leanprover / leanprover/lean4

revert fails with variable

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bug P-low
Dominant language
Lean
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Description

Prerequisites

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Description

revert fails with metavariables when a variable statement is used, but succeeds if a proper argument is used or nonrec is added.

Context

https://leanprover.zulipchat.com/#narrow/stream/270676-lean4/topic/revert.20and.20variable
affects also extract_goal in mathlib

Steps to Reproduce
variable {P : Prop}
theorem bug --adding nonrec fixes the issue
  --{P : Prop} --uncommenting this line fixes the issue
  (S : P → Prop) :
  ∃ (hx : P), S hx := by
  apply Exists.intro
  · revert P -- tactic 'clear' failed, target depends on 'bug'
    sorry

Expected behavior:

revert succeeds, and behaves identically for variables and parameters

Actual behavior:

revert succeeds only without variable

Versions

Lean 4.10.0 (also earlier)

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 by running the minimal reproducer with Lean 4.10.0 and compare the behavior of revert P with a proper parameter or nonrec. Trace the revert tactic and the related clear failure; done means variables and parameters behave identically and the example succeeds without the workaround.

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
45/100

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