X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FInst.lhs;h=f75d1d309197b9a79c1ef0a59833e80b40be2198;hb=8e67f5502e2e316245806ee3735a2f41a844b611;hp=0c1bff01c5775fc9d0e6b539c9ed6d565ccbcafd;hpb=f714e6b642fd614a9971717045ae47c3d871275e;p=ghc-hetmet.git diff --git a/ghc/compiler/typecheck/Inst.lhs b/ghc/compiler/typecheck/Inst.lhs index 0c1bff0..f75d1d3 100644 --- a/ghc/compiler/typecheck/Inst.lhs +++ b/ghc/compiler/typecheck/Inst.lhs @@ -5,16 +5,17 @@ \begin{code} module Inst ( - showLIE, - Inst, - pprInst, pprInsts, pprInstsInFull, pprDFuns, + + pprDFuns, pprDictsTheta, pprDictsInFull, -- User error messages + showLIE, pprInst, pprInsts, pprInstInFull, -- Debugging messages + tidyInsts, tidyMoreInsts, - newDictsFromOld, newDicts, cloneDict, + newDictsFromOld, newDicts, newDictsAtLoc, cloneDict, newOverloadedLit, newIPDict, newMethod, newMethodFromName, newMethodWithGivenTy, - tcInstClassOp, tcInstCall, tcInstDataCon, + tcInstClassOp, tcInstCall, tcInstStupidTheta, tcSyntaxName, tcStdSyntaxName, tyVarsOfInst, tyVarsOfInsts, tyVarsOfLIE, @@ -22,7 +23,7 @@ module Inst ( instLoc, getDictClassTys, dictPred, lookupInst, LookupInstResult(..), - tcExtendLocalInstEnv, tcGetInstEnvs, + tcExtendLocalInstEnv, tcGetInstEnvs, isDict, isClassDict, isMethod, isLinearInst, linearInstType, isIPDict, isInheritableInst, @@ -38,6 +39,7 @@ module Inst ( #include "HsVersions.h" import {-# SOURCE #-} TcExpr( tcCheckSigma ) +import {-# SOURCE #-} TcUnify ( unifyTauTy ) -- Used in checkKind (sigh) import HsSyn ( HsLit(..), HsOverLit(..), HsExpr(..), LHsExpr, mkHsApp ) import TcHsSyn ( TcId, TcIdSet, @@ -48,40 +50,45 @@ import TcRnMonad import TcEnv ( tcLookupId, checkWellStaged, topIdLvl, tcMetaTy ) import InstEnv ( DFunId, InstEnv, lookupInstEnv, checkFunDeps, extendInstEnv ) import TcIface ( loadImportedInsts ) -import TcMType ( zonkTcType, zonkTcTypes, zonkTcPredType, - zonkTcThetaType, tcInstTyVar, tcInstType, tcInstTyVars +import TcMType ( zonkTcType, zonkTcTypes, zonkTcPredType, zonkTcThetaType, + tcInstTyVar, tcInstType, tcSkolType ) -import TcType ( Type, TcType, TcThetaType, TcTyVarSet, - PredType(..), TyVarDetails(VanillaTv), - tcSplitForAllTys, tcSplitForAllTys, mkTyConApp, - tcSplitPhiTy, tcIsTyVarTy, tcSplitDFunTy, +import TcType ( Type, TcType, TcThetaType, TcTyVarSet, TcTyVar, TcPredType, + PredType(..), SkolemInfo(..), typeKind, mkSigmaTy, + tcSplitForAllTys, tcSplitForAllTys, + tcSplitPhiTy, tcIsTyVarTy, tcSplitDFunTy, tcSplitDFunHead, isIntTy,isFloatTy, isIntegerTy, isDoubleTy, tcIsTyVarTy, mkPredTy, mkTyVarTy, mkTyVarTys, tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, tidyPred, isClassPred, isTyVarClassPred, isLinearPred, getClassPredTys, getClassPredTys_maybe, mkPredName, - isInheritablePred, isIPPred, matchTys, + isInheritablePred, isIPPred, tidyType, tidyTypes, tidyFreeTyVars, tcSplitSigmaTy, - pprPred, pprParendType, pprThetaArrow, pprClassPred + pprPred, pprParendType, pprThetaArrow, pprTheta, pprClassPred ) +import Type ( TvSubst, substTy, substTyVar, substTyWith, substTheta, zipTopTvSubst, + notElemTvSubst, extendTvSubstList ) +import Unify ( tcMatchTys ) +import Kind ( isSubKind ) +import Packages ( isHomeModule ) import HscTypes ( ExternalPackageState(..) ) import CoreFVs ( idFreeTyVars ) -import DataCon ( DataCon,dataConSig ) -import Id ( Id, idName, idType, mkUserLocal, mkSysLocal, mkLocalId, setIdUnique ) +import DataCon ( DataCon, dataConTyVars, dataConStupidTheta, dataConName ) +import Id ( Id, idName, idType, mkUserLocal, mkLocalId ) import PrelInfo ( isStandardClass, isNoDictClass ) -import Name ( Name, mkMethodOcc, getOccName, getSrcLoc, isHomePackageName, isInternalName ) +import Name ( Name, mkMethodOcc, getOccName, getSrcLoc, nameModule, + isInternalName, setNameUnique, mkSystemVarNameEncoded ) import NameSet ( addOneToNameSet ) -import Subst ( substTy, substTyWith, substTheta, mkTyVarSubst ) import Literal ( inIntRange ) -import Var ( TyVar ) -import VarEnv ( TidyEnv, emptyTidyEnv, lookupSubstEnv, SubstResult(..) ) +import Var ( TyVar, tyVarKind, setIdType ) +import VarEnv ( TidyEnv, emptyTidyEnv ) import VarSet ( elemVarSet, emptyVarSet, unionVarSet, mkVarSet ) import TysWiredIn ( floatDataCon, doubleDataCon ) import PrelNames ( integerTyConName, fromIntegerName, fromRationalName, rationalTyConName ) import BasicTypes( IPName(..), mapIPName, ipNameName ) import UniqSupply( uniqsFromSupply ) -import SrcLoc ( mkSrcSpan, noLoc, Located(..) ) -import CmdLineOpts( DynFlags, DynFlag( Opt_AllowUndecidableInstances ), dopt ) +import SrcLoc ( mkSrcSpan, noLoc, unLoc, Located(..) ) +import CmdLineOpts( DynFlags ) import Maybes ( isJust ) import Outputable \end{code} @@ -94,9 +101,9 @@ instName :: Inst -> Name instName inst = idName (instToId inst) instToId :: Inst -> TcId -instToId (Dict id _ _) = id +instToId (LitInst nm _ ty _) = mkLocalId nm ty +instToId (Dict nm pred _) = mkLocalId nm (mkPredTy pred) instToId (Method id _ _ _ _ _) = id -instToId (LitInst id _ _ _) = id instLoc (Dict _ _ loc) = loc instLoc (Method _ _ _ _ _ loc) = loc @@ -218,8 +225,8 @@ newDicts orig theta newDictsAtLoc loc theta cloneDict :: Inst -> TcM Inst -cloneDict (Dict id ty loc) = newUnique `thenM` \ uniq -> - returnM (Dict (setIdUnique id uniq) ty loc) +cloneDict (Dict nm ty loc) = newUnique `thenM` \ uniq -> + returnM (Dict (setNameUnique nm uniq) ty loc) newDictsFromOld :: Inst -> TcThetaType -> TcM [Inst] newDictsFromOld (Dict _ _ loc) theta = newDictsAtLoc loc theta @@ -233,7 +240,7 @@ newDictsAtLoc inst_loc theta = newUniqueSupply `thenM` \ us -> returnM (zipWith mk_dict (uniqsFromSupply us) theta) where - mk_dict uniq pred = Dict (mkLocalId (mkPredName uniq loc pred) (mkPredTy pred)) + mk_dict uniq pred = Dict (mkPredName uniq loc pred) pred inst_loc loc = instLocSrcLoc inst_loc @@ -249,9 +256,9 @@ newIPDict orig ip_name ty let pred = IParam ip_name ty name = mkPredName uniq (instLocSrcLoc inst_loc) pred - id = mkLocalId name (mkPredTy pred) + dict = Dict name pred inst_loc in - returnM (mapIPName (\n -> id) ip_name, Dict id pred inst_loc) + returnM (mapIPName (\n -> instToId dict) ip_name, dict) \end{code} @@ -264,46 +271,28 @@ newIPDict orig ip_name ty \begin{code} -tcInstCall :: InstOrigin -> TcType -> TcM (ExprCoFn, TcType) +tcInstCall :: InstOrigin -> TcType -> TcM (ExprCoFn, [TcTyVar], TcType) tcInstCall orig fun_ty -- fun_ty is usually a sigma-type - = tcInstType VanillaTv fun_ty `thenM` \ (tyvars, theta, tau) -> - newDicts orig theta `thenM` \ dicts -> - extendLIEs dicts `thenM_` - let - inst_fn e = DictApp (mkHsTyApp (noLoc e) (mkTyVarTys tyvars)) (map instToId dicts) - in - returnM (mkCoercion inst_fn, tau) - -tcInstDataCon :: InstOrigin -> DataCon - -> TcM ([TcType], -- Types to instantiate at - [Inst], -- Existential dictionaries to apply to - [TcType], -- Argument types of constructor - TcType, -- Result type - [TyVar]) -- Existential tyvars -tcInstDataCon orig data_con - = let - (tvs, stupid_theta, ex_tvs, ex_theta, arg_tys, tycon) = dataConSig data_con - -- We generate constraints for the stupid theta even when - -- pattern matching (as the Report requires) - in - tcInstTyVars VanillaTv (tvs ++ ex_tvs) `thenM` \ (all_tvs', ty_args', tenv) -> - let - stupid_theta' = substTheta tenv stupid_theta - ex_theta' = substTheta tenv ex_theta - arg_tys' = map (substTy tenv) arg_tys - - n_normal_tvs = length tvs - ex_tvs' = drop n_normal_tvs all_tvs' - result_ty = mkTyConApp tycon (take n_normal_tvs ty_args') - in - newDicts orig stupid_theta' `thenM` \ stupid_dicts -> - newDicts orig ex_theta' `thenM` \ ex_dicts -> - - -- Note that we return the stupid theta *only* in the LIE; - -- we don't otherwise use it at all - extendLIEs stupid_dicts `thenM_` - - returnM (ty_args', ex_dicts, arg_tys', result_ty, ex_tvs') + = do { (tyvars, theta, tau) <- tcInstType fun_ty + ; dicts <- newDicts orig theta + ; extendLIEs dicts + ; let inst_fn e = unLoc (mkHsDictApp (mkHsTyApp (noLoc e) (mkTyVarTys tyvars)) + (map instToId dicts)) + ; return (mkCoercion inst_fn, tyvars, tau) } + +tcInstStupidTheta :: DataCon -> [TcType] -> TcM () +-- Instantiate the "stupid theta" of the data con, and throw +-- the constraints into the constraint set +tcInstStupidTheta data_con inst_tys + | null stupid_theta + = return () + | otherwise + = do { stupid_dicts <- newDicts (OccurrenceOf (dataConName data_con)) + (substTheta tenv stupid_theta) + ; extendLIEs stupid_dicts } + where + stupid_theta = dataConStupidTheta data_con + tenv = zipTopTvSubst (dataConTyVars data_con) inst_tys newMethodFromName :: InstOrigin -> TcType -> Name -> TcM TcId newMethodFromName origin ty name @@ -329,6 +318,11 @@ newMethodWithGivenTy orig id tys theta tau -- This is important because they are used by TcSimplify -- to simplify Insts +-- NB: the kind of the type variable to be instantiated +-- might be a sub-kind of the type to which it is applied, +-- notably when the latter is a type variable of kind ?? +-- Hence the call to checkKind +-- A worry: is this needed anywhere else? tcInstClassOp :: InstLoc -> Id -> [TcType] -> TcM Inst tcInstClassOp inst_loc sel_id tys = let @@ -337,8 +331,21 @@ tcInstClassOp inst_loc sel_id tys substTyWith tyvars tys rho (preds,tau) = tcSplitPhiTy rho_ty in + zipWithM_ checkKind tyvars tys `thenM_` newMethod inst_loc sel_id tys preds tau +checkKind :: TyVar -> TcType -> TcM () +-- Ensure that the type has a sub-kind of the tyvar +checkKind tv ty + = do { ty1 <- zonkTcType ty + ; if typeKind ty1 `isSubKind` tyVarKind tv + then return () + else do + { traceTc (text "checkKind: adding kind constraint" <+> ppr tv <+> ppr ty) + ; tv1 <- tcInstTyVar tv + ; unifyTauTy (mkTyVarTy tv1) ty1 }} + + --------------------------- newMethod inst_loc id tys theta tau = newUnique `thenM` \ new_uniq -> @@ -365,10 +372,10 @@ newOverloadedLit orig lit@(HsIntegral i fi) expected_ty -- Reason: tcSyntaxName does unification -- which is very inconvenient in tcSimplify -- ToDo: noLoc sadness - = tcSyntaxName orig expected_ty (fromIntegerName, noLoc (HsVar fi)) `thenM` \ (_,expr) -> - mkIntegerLit i `thenM` \ integer_lit -> - returnM (mkHsApp expr integer_lit) - + = tcSyntaxName orig expected_ty (fromIntegerName, HsVar fi) `thenM` \ (_,expr) -> + mkIntegerLit i `thenM` \ integer_lit -> + returnM (mkHsApp (noLoc expr) integer_lit) + -- The mkHsApp will get the loc from the literal | Just expr <- shortCutIntLit i expected_ty = returnM expr @@ -377,9 +384,10 @@ newOverloadedLit orig lit@(HsIntegral i fi) expected_ty newOverloadedLit orig lit@(HsFractional r fr) expected_ty | fr /= fromRationalName -- c.f. HsIntegral case - = tcSyntaxName orig expected_ty (fromRationalName, noLoc (HsVar fr)) `thenM` \ (_,expr) -> - mkRatLit r `thenM` \ rat_lit -> - returnM (mkHsApp expr rat_lit) + = tcSyntaxName orig expected_ty (fromRationalName, HsVar fr) `thenM` \ (_,expr) -> + mkRatLit r `thenM` \ rat_lit -> + returnM (mkHsApp (noLoc expr) rat_lit) + -- The mkHsApp will get the loc from the literal | Just expr <- shortCutFracLit r expected_ty = returnM expr @@ -392,8 +400,10 @@ newLitInst orig lit expected_ty = getInstLoc orig `thenM` \ loc -> newUnique `thenM` \ new_uniq -> let - lit_inst = LitInst lit_id lit expected_ty loc - lit_id = mkSysLocal FSLIT("lit") new_uniq expected_ty + lit_nm = mkSystemVarNameEncoded new_uniq FSLIT("lit") + -- The "encoded" bit means that we don't need to z-encode + -- the string every time we call this! + lit_inst = LitInst lit_nm lit expected_ty loc in extendLIE lit_inst `thenM_` returnM (L (instLocSrcSpan loc) (HsVar (instToId lit_inst))) @@ -434,15 +444,13 @@ mkRatLit r %* * %************************************************************************ -Zonking makes sure that the instance types are fully zonked, -but doesn't do the same for any of the Ids in an Inst. There's no -need, and it's a lot of extra work. +Zonking makes sure that the instance types are fully zonked. \begin{code} zonkInst :: Inst -> TcM Inst -zonkInst (Dict id pred loc) +zonkInst (Dict name pred loc) = zonkTcPredType pred `thenM` \ new_pred -> - returnM (Dict id new_pred loc) + returnM (Dict name new_pred loc) zonkInst (Method m id tys theta tau loc) = zonkId id `thenM` \ new_id -> @@ -455,9 +463,9 @@ zonkInst (Method m id tys theta tau loc) zonkTcType tau `thenM` \ new_tau -> returnM (Method m new_id new_tys new_theta new_tau loc) -zonkInst (LitInst id lit ty loc) +zonkInst (LitInst nm lit ty loc) = zonkTcType ty `thenM` \ new_ty -> - returnM (LitInst id lit new_ty loc) + returnM (LitInst nm lit new_ty loc) zonkInsts insts = mappM zonkInst insts \end{code} @@ -476,27 +484,33 @@ relevant in error messages. instance Outputable Inst where ppr inst = pprInst inst -pprInsts :: [Inst] -> SDoc -pprInsts insts = parens (sep (punctuate comma (map pprInst insts))) +pprDictsTheta :: [Inst] -> SDoc +-- Print in type-like fashion (Eq a, Show b) +pprDictsTheta dicts = pprTheta (map dictPred dicts) -pprInstsInFull insts - = vcat (map go insts) +pprDictsInFull :: [Inst] -> SDoc +-- Print in type-like fashion, but with source location +pprDictsInFull dicts + = vcat (map go dicts) where - go inst = sep [quotes (ppr inst), nest 2 (pprInstLoc (instLoc inst))] + go dict = sep [quotes (ppr (dictPred dict)), nest 2 (pprInstLoc (instLoc dict))] -pprInst (LitInst u lit ty loc) - = hsep [ppr lit, ptext SLIT("at"), ppr ty, show_uniq u] +pprInsts :: [Inst] -> SDoc +-- Debugging: print the evidence :: type +pprInsts insts = brackets (interpp'SP insts) -pprInst (Dict u pred loc) = pprPred pred <+> show_uniq u +pprInst, pprInstInFull :: Inst -> SDoc +-- Debugging: print the evidence :: type +pprInst (LitInst nm lit ty loc) = ppr nm <+> dcolon <+> ppr ty +pprInst (Dict nm pred loc) = ppr nm <+> dcolon <+> pprPred pred -pprInst m@(Method u id tys theta tau loc) - = hsep [ppr id, ptext SLIT("at"), - brackets (sep (map pprParendType tys)) {- , - ptext SLIT("theta"), ppr theta, - ptext SLIT("tau"), ppr tau - show_uniq u, - ppr (instToId m) -}] +pprInst m@(Method inst_id id tys theta tau loc) + = ppr inst_id <+> dcolon <+> + braces (sep [ppr id <+> ptext SLIT("at"), + brackets (sep (map pprParendType tys))]) +pprInstInFull inst + = sep [quotes (pprInst inst), nest 2 (pprInstLoc (instLoc inst))] pprDFuns :: [DFunId] -> SDoc -- Prints the dfun as an instance declaration @@ -507,11 +521,9 @@ pprDFuns dfuns = vcat [ hang (ppr (getSrcLoc dfun) <> colon) , let (_, theta, clas, tys) = tcSplitDFunTy (idType dfun) ] -- Print without the for-all, which the programmer doesn't write -show_uniq u = ifPprDebug (text "{-" <> ppr u <> text "-}") - tidyInst :: TidyEnv -> Inst -> Inst -tidyInst env (LitInst u lit ty loc) = LitInst u lit (tidyType env ty) loc -tidyInst env (Dict u pred loc) = Dict u (tidyPred env pred) loc +tidyInst env (LitInst nm lit ty loc) = LitInst nm lit (tidyType env ty) loc +tidyInst env (Dict nm pred loc) = Dict nm (tidyPred env pred) loc tidyInst env (Method u id tys theta tau loc) = Method u id (tidyTypes env tys) theta tau loc tidyMoreInsts :: TidyEnv -> [Inst] -> (TidyEnv, [Inst]) @@ -529,7 +541,7 @@ showLIE :: SDoc -> TcM () -- Debugging showLIE str = do { lie_var <- getLIEVar ; lie <- readMutVar lie_var ; - traceTc (str <+> pprInstsInFull (lieToList lie)) } + traceTc (str <+> vcat (map pprInstInFull (lieToList lie))) } \end{code} @@ -555,19 +567,30 @@ addInst :: DynFlags -> InstEnv -> DFunId -> TcM InstEnv -- Check that the proposed new instance is OK, -- and then add it to the home inst env addInst dflags home_ie dfun - = do { -- Load imported instances, so that we report + = do { -- Instantiate the dfun type so that we extend the instance + -- envt with completely fresh template variables + -- This is important because the template variables must + -- not overlap with anything in the things being looked up + -- (since we do unification). + -- We use tcSkolType because we don't want to allocate fresh + -- *meta* type variables. + (tvs', theta', tau') <- tcSkolType (InstSkol dfun) (idType dfun) + ; let (cls, tys') = tcSplitDFunHead tau' + dfun' = setIdType dfun (mkSigmaTy tvs' theta' tau') + + -- Load imported instances, so that we report -- duplicates correctly - pkg_ie <- loadImportedInsts cls tys + ; pkg_ie <- loadImportedInsts cls tys' -- Check functional dependencies - ; case checkFunDeps (pkg_ie, home_ie) dfun of + ; case checkFunDeps (pkg_ie, home_ie) dfun' of Just dfuns -> funDepErr dfun dfuns Nothing -> return () -- Check for duplicate instance decls - ; let { (matches, _) = lookupInstEnv dflags (pkg_ie, home_ie) cls tys + ; let { (matches, _) = lookupInstEnv dflags (pkg_ie, home_ie) cls tys' ; dup_dfuns = [dup_dfun | (_, (_, dup_tys, dup_dfun)) <- matches, - isJust (matchTys (mkVarSet tvs) tys dup_tys)] } + isJust (tcMatchTys (mkVarSet tvs') tys' dup_tys)] } -- Find memebers of the match list which -- dfun itself matches. If the match is 2-way, it's a duplicate ; case dup_dfuns of @@ -575,9 +598,8 @@ addInst dflags home_ie dfun [] -> return () -- OK, now extend the envt - ; return (extendInstEnv home_ie dfun) } - where - (tvs, _, cls, tys) = tcSplitDFunTy (idType dfun) + ; return (extendInstEnv home_ie dfun') } + traceDFuns dfuns = traceTc (text "Adding instances:" <+> vcat (map pp dfuns)) @@ -594,10 +616,11 @@ dupInstErr dfun dup_dfun 2 (pprDFuns [dfun, dup_dfun])) addDictLoc dfun thing_inside - = addSrcSpan (mkSrcSpan loc loc) thing_inside + = setSrcSpan (mkSrcSpan loc loc) thing_inside where loc = getSrcLoc dfun \end{code} + %************************************************************************ %* * @@ -606,12 +629,12 @@ addDictLoc dfun thing_inside %************************************************************************ \begin{code} -data LookupInstResult s +data LookupInstResult = NoInstance | SimpleInst (LHsExpr TcId) -- Just a variable, type application, or literal | GenInst [Inst] (LHsExpr TcId) -- The expression and its needed insts -lookupInst :: Inst -> TcM (LookupInstResult s) +lookupInst :: Inst -> TcM LookupInstResult -- It's important that lookupInst does not put any new stuff into -- the LIE. Instead, any Insts needed by the lookup are returned in -- the LookupInstResult, where they can be further processed by tcSimplify @@ -634,7 +657,7 @@ lookupInst inst@(Method _ id tys theta _ loc) -- may have done some unification by now] -lookupInst inst@(LitInst u (HsIntegral i from_integer_name) ty loc) +lookupInst inst@(LitInst _nm (HsIntegral i from_integer_name) ty loc) | Just expr <- shortCutIntLit i ty = returnM (GenInst [] expr) -- GenInst, not SimpleInst, because -- expr may be a constructor application @@ -647,7 +670,7 @@ lookupInst inst@(LitInst u (HsIntegral i from_integer_name) ty loc) (mkHsApp (L (instLocSrcSpan loc) (HsVar (instToId method_inst))) integer_lit)) -lookupInst inst@(LitInst u (HsFractional f from_rat_name) ty loc) +lookupInst inst@(LitInst _nm (HsFractional f from_rat_name) ty loc) | Just expr <- shortCutFracLit f ty = returnM (GenInst [] expr) @@ -661,27 +684,17 @@ lookupInst inst@(LitInst u (HsFractional f from_rat_name) ty loc) -- Dictionaries lookupInst dict@(Dict _ pred@(ClassP clas tys) loc) - = do { dflags <- getDOpts - ; if all tcIsTyVarTy tys && - not (dopt Opt_AllowUndecidableInstances dflags) - -- Common special case; no lookup - -- NB: tcIsTyVarTy... don't look through newtypes! - -- Don't take this short cut if we allow undecidable instances - -- because we might have "instance T a where ...". - -- [That means we need -fallow-undecidable-instances in the - -- client module, as well as the module with the instance decl.] - then return NoInstance - - else do - { pkg_ie <- loadImportedInsts clas tys + = do { pkg_ie <- loadImportedInsts clas tys -- Suck in any instance decls that may be relevant ; tcg_env <- getGblEnv + ; dflags <- getDOpts ; case lookupInstEnv dflags (pkg_ie, tcg_inst_env tcg_env) clas tys of { ([(tenv, (_,_,dfun_id))], []) -> instantiate_dfun tenv dfun_id pred loc ; (matches, unifs) -> do - { traceTc (text "lookupInst" <+> vcat [text "matches" <+> ppr matches, - text "unifs" <+> ppr unifs]) - ; return NoInstance } } } } + { traceTc (text "lookupInst fail" <+> vcat [text "dict" <+> ppr pred, + text "matches" <+> ppr matches, + text "unifs" <+> ppr unifs]) + ; return NoInstance } } } -- In the case of overlap (multiple matches) we report -- NoInstance here. That has the effect of making the -- context-simplifier return the dict as an irreducible one. @@ -691,30 +704,47 @@ lookupInst dict@(Dict _ pred@(ClassP clas tys) loc) lookupInst (Dict _ _ _) = returnM NoInstance ----------------- +instantiate_dfun :: TvSubst -> DFunId -> TcPredType -> InstLoc -> TcM LookupInstResult instantiate_dfun tenv dfun_id pred loc - = -- Record that this dfun is needed + = -- tenv is a substitution that instantiates the dfun_id + -- to match the requested result type. + -- + -- We ASSUME that the dfun is quantified over the very same tyvars + -- that are bound by the tenv. + -- + -- However, the dfun + -- might have some tyvars that *only* appear in arguments + -- dfun :: forall a b. C a b, Ord b => D [a] + -- We instantiate b to a flexi type variable -- it'll presumably + -- become fixed later via functional dependencies + traceTc (text "lookupInst success" <+> + vcat [text "dict" <+> ppr pred, + text "witness" <+> ppr dfun_id <+> ppr (idType dfun_id) ]) `thenM_` + -- Record that this dfun is needed record_dfun_usage dfun_id `thenM_` + getStage `thenM` \ use_stage -> + checkWellStaged (ptext SLIT("instance for") <+> quotes (ppr pred)) + (topIdLvl dfun_id) use_stage `thenM_` + -- It's possible that not all the tyvars are in -- the substitution, tenv. For example: -- instance C X a => D X where ... -- (presumably there's a functional dependency in class C) - -- Hence the mk_ty_arg to instantiate any un-substituted tyvars. - getStage `thenM` \ use_stage -> - checkWellStaged (ptext SLIT("instance for") <+> quotes (ppr pred)) - (topIdLvl dfun_id) use_stage `thenM_` + -- Hence the open_tvs to instantiate any un-substituted tyvars. let (tyvars, rho) = tcSplitForAllTys (idType dfun_id) - mk_ty_arg tv = case lookupSubstEnv tenv tv of - Just (DoneTy ty) -> returnM ty - Nothing -> tcInstTyVar VanillaTv tv `thenM` \ tc_tv -> - returnM (mkTyVarTy tc_tv) + open_tvs = filter (`notElemTvSubst` tenv) tyvars in - mappM mk_ty_arg tyvars `thenM` \ ty_args -> + mappM tcInstTyVar open_tvs `thenM` \ open_tvs' -> let - dfun_rho = substTy (mkTyVarSubst tyvars ty_args) rho + tenv' = extendTvSubstList tenv open_tvs (mkTyVarTys open_tvs') + -- Since the open_tvs' are freshly made, they cannot possibly be captured by + -- any nested for-alls in rho. So the in-scope set is unchanged + dfun_rho = substTy tenv' rho (theta, _) = tcSplitPhiTy dfun_rho - ty_app = mkHsTyApp (L (instLocSrcSpan loc) (HsVar dfun_id)) ty_args + ty_app = mkHsTyApp (L (instLocSrcSpan loc) (HsVar dfun_id)) + (map (substTyVar tenv') tyvars) in if null theta then returnM (SimpleInst ty_app) @@ -725,20 +755,21 @@ instantiate_dfun tenv dfun_id pred loc in returnM (GenInst dicts rhs) -record_dfun_usage dfun_id - | isInternalName dfun_name = return () -- From this module - | not (isHomePackageName dfun_name) = return () -- From another package package - | otherwise = getGblEnv `thenM` \ tcg_env -> - updMutVar (tcg_inst_uses tcg_env) +record_dfun_usage dfun_id = do + dflags <- getDOpts + let dfun_name = idName dfun_id + dfun_mod = nameModule dfun_name + if isInternalName dfun_name || not (isHomeModule dflags dfun_mod) + then return () -- internal, or in another package + else do tcg_env <- getGblEnv + updMutVar (tcg_inst_uses tcg_env) (`addOneToNameSet` idName dfun_id) - where - dfun_name = idName dfun_id tcGetInstEnvs :: TcM (InstEnv, InstEnv) --- Gets both the home-pkg inst env (includes module being compiled) --- and the external-package inst-env +-- Gets both the external-package inst-env +-- and the home-pkg inst env (includes module being compiled) tcGetInstEnvs = do { eps <- getEps; env <- getGblEnv; - return (tcg_inst_env env, eps_inst_env eps) } + return (eps_inst_env eps, tcg_inst_env env) } \end{code} @@ -775,41 +806,42 @@ just use the expression inline. \begin{code} tcSyntaxName :: InstOrigin -> TcType -- Type to instantiate it at - -> (Name, LHsExpr Name) -- (Standard name, user name) - -> TcM (Name, LHsExpr TcId) -- (Standard name, suitable expression) + -> (Name, HsExpr Name) -- (Standard name, user name) + -> TcM (Name, HsExpr TcId) -- (Standard name, suitable expression) -- NB: tcSyntaxName calls tcExpr, and hence can do unification. -- So we do not call it from lookupInst, which is called from tcSimplify -tcSyntaxName orig ty (std_nm, L span (HsVar user_nm)) +tcSyntaxName orig ty (std_nm, HsVar user_nm) | std_nm == user_nm - = addSrcSpan span (tcStdSyntaxName orig ty std_nm) + = tcStdSyntaxName orig ty std_nm tcSyntaxName orig ty (std_nm, user_nm_expr) = tcLookupId std_nm `thenM` \ std_id -> let -- C.f. newMethodAtLoc ([tv], _, tau) = tcSplitSigmaTy (idType std_id) - tau1 = substTyWith [tv] [ty] tau + sigma1 = substTyWith [tv] [ty] tau -- Actually, the "tau-type" might be a sigma-type in the -- case of locally-polymorphic methods. in - addErrCtxtM (syntaxNameCtxt user_nm_expr orig tau1) $ + addErrCtxtM (syntaxNameCtxt user_nm_expr orig sigma1) $ -- Check that the user-supplied thing has the - -- same type as the standard one - tcCheckSigma user_nm_expr tau1 `thenM` \ expr -> - returnM (std_nm, expr) + -- same type as the standard one. + -- Tiresome jiggling because tcCheckSigma takes a located expression + getSrcSpanM `thenM` \ span -> + tcCheckSigma (L span user_nm_expr) sigma1 `thenM` \ expr -> + returnM (std_nm, unLoc expr) tcStdSyntaxName :: InstOrigin -> TcType -- Type to instantiate it at -> Name -- Standard name - -> TcM (Name, LHsExpr TcId) -- (Standard name, suitable expression) + -> TcM (Name, HsExpr TcId) -- (Standard name, suitable expression) tcStdSyntaxName orig ty std_nm = newMethodFromName orig ty std_nm `thenM` \ id -> - getSrcSpanM `thenM` \ span -> - returnM (std_nm, L span (HsVar id)) + returnM (std_nm, HsVar id) syntaxNameCtxt name orig ty tidy_env = getInstLoc orig `thenM` \ inst_loc ->