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[Git][ghc/ghc][master] Use Haddock formatting in deprecation message of `initNameCache`
by Marge Bot (＠marge-bot) 03 Feb '26

03 Feb '26

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC Commits: 5f0dbeb6 by Simon Hengel at 2026-02-03T16:00:12-05:00 Use Haddock formatting in deprecation message of `initNameCache` - - - - - 1 changed file: - compiler/GHC/Types/Name/Cache.hs Changes: ===================================== compiler/GHC/Types/Name/Cache.hs ===================================== @@ -162,9 +162,7 @@ newNameCacheWith ut nc = NameCache (uniqueTag ut) <$> newMVar nc -- | This takes a tag for uniques to be generated and the list of knownKeyNames -- These must be initialized properly to ensure that names generated from this -- NameCache do not conflict with known key names. --- --- Use `newNameCache` or `newNameCacheWith` instead -{-# DEPRECATED initNameCache "Use newNameCache or newNameCacheWith instead" #-} +{-# DEPRECATED initNameCache "Use `newNameCache` or `newNameCacheWith` instead" #-} initNameCache :: UniqueTag -> [Name] -> IO NameCache initNameCache c names = newNameCacheWith c (initOrigNames names) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/5f0dbeb631c9582b40f3e0b05333219… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/5f0dbeb631c9582b40f3e0b05333219… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][master] ExplicitLevelImports: check staging for types just like for values
by Marge Bot (＠marge-bot) 03 Feb '26

03 Feb '26

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC Commits: c64cca1e by mangoiv at 2026-02-03T15:59:29-05:00 ExplicitLevelImports: check staging for types just like for values Previously, imported types were entirely exempted from staging checks as the implicit stage persistance assumed to be all imported types to be well staged. ExplicitLevelImports' change specification, however, does not do such an exemption. Thus we want to introduce such a check, just like we have for values. ExplicitLevelImports does not, however, talk about local names - from its perspective, we could theoretically keep treating locally introduced types specially - e.g. an ill-staged used in a quote would only emit a warning, not an error. To allow for a potential future migration away from such wrinkles as the staging check in notFound (see Note [Out of scope might be a staging error]) we consistently do the strict staging check that we also do for value if ExplicitLevelImports is on. Closes #26098 - - - - - 11 changed files: - compiler/GHC/Rename/HsType.hs - compiler/GHC/Rename/Splice.hs-boot - + testsuite/tests/th/T26098A_quote.hs - + testsuite/tests/th/T26098A_splice.hs - + testsuite/tests/th/T26098_local.hs - + testsuite/tests/th/T26098_local.stderr - + testsuite/tests/th/T26098_quote.hs - + testsuite/tests/th/T26098_quote.stderr - + testsuite/tests/th/T26098_splice.hs - + testsuite/tests/th/T26098_splice.stderr - testsuite/tests/th/all.T Changes: ===================================== compiler/GHC/Rename/HsType.hs ===================================== @@ -1,4 +1,5 @@ {-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE MultiWayIf #-} {- (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 @@ -42,7 +43,7 @@ module GHC.Rename.HsType ( import GHC.Prelude -import {-# SOURCE #-} GHC.Rename.Splice( rnSpliceType, checkThLocalTyName ) +import {-# SOURCE #-} GHC.Rename.Splice( rnSpliceType, checkThLocalTyName, checkThLocalNameNoLift ) import GHC.Core.TyCo.FVs ( tyCoVarsOfTypeList ) import GHC.Core.TyCon ( isKindName ) @@ -537,10 +538,18 @@ rnHsTyKi env tv@(HsTyVar _ ip (L loc rdr_name)) -- of PolyKinds (see #14710) ; name <- rnTyVar env rdr_name ; this_mod <- getModule - ; when (nameIsLocalOrFrom this_mod name) $ - checkThLocalTyName name + ; explicit_level_imports <- xoptM LangExt.ExplicitLevelImports + ; let loc_name_with_rdr = L loc $ WithUserRdr rdr_name name + ; if | explicit_level_imports + -- See Note [Strict level checks with ExplicitLevelImports] + -> checkThLocalNameNoLift loc_name_with_rdr + + | nameIsLocalOrFrom this_mod name + -> checkThLocalTyName name + + | otherwise -> pure () ; checkPromotedDataConName env tv Prefix ip name - ; return (HsTyVar noAnn ip (L loc $ WithUserRdr rdr_name name), unitFV name) } + ; return (HsTyVar noAnn ip loc_name_with_rdr, unitFV name) } rnHsTyKi env ty@(HsOpTy _ prom ty1 l_op ty2) = setSrcSpan (getLocA l_op) $ @@ -685,6 +694,37 @@ rnHsTyLit tyLit@(HsNumTy x i) = do pure (HsNumTy x i) rnHsTyLit (HsCharTy x c) = pure (HsCharTy x c) +{- +Note [Strict level checks with ExplicitLevelImports] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Since the proposed change specification of `ExplicitLevelImports` [1] talks about +all identifiers as if they were created equally in the context of TemplateHaskell, +we want to adhere to that specification and at the same time use this unique +chance of being able to guard the "correct" behaviour behind an extension, without +breaking too many users. That is why, if ExplicitLevelImports is on, we +- do not allow non-well-levelled types to be imported +- do not allow locally defined type names to be used in an ill-levelled way, more + most importantly, we do not allow locally defined names to be used in quotes. + +When doing level checks, we historically have been glancing over some +not-well-levelled programs - e.g. the following program was historically +accepted from the perspective of the stage restriction: + +type T = ExpQ +x = $(_ :: T) + +However, when type-checking the splice `$(_ :: T)`, we found that `T` +had not yet been made part of the type-checking environment - we would +insert an ad-hoc check in `notFound` which would report the staging error. + +See Note [Out of scope might be a staging error] + +This is obviously not very rigorous - our "specification" of a program +being well-staged becomes "if the type checker needs the thing to be in scope +and it is not, the program is not well-staged, otherwise it is". + +[1]: https://github.com/ghc-proposals/ghc-proposals/blob/8e4d0e9340c04b904373f9d… +-} rnHsMultAnnWith :: (LocatedA (mult GhcPs) -> RnM (LocatedA (mult GhcRn), FreeVars)) -> HsMultAnnOf (LocatedA (mult GhcPs)) GhcPs ===================================== compiler/GHC/Rename/Splice.hs-boot ===================================== @@ -16,3 +16,5 @@ rnSpliceDecl :: SpliceDecl GhcPs -> RnM (SpliceDecl GhcRn, FreeVars) rnTopSpliceDecls :: HsUntypedSplice GhcPs -> RnM ([LHsDecl GhcPs], FreeVars) checkThLocalTyName :: Name -> RnM () + +checkThLocalNameNoLift :: LIdOccP GhcRn -> RnM () ===================================== testsuite/tests/th/T26098A_quote.hs ===================================== @@ -0,0 +1,4 @@ +module T26098A_quote where + +data T = MkT + ===================================== testsuite/tests/th/T26098A_splice.hs ===================================== @@ -0,0 +1,7 @@ +module T26098A_splice where + +import Language.Haskell.TH + +data T = MkT + +type Foo = ExpQ ===================================== testsuite/tests/th/T26098_local.hs ===================================== @@ -0,0 +1,32 @@ +{-# LANGUAGE ExplicitLevelImports #-} +module T26098_local where + +import Language.Haskell.TH +import Data.Char +import Data.Proxy + +tardy :: forall a. Proxy a -> IO Type +tardy _ = [t| a |] + +tardy2 :: forall a. Proxy a -> IO Exp +tardy2 _ = [| id @a |] + +tardy3 :: forall a. Proxy a -> Code IO (a -> a) +tardy3 _ = [|| id @a ||] + +main :: IO () +main = do + tardy (Proxy @Int) >>= putStrLn . filt . show + tardy2 (Proxy @Int) >>= putStrLn . filt . show + examineCode (tardy3 (Proxy @Int)) >>= putStrLn . filt . show . unType + +-- ad-hoc filter uniques, a_12313 -> a +filt :: String -> String +filt = go where + go [] = [] + go ('_' : rest) = go (dropWhile isDigit rest) + go (c:cs) = c : go cs + +type T = ExpQ + +blup = $(3 :: T) ===================================== testsuite/tests/th/T26098_local.stderr ===================================== @@ -0,0 +1,16 @@ +T26098_local.hs:9:15: error: [GHC-28914] + • Level error: ‘a’ is bound at level 0 but used at level 1 + • In the Template Haskell quotation: [t| a |] + +T26098_local.hs:12:19: error: [GHC-28914] + • Level error: ‘a’ is bound at level 0 but used at level 1 + • In the Template Haskell quotation: [| id @a |] + +T26098_local.hs:15:20: error: [GHC-28914] + • Level error: ‘a’ is bound at level 0 but used at level 1 + • In the Template Haskell typed quotation: [|| id @a ||] + +T26098_local.hs:32:15: error: [GHC-28914] + • Level error: ‘T’ is bound at level 0 but used at level -1 + • In the untyped splice: $(3 :: T) + ===================================== testsuite/tests/th/T26098_quote.hs ===================================== @@ -0,0 +1,12 @@ +{-# LANGUAGE ExplicitLevelImports, DataKinds, TemplateHaskell #-} +module T26098_quote where + +import splice T26098A_quote +import T26098A_quote +import Language.Haskell.TH + +c :: Q Type +c = [t|T|] + +d :: Q Type +d = [t|'MkT|] ===================================== testsuite/tests/th/T26098_quote.stderr ===================================== @@ -0,0 +1,14 @@ +T26098_quote.hs:9:8: error: [GHC-28914] + • Level error: ‘T’ is bound at levels {-1, 0} but used at level 1 + • Available from the imports: + • imported from ‘T26098A_quote’ at T26098_quote.hs:5:1-20 + • imported from ‘T26098A_quote’ at -1 at T26098_quote.hs:4:1-27 + • In the Template Haskell quotation: [t| T |] + +T26098_quote.hs:12:8: error: [GHC-28914] + • Level error: ‘MkT’ is bound at levels {-1, 0} but used at level 1 + • Available from the imports: + • imported from ‘T26098A_quote’ at T26098_quote.hs:5:1-20 + • imported from ‘T26098A_quote’ at -1 at T26098_quote.hs:4:1-27 + • In the Template Haskell quotation: [t| 'MkT |] + ===================================== testsuite/tests/th/T26098_splice.hs ===================================== @@ -0,0 +1,9 @@ +{-# LANGUAGE ExplicitLevelImports, TemplateHaskell #-} +module T26098_splice where + +import T26098A_splice +import quote T26098A_splice + +import splice Prelude + +x = $(undefined :: Foo) ===================================== testsuite/tests/th/T26098_splice.stderr ===================================== @@ -0,0 +1,7 @@ +T26098_splice.hs:9:20: error: [GHC-28914] + • Level error: ‘Foo’ is bound at levels {0, 1} but used at level -1 + • Available from the imports: + • imported from ‘T26098A_splice’ at 1 at T26098_splice.hs:5:1-27 + • imported from ‘T26098A_splice’ at T26098_splice.hs:4:1-21 + • In the untyped splice: $(undefined :: Foo) + ===================================== testsuite/tests/th/all.T ===================================== @@ -624,6 +624,9 @@ test('T24997', normal, compile_and_run, ['']) test('T25256', normal, compile_and_run, ['']) test('T24572a', normal, compile, ['']) test('T24572b', normal, compile_fail, ['']) +test('T26098_splice', [extra_files(['T26098A_splice.hs'])], multimod_compile_fail, ['T26098_splice', '-v0 ' + config.ghc_th_way_flags]) +test('T26098_quote', [extra_files(['T26098A_quote.hs'])], multimod_compile_fail, ['T26098_quote', '-v0 ' + config.ghc_th_way_flags]) +test('T26098_local', normal, compile_fail, ['']) test('T24572c', normal, compile_fail, ['']) test('T26568', normal, compile_fail, ['']) test('T24572d', normal, compile, ['']) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/c64cca1ef667751c02ce2eb4141349e… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/c64cca1ef667751c02ce2eb4141349e… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][master] driver: Hide source paths at verbosity level 1 by default
by Marge Bot (＠marge-bot) 03 Feb '26

03 Feb '26

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC Commits: aa9c5e2c by Hécate Kleidukos at 2026-02-03T15:58:35-05:00 driver: Hide source paths at verbosity level 1 by default - - - - - 33 changed files: - compiler/GHC/Driver/Session.hs - docs/users_guide/9.16.1-notes.rst - hadrian/src/Settings/Builders/RunTest.hs - testsuite/mk/test.mk - testsuite/tests/backpack/cabal/bkpcabal08/bkpcabal08.stdout - testsuite/tests/driver/T20030/test1/all.T - testsuite/tests/driver/T20030/test2/all.T - testsuite/tests/driver/T20030/test3/all.T - testsuite/tests/driver/T20030/test4/all.T - testsuite/tests/driver/T20030/test5/all.T - testsuite/tests/driver/T20030/test6/all.T - testsuite/tests/driver/T8526/T8526.script - testsuite/tests/driver/bytecode-object/Makefile - testsuite/tests/driver/bytecode-object/bytecode_object19.stdout - testsuite/tests/driver/dynamicToo/dynamicToo001/Makefile - testsuite/tests/driver/fat-iface/fat014.script - testsuite/tests/driver/implicit-dyn-too/Makefile - testsuite/tests/driver/multipleHomeUnits/all.T - testsuite/tests/driver/multipleHomeUnits/multipleHomeUnits_recomp_th.stdout - − testsuite/tests/ghci/linking/T11531.stderr - testsuite/tests/ghci/prog018/prog018.script - testsuite/tests/ghci/scripts/T13869.script - testsuite/tests/ghci/scripts/T13997.script - testsuite/tests/ghci/scripts/T17669.script - testsuite/tests/ghci/scripts/T18330.script - testsuite/tests/ghci/scripts/T18330.stdout - testsuite/tests/ghci/scripts/T1914.script - testsuite/tests/ghci/scripts/T20217.script - testsuite/tests/ghci/scripts/T6105.script - testsuite/tests/ghci/scripts/T8042.script - testsuite/tests/ghci/scripts/T8042recomp.script - testsuite/tests/ghci/should_run/Makefile - testsuite/tests/rts/T13676.script The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/aa9c5e2ca0d42f7361fc465d79f5beb… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/aa9c5e2ca0d42f7361fc465d79f5beb… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/T26875] ghc-internal: avoid depending on GHC.Internal.Control.Monad.Fix
by Teo Camarasu (＠teo) 03 Feb '26

03 Feb '26

Teo Camarasu pushed to branch wip/T26875 at Glasgow Haskell Compiler / GHC Commits: f56da1de by Teo Camarasu at 2026-02-03T19:40:10+00:00 ghc-internal: avoid depending on GHC.Internal.Control.Monad.Fix This module contains the definition of MonadFix, since we want an instance for IO, that instance requires a lot of machinery and we want to avoid an orphan instance, this will naturally be quite high up in the dependency graph. So we want to avoid other modules depending on it as far as possible. Resolves #26875 - - - - - 11 changed files: - compiler/GHC/Builtin/Names.hs - libraries/base/src/Control/Arrow.hs - libraries/base/src/System/IO.hs - libraries/ghc-internal/src/GHC/Internal/Control/Arrow.hs - libraries/ghc-internal/src/GHC/Internal/Control/Monad/Fix.hs - libraries/ghc-internal/src/GHC/Internal/Control/Monad/ST/Lazy/Imp.hs - libraries/ghc-internal/src/GHC/Internal/Data/Functor/Identity.hs - libraries/ghc-internal/src/GHC/Internal/System/IO.hs - libraries/ghc-internal/src/GHC/Internal/TH/Monad.hs - testsuite/tests/interface-stability/base-exports.stdout - testsuite/tests/interface-stability/template-haskell-exports.stdout Changes: ===================================== compiler/GHC/Builtin/Names.hs ===================================== @@ -1489,7 +1489,9 @@ composeAName = varQual gHC_INTERNAL_DESUGAR (fsLit ">>>") composeAIdKey firstAName = varQual gHC_INTERNAL_ARROW (fsLit "first") firstAIdKey appAName = varQual gHC_INTERNAL_ARROW (fsLit "app") appAIdKey choiceAName = varQual gHC_INTERNAL_ARROW (fsLit "|||") choiceAIdKey -loopAName = varQual gHC_INTERNAL_ARROW (fsLit "loop") loopAIdKey +-- This is defined in Monad.Fix to flatten the module hierarchy of `ghc-internal` +-- It is the only thing from Control.Arrow that requires MonadFix +loopAName = varQual gHC_INTERNAL_MONAD_FIX (fsLit "loop") loopAIdKey -- Monad comprehensions guardMName, mzipName :: Name ===================================== libraries/base/src/Control/Arrow.hs ===================================== @@ -50,3 +50,4 @@ module Control.Arrow ) where import GHC.Internal.Control.Arrow +import GHC.Internal.Control.Monad.Fix (ArrowLoop(..)) ===================================== libraries/base/src/System/IO.hs ===================================== @@ -185,6 +185,7 @@ module System.IO ) where import GHC.Internal.System.IO +import GHC.Internal.Control.Monad.Fix (fixIO) -- $locking -- Implementations should enforce as far as possible, at least locally to the ===================================== libraries/ghc-internal/src/GHC/Internal/Control/Arrow.hs ===================================== @@ -45,13 +45,10 @@ module GHC.Internal.Control.Arrow ( ArrowChoice(..), -- * Arrow application ArrowApply(..), ArrowMonad(..), leftApp, - -- * Feedback - ArrowLoop(..) ) where -import GHC.Internal.Data.Tuple ( fst, snd, uncurry ) +import GHC.Internal.Data.Tuple ( uncurry ) import GHC.Internal.Data.Either -import GHC.Internal.Control.Monad.Fix import GHC.Internal.Control.Category import GHC.Internal.Base hiding ( (.), id ) import GHC.Internal.Generics (Generic, Generic1) @@ -419,55 +416,3 @@ leftApp :: ArrowApply a => a b c -> a (Either b d) (Either c d) leftApp f = arr ((\b -> (arr (\() -> b) >>> f >>> arr Left, ())) ||| (\d -> (arr (\() -> d) >>> arr Right, ()))) >>> app --- | The 'loop' operator expresses computations in which an output value --- is fed back as input, although the computation occurs only once. --- It underlies the @rec@ value recursion construct in arrow notation. --- 'loop' should satisfy the following laws: --- --- [/extension/] --- @'loop' ('arr' f) = 'arr' (\\ b -> 'fst' ('fix' (\\ (c,d) -> f (b,d))))@ --- --- [/left tightening/] --- @'loop' ('first' h >>> f) = h >>> 'loop' f@ --- --- [/right tightening/] --- @'loop' (f >>> 'first' h) = 'loop' f >>> h@ --- --- [/sliding/] --- @'loop' (f >>> 'arr' ('id' *** k)) = 'loop' ('arr' ('id' *** k) >>> f)@ --- --- [/vanishing/] --- @'loop' ('loop' f) = 'loop' ('arr' unassoc >>> f >>> 'arr' assoc)@ --- --- [/superposing/] --- @'second' ('loop' f) = 'loop' ('arr' assoc >>> 'second' f >>> 'arr' unassoc)@ --- --- where --- --- > assoc ((a,b),c) = (a,(b,c)) --- > unassoc (a,(b,c)) = ((a,b),c) --- -class Arrow a => ArrowLoop a where - -- | - -- - -- > ╭──────────────╮ - -- > b │ ╭───╮ │ c - -- > >───┼─────┤ ├────┼───> - -- > │ ┌─┤ ├─┐ │ - -- > │ d │ ╰───╯ │ │ - -- > │ └───<───┘ │ - -- > ╰──────────────╯ - loop :: a (b,d) (c,d) -> a b c - --- | @since base-2.01 -instance ArrowLoop (->) where - loop f b = let (c,d) = f (b,d) in c - --- | Beware that for many monads (those for which the '>>=' operation --- is strict) this instance will /not/ satisfy the right-tightening law --- required by the 'ArrowLoop' class. --- --- @since base-2.01 -instance MonadFix m => ArrowLoop (Kleisli m) where - loop (Kleisli f) = Kleisli (liftM fst . mfix . f') - where f' x y = f (x, snd y) ===================================== libraries/ghc-internal/src/GHC/Internal/Control/Monad/Fix.hs ===================================== @@ -24,7 +24,10 @@ module GHC.Internal.Control.Monad.Fix ( MonadFix(mfix), - fix + fix, + fixIO, + -- * Feedback for Arrow + ArrowLoop(..) ) where import GHC.Internal.Data.Either @@ -34,12 +37,19 @@ import GHC.Internal.Data.Monoid ( Monoid, Dual(..), Sum(..), Product(..) , First(..), Last(..), Alt(..), Ap(..) ) import GHC.Internal.Data.NonEmpty ( NonEmpty(..) ) import GHC.Internal.Data.Ord ( Down(..) ) -import GHC.Internal.Data.Tuple ( Solo(..), snd ) -import GHC.Internal.Base ( Monad, errorWithoutStackTrace, (.) ) +import GHC.Internal.Data.Tuple ( Solo(..), fst, snd ) +import GHC.Internal.Base ( IO, Monad, errorWithoutStackTrace, (.), return, liftM ) import GHC.Internal.Generics import GHC.Internal.List ( head, drop ) import GHC.Internal.Control.Monad.ST.Imp -import GHC.Internal.System.IO +import qualified GHC.Internal.Control.Monad.ST.Lazy.Imp as Lazy +import GHC.Internal.Data.Functor.Identity (Identity(..)) +import GHC.Internal.MVar +import GHC.Internal.IO.Unsafe +import GHC.Internal.IO.Exception +import GHC.Internal.TH.Monad +import GHC.Internal.Control.Exception +import GHC.Internal.Control.Arrow -- | Monads having fixed points with a \'knot-tying\' semantics. -- Instances of 'MonadFix' should satisfy the following laws: @@ -102,6 +112,86 @@ instance MonadFix NonEmpty where instance MonadFix IO where mfix = fixIO +-- --------------------------------------------------------------------------- +-- fixIO + +-- | The implementation of 'Control.Monad.Fix.mfix' for 'IO'. +-- +-- This operation may fail with: +-- +-- * 'FixIOException' if the function passed to 'fixIO' inspects its argument. +-- +-- ==== __Examples__ +-- +-- the IO-action is only executed once. The recursion is only on the values. +-- +-- >>> take 3 <$> fixIO (\x -> putStr ":D" >> (:x) <$> readLn @Int) +-- :D +-- 2 +-- [2,2,2] +-- +-- If we are strict in the value, just as with 'Data.Function.fix', we do not get termination: +-- +-- >>> fixIO (\x -> putStr x >> pure ('x' : x)) +-- * hangs forever * +-- +-- We can tie the knot of a structure within 'IO' using 'fixIO': +-- +-- @ +-- data Node = MkNode Int (IORef Node) +-- +-- foo :: IO () +-- foo = do +-- p \<- fixIO (\p -> newIORef (MkNode 0 p)) +-- q <- output p +-- r <- output q +-- _ <- output r +-- pure () +-- +-- output :: IORef Node -> IO (IORef Node) +-- output ref = do +-- MkNode x p <- readIORef ref +-- print x +-- pure p +-- @ +-- +-- >>> foo +-- 0 +-- 0 +-- 0 +fixIO :: (a -> IO a) -> IO a +fixIO k = do + m <- newEmptyMVar + ans <- unsafeDupableInterleaveIO + (readMVar m `catch` \BlockedIndefinitelyOnMVar -> + throwIO FixIOException) + result <- k ans + putMVar m result + return result + +-- Note [Blackholing in fixIO] +-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~ +-- We do our own explicit black holing here, because GHC's lazy +-- blackholing isn't enough. In an infinite loop, GHC may run the IO +-- computation a few times before it notices the loop, which is wrong. +-- +-- NOTE2: the explicit black-holing with an IORef ran into trouble +-- with multiple threads (see #5421), so now we use an MVar. We used +-- to use takeMVar with unsafeInterleaveIO. This, however, uses noDuplicate#, +-- which is not particularly cheap. Better to use readMVar, which can be +-- performed in multiple threads safely, and to use unsafeDupableInterleaveIO +-- to avoid the noDuplicate cost. +-- +-- What we'd ideally want is probably an IVar, but we don't quite have those. +-- STM TVars look like an option at first, but I don't think they are: +-- we'd need to be able to write to the variable in an IO context, which can +-- only be done using 'atomically', and 'atomically' is not allowed within +-- unsafePerformIO. We can't know if someone will try to use the result +-- of fixIO with unsafePerformIO! +-- +-- See also System.IO.Unsafe.unsafeFixIO. +-- + -- | @since base-2.01 instance MonadFix ((->) r) where mfix f = \ r -> let a = f a r in a @@ -116,6 +206,10 @@ instance MonadFix (Either e) where instance MonadFix (ST s) where mfix = fixST +-- | @since base-2.01 +instance MonadFix (Lazy.ST s) where + mfix = Lazy.fixST + -- Instances of Data.Monoid wrappers -- | @since base-4.8.0.0 @@ -171,3 +265,77 @@ instance (MonadFix f, MonadFix g) => MonadFix (f :*: g) where -- | @since base-4.12.0.0 instance MonadFix Down where mfix f = Down (fix (getDown . f)) + + +-- | @since base-4.8.0.0 +instance MonadFix Identity where + mfix f = Identity (fix (runIdentity . f)) + +-- | If the function passed to 'mfix' inspects its argument, +-- the resulting action will throw a 'FixIOException'. +-- +-- @since 2.17.0.0 +instance MonadFix Q where + -- We use the same blackholing approach as in fixIO. + -- See Note [Blackholing in fixIO]. + mfix k = do + m <- runIO newEmptyMVar + ans <- runIO (unsafeDupableInterleaveIO + (readMVar m `catch` \BlockedIndefinitelyOnMVar -> + throwIO FixIOException)) + result <- k ans + runIO (putMVar m result) + return result + +-- | The 'loop' operator expresses computations in which an output value +-- is fed back as input, although the computation occurs only once. +-- It underlies the @rec@ value recursion construct in arrow notation. +-- 'loop' should satisfy the following laws: +-- +-- [/extension/] +-- @'loop' ('arr' f) = 'arr' (\\ b -> 'fst' ('fix' (\\ (c,d) -> f (b,d))))@ +-- +-- [/left tightening/] +-- @'loop' ('first' h >>> f) = h >>> 'loop' f@ +-- +-- [/right tightening/] +-- @'loop' (f >>> 'first' h) = 'loop' f >>> h@ +-- +-- [/sliding/] +-- @'loop' (f >>> 'arr' ('id' *** k)) = 'loop' ('arr' ('id' *** k) >>> f)@ +-- +-- [/vanishing/] +-- @'loop' ('loop' f) = 'loop' ('arr' unassoc >>> f >>> 'arr' assoc)@ +-- +-- [/superposing/] +-- @'second' ('loop' f) = 'loop' ('arr' assoc >>> 'second' f >>> 'arr' unassoc)@ +-- +-- where +-- +-- > assoc ((a,b),c) = (a,(b,c)) +-- > unassoc (a,(b,c)) = ((a,b),c) +-- +class Arrow a => ArrowLoop a where + -- | + -- + -- > ╭──────────────╮ + -- > b │ ╭───╮ │ c + -- > >───┼─────┤ ├────┼───> + -- > │ ┌─┤ ├─┐ │ + -- > │ d │ ╰───╯ │ │ + -- > │ └───<───┘ │ + -- > ╰──────────────╯ + loop :: a (b,d) (c,d) -> a b c + +-- | @since base-2.01 +instance ArrowLoop (->) where + loop f b = let (c,d) = f (b,d) in c + +-- | Beware that for many monads (those for which the '>>=' operation +-- is strict) this instance will /not/ satisfy the right-tightening law +-- required by the 'ArrowLoop' class. +-- +-- @since base-2.01 +instance MonadFix m => ArrowLoop (Kleisli m) where + loop (Kleisli f) = Kleisli (liftM fst . mfix . f') + where f' x y = f (x, snd y) ===================================== libraries/ghc-internal/src/GHC/Internal/Control/Monad/ST/Lazy/Imp.hs ===================================== @@ -37,7 +37,6 @@ module GHC.Internal.Control.Monad.ST.Lazy.Imp ( unsafeIOToST ) where -import GHC.Internal.Control.Monad.Fix import GHC.Internal.Data.Tuple import qualified GHC.Internal.Control.Monad.ST.Imp as ST @@ -210,10 +209,6 @@ fixST m = ST (\ s -> -- itself is demanded directly in the `let` body. See also -- Note [Lazy ST: not producing lazy pairs]. --- | @since base-2.01 -instance MonadFix (ST s) where - mfix = fixST - -- | @since base-4.23.0.0 instance Semigroup a => Semigroup (ST s a) where (<>) = liftA2 (<>) ===================================== libraries/ghc-internal/src/GHC/Internal/Data/Functor/Identity.hs ===================================== @@ -33,7 +33,6 @@ module GHC.Internal.Data.Functor.Identity ( Identity(..), ) where -import GHC.Internal.Control.Monad.Fix import GHC.Internal.Data.Bits (Bits, FiniteBits) import GHC.Internal.Data.Coerce import GHC.Internal.Data.Foldable @@ -143,7 +142,3 @@ instance Applicative Identity where -- | @since base-4.8.0.0 instance Monad Identity where m >>= k = k (runIdentity m) - --- | @since base-4.8.0.0 -instance MonadFix Identity where - mfix f = Identity (fix (runIdentity . f)) ===================================== libraries/ghc-internal/src/GHC/Internal/System/IO.hs ===================================== @@ -20,7 +20,6 @@ module GHC.Internal.System.IO ( -- * The IO monad IO, - fixIO, -- * Files and handles @@ -258,7 +257,6 @@ import GHC.Internal.IO.Encoding import GHC.Internal.Text.Read import GHC.Internal.IO.StdHandles import GHC.Internal.Show -import GHC.Internal.MVar ----------------------------------------------------------------------------- -- Standard IO @@ -602,87 +600,6 @@ hReady h = hWaitForInput h 0 hPrint :: Show a => Handle -> a -> IO () hPrint hdl = hPutStrLn hdl . show - --- --------------------------------------------------------------------------- --- fixIO - --- | The implementation of 'Control.Monad.Fix.mfix' for 'IO'. --- --- This operation may fail with: --- --- * 'FixIOException' if the function passed to 'fixIO' inspects its argument. --- --- ==== __Examples__ --- --- the IO-action is only executed once. The recursion is only on the values. --- --- >>> take 3 <$> fixIO (\x -> putStr ":D" >> (:x) <$> readLn @Int) --- :D --- 2 --- [2,2,2] --- --- If we are strict in the value, just as with 'Data.Function.fix', we do not get termination: --- --- >>> fixIO (\x -> putStr x >> pure ('x' : x)) --- * hangs forever * --- --- We can tie the knot of a structure within 'IO' using 'fixIO': --- --- @ --- data Node = MkNode Int (IORef Node) --- --- foo :: IO () --- foo = do --- p \<- fixIO (\p -> newIORef (MkNode 0 p)) --- q <- output p --- r <- output q --- _ <- output r --- pure () --- --- output :: IORef Node -> IO (IORef Node) --- output ref = do --- MkNode x p <- readIORef ref --- print x --- pure p --- @ --- --- >>> foo --- 0 --- 0 --- 0 -fixIO :: (a -> IO a) -> IO a -fixIO k = do - m <- newEmptyMVar - ans <- unsafeDupableInterleaveIO - (readMVar m `catch` \BlockedIndefinitelyOnMVar -> - throwIO FixIOException) - result <- k ans - putMVar m result - return result - --- Note [Blackholing in fixIO] --- ~~~~~~~~~~~~~~~~~~~~~~~~~~~ --- We do our own explicit black holing here, because GHC's lazy --- blackholing isn't enough. In an infinite loop, GHC may run the IO --- computation a few times before it notices the loop, which is wrong. --- --- NOTE2: the explicit black-holing with an IORef ran into trouble --- with multiple threads (see #5421), so now we use an MVar. We used --- to use takeMVar with unsafeInterleaveIO. This, however, uses noDuplicate#, --- which is not particularly cheap. Better to use readMVar, which can be --- performed in multiple threads safely, and to use unsafeDupableInterleaveIO --- to avoid the noDuplicate cost. --- --- What we'd ideally want is probably an IVar, but we don't quite have those. --- STM TVars look like an option at first, but I don't think they are: --- we'd need to be able to write to the variable in an IO context, which can --- only be done using 'atomically', and 'atomically' is not allowed within --- unsafePerformIO. We can't know if someone will try to use the result --- of fixIO with unsafePerformIO! --- --- See also System.IO.Unsafe.unsafeFixIO. --- - -- | The function creates a temporary file in ReadWrite mode. -- The created file isn\'t deleted automatically, so you need to delete it manually. -- ===================================== libraries/ghc-internal/src/GHC/Internal/TH/Monad.hs ===================================== @@ -28,13 +28,8 @@ import Data.Data hiding (Fixity(..)) import Data.IORef import System.IO.Unsafe ( unsafePerformIO ) import Control.Monad.IO.Class (MonadIO (..)) -import Control.Monad.Fix (MonadFix (..)) -import Control.Exception (BlockedIndefinitelyOnMVar (..), catch, throwIO) -import Control.Exception.Base (FixIOException (..)) -import Control.Concurrent.MVar (newEmptyMVar, readMVar, putMVar) import System.IO ( hPutStrLn, stderr ) import qualified Data.Kind as Kind (Type) -import GHC.IO.Unsafe ( unsafeDupableInterleaveIO ) import GHC.Types (TYPE, RuntimeRep(..)) #else import GHC.Internal.Base hiding (NonEmpty(..),Type, Module, sequence) @@ -46,12 +41,8 @@ import GHC.Internal.Data.Foldable import GHC.Internal.Data.Typeable import GHC.Internal.Control.Monad.IO.Class import GHC.Internal.Control.Monad.Fail -import GHC.Internal.Control.Monad.Fix -import GHC.Internal.Control.Exception import GHC.Internal.Num import GHC.Internal.IO.Unsafe -import GHC.Internal.MVar -import GHC.Internal.IO.Exception import qualified GHC.Internal.Types as Kind (Type) #endif import GHC.Internal.ForeignSrcLang @@ -258,22 +249,6 @@ instance Semigroup a => Semigroup (Q a) where instance Monoid a => Monoid (Q a) where mempty = pure mempty --- | If the function passed to 'mfix' inspects its argument, --- the resulting action will throw a 'FixIOException'. --- --- @since 2.17.0.0 -instance MonadFix Q where - -- We use the same blackholing approach as in fixIO. - -- See Note [Blackholing in fixIO] in System.IO in base. - mfix k = do - m <- runIO newEmptyMVar - ans <- runIO (unsafeDupableInterleaveIO - (readMVar m `catch` \BlockedIndefinitelyOnMVar -> - throwIO FixIOException)) - result <- k ans - runIO (putMVar m result) - return result - ----------------------------------------------------- -- ===================================== testsuite/tests/interface-stability/base-exports.stdout ===================================== @@ -11527,8 +11527,6 @@ instance GHC.Internal.Control.Arrow.ArrowApply (->) -- Defined in ‘GHC.Interna instance forall (m :: * -> *). GHC.Internal.Base.Monad m => GHC.Internal.Control.Arrow.ArrowApply (GHC.Internal.Control.Arrow.Kleisli m) -- Defined in ‘GHC.Internal.Control.Arrow’ instance GHC.Internal.Control.Arrow.ArrowChoice (->) -- Defined in ‘GHC.Internal.Control.Arrow’ instance forall (m :: * -> *). GHC.Internal.Base.Monad m => GHC.Internal.Control.Arrow.ArrowChoice (GHC.Internal.Control.Arrow.Kleisli m) -- Defined in ‘GHC.Internal.Control.Arrow’ -instance GHC.Internal.Control.Arrow.ArrowLoop (->) -- Defined in ‘GHC.Internal.Control.Arrow’ -instance forall (m :: * -> *). GHC.Internal.Control.Monad.Fix.MonadFix m => GHC.Internal.Control.Arrow.ArrowLoop (GHC.Internal.Control.Arrow.Kleisli m) -- Defined in ‘GHC.Internal.Control.Arrow’ instance forall (m :: * -> *). GHC.Internal.Base.MonadPlus m => GHC.Internal.Control.Arrow.ArrowPlus (GHC.Internal.Control.Arrow.Kleisli m) -- Defined in ‘GHC.Internal.Control.Arrow’ instance forall (m :: * -> *). GHC.Internal.Base.MonadPlus m => GHC.Internal.Control.Arrow.ArrowZero (GHC.Internal.Control.Arrow.Kleisli m) -- Defined in ‘GHC.Internal.Control.Arrow’ instance forall (m :: * -> *). GHC.Internal.Base.Monad m => GHC.Internal.Control.Category.Category (GHC.Internal.Control.Arrow.Kleisli m) -- Defined in ‘GHC.Internal.Control.Arrow’ @@ -11544,6 +11542,8 @@ instance forall (f :: * -> *). GHC.Internal.Control.Monad.Fail.MonadFail f => GH instance GHC.Internal.Control.Monad.Fail.MonadFail GHC.Internal.Text.ParserCombinators.ReadP.P -- Defined in ‘GHC.Internal.Text.ParserCombinators.ReadP’ instance GHC.Internal.Control.Monad.Fail.MonadFail GHC.Internal.Text.ParserCombinators.ReadP.ReadP -- Defined in ‘GHC.Internal.Text.ParserCombinators.ReadP’ instance GHC.Internal.Control.Monad.Fail.MonadFail GHC.Internal.Text.ParserCombinators.ReadPrec.ReadPrec -- Defined in ‘GHC.Internal.Text.ParserCombinators.ReadPrec’ +instance GHC.Internal.Control.Monad.Fix.ArrowLoop (->) -- Defined in ‘GHC.Internal.Control.Monad.Fix’ +instance forall (m :: * -> *). GHC.Internal.Control.Monad.Fix.MonadFix m => GHC.Internal.Control.Monad.Fix.ArrowLoop (GHC.Internal.Control.Arrow.Kleisli m) -- Defined in ‘GHC.Internal.Control.Monad.Fix’ instance forall (f :: * -> *) (g :: * -> *). (GHC.Internal.Control.Monad.Fix.MonadFix f, GHC.Internal.Control.Monad.Fix.MonadFix g) => GHC.Internal.Control.Monad.Fix.MonadFix (f GHC.Internal.Generics.:*: g) -- Defined in ‘GHC.Internal.Control.Monad.Fix’ instance forall (f :: * -> *). GHC.Internal.Control.Monad.Fix.MonadFix f => GHC.Internal.Control.Monad.Fix.MonadFix (GHC.Internal.Data.Semigroup.Internal.Alt f) -- Defined in ‘GHC.Internal.Control.Monad.Fix’ instance forall (f :: * -> *). GHC.Internal.Control.Monad.Fix.MonadFix f => GHC.Internal.Control.Monad.Fix.MonadFix (GHC.Internal.Data.Monoid.Ap f) -- Defined in ‘GHC.Internal.Control.Monad.Fix’ @@ -11553,6 +11553,7 @@ instance forall e. GHC.Internal.Control.Monad.Fix.MonadFix (GHC.Internal.Data.Ei instance forall r. GHC.Internal.Control.Monad.Fix.MonadFix ((->) r) -- Defined in ‘GHC.Internal.Control.Monad.Fix’ instance GHC.Internal.Control.Monad.Fix.MonadFix GHC.Internal.Data.Monoid.First -- Defined in ‘GHC.Internal.Control.Monad.Fix’ instance GHC.Internal.Control.Monad.Fix.MonadFix GHC.Internal.Types.IO -- Defined in ‘GHC.Internal.Control.Monad.Fix’ +instance GHC.Internal.Control.Monad.Fix.MonadFix GHC.Internal.Data.Functor.Identity.Identity -- Defined in ‘GHC.Internal.Control.Monad.Fix’ instance GHC.Internal.Control.Monad.Fix.MonadFix GHC.Internal.Data.Monoid.Last -- Defined in ‘GHC.Internal.Control.Monad.Fix’ instance GHC.Internal.Control.Monad.Fix.MonadFix [] -- Defined in ‘GHC.Internal.Control.Monad.Fix’ instance forall (f :: * -> *) i (c :: GHC.Internal.Generics.Meta). GHC.Internal.Control.Monad.Fix.MonadFix f => GHC.Internal.Control.Monad.Fix.MonadFix (GHC.Internal.Generics.M1 i c f) -- Defined in ‘GHC.Internal.Control.Monad.Fix’ @@ -11560,14 +11561,14 @@ instance GHC.Internal.Control.Monad.Fix.MonadFix GHC.Internal.Maybe.Maybe -- Def instance GHC.Internal.Control.Monad.Fix.MonadFix GHC.Internal.Base.NonEmpty -- Defined in ‘GHC.Internal.Control.Monad.Fix’ instance GHC.Internal.Control.Monad.Fix.MonadFix GHC.Internal.Generics.Par1 -- Defined in ‘GHC.Internal.Control.Monad.Fix’ instance GHC.Internal.Control.Monad.Fix.MonadFix GHC.Internal.Data.Semigroup.Internal.Product -- Defined in ‘GHC.Internal.Control.Monad.Fix’ +instance GHC.Internal.Control.Monad.Fix.MonadFix GHC.Internal.TH.Monad.Q -- Defined in ‘GHC.Internal.Control.Monad.Fix’ instance forall (f :: * -> *). GHC.Internal.Control.Monad.Fix.MonadFix f => GHC.Internal.Control.Monad.Fix.MonadFix (GHC.Internal.Generics.Rec1 f) -- Defined in ‘GHC.Internal.Control.Monad.Fix’ +instance forall s. GHC.Internal.Control.Monad.Fix.MonadFix (GHC.Internal.Control.Monad.ST.Lazy.Imp.ST s) -- Defined in ‘GHC.Internal.Control.Monad.Fix’ instance forall s. GHC.Internal.Control.Monad.Fix.MonadFix (GHC.Internal.ST.ST s) -- Defined in ‘GHC.Internal.Control.Monad.Fix’ instance GHC.Internal.Control.Monad.Fix.MonadFix Solo -- Defined in ‘GHC.Internal.Control.Monad.Fix’ instance GHC.Internal.Control.Monad.Fix.MonadFix GHC.Internal.Data.Semigroup.Internal.Sum -- Defined in ‘GHC.Internal.Control.Monad.Fix’ instance forall a. GHC.Internal.Base.Monoid a => GHC.Internal.Control.Monad.Fix.MonadFix ((,) a) -- Defined in ‘GHC.Internal.Control.Monad.Fix’ -instance forall s. GHC.Internal.Control.Monad.Fix.MonadFix (GHC.Internal.Control.Monad.ST.Lazy.Imp.ST s) -- Defined in ‘GHC.Internal.Control.Monad.ST.Lazy.Imp’ instance GHC.Internal.Control.Monad.Fix.MonadFix Data.Complex.Complex -- Defined in ‘Data.Complex’ -instance GHC.Internal.Control.Monad.Fix.MonadFix GHC.Internal.Data.Functor.Identity.Identity -- Defined in ‘GHC.Internal.Data.Functor.Identity’ instance [safe] forall (f :: * -> *) (g :: * -> *). (GHC.Internal.Control.Monad.Fix.MonadFix f, GHC.Internal.Control.Monad.Fix.MonadFix g) => GHC.Internal.Control.Monad.Fix.MonadFix (Data.Functor.Product.Product f g) -- Defined in ‘Data.Functor.Product’ instance GHC.Internal.Control.Monad.Fix.MonadFix Data.Semigroup.First -- Defined in ‘Data.Semigroup’ instance GHC.Internal.Control.Monad.Fix.MonadFix Data.Semigroup.Last -- Defined in ‘Data.Semigroup’ ===================================== testsuite/tests/interface-stability/template-haskell-exports.stdout ===================================== @@ -2052,7 +2052,6 @@ instance GHC.Internal.Classes.Ord GHC.Internal.TH.Syntax.Type -- Defined in ‘G instance GHC.Internal.Classes.Ord GHC.Internal.TH.Syntax.TypeFamilyHead -- Defined in ‘GHC.Internal.TH.Syntax’ instance GHC.Internal.Classes.Ord GHC.Internal.LanguageExtensions.Extension -- Defined in ‘GHC.Internal.LanguageExtensions’ instance GHC.Internal.Control.Monad.Fail.MonadFail GHC.Internal.TH.Monad.Q -- Defined in ‘GHC.Internal.TH.Monad’ -instance GHC.Internal.Control.Monad.Fix.MonadFix GHC.Internal.TH.Monad.Q -- Defined in ‘GHC.Internal.TH.Monad’ instance GHC.Internal.Control.Monad.IO.Class.MonadIO GHC.Internal.TH.Monad.Q -- Defined in ‘GHC.Internal.TH.Monad’ instance GHC.Internal.Data.Foldable.Foldable GHC.Internal.TH.Syntax.TyVarBndr -- Defined in ‘GHC.Internal.TH.Syntax’ instance GHC.Internal.Data.Traversable.Traversable GHC.Internal.TH.Syntax.TyVarBndr -- Defined in ‘GHC.Internal.TH.Syntax’ View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/f56da1de1ccae276143bf32d727b77e… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/f56da1de1ccae276143bf32d727b77e… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/T26875] ghc-internal: avoid depending on GHC.Internal.Control.Monad.Fix
by Teo Camarasu (＠teo) 03 Feb '26

03 Feb '26

Teo Camarasu pushed to branch wip/T26875 at Glasgow Haskell Compiler / GHC Commits: 3d361b63 by Teo Camarasu at 2026-02-03T19:10:35+00:00 ghc-internal: avoid depending on GHC.Internal.Control.Monad.Fix This module contains the definition of MonadFix, since we want an instance for IO, that instance requires a lot of machinery and we want to avoid an orphan instance, this will naturally be quite high up in the dependency graph. So we want to avoid other modules depending on it as far as possible. One essential use remains. Control.Arrow's ArrowLoop is defined in terms of MoandFix Resolves #26875 - - - - - 4 changed files: - libraries/ghc-internal/src/GHC/Internal/Control/Monad/Fix.hs - libraries/ghc-internal/src/GHC/Internal/Control/Monad/ST/Lazy/Imp.hs - libraries/ghc-internal/src/GHC/Internal/Data/Functor/Identity.hs - libraries/ghc-internal/src/GHC/Internal/TH/Monad.hs Changes: ===================================== libraries/ghc-internal/src/GHC/Internal/Control/Monad/Fix.hs ===================================== @@ -35,11 +35,17 @@ import GHC.Internal.Data.Monoid ( Monoid, Dual(..), Sum(..), Product(..) import GHC.Internal.Data.NonEmpty ( NonEmpty(..) ) import GHC.Internal.Data.Ord ( Down(..) ) import GHC.Internal.Data.Tuple ( Solo(..), snd ) -import GHC.Internal.Base ( Monad, errorWithoutStackTrace, (.) ) +import GHC.Internal.Base ( Monad, errorWithoutStackTrace, (.), return ) import GHC.Internal.Generics import GHC.Internal.List ( head, drop ) import GHC.Internal.Control.Monad.ST.Imp -import GHC.Internal.System.IO +import qualified GHC.Internal.Control.Monad.ST.Lazy.Imp as Lazy +import GHC.Internal.Data.Functor.Identity (Identity(..)) +import GHC.Internal.MVar +import GHC.Internal.IO.Unsafe +import GHC.Internal.IO.Exception +import GHC.Internal.TH.Monad +import GHC.Internal.Control.Exception -- | Monads having fixed points with a \'knot-tying\' semantics. -- Instances of 'MonadFix' should satisfy the following laws: @@ -116,6 +122,10 @@ instance MonadFix (Either e) where instance MonadFix (ST s) where mfix = fixST +-- | @since base-2.01 +instance MonadFix (Lazy.ST s) where + mfix = Lazy.fixST + -- Instances of Data.Monoid wrappers -- | @since base-4.8.0.0 @@ -171,3 +181,24 @@ instance (MonadFix f, MonadFix g) => MonadFix (f :*: g) where -- | @since base-4.12.0.0 instance MonadFix Down where mfix f = Down (fix (getDown . f)) + + +-- | @since base-4.8.0.0 +instance MonadFix Identity where + mfix f = Identity (fix (runIdentity . f)) + +-- | If the function passed to 'mfix' inspects its argument, +-- the resulting action will throw a 'FixIOException'. +-- +-- @since 2.17.0.0 +instance MonadFix Q where + -- We use the same blackholing approach as in fixIO. + -- See Note [Blackholing in fixIO] in System.IO in base. + mfix k = do + m <- runIO newEmptyMVar + ans <- runIO (unsafeDupableInterleaveIO + (readMVar m `catch` \BlockedIndefinitelyOnMVar -> + throwIO FixIOException)) + result <- k ans + runIO (putMVar m result) + return result ===================================== libraries/ghc-internal/src/GHC/Internal/Control/Monad/ST/Lazy/Imp.hs ===================================== @@ -37,7 +37,6 @@ module GHC.Internal.Control.Monad.ST.Lazy.Imp ( unsafeIOToST ) where -import GHC.Internal.Control.Monad.Fix import GHC.Internal.Data.Tuple import qualified GHC.Internal.Control.Monad.ST.Imp as ST @@ -210,10 +209,6 @@ fixST m = ST (\ s -> -- itself is demanded directly in the `let` body. See also -- Note [Lazy ST: not producing lazy pairs]. --- | @since base-2.01 -instance MonadFix (ST s) where - mfix = fixST - -- | @since base-4.23.0.0 instance Semigroup a => Semigroup (ST s a) where (<>) = liftA2 (<>) ===================================== libraries/ghc-internal/src/GHC/Internal/Data/Functor/Identity.hs ===================================== @@ -33,7 +33,6 @@ module GHC.Internal.Data.Functor.Identity ( Identity(..), ) where -import GHC.Internal.Control.Monad.Fix import GHC.Internal.Data.Bits (Bits, FiniteBits) import GHC.Internal.Data.Coerce import GHC.Internal.Data.Foldable @@ -143,7 +142,3 @@ instance Applicative Identity where -- | @since base-4.8.0.0 instance Monad Identity where m >>= k = k (runIdentity m) - --- | @since base-4.8.0.0 -instance MonadFix Identity where - mfix f = Identity (fix (runIdentity . f)) ===================================== libraries/ghc-internal/src/GHC/Internal/TH/Monad.hs ===================================== @@ -28,13 +28,8 @@ import Data.Data hiding (Fixity(..)) import Data.IORef import System.IO.Unsafe ( unsafePerformIO ) import Control.Monad.IO.Class (MonadIO (..)) -import Control.Monad.Fix (MonadFix (..)) -import Control.Exception (BlockedIndefinitelyOnMVar (..), catch, throwIO) -import Control.Exception.Base (FixIOException (..)) -import Control.Concurrent.MVar (newEmptyMVar, readMVar, putMVar) import System.IO ( hPutStrLn, stderr ) import qualified Data.Kind as Kind (Type) -import GHC.IO.Unsafe ( unsafeDupableInterleaveIO ) import GHC.Types (TYPE, RuntimeRep(..)) #else import GHC.Internal.Base hiding (NonEmpty(..),Type, Module, sequence) @@ -46,12 +41,8 @@ import GHC.Internal.Data.Foldable import GHC.Internal.Data.Typeable import GHC.Internal.Control.Monad.IO.Class import GHC.Internal.Control.Monad.Fail -import GHC.Internal.Control.Monad.Fix -import GHC.Internal.Control.Exception import GHC.Internal.Num import GHC.Internal.IO.Unsafe -import GHC.Internal.MVar -import GHC.Internal.IO.Exception import qualified GHC.Internal.Types as Kind (Type) #endif import GHC.Internal.ForeignSrcLang @@ -258,22 +249,6 @@ instance Semigroup a => Semigroup (Q a) where instance Monoid a => Monoid (Q a) where mempty = pure mempty --- | If the function passed to 'mfix' inspects its argument, --- the resulting action will throw a 'FixIOException'. --- --- @since 2.17.0.0 -instance MonadFix Q where - -- We use the same blackholing approach as in fixIO. - -- See Note [Blackholing in fixIO] in System.IO in base. - mfix k = do - m <- runIO newEmptyMVar - ans <- runIO (unsafeDupableInterleaveIO - (readMVar m `catch` \BlockedIndefinitelyOnMVar -> - throwIO FixIOException)) - result <- k ans - runIO (putMVar m result) - return result - ----------------------------------------------------- -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/3d361b632a105cfc594d7692d5bcb35… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/3d361b632a105cfc594d7692d5bcb35… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc] Pushed new branch wip/T26875
by Teo Camarasu (＠teo) 03 Feb '26

03 Feb '26

Teo Camarasu pushed new branch wip/T26875 at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/T26875 You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc][wip/T26503] 42 commits: GC: don't use CAS without PARALLEL_GC on
by Brandon Chinn (＠brandonchinn178) 03 Feb '26

03 Feb '26

Brandon Chinn pushed to branch wip/T26503 at Glasgow Haskell Compiler / GHC Commits: 0491f08a by Sylvain Henry at 2026-01-22T03:44:26-05:00 GC: don't use CAS without PARALLEL_GC on If we're not using the parallel GC, there is no reason to do a costly CAS. This was flagged as taking time in a perf profile. - - - - - 211a8f56 by Sylvain Henry at 2026-01-22T03:44:26-05:00 GC: suffix parallel GC with "par" instead of "thr" Avoid some potential confusion (see discussion in !15351). - - - - - 77a23cbd by fendor at 2026-01-22T03:45:08-05:00 Remove blanket ignore that covers libraries/ - - - - - 18bf7f5c by Léana Jiang at 2026-01-22T08:58:45-05:00 doc: update Flavour type in hadrian user-settings - - - - - 3d5a1365 by Cheng Shao at 2026-01-22T08:59:28-05:00 hadrian: add missing notCross predicate for stage0 -O0 There are a few hard-coded hadrian args that pass -O0 when compiling some heavy modules in stage0, which only makes sense when not cross-compiling and when cross-compiling we need properly optimized stage0 packages. So this patch adds the missing `notCross` predicate in those places. - - - - - ee937134 by Matthew Pickering at 2026-01-22T09:00:10-05:00 Fix ghc-experimental GHC.Exception.Backtrace.Experimental module This module wasn't added to the cabal file so it was never compiled or included in the library. - - - - - 1b490f5a by Zubin Duggal at 2026-01-22T09:00:53-05:00 hadrian: Add ghc-{experimental,internal}.cabal to the list of dependencies of the doc target We need these files to detect the version of these libraries Fixes #26738 - - - - - cdb74049 by Cheng Shao at 2026-01-22T14:52:36-05:00 rts: avoid Cmm loop to initialize Array#/SmallArray# Previously, `newArray#`/`newSmallArray#` called an RTS C function to allocate the `Array#`/`SmallArray#`, then used a Cmm loop to initialize the elements. Cmm doesn't have native for-loop so the code is a bit awkward, and it's less efficient than a C loop, since the C compiler can effectively vectorize the loop with optimizations. So this patch moves the loop that initializes the elements to the C side. `allocateMutArrPtrs`/`allocateSmallMutArrPtrs` now takes a new `init` argument and initializes the elements if `init` is non-NULL. - - - - - 4c784f00 by Cheng Shao at 2026-01-22T14:53:19-05:00 Fix testsuite run for +ipe flavour transformer This patch makes the +ipe flavour transformer pass the entire testsuite: - An RTS debug option `-DI` is added, the IPE trace information is now only printed with `-DI`. The test cases that do require IPE trace are now run with `-DI`. - The testsuite config option `ghc_with_ipe` is added, enabled when running the testsuite with `+ipe`, which skips a few tests that are sensitive to eventlog output, allocation patterns etc that can fail under `+ipe`. This is the first step towards #26799. Co-authored-by: Codex <codex(a)openai.com> - - - - - be8e5236 by Ben Gamari at 2026-01-23T03:28:45-05:00 hadrian: Bump QuickCheck upper bound This patch bumps QuickCheck upper bound to 2.18. selftest rule manually tested to work with current latest QuickCheck-2.17.1.0. - - - - - 5aa328fb by Zubin Duggal at 2026-01-23T03:29:30-05:00 Add genindex to index.rst. This adds a link to the index in the navigation bar. Fixes #26437 - - - - - 917ab8ff by Oleg Grenrus at 2026-01-23T10:52:55-05:00 Export labelThread from Control.Concurrent - - - - - 3f5e8d80 by Cheng Shao at 2026-01-23T10:53:37-05:00 ci: only push perf notes on master/release branches This patch fixes push_perf_notes logic in ci.sh to only push perf notes on master/release branches. We used to unconditionally push perf notes even in MRs, but the perf numbers in the wip branches wouldn't be used as baseline anyway, plus this is causing a space leak in the ghc-performance-notes repo. See #25317 for the perf notes repo size problem. Co-authored-by: Codex <codex(a)openai.com> - - - - - 414b9593 by Cheng Shao at 2026-01-24T07:11:51-05:00 ci: remove duplicate keys in .gitlab-ci.yml This patch removes accidentally duplicate keys in `.gitlab-ci.yml`. The YAML spec doesn't allow duplicate keys in the first place, and according to GitLab docs (https://docs.gitlab.com/ci/yaml/yaml_optimization/#anchors) the latest key overrides the earlier entries. - - - - - e5cb5491 by Cheng Shao at 2026-01-24T07:12:34-05:00 hadrian: drop obsolete configure/make builder logic for libffi This patch drops obsolete hadrian logic around `Configure libffiPath`/`Make libffiPath` builders, they are no longer needed after libffi-clib has landed. Closes #26815. - - - - - 2d160222 by Simon Hengel at 2026-01-24T07:13:17-05:00 Fix typo in roles.rst - - - - - 56db94f7 by Peter Trommler at 2026-01-26T11:26:18+01:00 PPC NCG: Generate clear right insn at arch width The clear right immediate (clrrxi) is only available in word and doubleword width. Generate clrrxi instructions at architecture width for all MachOp widths. Fixes #24145 - - - - - 5957a8ad by Wolfgang Jeltsch at 2026-01-27T06:11:40-05:00 Add operations for obtaining operating-system handles This contribution implements CLC proposal #369. It adds operations for obtaining POSIX file descriptors and Windows handles that underlie Haskell handles. Those operating system handles can also be obtained without such additional operations, but this is more involved and, more importantly, requires using internals. - - - - - 86a0510c by Greg Steuck at 2026-01-27T06:12:34-05:00 Move flags to precede patterns for grep and read files directly This makes the tests pass with non-GNU (i.e. POSIX-complicant) tools. There's no reason to use cat and pipe where direct file argument works. - - - - - 50761451 by Cheng Shao at 2026-01-27T21:51:23-05:00 ci: update darwin boot ghc to 9.10.3 This patch updates darwin boot ghc to 9.10.3, along with other related updates, and pays off some technical debt here: - Update `nixpkgs` and use the `nixpkgs-25.05-darwin` channel. - Update the `niv` template. - Update LLVM to 21 and update `llvm-targets` to reflect LLVM 21 layout changes for arm64/x86_64 darwin targets. - Use `stdenvNoCC` to prevent nix packaged apple sdk from being used by boot ghc, and manually set `DEVELOPER_DIR`/`SDKROOT` to enforce the usage of system-wide command line sdk for macos. - When building nix derivation for boot ghc, run `configure` via the `arch` command so that `configure` and its subprocesses pick up the manually specified architecture. - Remove the previous horrible hack that obliterates `configure` to make autoconf test result in true. `configure` now properly does its job. - Remove the now obsolete configure args and post install settings file patching logic. - Use `scheme-small` for texlive to avoid build failures in certain unused texlive packages, especially on x86_64-darwin. - - - - - 94dcd15e by Matthew Pickering at 2026-01-27T21:52:05-05:00 Evaluate backtraces for "error" exceptions at the moment they are thrown See Note [Capturing the backtrace in throw] and Note [Hiding precise exception signature in throw] which explain the implementation. This commit makes `error` and `throw` behave the same with regard to backtraces. Previously, exceptions raised by `error` would not contain useful IPE backtraces. I did try and implement `error` in terms of `throw` but it started to involve putting diverging functions into hs-boot files, which seemed to risky if the compiler wouldn't be able to see if applying a function would diverge. CLC proposal: https://github.com/haskell/core-libraries-committee/issues/383 Fixes #26751 - - - - - ef35e3ea by Teo Camarasu at 2026-01-27T21:52:46-05:00 ghc-internal: move all Data instances to Data.Data Most instances of Data are defined in GHC.Internal.Data.Data. Let's move all remaining instance there. This moves other modules down in the dependency hierarchy allowing for more parallelism, and it decreases the likelihood that we would need to load this heavy .hi file if we don't actually need it. Resolves #26830 Metric Decrease: T12227 T16875 - - - - - 5e0ec555 by sheaf at 2026-01-28T06:56:38-05:00 Add test case for #25679 This commit adds the T25679 test case. The test now passes, thanks to commit 1e53277af36d3f0b6ad5491f70ffc5593a49dcfd. Fixes #25679 - - - - - f1cd1611 by sheaf at 2026-01-28T06:56:38-05:00 Improve defaulting of representational equalities This commit makes the defaulting of representational equalities, introduced in 1e53277a, a little bit more robust. Now, instead of calling the eager unifier, it calls the full-blown constraint solver, which means that it can handle some subtle situations, e.g. involving functional dependencies and type-family injectivity annotations, such as: type family F a = r | r -> a type instance F Int = Bool [W] F beta ~R Bool - - - - - 25edf516 by sheaf at 2026-01-28T06:56:38-05:00 Improve errors for unsolved representational equalities This commit adds a new field of CtLoc, CtExplanations, which allows the typechecker to leave some information about what it has done. For the moment, it is only used to improve error messages for unsolved representational equalities. The typechecker will now accumulate, when unifying at representational role: - out-of-scope newtype constructors, - type constructors that have nominal role in a certain argument, - over-saturated type constructors, - AppTys, e.g. `c a ~R# c b`, to report that we must assume that 'c' has nominal role in its parameters, - data family applications that do not reduce, potentially preventing newtype unwrapping. Now, instead of having to re-construct the possible errors after the fact, we simply consult the CtExplanations field. Additionally, this commit modifies the typechecker error messages that concern out-of-scope newtype constructors. The error message now depends on whether we have an import suggestion to provide to the user: - If we have an import suggestion for the newtype constructor, the message will be of the form: The data constructor MkN of the newtype N is out of scope Suggested fix: add 'MkN' to the import list in the import of 'M' - If we don't have any import suggestions, the message will be of the form: NB: The type 'N' is an opaque newtype, whose constructor is hidden Fixes #15850, #20289, #20468, #23731, #25949, #26137 - - - - - 4d0e6da1 by Simon Peyton Jones at 2026-01-28T06:57:19-05:00 Fix two bugs in short-cut constraint solving There are two main changes here: * Use `isSolvedWC` rather than `isEmptyWC` in `tryShortCutSolver` The residual constraint may have some fully-solved, but still-there implications, and we don't want them to abort short cut solving! That bug caused #26805. * In the short-cut solver, we abandon the fully-solved residual constraint; but we may thereby lose track of Givens that are needed, and either report them as redundant or prune evidence bindings that are in fact needed. This bug stopped the `constraints` package from compiling; see the trail in !15389. The second bug led me to (another) significant refactoring of the mechanism for tracking needed EvIds. See the new Note [Tracking needed EvIds] in GHC.Tc.Solver.Solve It's simpler and much less head-scratchy now. Some particulars: * An EvBindsVar now tracks NeededEvIds * We deal with NeededEvIds for an implication only when it is fully solved. Much simpler! * `tryShortCutTcS` now takes a `TcM WantedConstraints` rather than `TcM Bool`, so that is can plumb the needed EvIds correctly. * Remove `ic_need` and `ic_need_implic` from Implication (hooray), and add `ics_dm` and `ics_non_dm` to `IC_Solved`. Pure refactor * Shorten data constructor `CoercionHole` to `CH`, following general practice in GHC. * Rename `EvBindMap` to `EvBindsMap` for consistency - - - - - 662480b7 by Cheng Shao at 2026-01-28T06:58:00-05:00 ci: use debian validate bindists instead of fedora release bindists in testing stage This patch changes the `abi-test`, `hadrian-multi` and `perf` jobs in the full-ci pipeline testing stage to use debian validate bindists instead of fedora release bindists, to increase pipeline level parallelism and allow full-ci pipelines to complete earlier. Closes #26818. - - - - - 39581ec6 by Cheng Shao at 2026-01-28T06:58:40-05:00 ci: run perf test with -j$cores This patch makes the perf ci job compile Cabal with -j$cores to speed up the job. - - - - - 607b287b by Wolfgang Jeltsch at 2026-01-28T15:41:53+02:00 Remove `GHC.Desugar` from `base` `GHC.Desugar` was deprecated and should have been removed in GHC 9.14. However, the removal was forgotten, although there was a code block that was intended to trigger a compilation error when the GHC version in use was 9.14 or later. This code sadly didn’t work, because the `__GLASGOW_HASKELL__` macro was misspelled as `__GLASGOW_HASKELL`. - - - - - e8f5a45d by sterni at 2026-01-29T04:19:18-05:00 users_guide: fix runtime error during build with Sphinx 9.1.0 Appears that pathto is stricter about what it accepts now. Tested Sphinx 8.2.3 and 9.1.0 on the ghc-9.10 branch. Resolves #26810. Co-authored-by: Martin Weinelt <hexa(a)darmstadt.ccc.de> - - - - - ce2d62fb by Jessica Clarke at 2026-01-29T19:48:51-05:00 PPC NCG: Use libcall for 64-bit cmpxchg on 32-bit PowerPC There is no native instruction for this, and even if there were a register pair version we could use, the implementation here is assuming the values fit in a single register, and we end up only using / defining the low halves of the registers. Fixes: b4d39adbb5 ("PrimOps: Add CAS op for all int sizes") Fixes: #23969 - - - - - 43d97761 by Michael Karcher at 2026-01-29T19:49:43-05:00 NCG for PPC: add pattern for CmmRegOff to iselExpr64 Closes #26828 - - - - - aeeb4a20 by Matthew Pickering at 2026-01-30T11:42:47-05:00 determinism: Use deterministic map for Strings in TyLitMap When generating typeable evidence the types we need evidence for all cached in a TypeMap, the order terms are retrieved from a type map determines the order the bindings appear in the program. A TypeMap is quite diligent to use deterministic maps, apart from in the TyLitMap, which uses a UniqFM for storing strings, whose ordering depends on the Unique of the FastString. This can cause non-deterministic .hi and .o files. An unexpected side-effect is the error message but RecordDotSyntaxFail8 changing. I looked into this with Sam and this change caused the constraints to be solved in a different order which results in a slightly different error message. I have accepted the new test, since the output before was non-deterministic and the new output is consistent with the other messages in that file. Fixes #26846 - - - - - 9e4d70c2 by Andrew Lelechenko at 2026-01-30T11:43:29-05:00 Upgrade text submodule to 2.1.4 - - - - - 631fa5ae by Recursion Ninja at 2026-01-31T22:30:11+00:00 Decouple `L.S.H.Decls` from importing `GHC.Types.Basic` Data-types within `GHC.Types.Basic` which describe components of the AST are migrated to `Language.Haskell.Syntax.Basic`. Related function definitions are also moved. Types moved to L.H.S. because they are part of the AST: * TopLevelFlag * RuleName Types moved from L.H.S. to GHC.Hs. because they are not needed in the AST: * TyConFlavour * TypeOrData * NewOrData Migrated instances: * `Outputable` instances moved to in `GHC.Utils.Outputable` * `Binary` instance of `Boxity` moved to to `GHC.Utils.Binary` * Other `Binary` instances are orphans to be migrated later. The `OverlapMode` data-type is given a TTG extension point. The `OverlapFlag` data-type, which depends on `OverlapMode`, is updated to support `OverlapMode` with a GHC "pass" type paramerter. In order to avoid module import cycles, `OverlapMode` and `OverlapFlag` are migrated to new modules (no way around this). * Migrated `OverlapMode` to new module `Language.Haskell.Syntax.Overlap` * Migrated `OverlapFlag` to new module `GHC.Hs.Decls.Overlap` - - - - - 9769cc03 by Simon Hengel at 2026-02-01T04:21:03-05:00 Update the documentation for MultiWayIf (fixes #25376) (so that it matches the implementation) - - - - - 5fc9442a by Peter Trommler at 2026-02-01T04:21:44-05:00 hadrian: Fix dependency generation for assembler Assembler files allow # for comments unless in column 1. A modern cpp for C treats those a preprocessor directives. We tell gcc that a .S file is assembler with cpp and not C. Fixes #26819 - - - - - 269c4087 by Simon Peyton Jones at 2026-02-01T19:38:10-05:00 Include current phase in the range for rule/unfoldings This MR fixes a bad loop in the compiler: #26826. The fix is to add (WAR2) to Note [What is active in the RHS of a RULE or unfolding?] in GHC.Core.Opt.Simplify.Utils - - - - - ddf1434f by Vladislav Zavialov at 2026-02-01T19:38:52-05:00 Refactor: merge HsMultilineString into HsString (#26860) Before this patch, HsLit defined two separate constructors to represent single-line and multi-line strings: data HsLit x ... | HsString (XHsString x) FastString | HsMultilineString (XHsMultilineString x) FastString I found this to be an unnecessary complication and an obstacle to unifying HsLit with HsTyLit. Now we use HsString for both kinds of literals. One user-facing change here is `ppr (HsString st s)` behaving differently for single-line strings containing newlines: x = "first line \ \asdf\n\ \second line" Previously, the literal was fed to `ftext` with its newlines, producing an ill-formed SDoc. This issue is now addressed by using `split` for both single-line and multi-line strings: vcat $ map text $ split '\n' (unpackFS src) See the parser/should_fail/T26860ppr test. In addition (and unrelatedly to the main payload of this patch), drop the unused pmPprHsLit helper. - - - - - 2b4f463c by Simon Peyton Jones at 2026-02-02T17:32:32+00:00 Remove exprIsCheap from doFloatFromRhs See #26854 and Note [Float when expandable] This patch simplifies the code, by removing an extra unnecessary test. - - - - - 9db7f21f by Brandon Chinn at 2026-02-03T09:15:10-05:00 Refactor: make function patterns exhaustive Also added missing (==) logic for: * HsMultilineString * HsInt{8,16,32} * HsWord{8,16,32} - - - - - fe56c02f by Brandon Chinn at 2026-02-03T10:18:21-08:00 Implement QualifiedStrings (#26503) See Note [Implementation of QualifiedStrings] - - - - - 282 changed files: - .gitignore - .gitlab-ci.yml - .gitlab/ci.sh - .gitlab/darwin/nix/sources.json - .gitlab/darwin/toolchain.nix - compiler/GHC/Builtin/Types.hs - compiler/GHC/CmmToAsm/PPC/CodeGen.hs - compiler/GHC/Core/Coercion.hs - compiler/GHC/Core/FamInstEnv.hs - compiler/GHC/Core/InstEnv.hs - compiler/GHC/Core/Map/Type.hs - compiler/GHC/Core/Opt/OccurAnal.hs - compiler/GHC/Core/Opt/Simplify/Env.hs - compiler/GHC/Core/Opt/Simplify/Utils.hs - compiler/GHC/Core/Opt/WorkWrap.hs - compiler/GHC/Core/Predicate.hs - compiler/GHC/Core/TyCo/Rep.hs - compiler/GHC/Core/TyCo/Subst.hs - compiler/GHC/Core/TyCo/Tidy.hs - compiler/GHC/Core/TyCon/RecWalk.hs - compiler/GHC/Data/Maybe.hs - compiler/GHC/Driver/Flags.hs - compiler/GHC/Hs/Decls.hs - + compiler/GHC/Hs/Decls/Overlap.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/Instances.hs - compiler/GHC/Hs/Lit.hs - compiler/GHC/Hs/Pat.hs - compiler/GHC/Hs/Syn/Type.hs - compiler/GHC/Hs/Utils.hs - compiler/GHC/HsToCore/Errors/Types.hs - compiler/GHC/HsToCore/Expr.hs - compiler/GHC/HsToCore/Match/Literal.hs - compiler/GHC/HsToCore/Pmc/Desugar.hs - compiler/GHC/HsToCore/Pmc/Solver.hs - compiler/GHC/HsToCore/Quote.hs - compiler/GHC/HsToCore/Ticks.hs - compiler/GHC/Iface/Ext/Ast.hs - compiler/GHC/Iface/Syntax.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/Errors/Ppr.hs - compiler/GHC/Parser/Errors/Types.hs - compiler/GHC/Parser/Lexer.x - compiler/GHC/Parser/PostProcess.hs - compiler/GHC/Parser/String.hs - compiler/GHC/Rename/Bind.hs - compiler/GHC/Rename/Env.hs - compiler/GHC/Rename/Expr.hs - + compiler/GHC/Rename/Lit.hs - compiler/GHC/Rename/Module.hs - compiler/GHC/Rename/Names.hs - compiler/GHC/Rename/Pat.hs - compiler/GHC/Rename/Splice.hs - compiler/GHC/Rename/Unbound.hs - compiler/GHC/Tc/Deriv.hs - compiler/GHC/Tc/Deriv/Utils.hs - compiler/GHC/Tc/Errors.hs - compiler/GHC/Tc/Errors/Ppr.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/Gen/Default.hs - compiler/GHC/Tc/Gen/Expr.hs - compiler/GHC/Tc/Gen/Head.hs - compiler/GHC/Tc/Gen/HsType.hs - compiler/GHC/Tc/Gen/Pat.hs - compiler/GHC/Tc/Instance/Family.hs - compiler/GHC/Tc/Solver/Default.hs - compiler/GHC/Tc/Solver/Dict.hs - compiler/GHC/Tc/Solver/Equality.hs - compiler/GHC/Tc/Solver/InertSet.hs - compiler/GHC/Tc/Solver/Monad.hs - compiler/GHC/Tc/Solver/Solve.hs - compiler/GHC/Tc/TyCl/Instance.hs - compiler/GHC/Tc/TyCl/PatSyn.hs - compiler/GHC/Tc/Types/Constraint.hs - compiler/GHC/Tc/Types/CtLoc.hs - compiler/GHC/Tc/Types/Evidence.hs - compiler/GHC/Tc/Types/Origin.hs - compiler/GHC/Tc/Utils/Env.hs - compiler/GHC/Tc/Utils/Instantiate.hs - compiler/GHC/Tc/Utils/Monad.hs - compiler/GHC/Tc/Utils/TcMType.hs - compiler/GHC/Tc/Utils/Unify.hs - compiler/GHC/Tc/Zonk/TcType.hs - compiler/GHC/Tc/Zonk/Type.hs - compiler/GHC/ThToHs.hs - compiler/GHC/Types/Basic.hs - compiler/GHC/Types/Error/Codes.hs - compiler/GHC/Types/InlinePragma.hs - compiler/GHC/Types/Name.hs - compiler/GHC/Types/RepType.hs - compiler/GHC/Types/Var.hs - compiler/GHC/Unit/Types.hs - compiler/GHC/Utils/Binary.hs - compiler/GHC/Utils/Monad.hs - compiler/GHC/Utils/Outputable.hs - compiler/GHC/Utils/Trace.hs - compiler/Language/Haskell/Syntax/Basic.hs - compiler/Language/Haskell/Syntax/Decls.hs - + compiler/Language/Haskell/Syntax/Decls/Overlap.hs - compiler/Language/Haskell/Syntax/Expr.hs - compiler/Language/Haskell/Syntax/Extension.hs - compiler/Language/Haskell/Syntax/Lit.hs - compiler/Language/Haskell/Syntax/Pat.hs - compiler/ghc.cabal.in - docs/users_guide/9.16.1-notes.rst - docs/users_guide/exts/multiway_if.rst - + docs/users_guide/exts/qualified_strings.rst - docs/users_guide/exts/roles.rst - docs/users_guide/index.rst - docs/users_guide/rtd-theme/layout.html - docs/users_guide/runtime_control.rst - hadrian/doc/user-settings.md - hadrian/hadrian.cabal - hadrian/src/Builder.hs - hadrian/src/Context.hs - hadrian/src/Flavour.hs - hadrian/src/Rules/Compile.hs - hadrian/src/Rules/Documentation.hs - hadrian/src/Settings/Builders/Cc.hs - hadrian/src/Settings/Builders/Configure.hs - hadrian/src/Settings/Builders/Make.hs - hadrian/src/Settings/Packages.hs - libraries/base/base.cabal.in - libraries/base/changelog.md - libraries/base/src/Control/Concurrent.hs - − libraries/base/src/GHC/Desugar.hs - + libraries/base/src/System/IO/OS.hs - libraries/base/src/System/Timeout.hs - libraries/base/tests/IO/all.T - + libraries/base/tests/IO/osHandles001FileDescriptors.hs - + libraries/base/tests/IO/osHandles001FileDescriptors.stdout - + libraries/base/tests/IO/osHandles001WindowsHandles.hs - + libraries/base/tests/IO/osHandles001WindowsHandles.stdout - + libraries/base/tests/IO/osHandles002FileDescriptors.hs - + libraries/base/tests/IO/osHandles002FileDescriptors.stderr - + libraries/base/tests/IO/osHandles002FileDescriptors.stdin - + libraries/base/tests/IO/osHandles002FileDescriptors.stdout - + libraries/base/tests/IO/osHandles002WindowsHandles.hs - + libraries/base/tests/IO/osHandles002WindowsHandles.stderr - + libraries/base/tests/IO/osHandles002WindowsHandles.stdin - + libraries/base/tests/IO/osHandles002WindowsHandles.stdout - libraries/base/tests/T23454.stderr - libraries/base/tests/perf/Makefile - libraries/ghc-compact/tests/all.T - libraries/ghc-experimental/ghc-experimental.cabal.in - libraries/ghc-experimental/src/GHC/Exception/Backtrace/Experimental.hs - libraries/ghc-internal/ghc-internal.cabal.in - libraries/ghc-internal/src/GHC/Internal/Data/Data.hs - libraries/ghc-internal/src/GHC/Internal/Err.hs - libraries/ghc-internal/src/GHC/Internal/Exts.hs - libraries/ghc-internal/src/GHC/Internal/Functor/ZipList.hs - libraries/ghc-internal/src/GHC/Internal/LanguageExtensions.hs - + libraries/ghc-internal/src/GHC/Internal/System/IO/OS.hs - libraries/ghc-internal/tests/backtraces/all.T - libraries/ghc-internal/tests/stack-annotation/all.T - + libraries/ghc-internal/tests/stack-annotation/ann_frame005.hs - + libraries/ghc-internal/tests/stack-annotation/ann_frame005.stdout - libraries/text - llvm-targets - rts/AllocArray.c - rts/AllocArray.h - rts/ClosureTable.c - rts/Heap.c - rts/PrimOps.cmm - rts/RtsFlags.c - rts/Threads.c - rts/Trace.c - rts/Weak.c - rts/include/rts/Flags.h - rts/rts.cabal - rts/sm/Evac.c - rts/sm/Evac_thr.c → rts/sm/Evac_par.c - rts/sm/Scav_thr.c → rts/sm/Scav_par.c - testsuite/driver/testglobals.py - testsuite/driver/testlib.py - testsuite/tests/count-deps/CountDepsAst.stdout - testsuite/tests/count-deps/CountDepsParser.stdout - + testsuite/tests/default/T25825.hs - testsuite/tests/default/all.T - testsuite/tests/deriving/should_fail/T1496.stderr - testsuite/tests/deriving/should_fail/T4846.stderr - testsuite/tests/deriving/should_fail/T5498.stderr - testsuite/tests/deriving/should_fail/T6147.stderr - testsuite/tests/deriving/should_fail/T7148.stderr - testsuite/tests/deriving/should_fail/T7148a.stderr - testsuite/tests/deriving/should_fail/T8984.stderr - testsuite/tests/deriving/should_fail/deriving-via-fail.stderr - testsuite/tests/deriving/should_fail/deriving-via-fail4.stderr - testsuite/tests/deriving/should_fail/deriving-via-fail5.stderr - testsuite/tests/driver/T16318/Makefile - testsuite/tests/driver/T18125/Makefile - testsuite/tests/driver/T4437.hs - testsuite/tests/gadt/CasePrune.stderr - + testsuite/tests/ghc-api/TypeMapStringLiteral.hs - testsuite/tests/ghc-api/all.T - testsuite/tests/ghc-api/annotations-literals/literals.stdout - testsuite/tests/ghci.debugger/scripts/T8487.stdout - testsuite/tests/ghci.debugger/scripts/break011.stdout - testsuite/tests/ghci.debugger/scripts/break017.stdout - testsuite/tests/ghci.debugger/scripts/break025.stdout - testsuite/tests/indexed-types/should_fail/T9580.stderr - testsuite/tests/interface-stability/base-exports.stdout - testsuite/tests/interface-stability/base-exports.stdout-javascript-unknown-ghcjs - testsuite/tests/interface-stability/base-exports.stdout-mingw32 - testsuite/tests/interface-stability/base-exports.stdout-ws-32 - testsuite/tests/interface-stability/ghc-experimental-exports.stdout - testsuite/tests/interface-stability/ghc-experimental-exports.stdout-mingw32 - testsuite/tests/interface-stability/template-haskell-exports.stdout - testsuite/tests/linear/should_fail/LinearRole.stderr - testsuite/tests/parser/should_fail/RecordDotSyntaxFail8.stderr - + testsuite/tests/parser/should_fail/T26860ppr.hs - + testsuite/tests/parser/should_fail/T26860ppr.stderr - testsuite/tests/parser/should_fail/all.T - + testsuite/tests/qualified-strings/Makefile - + testsuite/tests/qualified-strings/should_compile/Example/Length.hs - + testsuite/tests/qualified-strings/should_compile/all.T - + testsuite/tests/qualified-strings/should_compile/qstrings_redundant_pattern.hs - + testsuite/tests/qualified-strings/should_compile/qstrings_redundant_pattern.stderr - + testsuite/tests/qualified-strings/should_fail/Example/Length.hs - + testsuite/tests/qualified-strings/should_fail/Makefile - + testsuite/tests/qualified-strings/should_fail/all.T - + testsuite/tests/qualified-strings/should_fail/qstrings_bad_expr.hs - + testsuite/tests/qualified-strings/should_fail/qstrings_bad_expr.stderr - + testsuite/tests/qualified-strings/should_fail/qstrings_bad_pat.hs - + testsuite/tests/qualified-strings/should_fail/qstrings_bad_pat.stderr - + testsuite/tests/qualified-strings/should_fail/qstrings_multiline_no_ext.hs - + testsuite/tests/qualified-strings/should_fail/qstrings_multiline_no_ext.stderr - + testsuite/tests/qualified-strings/should_run/Example/ByteStringAscii.hs - + testsuite/tests/qualified-strings/should_run/Example/ByteStringUtf8.hs - + testsuite/tests/qualified-strings/should_run/Example/Text.hs - + testsuite/tests/qualified-strings/should_run/Makefile - + testsuite/tests/qualified-strings/should_run/all.T - + testsuite/tests/qualified-strings/should_run/qstrings_expr.hs - + testsuite/tests/qualified-strings/should_run/qstrings_expr.stdout - + testsuite/tests/qualified-strings/should_run/qstrings_pat.hs - + testsuite/tests/qualified-strings/should_run/qstrings_pat.stdout - + testsuite/tests/qualified-strings/should_run/qstrings_th.hs - + testsuite/tests/qualified-strings/should_run/qstrings_th.stdout - testsuite/tests/roles/should_fail/RolesIArray.stderr - testsuite/tests/rts/Makefile - testsuite/tests/rts/all.T - testsuite/tests/rts/ipe/all.T - + testsuite/tests/simplCore/should_compile/T26805.hs - + testsuite/tests/simplCore/should_compile/T26805.stderr - + testsuite/tests/simplCore/should_compile/T26826.hs - testsuite/tests/simplCore/should_compile/all.T - + testsuite/tests/typecheck/should_compile/T26805a.hs - testsuite/tests/typecheck/should_compile/all.T - testsuite/tests/typecheck/should_fail/T10285.stderr - testsuite/tests/typecheck/should_fail/T10534.stderr - testsuite/tests/typecheck/should_fail/T10715b.stderr - testsuite/tests/typecheck/should_fail/T11347.stderr - testsuite/tests/typecheck/should_fail/T15801.stderr - + testsuite/tests/typecheck/should_fail/T15850.hs - + testsuite/tests/typecheck/should_fail/T15850.stderr - + testsuite/tests/typecheck/should_fail/T15850_Lib.hs - + testsuite/tests/typecheck/should_fail/T20289.hs - + testsuite/tests/typecheck/should_fail/T20289.stderr - + testsuite/tests/typecheck/should_fail/T20289_A.hs - testsuite/tests/typecheck/should_fail/T22645.stderr - testsuite/tests/typecheck/should_fail/T22924a.stderr - + testsuite/tests/typecheck/should_fail/T23731.hs - + testsuite/tests/typecheck/should_fail/T23731.stderr - + testsuite/tests/typecheck/should_fail/T23731b.hs - + testsuite/tests/typecheck/should_fail/T23731b.stderr - + testsuite/tests/typecheck/should_fail/T23731b_aux.hs - + testsuite/tests/typecheck/should_fail/T25679.hs - + testsuite/tests/typecheck/should_fail/T25679.stderr - + testsuite/tests/typecheck/should_fail/T25949.hs - + testsuite/tests/typecheck/should_fail/T25949.stderr - + testsuite/tests/typecheck/should_fail/T25949_aux.hs - + testsuite/tests/typecheck/should_fail/T26137.hs - + testsuite/tests/typecheck/should_fail/T26137.stderr - testsuite/tests/typecheck/should_fail/TcCoercibleFail.stderr - testsuite/tests/typecheck/should_fail/TcCoercibleFail3.stderr - testsuite/tests/typecheck/should_fail/all.T - utils/check-exact/ExactPrint.hs - utils/haddock/haddock-api/src/Haddock/Backends/Hoogle.hs - utils/haddock/haddock-api/src/Haddock/Backends/Hyperlinker/Parser.hs - utils/haddock/haddock-api/src/Haddock/Convert.hs - utils/haddock/haddock-api/src/Haddock/Interface/Rename.hs - utils/haddock/haddock-api/src/Haddock/Types.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/769c384eecc157b311e4477fe9e454… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/769c384eecc157b311e4477fe9e454… You're receiving this email because of your account on gitlab.haskell.org.

1 0

[Git][ghc/ghc][wip/T26859] Deleted 1 commit: wip: try without generic
by Teo Camarasu (＠teo) 03 Feb '26

03 Feb '26

Teo Camarasu pushed to branch wip/T26859 at Glasgow Haskell Compiler / GHC WARNING: The push did not contain any new commits, but force pushed to delete the commits and changes below. Deleted commits: bf1b9d51 by Teo Camarasu at 2026-02-03T12:34:14+00:00 wip: try without generic - - - - - 1 changed file: - libraries/base/src/Data/Ord.hs Changes: ===================================== libraries/base/src/Data/Ord.hs ===================================== @@ -37,7 +37,7 @@ import GHC.Internal.Num import GHC.Internal.Read import GHC.Internal.Real (Fractional, Real, RealFrac) import GHC.Internal.Show -import GHC.Internal.Generics +--import GHC.Internal.Generics import GHC.Internal.Data.Foldable import GHC.Internal.Data.Traversable import GHC.Internal.Control.Monad.Zip @@ -90,11 +90,11 @@ newtype Down a = Down , RealFrac -- ^ @since base-4.14.0.0 , RealFloat -- ^ @since base-4.14.0.0 , Storable -- ^ @since base-4.14.0.0 - , Generic -- ^ @since base-4.12.0.0 +-- , Generic -- ^ @since base-4.12.0.0 ) -- | @since base-4.12.0.0 -deriving instance Generic1 Down +--deriving instance Generic1 Down -- | @since base-4.12.0.0 deriving instance Foldable Down View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/bf1b9d51b1add491230754abc4b1660… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/bf1b9d51b1add491230754abc4b1660… You're receiving this email because of your account on gitlab.haskell.org.

1 0

[Git][ghc/ghc][wip/debug-join-point] WIP: debug panic
by sheaf (＠sheaf) 03 Feb '26

03 Feb '26

sheaf pushed to branch wip/debug-join-point at Glasgow Haskell Compiler / GHC Commits: e1786d46 by sheaf at 2026-02-03T16:47:35+01:00 WIP: debug panic - - - - - 3 changed files: - compiler/GHC/Core/Opt/Simplify/Env.hs - compiler/GHC/Core/Opt/Simplify/Iteration.hs - compiler/GHC/Core/SimpleOpt.hs Changes: ===================================== compiler/GHC/Core/Opt/Simplify/Env.hs ===================================== @@ -56,6 +56,7 @@ import GHC.Prelude import GHC.Core.Coercion.Opt ( OptCoercionOpts ) import GHC.Core.FamInstEnv ( FamInstEnv ) +import GHC.Core.SimpleOpt ( isJoinPointBinding ) import GHC.Core.Opt.Arity ( ArityOpts(..) ) import GHC.Core.Opt.Simplify.Monad import GHC.Core.Rules.Config ( RuleOpts(..) ) @@ -854,7 +855,7 @@ isEmptyJoinFloats = isNilOL unitLetFloat :: OutBind -> LetFloats -- This key function constructs a singleton float with the right form -unitLetFloat bind = assert (all (not . isJoinId) (bindersOf bind)) $ +unitLetFloat bind = assert (all (not . isJoinPointBinding) (bindersOf bind)) $ LetFloats (unitOL bind) (flag bind) where flag (Rec {}) = FltLifted @@ -867,7 +868,7 @@ unitLetFloat bind = assert (all (not . isJoinId) (bindersOf bind)) $ | otherwise = FltCareful unitJoinFloat :: OutBind -> JoinFloats -unitJoinFloat bind = assert (all isJoinId (bindersOf bind)) $ +unitJoinFloat bind = assert (all isJoinPointBinding (bindersOf bind)) $ unitOL bind mkFloatBind :: SimplEnv -> OutBind -> (SimplFloats, SimplEnv) @@ -1123,7 +1124,7 @@ simplRecBndrs :: SimplEnv -> [InBndr] -> SimplM SimplEnv -- Recursive let binders simplRecBndrs env@(SimplEnv {}) ids -- See Note [Bangs in the Simplifier] - = assert (all (not . isJoinId) ids) $ + = assert (all (not . isJoinPointBinding) ids) $ do { let (!env1, ids1) = mapAccumL substIdBndr env ids ; seqIds ids1 `seq` return env1 } @@ -1256,7 +1257,7 @@ simplRecJoinBndrs :: SimplEnv -> [InBndr] -- context being pushed inward may change types -- See Note [Return type for join points] simplRecJoinBndrs env@(SimplEnv {}) ids mult res_ty - = assert (all isJoinId ids) $ + = assert (all isJoinPointBinding ids) $ do { let (env1, ids1) = mapAccumL (simplJoinBndr mult res_ty) env ids ; seqIds ids1 `seq` return env1 } ===================================== compiler/GHC/Core/Opt/Simplify/Iteration.hs ===================================== @@ -38,7 +38,7 @@ import GHC.Core.Utils import GHC.Core.Opt.Arity ( ArityType, exprArity, arityTypeBotSigs_maybe , pushCoTyArg, pushCoValArg, exprIsDeadEnd , typeArity, arityTypeArity, etaExpandAT ) -import GHC.Core.SimpleOpt ( exprIsConApp_maybe, joinPointBinding_maybe, joinPointBindings_maybe ) +import GHC.Core.SimpleOpt ( exprIsConApp_maybe, joinPointBinding_maybe, joinPointBindings_maybe, isJoinPointBinding ) import GHC.Core.FVs ( mkRuleInfo {- exprsFreeIds -} ) import GHC.Core.Rules ( lookupRule, getRules ) import GHC.Core.Multiplicity @@ -316,8 +316,8 @@ simplLazyBind :: TopLevelFlag -> RecFlag -- Precondition: Ids only, no TyVars; not a JoinId -- Precondition: rhs obeys the let-can-float invariant simplLazyBind top_lvl is_rec (bndr,unf_se) (bndr1,env) (rhs,rhs_se) - = assert (isId bndr ) - assertPpr (not (isJoinId bndr)) (ppr bndr) $ + = assert (isId bndr) + assertPpr (not $ isJoinPointBinding bndr) (ppr bndr) $ -- pprTrace "simplLazyBind" ((ppr bndr <+> ppr bndr1) $$ ppr rhs $$ ppr (seIdSubst rhs_se)) $ do { let !rhs_env = rhs_se `setInScopeFromE` env -- See Note [Bangs in the Simplifier] (tvs, body) = case collectTyAndValBinders rhs of @@ -399,7 +399,7 @@ simplAuxBind :: String -- Precondition: rhs satisfies the let-can-float invariant simplAuxBind _str env bndr new_rhs - | assertPpr (isId bndr && not (isJoinId bndr)) (ppr bndr) $ + | assertPpr (isId bndr && not (isJoinPointBinding bndr)) (ppr bndr) $ isDeadBinder bndr -- Not uncommon; e.g. case (a,b) of c { (p,q) -> p } = return (emptyFloats env, env) -- Here c is dead, and we avoid -- creating the binding c = (a,b) @@ -1905,7 +1905,7 @@ simplNonRecE :: HasDebugCallStack -- Otherwise it may or may not satisfy it. simplNonRecE env from_what bndr (rhs, rhs_se) body cont - | assert (isId bndr && not (isJoinId bndr) ) $ + | assert (isId bndr && not (isJoinPointBinding bndr)) $ is_strict_bind = -- Evaluate RHS strictly simplExprF (rhs_se `setInScopeFromE` env) rhs @@ -1943,7 +1943,7 @@ simplRecE :: SimplEnv -- Precondition: not a join-point binding simplRecE env pairs body cont = do { let bndrs = map fst pairs - ; massert (all (not . isJoinId) bndrs) + ; massert (isNothing $ joinPointBindings_maybe pairs) ; env1 <- simplRecBndrs env bndrs -- NB: bndrs' don't have unfoldings or rules -- We add them as we go down @@ -2051,7 +2051,7 @@ simplNonRecJoinPoint :: SimplEnv -> InId -> InExpr -> InExpr -> SimplCont -> SimplM (SimplFloats, OutExpr) simplNonRecJoinPoint env bndr rhs body cont - = assert (isJoinId bndr ) $ + = assert (isJoinPointBinding bndr) $ wrapJoinCont env cont $ \ env cont -> do { -- We push join_cont into the join RHS and the body; -- and wrap wrap_cont around the whole thing @@ -4574,22 +4574,24 @@ simplLetUnfolding env bind_cxt id new_rhs rhs_ty arity unf | isStableUnfolding unf = simplStableUnfolding env bind_cxt id rhs_ty arity unf - | freshly_born_join_point id - = -- This is a tricky one! - -- See wrinkle (JU1) in Note [Do not add unfoldings to join points at birth] - return noUnfolding - | isExitJoinId id = -- See Note [Do not inline exit join points] in GHC.Core.Opt.Exitify return noUnfolding - | otherwise - = mkLetUnfolding env (bindContextLevel bind_cxt) VanillaSrc id is_join_point new_rhs + | freshly_born_join_point + = -- This is a tricky one! + -- See wrinkle (JU1) in Note [Do not add unfoldings to join points at birth] + return noUnfolding + | otherwise + = mkLetUnfolding env (bindContextLevel bind_cxt) VanillaSrc id' is_join new_rhs' where - is_join_point = isJoinId id - freshly_born_join_point id = is_join_point && isManyOccs (idOccInfo id) - -- OLD: too_many_occs (OneOcc { occ_n_br = n }) = n > 10 -- See #23627 + (id', new_rhs', is_join) = + case joinPointBinding_maybe id new_rhs of + Nothing -> (id, new_rhs, False) + Just (id', new_rhs') -> (id', new_rhs', True) + freshly_born_join_point = + is_join && (not (isJoinId id) || isManyOccs (idOccInfo id)) ------------------- mkLetUnfolding :: SimplEnv -> TopLevelFlag -> UnfoldingSource ===================================== compiler/GHC/Core/SimpleOpt.hs ===================================== @@ -12,6 +12,7 @@ module GHC.Core.SimpleOpt ( -- ** Join points joinPointBinding_maybe, joinPointBindings_maybe, + isJoinPointBinding, -- ** Predicates on expressions exprIsConApp_maybe, exprIsLiteral_maybe, exprIsLambda_maybe, @@ -1059,34 +1060,42 @@ and again its arity increases (#15517) -} --- | Returns Just (bndr,rhs) if the binding is a join point: --- If it's a JoinId, just return it --- If it's not yet a JoinId but is always tail-called, --- make it into a JoinId and return it. --- In the latter case, eta-expand the RHS if necessary, to make the --- lambdas explicit, as is required for join points --- --- Precondition: the InBndr has been occurrence-analysed, --- so its OccInfo is valid +-- | Returns @Just (bndr,rhs)@ if the binding is a join point or can be made +-- into a join point (it is always tail called). In the latter case, eta-expand +-- the RHS if necessary, to make the lambdas explicit, as is required for join points. joinPointBinding_maybe :: InBndr -> InExpr -> Maybe (InBndr, InExpr) joinPointBinding_maybe bndr rhs | not (isId bndr) = Nothing + -- NB: the 'OccInfo' of the 'InBndr' may have been zapped, e.g. if we + -- have inlined it. In this case, we may lose the join-point-hood of the + -- original binder. A later occurrence analysis pass may recover it. | isJoinId bndr - = Just (bndr, rhs) + = case tailCallInfo (idOccInfo bndr) of + NoTailCallInfo -> Nothing + AlwaysTailCalled {} -> Just (bndr, rhs) | AlwaysTailCalled join_arity <- tailCallInfo (idOccInfo bndr) , (bndrs, body) <- etaExpandToJoinPoint join_arity rhs , let str_sig = idDmdSig bndr str_arity = count isId bndrs -- Strictness demands are for Ids only - join_bndr = bndr `asJoinId` join_arity + join_bndr = bndr `asJoinId` join_arity `setIdDmdSig` etaConvertDmdSig str_arity str_sig = Just (join_bndr, mkLams bndrs body) | otherwise = Nothing +isJoinPointBinding :: InBndr -> Bool +isJoinPointBinding bndr + | not (isId bndr) + = False + | AlwaysTailCalled {} <- tailCallInfo (idOccInfo bndr) + = True + | otherwise + = False + joinPointBindings_maybe :: [(InBndr, InExpr)] -> Maybe [(InBndr, InExpr)] joinPointBindings_maybe bndrs = mapM (uncurry joinPointBinding_maybe) bndrs @@ -1443,7 +1452,7 @@ exprIsConApp_maybe ise@(ISE in_scope id_unf) expr in go subst' (float:floats) body (CC args mco) go subst floats (Let (NonRec bndr rhs) expr) cont - | not (isJoinId bndr) + | not (isJoinPointBinding bndr) -- Crucial guard! See Note [Don't float join points] = let rhs' = subst_expr subst rhs (subst', bndr') = subst_bndr subst bndr View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/e1786d46407b2ddf42a95d4d4721cde… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/e1786d46407b2ddf42a95d4d4721cde… You're receiving this email because of your account on gitlab.haskell.org.

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[Git][ghc/ghc] Pushed new branch wip/fix-26700
by recursion-ninja (＠recursion-ninja) 03 Feb '26

03 Feb '26

recursion-ninja pushed new branch wip/fix-26700 at Glasgow Haskell Compiler / GHC -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/tree/wip/fix-26700 You're receiving this email because of your account on gitlab.haskell.org.

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