X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcInteract.lhs;h=fd66d0ac0ce6d3d8245f863e33d1cdc429f163f3;hb=cbebca1c9164a5e5ae9b117d0dcf5ad217defc6d;hp=3f166cfe04fc6a7fd85dc9b154f1dc3880c5e9b7;hpb=50d0293555691012f96259de7f8682b94db58517;p=ghc-hetmet.git diff --git a/compiler/typecheck/TcInteract.lhs b/compiler/typecheck/TcInteract.lhs index 3f166cf..fd66d0a 100644 --- a/compiler/typecheck/TcInteract.lhs +++ b/compiler/typecheck/TcInteract.lhs @@ -225,22 +225,6 @@ Note [Basic plan] type AtomicInert = CanonicalCt -- constraint pulled from InertSet type WorkItem = CanonicalCt -- constraint pulled from WorkList --- A mixture of Given, Wanted, and Derived constraints. --- We split between equalities and the rest to process equalities first. -type WorkList = CanonicalCts - -unionWorkLists :: WorkList -> WorkList -> WorkList -unionWorkLists = andCCan - -isEmptyWorkList :: WorkList -> Bool -isEmptyWorkList = isEmptyCCan - -emptyWorkList :: WorkList -emptyWorkList = emptyCCan - -workListFromCCan :: CanonicalCt -> WorkList -workListFromCCan = singleCCan - ------------------------ data StopOrContinue = Stop -- Work item is consumed @@ -305,7 +289,7 @@ runSolverPipeline depth pipeline inerts workItem , sr_stop = ContinueWith work_item }) = do { itr <- stage depth work_item inerts ; traceTcS ("Stage result (" ++ name ++ ")") (ppr itr) - ; let itr' = itr { sr_new_work = accum_work `unionWorkLists` sr_new_work itr } + ; let itr' = itr { sr_new_work = accum_work `unionWorkList` sr_new_work itr } ; run_pipeline stages itr' } \end{code} @@ -365,7 +349,10 @@ solveInteract inert ws -> (ct,evVarPred ev)) ws) , text "inert = " <+> ppr inert ] - ; (flag, inert_ret) <- foldlBagM (tryPreSolveAndInteract sctx dyn_flags) (True,inert) ws + ; can_ws <- mkCanonicalFEVs ws + + ; (flag, inert_ret) + <- foldrWorkListM (tryPreSolveAndInteract sctx dyn_flags) (True,inert) can_ws ; traceTcS "solveInteract, after clever canonicalization (and interaction):" $ vcat [ text "No interaction happened = " <+> ppr flag @@ -373,29 +360,32 @@ solveInteract inert ws ; return (flag, inert_ret) } - tryPreSolveAndInteract :: SimplContext -> DynFlags + -> CanonicalCt -> (Bool, InertSet) - -> FlavoredEvVar -> TcS (Bool, InertSet) -- Returns: True if it was able to discharge this constraint AND all previous ones -tryPreSolveAndInteract sctx dyn_flags (all_previous_discharged, inert) - flavev@(EvVarX ev_var fl) +tryPreSolveAndInteract sctx dyn_flags ct (all_previous_discharged, inert) = do { let inert_cts = get_inert_cts (evVarPred ev_var) - ; this_one_discharged <- dischargeFromCCans inert_cts flavev + ; this_one_discharged <- + if isCFrozenErr ct then + return False + else + dischargeFromCCans inert_cts ev_var fl ; if this_one_discharged then return (all_previous_discharged, inert) else do - { extra_cts <- mkCanonical fl ev_var - ; inert_ret <- solveInteractWithDepth (ctxtStkDepth dyn_flags,0,[]) - inert extra_cts + { inert_ret <- solveOneWithDepth (ctxtStkDepth dyn_flags,0,[]) ct inert ; return (False, inert_ret) } } where + ev_var = cc_id ct + fl = cc_flavor ct + get_inert_cts (ClassP clas _) | simplEqsOnly sctx = emptyCCan | otherwise = fst (getRelevantCts clas (inert_dicts inert)) @@ -406,21 +396,26 @@ tryPreSolveAndInteract sctx dyn_flags (all_previous_discharged, inert) get_inert_cts (EqPred {}) = inert_eqs inert `unionBags` cCanMapToBag (inert_funeqs inert) -dischargeFromCCans :: CanonicalCts -> FlavoredEvVar -> TcS Bool -dischargeFromCCans cans (EvVarX ev fl) - = Bag.foldlBagM discharge_ct False cans - where discharge_ct :: Bool -> CanonicalCt -> TcS Bool - discharge_ct True _ct = return True - discharge_ct False ct - | evVarPred (cc_id ct) `tcEqPred` evVarPred ev - , cc_flavor ct `canSolve` fl - = do { when (isWanted fl) $ set_ev_bind ev (cc_id ct) - ; return True } - where set_ev_bind x y - | EqPred {} <- evVarPred y - = setEvBind x (EvCoercion (mkCoVarCoercion y)) - | otherwise = setEvBind x (EvId y) - discharge_ct False _ct = return False +dischargeFromCCans :: CanonicalCts -> EvVar -> CtFlavor -> TcS Bool +-- See if this (pre-canonicalised) work-item is identical to a +-- one already in the inert set. Reasons: +-- a) Avoid creating superclass constraints for millions of incoming (Num a) constraints +-- b) Termination for improve_eqs in TcSimplify.simpl_loop +dischargeFromCCans cans ev fl + = Bag.foldrBag discharge_ct (return False) cans + where + the_pred = evVarPred ev + + discharge_ct :: CanonicalCt -> TcS Bool -> TcS Bool + discharge_ct ct _rest + | evVarPred (cc_id ct) `eqPred` the_pred + , cc_flavor ct `canSolve` fl + = do { when (isWanted fl) $ setEvBind ev (evVarTerm (cc_id ct)) + -- Deriveds need no evidence + -- For Givens, we already have evidence, and we don't need it twice + ; return True } + + discharge_ct _ct rest = rest \end{code} Note [Avoiding the superclass explosion] @@ -439,16 +434,16 @@ canonicals. If so, we add nothing to the returned canonical constraints. \begin{code} -solveOne :: InertSet -> WorkItem -> TcS InertSet -solveOne inerts workItem +solveOne :: WorkItem -> InertSet -> TcS InertSet +solveOne workItem inerts = do { dyn_flags <- getDynFlags - ; solveOneWithDepth (ctxtStkDepth dyn_flags,0,[]) inerts workItem + ; solveOneWithDepth (ctxtStkDepth dyn_flags,0,[]) workItem inerts } ----------------- solveInteractWithDepth :: (Int, Int, [WorkItem]) - -> InertSet -> WorkList -> TcS InertSet -solveInteractWithDepth ctxt@(max_depth,n,stack) inert ws + -> WorkList -> InertSet -> TcS InertSet +solveInteractWithDepth ctxt@(max_depth,n,stack) ws inert | isEmptyWorkList ws = return inert @@ -458,26 +453,25 @@ solveInteractWithDepth ctxt@(max_depth,n,stack) inert ws | otherwise = do { traceTcS "solveInteractWithDepth" $ vcat [ text "Current depth =" <+> ppr n - , text "Max depth =" <+> ppr max_depth ] + , text "Max depth =" <+> ppr max_depth + , text "ws =" <+> ppr ws ] + - -- Solve equalities first - ; let (eqs, non_eqs) = Bag.partitionBag isCTyEqCan ws - ; is_from_eqs <- Bag.foldlBagM (solveOneWithDepth ctxt) inert eqs - ; Bag.foldlBagM (solveOneWithDepth ctxt) is_from_eqs non_eqs } + ; foldrWorkListM (solveOneWithDepth ctxt) inert ws } + -- use foldr to preserve the order ------------------ -- Fully interact the given work item with an inert set, and return a -- new inert set which has assimilated the new information. solveOneWithDepth :: (Int, Int, [WorkItem]) - -> InertSet -> WorkItem -> TcS InertSet -solveOneWithDepth (max_depth, depth, stack) inert work + -> WorkItem -> InertSet -> TcS InertSet +solveOneWithDepth (max_depth, depth, stack) work inert = do { traceFireTcS depth (text "Solving {" <+> ppr work) ; (new_inert, new_work) <- runSolverPipeline depth thePipeline inert work -- Recursively solve the new work generated -- from workItem, with a greater depth - ; res_inert <- solveInteractWithDepth (max_depth, depth+1, work:stack) - new_inert new_work + ; res_inert <- solveInteractWithDepth (max_depth, depth+1, work:stack) new_work new_inert ; traceFireTcS depth (text "Done }" <+> ppr work) @@ -727,9 +721,10 @@ solveWithIdentity cv wd tv xi ] ; setWantedTyBind tv xi - ; cv_given <- newGivenCoVar (mkTyVarTy tv) xi xi + ; let refl_xi = mkReflCo xi + ; cv_given <- newGivenCoVar (mkTyVarTy tv) xi refl_xi - ; when (isWanted wd) (setWantedCoBind cv xi) + ; when (isWanted wd) (setCoBind cv refl_xi) -- We don't want to do this for Derived, that's why we use 'when (isWanted wd)' ; return $ SPSolved (CTyEqCan { cc_id = cv_given @@ -738,14 +733,37 @@ solveWithIdentity cv wd tv xi \end{code} - - ********************************************************************************* * * The interact-with-inert Stage * * ********************************************************************************* +Note [The Solver Invariant] +~~~~~~~~~~~~~~~~~~~~~~~~~~~ +We always add Givens first. So you might think that the solver has +the invariant + + If the work-item is Given, + then the inert item must Given + +But this isn't quite true. Suppose we have, + c1: [W] beta ~ [alpha], c2 : [W] blah, c3 :[W] alpha ~ Int +After processing the first two, we get + c1: [G] beta ~ [alpha], c2 : [W] blah +Now, c3 does not interact with the the given c1, so when we spontaneously +solve c3, we must re-react it with the inert set. So we can attempt a +reaction between inert c2 [W] and work-item c3 [G]. + +It *is* true that [Solver Invariant] + If the work-item is Given, + AND there is a reaction + then the inert item must Given +or, equivalently, + If the work-item is Given, + and the inert item is Wanted/Derived + then there is no reaction + \begin{code} -- Interaction result of WorkItem <~> AtomicInert data InteractResult @@ -774,11 +792,16 @@ mkIRContinue rule wi keep newWork = return $ IR { ir_stop = ContinueWith wi, ir_inert_action = keep , ir_new_work = newWork, ir_fire = Just rule } -mkIRStop :: String -> WorkList -> TcS InteractResult -mkIRStop rule newWork +mkIRStopK :: String -> WorkList -> TcS InteractResult +mkIRStopK rule newWork = return $ IR { ir_stop = Stop, ir_inert_action = KeepInert , ir_new_work = newWork, ir_fire = Just rule } +mkIRStopD :: String -> WorkList -> TcS InteractResult +mkIRStopD rule newWork + = return $ IR { ir_stop = Stop, ir_inert_action = DropInert + , ir_new_work = newWork, ir_fire = Just rule } + noInteraction :: Monad m => WorkItem -> m InteractResult noInteraction wi = return $ IR { ir_stop = ContinueWith wi, ir_inert_action = KeepInert @@ -796,7 +819,8 @@ data WhichComesFromInert = LeftComesFromInert | RightComesFromInert interactWithInertEqsStage :: SimplifierStage interactWithInertEqsStage depth workItem inert - = Bag.foldlBagM (interactNext depth) initITR (inert_eqs inert) + = Bag.foldrBagM (interactNext depth) initITR (inert_eqs inert) + -- use foldr to preserve the order where initITR = SR { sr_inerts = inert { inert_eqs = emptyCCan } , sr_new_work = emptyWorkList @@ -814,7 +838,8 @@ interactWithInertsStage depth workItem inert initITR = SR { sr_inerts = inert_residual , sr_new_work = emptyWorkList , sr_stop = ContinueWith workItem } - in Bag.foldlBagM (interactNext depth) initITR relevant + in Bag.foldrBagM (interactNext depth) initITR relevant + -- use foldr to preserve the order where getISRelevant :: CanonicalCt -> InertSet -> (CanonicalCts, InertSet) getISRelevant (CFrozenErr {}) is = (emptyCCan, is) @@ -841,8 +866,8 @@ interactWithInertsStage depth workItem inert , inert_ips = emptyCCanMap , inert_funeqs = emptyCCanMap }) -interactNext :: SubGoalDepth -> StageResult -> AtomicInert -> TcS StageResult -interactNext depth it inert +interactNext :: SubGoalDepth -> AtomicInert -> StageResult -> TcS StageResult +interactNext depth inert it | ContinueWith work_item <- sr_stop it = do { let inerts = sr_inerts it @@ -854,7 +879,7 @@ interactNext depth it inert = text rule <+> keep_doc <+> vcat [ ptext (sLit "Inert =") <+> ppr inert , ptext (sLit "Work =") <+> ppr work_item - , ppUnless (isEmptyBag new_work) $ + , ppUnless (isEmptyWorkList new_work) $ ptext (sLit "New =") <+> ppr new_work ] keep_doc = case inert_action of KeepInert -> ptext (sLit "[keep]") @@ -870,22 +895,22 @@ interactNext depth it inert DropInert -> inerts ; return $ SR { sr_inerts = inerts_new - , sr_new_work = sr_new_work it `unionWorkLists` new_work + , sr_new_work = sr_new_work it `unionWorkList` new_work , sr_stop = stop } } | otherwise = return $ it { sr_inerts = (sr_inerts it) `updInertSet` inert } -- Do a single interaction of two constraints. interactWithInert :: AtomicInert -> WorkItem -> TcS InteractResult -interactWithInert inert workitem - = do { ctxt <- getTcSContext - ; let is_allowed = allowedInteraction (simplEqsOnly ctxt) inert workitem +interactWithInert inert workItem + = do { ctxt <- getTcSContext + ; let is_allowed = allowedInteraction (simplEqsOnly ctxt) inert workItem - ; if is_allowed then - doInteractWithInert inert workitem + ; if is_allowed then + doInteractWithInert inert workItem else - noInteraction workitem - } + noInteraction workItem + } allowedInteraction :: Bool -> AtomicInert -> WorkItem -> Bool -- Allowed interactions @@ -898,10 +923,10 @@ doInteractWithInert :: CanonicalCt -> CanonicalCt -> TcS InteractResult -- Identical class constraints. doInteractWithInert - (CDictCan { cc_id = d1, cc_flavor = fl1, cc_class = cls1, cc_tyargs = tys1 }) - workItem@(CDictCan { cc_id = d2, cc_flavor = fl2, cc_class = cls2, cc_tyargs = tys2 }) - | cls1 == cls2 && (and $ zipWith tcEqType tys1 tys2) - = solveOneFromTheOther (d1,fl1) workItem + inertItem@(CDictCan { cc_id = d1, cc_flavor = fl1, cc_class = cls1, cc_tyargs = tys1 }) + workItem@(CDictCan { cc_id = d2, cc_flavor = fl2, cc_class = cls2, cc_tyargs = tys2 }) + | cls1 == cls2 && eqTypes tys1 tys2 + = solveOneFromTheOther "Cls/Cls" (EvId d1,fl1) workItem | cls1 == cls2 && (not (isGiven fl1 && isGiven fl2)) = -- See Note [When improvement happens] @@ -918,34 +943,52 @@ doInteractWithInert ; case m of Nothing -> noInteraction workItem Just (rewritten_tys2, cos2, fd_work) - - | tcEqTypes tys1 rewritten_tys2 + | eqTypes tys1 rewritten_tys2 -> -- Solve him on the spot in this case - do { let dict_co = mkTyConCoercion (classTyCon cls1) cos2 - ; when (isWanted fl2) $ setDictBind d2 (EvCast d1 dict_co) - ; mkIRStop "Cls/Cls fundep (solved)" fd_work } + case fl2 of + Given {} -> pprPanic "Unexpected given" (ppr inertItem $$ ppr workItem) + Derived {} -> mkIRStopK "Cls/Cls fundep (solved)" fd_work + Wanted {} + | isDerived fl1 + -> do { setDictBind d2 (EvCast d1 dict_co) + ; let inert_w = inertItem { cc_flavor = fl2 } + -- A bit naughty: we take the inert Derived, + -- turn it into a Wanted, use it to solve the work-item + -- and put it back into the work-list + -- Maybe rather than starting again, we could *replace* the + -- inert item, but its safe and simple to restart + ; mkIRStopD "Cls/Cls fundep (solved)" $ + workListFromNonEq inert_w `unionWorkList` fd_work } + | otherwise + -> do { setDictBind d2 (EvCast d1 dict_co) + ; mkIRStopK "Cls/Cls fundep (solved)" fd_work } - | isWanted fl2 - -> -- We could not quite solve him, but we stil rewrite him + | otherwise + -> -- We could not quite solve him, but we still rewrite him -- Example: class C a b c | a -> b -- Given: C Int Bool x, Wanted: C Int beta y -- Then rewrite the wanted to C Int Bool y -- but note that is still not identical to the given -- The important thing is that the rewritten constraint is -- inert wrt the given. - -- In fact, it is inert wrt all the previous inerts too, so - -- we can keep on going rather than sending it back to the work list - do { let dict_co = mkTyConCoercion (classTyCon cls1) cos2 - ; d2' <- newDictVar cls1 rewritten_tys2 - ; setDictBind d2 (EvCast d2' dict_co) + -- However it is not necessarily inert wrt previous inert-set items. + -- class C a b c d | a -> b, b c -> d + -- Inert: c1: C b Q R S, c2: C P Q a b + -- Work: C P alpha R beta + -- Does not react with c1; reacts with c2, with alpha:=Q + -- NOW it reacts with c1! + -- So we must stop, and put the rewritten constraint back in the work list + do { d2' <- newDictVar cls1 rewritten_tys2 + ; case fl2 of + Given {} -> pprPanic "Unexpected given" (ppr inertItem $$ ppr workItem) + Wanted {} -> setDictBind d2 (EvCast d2' dict_co) + Derived {} -> return () ; let workItem' = workItem { cc_id = d2', cc_tyargs = rewritten_tys2 } - ; mkIRContinue "Cls/Cls fundep (partial)" workItem' KeepInert fd_work } + ; mkIRStopK "Cls/Cls fundep (partial)" $ + workListFromNonEq workItem' `unionWorkList` fd_work } - | otherwise - -> ASSERT (isDerived fl2) -- Derived constraints have no evidence, - -- so just produce the rewritten constraint - let workItem' = workItem { cc_tyargs = rewritten_tys2 } - in mkIRContinue "Cls/Cls fundep" workItem' KeepInert fd_work + where + dict_co = mkTyConAppCo (classTyCon cls1) cos2 } -- Class constraint and given equality: use the equality to rewrite @@ -964,7 +1007,7 @@ doInteractWithInert (CDictCan { cc_id = dv, cc_flavor = ifl, cc_class = cl, cc_t | wfl `canRewrite` ifl , tv `elemVarSet` tyVarsOfTypes xis = do { rewritten_dict <- rewriteDict (cv,tv,xi) (dv,ifl,cl,xis) - ; mkIRContinue "Cls/Eq" workItem DropInert (workListFromCCan rewritten_dict) } + ; mkIRContinue "Cls/Eq" workItem DropInert (workListFromNonEq rewritten_dict) } -- Class constraint and given equality: use the equality to rewrite -- the class constraint. @@ -980,7 +1023,7 @@ doInteractWithInert (CIPCan { cc_id = ipid, cc_flavor = ifl, cc_ip_nm = nm, cc_i | wfl `canRewrite` ifl , tv `elemVarSet` tyVarsOfType ty = do { rewritten_ip <- rewriteIP (cv,tv,xi) (ipid,ifl,nm,ty) - ; mkIRContinue "IP/Eq" workItem DropInert (workListFromCCan rewritten_ip) } + ; mkIRContinue "IP/Eq" workItem DropInert (workListFromNonEq rewritten_ip) } -- Two implicit parameter constraints. If the names are the same, -- but their types are not, we generate a wanted type equality @@ -997,15 +1040,22 @@ doInteractWithInert (CIPCan { cc_id = id1, cc_flavor = ifl, cc_ip_nm = nm1, cc_i -- we must *override* the outer one with the inner one mkIRContinue "IP/IP override" workItem DropInert emptyWorkList - | nm1 == nm2 && ty1 `tcEqType` ty2 - = solveOneFromTheOther (id1,ifl) workItem + | nm1 == nm2 && ty1 `eqType` ty2 + = solveOneFromTheOther "IP/IP" (EvId id1,ifl) workItem | nm1 == nm2 = -- See Note [When improvement happens] - do { co_var <- newWantedCoVar ty2 ty1 -- See Note [Efficient Orientation] - ; let flav = Wanted (combineCtLoc ifl wfl) - ; cans <- mkCanonical flav co_var - ; mkIRContinue "IP/IP fundep" workItem KeepInert cans } + do { co_var <- newCoVar ty2 ty1 -- See Note [Efficient Orientation] + ; let flav = Wanted (combineCtLoc ifl wfl) + ; cans <- mkCanonical flav co_var + ; case wfl of + Given {} -> pprPanic "Unexpected given IP" (ppr workItem) + Derived {} -> pprPanic "Unexpected derived IP" (ppr workItem) + Wanted {} -> + do { setIPBind (cc_id workItem) $ + EvCast id1 (mkSymCo (mkCoVarCo co_var)) + ; mkIRStopK "IP/IP interaction (solved)" cans } + } -- Never rewrite a given with a wanted equality, and a type function -- equality can never rewrite an equality. We rewrite LHS *and* RHS @@ -1019,7 +1069,7 @@ doInteractWithInert (CTyEqCan { cc_id = cv1, cc_flavor = ifl, cc_tyvar = tv, cc_ | ifl `canRewrite` wfl , tv `elemVarSet` tyVarsOfTypes (xi2:args) -- Rewrite RHS as well = do { rewritten_funeq <- rewriteFunEq (cv1,tv,xi1) (cv2,wfl,tc,args,xi2) - ; mkIRStop "Eq/FunEq" (workListFromCCan rewritten_funeq) } + ; mkIRStopK "Eq/FunEq" (workListFromEq rewritten_funeq) } -- Must Stop here, because we may no longer be inert after the rewritting. -- Inert: function equality, work item: equality @@ -1029,7 +1079,7 @@ doInteractWithInert (CFunEqCan {cc_id = cv1, cc_flavor = ifl, cc_fun = tc | wfl `canRewrite` ifl , tv `elemVarSet` tyVarsOfTypes (xi1:args) -- Rewrite RHS as well = do { rewritten_funeq <- rewriteFunEq (cv2,tv,xi2) (cv1,ifl,tc,args,xi1) - ; mkIRContinue "FunEq/Eq" workItem DropInert (workListFromCCan rewritten_funeq) } + ; mkIRContinue "FunEq/Eq" workItem DropInert (workListFromEq rewritten_funeq) } -- One may think that we could (KeepTransformedInert rewritten_funeq) -- but that is wrong, because it may end up not being inert with respect -- to future inerts. Example: @@ -1044,29 +1094,29 @@ doInteractWithInert (CFunEqCan { cc_id = cv1, cc_flavor = fl1, cc_fun = tc1 workItem@(CFunEqCan { cc_id = cv2, cc_flavor = fl2, cc_fun = tc2 , cc_tyargs = args2, cc_rhs = xi2 }) | fl1 `canSolve` fl2 && lhss_match - = do { cans <- rewriteEqLHS LeftComesFromInert (mkCoVarCoercion cv1,xi1) (cv2,fl2,xi2) - ; mkIRStop "FunEq/FunEq" cans } + = do { cans <- rewriteEqLHS LeftComesFromInert (mkCoVarCo cv1,xi1) (cv2,fl2,xi2) + ; mkIRStopK "FunEq/FunEq" cans } | fl2 `canSolve` fl1 && lhss_match - = do { cans <- rewriteEqLHS RightComesFromInert (mkCoVarCoercion cv2,xi2) (cv1,fl1,xi1) + = do { cans <- rewriteEqLHS RightComesFromInert (mkCoVarCo cv2,xi2) (cv1,fl1,xi1) ; mkIRContinue "FunEq/FunEq" workItem DropInert cans } where - lhss_match = tc1 == tc2 && and (zipWith tcEqType args1 args2) + lhss_match = tc1 == tc2 && eqTypes args1 args2 doInteractWithInert (CTyEqCan { cc_id = cv1, cc_flavor = fl1, cc_tyvar = tv1, cc_rhs = xi1 }) workItem@(CTyEqCan { cc_id = cv2, cc_flavor = fl2, cc_tyvar = tv2, cc_rhs = xi2 }) -- Check for matching LHS | fl1 `canSolve` fl2 && tv1 == tv2 - = do { cans <- rewriteEqLHS LeftComesFromInert (mkCoVarCoercion cv1,xi1) (cv2,fl2,xi2) - ; mkIRStop "Eq/Eq lhs" cans } + = do { cans <- rewriteEqLHS LeftComesFromInert (mkCoVarCo cv1,xi1) (cv2,fl2,xi2) + ; mkIRStopK "Eq/Eq lhs" cans } | fl2 `canSolve` fl1 && tv1 == tv2 - = do { cans <- rewriteEqLHS RightComesFromInert (mkCoVarCoercion cv2,xi2) (cv1,fl1,xi1) + = do { cans <- rewriteEqLHS RightComesFromInert (mkCoVarCo cv2,xi2) (cv1,fl1,xi1) ; mkIRContinue "Eq/Eq lhs" workItem DropInert cans } -- Check for rewriting RHS | fl1 `canRewrite` fl2 && tv1 `elemVarSet` tyVarsOfType xi2 = do { rewritten_eq <- rewriteEqRHS (cv1,tv1,xi1) (cv2,fl2,tv2,xi2) - ; mkIRStop "Eq/Eq rhs" rewritten_eq } + ; mkIRStopK "Eq/Eq rhs" rewritten_eq } | fl2 `canRewrite` fl1 && tv2 `elemVarSet` tyVarsOfType xi1 = do { rewritten_eq <- rewriteEqRHS (cv2,tv2,xi2) (cv1,fl1,tv1,xi1) @@ -1076,7 +1126,7 @@ doInteractWithInert (CTyEqCan { cc_id = cv1, cc_flavor = fl1, cc_tyvar = tv1, (CFrozenErr { cc_id = cv2, cc_flavor = fl2 }) | fl1 `canRewrite` fl2 && tv1 `elemVarSet` tyVarsOfEvVar cv2 = do { rewritten_frozen <- rewriteFrozen (cv1, tv1, xi1) (cv2, fl2) - ; mkIRStop "Frozen/Eq" rewritten_frozen } + ; mkIRStopK "Frozen/Eq" rewritten_frozen } doInteractWithInert (CFrozenErr { cc_id = cv2, cc_flavor = fl2 }) workItem@(CTyEqCan { cc_id = cv1, cc_flavor = fl1, cc_tyvar = tv1, cc_rhs = xi1 }) @@ -1091,13 +1141,13 @@ doInteractWithInert _ workItem = noInteraction workItem -- Equational Rewriting rewriteDict :: (CoVar, TcTyVar, Xi) -> (DictId, CtFlavor, Class, [Xi]) -> TcS CanonicalCt rewriteDict (cv,tv,xi) (dv,gw,cl,xis) - = do { let cos = substTysWith [tv] [mkCoVarCoercion cv] xis -- xis[tv] ~ xis[xi] + = do { let cos = map (liftCoSubstWith [tv] [mkCoVarCo cv]) xis -- xis[tv] ~ xis[xi] args = substTysWith [tv] [xi] xis con = classTyCon cl - dict_co = mkTyConCoercion con cos + dict_co = mkTyConAppCo con cos ; dv' <- newDictVar cl args ; case gw of - Wanted {} -> setDictBind dv (EvCast dv' (mkSymCoercion dict_co)) + Wanted {} -> setDictBind dv (EvCast dv' (mkSymCo dict_co)) Given {} -> setDictBind dv' (EvCast dv dict_co) Derived {} -> return () -- Derived dicts we don't set any evidence @@ -1108,11 +1158,11 @@ rewriteDict (cv,tv,xi) (dv,gw,cl,xis) rewriteIP :: (CoVar,TcTyVar,Xi) -> (EvVar,CtFlavor, IPName Name, TcType) -> TcS CanonicalCt rewriteIP (cv,tv,xi) (ipid,gw,nm,ty) - = do { let ip_co = substTyWith [tv] [mkCoVarCoercion cv] ty -- ty[tv] ~ t[xi] - ty' = substTyWith [tv] [xi] ty + = do { let ip_co = liftCoSubstWith [tv] [mkCoVarCo cv] ty -- ty[tv] ~ t[xi] + ty' = substTyWith [tv] [xi] ty ; ipid' <- newIPVar nm ty' ; case gw of - Wanted {} -> setIPBind ipid (EvCast ipid' (mkSymCoercion ip_co)) + Wanted {} -> setIPBind ipid (EvCast ipid' (mkSymCo ip_co)) Given {} -> setIPBind ipid' (EvCast ipid ip_co) Derived {} -> return () -- Derived ips: we don't set any evidence @@ -1123,22 +1173,23 @@ rewriteIP (cv,tv,xi) (ipid,gw,nm,ty) rewriteFunEq :: (CoVar,TcTyVar,Xi) -> (CoVar,CtFlavor,TyCon, [Xi], Xi) -> TcS CanonicalCt rewriteFunEq (cv1,tv,xi1) (cv2,gw, tc,args,xi2) -- cv2 :: F args ~ xi2 - = do { let arg_cos = substTysWith [tv] [mkCoVarCoercion cv1] args - args' = substTysWith [tv] [xi1] args - fun_co = mkTyConCoercion tc arg_cos -- fun_co :: F args ~ F args' + = do { let co_subst = liftCoSubstWith [tv] [mkCoVarCo cv1] + arg_cos = map co_subst args + args' = substTysWith [tv] [xi1] args + fun_co = mkTyConAppCo tc arg_cos -- fun_co :: F args ~ F args' xi2' = substTyWith [tv] [xi1] xi2 - xi2_co = substTyWith [tv] [mkCoVarCoercion cv1] xi2 -- xi2_co :: xi2 ~ xi2' - ; cv2' <- case gw of - Wanted {} -> do { cv2' <- newWantedCoVar (mkTyConApp tc args') xi2' - ; setWantedCoBind cv2 $ - fun_co `mkTransCoercion` - mkCoVarCoercion cv2' `mkTransCoercion` mkSymCoercion xi2_co - ; return cv2' } - Given {} -> newGivenCoVar (mkTyConApp tc args') xi2' $ - mkSymCoercion fun_co `mkTransCoercion` - mkCoVarCoercion cv2 `mkTransCoercion` xi2_co - Derived {} -> newDerivedId (EqPred (mkTyConApp tc args') xi2') + xi2_co = co_subst xi2 -- xi2_co :: xi2 ~ xi2' + + ; cv2' <- newCoVar (mkTyConApp tc args') xi2' + ; case gw of + Wanted {} -> setCoBind cv2 (fun_co `mkTransCo` + mkCoVarCo cv2' `mkTransCo` + mkSymCo xi2_co) + Given {} -> setCoBind cv2' (mkSymCo fun_co `mkTransCo` + mkCoVarCo cv2 `mkTransCo` + xi2_co) + Derived {} -> return () ; return (CFunEqCan { cc_id = cv2' , cc_flavor = gw @@ -1157,111 +1208,94 @@ rewriteEqRHS :: (CoVar,TcTyVar,Xi) -> (CoVar,CtFlavor,TcTyVar,Xi) -> TcS WorkLis rewriteEqRHS (cv1,tv1,xi1) (cv2,gw,tv2,xi2) | Just tv2' <- tcGetTyVar_maybe xi2' , tv2 == tv2' -- In this case xi2[xi1/tv1] = tv2, so we have tv2~tv2 - = do { when (isWanted gw) (setWantedCoBind cv2 (mkSymCoercion co2')) - ; return emptyCCan } + = do { when (isWanted gw) (setCoBind cv2 (mkSymCo co2')) + ; return emptyWorkList } | otherwise - = do { cv2' <- - case gw of - Wanted {} - -> do { cv2' <- newWantedCoVar (mkTyVarTy tv2) xi2' - ; setWantedCoBind cv2 $ - mkCoVarCoercion cv2' `mkTransCoercion` mkSymCoercion co2' - ; return cv2' } - Given {} - -> newGivenCoVar (mkTyVarTy tv2) xi2' $ - mkCoVarCoercion cv2 `mkTransCoercion` co2' - Derived {} - -> newDerivedId (EqPred (mkTyVarTy tv2) xi2') - - ; canEq gw cv2' (mkTyVarTy tv2) xi2' - } + = do { cv2' <- newCoVar (mkTyVarTy tv2) xi2' + ; case gw of + Wanted {} -> setCoBind cv2 $ mkCoVarCo cv2' `mkTransCo` + mkSymCo co2' + Given {} -> setCoBind cv2' $ mkCoVarCo cv2 `mkTransCo` + co2' + Derived {} -> return () + ; canEqToWorkList gw cv2' (mkTyVarTy tv2) xi2' } where xi2' = substTyWith [tv1] [xi1] xi2 - co2' = substTyWith [tv1] [mkCoVarCoercion cv1] xi2 -- xi2 ~ xi2[xi1/tv1] - + co2' = liftCoSubstWith [tv1] [mkCoVarCo cv1] xi2 -- xi2 ~ xi2[xi1/tv1] rewriteEqLHS :: WhichComesFromInert -> (Coercion,Xi) -> (CoVar,CtFlavor,Xi) -> TcS WorkList -- Used to ineract two equalities of the following form: -- First Equality: co1: (XXX ~ xi1) -- Second Equality: cv2: (XXX ~ xi2) --- Where the cv1 `canSolve` cv2 equality +-- Where the cv1 `canRewrite` cv2 equality -- We have an option of creating new work (xi1 ~ xi2) OR (xi2 ~ xi1), -- See Note [Efficient Orientation] for that -rewriteEqLHS which (co1,xi1) (cv2,gw,xi2) - = do { cv2' <- case (isWanted gw, which) of - (True,LeftComesFromInert) -> - do { cv2' <- newWantedCoVar xi2 xi1 - ; setWantedCoBind cv2 $ - co1 `mkTransCoercion` mkSymCoercion (mkCoVarCoercion cv2') - ; return cv2' } - (True,RightComesFromInert) -> - do { cv2' <- newWantedCoVar xi1 xi2 - ; setWantedCoBind cv2 $ - co1 `mkTransCoercion` mkCoVarCoercion cv2' - ; return cv2' } - (False,LeftComesFromInert) -> - if isGiven gw then - newGivenCoVar xi2 xi1 $ - mkSymCoercion (mkCoVarCoercion cv2) `mkTransCoercion` co1 - else newDerivedId (EqPred xi2 xi1) - (False,RightComesFromInert) -> - if isGiven gw then - newGivenCoVar xi1 xi2 $ - mkSymCoercion co1 `mkTransCoercion` mkCoVarCoercion cv2 - else newDerivedId (EqPred xi1 xi2) +rewriteEqLHS LeftComesFromInert (co1,xi1) (cv2,gw,xi2) + = do { cv2' <- newCoVar xi2 xi1 + ; case gw of + Wanted {} -> setCoBind cv2 $ + co1 `mkTransCo` mkSymCo (mkCoVarCo cv2') + Given {} -> setCoBind cv2' $ + mkSymCo (mkCoVarCo cv2) `mkTransCo` co1 + Derived {} -> return () + ; mkCanonical gw cv2' } + +rewriteEqLHS RightComesFromInert (co1,xi1) (cv2,gw,xi2) + = do { cv2' <- newCoVar xi1 xi2 + ; case gw of + Wanted {} -> setCoBind cv2 $ + co1 `mkTransCo` mkCoVarCo cv2' + Given {} -> setCoBind cv2' $ + mkSymCo co1 `mkTransCo` mkCoVarCo cv2 + Derived {} -> return () ; mkCanonical gw cv2' } - + rewriteFrozen :: (CoVar,TcTyVar,Xi) -> (CoVar,CtFlavor) -> TcS WorkList rewriteFrozen (cv1, tv1, xi1) (cv2, fl2) - = do { cv2' <- - case fl2 of - Wanted {} -> do { cv2' <- newWantedCoVar ty2a' ty2b' - -- ty2a[xi1/tv1] ~ ty2b[xi1/tv1] - ; setWantedCoBind cv2 $ - co2a' `mkTransCoercion` - mkCoVarCoercion cv2' `mkTransCoercion` - mkSymCoercion co2b' - ; return cv2' } - - Given {} -> newGivenCoVar ty2a' ty2b' $ - mkSymCoercion co2a' `mkTransCoercion` - mkCoVarCoercion cv2 `mkTransCoercion` - co2b' - - Derived {} -> newDerivedId (EqPred ty2a' ty2b') - ; return (singleCCan $ CFrozenErr { cc_id = cv2', cc_flavor = fl2 }) } + = do { cv2' <- newCoVar ty2a' ty2b' -- ty2a[xi1/tv1] ~ ty2b[xi1/tv1] + ; case fl2 of + Wanted {} -> setCoBind cv2 $ co2a' `mkTransCo` + mkCoVarCo cv2' `mkTransCo` + mkSymCo co2b' + + Given {} -> setCoBind cv2' $ mkSymCo co2a' `mkTransCo` + mkCoVarCo cv2 `mkTransCo` + co2b' + + Derived {} -> return () + + ; return (workListFromNonEq $ CFrozenErr { cc_id = cv2', cc_flavor = fl2 }) } where (ty2a, ty2b) = coVarKind cv2 -- cv2 : ty2a ~ ty2b ty2a' = substTyWith [tv1] [xi1] ty2a ty2b' = substTyWith [tv1] [xi1] ty2b - co2a' = substTyWith [tv1] [mkCoVarCoercion cv1] ty2a -- ty2a ~ ty2a[xi1/tv1] - co2b' = substTyWith [tv1] [mkCoVarCoercion cv1] ty2b -- ty2b ~ ty2b[xi1/tv1] + co2a' = liftCoSubstWith [tv1] [mkCoVarCo cv1] ty2a -- ty2a ~ ty2a[xi1/tv1] + co2b' = liftCoSubstWith [tv1] [mkCoVarCo cv1] ty2b -- ty2b ~ ty2b[xi1/tv1] -solveOneFromTheOther :: (EvVar, CtFlavor) -> CanonicalCt -> TcS InteractResult +solveOneFromTheOther :: String -> (EvTerm, CtFlavor) -> CanonicalCt -> TcS InteractResult -- First argument inert, second argument work-item. They both represent --- wanted/given/derived evidence for the *same* predicate so we try here to --- discharge one directly from the other. +-- wanted/given/derived evidence for the *same* predicate so +-- we can discharge one directly from the other. -- -- Precondition: value evidence only (implicit parameters, classes) -- not coercion -solveOneFromTheOther (iid,ifl) workItem +solveOneFromTheOther info (ev_term,ifl) workItem | isDerived wfl - = mkIRStop "Solved (derived)" emptyWorkList + = mkIRStopK ("Solved[DW] " ++ info) emptyWorkList - | ifl `canSolve` wfl - = do { when (isWanted wfl) $ setEvBind wid (EvId iid) - -- Overwrite the binding, if one exists - -- For Givens, which are lambda-bound, nothing to overwrite, - ; mkIRStop "Solved" emptyWorkList } - - | wfl `canSolve` ifl - = do { when (isWanted ifl) $ setEvBind iid (EvId wid) - ; mkIRContinue "Solved inert" workItem DropInert emptyWorkList } - - | otherwise -- The inert item is Derived, we can just throw it away, - = mkIRContinue "Discard derived inert" workItem DropInert emptyWorkList + | isDerived ifl -- The inert item is Derived, we can just throw it away, + -- The workItem is inert wrt earlier inert-set items, + -- so it's safe to continue on from this point + = mkIRContinue ("Solved[DI] " ++ info) workItem DropInert emptyWorkList + | otherwise + = ASSERT( ifl `canSolve` wfl ) + -- Because of Note [The Solver Invariant], plus Derived dealt with + do { when (isWanted wfl) $ setEvBind wid ev_term + -- Overwrite the binding, if one exists + -- If both are Given, we already have evidence; no need to duplicate + ; mkIRStopK ("Solved " ++ info) emptyWorkList } where wfl = cc_flavor workItem wid = cc_id workItem @@ -1705,13 +1739,13 @@ doTopReact workItem@(CDictCan { cc_id = dv, cc_flavor = fl@(Wanted loc) ; case m of Nothing -> return NoTopInt Just (xis',cos,fd_work) -> - do { let dict_co = mkTyConCoercion (classTyCon cls) cos + do { let dict_co = mkTyConAppCo (classTyCon cls) cos ; dv'<- newDictVar cls xis' ; setDictBind dv (EvCast dv' dict_co) ; let workItem' = CDictCan { cc_id = dv', cc_flavor = fl, cc_class = cls, cc_tyargs = xis' } ; return $ - SomeTopInt { tir_new_work = singleCCan workItem' `andCCan` fd_work + SomeTopInt { tir_new_work = workListFromNonEq workItem' `unionWorkList` fd_work , tir_new_inert = Stop } } } GenInst wtvs ev_term -- Solved @@ -1754,15 +1788,15 @@ doTopReact (CFunEqCan { cc_id = cv, cc_flavor = fl -- RHS of a type function, so that it never -- appears in an error message -- See Note [Type synonym families] in TyCon - coe = mkTyConApp coe_tc rep_tys + coe = mkAxInstCo coe_tc rep_tys ; cv' <- case fl of - Wanted {} -> do { cv' <- newWantedCoVar rhs_ty xi - ; setWantedCoBind cv $ - coe `mkTransCoercion` - mkCoVarCoercion cv' + Wanted {} -> do { cv' <- newCoVar rhs_ty xi + ; setCoBind cv $ + coe `mkTransCo` + mkCoVarCo cv' ; return cv' } Given {} -> newGivenCoVar xi rhs_ty $ - mkSymCoercion (mkCoVarCoercion cv) `mkTransCoercion` coe + mkSymCo (mkCoVarCo cv) `mkTransCo` coe Derived {} -> newDerivedId (EqPred xi rhs_ty) ; can_cts <- mkCanonical fl cv' ; return $ SomeTopInt can_cts Stop }