The main changes are in jvm_package_table.proto and ModuleMapping.kt.
With JvmPackageName, package parts can now have a JVM package name that
differs from their Kotlin name. So, in addition to the old package parts
which were stored as short names + short name of multifile facade (we
can't change this because of compatibility with old compilers), we now
store separately those package parts, which have a different JVM package
name. The format is optimized to avoid storing any package name more
than once as a string.
Another notable change is in KotlinCliJavaFileManagerImpl, where we now
load .kotlin_module files when determining whether or not a package
exists. Before this change, no PsiPackage (and thus, no JavaPackage and
eventually, no LazyJavaPackageFragment) was created unless there was at
least one file in the corresponding directory. Now we also create
packages if they are "mapped" to other JVM packages, i.e. if all package
parts in them have been annotated with JvmPackageName.
Most of the other changes are refactorings to allow internal names of
package parts/multifile classes where previously there were only short
names.
Note that now DeserializedClassDescriptor.getSealedSubclasses works a lot
faster than before, for all newly compiled sealed classes except empty ones. It
may be optimized further if we look at the metadata version of the file the
class was loaded from, however it's not easy currently because
DeserializedClassDescriptor is declared in common (non-JVM) code and has no
direct access to the binary version information.
This will also allow to add a reflection API to get subclasses of a sealed
class
#KT-12795 Fixed
Mikhael Bogdanov