leanprover-community / leanprover-community/mathlib4
Porting note: `dsimp` cannot prove this
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porting-notes
- Dominant language
- Lean
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Description
-- In Lean 3, `dsimp` would use theorems proved by `Iff.rfl`.
-- If that were still the case, this would useful as a `@[simp]` lemma,
-- despite the fact that it is provable by `simp` (by not `dsimp`).
Examples
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
Review the porting note and the referenced examples in Mathlib/Algebra/Free.lean, Mathlib/Data/Multiset/FinsetOps.lean, and Mathlib/GroupTheory/Subgroup/Basic.lean. Compare the reported dsimp behavior with the surrounding simp lemmas; completion requires an agreed resolution for the Lean 3 versus Lean 4 behavior.
Written by the indexing model from the issue text.
Assessment
- Domain
- tooling
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100