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FAQ

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Lukas Rytz edited this page Jan 25, 2018 · 90 revisions

This page should evolve over time, but already be useful now. When more official documentation is available, content can be replaced by links.

Collection Users

What are the breaking changes?

collection.breakOut no longer exists
Method to[C] was removed
MapProxy, SetProxy no longer exist
SynchronizedX no longer exist
Implicit conversions between Scala and Java collections no longer exist (convert.ImplicitConversions / ImplicitConversionsToJava / ImplicitConversionsToScala) -- NOTE: they are not deprecated in 2.12.

Are there new collection types?

Are there new operations on collections?

Are there new implementations of existing collection types (changes in performance characteristics)?

How do I cross-build my project against Scala 2.12 and Scala 2.13?

Compat library
Accept some deprecation warnings (?)
sbt's version-specific source folders if necessary, but should not be

Does `scala.Seq` change to mean `scala.collection.immutable.Seq`?

No, there are no plans to change the scala.Seq alias.

Historical discussion: https://groups.google.com/forum/#!topic/scala-internals/g_-gIWgB8Os

Collection Implementers

`CanBuildFrom` no longer exists - what were its uses and how can they be replaced?

How can I write generic extension methods?

How do I integrate my collection in the new design?

Read the draft document on the design of the Scala 2.13 collections: https://github.com/scalacenter/docs.scala-lang/blob/collection-strawman/_overviews/core/architecture-of-scala-collections.md

How can I cross-build my collection implementation against 2.12 and 2.13?

Examples