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[Git][ghc/ghc][wip/rafl/meaningful-main-return] 7 commits: Preserve sign of zero when parsing -0.0#
by Florian Ragwitz (＠rafl) 11 Oct '26

11 Oct '26

Florian Ragwitz pushed to branch wip/rafl/meaningful-main-return at Glasgow Haskell Compiler / GHC Commits: ffa56ae4 by sheaf at 2026-10-09T17:15:59+02:00 Preserve sign of zero when parsing -0.0# This commit leverages the recently added GHC.Types.Literal.Floating module in order to preserve the sign of negative zero from source-written floating-point literals. Fixes #27545 - - - - - d538cac9 by Facundo Domínguez at 2026-10-09T20:26:38-04:00 Propagate annotations to simple interfaces This allows annotations to be visible to plugins when run by haddock. The LiquidHaskell plugin needs the annotations, in particular. Fixes #26761 - - - - - 32c4f4ab by meooow25 at 2026-10-09T20:27:28-04:00 Bump containers submodule to 0.8.1 And fix affected tests. * T4086a: containers depends on template-haskell-lift now instead of template-haskell. * T22611: Updated to be less dependent on containers internals. - - - - - c786065e by sheaf at 2026-10-09T20:28:20-04:00 Use an explicit pattern match in toIfaceIdDetails The old wildcard pattern let this code bit rot: it did not properly account for recently added 'IdDetails' such as 'RepPolyId', which resulted in spurious 'pprTrace' messages that could even pollute HLS sessions. Fixes #23785 - - - - - e7cacf59 by sheaf at 2026-10-09T20:29:09-04:00 Take into account ifKind in freeNamesIfDecl Commit 3c2f4bb4 added the 'ifKind' field to various constructors of 'IfaceDecl', which preserves the original kind (before type synonym expansion) for better error messages. However, that commit forgot to update 'freeNamesIfDecl' correspondingly. This could result in a "urk! lookup local fingerpring" crash when e.g. a type's kind uses a type synonym defined later, as we failed to add a dependency on the type synonym during dependency analysis. Fixes #27916 - - - - - 7d7786e4 by Florian Ragwitz at 2026-10-10T18:36:21-07:00 Move exitWith into GHC.IO.Exception This is low enough within the hierarchy of base such that it can be imported into GHC.Essentials. The implementation of exitWith is slightly changed to avoid having to import Data.Bool, which would lead to a dependency cycle. We chose to keep it in base rather than moving it up all the way to GHC.Internal.IO.Exception to allow a reinstallable base to change it independently of GHC. With this, we can now have a known occurrence for GHC to reference in order to implement GHC proposal #631 (#24848). - - - - - eea8b99a by Florian Ragwitz at 2026-10-10T18:36:22-07:00 Implement MeaningfulMainReturn As per ghc-proposal#631, with one small adjustment explained in the comments. Fixes #24848. - - - - - 69 changed files: - + changelog.d/26761 - + changelog.d/MeaningfulMainReturn - + changelog.d/T23785 - + changelog.d/T27545 - + changelog.d/T27916 - compiler/GHC/Builtin/KnownOccs.hs - compiler/GHC/Core/Make.hs - compiler/GHC/CoreToIface.hs - compiler/GHC/Driver/Flags.hs - compiler/GHC/Driver/Session.hs - compiler/GHC/Hs/Lit.hs - compiler/GHC/HsToCore/Match/Literal.hs - compiler/GHC/Iface/Decl.hs - compiler/GHC/Iface/Syntax.hs - compiler/GHC/Iface/Tidy.hs - compiler/GHC/Tc/Errors/Ppr.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/Module.hs - compiler/GHC/Types/Error/Codes.hs - compiler/Language/Haskell/Syntax/Lit.hs - + docs/users_guide/exts/meaningful_main_return.rst - docs/users_guide/exts/misc.rst - docs/users_guide/using-warnings.rst - libraries/base/src/GHC/Essentials.hs - libraries/base/src/GHC/IO/Exception.hs - libraries/base/src/System/Exit.hs - libraries/containers - libraries/ghc-internal/src/GHC/Internal/LanguageExtensions.hs - testsuite/tests/driver/T4437.hs - + testsuite/tests/ghc-e/should_run/T9086.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/template-haskell-exports.stdout - + testsuite/tests/meaningful-main-return/MainReturn_constrained_disabled.stderr - + testsuite/tests/meaningful-main-return/MainReturn_exit_code_alias_disabled.stderr - + testsuite/tests/meaningful-main-return/MainReturn_exit_code_bottom_disabled.stderr - + testsuite/tests/meaningful-main-return/MainReturn_exit_code_bottom_enabled_run.stderr - + testsuite/tests/meaningful-main-return/MainReturn_exit_code_disabled.stderr - + testsuite/tests/meaningful-main-return/MainReturn_exit_success_disabled.stderr - + testsuite/tests/meaningful-main-return/MainReturn_family_always_exit_disabled.stderr - + testsuite/tests/meaningful-main-return/MainReturn_family_invalid_disabled.stderr - + testsuite/tests/meaningful-main-return/MainReturn_family_invalid_enabled.stderr - + testsuite/tests/meaningful-main-return/MainReturn_family_stuck_disabled.stderr - + testsuite/tests/meaningful-main-return/MainReturn_family_stuck_enabled.stderr - + testsuite/tests/meaningful-main-return/MainReturn_int_disabled.stderr - + testsuite/tests/meaningful-main-return/MainReturn_int_enabled.stderr - + testsuite/tests/meaningful-main-return/MainReturn_newtype_disabled.stderr - + testsuite/tests/meaningful-main-return/MainReturn_newtype_enabled.stderr - + testsuite/tests/meaningful-main-return/MeaningfulMainReturn.hs - + testsuite/tests/meaningful-main-return/all.T - + testsuite/tests/numeric/should_run/T27545.hs - + testsuite/tests/numeric/should_run/T27545.stdout - testsuite/tests/numeric/should_run/all.T - testsuite/tests/package/T4806a.stderr - testsuite/tests/package/all.T - testsuite/tests/parser/should_compile/T7476/T7476.hs - + testsuite/tests/plugins/T26761.hs - + testsuite/tests/plugins/T26761.stderr - + testsuite/tests/plugins/T26761Plugin.hs - + testsuite/tests/plugins/T26761a.hs - testsuite/tests/plugins/all.T - testsuite/tests/simplCore/should_compile/T22611.hs - testsuite/tests/simplCore/should_compile/T22611.stderr - + testsuite/tests/simplCore/should_compile/T22611a.hs - testsuite/tests/simplCore/should_compile/all.T - + testsuite/tests/typecheck/should_compile/T27916.hs - testsuite/tests/typecheck/should_compile/all.T - + testsuite/tests/typecheck/should_compile/tc104.stderr The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/29a91779a63413b1ae5976a003f322… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/29a91779a63413b1ae5976a003f322… 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/T26543b] 44 commits: Remove the call to hoistFlag from processCmdLineP
by Simon Peyton Jones (＠simonpj) 11 Oct '26

11 Oct '26

Simon Peyton Jones pushed to branch wip/T26543b at Glasgow Haskell Compiler / GHC Commits: 098bba70 by Facundo Domínguez at 2026-09-17T14:57:41-04:00 Remove the call to hoistFlag from processCmdLineP This call was undesirable because it was causing a reconstruction of the list of flag processors. Even relying on list fusion would not be sufficient because we want to replace the list with a data structure with faster lookups to address #25763. The removal is done in two moves: * We move CmdLineP to CmdLine.hs * Then we move the effect of hoisting to processArgs via a new function hoistEwM - - - - - e01799c7 by Facundo Domínguez at 2026-09-17T14:57:42-04:00 Do not create duplicate flag processors for the -W flag This makes simpler implementing the command line parser with a trie map holding flag processors. If we were to allow duplicate flag processors for any flag, the trie map would need to be a multimap. - - - - - 3875b257 by Facundo Domínguez at 2026-09-17T14:57:42-04:00 Replace the list of flag processors with a trie map in `processArgs` Previously `GHC.Driver.CmdLine.findArg` was called for each command-line argument, doing a linear search on the list of flag processors each time. This was somewhat costly as the list of flag processor has near 2000 elements. A lookup with a trie map is faster in general, but the speed up is only noticeable when calling `GHC.Driver.CmdLine.processArgs` sufficient times, so the amount of lookups piles up. This could happen in large projects with many units each having many dependencies. If only a module needs to be recompiled, the user still needs to wait for all of the flag parsing to complete. The benchmark at testsuite/tests/perf/compiler/cmdline-parser shows a 10x speed up when using the trie. The trie map is implemented in `GHC.Data.StringTrie`. The design is explained in Note [Processing command line argument fast] in GHC.Driver.Session. The commit also: * adds two property-based tests for trie map operations, * adds a benchmark of the command line parser, and * renames the predicate `arg_ok` to `valid_flag_suffix` to decide what flag processor should be used when there are multiple matching prefixes on a flag. Fixes #25763. - - - - - 5236634a by Andreas Klebinger at 2026-09-17T14:58:24-04:00 Compile Word64{Map,Set} with -O2 always. This is the hottest code and even if we build GHC with -O0 otherwise -O2 pays off for these modules. Fixes #27814. - - - - - 545fd4fb by ARATA Mizuki at 2026-09-22T15:03:24-04:00 Change the C types of hs_{bitrev,bswap}{16,32} to match the Haskell types bitReverse{16,32}# and byteSwap{16,32}# have the type Word# -> Word#, but their C correspondents took and returned StgWord{16,32}. The mismatch on bitReverse16# led to the problem reported in #27299. Although no similar issue is reported for bitReverse32# and byteSwap{16,32}#, it seemed wise to change them proactively. This commit fixes the mismatch by changing the C type. Fixes #27299 - - - - - bf17f289 by fendor at 2026-09-22T15:04:05-04:00 Don't lose instances from shadowed imported modules with the same name When we look for instances below the current module, we need to check the unit id as well when we check for whether the module is the current module, otherwise we ignore modules we import that have the same name as the import module. Adds regression test. - - - - - 53eead15 by Wolfgang Jeltsch at 2026-09-24T20:12:03-04:00 Correct the documentation of `explicitUnits` Resolves #27787. - - - - - 35bf6f4b by Simon Jakobi at 2026-09-24T20:12:49-04:00 Remove stale specHeader bullet from Note [Don't make fillers for constraint types] The Note said that Specialise.specHeader also calls mkAbsentFiller. abfc224a27c removed that call: the specialiser no longer drops dead arguments at all, see Note [Do not drop dead args from specialisations] in GHC.Core.Opt.Specialise. Assisted-by: Claude Fable 5.1 - - - - - 1abef1ef by Wolfgang Jeltsch at 2026-09-25T17:02:07-04:00 Improve the `mhu-closure` makefile - - - - - a79a68ea by Wolfgang Jeltsch at 2026-09-25T17:02:07-04:00 Make `ghci-multi` hide all unneeded packages - - - - - d6e72450 by Wolfgang Jeltsch at 2026-09-25T17:02:07-04:00 Improve the definition of the home unit closure property - - - - - c9a2766d by Wolfgang Jeltsch at 2026-09-25T17:02:07-04:00 Re-implement the home unit closure check Compared to the previous implementation, the new one has the following advantages: * It is correct. - It distinguishes between units that have the same unit ID but different ABI hashes. - When `-hide-all-packages` is not used, it considers as home unit dependencies also units that are made implicitly available because they are in the package database. * It seems to be faster in usual settings. - In particular, it does not have a preparation phase in which it merges the dependency information from all home units, so that its running time does not grow linearly with the size of the package database in normal Cabal scenarios. * It is (hopefully) clearer. * It is better documented. - - - - - fa96acf8 by Wolfgang Jeltsch at 2026-09-25T17:02:07-04:00 Remove erroneous GHC flag in `hadrian-multi` The flag was `-Werror=-Wno-error=incomplete-record-selectors`. Its purpose was to permit incomplete record selectors, but because of the illegal combination of `-Werror=` and `-Wno-error` it was ignored, without any negative consequences. - - - - - 9f48a5b9 by Alan Zimmerman at 2026-09-25T17:02:50-04:00 EPA: Add specific layout field to AnnList Up to now AnnList has effectively served to represent lists of things having layout, regardless of whether they do or not. In Haskell, layout is optional in many places, as there is also an alternative syntax using braces and semi-colons, which is free-form. This commit introduces AnnListLayout, a data structure capturing this distinction. It is deliberately set up similarly to EpLayout, so that these two can be merged in time. The transition is done mechanically, where AnnListBraces is not used yet, the original Nothing case maps to AnnListNoLayout, and the Just case to AnnListLayout. Later commits will fine tune these against the actual parser layout. - - - - - 234bab08 by Vladislav Zavialov at 2026-09-29T17:22:54-04:00 Add regression test for #7803 Commit 2effe18ab5, first shipped with GHC 8.2.1, fixed #7803 "Superclass methods are left unspecialized". This change turns the example from the ticket description into a regression test, checking that foo1 is fully specialised at Double, with no calls to the overloaded exp5Tail. Closes #7803 Assisted-by: Claude Opus 5 - - - - - c406135c by Andreas Klebinger at 2026-10-01T06:57:28-04:00 RTS: Update flag parsing/handling: Using 0 as argument to any of these flags now resets the flags setting to default: - ``-n0`` disables nursery chunking. - ``-K0`` (or a bare ``-K``) removes the stack size limit. - ``-M0`` removes the heap size limit. - ``-H0`` resets the suggested heap size, including the nursery scaling set by ``-H``. - ``-AL0`` makes the large object allocation limit follow ``-A`` again. GC Generations are now limited to 64. -n larger than -A now emits a warning and disables chunking. Fixes #27830 #27829 - - - - - 984ee82b by Andreas Klebinger at 2026-10-01T06:58:10-04:00 Fix MultiLayerModules timeout multiplier. We accidentally used the compile multiplier for ghci commands which use the run timeout setting to set the timeout. Fixes #26263 and #27796. - - - - - 50a9cf26 by Andreas Klebinger at 2026-10-01T06:58:10-04:00 testsuite: Include runtime in JUnit report. - - - - - e358619f by Alan Zimmerman at 2026-10-01T06:59:01-04:00 EPA: Use EpaLocation in EpVirtualBraces Haddock processing uses EpLayout.EpVirtualBraces to record the current layout column, for allocating haddock comments correctly. For exact printing, we need the line as well as the col, so we know how many lines to skip when the indented code block starts. This commit updates EpLayout.EpVirtualBraces so that it carries an EpaLocation instead of just the Int column, to allow it to be used for both purposes. It is a simple mechanical change, with no other impact, but it allows us to use EpLayout instead of AnnListLayout in AnnList, in the next commit in this series. - - - - - 1d2a26ee by Andrew Lelechenko at 2026-10-01T20:22:04-04:00 Remove bitSize from MINIMAL pragma of class Bits Cf. https://github.com/haskell/core-libraries-committee/issues/441 The function is deprecated for 12 years and has a default implementation, yet it was never removed from the MINIMAL pragma, putting library authors in a very awkward position. Let's finally remove bitSize from MINIMAL. - - - - - 3cc21e4c by Hannes Siebenhandl at 2026-10-01T20:22:59-04:00 Add regression test for #27641 - - - - - c35096f5 by Hannes Siebenhandl at 2026-10-01T20:23:00-04:00 Don't `:add` modules the loader will reject Only home modules can be actually added to the loader context, thus we only accept the module if it belongs to a home unit. - - - - - a563cb27 by Simon Jakobi at 2026-10-02T17:37:36-04:00 ci: accept modified changelog.d entries in lint-changelog The changelog guide says to extend an existing entry rather than add a new one when the feature is already documented. lint_changelog only counted added files, so such MRs failed before the validator ran. Fixes #27779. Assisted-by: Claude Fable 5.1 - - - - - 03082cd4 by Simon Jakobi at 2026-10-02T17:38:17-04:00 changelog.d: Fix warning flag name in the semaphore-v2 entry The entry refers to -Wsemaphore-version-mismatch, which does not exist. The warning GHC emits when it cannot use a -jsem semaphore, including on a protocol version mismatch, is -Wsemaphore-open-failure. Context: !15729, #25087 Assisted-by: Claude Fable 5.1 - - - - - a93705ee by Simon Jakobi at 2026-10-02T17:38:17-04:00 changelog.d: Fix the CLC proposal link in the T27455 entry The entry used the Sphinx :ref: role with a URL as its target. :ref: resolves only internal labels, so the generated release notes would show the proposal name without a link. Use the plain hyperlink form like the other entries. Context: !16274, #27455 Assisted-by: Claude Fable 5.1 - - - - - 54381079 by Hannes Siebenhandl at 2026-10-02T17:39:01-04:00 Extend the `TrustOverlay` for wired-in units The TrustOverlay only contained the `UnitId` of all on-disk units. However, wired-in units are referred to by their wired-in unit id, which is not the same as the on-disk unit id. Thus, trust checks for wired-in units failed because the lookup was using the wired-in unit, which wasn't present in the `TrustOverlay`. We fix #27834, by copying the trust info for wired-in unit ids. - - - - - f8cfb1a5 by Hécate Kleidukos at 2026-10-04T19:36:39+02:00 [CLC 341] Strict variants of mutable types This commit is the implementation of CLC Proposal 341 https://github.com/haskell/core-libraries-committee/issues/341 - - - - - 575c4bc6 by Rodrigo Mesquita at 2026-10-05T12:32:02-04:00 ttg: HsModuleName in the AST, ModuleName in GHC This commit makes the AST fully independent from GHC by parsing a "module name" as an `HsModuleName (= HText)` rather than constructing an `ModuleName (= FastString)` straight away. In the GHC side, everything remains as a `ModuleName`. We turn AST `HsModuleName`s into fast strings with the cheap `mkFastStringShortText` when we process the AST for manipulation within the compiler. There are no performance regressions introduced by this approach. This is the final piece of #21592 Alternative plans were discussed in gitlab.haskell.org/ghc/ghc/-/merge_requests/16546#note_694647, but the Simon suggested one won in simplicity and performance when compared against my attempt at implementing my original plan of having a family `ModuleNameP`. - - - - - b3b89d32 by mangoiv at 2026-10-05T22:03:32-04:00 hadrian: Persist the used flavour name in the build root (#20650) This executes the idea proposed in #20650, teaching Hadrian to persist the flavour used to build a build root. This both makes use of multiple build roots more ergonomic (as the user no longer needs to repeat themselves) and avoids a tiresome foot-gun (forgetting to specify a flavour, often wholly invalidating a build root). Closes #20650. Co-authored-by: Sylvain Henry <sylvain(a)haskus.fr> - - - - - f977837b by mangoiv at 2026-10-05T22:04:21-04:00 configure: fix sed script and subst tooldir script Fixes #27672 Adds sanity checking for SUBST_TOOLDIR Metric Decrease: LinkableUsage01 MultiLayerModulesTH_OneShot T10547 T12234 T12425 T13035 T13820 T18140 T18730 T18923 T9198 TcPlugin_RewritePerf mhu-perf - - - - - f1cb08be by Hannes Siebenhandl at 2026-10-05T22:05:03-04:00 Prepend in-memory unit database for backpack The packageDbFlags are stored in reverse order. Thus, prepending will ensure that the in-memory unit database is the last item on the unit database stack. Further, the in-memory unit database needs to be able to shadow units from earlier unit databases in the unit database stack. Moreover, a `-clear-package-db` would remove the in-memory database if it weren't the last item on the stack. Closes #27835 - - - - - 8d49ed42 by Kazu Yamamoto at 2026-10-06T19:37:25-04:00 Do not leave standard file descriptors free at startup (#24450) A process may be started with stdout closed -- `prog >&-` from a shell does exactly that. Nothing then reserves descriptor 1, and open(), pipe() and socket() hand out the lowest free descriptor, so the next descriptor the runtime creates for itself takes it: the ticker's pipe, or a capability's IO manager control pipe. 'GHC.Internal.IO.StdHandles.stdout' is a CAF, built the first time the program writes to stdout, which is long after that has happened. It builds a 'Handle' over descriptor 1, which now belongs to the runtime, and nothing reports an error because the descriptor is perfectly good. The program then writes its output into the runtime's own plumbing. What that looks like from the outside is a hang. The descriptor the Handle has taken over is the read end of a pipe, so poll() for POLLOUT on it never says yes and epoll_ctl() accepts a registration for it; the thread waiting to write blocks for ever. Closing the Handle at exit closes the runtime's descriptor, which is worse: the ticker then fails on every tick. 'hs_init_ghc' now opens /dev/null onto whichever of descriptors 0, 1 and 2 are closed, before the runtime creates any descriptor of its own. Each is opened for the access that descriptor would normally have, read-only for 0 and write-only for 1 and 2, so that writing to 'stdin' or reading from 'stdout' still fails rather than quietly succeeding against /dev/null. See Note [Standard file descriptors must be open]. Moving only the descriptors the runtime opens would not do: the first file the program itself opened would land on the free number instead. The fix has to leave no free number. A program run this way therefore finds stdout connected to /dev/null rather than failing with EBADF on the first write, which is what such a program would get from most other language runtimes. Co-Authored-By: Claude Opus 5 (1M context) <noreply(a)anthropic.com> - - - - - 65bcf9e9 by Simon Jakobi at 2026-10-06T19:38:09-04:00 changelog: Repair the sentence describing #27477 The description read "programs using could crash", the object of "using" having been lost. The synopsis already says which programs are affected, so drop the dangling word. Assisted-by: Claude Fable 5.1 - - - - - 15ece296 by mangoiv at 2026-10-08T15:14:56-04:00 ci: move hadrian/ghci into the lint category so it can be picked up by more runners Fixes #27817 - - - - - c0823135 by mangoiv at 2026-10-08T15:14:56-04:00 ci: make lint-adjacent jobs into platform independent - move lint jobs into lint-anyarch tag - unify lint jobs under the same platform independent container - - - - - f76464cf by Zubin Duggal at 2026-10-08T15:15:39-04:00 DmdAnal: Make AbsDmd neutral in maxDmd fixes #27845 - - - - - ffa56ae4 by sheaf at 2026-10-09T17:15:59+02:00 Preserve sign of zero when parsing -0.0# This commit leverages the recently added GHC.Types.Literal.Floating module in order to preserve the sign of negative zero from source-written floating-point literals. Fixes #27545 - - - - - d538cac9 by Facundo Domínguez at 2026-10-09T20:26:38-04:00 Propagate annotations to simple interfaces This allows annotations to be visible to plugins when run by haddock. The LiquidHaskell plugin needs the annotations, in particular. Fixes #26761 - - - - - 32c4f4ab by meooow25 at 2026-10-09T20:27:28-04:00 Bump containers submodule to 0.8.1 And fix affected tests. * T4086a: containers depends on template-haskell-lift now instead of template-haskell. * T22611: Updated to be less dependent on containers internals. - - - - - c786065e by sheaf at 2026-10-09T20:28:20-04:00 Use an explicit pattern match in toIfaceIdDetails The old wildcard pattern let this code bit rot: it did not properly account for recently added 'IdDetails' such as 'RepPolyId', which resulted in spurious 'pprTrace' messages that could even pollute HLS sessions. Fixes #23785 - - - - - e7cacf59 by sheaf at 2026-10-09T20:29:09-04:00 Take into account ifKind in freeNamesIfDecl Commit 3c2f4bb4 added the 'ifKind' field to various constructors of 'IfaceDecl', which preserves the original kind (before type synonym expansion) for better error messages. However, that commit forgot to update 'freeNamesIfDecl' correspondingly. This could result in a "urk! lookup local fingerpring" crash when e.g. a type's kind uses a type synonym defined later, as we failed to add a dependency on the type synonym during dependency analysis. Fixes #27916 - - - - - bc171365 by Simon Peyton Jones at 2026-10-11T01:21:45+01:00 Line up simpleUnifyCheck and check_ty_eq_rhs Even after #26543 was allegedly fixed, the original repo case in the Description continued to fail. The reason was that the QuickLook unifier, `qlUnify`, used `simpleUnifyCheck` for checking unification invariants; and `simpleUnifyCheck` conservatively rejected any RHS with a coercion hole in it. The upshot was that QuickLook was not as clever as it should be, wrongly failing to do an impredicative instantiation. Interestingly `check_ty_eq_rhs`, which does the same job, only during constraint solving, was more liberal: it just looked at the free vars of the coercion, and allowed coercion holes. This MR lines them up, adding some careful notes. See Note [simpleUnifyCheck] esp (SUC1) Note [Unification preconditions] esp (COERCIONS) Things are better than before, but I am still uncomfortable about the possibilty that a hole might be filled with a coercion that mentions the LHS type variable; for now I have left this discomfort documented in (SUC1). - - - - - 97b5ffc7 by Simon Peyton Jones at 2026-10-11T01:21:45+01:00 Fix order-dependence in QuickLook Ticket #27917 pointed out that QuickLook was order-dependent -- very bad! The solution is in `qlUnify`: spot when we are unifying a type with a definite monotype, and then monomorphise any free instantiation variables of that type. See (UQL8) and (UQL9) in Note [QuickLook unification]. - - - - - 98900237 by Simon Peyton Jones at 2026-10-11T01:22:02+01:00 Add some comments about RuntimeUnk This commit just adds comments explaining why we don't need to worry about RuntimeUnkTv in the constraint solver. It also tightens up docmentation of earlier (overlapping) commits in this MR. - - - - - 253 changed files: - .gitlab-ci.yml - .gitlab/ci.sh - + changelog.d/24450 - + changelog.d/25763-cmdline-opt - + changelog.d/26610 - + changelog.d/26761 - + changelog.d/27641 - + changelog.d/27845 - + changelog.d/T23785 - + changelog.d/T26543 - changelog.d/T27455 - + changelog.d/T27545 - + changelog.d/T27830-rts-flag-bounds - + changelog.d/T27916 - + changelog.d/clc-341-strict-mutable-data-types - changelog.d/fix-parallel-gc-selector-race-27477 - + changelog.d/hadrian-persist-flavour - changelog.d/semaphore-v2 - changelog.d/unit-index - compiler/GHC.hs - compiler/GHC/Builtin/Modules.hs - compiler/GHC/ByteCode/Asm.hs - compiler/GHC/ByteCode/Show.hs - compiler/GHC/Core/DataCon.hs - compiler/GHC/Core/FVs.hs - compiler/GHC/Core/Make.hs - compiler/GHC/Core/Opt/CallerCC/Types.hs - compiler/GHC/Core/Opt/WorkWrap/Utils.hs - compiler/GHC/Core/TyCo/FVs.hs - compiler/GHC/CoreToIface.hs - + compiler/GHC/Data/StringTrie.hs - compiler/GHC/Data/Word64Map/Internal.hs - compiler/GHC/Data/Word64Map/Strict/Internal.hs - compiler/GHC/Data/Word64Set/Internal.hs - compiler/GHC/Driver/Backpack.hs - compiler/GHC/Driver/CmdLine.hs - compiler/GHC/Driver/Downsweep.hs - compiler/GHC/Driver/Env.hs - compiler/GHC/Driver/Errors/Ppr.hs - compiler/GHC/Driver/Errors/Types.hs - compiler/GHC/Driver/Main/Compile.hs - compiler/GHC/Driver/Pipeline.hs-boot - compiler/GHC/Driver/Pipeline/Execute.hs - compiler/GHC/Driver/Pipeline/Phases.hs - compiler/GHC/Driver/Session.hs - compiler/GHC/Hs/Doc.hs - compiler/GHC/Hs/Dump.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/ImpExp.hs - compiler/GHC/Hs/Lit.hs - compiler/GHC/HsToCore/Docs.hs - compiler/GHC/HsToCore/Match/Literal.hs - compiler/GHC/HsToCore/Quote.hs - compiler/GHC/Iface/Decl.hs - compiler/GHC/Iface/Errors/Types.hs - compiler/GHC/Iface/Ext/Ast.hs - compiler/GHC/Iface/Ext/Debug.hs - compiler/GHC/Iface/Ext/Types.hs - compiler/GHC/Iface/Syntax.hs - compiler/GHC/Iface/Tidy.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/Annotation.hs - compiler/GHC/Parser/Errors/Types.hs - compiler/GHC/Parser/Header.hs - compiler/GHC/Parser/Lexer.x - compiler/GHC/Parser/PostProcess.hs - compiler/GHC/Parser/PostProcess/Haddock.hs - compiler/GHC/Parser/String.hs - compiler/GHC/Rename/Env.hs - compiler/GHC/Rename/Names.hs - compiler/GHC/Rename/Unbound.hs - compiler/GHC/Runtime/Heap/Inspect.hs - compiler/GHC/StgToJS/Linker/Linker.hs - compiler/GHC/Tc/Deriv/Generics.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/Gen/App.hs - compiler/GHC/Tc/Gen/Export.hs - compiler/GHC/Tc/Module.hs - compiler/GHC/Tc/Solver/Equality.hs - compiler/GHC/Tc/Solver/InertSet.hs - compiler/GHC/Tc/Solver/Monad.hs - compiler/GHC/Tc/Types.hs - compiler/GHC/Tc/Types/ErrCtxt.hs - compiler/GHC/Tc/Utils/TcMType.hs - compiler/GHC/Tc/Utils/TcType.hs - compiler/GHC/Tc/Utils/Unify.hs - compiler/GHC/ThToHs.hs - compiler/GHC/Types/Demand.hs - compiler/GHC/Types/Unique.hs - compiler/GHC/Types/UnresolvedImport.hs - compiler/GHC/Types/Var/FV.hs - compiler/GHC/Unit/Env.hs - compiler/GHC/Unit/External/Wired.hs - compiler/GHC/Unit/Home.hs - compiler/GHC/Unit/Module.hs - compiler/GHC/Unit/Module/Env.hs - + compiler/GHC/Unit/Module/Name.hs - compiler/GHC/Unit/Parser.hs - compiler/GHC/Unit/State.hs - compiler/GHC/Unit/Types.hs - compiler/GHC/Unit/Types.hs-boot - compiler/GHC/Utils/Binary.hs - compiler/GHC/Utils/Outputable.hs - compiler/Language/Haskell/Syntax.hs - compiler/Language/Haskell/Syntax/Expr.hs - compiler/Language/Haskell/Syntax/ImpExp.hs - compiler/Language/Haskell/Syntax/Lit.hs - compiler/Language/Haskell/Syntax/Module/Name.hs - compiler/Language/Haskell/Syntax/Text.hs - compiler/ghc.cabal.in - distrib/configure.ac.in - docs/users_guide/runtime_control.rst - ghc/GHC/Driver/Session/Mode.hs - ghc/GHCi/UI.hs - ghc/GHCi/UI/Info.hs - hadrian/doc/flavours.md - hadrian/ghci-multi-cabal.in - hadrian/src/Rules.hs - hadrian/src/Settings.hs - libraries/base/base.cabal.in - libraries/base/changelog.md - libraries/base/src/Control/Concurrent/Chan.hs - + libraries/base/src/Control/Concurrent/Chan/Strict.hs - libraries/base/src/Control/Concurrent/MVar.hs - + libraries/base/src/Control/Concurrent/MVar/Strict.hs - libraries/base/src/Data/IORef.hs - + libraries/base/src/Data/IORef/Strict.hs - libraries/containers - libraries/ghc-internal/src/GHC/Internal/Bits.hs - linters/lint-codes/LintCodes/Static.hs - m4/subst_tooldir.m4 - rts/RtsFlags.c - rts/RtsStartup.c - rts/include/rts/Flags.h - rts/include/rts/storage/GC.h - rts/include/stg/Prim.h - rts/prim/bitrev.c - rts/prim/bswap.c - rts/sm/GC.c - rts/sm/Storage.c - testsuite/driver/junit.py - testsuite/driver/testglobals.py - testsuite/driver/testlib.py - testsuite/tests/MiniQuickCheck.hs - + testsuite/tests/backpack/should_compile/T27835.bkp - + testsuite/tests/backpack/should_compile/T27835.stderr - testsuite/tests/backpack/should_compile/all.T - testsuite/tests/count-deps/CountDepsAst.stdout - testsuite/tests/count-deps/CountDepsParser.stdout - testsuite/tests/default/default-fail05.stderr - + testsuite/tests/dmdanal/should_run/T27845.hs - + testsuite/tests/dmdanal/should_run/T27845.stdout - + testsuite/tests/dmdanal/should_run/T27845_Lib.hs - + testsuite/tests/dmdanal/should_run/T27845b.hs - + testsuite/tests/dmdanal/should_run/T27845b.stdout - + testsuite/tests/dmdanal/should_run/T27845b_Lib.hs - testsuite/tests/dmdanal/should_run/all.T - testsuite/tests/driver/all.T - testsuite/tests/driver/multipleHomeUnits/mhu-closure/Makefile - testsuite/tests/driver/multipleHomeUnits/mhu-closure/mhu-closure.stderr - testsuite/tests/driver/multipleHomeUnits/mhu-closure/mhu-closure.stdout - + testsuite/tests/driver/stringtrie.hs - + testsuite/tests/driver/stringtrie.stdout - testsuite/tests/ghc-api/downsweep/IncrementalDownsweep.hs - testsuite/tests/ghc-api/exactprint/T22919.stderr - testsuite/tests/ghc-api/exactprint/Test20239.stderr - testsuite/tests/ghc-api/exactprint/ZeroWidthSemi.stderr - testsuite/tests/ghci.debugger/scripts/T14628.stderr - + testsuite/tests/ghci/prog-mhu008/Makefile - + testsuite/tests/ghci/prog-mhu008/a/M.hs - + testsuite/tests/ghci/prog-mhu008/all.T - + testsuite/tests/ghci/prog-mhu008/b/M.hs - + testsuite/tests/ghci/prog-mhu008/prog-mhu008.script - + testsuite/tests/ghci/prog-mhu008/prog-mhu008.stdout - + testsuite/tests/ghci/prog-mhu008/unitA - + testsuite/tests/ghci/prog-mhu008/unitB - + testsuite/tests/ghci/scripts/T27641.script - + testsuite/tests/ghci/scripts/T27641.stderr - + testsuite/tests/ghci/scripts/T27641.stdout - + testsuite/tests/ghci/scripts/T27834.hs - + testsuite/tests/ghci/scripts/T27834.script - + testsuite/tests/ghci/scripts/T27834.stdout - testsuite/tests/ghci/scripts/all.T - 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/hiefile/should_run/T24544.hs - + testsuite/tests/impredicative/T27917.hs - testsuite/tests/impredicative/all.T - testsuite/tests/indexed-types/should_fail/T1897b.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/module/mod185.stderr - + testsuite/tests/numeric/should_run/T27545.hs - + testsuite/tests/numeric/should_run/T27545.stdout - testsuite/tests/numeric/should_run/all.T - testsuite/tests/package/T4806a.stderr - testsuite/tests/package/all.T - 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/KindSigs.stderr - testsuite/tests/parser/should_compile/T14189.stderr - testsuite/tests/parser/should_compile/T15279.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/perf/compiler/T25763.stderr - testsuite/tests/perf/compiler/all.T - + testsuite/tests/plugins/T26761.hs - + testsuite/tests/plugins/T26761.stderr - + testsuite/tests/plugins/T26761Plugin.hs - + testsuite/tests/plugins/T26761a.hs - testsuite/tests/plugins/all.T - + testsuite/tests/primops/should_run/T27299.hs - + testsuite/tests/primops/should_run/T27299.stdout - testsuite/tests/primops/should_run/all.T - testsuite/tests/printer/AnnotationNoListTuplePuns.stdout - testsuite/tests/printer/T18791.stderr - testsuite/tests/printer/Test20297.stdout - testsuite/tests/printer/Test24533.stdout - testsuite/tests/profiling/should_run/caller-cc/CallerCcParser.hs - + testsuite/tests/rts/T24450.hs - + testsuite/tests/rts/T24450.stderr - testsuite/tests/rts/all.T - testsuite/tests/rts/rtsflags001.stderr-ws-32 - testsuite/tests/rts/rtsflags001.stderr-ws-64 - testsuite/tests/simplCore/should_compile/T22611.hs - testsuite/tests/simplCore/should_compile/T22611.stderr - + testsuite/tests/simplCore/should_compile/T22611a.hs - + testsuite/tests/simplCore/should_compile/T7803.hs - + testsuite/tests/simplCore/should_compile/T7803.stderr - + testsuite/tests/simplCore/should_compile/T7803a.hs - testsuite/tests/simplCore/should_compile/all.T - testsuite/tests/typecheck/should_compile/LocalGivenEqs.hs - + testsuite/tests/typecheck/should_compile/T26543_orig.hs - + testsuite/tests/typecheck/should_compile/T27916.hs - testsuite/tests/typecheck/should_compile/all.T - testsuite/tests/typecheck/should_fail/T22707.stderr - + testsuite/tests/typecheck/should_fail/T26543a.hs - + testsuite/tests/typecheck/should_fail/T26543a.stderr - testsuite/tests/typecheck/should_fail/all.T - + testsuite/tests/warnings/should_fail/WExpectedNoArgError.stderr - testsuite/tests/warnings/should_fail/all.T - utils/check-exact/ExactPrint.hs - utils/check-exact/Main.hs - utils/check-exact/Transform.hs - utils/haddock/haddock-api/src/Haddock/Backends/Hyperlinker/Renderer.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/785d28a06410e31d9f0e15e5f2ca6c… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/785d28a06410e31d9f0e15e5f2ca6c… 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/supersven/hadrian-cross-stage3] Generate default.target only from the successor stage for stage0
by Sven Tennie (＠supersven) 11 Oct '26

11 Oct '26

Sven Tennie pushed to branch wip/supersven/hadrian-cross-stage3 at Glasgow Haskell Compiler / GHC Commits: b2d34f97 by Sven Tennie at 2026-10-11T00:05:25+02:00 Generate default.target only from the successor stage for stage0 This mirrors the behaviour for the settings' rules. - - - - - 1 changed file: - hadrian/src/Rules/Generate.hs Changes: ===================================== hadrian/src/Rules/Generate.hs ===================================== @@ -287,7 +287,9 @@ generateRules = do isCrossStage <- if compilerStage < Stage3 then expr (crossStage compilerStage) else pure False - let libraryStage = if isCrossStage then succStage compilerStage else compilerStage + let libraryStage = case compilerStage of + Stage0 {} -> Stage1 + _ -> if isCrossStage then succStage compilerStage else compilerStage tgt <- expr (targetStage libraryStage) pure $ show tgt { tgtLocallyExecutable = not isCrossStage } View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/b2d34f9787bff31b3e906387bdd94b7… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/b2d34f9787bff31b3e906387bdd94b7… 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/substitution-via-mapper] 2 commits: Refactor type and coercion substitution
by Simon Peyton Jones (＠simonpj) 11 Oct '26

11 Oct '26

Simon Peyton Jones pushed to branch wip/substitution-via-mapper at Glasgow Haskell Compiler / GHC Commits: b944f5f9 by Simon Peyton Jones at 2026-10-10T23:01:15+01:00 Refactor type and coercion substitution This MR refactors type and coercion substitution so that they use TyCoMapper, rather than hand-rolled code. Fundamentally it's a simple idea, but I had to do quite a bit of refactoring to make it fly. I got Claude to help me this this refactoring, but I paid careful attention to every line of code. Main changes: * New module GHC.Core.TyCo.Make which defines TyCoMapper, and a bunch of other simple "smart constructors" for types and coercions. See GHC.Core.TyCo.Rep Note [The Type-related module hierarchy], esp (TRM1) * The new TyCoMapper has new fields `tcm_tcapp_ty` and `tcm_tcapp_co` to handle type-constructor applications. These replace `tcm_tycon`. * Rewrite GHC.Core.TyCo.Subst to use TyCoMapper * Rewrite GHC.Core.Type.expandTypeSynonyms to use TyCoMapper. * Implement `seqType` and `seqCo` with TyCoFolder. To to this I had to add a `tcf_lit` field to TyCoFolder. * A new module GHC.Utils.StrictIdentity to define a strict identity monad, which itself is used for substTyCoMapper :: TyCoMapper Subst StrictIdentity * I removed an apparently-unused instance for Binary Levity Refactoring `seq` functions * In GHC.Core.Seq, redefine `seqOneShot`, `seqRuleInfo`, and friends to return `SeqResult`, a new type defined in GHC.Types.Baseic, rather than `()`. We can define a Monoid instance for `SeqResult` that does the right thing. * This has knock-on effects across the compiler. - - - - - d8bfbf80 by Simon Peyton Jones at 2026-10-10T23:01:15+01:00 Refactor TyCoMapper to take a single monad; add StrictReaderT TyCoMapper used to be parameterised over both an environment and a monad, with fields like tcm_tyvar :: env -> TyVar -> m Type Now it is parameterised over just the monad: tcm_tyvar :: TyVar -> m Type If the mapping needs an environment, `m` is a reader monad over that environment. Many uses (e.g. zonkTcTypeMapper, swizzleMapper) need no environment at all, and used to pass a dummy (). The binder field becomes tcm_tycobinder :: forall r. TyCoVar -> ForAllTyFlag -> (TyCoVar -> m r) -> m r and runs the continuation in the extended environment. mapTyCoX is gone; only mapTyCo remains. To make this efficient, the reader monad must use the one-shot trick and be strict in the environment. So: * New module GHC.Utils.Monad.StrictReader defines newtype StrictReaderT r m a with hand-written instances. The builder of the pattern synonym `StrictReaderT` is a smart constructor that adds both `oneShot` and a bang on the environment, so every StrictReaderT computation is strict in the environment. See Note [Instances for StrictReaderT]. * ZonkT becomes type ZonkT = StrictReaderT ZonkEnv ZonkM becomes type ZonkM = StrictReaderT ZonkGblEnv IO replacing their own hand-written instances. * Substitution uses type SubstM = StrictReaderT Subst StrictIdentity substTyCoMapper :: TyCoMapper SubstM and similarly expandTypeSynonymMapper. * zonk_tycomapper :: TyCoMapper (ZonkT TcM) is now much simpler. * swizzleMapper uses StrictIdentity rather than Identity. * Module renaming, so that the strict monads are all peers in GHC.Utils.Monad: GHC.Utils.StrictIdentity ==> GHC.Utils.Monad.StrictIdentity GHC.Utils.Monad.State.Strict ==> GHC.Utils.Monad.StrictState alongside the new GHC.Utils.Monad.StrictReader. Co-Authored-By: Claude Opus 5.5 <noreply(a)anthropic.com> - - - - - 67 changed files: - compiler/GHC/Builtin/WiredIn/Prim.hs - compiler/GHC/Cmm/GenericOpt.hs - compiler/GHC/Cmm/UniqueRenamer.hs - compiler/GHC/CmmToAsm/Dwarf/Types.hs - compiler/GHC/CmmToAsm/Monad.hs - compiler/GHC/CmmToAsm/Reg/Graph/Spill.hs - compiler/GHC/CmmToAsm/Reg/Graph/SpillClean.hs - compiler/GHC/CmmToAsm/Reg/Graph/SpillCost.hs - compiler/GHC/CmmToAsm/Reg/Graph/Stats.hs - compiler/GHC/CmmToAsm/Reg/Linear/State.hs - compiler/GHC/CmmToAsm/Reg/Linear/Stats.hs - compiler/GHC/CmmToAsm/Reg/Liveness.hs - compiler/GHC/CmmToAsm/Wasm/Asm.hs - compiler/GHC/CmmToAsm/Wasm/Types.hs - compiler/GHC/CmmToC.hs - compiler/GHC/Core/Coercion.hs - compiler/GHC/Core/Coercion.hs-boot - compiler/GHC/Core/Opt/CallerCC.hs - compiler/GHC/Core/Opt/Exitify.hs - compiler/GHC/Core/Reduction.hs - compiler/GHC/Core/Seq.hs - compiler/GHC/Core/TyCo/Compare.hs - compiler/GHC/Core/TyCo/FVs.hs - + compiler/GHC/Core/TyCo/Make.hs - + compiler/GHC/Core/TyCo/Make.hs-boot - compiler/GHC/Core/TyCo/Rep.hs - compiler/GHC/Core/TyCo/Rep.hs-boot - compiler/GHC/Core/TyCo/Subst.hs - compiler/GHC/Core/Type.hs - compiler/GHC/Core/Type.hs-boot - compiler/GHC/Driver/Downsweep.hs - compiler/GHC/Driver/Main/Compile.hs - compiler/GHC/Iface/Ext/Utils.hs - compiler/GHC/Iface/Syntax.hs - compiler/GHC/Stg/BcPrep.hs - compiler/GHC/Stg/Debug.hs - compiler/GHC/Stg/EnforceEpt/Rewrite.hs - compiler/GHC/Stg/EnforceEpt/TagSig.hs - compiler/GHC/Stg/Subst.hs - compiler/GHC/Tc/Deriv/Functor.hs - compiler/GHC/Tc/Gen/App.hs - compiler/GHC/Tc/TyCl.hs - compiler/GHC/Tc/Utils/Unify.hs - compiler/GHC/Tc/Zonk/Env.hs - compiler/GHC/Tc/Zonk/Monad.hs - compiler/GHC/Tc/Zonk/TcType.hs - compiler/GHC/Tc/Zonk/Type.hs - compiler/GHC/Types/Arity.hs - compiler/GHC/Types/Basic.hs - compiler/GHC/Types/Cpr.hs - compiler/GHC/Types/Demand.hs - compiler/GHC/Types/Name/Env.hs - compiler/GHC/Types/Name/Occurrence.hs - compiler/GHC/Types/Unique/DSM.hs - compiler/GHC/Types/Unique/FM.hs - compiler/GHC/Types/Unique/Map.hs - compiler/GHC/Types/Unique/Set.hs - compiler/GHC/Types/Unique/Supply.hs - compiler/GHC/Types/Var/Set.hs - compiler/GHC/Utils/Binary.hs - + compiler/GHC/Utils/Monad/StrictIdentity.hs - + compiler/GHC/Utils/Monad/StrictReader.hs - compiler/GHC/Utils/Monad/State/Strict.hs → compiler/GHC/Utils/Monad/StrictState.hs - compiler/GHC/Utils/Outputable.hs - compiler/ghc.cabal.in - testsuite/tests/count-deps/CountDepsParser.stdout - utils/check-exact/Utils.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/298de237bda7b9b4604a90cc875b5e… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/298de237bda7b9b4604a90cc875b5e… 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/rafl/meaningful-main-return] Skip some work for the common IO () case
by Florian Ragwitz (＠rafl) 10 Oct '26

10 Oct '26

Florian Ragwitz pushed to branch wip/rafl/meaningful-main-return at Glasgow Haskell Compiler / GHC Commits: 29a91779 by Florian Ragwitz at 2026-10-10T13:37:09-07:00 Skip some work for the common IO () case - - - - - 3 changed files: - compiler/GHC/Tc/Module.hs - testsuite/tests/plugins/T23110.stdout - testsuite/tests/plugins/static-plugins.stdout Changes: ===================================== compiler/GHC/Tc/Module.hs ===================================== @@ -2042,35 +2042,33 @@ generateMainBinding tcg_env main_name = do -- https://github.com/ghc-proposals/ghc-proposals/pull/771. handleMainReturn :: Name -> TcType -> TcEvBinds -> LHsExpr GhcTc -> TcM (LHsExpr GhcTc) handleMainReturn main_name res_ty ev_binds main_expr = do - meaningful_main <- xoptM LangExt.MeaningfulMainReturn - void_ty <- mkTyConTy <$> tcLookupKnownOccTyCon voidTyConOcc - exit_code_ty <- mkTyConTy <$> tcLookupKnownOccTyCon exitCodeTyConOcc main_res_ty <- liftZonkM $ zonkTcType res_ty - - let unit_valid = isJust (tcUnifyTy main_res_ty unitTy) - void_valid = isJust (tcUnifyTy main_res_ty void_ty) - exit_code_valid = isJust (tcUnifyTy main_res_ty exit_code_ty) - - setSrcSpan (getSrcSpan main_name) $ - if meaningful_main - then checkTc - (unit_valid || void_valid || exit_code_valid) - (TcRnInvalidMainReturn main_name main_res_ty) - else diagnosticTc - (not (unit_valid || void_valid)) - (TcRnAmbiguousMainReturn main_name main_res_ty) - - let main_action = mkHsDictLet ev_binds main_expr - - if not meaningful_main || unit_valid || void_valid + if unifies main_res_ty unitTy then pure main_action else do - massertPpr exit_code_valid (ppr main_res_ty) - bind_io_id <- tcLookupKnownOccId bindIOIdOcc - exit_with_id <- tcLookupKnownOccId exitWithIdOcc - pure $ - nlHsTyApps bind_io_id [exit_code_ty, exit_code_ty] - [ main_action, nlHsTyApp exit_with_id [exit_code_ty] ] + void_ty <- mkTyConTy <$> tcLookupKnownOccTyCon voidTyConOcc + if unifies main_res_ty void_ty + then pure main_action + else do + meaningful_main <- xoptM LangExt.MeaningfulMainReturn + if not meaningful_main + then do + setSrcSpan (getSrcSpan main_name) $ + addDiagnosticTc (TcRnAmbiguousMainReturn main_name main_res_ty) + pure main_action + else wrapExitWith main_res_ty + where + main_action = mkHsDictLet ev_binds main_expr + unifies = (isJust .) . tcUnifyTy + wrapExitWith main_res_ty = do + exit_code_ty <- mkTyConTy <$> tcLookupKnownOccTyCon exitCodeTyConOcc + setSrcSpan (getSrcSpan main_name) $ + checkTc (unifies main_res_ty exit_code_ty) + (TcRnInvalidMainReturn main_name main_res_ty) + bind_io_id <- tcLookupKnownOccId bindIOIdOcc + exit_with_id <- tcLookupKnownOccId exitWithIdOcc + pure $ nlHsTyApps bind_io_id [exit_code_ty, exit_code_ty] + [ main_action, nlHsTyApp exit_with_id [exit_code_ty] ] getIOType :: TcM (TcType, TcType) -- Return (IO alpha, alpha) for fresh alpha ===================================== testsuite/tests/plugins/T23110.stdout ===================================== @@ -3,7 +3,6 @@ typeCheckPlugin (rn) interfacePlugin: GHC.Internal.Tuple interfacePlugin: GHC.Internal.Stack.Types interfacePlugin: GHC.Internal.Exception.Context -interfacePlugin: GHC.Internal.IO.Exception interfacePlugin: GHC.Internal.TopHandler typeCheckPlugin (tc) Collecting type info for 1 module(s) ... ===================================== testsuite/tests/plugins/static-plugins.stdout ===================================== @@ -13,7 +13,6 @@ interfacePlugin: GHC.Internal.Show typeCheckPlugin (rn) interfacePlugin: GHC.Internal.Stack.Types interfacePlugin: GHC.Internal.Exception.Context -interfacePlugin: GHC.Internal.IO.Exception interfacePlugin: GHC.Internal.TopHandler typeCheckPlugin (tc) interfacePlugin: GHC.Internal.Prim View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/29a91779a63413b1ae5976a003f3228… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/29a91779a63413b1ae5976a003f3228… 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/substitution-via-mapper] 2 commits: Refactor type and coercion substitution
by Simon Peyton Jones (＠simonpj) 10 Oct '26

10 Oct '26

Simon Peyton Jones pushed to branch wip/substitution-via-mapper at Glasgow Haskell Compiler / GHC Commits: 43ce380c by Simon Peyton Jones at 2026-10-10T20:54:49+01:00 Refactor type and coercion substitution This MR refactors type and coercion substitution so that they use TyCoMapper, rather than hand-rolled code. Fundamentally it's a simple idea, but I had to do quite a bit of refactoring to make it fly. I got Claude to help me this this refactoring, but I paid careful attention to every line of code. Main changes: * New module GHC.Core.TyCo.Make which defines TyCoMapper, and a bunch of other simple "smart constructors" for types and coercions. See GHC.Core.TyCo.Rep Note [The Type-related module hierarchy], esp (TRM1) * The new TyCoMapper has new fields `tcm_tcapp_ty` and `tcm_tcapp_co` to handle type-constructor applications. These replace `tcm_tycon`. * Rewrite GHC.Core.TyCo.Subst to use TyCoMapper * Rewrite GHC.Core.Type.expandTypeSynonyms to use TyCoMapper. * Implement `seqType` and `seqCo` with TyCoFolder. To to this I had to add a `tcf_lit` field to TyCoFolder. * A new module GHC.Utils.StrictIdentity to define a strict identity monad, which itself is used for substTyCoMapper :: TyCoMapper Subst StrictIdentity * I removed an apparently-unused instance for Binary Levity Refactoring `seq` functions * In GHC.Core.Seq, redefine `seqOneShot`, `seqRuleInfo`, and friends to return `SeqResult`, a new type defined in GHC.Types.Baseic, rather than `()`. We can define a Monoid instance for `SeqResult` that does the right thing. * This has knock-on effects across the compiler. - - - - - 298de237 by Simon Peyton Jones at 2026-10-10T20:56:50+01:00 Refactor TyCoMapper to take a single monad; add StrictReaderT TyCoMapper used to be parameterised over both an environment and a monad, with fields like tcm_tyvar :: env -> TyVar -> m Type Now it is parameterised over just the monad: tcm_tyvar :: TyVar -> m Type If the mapping needs an environment, `m` is a reader monad over that environment. Many uses (e.g. zonkTcTypeMapper, swizzleMapper) need no environment at all, and used to pass a dummy (). The binder field becomes tcm_tycobinder :: forall r. TyCoVar -> ForAllTyFlag -> (TyCoVar -> m r) -> m r and runs the continuation in the extended environment. mapTyCoX is gone; only mapTyCo remains. To make this efficient, the reader monad must use the one-shot trick and be strict in the environment. So: * New module GHC.Utils.Monad.StrictReader defines newtype StrictReaderT r m a with hand-written instances. The builder of the pattern synonym `StrictReaderT` is a smart constructor that adds both `oneShot` and a bang on the environment, so every StrictReaderT computation is strict in the environment. See Note [Instances for StrictReaderT]. * ZonkT becomes type ZonkT = StrictReaderT ZonkEnv ZonkM becomes type ZonkM = StrictReaderT ZonkGblEnv IO replacing their own hand-written instances. * Substitution uses type SubstM = StrictReaderT Subst StrictIdentity substTyCoMapper :: TyCoMapper SubstM and similarly expandTypeSynonymMapper. * zonk_tycomapper :: TyCoMapper (ZonkT TcM) is now much simpler. * swizzleMapper uses StrictIdentity rather than Identity. * Module renaming, so that the strict monads are all peers in GHC.Utils.Monad: GHC.Utils.StrictIdentity ==> GHC.Utils.Monad.StrictIdentity GHC.Utils.Monad.State.Strict ==> GHC.Utils.Monad.StrictState alongside the new GHC.Utils.Monad.StrictReader. Co-Authored-By: Claude Opus 5.5 <noreply(a)anthropic.com> - - - - - 67 changed files: - compiler/GHC/Builtin/WiredIn/Prim.hs - compiler/GHC/Cmm/GenericOpt.hs - compiler/GHC/Cmm/UniqueRenamer.hs - compiler/GHC/CmmToAsm/Dwarf/Types.hs - compiler/GHC/CmmToAsm/Monad.hs - compiler/GHC/CmmToAsm/Reg/Graph/Spill.hs - compiler/GHC/CmmToAsm/Reg/Graph/SpillClean.hs - compiler/GHC/CmmToAsm/Reg/Graph/SpillCost.hs - compiler/GHC/CmmToAsm/Reg/Graph/Stats.hs - compiler/GHC/CmmToAsm/Reg/Linear/State.hs - compiler/GHC/CmmToAsm/Reg/Linear/Stats.hs - compiler/GHC/CmmToAsm/Reg/Liveness.hs - compiler/GHC/CmmToAsm/Wasm/Asm.hs - compiler/GHC/CmmToAsm/Wasm/Types.hs - compiler/GHC/CmmToC.hs - compiler/GHC/Core/Coercion.hs - compiler/GHC/Core/Coercion.hs-boot - compiler/GHC/Core/Opt/CallerCC.hs - compiler/GHC/Core/Opt/Exitify.hs - compiler/GHC/Core/Reduction.hs - compiler/GHC/Core/Seq.hs - compiler/GHC/Core/TyCo/Compare.hs - compiler/GHC/Core/TyCo/FVs.hs - + compiler/GHC/Core/TyCo/Make.hs - + compiler/GHC/Core/TyCo/Make.hs-boot - compiler/GHC/Core/TyCo/Rep.hs - compiler/GHC/Core/TyCo/Rep.hs-boot - compiler/GHC/Core/TyCo/Subst.hs - compiler/GHC/Core/Type.hs - compiler/GHC/Core/Type.hs-boot - compiler/GHC/Driver/Downsweep.hs - compiler/GHC/Driver/Main/Compile.hs - compiler/GHC/Iface/Ext/Utils.hs - compiler/GHC/Iface/Syntax.hs - compiler/GHC/Stg/BcPrep.hs - compiler/GHC/Stg/Debug.hs - compiler/GHC/Stg/EnforceEpt/Rewrite.hs - compiler/GHC/Stg/EnforceEpt/TagSig.hs - compiler/GHC/Stg/Subst.hs - compiler/GHC/Tc/Deriv/Functor.hs - compiler/GHC/Tc/Gen/App.hs - compiler/GHC/Tc/TyCl.hs - compiler/GHC/Tc/Utils/Unify.hs - compiler/GHC/Tc/Zonk/Env.hs - compiler/GHC/Tc/Zonk/Monad.hs - compiler/GHC/Tc/Zonk/TcType.hs - compiler/GHC/Tc/Zonk/Type.hs - compiler/GHC/Types/Arity.hs - compiler/GHC/Types/Basic.hs - compiler/GHC/Types/Cpr.hs - compiler/GHC/Types/Demand.hs - compiler/GHC/Types/Name/Env.hs - compiler/GHC/Types/Name/Occurrence.hs - compiler/GHC/Types/Unique/DSM.hs - compiler/GHC/Types/Unique/FM.hs - compiler/GHC/Types/Unique/Map.hs - compiler/GHC/Types/Unique/Set.hs - compiler/GHC/Types/Unique/Supply.hs - compiler/GHC/Types/Var/Set.hs - compiler/GHC/Utils/Binary.hs - + compiler/GHC/Utils/Monad/StrictIdentity.hs - + compiler/GHC/Utils/Monad/StrictReader.hs - compiler/GHC/Utils/Monad/State/Strict.hs → compiler/GHC/Utils/Monad/StrictState.hs - compiler/GHC/Utils/Outputable.hs - compiler/ghc.cabal.in - testsuite/tests/count-deps/CountDepsParser.stdout - utils/check-exact/Utils.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/24a92554722e4204c561347e198748… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/24a92554722e4204c561347e198748… 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/rafl/meaningful-main-return] Skip some work for the common IO () case
by Florian Ragwitz (＠rafl) 10 Oct '26

10 Oct '26

Florian Ragwitz pushed to branch wip/rafl/meaningful-main-return at Glasgow Haskell Compiler / GHC Commits: b6355bc9 by Florian Ragwitz at 2026-10-10T12:08:05-07:00 Skip some work for the common IO () case - - - - - 1 changed file: - compiler/GHC/Tc/Module.hs Changes: ===================================== compiler/GHC/Tc/Module.hs ===================================== @@ -2042,35 +2042,36 @@ generateMainBinding tcg_env main_name = do -- https://github.com/ghc-proposals/ghc-proposals/pull/771. handleMainReturn :: Name -> TcType -> TcEvBinds -> LHsExpr GhcTc -> TcM (LHsExpr GhcTc) handleMainReturn main_name res_ty ev_binds main_expr = do - meaningful_main <- xoptM LangExt.MeaningfulMainReturn - void_ty <- mkTyConTy <$> tcLookupKnownOccTyCon voidTyConOcc - exit_code_ty <- mkTyConTy <$> tcLookupKnownOccTyCon exitCodeTyConOcc - main_res_ty <- liftZonkM $ zonkTcType res_ty - - let unit_valid = isJust (tcUnifyTy main_res_ty unitTy) - void_valid = isJust (tcUnifyTy main_res_ty void_ty) - exit_code_valid = isJust (tcUnifyTy main_res_ty exit_code_ty) - - setSrcSpan (getSrcSpan main_name) $ - if meaningful_main - then checkTc - (unit_valid || void_valid || exit_code_valid) - (TcRnInvalidMainReturn main_name main_res_ty) - else diagnosticTc - (not (unit_valid || void_valid)) - (TcRnAmbiguousMainReturn main_name main_res_ty) - let main_action = mkHsDictLet ev_binds main_expr - - if not meaningful_main || unit_valid || void_valid + main_res_ty <- liftZonkM $ zonkTcType res_ty + if isJust (tcUnifyTy main_res_ty unitTy) then pure main_action else do - massertPpr exit_code_valid (ppr main_res_ty) - bind_io_id <- tcLookupKnownOccId bindIOIdOcc - exit_with_id <- tcLookupKnownOccId exitWithIdOcc - pure $ - nlHsTyApps bind_io_id [exit_code_ty, exit_code_ty] - [ main_action, nlHsTyApp exit_with_id [exit_code_ty] ] + meaningful_main <- xoptM LangExt.MeaningfulMainReturn + void_ty <- mkTyConTy <$> tcLookupKnownOccTyCon voidTyConOcc + exit_code_ty <- mkTyConTy <$> tcLookupKnownOccTyCon exitCodeTyConOcc + + let void_valid = isJust (tcUnifyTy main_res_ty void_ty) + exit_code_valid = isJust (tcUnifyTy main_res_ty exit_code_ty) + + setSrcSpan (getSrcSpan main_name) $ + if meaningful_main + then checkTc + (void_valid || exit_code_valid) + (TcRnInvalidMainReturn main_name main_res_ty) + else diagnosticTc + (not void_valid) + (TcRnAmbiguousMainReturn main_name main_res_ty) + + if not meaningful_main || void_valid + then pure main_action + else do + massertPpr exit_code_valid (ppr main_res_ty) + bind_io_id <- tcLookupKnownOccId bindIOIdOcc + exit_with_id <- tcLookupKnownOccId exitWithIdOcc + pure $ + nlHsTyApps bind_io_id [exit_code_ty, exit_code_ty] + [ main_action, nlHsTyApp exit_with_id [exit_code_ty] ] getIOType :: TcM (TcType, TcType) -- Return (IO alpha, alpha) for fresh alpha View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/b6355bc9f2ee58eb3f04382a31502f2… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/b6355bc9f2ee58eb3f04382a31502f2… 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/supersven/hadrian-cross-stage3] 23 commits: [CLC 341] Strict variants of mutable types
by Sven Tennie (＠supersven) 10 Oct '26

10 Oct '26

Sven Tennie pushed to branch wip/supersven/hadrian-cross-stage3 at Glasgow Haskell Compiler / GHC Commits: f8cfb1a5 by Hécate Kleidukos at 2026-10-04T19:36:39+02:00 [CLC 341] Strict variants of mutable types This commit is the implementation of CLC Proposal 341 https://github.com/haskell/core-libraries-committee/issues/341 - - - - - 575c4bc6 by Rodrigo Mesquita at 2026-10-05T12:32:02-04:00 ttg: HsModuleName in the AST, ModuleName in GHC This commit makes the AST fully independent from GHC by parsing a "module name" as an `HsModuleName (= HText)` rather than constructing an `ModuleName (= FastString)` straight away. In the GHC side, everything remains as a `ModuleName`. We turn AST `HsModuleName`s into fast strings with the cheap `mkFastStringShortText` when we process the AST for manipulation within the compiler. There are no performance regressions introduced by this approach. This is the final piece of #21592 Alternative plans were discussed in gitlab.haskell.org/ghc/ghc/-/merge_requests/16546#note_694647, but the Simon suggested one won in simplicity and performance when compared against my attempt at implementing my original plan of having a family `ModuleNameP`. - - - - - b3b89d32 by mangoiv at 2026-10-05T22:03:32-04:00 hadrian: Persist the used flavour name in the build root (#20650) This executes the idea proposed in #20650, teaching Hadrian to persist the flavour used to build a build root. This both makes use of multiple build roots more ergonomic (as the user no longer needs to repeat themselves) and avoids a tiresome foot-gun (forgetting to specify a flavour, often wholly invalidating a build root). Closes #20650. Co-authored-by: Sylvain Henry <sylvain(a)haskus.fr> - - - - - f977837b by mangoiv at 2026-10-05T22:04:21-04:00 configure: fix sed script and subst tooldir script Fixes #27672 Adds sanity checking for SUBST_TOOLDIR Metric Decrease: LinkableUsage01 MultiLayerModulesTH_OneShot T10547 T12234 T12425 T13035 T13820 T18140 T18730 T18923 T9198 TcPlugin_RewritePerf mhu-perf - - - - - f1cb08be by Hannes Siebenhandl at 2026-10-05T22:05:03-04:00 Prepend in-memory unit database for backpack The packageDbFlags are stored in reverse order. Thus, prepending will ensure that the in-memory unit database is the last item on the unit database stack. Further, the in-memory unit database needs to be able to shadow units from earlier unit databases in the unit database stack. Moreover, a `-clear-package-db` would remove the in-memory database if it weren't the last item on the stack. Closes #27835 - - - - - 8d49ed42 by Kazu Yamamoto at 2026-10-06T19:37:25-04:00 Do not leave standard file descriptors free at startup (#24450) A process may be started with stdout closed -- `prog >&-` from a shell does exactly that. Nothing then reserves descriptor 1, and open(), pipe() and socket() hand out the lowest free descriptor, so the next descriptor the runtime creates for itself takes it: the ticker's pipe, or a capability's IO manager control pipe. 'GHC.Internal.IO.StdHandles.stdout' is a CAF, built the first time the program writes to stdout, which is long after that has happened. It builds a 'Handle' over descriptor 1, which now belongs to the runtime, and nothing reports an error because the descriptor is perfectly good. The program then writes its output into the runtime's own plumbing. What that looks like from the outside is a hang. The descriptor the Handle has taken over is the read end of a pipe, so poll() for POLLOUT on it never says yes and epoll_ctl() accepts a registration for it; the thread waiting to write blocks for ever. Closing the Handle at exit closes the runtime's descriptor, which is worse: the ticker then fails on every tick. 'hs_init_ghc' now opens /dev/null onto whichever of descriptors 0, 1 and 2 are closed, before the runtime creates any descriptor of its own. Each is opened for the access that descriptor would normally have, read-only for 0 and write-only for 1 and 2, so that writing to 'stdin' or reading from 'stdout' still fails rather than quietly succeeding against /dev/null. See Note [Standard file descriptors must be open]. Moving only the descriptors the runtime opens would not do: the first file the program itself opened would land on the free number instead. The fix has to leave no free number. A program run this way therefore finds stdout connected to /dev/null rather than failing with EBADF on the first write, which is what such a program would get from most other language runtimes. Co-Authored-By: Claude Opus 5 (1M context) <noreply(a)anthropic.com> - - - - - 65bcf9e9 by Simon Jakobi at 2026-10-06T19:38:09-04:00 changelog: Repair the sentence describing #27477 The description read "programs using could crash", the object of "using" having been lost. The synopsis already says which programs are affected, so drop the dangling word. Assisted-by: Claude Fable 5.1 - - - - - 15ece296 by mangoiv at 2026-10-08T15:14:56-04:00 ci: move hadrian/ghci into the lint category so it can be picked up by more runners Fixes #27817 - - - - - c0823135 by mangoiv at 2026-10-08T15:14:56-04:00 ci: make lint-adjacent jobs into platform independent - move lint jobs into lint-anyarch tag - unify lint jobs under the same platform independent container - - - - - f76464cf by Zubin Duggal at 2026-10-08T15:15:39-04:00 DmdAnal: Make AbsDmd neutral in maxDmd fixes #27845 - - - - - ffa56ae4 by sheaf at 2026-10-09T17:15:59+02:00 Preserve sign of zero when parsing -0.0# This commit leverages the recently added GHC.Types.Literal.Floating module in order to preserve the sign of negative zero from source-written floating-point literals. Fixes #27545 - - - - - d538cac9 by Facundo Domínguez at 2026-10-09T20:26:38-04:00 Propagate annotations to simple interfaces This allows annotations to be visible to plugins when run by haddock. The LiquidHaskell plugin needs the annotations, in particular. Fixes #26761 - - - - - 32c4f4ab by meooow25 at 2026-10-09T20:27:28-04:00 Bump containers submodule to 0.8.1 And fix affected tests. * T4086a: containers depends on template-haskell-lift now instead of template-haskell. * T22611: Updated to be less dependent on containers internals. - - - - - c786065e by sheaf at 2026-10-09T20:28:20-04:00 Use an explicit pattern match in toIfaceIdDetails The old wildcard pattern let this code bit rot: it did not properly account for recently added 'IdDetails' such as 'RepPolyId', which resulted in spurious 'pprTrace' messages that could even pollute HLS sessions. Fixes #23785 - - - - - e7cacf59 by sheaf at 2026-10-09T20:29:09-04:00 Take into account ifKind in freeNamesIfDecl Commit 3c2f4bb4 added the 'ifKind' field to various constructors of 'IfaceDecl', which preserves the original kind (before type synonym expansion) for better error messages. However, that commit forgot to update 'freeNamesIfDecl' correspondingly. This could result in a "urk! lookup local fingerpring" crash when e.g. a type's kind uses a type synonym defined later, as we failed to add a dependency on the type synonym during dependency analysis. Fixes #27916 - - - - - 0ca15959 by Sven Tennie at 2026-10-10T19:24:06+02:00 hadrian: Add Stage3 cross-compiled target bindist (#26924) Add a `binary-dist-stage3` Hadrian target that packages target executables (produced by the stage2 compiler) into a separate '_build/bindist-stage3/' folder, distinct from the stage2 regular or cross-compiler bindist in '_build/bindist/'. This allows a single CI pipeline job to produce both a cross-compiler bindist (e.g. x86_64 -> RISC-V) and a target-architecture bindist (e.g. RISC-V -> RISC-V) that can be installed and run natively on the target. To avoid issues with stale files or race-conditions on them, generate the `configure` script per stage in `_build/<stage>/distrib` directories. - - - - - 51b19449 by Sven Tennie at 2026-10-10T19:24:06+02:00 ci: Build Stage3 and Stage2 bindists for cross targets in one job (#26924) Building the stage3 target bindist already produces most of the stage2 cross-compiler bindist as a byproduct, so building them in separate jobs duplicates the build efforts for no benefit. Instead of a separate CROSS_STAGE=3 job, the stage3 job now also builds and publishes the stage2 bindist. The stage3 tarball is named and versioned as if it were built natively on the target (target triple prefix, non-cross opsys), so its artifact name stays what downstream consumers already expect and no changes are needed on their side. For now, this is only enabled for the RISC-V job. Others can easily follow. - - - - - defb092b by Sven Tennie at 2026-10-10T19:24:07+02:00 ci: model cross targets as structured TargetPlatform triples Storing the cross target as a raw triple forced ad-hoc parsing at every use, and broke the single responsibility rule. Modelling it as a structured `TargetPlatform`` instead, avoids parsing and provides a clear separation of concerns. - - - - - 3957570f by Sven Tennie at 2026-10-10T19:24:07+02:00 ci: use a scalar cross-stage switch, FINAL_CROSS_STAGE=2|3 For cross-compilers, Stage2 bindists are (almost) a by-product of Stage3 bindists. Thus, we either build Stage2 or Stage2 + Stage3 bindists. The commit at hand reflects this fact in types. - - - - - 328511a4 by Sven Tennie at 2026-10-10T19:24:07+02:00 ci: extract the cross smoke tests into a separate smoke_test command This reduces if-nesting and complexity of the main `test_hadrian` command. The decision how to test is now made by the caller. This is a fair choice, because most test cases can run under emulation - they are just very slow then. - - - - - 2ef533f6 by Sven Tennie at 2026-10-10T19:24:07+02:00 ci: inline the FINAL_CROSS_STAGE renderer `finalCrossStageEnvVal` was small and only used in one place. - - - - - 484c4bf1 by Sven Tennie at 2026-10-10T19:24:07+02:00 hadrian: clarify cross-stage settings and project.mk comments Reword the settings-rule comment to name the two stage roles (compilerStage vs libraryStage) and explain what 'the final architecture' in terms of project.mk generation means. - - - - - 8fb99740 by Sven Tennie at 2026-10-10T19:24:07+02:00 Fix intepreter settings for native target bindists Stage3 cross-compiled bindists wrongly assumed they cannot run the interpreter natively. Fix this by adjusting compile flags and choosing the correct libs/target/default.target files per compiler stage. - - - - - 164 changed files: - .gitignore - .gitlab-ci.yml - .gitlab/ci.sh - .gitlab/generate-ci/gen_ci.hs - .gitlab/jobs.yaml - + changelog.d/24450 - + changelog.d/26761 - + changelog.d/27845 - + changelog.d/T23785 - + changelog.d/T27545 - + changelog.d/T27916 - + changelog.d/clc-341-strict-mutable-data-types - changelog.d/fix-parallel-gc-selector-race-27477 - + changelog.d/hadrian-persist-flavour - + changelog.d/stage3-cross-bindists - changelog.d/unit-index - compiler/GHC.hs - compiler/GHC/Builtin/Modules.hs - compiler/GHC/ByteCode/Asm.hs - compiler/GHC/ByteCode/Show.hs - compiler/GHC/Core/DataCon.hs - compiler/GHC/Core/Make.hs - compiler/GHC/Core/Opt/CallerCC/Types.hs - compiler/GHC/CoreToIface.hs - compiler/GHC/Driver/Backpack.hs - compiler/GHC/Driver/Main/Compile.hs - compiler/GHC/Driver/Pipeline.hs-boot - compiler/GHC/Driver/Pipeline/Execute.hs - compiler/GHC/Driver/Pipeline/Phases.hs - compiler/GHC/Hs/Doc.hs - compiler/GHC/Hs/Dump.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/ImpExp.hs - compiler/GHC/Hs/Lit.hs - compiler/GHC/HsToCore/Docs.hs - compiler/GHC/HsToCore/Match/Literal.hs - compiler/GHC/HsToCore/Quote.hs - compiler/GHC/Iface/Decl.hs - compiler/GHC/Iface/Errors/Types.hs - compiler/GHC/Iface/Ext/Ast.hs - compiler/GHC/Iface/Ext/Debug.hs - compiler/GHC/Iface/Ext/Types.hs - compiler/GHC/Iface/Syntax.hs - compiler/GHC/Iface/Tidy.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/Errors/Types.hs - compiler/GHC/Parser/Header.hs - compiler/GHC/Parser/Lexer.x - compiler/GHC/Parser/PostProcess.hs - compiler/GHC/Parser/String.hs - compiler/GHC/Rename/Env.hs - compiler/GHC/Rename/Names.hs - compiler/GHC/Rename/Unbound.hs - compiler/GHC/StgToJS/Linker/Linker.hs - compiler/GHC/Tc/Deriv/Generics.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/Gen/Export.hs - compiler/GHC/Tc/Module.hs - compiler/GHC/Tc/Types.hs - compiler/GHC/Tc/Types/ErrCtxt.hs - compiler/GHC/ThToHs.hs - compiler/GHC/Types/Demand.hs - compiler/GHC/Types/Unique.hs - compiler/GHC/Types/UnresolvedImport.hs - compiler/GHC/Unit/Home.hs - compiler/GHC/Unit/Module.hs - compiler/GHC/Unit/Module/Env.hs - + compiler/GHC/Unit/Module/Name.hs - compiler/GHC/Unit/Parser.hs - compiler/GHC/Unit/Types.hs - compiler/GHC/Unit/Types.hs-boot - compiler/GHC/Utils/Binary.hs - compiler/GHC/Utils/Outputable.hs - compiler/Language/Haskell/Syntax.hs - compiler/Language/Haskell/Syntax/Expr.hs - compiler/Language/Haskell/Syntax/ImpExp.hs - compiler/Language/Haskell/Syntax/Lit.hs - compiler/Language/Haskell/Syntax/Module/Name.hs - compiler/Language/Haskell/Syntax/Text.hs - compiler/ghc.cabal.in - distrib/configure.ac.in - ghc/GHCi/UI.hs - ghc/GHCi/UI/Info.hs - hadrian/doc/flavours.md - hadrian/src/BindistConfig.hs - hadrian/src/Rules.hs - hadrian/src/Rules/BinaryDist.hs - hadrian/src/Rules/Generate.hs - hadrian/src/Settings.hs - hadrian/src/Settings/Packages.hs - libraries/base/base.cabal.in - libraries/base/changelog.md - libraries/base/src/Control/Concurrent/Chan.hs - + libraries/base/src/Control/Concurrent/Chan/Strict.hs - libraries/base/src/Control/Concurrent/MVar.hs - + libraries/base/src/Control/Concurrent/MVar/Strict.hs - libraries/base/src/Data/IORef.hs - + libraries/base/src/Data/IORef/Strict.hs - libraries/containers - linters/lint-codes/LintCodes/Static.hs - m4/subst_tooldir.m4 - rts/RtsStartup.c - + testsuite/tests/backpack/should_compile/T27835.bkp - + testsuite/tests/backpack/should_compile/T27835.stderr - testsuite/tests/backpack/should_compile/all.T - testsuite/tests/count-deps/CountDepsAst.stdout - testsuite/tests/count-deps/CountDepsParser.stdout - + testsuite/tests/dmdanal/should_run/T27845.hs - + testsuite/tests/dmdanal/should_run/T27845.stdout - + testsuite/tests/dmdanal/should_run/T27845_Lib.hs - + testsuite/tests/dmdanal/should_run/T27845b.hs - + testsuite/tests/dmdanal/should_run/T27845b.stdout - + testsuite/tests/dmdanal/should_run/T27845b_Lib.hs - testsuite/tests/dmdanal/should_run/all.T - testsuite/tests/ghc-api/downsweep/IncrementalDownsweep.hs - 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/hiefile/should_run/T24544.hs - 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/module/mod185.stderr - + testsuite/tests/numeric/should_run/T27545.hs - + testsuite/tests/numeric/should_run/T27545.stdout - testsuite/tests/numeric/should_run/all.T - testsuite/tests/package/T4806a.stderr - testsuite/tests/package/all.T - 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/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/plugins/T26761.hs - + testsuite/tests/plugins/T26761.stderr - + testsuite/tests/plugins/T26761Plugin.hs - + testsuite/tests/plugins/T26761a.hs - testsuite/tests/plugins/all.T - testsuite/tests/printer/AnnotationNoListTuplePuns.stdout - testsuite/tests/printer/T18791.stderr - testsuite/tests/printer/Test20297.stdout - testsuite/tests/printer/Test24533.stdout - testsuite/tests/profiling/should_run/caller-cc/CallerCcParser.hs - + testsuite/tests/rts/T24450.hs - + testsuite/tests/rts/T24450.stderr - testsuite/tests/rts/all.T - testsuite/tests/simplCore/should_compile/T22611.hs - testsuite/tests/simplCore/should_compile/T22611.stderr - + testsuite/tests/simplCore/should_compile/T22611a.hs - testsuite/tests/simplCore/should_compile/all.T - + testsuite/tests/typecheck/should_compile/T27916.hs - testsuite/tests/typecheck/should_compile/all.T - utils/check-exact/ExactPrint.hs - utils/haddock/haddock-api/src/Haddock/Backends/Hyperlinker/Renderer.hs The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/b1e9280d8a20203ee0d498cda2b81c… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/b1e9280d8a20203ee0d498cda2b81c… 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/rafl/meaningful-main-return] Does this introduce the allocations?
by Florian Ragwitz (＠rafl) 10 Oct '26

10 Oct '26

Florian Ragwitz pushed to branch wip/rafl/meaningful-main-return at Glasgow Haskell Compiler / GHC Commits: f9b6b8cb by Florian Ragwitz at 2026-10-10T10:22:56-07:00 Does this introduce the allocations? - - - - - 1 changed file: - compiler/GHC/Tc/Module.hs Changes: ===================================== compiler/GHC/Tc/Module.hs ===================================== @@ -1975,12 +1975,10 @@ generateMainBinding tcg_env main_name = do main_expr_rn = L (noAnnSrcSpan loc) (mkHsVar (L (noAnnSrcSpan loc) main_name)) -- Solve the constraints arising from checking `main` before deciding how -- to handle its result. - -- ; ((ev_binds, main_expr), main_wanteds) <- captureTopConstraints $ - -- setMainCtxt main_name io_ty $ tcCheckMonoExpr main_expr_rn io_ty - -- ; main_ev_binds <- simplifyTop main_wanteds - -- ; main_action <- handleMainReturn main_name res_ty ev_binds main_expr - ; (ev_binds, main_expr) <- setMainCtxt main_name io_ty $ - tcCheckMonoExpr main_expr_rn io_ty + ; ((ev_binds, main_expr), main_wanteds) <- captureTopConstraints $ + setMainCtxt main_name io_ty $ tcCheckMonoExpr main_expr_rn io_ty + ; main_ev_binds <- simplifyTop main_wanteds + ; main_action <- handleMainReturn main_name res_ty ev_binds main_expr -- See Note [Root-main Id] -- Construct the binding @@ -1995,9 +1993,7 @@ generateMainBinding tcg_env main_name = do -- type errors when type of `main` is not `IO a`. The `ev_binds` -- must be put inside `runMainIO` to ensure the deferred type -- error can be emitted correctly. See #13838. - -- ; rhs = nlHsApp (mkLHsWrap co (nlHsVar run_main_id)) main_action - ; rhs = nlHsApp (mkLHsWrap co (nlHsVar run_main_id)) $ - mkHsDictLet ev_binds main_expr + ; rhs = nlHsApp (mkLHsWrap co (nlHsVar run_main_id)) main_action ; main_bind = mkVarBind root_main_id rhs } ; return (tcg_env { tcg_main = Just main_name @@ -2007,12 +2003,9 @@ generateMainBinding tcg_env main_name = do `plusDU` usesOnly (unitFN main_name) } -- Record the use of 'main', so that we don't -- complain about it being defined but not used - -- `addEvBinds` main_ev_binds) - ) + `addEvBinds` main_ev_binds) } -{- - -- Implement GHC proposal #631 -- (https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0631-m…) -- @@ -2048,7 +2041,10 @@ generateMainBinding tcg_env main_name = do -- An amendment to the original proposal to this effect has been submitted at -- https://github.com/ghc-proposals/ghc-proposals/pull/771. handleMainReturn :: Name -> TcType -> TcEvBinds -> LHsExpr GhcTc -> TcM (LHsExpr GhcTc) -handleMainReturn main_name res_ty ev_binds main_expr = do +handleMainReturn _main_name _res_ty ev_binds main_expr = do + pure (mkHsDictLet ev_binds main_expr) + +{- meaningful_main <- xoptM LangExt.MeaningfulMainReturn void_ty <- mkTyConTy <$> tcLookupKnownOccTyCon voidTyConOcc exit_code_ty <- mkTyConTy <$> tcLookupKnownOccTyCon exitCodeTyConOcc View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/f9b6b8cb6638edc464fda235c0f5128… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/f9b6b8cb6638edc464fda235c0f5128… 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/supersven/hadrian-cross-stage3] Fix intepreter settings for native target bindists
by Sven Tennie (＠supersven) 10 Oct '26

10 Oct '26

Sven Tennie pushed to branch wip/supersven/hadrian-cross-stage3 at Glasgow Haskell Compiler / GHC Commits: b1e9280d by GHC GitLab CI at 2026-10-10T18:27:27+02:00 Fix intepreter settings for native target bindists Stage3 cross-compiled bindists wrongly assumed they cannot run the interpreter natively. Fix this by adjusting compile flags and choosing the correct libs/target/default.target files per compiler stage. - - - - - 4 changed files: - .gitlab/ci.sh - hadrian/src/Rules/BinaryDist.hs - hadrian/src/Rules/Generate.hs - hadrian/src/Settings/Packages.hs Changes: ===================================== .gitlab/ci.sh ===================================== @@ -701,7 +701,20 @@ function smoke_test() { info "Smoke-testing stage3 compiler..." file "$stage3_ghc" - run ${CROSS_EMULATOR} "$stage3_ghc" --info + run ${CROSS_EMULATOR} "$stage3_ghc" --info > stage3-info + cat stage3-info + + # The stage3 compiler is a native target compiler: it must not consider + # itself a cross-compiler, and GHCi support must be compiled in when the + # target supports it. + grep -q '"cross compiling","NO"' stage3-info \ + || fail "stage3 compiler reports itself as cross-compiling" + + if grep -q '"Use interpreter","YES"' stage3-info; then + echo 'ghci works' > ghci-expected + ${CROSS_EMULATOR:-} "$stage3_ghc" -e 'putStrLn "ghci works"' > ghci-actual + run diff -w ghci-expected ghci-actual + fi run ${CROSS_EMULATOR} "$stage3_ghc" -package ghc "$TOP/.gitlab/hello.hs" -o hello-stage3 ===================================== hadrian/src/Rules/BinaryDist.hs ===================================== @@ -70,6 +70,13 @@ These are the steps to build a bindist: to <build root>/<bindist-dir>/ghc-<X>.<Y>.<Z>-<arch>-<os>/lib +- for cross-compilers, overwrite the implicitly copied (previous step) + <build root>/<library-stage-dir>/lib/targets/default.target file with that of + the executable stage. I.e. copy: + <build root>/<executable-stage-dir>/lib/targets/default.target + to + <build root>/<bindist-dir>/ghc-<X>.<Y>.<Z>-<arch>-<os>/lib/targets/default.target + - copy the generated docs (user guide, haddocks, etc): <build root>/doc/ to @@ -248,6 +255,13 @@ buildBinDistDir root conf@BindistConfig{..} = do copyDirectory (ghcBuildDir -/- "lib") bindistFilesDir + -- For cross-compilers we need to override the `targets/default.target` + -- file that was implicitly copied from the library stage, because this + -- describes a target native compiler (stage3) and not a cross-compiler. + when (library_stage /= executable_stage) $ + copyFile (root -/- stageString executable_stage -/- "lib" -/- "targets" -/- "default.target") + (bindistFilesDir -/- "lib" -/- "targets" -/- "default.target") + -- Regenerate settings file without LibDir. For bindists, LibDir should -- be derived from topdir at runtime such that the GHC binary is -- relocatable. The package DB is always at "package.conf.d" relative to ===================================== hadrian/src/Rules/Generate.hs ===================================== @@ -276,11 +276,21 @@ generateRules = do else root -/- stageString libraryStage -/- "lib" relPkgDb = makeRelativeNoSysLink libTopDir pkgDb go (generateSettings out True relPkgDb libraryStage) out - (prefix -/- "targets" -/- "default.target") %> \out -> go (show <$> expr (targetStage (succStage compilerStage))) out + (prefix -/- "targets" -/- "default.target") %> \out -> + go (generateTargetFile compilerStage) out where file <~+ gen = file %> \out -> generate out emptyTarget gen >> makeExecutable out + generateTargetFile :: Stage -> Expr String + generateTargetFile compilerStage = do + isCrossStage <- if compilerStage < Stage3 + then expr (crossStage compilerStage) + else pure False + let libraryStage = if isCrossStage then succStage compilerStage else compilerStage + tgt <- expr (targetStage libraryStage) + pure $ show tgt { tgtLocallyExecutable = not isCrossStage } + -- TODO: Use the Types, Luke! (drop partial function) -- We sometimes need to evaluate expressions that do not require knowing all -- information about the context. In this case, we don't want to know anything. ===================================== hadrian/src/Settings/Packages.hs ===================================== @@ -112,8 +112,11 @@ packageArgs = do , compilerStageOption ghcDebugAssertions ? arg "-DDEBUG" ] , builder (Cabal Flags) ? mconcat - [ andM [expr (ghcWithInterpreter stage), orM [expr (notM cross), stage1]] `cabalFlag` "interpreter" - , andM [expr (ghcWithInterpreter stage), notM (expr cross)] `cabalFlag` "internal-interpreter" + -- In the context of cross-compilation, stage2 runs on the target + -- and thus can - if the architecture supports it - provide the + -- interpreter natively. + [ andM [expr (ghcWithInterpreter stage), orM [expr (notM cross), stage1, stage2]] `cabalFlag` "interpreter" + , andM [expr (ghcWithInterpreter stage), orM [expr (notM cross), stage2]] `cabalFlag` "internal-interpreter" , ifM stage0 -- We build a threaded stage 1 if the bootstrapping compiler -- supports it. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/b1e9280d8a20203ee0d498cda2b81ce… -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/b1e9280d8a20203ee0d498cda2b81ce… 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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