Simon Jakobi pushed to branch wip/sjakobi/T27096 at Glasgow Haskell Compiler / GHC Commits: 2dadf3b0 by sheaf at 2026-04-16T13:28:39-04:00 Simplify mkTick This commit simplifies 'GHC.Core.Utils.mkTick', removing the accumulating parameter 'rest' which was suspiciously treating a bunch of different ticks as a group, and moving the group as a whole around the AST, ignoring that the ticks in the group might have different placement properties. The most important change is that we revert the logic (added in 85b0aae2) that allowed ticks to be placed around coercions, which caused serious issues (e.g. #27121). It was just a mistake, as it doesn't make sense to put a tick around a coercion. Also adds Note [Pushing SCCs inwards] which clarifies the logic for pushing SCCs into lambdas, constructor applications, and dropping SCCs around non-function variables (in particular the treatment of splittable ticks). A few other changes are also implemented: - simplify 'can_split' predicate (no functional change) - combine profiling ticks into one when possible Fixes #26878, #26941 and #27121 Co-authored-by: simonpj <simon.peytonjones@gmail.com> - - - - - a0d6f1f4 by Simon Jakobi at 2026-04-16T13:29:28-04:00 Add regression test for #9074 Closes #9074. - - - - - d178ee89 by Sylvain Henry at 2026-04-16T13:30:25-04:00 Add changelog for #15973 - - - - - e8a196c6 by sheaf at 2026-04-16T13:31:19-04:00 Deal with 'noSpec' in 'coreExprToPmLit' This commit makes two separate changes relating to 'GHC.HsToCore.Pmc.Solver.Types.coreExprAsPmLit': 1. Commit 7124e4ad mistakenly marked deferred errors as non-canonical, which led to the introduction of 'nospec' wrappers in the generated Core. This reverts that accident by declaring deferred errors as being canonical, avoiding spurious 'nospec' wrapping. 2. Look through magic identity-like Ids such as 'nospec', 'inline' and 'lazy' in 'coreExprAsPmLit', just like Core Prep does. There might genuinely be incoherent evidence, but that shouldn't obstruct the pattern match checker. See test T27124a. Fixes #25926 #27124 ------------------------- Metric Decrease: T3294 ------------------------- - - - - - 8cb99552 by Sylvain Henry at 2026-04-16T19:22:43-04:00 hadrian: warn when package index is missing (#16484) Since cabal-install 3.0 we can query the path of remote-repo-cache and check if hackage package index is present. Fixes #16484 - - - - - d6ce7477 by Richard Eisenberg at 2026-04-16T19:23:25-04:00 Teach hadrian to --skip-test. Fixes #27188. This adds the --skip-test flag to `hadrian build`, as documented in the patch. - - - - - 7666f4a9 by Fendor at 2026-04-17T22:29:51-04:00 Migrate `ghc-pkg` to use `OsPath` and `file-io` `ghc-pkg` should use UNC paths as much as possible to avoid MAX_PATH issues on windows. `file-io` uses UNC Paths by default on windows, ensuring we use the correct APIs and that we finally are no longer plagued by MAX_PATH issues in CI and private machines. On top of it, the higher correctness of `OsPath` is appreciated in this small codebase. Also, we improve memory usage very slightly, due to the more efficient memory representation of `OsPath` over `FilePath` Adds `ghc-pkg` regression test for MAX_PATH on windows Make sure `ghc-pkg` behaves as expected when long paths (> 255) are involved on windows. Let's generate a testcase where we can actually observe that `ghc-pkg` behaves as epxected. See the documentation for windows on Maximum Path Length Limitation: * `https://learn.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation` Adds changelog entry for long path support in ghc-pkg. - - - - - 78434e8c by Simon Peyton Jones at 2026-04-17T22:30:38-04:00 Kill off the substitution in Lint Now that we have invariant (NoTypeShadowing) we no longer need Lint to carry an ambient substitution. This makes it simpler and faster. A really worthwhile refactor. There are some knock-on effects * Linting join points after worker/wrapper. See Note [Join points and beta redexes] * Running a type substitution after the desugarer. See Note [Substituting type-lets] in the new module GHC.Core.SubstTypeLets Implements #27078 Most perf tests don't use Lint so we won't see a perf incresae. But T1969, which uses -O0 and Lint, gets 1.3% worse because it has to run the SubstTypeLets pass which is a somewhat expensive no-op Overall though compile-time allocations are down 0.1%. Metric Increase: T1969 - - - - - 86ca6c2c by mangoiv at 2026-04-17T22:31:22-04:00 testsuite: inline elemCoreTest Some weird (probably python scoping) rule caused elemCoreTest, a regex being out of scope on ubuntu, presumably because of a newer python version. This patch just inlines the regex, which fixes the issue. Fixes #27193 - - - - - 029a9139 by Simon Jakobi at 2026-04-18T14:00:25+02:00 Implement List.elem via foldr ...in order to allow specialization to Eq instances. The implementation of notElem is updated for consistency.` Addresses #27096. - - - - - 64 changed files: - + changelog.d/T15973 - + changelog.d/T27121.md - + changelog.d/T27124.md - + changelog.d/elem-via-foldr-27096 - + changelog.d/ghc-pkg-long-path-support - + changelog.d/hadrian-warn-missing-package-index-16484 - + changelog.d/skip-test - compiler/GHC/Core/Lint.hs - + compiler/GHC/Core/Lint/SubstTypeLets.hs - compiler/GHC/Core/Opt/FloatOut.hs - compiler/GHC/Core/Opt/OccurAnal.hs - compiler/GHC/Core/Opt/WorkWrap/Utils.hs - compiler/GHC/Core/Subst.hs - compiler/GHC/Core/Utils.hs - compiler/GHC/CoreToStg/Prep.hs - compiler/GHC/Driver/Config/Core/Lint.hs - compiler/GHC/HsToCore/Pmc/Solver/Types.hs - compiler/GHC/Stg/Debug.hs - compiler/GHC/Tc/Errors.hs - compiler/GHC/Types/Tickish.hs - compiler/GHC/Unit/State.hs - compiler/ghc.cabal.in - hadrian/build-cabal - hadrian/build-cabal.bat - hadrian/doc/make.md - hadrian/doc/testsuite.md - hadrian/src/CommandLine.hs - hadrian/src/Settings/Builders/RunTest.hs - libraries/base/tests/perf/ElemNoFusion_O1.stderr - libraries/base/tests/perf/ElemNoFusion_O2.stderr - libraries/base/tests/perf/all.T - libraries/ghc-boot/GHC/Unit/Database.hs - libraries/ghc-boot/ghc-boot.cabal.in - libraries/ghc-heap/tests/tso_and_stack_closures.hs - libraries/ghc-internal/src/GHC/Internal/List.hs - testsuite/driver/runtests.py - testsuite/driver/testglobals.py - testsuite/driver/testlib.py - testsuite/tests/cabal/Makefile - testsuite/tests/cabal/all.T - + testsuite/tests/cabal/ghcpkg10.stdout - testsuite/tests/corelint/LintEtaExpand.stderr - testsuite/tests/corelint/T21115b.stderr - + testsuite/tests/ghci/T9074/Makefile - + testsuite/tests/ghci/T9074/T9074.hs - + testsuite/tests/ghci/T9074/T9074.stdout - + testsuite/tests/ghci/T9074/T9074a.c - + testsuite/tests/ghci/T9074/T9074b.c - + testsuite/tests/ghci/T9074/all.T - + testsuite/tests/overloadedstrings/should_fail/T25926.hs - + testsuite/tests/overloadedstrings/should_fail/T25926.stderr - + testsuite/tests/overloadedstrings/should_fail/T27124.hs - + testsuite/tests/overloadedstrings/should_fail/T27124.stderr - + testsuite/tests/overloadedstrings/should_fail/all.T - + testsuite/tests/overloadedstrings/should_run/T27124a.hs - testsuite/tests/overloadedstrings/should_run/all.T - + testsuite/tests/profiling/should_compile/T27121.hs - + testsuite/tests/profiling/should_compile/T27121_aux.hs - testsuite/tests/profiling/should_compile/all.T - + testsuite/tests/simplCore/should_compile/T26941.hs - + testsuite/tests/simplCore/should_compile/T26941_aux.hs - testsuite/tests/simplCore/should_compile/all.T - utils/ghc-pkg/Main.hs - utils/ghc-pkg/ghc-pkg.cabal.in The diff was not included because it is too large. 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