Currently if code is compiled against unexported package following error is reported
javac -d modules --module-path modules --module-source-path src src/m2/pkg2/B.java
src\m2\pkg2\B.java:1: error: package pkg1 does not exist
package pkg2; /** Klass B */ public class B { /** Field f */ public pkg1.A f; }

Can javac report something like "pkg1 is not exported by module m1"?