There is no Messages dialog in newer versions of IDEA/Android Studio in which the error messages were mapped before. The new Build window shows only the original locations, so now we need to replace Java file diagnostics with ones mapped to Kotlin source files.
The side effect is that diagnostics on the same locations are automatically merged.
Placing location table inside .java file triggers annotation processor to run on each line table modification (even when the stub declarations themselves are the same). So we move it to the separate file.
Dmitriy Novozhilov