Marge Bot pushed to branch wip/marge_bot_batch_merge_job at Glasgow Haskell Compiler / GHC Commits: 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> - - - - - 80aca549 by Florian Ragwitz at 2026-10-11T17:08:42-07:00 hpc: Improve coverage semantics for instance methods and instances Users care about which of their explicitly written methods are or aren't covered, not whether all of the inherited methods are covered as well. Those should be covered where they are implemented. We therefore skip generating top-level boxes for inherited methods which will appear as uncovered with no clear indication as to why, and no way to fix other than exercising code the user has not written. Previously, top-level boxes for those inherited methods would use the instance head as their source span. Now that those boxes are gone, we can use that source span for another purpose: We introduce a new top-level box for each class instance with its instance head as the source span, and use that to indicate whether or not an instance has been covered at all. We do this by making any method of the instance, inherited/generated or otherwise, tick the box for the instance head. Excluded from this are methodless classes, which could never be covered using the current mechanism. This could be improved upon further. These changes apply to ticking for program coverage only, and don't affect source notes. Additionally, we update the scope of record selector ticking to be limited to program coverage as well, as the oversight to also extend it to source notes has previously caused bugs and because record selector ticking is coverage-specific. Fixes #17155, #15932. - - - - - 9770f45b by Sylvain Henry at 2026-10-12T06:26:42-04:00 NCG x86: track the current block after word-to-float conversion (#27915) On x86-64, genWordToFloat introduces new basic blocks, but it was dispatched via genSimplePrim, which assumes no new blocks. The new current block was not given back to stmtsToInstrs, so a second conversion in the same Cmm block updated the CFG relative to a stale block id. This caused the panic "Can't find weight for edge that should have one" when the register allocator inserted a fixup block. genWordToFloat now returns the new current block and MO_UF_Conv is handled with the other block-introducing primops in genPrim. See Note [Keeping track of the current block]. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> - - - - - 80 changed files: - .gitlab/hello.hs - + changelog.d/27915 - + changelog.d/T27731 - + changelog.d/fix-cross-ghc-info-unit-id - + changelog.d/hpc-classinsts - compiler/GHC/Builtin/WiredIn/Ids.hs - compiler/GHC/CmmToAsm/X86/CodeGen.hs - compiler/GHC/Core/Opt/Specialise.hs - compiler/GHC/CoreToIface.hs - compiler/GHC/Driver/Session.hs - compiler/GHC/HsToCore.hs - compiler/GHC/HsToCore/Ticks.hs - compiler/GHC/Rename/Module.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/TyCl/Instance.hs - compiler/GHC/Tc/Types/Constraint.hs - compiler/GHC/Tc/Utils/Monad.hs - compiler/GHC/Types/Id/Info.hs - distrib/configure.ac.in - hadrian/bindist/Makefile - hadrian/bindist/config.mk.in - hadrian/src/Rules/BinaryDist.hs - hadrian/src/Rules/Generate.hs - + testsuite/tests/codeGen/should_run/T27915.hs - + testsuite/tests/codeGen/should_run/T27915.stdout - testsuite/tests/codeGen/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/hpc/instmeths/instmeths.hs - + testsuite/tests/hpc/instmeths/instmeths.stdout - + testsuite/tests/hpc/instmeths/test.T - testsuite/tests/module/mod130.stderr - testsuite/tests/overloadedstrings/should_fail/T25926.stderr - testsuite/tests/overloadedstrings/should_fail/T27124.stderr - testsuite/tests/patsyn/should_fail/records-nofieldselectors.stderr - 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/T22375.stderr - testsuite/tests/simplCore/should_compile/T22375DataFamily.stderr - testsuite/tests/typecheck/should_compile/T11254.stderr - testsuite/tests/typecheck/should_compile/T15370.stderr - 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/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/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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