September 2026 - ghc-commits

[Git][ghc/ghc][wip/T26543b] Line up simpleUnifyCheck and check_ty_eq_rhs
by Simon Peyton Jones (＠simonpj) 03 Sep '26

03 Sep '26

Simon Peyton Jones pushed to branch wip/T26543b at Glasgow Haskell Compiler / GHC Commits: f7571be8 by Simon Peyton Jones at 2026-09-03T14:48:54+01:00 Line up simpleUnifyCheck and check_ty_eq_rhs Even after #26543 was allegedly fixed, the original repo case in the Description continued to fail. The reason was that the QuickLook unifier, `qlUnify`, used `simpleUnifyCheck` for checking unification invariants; and `simpleUnifyCheck` conservatively rejected any RHS with a coercion hole in it. The upshot was that QuickLook was not as clever as it should be, wrongly failing to do an impredicative instantiation. Interestingly `check_ty_eq_rhs`, which does the same job, only during constraint solving, was more liberal: it just looked at the free vars of the coercion, and allowed coercion holes. This MR lines them up, adding some careful notes. See Note [simpleUnifyCheck] esp (SUC1) Note [Unification preconditions] esp (COERCIONS) Things are better than before, but I am still uncomfortable about the possibilty that a hole might be filled with a coercion that mentions the LHS type variable; for now I have left this discomfort documented in (SUC1). - - - - - 6 changed files: - + changelog.d/T26543 - compiler/GHC/Core/TyCo/FVs.hs - compiler/GHC/Tc/Gen/App.hs - compiler/GHC/Tc/Utils/Unify.hs - + testsuite/tests/typecheck/should_compile/T26543_orig.hs - testsuite/tests/typecheck/should_compile/all.T Changes: ===================================== changelog.d/T26543 ===================================== @@ -0,0 +1,7 @@ +section: compiler +synopsis: Fix a bug in ImpredicativeTypes +description: + The QuickLook algorithm (which implements `ImpredicativeTypes`) was defeated if there + was a kind coercion in the types being unified. That bug is now fixed. +mrs: !16566 +issues: #26543 ===================================== compiler/GHC/Core/TyCo/FVs.hs ===================================== @@ -850,15 +850,15 @@ invisibleVarsOfTypes = foldr (unionVarSet . invisibleVarsOfType) emptyVarSet {-# INLINE afvFolder #-} -- so that specialization to (const True) works afvFolder :: (TyCoVar -> Bool) -> TyCoFolder (FV TyCoVarSet DM.Any) -- 'afvFolder' is short for "any-free-var folder", good for checking --- if any free var of a type satisfies a predicate `check_fv` +-- if any shallow free var of a type satisfies a predicate `check_fv` afvFolder check_fv = TyCoFolder { tcf_view = noView -- See Note [Free vars and synonyms] , tcf_tyvar = do_tcv, tcf_covar = do_tcv , tcf_hole = do_hole , tcf_tycobinder = addBndrFV } where - do_tcv tv = MkFV $ \ bvs -> - Any (not (tv `elemVarSet` bvs) && check_fv tv) - do_hole _ = mempty -- I'm unsure; probably never happens + do_tcv tv = MkFV $ \ bvs -> + Any (not (tv `elemVarSet` bvs) && check_fv tv) + do_hole hole = do_tcv (coHoleCoVar hole) anyFreeVarsOfType :: (TyCoVar -> Bool) -> Type -> Bool anyFreeVarsOfType check_fv ty = DM.getAny (runFVTop (f ty)) ===================================== compiler/GHC/Tc/Gen/App.hs ===================================== @@ -631,11 +631,13 @@ tcInstFun :: QLFlag -- plus the modification in Fig 5, of the QL paper: -- "A quick look at impredicativity" (ICFP'20). tcInstFun do_ql inst_final rn_head@(_, fun_lspan) tc_fun fun_sigma rn_args - = do { traceTc "tcInstFun" (vcat [ text "tc_fun" <+> ppr tc_fun + = do { lvl <- getTcLevel + ; traceTc "tcInstFun" (vcat [ text "tc_fun" <+> ppr tc_fun , text "rn_fun" <+> ppr rn_head , text "fun_sigma" <+> ppr fun_sigma , text "args:" <+> ppr rn_args - , text "do_ql" <+> ppr do_ql]) + , text "do_ql" <+> ppr do_ql + , text "lvl:" <+> ppr lvl ]) ; fun_origin <- mk_origin rn_head ; res@(_, fun_ty) <- go fun_origin 1 [] fun_sigma rn_args ; traceTc "tcInstFun:ret" (ppr fun_ty) @@ -1377,13 +1379,15 @@ tc_inst_forall_arg conc_tvs (tvb, inner_ty) hs_ty -- is not fully zonked, because ty_arg is fully zonked. -- See Note [Type application substitution]. + ; lvl <- getTcLevel ; traceTc "tc_inst_forall_arg (VTA/VDQ)" ( vcat [ text "fun_ty" <+> ppr fun_ty , text "tv" <+> ppr tv <+> dcolon <+> debugPprType kind , text "ty_arg" <+> debugPprType ty_arg <+> dcolon <+> debugPprType (typeKind ty_arg) , text "inner_ty" <+> debugPprType inner_ty - , text "insted_ty" <+> debugPprType insted_ty ]) + , text "insted_ty" <+> debugPprType insted_ty + , text "lvl:" <+> ppr lvl ]) ; return (ty_arg, insted_ty) } {- Note [Visible type application and abstraction] @@ -1934,11 +1938,13 @@ quickLookArg1 pos app_lspan rn_head larg@(L _ arg) sc_arg_ty@(Scaled _ orig_arg_ -- capture and save it in the `EValArgQL`. See (QLA6) in -- Note [Quick Look at value arguments] + ; lvl <- getTcLevel ; traceTc "quickLookArg {" $ vcat [ text "arg:" <+> ppr arg , text "orig_arg_rho:" <+> ppr orig_arg_rho , text "head:" <+> ppr rn_fun_arg <+> dcolon <+> ppr mb_fun_ty - , text "args:" <+> ppr rn_args ] + , text "args:" <+> ppr rn_args + , text "level:" <+> ppr lvl ] ; case mb_fun_ty of { Nothing -> skipQuickLook app_lspan larg sc_arg_ty ; -- fun is too complicated @@ -2158,18 +2164,23 @@ qlUnify :: TcType -> TcType -> TcM () -- * It may return without having made the argument types equal, of course; -- it just makes best efforts. qlUnify ty1 ty2 - = do { traceTc "qlUnify" (ppr ty1 $$ ppr ty2) + = do { lvl <- getTcLevel + ; traceTc "qlUnify" (ppr lvl $$ ppr ty1 $$ ppr ty2) ; go ty1 ty2 } where go :: TcType -> TcType -> TcM () + go t1 t2 = do { traceTc "qlUinfy:go" (ppr t1 <+> char '~' <+> ppr t2) + ; go' t1 t2 } + -- Decompose (arg1 -> res1) ~ (arg2 -> res2) -- and (c1 => res1) ~ (c2 => res2) -- But for the latter we only learn instantiation info from res1~res2 - go (FunTy { ft_af = af1, ft_arg = arg1, ft_res = res1 }) + go' (FunTy { ft_af = af1, ft_arg = arg1, ft_res = res1 }) (FunTy { ft_af = af2, ft_arg = arg2, ft_res = res2 }) | af1 == af2 -- Match the arrow TyCon - = do { when (isVisibleFunArg af1) (go arg1 arg2) + = do { traceTc "go_fun" (ppr arg1 $$ ppr arg2) + ; when (isVisibleFunArg af1) (go arg1 arg2) -- NB: we do not unify the multiplicities; that would be too strong. -- We might only require mult1 ⩽ mult2, as in Note [Multiplicity in deep subsumption]. @@ -2178,30 +2189,30 @@ qlUnify ty1 ty2 ; go res1 res2 } -- Make sure to not unify "kappa := (a %1 -> b)". See (UQL5). - go (FunTy { ft_mult = OneTy }) _ = return () - go _ (FunTy { ft_mult = OneTy }) = return () + go' (FunTy { ft_mult = OneTy }) _ = return () + go' _ (FunTy { ft_mult = OneTy }) = return () -- NB: we do want to be able to unify "kappa := a => b", as that's -- the main point of QuickLook (allowing meta-variables to be unified -- with qualified types). - go (TyVarTy tv) ty2 + go' (TyVarTy tv) ty2 | isMetaTyVar tv = go_kappa tv ty2 - go ty1 (TyVarTy tv) + go' ty1 (TyVarTy tv) | isMetaTyVar tv = go_kappa tv ty1 - go (CastTy ty1 _) ty2 = go ty1 ty2 - go ty1 (CastTy ty2 _) = go ty1 ty2 + go' (CastTy ty1 _) ty2 = go ty1 ty2 + go' ty1 (CastTy ty2 _) = go ty1 ty2 - go (TyConApp tc1 []) (TyConApp tc2 []) + go' (TyConApp tc1 []) (TyConApp tc2 []) | tc1 == tc2 -- See GHC.Tc.Utils.Unify = return () -- Note [Expanding synonyms during unification] -- Now, and only now, expand synonyms - go rho1 rho2 + go' rho1 rho2 | Just rho1 <- coreView rho1 = go rho1 rho2 | Just rho2 <- coreView rho2 = go rho1 rho2 - go (TyConApp tc1 tys1) (TyConApp tc2 tys2) + go' (TyConApp tc1 tys1) (TyConApp tc2 tys2) | tc1 == tc2 , not (isTypeFamilyTyCon tc1) , tys1 `equalLength` tys2 @@ -2209,14 +2220,14 @@ qlUnify ty1 ty2 -- Don't allow unifying (a => b) with the AppTy 'arr[tau] a b'. -- To ensure this, use 'tcSplitAppTyNoView_maybe' which does not split (=>). - go (AppTy t1a t1b) ty2 + go' (AppTy t1a t1b) ty2 | Just (t2a, t2b) <- tcSplitAppTyNoView_maybe ty2 = do { go t1a t2a; go t1b t2b } - go ty1 (AppTy t2a t2b) + go' ty1 (AppTy t2a t2b) | Just (t1a, t1b) <- tcSplitAppTyNoView_maybe ty1 = do { go t1a t2a; go t1b t2b } - go _ _ = return () + go' _ _ = return () -- Don't look under foralls; see (UQL4) of Note [QuickLook unification] ---------------- @@ -2244,7 +2255,11 @@ qlUnify ty1 ty2 -- Here we are in the TcM monad, which does not track enclosing -- Given equalities; so for quick-look unification we conservatively -- treat /any/ level outside this one as untouchable. Hence cur_lvl. + ; traceTc "go_flexi1" (ppr kappa $$ ppr ty2) ; case simpleUnifyCheck UC_QuickLook cur_lvl kappa ty2 of + -- qlUnify depends, regrettably delicately, on the exact choices made + -- by `simpleUnifyCheck`. See (SUC1) in + -- Note [simpleUnifyCheck] in GHC.Tc.Utils.Unify SUC_CanUnify -> do { co <- unifyKind (Just (TypeThing ty2)) ty2_kind kappa_kind -- unifyKind: see (UQL2) in Note [QuickLook unification] @@ -2253,7 +2268,8 @@ qlUnify ty1 ty2 ; traceTc "qlUnify:update" $ ppr kappa <+> text ":=" <+> ppr ty2 ; liftZonkM $ writeMetaTyVar kappa ty2' } - _ -> return () -- e.g. occurs-check or forall-bound variable + suc -> do { traceTc "go_flexi2" (ppr suc $$ ppr kappa $$ ppr ty2) + ; return () } -- e.g. occurs-check or forall-bound variable } where kappa_kind = tyVarKind kappa ===================================== compiler/GHC/Tc/Utils/Unify.hs ===================================== @@ -103,7 +103,6 @@ import GHC.Types.Id( idType ) import GHC.Types.Var as Var import GHC.Types.Var.Set import GHC.Types.Var.Env -import GHC.Types.Var.FV import GHC.Types.Basic import GHC.Types.Unique.Set (nonDetEltsUniqSet) @@ -120,7 +119,6 @@ import GHC.Data.Maybe (firstJusts) import Control.Monad import Data.Functor.Identity (Identity(..)) import qualified Data.List.NonEmpty as NE -import Data.Monoid as DM ( Any(..) ) import qualified Data.Semigroup as S ( (<>) ) import Data.Traversable (for) @@ -3143,6 +3141,7 @@ uUnfilledVar2 env@(UE { u_defer = def_eq_ref, u_given_eq_lvl = given_eq_lvl }) do { traceTc "uUnfilledVar2 not ok" $ vcat [ text "tv1:" <+> ppr tv1 , text "ty2:" <+> ppr ty2 + , text "given_eq_lvl:" <+> ppr given_eq_lvl , text "simple-unify-chk:" <+> ppr (simpleUnifyCheck UC_OnTheFly given_eq_lvl tv1 ty2) ] -- Occurs check or an untouchable: just defer @@ -3246,6 +3245,7 @@ lhsPriority tv ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Question: given a homogeneous equality (alpha ~# ty), when is it OK to unify alpha := ty? + (This note only applies to /homogeneous/ equalities, in which both sides have the same kind.) @@ -3354,6 +3354,14 @@ Needless to say, all there are wrinkles: GHC.Tc.Solver.floatEqualities, around Nov 2020. It's much easier to unify in-place, with no floating. +* (COERCIONS) What if there are coercions in the RHS? E.g. + alpha ~ (ty |> co) + or alpha ~ (ty co) + We only recurse into the `coercionType` of `co` rather than `co` itself. + Why? Mainly because `co` might be a coercion hole, in which case we /can't/ + recurse into the coercion that will eventually fill the hole. This came + up in #26543. + Note [TyVar/TyVar orientation] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ See also Note [Fundeps with instances, and equality orientation] @@ -3619,6 +3627,8 @@ simpleUnifyCheck :: UnifyCheckCaller -> TcLevel -> TcTyVar -> TcType -> SimpleUn -- unification might still be OK, but it'll take more work to do -- (use the full 'checkTypeEq'). -- +-- See Note [simpleUnifyCheck] +-- -- * Rejects if lhs_tv occurs in rhs_ty (occurs check) -- * Rejects foralls unless -- lhs_tv is RuntimeUnk (used by GHCi debugger) @@ -3638,12 +3648,10 @@ simpleUnifyCheck caller given_eq_lvl lhs_tv rhs | otherwise = SUC_NotSure where - lhs_info = metaTyVarInfo lhs_tv - - !(occ_in_ty, occ_in_co) = mkOccFolders (tyVarName lhs_tv) - + lhs_info = metaTyVarInfo lhs_tv lhs_tv_lvl = tcTyVarLevel lhs_tv lhs_tv_is_concrete = isConcreteTyVar lhs_tv + lhs_tv_nm = tyVarName lhs_tv forall_ok = case caller of UC_QuickLook -> isQLInstTyVar lhs_tv @@ -3660,11 +3668,11 @@ simpleUnifyCheck caller given_eq_lvl lhs_tv rhs UC_OnTheFly -> False rhs_is_ok (TyVarTy tv) - | lhs_tv == tv = False - | tcTyVarLevel tv `strictlyDeeperThan` lhs_tv_lvl = False - | lhs_tv_is_concrete, not (isConcreteTyVar tv) = False - | occ_in_ty $! (tyVarKind tv) = False - | otherwise = True + -- c.f. checkTyVar, the TEFTyVar case + | tcTyVarLevel tv `strictlyDeeperThan` lhs_tv_lvl = False + | lhs_tv_is_concrete, not (isConcreteTyVar tv) = False + | simple_occurs_check lhs_tv_nm tv = False + | otherwise = True rhs_is_ok (FunTy {ft_af = af, ft_mult = w, ft_arg = a, ft_res = r}) | not forall_ok, isInvisibleFunArg af = False @@ -3681,33 +3689,47 @@ simpleUnifyCheck caller given_eq_lvl lhs_tv rhs | otherwise = False rhs_is_ok (AppTy t1 t2) = rhs_is_ok t1 && rhs_is_ok t2 - rhs_is_ok (CastTy ty co) = not (occ_in_co co) && rhs_is_ok ty - rhs_is_ok (CoercionTy co) = not (occ_in_co co) + rhs_is_ok (CastTy ty co) = co_is_ok co && rhs_is_ok ty + rhs_is_ok (CoercionTy co) = co_is_ok co rhs_is_ok (LitTy {}) = True + -- For coercions we look only in the /type/ of the coercion + -- See (SUC1) in Note [simpleUnifyCheck] + co_is_ok co = rhs_is_ok (coercionType co) -mkOccFolders :: Name -> (TcType -> Bool, TcCoercion -> Bool) --- These functions return True --- * if lhs_tv occurs (incl deeply, in the kind of variable) --- * if there is a coercion hole --- No expansion of type synonyms -mkOccFolders lhs_tv = ( getAny . runFVTop . check_ty - , getAny . runFVTop . check_co) - where - check_ty :: Type -> FV BoundVars Any - !(check_ty, _, check_co, _) = foldTyCo occ_folder - - occ_folder :: TyCoFolder (FV BoundVars Any) - occ_folder = TyCoFolder { tcf_view = noView -- Don't expand synonyms - , tcf_tyvar = do_tcv, tcf_covar = do_tcv - , tcf_hole = do_hole - , tcf_tycobinder = addBndrFV } - - do_tcv v = (MkFV $ \ bvs -> - Any (not (v `elemVarSet` bvs) && tyVarName v == lhs_tv)) - `mappend` check_ty (varType v) - - do_hole _hole = MkFV $ \ _bvs -> DM.Any True -- Reject coercion holes +{- Note [simpleUnifyCheck] +~~~~~~~~~~~~~~~~~~~~~~~~~~ +The function `simpleUnifyCheck` is asimple, /fast/ check for unifying (tv ~ rhs). +It can return a definite decision (SUC_CannotUnify of SUC_CanUnify), or uncertainty +(SUC_NotSure). In the latter case we will later use `checkTyEqRhs` to resolve. +In particular, `simpleUnifyCheck`: + +* Rejects if lhs_tv occurs in rhs_ty (occurs check) +* Rejects foralls unless + lhs_tv is RuntimeUnk (used by GHCi debugger) + or is a QL instantiation variable +* Rejects a non-concrete type if lhs_tv is concrete +* Rejects type families unless fam_ok=True +* Does a level-check for type variables, to avoid skolem escape + +This function is pretty heavily used, so it's optimised not to allocate. + +(SUC1) `simpleUnifyCheck` used by QuickLook's `qlUnify`, and anything other than + SUC_CanUnify will tell `qlUnify` not to proceed. That makes QuickLook depend + (regrettably, delicately) on the exact choices made by `simpleUnifyCheck`. + + A case in point: in #26543. In the repro case in the Descriptions, `qlUnify` failed + because there was a coercion /hole/ in the RHS; but one that was ultimately Refl. + + So in `simpleUnifyCheck` we only look at the /kind/ of a coercion, not the + evidence itself. I'm a bit worried about building a loop, if the evidence + mentions the LHS unification variable; but I can't see how that can happen, and + I /really/ don't want to be super-conservative for coercion holes (#26543). So, + for now at least, we look just at the kind of the coercion. + + Note that this (unsatisfactorily) differs from the choice in `checkCo`, but + changing that too is an unforced change so I have left the inconsistency. +-} {- ********************************************************************* * * @@ -4337,7 +4359,11 @@ checkCo flags co = -- Occurs check (can promote) | OC_Check lhs_tv occ_prob <- occ , LC_Promote { lc_lvlp = lhs_tv_lvl } <- lc - -> do { reason <- checkPromoteFreeVars occ_prob lhs_tv lhs_tv_lvl (tyCoVarsOfCo co) + -> do { reason <- checkPromoteFreeVars occ_prob lhs_tv lhs_tv_lvl $ + tyCoVarsOfCo co + -- Maybe we should just check the free vars of the + -- /type/ of the coercion, to line up with + -- (SUC1) in Note [simpleUnifyCheck] ; return $ if cterHasNoProblem reason then pure co @@ -4697,12 +4723,18 @@ simpleOccursCheck :: OccursCheck -> TcTyVar -> TyVarCheckResult m simpleOccursCheck OC_None _ = TyVarCheck_Success simpleOccursCheck (OC_Check lhs_tv occ_prob) occ_tv - | lhs_tv == tyVarName occ_tv || check_kind (tyVarKind occ_tv) - = TyVarCheck_Error (cteProblem occ_prob) - | otherwise - = TyVarCheck_Success + | simple_occurs_check lhs_tv occ_tv = TyVarCheck_Error (cteProblem occ_prob) + | otherwise = TyVarCheck_Success + +simple_occurs_check :: Name -> TcTyVar -> Bool -- True <=> occurs check +-- Check for an occurrence of lhs_tv in occ_tv or its kind +-- This is a heavily-used bit of code +simple_occurs_check lhs_tv occ_tv + = go occ_tv where - (check_kind, _) = mkOccFolders lhs_tv + go occ_tv | lhs_tv == tyVarName occ_tv = True + | anyFreeVarsOfType go (tyVarKind occ_tv) = True + | otherwise = False ------------------------- tyVarLevelCheck :: LevelCheck m -> TcTyVar -> TyVarCheckResult m ===================================== testsuite/tests/typecheck/should_compile/T26543_orig.hs ===================================== @@ -0,0 +1,36 @@ +-- This test is from the Description of #26543 + +{-# LANGUAGE GHC2024, TypeAbstractions, AllowAmbiguousTypes, NoImplicitPrelude, + TypeFamilies, UndecidableInstances #-} +module T26543_orig where + +import Data.Kind +import Control.Applicative (Applicative(..)) +import Prelude (type (~), ($)) + +type CAT k = k -> k -> Type + +type family (~>) :: CAT k +type family Ob (a :: k) :: Constraint +type family UN (w :: j -> k) (wa :: k) :: j + +class HasBinaryProducts k where + type (a :: k) && (b :: k) :: k + withObProd :: (Ob (a :: k), Ob b) => ((Ob (a && b)) => r) -> r + (&&&) :: ((a :: k) ~> x) -> (a ~> y) -> (a ~> (x && y)) + +data AP (f :: Type -> Type) k = A k +type instance UN A (A k) = k + +type Ap :: CAT (AP f k) +data Ap a b where + Ap :: forall {k} a b f. (Ob a, Ob b) => f (a ~> b) -> Ap (A a :: AP f k) (A b) + +type instance (~>) = Ap +type instance Ob a = (a ~ A (UN A a), Ob (UN A a)) + +instance (Applicative f, HasBinaryProducts k) => HasBinaryProducts (AP f k) where + type a && b = A (UN A a && UN A b) + withObProd @(A a) @(A b) r = withObProd @k @a @b r + -- (&&&) :: Ap (a :: AP f k) x -> Ap a y -> Ap a (x && y) + Ap @_ @x f &&& Ap @_ @y g = withObProd @k @x @y $ Ap (liftA2 (&&&) f g) ===================================== testsuite/tests/typecheck/should_compile/all.T ===================================== @@ -969,3 +969,4 @@ test('ExpansionQLIm', normal, compile, ['']) test('T23135', normal, compile, ['']) test('LazyFieldAnnotations', normal, compile, ['']) test('T27557', normal, compile, ['']) +test('T26543_orig', normal, compile, ['']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/f7571be8581071281f848de09966eab… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/f7571be8581071281f848de09966eab… You're receiving this email because of your account on gitlab.haskell.org. 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[Git][ghc/ghc][wip/10.0.1-backports] 53 commits: Bump Cabal submodule to 3.18.1.0
by Zubin (＠wz1000) 03 Sep '26

03 Sep '26

Zubin pushed to branch wip/10.0.1-backports at Glasgow Haskell Compiler / GHC Commits: b11f2da2 by Zubin Duggal at 2026-09-03T13:18:46+05:30 Bump Cabal submodule to 3.18.1.0 - - - - - ad7709f1 by Cheng Shao at 2026-09-03T13:18:46+05:30 rts: always use StgInt to represent cost center id Currently cost center id is modeled as `Int` and it should be `StgInt` uniformly in the RTS, hence this patch. Fixes #27524. (cherry picked from commit ab9ab8952b1ff20ed8b092ff95d6a9f8d822c033) - - - - - e2496d4f by Zubin Duggal at 2026-09-03T13:18:46+05:30 UniqueDFM: alter should preserve insertion order Before it always inserting new elements at the end. This is problematic because instances get inserted into the map with `alterF`, which can change ordering of how instances are printed with `:info` depending on the order in which we consult interfaces I expect `alter id k = id` and `alter (fmap f) k = adjust f k`. Moving keys to the end breaks that (`adjust` already preserves position). Fixes #27532 (cherry picked from commit f6f2343fbbfdfd8aaed9babf5983e3e24c08ca85) - - - - - 507f6920 by Duncan Coutts at 2026-09-03T13:18:46+05:30 Add missing updateRemembSetPushClosure in poll I/O manager For the non-moving GC. (cherry picked from commit daf2bd6f71b7ee309374dddf0d4793bbc0ed066d) - - - - - 0e505903 by Duncan Coutts at 2026-09-03T13:18:46+05:30 Eliminate STM_AWOKEN It was used as nullary closure for the block_info.closure in the case of a thread being awoken after an STM transaction. However, while it was written, it was never read, so contributed nothing to the behaviour. Furthermore, in the only place it was set (in tryWakeupThread) the why_blocked was immediately overwritten by the NotBlocked status, and the block_info was updated accordingly (by appendToRunQueue). So it didn't even serve a purpose of clarifying an intermediate state, there really was no such intermediate state. Cleaning this up will allow the BlockedOnSTM case to follow the same pattern as the other why_blocked cases that do not use the block_info, and in turn this reduces the number of different categories. (cherry picked from commit 4d798b17c9b83f280c102ca7f96047bc0ad52df1) - - - - - 11bf7aa0 by Duncan Coutts at 2026-09-03T13:18:46+05:30 Document that eventlog thread stop code ThreadBlocked is no longer used It has not been used since GHC 7.0.x (2011). In 7.2 all the BlockedOn* codes were added, and these were and are used instead of ThreadBlocked. (cherry picked from commit e1cece79a6c8e53796188acd543a8b565b18a3fb) - - - - - 8b9bb52c by Duncan Coutts at 2026-09-03T13:18:46+05:30 Add a proper mapping to eventlog external thread stop status That is the mapping from rts-internal codes, to the coes used in the status field in the eventlog EVENT_STOP_THREAD event. See issue #9003 for what goes wrong when we mess this up. In that ticket, people note that we should really not require the internal tso->why_blocked codes to leak into the external eventlog thread stop codes. The same principle applies to the StgThreadReturnCode. This change properly separates them, and explicitly maps between them using a pair of (compact, constant) tables. These tables are pretty small (with no alignment constraints) and will soon shrink so it seems a sensible tradeoff. We also introduce and use proper EVENT_STOP_THREAD constants in the event log format header. Previously there was not specification in the code for these (only in the docs): the values were encoded into the conversion code. This will allow us to renumber the internal why_blockd codes without breaking the eventlog output. (cherry picked from commit 795db1151237be5a3d0d2cdccb4c43309b587cdf) - - - - - 9d0f584a by Duncan Coutts at 2026-09-03T13:18:46+05:30 Remove unused tso->block_info.wakeup member Presumably it was used once, but not now. (cherry picked from commit 6f1c8efa1b4c78273daca99f9dda0a7e3d771330) - - - - - 74546fac by Duncan Coutts at 2026-09-03T13:18:46+05:30 Document StgTSOBlockInfo to say what cases use what members In principle, tso->why_blocked is the tag for the StgTSOBlockInfo union, so we should be able to say for each union member the why_blocked cases that use that member. (cherry picked from commit 740b88a980c4aa7f28fcf3aa89f7df8aea2813a9) - - - - - 4a8b97c1 by Duncan Coutts at 2026-09-03T13:18:46+05:30 Add a tso->block_info.mvar member and use it in preference to the generic block_info.closure union member, with casts. The plan is that when we know what case we're in (via tso->why_blocked) then we can always access the correct union member, and so we will only need to access block_info.closure for generic cases where we don't know or don't care. (cherry picked from commit 5b92eae2638db71ff8725295ec2a8ca254c0720b) - - - - - 0be9dc88 by Duncan Coutts at 2026-09-03T13:18:46+05:30 Add a tso->block_info.unused member and use it in preference to the generic block_info.closure union member, with casts. The plan is that when we know what case we're in (via tso->why_blocked) then we can always access the correct union member, and so we will only need to access block_info.closure for generic cases where we don't know or don't care. (cherry picked from commit d931715fbea83ccd402d280965a5d096a9f72949) - - - - - cb326511 by Duncan Coutts at 2026-09-03T13:18:46+05:30 Avoid storing to tso->block_info.closure In one case we can use a specific union member (.prev) instead. In several cases the stores were in fact redundant because of subsequent overwrites. In scavengeTSO we replace setting tso->block_info.closure to a valid closure, with an assertion that the block_info.unused is already set to END_TSO_QUEUE which is a valid (static) closure. (cherry picked from commit 47e28ebbb4e22ad2ddb27c3f4acc5df291276743) - - - - - 57cd71ad by Duncan Coutts at 2026-09-03T13:18:46+05:30 Renumber the tso->why_blocked constants We can do this now because we have separated the internal values from the external ones used in the eventlog. This lets us put them back into a deliberate order and consolodate some gaps. More importantly, it is a prepation for a slightly more sophisticated encoding. (cherry picked from commit 96e4749d9f9b75e99d7b860325b92a5b3704e784) - - - - - 562e4370 by Duncan Coutts at 2026-09-03T13:18:46+05:30 Define constants for the existing stg_threadStatuszh return codes The stg_threadStatuszh reuses the internal tso->why_blocked codes but also extends them with a couple previously magic values. This is awkward since we need to know what those magic values are so we don't accidentally use those values to mean something else. By pulling a definition up to where the why_blocked codes are defined we will be able to avoid mistakenly assining those codes some meaning (or just changing the BlockedThreadComplete, BlockedThreadKilled code if necessary). (cherry picked from commit 8f62661c133338100803347084de3566e325e64c) - - - - - 2adb7139 by Duncan Coutts at 2026-09-03T13:18:46+05:30 Extend the tso->why_blocked encoding to indicate block_info closures We use some bit tricks to cheaply and generically test if a tso->why_blocked tag implies that the corresponding tso->block_info will contain a non-trivial valid closure (i.e. not just block_info.unused set to END_TSO_QUEUE). In particular we arrange for most why_blocked values to naturally have a distinguishing bit, but for the BlockedOn{Read,Write,Delay} cases, they can come in either non-closure or closure forms. We allow an additional bit to distinguish these cases. The non-closure forms are only from legacy I/O managers: select and win32-legacy. So this extra bit mechanism will be able to be retired once the legacy I/O managers are themselves retired. This means in a few places we need to untag the why_blocked value before inspecting it, but in most places we do not. (cherry picked from commit 42c69ae2d58310c703abaa4ec933973fa9b136d3) - - - - - 228a625b by Duncan Coutts at 2026-09-03T13:18:46+05:30 Use BlockInfoForceNonClosure in the select I/O manager (cherry picked from commit 7c64632b46ac660fc0779ae96d9a05d11537b743) - - - - - e768d359 by Duncan Coutts at 2026-09-03T13:18:46+05:30 Use BlockInfoForceNonClosure in the win32-legacy I/O manager for the BlockedOn{Read,Write} since these use the non-heap allocated StgAsyncIOResult. (cherry picked from commit 8fd7104a0d63208f8408a7e5cd185bd2020225c8) - - - - - c6092e3d by Duncan Coutts at 2026-09-03T13:18:46+05:30 Enforce the why_blocked and block_info rules in checkTSO We now check the cases wher IsBlockInfoClosure should hold, the cases that are supposed to use block_info.unused == END_TSO_QUEUE, and which cases are allowed to use BlockInfoForceNonClosure. This partially enforces the use of why_blocked as a tag for the block_info union. We could be stricter and check for the correct expected info table for the closure cases. (cherry picked from commit e0da603b8e24cfc633f29990be9ca7008f45b3c2) - - - - - 205bce9a by Duncan Coutts at 2026-09-03T13:18:46+05:30 Use IsBlockInfoClosure to simplify several tests In GC and generic traversal we need to know if we should look at the block_info.closure or not. Now we can do just that using a cheap bit test on the why_blocked tag. This fixes issue 26717, where the problem was that some GC modes did not know when to look at block_info.closure, because the poll I/O manager uses a closure for BlockedOn{Read,Write} while the select I/O manager uses a non-closure. Now this information is in the why_blocked tag itself. (cherry picked from commit 1dd0f381ab96d3f46e113c90858870e95bd3caba) - - - - - 6fa33e9b by Duncan Coutts at 2026-09-03T13:18:46+05:30 Remove the now-unused scavengeTSOIOManager The GC no longer has to delegate to the I/O manager, since it can use IsBlockInfoClosure to decide things itself. (cherry picked from commit 7a00ffbc311e6ee53e8b1b9181e37c3795a7b884) - - - - - 0f5b227d by Duncan Coutts at 2026-09-03T13:18:46+05:30 Remove duplicate assertion (cherry picked from commit 522a481f5f1e51a8bdd0902012bdc467535a0382) - - - - - f5342612 by Duncan Coutts at 2026-09-03T13:18:46+05:30 Follow atomic access rules more consistently for tso->why_blocked The rule is this: store block_info *before* why_blocked store why_blocked using store release load why_blocked using load acquire load block_info *after* why_blocked This is a an atomic store release / load acquire pair and (if the reads are in a separate thread to the writes, and the read receives the value stored) then this guarantees a full "happens before" relationship of these stores and loads. In some cases, we do not need a full load acquire, because we don't read the block_info at all and so do not need any ordering. In this case we just need an atomic relaxed load. This was being followed in most places, but not all. If there's good reason in any case that we don't need atomic access, then we should document that in a comment. In the absence of that I think it's easier to follow the rule everywhere. (cherry picked from commit 0874d965ef1fec847561418857e63c067b91b0b7) - - - - - 733924c3 by Duncan Coutts at 2026-09-03T13:18:46+05:30 Add a changelog entry (cherry picked from commit 8f0bdbe138a2e1914cba7963b6931402f99c8710) - - - - - 54345072 by Cheng Shao at 2026-09-03T14:39:44+05:30 configure: bump LlvmMaxVersion to 23 This patch bumps `LlvmMaxVersion` to 23 to support LLVM 22.x releases. (cherry picked from commit cc9cc6d5df7fb3845b1409fe708e1097896252a7) - - - - - dd3ae55b by Cheng Shao at 2026-09-03T14:39:44+05:30 changelog: add llvm 22.x support (cherry picked from commit 2ea7ef8ef090fa44a0191271f644a0917908ef40) - - - - - b593915c by fendor at 2026-09-03T14:39:44+05:30 Drop `preloadClosure` from `UnitState` It is always hard-coded to the same value. Backpack Unit instantiation isn't using it any more. Allows us to simplify the API and get rid of `improveUnit`. (cherry picked from commit fb5246adb7e10bd9ef07de314eaf98fbcfb729a1) - - - - - 3110b6f2 by fendor at 2026-09-03T14:42:48+05:30 Introduce global unit database cache As a first step for better sharing of `UnitInfo` across `UnitEnv`, we introduce a new datatype called `ExternalUnitDatabases`. It primarily serves as an in-memory representation of *all* `UnitDatabase`s across `UnitEnv`. This means, if multiple `HomeUnitEnv`s depend on the same database, one way or another, we make sure that we don't parse from disk every time. Instead, we store the in-memory representation in `ExternalUnitDatabases`. `ExternalUnitDatabaseCache` is the equivalent of `ExternalUnitState` in the `UnitEnv`. It is a mutable variable wrapping `ExternalUnitDatabases`. The mutable `ExternalUnitDatabaseCache` is used in `initUnits` to make sure we don't parse the same unit database multiple times. Almost by accident, we change the semantics of `initUnits` to honour modifications to `packageDBFlags`. The inability to change `packageDBFlags` while also reusing the already parsed `UnitDatabase`s was reported in #26423 as a bug. Hence, we think this behaviour change is warranted and acceptable, especially since it comes with a breaking change to the `initUnits` API. Add regression test for #26423 Closes #26423 (cherry picked from commit 5d0ab71ac1d01c2ef19bf3146adb7dac8733dca5) - - - - - fcc004c0 by fendor at 2026-09-03T17:39:18+05:30 Introduce UnitIndex for global external unit caching `UnitInfo`s have been observed to cause a lot of memory usage in #27500. Especially with multiple home units, as the same (external) units are processed from scratch, even though most of the time we end up with exactly the same `UnitInfo`. We introduce a `UnitEnv` global cache that allows us to store external unit information that is used across all `HomeUnitEnv`s. The most important change in this commit is the introduction of the `UnitIndex`. It stores a global mapping of `UnitId` -> `UnitInfo`, and `initUnits` always uses the cached `UnitInfo` entry to populate each `HomeUnitEnv`'s `UnitState`. This allows us to ensure the following property: > Each `UnitInfo` should be alive exactly once in GHC. All `UnitState`s should reference 'UnitInfo's stored in the 'UnitIndex'. This ensured by calling 'initUnits' with the 'UnitIndex'. In addition, the `ExternalUnitDatabases` may also hold a reference to each on-disk representation of `UnitInfo`. This means, we impose an hard upper bound on the number of `UnitInfo`s alive in the GHC session: > The number of alive `UnitInfo`s closure objects must be the > sum of all loaded unit database times two. We add performance regression tests that make sure the number of live `UnitInfo` cannot exceed this threshold. Closes #27500 ------------------------- Metric Decrease: MultiComponentModules MultiComponentModulesRecomp MultiComponentModulesRecomp100 mhu-perf LinkableUsage02 ------------------------- These metrics increases are especially notable, as we are not even sharing anything big but merely the global package database with 50 entries. It shows how careful sharing of `UnitInfo` can improve memory usage. We expect this to be much more notable when the whole cabal package database is shared across multiple home units. `LinkableUsage02` metric decreases on unreg and i386 platform, only. --- Technical details To share the `UnitInfo`s correctly, it is important that we extract the `WireMap` into the `UnitIndex`. At the moment of writing, `WireMap` must be globally the same for all `HomeUnitEnv`s. This is important, as we could otherwise not cache the "fully-resolved" `UnitInfo`, as we don't change the `UnitId` or `unitAbiHash` when resolving wired-in units. Thus, there could be ambiguities, when the `WireMap` is not the same for all `UnitState`s across the `UnitEnv`. We consider a `UnitInfo` fully-resolved, if wired-in units have been updated, the `UnitInfo` has been validated and variables in the unit config, such as `${pkgroot}` have been resolved. Updating the wired-in units requires the `WireMap` to be globally the same. (cherry picked from commit 6cce494a7ec43953c7a949e0d8ce712abfe73da7) - - - - - 9d0fd696 by Ben Gamari at 2026-09-03T17:39:18+05:30 base: Don't drop exception context in SomeException(toException) For reasons that are lost to time, the implementation of [CLC #200] that was merged inappropriately dropped `ExceptionContext` in the `toException` implementation given to `SomeException`. Fix this infelicity. [CLC #200]: https://github.com/haskell/core-libraries-committee/issues/200 (cherry picked from commit 2ab02c579a9625438f5281a258051cb32ba40004) - - - - - 7ccf9b9c by Vladislav Zavialov at 2026-09-03T17:39:18+05:30 Discard type arguments in tcPatToExpr (#27440, #27583) The builder expression of an implicitly bidirectional pattern synonym must not mention types written in the RHS: * Invisible type arguments led to a panic (#27440) * Required type arguments failed with out-of-scope variables (#27583) Both are now discarded, following the precedent established by pattern signatures (#9867). Discarding type arguments takes some care: a type pattern cannot be told from a value pattern by syntax alone, as the `type` keyword may be omitted. Consider: data T a b c where MkT :: forall a. forall b c -> a -> T a b c pattern P :: x -> T x y z pattern P x = MkT @a (type b) c x In P's right-hand side, `@a` and `type b` are clearly type arguments, but what about `c` and `x`? We can only tell by matching the patterns against MkT's type. So tcPatToExpr now runs in TcM and matches the arguments against the constructor's TyVarBinders using zipPatsBndrs, which is made public for this purpose. The resulting builder is $bP x = MkT _ _ x. See Note [Discarding types in the builder expression]. Test cases: T27440a T27440b T27440c T27440d T27440e T27583a T27583b T27583c T27583d T27583e T27583f T27583g Metric Increase: LinkableUsage02 Metric Decrease: T27336 Assisted-by: Claude Opus 5 (cherry picked from commit 4f98510802423dcd98fa62af77997189ee97a111) - - - - - 23e3630a by sheaf at 2026-09-03T17:39:18+05:30 mkWpFun_FRR: fix ordering of coercion composition When the subsumption machinery generates an eta-expansion, we must perform a representation polymorphism check to ensure the lambda binder it introduces has a fixed runtime representation. This is done in GHC.Tc.Utils.mkWpFun_FRR. This check involves composing quite a few coercions, arising from representation-polymorphism checks on both the actual and expected argument types. These coercions are then chained using HsWrapper composition, <.>. The ordering of composition was incorrect, leading to the Core Lint failure reported in #27639. This commit fixes that. Fixes #27639 (cherry picked from commit eb1dcd4d98548b7bc64c323dc352ddbf149a91ec) - - - - - e6e6ac3f by Bernhard M. Wiedemann at 2026-09-03T17:39:18+05:30 driver: Link object files in a deterministic order The object files handed to the linker come from the HomePackageTable, which is ordered by the order in which modules finished compiling. With -j1 that is the build plan order, with -jN it is whatever the scheduler produced, so the same sources can link to different (but equivalent) binaries. The order reaches the output: .text and .rodata contributions are concatenated in link order, so e.g. building the hdav executable of the DAV package twice, once with -j1 and once with -j4, yields two binaries that differ in ~100kB of section contents. Sort the home modules by module before collecting their linkables, guarded under `Opt_ObjectDeterminism` . Fixes #27612 Signed-off-by: Bernhard M. Wiedemann <bwiedemann(a)suse.de> (cherry picked from commit e8d1a0d68067ba344fdff816f6b84f0117ffdc59) - - - - - 2ce5dbb2 by Zubin Duggal at 2026-09-03T17:39:18+05:30 hadrian: Fix links to remaining doc sites to not use the package hash for haddock links In 07267f79d91169f474cacc8bcd38d76a6e97887d we changed hadrian to not include the package hash in the haddock directory. This patch takes care of a few remaining links that were missed in that patch Fixes #27671 (cherry picked from commit 1446bb039a635f2b836be19f062cbffa568fe4c5) - - - - - 8f3d32ce by Vladislav Zavialov at 2026-09-03T17:39:19+05:30 Fix tcLookupId panic with RequiredTypeArguments and PatternSynonyms (#27586) The arguments declared on the left-hand side of a pattern synonym are looked up as term variables bound by its right-hand side. Prior to this patch, that lookup panicked with RequiredTypeArguments: data T a where MkT :: forall a -> T a pattern P :: Int -> T Int pattern P x = MkT x On the RHS, `x` looks like a term argument, so the renamer binds it in the term namespace. Only during type checking does it turn out to be a type variable, so the lookup on the LHS finds an ATyVar rather than an ATcId. As the lookup was done with tcLookupId, it resulted in a panic. Now the arguments are looked up with tcLookupPatSynArg, which reports an illegal term-level use of `x`, just as an ordinary function definition `f (MkT x) = x` does. Test cases: T27586a T27586b T27586c Assisted-by: Claude Opus 5 (cherry picked from commit b757727a78613e7437a713058c24b94e10697f47) - - - - - 1b1f677a by Zubin Duggal at 2026-09-03T17:39:19+05:30 DmdAnal: Fix maxDmdType We need to eta expand the smaller DmdType using defaultArgDmd, like in lubDmdType. Introduce zipDmdType as a common combinator to implement both maxDmdType and lubDmdType uniformly. fixes #27626 (cherry picked from commit e31885816b7c597ad89b05da64b21c5a241bf674) - - - - - e7854977 by Andreas Klebinger at 2026-09-03T17:39:19+05:30 cmm dumps: Add machop width info with -dppr-debug for infix ops. (cherry picked from commit e9bbe8f924ec0b9d0772cf3d4f20aa6a25f28345) - - - - - 8c36cb1d by Andreas Klebinger at 2026-09-03T17:39:19+05:30 CmmLint: Check for unsupported MachOp widths machOpArgReps now maps MachOp + Width to a list of supported argument widths or Nothing if the given operation is not supported at the given width. This allows us to check for nonsensical combinations like FloatToInt at Word16. Similarly we now check that every address is actually wordwidth. (cherry picked from commit 86e3a9d8d0a85b5c80dad212cf3ec8fbf1ba72e6) - - - - - 6968969f by Andreas Klebinger at 2026-09-03T17:39:19+05:30 arm64 ncg: The big subword truncation fix. A set of slightly related fixes to arm subword handling: Bitmask immediates: Don't produce overflowing assembly literals. There is still another bug here that causes us to miss some valid literals but we will fix that later. Improve subword truncation handling: We now use a small set of helpers to truncate `Register` values rather than truncating immediate `Reg` values which greatly simplifies the code structure. This fixes a great many bugs to do with sign/zero extending subwords or the lack thereof. We now establish the invariant that subword values are zero-extended at every site at which they come into "scope" of the ncg, and rely on the invariant throughout rather than pessimistically inserting redundant extensions in a hodgepodge manner at the use sites of these values. This fixes at least the bugs described in issues #27533, #27430 #27537, #27538, #27539, and #27550. But likely more bugs yet not found. Subword ffi results: Apply truncations when calling functions returning subword values. genCondJump: Don't sign extend signed values in the input register as it might map to a local variable, corrupting the value stored within. Fix subword store/load instructions.: We used to read those at 32bit width even for smaller values possibly resulting in invalid memory access. Now we construct the suffix for subword variants based on the instruction format for these. (cherry picked from commit 13781cca5c24c2671d651fd2b13a561c7386fe3a) - - - - - b9079f99 by Andreas Klebinger at 2026-09-03T17:39:19+05:30 arm64 ncg: Fix MO_V_Broadcast for non-literals. We now use OpReg instead of OpScalarAsVec as required since we broadcast a gp register. Also adds a test. Fixes #27565. (cherry picked from commit d8fa5d7cc060aa7d3bee8a68b922c85b626cbe8c) - - - - - 78a79218 by Andreas Klebinger at 2026-09-03T17:39:19+05:30 Add some test cases covering bugs in the arm ncg. * Test for #27430 (subword ffi results) * #27537 - subword conversions * #27538 - subwords used in conditional * #27533 - single byte read (cherry picked from commit 94822c951c2a6f77c7766720e0d4ff7d4afb7290) - - - - - ccab2dbe by Andreas Klebinger at 2026-09-03T17:39:19+05:30 cmmLint: Lint against MO_FS_Truncate subword use. (cherry picked from commit dd1ba88a70f47bead722e9dae8e91f9a617258aa) - - - - - 2bdf5ced by Rodrigo Mesquita at 2026-09-03T17:39:19+05:30 rts: refactor to reduce THREADED_RTS in MSG_UPD_TSO_FLAGS - No behavior change in this commit (well, a small optimization here makes us do less work if the target TSO owned by the curr. capability) - Move all THREADED_RTS CPP needed into `updThreadFlag` - Merge MSG_SET_TSO_FLAGS and MSG_UNSET_TSO_FLAGS into MSG_UPD_TSO_FLAGS plus a `set` bool field in the MessageUpdTSOFlag struct Towards #27729 (cherry picked from commit bb3241717c8ee46e31fbdb3cfaed9736ba7257ea) - - - - - 030362c7 by Rodrigo Mesquita at 2026-09-03T17:39:19+05:30 rts: Fix race condition in MSG_UPD_TSO_FLAGS execution The code for processing the MSG_UPD_TSO_FLAGS message was not taking into consideration that the TSO's owner might have moved in between that capability receiving the message (since it was its previous owner) and starting to process its inbox (a point at which it was no longer the owner) Added Note [TSO owner may change in between Msg being sent and received] to explain this race and the pattern used to fix this, where we just forward the message to the new owner. Fixes #27729 (cherry picked from commit ed99b7b7bed699f3f2047672be7709c6d22b6df7) - - - - - 95aeec9e by fendor at 2026-09-03T17:39:19+05:30 GHCi: Fix order of `PackageDBFlag`s for interactive home unit `PackageDBFlag`s are stored in reverse order of cli specification. When sorting the `PackageDBFlag`s by longest common prefix, we need thus to reverse the package db stacks before calculating the prefix. We make sure to reverse the package db stack for the interactive home unit to uphold that later specified package dbs overwrite earlier ones. Resolved and adds regression test for #27640 (cherry picked from commit 06fde293f2e8c80db11f4d01fcdfc482c1128db5) - - - - - 584ad45c by fendor at 2026-09-03T17:39:19+05:30 Reuse the UnitIndexCache after initialising multiple home units (cherry picked from commit 024c4d04a98f7e27b3dcb93f9b038f9b6b5a1ad9) - - - - - b714ea9b by Andreas Klebinger at 2026-09-03T17:39:19+05:30 Specialise: Stop looping on recursive dictionaries in interestingDict interestingDict now doesn't look through loopbreaker unfoldings. Doing so would cause infinite loops on certain dictionaries. Fixes #27705. (cherry picked from commit 578bd18509f0d2aeb004231a197f7f3898f86a2a) - - - - - 6e559c09 by Simon Peyton Jones at 2026-09-03T17:39:19+05:30 Never make an absent filler for a constraint type mkAbsentFiller used isTerminatingType to decide, but that is not enough. Consider class Eq a => UC a where {} let u :: UC Int -- UC Int is a "non-terminating type" u = error "Absent" let e :: Eq Int -- Eq Int is a "terminating type" e = $p1UC u We clearly must not make a filler for `e`, because we speculatively evaluate it. But speculatively evaluating `e` forces `u`, so we must not make one for `u` either. Asking isDictTy instead is not enough either, because it does not catch a constraint hidden behind an unreduced type family application: type family F a :: Constraint type instance F W = TC W a :: F W => Int -> Int -- (F W) argument is absent Oops! Entered absent arg Arg: irred Type: F W So play safe and use isPredTy: never make an absent filler for any constraint-kinded type. Fixes #27627 (cherry picked from commit 7bf546fc423e23cb649580016ee494efbfe144ab) - - - - - 97e3de95 by Zubin Duggal at 2026-09-03T17:39:19+05:30 Add tests for absent fillers at dictionary types T27627 a unary class whose superclass is a non-unary class T27627a ...whose superclass is a Constraint-kinded type family T27627b ...whose superclass is a quantified constraint T27627c a unary class applied to itself, (UC (UC (TC a))) T27627e a (forall b. P b) dictionary that loops (cherry picked from commit 5f474953d1880232b5e6c5741f08746e28cd25ab) - - - - - 61ec7bf7 by Zubin Duggal at 2026-09-03T17:39:19+05:30 An abstract TyCon may hide a unary class A class declared in an hs-boot file is an AbstractTyCon inside the module loop, and compiling the real declaration may reveal it to be a UnaryClassTyCon. - isTerminatingType returned True for such AbstractTyCons - IfaceToCore set the unary flag to False in the DFunId So we could end up speculating bottom dictionaries because inside a module loop we see an UnaryClassTyCon as an AbstractTyCon Use isTerminatingTyCon, which returns False for an abstract TyCon. The Bool in DFunId is now a cache for isTerminatingTyCon, set in mkDFunIdDetails. Fixes #27704 (cherry picked from commit cd5c6bcc0a59c7b4dc4627fdc7471dc7938d07c2) - - - - - 16e71969 by Zubin Duggal at 2026-09-03T17:39:19+05:30 Specialise: don't replace dead args with absent fillers specHeader decides an argument is dead by calling isDeadBinder on a binder of the /optimised RHS/, then applies the filler to the /stable unfolding/ template instead. The two may differ, so the argument can be dead in the RHS and not in the template. The specialised function's unfolding then has an absent filler, and any call site that inlines it evaluates the error thunk. Dropping dead args in the specialiser is rarely worth it, to quote Simon, "The later worker/wrapper pass will pick up the dead arg later if it is really dead. Keeps the specialiser simpler." So instead of trying to check if the arg really is dead in the stable unfolding, just drop the logic for dropping dead args in the specialiser altogeher. Fixes #27703 (cherry picked from commit abfc224a27cf499390efc5fe1348301fefebb910) - - - - - b2b95f0e by Zubin Duggal at 2026-09-03T17:39:19+05:30 CorePrep: don't speculate a call across an hs-boot edge We take care not to evaluate things that might be bottom, like a looping dictionary group, but our analysis is defeated by boot files. We only track recursion within a module, so two dictionaries that depend on each other across a module loop each look non-recursive, and we might speculate them. Any recursion we cannot see must cross an hs-boot edge, so refuse to speculate calls that cross one. Fixes #27717 (cherry picked from commit 1557fd1cfb802d2608cb5b138eab664564f57fb7) - - - - - 7f2d6ee4 by Cheng Shao at 2026-09-03T17:39:19+05:30 autoconf/ghc-toolchain: bump llvm upper bound to support llvm 23 This commit bumps llvm upper bound to support llvm 23. (cherry picked from commit 56291fc550ec00784e46ec0c89ee65081090ae9f) - - - - - 2c3add31 by Cheng Shao at 2026-09-03T17:39:19+05:30 rts: fix compilation issues with clang 23 clang 23 has broadened `-Wall`/`-Wextra` ranges, exposing some minor issues in the rts when building with validate flavours: - Unused locals - `#pragma GCC diagnostic pop` mismatch This commit fixes those. (cherry picked from commit 20eb3f415f9e04a003322d1a49d95e0aaf1029f2) - - - - - 289 changed files: - + changelog.d/27532 - + changelog.d/27626 - + changelog.d/27627 - + changelog.d/27703 - + changelog.d/27704 - + changelog.d/27717 - + changelog.d/T26423 - + changelog.d/T26716 - changelog.d/T27202 - + changelog.d/T27308 - + changelog.d/T27440 - + changelog.d/T27455 - + changelog.d/T27583 - + changelog.d/T27586 - + changelog.d/T27639 - + changelog.d/T27705 - + changelog.d/arm_ncg_fixes_T27430 - + changelog.d/link-deterministic-order - + changelog.d/llvm-22 - + changelog.d/llvm-23 - + changelog.d/unit-index - compiler/GHC.hs - compiler/GHC/Cmm/Expr.hs - compiler/GHC/Cmm/Lint.hs - compiler/GHC/Cmm/MachOp.hs - compiler/GHC/Cmm/Parser.y - compiler/GHC/CmmToAsm/AArch64/CodeGen.hs - compiler/GHC/CmmToAsm/AArch64/Instr.hs - compiler/GHC/CmmToAsm/AArch64/Ppr.hs - compiler/GHC/Core.hs - compiler/GHC/Core/Opt/Specialise.hs - compiler/GHC/Core/Opt/WorkWrap/Utils.hs - compiler/GHC/Core/TyCon.hs - compiler/GHC/Core/Type.hs - compiler/GHC/Core/Utils.hs - compiler/GHC/CoreToStg/Prep.hs - compiler/GHC/Driver/Backpack.hs - compiler/GHC/Driver/Env.hs - compiler/GHC/Driver/Main.hs - compiler/GHC/Driver/Pipeline.hs - compiler/GHC/Driver/Session/Units.hs - compiler/GHC/Iface/Load.hs - compiler/GHC/Iface/Recomp.hs - compiler/GHC/IfaceToCore.hs - compiler/GHC/Tc/Gen/Pat.hs - compiler/GHC/Tc/TyCl/PatSyn.hs - compiler/GHC/Tc/Utils/Unify.hs - compiler/GHC/Types/Demand.hs - compiler/GHC/Types/Id/Info.hs - compiler/GHC/Types/Id/Make.hs - compiler/GHC/Types/Literal.hs - compiler/GHC/Types/Unique.hs - compiler/GHC/Types/Unique/DFM.hs - compiler/GHC/Unit.hs - compiler/GHC/Unit/Env.hs - + compiler/GHC/Unit/External/Database.hs - + compiler/GHC/Unit/External/Index.hs - + compiler/GHC/Unit/External/ModuleOrigin.hs - + compiler/GHC/Unit/External/Providers.hs - + compiler/GHC/Unit/External/Query.hs - + compiler/GHC/Unit/External/Substitution.hs - + compiler/GHC/Unit/External/Validate.hs - + compiler/GHC/Unit/External/Visibility.hs - + compiler/GHC/Unit/External/Wired.hs - compiler/GHC/Unit/Home/Graph.hs - compiler/GHC/Unit/Info.hs - compiler/GHC/Unit/State.hs - compiler/GHC/Unit/State.hs-boot - compiler/GHC/Unit/Types.hs - compiler/ghc.cabal.in - configure.ac - docs/index.html.in - docs/users_guide/eventlog-formats.rst - docs/users_guide/ghc_config.py.in - ghc/GHCi/UI.hs - hadrian/src/Rules/Generate.hs - libraries/Cabal - libraries/base/changelog.md - libraries/ghc-heap/GHC/Exts/Heap/FFIClosures_ProfilingDisabled.hsc - libraries/ghc-heap/GHC/Exts/Heap/FFIClosures_ProfilingEnabled.hsc - libraries/ghc-internal/src/GHC/Internal/Conc/Sync.hs - libraries/ghc-internal/src/GHC/Internal/Exception/Type.hs - rts/CloneStack.c - rts/IOManager.c - rts/IOManager.h - rts/Interpreter.c - rts/Messages.c - rts/PrimOps.cmm - rts/ProfHeap.c - rts/Profiling.c - rts/RaiseAsync.c - rts/RaiseAsync.h - rts/STM.c - rts/Schedule.c - rts/StgMiscClosures.cmm - rts/Threads.c - rts/Threads.h - rts/Trace.c - rts/Trace.h - rts/TraverseHeap.c - rts/eventlog/EventLog.c - rts/eventlog/EventLog.h - rts/include/Cmm.h - rts/include/rts/Constants.h - rts/include/rts/EventLogFormat.h - rts/include/rts/storage/Closures.h - rts/include/rts/storage/TSO.h - rts/include/stg/MiscClosures.h - rts/posix/Poll.c - rts/posix/Select.c - rts/posix/Timeout.c - rts/prim/atomic.c - rts/sm/Compact.c - rts/sm/NonMovingMark.c - rts/sm/Sanity.c - rts/sm/Scav.c - rts/win32/AsyncMIO.c - testsuite/tests/cabal/cabal06/Makefile - testsuite/tests/cabal/pkg_bytecode.stderr - testsuite/tests/cabal/pkg_bytecode_foreign.stderr - testsuite/tests/cabal/pkg_bytecode_with_gbc.stderr - testsuite/tests/cabal/pkg_bytecode_with_o.stderr - + testsuite/tests/codeGen/should_run/T27430.hs - + testsuite/tests/codeGen/should_run/T27430.stdout - + testsuite/tests/codeGen/should_run/T27430_c.c - + testsuite/tests/codeGen/should_run/T27533.hs - + testsuite/tests/codeGen/should_run/T27533.stdout - + testsuite/tests/codeGen/should_run/T27533_cmm.cmm - + testsuite/tests/codeGen/should_run/T27537.hs - + testsuite/tests/codeGen/should_run/T27537.stdout - + testsuite/tests/codeGen/should_run/T27538.hs - + testsuite/tests/codeGen/should_run/T27538.stdout - testsuite/tests/codeGen/should_run/all.T - + testsuite/tests/core-to-stg/T27627/Callee.hs - + testsuite/tests/core-to-stg/T27627/Caller.hs - + testsuite/tests/core-to-stg/T27627/Main.hs - + testsuite/tests/core-to-stg/T27627/T27627.stdout - + testsuite/tests/core-to-stg/T27627/all.T - + testsuite/tests/core-to-stg/T27627a/Callee.hs - + testsuite/tests/core-to-stg/T27627a/Caller.hs - + testsuite/tests/core-to-stg/T27627a/Main.hs - + testsuite/tests/core-to-stg/T27627a/T27627a.stdout - + testsuite/tests/core-to-stg/T27627a/all.T - + testsuite/tests/core-to-stg/T27627b/Callee.hs - + testsuite/tests/core-to-stg/T27627b/Caller.hs - + testsuite/tests/core-to-stg/T27627b/Main.hs - + testsuite/tests/core-to-stg/T27627b/T27627b.stdout - + testsuite/tests/core-to-stg/T27627b/all.T - + testsuite/tests/core-to-stg/T27627c/Callee.hs - + testsuite/tests/core-to-stg/T27627c/Caller.hs - + testsuite/tests/core-to-stg/T27627c/Main.hs - + testsuite/tests/core-to-stg/T27627c/T27627c.stdout - + testsuite/tests/core-to-stg/T27627c/all.T - + testsuite/tests/core-to-stg/T27627e.hs - + testsuite/tests/core-to-stg/T27627e.stdout - + testsuite/tests/core-to-stg/T27627f/Callee.hs - + testsuite/tests/core-to-stg/T27627f/Caller.hs - + testsuite/tests/core-to-stg/T27627f/Inst.hs - + testsuite/tests/core-to-stg/T27627f/Main.hs - + testsuite/tests/core-to-stg/T27627f/T27627f.stdout - + testsuite/tests/core-to-stg/T27627f/all.T - + testsuite/tests/core-to-stg/T27704/Callee.hs - + testsuite/tests/core-to-stg/T27704/Callee.hs-boot - + testsuite/tests/core-to-stg/T27704/Main.hs - + testsuite/tests/core-to-stg/T27704/Mid.hs - + testsuite/tests/core-to-stg/T27704/T27704.stdout - + testsuite/tests/core-to-stg/T27704/all.T - + testsuite/tests/core-to-stg/T27704a/Callee.hs - + testsuite/tests/core-to-stg/T27704a/Callee.hs-boot - + testsuite/tests/core-to-stg/T27704a/Main.hs - + testsuite/tests/core-to-stg/T27704a/Mid.hs - + testsuite/tests/core-to-stg/T27704a/T27704a.stdout - 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+ testsuite/tests/driver/T26423/test/test.pkg - testsuite/tests/driver/T4437.hs - testsuite/tests/driver/T4437.stdout - + testsuite/tests/driver/TUnitInfo/Foo.hs - + testsuite/tests/driver/TUnitInfo/Makefile - + testsuite/tests/driver/TUnitInfo/all.T - + testsuite/tests/driver/TUnitInfo/genMhu.sh - + testsuite/tests/driver/TUnitInfo/generic-unit-info-space-mhu.stdout - + testsuite/tests/driver/TUnitInfo/generic-unit-info-space-single.stdout - + testsuite/tests/driver/TUnitInfo/generic-unit-info-space.hs - + testsuite/tests/driver/TUnitInfo/generic-unit-info-space.stdout - testsuite/tests/ghc-e/should_fail/T18441fail7.stderr - testsuite/tests/ghc-e/should_run/ghc-e005.stderr - testsuite/tests/ghci/T16793/T16793.stdout - testsuite/tests/ghci/T18060/T18060.stdout - + testsuite/tests/ghci/T27532/Makefile - + testsuite/tests/ghci/T27532/T27532.stdout - + testsuite/tests/ghci/T27532/T27532j4.stdout - + testsuite/tests/ghci/T27532/a.script - + testsuite/tests/ghci/T27532/all.T - + testsuite/tests/ghci/T27532/b.script - + testsuite/tests/ghci/T27532/genT27532Modules - + testsuite/tests/ghci/prog-mhu007/Makefile - + testsuite/tests/ghci/prog-mhu007/a/A.hs - + testsuite/tests/ghci/prog-mhu007/all.T - + testsuite/tests/ghci/prog-mhu007/b/B.hs - + testsuite/tests/ghci/prog-mhu007/prog-mhu007.script - + testsuite/tests/ghci/prog-mhu007/prog-mhu007.stdout - + testsuite/tests/ghci/prog-mhu007/testpkg-bar/Bar.hs - + testsuite/tests/ghci/prog-mhu007/testpkg-bar/testpkg-bar.pkg - + testsuite/tests/ghci/prog-mhu007/testpkg-foo/Foo.hs - + testsuite/tests/ghci/prog-mhu007/testpkg-foo/testpkg-foo.pkg - + testsuite/tests/ghci/prog-mhu007/unitA - + testsuite/tests/ghci/prog-mhu007/unitB - testsuite/tests/ghci/scripts/ListTuplePunsPpr.stdout - testsuite/tests/ghci/scripts/T4175.stdout - testsuite/tests/ghci/scripts/T8469.stdout - testsuite/tests/ghci/scripts/T8535.stdout - testsuite/tests/ghci/scripts/T9881.stdout - testsuite/tests/ghci/scripts/ghci020.stdout - testsuite/tests/ghci/scripts/ghci064.stdout - testsuite/tests/ghci/should_run/T10145.stdout - testsuite/tests/ghci/should_run/T18594.stdout - testsuite/tests/partial-sigs/should_compile/ExtraConstraints3.stderr - + testsuite/tests/patsyn/should_compile/T27440a.hs - + testsuite/tests/patsyn/should_compile/T27440b.hs - + testsuite/tests/patsyn/should_compile/T27440c.hs - testsuite/tests/patsyn/should_compile/all.T - + testsuite/tests/patsyn/should_fail/T27440d.hs - + testsuite/tests/patsyn/should_fail/T27440d.stderr - testsuite/tests/patsyn/should_fail/all.T - + testsuite/tests/rep-poly/T27639.hs - testsuite/tests/rep-poly/all.T - testsuite/tests/roles/should_compile/Roles14.stderr - testsuite/tests/roles/should_compile/Roles3.stderr - testsuite/tests/roles/should_compile/Roles4.stderr - testsuite/tests/roles/should_compile/T8958.stderr - + testsuite/tests/simd/should_run/T27565.hs - + testsuite/tests/simd/should_run/T27565.stdout - testsuite/tests/simd/should_run/all.T - testsuite/tests/simplCore/should_compile/T17966.stderr - testsuite/tests/simplCore/should_compile/T7785.stderr - testsuite/tests/simplCore/should_compile/spec004.hs - testsuite/tests/simplCore/should_compile/spec004.stderr - + testsuite/tests/simplCore/should_run/T27703/Lib.hs - + testsuite/tests/simplCore/should_run/T27703/Main.hs - + testsuite/tests/simplCore/should_run/T27703/T27703.stdout - + testsuite/tests/simplCore/should_run/T27703/all.T - + testsuite/tests/simplCore/should_run/T27705.hs - + testsuite/tests/simplCore/should_run/T27705.stdout - + testsuite/tests/simplCore/should_run/T27705_Inst.hs - testsuite/tests/simplCore/should_run/all.T - testsuite/tests/typecheck/should_compile/T18406b.stderr - testsuite/tests/typecheck/should_compile/T18529.stderr - testsuite/tests/typecheck/should_fail/T5300.stderr - + testsuite/tests/vdq-rta/should_compile/T27583a.hs - + testsuite/tests/vdq-rta/should_compile/T27583b.hs - + testsuite/tests/vdq-rta/should_compile/T27583c.hs - + testsuite/tests/vdq-rta/should_compile/T27583d.hs - + testsuite/tests/vdq-rta/should_compile/T27583e.hs - + testsuite/tests/vdq-rta/should_compile/T27583g.hs - testsuite/tests/vdq-rta/should_compile/all.T - + testsuite/tests/vdq-rta/should_fail/T27440e.hs - + testsuite/tests/vdq-rta/should_fail/T27440e.stderr - + testsuite/tests/vdq-rta/should_fail/T27583f.hs - + testsuite/tests/vdq-rta/should_fail/T27583f.stderr - + testsuite/tests/vdq-rta/should_fail/T27586a.hs - + testsuite/tests/vdq-rta/should_fail/T27586a.stderr - + testsuite/tests/vdq-rta/should_fail/T27586b.hs - + testsuite/tests/vdq-rta/should_fail/T27586b.stderr - + testsuite/tests/vdq-rta/should_fail/T27586c.hs - + testsuite/tests/vdq-rta/should_fail/T27586c.stderr - testsuite/tests/vdq-rta/should_fail/all.T - utils/haddock/haddock-api/src/Haddock.hs - utils/haddock/haddock-test/src/Test/Haddock/Config.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/2a27443fade797e9b5db4163f43db5… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/2a27443fade797e9b5db4163f43db5… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/jeltsch/ghc-9-14-building-base] Switch to using a `Setup.hs` file
by Wolfgang Jeltsch (＠jeltsch) 03 Sep '26

03 Sep '26

Wolfgang Jeltsch pushed to branch wip/jeltsch/ghc-9-14-building-base at Glasgow Haskell Compiler / GHC Commits: 1440bf4c by Wolfgang Jeltsch at 2026-09-03T15:11:06+03:00 Switch to using a `Setup.hs` file - - - - - 1 changed file: - .gitlab/base-ci.sh Changes: ===================================== .gitlab/base-ci.sh ===================================== @@ -7,6 +7,10 @@ # # Currently, this script can only test that the in-tree `base` can be *built* # with certain *released* GHCs. +# +# This script can run on both Unix and Windows. Since GHC’s infrastructure does +# not offer Cabal pre-installed on Windows, this script uses a `Setup.hs` file +# to build `base`, which works across operating systems. # Establish error propagation set -e -o pipefail @@ -22,25 +26,30 @@ platform=$1 shift ghc_versions=$* +# Save project root +project_root=$PWD + # Create directories for other GHCs mkdir other-ghcs mkdir other-ghcs/src mkdir other-ghcs/opt -# Save project root -project_root=$PWD - -# Create Cabal file for `base` +# Amend the `base` sources cd libraries/base sed -E -e 's/^( *ghc-internal)[^[:alnum:]-].*(,|$)/\1\2/' \ < base.cabal.in \ > base.cabal +cat <<. >Setup.hs +import Distribution.Simple +main = defaultMain +. cd ${project_root} # Build `base` with the different GHCs for ghc_version in ${ghc_versions} do # Install the GHC + ghc_installation=${project_root}/other-ghcs/opt/${ghc_version} cd other-ghcs/src archive_file=ghc-${ghc_version}-${platform}.tar.xz curl https://downloads.haskell.org/~ghc/${ghc_version}/${archive_file} \ @@ -49,18 +58,18 @@ do if [ -f ghc-${ghc_version}-*/configure ] then # Unix cd ghc-${ghc_version}-* - ./configure --prefix "${project_root}/other-ghcs/opt/${ghc_version}" + ./configure --prefix "${ghc_installation}" make install else # Windows - mv ghc-${ghc_version}-* "${project_root}/other-ghcs/opt/${ghc_version}" + mv ghc-${ghc_version}-* "${ghc_installation}" fi cd ${project_root} # Build `base` with the installed GHC cd libraries/base - cabal build \ - --with-compiler "${project_root}/other-ghcs/opt/${ghc_version}/bin/ghc" \ - --allow-boot-library-installs \ + "${ghc_installation}/bin/runghc" Setup.hs configure \ + --with-compiler "${ghc_installation}/bin/ghc" \ -O0 + "${ghc_installation}/bin/runghc" Setup.hs build cd ${project_root} done View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/1440bf4cb944edb80ebc32a8135e090… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/1440bf4cb944edb80ebc32a8135e090… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/dcoutts/printf-warnings] FIXUP: _yet more_ format fixes, found in CI
by Duncan Coutts (＠dcoutts) 03 Sep '26

03 Sep '26

Duncan Coutts pushed to branch wip/dcoutts/printf-warnings at Glasgow Haskell Compiler / GHC Commits: 2cb7c0a9 by Duncan Coutts at 2026-09-03T11:51:35+01:00 FIXUP: _yet more_ format fixes, found in CI - - - - - 3 changed files: - rts/Schedule.c - rts/Sparks.c - rts/posix/Poll.c Changes: ===================================== rts/Schedule.c ===================================== @@ -1157,8 +1157,9 @@ scheduleHandleHeapOverflow( Capability *cap, StgTSO *t ) #if defined(DEBUG) debugTrace(DEBUG_sched, - "--<< thread %ld (%s) stopped: requesting a large block (size %ld)\n", - (long)t->id, what_next_strs[t->what_next], blocks); + "--<< thread %" FMT_StgThreadID " (%s) stopped: " + "requesting a large block (size %" FMT_Word ")\n", + t->id, what_next_strs[t->what_next], blocks); #endif // don't do this if the nursery is (nearly) full, we'll GC first. ===================================== rts/Sparks.c ===================================== @@ -140,7 +140,8 @@ pruneSparkQueue (bool nonmovingMarkFinished, Capability *cap) pool->top &= pool->moduloSize; debugTrace(DEBUG_sparks, - "markSparkQueue: current spark queue len=%ld; (hd=%ld; tl=%ld)", + "markSparkQueue: current spark queue len=%ld; " + "(hd=%" FMT_Int "; tl=%" FMT_Int ")", sparkPoolSize(pool), pool->bottom, pool->top); ASSERT_WSDEQUE_INVARIANTS(pool); @@ -288,7 +289,7 @@ pruneSparkQueue (bool nonmovingMarkFinished, Capability *cap) debugTrace(DEBUG_sparks, "pruned %d sparks", pruned_sparks); debugTrace(DEBUG_sparks, - "new spark queue len=%ld; (hd=%ld; tl=%ld)", + "new spark queue len=%ld; (hd=%" FMT_Int "; tl=%" FMT_Int ")", sparkPoolSize(pool), pool->bottom, pool->top); ASSERT_WSDEQUE_INVARIANTS(pool); @@ -322,7 +323,8 @@ traverseSparkQueue (evac_fn evac, void *user, Capability *cap) } debugTrace(DEBUG_sparks, - "traversed spark queue, len=%ld; (hd=%ld; tl=%ld)", + "traversed spark queue, len=%ld; " + "(hd=%" FMT_Int "; tl=%" FMT_Int ")", sparkPoolSize(pool), pool->bottom, pool->top); } ===================================== rts/posix/Poll.c ===================================== @@ -512,10 +512,11 @@ bool awaitCompletedTimeoutsOrIOPoll(CapIOManager *iomgr) int res = ppoll(poll_table, nfds, timeout_ns, NULL); debugTrace(DEBUG_iomanager, - "ppoll(nfds = %lu, timeout.sec = %lu, timeout.nsec = %lu) = %d", + "ppoll(nfds = %lu, timeout.sec = %lld, timeout.nsec = %lld)" + " = %d", (unsigned long) nfds, - timeout_ns == NULL ? -1 : timeout_ns->tv_sec, - timeout_ns == NULL ? 0 : timeout_ns->tv_nsec, + (long long) timeout_ns == NULL ? -1 : timeout_ns->tv_sec, + (long long) timeout_ns == NULL ? 0 : timeout_ns->tv_nsec, res); #else int res = poll(poll_table, nfds, timeout_ms); View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/2cb7c0a9f718ad3518cb9ca58a5a45b… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/2cb7c0a9f718ad3518cb9ca58a5a45b… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/T27731] Simplify the error-suppression mechanism in GHC.Tc.Errors
by Simon Peyton Jones (＠simonpj) 03 Sep '26

03 Sep '26

Simon Peyton Jones pushed to branch wip/T27731 at Glasgow Haskell Compiler / GHC Commits: be4acc52 by Simon Peyton Jones at 2026-09-03T11:22:18+01:00 Simplify the error-suppression mechanism in GHC.Tc.Errors In GHC.Tc.Errors.reportWanteds we suppress some errors in favour of others. But the mechanism had grown crufty, and #27331 exposed a bug. This MR makes it simpler and more uniform, by doing everything via the `ei_suppress` field of the ErrorItem. Claude then found another closely-related bug (see the review linked on !16564). That bug is immortalised in new test T18851d. I'm still not happy with `ignoreConstraint` but we can worry about that another day; I have not touched it. - - - - - 8 changed files: - + changelog.d/T27731 - compiler/GHC/Tc/Errors.hs - compiler/GHC/Tc/Types/Constraint.hs - testsuite/tests/typecheck/should_fail/FunDepOrigin1b.hs - + testsuite/tests/typecheck/should_fail/T18851d.hs - + testsuite/tests/typecheck/should_fail/T27731.hs - + testsuite/tests/typecheck/should_fail/T27731.stderr - testsuite/tests/typecheck/should_fail/all.T Changes: ===================================== changelog.d/T27731 ===================================== @@ -0,0 +1,11 @@ +section: compiler +synopsis: Fix a compiler crash after typechecking +issues: #27731 +mrs: !16564 +description: { + The type checker was failing to report an error, even though it had found one, + due to over-zealous error suppression. That led to subsequent chaos. This + MR fixes it *and* simplifies the code. + + Claude found a second, closely-related bug, now immortalised as test ``T18851d``. +} ===================================== compiler/GHC/Tc/Errors.hs ===================================== @@ -263,11 +263,11 @@ report_unsolved type_errors expr_holes , cec_type_holes = type_holes , cec_out_of_scope_holes = out_of_scope_holes , cec_suppress = insolubleWC wanted - -- See Note [Suppressing error messages] - -- Suppress low-priority errors if there - -- are insoluble errors anywhere; - -- See #15539 and c.f. setting ic_status - -- in GHC.Tc.Solver.setImplicationStatus + -- See (SLIE1) in + -- Note [cec_suppress: suppressing less-important error messages] + -- Suppress low-priority errors if there are insoluble errors + -- anywhere in the treee. See #15539 and c.f. setting ic_status + -- in GHC.Tc.Solver.setImplicationStatus , cec_warn_redundant = warn_redundant , cec_expand_syns = exp_syns , cec_binds = binds_var } @@ -322,30 +322,123 @@ we just switch off deferred type errors altogether. See #14605. This is done by maybeSwitchOffDefer. It's also useful in one other place: see Note [Wrapping failing kind equalities] in GHC.Tc.Solver. -Note [Suppressing error messages] -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -The cec_suppress flag says "don't report any errors". Instead, just create -evidence bindings (as usual). It's used when more important errors have occurred. - -Specifically (see reportWanteds) - * If there are insoluble Givens, then we are in unreachable code and all bets - are off. So don't report any further errors. - * If there are any insolubles (eg Int~Bool), here or in a nested implication, - then suppress errors from the simple constraints here. Sometimes the - simple-constraint errors are a knock-on effect of the insolubles. - -This suppression behaviour is controlled by the Bool flag in -ReportErrorSpec, as used in reportWanteds. - -But we need to take care: flags can turn errors into warnings, and we -don't want those warnings to suppress subsequent errors (including -suppressing the essential addTcEvBind for them: #15152). So in -tryReporter we use askNoErrs to see if any error messages were -/actually/ produced; if not, we don't switch on suppression. - -A consequence is that warnings never suppress warnings, so turning an -error into a warning may allow subsequent warnings to appear that were -previously suppressed. (e.g. partial-sigs/should_fail/T14584) +Note [cec_suppress: suppressing less-important error messages] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The cec_suppress flag says "don't report any less-important errors". Instead, just create +evidence bindings (as usual). It's used when more important errors have occurred +(or will occur) eleswhere. + +(SLIE0) + * Note that `cec_suppress` does not affect more-important errors, namely the `report1` + group in `reportWanteds` + * But `cec_suppress` /does/ affect the less-important errors, namely the `report2` group. + To see this, look at the plumbing of cec suppress in `reportWanteds` + +(SLIE1) When we begin `reportAllUnsolved` we set `cec_suppress` if there are insoluble + wanteds /anywhere/ in the tree, via `insolubleWC`. That means we'll suppress all + less-important errors in favour of the more important (insolbule) ones + +(SLIE2) But we need to take care: flags can turn errors into warnings, and we + don't want those warnings to suppress subsequent errors (including + suppressing the essential addTcEvBind for them: #15152). So in + tryReporter we use askNoErrs to see if any error messages were + /actually/ produced; if not, we don't switch on suppression. + + A consequence is that warnings never suppress warnings, so turning an + error into a warning may allow subsequent warnings to appear that were + previously suppressed. (e.g. partial-sigs/should_fail/T14584) + +(SLIE3) There is a tricky interaction between + * `cec_suppress` (a global flag) and + * `ei_suppress` (a local, per-error-item flag), + see Note [ei_suppress: suppressing confusing errors] + Suppose cec_suppress is True because of an insoluble constraint arising from a + superclass constraint -- this constraint will have ei_suppress=True. + + + +Note [ei_suppress: suppressing confusing errors] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Certain errors we might encounter are potentially confusing to users. +If there are any other errors to report, at all, we want to suppress these. +We achieve this by setting the `ei_suppress` flag in the `ErrorItem`. + +Which errors should be suppressed? + +(SCE1) Non-empty rewriter sets. See Note [Wanteds rewrite Wanteds: rewriter-sets] + in GHC.Tc.Types.Constraint + +(SCE2) Superclasses of Wanteds. These are generated only in case they trigger functional + dependencies. If such a constraint is unsolved, then its "parent" constraint must + also be unsolved, and is much more informative to the user. Example (#26255): + class (MinVersion <= F era) => Era era where { ... } + f :: forall era. EraFamily era -> IO () + f = ..blah... -- [W] Era era + Here we have simply omitted "Era era =>" from f's type. But we'll end up with + /two/ Wanted constraints: + [W] d1 : Era era + [W] d2 : MinVersion <= F era -- Superclass of d1 + We definitely want to report d1 and not d2! Happily it's easy to filter out those + superclass-Wanteds, becuase their Origin betrays them. + +There are wrinkles + +(SCE3) In rare cases we may suppress /all/ errors. That is catastrophic: GHC proceeds + to desugar and optimise the program, even though it is full of type errors (#22702, + #22793), and/or we fail to bind evidence (#27731). + + If this happens, unless we are sure that an error will be reported some other way + (details in the defn of `tidy_items` in `reportWanteds), we just un-suppress the lot, + which is brutal but safe. It's a rare case. + + How can it happen that there are /all/ errors are suppressed? + * See test T18851 for an example of how it is (just, barely) possible for the + /only/ errors to be superclass-of-Wanted constraints. + * Similarly #27731, which also involves a superclass-of-Wanted: + class (a ~ F b) => Ren a b + If we have a [W] Ren a b, we'll emit the superclass [W] a ~ F b, which will + rewrite the original class constraint to [W] Ren (F b) b. Now we have two + constraints: one has a non-empty rewriter set (SEC1) and one is a superclass of + a Wanted (SEC2). + * Also see Wrinkle (PER2) in Note [Prioritise Wanteds with empty + CoHoleSet] in GHC.Tc.Types.Constraint. + +Historical note. We used to suppress errors arising from the interaction of two + fundep constraints. But nowadays fundep constraints never "escape" into the main + solver and so never show up in error messages. See (SOLVE-FD) in Note [Overview + of functional dependencies in type inference] in GHC.Tc.Solver.FunDeps. So this + wrinkle is now just a historical note. + + Errors which arise from the interaction of two Wanted fun-dep constraints. + Example: + + class C a b | a -> b where + op :: a -> b -> b + + foo _ = op True Nothing + + bar _ = op False [] + + Here, we could infer + foo :: C Bool (Maybe a) => p -> Maybe a + bar :: C Bool [a] => p -> [a] + + (The unused arguments suppress the monomorphism restriction.) The problem + is that these types can't both be correct, as they violate the functional + dependency. Yet reporting an error here is awkward: we must + non-deterministically choose either foo or bar to reject. We thus want + to report this problem only when there is nothing else to report. + See typecheck/should_fail/T13506 for an example of when to suppress + the error. The case above is actually accepted, because foo and bar + are checked separately, and thus the two fundep constraints never + encounter each other. It is test case typecheck/should_compile/FunDepOrigin1. + + This case applies only when both fundeps are *Wanted* fundeps; when + both are givens, the error represents unreachable code. For + a Given/Wanted case, see #9612. + + End of historical note + -} reportImplic :: SolverReportErrCtxt -> Implication -> TcM () @@ -452,16 +545,6 @@ reportBadTelescope ctxt env (ForAllSkol telescope) skols reportBadTelescope _ _ skol_info skols = pprPanic "reportBadTelescope" (ppr skol_info $$ ppr skols) --- | Should we completely ignore this constraint in error reporting? --- It *must* be the case that any constraint for which this returns True --- somehow causes an error to be reported elsewhere. --- See Note [Constraints to ignore]. -ignoreConstraint :: Ct -> Bool -ignoreConstraint ct - = case ctOrigin ct of - AssocFamPatOrigin -> True -- See (CIG1) - _ -> False - -- | Makes an error item from a constraint, calculating whether or not the item -- should be suppressed. See Note [Wanteds rewrite Wanteds: rewriter-sets] -- in GHC.Tc.Types.Constraint. Returns Nothing if we should just ignore @@ -473,56 +556,105 @@ mkErrorItem ct ; return Nothing } -- See Note [Constraints to ignore] | otherwise - = do { let loc = ctLoc ct - flav = ctFlavour ct + = do { let ev = ctEvidence ct + + m_evdest = case ev of + CtGiven {} -> Nothing + CtWanted (WantedCt { ctev_dest = dest }) -> Just dest - -- For this `suppress` stuff see - -- Note [Wanteds rewrite Wanteds: rewriter-sets] in GHC.Tc.Types.Constraint - (suppress, m_evdest) = case ctEvidence ct of - CtGiven {} -> (False, Nothing) - CtWanted (WantedCt { ctev_rewriters = rws, ctev_dest = dest }) - -> (not (isEmptyCoHoleSet rws), Just dest) - ; let m_reason = case ct of + m_reason = case ct of CIrredCan (IrredCt { ir_reason = reason }) -> Just reason _ -> Nothing - insoluble_ct = insolubleCt ct - ; return $ Just $ EI { ei_pred = ctPred ct , ei_evdest = m_evdest - , ei_flavour = flav - , ei_loc = loc + , ei_flavour = ctFlavour ct + , ei_loc = ctLoc ct , ei_m_reason = m_reason - , ei_insoluble = insoluble_ct - , ei_suppress = suppress }} + , ei_insoluble = insolubleCt ct + , ei_suppress = suppressCtError ev }} -- | Actually report this 'ErrorItem'. unsuppressErrorItem :: ErrorItem -> ErrorItem unsuppressErrorItem ei = ei { ei_suppress = False } +-- | Should we completely ignore this constraint in error reporting? +-- It *must* be the case that any constraint for which this returns True +-- somehow causes an error to be reported elsewhere. +-- See Note [Constraints to ignore]. +ignoreConstraint :: Ct -> Bool +ignoreConstraint ct + = case ctOrigin ct of + AssocFamPatOrigin -> True -- See (CIG1) + _ -> False + +suppressCtError :: CtEvidence -> Bool +-- See Note [ei_suppress: suppressing confusing errors] +suppressCtError (CtGiven {}) + = False +suppressCtError (CtWanted (WantedCt { ctev_rewriters = rws, ctev_loc = loc })) + | not (isEmptyCoHoleSet rws) + = True -- See (SCE1) + + | isWantedSuperclassOrigin (ctLocOrigin loc) + = True -- See (SCE2) + + | otherwise + = False + +{- Note [Constraints to ignore] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Some constraints are meant only to aid the solver by unification; a failure +to solve them is not necessarily an error to report to the user. It is critical +that compilation is aborted elsewhere if there are any ignored constraints here; +they will remain unfilled, and might have been used to rewrite another constraint. + +Currently, the constraints to ignore are: + +(CIG1) Constraints generated in order to unify associated type instance parameters + with class parameters. Here are two illustrative examples: + + class C (a :: k) where + type F (b :: k) + + instance C True where + type F a = Int + + instance C Left where + type F (Left :: a -> Either a b) = Bool + + In the first instance, we want to infer that `a` has type Bool. So we emit + a constraint unifying kappa (the guessed type of `a`) with Bool. All is well. + + In the second instance, we process the associated type instance only + after fixing the quantified type variables of the class instance. We thus + have skolems a1 and b1 such that the class instance is for (Left :: a1 -> Either a1 b1). + Unifying a1 and b1 with a and b in the type instance will fail, but harmlessly so. + checkConsistentFamInst checks for this, and will fail if anything has gone + awry. Really the equality constraints emitted are just meant as an aid, not + a requirement. This is test case T13972. + + We detect this case by looking for an origin of AssocFamPatOrigin; constraints + with this origin are dropped entirely during error message reporting. + + If there is any trouble, checkValidFamInst bleats, aborting compilation. + +(Note: Aug 25: this seems a rather tricky corner; + c.f. Note [ei_suppress: suppressing confusing errors]) +-} + ---------------------------------------------------------------- reportWanteds :: SolverReportErrCtxt -> TcLevel -> WantedConstraints -> TcM () reportWanteds ctxt tc_lvl wc@(WC { wc_simple = simples, wc_impl = implics , wc_errors = errs }) - | isEmptyWC wc = traceTc "reportWanteds empty WC" empty + | isEmptyWC wc + = traceTc "reportWanteds empty WC" empty | otherwise = do { tidy_items1 <- mapMaybeM mkErrorItem tidy_cts - ; traceTc "reportWanteds 1" (vcat [ text "Simples =" <+> ppr simples - , text "Suppress =" <+> ppr (cec_suppress ctxt) - , text "tidy_cts =" <+> ppr tidy_cts - , text "tidy_items1 =" <+> ppr tidy_items1 - , text "tidy_errs =" <+> ppr tidy_errs ]) -- Catch an awkward (and probably rare) case in which /all/ errors are - -- suppressed: see Wrinkle (PER2) in Note [Prioritise Wanteds with empty - -- CoHoleSet] in GHC.Tc.Types.Constraint. - -- - -- Unless we are sure that an error will be reported some other way - -- (details in the defn of tidy_items) un-suppress the lot. This makes - -- sure we don't forget to report an error at all, which is - -- catastrophic: GHC proceeds to desguar and optimise the program, even - -- though it is full of type errors (#22702, #22793) + -- suppressed: see (SCE3) in Note [ie_suppress: suppressing confusing errors] ; errs_already <- ifErrsM (return True) (return False) ; let tidy_items | not errs_already -- Have not already reported an error (perhaps @@ -530,43 +662,54 @@ reportWanteds ctxt tc_lvl wc@(WC { wc_simple = simples, wc_impl = implics , not (any ignoreConstraint simples) -- No error is ignorable (is reported elsewhere) , all ei_suppress tidy_items1 -- All errors are suppressed = map unsuppressErrorItem tidy_items1 + | otherwise = tidy_items1 + ; traceTc "reportWanteds 1" (vcat [ text "Simples =" <+> ppr simples + , text "Suppress =" <+> ppr (cec_suppress ctxt) + , text "tidy_cts =" <+> ppr tidy_cts + , text "tidy_items1 =" <+> ppr tidy_items1 + , text "tidy_errs =" <+> ppr tidy_errs ]) + -- First, deal with any out-of-scope errors: ; let (out_of_scope, other_holes, not_conc_errs, mult_co_errs) = partition_errors tidy_errs - -- don't suppress out-of-scope errors + -- Don't suppress out-of-scope errors + -- See (SLIE0) in Note [cec_suppress: suppressing less-important error messages] ctxt_for_scope_errs = ctxt { cec_suppress = False } ; (_, no_out_of_scope) <- askNoErrs $ reportHoles tidy_items ctxt_for_scope_errs out_of_scope -- Next, deal with things that are utterly wrong - -- Like Int ~ Bool (incl nullary TyCons) - -- or Int ~ t a (AppTy on one side) - -- These /ones/ are not suppressed by the incoming context - -- (but will be by out-of-scope errors) + -- These should not be suppressed by the incoming context + -- (but should be suppressed by out-of-scope errors) + -- See (SLIE0) in Note [cec_suppress: suppressing less-important error messages] ; let ctxt_for_insols = ctxt { cec_suppress = not no_out_of_scope } - ; reportHoles tidy_items ctxt_for_insols other_holes - -- holes never suppress + -- Don't suppress holes or concreteness errors unless we have scope errors + ; reportHoles tidy_items ctxt_for_insols other_holes ; reportNotConcreteErrs ctxt_for_insols not_conc_errs -- We only want to report multiplicity coercion errors for multiplicity -- constraints which are /solved/ with a non-reflexivity coercion. We -- over approximate here: we only report multiplicity coercion errors - -- when /all/ constraints are solved. + -- when /all/ other constraints are solved. -- See wrinkle (DME1) in Note [Coercion errors in tcSubMult] in GHC.Tc.Utils.Unify. - ; when (null simples) $ reportMultiplicityCoercionErrs ctxt_for_insols mult_co_errs + ; when (null simples) $ + reportMultiplicityCoercionErrs ctxt_for_insols mult_co_errs - -- See Note [Suppressing confusing errors] - ; let (suppressed_items, reportable_items) = partition suppressItem tidy_items - ; traceTc "reportWanteds suppressed:" (ppr suppressed_items) - ; (ctxt1, items1) <- tryReporters ctxt_for_insols report1 reportable_items + -- Now the main batch of utterly-wrong things + -- Like Int ~ Bool (incl nullary TyCons) + -- or Int ~ t a (AppTy on one side) + ; (ctxt1, items1) <- tryReporters ctxt_for_insols report1 tidy_items -- Now all the other constraints. We suppress errors here if - -- any of the first batch failed, or if the enclosing context - -- says to suppress - ; let ctxt2 = ctxt1 { cec_suppress = cec_suppress ctxt || cec_suppress ctxt1 } + -- any of the first batch failed (ctxt1), or if the enclosing context + -- says to suppress AND there are no local insolubles + -- Why the AND part? In case all those local insolubles are suppressed. + -- See (SLIE3) in Note [cec_suppress: suppressing less-important error messages] + ; let ctxt2 = ctxt1 { cec_suppress = cec_suppress ctxt1 + || (cec_suppress ctxt && not (any ei_insoluble tidy_items)) } ; (_, leftovers) <- tryReporters ctxt2 report2 items1 ; massertPpr (null leftovers) (text "The following unsolved Wanted constraints \ @@ -577,21 +720,10 @@ reportWanteds ctxt tc_lvl wc@(WC { wc_simple = simples, wc_impl = implics -- NB ctxt2: don't suppress inner insolubles if there's only a -- wanted insoluble here; but do suppress inner insolubles -- if there's a *given* insoluble here (= inaccessible code) - - -- If there are no other errors to report, report suppressed errors. - -- See (SCE3) in Note [Suppressing confusing errors]. - -- NB: with -fdefer-type-errors we might have reported warnings only from - -- reportable_items`, but we still want to suppress the `suppressed_items`. - ; when (null reportable_items) $ - do { (_, more_leftovers) <- tryReporters ctxt_for_insols (report1++report2) - suppressed_items - -- ctxt_for_insols: the suppressed errors can be Int~Bool, which - -- will have made the incoming `ctxt` be True; don't make that - -- suppress the Int~Bool error! - ; massertPpr (null more_leftovers) (ppr more_leftovers) } } + } where env = cec_tidy ctxt - tidy_cts = bagToList (mapBag (tidyCt env) simples) + tidy_cts = bagToList (mapBag (tidyCt env) simples) tidy_errs = bagToList (mapBag (tidyDelayedError env) errs) partition_errors :: [DelayedError] -> ([Hole], [Hole], [NotConcreteError], [(TcCoercion, CtLoc)]) @@ -610,8 +742,8 @@ reportWanteds ctxt tc_lvl wc@(WC { wc_simple = simples, wc_impl = implics DE_Multiplicity mult_co loc -> (es1, es2, es3, (mult_co, loc):es4) - -- report1: ones that should *not* be suppressed by - -- an insoluble somewhere else in the tree + -- report1: ones that should *not* be suppressed by cec_suppress, + -- (i.e. by an insoluble somewhere else in the tree) -- It's crucial that anything that is considered insoluble -- (see GHC.Tc.Utils.insolublWantedCt) is caught here, otherwise -- we might suppress its error message, and proceed on past @@ -752,15 +884,6 @@ reportWanteds ctxt tc_lvl wc@(WC { wc_simple = simples, wc_impl = implics = has_gadt_match implics --------------- -suppressItem :: ErrorItem -> Bool - -- See Note [Suppressing confusing errors] -suppressItem item - | Wanted <- ei_flavour item - , let orig = errorItemOrigin item - = isWantedSuperclassOrigin orig -- See (SCE1) - | otherwise - = False - isSkolemTy :: TcLevel -> Type -> Bool -- The type is a skolem tyvar isSkolemTy tc_lvl ty @@ -778,113 +901,8 @@ isTyFun_maybe ty = case tcSplitTyConApp_maybe ty of Just (tc,_) | isTypeFamilyTyCon tc -> Just tc _ -> Nothing -{- Note [Suppressing confusing errors] -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Certain errors we might encounter are potentially confusing to users. -If there are any other errors to report, at all, we want to suppress these. - -Which errors should be suppressed? - -(SCE1) Superclasses of Wanteds. These are generated only in case they trigger functional - dependencies. If such a constraint is unsolved, then its "parent" constraint must - also be unsolved, and is much more informative to the user. Example (#26255): - class (MinVersion <= F era) => Era era where { ... } - f :: forall era. EraFamily era -> IO () - f = ..blah... -- [W] Era era - Here we have simply omitted "Era era =>" from f's type. But we'll end up with - /two/ Wanted constraints: - [W] d1 : Era era - [W] d2 : MinVersion <= F era -- Superclass of d1 - We definitely want to report d1 and not d2! Happily it's easy to filter out those - superclass-Wanteds, becuase their Origin betrays them. - -Historical (SCE2). Fundep constraints never "escape" into the - main solver and so never show up in error messages. - See (SOLVE-FD) in Note [Overview of functional dependencies in type inference] - in GHC.Tc.Solver.FunDeps. So this wrinkle is now just a historical note. - - Errors which arise from the interaction of two Wanted fun-dep constraints. - Example: - - class C a b | a -> b where - op :: a -> b -> b - - foo _ = op True Nothing - - bar _ = op False [] - - Here, we could infer - foo :: C Bool (Maybe a) => p -> Maybe a - bar :: C Bool [a] => p -> [a] - - (The unused arguments suppress the monomorphism restriction.) The problem - is that these types can't both be correct, as they violate the functional - dependency. Yet reporting an error here is awkward: we must - non-deterministically choose either foo or bar to reject. We thus want - to report this problem only when there is nothing else to report. - See typecheck/should_fail/T13506 for an example of when to suppress - the error. The case above is actually accepted, because foo and bar - are checked separately, and thus the two fundep constraints never - encounter each other. It is test case typecheck/should_compile/FunDepOrigin1. - - This case applies only when both fundeps are *Wanted* fundeps; when - both are givens, the error represents unreachable code. For - a Given/Wanted case, see #9612. - - End of historical (SCE2) - -(SCE3) How can it happen that there are /only/ suppressed errors? See test T18851 - for an example of how it is (just, barely) possible for the /only/ errors to - be superclass-of-Wanted constraints. - -Mechanism: - -We use the `suppress` function within reportWanteds to filter out these -"suppress" cases, then report all other errors. After doing so, we return to these -suppressed ones and report them only if there have been no errors so far. - -Note [Constraints to ignore] -~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Some constraints are meant only to aid the solver by unification; a failure -to solve them is not necessarily an error to report to the user. It is critical -that compilation is aborted elsewhere if there are any ignored constraints here; -they will remain unfilled, and might have been used to rewrite another constraint. - -Currently, the constraints to ignore are: - -(CIG1) Constraints generated in order to unify associated type instance parameters - with class parameters. Here are two illustrative examples: - - class C (a :: k) where - type F (b :: k) - - instance C True where - type F a = Int - - instance C Left where - type F (Left :: a -> Either a b) = Bool - - In the first instance, we want to infer that `a` has type Bool. So we emit - a constraint unifying kappa (the guessed type of `a`) with Bool. All is well. - - In the second instance, we process the associated type instance only - after fixing the quantified type variables of the class instance. We thus - have skolems a1 and b1 such that the class instance is for (Left :: a1 -> Either a1 b1). - Unifying a1 and b1 with a and b in the type instance will fail, but harmlessly so. - checkConsistentFamInst checks for this, and will fail if anything has gone - awry. Really the equality constraints emitted are just meant as an aid, not - a requirement. This is test case T13972. - - We detect this case by looking for an origin of AssocFamPatOrigin; constraints - with this origin are dropped entirely during error message reporting. - - If there is any trouble, checkValidFamInst bleats, aborting compilation. - -(Note: Aug 25: this seems a rather tricky corner; - c.f. Note [Suppressing confusing errors]) - -Note [Implementation of Unsatisfiable constraints] -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +{- Note [Implementation of Unsatisfiable constraints] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The Unsatisfiable constraint was introduced in GHC proposal #433 (https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0433-u…) See Note [The Unsatisfiable constraint] in GHC.TypeError. @@ -1317,9 +1335,15 @@ maybeReportError :: SolverReportErrCtxt maybeReportError ctxt items@(item1:|_) (SolverReport { sr_important_msg = important , sr_supplementary = supp , sr_hints = hints }) - | suppress_group = return () - | otherwise = do { msg <- mkErrorReport loc_env diag (Just ctxt) supp hints - ; reportDiagnostic msg } + | suppress_group + = -- Suppress the report entirely + -- But NB we still create the evidence binding; see `reportGroup`. + return () + + | otherwise + = -- Spit out an error or warning + do { msg <- mkErrorReport loc_env diag (Just ctxt) supp hints + ; reportDiagnostic msg } where reason | any (nonDeferrableOrigin . errorItemOrigin) items = ErrorWithoutFlag | otherwise = cec_defer_type_errors ctxt @@ -1328,11 +1352,6 @@ maybeReportError ctxt items@(item1:|_) (SolverReport { sr_important_msg = import loc_env = ctLocEnv (errorItemCtLoc item1) suppress_group - | all ei_suppress items - = True -- If they are all suppressed (notably, have been rewritten by another unsolved wanted) - -- report nothing. (If at least one is not suppressed, do report: the function that - -- generates the error message should look for an unsuppressed error item.) - -- It is tempting to say that we always want to see all insoluble errors -- But then we get a bit more than we want. Examples: -- a ~ t a occurs check errors (T2534, mc25) @@ -1344,6 +1363,12 @@ maybeReportError ctxt items@(item1:|_) (SolverReport { sr_important_msg = import | cec_suppress ctxt = True -- Some earlier error has occurred, so suppress this diagnostic + | all ei_suppress items + = True -- If they are all suppressed (notably, have been rewritten by another unsolved + -- wanted) report nothing. (If at least one is not suppressed, do report: + -- the function that generates the error message should look for an + -- unsuppressed error item.) + | otherwise = False @@ -1402,11 +1427,11 @@ mkErrorTerm ct_loc ty ctxt msg supp hints ; return $ evDelayedError ty err_str } -tryReporters :: SolverReportErrCtxt -> [ReporterSpec] -> [ErrorItem] -> TcM (SolverReportErrCtxt, [ErrorItem]) +tryReporters :: SolverReportErrCtxt -> [ReporterSpec] -> [ErrorItem] + -> TcM (SolverReportErrCtxt, [ErrorItem]) -- Use the first reporter in the list whose predicate says True tryReporters ctxt reporters items - = do { let (vis_items, invis_items) - = partition (isVisibleOrigin . errorItemOrigin) items + = do { let (vis_items, invis_items) = partition (isVisibleOrigin . errorItemOrigin) items ; traceTc "tryReporters {" (ppr vis_items $$ ppr invis_items) ; (ctxt', items') <- go ctxt reporters vis_items invis_items ; traceTc "tryReporters }" (ppr items') @@ -1416,9 +1441,9 @@ tryReporters ctxt reporters items = return (ctxt, vis_items ++ invis_items) go ctxt (r : rs) vis_items invis_items - -- always look at *visible* Origins before invisible ones + -- Always look at *visible* Origins before invisible ones -- this is the whole point of isVisibleOrigin - = do { (ctxt', vis_items') <- tryReporter ctxt r vis_items + = do { (ctxt', vis_items') <- tryReporter ctxt r vis_items ; (ctxt'', invis_items') <- tryReporter ctxt' r invis_items ; go ctxt'' rs vis_items' invis_items' } -- Carry on with the rest, because we must make @@ -1432,7 +1457,7 @@ tryReporter ctxt (str, keep_me, suppress_after, reporter) items = case nonEmpty { traceTc "tryReporter{ " (text str <+> ppr yeses) ; (_, no_errs) <- askNoErrs (reporter ctxt yeses) ; let suppress_now = not no_errs && suppress_after - -- See Note [Suppressing error messages] + -- See (SLIE2) in Note [cec_suppress: suppressing less-important error messages] ctxt' = ctxt { cec_suppress = suppress_now || cec_suppress ctxt } ; traceTc "tryReporter end }" (text str <+> ppr (cec_suppress ctxt) <+> ppr suppress_after) ; return (ctxt', nos) } ===================================== compiler/GHC/Tc/Types/Constraint.hs ===================================== @@ -1214,15 +1214,16 @@ insolubleWantedCt :: Ct -> Bool -- -- See Note [Insoluble Wanteds] insolubleWantedCt ct - | CtWanted (WantedCt { ctev_loc = loc, ctev_rewriters = rewriters }) - <- ctEvidence ct + | CtWanted (WantedCt {}) <- ctEvidence ct -- It's a Wanted , insolubleCt ct -- It's insoluble - , isEmptyCoHoleSet rewriters +-- , isEmptyCoHoleSet rewriters -- It has no rewriters – see (IW1) in Note [Insoluble Wanteds] - , not (isGivenLoc loc) - -- isGivenLoc: see (IW2) in Note [Insoluble Wanteds] + +-- I don't understand IW2 so I'm going to get rid of it +-- , not (isGivenLoc loc) +-- -- isGivenLoc: see (IW2) in Note [Insoluble Wanteds] -- See also historical (IW3) in Note [Insoluble Wanteds] = True ===================================== testsuite/tests/typecheck/should_fail/FunDepOrigin1b.hs ===================================== @@ -8,4 +8,4 @@ class C a b | a -> b where -- foo :: (C Bool (Maybe a), C Bool [b]) => x -> (Maybe a, [b]) foo _ = (op True Nothing, op False []) --- See Note [Suppressing confusing errors] in GHC.Tc.Errors +-- See Note [ei_suppress: suppressing confusing errors] in GHC.Tc.Errors ===================================== testsuite/tests/typecheck/should_fail/T18851d.hs ===================================== @@ -0,0 +1,39 @@ +{-# LANGUAGE FunctionalDependencies, FlexibleInstances, UndecidableInstances, + ScopedTypeVariables, TypeFamilies, TypeApplications, + FlexibleContexts, AllowAmbiguousTypes, ExtendedDefaultRules #-} + +module T18851d where + +default (Int) + +type family C_FD a +class C_FD a ~ b => C a b + +type instance C_FD Int = Bool -- just for Show (C_FD Int) +instance C Int b => C Int b + +class IsInt int +instance int ~ Int => IsInt int + +data A +instance Show A where + show _ = "A" +data B +instance Show B where + show _ = "B" + +data D + +f :: forall a b c int + . ( Show c, Num int + , C int a, C int b, C int c + -- , c ~ C_FD int -- add this to get rid of ambiguity error + ) + => String +f = show (undefined :: c) + +g :: String +g = f @A @B ++ show (undefined :: D) + -- This variant, suggested by Claude in a review of !16564, + -- has an unsolved (Show D) constraint. It must not be suppressed + -- by the insoluble-but-suppressed constraints arising from (C Int a) ===================================== testsuite/tests/typecheck/should_fail/T27731.hs ===================================== @@ -0,0 +1,36 @@ +{-# LANGUAGE ImplicitParams, TypeFamilies #-} + +module Bug where + +type family St (a :: k) :: * +type family Ev (a :: k) :: * -> * + +data T1 a = C1 a +data T2 h g = C2 (h ()) + +class (h ~ Ev g, s ~ St g) => Ren s h g + +f1 :: + (s ~ St h, Ren s h g, ?settings :: settings) + => (g v -> g ()) -> g v -> g () +f1 form = (\_ a -> a) (C1 (f2 {-@g-})) form + +f2 :: forall g h s. ( s ~ St h, Ren s h g) => T2 h g +f2 = error "urk" + +{- Call of f2 + +[W] s ~ St h --> St g ~ St h --> St g ~ St (Ev g) +[W] Ren s h g +[W] s ~ St g -- Superclass of wanted +[W] h ~ Ev g -- Superclass of wanted +-} + +{- +f3 :: + T1 () + -> (g v -> g ()) + -> g v -> g () +f3 wd form = ((\_ a -> a) wd form) + +-} ===================================== testsuite/tests/typecheck/should_fail/T27731.stderr ===================================== @@ -0,0 +1,16 @@ +T27731.hs:16:28: [GHC-05617] + • Could not deduce ‘St (Ev g0) ~ St g0’ + arising from a superclass required to satisfy ‘Ren + (St (Ev g0)) (Ev g0) g0’, + arising from a use of ‘f2’ + from the context: (s ~ St h, Ren s h g, ?settings::settings) + bound by the type signature for: + f1 :: forall s (h :: * -> *) (g :: * -> *) settings v. + (s ~ St h, Ren s h g, ?settings::settings) => + (g v -> g ()) -> g v -> g () + at T27731.hs:(13,1)-(15,33) + Note: ‘St’ is a non-injective type family. + The type variable ‘g0’ is ambiguous + • In the first argument of ‘C1’, namely ‘(f2)’ + In the first argument of ‘\ _ a -> a’, namely ‘(C1 (f2))’ + In the expression: (\ _ a -> a) (C1 (f2)) form ===================================== testsuite/tests/typecheck/should_fail/all.T ===================================== @@ -565,6 +565,7 @@ test('T17563', normal, compile_fail, ['']) test('T18851', normal, compile_fail, ['']) test('T18851b', normal, compile, ['']) test('T18851c', normal, compile, ['']) +test('T18851d', normal, compile, ['']) test('T16946', normal, compile_fail, ['']) test('T16502', expect_broken(12854), compile, ['']) test('T17566b', normal, compile_fail, ['']) @@ -763,3 +764,4 @@ test('T26861', normal, compile_fail, ['']) test('T26862', normal, compile_fail, ['']) test('T27210', normal, compile_fail, ['']) test('T26532', normal, compile_fail, ['']) +test('T27731', normal, compile_fail, ['']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/be4acc52911ebb0dd9c2060e148faba… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/be4acc52911ebb0dd9c2060e148faba… You're receiving this email because of your account on gitlab.haskell.org. 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[Git][ghc/ghc][wip/T27629] Re-introduce the "weird SpecDict" case
by Simon Peyton Jones (＠simonpj) 03 Sep '26

03 Sep '26

Simon Peyton Jones pushed to branch wip/T27629 at Glasgow Haskell Compiler / GHC Commits: eed2f9cc by Simon Peyton Jones at 2026-09-03T11:17:07+01:00 Re-introduce the "weird SpecDict" case In this commit commit f80375dd4945350a1d784e436975b48b9c736eaf Author: Simon Peyton Jones <simon.peytonjones(a)gmail.com> Date: Sun Jun 29 15:26:58 2025 +0100 Refactor of Specialise.hs I removed a test for a dictionary with unbound type variables. This turned out to be wrong; see #27629. So this MR re-introduces it. - - - - - 6 changed files: - compiler/GHC/Core/Opt/Specialise.hs - testsuite/tests/simplCore/should_compile/Makefile - + testsuite/tests/simplCore/should_compile/T27629.hs - + testsuite/tests/simplCore/should_compile/T27629.stderr - + testsuite/tests/simplCore/should_compile/T27629Plugin.hs - testsuite/tests/simplCore/should_compile/all.T Changes: ===================================== compiler/GHC/Core/Opt/Specialise.hs ===================================== @@ -1713,9 +1713,7 @@ specCalls spec_imp env existing_rules calls_for_me fn rhs ; let spec_rhs_bndrs = spec_bndrs ++ inner_rhs_bndrs' (rhs_uds2, inner_dumped_dbs) = dumpUDs spec_rhs_bndrs $ dx_binds `consDictBinds` rhs_uds - -- dx_binds comes from the arguments to the call, - -- and so can mention poly_qvars but no other local binders - spec_rhs = mkLams spec_rhs_bndrs $ + spec_rhs = mkLams spec_rhs_bndrs $ wrapDictBindsE inner_dumped_dbs rhs_body' rule_rhs_args = spec_bndrs @@ -1784,8 +1782,7 @@ specCalls spec_imp env existing_rules calls_for_me fn rhs , text "rule_act" <+> ppr rule_act ] --- ; pprTrace "spec_call: rule" (vcat [ -- text "poly_qvars" <+> ppr poly_qvars --- text "rule_bndrs" <+> ppr rule_bndrs +-- ; pprTrace "spec_call: rule" (vcat [ text "rule_bndrs" <+> ppr rule_bndrs -- , text "rule_lhs_args" <+> ppr rule_lhs_args -- , text "all_call_args" <+> ppr all_call_args -- , ppr spec_rule ]) $ @@ -2611,6 +2608,14 @@ specHeader subst (bndr:bndrs) (UnspecType : args) -- a wildcard binder to match the dictionary (See Note [Specialising Calls] for -- the nitty-gritty), as a LHS rule and unfolding details. specHeader subst (bndr:bndrs) (SpecDict dict_arg : args) + | let in_scope = getInScopeVars (substInScopeSet subst) + bad_dict_fv v = isLocalVar v && not (v `elemVarSet` in_scope) + , not $ isEmptyVarSet $ exprSomeFreeVars bad_dict_fv dict_arg + = -- Do not specialise if `dict_arg` has any any free vars that are /not/ in scope + -- See Note [Weird special case for SpecDict] + specHeader mod subst (bndr:bndrs) (UnspecArg : args) + + | otherwise = do { -- Make up a fresh binder to use in the RULE -- It might turn into a dict binding (via bindAuxiliaryDict) which we -- then float, so we use cloneIdBndr to get a completely fresh binder @@ -2886,13 +2891,15 @@ We could zap `k` to (Any @Type) and `a` to (Any @(Any @Type)), but that is a lot of hard work for a very strange case. So we simply refrain from specialising in this case; hence the guard - allVarSet (`elemInScopeSet` in_scope) (exprFreeVars d) -in the SpecDict cased of specHeader. - -How did this strange polymorphic mkD arise in the first place? -From GHC.Core.Opt.Utils.abstractFloats, which was abstracting -over too many type variables. But that too is now fixed; -see Note [Which type variables to abstract over] in that module. + not $ isEmptyVarSet $ exprSomeFreeVars bad_dict_fv dict_arg +in the SpecDict case of `specHeader`. + +How did this strange polymorphic mkD arise in the first place? From +GHC.Core.Opt.Utils.abstractFloats, which was abstracting over too many type +variables. But that too is now fixed; see Note [Which type variables to abstract +over] in that module. So we don't actually have a Haskell source program that +triggers it (see #27629) -- only test T27629 that uses a plugin to inject a strange +definition. -} instance Outputable DictBind where ===================================== testsuite/tests/simplCore/should_compile/Makefile ===================================== @@ -3,6 +3,12 @@ include $(TOP)/mk/boilerplate.mk include $(TOP)/mk/test.mk +# T27629 runs a plugin that injects a Core binding +# that made the specialiser crash +T27629: + '$(TEST_HC)' $(TEST_HC_OPTS) --make -package ghc -dynamic-too -c T27629Plugin.hs + '$(TEST_HC)' $(TEST_HC_OPTS) -c -O -fpolymorphic-specialisation -dcore-lint T27629.hs + # T18815 should not have a non-recursive join-point for 'go' # Previously we ended up with # join {go_sPI w_sQ3 = case w_sQ3 of { GHC.Types.I# ww1_sQ6 -> ===================================== testsuite/tests/simplCore/should_compile/T27629.hs ===================================== @@ -0,0 +1,29 @@ +{-# LANGUAGE AllowAmbiguousTypes #-} +{-# OPTIONS_GHC -fplugin=T27629Plugin #-} + +-- The plugin rewrites 'poly' to the example of +-- Note [Weird special case for SpecDict]: +-- +-- poly = /\x. \t. split @T (mkD @x MkT) [t] +-- +-- where mkD :: forall a. T -> C T is a new top-level binding +-- (mkD = /\a. \_. $fCT), so the tyvar x is free in the dictionary +-- *expression* but not in its *type* (C T). +module T27629 (poly, split, T (..), C (..)) where + +import Data.Kind (Type) + +data T = MkT + +class C b where + meth :: b -> b + +instance C T where + meth x = x + +split :: C b => [b] -> [b] +split [] = [] +split (x : xs) = meth x : split xs + +poly :: forall (x :: Type). T -> [T] +poly t = [t] ===================================== testsuite/tests/simplCore/should_compile/T27629.stderr ===================================== @@ -0,0 +1 @@ +ReproPlugin: injected weird SpecDict call into poly ===================================== testsuite/tests/simplCore/should_compile/T27629Plugin.hs ===================================== @@ -0,0 +1,94 @@ +-- Injects the example of Note [Weird special case for SpecDict] in +-- GHC.Core.Opt.Specialise, which cannot be written in source Haskell: +-- a call whose dictionary argument mentions a type variable that is +-- free in the dictionary expression but not in its type. +-- +-- Runs before the main Core pipeline (in particular before the +-- Specialiser). It adds +-- +-- mkD :: forall a. T -> C T {-# NOINLINE mkD #-} +-- mkD = /\a. \_. $fCT +-- +-- and rewrites poly = /\x. \t. [t] +-- to poly = /\x. \t. split @T (mkD @x MkT) [t] +{-# LANGUAGE CPP #-} +module T27629Plugin (plugin) where + +import GHC.Core.Make (mkCoreApps, mkListExpr) +import GHC.Core.Predicate (getClassPredTys_maybe) +import GHC.Plugins +#if __GLASGOW_HASKELL__ >= 1000 +import GHC.Types.InlinePragma (neverInlinePragma) +#else +import GHC.Types.Basic (neverInlinePragma) +#endif + +plugin :: Plugin +plugin = + defaultPlugin + { installCoreToDos = \_ todos -> + return (CoreDoPluginPass "inject-weird-specdict" pass : todos) + , pluginRecompile = purePlugin + } + +pass :: ModGuts -> CoreM ModGuts +pass guts = do + let binds = mg_binds guts + + dfun = case [b | b <- bindersOfBinds binds, isDFunId b] of + (b : _) -> b + [] -> panic "ReproPlugin: no dfun binding in module" + + dictTy = idType dfun -- C T + tyT = case getClassPredTys_maybe dictTy of + Just (_cls, [t]) -> t + _ -> panic "ReproPlugin: dfun type is not C T" + + mkTCon = case tyConDataCons (tyConAppTyCon tyT) of + (dc : _) -> dataConWorkId dc + [] -> panic "ReproPlugin: T has no data constructors" + + findTopId nm = + case [b | b <- bindersOfBinds binds, occNameString (getOccName b) == nm] of + (b : _) -> b + [] -> panic ("ReproPlugin: no top-level binding " ++ nm) + + splitId = findTopId "split" + polyId = findTopId "poly" + + uMkD <- getUniqueM + uTv <- getUniqueM + uWild <- getUniqueM + + let aTv = mkTyVar (mkSystemName uTv (mkTyVarOcc "a")) liftedTypeKind + mkDTy = mkSpecForAllTys [aTv] (mkFunctionType ManyTy tyT dictTy) + mkDId = + setInlinePragma + (mkExportedVanillaId (mkSystemName uMkD (mkVarOcc "mkD")) mkDTy) + neverInlinePragma + wild = mkSysLocal (fsLit "eta") uWild ManyTy tyT + mkDBind = NonRec mkDId (mkLams [aTv, wild] (Var dfun)) + + rewritePoly rhs + | (bndrs, _body) <- collectBinders rhs + , (x : _) <- reverse (filter isTyVar bndrs) + , (t : _) <- filter isId bndrs + = mkLams bndrs $ + mkCoreApps + (Var splitId) + [ Type tyT + , mkCoreApps (Var mkDId) [Type (mkTyVarTy x), Var mkTCon] + , mkListExpr tyT [Var t] + ] + | otherwise = + pprPanic "ReproPlugin: unexpected shape of poly" (ppr rhs) + + go (b, rhs) + | b == polyId = (b, rewritePoly rhs) + | otherwise = (b, rhs) + + -- One top-level Rec, so bind order is irrelevant. + binds' = [Rec (map go (flattenBinds binds) ++ flattenBinds [mkDBind])] + + putMsgS "ReproPlugin: injected weird SpecDict call into poly" + return guts {mg_binds = binds'} ===================================== testsuite/tests/simplCore/should_compile/all.T ===================================== @@ -611,3 +611,4 @@ test('T27296', [], makefile_test, ['T27296']) test('T27296b', [], makefile_test, ['T27296b']) test('T27589', [grep_errmsg(r'wombat')], compile, ['-O -ddump-simpl -dno-typeable-binds -dsuppress-uniques']) test('T27590', [grep_errmsg(r'wombat')], compile, ['-O -ddump-simpl -dno-typeable-binds -dsuppress-uniques']) +test('T27629', only_ways(['optasm']), makefile_test, ['T27629']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/eed2f9cccb80bddaa047bab6f754b49… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/eed2f9cccb80bddaa047bab6f754b49… You're receiving this email because of your account on gitlab.haskell.org. 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[Git][ghc/ghc][wip/9.14.2-rc2] 34 commits: base: Don't drop exception context in SomeException(toException)
by Zubin (＠wz1000) 03 Sep '26

03 Sep '26

Zubin pushed to branch wip/9.14.2-rc2 at Glasgow Haskell Compiler / GHC Commits: 08cc4abd by Ben Gamari at 2026-09-03T12:23:52+05:30 base: Don't drop exception context in SomeException(toException) For reasons that are lost to time, the implementation of [CLC #200] that was merged inappropriately dropped `ExceptionContext` in the `toException` implementation given to `SomeException`. Fix this infelicity. [CLC #200]: https://github.com/haskell/core-libraries-committee/issues/200 (cherry picked from commit 2ab02c579a9625438f5281a258051cb32ba40004) - - - - - c37cb584 by Vladislav Zavialov at 2026-09-03T12:24:15+05:30 Discard type arguments in tcPatToExpr (#27440, #27583) The builder expression of an implicitly bidirectional pattern synonym must not mention types written in the RHS: * Invisible type arguments led to a panic (#27440) * Required type arguments failed with out-of-scope variables (#27583) Both are now discarded, following the precedent established by pattern signatures (#9867). Discarding type arguments takes some care: a type pattern cannot be told from a value pattern by syntax alone, as the `type` keyword may be omitted. Consider: data T a b c where MkT :: forall a. forall b c -> a -> T a b c pattern P :: x -> T x y z pattern P x = MkT @a (type b) c x In P's right-hand side, `@a` and `type b` are clearly type arguments, but what about `c` and `x`? We can only tell by matching the patterns against MkT's type. So tcPatToExpr now runs in TcM and matches the arguments against the constructor's TyVarBinders using zipPatsBndrs, which is made public for this purpose. The resulting builder is $bP x = MkT _ _ x. See Note [Discarding types in the builder expression]. Test cases: T27440a T27440b T27440c T27440d T27440e T27583a T27583b T27583c T27583d T27583e T27583f T27583g Metric Increase: LinkableUsage02 Metric Decrease: T27336 Assisted-by: Claude Opus 5 (cherry picked from commit 4f98510802423dcd98fa62af77997189ee97a111) - - - - - 768a7203 by sheaf at 2026-09-03T12:24:43+05:30 mkWpFun_FRR: fix ordering of coercion composition When the subsumption machinery generates an eta-expansion, we must perform a representation polymorphism check to ensure the lambda binder it introduces has a fixed runtime representation. This is done in GHC.Tc.Utils.mkWpFun_FRR. This check involves composing quite a few coercions, arising from representation-polymorphism checks on both the actual and expected argument types. These coercions are then chained using HsWrapper composition, <.>. The ordering of composition was incorrect, leading to the Core Lint failure reported in #27639. This commit fixes that. Fixes #27639 (cherry picked from commit eb1dcd4d98548b7bc64c323dc352ddbf149a91ec) - - - - - 3df33eca by Vladislav Zavialov at 2026-09-03T12:25:11+05:30 Fix tcLookupId panic with RequiredTypeArguments and PatternSynonyms (#27586) The arguments declared on the left-hand side of a pattern synonym are looked up as term variables bound by its right-hand side. Prior to this patch, that lookup panicked with RequiredTypeArguments: data T a where MkT :: forall a -> T a pattern P :: Int -> T Int pattern P x = MkT x On the RHS, `x` looks like a term argument, so the renamer binds it in the term namespace. Only during type checking does it turn out to be a type variable, so the lookup on the LHS finds an ATyVar rather than an ATcId. As the lookup was done with tcLookupId, it resulted in a panic. Now the arguments are looked up with tcLookupPatSynArg, which reports an illegal term-level use of `x`, just as an ordinary function definition `f (MkT x) = x` does. Test cases: T27586a T27586b T27586c Assisted-by: Claude Opus 5 (cherry picked from commit b757727a78613e7437a713058c24b94e10697f47) - - - - - d8eb75ae by Zubin Duggal at 2026-09-03T12:27:35+05:30 ghc-internal: annotateSTM should use catchSTM# rather than catch# A catch# frame inside a transaction breaks retry and async exception delivery. Fixes #27657 (cherry picked from commit fd22f71ee92595f4634206455d8eab111488d836) - - - - - 21670d7a by fendor at 2026-09-03T12:28:40+05:30 GHCi: Fix order of `PackageDBFlag`s for interactive home unit `PackageDBFlag`s are stored in reverse order of cli specification. When sorting the `PackageDBFlag`s by longest common prefix, we need thus to reverse the package db stacks before calculating the prefix. We make sure to reverse the package db stack for the interactive home unit to uphold that later specified package dbs overwrite earlier ones. Resolved and adds regression test for #27640 (cherry picked from commit 06fde293f2e8c80db11f4d01fcdfc482c1128db5) - - - - - aaff8ff7 by Simon Peyton Jones at 2026-09-03T12:29:56+05:30 Never make an absent filler for a constraint type mkAbsentFiller used isTerminatingType to decide, but that is not enough. Consider class Eq a => UC a where {} let u :: UC Int -- UC Int is a "non-terminating type" u = error "Absent" let e :: Eq Int -- Eq Int is a "terminating type" e = $p1UC u We clearly must not make a filler for `e`, because we speculatively evaluate it. But speculatively evaluating `e` forces `u`, so we must not make one for `u` either. Asking isDictTy instead is not enough either, because it does not catch a constraint hidden behind an unreduced type family application: type family F a :: Constraint type instance F W = TC W a :: F W => Int -> Int -- (F W) argument is absent Oops! Entered absent arg Arg: irred Type: F W So play safe and use isPredTy: never make an absent filler for any constraint-kinded type. Fixes #27627 (cherry picked from commit 7bf546fc423e23cb649580016ee494efbfe144ab) - - - - - bc85dcac by Zubin Duggal at 2026-09-03T12:29:57+05:30 Add tests for absent fillers at dictionary types T27627 a unary class whose superclass is a non-unary class T27627a ...whose superclass is a Constraint-kinded type family T27627b ...whose superclass is a quantified constraint T27627c a unary class applied to itself, (UC (UC (TC a))) T27627e a (forall b. P b) dictionary that loops (cherry picked from commit 5f474953d1880232b5e6c5741f08746e28cd25ab) - - - - - 8e59b385 by Zubin Duggal at 2026-09-03T12:29:57+05:30 An abstract TyCon may hide a unary class A class declared in an hs-boot file is an AbstractTyCon inside the module loop, and compiling the real declaration may reveal it to be a UnaryClassTyCon. - isTerminatingType returned True for such AbstractTyCons - IfaceToCore set the unary flag to False in the DFunId So we could end up speculating bottom dictionaries because inside a module loop we see an UnaryClassTyCon as an AbstractTyCon Use isTerminatingTyCon, which returns False for an abstract TyCon. The Bool in DFunId is now a cache for isTerminatingTyCon, set in mkDFunIdDetails. Fixes #27704 (cherry picked from commit cd5c6bcc0a59c7b4dc4627fdc7471dc7938d07c2) - - - - - 0a73317b by Zubin Duggal at 2026-09-03T12:30:29+05:30 Specialise: don't replace dead args with absent fillers specHeader decides an argument is dead by calling isDeadBinder on a binder of the /optimised RHS/, then applies the filler to the /stable unfolding/ template instead. The two may differ, so the argument can be dead in the RHS and not in the template. The specialised function's unfolding then has an absent filler, and any call site that inlines it evaluates the error thunk. Dropping dead args in the specialiser is rarely worth it, to quote Simon, "The later worker/wrapper pass will pick up the dead arg later if it is really dead. Keeps the specialiser simpler." So instead of trying to check if the arg really is dead in the stable unfolding, just drop the logic for dropping dead args in the specialiser altogeher. Fixes #27703 (cherry picked from commit abfc224a27cf499390efc5fe1348301fefebb910) - - - - - 07fc3695 by Zubin Duggal at 2026-09-03T12:30:29+05:30 CorePrep: don't speculate a call across an hs-boot edge We take care not to evaluate things that might be bottom, like a looping dictionary group, but our analysis is defeated by boot files. We only track recursion within a module, so two dictionaries that depend on each other across a module loop each look non-recursive, and we might speculate them. Any recursion we cannot see must cross an hs-boot edge, so refuse to speculate calls that cross one. Fixes #27717 (cherry picked from commit 1557fd1cfb802d2608cb5b138eab664564f57fb7) - - - - - 60441138 by Cheng Shao at 2026-09-03T12:31:17+05:30 configure: bump LlvmMaxVersion to 23 This patch bumps `LlvmMaxVersion` to 23 to support LLVM 22.x releases. (cherry picked from commit cc9cc6d5df7fb3845b1409fe708e1097896252a7) - - - - - b6c4fbea by Cheng Shao at 2026-09-03T12:31:38+05:30 autoconf/ghc-toolchain: bump llvm upper bound to support llvm 23 This commit bumps llvm upper bound to support llvm 23. (cherry picked from commit 56291fc550ec00784e46ec0c89ee65081090ae9f) - - - - - c0329e1d by Cheng Shao at 2026-09-03T12:31:38+05:30 rts: fix compilation issues with clang 23 clang 23 has broadened `-Wall`/`-Wextra` ranges, exposing some minor issues in the rts when building with validate flavours: - Unused locals - `#pragma GCC diagnostic pop` mismatch This commit fixes those. (cherry picked from commit 20eb3f415f9e04a003322d1a49d95e0aaf1029f2) - - - - - fca9490e by Zubin Duggal at 2026-09-03T12:42:47+05:30 fixup! base: Don't drop exception context in SomeException(toException) - - - - - 7a4a0c45 by Cheng Shao at 2026-09-03T12:43:23+05:30 libffi: update to 3.7.1 Bumps libffi submodule. (cherry picked from commit d7e36a486b224908b1e1f6e5d9eb04084819c805) - - - - - c8afb3f2 by Andreas Klebinger at 2026-09-03T12:56:15+05:30 cmm dumps: Add machop width info with -dppr-debug for infix ops. (cherry picked from commit e9bbe8f924ec0b9d0772cf3d4f20aa6a25f28345) - - - - - b7115dbb by Andreas Klebinger at 2026-09-03T12:56:22+05:30 CmmLint: Check for unsupported MachOp widths machOpArgReps now maps MachOp + Width to a list of supported argument widths or Nothing if the given operation is not supported at the given width. This allows us to check for nonsensical combinations like FloatToInt at Word16. Similarly we now check that every address is actually wordwidth. (cherry picked from commit 86e3a9d8d0a85b5c80dad212cf3ec8fbf1ba72e6) - - - - - 6298575d by Andreas Klebinger at 2026-09-03T12:59:38+05:30 arm64 ncg: The big subword truncation fix. A set of slightly related fixes to arm subword handling: Bitmask immediates: Don't produce overflowing assembly literals. There is still another bug here that causes us to miss some valid literals but we will fix that later. Improve subword truncation handling: We now use a small set of helpers to truncate `Register` values rather than truncating immediate `Reg` values which greatly simplifies the code structure. This fixes a great many bugs to do with sign/zero extending subwords or the lack thereof. We now establish the invariant that subword values are zero-extended at every site at which they come into "scope" of the ncg, and rely on the invariant throughout rather than pessimistically inserting redundant extensions in a hodgepodge manner at the use sites of these values. This fixes at least the bugs described in issues #27533, #27430 #27537, #27538, #27539, and #27550. But likely more bugs yet not found. Subword ffi results: Apply truncations when calling functions returning subword values. genCondJump: Don't sign extend signed values in the input register as it might map to a local variable, corrupting the value stored within. Fix subword store/load instructions.: We used to read those at 32bit width even for smaller values possibly resulting in invalid memory access. Now we construct the suffix for subword variants based on the instruction format for these. (cherry picked from commit 13781cca5c24c2671d651fd2b13a561c7386fe3a) - - - - - bfe79214 by Andreas Klebinger at 2026-09-03T13:04:08+05:30 Add some test cases covering bugs in the arm ncg. * Test for #27430 (subword ffi results) * #27537 - subword conversions * #27538 - subwords used in conditional * #27533 - single byte read (cherry picked from commit 94822c951c2a6f77c7766720e0d4ff7d4afb7290) - - - - - 96224bce by Andreas Klebinger at 2026-09-03T13:04:12+05:30 cmmLint: Lint against MO_FS_Truncate subword use. (cherry picked from commit dd1ba88a70f47bead722e9dae8e91f9a617258aa) - - - - - c7df4cfc by Zubin Duggal at 2026-09-03T13:06:38+05:30 fixup! Add a deprecation warning for static forms - - - - - 604c6824 by Zubin Duggal at 2026-09-03T13:56:37+05:30 fixup! base: Don't drop exception context in SomeException(toException) - - - - - b414e021 by fendor at 2026-09-03T14:07:32+05:30 Drop `preloadClosure` from `UnitState` It is always hard-coded to the same value. Backpack Unit instantiation isn't using it any more. Allows us to simplify the API and get rid of `improveUnit`. (cherry picked from commit fb5246adb7e10bd9ef07de314eaf98fbcfb729a1) - - - - - 811da397 by fendor at 2026-09-03T14:07:53+05:30 Introduce global unit database cache As a first step for better sharing of `UnitInfo` across `UnitEnv`, we introduce a new datatype called `ExternalUnitDatabases`. It primarily serves as an in-memory representation of *all* `UnitDatabase`s across `UnitEnv`. This means, if multiple `HomeUnitEnv`s depend on the same database, one way or another, we make sure that we don't parse from disk every time. Instead, we store the in-memory representation in `ExternalUnitDatabases`. `ExternalUnitDatabaseCache` is the equivalent of `ExternalUnitState` in the `UnitEnv`. It is a mutable variable wrapping `ExternalUnitDatabases`. The mutable `ExternalUnitDatabaseCache` is used in `initUnits` to make sure we don't parse the same unit database multiple times. Almost by accident, we change the semantics of `initUnits` to honour modifications to `packageDBFlags`. The inability to change `packageDBFlags` while also reusing the already parsed `UnitDatabase`s was reported in #26423 as a bug. Hence, we think this behaviour change is warranted and acceptable, especially since it comes with a breaking change to the `initUnits` API. Add regression test for #26423 Closes #26423 (cherry picked from commit 5d0ab71ac1d01c2ef19bf3146adb7dac8733dca5) - - - - - 9fa88e7b by fendor at 2026-09-03T14:29:45+05:30 Introduce UnitIndex for global external unit caching `UnitInfo`s have been observed to cause a lot of memory usage in #27500. Especially with multiple home units, as the same (external) units are processed from scratch, even though most of the time we end up with exactly the same `UnitInfo`. We introduce a `UnitEnv` global cache that allows us to store external unit information that is used across all `HomeUnitEnv`s. The most important change in this commit is the introduction of the `UnitIndex`. It stores a global mapping of `UnitId` -> `UnitInfo`, and `initUnits` always uses the cached `UnitInfo` entry to populate each `HomeUnitEnv`'s `UnitState`. This allows us to ensure the following property: > Each `UnitInfo` should be alive exactly once in GHC. All `UnitState`s should reference 'UnitInfo's stored in the 'UnitIndex'. This ensured by calling 'initUnits' with the 'UnitIndex'. In addition, the `ExternalUnitDatabases` may also hold a reference to each on-disk representation of `UnitInfo`. This means, we impose an hard upper bound on the number of `UnitInfo`s alive in the GHC session: > The number of alive `UnitInfo`s closure objects must be the > sum of all loaded unit database times two. We add performance regression tests that make sure the number of live `UnitInfo` cannot exceed this threshold. Closes #27500 ------------------------- Metric Decrease: MultiComponentModules MultiComponentModulesRecomp MultiComponentModulesRecomp100 mhu-perf LinkableUsage02 ------------------------- These metrics increases are especially notable, as we are not even sharing anything big but merely the global package database with 50 entries. It shows how careful sharing of `UnitInfo` can improve memory usage. We expect this to be much more notable when the whole cabal package database is shared across multiple home units. `LinkableUsage02` metric decreases on unreg and i386 platform, only. --- Technical details To share the `UnitInfo`s correctly, it is important that we extract the `WireMap` into the `UnitIndex`. At the moment of writing, `WireMap` must be globally the same for all `HomeUnitEnv`s. This is important, as we could otherwise not cache the "fully-resolved" `UnitInfo`, as we don't change the `UnitId` or `unitAbiHash` when resolving wired-in units. Thus, there could be ambiguities, when the `WireMap` is not the same for all `UnitState`s across the `UnitEnv`. We consider a `UnitInfo` fully-resolved, if wired-in units have been updated, the `UnitInfo` has been validated and variables in the unit config, such as `${pkgroot}` have been resolved. Updating the wired-in units requires the `WireMap` to be globally the same. (cherry picked from commit 6cce494a7ec43953c7a949e0d8ce712abfe73da7) - - - - - 481dc5ce by fendor at 2026-09-03T14:30:47+05:30 Reuse the UnitIndexCache after initialising multiple home units (cherry picked from commit 024c4d04a98f7e27b3dcb93f9b038f9b6b5a1ad9) - - - - - 9fc20ad3 by Andreas Klebinger at 2026-09-03T14:30:52+05:30 Specialise: Stop looping on recursive dictionaries in interestingDict interestingDict now doesn't look through loopbreaker unfoldings. Doing so would cause infinite loops on certain dictionaries. Fixes #27705. (cherry picked from commit 578bd18509f0d2aeb004231a197f7f3898f86a2a) - - - - - a764f8ce by Zubin Duggal at 2026-09-03T15:14:37+05:30 hadrian: constrain splitmix to keep building on Debian 9 - - - - - f37ae7a6 by Zubin Duggal at 2026-09-03T15:14:37+05:30 Bump file-io submodule to 0.1.6 - - - - - 0aa35678 by Zubin Duggal at 2026-09-03T15:14:37+05:30 Bump haskeline submodule to 0.8.5.0 - - - - - 1e794061 by Zubin Duggal at 2026-09-03T15:14:37+05:30 Bump os-string submodule to 2.0.10 - - - - - cd61daa7 by Zubin Duggal at 2026-09-03T15:14:37+05:30 Bump directory submodule to 1.3.11.0 - - - - - 08f58e96 by Zubin Duggal at 2026-09-03T15:15:01+05:30 Prepare 9.14.2-rc2 - - - - - 206 changed files: - − changelog.d/27626 - − changelog.d/T26716 - compiler/GHC.hs - compiler/GHC/Cmm/Expr.hs - compiler/GHC/Cmm/Lint.hs - compiler/GHC/Cmm/MachOp.hs - compiler/GHC/Cmm/Parser.y - compiler/GHC/CmmToAsm/AArch64/CodeGen.hs - compiler/GHC/CmmToAsm/AArch64/Instr.hs - compiler/GHC/CmmToAsm/AArch64/Ppr.hs - compiler/GHC/Core.hs - 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+ testsuite/tests/driver/T26423/Makefile - + testsuite/tests/driver/T26423/T26423.hs - + testsuite/tests/driver/T26423/T26423.stderr - + testsuite/tests/driver/T26423/T26423.stdout - + testsuite/tests/driver/T26423/all.T - + testsuite/tests/driver/T26423/test/Test.hs - + testsuite/tests/driver/T26423/test/test.pkg - + testsuite/tests/driver/TUnitInfo/Foo.hs - + testsuite/tests/driver/TUnitInfo/Makefile - + testsuite/tests/driver/TUnitInfo/all.T - + testsuite/tests/driver/TUnitInfo/genMhu.sh - + testsuite/tests/driver/TUnitInfo/generic-unit-info-space-mhu.stdout - + testsuite/tests/driver/TUnitInfo/generic-unit-info-space-single.stdout - + testsuite/tests/driver/TUnitInfo/generic-unit-info-space.hs - + testsuite/tests/driver/TUnitInfo/generic-unit-info-space.stdout - testsuite/tests/ghc-e/should_fail/T9930fail.stderr - testsuite/tests/ghc-e/should_run/ghc-e005.stderr - + testsuite/tests/ghci/prog-mhu007/Makefile - + testsuite/tests/ghci/prog-mhu007/a/A.hs - + testsuite/tests/ghci/prog-mhu007/all.T - + testsuite/tests/ghci/prog-mhu007/b/B.hs - + testsuite/tests/ghci/prog-mhu007/prog-mhu007.script - + testsuite/tests/ghci/prog-mhu007/prog-mhu007.stdout - + testsuite/tests/ghci/prog-mhu007/testpkg-bar/Bar.hs - + testsuite/tests/ghci/prog-mhu007/testpkg-bar/testpkg-bar.pkg - + testsuite/tests/ghci/prog-mhu007/testpkg-foo/Foo.hs - + testsuite/tests/ghci/prog-mhu007/testpkg-foo/testpkg-foo.pkg - + testsuite/tests/ghci/prog-mhu007/unitA - + testsuite/tests/ghci/prog-mhu007/unitB - + testsuite/tests/patsyn/should_compile/T27440a.hs - + testsuite/tests/patsyn/should_compile/T27440b.hs - + testsuite/tests/patsyn/should_compile/T27440c.hs - testsuite/tests/patsyn/should_compile/all.T - + testsuite/tests/patsyn/should_fail/T27440d.hs - + testsuite/tests/patsyn/should_fail/T27440d.stderr - testsuite/tests/patsyn/should_fail/all.T - + testsuite/tests/rep-poly/T27639.hs - testsuite/tests/rep-poly/all.T - testsuite/tests/simplCore/should_compile/T17966.stderr - testsuite/tests/simplCore/should_compile/T7785.stderr - testsuite/tests/simplCore/should_compile/spec004.hs - testsuite/tests/simplCore/should_compile/spec004.stderr - + testsuite/tests/simplCore/should_run/T27703/Lib.hs - + testsuite/tests/simplCore/should_run/T27703/Main.hs - + testsuite/tests/simplCore/should_run/T27703/T27703.stdout - + testsuite/tests/simplCore/should_run/T27703/all.T - + testsuite/tests/simplCore/should_run/T27705.hs - + testsuite/tests/simplCore/should_run/T27705.stdout - + testsuite/tests/simplCore/should_run/T27705_Inst.hs - testsuite/tests/simplCore/should_run/all.T - testsuite/tests/typecheck/should_compile/T26718.stderr - + testsuite/tests/typecheck/should_compile/T27664.hs - testsuite/tests/typecheck/should_compile/all.T - + testsuite/tests/vdq-rta/should_compile/T27583a.hs - + testsuite/tests/vdq-rta/should_compile/T27583b.hs - + testsuite/tests/vdq-rta/should_compile/T27583c.hs - + testsuite/tests/vdq-rta/should_compile/T27583d.hs - + testsuite/tests/vdq-rta/should_compile/T27583e.hs - + testsuite/tests/vdq-rta/should_compile/T27583g.hs - testsuite/tests/vdq-rta/should_compile/all.T - + testsuite/tests/vdq-rta/should_fail/T27440e.hs - + testsuite/tests/vdq-rta/should_fail/T27440e.stderr - + testsuite/tests/vdq-rta/should_fail/T27583f.hs - + testsuite/tests/vdq-rta/should_fail/T27583f.stderr - + testsuite/tests/vdq-rta/should_fail/T27586a.hs - + testsuite/tests/vdq-rta/should_fail/T27586a.stderr - + testsuite/tests/vdq-rta/should_fail/T27586b.hs - + testsuite/tests/vdq-rta/should_fail/T27586b.stderr - + testsuite/tests/vdq-rta/should_fail/T27586c.hs - + testsuite/tests/vdq-rta/should_fail/T27586c.stderr - testsuite/tests/vdq-rta/should_fail/all.T - utils/haddock/haddock-api/src/Haddock.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/03babb4526e14779588476693e7826… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/03babb4526e14779588476693e7826… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/27323] Don't report -XStrict-generated bangs under -Wredundant-bang-patterns
by Sasha Bogicevic (＠Bogicevic) 03 Sep '26

03 Sep '26

Sasha Bogicevic pushed to branch wip/27323 at Glasgow Haskell Compiler / GHC Commits: f14b27ba by Sasha Bogicevic at 2026-09-03T11:28:23+02:00 Don't report -XStrict-generated bangs under -Wredundant-bang-patterns With -XStrict, decideBangHood inserts bang patterns on binders. When such a bang cannot force anything (e.g. on a binder of unlifted type), -Wredundant-bang-patterns reported it, even though there is no bang in the source to remove. The desugarer now tracks whether it is desugaring compiler-generated code, mirroring tcl_in_gen_code in the typechecker: * decideBangHood places the bangs it inserts at a generatedSrcSpan. * DsLclEnv gains a dsl_in_generated_code field, maintained solely by putSrcSpanDs: a real span clears it, a generated span sets it. * The pattern-match checker's desugaring (desugarLPat) pushes each pattern's location, and on a bang in generated code emits a PmBang with no SrcInfo: it is still divergence-checked (so inaccessible-RHS warnings under -XStrict survive, #21761), but never reported as redundant. See Note [Desugaring -XStrict matches in Pmc] in GHC.HsToCore.Pmc.Desugar. Making these bangs proper expanded patterns instead is tracked as #27677. - - - - - 7 changed files: - + changelog.d/T27323 - compiler/GHC/HsToCore/Monad.hs - compiler/GHC/HsToCore/Pmc/Desugar.hs - compiler/GHC/HsToCore/Types.hs - compiler/GHC/HsToCore/Utils.hs - + testsuite/tests/pmcheck/should_compile/T27323.hs - testsuite/tests/pmcheck/should_compile/all.T Changes: ===================================== changelog.d/T27323 ===================================== @@ -0,0 +1,7 @@ +section: compiler +synopsis: Don't report ``-XStrict``-generated bang patterns under ``-Wredundant-bang-patterns`` +description: + Bangs introduced by ``-XStrict`` are no longer reported as redundant under + ``-Wredundant-bang-patterns``, as they are not user-written. +issues: #27323 +mrs: !16395 ===================================== compiler/GHC/HsToCore/Monad.hs ===================================== @@ -15,7 +15,7 @@ module GHC.HsToCore.Monad ( duplicateLocalDs, newSysLocalDs, newSysLocalsDs, newSysLocalMDs, newSysLocalsMDs, newFailLocalMDs, newUniqueId, newPredVarDs, newStaticId, - getSrcSpanDs, putSrcSpanDs, putSrcSpanDsA, + getSrcSpanDs, inGeneratedCodeDs, putSrcSpanDs, putSrcSpanDsA, mkNamePprCtxDs, newUnique, UniqSupply, newUniqueSupply, @@ -584,6 +584,7 @@ mkDsEnvs unit_env mod rdr_env type_env fam_inst_env tcm_plugins ptc msg_var , dsl_loc = real_span , dsl_nablas = Ldi initNablas , dsl_unspecables = Just emptyVarSet + , dsl_in_generated_code = False } in (gbl_env, lcl_env) @@ -676,13 +677,17 @@ getSrcSpanDs :: DsM SrcSpan getSrcSpanDs = do { env <- getLclEnv ; return (RealSrcSpan (dsl_loc env) Strict.Nothing) } +-- | See 'dsl_in_generated_code' +inGeneratedCodeDs :: DsM Bool +inGeneratedCodeDs = dsl_in_generated_code <$> getLclEnv + putSrcSpanDs :: SrcSpan -> DsM a -> DsM a putSrcSpanDs (RealSrcSpan real_span _) thing_inside - = updLclEnv (\ env -> env {dsl_loc = real_span}) thing_inside + = updLclEnv (\ env -> env {dsl_loc = real_span, dsl_in_generated_code = False}) thing_inside putSrcSpanDs UnhelpfulSpan{} thing_inside = thing_inside putSrcSpanDs GeneratedSrcSpan{} thing_inside - = thing_inside + = updLclEnv (\ env -> env {dsl_in_generated_code = True}) thing_inside putSrcSpanDsA :: EpAnn ann -> DsM a -> DsM a putSrcSpanDsA loc = putSrcSpanDs (locA loc) ===================================== compiler/GHC/HsToCore/Pmc/Desugar.hs ===================================== @@ -155,11 +155,15 @@ desugarPat x pat = case pat of VarPat _ y -> pure (mkPmLetVar (unLoc y) x) ParPat _ p -> desugarLPat x p LazyPat _ _ -> pure GdEnd -- like a wildcard - BangPat _ p@(L l p') -> + BangPat _ p@(L l p') -> do -- Add the bang in front of the list, because it will happen before any -- nested stuff. + in_gen <- inGeneratedCodeDs + -- A bang inserted by -XStrict (decideBangHood) has no SrcInfo: it is + -- divergence-checked but never reported as redundant (#27323). + let pm_loc | in_gen = Nothing + | otherwise = Just (SrcInfo (L (locA l) (ppr p'))) consGrdDag (PmBang x pm_loc) <$> desugarLPat x p - where pm_loc = Just (SrcInfo (L (locA l) (ppr p'))) -- (x@pat) ==> Desugar pat with x as match var and handle impedance -- mismatch with incoming match var @@ -311,7 +315,7 @@ desugarPatV pat = do pure (x, grds) desugarLPat :: Id -> LPat GhcTc -> DsM GrdDag -desugarLPat x = desugarPat x . unLoc +desugarLPat x (L loc pat) = putSrcSpanDsA loc (desugarPat x pat) -- | 'desugarLPat', but also select and return a new match var. desugarLPatV :: LPat GhcTc -> DsM (Id, GrdDag) @@ -650,4 +654,19 @@ user *had* written a bang: + In an equation for ‘idV’: idV !v = ... So we live with the duplication. + +Note that 'decideBangHood' places the bangs it inserts at a 'generatedSrcSpan'. +When 'desugarLPat' enters such a span, 'putSrcSpanDs' (GHC.HsToCore.Monad) +records in 'dsl_in_generated_code' that we are desugaring compiler-generated +code. For a bang in generated code, 'desugarPat' emits a 'PmBang' with no +'SrcInfo': the checker still performs the divergence check (so the +inaccessible-RHS warning above survives), but -Wredundant-bang-patterns only +ever reports bangs the user actually wrote (#27323). See +Note [Dead bang patterns] in GHC.HsToCore.Pmc.Check. + +Eventually the bangs inserted by -XStrict should become expanded patterns, +following Note [Handling overloaded and rebindable constructs] in +GHC.Rename.Expr. That would let warnings always display the original +user-written code, making the decideBangHood duplication described above +unnecessary. This is tracked as #27677. -} ===================================== compiler/GHC/HsToCore/Types.hs ===================================== @@ -11,7 +11,7 @@ module GHC.HsToCore.Types ( DsMetaEnv, DsMetaVal(..), CompleteMatches ) where -import GHC.Prelude (Int) +import GHC.Prelude (Bool, Int) import Data.IORef @@ -125,6 +125,7 @@ data DsLclEnv -- ^ See Note [Desugaring non-canonical evidence] -- This field collects all un-specialisable evidence variables in scope. -- Nothing <=> don't collect this info (used for the LHS of Rules) + , dsl_in_generated_code :: Bool -- Desugaring compiler-generated or user-written code } -- Inside [| |] brackets, the desugarer looks ===================================== compiler/GHC/HsToCore/Utils.hs ===================================== @@ -951,6 +951,9 @@ Specifically: -- | Use -XStrict to add a ! or remove a ~ +-- The bang we insert is compiler-generated, so we put it at a generatedSrcSpan. +-- The pattern-match checker uses this (via dsl_in_generated_code) to avoid reporting +-- such bangs under -Wredundant-bang-patterns (#27323). -- See Note [decideBangHood] decideBangHood :: DynFlags -> LPat GhcTc -- ^ Original pattern @@ -966,7 +969,7 @@ decideBangHood dflags lpat ParPat x p -> L l (ParPat x (go p)) LazyPat _ lp' -> lp' BangPat _ _ -> lp - _ -> L l (BangPat noExtField lp) + _ -> L (noAnnSrcSpan generatedSrcSpan) (BangPat noExtField lp) isTrueLHsExpr :: LHsExpr GhcTc -> Maybe (CoreExpr -> DsM CoreExpr) ===================================== testsuite/tests/pmcheck/should_compile/T27323.hs ===================================== @@ -0,0 +1,9 @@ +{-# LANGUAGE MagicHash, Strict #-} +{-# OPTIONS_GHC -Wredundant-bang-patterns #-} + +import GHC.Prim (Int#) + +idInt# :: Int# -> Int# +idInt# x = x + +main = pure () ===================================== testsuite/tests/pmcheck/should_compile/all.T ===================================== @@ -190,4 +190,5 @@ test('T24845', [], compile, [overlapping_incomplete]) test('T22652', [], compile, [overlapping_incomplete]) test('T22652a', [], compile, [overlapping_incomplete]) test('T24867', [], compile_fail, [overlapping_incomplete]) +test('T27323', normal, compile, ['-Wredundant-bang-patterns']) test('T27360', normal, compile, [overlapping_incomplete + '-g3']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/f14b27ba9cd7043cb32c00ad0e522e8… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/f14b27ba9cd7043cb32c00ad0e522e8… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/mangoiv/ci-stages] ci: clean up env before running tests even more
by Magnus (＠MangoIV) 03 Sep '26

03 Sep '26

Magnus pushed to branch wip/mangoiv/ci-stages at Glasgow Haskell Compiler / GHC Commits: 43337463 by mangoiv at 2026-09-03T11:13:40+02:00 ci: clean up env before running tests even more - - - - - 1 changed file: - .gitlab/ci.sh Changes: ===================================== .gitlab/ci.sh ===================================== @@ -968,7 +968,7 @@ function run_hadrian() { if [ -n "${VERBOSE:-}" ]; then args+=("-V"); fi # Before running the compiler, unset variables gitlab env vars as these # can destabilise the performance test (see #20341) - (unset $(compgen -v | grep CI_*); + (unset $(compgen -v | grep -E '^(CI_|FF_|GITLAB_)'); # dump the env before running hdarian itself. start_section run_hadrian_env "env for runnning hadrian"; env; end_section run_hadrian_env run "${HADRIAN_PATH:-hadrian/build-cabal}" \ View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/4333746379de774b9727fdfea777ef1… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/4333746379de774b9727fdfea777ef1… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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[Git][ghc/ghc][wip/T27664] 47 commits: testsuite: Use sigkill in process009.
by Simon Peyton Jones (＠simonpj) 03 Sep '26

03 Sep '26

Simon Peyton Jones pushed to branch wip/T27664 at Glasgow Haskell Compiler / GHC Commits: fed942ac by Andreas Klebinger at 2026-08-17T12:11:57-04:00 testsuite: Use sigkill in process009. SIGHUB might have been blocked by a (grand)*parent of the test. In such cases the test would fail as the python process would simply exist gracefully instead of committing to a premature end. By using SIGKILL we can rely on the signal not being blocked, fixing #27578 in the process. - - - - - 574c875f by Andreas Klebinger at 2026-08-17T12:12:39-04:00 Simplify comparison in DFM.hs Fixes #27669 - - - - - d8f1a2a3 by Alan Zimmerman at 2026-08-17T12:13:18-04:00 TTG: Add extension points to BooleanFormula They are currently unused, but will be used for exact print annotations next, allowing us to get rid of LocatedBF / SrcSpanAnnBF - - - - - 93a2b20f by Andreas Klebinger at 2026-08-18T04:31:04-04:00 Fix a number of incorrect module references: Fix module reference in Note [DataCon wrappers are conlike]. Fix module reference in Note [Detailed InertCans Invariants]. Fix module reference in Note [GHC's data format representations]. Fix module reference in Note [Grand plan for static forms]. Fix module reference in Note [How tuples work]. Fix module reference in Note [Solved dictionaries]. Fix module reference in Note [Stacktraces from Info Table Provenance Entries (IPE based stack unwinding)]. Fix module reference in Note [The VarBndr type and its uses]. Found the incorrect references with a llm. - - - - - eb0dfb01 by Simon Jakobi at 2026-08-18T04:31:44-04:00 ci: Run stack-hadrian-build only in full-ci pipelines The job exists to catch changes that break hadrian/build-stack (#18726), but nothing in the pipeline depends on it, and it can only break when hadrian's dependencies change. Restricting it to full-ci (like hadrian-multi) still covers marge-bot merge batches, so such breakage cannot reach master unnoticed, while ordinary validate pipelines skip the job. Assisted-by: Claude Fable 5 - - - - - b9160962 by Simon Jakobi at 2026-08-20T14:57:52-04:00 testsuite: Show baseline sample count and range in perf failures A perf baseline is the mean of all samples recorded for a commit, and it prints as a single number, hiding how far the samples spread. When the spread is wide, this can indicate an unstable metric that isn't actually useful as a signal for the perf tests. For example, in #27602, T27336's peak_megabytes_allocated baseline showed as 757 when the underlying samples were 605 and 909. When the baseline is averaged from more than one sample, say so in the failure output: the one-line stat-failure reason shows the sample range, and the detail block lists the raw samples. Single-sample baselines print exactly as before. Context: #27602 Assisted-by: Claude Fable 5 - - - - - a4979877 by Simon Jakobi at 2026-08-20T14:57:52-04:00 testsuite: Fold Baseline into CommitMetric A Baseline was just a CommitMetric plus the commit it came from, built by copying fields across. Since get_commit_metric already knows that commit, record it on CommitMetric itself and drop Baseline. This also collapses both branches of find_baseline into plain returns. Assisted-by: Claude Fable 5 - - - - - 99fb8d68 by Simon Jakobi at 2026-08-20T14:57:52-04:00 ci: Clarify comment on pushing perf notes after failures Context: #27602 Assisted-by: Claude Fable 5 - - - - - 2ca87972 by Alan Zimmerman at 2026-08-20T14:58:36-04:00 EPA: Remove LocatedBC / SrcSpanBF The custom annotations are now in the BooleanFormula TTG extension points, so LBooleanFormula can now use the standard LocatedA. - - - - - d2bc32aa by Simon Peyton Jones at 2026-08-21T12:59:26-04:00 Better handling of serialisation of wired-in names Fixes #27501 - - - - - d2795ffc by Alan Zimmerman at 2026-08-21T13:00:05-04:00 EPA: Remove NoEpTok/NoEpUniTok, using an unhelpful SrcSpan instead Also introduce helper functions noEpTok and noEpUniTok to serve as simple replacements in code inserting an token annotation without location information. - - - - - b5d29ab8 by Brandon Chinn at 2026-08-25T18:42:08-04:00 Add Data.RealFloat and Infinity/NegInfinity/NaN pattern synonyms (#26961) - - - - - e60eb3bc by Andreas Klebinger at 2026-08-25T18:42:59-04:00 rts linker: Fix pointer arithmetic issue in flushInstructionCacheRISCV64 We accidentally operated over `uint64_t*` when we should use `uint8_t`. Fixes #27569 - - - - - e9bbe8f9 by Andreas Klebinger at 2026-08-26T15:09:23-04:00 cmm dumps: Add machop width info with -dppr-debug for infix ops. - - - - - 86e3a9d8 by Andreas Klebinger at 2026-08-26T15:09:24-04:00 CmmLint: Check for unsupported MachOp widths machOpArgReps now maps MachOp + Width to a list of supported argument widths or Nothing if the given operation is not supported at the given width. This allows us to check for nonsensical combinations like FloatToInt at Word16. Similarly we now check that every address is actually wordwidth. - - - - - 13781cca by Andreas Klebinger at 2026-08-26T15:09:24-04:00 arm64 ncg: The big subword truncation fix. A set of slightly related fixes to arm subword handling: Bitmask immediates: Don't produce overflowing assembly literals. There is still another bug here that causes us to miss some valid literals but we will fix that later. Improve subword truncation handling: We now use a small set of helpers to truncate `Register` values rather than truncating immediate `Reg` values which greatly simplifies the code structure. This fixes a great many bugs to do with sign/zero extending subwords or the lack thereof. We now establish the invariant that subword values are zero-extended at every site at which they come into "scope" of the ncg, and rely on the invariant throughout rather than pessimistically inserting redundant extensions in a hodgepodge manner at the use sites of these values. This fixes at least the bugs described in issues #27533, #27430 #27537, #27538, #27539, and #27550. But likely more bugs yet not found. Subword ffi results: Apply truncations when calling functions returning subword values. genCondJump: Don't sign extend signed values in the input register as it might map to a local variable, corrupting the value stored within. Fix subword store/load instructions.: We used to read those at 32bit width even for smaller values possibly resulting in invalid memory access. Now we construct the suffix for subword variants based on the instruction format for these. - - - - - d8fa5d7c by Andreas Klebinger at 2026-08-26T15:09:24-04:00 arm64 ncg: Fix MO_V_Broadcast for non-literals. We now use OpReg instead of OpScalarAsVec as required since we broadcast a gp register. Also adds a test. Fixes #27565. - - - - - 94822c95 by Andreas Klebinger at 2026-08-26T15:09:24-04:00 Add some test cases covering bugs in the arm ncg. * Test for #27430 (subword ffi results) * #27537 - subword conversions * #27538 - subwords used in conditional * #27533 - single byte read - - - - - dd1ba88a by Andreas Klebinger at 2026-08-26T15:09:24-04:00 cmmLint: Lint against MO_FS_Truncate subword use. - - - - - fd22f71e by Zubin Duggal at 2026-08-26T15:10:20-04:00 ghc-internal: annotateSTM should use catchSTM# rather than catch# A catch# frame inside a transaction breaks retry and async exception delivery. Fixes #27657 - - - - - bb324171 by Rodrigo Mesquita at 2026-08-26T15:10:59-04:00 rts: refactor to reduce THREADED_RTS in MSG_UPD_TSO_FLAGS - No behavior change in this commit (well, a small optimization here makes us do less work if the target TSO owned by the curr. capability) - Move all THREADED_RTS CPP needed into `updThreadFlag` - Merge MSG_SET_TSO_FLAGS and MSG_UNSET_TSO_FLAGS into MSG_UPD_TSO_FLAGS plus a `set` bool field in the MessageUpdTSOFlag struct Towards #27729 - - - - - ed99b7b7 by Rodrigo Mesquita at 2026-08-26T15:10:59-04:00 rts: Fix race condition in MSG_UPD_TSO_FLAGS execution The code for processing the MSG_UPD_TSO_FLAGS message was not taking into consideration that the TSO's owner might have moved in between that capability receiving the message (since it was its previous owner) and starting to process its inbox (a point at which it was no longer the owner) Added Note [TSO owner may change in between Msg being sent and received] to explain this race and the pattern used to fix this, where we just forward the message to the new owner. Fixes #27729 - - - - - cd653714 by Alan Zimmerman at 2026-08-26T15:11:49-04:00 EPA: Uses Parsers.parseModule for exactprint tests Parsers.parseModule is the advertised way to parse for use for exact printing in the ghc-exactprint library. This commit updates the GHC exact print testing to use it. This requires moving the comment balancing that was occurring only in the test path into the advertising parser path, so it moves from Transforms.hs to Utils.hs. Also update the comment adding to honour trailing annotations - - - - - d1d01fa5 by Wolfgang Jeltsch at 2026-08-27T13:17:59+03:00 Add `rethrowSTM` and improve STM-related documentation Adding `rethrowSTM` resolves #26758. The implementation of `rethrowSTM` is completely analogous to the one of `rethrowIO`. The following is established for the documentation of `throwSTM` and `catchSTM`: * Both operations are directly described as analogs of their `IO` counterparts. * There is no reference to `throw` in the documentation of `throwSTM`, because, although such a reference is great in the documentation of `throwIO`, it is somewhat out of place in the documentation of `throwSTM`. * Instead of repeating part of `throwIO`’s documentation, the documentation of `throwSTM` just recommends using `throwSTM` instead of `throw` and references the corresponding arguments in the documentation of `throwIO`. - - - - - 06fde293 by fendor at 2026-08-28T06:06:44-04:00 GHCi: Fix order of `PackageDBFlag`s for interactive home unit `PackageDBFlag`s are stored in reverse order of cli specification. When sorting the `PackageDBFlag`s by longest common prefix, we need thus to reverse the package db stacks before calculating the prefix. We make sure to reverse the package db stack for the interactive home unit to uphold that later specified package dbs overwrite earlier ones. Resolved and adds regression test for #27640 - - - - - 024c4d04 by fendor at 2026-08-28T06:07:23-04:00 Reuse the UnitIndexCache after initialising multiple home units - - - - - 55326fa0 by Alan Zimmerman at 2026-08-28T06:08:03-04:00 EPA: Some Haddock processing tweaks These changes to the Haddock postprocessing should not change behaviour, but just bring it more closely in line with the original, changed at 44309cd377f And add some haddock exactprint tests to show they work. - - - - - b3ddee95 by Andreas Klebinger at 2026-08-28T13:57:46-04:00 hadrian: Deprecate quickest flavour. It was more of a trap for new users than actually beneficial so we deprecate it and suggest quick+no_dynamic_libs to users instead. - - - - - a1d81390 by Andreas Klebinger at 2026-08-28T13:58:37-04:00 cmm: Always favour entry block during block deduplication. We now always keep the first block in the CmmGraph. This way we avoid the need to update the entry info table. Failing to do so caused #27722. Fixes #27722. - - - - - 5bd65f00 by Andreas Klebinger at 2026-08-28T13:59:16-04:00 test: FamAppCachePerf - Only collect bytes allocated. Fixes 27747 - - - - - ced53ce6 by mangoiv at 2026-08-29T07:15:24-04:00 nightlies: output yaml to file only Previously we would just output the metadata to stdout which risks that it's clobbered by incidental debugt output. We now output to file only. Fixes #27511 - - - - - 578bd185 by Andreas Klebinger at 2026-08-29T07:16:05-04:00 Specialise: Stop looping on recursive dictionaries in interestingDict interestingDict now doesn't look through loopbreaker unfoldings. Doing so would cause infinite loops on certain dictionaries. Fixes #27705. - - - - - 7bf546fc by Simon Peyton Jones at 2026-08-31T23:48:53-04:00 Never make an absent filler for a constraint type mkAbsentFiller used isTerminatingType to decide, but that is not enough. Consider class Eq a => UC a where {} let u :: UC Int -- UC Int is a "non-terminating type" u = error "Absent" let e :: Eq Int -- Eq Int is a "terminating type" e = $p1UC u We clearly must not make a filler for `e`, because we speculatively evaluate it. But speculatively evaluating `e` forces `u`, so we must not make one for `u` either. Asking isDictTy instead is not enough either, because it does not catch a constraint hidden behind an unreduced type family application: type family F a :: Constraint type instance F W = TC W a :: F W => Int -> Int -- (F W) argument is absent Oops! Entered absent arg Arg: irred Type: F W So play safe and use isPredTy: never make an absent filler for any constraint-kinded type. Fixes #27627 - - - - - 5f474953 by Zubin Duggal at 2026-08-31T23:48:53-04:00 Add tests for absent fillers at dictionary types T27627 a unary class whose superclass is a non-unary class T27627a ...whose superclass is a Constraint-kinded type family T27627b ...whose superclass is a quantified constraint T27627c a unary class applied to itself, (UC (UC (TC a))) T27627e a (forall b. P b) dictionary that loops - - - - - cd5c6bcc by Zubin Duggal at 2026-08-31T23:48:53-04:00 An abstract TyCon may hide a unary class A class declared in an hs-boot file is an AbstractTyCon inside the module loop, and compiling the real declaration may reveal it to be a UnaryClassTyCon. - isTerminatingType returned True for such AbstractTyCons - IfaceToCore set the unary flag to False in the DFunId So we could end up speculating bottom dictionaries because inside a module loop we see an UnaryClassTyCon as an AbstractTyCon Use isTerminatingTyCon, which returns False for an abstract TyCon. The Bool in DFunId is now a cache for isTerminatingTyCon, set in mkDFunIdDetails. Fixes #27704 - - - - - abfc224a by Zubin Duggal at 2026-08-31T23:48:53-04:00 Specialise: don't replace dead args with absent fillers specHeader decides an argument is dead by calling isDeadBinder on a binder of the /optimised RHS/, then applies the filler to the /stable unfolding/ template instead. The two may differ, so the argument can be dead in the RHS and not in the template. The specialised function's unfolding then has an absent filler, and any call site that inlines it evaluates the error thunk. Dropping dead args in the specialiser is rarely worth it, to quote Simon, "The later worker/wrapper pass will pick up the dead arg later if it is really dead. Keeps the specialiser simpler." So instead of trying to check if the arg really is dead in the stable unfolding, just drop the logic for dropping dead args in the specialiser altogeher. Fixes #27703 - - - - - 1557fd1c by Zubin Duggal at 2026-08-31T23:48:53-04:00 CorePrep: don't speculate a call across an hs-boot edge We take care not to evaluate things that might be bottom, like a looping dictionary group, but our analysis is defeated by boot files. We only track recursion within a module, so two dictionaries that depend on each other across a module loop each look non-recursive, and we might speculate them. Any recursion we cannot see must cross an hs-boot edge, so refuse to speculate calls that cross one. Fixes #27717 - - - - - 4117e5ae by Wolfgang Jeltsch at 2026-08-31T23:49:35-04:00 Incorporate the `rethrowSTM` reexport into the `stm` submodule - - - - - 4bfbf5c8 by ARATA Mizuki at 2026-09-01T18:55:08-04:00 testsuite: Fix out-of-bounds access in T3586 unsafeRead and unsafeWrite use 0-based index. Looking at #3586, the expected output seems to be 2.8e8. Addresses #27596 - - - - - 3f9db6d4 by ARATA Mizuki at 2026-09-01T18:55:08-04:00 testsuite: Fix out-of-bounds access in T21305 writeInt64Array# takes an index measured in units of Int64 elements. Fixes #27596 - - - - - 44d7788f by Simon Peyton Jones at 2026-09-01T18:55:53-04:00 Fix buglet in INLINE-arity calculation for pattern synonyms This fixes #27744. The buglet was accidentally introduced by commit 3a0f9a51c1dacc474c7fd128082edd8bf4081256 Author: Simon Peyton Jones <simon.peytonjones(a)gmail.com> Date: Sat Aug 1 00:13:02 2026 +0100 Fix three bugs related to required type args and INLINE pragmas I failed to find all the calls to `addInlinePragArity`! - - - - - df058f1d by Simon Jakobi at 2026-09-02T07:18:06-04:00 testsuite: Migrate perf tests off collect_compiler_stats('all') The 'all' metric argument applies a single tolerance to bytes allocated, max_bytes_used and peak_megabytes_allocated, although their noise profiles are incompatible (#27653): allocations are nearly deterministic, residency needs 10-20%, and peak is quantized to 1 MB. Any single tolerance is too tight for one metric or too slack for another. This migrates the remaining users of 'all' (and of the 'all' default) to explicit per-metric collection, ahead of removing 'all' from the driver. peak_megabytes_allocated is dropped everywhere: its 1 MB granularity makes tight relative windows meaningless (#27613), and it is sensitive to GC timing. In #27489 it drifted by -5.3% while max_bytes_used moved by less than 0.1%. Where a test guards a memory property, max_bytes_used covers it at byte granularity. Where the motivating ticket was about compile-time memory (T11545, T15304, T26425), residency remains gated via max_bytes_used, now with a residency-appropriate tolerance. max_bytes_used is dropped where residency was only ever an accident of 'all': * T15630, T15630a, T20261: the underlying tickets (#15630, #20261) contain no memory data at all. One is a simplifier-ticks blowup and the other is stated entirely in allocation numbers, so the 20% window never had teeth. * T21839c: #21839's measurements show residency essentially flat (+0.16%) while allocations moved +7%, so allocations are the discriminating metric. They are already gated at 1% via collect_compiler_runtime. The ghc/max gate had previously broken CI spuriously (9fd11585eb widened it from 1% to 10% for that reason). Allocation tolerances are tightened to the testsuite's conventional 2% where 'all' previously left them at 10-20%. Assisted-by: Claude Fable 5 - - - - - 72dd2432 by Simon Jakobi at 2026-09-02T07:18:06-04:00 testsuite: Remove the 'all' metric argument of collect_stats 'all' gated bytes allocated, max_bytes_used and peak_megabytes_allocated at a single tolerance, although their noise profiles are incompatible, making such tests either flaky or toothless (#27653). Closes #27653. Assisted-by: Claude Fable 5 - - - - - 2228cb30 by Simon Jakobi at 2026-09-02T07:18:06-04:00 testsuite: Make the deviation argument of collect_stats mandatory Almost every caller passes an explicit tolerance matched to the metric's noise profile, and the silent 20% default is far slacker than 'bytes allocated' merits. Only two tests relied on it. They now state their tolerance explicitly: large-project gets 10%, in line with other large compile-time tests. T9848 gets 2%: its metric is byte-for-byte deterministic across CI jobs and platforms of a given test_env, has drifted only about 2.5% since 2015, and the fusion failure it guards against would show up as a roughly +30000% jump. Assisted-by: Claude Fable 5 - - - - - 56291fc5 by Cheng Shao at 2026-09-02T07:18:45-04:00 autoconf/ghc-toolchain: bump llvm upper bound to support llvm 23 This commit bumps llvm upper bound to support llvm 23. - - - - - 20eb3f41 by Cheng Shao at 2026-09-02T07:18:45-04:00 rts: fix compilation issues with clang 23 clang 23 has broadened `-Wall`/`-Wextra` ranges, exposing some minor issues in the rts when building with validate flavours: - Unused locals - `#pragma GCC diagnostic pop` mismatch This commit fixes those. - - - - - 421ef3f6 by Simon Peyton Jones at 2026-09-03T10:09:12+01:00 Move HsStatic free-var test to typechecker A `static` form should have no free *term* variables, but it can have free *type* variables. Alas, the renamer does not really know what is a term variable and what is a type variable, because of required type arguments. This patch moves the test to the typechecker, which does know. Addresses #27664 - - - - - 255 changed files: - .gitlab-ci.yml - .gitlab/ci.sh - .gitlab/rel_eng/mk-ghcup-metadata/mk_ghcup_metadata.py - + changelog.d/27627 - + changelog.d/27703 - + changelog.d/27704 - + changelog.d/27717 - changelog.d/T27202 - + changelog.d/T27657 - + changelog.d/T27705 - + changelog.d/T27722-cbe-entry-block.md - + changelog.d/T27744 - + changelog.d/T27764 - + changelog.d/arm_ncg_fixes_T27430 - + changelog.d/llvm-23 - + changelog.d/rethrow-stm - changelog.d/unit-index - compiler/GHC/Builtin.hs - compiler/GHC/Builtin/WiredIn/Types.hs - compiler/GHC/Cmm/CommonBlockElim.hs - compiler/GHC/Cmm/Expr.hs - compiler/GHC/Cmm/Lint.hs - compiler/GHC/Cmm/MachOp.hs - compiler/GHC/Cmm/Parser.y - compiler/GHC/CmmToAsm/AArch64/CodeGen.hs - compiler/GHC/CmmToAsm/AArch64/Instr.hs - compiler/GHC/CmmToAsm/AArch64/Ppr.hs - compiler/GHC/CmmToAsm/Format.hs - compiler/GHC/Core.hs - compiler/GHC/Core/Class.hs - compiler/GHC/Core/Opt/Specialise.hs - compiler/GHC/Core/Opt/WorkWrap/Utils.hs - compiler/GHC/Core/TyCon.hs - compiler/GHC/Core/Type.hs - compiler/GHC/Core/Utils.hs - compiler/GHC/CoreToIface.hs - compiler/GHC/CoreToStg/Prep.hs - compiler/GHC/Data/BooleanFormula.hs - compiler/GHC/Data/Word64Map/Internal.hs - compiler/GHC/Data/Word64Map/Lazy.hs - compiler/GHC/Data/Word64Map/Strict.hs - compiler/GHC/Data/Word64Map/Strict/Internal.hs - compiler/GHC/Driver/GenerateCgIPEStub.hs - compiler/GHC/Driver/Session/Units.hs - compiler/GHC/Hs.hs - compiler/GHC/Hs/Dump.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/Utils.hs - compiler/GHC/Iface/Binary.hs - compiler/GHC/Iface/Ext/Ast.hs - compiler/GHC/Iface/Syntax.hs - compiler/GHC/Iface/Tidy/StaticPtrTable.hs - compiler/GHC/IfaceToCore.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/Annotation.hs - compiler/GHC/Parser/PostProcess.hs - compiler/GHC/Parser/PostProcess/Haddock.hs - compiler/GHC/Rename/Expr.hs - compiler/GHC/Tc/Gen/Expr.hs - compiler/GHC/Tc/Solver/InertSet.hs - compiler/GHC/Tc/TyCl/Class.hs - compiler/GHC/Tc/TyCl/PatSyn.hs - compiler/GHC/Types/Demand.hs - compiler/GHC/Types/Id/Info.hs - compiler/GHC/Types/Id/Make.hs - compiler/GHC/Types/Literal.hs - compiler/GHC/Types/Unique/DFM.hs - compiler/GHC/Types/Var.hs - compiler/Language/Haskell/Syntax/BooleanFormula.hs - compiler/Language/Haskell/Syntax/Extension.hs - configure.ac - ghc/GHCi/UI.hs - hadrian/README.md - hadrian/doc/cross-compile.md - hadrian/doc/flavours.md - hadrian/doc/make.md - hadrian/doc/windows.md - hadrian/hadrian.cabal - hadrian/src/CommandLine.hs - hadrian/src/Flavour.hs - hadrian/src/Settings.hs - − hadrian/src/Settings/Flavours/Quickest.hs - libraries/base/base.cabal.in - libraries/base/changelog.md - + libraries/base/src/Data/RealFloat.hs - libraries/base/src/GHC/Conc.hs - libraries/base/tests/all.T - libraries/ghc-internal/src/GHC/Internal/STM.hs - libraries/stm - rts/CloneStack.c - rts/Interpreter.c - rts/Messages.c - rts/ProfHeap.c - rts/StgMiscClosures.cmm - rts/Threads.c - rts/Threads.h - rts/eventlog/EventLog.c - rts/include/rts/storage/Closures.h - rts/include/stg/MiscClosures.h - rts/linker/elf_reloc_riscv64.c - rts/prim/atomic.c - testsuite/driver/README.md - testsuite/driver/perf_notes.py - testsuite/driver/testglobals.py - testsuite/driver/testlib.py - testsuite/tests/cmm/should_compile/Makefile - + testsuite/tests/cmm/should_compile/T27368-ppr-debug.stderr - − testsuite/tests/cmm/should_compile/T27368-ppr-debug.stdout - testsuite/tests/cmm/should_compile/all.T - + testsuite/tests/codeGen/should_run/T27430.hs - + testsuite/tests/codeGen/should_run/T27430.stdout - + testsuite/tests/codeGen/should_run/T27430_c.c - + testsuite/tests/codeGen/should_run/T27533.hs - + testsuite/tests/codeGen/should_run/T27533.stdout - + testsuite/tests/codeGen/should_run/T27533_cmm.cmm - + testsuite/tests/codeGen/should_run/T27537.hs - + testsuite/tests/codeGen/should_run/T27537.stdout - + testsuite/tests/codeGen/should_run/T27538.hs - + testsuite/tests/codeGen/should_run/T27538.stdout - testsuite/tests/codeGen/should_run/all.T - + testsuite/tests/concurrent/should_run/T27657a.hs - 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testsuite/tests/printer/Test20297.stdout - testsuite/tests/printer/Test24533.stdout - testsuite/tests/printer/all.T - testsuite/tests/process/process009.hs - testsuite/tests/process/process009.stdout - testsuite/tests/rename/should_fail/RnStaticPointersFail01.stderr - testsuite/tests/rename/should_fail/RnStaticPointersFail03.stderr - testsuite/tests/rename/should_fail/T26545.stderr - + testsuite/tests/simd/should_run/T27565.hs - + testsuite/tests/simd/should_run/T27565.stdout - testsuite/tests/simd/should_run/all.T - testsuite/tests/simplCore/should_compile/T17966.stderr - testsuite/tests/simplCore/should_compile/T7785.stderr - testsuite/tests/simplCore/should_compile/spec004.hs - testsuite/tests/simplCore/should_compile/spec004.stderr - + testsuite/tests/simplCore/should_run/T27703/Lib.hs - + testsuite/tests/simplCore/should_run/T27703/Main.hs - + testsuite/tests/simplCore/should_run/T27703/T27703.stdout - + testsuite/tests/simplCore/should_run/T27703/all.T - + testsuite/tests/simplCore/should_run/T27705.hs - + testsuite/tests/simplCore/should_run/T27705.stdout - + testsuite/tests/simplCore/should_run/T27705_Inst.hs - testsuite/tests/simplCore/should_run/all.T - + testsuite/tests/typecheck/should_compile/T27664.hs - testsuite/tests/typecheck/should_compile/all.T - utils/check-exact/ExactPrint.hs - utils/check-exact/Main.hs - utils/check-exact/Parsers.hs - utils/check-exact/Transform.hs - utils/check-exact/Utils.hs - utils/ghc-toolchain/src/GHC/Toolchain/Program.hs - utils/ghc-toolchain/src/GHC/Toolchain/Target.hs - utils/haddock/haddock-api/src/Haddock/Backends/Xhtml/Decl.hs - utils/haddock/haddock-api/src/Haddock/Interface/Rename.hs - utils/haddock/haddock-api/src/Haddock/Types.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/16157a5dbd87a605534ddb19bcbb63… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/16157a5dbd87a605534ddb19bcbb63… You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help

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