leanprover / leanprover/lean4

simp only [Option.some_bind] -> maximum recursion depth has been reached

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bug P-medium
Dominant language
Lean
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Description

Prerequisites

Please put an X between the brackets as you perform the following steps:

Description
theorem extracted_1 (e : Option (BitVec 32)) :
  none =
    Option.bind e fun x =>
      if x ≥ 32 then none
      else
        (some ((BitVec.ofInt 32 (-33)).sshiftRight x.toNat)).bind fun y =>
          if y = 0#32 then none else some 0#32 := by
  simp only [Option.some_bind]
/-
tactic 'simp' failed, nested error:
maximum recursion depth has been reached
use `set_option maxRecDepth <num>` to increase limit
use `set_option diagnostics true` to get diagnostic information
-/
Context

I checked with @hargoniX and this seems to be a bug.

Steps to Reproduce
  1. Copy into live.lean-lang.org
  2. Observe the error

Expected behavior: No error recursion error

Actual behavior: Either simp successfully terminating or reporting that it could not find a simp-lemma to apply

Versions

Lean 4.14.0-nightly-2024-11-03
Target: x86_64-unknown-linux-gnu

Further information

On our dataset, this (or a similar) simp error fires 82 times.

Impact

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Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the minimal reproducer in live.lean-lang.org and inspect the behavior of simp only [Option.some_bind] on the shown theorem. Done means the command terminates without a maximum-recursion-depth error, either simplifying the goal or reporting that no applicable simp lemma was found.

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
Active
Clarity
Clearly specified
Newbie friendliness
45/100

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