shapeless 2.2.0-RC5 released

Posted
04 May 2015
by
Miles Sabin

Miles Sabin — 04 May 2015 [edit]

I’ve just published the latest release candidate for shapeless-2.2.0 … RC5. I’d hoped that RC4 would be the last release candidate before final, but experience while updating shapeless-contrib to shapeless 2.2.0 from 2.0.0 led me to the inescapable conclusion that we weren’t quite there yet. This also provided a little more time for a few low risk bug fixes and features to land as well …

Thanks to everyone who contributed … release notes follow …

This is the fifth release candidate for 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.

Experience with updating shapeless-contrib to shapeless 2.2.0 has led to some significant changes being made since RC4, and also opened up a window for a few low-risk additions and bug fixes,

  • 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.

  • 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.

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

  • 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.

  • The ToList and ToTraversable are now serializable so long as a serializable instances of CanBuildFrom is available.

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

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

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

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

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

  • A hygiene bug in Typeable has been fixed.

  • A bug in the handling of singleton types in Generic1 was fixed.

Since the shapeless 2.2.0-RC3 release a bug was found and fixed in the new SingletonProductArgs implementation.

Since the shapeless 2.2.0-RC2 release a bug was found and fixed in the new SingletonProductArgs implementation.

Since the shapeless 2.2.0-RC1 release the following changes have been made,

  • 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.

  • All the major types and type classes now extend Serializable for compatibility with libraries and systems which use Java serialization.

  • A mechanism to replace Scala’s now deprecated auto-tupling has been added via the ProductArgs and SingletonProductArgs traits.

  • A number of issues relating to the generation of Generic instances for method local case classes have been fixed.

The earlier 2.2.0-RC1 release included a number of bug fixes and the following new features and enhancements,

  • 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.

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

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

  • Added a useful toString to Sized containers.

  • Improved the CSV serialization example.

  • 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.

A big “Thank You!” to everyone who has contributed to this release,

shapeless is an exploration of type class and dependent type based generic programming in Scala.

Find the project online,

Some articles on the techniques used have appeared here

shapeless is an Open Source project under the Apache License v2.