This bug was originally reported as javadoc bug, but it is reproducible
with javac as well.
When javadoc tool asks for the module of the type element, using the following
ModuleElement mdle = toolEnv.elements.getModuleOf(getPackageOf(klass));
In the above case, for klass = "m2pub.A" module m1 is returned instead of m2.

Here is a javac reproducer:
=================
./src/m2/m2pub/A.java
=================
package m2pub;
public class A {}


=================
./src/m2/module-info.java
=================
module m2 {
    exports m2pub;
}


=================
./src/m1/m1pub/A.java
=================
package m1pub;
public class A {}


=================
./src/m1/module-info.java
=================
module m1 {
    exports m1pub;
}

% $JAVA_HOME/bin/javac -d out --source-path src/m1 src/m2/m2pub/A.java

% $JAVA_HOME/bin/javap -v out/module-info.class | egrep 'module m'
module m1 <---- Note: m2 maybe, but definitely not m1.