Monad of no Return

[Bodigrim]

Defining return serves no purpose, let's clean it up. Also cf. haskell/core-libraries-committee#418

Template B: This PR does not modify behaviour or interface

• Patches conform to the coding conventions.
• Is this a PR that fixes CI? If so, it will need to be backported to older cabal release branches (ask maintainers for directions).

[mergify]

Queued — the merge queue status continues in this comment ↓.

[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-06-26 19:33 UTC · Rule: default · triggered by rule Put pull requests in the rebase+merge queue
• ❌ Checks failed · on draft merge queue: checking master (ee7d5da) and #12006 together #12025
• 🚫 Left the queue — 2026-06-27 01:45 UTC · at 2736b8776ee12640ebdd08b677b393afcafc313d

This pull request spent 6 hours 11 minutes 56 seconds in the queue, including 6 hours 1 minute 6 seconds running CI.

Waiting for any of

• check-neutral = Validate post job
• check-skipped = Validate post job
• check-success = Validate post job

All conditions

• any of [🛡 GitHub branch protection]:
  • check-neutral = Validate post job
  • check-skipped = Validate post job
  • check-success = Validate post job
• #approved-reviews-by >= 2 [🛡 GitHub branch protection]
  • Monad of no Return #12006
• #review-threads-unresolved = 0 [🛡 GitHub branch protection]
  • Monad of no Return #12006
• any of [🛡 GitHub branch protection]:
  • check-success = Doctest Cabal
  • check-neutral = Doctest Cabal
  • check-skipped = Doctest Cabal
• any of [🛡 GitHub branch protection]:
  • check-success = Meta checks
  • check-neutral = Meta checks
  • check-skipped = Meta checks
• any of [🛡 GitHub branch protection]:
  • check-success = docs/readthedocs.org:cabal
  • check-neutral = docs/readthedocs.org:cabal
  • check-skipped = docs/readthedocs.org:cabal
• any of [🛡 GitHub branch protection]:
  • check-success = fourmolu
  • check-neutral = fourmolu
  • check-skipped = fourmolu
• any of [🛡 GitHub branch protection]:
  • check-success = hlint
  • check-neutral = hlint
  • check-skipped = hlint
• any of [🛡 GitHub branch protection]:
  • check-success = Bootstrap post job
  • check-neutral = Bootstrap post job
  • check-skipped = Bootstrap post job
• any of [🛡 GitHub branch protection]:
  • check-success = whitespace
  • check-neutral = whitespace
  • check-skipped = whitespace
• any of [🛡 GitHub branch protection]:
  • check-success = Check sdist post job
  • check-neutral = Check sdist post job
  • check-skipped = Check sdist post job
• any of [🛡 GitHub branch protection]:
  • check-success = Changelogs
  • check-neutral = Changelogs
  • check-skipped = Changelogs

Reason

The merge conditions cannot be satisfied due to failing checks

• Doctest Cabal
• Meta checks
• docs/readthedocs.org:cabal
• Validate post job
• fourmolu
• hlint
• Bootstrap post job
• whitespace
• Check sdist post job
• Changelogs

Failing checks:

• ❌ Validate post job (job log)

Hint

You may have to fix your CI before adding the pull request to the queue again.
If you update this pull request, to fix the CI, it will automatically be requeued once the queue conditions match again.
If you think this was a flaky issue instead, you can requeue the pull request, without updating it, by posting a @mergifyio queue comment.

Requeued — the merge queue status continues in this comment ↓.

[zlonast]

@Mergifyio queue

[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-06-27 12:03 UTC · Rule: default · triggered by @zlonast with the @mergifyio queue command
• ❌ Checks failed — 2026-06-27 12:21 UTC · on draft merge queue: checking master (ee7d5da) and [#12012 + #12017 + #12006] together #12038
• ✂️ Bisecting to identify the failing PR (round 1/1)
• ❌ Checks failed — 2026-06-27 14:41 UTC · on draft merge queue: checking master (ee7d5da) and [#12017 + #12006] together #12041
• ✂️ Bisecting to identify the failing PR (round 2/1)
• 🚫 Left the queue — 2026-06-27 22:30 UTC · at 2736b8776ee12640ebdd08b677b393afcafc313d

This pull request spent 10 hours 27 minutes 24 seconds in the queue, including 8 hours 15 minutes 53 seconds running CI.

Reason

The merge conditions cannot be satisfied due to failing checks

• Doctest Cabal
• Meta checks
• docs/readthedocs.org:cabal
• Validate post job
• fourmolu
• hlint
• Bootstrap post job
• whitespace
• Check sdist post job
• Changelogs

Failing checks:

• ❌ Validate post job (job log)
• 🛑 Validate ubuntu-latest ghc-9.10.3 (job log)

Hint

You may have to fix your CI before adding the pull request to the queue again.
If you update this pull request, to fix the CI, it will automatically be requeued once the queue conditions match again.
If you think this was a flaky issue instead, you can requeue the pull request, without updating it, by posting a @mergifyio queue comment.

[zlonast]

@Mergifyio queue

[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-06-28 06:54 UTC · Rule: default · triggered by @zlonast with the @mergifyio queue command
• ✅ Checks passed · on draft merge queue: checking master (d64d329), #12010, #12016, #12012 and #12006 together #12048
• ✅ Merged — 2026-06-28 08:52 UTC · at 2736b8776ee12640ebdd08b677b393afcafc313d · merge

This pull request spent 1 hour 57 minutes 50 seconds in the queue, including 1 hour 46 minutes 57 seconds running CI.

Required conditions to merge

• #approved-reviews-by >= 2 [🛡 GitHub branch protection]
  • Monad of no Return #12006
• #review-threads-unresolved = 0 [🛡 GitHub branch protection]
  • Monad of no Return #12006
• any of [🛡 GitHub branch protection]:
  • check-success = Doctest Cabal
  • check-neutral = Doctest Cabal
  • check-skipped = Doctest Cabal
• any of [🛡 GitHub branch protection]:
  • check-success = Meta checks
  • check-neutral = Meta checks
  • check-skipped = Meta checks
• any of [🛡 GitHub branch protection]:
  • check-success = docs/readthedocs.org:cabal
  • check-neutral = docs/readthedocs.org:cabal
  • check-skipped = docs/readthedocs.org:cabal
• any of [🛡 GitHub branch protection]:
  • check-success = Validate post job
  • check-neutral = Validate post job
  • check-skipped = Validate post job
• any of [🛡 GitHub branch protection]:
  • check-success = fourmolu
  • check-neutral = fourmolu
  • check-skipped = fourmolu
• any of [🛡 GitHub branch protection]:
  • check-success = hlint
  • check-neutral = hlint
  • check-skipped = hlint
• any of [🛡 GitHub branch protection]:
  • check-success = Bootstrap post job
  • check-neutral = Bootstrap post job
  • check-skipped = Bootstrap post job
• any of [🛡 GitHub branch protection]:
  • check-success = whitespace
  • check-neutral = whitespace
  • check-skipped = whitespace
• any of [🛡 GitHub branch protection]:
  • check-success = Check sdist post job
  • check-neutral = Check sdist post job
  • check-skipped = Check sdist post job
• any of [🛡 GitHub branch protection]:
  • check-success = Changelogs
  • check-neutral = Changelogs
  • check-skipped = Changelogs