Cats 2.3.0-M1

We are proud to announce the first Dotty release of Cats! All modules of Cats are cross-built and released for Scala 2.12.x, 2.13.x, and Dotty 0.27. Other than that, this release contains relatively few new features.

Dotty

The purpose of this milestone is that adventurous users can try out first-class Dotty support before we cut a final 2.3.0 release. Note that for the Dotty builds, binary compatibility between this milestone release and 2.3.0 may break in some situations. Also, if you are using the laws, sbt may complain about conflicting Scala version suffixes. This will be fixed in time for the final release.

Binary compatibility (Scala 2)

As usual, the 2.3.x series is backward binary-compatible with all previous 2.x releases (and with 1.x for the non-laws modules).

Changes & additions

• #3603 distinct for TraverseFilter by @takayahilton
• #3620, #3624 instances for immutable.Seq by @JosephMoniz
• #3630 methods to narrow input/widen output types on FunctionK by @bplommer
• #3636 Dotty support by @LukaJCB and @larsrh
• #3647 traverseTap by @majk-p
• #3648 add a law relating defer and fix in Defer by @johnynek

Other improvements

• #3373 test for zipWithIndex stack safety by @dantb
• #3595 migrate from tut to mdoc by @keynmol
• #3608 document scalafixAll to migrate test code as well by @bjaglin
• #3609 Cats ecosystem website by @benkio
• #3616 documentation on ApplicativeError by @dhinojosa
• #3616 documentation on Writer and WriterT by @benkio