See the attached example - unpack, fill "TEST_JAVA_HOME" into "run.sh" and execute "run.exe". Will produce:
---
src/p/Test.java:1: error: Second.test() in package p2 is not accessible
package p; public class Test { { p1.First.get().test(); } }
                                               ^
  (package p2 is declared in module , which does not export it)
1 error
---

That is wrong, the compilation should succeed. Add:
---
import p2.*;
---

to src/p/Test.java allows the compilation to succeed.

Reported here:
http://mail.openjdk.java.net/pipermail/jdk9-dev/2017-March/005672.html
http://mail.openjdk.java.net/pipermail/jigsaw-dev/2017-March/011755.html