Update 2.12's scala.annotation.nowarn once 2.12.13 is out

[dwijnand]

See scala/scala-lang#1184 (comment)

2.12.13 is coming out imminently (today?). Once it's out, probably best when bumping to 2.12.13, it would be good to move that noop to 2.11 only.

But two scenarios to think about:

1. users that upgrade scalaVersion but not scala-collection-compat (or if we don't implement this change): it's unclear what classfile for @nowarn they'll class load, which could break the configurable warning feature

2. users that upgrade scala-collection-compat (with this implemented) but not scalaVersion: won't have a @nowarn in they're classpath any more... 😕 🤔 ...

[lrytz]

• users that upgrade scalaVersion but not scala-collection-compat (or if we don't implement this change): it's unclear what classfile for @nowarn they'll class load, which could break the configurable warning feature

are you sure things would break? even if

lazy val NowarnClass                = getClassIfDefined("scala.annotation.nowarn")

picks up the classfile from collection-compat, things could still work.

Ah, the problem is that the one here extends StaticAnnotation, but the one in 2.12.13 extends ClassfileAnnotation, so the 2.12.13 compiler would look for the string parameter in the wrong spot (annotationInfo.assocs instead of annotationInfo.args).

[SethTisue]

@lrytz want to do one more round of thinking about this now that 2.12.13 is out...? I'm happy to pull publishing levers as needed once we're sure what the right thing is.

[lrytz]

Maybe we can find some workaround by making scala.annotation.nowarn a type alias in this library?

Another option is to add this patch to the compiler, it would make the 2.12 nowarn implementation work with the annotation from this library (which extends StaticAnnotation instead of ClassfileAnnotation). The patch is from some other WIP branch of mine. scala/scala@6816ff0. This would only be in 2.12.14 though.

Another option is to change the annotation in this library to extends ClassfileAnnotation, i.e., make it identical to the one in 2.12.13.

[SethTisue]

Another option is to change the annotation in this library to extends ClassfileAnnotation, i.e., make it identical to the one in 2.12.13.

Is there some downside to that?

[lrytz]

I can't think of any issues that change would cause.

[NthPortal]

is that binary compatible?

[SethTisue]

technically no, but it shouldn't matter since it's an annotation. at least, I cannot contrive a situation in which it matters, and in a similar situation over at scala/scala#9336 (comment) , @lrytz wrote:

Changing the annotation to extends ConstantAnnotation [is] not binary compatible, but since it's an annotation that doesn't matter

[SethTisue]

#417