leanprover-community / leanprover-community/mathlib4

cases' and unsynthesized placeholder

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Description

cases' currently suffers from the same bug as rcases reported here: https://github.com/leanprover/lean4/issues/5723

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 reading the linked Lean issue 5723 and reproducing the reported behavior for rcases, then compare it with the cases' behavior described here. Identify the relevant mathlib4 tactic entry point and add a regression test showing that the unsynthesized placeholder is handled correctly.

Written by the indexing model from the issue text.

Assessment

Domain
compilers
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
30/100

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