2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[Inst]{The @Inst@ type: dictionaries or method instances}
8 LIE, emptyLIE, unitLIE, plusLIE, consLIE, zonkLIE,
9 plusLIEs, mkLIE, isEmptyLIE, lieToList, listToLIE,
11 Inst, OverloadedLit(..),
12 pprInst, pprInsts, pprInstsInFull, tidyInst, tidyInsts,
16 newDictFromOld, newDicts, newClassDicts, newDictsAtLoc,
17 newMethod, newMethodWithGivenTy, newOverloadedLit,
18 newIPDict, instOverloadedFun,
20 tyVarsOfInst, tyVarsOfInsts, tyVarsOfLIE, instLoc, getDictClassTys,
21 getFunDeps, getFunDepsOfLIE,
23 getAllFunDeps, getAllFunDepsOfLIE,
26 lookupInst, lookupSimpleInst, LookupInstResult(..),
28 isDict, isClassDict, isTyVarDict, isStdClassTyVarDict, isMethodFor, notFunDep,
29 instBindingRequired, instCanBeGeneralised,
31 zonkInst, zonkInsts, zonkFunDeps, zonkTvFunDeps,
32 instToId, instToIdBndr, ipToId,
34 InstOrigin(..), InstLoc, pprInstLoc
37 #include "HsVersions.h"
39 import HsSyn ( HsLit(..), HsExpr(..) )
40 import RnHsSyn ( RenamedArithSeqInfo, RenamedHsExpr, RenamedPat )
41 import TcHsSyn ( TcExpr, TcId,
42 mkHsTyApp, mkHsDictApp, zonkId
45 import TcEnv ( TcIdSet, tcLookupValueByKey, tcLookupTyConByKey )
46 import TcType ( TcThetaType,
47 TcType, TcTauType, TcTyVarSet,
48 zonkTcTyVars, zonkTcType, zonkTcTypes,
52 import Class ( classInstEnv, Class )
53 import FunDeps ( instantiateFdClassTys )
54 import Id ( Id, idFreeTyVars, idType, mkUserLocal, mkSysLocal )
55 import PrelInfo ( isStandardClass, isCcallishClass, isNoDictClass )
56 import Name ( OccName, Name, mkDictOcc, mkMethodOcc, mkIPOcc,
57 getOccName, nameUnique )
58 import PprType ( pprPred )
59 import InstEnv ( InstEnv, lookupInstEnv )
60 import SrcLoc ( SrcLoc )
61 import Type ( Type, PredType(..), ThetaType,
62 mkTyVarTy, isTyVarTy, mkDictTy, mkPredTy,
63 splitForAllTys, splitSigmaTy,
64 splitRhoTy, tyVarsOfType, tyVarsOfTypes, tyVarsOfPred,
65 mkSynTy, tidyOpenType, tidyOpenTypes
67 import InstEnv ( InstEnv )
68 import Subst ( emptyInScopeSet, mkSubst,
69 substTy, substClasses, mkTyVarSubst, mkTopTyVarSubst
71 import TyCon ( TyCon )
73 import VarEnv ( lookupVarEnv, TidyEnv,
74 lookupSubstEnv, SubstResult(..)
76 import VarSet ( elemVarSet, emptyVarSet, unionVarSet )
77 import TysPrim ( intPrimTy, floatPrimTy, doublePrimTy )
78 import TysWiredIn ( intDataCon, isIntTy, inIntRange,
79 floatDataCon, isFloatTy,
80 doubleDataCon, isDoubleTy,
81 integerTy, isIntegerTy
83 import Unique ( fromRationalClassOpKey, rationalTyConKey,
84 fromIntClassOpKey, fromIntegerClassOpKey, Unique
86 import Maybes ( expectJust )
87 import List ( partition )
88 import Maybe ( catMaybes )
89 import Util ( thenCmp, zipWithEqual, mapAccumL )
93 %************************************************************************
95 \subsection[Inst-collections]{LIE: a collection of Insts}
97 %************************************************************************
102 isEmptyLIE = isEmptyBag
104 unitLIE inst = unitBag inst
105 mkLIE insts = listToBag insts
106 plusLIE lie1 lie2 = lie1 `unionBags` lie2
107 consLIE inst lie = inst `consBag` lie
108 plusLIEs lies = unionManyBags lies
109 lieToList = bagToList
110 listToLIE = listToBag
112 zonkLIE :: LIE -> NF_TcM s LIE
113 zonkLIE lie = mapBagNF_Tc zonkInst lie
115 pprInsts :: [Inst] -> SDoc
116 pprInsts insts = parens (sep (punctuate comma (map pprInst insts)))
120 = vcat (map go insts)
122 go inst = quotes (ppr inst) <+> pprInstLoc (instLoc inst)
125 %************************************************************************
127 \subsection[Inst-types]{@Inst@ types}
129 %************************************************************************
131 An @Inst@ is either a dictionary, an instance of an overloaded
132 literal, or an instance of an overloaded value. We call the latter a
133 ``method'' even though it may not correspond to a class operation.
134 For example, we might have an instance of the @double@ function at
135 type Int, represented by
137 Method 34 doubleId [Int] origin
149 TcId -- The overloaded function
150 -- This function will be a global, local, or ClassOpId;
151 -- inside instance decls (only) it can also be an InstId!
152 -- The id needn't be completely polymorphic.
153 -- You'll probably find its name (for documentation purposes)
154 -- inside the InstOrigin
156 [TcType] -- The types to which its polymorphic tyvars
157 -- should be instantiated.
158 -- These types must saturate the Id's foralls.
160 TcThetaType -- The (types of the) dictionaries to which the function
161 -- must be applied to get the method
163 TcTauType -- The type of the method
167 -- INVARIANT: in (Method u f tys theta tau loc)
168 -- type of (f tys dicts(from theta)) = tau
173 TcType -- The type at which the literal is used
177 Class -- the class from which this arises
178 [([TcType], [TcType])]
182 = OverloadedIntegral Integer -- The number
183 | OverloadedFractional Rational -- The number
188 @Insts@ are ordered by their class/type info, rather than by their
189 unique. This allows the context-reduction mechanism to use standard finite
190 maps to do their stuff.
193 instance Ord Inst where
195 instance Ord PredType where
198 instance Eq Inst where
199 (==) i1 i2 = case i1 `cmpInst` i2 of
202 instance Eq PredType where
203 (==) p1 p2 = case p1 `cmpPred` p2 of
207 cmpInst (Dict _ pred1 _) (Dict _ pred2 _)
208 = (pred1 `cmpPred` pred2)
209 cmpInst (Dict _ _ _) other
212 cmpInst (Method _ _ _ _ _ _) (Dict _ _ _)
214 cmpInst (Method _ id1 tys1 _ _ _) (Method _ id2 tys2 _ _ _)
215 = (id1 `compare` id2) `thenCmp` (tys1 `compare` tys2)
216 cmpInst (Method _ _ _ _ _ _) other
219 cmpInst (LitInst _ lit1 ty1 _) (LitInst _ lit2 ty2 _)
220 = (lit1 `cmpOverLit` lit2) `thenCmp` (ty1 `compare` ty2)
221 cmpInst (LitInst _ _ _ _) (FunDep _ _ _)
223 cmpInst (LitInst _ _ _ _) other
226 cmpInst (FunDep clas1 fds1 _) (FunDep clas2 fds2 _)
227 = (clas1 `compare` clas2) `thenCmp` (fds1 `compare` fds2)
228 cmpInst (FunDep _ _ _) other
231 cmpPred (Class c1 tys1) (Class c2 tys2)
232 = (c1 `compare` c2) `thenCmp` (tys1 `compare` tys2)
233 cmpPred (IParam n1 ty1) (IParam n2 ty2)
234 = (n1 `compare` n2) `thenCmp` (ty1 `compare` ty2)
235 cmpPred (Class _ _) (IParam _ _) = LT
238 cmpOverLit (OverloadedIntegral i1) (OverloadedIntegral i2) = i1 `compare` i2
239 cmpOverLit (OverloadedFractional f1) (OverloadedFractional f2) = f1 `compare` f2
240 cmpOverLit (OverloadedIntegral _) (OverloadedFractional _) = LT
241 cmpOverLit (OverloadedFractional _) (OverloadedIntegral _) = GT
248 instLoc (Dict u pred loc) = loc
249 instLoc (Method u _ _ _ _ loc) = loc
250 instLoc (LitInst u lit ty loc) = loc
251 instLoc (FunDep _ _ loc) = loc
253 getDictClassTys (Dict u (Class clas tys) _) = (clas, tys)
255 getFunDeps (FunDep clas fds _) = Just (clas, fds)
256 getFunDeps _ = Nothing
258 getFunDepsOfLIE lie = catMaybes (map getFunDeps (lieToList lie))
260 getIPsOfPred (IParam n ty) = [(n, ty)]
262 getIPsOfTheta theta = concatMap getIPsOfPred theta
264 getIPs (Dict u (IParam n ty) loc) = [(n, ty)]
265 getIPs (Method u id _ theta t loc) = getIPsOfTheta theta
268 getIPsOfLIE lie = concatMap getIPs (lieToList lie)
270 getAllFunDeps (FunDep clas fds _) = fds
271 getAllFunDeps inst = map (\(n,ty) -> ([], [ty])) (getIPs inst)
273 getAllFunDepsOfLIE lie = concat (map getAllFunDeps (lieToList lie))
275 partitionLIEbyMeth pred lie
276 = foldlTc (partMethod pred) (emptyLIE, emptyLIE) insts
277 where insts = lieToList lie
279 partMethod pred (ips, lie) m@(Method u id tys theta tau loc)
281 returnTc (ips, consLIE m lie)
282 else if null theta_ then
283 returnTc (consLIE m ips, lie)
285 newMethodWith id tys theta_ tau loc `thenTc` \ new_m2 ->
286 let id_m1 = instToIdBndr new_m2
287 new_m1 = Method u id_m1 {- tys -} [] ips_ tau loc in
288 -- newMethodWith id_m1 tys ips_ tau loc `thenTc` \ new_m1 ->
289 returnTc (consLIE new_m1 ips, consLIE new_m2 lie)
290 where (ips_, theta_) = partition pred theta
292 tyVarsOfInst :: Inst -> TcTyVarSet
293 tyVarsOfInst (Dict _ pred _) = tyVarsOfPred pred
294 tyVarsOfInst (Method _ id tys _ _ _) = tyVarsOfTypes tys `unionVarSet` idFreeTyVars id
295 -- The id might have free type variables; in the case of
296 -- locally-overloaded class methods, for example
297 tyVarsOfInst (LitInst _ _ ty _) = tyVarsOfType ty
298 tyVarsOfInst (FunDep _ fds _)
299 = foldr unionVarSet emptyVarSet (map tyVarsOfFd fds)
300 where tyVarsOfFd (ts1, ts2) =
301 tyVarsOfTypes ts1 `unionVarSet` tyVarsOfTypes ts2
304 = foldr unionVarSet emptyVarSet (map tyVarsOfInst insts)
307 = foldr unionVarSet emptyVarSet (map tyVarsOfInst insts)
308 where insts = lieToList lie
314 isDict :: Inst -> Bool
315 isDict (Dict _ _ _) = True
317 isClassDict :: Inst -> Bool
318 isClassDict (Dict _ (Class _ _) _) = True
319 isClassDict other = False
321 isMethodFor :: TcIdSet -> Inst -> Bool
322 isMethodFor ids (Method uniq id tys _ _ loc)
323 = id `elemVarSet` ids
327 isTyVarDict :: Inst -> Bool
328 isTyVarDict (Dict _ (Class _ tys) _) = all isTyVarTy tys
329 isTyVarDict other = False
331 isStdClassTyVarDict (Dict _ (Class clas [ty]) _)
332 = isStandardClass clas && isTyVarTy ty
333 isStdClassTyVarDict other
336 notFunDep :: Inst -> Bool
337 notFunDep (FunDep _ _ _) = False
338 notFunDep other = True
341 Two predicates which deal with the case where class constraints don't
342 necessarily result in bindings. The first tells whether an @Inst@
343 must be witnessed by an actual binding; the second tells whether an
344 @Inst@ can be generalised over.
347 instBindingRequired :: Inst -> Bool
348 instBindingRequired (Dict _ (Class clas _) _) = not (isNoDictClass clas)
349 instBindingRequired (Dict _ (IParam _ _) _) = False
350 instBindingRequired other = True
352 instCanBeGeneralised :: Inst -> Bool
353 instCanBeGeneralised (Dict _ (Class clas _) _) = not (isCcallishClass clas)
354 instCanBeGeneralised other = True
362 newDicts :: InstOrigin
364 -> NF_TcM s (LIE, [TcId])
366 = tcGetInstLoc orig `thenNF_Tc` \ loc ->
367 newDictsAtLoc loc theta `thenNF_Tc` \ (dicts, ids) ->
368 returnNF_Tc (listToBag dicts, ids)
370 newClassDicts :: InstOrigin
371 -> [(Class,[TcType])]
372 -> NF_TcM s (LIE, [TcId])
373 newClassDicts orig theta
374 = newDicts orig (map (uncurry Class) theta)
376 -- Local function, similar to newDicts,
377 -- but with slightly different interface
378 newDictsAtLoc :: InstLoc
380 -> NF_TcM s ([Inst], [TcId])
381 newDictsAtLoc loc theta =
382 tcGetUniques (length theta) `thenNF_Tc` \ new_uniqs ->
384 mk_dict u pred = Dict u pred loc
385 dicts = zipWithEqual "newDictsAtLoc" mk_dict new_uniqs theta
387 returnNF_Tc (dicts, map instToId dicts)
389 newDictFromOld :: Inst -> Class -> [TcType] -> NF_TcM s Inst
390 newDictFromOld (Dict _ _ loc) clas tys
391 = tcGetUnique `thenNF_Tc` \ uniq ->
392 returnNF_Tc (Dict uniq (Class clas tys) loc)
395 newMethod :: InstOrigin
398 -> NF_TcM s (LIE, TcId)
399 newMethod orig id tys
400 = -- Get the Id type and instantiate it at the specified types
402 (tyvars, rho) = splitForAllTys (idType id)
403 rho_ty = substTy (mkTyVarSubst tyvars tys) rho
404 (theta, tau) = splitRhoTy rho_ty
406 newMethodWithGivenTy orig id tys theta tau `thenNF_Tc` \ meth_inst ->
407 returnNF_Tc (unitLIE meth_inst, instToId meth_inst)
409 instOverloadedFun orig (HsVar v) arg_tys theta tau
410 = newMethodWithGivenTy orig v arg_tys theta tau `thenNF_Tc` \ inst ->
411 instFunDeps orig theta `thenNF_Tc` \ fds ->
412 returnNF_Tc (HsVar (instToId inst), mkLIE (inst : fds))
414 instFunDeps orig theta
415 = tcGetInstLoc orig `thenNF_Tc` \ loc ->
416 let ifd (Class clas tys) =
417 let fds = instantiateFdClassTys clas tys in
418 if null fds then Nothing else Just (FunDep clas fds loc)
420 in returnNF_Tc (catMaybes (map ifd theta))
422 newMethodWithGivenTy orig id tys theta tau
423 = tcGetInstLoc orig `thenNF_Tc` \ loc ->
424 newMethodWith id tys theta tau loc
426 newMethodWith id tys theta tau loc
427 = tcGetUnique `thenNF_Tc` \ new_uniq ->
428 returnNF_Tc (Method new_uniq id tys theta tau loc)
430 newMethodAtLoc :: InstLoc
432 -> NF_TcM s (Inst, TcId)
433 newMethodAtLoc loc real_id tys -- Local function, similar to newMethod but with
434 -- slightly different interface
435 = -- Get the Id type and instantiate it at the specified types
436 tcGetUnique `thenNF_Tc` \ new_uniq ->
438 (tyvars,rho) = splitForAllTys (idType real_id)
439 rho_ty = ASSERT( length tyvars == length tys )
440 substTy (mkTopTyVarSubst tyvars tys) rho
441 (theta, tau) = splitRhoTy rho_ty
442 meth_inst = Method new_uniq real_id tys theta tau loc
444 returnNF_Tc (meth_inst, instToId meth_inst)
447 In newOverloadedLit we convert directly to an Int or Integer if we
448 know that's what we want. This may save some time, by not
449 temporarily generating overloaded literals, but it won't catch all
450 cases (the rest are caught in lookupInst).
453 newOverloadedLit :: InstOrigin
456 -> NF_TcM s (TcExpr, LIE)
457 newOverloadedLit orig (OverloadedIntegral i) ty
458 | isIntTy ty && inIntRange i -- Short cut for Int
459 = returnNF_Tc (int_lit, emptyLIE)
461 | isIntegerTy ty -- Short cut for Integer
462 = returnNF_Tc (integer_lit, emptyLIE)
465 intprim_lit = HsLitOut (HsIntPrim i) intPrimTy
466 integer_lit = HsLitOut (HsInt i) integerTy
467 int_lit = HsCon intDataCon [] [intprim_lit]
469 newOverloadedLit orig lit ty -- The general case
470 = tcGetInstLoc orig `thenNF_Tc` \ loc ->
471 tcGetUnique `thenNF_Tc` \ new_uniq ->
473 lit_inst = LitInst new_uniq lit ty loc
475 returnNF_Tc (HsVar (instToId lit_inst), unitLIE lit_inst)
479 newIPDict name ty loc
480 = tcGetUnique `thenNF_Tc` \ new_uniq ->
481 let d = Dict new_uniq (IParam name ty) loc in
486 instToId :: Inst -> TcId
487 instToId inst = instToIdBndr inst
489 instToIdBndr :: Inst -> TcId
490 instToIdBndr (Dict u (Class clas ty) (_,loc,_))
491 = mkUserLocal (mkDictOcc (getOccName clas)) u (mkDictTy clas ty) loc
492 instToIdBndr (Dict u (IParam n ty) (_,loc,_))
495 instToIdBndr (Method u id tys theta tau (_,loc,_))
496 = mkUserLocal (mkMethodOcc (getOccName id)) u tau loc
498 instToIdBndr (LitInst u list ty loc)
499 = mkSysLocal SLIT("lit") u ty
501 instToIdBndr (FunDep clas fds _)
502 = panic "FunDep escaped!!!"
505 = mkUserLocal (mkIPOcc (getOccName n)) (nameUnique n) (mkPredTy (IParam n ty)) loc
511 Zonking makes sure that the instance types are fully zonked,
512 but doesn't do the same for the Id in a Method. There's no
513 need, and it's a lot of extra work.
516 zonkPred :: TcPredType -> NF_TcM s TcPredType
517 zonkPred (Class clas tys)
518 = zonkTcTypes tys `thenNF_Tc` \ new_tys ->
519 returnNF_Tc (Class clas new_tys)
520 zonkPred (IParam n ty)
521 = zonkTcType ty `thenNF_Tc` \ new_ty ->
522 returnNF_Tc (IParam n new_ty)
524 zonkInst :: Inst -> NF_TcM s Inst
525 zonkInst (Dict u pred loc)
526 = zonkPred pred `thenNF_Tc` \ new_pred ->
527 returnNF_Tc (Dict u new_pred loc)
529 zonkInst (Method u id tys theta tau loc)
530 = zonkId id `thenNF_Tc` \ new_id ->
531 -- Essential to zonk the id in case it's a local variable
532 -- Can't use zonkIdOcc because the id might itself be
533 -- an InstId, in which case it won't be in scope
535 zonkTcTypes tys `thenNF_Tc` \ new_tys ->
536 zonkTcThetaType theta `thenNF_Tc` \ new_theta ->
537 zonkTcType tau `thenNF_Tc` \ new_tau ->
538 returnNF_Tc (Method u new_id new_tys new_theta new_tau loc)
540 zonkInst (LitInst u lit ty loc)
541 = zonkTcType ty `thenNF_Tc` \ new_ty ->
542 returnNF_Tc (LitInst u lit new_ty loc)
544 zonkInst (FunDep clas fds loc)
545 = zonkFunDeps fds `thenNF_Tc` \ fds' ->
546 returnNF_Tc (FunDep clas fds' loc)
548 zonkInsts insts = mapNF_Tc zonkInst insts
550 zonkFunDeps fds = mapNF_Tc zonkFd fds
553 = zonkTcTypes ts1 `thenNF_Tc` \ ts1' ->
554 zonkTcTypes ts2 `thenNF_Tc` \ ts2' ->
555 returnNF_Tc (ts1', ts2')
557 zonkTvFunDeps fds = mapNF_Tc zonkFd fds
560 = zonkTcTyVars tvs1 `thenNF_Tc` \ tvs1' ->
561 zonkTcTyVars tvs2 `thenNF_Tc` \ tvs2' ->
562 returnNF_Tc (tvs1', tvs2')
568 ToDo: improve these pretty-printing things. The ``origin'' is really only
569 relevant in error messages.
572 instance Outputable Inst where
573 ppr inst = pprInst inst
575 pprInst (LitInst u lit ty loc)
577 OverloadedIntegral i -> integer i
578 OverloadedFractional f -> rational f,
583 pprInst (Dict u pred loc) = pprPred pred <+> show_uniq u
585 pprInst (Method u id tys _ _ loc)
586 = hsep [ppr id, ptext SLIT("at"),
587 brackets (interppSP tys),
590 pprInst (FunDep clas fds loc)
591 = hsep [ppr clas, ppr fds]
593 tidyPred :: TidyEnv -> TcPredType -> (TidyEnv, TcPredType)
594 tidyPred env (Class clas tys)
595 = (env', Class clas tys')
597 (env', tys') = tidyOpenTypes env tys
598 tidyPred env (IParam n ty)
599 = (env', IParam n ty')
601 (env', ty') = tidyOpenType env ty
603 tidyInst :: TidyEnv -> Inst -> (TidyEnv, Inst)
604 tidyInst env (LitInst u lit ty loc)
605 = (env', LitInst u lit ty' loc)
607 (env', ty') = tidyOpenType env ty
609 tidyInst env (Dict u pred loc)
610 = (env', Dict u pred' loc)
612 (env', pred') = tidyPred env pred
614 tidyInst env (Method u id tys theta tau loc)
615 = (env', Method u id tys' theta tau loc)
616 -- Leave theta, tau alone cos we don't print them
618 (env', tys') = tidyOpenTypes env tys
620 -- this case shouldn't arise... (we never print fundeps)
621 tidyInst env fd@(FunDep clas fds loc)
624 tidyInsts env insts = mapAccumL tidyInst env insts
626 show_uniq u = ifPprDebug (text "{-" <> ppr u <> text "-}")
630 %************************************************************************
632 \subsection[InstEnv-types]{Type declarations}
634 %************************************************************************
637 type InstanceMapper = Class -> InstEnv
640 A @ClassInstEnv@ lives inside a class, and identifies all the instances
641 of that class. The @Id@ inside a ClassInstEnv mapping is the dfun for
644 There is an important consistency constraint between the @MatchEnv@s
645 in and the dfun @Id@s inside them: the free type variables of the
646 @Type@ key in the @MatchEnv@ must be a subset of the universally-quantified
647 type variables of the dfun. Thus, the @ClassInstEnv@ for @Eq@ might
648 contain the following entry:
650 [a] ===> dfun_Eq_List :: forall a. Eq a => Eq [a]
652 The "a" in the pattern must be one of the forall'd variables in
656 data LookupInstResult s
658 | SimpleInst TcExpr -- Just a variable, type application, or literal
659 | GenInst [Inst] TcExpr -- The expression and its needed insts
662 -> NF_TcM s (LookupInstResult s)
666 lookupInst dict@(Dict _ (Class clas tys) loc)
667 = case lookupInstEnv (ppr clas) (classInstEnv clas) tys of
671 subst = mkSubst (tyVarsOfTypes tys) tenv
672 (tyvars, rho) = splitForAllTys (idType dfun_id)
673 ty_args = map subst_tv tyvars
674 dfun_rho = substTy subst rho
675 (theta, tau) = splitRhoTy dfun_rho
676 ty_app = mkHsTyApp (HsVar dfun_id) ty_args
677 subst_tv tv = case lookupSubstEnv tenv tv of
678 Just (DoneTy ty) -> ty
679 -- tenv should bind all the tyvars
682 returnNF_Tc (SimpleInst ty_app)
684 newDictsAtLoc loc theta `thenNF_Tc` \ (dicts, dict_ids) ->
686 rhs = mkHsDictApp ty_app dict_ids
688 returnNF_Tc (GenInst dicts rhs)
690 Nothing -> returnNF_Tc NoInstance
691 lookupInst dict@(Dict _ _ loc) = returnNF_Tc NoInstance
695 lookupInst inst@(Method _ id tys theta _ loc)
696 = newDictsAtLoc loc theta `thenNF_Tc` \ (dicts, dict_ids) ->
697 returnNF_Tc (GenInst dicts (mkHsDictApp (mkHsTyApp (HsVar id) tys) dict_ids))
701 lookupInst inst@(LitInst u (OverloadedIntegral i) ty loc)
702 | isIntTy ty && in_int_range -- Short cut for Int
703 = returnNF_Tc (GenInst [] int_lit)
704 -- GenInst, not SimpleInst, because int_lit is actually a constructor application
706 | isIntegerTy ty -- Short cut for Integer
707 = returnNF_Tc (GenInst [] integer_lit)
709 | in_int_range -- It's overloaded but small enough to fit into an Int
710 = tcLookupValueByKey fromIntClassOpKey `thenNF_Tc` \ from_int ->
711 newMethodAtLoc loc from_int [ty] `thenNF_Tc` \ (method_inst, method_id) ->
712 returnNF_Tc (GenInst [method_inst] (HsApp (HsVar method_id) int_lit))
714 | otherwise -- Alas, it is overloaded and a big literal!
715 = tcLookupValueByKey fromIntegerClassOpKey `thenNF_Tc` \ from_integer ->
716 newMethodAtLoc loc from_integer [ty] `thenNF_Tc` \ (method_inst, method_id) ->
717 returnNF_Tc (GenInst [method_inst] (HsApp (HsVar method_id) integer_lit))
719 in_int_range = inIntRange i
720 intprim_lit = HsLitOut (HsIntPrim i) intPrimTy
721 integer_lit = HsLitOut (HsInt i) integerTy
722 int_lit = HsCon intDataCon [] [intprim_lit]
724 -- similar idea for overloaded floating point literals: if the literal is
725 -- *definitely* a float or a double, generate the real thing here.
726 -- This is essential (see nofib/spectral/nucleic).
728 lookupInst inst@(LitInst u (OverloadedFractional f) ty loc)
729 | isFloatTy ty = returnNF_Tc (GenInst [] float_lit)
730 | isDoubleTy ty = returnNF_Tc (GenInst [] double_lit)
733 = tcLookupValueByKey fromRationalClassOpKey `thenNF_Tc` \ from_rational ->
735 -- The type Rational isn't wired in so we have to conjure it up
736 tcLookupTyConByKey rationalTyConKey `thenNF_Tc` \ rational_tycon ->
738 rational_ty = mkSynTy rational_tycon []
739 rational_lit = HsLitOut (HsFrac f) rational_ty
741 newMethodAtLoc loc from_rational [ty] `thenNF_Tc` \ (method_inst, method_id) ->
742 returnNF_Tc (GenInst [method_inst] (HsApp (HsVar method_id) rational_lit))
745 floatprim_lit = HsLitOut (HsFloatPrim f) floatPrimTy
746 float_lit = HsCon floatDataCon [] [floatprim_lit]
747 doubleprim_lit = HsLitOut (HsDoublePrim f) doublePrimTy
748 double_lit = HsCon doubleDataCon [] [doubleprim_lit]
750 -- there are no `instances' of functional dependencies or implicit params
752 lookupInst _ = returnNF_Tc NoInstance
756 There is a second, simpler interface, when you want an instance of a
757 class at a given nullary type constructor. It just returns the
758 appropriate dictionary if it exists. It is used only when resolving
759 ambiguous dictionaries.
762 lookupSimpleInst :: InstEnv
764 -> [Type] -- Look up (c,t)
765 -> NF_TcM s (Maybe [(Class,[Type])]) -- Here are the needed (c,t)s
767 lookupSimpleInst class_inst_env clas tys
768 = case lookupInstEnv (ppr clas) class_inst_env tys of
769 Nothing -> returnNF_Tc Nothing
772 -> returnNF_Tc (Just (substClasses (mkSubst emptyInScopeSet tenv) theta'))
774 (_, theta, _) = splitSigmaTy (idType dfun)
775 theta' = map (\(Class clas tys) -> (clas,tys)) theta