Marge Bot pushed to branch wip/marge_bot_batch_merge_job at Glasgow Haskell Compiler / GHC Commits: 4f985108 by Vladislav Zavialov at 2026-08-07T17:49:50-04:00 Discard type arguments in tcPatToExpr (#27440, #27583) The builder expression of an implicitly bidirectional pattern synonym must not mention types written in the RHS: * Invisible type arguments led to a panic (#27440) * Required type arguments failed with out-of-scope variables (#27583) Both are now discarded, following the precedent established by pattern signatures (#9867). Discarding type arguments takes some care: a type pattern cannot be told from a value pattern by syntax alone, as the `type` keyword may be omitted. Consider: data T a b c where MkT :: forall a. forall b c -> a -> T a b c pattern P :: x -> T x y z pattern P x = MkT @a (type b) c x In P's right-hand side, `@a` and `type b` are clearly type arguments, but what about `c` and `x`? We can only tell by matching the patterns against MkT's type. So tcPatToExpr now runs in TcM and matches the arguments against the constructor's TyVarBinders using zipPatsBndrs, which is made public for this purpose. The resulting builder is $bP x = MkT _ _ x. See Note [Discarding types in the builder expression]. Test cases: T27440a T27440b T27440c T27440d T27440e T27583a T27583b T27583c T27583d T27583e T27583f T27583g Metric Increase: LinkableUsage02 Metric Decrease: T27336 Assisted-by: Claude Opus 5 - - - - - eb1dcd4d by sheaf at 2026-08-07T17:50:40-04:00 mkWpFun_FRR: fix ordering of coercion composition When the subsumption machinery generates an eta-expansion, we must perform a representation polymorphism check to ensure the lambda binder it introduces has a fixed runtime representation. This is done in GHC.Tc.Utils.mkWpFun_FRR. This check involves composing quite a few coercions, arising from representation-polymorphism checks on both the actual and expected argument types. These coercions are then chained using HsWrapper composition, <.>. The ordering of composition was incorrect, leading to the Core Lint failure reported in #27639. This commit fixes that. Fixes #27639 - - - - - 98d0f540 by Simon Jakobi at 2026-08-09T11:09:47-04:00 Word64Map: add compareSize compareSize m c compares the size of a map to an Int, but unlike compare (size m) c it stops traversing the map once the outcome is determined. Based on https://github.com/haskell/containers/pull/1139 Assisted-by: Claude Opus 5 - - - - - 15080c42 by Simon Jakobi at 2026-08-09T11:09:47-04:00 Use a pigeonhole sort for deterministic UniqDFM iteration Deterministic UniqDFM iteration used a list mergesort, allocating O(n log n) cons cells and contributing significantly to compiler allocations (#27459). Use a pigeonhole sort where appropriate, while retaining the mergesort fallback. See Note [Sorting a UDFM] and Note [Cost of deterministic iteration]. The peak_megabytes_allocated increase for LinkableUsage02 is probably due to GC timing noise. See #27613. ------------------------- Metric Decrease: InstanceMatching InstanceMatching1 ManyAlternatives T12707 T13379 T13719 T24471 T27336 T5321FD T5321Fun T783 Metric Increase 'peak_megabytes_allocated': LinkableUsage02 ------------------------- Assisted-by: gpt-5.6-sol via Codex CLI - - - - - 16326d09 by sheaf at 2026-08-09T11:09:48-04:00 Testsuite: don't measure max residency for T27336 We really care more about total allocations for this test, so this commit removes the maximum residency measurement. - - - - - a2dcad43 by Alan Zimmerman at 2026-08-09T11:09:49-04:00 EPA: Remove LocatedE, replace with LocatedA This gets rid of one more LocatedXXX occurrence - - - - - 57 changed files: - + changelog.d/T27440 - + changelog.d/T27583 - + changelog.d/T27639 - compiler/GHC/Data/Word64Map/Internal.hs - compiler/GHC/Data/Word64Map/Lazy.hs - compiler/GHC/Data/Word64Map/Strict.hs - compiler/GHC/Data/Word64Map/Strict/Internal.hs - compiler/GHC/Hs/Decls.hs - compiler/GHC/Hs/Expr.hs - compiler/GHC/Hs/Pat.hs - compiler/GHC/Hs/Utils.hs - compiler/GHC/Iface/Ext/Ast.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/Annotation.hs - compiler/GHC/Parser/PostProcess.hs - compiler/GHC/Rename/Pat.hs - compiler/GHC/Tc/Gen/Pat.hs - compiler/GHC/Tc/TyCl/PatSyn.hs - compiler/GHC/Tc/Utils/Unify.hs - compiler/GHC/Types/Unique/DFM.hs - compiler/GHC/Unit/Module/Warnings.hs - testsuite/tests/ghc-api/exactprint/T22919.stderr - testsuite/tests/ghc-api/exactprint/ZeroWidthSemi.stderr - testsuite/tests/module/mod185.stderr - 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/DumpTypecheckedAst.stderr - testsuite/tests/parser/should_compile/KindSigs.stderr - testsuite/tests/parser/should_compile/T20718.stderr - testsuite/tests/parser/should_compile/T20846.stderr - + testsuite/tests/patsyn/should_compile/T27440a.hs - + testsuite/tests/patsyn/should_compile/T27440b.hs - + testsuite/tests/patsyn/should_compile/T27440c.hs - testsuite/tests/patsyn/should_compile/all.T - + testsuite/tests/patsyn/should_fail/T27440d.hs - + testsuite/tests/patsyn/should_fail/T27440d.stderr - testsuite/tests/patsyn/should_fail/all.T - testsuite/tests/perf/compiler/all.T - testsuite/tests/printer/Test20297.stdout - testsuite/tests/printer/Test24533.stdout - + testsuite/tests/rep-poly/T27639.hs - testsuite/tests/rep-poly/all.T - + testsuite/tests/vdq-rta/should_compile/T27583a.hs - + testsuite/tests/vdq-rta/should_compile/T27583b.hs - + testsuite/tests/vdq-rta/should_compile/T27583c.hs - + testsuite/tests/vdq-rta/should_compile/T27583d.hs - + testsuite/tests/vdq-rta/should_compile/T27583e.hs - + testsuite/tests/vdq-rta/should_compile/T27583g.hs - testsuite/tests/vdq-rta/should_compile/all.T - + testsuite/tests/vdq-rta/should_fail/T27440e.hs - + testsuite/tests/vdq-rta/should_fail/T27440e.stderr - + testsuite/tests/vdq-rta/should_fail/T27583f.hs - + testsuite/tests/vdq-rta/should_fail/T27583f.stderr - testsuite/tests/vdq-rta/should_fail/all.T - utils/check-exact/ExactPrint.hs The diff was not included because it is too large. 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