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,
15 dataConEqSpec, eqSpecPreds, dataConTheta, dataConStupidTheta,
16 dataConInstArgTys, dataConOrigArgTys, dataConOrigResTy,
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)
291 dcOrigResTy :: Type, -- Original result type
292 -- NB: for a data instance, the original user result type may
293 -- differ from the DataCon's representation TyCon. Example
294 -- data instance T [a] where MkT :: a -> T [a]
295 -- The OrigResTy is T [a], but the dcRepTyCon might be :T123
297 -- Now the strictness annotations and field labels of the constructor
298 dcStrictMarks :: [StrictnessMark],
299 -- Strictness annotations as decided by the compiler.
300 -- Does *not* include the existential dictionaries
301 -- length = dataConSourceArity dataCon
303 dcFields :: [FieldLabel],
304 -- Field labels for this constructor, in the
305 -- same order as the dcOrigArgTys;
306 -- length = 0 (if not a record) or dataConSourceArity.
308 -- Constructor representation
309 dcRepArgTys :: [Type], -- Final, representation argument types,
310 -- after unboxing and flattening,
311 -- and *including* existential dictionaries
313 dcRepStrictness :: [StrictnessMark], -- One for each *representation* argument
314 -- See also Note [Data-con worker strictness] in MkId.lhs
316 -- Result type of constructor is T t1..tn
317 dcRepTyCon :: TyCon, -- Result tycon, T
319 dcRepType :: Type, -- Type of the constructor
320 -- forall a x y. (a:=:(x,y), Ord x) => x -> y -> MkT a
321 -- (this is *not* of the constructor wrapper Id:
322 -- see Note [Data con representation] below)
323 -- Notice that the existential type parameters come *second*.
324 -- Reason: in a case expression we may find:
325 -- case (e :: T t) of { MkT b (d:Ord b) (x:t) (xs:[b]) -> ... }
326 -- It's convenient to apply the rep-type of MkT to 't', to get
327 -- forall b. Ord b => ...
328 -- and use that to check the pattern. Mind you, this is really only
332 -- Finally, the curried worker function that corresponds to the constructor
333 -- It doesn't have an unfolding; the code generator saturates these Ids
334 -- and allocates a real constructor when it finds one.
336 -- An entirely separate wrapper function is built in TcTyDecls
339 dcInfix :: Bool -- True <=> declared infix
340 -- Used for Template Haskell and 'deriving' only
341 -- The actual fixity is stored elsewhere
345 = DCIds (Maybe Id) Id -- Algebraic data types always have a worker, and
346 -- may or may not have a wrapper, depending on whether
347 -- the wrapper does anything. Newtypes just have a worker
349 -- _Neither_ the worker _nor_ the wrapper take the dcStupidTheta dicts as arguments
351 -- The wrapper takes dcOrigArgTys as its arguments
352 -- The worker takes dcRepArgTys as its arguments
353 -- If the worker is absent, dcRepArgTys is the same as dcOrigArgTys
355 -- The 'Nothing' case of DCIds is important
356 -- Not only is this efficient,
357 -- but it also ensures that the wrapper is replaced
358 -- by the worker (becuase it *is* the worker)
359 -- even when there are no args. E.g. in
361 -- the (:) *is* the worker.
362 -- This is really important in rule matching,
363 -- (We could match on the wrappers,
364 -- but that makes it less likely that rules will match
365 -- when we bring bits of unfoldings together.)
370 fIRST_TAG = 1 -- Tags allocated from here for real constructors
373 Note [Data con representation]
374 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
375 The dcRepType field contains the type of the representation of a contructor
376 This may differ from the type of the contructor *Id* (built
377 by MkId.mkDataConId) for two reasons:
378 a) the constructor Id may be overloaded, but the dictionary isn't stored
379 e.g. data Eq a => T a = MkT a a
381 b) the constructor may store an unboxed version of a strict field.
383 Here's an example illustrating both:
384 data Ord a => T a = MkT Int! a
386 T :: Ord a => Int -> a -> T a
388 Trep :: Int# -> a -> T a
389 Actually, the unboxed part isn't implemented yet!
392 %************************************************************************
394 \subsection{Instances}
396 %************************************************************************
399 instance Eq DataCon where
400 a == b = getUnique a == getUnique b
401 a /= b = getUnique a /= getUnique b
403 instance Ord DataCon where
404 a <= b = getUnique a <= getUnique b
405 a < b = getUnique a < getUnique b
406 a >= b = getUnique a >= getUnique b
407 a > b = getUnique a > getUnique b
408 compare a b = getUnique a `compare` getUnique b
410 instance Uniquable DataCon where
413 instance NamedThing DataCon where
416 instance Outputable DataCon where
417 ppr con = ppr (dataConName con)
419 instance Show DataCon where
420 showsPrec p con = showsPrecSDoc p (ppr con)
424 %************************************************************************
426 \subsection{Construction}
428 %************************************************************************
432 -> Bool -- Declared infix
433 -> [StrictnessMark] -> [FieldLabel]
434 -> [TyVar] -> [TyVar]
435 -> [(TyVar,Type)] -> ThetaType
437 -> ThetaType -> DataConIds
439 -- Can get the tag from the TyCon
441 mkDataCon name declared_infix
442 arg_stricts -- Must match orig_arg_tys 1-1
448 -- Warning: mkDataCon is not a good place to check invariants.
449 -- If the programmer writes the wrong result type in the decl, thus:
450 -- data T a where { MkT :: S }
451 -- then it's possible that the univ_tvs may hit an assertion failure
452 -- if you pull on univ_tvs. This case is checked by checkValidDataCon,
453 -- so the error is detected properly... it's just that asaertions here
454 -- are a little dodgy.
456 = ASSERT( not (any isEqPred theta) )
457 -- We don't currently allow any equality predicates on
458 -- a data constructor (apart from the GADT ones in eq_spec)
461 is_vanilla = null ex_tvs && null eq_spec && null theta
462 con = MkData {dcName = name, dcUnique = nameUnique name,
463 dcVanilla = is_vanilla, dcInfix = declared_infix,
464 dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs,
466 dcStupidTheta = stupid_theta, dcTheta = theta,
467 dcOrigArgTys = orig_arg_tys, dcOrigResTy = orig_res_ty,
469 dcRepArgTys = rep_arg_tys,
470 dcStrictMarks = arg_stricts,
471 dcRepStrictness = rep_arg_stricts,
472 dcFields = fields, dcTag = tag, dcRepType = ty,
475 -- Strictness marks for source-args
476 -- *after unboxing choices*,
477 -- but *including existential dictionaries*
479 -- The 'arg_stricts' passed to mkDataCon are simply those for the
480 -- source-language arguments. We add extra ones for the
481 -- dictionary arguments right here.
482 dict_tys = mkPredTys theta
483 real_arg_tys = dict_tys ++ orig_arg_tys
484 real_stricts = map mk_dict_strict_mark theta ++ arg_stricts
487 -- data instance T [a] where
488 -- TI :: forall b. b -> T [Maybe b]
489 -- The representation tycon looks like this:
491 -- TI :: forall b c. (c :=: Maybe b) b -> :R7T c
493 | Just (fam_tc, fam_tys) <- tyConFamInst_maybe tycon
494 , let fam_subst = zipTopTvSubst (tyConTyVars fam_tc) res_tys
495 = mkTyConApp fam_tc (substTys fam_subst fam_tys)
497 = mkTyConApp tycon res_tys
499 res_tys = substTyVars (mkTopTvSubst eq_spec) univ_tvs
500 -- In the example above, res_tys is a singleton, (Maybe b)
502 -- Representation arguments and demands
503 -- To do: eliminate duplication with MkId
504 (rep_arg_stricts, rep_arg_tys) = computeRep real_stricts real_arg_tys
506 tag = assoc "mkDataCon" (tyConDataCons tycon `zip` [fIRST_TAG..]) con
507 ty = mkForAllTys univ_tvs $ mkForAllTys ex_tvs $
508 mkFunTys (mkPredTys (eqSpecPreds eq_spec)) $
509 -- NB: the dict args are already in rep_arg_tys
510 -- because they might be flattened..
511 -- but the equality predicates are not
512 mkFunTys rep_arg_tys $
513 mkTyConApp tycon (mkTyVarTys univ_tvs)
515 eqSpecPreds :: [(TyVar,Type)] -> ThetaType
516 eqSpecPreds spec = [ mkEqPred (mkTyVarTy tv, ty) | (tv,ty) <- spec ]
518 mk_dict_strict_mark pred | isStrictPred pred = MarkedStrict
519 | otherwise = NotMarkedStrict
523 dataConName :: DataCon -> Name
526 -- generate a name in the format: package:Module.OccName
527 -- and the unique identity of the name
528 dataConIdentity :: DataCon -> String
529 dataConIdentity dataCon
532 prettyName = pretty packageModule ++ "." ++ pretty occ
534 packageModule = nameModule nm
535 occ = getOccName dataCon
536 pretty :: Outputable a => a -> String
537 pretty = showSDoc . ppr
539 dataConTag :: DataCon -> ConTag
542 dataConTyCon :: DataCon -> TyCon
543 dataConTyCon = dcRepTyCon
545 dataConRepType :: DataCon -> Type
546 dataConRepType = dcRepType
548 dataConIsInfix :: DataCon -> Bool
549 dataConIsInfix = dcInfix
551 dataConUnivTyVars :: DataCon -> [TyVar]
552 dataConUnivTyVars = dcUnivTyVars
554 dataConExTyVars :: DataCon -> [TyVar]
555 dataConExTyVars = dcExTyVars
557 dataConAllTyVars :: DataCon -> [TyVar]
558 dataConAllTyVars (MkData { dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs })
561 dataConEqSpec :: DataCon -> [(TyVar,Type)]
562 dataConEqSpec = dcEqSpec
564 dataConTheta :: DataCon -> ThetaType
565 dataConTheta = dcTheta
567 dataConWorkId :: DataCon -> Id
568 dataConWorkId dc = case dcIds dc of
569 DCIds _ wrk_id -> wrk_id
571 dataConWrapId_maybe :: DataCon -> Maybe Id
572 -- Returns Nothing if there is no wrapper for an algebraic data con
573 -- and also for a newtype (whose constructor is inlined compulsorily)
574 dataConWrapId_maybe dc = case dcIds dc of
575 DCIds mb_wrap _ -> mb_wrap
577 dataConWrapId :: DataCon -> Id
578 -- Returns an Id which looks like the Haskell-source constructor
579 dataConWrapId dc = case dcIds dc of
580 DCIds (Just wrap) _ -> wrap
581 DCIds Nothing wrk -> wrk -- worker=wrapper
583 dataConImplicitIds :: DataCon -> [Id]
584 dataConImplicitIds dc = case dcIds dc of
585 DCIds (Just wrap) work -> [wrap,work]
586 DCIds Nothing work -> [work]
588 dataConFieldLabels :: DataCon -> [FieldLabel]
589 dataConFieldLabels = dcFields
591 dataConFieldType :: DataCon -> FieldLabel -> Type
592 dataConFieldType con label = expectJust "unexpected label" $
593 lookup label (dcFields con `zip` dcOrigArgTys con)
595 dataConStrictMarks :: DataCon -> [StrictnessMark]
596 dataConStrictMarks = dcStrictMarks
598 dataConExStricts :: DataCon -> [StrictnessMark]
599 -- Strictness of *existential* arguments only
600 -- Usually empty, so we don't bother to cache this
601 dataConExStricts dc = map mk_dict_strict_mark (dcTheta dc)
603 dataConSourceArity :: DataCon -> Arity
604 -- Source-level arity of the data constructor
605 dataConSourceArity dc = length (dcOrigArgTys dc)
607 -- dataConRepArity gives the number of actual fields in the
608 -- {\em representation} of the data constructor. This may be more than appear
609 -- in the source code; the extra ones are the existentially quantified
611 dataConRepArity (MkData {dcRepArgTys = arg_tys}) = length arg_tys
613 isNullarySrcDataCon, isNullaryRepDataCon :: DataCon -> Bool
614 isNullarySrcDataCon dc = null (dcOrigArgTys dc)
615 isNullaryRepDataCon dc = null (dcRepArgTys dc)
617 dataConRepStrictness :: DataCon -> [StrictnessMark]
618 -- Give the demands on the arguments of a
619 -- Core constructor application (Con dc args)
620 dataConRepStrictness dc = dcRepStrictness dc
622 dataConSig :: DataCon -> ([TyVar], ThetaType, [Type], Type)
623 dataConSig (MkData {dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs, dcEqSpec = eq_spec,
624 dcTheta = theta, dcOrigArgTys = arg_tys, dcOrigResTy = res_ty})
625 = (univ_tvs ++ ex_tvs, eqSpecPreds eq_spec ++ theta, arg_tys, res_ty)
627 dataConFullSig :: DataCon
628 -> ([TyVar], [TyVar], [(TyVar,Type)], ThetaType, [Type], Type)
629 dataConFullSig (MkData {dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs, dcEqSpec = eq_spec,
630 dcTheta = theta, dcOrigArgTys = arg_tys, dcOrigResTy = res_ty})
631 = (univ_tvs, ex_tvs, eq_spec, theta, arg_tys, res_ty)
633 dataConOrigResTy :: DataCon -> Type
634 dataConOrigResTy dc = dcOrigResTy dc
636 dataConStupidTheta :: DataCon -> ThetaType
637 dataConStupidTheta dc = dcStupidTheta dc
639 dataConUserType :: DataCon -> Type
640 -- The user-declared type of the data constructor
641 -- in the nice-to-read form
642 -- T :: forall a. a -> T [a]
644 -- T :: forall b. forall a. (a=[b]) => a -> T b
645 -- NB: If the constructor is part of a data instance, the result type
646 -- mentions the family tycon, not the internal one.
647 dataConUserType (MkData { dcUnivTyVars = univ_tvs,
648 dcExTyVars = ex_tvs, dcEqSpec = eq_spec,
649 dcTheta = theta, dcOrigArgTys = arg_tys,
650 dcOrigResTy = res_ty })
651 = mkForAllTys ((univ_tvs `minusList` map fst eq_spec) ++ ex_tvs) $
652 mkFunTys (mkPredTys theta) $
656 dataConInstArgTys :: DataCon
657 -> [Type] -- Instantiated at these types
658 -- NB: these INCLUDE the existentially quantified arg types
659 -> [Type] -- Needs arguments of these types
660 -- NB: these INCLUDE the existentially quantified dict args
661 -- but EXCLUDE the data-decl context which is discarded
662 -- It's all post-flattening etc; this is a representation type
663 dataConInstArgTys dc@(MkData {dcRepArgTys = arg_tys,
664 dcUnivTyVars = univ_tvs,
665 dcExTyVars = ex_tvs}) inst_tys
666 = ASSERT2 ( length tyvars == length inst_tys
667 , ptext SLIT("dataConInstArgTys") <+> ppr dc $$ ppr tyvars $$ ppr inst_tys)
669 map (substTyWith tyvars inst_tys) arg_tys
671 tyvars = univ_tvs ++ ex_tvs
674 -- And the same deal for the original arg tys
675 dataConInstOrigArgTys :: DataCon -> [Type] -> [Type]
676 dataConInstOrigArgTys dc@(MkData {dcOrigArgTys = arg_tys,
677 dcUnivTyVars = univ_tvs,
678 dcExTyVars = ex_tvs}) inst_tys
679 = ASSERT2( length tyvars == length inst_tys
680 , ptext SLIT("dataConInstOrigArgTys") <+> ppr dc $$ ppr tyvars $$ ppr inst_tys )
681 map (substTyWith tyvars inst_tys) arg_tys
683 tyvars = univ_tvs ++ ex_tvs
686 These two functions get the real argument types of the constructor,
687 without substituting for any type variables.
689 dataConOrigArgTys returns the arg types of the wrapper, excluding all dictionary args.
691 dataConRepArgTys retuns the arg types of the worker, including all dictionaries, and
692 after any flattening has been done.
695 dataConOrigArgTys :: DataCon -> [Type]
696 dataConOrigArgTys dc = dcOrigArgTys dc
698 dataConRepArgTys :: DataCon -> [Type]
699 dataConRepArgTys dc = dcRepArgTys dc
704 isTupleCon :: DataCon -> Bool
705 isTupleCon (MkData {dcRepTyCon = tc}) = isTupleTyCon tc
707 isUnboxedTupleCon :: DataCon -> Bool
708 isUnboxedTupleCon (MkData {dcRepTyCon = tc}) = isUnboxedTupleTyCon tc
710 isVanillaDataCon :: DataCon -> Bool
711 isVanillaDataCon dc = dcVanilla dc
716 classDataCon :: Class -> DataCon
717 classDataCon clas = case tyConDataCons (classTyCon clas) of
718 (dict_constr:no_more) -> ASSERT( null no_more ) dict_constr
719 [] -> panic "classDataCon"
722 %************************************************************************
724 \subsection{Splitting products}
726 %************************************************************************
729 splitProductType_maybe
730 :: Type -- A product type, perhaps
731 -> Maybe (TyCon, -- The type constructor
732 [Type], -- Type args of the tycon
733 DataCon, -- The data constructor
734 [Type]) -- Its *representation* arg types
736 -- Returns (Just ...) for any
737 -- concrete (i.e. constructors visible)
738 -- single-constructor
739 -- not existentially quantified
740 -- type whether a data type or a new type
742 -- Rejecing existentials is conservative. Maybe some things
743 -- could be made to work with them, but I'm not going to sweat
744 -- it through till someone finds it's important.
746 splitProductType_maybe ty
747 = case splitTyConApp_maybe ty of
749 | isProductTyCon tycon -- Includes check for non-existential,
750 -- and for constructors visible
751 -> Just (tycon, ty_args, data_con, dataConInstArgTys data_con ty_args)
753 data_con = head (tyConDataCons tycon)
756 splitProductType str ty
757 = case splitProductType_maybe ty of
759 Nothing -> pprPanic (str ++ ": not a product") (pprType ty)
762 deepSplitProductType_maybe ty
763 = do { (res@(tycon, tycon_args, _, _)) <- splitProductType_maybe ty
765 | isClosedNewTyCon tycon && not (isRecursiveTyCon tycon)
766 = deepSplitProductType_maybe (newTyConInstRhs tycon tycon_args)
767 | isNewTyCon tycon = Nothing -- cannot unbox through recursive
768 -- newtypes nor through families
769 | otherwise = Just res}
773 deepSplitProductType str ty
774 = case deepSplitProductType_maybe ty of
776 Nothing -> pprPanic (str ++ ": not a product") (pprType ty)
778 computeRep :: [StrictnessMark] -- Original arg strictness
779 -> [Type] -- and types
780 -> ([StrictnessMark], -- Representation arg strictness
783 computeRep stricts tys
784 = unzip $ concat $ zipWithEqual "computeRep" unbox stricts tys
786 unbox NotMarkedStrict ty = [(NotMarkedStrict, ty)]
787 unbox MarkedStrict ty = [(MarkedStrict, ty)]
788 unbox MarkedUnboxed ty = zipEqual "computeRep" (dataConRepStrictness arg_dc) arg_tys
790 (_tycon, _tycon_args, arg_dc, arg_tys)
791 = deepSplitProductType "unbox_strict_arg_ty" ty