class Stream.Cons and object Stream.cons are clashing with each other

[sjrd]

In object Stream, there is a class Cons and an object cons.

This happens not to cause any issue on the JVM, even on Windows. That's because Stream$cons$ being a nested object, scalac does not generate static forwarders for it in Stream$cons. However Scala.js generates more static forwarders, to be able to correctly define static methods in nested static classes of JDK APIs.

This basically prevents from building Scala.js 1.x with 2.13.x on Windows.

I don't know what to do about this, given the binary compat guarantees. 😰

[joroKr21]

Running on Mac, I do see linking errors when building OSS projects that upgraded to Scala.js 1.x
I haven't investigated but this could be the reason.

[dwijnand]

with 2.13.x

Same with 2.12.x, right? Seeing as it's the same: https://github.com/scala/scala/blob/v2.12.11/src/library/scala/collection/immutable/Stream.scala#L1149-L1163

[sjrd]

I've never observed the issue with 2.12.x. And our build uses 2.12.x by default, so I'm constantly building on 2.12.x.

I guess this is because in 2.12.x, object cons comes before class Cons. So when we compile object cons, we generate Stream$cons$.class and Stream$cons.class. And then when we arrive at class Cons, we overwrite Stream$cons.class with the one for Cons. We lose the static forwarders for Stream$cons$, but we never observe that, because it's not a JDK class.

If my analysis is correct, we could work around the issue by swapping the order of the definitions in the 2.13.x source!

[dwijnand]

Fixed in scala/scala#9035.