I found answer in the following topic: http://sonarqube.15.x6.nabble.com/sonar-dev-sonar-squid-needs-class-file-td5019909.html#a5019937
As title of this topic says: "sonar squid needs class file"
In this topic we can read that files *.class from our project are required.
I haven't build my project. So there weren't any *.class files.
It's not clearly stated in rules description or other places that *.class files are required.