leanprover-community / leanprover-community/mathlib4
Make `inhabit` use `simp [nontriviality]` in `[IsEmpty]` case
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Description
The tactic nontriviality α can do case split on Subsingleton α ∨ Nontrivial α, then discard the first branch using simp [nontriviality]. It would be nice to add a similar logic to
inhabit: case split on IsEmpty α ∨ Nonempty α, then discard the
first case using simp [nontriviality]. I think that both tactics
should use the same simp set because sometimes, e.g., [IsEmpty α]
implies [Subsingleton (α → β)].
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
Locate the implementations of inhabit and nontriviality, then compare the simp sets they currently use. Verify the change with the existing tactic tests, ensuring the [IsEmpty] branch is discarded and the corresponding nonempty behavior still works.
Written by the indexing model from the issue text.
Assessment
- Domain
- tooling
- Issue type
- Feature
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 39/100