Hello,
Thanks for raising the issue of the rewrite tool.
The tool itself exists, it’s scalafix, which is a stable product. However, so far very few rules have been written for the Scala 3 migration.
scalafix has already been demonstrated to be successful in the real-world. Two prominent examples are:
- scalafix was used to a great extent to migrate the Akka codebase from 2.12 to 2.13 (https://github.com/akka/akka/pull/26043)
- scalafix is used in combination with Scala Steward to automatically submit upgrade PRs that automatically include the required source changes: https://www.scala-lang.org/blog/2019/07/10/announcing-scala-steward.html
I think those two examples validate that the tool works seamlessly enough.
Regarding the specific rules for the Scala 3 migration, this is now a priority at the Scala Center for the upcoming months.