Simon Peyton Jones pushed to branch wip/T27844 at Glasgow Haskell Compiler / GHC Commits: 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 - - - - - 41e80f41 by Simon Peyton Jones at 2026-10-11T14:38:51-04:00 Simplify the error-suppression mechanism in GHC.Tc.Errors In `GHC.Tc.Errors.reportWanteds` we suppress some errors in favour of others. But the mechanism had grown crufty, and #27331 exposed a bug. This MR makes it simpler and more uniform, by doing everything via the `ei_suppress` field of the ErrorItem. Claude then found another closely-related bug (see the review linked on !16564). That bug is immortalised in new test T18851d. I'm still not happy with `ignoreConstraint` but we can worry about that another day; I have not touched it. Main changes * Instead of /predicting/ when an error will be reported, we set `cec_error_reported` when an error is /actually/ reported. (I renamed it from `cec_suppress` to reflect this change.) Now errors are suppressed only when a preceding error has actually been reported. Simpler and more robust. See `Note [cec_error_reported: suppressing less-serious errors]` The big changes are in `reportWanteds` which looks very different. * New `Note [ei_suppress: suppressing confusing errors]` describes the (quite separate) `ei_suppress` mechanism for suppressing confusing errors, mainly arising from non-empty rewriter sets * In `tryTypeClassDefaulting`, instead of switching off type-class defaulting if there is an insoluble /anywhere/, we just switch it off locally when we find an insoluble sub-tree. See Note [When to do type-class defaulting] and (W5) in Note [ApproximateWC] * Greatly simplify `insolubleWantedCt`. * I made type-class-defaulting be a bit more eager, only switched off when a peer or ancestor (but not child) constraint is insoluble. See Note [When to do type-class defaulting]. Small refactorings * Rename `askNoErrs` to `askErrsFound` and flip its polarity * The code for "check if ei_suppress is true of all items" code is moved to `mkErrorItems` rather than in the large `reportWanteds`. * Code for `has_gadt_match` moves to `mkGivenErrorReporter`, rather than polluting the large `reportWanteds`. * Many tests with `-fdefer-type-errors` get more warnings, especially about ambiguous (Num a) constraints. This is by-design: see Note [Always warn with -fdefer-type-errors]. Previously GHC was not honouring this Note but now it is, hence the extra errors. - - - - - f217fc31 by Cheng Shao at 2026-10-11T14:39:33-04:00 compiler: ensure cross ghc --info output target unit ids Previously, for cross ghcs, the base/ghc/ghc-internal unit ids in --info output do not match the target unit ids reported by ghc-pkg, breaking cross ghc release builds with hash-unit-ids when being used with cabal 3.18. This patch fixes it by making --info output target unit ids. Fixes #27919. Co-authored-by: Codex <codex@openai.com> - - - - - a2bb72a2 by Simon Peyton Jones at 2026-10-12T09:29:29+01:00 Refactor and simplify solver's unification code Ticket #27844 showed that GHC's constraint solver could miss an occurs check, and thereby build an infinite type. This patch significantly simplifes the code in GHC.Tc.Solver.Equality.canEqCanLHSFinish_try_unification GHC.Tc.Solver.Equality.canEqCanLHSFinish_no_unification It is now significantly simpler, and requires much less subtle reasoning to understand. Main changes * If `canEqCanLHSFinish_try_unification` fails to unify, it now /always/ calls `canEqCanLHSFinish_no_unification` rather than trying to finish the job itself. * `GHC.Tc.Solver.Monad.checkTypeEq` is moved from Monad into Equality, and renamed to `GHC.Tc.Solver.Equality.checkTypeEqNoUnification`. * `canEqCanLHSFinish_no_unification` calls `checkTypeEqNoUnification` to test the invariants for an inert equality. Before this MR there was a special case for `do_not_prevent_rewriting`, but that has gone; instead it's just a consequence of the flags passed to `checkTyEqRhs`, documented in the `PuOK` case of `canEqCanLHSFinish_no_unification`. * There is only one bit of "swap back" code, in `finish_no_unify` in `canEqCanLHSFinish_try_unification. Previously this code was duplicated. * `kickOutAfterFillingCoercionHole` should account for equalities with a TyFamLHS. See (KOC5) in Note [Kick out after filling a coercion hole] * No need to gather coercion holes in the `PuOK` case of `canEqCanLHSFinish_no_unification`. See documentation with that code. - - - - - 111 changed files: - .gitlab-ci.yml - .gitlab/hello.hs - + changelog.d/26761 - + changelog.d/27845 - + changelog.d/T23785 - + changelog.d/T27545 - + changelog.d/T27731 - + changelog.d/T27844 - + changelog.d/T27916 - + changelog.d/fix-cross-ghc-info-unit-id - compiler/GHC/Builtin/WiredIn/Ids.hs - compiler/GHC/Core/Make.hs - compiler/GHC/CoreToIface.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/Rename/Module.hs - compiler/GHC/Runtime/Heap/Inspect.hs - compiler/GHC/Settings.hs - compiler/GHC/Settings/IO.hs - compiler/GHC/Tc/Errors.hs - compiler/GHC/Tc/Errors/Ppr.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/Instance/Family.hs - compiler/GHC/Tc/Solver/Default.hs - compiler/GHC/Tc/Solver/Equality.hs - compiler/GHC/Tc/Solver/InertSet.hs - compiler/GHC/Tc/Solver/Monad.hs - compiler/GHC/Tc/Types/Constraint.hs - compiler/GHC/Tc/Utils/Monad.hs - compiler/GHC/Tc/Utils/Unify.hs - compiler/GHC/Types/Demand.hs - compiler/Language/Haskell/Syntax/Lit.hs - distrib/configure.ac.in - hadrian/bindist/Makefile - hadrian/bindist/config.mk.in - hadrian/src/Rules/BinaryDist.hs - hadrian/src/Rules/Generate.hs - libraries/containers - + 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/ghci/prog020/ghci.prog020a.stderr - testsuite/tests/ghci/prog020/ghci.prog020b.stderr - testsuite/tests/ghci/prog021/prog021a.stderr - testsuite/tests/ghci/prog021/prog021b.stderr - testsuite/tests/ghci/prog022/ghci.prog022a.stderr - testsuite/tests/ghci/prog022/ghci.prog022b.stderr - testsuite/tests/ghci/prog022/ghci.prog022c.stderr - testsuite/tests/ghci/prog022/ghci.prog022d.stderr - testsuite/tests/ghci/prog022/ghci.prog022e.stderr - testsuite/tests/ghci/prog022/ghci.prog022f.stderr - testsuite/tests/ghci/scripts/Defer02.stderr - testsuite/tests/indexed-types/should_fail/T9662.stderr - testsuite/tests/module/mod130.stderr - + testsuite/tests/numeric/should_run/T27545.hs - + testsuite/tests/numeric/should_run/T27545.stdout - testsuite/tests/numeric/should_run/all.T - testsuite/tests/overloadedstrings/should_fail/T25926.stderr - testsuite/tests/overloadedstrings/should_fail/T27124.stderr - testsuite/tests/package/T4806a.stderr - testsuite/tests/package/all.T - testsuite/tests/patsyn/should_fail/records-nofieldselectors.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/T17697.stderr - testsuite/tests/rename/should_fail/T15607.stderr - testsuite/tests/rename/should_fail/T19843b.stderr - testsuite/tests/safeHaskell/ghci/p4.stderr - testsuite/tests/safeHaskell/ghci/p6.stderr - 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/T11254.stderr - testsuite/tests/typecheck/should_compile/T15370.stderr - + testsuite/tests/typecheck/should_compile/T27916.hs - testsuite/tests/typecheck/should_compile/all.T - testsuite/tests/typecheck/should_compile/valid_hole_fits.stderr - testsuite/tests/typecheck/should_fail/ClassOperator.stderr - testsuite/tests/typecheck/should_fail/DoExpansion2.stderr - testsuite/tests/typecheck/should_fail/DoExpansion3.stderr - testsuite/tests/typecheck/should_fail/FunDepOrigin1b.hs - testsuite/tests/typecheck/should_fail/T12785b.stderr - testsuite/tests/typecheck/should_fail/T18851.stderr - + testsuite/tests/typecheck/should_fail/T18851e.hs - + testsuite/tests/typecheck/should_fail/T18851e.stderr - + testsuite/tests/typecheck/should_fail/T18851f.hs - + testsuite/tests/typecheck/should_fail/T18851f.stderr - testsuite/tests/typecheck/should_fail/T22940.stderr - testsuite/tests/typecheck/should_fail/T26823.stderr - + testsuite/tests/typecheck/should_fail/T27731.hs - + testsuite/tests/typecheck/should_fail/T27731.stderr - + testsuite/tests/typecheck/should_fail/T27844.hs - + testsuite/tests/typecheck/should_fail/T27844.stderr - testsuite/tests/typecheck/should_fail/T5691.stderr - testsuite/tests/typecheck/should_fail/T7437.stderr - testsuite/tests/typecheck/should_fail/all.T - testsuite/tests/typecheck/should_fail/mc24.stderr - testsuite/tests/typecheck/should_fail/tcfail019.stderr - testsuite/tests/typecheck/should_fail/tcfail189.stderr The diff was not included because it is too large. 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