The problem in KT-19833 is caused by the fact that the application
environment instance is shared between consecutive runs of the compiler
in one Make action (KotlinCoreEnvironment.ourApplicationEnvironment).
If the JDK 8 module is compiled first, the created application
environment has no JRT file system, and once the JDK 9 module is
compiled later, that environment is not recreated and thus classes from
JDK 9 are unresolved.
To mitigate this, split the CoreJrtFileSystem implementation into the
file system itself which is global per application, and CoreJrtHandler
which is bound to a particular JDK home location. CoreJrtVirtualFile
paths now consist of the path to the JDK home, the "!/" separator, and
the path to the file itself, e.g.
"/usr/lib/jvm/java9!/modules/java.base/java/lang/Object.class". The
implementation is inspired by CoreJarFileSystem & CoreJarHandler.
No tests added because the application environment is _not_ shared in
tests. Also, a JDK 9 module is going to be added to the Kotlin project
soon, and that will serve as a test
#KT-19833 Fixed
Alexander Udalov
08e090bf5e