Deep kernel reduction detected after `simp`
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- Lean
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Description
Prerequisites
Please put an X between the brackets as you perform the following steps:
- Check that your issue is not already filed:
https://github.com/leanprover/lean4/issues - Reduce the issue to a minimal, self-contained, reproducible test case.
Avoid dependencies to Mathlib or Batteries. - Test your test case against the latest nightly release, for example on
https://live.lean-lang.org/#project=lean-nightly
(You can also use the settings there to switch to “Lean nightly”)
Description
The following lean code leads to a deep kernel reduction detected error in Lean.
theorem minimal6 : ∀ (x : BitVec 32),
((some x).bind fun x =>
(if False then none else some (x.sshiftRight 1)).bind fun x' =>
some (x'.sshiftRight 1))
= (some x) := by
intro x
simp only [Option.some_bind]
sorry
Steps to Reproduce
- Copy into lean
- Observe the red line under the theorem name
Expected behavior: [Clear and concise description of what you expect to happen]
- simp should apply the lemma
- the proof should be marked as
sorrywith an orange line under the theorem name - no kernel error
Versions
"4.12.0-nightly-2024-10-15"
Impact
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This issue was reduced by @lfrenot.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with the minimal6 theorem and reproduce it using Lean version 4.12.0-nightly-2024-10-15. Investigate the interaction between simp, Option.some_bind, BitVec.sshiftRight, and kernel reduction. Done means simp applies the lemma, the proof remains marked sorry, and no deep kernel reduction error is reported.
Written by the indexing model from the issue text.
Assessment
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100