A Java compiler that will invalidate class files from a forked java compiler by adding a new classes directory to the beginning of the -classpath compiler option where we will write an empty class file for every invalidated class file. This empty class file will force the javac compiler to output an error similar to:

/path/to/File.java:1 error: cannot access Bar

bad class file: ./B.class class file contains wrong class: java.lang.Object Please remove or make sure it appears in the correct subdirectory of the classpath.

Fortunately, the last bit is not parsed by Zinc's JavacParser and doesn't show up as a reported Zinc problem. The first bit does show up and it's a good enough error to intuit that the symbol might not exist, so we leave it there. We cannot replace that error with a custom one because it would be confusing if the accessibility error is real and not caused by our invalidation trick.