leanprover / leanprover/lean4

Conv changing goals to metavariables with `pattern`.

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bug P-medium
Dominant language
Lean
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Description

Prerequisites
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    • Check that your issue is not already filed.
    • Reduce the issue to a minimal, self-contained, reproducible test case. Avoid dependencies to mathlib4 or std4.
Description
example : ∀ p : Prop, p ↔ p := by
  conv => ext p; pattern p ↔ p; rw [iff_self]

/-
(kernel) declaration has metavariables '_example'

unsolved goals
⊢ ∀ (p : Prop), ?m.13 p -/
Context

https://leanprover.zulipchat.com/#narrow/stream/270676-lean4/topic/conv.20giving.20metavariables is the Zulip thread about it.

Expected behavior: The unsolved goal should be ∀ (p : Prop), True.

Actual behavior: The unsolved goal is ⊢ ∀ (p : Prop), ?m.13 p, which is a weird metavariable.

Versions

Lean (version 4.3.0-rc1, commit baa4b68a7192, Release), OSX Sonoma 14.0

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 conv and pattern reproduction under Lean 4.3.0-rc1 and compare the actual metavariable goal with the expected ∀ (p : Prop), True. Trace the conv/pattern behavior described in the issue; done means the example no longer leaves the _example metavariable unsolved.

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
Clearly specified
Newbie friendliness
35/100

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