Marge Bot pushed to branch wip/marge_bot_batch_merge_job at Glasgow Haskell Compiler / GHC

Commits:

• 7b616b9f
  by Cheng Shao at 2026-01-16T06:45:00-05:00

  compiler: fix regression when compiling foreign stubs in the rts unit
  
  This patch fixes a regression when compiling foreign stubs in the rts
  unit introduced in 05e25647f72bc102061af3f20478aa72bff6ff6e. A simple
  revert would fix it, but it's better to implement a proper fix with
  comment for better understanding of the underlying problem, see the
  added comment for explanation.
  
  Co-authored-by: Codex <codex@openai.com>
  

• c343ef64
  by Sylvain Henry at 2026-01-16T06:45:51-05:00

  base: remove GHC.JS.Prim.Internal.Build (#23432)
  
  See accepted CLC proposal https://github.com/haskell/core-libraries-committee/issues/329
  

• e114327a
  by Simon Peyton Jones at 2026-01-16T07:17:40-05:00

  Improve newtype unwrapping
  
  Ticket #26746 describes several relatively-minor shortcomings of newtype
  unwrapping.  This MR addresses them, while also (arguably) simplifying
  the code a bit.
  
  See new Note [Solving newtype equalities: overview]
  and     Note [Decomposing newtype equalities]
  and     Note [Eager newtype decomposition]
  and     Note [Even more eager newtype decomposition]
  
  For some reason, on Windows only, runtime allocations decrease for test
  T5205 (from 52k to 48k).  I have not idea why. No change at all on Linux.
  I'm just going to accept the change.  (I saw this same effect in another
  MR so I think it's a fault in the baseline.)
  
  Metric Decrease:
      T5205
  

• 1c92069b
  by Andreas Klebinger at 2026-01-16T07:17:41-05:00

  testsuite: Widen acceptance window for T5205.
  
  Fixes #26782
  

21 changed files:

• compiler/GHC/Core/FamInstEnv.hs
• compiler/GHC/Driver/CodeOutput.hs
• compiler/GHC/Tc/Instance/Family.hs
• compiler/GHC/Tc/Solver/Equality.hs
• compiler/GHC/Tc/Solver/Monad.hs
• libraries/base/base.cabal.in
• libraries/base/changelog.md
• − libraries/base/src/GHC/JS/Prim/Internal/Build.hs
• testsuite/tests/deriving/should_fail/T8984.stderr
• testsuite/tests/deriving/should_fail/deriving-via-fail.stderr
• testsuite/tests/deriving/should_fail/deriving-via-fail4.stderr
• testsuite/tests/deriving/should_fail/deriving-via-fail5.stderr
• testsuite/tests/interface-stability/base-exports.stdout-javascript-unknown-ghcjs
• testsuite/tests/perf/should_run/all.T
• + testsuite/tests/typecheck/should_compile/T26746.hs
• testsuite/tests/typecheck/should_compile/all.T
• testsuite/tests/typecheck/should_fail/T15801.stderr
• testsuite/tests/typecheck/should_fail/T22924b.stderr
• testsuite/tests/typecheck/should_fail/TcCoercibleFail.hs
• testsuite/tests/typecheck/should_fail/TcCoercibleFail.stderr
• testsuite/tests/typecheck/should_fail/all.T

The diff was not included because it is too large.