X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FInst.lhs;h=aa6549833d479ced0e0f65b5dbad5478f026400f;hb=d4e0a55c3761544989209a2180d6d0489470db3d;hp=562cd6c2a2891ee0a8e15611112c3e39aee1a78d;hpb=ae45ff0e9831a0dc862a5d68d03e355d7e323c62;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/Inst.lhs b/ghc/compiler/typecheck/Inst.lhs index 562cd6c..aa65498 100644 --- a/ghc/compiler/typecheck/Inst.lhs +++ b/ghc/compiler/typecheck/Inst.lhs @@ -1,74 +1,93 @@ % -% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996 +% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % \section[Inst]{The @Inst@ type: dictionaries or method instances} \begin{code} -#include "HsVersions.h" - -module Inst ( - Inst(..), -- Visible only to TcSimplify - - InstOrigin(..), OverloadedLit(..), - LIE(..), emptyLIE, unitLIE, plusLIE, consLIE, zonkLIE, plusLIEs, +module Inst ( + LIE, emptyLIE, unitLIE, plusLIE, consLIE, zonkLIE, + plusLIEs, mkLIE, isEmptyLIE, lieToList, listToLIE, - InstanceMapper(..), + Inst, OverloadedLit(..), + pprInst, pprInsts, pprInstsInFull, tidyInst, tidyInsts, - newDicts, newDictsAtLoc, newMethod, newMethodWithGivenTy, newOverloadedLit, + InstanceMapper, - instType, tyVarsOfInst, lookupInst, lookupSimpleInst, + newDictFromOld, newDicts, newClassDicts, newDictsAtLoc, + newMethod, newMethodWithGivenTy, newOverloadedLit, + newIPDict, instOverloadedFun, - isDict, isTyVarDict, + tyVarsOfInst, tyVarsOfInsts, tyVarsOfLIE, instLoc, getDictClassTys, + getDictPred_maybe, getMethodTheta_maybe, + getFunDeps, getFunDepsOfLIE, + getIPs, getIPsOfLIE, + getAllFunDeps, getAllFunDepsOfLIE, - zonkInst, instToId, + lookupInst, lookupSimpleInst, LookupInstResult(..), - matchesInst, + isDict, isClassDict, isTyVarDict, isStdClassTyVarDict, isMethodFor, notFunDep, instBindingRequired, instCanBeGeneralised, - - pprInst - ) where -IMP_Ubiq() + zonkInst, zonkInsts, zonkFunDeps, zonkTvFunDeps, + instToId, instToIdBndr, ipToId, -import HsSyn ( HsLit(..), HsExpr(..), HsBinds, - InPat, OutPat, Stmt, Qualifier, Match, - ArithSeqInfo, PolyType, Fake ) -import RnHsSyn ( RenamedArithSeqInfo(..), RenamedHsExpr(..) ) -import TcHsSyn ( TcIdOcc(..), TcExpr(..), TcIdBndr(..), - mkHsTyApp, mkHsDictApp, tcIdTyVars ) + InstOrigin(..), InstLoc, pprInstLoc + ) where -import TcMonad hiding ( rnMtoTcM ) -import TcEnv ( tcLookupGlobalValueByKey, tcLookupTyConByKey ) -import TcType ( TcType(..), TcRhoType(..), TcMaybe, TcTyVarSet(..), - tcInstType, zonkTcType ) +#include "HsVersions.h" -import Bag ( emptyBag, unitBag, unionBags, unionManyBags, listToBag, consBag ) -import Class ( isCcallishClass, isNoDictClass, classInstEnv, - Class(..), GenClass, ClassInstEnv(..) +import HsSyn ( HsLit(..), HsExpr(..) ) +import RnHsSyn ( RenamedArithSeqInfo, RenamedHsExpr, RenamedPat ) +import TcHsSyn ( TcExpr, TcId, + mkHsTyApp, mkHsDictApp, mkHsConApp, zonkId ) -import ErrUtils ( addErrLoc, Error(..) ) -import Id ( GenId, idType, mkInstId ) -import MatchEnv ( lookupMEnv, insertMEnv ) -import Name ( mkLocalName, getLocalName, Name ) -import Outputable -import PprType ( GenClass, TyCon, GenType, GenTyVar ) -import PprStyle ( PprStyle(..) ) -import Pretty -import RnHsSyn ( RnName{-instance NamedThing-} ) -import SpecEnv ( SpecEnv(..) ) -import SrcLoc ( SrcLoc, mkUnknownSrcLoc ) -import Type ( GenType, eqSimpleTy, instantiateTy, - isTyVarTy, mkDictTy, splitForAllTy, splitSigmaTy, - splitRhoTy, matchTy, tyVarsOfType, tyVarsOfTypes, - mkSynTy +import TcMonad +import TcEnv ( TcIdSet, tcLookupValueByKey, tcLookupTyConByKey ) +import TcType ( TcThetaType, + TcType, TcTauType, TcTyVarSet, + zonkTcTyVars, zonkTcType, zonkTcTypes, + zonkTcThetaType + ) +import Bag +import Class ( classInstEnv, Class ) +import FunDeps ( instantiateFdClassTys ) +import Id ( Id, idFreeTyVars, idType, mkUserLocal, mkSysLocal ) +import PrelInfo ( isStandardClass, isCcallishClass, isNoDictClass ) +import Name ( OccName, Name, mkDictOcc, mkMethodOcc, mkIPOcc, + getOccName, nameUnique ) +import PprType ( pprPred ) +import InstEnv ( InstEnv, lookupInstEnv ) +import SrcLoc ( SrcLoc ) +import Type ( Type, PredType(..), ThetaType, + mkTyVarTy, isTyVarTy, mkDictTy, mkPredTy, + splitForAllTys, splitSigmaTy, + splitRhoTy, tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, + mkSynTy, tidyOpenType, tidyOpenTypes + ) +import InstEnv ( InstEnv ) +import Subst ( emptyInScopeSet, mkSubst, + substTy, substClasses, mkTyVarSubst, mkTopTyVarSubst ) -import TyVar ( unionTyVarSets, GenTyVar ) -import TysPrim ( intPrimTy ) -import TysWiredIn ( intDataCon, integerTy ) -import Unique ( showUnique, fromRationalClassOpKey, rationalTyConKey, +import TyCon ( TyCon ) +import Literal ( inIntRange ) +import Var ( TyVar ) +import VarEnv ( lookupVarEnv, TidyEnv, + lookupSubstEnv, SubstResult(..) + ) +import VarSet ( elemVarSet, emptyVarSet, unionVarSet ) +import TysPrim ( intPrimTy, floatPrimTy, doublePrimTy ) +import TysWiredIn ( intDataCon, isIntTy, + floatDataCon, isFloatTy, + doubleDataCon, isDoubleTy, + integerTy, isIntegerTy + ) +import Unique ( fromRationalClassOpKey, rationalTyConKey, fromIntClassOpKey, fromIntegerClassOpKey, Unique ) -import Util ( panic, zipEqual, zipWithEqual, assoc, assertPanic, pprTrace{-ToDo:rm-} ) +import Maybes ( expectJust ) +import Maybe ( catMaybes ) +import Util ( thenCmp, zipWithEqual, mapAccumL ) +import Outputable \end{code} %************************************************************************ @@ -78,16 +97,29 @@ import Util ( panic, zipEqual, zipWithEqual, assoc, assertPanic, pprTrace{-ToDo: %************************************************************************ \begin{code} -type LIE s = Bag (Inst s) +type LIE = Bag Inst +isEmptyLIE = isEmptyBag emptyLIE = emptyBag unitLIE inst = unitBag inst +mkLIE insts = listToBag insts plusLIE lie1 lie2 = lie1 `unionBags` lie2 consLIE inst lie = inst `consBag` lie plusLIEs lies = unionManyBags lies +lieToList = bagToList +listToLIE = listToBag -zonkLIE :: LIE s -> NF_TcM s (LIE s) +zonkLIE :: LIE -> NF_TcM s LIE zonkLIE lie = mapBagNF_Tc zonkInst lie + +pprInsts :: [Inst] -> SDoc +pprInsts insts = parens (sep (punctuate comma (map pprInst insts))) + + +pprInstsInFull insts + = vcat (map go insts) + where + go inst = quotes (ppr inst) <+> pprInstLoc (instLoc inst) \end{code} %************************************************************************ @@ -105,153 +137,361 @@ type Int, represented by Method 34 doubleId [Int] origin \begin{code} -data Inst s +data Inst = Dict Unique - Class -- The type of the dict is (c t), where - (TcType s) -- c is the class and t the type; - (InstOrigin s) - SrcLoc + TcPredType + InstLoc | Method Unique - (TcIdOcc s) -- The overloaded function + TcId -- The overloaded function -- This function will be a global, local, or ClassOpId; -- inside instance decls (only) it can also be an InstId! -- The id needn't be completely polymorphic. -- You'll probably find its name (for documentation purposes) -- inside the InstOrigin - [TcType s] -- The types to which its polymorphic tyvars + [TcType] -- The types to which its polymorphic tyvars -- should be instantiated. -- These types must saturate the Id's foralls. - (TcRhoType s) -- Cached: (type-of-id applied to inst_tys) - -- If this type is (theta => tau) then the type of the Method - -- is tau, and the method can be built by saying - -- id inst_tys dicts - -- where dicts are constructed from theta + TcThetaType -- The (types of the) dictionaries to which the function + -- must be applied to get the method + + TcTauType -- The type of the method + + InstLoc - (InstOrigin s) - SrcLoc + -- INVARIANT: in (Method u f tys theta tau loc) + -- type of (f tys dicts(from theta)) = tau | LitInst Unique OverloadedLit - (TcType s) -- The type at which the literal is used - (InstOrigin s) -- Always a literal; but more convenient to carry this around - SrcLoc + TcType -- The type at which the literal is used + InstLoc + + | FunDep + Class -- the class from which this arises + [([TcType], [TcType])] + InstLoc data OverloadedLit = OverloadedIntegral Integer -- The number | OverloadedFractional Rational -- The number +\end{code} + +Ordering +~~~~~~~~ +@Insts@ are ordered by their class/type info, rather than by their +unique. This allows the context-reduction mechanism to use standard finite +maps to do their stuff. + +\begin{code} +instance Ord Inst where + compare = cmpInst +instance Ord PredType where + compare = cmpPred + +instance Eq Inst where + (==) i1 i2 = case i1 `cmpInst` i2 of + EQ -> True + other -> False +instance Eq PredType where + (==) p1 p2 = case p1 `cmpPred` p2 of + EQ -> True + other -> False + +cmpInst (Dict _ pred1 _) (Dict _ pred2 _) + = (pred1 `cmpPred` pred2) +cmpInst (Dict _ _ _) other + = LT + +cmpInst (Method _ _ _ _ _ _) (Dict _ _ _) + = GT +cmpInst (Method _ id1 tys1 _ _ _) (Method _ id2 tys2 _ _ _) + = (id1 `compare` id2) `thenCmp` (tys1 `compare` tys2) +cmpInst (Method _ _ _ _ _ _) other + = LT + +cmpInst (LitInst _ lit1 ty1 _) (LitInst _ lit2 ty2 _) + = (lit1 `cmpOverLit` lit2) `thenCmp` (ty1 `compare` ty2) +cmpInst (LitInst _ _ _ _) (FunDep _ _ _) + = LT +cmpInst (LitInst _ _ _ _) other + = GT + +cmpInst (FunDep clas1 fds1 _) (FunDep clas2 fds2 _) + = (clas1 `compare` clas2) `thenCmp` (fds1 `compare` fds2) +cmpInst (FunDep _ _ _) other + = GT + +cmpPred (Class c1 tys1) (Class c2 tys2) + = (c1 `compare` c2) `thenCmp` (tys1 `compare` tys2) +cmpPred (IParam n1 ty1) (IParam n2 ty2) + = (n1 `compare` n2) `thenCmp` (ty1 `compare` ty2) +cmpPred (Class _ _) (IParam _ _) = LT +cmpPred _ _ = GT + +cmpOverLit (OverloadedIntegral i1) (OverloadedIntegral i2) = i1 `compare` i2 +cmpOverLit (OverloadedFractional f1) (OverloadedFractional f2) = f1 `compare` f2 +cmpOverLit (OverloadedIntegral _) (OverloadedFractional _) = LT +cmpOverLit (OverloadedFractional _) (OverloadedIntegral _) = GT +\end{code} + + +Selection +~~~~~~~~~ +\begin{code} +instLoc (Dict u pred loc) = loc +instLoc (Method u _ _ _ _ loc) = loc +instLoc (LitInst u lit ty loc) = loc +instLoc (FunDep _ _ loc) = loc + +getDictPred_maybe (Dict _ p _) = Just p +getDictPred_maybe _ = Nothing + +getMethodTheta_maybe (Method _ _ _ theta _ _) = Just theta +getMethodTheta_maybe _ = Nothing + +getDictClassTys (Dict u (Class clas tys) _) = (clas, tys) + +getFunDeps (FunDep clas fds _) = Just (clas, fds) +getFunDeps _ = Nothing + +getFunDepsOfLIE lie = catMaybes (map getFunDeps (lieToList lie)) + +getIPsOfPred (IParam n ty) = [(n, ty)] +getIPsOfPred _ = [] +getIPsOfTheta theta = concatMap getIPsOfPred theta -getInstOrigin (Dict u clas ty origin loc) = origin -getInstOrigin (Method u clas ty rho origin loc) = origin -getInstOrigin (LitInst u lit ty origin loc) = origin +getIPs (Dict u (IParam n ty) loc) = [(n, ty)] +getIPs (Method u id _ theta t loc) = getIPsOfTheta theta +getIPs _ = [] + +getIPsOfLIE lie = concatMap getIPs (lieToList lie) + +getAllFunDeps (FunDep clas fds _) = fds +getAllFunDeps inst = map (\(n,ty) -> ([], [ty])) (getIPs inst) + +getAllFunDepsOfLIE lie = concat (map getAllFunDeps (lieToList lie)) + +tyVarsOfInst :: Inst -> TcTyVarSet +tyVarsOfInst (Dict _ pred _) = tyVarsOfPred pred +tyVarsOfInst (Method _ id tys _ _ _) = tyVarsOfTypes tys `unionVarSet` idFreeTyVars id + -- The id might have free type variables; in the case of + -- locally-overloaded class methods, for example +tyVarsOfInst (LitInst _ _ ty _) = tyVarsOfType ty +tyVarsOfInst (FunDep _ fds _) + = foldr unionVarSet emptyVarSet (map tyVarsOfFd fds) + where tyVarsOfFd (ts1, ts2) = + tyVarsOfTypes ts1 `unionVarSet` tyVarsOfTypes ts2 + +tyVarsOfInsts insts + = foldr unionVarSet emptyVarSet (map tyVarsOfInst insts) + +tyVarsOfLIE lie + = foldr unionVarSet emptyVarSet (map tyVarsOfInst insts) + where insts = lieToList lie \end{code} +Predicates +~~~~~~~~~~ +\begin{code} +isDict :: Inst -> Bool +isDict (Dict _ _ _) = True +isDict other = False +isClassDict :: Inst -> Bool +isClassDict (Dict _ (Class _ _) _) = True +isClassDict other = False + +isMethodFor :: TcIdSet -> Inst -> Bool +isMethodFor ids (Method uniq id tys _ _ loc) + = id `elemVarSet` ids +isMethodFor ids inst + = False + +isTyVarDict :: Inst -> Bool +isTyVarDict (Dict _ (Class _ tys) _) = all isTyVarTy tys +isTyVarDict other = False + +isStdClassTyVarDict (Dict _ (Class clas [ty]) _) + = isStandardClass clas && isTyVarTy ty +isStdClassTyVarDict other + = False + +notFunDep :: Inst -> Bool +notFunDep (FunDep _ _ _) = False +notFunDep other = True +\end{code} + +Two predicates which deal with the case where class constraints don't +necessarily result in bindings. The first tells whether an @Inst@ +must be witnessed by an actual binding; the second tells whether an +@Inst@ can be generalised over. + +\begin{code} +instBindingRequired :: Inst -> Bool +instBindingRequired (Dict _ (Class clas _) _) = not (isNoDictClass clas) +instBindingRequired (Dict _ (IParam _ _) _) = False +instBindingRequired other = True + +instCanBeGeneralised :: Inst -> Bool +instCanBeGeneralised (Dict _ (Class clas _) _) = not (isCcallishClass clas) +instCanBeGeneralised other = True +\end{code} + + Construction ~~~~~~~~~~~~ \begin{code} -newDicts :: InstOrigin s - -> [(Class, TcType s)] - -> NF_TcM s (LIE s, [TcIdOcc s]) +newDicts :: InstOrigin + -> TcThetaType + -> NF_TcM s (LIE, [TcId]) newDicts orig theta - = tcGetSrcLoc `thenNF_Tc` \ loc -> - tcGetUniques (length theta) `thenNF_Tc` \ new_uniqs -> - let - mk_dict u (clas, ty) = Dict u clas ty orig loc - dicts = zipWithEqual "newDicts" mk_dict new_uniqs theta - in - returnNF_Tc (listToBag dicts, map instToId dicts) - -newDictsAtLoc orig loc theta -- Local function, similar to newDicts, - -- but with slightly different interface - = tcGetUniques (length theta) `thenNF_Tc` \ new_uniqs -> - let - mk_dict u (clas, ty) = Dict u clas ty orig loc - dicts = zipWithEqual "newDictsAtLoc" mk_dict new_uniqs theta - in - returnNF_Tc (dicts, map instToId dicts) - -newMethod :: InstOrigin s - -> TcIdOcc s - -> [TcType s] - -> NF_TcM s (LIE s, TcIdOcc s) + = tcGetInstLoc orig `thenNF_Tc` \ loc -> + newDictsAtLoc loc theta `thenNF_Tc` \ (dicts, ids) -> + returnNF_Tc (listToBag dicts, ids) + +newClassDicts :: InstOrigin + -> [(Class,[TcType])] + -> NF_TcM s (LIE, [TcId]) +newClassDicts orig theta + = newDicts orig (map (uncurry Class) theta) + +-- Local function, similar to newDicts, +-- but with slightly different interface +newDictsAtLoc :: InstLoc + -> TcThetaType + -> NF_TcM s ([Inst], [TcId]) +newDictsAtLoc loc theta = + tcGetUniques (length theta) `thenNF_Tc` \ new_uniqs -> + let + mk_dict u pred = Dict u pred loc + dicts = zipWithEqual "newDictsAtLoc" mk_dict new_uniqs theta + in + returnNF_Tc (dicts, map instToId dicts) + +newDictFromOld :: Inst -> Class -> [TcType] -> NF_TcM s Inst +newDictFromOld (Dict _ _ loc) clas tys + = tcGetUnique `thenNF_Tc` \ uniq -> + returnNF_Tc (Dict uniq (Class clas tys) loc) + + +newMethod :: InstOrigin + -> TcId + -> [TcType] + -> NF_TcM s (LIE, TcId) newMethod orig id tys = -- Get the Id type and instantiate it at the specified types - (case id of - RealId id -> let (tyvars, rho) = splitForAllTy (idType id) - in - (if length tyvars /= length tys then pprTrace "newMethod" (ppr PprDebug (idType id)) else \x->x) $ - tcInstType (zip{-Equal "newMethod"-} tyvars tys) rho - TcId id -> let (tyvars, rho) = splitForAllTy (idType id) - in returnNF_Tc (instantiateTy (zipEqual "newMethod(2)" tyvars tys) rho) - ) `thenNF_Tc` \ rho_ty -> - -- Our friend does the rest - newMethodWithGivenTy orig id tys rho_ty - - -newMethodWithGivenTy orig id tys rho_ty - = tcGetSrcLoc `thenNF_Tc` \ loc -> - tcGetUnique `thenNF_Tc` \ new_uniq -> let - meth_inst = Method new_uniq id tys rho_ty orig loc + (tyvars, rho) = splitForAllTys (idType id) + rho_ty = substTy (mkTyVarSubst tyvars tys) rho + (theta, tau) = splitRhoTy rho_ty in + newMethodWithGivenTy orig id tys theta tau `thenNF_Tc` \ meth_inst -> returnNF_Tc (unitLIE meth_inst, instToId meth_inst) -newMethodAtLoc :: InstOrigin s -> SrcLoc -> Id -> [TcType s] -> NF_TcM s (Inst s, TcIdOcc s) -newMethodAtLoc orig loc real_id tys -- Local function, similar to newMethod but with +instOverloadedFun orig (HsVar v) arg_tys theta tau + = newMethodWithGivenTy orig v arg_tys theta tau `thenNF_Tc` \ inst -> + instFunDeps orig theta `thenNF_Tc` \ fds -> + returnNF_Tc (HsVar (instToId inst), mkLIE (inst : fds)) + +instFunDeps orig theta + = tcGetInstLoc orig `thenNF_Tc` \ loc -> + let ifd (Class clas tys) = + let fds = instantiateFdClassTys clas tys in + if null fds then Nothing else Just (FunDep clas fds loc) + ifd _ = Nothing + in returnNF_Tc (catMaybes (map ifd theta)) + +newMethodWithGivenTy orig id tys theta tau + = tcGetInstLoc orig `thenNF_Tc` \ loc -> + newMethodWith id tys theta tau loc + +newMethodWith id tys theta tau loc + = tcGetUnique `thenNF_Tc` \ new_uniq -> + returnNF_Tc (Method new_uniq id tys theta tau loc) + +newMethodAtLoc :: InstLoc + -> Id -> [TcType] + -> NF_TcM s (Inst, TcId) +newMethodAtLoc loc real_id tys -- Local function, similar to newMethod but with -- slightly different interface = -- Get the Id type and instantiate it at the specified types + tcGetUnique `thenNF_Tc` \ new_uniq -> let - (tyvars,rho) = splitForAllTy (idType real_id) - in - tcInstType (zipEqual "newMethodAtLoc" tyvars tys) rho `thenNF_Tc` \ rho_ty -> - tcGetUnique `thenNF_Tc` \ new_uniq -> - let - meth_inst = Method new_uniq (RealId real_id) tys rho_ty orig loc + (tyvars,rho) = splitForAllTys (idType real_id) + rho_ty = ASSERT( length tyvars == length tys ) + substTy (mkTopTyVarSubst tyvars tys) rho + (theta, tau) = splitRhoTy rho_ty + meth_inst = Method new_uniq real_id tys theta tau loc in returnNF_Tc (meth_inst, instToId meth_inst) +\end{code} -newOverloadedLit :: InstOrigin s +In newOverloadedLit we convert directly to an Int or Integer if we +know that's what we want. This may save some time, by not +temporarily generating overloaded literals, but it won't catch all +cases (the rest are caught in lookupInst). + +\begin{code} +newOverloadedLit :: InstOrigin -> OverloadedLit - -> TcType s - -> NF_TcM s (LIE s, TcIdOcc s) -newOverloadedLit orig lit ty - = tcGetSrcLoc `thenNF_Tc` \ loc -> + -> TcType + -> NF_TcM s (TcExpr, LIE) +newOverloadedLit orig (OverloadedIntegral i) ty + | isIntTy ty && inIntRange i -- Short cut for Int + = returnNF_Tc (int_lit, emptyLIE) + + | isIntegerTy ty -- Short cut for Integer + = returnNF_Tc (integer_lit, emptyLIE) + + where + intprim_lit = HsLitOut (HsIntPrim i) intPrimTy + integer_lit = HsLitOut (HsInt i) integerTy + int_lit = mkHsConApp intDataCon [] [intprim_lit] + +newOverloadedLit orig lit ty -- The general case + = tcGetInstLoc orig `thenNF_Tc` \ loc -> tcGetUnique `thenNF_Tc` \ new_uniq -> let - lit_inst = LitInst new_uniq lit ty orig loc + lit_inst = LitInst new_uniq lit ty loc in - returnNF_Tc (unitLIE lit_inst, instToId lit_inst) + returnNF_Tc (HsVar (instToId lit_inst), unitLIE lit_inst) \end{code} - \begin{code} -instToId :: Inst s -> TcIdOcc s -instToId (Dict u clas ty orig loc) - = TcId (mkInstId u (mkDictTy clas ty) (mkLocalName u str False{-emph name-} loc)) - where - str = SLIT("d.") _APPEND_ (getLocalName clas) -instToId (Method u id tys rho_ty orig loc) - = TcId (mkInstId u tau_ty (mkLocalName u str False{-emph name-} loc)) - where - (_, tau_ty) = splitRhoTy rho_ty -- NB The method Id has just the tau type - str = SLIT("m.") _APPEND_ (getLocalName id) - -instToId (LitInst u list ty orig loc) - = TcId (mkInstId u ty (mkLocalName u SLIT("lit") True{-emph uniq-} loc)) +newIPDict name ty loc + = tcGetUnique `thenNF_Tc` \ new_uniq -> + let d = Dict new_uniq (IParam name ty) loc in + returnNF_Tc d \end{code} \begin{code} -instType :: Inst s -> TcType s -instType (Dict _ clas ty _ _) = mkDictTy clas ty -instType (LitInst _ _ ty _ _) = ty -instType (Method _ id tys ty _ _) = ty +instToId :: Inst -> TcId +instToId inst = instToIdBndr inst + +instToIdBndr :: Inst -> TcId +instToIdBndr (Dict u (Class clas ty) (_,loc,_)) + = mkUserLocal (mkDictOcc (getOccName clas)) u (mkDictTy clas ty) loc +instToIdBndr (Dict u (IParam n ty) (_,loc,_)) + = ipToId n ty loc + +instToIdBndr (Method u id tys theta tau (_,loc,_)) + = mkUserLocal (mkMethodOcc (getOccName id)) u tau loc + +instToIdBndr (LitInst u list ty loc) + = mkSysLocal SLIT("lit") u ty + +instToIdBndr (FunDep clas fds _) + = panic "FunDep escaped!!!" + +ipToId n ty loc + = mkUserLocal (mkIPOcc (getOccName n)) (nameUnique n) (mkPredTy (IParam n ty)) loc \end{code} @@ -262,81 +502,54 @@ but doesn't do the same for the Id in a Method. There's no need, and it's a lot of extra work. \begin{code} -zonkInst :: Inst s -> NF_TcM s (Inst s) -zonkInst (Dict u clas ty orig loc) - = zonkTcType ty `thenNF_Tc` \ new_ty -> - returnNF_Tc (Dict u clas new_ty orig loc) - -zonkInst (Method u id tys rho orig loc) -- Doesn't zonk the id! - = mapNF_Tc zonkTcType tys `thenNF_Tc` \ new_tys -> - zonkTcType rho `thenNF_Tc` \ new_rho -> - returnNF_Tc (Method u id new_tys new_rho orig loc) - -zonkInst (LitInst u lit ty orig loc) +zonkPred :: TcPredType -> NF_TcM s TcPredType +zonkPred (Class clas tys) + = zonkTcTypes tys `thenNF_Tc` \ new_tys -> + returnNF_Tc (Class clas new_tys) +zonkPred (IParam n ty) = zonkTcType ty `thenNF_Tc` \ new_ty -> - returnNF_Tc (LitInst u lit new_ty orig loc) -\end{code} + returnNF_Tc (IParam n new_ty) +zonkInst :: Inst -> NF_TcM s Inst +zonkInst (Dict u pred loc) + = zonkPred pred `thenNF_Tc` \ new_pred -> + returnNF_Tc (Dict u new_pred loc) -\begin{code} -tyVarsOfInst :: Inst s -> TcTyVarSet s -tyVarsOfInst (Dict _ _ ty _ _) = tyVarsOfType ty -tyVarsOfInst (Method _ id tys rho _ _) = tyVarsOfTypes tys `unionTyVarSets` tcIdTyVars id - -- The id might not be a RealId; in the case of - -- locally-overloaded class methods, for example -tyVarsOfInst (LitInst _ _ ty _ _) = tyVarsOfType ty -\end{code} +zonkInst (Method u id tys theta tau loc) + = zonkId id `thenNF_Tc` \ new_id -> + -- Essential to zonk the id in case it's a local variable + -- Can't use zonkIdOcc because the id might itself be + -- an InstId, in which case it won't be in scope -@matchesInst@ checks when two @Inst@s are instances of the same -thing at the same type, even if their uniques differ. + zonkTcTypes tys `thenNF_Tc` \ new_tys -> + zonkTcThetaType theta `thenNF_Tc` \ new_theta -> + zonkTcType tau `thenNF_Tc` \ new_tau -> + returnNF_Tc (Method u new_id new_tys new_theta new_tau loc) -\begin{code} -matchesInst :: Inst s -> Inst s -> Bool +zonkInst (LitInst u lit ty loc) + = zonkTcType ty `thenNF_Tc` \ new_ty -> + returnNF_Tc (LitInst u lit new_ty loc) -matchesInst (Dict _ clas1 ty1 _ _) (Dict _ clas2 ty2 _ _) - = clas1 == clas2 && ty1 `eqSimpleTy` ty2 +zonkInst (FunDep clas fds loc) + = zonkFunDeps fds `thenNF_Tc` \ fds' -> + returnNF_Tc (FunDep clas fds' loc) -matchesInst (Method _ id1 tys1 _ _ _) (Method _ id2 tys2 _ _ _) - = id1 == id2 - && and (zipWith eqSimpleTy tys1 tys2) - && length tys1 == length tys2 +zonkPreds preds = mapNF_Tc zonkPred preds +zonkInsts insts = mapNF_Tc zonkInst insts -matchesInst (LitInst _ lit1 ty1 _ _) (LitInst _ lit2 ty2 _ _) - = lit1 `eq` lit2 && ty1 `eqSimpleTy` ty2 +zonkFunDeps fds = mapNF_Tc zonkFd fds where - (OverloadedIntegral i1) `eq` (OverloadedIntegral i2) = i1 == i2 - (OverloadedFractional f1) `eq` (OverloadedFractional f2) = f1 == f2 - _ `eq` _ = False - -matchesInst other1 other2 = False -\end{code} + zonkFd (ts1, ts2) + = zonkTcTypes ts1 `thenNF_Tc` \ ts1' -> + zonkTcTypes ts2 `thenNF_Tc` \ ts2' -> + returnNF_Tc (ts1', ts2') - -Predicates -~~~~~~~~~~ -\begin{code} -isDict :: Inst s -> Bool -isDict (Dict _ _ _ _ _) = True -isDict other = False - -isTyVarDict :: Inst s -> Bool -isTyVarDict (Dict _ _ ty _ _) = isTyVarTy ty -isTyVarDict other = False -\end{code} - -Two predicates which deal with the case where class constraints don't -necessarily result in bindings. The first tells whether an @Inst@ -must be witnessed by an actual binding; the second tells whether an -@Inst@ can be generalised over. - -\begin{code} -instBindingRequired :: Inst s -> Bool -instBindingRequired (Dict _ clas _ _ _) = not (isNoDictClass clas) -instBindingRequired other = True - -instCanBeGeneralised :: Inst s -> Bool -instCanBeGeneralised (Dict _ clas _ _ _) = not (isCcallishClass clas) -instCanBeGeneralised other = True +zonkTvFunDeps fds = mapNF_Tc zonkFd fds + where + zonkFd (tvs1, tvs2) + = zonkTcTyVars tvs1 `thenNF_Tc` \ tvs1' -> + zonkTcTyVars tvs2 `thenNF_Tc` \ tvs2' -> + returnNF_Tc (tvs1', tvs2') \end{code} @@ -346,38 +559,66 @@ ToDo: improve these pretty-printing things. The ``origin'' is really only relevant in error messages. \begin{code} -instance Outputable (Inst s) where - ppr sty inst = ppr_inst sty ppNil (\ o l -> ppNil) inst - -pprInst sty hdr inst = ppr_inst sty hdr (\ o l -> pprOrigin hdr o l sty) inst - -ppr_inst sty hdr ppr_orig (LitInst u lit ty orig loc) - = ppHang (ppr_orig orig loc) - 4 (ppCat [case lit of - OverloadedIntegral i -> ppInteger i - OverloadedFractional f -> ppRational f, - ppStr "at", - ppr sty ty, - show_uniq sty u]) - -ppr_inst sty hdr ppr_orig (Dict u clas ty orig loc) - = ppHang (ppr_orig orig loc) - 4 (ppCat [ppr sty clas, ppr sty ty, show_uniq sty u]) - -ppr_inst sty hdr ppr_orig (Method u id tys rho orig loc) - = ppHang (ppr_orig orig loc) - 4 (ppCat [ppr sty id, ppStr "at", interppSP sty tys, show_uniq sty u]) - -show_uniq PprDebug u = ppr PprDebug u -show_uniq sty u = ppNil -\end{code} +instance Outputable Inst where + ppr inst = pprInst inst + +pprInst (LitInst u lit ty loc) + = hsep [case lit of + OverloadedIntegral i -> integer i + OverloadedFractional f -> rational f, + ptext SLIT("at"), + ppr ty, + show_uniq u] + +pprInst (Dict u pred loc) = pprPred pred <+> show_uniq u + +pprInst m@(Method u id tys theta tau loc) + = hsep [ppr id, ptext SLIT("at"), + brackets (interppSP tys), + ppr theta, ppr tau, + show_uniq u, + ppr (instToId m)] + +pprInst (FunDep clas fds loc) + = hsep [ppr clas, ppr fds] + +tidyPred :: TidyEnv -> TcPredType -> (TidyEnv, TcPredType) +tidyPred env (Class clas tys) + = (env', Class clas tys') + where + (env', tys') = tidyOpenTypes env tys +tidyPred env (IParam n ty) + = (env', IParam n ty') + where + (env', ty') = tidyOpenType env ty -Printing in error messages +tidyInst :: TidyEnv -> Inst -> (TidyEnv, Inst) +tidyInst env (LitInst u lit ty loc) + = (env', LitInst u lit ty' loc) + where + (env', ty') = tidyOpenType env ty -\begin{code} -noInstanceErr inst sty = ppHang (ppPStr SLIT("No instance for:")) 4 (ppr sty inst) +tidyInst env (Dict u pred loc) + = (env', Dict u pred' loc) + where + (env', pred') = tidyPred env pred + +tidyInst env (Method u id tys theta tau loc) + = (env', Method u id tys' theta tau loc) + -- Leave theta, tau alone cos we don't print them + where + (env', tys') = tidyOpenTypes env tys + +-- this case shouldn't arise... (we never print fundeps) +tidyInst env fd@(FunDep clas fds loc) + = (env, fd) + +tidyInsts env insts = mapAccumL tidyInst env insts + +show_uniq u = ifPprDebug (text "{-" <> ppr u <> text "-}") \end{code} + %************************************************************************ %* * \subsection[InstEnv-types]{Type declarations} @@ -385,7 +626,7 @@ noInstanceErr inst sty = ppHang (ppPStr SLIT("No instance for:")) 4 (ppr sty ins %************************************************************************ \begin{code} -type InstanceMapper = Class -> (ClassInstEnv, ClassOp -> SpecEnv) +type InstanceMapper = Class -> InstEnv \end{code} A @ClassInstEnv@ lives inside a class, and identifies all the instances @@ -404,63 +645,84 @@ The "a" in the pattern must be one of the forall'd variables in the dfun type. \begin{code} -lookupInst :: Inst s - -> TcM s ([Inst s], - (TcIdOcc s, TcExpr s)) -- The new binding +data LookupInstResult s + = NoInstance + | SimpleInst TcExpr -- Just a variable, type application, or literal + | GenInst [Inst] TcExpr -- The expression and its needed insts + +lookupInst :: Inst + -> NF_TcM s (LookupInstResult s) -- Dictionaries -lookupInst dict@(Dict _ clas ty orig loc) - = case lookupMEnv matchTy (get_inst_env clas orig) ty of - Nothing -> tcAddSrcLoc loc $ - tcAddErrCtxt (pprOrigin ""{-hdr-} orig loc) $ - failTc (noInstanceErr dict) +lookupInst dict@(Dict _ (Class clas tys) loc) + = case lookupInstEnv (ppr clas) (classInstEnv clas) tys of - Just (dfun_id, tenv) + Just (tenv, dfun_id) -> let - (tyvars, rho) = splitForAllTy (idType dfun_id) - ty_args = map (assoc "lookupInst" tenv) tyvars - -- tenv should bind all the tyvars + subst = mkSubst (tyVarsOfTypes tys) tenv + (tyvars, rho) = splitForAllTys (idType dfun_id) + ty_args = map subst_tv tyvars + dfun_rho = substTy subst rho + (theta, tau) = splitRhoTy dfun_rho + ty_app = mkHsTyApp (HsVar dfun_id) ty_args + subst_tv tv = case lookupSubstEnv tenv tv of + Just (DoneTy ty) -> ty + -- tenv should bind all the tyvars in - tcInstType tenv rho `thenNF_Tc` \ dfun_rho -> - let - (theta, tau) = splitRhoTy dfun_rho - in - newDictsAtLoc orig loc theta `thenNF_Tc` \ (dicts, dict_ids) -> + if null theta then + returnNF_Tc (SimpleInst ty_app) + else + newDictsAtLoc loc theta `thenNF_Tc` \ (dicts, dict_ids) -> let - rhs = mkHsDictApp (mkHsTyApp (HsVar (RealId dfun_id)) ty_args) dict_ids + rhs = mkHsDictApp ty_app dict_ids in - returnTc (dicts, (instToId dict, rhs)) - + returnNF_Tc (GenInst dicts rhs) + + Nothing -> returnNF_Tc NoInstance +lookupInst dict@(Dict _ _ loc) = returnNF_Tc NoInstance -- Methods -lookupInst inst@(Method _ id tys rho orig loc) - = newDictsAtLoc orig loc theta `thenNF_Tc` \ (dicts, dict_ids) -> - returnTc (dicts, (instToId inst, mkHsDictApp (mkHsTyApp (HsVar id) tys) dict_ids)) - where - (theta,_) = splitRhoTy rho +lookupInst inst@(Method _ id tys theta _ loc) + = newDictsAtLoc loc theta `thenNF_Tc` \ (dicts, dict_ids) -> + returnNF_Tc (GenInst dicts (mkHsDictApp (mkHsTyApp (HsVar id) tys) dict_ids)) -- Literals -lookupInst inst@(LitInst u (OverloadedIntegral i) ty orig loc) - | i >= toInteger minInt && i <= toInteger maxInt - = -- It's overloaded but small enough to fit into an Int - tcLookupGlobalValueByKey fromIntClassOpKey `thenNF_Tc` \ from_int -> - newMethodAtLoc orig loc from_int [ty] `thenNF_Tc` \ (method_inst, method_id) -> - returnTc ([method_inst], (instToId inst, HsApp (HsVar method_id) int_lit)) +lookupInst inst@(LitInst u (OverloadedIntegral i) ty loc) + | isIntTy ty && in_int_range -- Short cut for Int + = returnNF_Tc (GenInst [] int_lit) + -- GenInst, not SimpleInst, because int_lit is actually a constructor application - | otherwise - = -- Alas, it is overloaded and a big literal! - tcLookupGlobalValueByKey fromIntegerClassOpKey `thenNF_Tc` \ from_integer -> - newMethodAtLoc orig loc from_integer [ty] `thenNF_Tc` \ (method_inst, method_id) -> - returnTc ([method_inst], (instToId inst, HsApp (HsVar method_id) (HsLitOut (HsInt i) integerTy))) + | isIntegerTy ty -- Short cut for Integer + = returnNF_Tc (GenInst [] integer_lit) + + | in_int_range -- It's overloaded but small enough to fit into an Int + = tcLookupValueByKey fromIntClassOpKey `thenNF_Tc` \ from_int -> + newMethodAtLoc loc from_int [ty] `thenNF_Tc` \ (method_inst, method_id) -> + returnNF_Tc (GenInst [method_inst] (HsApp (HsVar method_id) int_lit)) + + | otherwise -- Alas, it is overloaded and a big literal! + = tcLookupValueByKey fromIntegerClassOpKey `thenNF_Tc` \ from_integer -> + newMethodAtLoc loc from_integer [ty] `thenNF_Tc` \ (method_inst, method_id) -> + returnNF_Tc (GenInst [method_inst] (HsApp (HsVar method_id) integer_lit)) where + in_int_range = inIntRange i intprim_lit = HsLitOut (HsIntPrim i) intPrimTy - int_lit = HsApp (HsVar (RealId intDataCon)) intprim_lit + integer_lit = HsLitOut (HsInt i) integerTy + int_lit = mkHsConApp intDataCon [] [intprim_lit] + +-- similar idea for overloaded floating point literals: if the literal is +-- *definitely* a float or a double, generate the real thing here. +-- This is essential (see nofib/spectral/nucleic). + +lookupInst inst@(LitInst u (OverloadedFractional f) ty loc) + | isFloatTy ty = returnNF_Tc (GenInst [] float_lit) + | isDoubleTy ty = returnNF_Tc (GenInst [] double_lit) -lookupInst inst@(LitInst u (OverloadedFractional f) ty orig loc) - = tcLookupGlobalValueByKey fromRationalClassOpKey `thenNF_Tc` \ from_rational -> + | otherwise + = tcLookupValueByKey fromRationalClassOpKey `thenNF_Tc` \ from_rational -> -- The type Rational isn't wired in so we have to conjure it up tcLookupTyConByKey rationalTyConKey `thenNF_Tc` \ rational_tycon -> @@ -468,194 +730,39 @@ lookupInst inst@(LitInst u (OverloadedFractional f) ty orig loc) rational_ty = mkSynTy rational_tycon [] rational_lit = HsLitOut (HsFrac f) rational_ty in - newMethodAtLoc orig loc from_rational [ty] `thenNF_Tc` \ (method_inst, method_id) -> - returnTc ([method_inst], (instToId inst, HsApp (HsVar method_id) rational_lit)) -\end{code} + newMethodAtLoc loc from_rational [ty] `thenNF_Tc` \ (method_inst, method_id) -> + returnNF_Tc (GenInst [method_inst] (HsApp (HsVar method_id) rational_lit)) -There is a second, simpler interface, when you want an instance of a -class at a given nullary type constructor. It just returns the -appropriate dictionary if it exists. It is used only when resolving -ambiguous dictionaries. - -\begin{code} -lookupSimpleInst :: ClassInstEnv - -> Class - -> Type -- Look up (c,t) - -> TcM s [(Class,Type)] -- Here are the needed (c,t)s - -lookupSimpleInst class_inst_env clas ty - = case (lookupMEnv matchTy class_inst_env ty) of - Nothing -> failTc (noSimpleInst clas ty) - Just (dfun,tenv) -> returnTc [(c,instantiateTy tenv t) | (c,t) <- theta] - where - (_, theta, _) = splitSigmaTy (idType dfun) - -noSimpleInst clas ty sty - = ppSep [ppStr "No instance for class", ppQuote (ppr sty clas), - ppStr "at type", ppQuote (ppr sty ty)] -\end{code} - - -@mkInstSpecEnv@ is used to construct the @SpecEnv@ for a dfun. -It does it by filtering the class's @InstEnv@. All pretty shady stuff. - -\begin{code} -mkInstSpecEnv clas inst_ty inst_tvs inst_theta = panic "mkInstSpecEnv" -\end{code} - -\begin{pseudocode} -mkInstSpecEnv :: Class -- class - -> Type -- instance type - -> [TyVarTemplate] -- instance tyvars - -> ThetaType -- superclasses dicts - -> SpecEnv -- specenv for dfun of instance - -mkInstSpecEnv clas inst_ty inst_tvs inst_theta - = mkSpecEnv (catMaybes (map maybe_spec_info matches)) where - matches = matchMEnv matchTy (classInstEnv clas) inst_ty + floatprim_lit = HsLitOut (HsFloatPrim f) floatPrimTy + float_lit = mkHsConApp floatDataCon [] [floatprim_lit] + doubleprim_lit = HsLitOut (HsDoublePrim f) doublePrimTy + double_lit = mkHsConApp doubleDataCon [] [doubleprim_lit] - maybe_spec_info (_, match_info, MkInstTemplate dfun _ []) - = Just (SpecInfo (map (assocMaybe match_info) inst_tvs) (length inst_theta) dfun) - maybe_spec_info (_, match_info, _) - = Nothing -\end{pseudocode} +-- there are no `instances' of functional dependencies or implicit params +lookupInst _ = returnNF_Tc NoInstance -\begin{code} -addClassInst - :: ClassInstEnv -- Incoming envt - -> Type -- The instance type: inst_ty - -> Id -- Dict fun id to apply. Free tyvars of inst_ty must - -- be the same as the forall'd tyvars of the dfun id. - -> MaybeErr - ClassInstEnv -- Success - (Type, Id) -- Offending overlap - -addClassInst inst_env inst_ty dfun_id = insertMEnv matchTy inst_env inst_ty dfun_id \end{code} - - -%************************************************************************ -%* * -\subsection[Inst-origin]{The @InstOrigin@ type} -%* * -%************************************************************************ - -The @InstOrigin@ type gives information about where a dictionary came from. -This is important for decent error message reporting because dictionaries -don't appear in the original source code. Doubtless this type will evolve... - -\begin{code} -data InstOrigin s - = OccurrenceOf (TcIdOcc s) -- Occurrence of an overloaded identifier - | OccurrenceOfCon Id -- Occurrence of a data constructor - - | RecordUpdOrigin - - | DataDeclOrigin -- Typechecking a data declaration - - | InstanceDeclOrigin -- Typechecking an instance decl - - | LiteralOrigin HsLit -- Occurrence of a literal - - | ArithSeqOrigin RenamedArithSeqInfo -- [x..], [x..y] etc - - | SignatureOrigin -- A dict created from a type signature - - | DoOrigin -- The monad for a do expression - - | ClassDeclOrigin -- Manufactured during a class decl - --- NO MORE! --- | DerivingOrigin InstanceMapper --- Class --- TyCon - - -- During "deriving" operations we have an ever changing - -- mapping of classes to instances, so we record it inside the - -- origin information. This is a bit of a hack, but it works - -- fine. (Simon is to blame [WDP].) - - | InstanceSpecOrigin InstanceMapper - Class -- in a SPECIALIZE instance pragma - Type - - -- When specialising instances the instance info attached to - -- each class is not yet ready, so we record it inside the - -- origin information. This is a bit of a hack, but it works - -- fine. (Patrick is to blame [WDP].) - --- | DefaultDeclOrigin -- Related to a `default' declaration - - | ValSpecOrigin Name -- in a SPECIALIZE pragma for a value - - -- Argument or result of a ccall - -- Dictionaries with this origin aren't actually mentioned in the - -- translated term, and so need not be bound. Nor should they - -- be abstracted over. - - | CCallOrigin String -- CCall label - (Maybe RenamedHsExpr) -- Nothing if it's the result - -- Just arg, for an argument - - | LitLitOrigin String -- the litlit - - | UnknownOrigin -- Help! I give up... -\end{code} +There is a second, simpler interface, when you want an instance of a +class at a given nullary type constructor. It just returns the +appropriate dictionary if it exists. It is used only when resolving +ambiguous dictionaries. \begin{code} --- During deriving and instance specialisation operations --- we can't get the instances of the class from inside the --- class, because the latter ain't ready yet. Instead we --- find a mapping from classes to envts inside the dict origin. - -get_inst_env :: Class -> InstOrigin s -> ClassInstEnv --- get_inst_env clas (DerivingOrigin inst_mapper _ _) --- = fst (inst_mapper clas) -get_inst_env clas (InstanceSpecOrigin inst_mapper _ _) - = fst (inst_mapper clas) -get_inst_env clas other_orig = classInstEnv clas - - -pprOrigin :: String -> InstOrigin s -> SrcLoc -> Error - -pprOrigin hdr orig locn - = addErrLoc locn hdr $ \ sty -> - case orig of - OccurrenceOf id -> - ppBesides [ppPStr SLIT("at a use of an overloaded identifier: `"), - ppr sty id, ppChar '\''] - OccurrenceOfCon id -> - ppBesides [ppPStr SLIT("at a use of an overloaded constructor: `"), - ppr sty id, ppChar '\''] - InstanceDeclOrigin -> - ppStr "in an instance declaration" - LiteralOrigin lit -> - ppCat [ppStr "at an overloaded literal:", ppr sty lit] - ArithSeqOrigin seq -> - ppCat [ppStr "at an arithmetic sequence:", ppr sty seq] - SignatureOrigin -> - ppStr "in a type signature" - DoOrigin -> - ppStr "in a do statement" - ClassDeclOrigin -> - ppStr "in a class declaration" - InstanceSpecOrigin _ clas ty -> - ppBesides [ppStr "in a SPECIALIZE instance pragma; class \"", - ppr sty clas, ppStr "\" type: ", ppr sty ty] - ValSpecOrigin name -> - ppBesides [ppStr "in a SPECIALIZE user-pragma for `", - ppr sty name, ppStr "'"] - CCallOrigin clabel Nothing{-ccall result-} -> - ppBesides [ppStr "in the result of the _ccall_ to `", - ppStr clabel, ppStr "'"] - CCallOrigin clabel (Just arg_expr) -> - ppBesides [ppStr "in an argument in the _ccall_ to `", - ppStr clabel, ppStr "', namely: ", ppr sty arg_expr] - LitLitOrigin s -> - ppBesides [ppStr "in this ``literal-literal'': ", ppStr s] - UnknownOrigin -> - ppStr "in... oops -- I don't know where the overloading came from!" +lookupSimpleInst :: InstEnv + -> Class + -> [Type] -- Look up (c,t) + -> NF_TcM s (Maybe [(Class,[Type])]) -- Here are the needed (c,t)s + +lookupSimpleInst class_inst_env clas tys + = case lookupInstEnv (ppr clas) class_inst_env tys of + Nothing -> returnNF_Tc Nothing + + Just (tenv, dfun) + -> returnNF_Tc (Just (substClasses (mkSubst emptyInScopeSet tenv) theta')) + where + (_, theta, _) = splitSigmaTy (idType dfun) + theta' = map (\(Class clas tys) -> (clas,tys)) theta \end{code}