Simon Peyton Jones pushed to branch wip/T27078 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. - - - - - 50829162 by Simon Peyton Jones at 2026-04-17T10:33:39+01:00 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 a bit worse because it has to run the SubstTypeLets pass which is a somewhat expensive no-op Metric Iecrease: T1969 - - - - - 50 changed files: - + changelog.d/T15973 - + changelog.d/T27121.md - + changelog.d/T27124.md - + 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.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/ghc-heap/tests/tso_and_stack_closures.hs - testsuite/driver/runtests.py - testsuite/driver/testglobals.py - testsuite/driver/testlib.py - 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 The diff was not included because it is too large. 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