implement ext? suggesting a rcases pattern
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Description
When upstreaming ext from Std in #3306, we noticed that there are todo stubs for an ext? tactic which makes suggestions about an rcases-style pattern that can be used to named the introduced arguments.
I have removed these stubs, and this issue can serve to track this TODO.
The removed syntaxes were:
-- TODO
/-- `ext1? pat*` is like `ext1 pat*` but gives a suggestion on what pattern to use -/
syntax "ext1?" (colGt ppSpace rintroPat)* : tactic
/-- `ext? pat*` is like `ext pat*` but gives a suggestion on what pattern to use -/
syntax "ext?" (colGt ppSpace rintroPat)* (" : " num)? : tactic
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
Start by reviewing the removed ext1? and ext? syntax in this issue and the upstreaming change from #3306. The work is done when both tactics can suggest an rcases-style pattern for naming introduced arguments, with behavior matching the documented intent.
Written by the indexing model from the issue text.
Assessment
- Domain
- compilers
- Issue type
- Feature
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 25/100