publish bootstrapping sources from `library-aux` in `-sources.jar` artefacts

[unkarjedy]

This is needed to show documentation of definitions inside those classes inside IDE.
See https://youtrack.jetbrains.com/issue/SCL-22167 (with comments)

The sources are located here:
https://github.com/scala/scala/tree/2.13.x/src/library-aux

It's already done for scala docs—they are published in -javadoc.jar artifacts.

[SethTisue]

@lrytz did we want to try to squeeze this into 2.13.14?

[lrytz]

👍

[unkarjedy]

BTW, can anyone tell why these source files are special that they are located in a separate library-aux directory?
How e.g. Unit is different?
Also, why do Unit, AnyRef, Int have .class files but Any and Singleton do not?

[lrytz]

I guess Int and the others can be represented precisely (enough) in Scala source so that the compiler can build its symbols and types from source. The backend of course intercepts primitives to emit them accordingly.

Trying to do the same with Nothing / Any / ... would need more magic in the compiler, I assume it was easier to create these symbols synthetically (https://github.com/scala/scala/blob/v2.13.13/src/reflect/scala/reflect/internal/Definitions.scala#L337-L354).

[unkarjedy]

Similar Scala 3 ticket: scala/scala3#20073