July 2026 - ghc-commits

[Git][ghc/ghc][wip/marge_bot_batch_merge_job] 4 commits: Ignore ticks in the pattern-match term oracle
by Marge Bot (＠marge-bot) 19 Jul '26

19 Jul '26

Marge Bot pushed to branch wip/marge_bot_batch_merge_job at Glasgow Haskell Compiler / GHC Commits: b388d093 by Brian McKenna at 2026-07-18T17:51:50-04:00 Ignore ticks in the pattern-match term oracle The term-oracle in the pattern-match checker is keyed by a canonical form of the scrutinee, computed by `makeDictsCoherent`. That canonical form was tick-sensitive: two occurrences of an otherwise identical expression that happened to carry different ticks were treated as distinct values, breaking long-distance information. This shows up in practice under `-finfo-table-map`, because the desugarer wraps every record-selector use site in a `SourceNote` carrying that site's span. For example: data Box = Box { unBox :: Maybe Int } f b = case unBox b of Nothing -> 0 Just _ -> let Just x = unBox b in x The two `unBox b` expressionss carry different SourceNote spans, the pattern-match checker sees them as different, the long-distance information from the outer `Just _` branch never reaches the let-pattern, and `Just x = unBox b` is wrongly reported as non-exhaustive. We now strip all ticks in `makeDictsCoherent`. This is documented as Wrinkle (UD1) of Note [Unique dictionaries in the TmOracle CoreMap]. Fixes #27314 - - - - - c23e1acb by Mrjtjmn at 2026-07-18T17:52:45-04:00 Add explanations for unsolved Typeable constraints This commit adds explanations for unsolved 'Typeable' constraints. GHC will now provide additional explanations for an unsolved constraint of the form 'Typeable ty', explain why GHC did not solve Typeable constraint. e.g.: - 'ty' is a polymorphic type (e.g. forall a. a -> a) - 'ty' is a qualified type (e.g. Eq Int => Int) - 'ty' is an unboxed sum type - 'ty' is an unreduced type family application - 'ty' whose kind is not typeable Fixes #26532 - - - - - 3d51b87e by Artem Pelenitsyn at 2026-07-19T04:39:33-04:00 ghc-internal: Lock.hs: fix typo and indentation - - - - - 622b50f4 by Duncan Coutts at 2026-07-19T04:39:34-04:00 Fix failing test GcStaticPointers for non-moving GC Minor mistake in asserting something before checking for that same thing. Specifically, Bdescr asserts HEAP_ALLOCED_GC, but Bdescr was being used prior to a guard that checks HEAP_ALLOCED_GC. The solution is just to move the use of Bdescr after the guard. Thanks to Simon Jakobi for identifying the problem. - - - - - 17 changed files: - + changelog.d/T26532 - + changelog.d/T27314.md - compiler/GHC/HsToCore/Pmc/Solver.hs - compiler/GHC/Tc/Errors.hs - compiler/GHC/Tc/Errors/Ppr.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/Instance/Typeable.hs - libraries/ghc-internal/src/GHC/Internal/IO/Handle/Lock.hs - rts/sm/NonMovingMark.c - + testsuite/tests/pmcheck/should_compile/T27314.hs - testsuite/tests/pmcheck/should_compile/all.T - testsuite/tests/typecheck/should_fail/T15067.stderr - + testsuite/tests/typecheck/should_fail/T26532.hs - + testsuite/tests/typecheck/should_fail/T26532.stderr - testsuite/tests/typecheck/should_fail/T9858b.stderr - testsuite/tests/typecheck/should_fail/TcStaticPointersFail02.stderr - testsuite/tests/typecheck/should_fail/all.T Changes: ===================================== changelog.d/T26532 ===================================== @@ -0,0 +1,8 @@ +section: compiler +issues: #26532 +mrs: !16351 +synopsis: + Add explanations for unsolved Typeable constraints +description: + GHC now provides additional explanations for an unsolved constraint of the + form ``Typeable ty``, explain why GHC did not solve ``Typeable`` constraint. ===================================== changelog.d/T27314.md ===================================== @@ -0,0 +1,10 @@ +section: compiler +issues: #27314 +mrs: !16118 +synopsis: + Fix spurious ``-Wincomplete-uni-patterns`` warning under ``-finfo-table-map``. +description: + The pattern-match checker now ignores ticks when comparing scrutinees in + its CoreMap, so long-distance information is no longer lost across + function-application scrutinees because debug source annotations + (e.g. SourceNotes added by ``-finfo-table-map``) were inserted. ===================================== compiler/GHC/HsToCore/Pmc/Solver.hs ===================================== @@ -1000,8 +1000,9 @@ makeDictsCoherent (Case scrut bndr ty alts) , let expr' = makeDictsCoherent expr ] makeDictsCoherent (Cast expr co) = Cast (makeDictsCoherent expr) co -makeDictsCoherent (Tick tick expr) - = Tick tick (makeDictsCoherent expr) +makeDictsCoherent (Tick _tick expr) + -- See Wrinkle (UD1) in Note [Unique dictionaries in the TmOracle CoreMap] + = makeDictsCoherent expr makeDictsCoherent ty@(Type {}) = ty makeDictsCoherent co@(Coercion {}) @@ -1061,6 +1062,25 @@ In the end, replacing dictionaries with an error value in the pattern-match checker was the most self-contained, although we might want to revisit once we implement a more robust approach to computing equality in the pattern-match checker (see #19272). + +Wrinkle (UD1): ticks +-------------------- +'makeDictsCoherent' also drops all ticks. The CoreMap key represents +value-level equality, which ticks never affect. + +Example (#27314): with -finfo-table-map every record-selector use site is +wrapped in a 'SourceNote' carrying that site's span (see +Note [Record-selector ticks] in GHC.HsToCore.Ticks). Given + + data Box = Box { unBox :: Maybe Int } + f b = case unBox b of + Nothing -> 0 + Just _ -> let Just x = unBox b in x + +the two `unBox b`s carry different SourceNote spans. Without tick stripping +the CoreMap treats them as distinct expressions. Long-distance information +from the outer `Just _` branch therefore never reaches the let-pattern, and +`Just x = unBox b` is wrongly reported as non-exhaustive. -} {- Note [The Pos/Neg invariant] ===================================== compiler/GHC/Tc/Errors.hs ===================================== @@ -12,7 +12,7 @@ module GHC.Tc.Errors( import GHC.Prelude -import GHC.Builtin.Names (hasFieldClassName) +import GHC.Builtin.Names (hasFieldClassName, typeableClassName) import GHC.Driver.Env (hsc_units) import GHC.Driver.DynFlags @@ -21,6 +21,7 @@ import GHC.Driver.Config.Diagnostic import GHC.Rename.Unbound +import GHC.Tc.Instance.Typeable (kindIsTypeable) import GHC.Tc.Types import GHC.Tc.Utils.Monad import GHC.Tc.Errors.Types @@ -2565,9 +2566,52 @@ getNoBuiltinInstMsg item = do { rdr_env <- getGlobalRdrEnv ; fam_envs <- tcGetFamInstEnvs ; mbNoHasFieldMsg <- hasFieldInfo_maybe rdr_env fam_envs item - ; return $ fmap NoBuiltinHasFieldMsg mbNoHasFieldMsg + ; mbNoTypeableMsg <- typeableInfo_maybe item + ; return $ case (mbNoHasFieldMsg, mbNoTypeableMsg) of + (Just hasFieldMsg, _) -> Just $ NoBuiltinHasFieldMsg hasFieldMsg + (_, Just typeableMsg) -> Just $ NoBuiltinTypeableMsg typeableMsg + _ -> Nothing } +-- | Try to produce an explanatory message for why GHC was not able to use +-- a built-in instance to solve a 'Typeable' constraint. +typeableInfo_maybe :: ErrorItem -> TcM (Maybe TypeableMsg) +typeableInfo_maybe item + | Just ty <- typeable_maybe (errorItemPred item) + = if -- Polymorphic types like (forall a. a -> a) are not typeable + -- see Note [No Typeable for polytypes or qualified types] in GHC.Tc.Instance.Class + | isForAllTy ty -> return $ Just $ NoTypeableForPolytype ty + + -- Qualified types like (Num a => blah) are not typeable + | Just (af,_mult_,_arg,_ret) <- splitFunTy_maybe ty + , not $ isVisibleFunArg af + -> return $ Just $ NoTypeableForQualifiedType ty + + -- Unboxed sum types like (# Int, Int #) are not typeable + | Just (tc, _tys) <- splitTyConApp_maybe ty + , isUnboxedSumTyCon tc -> return $ Just $ NoTypeableForUnboxedSumType ty + + -- Unreduced type family applications are not typeable + | Just (tc, _tys) <- splitTyConApp_maybe ty + , isTypeFamilyTyCon tc -> return $ Just $ NoTypeableForUnreducedTypeFamilyApplication ty + + -- TyCons whose kind is non-typeable, are not typeable + | Just (tc, _tys) <- splitTyConApp_maybe ty + , not (kindIsTypeable (tyConKind tc)) + -> return $ Just $ NoTypeableForTyConWithNonTypeableKind ty (tyConKind tc) + + | otherwise -> return Nothing + | otherwise = return Nothing + +-- | Is this constraint definitely a 'Typeable' constraint? +typeable_maybe :: PredType -> Maybe Type +typeable_maybe pred = + case classifyPredType pred of + ClassPred cls tys + | className cls == typeableClassName, [_k, ty] <- tys -> Just ty + _ -> Nothing + + {- Note [Error messages for unsolved HasField constraints] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The HasField type-class has special instance solving logic, implemented in @@ -2781,7 +2825,7 @@ hasFieldInfo_maybe rdr_env fam_inst_envs item -> TcM (Maybe (Either (PatSyn, SimilarName) (TyCon, SimilarName))) with_parent n = fmap (bimap (,n) (,n)) <$> get_parent n --- | Is this constraint definitely 'HasField'? +-- | Is this constraint definitely a 'HasField' constraint? hasField_maybe :: PredType -> Maybe (Type, Type, Type) hasField_maybe pred = case classifyPredType pred of ===================================== compiler/GHC/Tc/Errors/Ppr.hs ===================================== @@ -4314,15 +4314,6 @@ pprTcSolverReportMsg ctxt | any isFunTy (filterOutInvisibleTypes (classTyCon clas) tys) = text "(maybe you haven't applied a function to enough arguments?)" - -- Clarify the mysterious "No instance for (Typeable T) - | className clas == typeableClassName - , [_,ty] <- tys -- Look for (Typeable (k->*) (T k)) - , Just (tc,_) <- tcSplitTyConApp_maybe ty - , not (isTypeFamilyTyCon tc) - = hang (text "GHC can't yet do polykinded") - 2 (text "Typeable" <+> - parens (ppr ty <+> dcolon <+> ppr (typeKind ty))) - | otherwise = empty @@ -5200,6 +5191,7 @@ pprCoercibleMsg (OutOfScopeNewtypeConstructor dc import_suggs) = pprNoBuiltinInstanceMsg :: NoBuiltinInstanceMsg -> SDoc pprNoBuiltinInstanceMsg = \case NoBuiltinHasFieldMsg msg -> pprHasFieldMsg msg + NoBuiltinTypeableMsg msg -> pprTypeableMsg msg pprHasFieldMsg :: HasFieldMsg -> SDoc pprHasFieldMsg = \case @@ -5278,6 +5270,28 @@ pprHasFieldPatSynMsg fld pat_syns = in packHText occ == field_label fld +pprTypeableMsg :: TypeableMsg -> SDoc +pprTypeableMsg = \case + NoTypeableForPolytype ty -> + ppr_is ty "a polymorphic type" + NoTypeableForQualifiedType ty -> + ppr_is ty "a qualified type" + NoTypeableForUnboxedSumType ty -> + ppr_is ty "an unboxed sum type" + NoTypeableForUnreducedTypeFamilyApplication ty -> + ppr_is ty "an unreduced type family application" + NoTypeableForTyConWithNonTypeableKind ty k -> + vcat + [ text "NB:" <+> "The kind of" <+> quotes (ppr ty) + , nest 2 (quotes (ppr k)) <+> "contains foralls," + , "for which the built-in" + <+> quotes (text "Typeable") <+> text "solver cannot produce evidence." ] + where + ppr_is ty reason = + text "NB:" <+> quotes (ppr ty) <+> text "is" <+> text reason + $$ "for which the built-in" + <+> quotes (text "Typeable") <+> text "solver cannot produce evidence." + pprWhenMatching :: SolverReportErrCtxt -> WhenMatching -> SDoc pprWhenMatching ctxt (WhenMatching cty1 cty2 sub_o mb_sub_t_or_k) = sdocOption sdocPrintExplicitCoercions $ \printExplicitCoercions -> @@ -5516,6 +5530,7 @@ tcSolverReportMsgHints ctxt = \case noBuiltinInstanceHints :: NoBuiltinInstanceMsg -> [GhcHint] noBuiltinInstanceHints = \case NoBuiltinHasFieldMsg noHasFieldMsg -> hasFieldMsgHints noHasFieldMsg + NoBuiltinTypeableMsg _ -> noHints hasFieldMsgHints :: HasFieldMsg -> [GhcHint] hasFieldMsgHints = \case @@ -7998,4 +8013,3 @@ pprHsCtxt = \case ppr_stmt (TransStmt { trS_by = by, trS_using = using , trS_form = form }) = pprTransStmt by using form ppr_stmt stmt = pprStmt stmt - ===================================== compiler/GHC/Tc/Errors/Types.hs ===================================== @@ -78,6 +78,7 @@ module GHC.Tc.Errors.Types ( , CoercibleMsg(..) , NoBuiltinInstanceMsg(..) , HasFieldMsg(..) + , TypeableMsg(..) , TooFancyField(..) , PotentialInstances(..) , UnsupportedCallConvention(..) @@ -6034,9 +6035,9 @@ data CoercibleMsg -- a particular class. data NoBuiltinInstanceMsg = NoBuiltinHasFieldMsg HasFieldMsg + | NoBuiltinTypeableMsg TypeableMsg -- Other useful constructors might be: - -- NoBuiltinTypeableMsg -- explains polykinded Typeable restrictions -- NoBuiltinDataToTagMsg -- see conditions in Note [DataToTag overview] -- NoBuiltinWithDictMsg -- see Note [withDict] @@ -6066,6 +6067,20 @@ data HasFieldMsg -- | Using -XRebindableSyntax and a different 'HasField'. | CustomHasField TyCon -- ^ the custom HasField TyCon +-- | Explains why GHC wasn't able to provide a built-in 'Typeable' instance +-- for the given types. +data TypeableMsg + -- | Polymorphic types are not typeable. + = NoTypeableForPolytype Type + -- | Qualified types are not typeable. + | NoTypeableForQualifiedType Type + -- | Unboxed sum types are not typeable. + | NoTypeableForUnboxedSumType Type + -- | Unreduced Type Family Applications are not typeable. + | NoTypeableForUnreducedTypeFamilyApplication Type + -- | TyCons whose kind is not typeable are not typeable. + | NoTypeableForTyConWithNonTypeableKind Type Kind + -- | Why is a record field "too fancy" for GHC to be able to properly -- solve a 'HasField' constraint? data TooFancyField ===================================== compiler/GHC/Tc/Instance/Typeable.hs ===================================== @@ -7,7 +7,12 @@ {-# LANGUAGE RecordWildCards #-} {-# LANGUAGE TypeFamilies #-} -module GHC.Tc.Instance.Typeable(mkTypeableBinds, tyConIsTypeable) where +module GHC.Tc.Instance.Typeable ( + mkTypeableBinds + , tyConIsTypeable + , kindIsTypeable + ) +where import GHC.Prelude import GHC.Platform ===================================== libraries/ghc-internal/src/GHC/Internal/IO/Handle/Lock.hs ===================================== @@ -40,14 +40,14 @@ import GHC.Internal.IO.Handle.Lock.NoOp -- to interrupt it with asynchronous exceptions and/or for other threads to -- continue working, you MUST use threaded version of the runtime system. -- --- 2. The implementation uses relies on any of a number of locking --- facilities, depending upon what the platform supports: +-- 2. The implementation relies on any of a number of locking +-- facilities, depending upon what the platform supports: -- --- * 'LockFileEx' is used on Windows --- * On platforms that support it we use the @F_OFD_SETLK@ and @F_OFD_SETLKW@ @fnctl@s. --- * Otherwise we use @flock@ +-- * 'LockFileEx' is used on Windows +-- * On platforms that support it we use the @F_OFD_SETLK@ and @F_OFD_SETLKW@ @fnctl@s. +-- * Otherwise we use @flock@ -- --- hence all of their caveats also apply here. +-- All of their caveats also apply here. -- -- 3. On non-Windows platforms that don't support 'flock' (e.g. Solaris) this -- function throws 'FileLockingNotImplemented'. We deliberately choose to not ===================================== rts/sm/NonMovingMark.c ===================================== @@ -2018,8 +2018,10 @@ bool nonmovingTidyWeaks (struct MarkQueue_ *queue) // See Note [Weak pointer processing and the non-moving GC] in // MarkWeak.c - bdescr *key_bd = Bdescr((StgPtr) w->key); - bool key_in_nonmoving = HEAP_ALLOCED_GC(w->key) && block_get_flags(key_bd) & BF_NONMOVING; + bool key_in_nonmoving = + HEAP_ALLOCED_GC(w->key) && + block_get_flags(Bdescr((StgPtr) w->key)) & BF_NONMOVING; + if (!key_in_nonmoving || nonmovingIsNowAlive(w->key)) { nonmovingMarkLiveWeak(queue, w); did_work = true; ===================================== testsuite/tests/pmcheck/should_compile/T27314.hs ===================================== @@ -0,0 +1,8 @@ +module T27314 where + +data Box = Box { unBox :: Maybe Int } + +f :: Box -> Int +f b = case unBox b of + Nothing -> 0 + Just _ -> let Just x = unBox b in x ===================================== testsuite/tests/pmcheck/should_compile/all.T ===================================== @@ -93,6 +93,14 @@ test('T21360', normal, compile, [overlapping_incomplete+'-Wincomplete-record-upd test('T21360b', normal, compile, [overlapping_incomplete+'-Wincomplete-record-updates']) test('T23520', normal, compile, [overlapping_incomplete+'-Wincomplete-record-updates']) test('T25164', [extra_files(['T25164_aux.hs']), req_th], multimod_compile, ['T25164', '-v0']) +test( + 'T27314', + [ omit_ways(llvm_ways), # -finfo-table-map does not work with -fllvm (#26435) + when(js_arch(), skip) # javascript doesn't support -finfo-table-map yet and yields a warning we don't want to handle here + ], + compile, + ['-Wincomplete-uni-patterns -finfo-table-map'] +) # Other tests test('pmc001', [], compile, [overlapping_incomplete]) ===================================== testsuite/tests/typecheck/should_fail/T15067.stderr ===================================== @@ -1,13 +1,7 @@ T15067.hs:9:14: error: [GHC-39999] • No instance for ‘Typeable (# | #)’ arising from a use of ‘typeRep’ - GHC can't yet do polykinded - Typeable ((# | #) :: * - -> * - -> TYPE - (GHC.Internal.Types.SumRep - [GHC.Internal.Types.LiftedRep, - GHC.Internal.Types.LiftedRep])) + NB: ‘(# | #)’ is an unboxed sum type + for which the built-in ‘Typeable’ solver cannot produce evidence. • In the expression: typeRep In an equation for ‘floopadoop’: floopadoop = typeRep - ===================================== testsuite/tests/typecheck/should_fail/T26532.hs ===================================== @@ -0,0 +1,35 @@ +{-# LANGUAGE ImpredicativeTypes #-} +{-# LANGUAGE UnboxedSums #-} +{-# LANGUAGE TypeFamilies #-} + +module T26532 where + +import Data.Kind +import Type.Reflection + +test1 :: TypeRep (forall a. a -> a) +test1 = typeRep + +test2 :: TypeRep (Eq Int => Int) +test2 = typeRep + +test3 :: TypeRep (((),()) => Int) +test3 = typeRep + +test4 :: TypeRep (# Int | Bool #) +test4 = typeRep + +type F :: Type -> Type +type family F a where {} + +test5 :: TypeRep (F Int) +test5 = typeRep + +type PolyDF :: forall k. Type -> k +data family PolyDF a + +type ProxyPolyDF :: (forall k. Type -> k) -> Type +data ProxyPolyDF f = MkProxy + +test6 :: TypeRep (ProxyPolyDF PolyDF) +test6 = typeRep ===================================== testsuite/tests/typecheck/should_fail/T26532.stderr ===================================== @@ -0,0 +1,50 @@ +T26532.hs:11:9: error: [GHC-39999] + • No instance for ‘Typeable (forall a. a -> a)’ + arising from a use of ‘typeRep’ + NB: ‘forall a. a -> a’ is a polymorphic type + for which the built-in ‘Typeable’ solver cannot produce evidence. + • In the expression: typeRep + In an equation for ‘test1’: test1 = typeRep + +T26532.hs:14:9: error: [GHC-39999] + • No instance for ‘Typeable (Eq Int => Int)’ + arising from a use of ‘typeRep’ + NB: ‘Eq Int => Int’ is a qualified type + for which the built-in ‘Typeable’ solver cannot produce evidence. + • In the expression: typeRep + In an equation for ‘test2’: test2 = typeRep + +T26532.hs:17:9: error: [GHC-39999] + • No instance for ‘Typeable + ((() :: Constraint, () :: Constraint) => Int)’ + arising from a use of ‘typeRep’ + NB: ‘(() :: Constraint, () :: Constraint) => + Int’ is a qualified type + for which the built-in ‘Typeable’ solver cannot produce evidence. + • In the expression: typeRep + In an equation for ‘test3’: test3 = typeRep + +T26532.hs:20:9: error: [GHC-39999] + • No instance for ‘Typeable (# | #)’ + arising from a use of ‘typeRep’ + NB: ‘(# | #)’ is an unboxed sum type + for which the built-in ‘Typeable’ solver cannot produce evidence. + • In the expression: typeRep + In an equation for ‘test4’: test4 = typeRep + +T26532.hs:26:9: error: [GHC-39999] + • No instance for ‘Typeable (F Int)’ + arising from a use of ‘typeRep’ + NB: ‘F Int’ is an unreduced type family application + for which the built-in ‘Typeable’ solver cannot produce evidence. + • In the expression: typeRep + In an equation for ‘test5’: test5 = typeRep + +T26532.hs:35:9: error: [GHC-39999] + • No instance for ‘Typeable ProxyPolyDF’ + arising from a use of ‘typeRep’ + NB: The kind of ‘ProxyPolyDF’ + ‘(forall k. * -> k) -> *’ contains foralls, + for which the built-in ‘Typeable’ solver cannot produce evidence. + • In the expression: typeRep + In an equation for ‘test6’: test6 = typeRep ===================================== testsuite/tests/typecheck/should_fail/T9858b.stderr ===================================== @@ -2,7 +2,8 @@ T9858b.hs:7:8: error: [GHC-39999] • No instance for ‘Typeable (Eq Int => Int)’ arising from a use of ‘typeRep’ - (maybe you haven't applied a function to enough arguments?) + NB: ‘Eq Int => Int’ is a qualified type + for which the built-in ‘Typeable’ solver cannot produce evidence. • In the expression: typeRep (Proxy :: Proxy (Eq Int => Int)) In an equation for ‘test’: test = typeRep (Proxy :: Proxy (Eq Int => Int)) ===================================== testsuite/tests/typecheck/should_fail/TcStaticPointersFail02.stderr ===================================== @@ -11,6 +11,7 @@ TcStaticPointersFail02.hs:12:6: error: [GHC-39999] • No instance for ‘ghc-internal-0.1.0.0:GHC.Internal.Data.Typeable.Internal.Typeable (Monad m => a -> m a)’ arising from a static form - (maybe you haven't applied a function to enough arguments?) + NB: ‘Monad m => a -> m a’ is a qualified type + for which the built-in ‘Typeable’ solver cannot produce evidence. • In the expression: static return In an equation for ‘f2’: f2 = static return ===================================== testsuite/tests/typecheck/should_fail/all.T ===================================== @@ -761,3 +761,4 @@ test('T26823', normal, compile_fail, ['']) test('T26861', normal, compile_fail, ['']) test('T26862', normal, compile_fail, ['']) test('T27210', normal, compile_fail, ['']) +test('T26532', normal, compile_fail, ['']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/093125f22169b65bc0e9b00490ea2a… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/093125f22169b65bc0e9b00490ea2a… You're receiving this email because of your account on gitlab.haskell.org. 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[Git][ghc/ghc][wip/sjakobi/nonmoving-gc-timeout] 25 commits: Coercion optimisation: avoid double-Sym for InstCo
by Simon Jakobi (＠sjakobi2) 19 Jul '26

19 Jul '26

Simon Jakobi pushed to branch wip/sjakobi/nonmoving-gc-timeout at Glasgow Haskell Compiler / GHC Commits: 722236dd by sheaf at 2026-07-18T08:48:31-04:00 Coercion optimisation: avoid double-Sym for InstCo Ticket #27374 pointed out an issue with GHC.Core.Coercion.Opt.optCoercion's handling of InstCo: it contravened (LC2) in Note [The LiftingContext in optCoercion] because it applied the ambient 'sym' to a coercion that was then added to the lifting context substitution. Fixes #27374 Co-authored-by: Simon Jakobi <simon.jakobi(a)gmail.com> - - - - - ff70fc75 by sheaf at 2026-07-18T08:48:31-04:00 Coercion optimisation: avoid exponential behaviour The change to coercion optimisation of 'InstCo' in the previous commit introduces exponential behaviour to the coercion optimiser. To avoid this, this commit provides a way to push in 'Sym' of an already-optimised coercion: GHC.Core.Coercion.Opt.mkDeepSymCo. See Note [Pushing Sym without re-optimising] in GHC.Core.Coercion.Opt. - - - - - dfef27f0 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Move THREADED_RTS-conditional struct members to end of Capability Accessing members of the Capability struct from CMM code rely on accessor macros. (The macros are generated by deriveConstants). These macros have a single definition. This means that the offsets of all struct members must *not* vary based on THREADED_RTS vs !THREADED_RTS. This requires that any struct members that are conditional on THREADED_RTS must occur after the unconditional struct members. Hence we move all the ones that are conditional on THREADED_RTS to the end. Add a deriveConstants entry for the iomgr member of the Capability struct, which was the motivation for this change. Add warning messages to help our future selves. Debugging this took me a couple hours in gdb! - - - - - c254e022 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Make the IOManager API use CapIOManager rather than Capability This makes the API somewhat more self-contained and more consistent. Now the IOManager API and each of the backends takes just the I/O manager structure. Previously we had a bit of a mixture, depending on whether the function needed access to the Capability or just the CapIOManager. We still need access to the cap, so we introduce a back reference to reach the capability, via iomgr->cap. Convert all uses in select and poll backends, but not win32 ones. Convert callers in the scheduler and elsewhere. Also convert the three CMM primops that call IOManager APIs. They just need to use Capability_iomgr(MyCapability()). - - - - - 4f3d8f31 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Split posix/MIO.c out of posix/Signals.c The MIO I/O manager was secretly living inside the Signals file. Now it gets its own file, like any other self-respecting I/O manager. - - - - - 52ce04a9 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Rationalise some scheduler run queue utilities Move them all to the same place in the file. Make some static that were used only internally. Also remove a redundant assignment after calling truncateRunQueue that is already done within truncateRunQueue. - - - - - 75bbdebc by Duncan Coutts at 2026-07-18T08:49:12-04:00 Rename initIOManager{AfterFork} to {re}startIOManager These are more accurate names, since these actions happen after initialisation and are really about starting (or restarting) background threads. - - - - - 724c0517 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Free per-cap I/O managers during shutdown and forkProcess Historically this was not strictly necessary. The select and win32 legacy I/O managers did not maintain any dynamically allocated resources. The new poll one does (an auxillary table), and so this should be freed. After forkProcess, all threads get deleted. This includes threads waiting on I/O or timers. So as of this patch, resetting the I/O manager is just about tidying things up. For example, for the poll I/O manager this will reset the size of the AIOP table (which otherwise grows but never shrinks). In future however the re-initialising will become neeecessary for functionality, since some I/O managers will need to re-initialise wakeup fds that are set CLOEXEC. - - - - - c007d122 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Add a TODO to the MIO I/O manager The direction of travel is to make I/O managers per-capability and have all their state live in the struct CapIOManager. The MIO I/O manager however still has a number of global variables. It's not obvious how handle these globals however. - - - - - b65ab7b3 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Add a FIXME note in the Poll I/O manager - - - - - daf2bd6f by Duncan Coutts at 2026-07-18T08:49:12-04:00 Add missing updateRemembSetPushClosure in poll I/O manager For the non-moving GC. - - - - - e33ca830 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Minor doc improvement to struct StgAsyncIOOp member outcome Mention the enumeration names, as well as their numeric values. The rest of the code uses the enum names. - - - - - 4edd2579 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Minor doc improvements for StgTSOBlockInfo Clarify that certain union members are used only by certain legacy I/O managers. Hopefully we will be able to remove these at some point. - - - - - 536bedbb by Duncan Coutts at 2026-07-18T08:49:12-04:00 Avoid exporting various win32-specific rts symbols The BeginPrivate.h / EndPrivate.h scheme works perfectly well on Windows, but all of the rts/win32/*.h files were not using it. - - - - - 8139b5ac by Duncan Coutts at 2026-07-18T08:49:12-04:00 Remove wakeupIOManager, ioManagerWakeup and setIOManagerWakeupFd We no longer need wakeupIOManager for the threaded RTS case, so we can remove it and the bits only needed to support it. This includes the pipe/eventfd fd shared between the RTS and the in-library I/O manager used for waking up the I/O manager thread. The pipe/eventfd still exists, but it no longer has to be communicated to the RTS, since the RTS no longer needs to use it. So we remove the RTS API export setIOManagerWakeupFd, and remove uses of it within the I/O managers in ghc-internal. - - - - - 74fe7c66 by Duncan Coutts at 2026-07-18T08:49:12-04:00 Add a new interruptIOManager API for the I/O managers It will be used to interrupt awaitCompletedTimeoutsOrIO. Also update the return type and docs for awaitCompletedTimeoutsOrIO to have it return false when it gets interrupted, and have no useful post condition in that case. - - - - - 38792843 by Duncan Coutts at 2026-07-18T08:49:13-04:00 Add interruptIOManager support for select I/O manager Uses the FdWakup mechanism. - - - - - 2f3b00aa by Duncan Coutts at 2026-07-18T08:49:13-04:00 Add interruptIOManager support for poll I/O manager Uses the FdWakup mechanism. A quirk we have to cope with is that we now need to poll one more fd -- the wakeup_fd_r -- but this fd has no corresponding entry in the aiop_table. This is awkward since we have set up our aiop_poll_table to be an auxilliary table with matching indicies. The solution this patch uses (and described in the comments) is to have two tables: struct pollfd *aiop_poll_table, *full_poll_table; and to have the aiop_poll_table alias the tail of the full_poll_table. The head entry in the full_poll_table is the extra fd. So we poll the full_poll_table, while the aiop_poll_table still has matching indicies with the aiop_table. Hurrah for C aliasing rules. - - - - - cee50131 by Duncan Coutts at 2026-07-18T08:49:13-04:00 Add interruptIOManager support for win32 legacy I/O manager And remove unused related helper resetAbandonRequestWait. It is not called because the event is created in auto-reset mode, so never needs to be reset manually. - - - - - cf453143 by Duncan Coutts at 2026-07-18T08:49:13-04:00 Note lack of interruptIOManager support for WinIO I/O manager Though there's a plausible design, we can't sanely test it at the moment due to related WinIO bugs. Filed as issue #27403. - - - - - 1b74a0ad by Duncan Coutts at 2026-07-18T08:49:13-04:00 Be more explicit about enum IOReadOrWrite values, and type within cmm Belt and braces. - - - - - b388d093 by Brian McKenna at 2026-07-18T17:51:50-04:00 Ignore ticks in the pattern-match term oracle The term-oracle in the pattern-match checker is keyed by a canonical form of the scrutinee, computed by `makeDictsCoherent`. That canonical form was tick-sensitive: two occurrences of an otherwise identical expression that happened to carry different ticks were treated as distinct values, breaking long-distance information. This shows up in practice under `-finfo-table-map`, because the desugarer wraps every record-selector use site in a `SourceNote` carrying that site's span. For example: data Box = Box { unBox :: Maybe Int } f b = case unBox b of Nothing -> 0 Just _ -> let Just x = unBox b in x The two `unBox b` expressionss carry different SourceNote spans, the pattern-match checker sees them as different, the long-distance information from the outer `Just _` branch never reaches the let-pattern, and `Just x = unBox b` is wrongly reported as non-exhaustive. We now strip all ticks in `makeDictsCoherent`. This is documented as Wrinkle (UD1) of Note [Unique dictionaries in the TmOracle CoreMap]. Fixes #27314 - - - - - c23e1acb by Mrjtjmn at 2026-07-18T17:52:45-04:00 Add explanations for unsolved Typeable constraints This commit adds explanations for unsolved 'Typeable' constraints. GHC will now provide additional explanations for an unsolved constraint of the form 'Typeable ty', explain why GHC did not solve Typeable constraint. e.g.: - 'ty' is a polymorphic type (e.g. forall a. a -> a) - 'ty' is a qualified type (e.g. Eq Int => Int) - 'ty' is an unboxed sum type - 'ty' is an unreduced type family application - 'ty' whose kind is not typeable Fixes #26532 - - - - - c3546dfa by Duncan Coutts at 2026-07-19T03:43:03+02:00 Fix failing test GcStaticPointers for non-moving GC Minor mistake in asserting something before checking for that same thing. Specifically, Bdescr asserts HEAP_ALLOCED_GC, but Bdescr was being used prior to a guard that checks HEAP_ALLOCED_GC. The solution is just to move the use of Bdescr after the guard. Thanks to Simon Jakobi for identifying the problem. - - - - - 001820d5 by Simon Jakobi at 2026-07-19T03:43:03+02:00 ci: Extend nonmoving GC job timeouts Give jobs which validate the nonmoving GC a 16-hour timeout. These jobs exercise several additional test ways and can exceed the default limit. Assisted-by: gpt-5.6-sol via Codex CLI - - - - - 62 changed files: - .gitlab/generate-ci/gen_ci.hs - .gitlab/jobs.yaml - + changelog.d/T26532 - + changelog.d/T27314.md - + changelog.d/T27374 - compiler/GHC/Core/Coercion/Opt.hs - compiler/GHC/HsToCore/Pmc/Solver.hs - compiler/GHC/Tc/Errors.hs - compiler/GHC/Tc/Errors/Ppr.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/Instance/Typeable.hs - libraries/ghc-internal/src/GHC/Internal/Event/Control.hs - libraries/ghc-internal/src/GHC/Internal/Event/Manager.hs - libraries/ghc-internal/src/GHC/Internal/Event/TimerManager.hs - rts/Capability.c - rts/Capability.h - rts/IOManager.c - rts/IOManager.h - rts/IOManagerInternals.h - rts/PrimOps.cmm - rts/RaiseAsync.c - rts/RtsStartup.c - rts/RtsSymbols.c - rts/Schedule.c - rts/Schedule.h - rts/include/rts/IOInterface.h - rts/include/rts/storage/Closures.h - rts/include/rts/storage/TSO.h - rts/posix/FdWakeup.h - + rts/posix/MIO.c - + rts/posix/MIO.h - rts/posix/Poll.c - rts/posix/Poll.h - rts/posix/Select.c - rts/posix/Select.h - rts/posix/Signals.c - rts/posix/Signals.h - rts/posix/Timeout.c - rts/posix/Timeout.h - rts/rts.cabal - rts/sm/NonMovingMark.c - rts/win32/AsyncMIO.c - rts/win32/AsyncMIO.h - rts/win32/AsyncWinIO.h - rts/win32/AwaitEvent.c - rts/win32/AwaitEvent.h - rts/win32/ConsoleHandler.h - rts/win32/MIOManager.h - rts/win32/ThrIOManager.h - rts/win32/WorkQueue.h - rts/win32/veh_excn.h - + testsuite/tests/corelint/T27374.hs - testsuite/tests/corelint/all.T - + testsuite/tests/pmcheck/should_compile/T27314.hs - testsuite/tests/pmcheck/should_compile/all.T - testsuite/tests/typecheck/should_fail/T15067.stderr - + testsuite/tests/typecheck/should_fail/T26532.hs - + testsuite/tests/typecheck/should_fail/T26532.stderr - testsuite/tests/typecheck/should_fail/T9858b.stderr - testsuite/tests/typecheck/should_fail/TcStaticPointersFail02.stderr - testsuite/tests/typecheck/should_fail/all.T - utils/deriveConstants/Main.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/0c832e7dd4510386b205eedced9cc2… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/0c832e7dd4510386b205eedced9cc2… 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/sjakobi/nonmoving-gc-timeout] 25 commits: Fix failing test GcStaticPointers for non-moving GC
by Simon Jakobi (＠sjakobi2) 19 Jul '26

19 Jul '26

Simon Jakobi pushed to branch wip/sjakobi/nonmoving-gc-timeout at Glasgow Haskell Compiler / GHC Commits: a476c9a2 by Duncan Coutts at 2026-07-19T00:26:43+01:00 Fix failing test GcStaticPointers for non-moving GC Minor mistake in asserting something before checking for that same thing. Specifically, Bdescr asserts HEAP_ALLOCED_GC, but Bdescr was being used prior to a guard that checks HEAP_ALLOCED_GC. The solution is just to move the use of Bdescr after the guard. Thanks to Simon Jakobi for identifying the problem. - - - - - 453899bf by sheaf at 2026-07-19T03:37:59+02:00 Coercion optimisation: avoid double-Sym for InstCo Ticket #27374 pointed out an issue with GHC.Core.Coercion.Opt.optCoercion's handling of InstCo: it contravened (LC2) in Note [The LiftingContext in optCoercion] because it applied the ambient 'sym' to a coercion that was then added to the lifting context substitution. Fixes #27374 Co-authored-by: Simon Jakobi <simon.jakobi(a)gmail.com> - - - - - da40a4c3 by sheaf at 2026-07-19T03:37:59+02:00 Coercion optimisation: avoid exponential behaviour The change to coercion optimisation of 'InstCo' in the previous commit introduces exponential behaviour to the coercion optimiser. To avoid this, this commit provides a way to push in 'Sym' of an already-optimised coercion: GHC.Core.Coercion.Opt.mkDeepSymCo. See Note [Pushing Sym without re-optimising] in GHC.Core.Coercion.Opt. - - - - - f0463461 by Duncan Coutts at 2026-07-19T03:37:59+02:00 Move THREADED_RTS-conditional struct members to end of Capability Accessing members of the Capability struct from CMM code rely on accessor macros. (The macros are generated by deriveConstants). These macros have a single definition. This means that the offsets of all struct members must *not* vary based on THREADED_RTS vs !THREADED_RTS. This requires that any struct members that are conditional on THREADED_RTS must occur after the unconditional struct members. Hence we move all the ones that are conditional on THREADED_RTS to the end. Add a deriveConstants entry for the iomgr member of the Capability struct, which was the motivation for this change. Add warning messages to help our future selves. Debugging this took me a couple hours in gdb! - - - - - e02915b4 by Duncan Coutts at 2026-07-19T03:37:59+02:00 Make the IOManager API use CapIOManager rather than Capability This makes the API somewhat more self-contained and more consistent. Now the IOManager API and each of the backends takes just the I/O manager structure. Previously we had a bit of a mixture, depending on whether the function needed access to the Capability or just the CapIOManager. We still need access to the cap, so we introduce a back reference to reach the capability, via iomgr->cap. Convert all uses in select and poll backends, but not win32 ones. Convert callers in the scheduler and elsewhere. Also convert the three CMM primops that call IOManager APIs. They just need to use Capability_iomgr(MyCapability()). - - - - - 4729a95a by Duncan Coutts at 2026-07-19T03:38:00+02:00 Split posix/MIO.c out of posix/Signals.c The MIO I/O manager was secretly living inside the Signals file. Now it gets its own file, like any other self-respecting I/O manager. - - - - - ae627655 by Duncan Coutts at 2026-07-19T03:38:00+02:00 Rationalise some scheduler run queue utilities Move them all to the same place in the file. Make some static that were used only internally. Also remove a redundant assignment after calling truncateRunQueue that is already done within truncateRunQueue. - - - - - 437caa2d by Duncan Coutts at 2026-07-19T03:38:00+02:00 Rename initIOManager{AfterFork} to {re}startIOManager These are more accurate names, since these actions happen after initialisation and are really about starting (or restarting) background threads. - - - - - 3ec6a118 by Duncan Coutts at 2026-07-19T03:38:00+02:00 Free per-cap I/O managers during shutdown and forkProcess Historically this was not strictly necessary. The select and win32 legacy I/O managers did not maintain any dynamically allocated resources. The new poll one does (an auxillary table), and so this should be freed. After forkProcess, all threads get deleted. This includes threads waiting on I/O or timers. So as of this patch, resetting the I/O manager is just about tidying things up. For example, for the poll I/O manager this will reset the size of the AIOP table (which otherwise grows but never shrinks). In future however the re-initialising will become neeecessary for functionality, since some I/O managers will need to re-initialise wakeup fds that are set CLOEXEC. - - - - - 961ce436 by Duncan Coutts at 2026-07-19T03:38:00+02:00 Add a TODO to the MIO I/O manager The direction of travel is to make I/O managers per-capability and have all their state live in the struct CapIOManager. The MIO I/O manager however still has a number of global variables. It's not obvious how handle these globals however. - - - - - 738b73c5 by Duncan Coutts at 2026-07-19T03:38:00+02:00 Add a FIXME note in the Poll I/O manager - - - - - 87f92e7e by Duncan Coutts at 2026-07-19T03:38:00+02:00 Add missing updateRemembSetPushClosure in poll I/O manager For the non-moving GC. - - - - - 1b556271 by Duncan Coutts at 2026-07-19T03:38:00+02:00 Minor doc improvement to struct StgAsyncIOOp member outcome Mention the enumeration names, as well as their numeric values. The rest of the code uses the enum names. - - - - - 1f2fe974 by Duncan Coutts at 2026-07-19T03:38:00+02:00 Minor doc improvements for StgTSOBlockInfo Clarify that certain union members are used only by certain legacy I/O managers. Hopefully we will be able to remove these at some point. - - - - - 88247e92 by Duncan Coutts at 2026-07-19T03:38:00+02:00 Avoid exporting various win32-specific rts symbols The BeginPrivate.h / EndPrivate.h scheme works perfectly well on Windows, but all of the rts/win32/*.h files were not using it. - - - - - 6083ac68 by Duncan Coutts at 2026-07-19T03:38:00+02:00 Remove wakeupIOManager, ioManagerWakeup and setIOManagerWakeupFd We no longer need wakeupIOManager for the threaded RTS case, so we can remove it and the bits only needed to support it. This includes the pipe/eventfd fd shared between the RTS and the in-library I/O manager used for waking up the I/O manager thread. The pipe/eventfd still exists, but it no longer has to be communicated to the RTS, since the RTS no longer needs to use it. So we remove the RTS API export setIOManagerWakeupFd, and remove uses of it within the I/O managers in ghc-internal. - - - - - 5eea759f by Duncan Coutts at 2026-07-19T03:38:00+02:00 Add a new interruptIOManager API for the I/O managers It will be used to interrupt awaitCompletedTimeoutsOrIO. Also update the return type and docs for awaitCompletedTimeoutsOrIO to have it return false when it gets interrupted, and have no useful post condition in that case. - - - - - 30efd471 by Duncan Coutts at 2026-07-19T03:38:00+02:00 Add interruptIOManager support for select I/O manager Uses the FdWakup mechanism. - - - - - 8b2f31b8 by Duncan Coutts at 2026-07-19T03:38:00+02:00 Add interruptIOManager support for poll I/O manager Uses the FdWakup mechanism. A quirk we have to cope with is that we now need to poll one more fd -- the wakeup_fd_r -- but this fd has no corresponding entry in the aiop_table. This is awkward since we have set up our aiop_poll_table to be an auxilliary table with matching indicies. The solution this patch uses (and described in the comments) is to have two tables: struct pollfd *aiop_poll_table, *full_poll_table; and to have the aiop_poll_table alias the tail of the full_poll_table. The head entry in the full_poll_table is the extra fd. So we poll the full_poll_table, while the aiop_poll_table still has matching indicies with the aiop_table. Hurrah for C aliasing rules. - - - - - 2828ff00 by Duncan Coutts at 2026-07-19T03:38:00+02:00 Add interruptIOManager support for win32 legacy I/O manager And remove unused related helper resetAbandonRequestWait. It is not called because the event is created in auto-reset mode, so never needs to be reset manually. - - - - - 0b122300 by Duncan Coutts at 2026-07-19T03:38:00+02:00 Note lack of interruptIOManager support for WinIO I/O manager Though there's a plausible design, we can't sanely test it at the moment due to related WinIO bugs. Filed as issue #27403. - - - - - 7ff9f271 by Duncan Coutts at 2026-07-19T03:38:00+02:00 Be more explicit about enum IOReadOrWrite values, and type within cmm Belt and braces. - - - - - 4caa8949 by Brian McKenna at 2026-07-19T03:38:00+02:00 Ignore ticks in the pattern-match term oracle The term-oracle in the pattern-match checker is keyed by a canonical form of the scrutinee, computed by `makeDictsCoherent`. That canonical form was tick-sensitive: two occurrences of an otherwise identical expression that happened to carry different ticks were treated as distinct values, breaking long-distance information. This shows up in practice under `-finfo-table-map`, because the desugarer wraps every record-selector use site in a `SourceNote` carrying that site's span. For example: data Box = Box { unBox :: Maybe Int } f b = case unBox b of Nothing -> 0 Just _ -> let Just x = unBox b in x The two `unBox b` expressionss carry different SourceNote spans, the pattern-match checker sees them as different, the long-distance information from the outer `Just _` branch never reaches the let-pattern, and `Just x = unBox b` is wrongly reported as non-exhaustive. We now strip all ticks in `makeDictsCoherent`. This is documented as Wrinkle (UD1) of Note [Unique dictionaries in the TmOracle CoreMap]. Fixes #27314 - - - - - 7cafdd38 by Mrjtjmn at 2026-07-19T03:38:00+02:00 Add explanations for unsolved Typeable constraints This commit adds explanations for unsolved 'Typeable' constraints. GHC will now provide additional explanations for an unsolved constraint of the form 'Typeable ty', explain why GHC did not solve Typeable constraint. e.g.: - 'ty' is a polymorphic type (e.g. forall a. a -> a) - 'ty' is a qualified type (e.g. Eq Int => Int) - 'ty' is an unboxed sum type - 'ty' is an unreduced type family application - 'ty' whose kind is not typeable Fixes #26532 - - - - - 0c832e7d by Simon Jakobi at 2026-07-19T03:38:00+02:00 ci: Extend nonmoving GC job timeouts Give jobs which validate the nonmoving GC a 16-hour timeout. These jobs exercise several additional test ways and can exceed the default limit. Assisted-by: gpt-5.6-sol via Codex CLI - - - - - 62 changed files: - .gitlab/generate-ci/gen_ci.hs - .gitlab/jobs.yaml - + changelog.d/T26532 - + changelog.d/T27314.md - + changelog.d/T27374 - compiler/GHC/Core/Coercion/Opt.hs - compiler/GHC/HsToCore/Pmc/Solver.hs - compiler/GHC/Tc/Errors.hs - compiler/GHC/Tc/Errors/Ppr.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/Instance/Typeable.hs - libraries/ghc-internal/src/GHC/Internal/Event/Control.hs - libraries/ghc-internal/src/GHC/Internal/Event/Manager.hs - libraries/ghc-internal/src/GHC/Internal/Event/TimerManager.hs - rts/Capability.c - rts/Capability.h - rts/IOManager.c - rts/IOManager.h - rts/IOManagerInternals.h - rts/PrimOps.cmm - rts/RaiseAsync.c - rts/RtsStartup.c - rts/RtsSymbols.c - rts/Schedule.c - rts/Schedule.h - rts/include/rts/IOInterface.h - rts/include/rts/storage/Closures.h - rts/include/rts/storage/TSO.h - rts/posix/FdWakeup.h - + rts/posix/MIO.c - + rts/posix/MIO.h - rts/posix/Poll.c - rts/posix/Poll.h - rts/posix/Select.c - rts/posix/Select.h - rts/posix/Signals.c - rts/posix/Signals.h - rts/posix/Timeout.c - rts/posix/Timeout.h - rts/rts.cabal - rts/sm/NonMovingMark.c - rts/win32/AsyncMIO.c - rts/win32/AsyncMIO.h - rts/win32/AsyncWinIO.h - rts/win32/AwaitEvent.c - rts/win32/AwaitEvent.h - rts/win32/ConsoleHandler.h - rts/win32/MIOManager.h - rts/win32/ThrIOManager.h - rts/win32/WorkQueue.h - rts/win32/veh_excn.h - + testsuite/tests/corelint/T27374.hs - testsuite/tests/corelint/all.T - + testsuite/tests/pmcheck/should_compile/T27314.hs - testsuite/tests/pmcheck/should_compile/all.T - testsuite/tests/typecheck/should_fail/T15067.stderr - + testsuite/tests/typecheck/should_fail/T26532.hs - + testsuite/tests/typecheck/should_fail/T26532.stderr - testsuite/tests/typecheck/should_fail/T9858b.stderr - testsuite/tests/typecheck/should_fail/TcStaticPointersFail02.stderr - testsuite/tests/typecheck/should_fail/all.T - utils/deriveConstants/Main.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/1d7cabd4dde5c08ed8871ee3919ff2… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/1d7cabd4dde5c08ed8871ee3919ff2… 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] Pushed new branch wip/sjakobi/nonmoving-gc-timeout
by Simon Jakobi (＠sjakobi2) 19 Jul '26

19 Jul '26

Simon Jakobi pushed new branch wip/sjakobi/nonmoving-gc-timeout at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/sjakobi/nonmoving-gc-timeout 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/issue-27284] Fix failing test GcStaticPointers for non-moving GC
by Duncan Coutts (＠dcoutts) 18 Jul '26

18 Jul '26

Duncan Coutts pushed to branch wip/dcoutts/issue-27284 at Glasgow Haskell Compiler / GHC Commits: a476c9a2 by Duncan Coutts at 2026-07-19T00:26:43+01:00 Fix failing test GcStaticPointers for non-moving GC Minor mistake in asserting something before checking for that same thing. Specifically, Bdescr asserts HEAP_ALLOCED_GC, but Bdescr was being used prior to a guard that checks HEAP_ALLOCED_GC. The solution is just to move the use of Bdescr after the guard. Thanks to Simon Jakobi for identifying the problem. - - - - - 1 changed file: - rts/sm/NonMovingMark.c Changes: ===================================== rts/sm/NonMovingMark.c ===================================== @@ -2018,8 +2018,10 @@ bool nonmovingTidyWeaks (struct MarkQueue_ *queue) // See Note [Weak pointer processing and the non-moving GC] in // MarkWeak.c - bdescr *key_bd = Bdescr((StgPtr) w->key); - bool key_in_nonmoving = HEAP_ALLOCED_GC(w->key) && block_get_flags(key_bd) & BF_NONMOVING; + bool key_in_nonmoving = + HEAP_ALLOCED_GC(w->key) && + block_get_flags(Bdescr((StgPtr) w->key)) & BF_NONMOVING; + if (!key_in_nonmoving || nonmovingIsNowAlive(w->key)) { nonmovingMarkLiveWeak(queue, w); did_work = true; View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/a476c9a2b62c5c543bbabeac360786a… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/a476c9a2b62c5c543bbabeac360786a… 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] Pushed new branch wip/dcoutts/T27105-is-fragile
by Duncan Coutts (＠dcoutts) 18 Jul '26

18 Jul '26

Duncan Coutts pushed new branch wip/dcoutts/T27105-is-fragile at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/dcoutts/T27105-is-fragile 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] Pushed new branch wip/sjakobi/T27016-rebase
by Simon Jakobi (＠sjakobi2) 18 Jul '26

18 Jul '26

Simon Jakobi pushed new branch wip/sjakobi/T27016-rebase at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/sjakobi/T27016-rebase 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][master] Add explanations for unsolved Typeable constraints
by Marge Bot (＠marge-bot) 18 Jul '26

18 Jul '26

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC Commits: c23e1acb by Mrjtjmn at 2026-07-18T17:52:45-04:00 Add explanations for unsolved Typeable constraints This commit adds explanations for unsolved 'Typeable' constraints. GHC will now provide additional explanations for an unsolved constraint of the form 'Typeable ty', explain why GHC did not solve Typeable constraint. e.g.: - 'ty' is a polymorphic type (e.g. forall a. a -> a) - 'ty' is a qualified type (e.g. Eq Int => Int) - 'ty' is an unboxed sum type - 'ty' is an unreduced type family application - 'ty' whose kind is not typeable Fixes #26532 - - - - - 11 changed files: - + changelog.d/T26532 - compiler/GHC/Tc/Errors.hs - compiler/GHC/Tc/Errors/Ppr.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/Instance/Typeable.hs - testsuite/tests/typecheck/should_fail/T15067.stderr - + testsuite/tests/typecheck/should_fail/T26532.hs - + testsuite/tests/typecheck/should_fail/T26532.stderr - testsuite/tests/typecheck/should_fail/T9858b.stderr - testsuite/tests/typecheck/should_fail/TcStaticPointersFail02.stderr - testsuite/tests/typecheck/should_fail/all.T Changes: ===================================== changelog.d/T26532 ===================================== @@ -0,0 +1,8 @@ +section: compiler +issues: #26532 +mrs: !16351 +synopsis: + Add explanations for unsolved Typeable constraints +description: + GHC now provides additional explanations for an unsolved constraint of the + form ``Typeable ty``, explain why GHC did not solve ``Typeable`` constraint. ===================================== compiler/GHC/Tc/Errors.hs ===================================== @@ -12,7 +12,7 @@ module GHC.Tc.Errors( import GHC.Prelude -import GHC.Builtin.Names (hasFieldClassName) +import GHC.Builtin.Names (hasFieldClassName, typeableClassName) import GHC.Driver.Env (hsc_units) import GHC.Driver.DynFlags @@ -21,6 +21,7 @@ import GHC.Driver.Config.Diagnostic import GHC.Rename.Unbound +import GHC.Tc.Instance.Typeable (kindIsTypeable) import GHC.Tc.Types import GHC.Tc.Utils.Monad import GHC.Tc.Errors.Types @@ -2565,9 +2566,52 @@ getNoBuiltinInstMsg item = do { rdr_env <- getGlobalRdrEnv ; fam_envs <- tcGetFamInstEnvs ; mbNoHasFieldMsg <- hasFieldInfo_maybe rdr_env fam_envs item - ; return $ fmap NoBuiltinHasFieldMsg mbNoHasFieldMsg + ; mbNoTypeableMsg <- typeableInfo_maybe item + ; return $ case (mbNoHasFieldMsg, mbNoTypeableMsg) of + (Just hasFieldMsg, _) -> Just $ NoBuiltinHasFieldMsg hasFieldMsg + (_, Just typeableMsg) -> Just $ NoBuiltinTypeableMsg typeableMsg + _ -> Nothing } +-- | Try to produce an explanatory message for why GHC was not able to use +-- a built-in instance to solve a 'Typeable' constraint. +typeableInfo_maybe :: ErrorItem -> TcM (Maybe TypeableMsg) +typeableInfo_maybe item + | Just ty <- typeable_maybe (errorItemPred item) + = if -- Polymorphic types like (forall a. a -> a) are not typeable + -- see Note [No Typeable for polytypes or qualified types] in GHC.Tc.Instance.Class + | isForAllTy ty -> return $ Just $ NoTypeableForPolytype ty + + -- Qualified types like (Num a => blah) are not typeable + | Just (af,_mult_,_arg,_ret) <- splitFunTy_maybe ty + , not $ isVisibleFunArg af + -> return $ Just $ NoTypeableForQualifiedType ty + + -- Unboxed sum types like (# Int, Int #) are not typeable + | Just (tc, _tys) <- splitTyConApp_maybe ty + , isUnboxedSumTyCon tc -> return $ Just $ NoTypeableForUnboxedSumType ty + + -- Unreduced type family applications are not typeable + | Just (tc, _tys) <- splitTyConApp_maybe ty + , isTypeFamilyTyCon tc -> return $ Just $ NoTypeableForUnreducedTypeFamilyApplication ty + + -- TyCons whose kind is non-typeable, are not typeable + | Just (tc, _tys) <- splitTyConApp_maybe ty + , not (kindIsTypeable (tyConKind tc)) + -> return $ Just $ NoTypeableForTyConWithNonTypeableKind ty (tyConKind tc) + + | otherwise -> return Nothing + | otherwise = return Nothing + +-- | Is this constraint definitely a 'Typeable' constraint? +typeable_maybe :: PredType -> Maybe Type +typeable_maybe pred = + case classifyPredType pred of + ClassPred cls tys + | className cls == typeableClassName, [_k, ty] <- tys -> Just ty + _ -> Nothing + + {- Note [Error messages for unsolved HasField constraints] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The HasField type-class has special instance solving logic, implemented in @@ -2781,7 +2825,7 @@ hasFieldInfo_maybe rdr_env fam_inst_envs item -> TcM (Maybe (Either (PatSyn, SimilarName) (TyCon, SimilarName))) with_parent n = fmap (bimap (,n) (,n)) <$> get_parent n --- | Is this constraint definitely 'HasField'? +-- | Is this constraint definitely a 'HasField' constraint? hasField_maybe :: PredType -> Maybe (Type, Type, Type) hasField_maybe pred = case classifyPredType pred of ===================================== compiler/GHC/Tc/Errors/Ppr.hs ===================================== @@ -4314,15 +4314,6 @@ pprTcSolverReportMsg ctxt | any isFunTy (filterOutInvisibleTypes (classTyCon clas) tys) = text "(maybe you haven't applied a function to enough arguments?)" - -- Clarify the mysterious "No instance for (Typeable T) - | className clas == typeableClassName - , [_,ty] <- tys -- Look for (Typeable (k->*) (T k)) - , Just (tc,_) <- tcSplitTyConApp_maybe ty - , not (isTypeFamilyTyCon tc) - = hang (text "GHC can't yet do polykinded") - 2 (text "Typeable" <+> - parens (ppr ty <+> dcolon <+> ppr (typeKind ty))) - | otherwise = empty @@ -5200,6 +5191,7 @@ pprCoercibleMsg (OutOfScopeNewtypeConstructor dc import_suggs) = pprNoBuiltinInstanceMsg :: NoBuiltinInstanceMsg -> SDoc pprNoBuiltinInstanceMsg = \case NoBuiltinHasFieldMsg msg -> pprHasFieldMsg msg + NoBuiltinTypeableMsg msg -> pprTypeableMsg msg pprHasFieldMsg :: HasFieldMsg -> SDoc pprHasFieldMsg = \case @@ -5278,6 +5270,28 @@ pprHasFieldPatSynMsg fld pat_syns = in packHText occ == field_label fld +pprTypeableMsg :: TypeableMsg -> SDoc +pprTypeableMsg = \case + NoTypeableForPolytype ty -> + ppr_is ty "a polymorphic type" + NoTypeableForQualifiedType ty -> + ppr_is ty "a qualified type" + NoTypeableForUnboxedSumType ty -> + ppr_is ty "an unboxed sum type" + NoTypeableForUnreducedTypeFamilyApplication ty -> + ppr_is ty "an unreduced type family application" + NoTypeableForTyConWithNonTypeableKind ty k -> + vcat + [ text "NB:" <+> "The kind of" <+> quotes (ppr ty) + , nest 2 (quotes (ppr k)) <+> "contains foralls," + , "for which the built-in" + <+> quotes (text "Typeable") <+> text "solver cannot produce evidence." ] + where + ppr_is ty reason = + text "NB:" <+> quotes (ppr ty) <+> text "is" <+> text reason + $$ "for which the built-in" + <+> quotes (text "Typeable") <+> text "solver cannot produce evidence." + pprWhenMatching :: SolverReportErrCtxt -> WhenMatching -> SDoc pprWhenMatching ctxt (WhenMatching cty1 cty2 sub_o mb_sub_t_or_k) = sdocOption sdocPrintExplicitCoercions $ \printExplicitCoercions -> @@ -5516,6 +5530,7 @@ tcSolverReportMsgHints ctxt = \case noBuiltinInstanceHints :: NoBuiltinInstanceMsg -> [GhcHint] noBuiltinInstanceHints = \case NoBuiltinHasFieldMsg noHasFieldMsg -> hasFieldMsgHints noHasFieldMsg + NoBuiltinTypeableMsg _ -> noHints hasFieldMsgHints :: HasFieldMsg -> [GhcHint] hasFieldMsgHints = \case @@ -7998,4 +8013,3 @@ pprHsCtxt = \case ppr_stmt (TransStmt { trS_by = by, trS_using = using , trS_form = form }) = pprTransStmt by using form ppr_stmt stmt = pprStmt stmt - ===================================== compiler/GHC/Tc/Errors/Types.hs ===================================== @@ -78,6 +78,7 @@ module GHC.Tc.Errors.Types ( , CoercibleMsg(..) , NoBuiltinInstanceMsg(..) , HasFieldMsg(..) + , TypeableMsg(..) , TooFancyField(..) , PotentialInstances(..) , UnsupportedCallConvention(..) @@ -6034,9 +6035,9 @@ data CoercibleMsg -- a particular class. data NoBuiltinInstanceMsg = NoBuiltinHasFieldMsg HasFieldMsg + | NoBuiltinTypeableMsg TypeableMsg -- Other useful constructors might be: - -- NoBuiltinTypeableMsg -- explains polykinded Typeable restrictions -- NoBuiltinDataToTagMsg -- see conditions in Note [DataToTag overview] -- NoBuiltinWithDictMsg -- see Note [withDict] @@ -6066,6 +6067,20 @@ data HasFieldMsg -- | Using -XRebindableSyntax and a different 'HasField'. | CustomHasField TyCon -- ^ the custom HasField TyCon +-- | Explains why GHC wasn't able to provide a built-in 'Typeable' instance +-- for the given types. +data TypeableMsg + -- | Polymorphic types are not typeable. + = NoTypeableForPolytype Type + -- | Qualified types are not typeable. + | NoTypeableForQualifiedType Type + -- | Unboxed sum types are not typeable. + | NoTypeableForUnboxedSumType Type + -- | Unreduced Type Family Applications are not typeable. + | NoTypeableForUnreducedTypeFamilyApplication Type + -- | TyCons whose kind is not typeable are not typeable. + | NoTypeableForTyConWithNonTypeableKind Type Kind + -- | Why is a record field "too fancy" for GHC to be able to properly -- solve a 'HasField' constraint? data TooFancyField ===================================== compiler/GHC/Tc/Instance/Typeable.hs ===================================== @@ -7,7 +7,12 @@ {-# LANGUAGE RecordWildCards #-} {-# LANGUAGE TypeFamilies #-} -module GHC.Tc.Instance.Typeable(mkTypeableBinds, tyConIsTypeable) where +module GHC.Tc.Instance.Typeable ( + mkTypeableBinds + , tyConIsTypeable + , kindIsTypeable + ) +where import GHC.Prelude import GHC.Platform ===================================== testsuite/tests/typecheck/should_fail/T15067.stderr ===================================== @@ -1,13 +1,7 @@ T15067.hs:9:14: error: [GHC-39999] • No instance for ‘Typeable (# | #)’ arising from a use of ‘typeRep’ - GHC can't yet do polykinded - Typeable ((# | #) :: * - -> * - -> TYPE - (GHC.Internal.Types.SumRep - [GHC.Internal.Types.LiftedRep, - GHC.Internal.Types.LiftedRep])) + NB: ‘(# | #)’ is an unboxed sum type + for which the built-in ‘Typeable’ solver cannot produce evidence. • In the expression: typeRep In an equation for ‘floopadoop’: floopadoop = typeRep - ===================================== testsuite/tests/typecheck/should_fail/T26532.hs ===================================== @@ -0,0 +1,35 @@ +{-# LANGUAGE ImpredicativeTypes #-} +{-# LANGUAGE UnboxedSums #-} +{-# LANGUAGE TypeFamilies #-} + +module T26532 where + +import Data.Kind +import Type.Reflection + +test1 :: TypeRep (forall a. a -> a) +test1 = typeRep + +test2 :: TypeRep (Eq Int => Int) +test2 = typeRep + +test3 :: TypeRep (((),()) => Int) +test3 = typeRep + +test4 :: TypeRep (# Int | Bool #) +test4 = typeRep + +type F :: Type -> Type +type family F a where {} + +test5 :: TypeRep (F Int) +test5 = typeRep + +type PolyDF :: forall k. Type -> k +data family PolyDF a + +type ProxyPolyDF :: (forall k. Type -> k) -> Type +data ProxyPolyDF f = MkProxy + +test6 :: TypeRep (ProxyPolyDF PolyDF) +test6 = typeRep ===================================== testsuite/tests/typecheck/should_fail/T26532.stderr ===================================== @@ -0,0 +1,50 @@ +T26532.hs:11:9: error: [GHC-39999] + • No instance for ‘Typeable (forall a. a -> a)’ + arising from a use of ‘typeRep’ + NB: ‘forall a. a -> a’ is a polymorphic type + for which the built-in ‘Typeable’ solver cannot produce evidence. + • In the expression: typeRep + In an equation for ‘test1’: test1 = typeRep + +T26532.hs:14:9: error: [GHC-39999] + • No instance for ‘Typeable (Eq Int => Int)’ + arising from a use of ‘typeRep’ + NB: ‘Eq Int => Int’ is a qualified type + for which the built-in ‘Typeable’ solver cannot produce evidence. + • In the expression: typeRep + In an equation for ‘test2’: test2 = typeRep + +T26532.hs:17:9: error: [GHC-39999] + • No instance for ‘Typeable + ((() :: Constraint, () :: Constraint) => Int)’ + arising from a use of ‘typeRep’ + NB: ‘(() :: Constraint, () :: Constraint) => + Int’ is a qualified type + for which the built-in ‘Typeable’ solver cannot produce evidence. + • In the expression: typeRep + In an equation for ‘test3’: test3 = typeRep + +T26532.hs:20:9: error: [GHC-39999] + • No instance for ‘Typeable (# | #)’ + arising from a use of ‘typeRep’ + NB: ‘(# | #)’ is an unboxed sum type + for which the built-in ‘Typeable’ solver cannot produce evidence. + • In the expression: typeRep + In an equation for ‘test4’: test4 = typeRep + +T26532.hs:26:9: error: [GHC-39999] + • No instance for ‘Typeable (F Int)’ + arising from a use of ‘typeRep’ + NB: ‘F Int’ is an unreduced type family application + for which the built-in ‘Typeable’ solver cannot produce evidence. + • In the expression: typeRep + In an equation for ‘test5’: test5 = typeRep + +T26532.hs:35:9: error: [GHC-39999] + • No instance for ‘Typeable ProxyPolyDF’ + arising from a use of ‘typeRep’ + NB: The kind of ‘ProxyPolyDF’ + ‘(forall k. * -> k) -> *’ contains foralls, + for which the built-in ‘Typeable’ solver cannot produce evidence. + • In the expression: typeRep + In an equation for ‘test6’: test6 = typeRep ===================================== testsuite/tests/typecheck/should_fail/T9858b.stderr ===================================== @@ -2,7 +2,8 @@ T9858b.hs:7:8: error: [GHC-39999] • No instance for ‘Typeable (Eq Int => Int)’ arising from a use of ‘typeRep’ - (maybe you haven't applied a function to enough arguments?) + NB: ‘Eq Int => Int’ is a qualified type + for which the built-in ‘Typeable’ solver cannot produce evidence. • In the expression: typeRep (Proxy :: Proxy (Eq Int => Int)) In an equation for ‘test’: test = typeRep (Proxy :: Proxy (Eq Int => Int)) ===================================== testsuite/tests/typecheck/should_fail/TcStaticPointersFail02.stderr ===================================== @@ -11,6 +11,7 @@ TcStaticPointersFail02.hs:12:6: error: [GHC-39999] • No instance for ‘ghc-internal-0.1.0.0:GHC.Internal.Data.Typeable.Internal.Typeable (Monad m => a -> m a)’ arising from a static form - (maybe you haven't applied a function to enough arguments?) + NB: ‘Monad m => a -> m a’ is a qualified type + for which the built-in ‘Typeable’ solver cannot produce evidence. • In the expression: static return In an equation for ‘f2’: f2 = static return ===================================== testsuite/tests/typecheck/should_fail/all.T ===================================== @@ -761,3 +761,4 @@ test('T26823', normal, compile_fail, ['']) test('T26861', normal, compile_fail, ['']) test('T26862', normal, compile_fail, ['']) test('T27210', normal, compile_fail, ['']) +test('T26532', normal, compile_fail, ['']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/c23e1acb6f748296a421340e2df564d… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/c23e1acb6f748296a421340e2df564d… You're receiving this email because of your account on gitlab.haskell.org. 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[Git][ghc/ghc][master] Ignore ticks in the pattern-match term oracle
by Marge Bot (＠marge-bot) 18 Jul '26

18 Jul '26

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC Commits: b388d093 by Brian McKenna at 2026-07-18T17:51:50-04:00 Ignore ticks in the pattern-match term oracle The term-oracle in the pattern-match checker is keyed by a canonical form of the scrutinee, computed by `makeDictsCoherent`. That canonical form was tick-sensitive: two occurrences of an otherwise identical expression that happened to carry different ticks were treated as distinct values, breaking long-distance information. This shows up in practice under `-finfo-table-map`, because the desugarer wraps every record-selector use site in a `SourceNote` carrying that site's span. For example: data Box = Box { unBox :: Maybe Int } f b = case unBox b of Nothing -> 0 Just _ -> let Just x = unBox b in x The two `unBox b` expressionss carry different SourceNote spans, the pattern-match checker sees them as different, the long-distance information from the outer `Just _` branch never reaches the let-pattern, and `Just x = unBox b` is wrongly reported as non-exhaustive. We now strip all ticks in `makeDictsCoherent`. This is documented as Wrinkle (UD1) of Note [Unique dictionaries in the TmOracle CoreMap]. Fixes #27314 - - - - - 4 changed files: - + changelog.d/T27314.md - compiler/GHC/HsToCore/Pmc/Solver.hs - + testsuite/tests/pmcheck/should_compile/T27314.hs - testsuite/tests/pmcheck/should_compile/all.T Changes: ===================================== changelog.d/T27314.md ===================================== @@ -0,0 +1,10 @@ +section: compiler +issues: #27314 +mrs: !16118 +synopsis: + Fix spurious ``-Wincomplete-uni-patterns`` warning under ``-finfo-table-map``. +description: + The pattern-match checker now ignores ticks when comparing scrutinees in + its CoreMap, so long-distance information is no longer lost across + function-application scrutinees because debug source annotations + (e.g. SourceNotes added by ``-finfo-table-map``) were inserted. ===================================== compiler/GHC/HsToCore/Pmc/Solver.hs ===================================== @@ -1000,8 +1000,9 @@ makeDictsCoherent (Case scrut bndr ty alts) , let expr' = makeDictsCoherent expr ] makeDictsCoherent (Cast expr co) = Cast (makeDictsCoherent expr) co -makeDictsCoherent (Tick tick expr) - = Tick tick (makeDictsCoherent expr) +makeDictsCoherent (Tick _tick expr) + -- See Wrinkle (UD1) in Note [Unique dictionaries in the TmOracle CoreMap] + = makeDictsCoherent expr makeDictsCoherent ty@(Type {}) = ty makeDictsCoherent co@(Coercion {}) @@ -1061,6 +1062,25 @@ In the end, replacing dictionaries with an error value in the pattern-match checker was the most self-contained, although we might want to revisit once we implement a more robust approach to computing equality in the pattern-match checker (see #19272). + +Wrinkle (UD1): ticks +-------------------- +'makeDictsCoherent' also drops all ticks. The CoreMap key represents +value-level equality, which ticks never affect. + +Example (#27314): with -finfo-table-map every record-selector use site is +wrapped in a 'SourceNote' carrying that site's span (see +Note [Record-selector ticks] in GHC.HsToCore.Ticks). Given + + data Box = Box { unBox :: Maybe Int } + f b = case unBox b of + Nothing -> 0 + Just _ -> let Just x = unBox b in x + +the two `unBox b`s carry different SourceNote spans. Without tick stripping +the CoreMap treats them as distinct expressions. Long-distance information +from the outer `Just _` branch therefore never reaches the let-pattern, and +`Just x = unBox b` is wrongly reported as non-exhaustive. -} {- Note [The Pos/Neg invariant] ===================================== testsuite/tests/pmcheck/should_compile/T27314.hs ===================================== @@ -0,0 +1,8 @@ +module T27314 where + +data Box = Box { unBox :: Maybe Int } + +f :: Box -> Int +f b = case unBox b of + Nothing -> 0 + Just _ -> let Just x = unBox b in x ===================================== testsuite/tests/pmcheck/should_compile/all.T ===================================== @@ -93,6 +93,14 @@ test('T21360', normal, compile, [overlapping_incomplete+'-Wincomplete-record-upd test('T21360b', normal, compile, [overlapping_incomplete+'-Wincomplete-record-updates']) test('T23520', normal, compile, [overlapping_incomplete+'-Wincomplete-record-updates']) test('T25164', [extra_files(['T25164_aux.hs']), req_th], multimod_compile, ['T25164', '-v0']) +test( + 'T27314', + [ omit_ways(llvm_ways), # -finfo-table-map does not work with -fllvm (#26435) + when(js_arch(), skip) # javascript doesn't support -finfo-table-map yet and yields a warning we don't want to handle here + ], + compile, + ['-Wincomplete-uni-patterns -finfo-table-map'] +) # Other tests test('pmc001', [], compile, [overlapping_incomplete]) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/b388d0934c0933c1cdb47226489634e… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/b388d0934c0933c1cdb47226489634e… You're receiving this email because of your account on gitlab.haskell.org. 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[Git][ghc/ghc] Pushed new branch wip/sjakobi/changelog-lint-no-submodules
by Simon Jakobi (＠sjakobi2) 18 Jul '26

18 Jul '26

Simon Jakobi pushed new branch wip/sjakobi/changelog-lint-no-submodules at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/sjakobi/changelog-lint-no-sub… 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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