leanprover-community / leanprover-community/mathlib4
tracking issue for change in behaviour in `@[simp] def`
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- Dominant language
- Lean
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Description
Back in Lean 3, @[simp] def f only unfolded suitably applied appearances of f. In Lean 4, it means it can be unfolded unapplied.
This resulted in many @[simp] attributes being removed from definitions, and replaced by explicit @[simp] lemmas.
This issue is a tracking issue for places where adaptations were required for this that may warrant further investigation. Often during the port this was worked around using @[eqns], but with changes to the generation of equation lemmas this approach has become less reliable.
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 reported Lean 3/Lean 4 simp behavior and search mathlib4 for the adaptations and uses of @[eqns] described in the issue. Determine which cases still need investigation and document or resolve each confirmed case; no files or tests are named, so repository-wide search is the starting point.
Written by the indexing model from the issue text.
Assessment
- Domain
- tooling
- Issue type
- Refactor
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 20/100