typelevel / typelevel/sbt-typelevel
RFC: use `_` instead of `*` for kind-projector
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- Dominant language
- Scala
- Stars
- 185
- Forks
- 62
- PR merge metrics
- No merged PRs in 30d
Description
Scala 3 uses _ for kind projector and ? for existential wildcards, but supports the old */_ for compatibility with Scala 2.
I just discovered that Scala 2.12 and 2.13 can also be configured to use the new syntax.
https://github.com/typelevel/kind-projector#inline-underscore-syntax
One of the goals of sbt-typelevel v0.5.0 is to configure scalac so that it behaves more like "true" Scala 3. So I feel very tempted to make this change. We're already using the new syntax in Scala 3-only builds which has been a source of confusion when removing Scala 2 from the cross versions.
However this is a somewhat drastic change already into the RC cycle and will require a lot of existing code to be rewritten, I'm not sure how well find-replace could work.
Thoughts?
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 with the sbt-typelevel v0.5.0 Scala compiler configuration and the kind-projector inline underscore syntax documentation linked in the issue. Determine the scope of rewriting existing Scala 2.12/2.13 code from * and _, and treat a maintainer decision on whether to make the syntax change as the completion criterion.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- scala
- Domain
- build-system
- Issue type
- Feature
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100