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[Git][ghc/ghc][master] Better handling of serialisation of wired-in names
by Marge Bot (＠marge-bot) 21 Aug '26

21 Aug '26

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC Commits: d2bc32aa by Simon Peyton Jones at 2026-08-21T12:59:26-04:00 Better handling of serialisation of wired-in names Fixes #27501 - - - - - 2 changed files: - compiler/GHC/Builtin.hs - compiler/GHC/Iface/Binary.hs Changes: ===================================== compiler/GHC/Builtin.hs ===================================== @@ -27,8 +27,7 @@ module GHC.Builtin ( knownKeyOccName, knownKeyOccName_maybe, -- * Known names - lookupWiredInKnownKeyName, - lookupKnownNameInfo, + wiredInNamesMap, lookupKnownNameInfo, -- * Random other things maybeCharLikeCon, maybeIntLikeCon, @@ -45,7 +44,6 @@ module GHC.Builtin ( import GHC.Prelude -import GHC.Builtin.Uniques import GHC.Builtin.PrimOps import GHC.Builtin.PrimOps.Ids import GHC.Builtin.WiredIn.Types @@ -76,9 +74,6 @@ import GHC.Data.List.SetOps import GHC.Data.FastString import qualified GHC.Data.List.Infinite as Inf -import Control.Applicative ((<|>)) - - {- ********************************************************************* * * @@ -624,7 +619,7 @@ See also wiredInNames :: [Name] wiredInNames | debugIsOn - , Just badNamesDoc <- knownKeyNamesOkay all_names + , Just badNamesDoc <- wiredInNamesOkay all_names = pprPanic "badAllKnownKeyNames" badNamesDoc | otherwise = all_names @@ -672,8 +667,8 @@ wiredInNames -- | Check the known-key names list of consistency. -- (a) Unique is in-range -- (b) Distinct uniques -knownKeyNamesOkay :: [Name] -> Maybe SDoc -knownKeyNamesOkay all_names +wiredInNamesOkay :: [Name] -> Maybe SDoc +wiredInNamesOkay all_names | ns@(_:_) <- filter (not . isValidKnownKeyUnique . getUnique) all_names = Just $ text " Out-of-range known-key uniques: " <> brackets (pprWithCommas (ppr . nameOccName) ns) @@ -697,15 +692,6 @@ knownKeyNamesOkay all_names text ": " <> brackets (pprWithCommas (ppr . nameOccName) ns) --- | Given a 'Unique' lookup its associated 'Name' if it corresponds to a --- wired-in thing. --- --- See Note [Symbol table representation of names] for when this function is --- used to reconstruct a wired-in name from its unique -lookupWiredInKnownKeyName :: Unique -> Maybe Name -lookupWiredInKnownKeyName u = - knownUniqueTupleName u <|> lookupUFM_Directly wiredInNamesMap u - -- | Maps 'Unique's to wired-in known-key names. -- -- The type is @UniqFM Name Name@ to denote that the 'Unique's used ===================================== compiler/GHC/Iface/Binary.hs ===================================== @@ -32,7 +32,9 @@ module GHC.Iface.Binary ( import GHC.Prelude -import GHC.Builtin ( knownKeyOccMap, lookupWiredInKnownKeyName ) +import GHC.Builtin ( knownKeyOccMap, wiredInNamesMap ) +import GHC.Builtin.Uniques( knownUniqueTupleName ) + import GHC.Utils.Panic import GHC.Utils.Binary as Binary import GHC.Utils.Outputable @@ -41,6 +43,7 @@ import GHC.Types.Name import GHC.Types.Unique import GHC.Types.SrcLoc import GHC.Types.Name.Cache +import GHC.Types.Unique.FM import GHC.Unit import GHC.Unit.Module.ModIface @@ -721,25 +724,84 @@ getSymbolTable bh name_cache = do {- Note [Symbol table representation of names] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -An occurrence of a name in an interface file is serialized as a single 32-bit -word. The format of this word is: - 00xxxxxx xxxxxxxx xxxxxxxx xxxxxxxx - A normal name. x is an index into the symbol table - 10xxxxxx xxyyyyyy yyyyyyyy yyyyyyyy - A wired-in name. x is the Unique's Char, y is the int part. We assume that - all wired-in known-key uniques fit in this space. This is asserted by - GHC.Builtin.knownKeyNamesOkay. - -During serialization we check for tuples or wired-in things with 'lookupWiredInKnownKeyName'. -During deserialization we use 'lookupWiredInKnownKeyName' to get from the -unique back to its tuple or corresponding Name. We use the same oracle function -in both directions to make sure it is symmetric. - -Tuples are a special case of wired-in names that we can construct from the -unique alone (see 'knownUniqueTupleName'). Tuples aren't included in the -wired-in names map: see Note [Infinite families of known-key names]. +For serialisation we divide Names into two classes: + * Compact Names are serialised simply as their unique. + * Non-compact Names are entered into the Symbol Table of the interface file, + and serialised as the index into that table + +In more detail: +* Compact Names comprise + - All WiredIn Names + - All Names related to tuples, whether WiredIn or not. See (ST2) below. + +* The key property of a compact Name is that GHC can compute the Name from + its Unique, via `lookupCompactName`: + - For most wired-in names, we look up in the `wiredInNameMap`. + - For names related to tuples, we use `knownUniqueTupleName` + Tuples aren't included in the wired-in names map: see (ST1) below + +* Serialisation is done by `putName`: + - When we serialise a compact Name, + we serialise it as a single 32-bit word: + 10xxxxxx xxyyyyyy yyyyyyyy yyyyyyyy + where xxxx is the tag, and yyyy is the payload. + The function `wiredInNamesOkay` checks that the wired-in names all have + uniques that fit into the `yyy` field. + + - When we serialise a non-compact name: + - We look it up in the (stateful, growing) symbol table + - If it not there we add it to the symbol table + - We serialise the occurrenc to a single 32-bit word: + 00xxxxxx xxxxxxxx xxxxxxxx xxxxxxxx + where `xxxxx` is an index into the symbol table. + +* Deserialision is done by `getName`. We read a 32-bit word + - If the MSB is `10` it must be a compact name, so we use + `lookupCompactName` to get from the Unique to the Name. + - If the MSB is `00` it must be a non-compact Name, + so we look it up in the symbol table. + +Wrinkles: + +(ST1) There are many, many tuple types and constructors, so we don't put + them in the wiredInNameMap. Instead we put them in a distinct part of the + Unique namespace, and provide + knownUniqueTupleName :: Unique -> Maybe Name + to identify such a Unique and map it to the corresponding Name. + See Note [Infinite families of known-key names]. + +(ST2) A wired-in data constructor, like (#,#) has a related, also wired-in + (promoted) type constructor; see `mkPromotedDataCon`. That type constructor + in turn contains its `TyConRepName` (e.g. $tc'(#,#)) to support Typeable. + + That `TyConRepName` is built by `mkPrelTyConRepName`, but it is /not/ + wired-in. Why not? Because its definition involves fingerprints etc. (Maybe + it could be made wired-in, but it would tricky, and there is no point.) + + Nevertheless, although it is not wired-in, it is /compact/; that is, we can + serialise and de-serialise it using the mechanisms above. + + This idea is, however, entirely optional. You could delete the line in + `isCompactName` that tests for `knownUniqueTupleName` and then the + TyConRepNames would be serialised as non-compact names, and everything would + work. Fewer tests, but Typeable-heavy code might have bigger interface files. -} +isCompactName :: Name -> Bool +-- See Note [Symbol table representation of names] +isCompactName n + | isWiredInName n = True -- This will catch tuples too! + | isJust (knownUniqueTupleName (nameUnique n)) = True -- Optional: see wrinkle (ST2) + | otherwise = False + +lookupCompactName :: Unique -> Name +-- See Note [Symbol table representation of names] +lookupCompactName u + | Just n <- knownUniqueTupleName u = n -- See wrinkle (ST1) + | Just n <- lookupUFM_Directly wiredInNamesMap u = n + | otherwise = pprPanic "lookupCompactName" (ppr u $$ char tag $$ ppr ix) + where + (tag, ix) = unpkUniqueGrimily u -- See Note [Symbol table representation of names] putName :: BinSymbolTable -> WriteBinHandle -> Name -> IO () @@ -747,7 +809,7 @@ putName BinSymbolTable{ bin_symtab_map = symtab_map_ref, bin_symtab_next = symtab_next } bh name - | Just _ <- lookupWiredInKnownKeyName (nameUnique name) + | isCompactName name , let (c, u) = unpkUniqueGrimily (nameUnique name) -- INVARIANT: (ord c) fits in 8 bits = -- assert (u < 2^(22 :: Int)) put_ bh (0x80000000 @@ -783,16 +845,10 @@ getSymtabName symtab bh = do i :: Word32 <- get bh case i .&. 0xC0000000 of 0x00000000 -> return $! symtab ! fromIntegral i - - 0x80000000 -> - let + 0x80000000 -> return $! lookupCompactName u + where tag = chr (fromIntegral ((i .&. 0x3FC00000) `shiftR` 22)) ix = fromIntegral i .&. 0x003FFFFF u = mkUniqueGrimilyWithTag tag ix - in - return $! case lookupWiredInKnownKeyName u of - Nothing -> pprPanic "getSymtabName:unknown known-key unique" - (ppr i $$ ppr u $$ char tag $$ ppr ix) - Just n -> n _ -> pprPanic "getSymtabName:unknown name tag" (ppr i) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/d2bc32aa4ac13ae1cc1770e6f11db73… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/d2bc32aa4ac13ae1cc1770e6f11db73… 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/name-srcspan-docs
by Simon Jakobi (＠sjakobi) 21 Aug '26

21 Aug '26

Simon Jakobi pushed new branch wip/sjakobi/name-srcspan-docs at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/sjakobi/name-srcspan-docs 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/T16836-implicit-field-strictness] Add -Wimplicit-field-strictness (#16836)
by Simon Jakobi (＠sjakobi) 21 Aug '26

21 Aug '26

Simon Jakobi pushed to branch wip/sjakobi/T16836-implicit-field-strictness at Glasgow Haskell Compiler / GHC Commits: f2ea3903 by Simon Jakobi at 2026-08-21T18:08:32+02:00 Add -Wimplicit-field-strictness (#16836) This opt-in warning fires when a data constructor field lacks an explicit strictness annotation (`!` or `~`). It complements the LazyFieldAnnotations extension (4762a8bf30f) from GHC proposal 752, which makes `~` annotations available for this purpose. The diagnostic is emitted once per data declaration, grouped by constructor. Closes #16836. Assisted-by: Claude Fable 5 - - - - - 18 changed files: - + changelog.d/implicit-field-strictness-warning - changelog.d/lazy-field-annotations - compiler/GHC/Driver/Flags.hs - compiler/GHC/Driver/Session.hs - compiler/GHC/Tc/Errors/Ppr.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/TyCl.hs - compiler/GHC/Types/Error/Codes.hs - compiler/GHC/Types/Hint.hs - compiler/GHC/Types/Hint/Ppr.hs - docs/users_guide/exts/strict.rst - docs/users_guide/using-warnings.rst - + testsuite/tests/warnings/should_compile/T16836a.hs - + testsuite/tests/warnings/should_compile/T16836a.stderr - + testsuite/tests/warnings/should_compile/T16836b.hs - + testsuite/tests/warnings/should_compile/T16836c.hs - + testsuite/tests/warnings/should_compile/T16836c.stderr - testsuite/tests/warnings/should_compile/all.T Changes: ===================================== changelog.d/implicit-field-strictness-warning ===================================== @@ -0,0 +1,10 @@ +section: compiler +synopsis: Add `-Wimplicit-field-strictness` +issues: #16836 +mrs: !16555 + +description: { + The new opt-in warning :ghc-flag:`-Wimplicit-field-strictness` reports + data constructor fields that lack an explicit strictness annotation + (``!`` or ``~``). +} ===================================== changelog.d/lazy-field-annotations ===================================== @@ -11,4 +11,7 @@ description: { continues to control the default strictness of unannotated fields. See `GHC Proposal #752 <https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0752-l…>`_. + + Also note the new opt-in :ghc-flag:`-Wimplicit-field-strictness` warning, which + reports fields lacking an explicit annotation. } ===================================== compiler/GHC/Driver/Flags.hs ===================================== @@ -1142,6 +1142,7 @@ data WarningFlag = | Opt_WarnUnrecognisedModifiers -- ^ @since 10.0 | Opt_WarnSemaphoreOpenFailure -- Since 10.0.1 | Opt_WarnDefaultedCallStack -- ^ @since 10.2 + | Opt_WarnImplicitFieldStrictness -- ^ @since 10.2 deriving (Eq, Ord, Show, Enum, Bounded) -- | Return the names of a WarningFlag @@ -1251,6 +1252,7 @@ warnFlagNames wflag = case wflag of Opt_WarnTypeEqualityRequiresOperators -> "type-equality-requires-operators" :| [] Opt_WarnMissingRoleAnnotations -> "missing-role-annotations" :| [] Opt_WarnImplicitRhsQuantification -> "implicit-rhs-quantification" :| [] + Opt_WarnImplicitFieldStrictness -> "implicit-field-strictness" :| [] Opt_WarnIncompleteExportWarnings -> "incomplete-export-warnings" :| [] Opt_WarnIncompleteRecordSelectors -> "incomplete-record-selectors" :| [] Opt_WarnBadlyLevelledTypes -> "badly-levelled-types" :| [] ===================================== compiler/GHC/Driver/Session.hs ===================================== @@ -2449,6 +2449,7 @@ wWarningFlagsDeps = [minBound..maxBound] >>= \x -> case x of Opt_WarnUnrecognisedModifiers -> warnSpec x Opt_WarnSemaphoreOpenFailure -> warnSpec x Opt_WarnDefaultedCallStack -> warnSpec x + Opt_WarnImplicitFieldStrictness -> warnSpec x warningGroupsDeps :: [(Deprecation, FlagSpec WarningGroup)] warningGroupsDeps = map mk warningGroups ===================================== compiler/GHC/Tc/Errors/Ppr.hs ===================================== @@ -1384,6 +1384,21 @@ instance Diagnostic TcRnMessage where hang (text "Missing role annotation" <> colon) 2 (text "type role" <+> ppr name <+> hsep (map ppr roles)) + TcRnImplicitFieldStrictness _name _lazy_anns cons -> mkSimpleDecorated $ + hang (text "These constructor fields have no explicit strictness annotation" <> colon) + 2 (vcat (map ppr_con cons)) + where + ppr_con (con, fields) = + bullet <+> text "In" <+> quotes (ppr con) <> colon <+> ppr_fields fields + ppr_fields fields + | let names = concat [ns | ImplicitStrictnessRecField ns <- fields] + , not (null names) + = text "field" <> plural names <+> quotedListWithAnd (map ppr names) + | otherwise + = let poss = [i | ImplicitStrictnessPosField i <- fields] + in text "field" <> plural poss + <+> unquotedListWith (text "and") (map int poss) + TcRnIllformedTypePattern p -> mkSimpleDecorated $ hang (text "Ill-formed type pattern:") 2 (ppr p) @@ -2693,6 +2708,8 @@ instance Diagnostic TcRnMessage where -> ErrorWithoutFlag TcRnMissingRoleAnnotation{} -> WarningWithFlag Opt_WarnMissingRoleAnnotations + TcRnImplicitFieldStrictness{} + -> WarningWithFlag Opt_WarnImplicitFieldStrictness TcRnIllegalInvisTyVarBndr{} -> ErrorWithoutFlag TcRnIllegalWildcardTyVarBndr{} @@ -3428,6 +3445,12 @@ instance Diagnostic TcRnMessage where -> noHints TcRnMissingRoleAnnotation{} -> noHints + TcRnImplicitFieldStrictness _ lazy_anns _ + -> SuggestExplicitFieldStrictness + : [ useExtensionInOrderTo + (text "to allow" <+> quotes (char '~') <+> text "annotations") + LangExt.LazyFieldAnnotations + | not lazy_anns ] TcRnIllegalInvisTyVarBndr{} -> [suggestExtension LangExt.TypeAbstractions] TcRnIllegalWildcardTyVarBndr{} ===================================== compiler/GHC/Tc/Errors/Types.hs ===================================== @@ -123,6 +123,7 @@ module GHC.Tc.Errors.Types ( , TypeSyntax(..) , typeSyntaxExtension , SuggestLinear(..) + , ImplicitStrictnessField(..) -- * Errors for hs-boot and signature files , BadBootDecls(..) @@ -4235,6 +4236,24 @@ data TcRnMessage where -} TcRnMissingRoleAnnotation :: Name -> [Role] -> TcRnMessage + + {-| TcRnImplicitFieldStrictness is a warning that occurs when a data + constructor field lacks an explicit strictness annotation (@!@ or @~@) + + Controlled by flags: + - Wimplicit-field-strictness + + Test cases: + T16836a, T16836b + + -} + TcRnImplicitFieldStrictness + :: Name -- ^ the type constructor + -> Bool -- ^ whether @LazyFieldAnnotations@ is enabled + -> [(Name, [ImplicitStrictnessField])] + -- ^ per data constructor, the fields lacking annotations + -> TcRnMessage + {-| TcRnPatersonCondFailure is an error that occurs when an instance declaration fails to conform to the Paterson conditions. Which particular condition fails depends on the constructor of PatersonCondFailure @@ -6399,6 +6418,14 @@ data PatSynInvalidRhsReason | PatSynUnboundVar !Name deriving (Generic) +-- | A constructor field lacking an explicit strictness annotation, as +-- reported by 'TcRnImplicitFieldStrictness'. +data ImplicitStrictnessField + -- | A record field group @x, y :: ty@ sharing one (absent) annotation + = ImplicitStrictnessRecField [RdrName] + -- | A positional argument (1-based index) + | ImplicitStrictnessPosField Int + data BadFieldAnnotationReason where {-| A lazy data type field annotation (~) was used without enabling the extension LazyFieldAnnotations. ===================================== compiler/GHC/Tc/TyCl.hs ===================================== @@ -4023,8 +4023,38 @@ dataDeclChecks tc_name mctxt cons ; is_boot <- tcIsHsBootOrSig -- Are we compiling an hs-boot file? ; unless (not (null cons) || empty_data_decls || is_boot) $ addErrTc (TcRnEmptyDataDeclsDisabled tc_name) + + ; warn_implicit_strictness <- woptM Opt_WarnImplicitFieldStrictness + ; when warn_implicit_strictness $ case cons of + DataTypeCons False data_cons + | let offenders = concatMap conImplicitStrictnessFields data_cons + , not (null offenders) + -> do { lazy_anns <- xoptM LangExt.LazyFieldAnnotations + ; addDiagnosticTc $ + TcRnImplicitFieldStrictness tc_name lazy_anns offenders } + _ -> return () + ; return gadt_syntax } +conImplicitStrictnessFields :: LConDecl GhcRn -> [(Name, [ImplicitStrictnessField])] +conImplicitStrictnessFields (L _ con) + | null fields = [] + | otherwise = [ (unLoc n, fields) | n <- getConNames con ] + where + fields = case con of + ConDeclH98 { con_args = PrefixCon _ args } -> pos_fields args + ConDeclH98 { con_args = InfixCon _ a1 a2 } -> pos_fields [a1, a2] + ConDeclH98 { con_args = RecCon _ (L _ flds) } -> rec_fields flds + ConDeclGADT { con_g_args = PrefixConGADT _ args } -> pos_fields args + ConDeclGADT { con_g_args = RecConGADT _ (L _ flds) } -> rec_fields flds + + pos_fields args = [ ImplicitStrictnessPosField i + | (i, f) <- zip [1 :: Int ..] args + , cdf_bang f == NoSrcStrict ] + rec_fields flds = [ ImplicitStrictnessRecField [ rdr | L _ (FieldOcc rdr _) <- names ] + | L _ (HsConDeclRecField _ names spec) <- flds + , cdf_bang spec == NoSrcStrict ] + ----------------------------------- data DataDeclInfo ===================================== compiler/GHC/Types/Error/Codes.hs ===================================== @@ -542,6 +542,7 @@ type family GhcDiagnosticCode c = n | n -> c where GhcDiagnosticCode "TcRnNegativeNumTypeLiteral" = 93632 GhcDiagnosticCode "TcRnUnusedQuantifiedTypeVar" = 54180 GhcDiagnosticCode "TcRnMissingRoleAnnotation" = 65490 + GhcDiagnosticCode "TcRnImplicitFieldStrictness" = 47032 GhcDiagnosticCode "TcRnUntickedPromotedThing" = 49957 GhcDiagnosticCode "TcRnIllegalBuiltinSyntax" = 39716 ===================================== compiler/GHC/Types/Hint.hs ===================================== @@ -343,6 +343,14 @@ data GhcHint -} | SuggestAddStandaloneKindSignature Name + {-| Suggests to annotate each constructor field with explicit strictness + (@!@ or @~@). + + Triggered by: 'GHC.Tc.Errors.Types.TcRnImplicitFieldStrictness' + Test case(s): warnings/should_compile/T16836a + -} + | SuggestExplicitFieldStrictness + {-| Suggests the user to fill in the wildcard constraint to disambiguate which constraint that is. ===================================== compiler/GHC/Types/Hint/Ppr.hs ===================================== @@ -185,6 +185,9 @@ instance Outputable GhcHint where -> text "Use a standalone deriving declaration instead" SuggestAddStandaloneKindSignature name -> text "Add a standalone kind signature for" <+> quotes (ppr name) + SuggestExplicitFieldStrictness + -> text "Annotate each field with" <+> quotes (char '!') + <+> text "(strict) or" <+> quotes (char '~') <+> text "(lazy)" SuggestFillInWildcardConstraint -> text "Fill in the wildcard constraint yourself" SuggestAppropriateTHTick ns ===================================== docs/users_guide/exts/strict.rst ===================================== @@ -194,6 +194,9 @@ The ``~`` annotation must be written in prefix form:: See `GHC Proposal #229 <https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0229-w…>`__ for the precise rules. +See also :ghc-flag:`-Wimplicit-field-strictness`, which warns about +fields lacking an explicit annotation. + .. _strict-data: Strict-by-default data types ===================================== docs/users_guide/using-warnings.rst ===================================== @@ -2505,6 +2505,21 @@ of ``-W(no-)*``. In other words the type-class role cannot be accidentally left representational or phantom, which could affected the code correctness. +.. ghc-flag:: -Wimplicit-field-strictness + :shortdesc: warn when constructor fields lack explicit strictness annotations + :type: dynamic + :reverse: -Wno-implicit-field-strictness + :category: + + :since: 10.2.1 + :default: off + + .. index:: + single: strictness annotations, missing + + This warning reports data constructor fields that lack an explicit + strictness annotation (``!`` or ``~``). + .. ghc-flag:: -Wimplicit-rhs-quantification :shortdesc: warn when type variables on the RHS of a type synonym are implicitly quantified :type: dynamic ===================================== testsuite/tests/warnings/should_compile/T16836a.hs ===================================== @@ -0,0 +1,37 @@ +{-# OPTIONS_GHC -Wimplicit-field-strictness #-} +{-# LANGUAGE GADTs #-} +{-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE TypeOperators #-} +module T16836a where + +-- plain multi-constructor data +-- warns for both constructors +data T a = MkT a Bool + | MkT2 !Int a + +-- record with a shared field group +-- warns for x, y and z; not for b +data R = MkR { x, y :: Int, z :: Char, b :: !Bool } + +-- infix constructor +-- warns for the first argument +data I = Int :+: !Bool + +-- GADT syntax +-- warns for the first argument +data G a where + MkG :: Int -> !Bool -> G a + +-- GADT record syntax +-- warns for gx +data GR a where + MkGR :: { gx :: Int, gy :: !Bool } -> GR a + +-- data family instance +-- warns +data family F a +data instance F Int = MkF Char + +-- fully annotated +-- doesn't warn +data S = MkS !Int !Bool ===================================== testsuite/tests/warnings/should_compile/T16836a.stderr ===================================== @@ -0,0 +1,55 @@ +T16836a.hs:9:1: warning: [GHC-47032] [-Wimplicit-field-strictness] + • These constructor fields have no explicit strictness annotation: + • In ‘MkT’: fields 1 and 2 + • In ‘MkT2’: field 2 + • In the data type declaration for ‘T’ + Suggested fixes: + • Annotate each field with ‘!’ (strict) or ‘~’ (lazy) + • Use the ‘LazyFieldAnnotations’ extension (implied by ‘StrictData’) + to allow ‘~’ annotations + +T16836a.hs:14:1: warning: [GHC-47032] [-Wimplicit-field-strictness] + • These constructor fields have no explicit strictness annotation: + • In ‘MkR’: fields ‘x’, ‘y’ and ‘z’ + • In the data type declaration for ‘R’ + Suggested fixes: + • Annotate each field with ‘!’ (strict) or ‘~’ (lazy) + • Use the ‘LazyFieldAnnotations’ extension (implied by ‘StrictData’) + to allow ‘~’ annotations + +T16836a.hs:18:1: warning: [GHC-47032] [-Wimplicit-field-strictness] + • These constructor fields have no explicit strictness annotation: + • In ‘:+:’: field 1 + • In the data type declaration for ‘I’ + Suggested fixes: + • Annotate each field with ‘!’ (strict) or ‘~’ (lazy) + • Use the ‘LazyFieldAnnotations’ extension (implied by ‘StrictData’) + to allow ‘~’ annotations + +T16836a.hs:22:1: warning: [GHC-47032] [-Wimplicit-field-strictness] + • These constructor fields have no explicit strictness annotation: + • In ‘MkG’: field 1 + • In the data type declaration for ‘G’ + Suggested fixes: + • Annotate each field with ‘!’ (strict) or ‘~’ (lazy) + • Use the ‘LazyFieldAnnotations’ extension (implied by ‘StrictData’) + to allow ‘~’ annotations + +T16836a.hs:27:1: warning: [GHC-47032] [-Wimplicit-field-strictness] + • These constructor fields have no explicit strictness annotation: + • In ‘MkGR’: field ‘gx’ + • In the data type declaration for ‘GR’ + Suggested fixes: + • Annotate each field with ‘!’ (strict) or ‘~’ (lazy) + • Use the ‘LazyFieldAnnotations’ extension (implied by ‘StrictData’) + to allow ‘~’ annotations + +T16836a.hs:33:1: warning: [GHC-47032] [-Wimplicit-field-strictness] + • These constructor fields have no explicit strictness annotation: + • In ‘MkF’: field 1 + • In the data family instance declaration for ‘F’ + Suggested fixes: + • Annotate each field with ‘!’ (strict) or ‘~’ (lazy) + • Use the ‘LazyFieldAnnotations’ extension (implied by ‘StrictData’) + to allow ‘~’ annotations + ===================================== testsuite/tests/warnings/should_compile/T16836b.hs ===================================== @@ -0,0 +1,25 @@ +{-# OPTIONS_GHC -Wimplicit-field-strictness #-} +{-# LANGUAGE GADTs #-} +{-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE TypeData #-} +{-# LANGUAGE EmptyDataDecls #-} +{-# LANGUAGE LazyFieldAnnotations #-} +module T16836b where + +-- fully annotated declarations don't warn +data T a = MkT ~a !Bool +data R = MkR { x, y :: !Int, z :: ~Char } +data G a where + MkG :: !Int -> ~Bool -> G a +data family F a +data instance F Int = MkF !Char + +-- newtypes can't have annotations; exempt +newtype N = MkN Int + +-- 'type data' can't have annotations; exempt +type data TD = MkTD Bool + +-- no fields, nothing to annotate +data E +data Nullary = A | B ===================================== testsuite/tests/warnings/should_compile/T16836c.hs ===================================== @@ -0,0 +1,6 @@ +{-# OPTIONS_GHC -Wimplicit-field-strictness #-} +{-# LANGUAGE StrictData #-} +module T16836c where + +-- unannotated fields warn under StrictData too +data T a = MkT a !Bool ~Char ===================================== testsuite/tests/warnings/should_compile/T16836c.stderr ===================================== @@ -0,0 +1,6 @@ +T16836c.hs:6:1: warning: [GHC-47032] [-Wimplicit-field-strictness] + • These constructor fields have no explicit strictness annotation: + • In ‘MkT’: field 1 + • In the data type declaration for ‘T’ + Suggested fix: Annotate each field with ‘!’ (strict) or ‘~’ (lazy) + ===================================== testsuite/tests/warnings/should_compile/all.T ===================================== @@ -91,3 +91,6 @@ test('T25901_imp_unused_3', [extra_files(['T25901_helper_3.hs'])], multimod_comp test('T25901_imp_unused_4', normal, compile, ['-Wunused-imports']) test('T25901_imp_dodgy_1', [extra_files(['T25901_helper_1.hs'])], multimod_compile, ['T25901_imp_dodgy_1', '-v0 -Wdodgy-imports']) test('T25901_imp_dodgy_2', [extra_files(['T25901_helper_2.hs'])], multimod_compile, ['T25901_imp_dodgy_2', '-v0 -Wdodgy-imports']) +test('T16836a', normal, compile, ['']) +test('T16836b', normal, compile, ['']) +test('T16836c', normal, compile, ['']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/f2ea39038b9d1aeb413d79fbcf19c8a… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/f2ea39038b9d1aeb413d79fbcf19c8a… You're receiving this email because of your account on gitlab.haskell.org. 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[Git][ghc/ghc][wip/romes/27729] rts: Fix race condition in MSG_UPD_TSO_FLAGS execution
by Rodrigo Mesquita (＠alt-romes) 21 Aug '26

21 Aug '26

Rodrigo Mesquita pushed to branch wip/romes/27729 at Glasgow Haskell Compiler / GHC Commits: 7f843566 by Rodrigo Mesquita at 2026-08-21T16:07:58+01:00 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 - - - - - 2 changed files: - rts/CloneStack.c - rts/Messages.c Changes: ===================================== rts/CloneStack.c ===================================== @@ -88,6 +88,7 @@ void sendCloneStackMessage(StgTSO *tso, HsStablePtr mvar) { void handleCloneStackMessage(Capability *cap, MessageCloneStack *msg){ // We must check that the current owner of the thread we want to clone the stack for // is still this capability. + // See Note [TSO owner may change in between Msg being sent and received] Capability *owner = RELAXED_LOAD(&msg->tso->cap); if (owner != cap) { // The target TSO may have migrated after the message was queued on the old ===================================== rts/Messages.c ===================================== @@ -66,6 +66,48 @@ void sendMessage(Capability *from_cap, Capability *to_cap, Message *msg) Handle a message ------------------------------------------------------------------------- */ +/* +Note [TSO owner may change in between Msg being sent and received] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +When a message is sent from Capability (C1) to a target TSO (T2) (e.g. +MessageUpdTSOFlag, MessageCloneStack, ...), it is queued on the TSO's owner +Capability (C3) inbox (inboxes are owned by Capabilities, not TSOs). + +At a later point, the Capability (C3) will process its inbox. Upon receiving +the message meant for a specific TSO (T2), it must first always check that the +TSO's owner is *still* itself (C3). + +The target TSO (T2) may have migrated after the message was queued on its old +capability (C3). In that case we must forward the request to the new owner +(say, C4); otherwise the Capability C3 could be modifying a TSO it no longer +owns, racing with its actual owner mutating it, since it is no longer the owner. + +The message meant for a TSO should only be executed when the receiving +Capability is still the owner of that TSO. Otherwise, it must be forwarded to +the new owner. The pseudo code for handling a message that targets a particular +TSO will look something like: + + executeMessage(...) { + + if (i == &stg_MY_MSG_info) { + + MessageMyMsg* msg = (MessageMyMsg*) m + + Capability *owner = RELAXED_LOAD(&msg->tso->cap); + if (owner != cap) { + sendMessage(cap, owner, (Message *)msg); + return; + } + + actuallyExecute(...) + + } + } + +See `executeMessage`'s `stg_MSG_UPD_TSO_FLAG_info` and +`stg_MSG_CLONE_STACK_info` for two live examples. +*/ + #if defined(THREADED_RTS) void @@ -142,12 +184,18 @@ loop: } else if(i == &stg_MSG_UPD_TSO_FLAG_info){ MessageUpdTSOFlag *u = (MessageUpdTSOFlag*) m; - if (u->set) { - u->tso->flags |= u->flag; - } - else { - u->tso->flags &= ~u->flag; + + // We must check that the current owner of the thread is still this capability. + // See Note [TSO owner may change in between Msg being sent and received] + Capability *owner = RELAXED_LOAD(&u->tso->cap); + if (owner != cap) { + sendMessage(cap, owner, (Message *)u); + return; } + + if (u->set) { u->tso->flags |= u->flag; } + else { u->tso->flags &= ~u->flag; } + return; } else View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/7f84356660ba202f676e67073b96fd3… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/7f84356660ba202f676e67073b96fd3… 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/romes/27729
by Rodrigo Mesquita (＠alt-romes) 21 Aug '26

21 Aug '26

Rodrigo Mesquita pushed new branch wip/romes/27729 at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/romes/27729 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/T16836-implicit-field-strictness] Add -Wimplicit-field-strictness (#16836)
by Simon Jakobi (＠sjakobi) 21 Aug '26

21 Aug '26

Simon Jakobi pushed to branch wip/sjakobi/T16836-implicit-field-strictness at Glasgow Haskell Compiler / GHC Commits: 817d99a9 by Simon Jakobi at 2026-08-21T15:58:07+02:00 Add -Wimplicit-field-strictness (#16836) This opt-in warning fires when a data constructor field lacks an explicit strictness annotation (`!` or `~`). It complements the LazyFieldAnnotations extension (4762a8bf30f) from GHC proposal 752, which makes `~` annotations available for this purpose. One diagnostic is emitted per data declaration, grouped by constructor. Closes #16836. Assisted-by: Claude Fable 5 - - - - - 18 changed files: - + changelog.d/implicit-field-strictness-warning - changelog.d/lazy-field-annotations - compiler/GHC/Driver/Flags.hs - compiler/GHC/Driver/Session.hs - compiler/GHC/Tc/Errors/Ppr.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/TyCl.hs - compiler/GHC/Types/Error/Codes.hs - compiler/GHC/Types/Hint.hs - compiler/GHC/Types/Hint/Ppr.hs - docs/users_guide/exts/strict.rst - docs/users_guide/using-warnings.rst - + testsuite/tests/warnings/should_compile/T16836a.hs - + testsuite/tests/warnings/should_compile/T16836a.stderr - + testsuite/tests/warnings/should_compile/T16836b.hs - + testsuite/tests/warnings/should_compile/T16836c.hs - + testsuite/tests/warnings/should_compile/T16836c.stderr - testsuite/tests/warnings/should_compile/all.T Changes: ===================================== changelog.d/implicit-field-strictness-warning ===================================== @@ -0,0 +1,10 @@ +section: compiler +synopsis: Add `-Wimplicit-field-strictness` +issues: #16836 +mrs: !16555 + +description: { + The new opt-in warning :ghc-flag:`-Wimplicit-field-strictness` reports + data constructor fields that lack an explicit strictness annotation + (``!`` or ``~``). +} ===================================== changelog.d/lazy-field-annotations ===================================== @@ -11,4 +11,7 @@ description: { continues to control the default strictness of unannotated fields. See `GHC Proposal #752 <https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0752-l…>`_. + + Also note the new opt-in :ghc-flag:`-Wimplicit-field-strictness` warning, which + reports fields lacking an explicit annotation. } ===================================== compiler/GHC/Driver/Flags.hs ===================================== @@ -1142,6 +1142,7 @@ data WarningFlag = | Opt_WarnUnrecognisedModifiers -- ^ @since 10.0 | Opt_WarnSemaphoreOpenFailure -- Since 10.0.1 | Opt_WarnDefaultedCallStack -- ^ @since 10.2 + | Opt_WarnImplicitFieldStrictness -- ^ @since 10.2 deriving (Eq, Ord, Show, Enum, Bounded) -- | Return the names of a WarningFlag @@ -1251,6 +1252,7 @@ warnFlagNames wflag = case wflag of Opt_WarnTypeEqualityRequiresOperators -> "type-equality-requires-operators" :| [] Opt_WarnMissingRoleAnnotations -> "missing-role-annotations" :| [] Opt_WarnImplicitRhsQuantification -> "implicit-rhs-quantification" :| [] + Opt_WarnImplicitFieldStrictness -> "implicit-field-strictness" :| [] Opt_WarnIncompleteExportWarnings -> "incomplete-export-warnings" :| [] Opt_WarnIncompleteRecordSelectors -> "incomplete-record-selectors" :| [] Opt_WarnBadlyLevelledTypes -> "badly-levelled-types" :| [] ===================================== compiler/GHC/Driver/Session.hs ===================================== @@ -2449,6 +2449,7 @@ wWarningFlagsDeps = [minBound..maxBound] >>= \x -> case x of Opt_WarnUnrecognisedModifiers -> warnSpec x Opt_WarnSemaphoreOpenFailure -> warnSpec x Opt_WarnDefaultedCallStack -> warnSpec x + Opt_WarnImplicitFieldStrictness -> warnSpec x warningGroupsDeps :: [(Deprecation, FlagSpec WarningGroup)] warningGroupsDeps = map mk warningGroups ===================================== compiler/GHC/Tc/Errors/Ppr.hs ===================================== @@ -1384,6 +1384,21 @@ instance Diagnostic TcRnMessage where hang (text "Missing role annotation" <> colon) 2 (text "type role" <+> ppr name <+> hsep (map ppr roles)) + TcRnImplicitFieldStrictness _name _lazy_anns cons -> mkSimpleDecorated $ + hang (text "These constructor fields have no explicit strictness annotation" <> colon) + 2 (vcat (map ppr_con cons)) + where + ppr_con (con, fields) = + bullet <+> text "In" <+> quotes (ppr con) <> colon <+> ppr_fields fields + ppr_fields fields + | let names = concat [ns | ImplicitStrictnessRecField _ ns <- fields] + , not (null names) + = text "field" <> plural names <+> quotedListWithAnd (map ppr names) + | otherwise + = let poss = [i | ImplicitStrictnessPosField _ i <- fields] + in text "field" <> plural poss + <+> unquotedListWith (text "and") (map int poss) + TcRnIllformedTypePattern p -> mkSimpleDecorated $ hang (text "Ill-formed type pattern:") 2 (ppr p) @@ -2693,6 +2708,8 @@ instance Diagnostic TcRnMessage where -> ErrorWithoutFlag TcRnMissingRoleAnnotation{} -> WarningWithFlag Opt_WarnMissingRoleAnnotations + TcRnImplicitFieldStrictness{} + -> WarningWithFlag Opt_WarnImplicitFieldStrictness TcRnIllegalInvisTyVarBndr{} -> ErrorWithoutFlag TcRnIllegalWildcardTyVarBndr{} @@ -3428,6 +3445,12 @@ instance Diagnostic TcRnMessage where -> noHints TcRnMissingRoleAnnotation{} -> noHints + TcRnImplicitFieldStrictness _ lazy_anns _ + -> SuggestExplicitFieldStrictness + : [ useExtensionInOrderTo + (text "to allow" <+> quotes (char '~') <+> text "annotations") + LangExt.LazyFieldAnnotations + | not lazy_anns ] TcRnIllegalInvisTyVarBndr{} -> [suggestExtension LangExt.TypeAbstractions] TcRnIllegalWildcardTyVarBndr{} ===================================== compiler/GHC/Tc/Errors/Types.hs ===================================== @@ -123,6 +123,7 @@ module GHC.Tc.Errors.Types ( , TypeSyntax(..) , typeSyntaxExtension , SuggestLinear(..) + , ImplicitStrictnessField(..) -- * Errors for hs-boot and signature files , BadBootDecls(..) @@ -4235,6 +4236,24 @@ data TcRnMessage where -} TcRnMissingRoleAnnotation :: Name -> [Role] -> TcRnMessage + + {-| TcRnImplicitFieldStrictness is a warning that occurs when a data + constructor field lacks an explicit strictness annotation (@!@ or @~@) + + Controlled by flags: + - Wimplicit-field-strictness + + Test cases: + T16836a, T16836b + + -} + TcRnImplicitFieldStrictness + :: Name -- ^ the type constructor + -> Bool -- ^ whether @LazyFieldAnnotations@ is enabled + -> [(Name, [ImplicitStrictnessField])] + -- ^ per data constructor, the fields lacking annotations + -> TcRnMessage + {-| TcRnPatersonCondFailure is an error that occurs when an instance declaration fails to conform to the Paterson conditions. Which particular condition fails depends on the constructor of PatersonCondFailure @@ -6399,6 +6418,14 @@ data PatSynInvalidRhsReason | PatSynUnboundVar !Name deriving (Generic) +-- | A constructor field lacking an explicit strictness annotation, as +-- reported by 'TcRnImplicitFieldStrictness'. +data ImplicitStrictnessField + -- | A record field group @x, y :: ty@ sharing one (absent) annotation + = ImplicitStrictnessRecField SrcSpan [RdrName] + -- | A positional argument (1-based index) + | ImplicitStrictnessPosField SrcSpan Int + data BadFieldAnnotationReason where {-| A lazy data type field annotation (~) was used without enabling the extension LazyFieldAnnotations. ===================================== compiler/GHC/Tc/TyCl.hs ===================================== @@ -4023,8 +4023,39 @@ dataDeclChecks tc_name mctxt cons ; is_boot <- tcIsHsBootOrSig -- Are we compiling an hs-boot file? ; unless (not (null cons) || empty_data_decls || is_boot) $ addErrTc (TcRnEmptyDataDeclsDisabled tc_name) + + ; warn_implicit_strictness <- woptM Opt_WarnImplicitFieldStrictness + ; when warn_implicit_strictness $ case cons of + DataTypeCons False data_cons + | let offenders = concatMap conImplicitStrictnessFields data_cons + , not (null offenders) + -> do { lazy_anns <- xoptM LangExt.LazyFieldAnnotations + ; setSrcSpan (getSrcSpan tc_name) $ addDiagnosticTc $ + TcRnImplicitFieldStrictness tc_name lazy_anns offenders } + _ -> return () + ; return gadt_syntax } +conImplicitStrictnessFields :: LConDecl GhcRn -> [(Name, [ImplicitStrictnessField])] +conImplicitStrictnessFields (L _ con) + | null fields = [] + | otherwise = [ (unLoc n, fields) | n <- getConNames con ] + where + fields = case con of + ConDeclH98 { con_args = PrefixCon _ args } -> pos_fields args + ConDeclH98 { con_args = InfixCon _ a1 a2 } -> pos_fields [a1, a2] + ConDeclH98 { con_args = RecCon _ (L _ flds) } -> rec_fields flds + ConDeclGADT { con_g_args = PrefixConGADT _ args } -> pos_fields args + ConDeclGADT { con_g_args = RecConGADT _ (L _ flds) } -> rec_fields flds + + pos_fields args = [ ImplicitStrictnessPosField (getLocA (cdf_type f)) i + | (i, f) <- zip [1 :: Int ..] args + , cdf_bang f == NoSrcStrict ] + rec_fields flds = [ ImplicitStrictnessRecField (getLocA (cdf_type spec)) + [ rdr | L _ (FieldOcc rdr _) <- names ] + | L _ (HsConDeclRecField _ names spec) <- flds + , cdf_bang spec == NoSrcStrict ] + ----------------------------------- data DataDeclInfo ===================================== compiler/GHC/Types/Error/Codes.hs ===================================== @@ -542,6 +542,7 @@ type family GhcDiagnosticCode c = n | n -> c where GhcDiagnosticCode "TcRnNegativeNumTypeLiteral" = 93632 GhcDiagnosticCode "TcRnUnusedQuantifiedTypeVar" = 54180 GhcDiagnosticCode "TcRnMissingRoleAnnotation" = 65490 + GhcDiagnosticCode "TcRnImplicitFieldStrictness" = 47032 GhcDiagnosticCode "TcRnUntickedPromotedThing" = 49957 GhcDiagnosticCode "TcRnIllegalBuiltinSyntax" = 39716 ===================================== compiler/GHC/Types/Hint.hs ===================================== @@ -343,6 +343,14 @@ data GhcHint -} | SuggestAddStandaloneKindSignature Name + {-| Suggests to annotate each constructor field with explicit strictness + (@!@ or @~@). + + Triggered by: 'GHC.Tc.Errors.Types.TcRnImplicitFieldStrictness' + Test case(s): warnings/should_compile/T16836a + -} + | SuggestExplicitFieldStrictness + {-| Suggests the user to fill in the wildcard constraint to disambiguate which constraint that is. ===================================== compiler/GHC/Types/Hint/Ppr.hs ===================================== @@ -185,6 +185,9 @@ instance Outputable GhcHint where -> text "Use a standalone deriving declaration instead" SuggestAddStandaloneKindSignature name -> text "Add a standalone kind signature for" <+> quotes (ppr name) + SuggestExplicitFieldStrictness + -> text "Annotate each field with" <+> quotes (char '!') + <+> text "(strict) or" <+> quotes (char '~') <+> text "(lazy)" SuggestFillInWildcardConstraint -> text "Fill in the wildcard constraint yourself" SuggestAppropriateTHTick ns ===================================== docs/users_guide/exts/strict.rst ===================================== @@ -194,6 +194,9 @@ The ``~`` annotation must be written in prefix form:: See `GHC Proposal #229 <https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0229-w…>`__ for the precise rules. +See also :ghc-flag:`-Wimplicit-field-strictness`, which warns about +fields lacking an explicit annotation. + .. _strict-data: Strict-by-default data types ===================================== docs/users_guide/using-warnings.rst ===================================== @@ -2505,6 +2505,21 @@ of ``-W(no-)*``. In other words the type-class role cannot be accidentally left representational or phantom, which could affected the code correctness. +.. ghc-flag:: -Wimplicit-field-strictness + :shortdesc: warn when constructor fields lack explicit strictness annotations + :type: dynamic + :reverse: -Wno-implicit-field-strictness + :category: + + :since: 10.2.1 + :default: off + + .. index:: + single: strictness annotations, missing + + This warning reports data constructor fields that lack an explicit + strictness annotation (``!`` or ``~``). + .. ghc-flag:: -Wimplicit-rhs-quantification :shortdesc: warn when type variables on the RHS of a type synonym are implicitly quantified :type: dynamic ===================================== testsuite/tests/warnings/should_compile/T16836a.hs ===================================== @@ -0,0 +1,37 @@ +{-# OPTIONS_GHC -Wimplicit-field-strictness #-} +{-# LANGUAGE GADTs #-} +{-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE TypeOperators #-} +module T16836a where + +-- plain multi-constructor data +-- warns for both constructors +data T a = MkT a Bool + | MkT2 !Int a + +-- record with a shared field group +-- warns for x, y and z; not for b +data R = MkR { x, y :: Int, z :: Char, b :: !Bool } + +-- infix constructor +-- warns for the first argument +data I = Int :+: !Bool + +-- GADT syntax +-- warns for the first argument +data G a where + MkG :: Int -> !Bool -> G a + +-- GADT record syntax +-- warns for gx +data GR a where + MkGR :: { gx :: Int, gy :: !Bool } -> GR a + +-- data family instance +-- warns +data family F a +data instance F Int = MkF Char + +-- fully annotated +-- doesn't warn +data S = MkS !Int !Bool ===================================== testsuite/tests/warnings/should_compile/T16836a.stderr ===================================== @@ -0,0 +1,55 @@ +T16836a.hs:9:1: warning: [GHC-47032] [-Wimplicit-field-strictness] + • These constructor fields have no explicit strictness annotation: + • In ‘MkT’: fields 1 and 2 + • In ‘MkT2’: field 2 + • In the data type declaration for ‘T’ + Suggested fixes: + • Annotate each field with ‘!’ (strict) or ‘~’ (lazy) + • Use the ‘LazyFieldAnnotations’ extension (implied by ‘StrictData’) + to allow ‘~’ annotations + +T16836a.hs:14:1: warning: [GHC-47032] [-Wimplicit-field-strictness] + • These constructor fields have no explicit strictness annotation: + • In ‘MkR’: fields ‘x’, ‘y’ and ‘z’ + • In the data type declaration for ‘R’ + Suggested fixes: + • Annotate each field with ‘!’ (strict) or ‘~’ (lazy) + • Use the ‘LazyFieldAnnotations’ extension (implied by ‘StrictData’) + to allow ‘~’ annotations + +T16836a.hs:18:1: warning: [GHC-47032] [-Wimplicit-field-strictness] + • These constructor fields have no explicit strictness annotation: + • In ‘:+:’: field 1 + • In the data type declaration for ‘I’ + Suggested fixes: + • Annotate each field with ‘!’ (strict) or ‘~’ (lazy) + • Use the ‘LazyFieldAnnotations’ extension (implied by ‘StrictData’) + to allow ‘~’ annotations + +T16836a.hs:22:1: warning: [GHC-47032] [-Wimplicit-field-strictness] + • These constructor fields have no explicit strictness annotation: + • In ‘MkG’: field 1 + • In the data type declaration for ‘G’ + Suggested fixes: + • Annotate each field with ‘!’ (strict) or ‘~’ (lazy) + • Use the ‘LazyFieldAnnotations’ extension (implied by ‘StrictData’) + to allow ‘~’ annotations + +T16836a.hs:27:1: warning: [GHC-47032] [-Wimplicit-field-strictness] + • These constructor fields have no explicit strictness annotation: + • In ‘MkGR’: field ‘gx’ + • In the data type declaration for ‘GR’ + Suggested fixes: + • Annotate each field with ‘!’ (strict) or ‘~’ (lazy) + • Use the ‘LazyFieldAnnotations’ extension (implied by ‘StrictData’) + to allow ‘~’ annotations + +T16836a.hs:32:1: warning: [GHC-47032] [-Wimplicit-field-strictness] + • These constructor fields have no explicit strictness annotation: + • In ‘MkF’: field 1 + • In the data family instance declaration for ‘F’ + Suggested fixes: + • Annotate each field with ‘!’ (strict) or ‘~’ (lazy) + • Use the ‘LazyFieldAnnotations’ extension (implied by ‘StrictData’) + to allow ‘~’ annotations + ===================================== testsuite/tests/warnings/should_compile/T16836b.hs ===================================== @@ -0,0 +1,25 @@ +{-# OPTIONS_GHC -Wimplicit-field-strictness #-} +{-# LANGUAGE GADTs #-} +{-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE TypeData #-} +{-# LANGUAGE EmptyDataDecls #-} +{-# LANGUAGE LazyFieldAnnotations #-} +module T16836b where + +-- fully annotated declarations don't warn +data T a = MkT ~a !Bool +data R = MkR { x, y :: !Int, z :: ~Char } +data G a where + MkG :: !Int -> ~Bool -> G a +data family F a +data instance F Int = MkF !Char + +-- newtypes can't have annotations; exempt +newtype N = MkN Int + +-- 'type data' can't have annotations; exempt +type data TD = MkTD Bool + +-- no fields, nothing to annotate +data E +data Nullary = A | B ===================================== testsuite/tests/warnings/should_compile/T16836c.hs ===================================== @@ -0,0 +1,6 @@ +{-# OPTIONS_GHC -Wimplicit-field-strictness #-} +{-# LANGUAGE StrictData #-} +module T16836c where + +-- unannotated fields warn under StrictData too +data T a = MkT a !Bool ~Char ===================================== testsuite/tests/warnings/should_compile/T16836c.stderr ===================================== @@ -0,0 +1,6 @@ +T16836c.hs:6:1: warning: [GHC-47032] [-Wimplicit-field-strictness] + • These constructor fields have no explicit strictness annotation: + • In ‘MkT’: field 1 + • In the data type declaration for ‘T’ + Suggested fix: Annotate each field with ‘!’ (strict) or ‘~’ (lazy) + ===================================== testsuite/tests/warnings/should_compile/all.T ===================================== @@ -91,3 +91,6 @@ test('T25901_imp_unused_3', [extra_files(['T25901_helper_3.hs'])], multimod_comp test('T25901_imp_unused_4', normal, compile, ['-Wunused-imports']) test('T25901_imp_dodgy_1', [extra_files(['T25901_helper_1.hs'])], multimod_compile, ['T25901_imp_dodgy_1', '-v0 -Wdodgy-imports']) test('T25901_imp_dodgy_2', [extra_files(['T25901_helper_2.hs'])], multimod_compile, ['T25901_imp_dodgy_2', '-v0 -Wdodgy-imports']) +test('T16836a', normal, compile, ['']) +test('T16836b', normal, compile, ['']) +test('T16836c', normal, compile, ['']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/817d99a9846cf4321f895d1f7b937ce… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/817d99a9846cf4321f895d1f7b937ce… You're receiving this email because of your account on gitlab.haskell.org. 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[Git][ghc/ghc][wip/marge_bot_batch_merge_job] 6 commits: testsuite: Show baseline sample count and range in perf failures
by Marge Bot (＠marge-bot) 21 Aug '26

21 Aug '26

Marge Bot pushed to branch wip/marge_bot_batch_merge_job at Glasgow Haskell Compiler / GHC Commits: 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. - - - - - d7bdcbc3 by Simon Peyton Jones at 2026-08-21T08:29:14-04:00 Better handling of serialisation of wired-in names Fixes #27501 - - - - - f2adf12c by Alan Zimmerman at 2026-08-21T08:29:14-04:00 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. - - - - - 44 changed files: - .gitlab/ci.sh - compiler/GHC/Builtin.hs - compiler/GHC/Data/BooleanFormula.hs - compiler/GHC/Hs.hs - compiler/GHC/Hs/Dump.hs - compiler/GHC/Hs/Utils.hs - compiler/GHC/Iface/Binary.hs - compiler/GHC/Iface/Ext/Ast.hs - compiler/GHC/Iface/Syntax.hs - compiler/GHC/IfaceToCore.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/Annotation.hs - compiler/GHC/Parser/PostProcess.hs - testsuite/driver/perf_notes.py - testsuite/driver/testglobals.py - testsuite/tests/ghc-api/exactprint/T22919.stderr - testsuite/tests/ghc-api/exactprint/Test20239.stderr - testsuite/tests/ghc-api/exactprint/ZeroWidthSemi.stderr - testsuite/tests/haddock/should_compile_flag_haddock/T17544.stderr - testsuite/tests/haddock/should_compile_flag_haddock/T17544_kw.stderr - testsuite/tests/haddock/should_compile_flag_haddock/T24221.stderr - testsuite/tests/module/mod185.stderr - testsuite/tests/parser/should_compile/DumpParsedAst.stderr - testsuite/tests/parser/should_compile/DumpParsedAstComments.stderr - testsuite/tests/parser/should_compile/DumpRenamedAst.stderr - testsuite/tests/parser/should_compile/DumpSemis.stderr - testsuite/tests/parser/should_compile/DumpTypecheckedAst.stderr - testsuite/tests/parser/should_compile/KindSigs.stderr - testsuite/tests/parser/should_compile/T14189.stderr - testsuite/tests/parser/should_compile/T15323.stderr - testsuite/tests/parser/should_compile/T20452.stderr - testsuite/tests/parser/should_compile/T20718.stderr - testsuite/tests/parser/should_compile/T20718b.stderr - testsuite/tests/parser/should_compile/T20846.stderr - testsuite/tests/parser/should_compile/T23315/T23315.stderr - testsuite/tests/printer/AnnotationNoListTuplePuns.stdout - testsuite/tests/printer/T18791.stderr - testsuite/tests/printer/Test20297.stdout - testsuite/tests/printer/Test24533.stdout - utils/check-exact/ExactPrint.hs - utils/check-exact/Parsers.hs - utils/check-exact/Transform.hs - utils/check-exact/Utils.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/8bb8a88e4d1cf7b61f22d10977a18d… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/8bb8a88e4d1cf7b61f22d10977a18d… 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] Change the actual installation procedure for Windows
by Wolfgang Jeltsch (＠jeltsch) 21 Aug '26

21 Aug '26

Wolfgang Jeltsch pushed to branch wip/jeltsch/ghc-9-14-building-base at Glasgow Haskell Compiler / GHC Commits: 0ce7adde by Wolfgang Jeltsch at 2026-08-21T15:05:15+03:00 Change the actual installation procedure for Windows - - - - - 1 changed file: - .gitlab/base-ci.sh Changes: ===================================== .gitlab/base-ci.sh ===================================== @@ -46,9 +46,14 @@ do curl https://downloads.haskell.org/~ghc/${ghc_version}/${archive_file} \ >${ghc_version}.tar.xz tar -xJf ${ghc_version}.tar.xz - cd ghc-${ghc_version}-* - ./configure --prefix "${project_root}/other-ghcs/opt/${ghc_version}" - make install + if [ -f ghc-${ghc_version}-*/configure ] + then # Unix + cd ghc-${ghc_version}-* + ./configure --prefix "${project_root}/other-ghcs/opt/${ghc_version}" + make install + else # Windows + mv ghc-${ghc_version}-* "${project_root}/other-ghcs/opt/${ghc_version}" + fi cd ${project_root} # Build `base` with the installed GHC View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/0ce7adde3da59839dae53b8a07ff26c… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/0ce7adde3da59839dae53b8a07ff26c… 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/27627] 4 commits: An abstract TyCon may hide a unary class
by Zubin (＠wz1000) 21 Aug '26

21 Aug '26

Zubin pushed to branch wip/27627 at Glasgow Haskell Compiler / GHC Commits: 036c9e62 by Zubin Duggal at 2026-08-21T14:03:40+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 mayBeUnaryClassTyCon instead of isUnaryClassTyCon, which returns True for an abstract TyCon. Fixes #27704 - - - - - 11e617d0 by Zubin Duggal at 2026-08-21T14:03:40+05:30 Specialise: don't drop a dead arg that the stable unfolding uses 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. Thread the template's binders through specHeader alongside the RHS binders and make a filler only when the argument is dead in both. See Note [Dead args and stable unfoldings]. Fixes #27703 - - - - - 13fe1031 by Zubin Duggal at 2026-08-21T14:03:41+05:30 Never make an absent filler at a constraint type, isDictTy doesn't catch constraints hidden behind unreduced type family applications Example: 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 also in the test T27627f Use `ConstraintLike <- typeTypeOrConstraint arg_ty` instead??? - - - - - 14d04e9b by Zubin Duggal at 2026-08-21T14:03:41+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 - - - - - 38 changed files: - compiler/GHC/Core.hs - compiler/GHC/Core/Opt/Specialise.hs - compiler/GHC/Core/Opt/WorkWrap/Utils.hs - compiler/GHC/Core/Predicate.hs - compiler/GHC/Core/TyCon.hs - compiler/GHC/Core/Type.hs - compiler/GHC/CoreToStg/Prep.hs - compiler/GHC/IfaceToCore.hs - compiler/GHC/Types/Literal.hs - + 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 - + testsuite/tests/core-to-stg/T27704a/all.T - + testsuite/tests/core-to-stg/T27717/Callee.hs - + testsuite/tests/core-to-stg/T27717/Callee.hs-boot - + testsuite/tests/core-to-stg/T27717/Main.hs - + testsuite/tests/core-to-stg/T27717/Mid.hs - + testsuite/tests/core-to-stg/T27717/T27717.stdout - + testsuite/tests/core-to-stg/T27717/Ty.hs - + testsuite/tests/core-to-stg/T27717/all.T - + 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 The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/a307ee3bbef579fbd04bcec71844ba… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/a307ee3bbef579fbd04bcec71844ba… 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/ak/spec-loop
by Andreas Klebinger (＠AndreasK) 21 Aug '26

21 Aug '26

Andreas Klebinger pushed new branch wip/ak/spec-loop at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/ak/spec-loop 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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