Release notes: shapeless 2.2.0

This is the final release of shapeless-2.2.0. These release notes provide a summary of changes since shapeless 2.1.0. shapeless 2.2.0 should be source and binary compatible with shapeless 2.1.0, and for migration from shapeless 2.0.0 the earlier migration guide from shapeless 2.0.0 to 2.1.0 is still applicable and is available on the shapeless wiki.

Contributors for shapeless 2.2.0 are:

• Alexander Konovalov (@alexknvl)
• Alexandre Archambault (@alxarchambault)
• Alistair Johnson
• Ben Hutchison (@ben_hutchison)
• Dale Wijnand (@dwijnand)
• David Barri (@japgolly)
• Denis Mikhaylov @notxcain
• Jean-Remi Desjardins (@jrdesjardins)
• Johnny Everson (@johnny_everson)
• Pascal Voitot @mandubian
• Sam Halliday @fommil
• Sébastien Doeraene (@sjrdoeraene)
• Simon Hafner (@reactormonk)
• Vladimir Matveev (@netvlm)

Many thanks to all of you and everyone else who has contributed ideas, enthusiasm and encouragement.

There are a large number of new features, refactorings and bug fixes in shapeless 2.2.0. The most significant of these are,

• Scala.js is now officially supported. Many thanks to Alistair Johnson, Ben Hutchison, David Barri and Sébastien Doeraene for their assistance with this.

• Support for Spark (and other libraries and systems which use Java serialization) has been improved by having all the major types and type classes extend Serializable.

• Added support for derivation of type classes for higher-kinded types. See in particular the new example illustrating the application of this to the automatic derivation of Functor type class instances for ADTs.

• Generic derivation for coproducts now correctly handles cases where the type parameters of constructors is a subset and/or permutation of the type parameters of the data type. This allows correct type class derivation for types like Cat's Xor and Ior, and Scalaz's disjunction.

• Added support for Generic representation of types with repeated (ie. vararg) constructor arguments.

• There are now Generic instances for ADTs with constructors which are included via multiple inheritance paths.

• The test for "case-class-likeness" has been tightened to exclude some unexpected types (notably arrays).

• A mechanism providing greater control over the implicit priority of derived orphan type class instances has been added. This finally allows shapeless-contrib to be updated to use shapeless-2.2.0.

• A mechanism allowing expensive implicit definitions to be cached simply has been added.

• Witness instances are now available for the singleton types of stable values.

• A mechanism to replace Scala's now deprecated auto-tupling has been added via the ProductArgs and SingletonProductArgs traits. This supports some new examples illustrating a generic solution to the common problem of functional update of a family of case classes through their common supertype.

• A Max type class has been added for Nat types.

• A fields method has been added to records and unions.

• Added a useful toString to instances of the Typeable type class.

• Added a useful toString to Sized containers.

• Improved the CSV serialization example.

• Added an example of merging instances of one case class into another.

• With the addition of Scala.js support there are now four branches to release from simultaneously. Many thanks to Johnny Everson for his contribution of a script to automate this process.

• A number of tests have been made more portable so that they don't fail when run under Scala.js due to spurious platform-specifics.

• If you are using Scala 2.10.x it is no longer necessary to provide an explicit Scala version suffix for your shapeless dependency. You must still ensure that you are using Scala version 2.10.2 or greater, with Scala 2.10.5 (or switching to 2.11.x) strongly recommended.

• Reorganized the SBT project modules. The "shapeless-" prefix has been dropped from all the module names and it is now possible to drop into the Scala REPL with shapeless on the classpath using just the "console" command.