X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcSimplify.lhs;h=8632895b10893c194b036a2ab034c8f7490d6d0c;hb=2f223e8f4a4e2fb22a8bb0638cd48256e9f2f0e2;hp=b5bcc5b45e3e741650432870b89ebc0bd06d5011;hpb=e47c481d3e69601d902ce525f54de9246a80bcda;p=ghc-hetmet.git diff --git a/compiler/typecheck/TcSimplify.lhs b/compiler/typecheck/TcSimplify.lhs index b5bcc5b..8632895 100644 --- a/compiler/typecheck/TcSimplify.lhs +++ b/compiler/typecheck/TcSimplify.lhs @@ -16,6 +16,8 @@ module TcSimplify ( tcSimplifyDeriv, tcSimplifyDefault, bindInstsOfLocalFuns, + + tcSimplifyStagedExpr, misMatchMsg ) where @@ -43,7 +45,6 @@ import Class import FunDeps import PrelInfo import PrelNames -import Type import TysWiredIn import ErrUtils import BasicTypes @@ -52,12 +53,12 @@ import VarEnv import FiniteMap import Bag import Outputable -import Maybes import ListSetOps import Util import SrcLoc import DynFlags import FastString + import Control.Monad import Data.List \end{code} @@ -656,7 +657,7 @@ tcSimplifyInfer doc tau_tvs wanted ; gbl_tvs <- tcGetGlobalTyVars ; let preds1 = fdPredsOfInsts wanted' gbl_tvs1 = oclose preds1 gbl_tvs - qtvs = grow preds1 tau_tvs1 `minusVarSet` gbl_tvs1 + qtvs = growInstsTyVars wanted' tau_tvs1 `minusVarSet` gbl_tvs1 -- See Note [Choosing which variables to quantify] -- To maximise sharing, remove from consideration any @@ -665,7 +666,7 @@ tcSimplifyInfer doc tau_tvs wanted ; extendLIEs free -- To make types simple, reduce as much as possible - ; traceTc (text "infer" <+> (ppr preds1 $$ ppr (grow preds1 tau_tvs1) $$ ppr gbl_tvs $$ + ; traceTc (text "infer" <+> (ppr preds1 $$ ppr (growInstsTyVars wanted' tau_tvs1) $$ ppr gbl_tvs $$ ppr gbl_tvs1 $$ ppr free $$ ppr bound)) ; (irreds1, binds1) <- tryHardCheckLoop doc bound @@ -706,7 +707,13 @@ tcSimplifyInfer doc tau_tvs wanted -- Then b is fixed by gbl_tvs, so (C a b) will be in free, and -- irreds2 will be empty. But we don't want to generalise over b! ; let preds2 = fdPredsOfInsts irreds2 -- irreds2 is zonked - qtvs = grow preds2 tau_tvs2 `minusVarSet` oclose preds2 gbl_tvs2 + qtvs = growInstsTyVars irreds2 tau_tvs2 `minusVarSet` oclose preds2 gbl_tvs2 + --------------------------------------------------- + -- BUG WARNING: there's a nasty bug lurking here + -- fdPredsOfInsts may return preds that mention variables quantified in + -- one of the implication constraints in irreds2; and that is clearly wrong: + -- we might quantify over too many variables through accidental capture + --------------------------------------------------- ; let (free, irreds3) = partition (isFreeWhenInferring qtvs) irreds2 ; extendLIEs free @@ -861,7 +868,7 @@ Note [NO TYVARS] The excitement comes when simplifying the bindings for h. Initially try to simplify {y @ [[t1]] t2, 0 @ t1}, with initial qtvs = {t2}. -From this we get t1:=:t2, but also various bindings. We can't forget +From this we get t1~t2, but also various bindings. We can't forget the bindings (because of [LOOP]), but in fact t1 is what g is polymorphic in. @@ -977,7 +984,7 @@ makeImplicationBind :: InstLoc -> [TcTyVar] -- (ir1, .., irn) = f qtvs givens -- where f is (evidence for) the new implication constraint -- f :: forall qtvs. givens => (ir1, .., irn) --- qtvs includes coercion variables. +-- qtvs includes coercion variables -- -- This binding must line up the 'rhs' in reduceImplication makeImplicationBind loc all_tvs @@ -997,7 +1004,7 @@ makeImplicationBind loc all_tvs name = mkInternalName uniq (mkVarOcc "ic") span implic_inst = ImplicInst { tci_name = name, tci_tyvars = all_tvs, - tci_given = (eq_givens ++ dict_givens), + tci_given = eq_givens ++ dict_givens, -- same order as binders tci_wanted = irreds, tci_loc = loc } @@ -1106,7 +1113,9 @@ checkLoop env wanteds ; env' <- zonkRedEnv env ; wanteds' <- zonkInsts wanteds - ; (improved, binds, irreds) <- reduceContext env' wanteds' + ; (improved, tybinds, binds, irreds) + <- reduceContext env' wanteds' + ; execTcTyVarBinds tybinds ; if null irreds || not improved then return (irreds, binds) @@ -1262,9 +1271,23 @@ the givens, as you can see from the derivation described above. Conclusion: in the very special case of tcSimplifySuperClasses we have one 'given' (namely the "this" dictionary) whose superclasses -must not be added to 'givens' by addGiven. That is the *whole* reason -for the red_given_scs field in RedEnv, and the function argument to -addGiven. +must not be added to 'givens' by addGiven. + +There is a complication though. Suppose there are equalities + instance (Eq a, a~b) => Num (a,b) +Then we normalise the 'givens' wrt the equalities, so the original +given "this" dictionary is cast to one of a different type. So it's a +bit trickier than before to identify the "special" dictionary whose +superclasses must not be added. See test + indexed-types/should_run/EqInInstance + +We need a persistent property of the dictionary to record this +special-ness. Current I'm using the InstLocOrigin (a bit of a hack, +but cool), which is maintained by dictionary normalisation. +Specifically, the InstLocOrigin is + NoScOrigin +then the no-superclass thing kicks in. WATCH OUT if you fiddle +with InstLocOrigin! \begin{code} tcSimplifySuperClasses @@ -1276,20 +1299,23 @@ tcSimplifySuperClasses -> TcM TcDictBinds tcSimplifySuperClasses loc this givens sc_wanteds = do { traceTc (text "tcSimplifySuperClasses") + + -- Note [Recursive instances and superclases] + ; no_sc_loc <- getInstLoc NoScOrigin + ; let no_sc_this = setInstLoc this no_sc_loc + + ; let env = RedEnv { red_doc = pprInstLoc loc, + red_try_me = try_me, + red_givens = no_sc_this : givens, + red_stack = (0,[]), + red_improve = False } -- No unification vars + + ; (irreds,binds1) <- checkLoop env sc_wanteds ; let (tidy_env, tidy_irreds) = tidyInsts irreds - ; reportNoInstances tidy_env (Just (loc, givens)) tidy_irreds + ; reportNoInstances tidy_env (Just (loc, givens)) [] tidy_irreds ; return binds1 } where - env = RedEnv { red_doc = pprInstLoc loc, - red_try_me = try_me, - red_givens = this:givens, - red_given_scs = add_scs, - red_stack = (0,[]), - red_improve = False } -- No unification vars - add_scs g | g==this = NoSCs - | otherwise = AddSCs - try_me _ = ReduceMe -- Try hard, so we completely solve the superclass -- constraints right here. See Note [SUPERCLASS-LOOP 1] \end{code} @@ -1412,7 +1438,7 @@ tcSimplifyRestricted -- Used for restricted binding groups tcSimplifyRestricted doc top_lvl bndrs tau_tvs wanteds -- Zonk everything in sight = do { traceTc (text "tcSimplifyRestricted") - ; wanteds' <- zonkInsts wanteds + ; wanteds_z <- zonkInsts wanteds -- 'ReduceMe': Reduce as far as we can. Don't stop at -- dicts; the idea is to get rid of as many type @@ -1424,7 +1450,8 @@ tcSimplifyRestricted doc top_lvl bndrs tau_tvs wanteds -- HOWEVER, some unification may take place, if we instantiate -- a method Inst with an equality constraint ; let env = mkNoImproveRedEnv doc (\_ -> ReduceMe) - ; (_imp, _binds, constrained_dicts) <- reduceContext env wanteds' + ; (_imp, _tybinds, _binds, constrained_dicts) + <- reduceContext env wanteds_z -- Next, figure out the tyvars we will quantify over ; tau_tvs' <- zonkTcTyVarsAndFV (varSetElems tau_tvs) @@ -1473,7 +1500,8 @@ tcSimplifyRestricted doc top_lvl bndrs tau_tvs wanteds (is_nested_group || isDict inst) = Stop | otherwise = ReduceMe env = mkNoImproveRedEnv doc try_me - ; (_imp, binds, irreds) <- reduceContext env wanteds' + ; (_imp, tybinds, binds, irreds) <- reduceContext env wanteds_z + ; execTcTyVarBinds tybinds -- See "Notes on implicit parameters, Question 4: top level" ; ASSERT( all (isFreeWrtTyVars qtvs) irreds ) -- None should be captured @@ -1559,13 +1587,23 @@ Simpler, maybe, but alas not simple (see Trac #2494) tcSimplifyRuleLhs :: [Inst] -> TcM ([Inst], TcDictBinds) tcSimplifyRuleLhs wanteds = do { wanteds' <- zonkInsts wanteds - ; (irreds, binds) <- go [] emptyBag wanteds' + + -- Simplify equalities + -- It's important to do this: Trac #3346 for example + ; (_, wanteds'', tybinds, binds1) <- tcReduceEqs [] wanteds' + ; execTcTyVarBinds tybinds + + -- Simplify other constraints + ; (irreds, binds2) <- go [] emptyBag wanteds'' + + -- Report anything that is left ; let (dicts, bad_irreds) = partition isDict irreds ; traceTc (text "tcSimplifyrulelhs" <+> pprInsts bad_irreds) ; addNoInstanceErrs (nub bad_irreds) -- The nub removes duplicates, which has -- not happened otherwise (see notes above) - ; return (dicts, binds) } + + ; return (dicts, binds1 `unionBags` binds2) } where go :: [Inst] -> TcDictBinds -> [Inst] -> TcM ([Inst], TcDictBinds) go irreds binds [] @@ -1607,7 +1645,7 @@ this bracket again at its usage site. \begin{code} tcSimplifyBracket :: [Inst] -> TcM () tcSimplifyBracket wanteds - = do { tryHardCheckLoop doc wanteds + = do { _ <- tryHardCheckLoop doc wanteds ; return () } where doc = text "tcSimplifyBracket" @@ -1650,7 +1688,8 @@ tcSimplifyIPs given_ips wanteds -- Unusually for checking, we *must* zonk the given_ips ; let env = mkRedEnv doc try_me given_ips' - ; (improved, binds, irreds) <- reduceContext env wanteds' + ; (improved, tybinds, binds, irreds) <- reduceContext env wanteds' + ; execTcTyVarBinds tybinds ; if null irreds || not improved then ASSERT( all is_free irreds ) @@ -1751,8 +1790,6 @@ data RedEnv -- Always dicts & equalities -- but see Note [Rigidity] - , red_given_scs :: Inst -> WantSCs -- See Note [Recursive instances and superclases] - , red_stack :: (Int, [Inst]) -- Recursion stack (for err msg) -- See Note [RedStack] } @@ -1775,7 +1812,6 @@ mkRedEnv :: SDoc -> (Inst -> WhatToDo) -> [Inst] -> RedEnv mkRedEnv doc try_me givens = RedEnv { red_doc = doc, red_try_me = try_me, red_givens = givens, - red_given_scs = const AddSCs, red_stack = (0,[]), red_improve = True } @@ -1784,7 +1820,6 @@ mkInferRedEnv :: SDoc -> (Inst -> WhatToDo) -> RedEnv mkInferRedEnv doc try_me = RedEnv { red_doc = doc, red_try_me = try_me, red_givens = [], - red_given_scs = const AddSCs, red_stack = (0,[]), red_improve = True } @@ -1793,7 +1828,6 @@ mkNoImproveRedEnv :: SDoc -> (Inst -> WhatToDo) -> RedEnv mkNoImproveRedEnv doc try_me = RedEnv { red_doc = doc, red_try_me = try_me, red_givens = [], - red_given_scs = const AddSCs, red_stack = (0,[]), red_improve = True } @@ -1844,6 +1878,7 @@ discharge with the explicit instance. reduceContext :: RedEnv -> [Inst] -- Wanted -> TcM (ImprovementDone, + TcTyVarBinds, -- Type variable bindings TcDictBinds, -- Dictionary bindings [Inst]) -- Irreducible @@ -1870,15 +1905,15 @@ reduceContext env wanteds0 givens = red_givens env ; (givens', wanteds', - normalise_binds, - eq_improved) <- tcReduceEqs givens wanteds + tybinds, + normalise_binds) <- tcReduceEqs givens wanteds ; traceTc $ text "reduceContext: tcReduceEqs result" <+> vcat - [ppr givens', ppr wanteds', ppr normalise_binds] + [ppr givens', ppr wanteds', ppr tybinds, + ppr normalise_binds] -- Build the Avail mapping from "given_dicts" ; (init_state, _) <- getLIE $ do - { init_state <- foldlM (addGiven (red_given_scs env)) - emptyAvails givens' + { init_state <- foldlM addGiven emptyAvails givens' ; return init_state } @@ -1914,7 +1949,7 @@ reduceContext env wanteds0 -- Collect all irreducible instances, and determine whether we should -- go round again. We do so in either of two cases: -- (1) If dictionary reduction or equality solving led to - -- improvement (i.e., instantiated type variables). + -- improvement (i.e., bindings for type variables). -- (2) If we reduced dictionaries (i.e., got dictionary bindings), -- they may have exposed further opportunities to normalise -- family applications. See Note [Dictionary Improvement] @@ -1927,6 +1962,7 @@ reduceContext env wanteds0 ; let all_irreds = dict_irreds ++ implic_irreds ++ extra_eqs avails_improved = availsImproved avails + eq_improved = anyBag (not . isCoVarBind) tybinds improvedFlexible = avails_improved || eq_improved reduced_dicts = not (isEmptyBag dict_binds) improved = improvedFlexible || reduced_dicts @@ -1940,6 +1976,7 @@ reduceContext env wanteds0 text "given" <+> ppr givens, text "wanted" <+> ppr wanteds0, text "----", + text "tybinds" <+> ppr tybinds, text "avails" <+> pprAvails avails, text "improved =" <+> ppr improved <+> text improvedHint, text "(all) irreds = " <+> ppr all_irreds, @@ -1949,10 +1986,13 @@ reduceContext env wanteds0 ])) ; return (improved, + tybinds, normalise_binds `unionBags` dict_binds `unionBags` implic_binds, all_irreds) } + where + isCoVarBind (TcTyVarBind tv _) = isCoVar tv tcImproveOne :: Avails -> Inst -> TcM ImprovementDone tcImproveOne avails inst @@ -2592,14 +2632,19 @@ addWanted want_scs avails wanted rhs_expr wanteds where avail = Rhs rhs_expr wanteds -addGiven :: (Inst -> WantSCs) -> Avails -> Inst -> TcM Avails -addGiven want_scs avails given = addAvailAndSCs (want_scs given) avails given (Given given) - -- Conditionally add superclasses for 'givens' +addGiven :: Avails -> Inst -> TcM Avails +addGiven avails given + = addAvailAndSCs want_scs avails given (Given given) + where + want_scs = case instLocOrigin (instLoc given) of + NoScOrigin -> NoSCs + _other -> AddSCs + -- Conditionally add superclasses for 'given' -- See Note [Recursive instances and superclases] - -- - -- No ASSERT( not (given `elemAvails` avails) ) because in an instance - -- decl for Ord t we can add both Ord t and Eq t as 'givens', - -- so the assert isn't true + + -- No ASSERT( not (given `elemAvails` avails) ) because in an + -- instance decl for Ord t we can add both Ord t and Eq t as + -- 'givens', so the assert isn't true \end{code} \begin{code} @@ -2819,6 +2864,7 @@ disambiguate doc interactive dflags insts where extended_defaulting = interactive || dopt Opt_ExtendedDefaultRules dflags + -- See also Trac #1974 ovl_strings = dopt Opt_OverloadedStrings dflags unaries :: [(Inst, Class, TcTyVar)] -- (C tv) constraints @@ -2865,12 +2911,16 @@ disambigGroup :: [Type] -- The default types -> TcM () -- Just does unification, to fix the default types disambigGroup default_tys dicts - = try_default default_tys + = do { mb_chosen_ty <- try_default default_tys + ; case mb_chosen_ty of + Nothing -> return () + Just chosen_ty -> do { _ <- unifyType chosen_ty (mkTyVarTy tyvar) + ; warnDefault dicts chosen_ty } } where (_,_,tyvar) = ASSERT(not (null dicts)) head dicts -- Should be non-empty classes = [c | (_,c,_) <- dicts] - try_default [] = return () + try_default [] = return Nothing try_default (default_ty : default_tys) = tryTcLIE_ (try_default default_tys) $ do { tcSimplifyDefault [mkClassPred clas [default_ty] | clas <- classes] @@ -2880,10 +2930,7 @@ disambigGroup default_tys dicts -- For example, if Real a is reqd, but the only type in the -- default list is Int. - -- After this we can't fail - ; warnDefault dicts default_ty - ; unifyType default_ty (mkTyVarTy tyvar) - ; return () -- TOMDO: do something with the coercion + ; return (Just default_ty) -- TOMDO: do something with the coercion } @@ -2970,7 +3017,8 @@ tcSimplifyDeriv orig tyvars theta ; (irreds, _) <- tryHardCheckLoop doc wanteds ; let (tv_dicts, others) = partition ok irreds - ; addNoInstanceErrs others + (tidy_env, tidy_insts) = tidyInsts others + ; reportNoInstances tidy_env Nothing [alt_fix] tidy_insts -- See Note [Exotic derived instance contexts] in TcMType ; let rev_env = zipTopTvSubst tvs (mkTyVarTys tyvars) @@ -2984,6 +3032,8 @@ tcSimplifyDeriv orig tyvars theta ok dict | isDict dict = validDerivPred (dictPred dict) | otherwise = False + alt_fix = vcat [ptext (sLit "use a standalone 'deriving instance' declaration instead,"), + ptext (sLit "so you can specify the instance context yourself")] \end{code} @@ -2998,7 +3048,7 @@ tcSimplifyDefault :: ThetaType -- Wanted; has no type variables in it tcSimplifyDefault theta = do wanteds <- newDictBndrsO DefaultOrigin theta (irreds, _) <- tryHardCheckLoop doc wanteds - addNoInstanceErrs irreds + addNoInstanceErrs irreds if null irreds then return () else @@ -3007,6 +3057,26 @@ tcSimplifyDefault theta = do doc = ptext (sLit "default declaration") \end{code} +@tcSimplifyStagedExpr@ performs a simplification but does so at a new +stage. This is used when typechecking annotations and splices. + +\begin{code} + +tcSimplifyStagedExpr :: ThStage -> TcM a -> TcM (a, TcDictBinds) +-- Type check an expression that runs at a top level stage as if +-- it were going to be spliced and then simplify it +tcSimplifyStagedExpr stage tc_action + = setStage stage $ do { + -- Typecheck the expression + (thing', lie) <- getLIE tc_action + + -- Solve the constraints + ; const_binds <- tcSimplifyTop lie + + ; return (thing', const_binds) } + +\end{code} + %************************************************************************ %* * @@ -3074,7 +3144,7 @@ addNoInstanceErrs :: [Inst] -- Wanted (can include implications) -> TcM () addNoInstanceErrs insts = do { let (tidy_env, tidy_insts) = tidyInsts insts - ; reportNoInstances tidy_env Nothing tidy_insts } + ; reportNoInstances tidy_env Nothing [] tidy_insts } reportNoInstances :: TidyEnv @@ -3082,14 +3152,15 @@ reportNoInstances -- Nothing => top level -- Just (d,g) => d describes the construct -- with givens g + -> [SDoc] -- Alternative fix for no-such-instance -> [Inst] -- What is wanted (can include implications) -> TcM () -reportNoInstances tidy_env mb_what insts - = groupErrs (report_no_instances tidy_env mb_what) insts +reportNoInstances tidy_env mb_what alt_fix insts + = groupErrs (report_no_instances tidy_env mb_what alt_fix) insts -report_no_instances :: TidyEnv -> Maybe (InstLoc, [Inst]) -> [Inst] -> TcM () -report_no_instances tidy_env mb_what insts +report_no_instances :: TidyEnv -> Maybe (InstLoc, [Inst]) -> [SDoc] -> [Inst] -> TcM () +report_no_instances tidy_env mb_what alt_fixes insts = do { inst_envs <- tcGetInstEnvs ; let (implics, insts1) = partition isImplicInst insts (insts2, overlaps) = partitionWith (check_overlap inst_envs) insts1 @@ -3107,7 +3178,7 @@ report_no_instances tidy_env mb_what insts complain_implic inst -- Recurse! = reportNoInstances tidy_env (Just (tci_loc inst, tci_given inst)) - (tci_wanted inst) + alt_fixes (tci_wanted inst) check_overlap :: (InstEnv,InstEnv) -> Inst -> Either Inst SDoc -- Right msg => overlap message @@ -3155,13 +3226,13 @@ report_no_instances tidy_env mb_what insts = vcat [ addInstLoc insts $ sep [ ptext (sLit "Could not deduce") <+> pprDictsTheta insts , nest 2 $ ptext (sLit "from the context") <+> pprDictsTheta givens] - , show_fixes (fix1 loc : fixes2) ] + , show_fixes (fix1 loc : fixes2 ++ alt_fixes) ] | otherwise -- Top level = vcat [ addInstLoc insts $ ptext (sLit "No instance") <> plural insts <+> ptext (sLit "for") <+> pprDictsTheta insts - , show_fixes fixes2 ] + , show_fixes (fixes2 ++ alt_fixes) ] where fix1 loc = sep [ ptext (sLit "add") <+> pprDictsTheta insts