and the unique identity of the name
506 dataConIdentity :: DataCon -> String
507 dataConIdentity dataCon
510 prettyName = pretty packageModule ++ "." ++ pretty occ
512 packageModule = nameModule nm
513 occ = getOccName dataCon
514 pretty :: Outputable a => a -> String
515 pretty = showSDoc . ppr
517 dataConTag :: DataCon -> ConTag
520 dataConTyCon :: DataCon -> TyCon
521 dataConTyCon = dcTyCon
523 dataConRepType :: DataCon -> Type
524 dataConRepType = dcRepType
526 dataConIsInfix :: DataCon -> Bool
527 dataConIsInfix = dcInfix
529 dataConUnivTyVars :: DataCon -> [TyVar]
530 dataConUnivTyVars = dcUnivTyVars
532 dataConExTyVars :: DataCon -> [TyVar]
533 dataConExTyVars = dcExTyVars
535 dataConAllTyVars :: DataCon -> [TyVar]
536 dataConAllTyVars (MkData { dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs })
539 dataConEqSpec :: DataCon -> [(TyVar,Type)]
540 dataConEqSpec = dcEqSpec
542 dataConTheta :: DataCon -> ThetaType
543 dataConTheta = dcTheta
545 dataConWorkId :: DataCon -> Id
546 dataConWorkId dc = case dcIds dc of
547 DCIds _ wrk_id -> wrk_id
549 dataConWrapId_maybe :: DataCon -> Maybe Id
550 -- Returns Nothing if there is no wrapper for an algebraic data con
551 -- and also for a newtype (whose constructor is inlined compulsorily)
552 dataConWrapId_maybe dc = case dcIds dc of
553 DCIds mb_wrap _ -> mb_wrap
555 dataConWrapId :: DataCon -> Id
556 -- Returns an Id which looks like the Haskell-source constructor
557 dataConWrapId dc = case dcIds dc of
558 DCIds (Just wrap) _ -> wrap
559 DCIds Nothing wrk -> wrk -- worker=wrapper
561 dataConImplicitIds :: DataCon -> [Id]
562 dataConImplicitIds dc = case dcIds dc of
563 DCIds (Just wrap) work -> [wrap,work]
564 DCIds Nothing work -> [work]
566 dataConFieldLabels :: DataCon -> [FieldLabel]
567 dataConFieldLabels = dcFields
569 dataConFieldType :: DataCon -> FieldLabel -> Type
570 dataConFieldType con label = expectJust "unexpected label" $
571 lookup label (dcFields con `zip` dcOrigArgTys con)
573 dataConStrictMarks :: DataCon -> [StrictnessMark]
574 dataConStrictMarks = dcStrictMarks
576 dataConExStricts :: DataCon -> [StrictnessMark]
577 -- Strictness of *existential* arguments only
578 -- Usually empty, so we don't bother to cache this
579 dataConExStricts dc = map mk_dict_strict_mark (dcTheta dc)
581 dataConSourceArity :: DataCon -> Arity
582 -- Source-level arity of the data constructor
583 dataConSourceArity dc = length (dcOrigArgTys dc)
585 -- dataConRepArity gives the number of actual fields in the
586 -- {\em representation} of the data constructor. This may be more than appear
587 -- in the source code; the extra ones are the existentially quantified
589 dataConRepArity (MkData {dcRepArgTys = arg_tys}) = length arg_tys
591 isNullarySrcDataCon, isNullaryRepDataCon :: DataCon -> Bool
592 isNullarySrcDataCon dc = null (dcOrigArgTys dc)
593 isNullaryRepDataCon dc = null (dcRepArgTys dc)
595 dataConRepStrictness :: DataCon -> [StrictnessMark]
596 -- Give the demands on the arguments of a
597 -- Core constructor application (Con dc args)
598 dataConRepStrictness dc = dcRepStrictness dc
600 dataConSig :: DataCon -> ([TyVar], ThetaType, [Type])
601 dataConSig (MkData {dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs, dcEqSpec = eq_spec,
602 dcTheta = theta, dcOrigArgTys = arg_tys, dcTyCon = tycon})
603 = (univ_tvs ++ ex_tvs, eqSpecPreds eq_spec ++ theta, arg_tys)
605 dataConFullSig :: DataCon
606 -> ([TyVar], [TyVar], [(TyVar,Type)], ThetaType, [Type])
607 dataConFullSig (MkData {dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs, dcEqSpec = eq_spec,
608 dcTheta = theta, dcOrigArgTys = arg_tys, dcTyCon = tycon})
609 = (univ_tvs, ex_tvs, eq_spec, theta, arg_tys)
611 dataConStupidTheta :: DataCon -> ThetaType
612 dataConStupidTheta dc = dcStupidTheta dc
614 dataConResTys :: DataCon -> [Type]
615 dataConResTys dc = [substTyVar env tv | tv <- dcUnivTyVars dc]
617 env = mkTopTvSubst (dcEqSpec dc)
619 dataConUserType :: DataCon -> Type
620 -- The user-declared type of the data constructor
621 -- in the nice-to-read form
622 -- T :: forall a. a -> T [a]
624 -- T :: forall b. forall a. (a=[b]) => a -> T b
625 -- NB: If the constructor is part of a data instance, the result type
626 -- mentions the family tycon, not the internal one.
627 dataConUserType (MkData { dcUnivTyVars = univ_tvs,
628 dcExTyVars = ex_tvs, dcEqSpec = eq_spec,
629 dcTheta = theta, dcOrigArgTys = arg_tys,
631 = mkForAllTys ((univ_tvs `minusList` map fst eq_spec) ++ ex_tvs) $
632 mkFunTys (mkPredTys theta) $
634 case tyConFamInst_maybe tycon of
635 Nothing -> mkTyConApp tycon (substTyVars subst univ_tvs)
636 Just (ftc, insttys) -> mkTyConApp ftc insttys -- data instance
638 subst = mkTopTvSubst eq_spec
640 dataConInstArgTys :: DataCon
641 -> [Type] -- Instantiated at these types
642 -- NB: these INCLUDE the existentially quantified arg types
643 -> [Type] -- Needs arguments of these types
644 -- NB: these INCLUDE the existentially quantified dict args
645 -- but EXCLUDE the data-decl context which is discarded
646 -- It's all post-flattening etc; this is a representation type
647 dataConInstArgTys (MkData {dcRepArgTys = arg_tys,
648 dcUnivTyVars = univ_tvs,
649 dcExTyVars = ex_tvs}) inst_tys
650 = ASSERT( length tyvars == length inst_tys )
651 map (substTyWith tyvars inst_tys) arg_tys
653 tyvars = univ_tvs ++ ex_tvs
656 -- And the same deal for the original arg tys
657 dataConInstOrigArgTys :: DataCon -> [Type] -> [Type]
658 dataConInstOrigArgTys dc@(MkData {dcOrigArgTys = arg_tys,
659 dcUnivTyVars = univ_tvs,
660 dcExTyVars = ex_tvs}) inst_tys
661 = ASSERT2( length tyvars == length inst_tys, ptext SLIT("dataConInstOrigArgTys") <+> ppr dc <+> ppr inst_tys )
662 map (substTyWith tyvars inst_tys) arg_tys
664 tyvars = univ_tvs ++ ex_tvs
667 These two functions get the real argument types of the constructor,
668 without substituting for any type variables.
670 dataConOrigArgTys returns the arg types of the wrapper, excluding all dictionary args.
672 dataConRepArgTys retuns the arg types of the worker, including all dictionaries, and
673 after any flattening has been done.
676 dataConOrigArgTys :: DataCon -> [Type]
677 dataConOrigArgTys dc = dcOrigArgTys dc
679 dataConRepArgTys :: DataCon -> [Type]
680 dataConRepArgTys dc = dcRepArgTys dc
685 isTupleCon :: DataCon -> Bool
686 isTupleCon (MkData {dcTyCon = tc}) = isTupleTyCon tc
688 isUnboxedTupleCon :: DataCon -> Bool
689 isUnboxedTupleCon (MkData {dcTyCon = tc}) = isUnboxedTupleTyCon tc
691 isVanillaDataCon :: DataCon -> Bool
692 isVanillaDataCon dc = dcVanilla dc
697 classDataCon :: Class -> DataCon
698 classDataCon clas = case tyConDataCons (classTyCon clas) of
699 (dict_constr:no_more) -> ASSERT( null no_more ) dict_constr
702 %************************************************************************
704 \subsection{Splitting products}
706 %************************************************************************
709 splitProductType_maybe
710 :: Type -- A product type, perhaps
711 -> Maybe (TyCon, -- The type constructor
712 [Type], -- Type args of the tycon
713 DataCon, -- The data constructor
714 [Type]) -- Its *representation* arg types
716 -- Returns (Just ...) for any
717 -- concrete (i.e. constructors visible)
718 -- single-constructor
719 -- not existentially quantified
720 -- type whether a data type or a new type
722 -- Rejecing existentials is conservative. Maybe some things
723 -- could be made to work with them, but I'm not going to sweat
724 -- it through till someone finds it's important.
726 splitProductType_maybe ty
727 = case splitTyConApp_maybe ty of
729 | isProductTyCon tycon -- Includes check for non-existential,
730 -- and for constructors visible
731 -> Just (tycon, ty_args, data_con, dataConInstArgTys data_con ty_args)
733 data_con = head (tyConDataCons tycon)
736 splitProductType str ty
737 = case splitProductType_maybe ty of
739 Nothing -> pprPanic (str ++ ": not a product") (pprType ty)
742 deepSplitProductType_maybe ty
743 = do { (res@(tycon, tycon_args, _, _)) <- splitProductType_maybe ty
745 | isClosedNewTyCon tycon && not (isRecursiveTyCon tycon)
746 = deepSplitProductType_maybe (newTyConInstRhs tycon tycon_args)
747 | isNewTyCon tycon = Nothing -- cannot unbox through recursive
748 -- newtypes nor through families
749 | otherwise = Just res}
753 deepSplitProductType str ty
754 = case deepSplitProductType_maybe ty of
756 Nothing -> pprPanic (str ++ ": not a product") (pprType ty)
758 computeRep :: [StrictnessMark] -- Original arg strictness
759 -> [Type] -- and types
760 -> ([StrictnessMark], -- Representation arg strictness
763 computeRep stricts tys
764 = unzip $ concat $ zipWithEqual "computeRep" unbox stricts tys
766 unbox NotMarkedStrict ty = [(NotMarkedStrict, ty)]
767 unbox MarkedStrict ty = [(MarkedStrict, ty)]
768 unbox MarkedUnboxed ty = zipEqual "computeRep" (dataConRepStrictness arg_dc) arg_tys
770 (_tycon, _tycon_args, arg_dc, arg_tys)
771 = deepSplitProductType "unbox_strict_arg_ty" ty