This is the first release with support for type class derivation on Scala 3! 🥳

It adds derivation for the type classes FunctorK, ContravariantK, InvariantK, SemigroupalK and ApplyK. One caveat compared to Scala 2 is that algebras with type members are not supported. The derivation macros are experimental meaning that call-sites need to be annotated with @experimental. Alternatively, users can enable the -experimental compiler option starting with Scala 3.4. The reasons for both limitations are rooted in the underlying macro APIs.

What's Changed

• Update scala3-library, ... to 3.3.0 by @pomadchin in https://github.com/typelevel/cats-tagless/pull/429
• check binary compatibility with v0.14.0 wherever possible by @bpholt in https://github.com/typelevel/cats-tagless/pull/430
• Added examples project by @vasiliybondarenko in https://github.com/typelevel/cats-tagless/pull/418
• Fix microsite links by @joroKr21 in https://github.com/typelevel/cats-tagless/pull/437
• Support Semigroupal for more complex types by @joroKr21 in https://github.com/typelevel/cats-tagless/pull/438
• Quality of life improvements in DeriveMacros by @joroKr21 in https://github.com/typelevel/cats-tagless/pull/439
• Fix FunctorK when F occurs only in contravariant position by @joroKr21 in https://github.com/typelevel/cats-tagless/pull/440
• Add FunctorK instance for FS2 Stream by @m50d in https://github.com/typelevel/cats-tagless/pull/443
• Derive SemigroupK by @joroKr21 in https://github.com/typelevel/cats-tagless/pull/441
• Derive MonoidK, fix SemigroupK by @joroKr21 in https://github.com/typelevel/cats-tagless/pull/445
• Update Ruby and Jekyll by @joroKr21 in https://github.com/typelevel/cats-tagless/pull/507
• Exclude metals.sbt from scalafmt by @joroKr21 in https://github.com/typelevel/cats-tagless/pull/511
• Scala3 FunctorK macros by @pomadchin in https://github.com/typelevel/cats-tagless/pull/442
• Scala3 SemigroupalK and InvariantK macros by @pomadchin in https://github.com/typelevel/cats-tagless/pull/513
• Scala3 ContravariantK macros by @pomadchin in https://github.com/typelevel/cats-tagless/pull/518
• Scala3 ApplyK macros and SemigroupalK derivation improvement by @pomadchin in https://github.com/typelevel/cats-tagless/pull/516
• Handle repeated and by-name parameters by @joroKr21 in https://github.com/typelevel/cats-tagless/pull/519
• Hacky solution of the Tuple2K problem by @joroKr21 in https://github.com/typelevel/cats-tagless/pull/520
• [Scala 3] Use Semigroup to combine results in SemigroupalK derivation by @joroKr21 in https://github.com/typelevel/cats-tagless/pull/521
• Consolidate Derive API between Scala 2 and Scala 3 by @joroKr21 in https://github.com/typelevel/cats-tagless/pull/522

Dependency Updates

New Contributors

• @vasiliybondarenko made their first contribution in https://github.com/typelevel/cats-tagless/pull/418
• @m50d made their first contribution in https://github.com/typelevel/cats-tagless/pull/443

Full Changelog: https://github.com/typelevel/cats-tagless/compare/v0.15.0...v0.16.0