To what degree can I use java 8 in a mixed java / scala 2.10 sbt project?
Can I emit java 8 bytecode? Use java 8 language features? Or are there features in scala 2.11 that are necessary? Is there an interop story?
2.10.4 Scala release notes:
New ByteCode emitter based on ASM
Can target JDK 1.5, 1.6 and 1.7
Emits 1.6 bytecode by default
Old 1.5 backend is deprecated
The official Scala 2.12 distribution will be built for Java 8 (and thus require it).
More background info of when you can expect to fully use Java 8:
The Scala 2.11.x series targets Java 6, with (evolving) experimental >support for Java 8. In 2.11.1, Java 8 support is mostly limited to reading >Java 8 bytecode and parsing Java 8 source. Stay tuned for more complete >(experimental) Java 8 support. The next major release, 2.12, will most >likely target Java 8 by default.
Planned future Java 8-centric additions for Scala 2.12 include Java 8 >style closures, which will allow the Scala compiler to emit closure >classes (lambdas) just as you can with Java 8. There’s also planned lambda >syntax for SAM types. Again, in Java 8 fashion, this lets you instantiate >any type with one single abstract method by passing a lambda, improving >the user experiences for libraries written for Java 8 in Scala.