Instead of generating these annotation classes as package-private on
JVM, serialize their metadata to the .kotlin_module file, and load it
when compiling dependent multiplatform modules.
The problem with generating them as package-private was that
kotlin-stdlib for JVM would end up declaring symbols from other
platforms, which would include some annotations from package
kotlin.native. But using that package is discouraged by some tools
because it has a Java keyword in its name. In particular, jlink refused
to work with such artifact altogether (KT-21266).
#KT-38652 Fixed
After this change, optional expected annotations will be compiled to
physical class files on JVM, and stored to metadata on other platforms,
to allow their usages from dependent platform modules. For example:
@OptionalExpectation
expect annotation class A
When compiling this code on JVM, A.class will be produced as if the
class A did neither have the 'expect' modifier, nor had it been
annotated with OptionalExpectation. Note that if there's no actual
annotation class for A, then usages (which can only be usages as
annotation entries) are simply skipped.
Class A will be public from Kotlin's point of view (since it should
be possible to use it in Kotlin sources), but _package-private_ in Java
to disallow its usages outside of the declaring module.
#KT-18882 Fixed
#KT-24617 Fixed
Alexander Udalov