IllegalAccessError from ThreeLetterTimeZoneID with JDK 16

[tbroyer]

Description of the problem / feature request:

> Task :compileJava FAILED
/private/var/folders/jf/29g0fz_16w9_3y2db8ylkl540000gn/T/junit1380605189140352106/src/main/java/test/TimeZoneJava16.java:7: error: An unhandled exception was thrown by the Error Prone static analysis plugin.
        return TimeZone.getTimeZone("PST");
                                   ^
     Please report this at https://github.com/google/error-prone/issues/new and include the following:
  
     error-prone version: 2.5.1
     BugPattern: ThreeLetterTimeZoneID
     Stack Trace:
     java.lang.IllegalAccessError: class com.google.errorprone.VisitorState (in unnamed module @0x51b6b93c) cannot access class com.sun.tools.javac.model.JavacElements (in module jdk.compiler) because module jdk.compiler does not export com.sun.tools.javac.model to unnamed module @0x51b6b93c
  	at com.google.errorprone.VisitorState.getElements(VisitorState.java:244)
  	at com.google.errorprone.bugpatterns.ThreeLetterTimeZoneID.matchMethodInvocation(ThreeLetterTimeZoneID.java:79)
  	at com.google.errorprone.scanner.ErrorProneScanner.processMatchers(ErrorProneScanner.java:450)

Bugs: what's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

See tbroyer/gradle-errorprone-plugin#58

--add-opens=jdk.compiler/com.sun.tools.javac.model=ALL-UNNAMED fixes it.

Could there be an automated way of finding out all those cases? From the unit tests exercising all the bug patterns maybe?

What version of Error Prone are you using?

2.5.1

Have you found anything relevant by searching the web?

Related to #1157

[tbroyer]

Playing with grep reveals that this could be the only missing bit; also --add-exports might be enough:

$ git grep -h  '^import com.sun.*' |grep -o 'com.sun.[a-z.]*' |sort -u
com.sun.source.doctree.
com.sun.source.tree.
com.sun.source.util.
com.sun.tools.javac.api.
com.sun.tools.javac.code.
com.sun.tools.javac.comp.
com.sun.tools.javac.file.
com.sun.tools.javac.main.
com.sun.tools.javac.model.
com.sun.tools.javac.parser.
com.sun.tools.javac.processing.
com.sun.tools.javac.tree.
com.sun.tools.javac.util.

(where com.sun.source.{doctree,tree,util} are already exported: https://docs.oracle.com/en/java/javase/16/docs/api/jdk.compiler/module-summary.html)
BTW, how about sorting the options in the docs to make comparison easier? 😉

I also note that the doc suggests both --add-opens and -add-exports for com.sun.tools.javac.code. IIUC, --add-opens is a superset of --add-exports so --add-opens alone would be enough.