public class Test {

    public static void main(String[] args) {
        System.out.println(com.sun.jndi.dns.DnsContextFactory.class);
    }
}

Compiles the above test against JDK 9 build 144, like the below,
<JDK 9-ea+144>/bin/javac --add-exports jdk.naming.dns/com.sun.jndi.dns=ALL-UNNAMED Test.java
The output is:
warning: [options] module name in --add-exports option not found: jdk.naming.dns
Test.java:4: error: package com.sun.jndi.dns does not exist
System.out.println(com.sun.jndi.dns.DnsContextFactory.class);
                                   ^
1 error
1 warning

There's similar issue on module jdk.naming.rmi