TASTy Compatibility After a Scala 2.13→3 Upgrade: Clean Rollback
Goal Restore a project to a working Scala 2.13 state after a partially applied upgrade to Scala 3, without leaving mixed‑version artifacts that could corrupt future builds. Constraints Scala 3 compiles to TASTy files that embed a format version. The 2.13 compiler cannot consume TASTy produced by a newer compiler, so any leftover Scala 3 TASTy in the classpat
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