X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FInst.lhs;h=96bc7c1b921b9f4be100255898a14958fadf8c6f;hb=4161ba13916463f8e67259498eacf22744160e1f;hp=052d79631980dca7959f10f8d2d7520e5d5dfebe;hpb=dabfa71f33eabc5a2d10959728f772aa016f1c84;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/Inst.lhs b/ghc/compiler/typecheck/Inst.lhs index 052d796..96bc7c1 100644 --- a/ghc/compiler/typecheck/Inst.lhs +++ b/ghc/compiler/typecheck/Inst.lhs @@ -1,67 +1,84 @@ % -% (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, + pprInst, pprInsts, pprInstsInFull, tidyInst, tidyInsts, - newDicts, newDictsAtLoc, newMethod, newMethodWithGivenTy, newOverloadedLit, + newDictFromOld, newDicts, newClassDicts, newDictsAtLoc, + newMethod, newMethodWithGivenTy, newOverloadedLit, + newIPDict, instOverloadedFun, + instantiateFdClassTys, instFunDeps, instFunDepsOfTheta, + newFunDepFromDict, - instType, tyVarsOfInst, lookupInst, lookupSimpleInst, + tyVarsOfInst, tyVarsOfInsts, tyVarsOfLIE, instLoc, getDictClassTys, + getDictPred_maybe, getMethodTheta_maybe, + getFunDeps, getFunDepsOfLIE, + getIPs, getIPsOfLIE, + getAllFunDeps, getAllFunDepsOfLIE, - isDict, isTyVarDict, + lookupInst, lookupSimpleInst, LookupInstResult(..), - zonkInst, instToId, + isDict, isClassDict, isMethod, + isTyVarDict, isStdClassTyVarDict, isMethodFor, notFunDep, + instBindingRequired, instCanBeGeneralised, - matchesInst, - instBindingRequired, instCanBeGeneralised + zonkInst, zonkInsts, zonkFunDeps, zonkTvFunDeps, + instToId, instToIdBndr, ipToId, + InstOrigin(..), InstLoc, pprInstLoc ) where -import Ubiq - -import HsSyn ( HsLit(..), HsExpr(..), HsBinds, - InPat, OutPat, Stmt, Qual, Match, - ArithSeqInfo, PolyType, Fake ) -import RnHsSyn ( RenamedArithSeqInfo(..), RenamedHsExpr(..) ) -import TcHsSyn ( TcIdOcc(..), TcExpr(..), TcIdBndr(..), - mkHsTyApp, mkHsDictApp ) - -import TcMonad hiding ( rnMtoTcM ) -import TcEnv ( tcLookupGlobalValueByKey ) -import TcType ( TcType(..), TcRhoType(..), TcMaybe, TcTyVarSet(..), - tcInstType, zonkTcType ) - -import Bag ( emptyBag, unitBag, unionBags, unionManyBags, listToBag, consBag ) -import Class ( Class(..), GenClass, ClassInstEnv(..), classInstEnv ) -import Id ( GenId, idType, mkInstId ) -import MatchEnv ( lookupMEnv, insertMEnv ) -import Name ( mkLocalName, getLocalName, Name ) +#include "HsVersions.h" + +import HsSyn ( HsLit(..), HsOverLit(..), HsExpr(..) ) +import RnHsSyn ( RenamedHsOverLit ) +import TcHsSyn ( TcExpr, TcId, + mkHsTyApp, mkHsDictApp, mkHsConApp, zonkId + ) +import TcMonad +import TcEnv ( TcIdSet, tcGetInstEnv, tcLookupGlobalId ) +import InstEnv ( InstLookupResult(..), lookupInstEnv ) +import TcType ( TcThetaType, + TcType, TcTauType, TcTyVarSet, + zonkTcTyVars, zonkTcType, zonkTcTypes, + zonkTcThetaType + ) +import CoreFVs ( idFreeTyVars ) +import Class ( Class, FunDep ) +import FunDeps ( instantiateFdClassTys ) +import Id ( Id, idType, mkUserLocal, mkSysLocal ) +import PrelInfo ( isStandardClass, isCcallishClass, isNoDictClass ) +import Name ( mkDictOcc, mkMethodOcc, mkIPOcc, getOccName, nameUnique ) +import PprType ( pprPred ) +import Type ( Type, PredType(..), + isTyVarTy, mkDictTy, mkPredTy, + splitForAllTys, splitSigmaTy, funArgTy, + splitRhoTy, tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, + tidyOpenType, tidyOpenTypes + ) +import Subst ( emptyInScopeSet, mkSubst, mkInScopeSet, + substTy, substClasses, mkTyVarSubst, mkTopTyVarSubst + ) +import Literal ( inIntRange ) +import VarEnv ( TidyEnv, lookupSubstEnv, SubstResult(..) ) +import VarSet ( elemVarSet, emptyVarSet, unionVarSet ) +import TysWiredIn ( isIntTy, + floatDataCon, isFloatTy, + doubleDataCon, isDoubleTy, + isIntegerTy, voidTy + ) +import PrelNames( Unique, hasKey, fromIntName, fromIntegerClassOpKey ) +import Maybe ( catMaybes ) +import Util ( thenCmp, zipWithEqual, mapAccumL ) +import Bag 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 ) -import TyVar ( GenTyVar ) -import TysPrim ( intPrimTy ) -import TysWiredIn ( intDataCon ) -import Unique ( Unique, showUnique, - fromRationalClassOpKey, fromIntClassOpKey, fromIntegerClassOpKey ) -import Util ( panic, zipEqual, zipWithEqual, assoc, assertPanic ) \end{code} %************************************************************************ @@ -71,16 +88,29 @@ import Util ( panic, zipEqual, zipWithEqual, assoc, assertPanic ) %************************************************************************ \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 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} %************************************************************************ @@ -98,219 +128,168 @@ 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 - (InstOrigin s) - SrcLoc + InstLoc + + -- 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 - -data OverloadedLit - = OverloadedIntegral Integer -- The number - | OverloadedFractional Rational -- The number - -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 + RenamedHsOverLit -- The literal from the occurrence site + TcType -- The type at which the literal is used + InstLoc + + | FunDep + Unique + Class -- the class from which this arises + [FunDep TcType] + InstLoc \end{code} -Construction -~~~~~~~~~~~~ +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} -newDicts :: InstOrigin s - -> [(Class, TcType s)] - -> NF_TcM s (LIE s, [TcIdOcc s]) -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) +instance Ord Inst where + compare = cmpInst -newMethod :: InstOrigin s - -> TcIdOcc s - -> [TcType s] - -> NF_TcM s (LIE s, TcIdOcc s) -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 tcInstType (zipEqual "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 - in - returnNF_Tc (unitLIE meth_inst, instToId meth_inst) +instance Eq Inst where + (==) i1 i2 = case i1 `cmpInst` i2 of + EQ -> True + other -> False -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 - -- slightly different interface - = -- Get the Id type and instantiate it at the specified types - 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 - in - returnNF_Tc (meth_inst, instToId meth_inst) +cmpInst (Dict _ pred1 _) (Dict _ pred2 _) = (pred1 `compare` pred2) +cmpInst (Dict _ _ _) other = LT -newOverloadedLit :: InstOrigin s - -> OverloadedLit - -> TcType s - -> NF_TcM s (LIE s, TcIdOcc s) -newOverloadedLit orig lit ty - = tcGetSrcLoc `thenNF_Tc` \ loc -> - tcGetUnique `thenNF_Tc` \ new_uniq -> - let - lit_inst = LitInst new_uniq lit ty orig loc - in - returnNF_Tc (unitLIE lit_inst, instToId lit_inst) -\end{code} +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 `compare` lit2) `thenCmp` (ty1 `compare` ty2) +cmpInst (LitInst _ _ _ _) (FunDep _ _ _ _) = LT +cmpInst (LitInst _ _ _ _) other = GT -\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) +cmpInst (FunDep _ clas1 fds1 _) (FunDep _ clas2 fds2 _) = (clas1 `compare` clas2) `thenCmp` (fds1 `compare` fds2) +cmpInst (FunDep _ _ _ _) other = GT -instToId (LitInst u list ty orig loc) - = TcId (mkInstId u ty (mkLocalName u SLIT("lit") True{-emph uniq-} loc)) +-- and they can only have HsInt or HsFracs in them. \end{code} + +Selection +~~~~~~~~~ \begin{code} -instType :: Inst s -> TcType s -instType (Dict _ clas ty _ _) = mkDictTy clas ty -instType (LitInst _ _ ty _ _) = ty -instType (Method _ id tys ty _ _) = ty -\end{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 -Zonking -~~~~~~~ -Zonking makes sure that the instance types are fully zonked, -but doesn't do the same for the Id in a Method. There's no -need, and it's a lot of extra work. +getMethodTheta_maybe (Method _ _ _ theta _ _) = Just theta +getMethodTheta_maybe _ = Nothing -\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) +getDictClassTys (Dict u (Class clas tys) _) = (clas, tys) -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) +getFunDeps (FunDep _ clas fds _) = Just (clas, fds) +getFunDeps _ = Nothing -zonkInst (LitInst u lit ty orig loc) - = zonkTcType ty `thenNF_Tc` \ new_ty -> - returnNF_Tc (LitInst u lit new_ty orig loc) -\end{code} +getFunDepsOfLIE lie = catMaybes (map getFunDeps (lieToList lie)) +getIPsOfPred (IParam n ty) = [(n, ty)] +getIPsOfPred _ = [] +getIPsOfTheta theta = concatMap getIPsOfPred theta -\begin{code} -tyVarsOfInst :: Inst s -> TcTyVarSet s -tyVarsOfInst (Dict _ _ ty _ _) = tyVarsOfType ty -tyVarsOfInst (Method _ _ tys rho _ _) = tyVarsOfTypes tys -tyVarsOfInst (LitInst _ _ ty _ _) = tyVarsOfType ty -\end{code} +getIPs (Dict u (IParam n ty) loc) = [(n, ty)] +getIPs (Method u id _ theta t loc) = getIPsOfTheta theta +getIPs _ = [] -@matchesInst@ checks when two @Inst@s are instances of the same -thing at the same type, even if their uniques differ. +getIPsOfLIE lie = concatMap getIPs (lieToList lie) -\begin{code} -matchesInst :: Inst s -> Inst s -> Bool +getAllFunDeps (FunDep _ clas fds _) = fds +getAllFunDeps inst = map (\(n,ty) -> ([], [ty])) (getIPs inst) -matchesInst (Dict _ clas1 ty1 _ _) (Dict _ clas2 ty2 _ _) - = clas1 == clas2 && ty1 `eqSimpleTy` ty2 +getAllFunDepsOfLIE lie = concat (map getAllFunDeps (lieToList lie)) -matchesInst (Method _ id1 tys1 _ _ _) (Method _ id2 tys2 _ _ _) - = id1 == id2 - && and (zipWith eqSimpleTy tys1 tys2) - && length tys1 == length tys2 +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 -matchesInst (LitInst _ lit1 ty1 _ _) (LitInst _ lit2 ty2 _ _) - = lit1 `eq` lit2 && ty1 `eqSimpleTy` ty2 - where - (OverloadedIntegral i1) `eq` (OverloadedIntegral i2) = i1 == i2 - (OverloadedFractional f1) `eq` (OverloadedFractional f2) = f1 == f2 - _ `eq` _ = False +tyVarsOfInsts insts + = foldr unionVarSet emptyVarSet (map tyVarsOfInst insts) -matchesInst other1 other2 = False +tyVarsOfLIE lie + = foldr unionVarSet emptyVarSet (map tyVarsOfInst insts) + where insts = lieToList lie \end{code} - 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 +isDict :: Inst -> Bool +isDict (Dict _ _ _) = True +isDict other = False + +isClassDict :: Inst -> Bool +isClassDict (Dict _ (Class _ _) _) = True +isClassDict other = False + +isMethod :: Inst -> Bool +isMethod (Method _ _ _ _ _ _) = True +isMethod 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 @@ -319,343 +298,433 @@ must be witnessed by an actual binding; the second tells whether an @Inst@ can be generalised over. \begin{code} -instBindingRequired :: Inst s -> Bool -instBindingRequired inst - = case getInstOrigin inst of - CCallOrigin _ _ -> False -- No binding required - LitLitOrigin _ -> False - OccurrenceOfCon _ -> False - other -> True - -instCanBeGeneralised :: Inst s -> Bool -instCanBeGeneralised inst - = case getInstOrigin inst of - CCallOrigin _ _ -> False -- Can't be generalised - LitLitOrigin _ -> False -- Can't be generalised - other -> True +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} -Printing -~~~~~~~~ -ToDo: improve these pretty-printing things. The ``origin'' is really only -relevant in error messages. +Construction +~~~~~~~~~~~~ \begin{code} -instance Outputable (Inst s) where - ppr sty (LitInst uniq lit ty orig loc) - = ppSep [case lit of - OverloadedIntegral i -> ppInteger i - OverloadedFractional f -> ppRational f, - ppStr "at", - ppr sty ty, - show_uniq sty uniq - ] - - ppr sty (Dict uniq clas ty orig loc) - = ppSep [ppr sty clas, - ppStr "at", - ppr sty ty, - show_uniq sty uniq - ] - - ppr sty (Method uniq id tys rho orig loc) - = ppSep [ppr sty id, - ppStr "at", - ppr sty tys, - show_uniq sty uniq - ] - -show_uniq PprDebug uniq = ppr PprDebug uniq -show_uniq sty uniq = ppNil +newDicts :: InstOrigin + -> TcThetaType + -> NF_TcM (LIE, [TcId]) +newDicts orig theta + = tcGetInstLoc orig `thenNF_Tc` \ loc -> + newDictsAtLoc loc theta `thenNF_Tc` \ (dicts, ids) -> + returnNF_Tc (listToBag dicts, ids) + +newClassDicts :: InstOrigin + -> [(Class,[TcType])] + -> NF_TcM (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 ([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 Inst +newDictFromOld (Dict _ _ loc) clas tys + = tcGetUnique `thenNF_Tc` \ uniq -> + returnNF_Tc (Dict uniq (Class clas tys) loc) + + +newMethod :: InstOrigin + -> TcId + -> [TcType] + -> NF_TcM (LIE, TcId) +newMethod orig id tys + = -- Get the Id type and instantiate it at the specified types + let + (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) +instOverloadedFun orig v arg_tys theta tau +-- This is where we introduce new functional dependencies into the LIE + = newMethodWithGivenTy orig v arg_tys theta tau `thenNF_Tc` \ inst -> + instFunDeps orig theta `thenNF_Tc` \ fds -> + returnNF_Tc (instToId inst, mkLIE (inst : fds)) + +instFunDeps orig theta + = tcGetUnique `thenNF_Tc` \ uniq -> + tcGetInstLoc orig `thenNF_Tc` \ loc -> + let ifd (Class clas tys) = + let fds = instantiateFdClassTys clas tys in + if null fds then Nothing else Just (FunDep uniq clas fds loc) + ifd _ = Nothing + in returnNF_Tc (catMaybes (map ifd theta)) + +instFunDepsOfTheta theta + = let ifd (Class clas tys) = instantiateFdClassTys clas tys + ifd (IParam n ty) = [([], [ty])] + in concat (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 (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) = 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} -Printing in error messages +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} -noInstanceErr inst sty = ppHang (ppPStr SLIT("No instance for:")) 4 (ppr sty inst) -\end{code} +newOverloadedLit :: InstOrigin + -> RenamedHsOverLit + -> TcType + -> NF_TcM (TcExpr, LIE) +newOverloadedLit orig (HsIntegral i _) ty + | isIntTy ty && inIntRange i -- Short cut for Int + = returnNF_Tc (int_lit, emptyLIE) -%************************************************************************ -%* * -\subsection[InstEnv-types]{Type declarations} -%* * -%************************************************************************ + | isIntegerTy ty -- Short cut for Integer + = returnNF_Tc (integer_lit, emptyLIE) + + where + int_lit = HsLit (HsInt i) + integer_lit = HsLit (HsInteger i) + +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 loc + in + returnNF_Tc (HsVar (instToId lit_inst), unitLIE lit_inst) +\end{code} \begin{code} -type InstanceMapper = Class -> (ClassInstEnv, ClassOp -> SpecEnv) +newFunDepFromDict dict + | isClassDict dict + = tcGetUnique `thenNF_Tc` \ uniq -> + let (clas, tys) = getDictClassTys dict + fds = instantiateFdClassTys clas tys + inst = FunDep uniq clas fds (instLoc dict) + in + if null fds then returnNF_Tc Nothing else returnNF_Tc (Just inst) + | otherwise + = returnNF_Tc Nothing \end{code} -A @ClassInstEnv@ lives inside a class, and identifies all the instances -of that class. The @Id@ inside a ClassInstEnv mapping is the dfun for -that instance. - -There is an important consistency constraint between the @MatchEnv@s -in and the dfun @Id@s inside them: the free type variables of the -@Type@ key in the @MatchEnv@ must be a subset of the universally-quantified -type variables of the dfun. Thus, the @ClassInstEnv@ for @Eq@ might -contain the following entry: -@ - [a] ===> dfun_Eq_List :: forall a. Eq a => Eq [a] -@ -The "a" in the pattern must be one of the forall'd variables in -the dfun type. +\begin{code} +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} -lookupInst :: Inst s - -> TcM s ([Inst s], - (TcIdOcc s, TcExpr s)) -- The new binding +instToId :: Inst -> TcId +instToId inst = instToIdBndr inst --- Dictionaries +instToIdBndr :: Inst -> TcId +instToIdBndr (Dict u (Class clas tys) (_,loc,_)) + = mkUserLocal (mkDictOcc (getOccName clas)) u (mkDictTy clas tys) loc +instToIdBndr (Dict u (IParam n ty) (_,loc,_)) + = ipToId n ty loc -lookupInst dict@(Dict _ clas ty orig loc) - = case lookupMEnv matchTy (get_inst_env clas orig) ty of - Nothing -> tcAddSrcLoc loc $ - tcAddErrCtxt (pprOrigin orig) $ - failTc (noInstanceErr dict) +instToIdBndr (Method u id tys theta tau (_,loc,_)) + = mkUserLocal (mkMethodOcc (getOccName id)) u tau loc - Just (dfun_id, tenv) - -> let - (tyvars, rho) = splitForAllTy (idType dfun_id) - ty_args = map (assoc "lookupInst" tenv) tyvars - -- 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) -> - let - rhs = mkHsDictApp (mkHsTyApp (HsVar (RealId dfun_id)) ty_args) dict_ids - in - returnTc (dicts, (instToId dict, rhs)) - +instToIdBndr (LitInst u list ty loc) + = mkSysLocal SLIT("lit") u ty --- Methods +instToIdBndr (FunDep u clas fds _) + = mkSysLocal SLIT("FunDep") u voidTy -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 +ipToId n ty loc + = mkUserLocal (mkIPOcc (getOccName n)) (nameUnique n) (mkPredTy (IParam n ty)) loc +\end{code} --- 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)) +Zonking +~~~~~~~ +Zonking makes sure that the instance types are fully zonked, +but doesn't do the same for the Id in a Method. There's no +need, and it's a lot of extra work. - | 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) ty))) +\begin{code} +zonkPred :: TcPredType -> NF_TcM 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 (IParam n new_ty) + +zonkInst :: Inst -> NF_TcM Inst +zonkInst (Dict u pred loc) + = zonkPred pred `thenNF_Tc` \ new_pred -> + returnNF_Tc (Dict u new_pred loc) + +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 + + 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) + +zonkInst (LitInst u lit ty loc) + = zonkTcType ty `thenNF_Tc` \ new_ty -> + returnNF_Tc (LitInst u lit new_ty loc) + +zonkInst (FunDep u clas fds loc) + = zonkFunDeps fds `thenNF_Tc` \ fds' -> + returnNF_Tc (FunDep u clas fds' loc) + +zonkInsts insts = mapNF_Tc zonkInst insts + +zonkFunDeps fds = mapNF_Tc zonkFd fds where - intprim_lit = HsLitOut (HsIntPrim i) intPrimTy - int_lit = HsApp (HsVar (RealId intDataCon)) intprim_lit + zonkFd (ts1, ts2) + = zonkTcTypes ts1 `thenNF_Tc` \ ts1' -> + zonkTcTypes ts2 `thenNF_Tc` \ ts2' -> + returnNF_Tc (ts1', ts2') -lookupInst inst@(LitInst u (OverloadedFractional f) ty orig loc) - = tcLookupGlobalValueByKey fromRationalClassOpKey `thenNF_Tc` \ from_rational -> - newMethodAtLoc orig loc from_rational [ty] `thenNF_Tc` \ (method_inst, method_id) -> - returnTc ([method_inst], (instToId inst, HsApp (HsVar method_id) (HsLitOut (HsFrac f) ty))) +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} -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. + +Printing +~~~~~~~~ +ToDo: improve these pretty-printing things. The ``origin'' is really only +relevant in error messages. \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} +instance Outputable Inst where + ppr inst = pprInst inst +pprInst (LitInst u lit ty loc) + = hsep [ppr lit, ptext SLIT("at"), ppr ty, show_uniq u] -@mkInstSpecEnv@ is used to construct the @SpecEnv@ for a dfun. -It does it by filtering the class's @InstEnv@. All pretty shady stuff. +pprInst (Dict u pred loc) = pprPred pred <+> show_uniq u -\begin{code} -mkInstSpecEnv clas inst_ty inst_tvs inst_theta = panic "mkInstSpecEnv" -\end{code} +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] -\begin{pseudocode} -mkInstSpecEnv :: Class -- class - -> Type -- instance type - -> [TyVarTemplate] -- instance tyvars - -> ThetaType -- superclasses dicts - -> SpecEnv -- specenv for dfun of instance +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 -mkInstSpecEnv clas inst_ty inst_tvs inst_theta - = mkSpecEnv (catMaybes (map maybe_spec_info matches)) +tidyInst :: TidyEnv -> Inst -> (TidyEnv, Inst) +tidyInst env (LitInst u lit ty loc) + = (env', LitInst u lit ty' loc) where - matches = matchMEnv matchTy (classInstEnv clas) inst_ty + (env', ty') = tidyOpenType env ty - 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} +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 -\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} +-- 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[Inst-origin]{The @InstOrigin@ type} +\subsection[InstEnv-types]{Type declarations} %* * %************************************************************************ -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 +data LookupInstResult s + = NoInstance + | SimpleInst TcExpr -- Just a variable, type application, or literal + | GenInst [Inst] TcExpr -- The expression and its needed insts - | RecordUpdOrigin +lookupInst :: Inst + -> NF_TcM (LookupInstResult s) - | DataDeclOrigin -- Typechecking a data declaration - - | InstanceDeclOrigin -- Typechecking an instance decl - - | LiteralOrigin HsLit -- Occurrence of a literal +-- Dictionaries - | ArithSeqOrigin RenamedArithSeqInfo -- [x..], [x..y] etc +lookupInst dict@(Dict _ (Class clas tys) loc) + = tcGetInstEnv `thenNF_Tc` \ inst_env -> + case lookupInstEnv inst_env clas tys of - | SignatureOrigin -- A dict created from a type signature + FoundInst tenv dfun_id + -> let + subst = mkSubst (mkInScopeSet (tyVarsOfTypes tys)) tenv + (tyvars, rho) = splitForAllTys (idType dfun_id) + ty_args = map subst_tv tyvars + dfun_rho = substTy subst rho + (theta, _) = 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 + if null theta then + returnNF_Tc (SimpleInst ty_app) + else + newDictsAtLoc loc theta `thenNF_Tc` \ (dicts, dict_ids) -> + let + rhs = mkHsDictApp ty_app dict_ids + in + returnNF_Tc (GenInst dicts rhs) - | DoOrigin -- The monad for a do expression + other -> returnNF_Tc NoInstance +lookupInst dict@(Dict _ _ loc) = returnNF_Tc NoInstance - | ClassDeclOrigin -- Manufactured during a class decl +-- Methods --- NO MORE! --- | DerivingOrigin InstanceMapper --- Class --- TyCon +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)) - -- 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].) +-- Literals - | InstanceSpecOrigin InstanceMapper - Class -- in a SPECIALIZE instance pragma - Type +lookupInst inst@(LitInst u (HsIntegral i from_integer_name) 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 + + | 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 + && from_integer_name `hasKey` fromIntegerClassOpKey -- And it's the built-in prelude fromInteger + -- (i.e. no funny business with user-defined + -- packages of numeric classes) + = -- So we can use the Prelude fromInt + tcLookupGlobalId fromIntName `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! + = tcLookupGlobalId from_integer_name `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 + integer_lit = HsLit (HsInteger i) + int_lit = HsLit (HsInt i) - -- 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].) +-- 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). --- | DefaultDeclOrigin -- Related to a `default' declaration +lookupInst inst@(LitInst u (HsFractional f from_rat_name) ty loc) + | isFloatTy ty = returnNF_Tc (GenInst [] float_lit) + | isDoubleTy ty = returnNF_Tc (GenInst [] double_lit) - | ValSpecOrigin Name -- in a SPECIALIZE pragma for a value + | otherwise + = tcLookupGlobalId from_rat_name `thenNF_Tc` \ from_rational -> + newMethodAtLoc loc from_rational [ty] `thenNF_Tc` \ (method_inst, method_id) -> + let + rational_ty = funArgTy (idType method_id) + rational_lit = HsLit (HsRat f rational_ty) + in + returnNF_Tc (GenInst [method_inst] (HsApp (HsVar method_id) rational_lit)) - -- 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. + where + floatprim_lit = HsLit (HsFloatPrim f) + float_lit = mkHsConApp floatDataCon [] [floatprim_lit] + doubleprim_lit = HsLit (HsDoublePrim f) + double_lit = mkHsConApp doubleDataCon [] [doubleprim_lit] - | CCallOrigin String -- CCall label - (Maybe RenamedHsExpr) -- Nothing if it's the result - -- Just arg, for an argument +-- there are no `instances' of functional dependencies or implicit params - | LitLitOrigin String -- the litlit +lookupInst _ = returnNF_Tc NoInstance - | 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 :: InstOrigin s -> PprStyle -> Pretty - -pprOrigin (OccurrenceOf id) sty - = ppBesides [ppPStr SLIT("at a use of an overloaded identifier: `"), - ppr sty id, ppChar '\''] -pprOrigin (OccurrenceOfCon id) sty - = ppBesides [ppPStr SLIT("at a use of an overloaded constructor: `"), - ppr sty id, ppChar '\''] -pprOrigin (InstanceDeclOrigin) sty - = ppStr "in an instance declaration" -pprOrigin (LiteralOrigin lit) sty - = ppCat [ppStr "at an overloaded literal:", ppr sty lit] -pprOrigin (ArithSeqOrigin seq) sty - = ppCat [ppStr "at an arithmetic sequence:", ppr sty seq] -pprOrigin (SignatureOrigin) sty - = ppStr "in a type signature" -pprOrigin (DoOrigin) sty - = ppStr "in a do statement" -pprOrigin (ClassDeclOrigin) sty - = ppStr "in a class declaration" --- pprOrigin (DerivingOrigin _ clas tycon) sty --- = ppBesides [ppStr "in a `deriving' clause; class `", --- ppr sty clas, --- ppStr "'; offending type `", --- ppr sty tycon, --- ppStr "'"] -pprOrigin (InstanceSpecOrigin _ clas ty) sty - = ppBesides [ppStr "in a SPECIALIZE instance pragma; class \"", - ppr sty clas, ppStr "\" type: ", ppr sty ty] --- pprOrigin (DefaultDeclOrigin) sty --- = ppStr "in a `default' declaration" -pprOrigin (ValSpecOrigin name) sty - = ppBesides [ppStr "in a SPECIALIZE user-pragma for `", - ppr sty name, ppStr "'"] -pprOrigin (CCallOrigin clabel Nothing{-ccall result-}) sty - = ppBesides [ppStr "in the result of the _ccall_ to `", - ppStr clabel, ppStr "'"] -pprOrigin (CCallOrigin clabel (Just arg_expr)) sty - = ppBesides [ppStr "in an argument in the _ccall_ to `", - ppStr clabel, ppStr "', namely: ", ppr sty arg_expr] -pprOrigin (LitLitOrigin s) sty - = ppBesides [ppStr "in this ``literal-literal'': ", ppStr s] -pprOrigin UnknownOrigin sty - = ppStr "in... oops -- I don't know where the overloading came from!" +lookupSimpleInst :: Class + -> [Type] -- Look up (c,t) + -> NF_TcM (Maybe [(Class,[Type])]) -- Here are the needed (c,t)s + +lookupSimpleInst clas tys + = tcGetInstEnv `thenNF_Tc` \ inst_env -> + case lookupInstEnv inst_env clas tys of + FoundInst tenv dfun + -> returnNF_Tc (Just (substClasses (mkSubst emptyInScopeSet tenv) theta')) + where + (_, theta, _) = splitSigmaTy (idType dfun) + theta' = map (\(Class clas tys) -> (clas,tys)) theta + + other -> returnNF_Tc Nothing \end{code} -