Clion doesn't handle properly header files only library

When creating a header file only library (an INTERFACE LIBRARY in terms of CMake), the CLion indexer is not able to properly make the job.
At this point (with the 2018.3 release), I have the completion working (fine) thanks to the "Mark directory as project files" but there is still missing the go to definition (or CTRL+click).

My project structure is as following:

My CMakeLists.txt is as following:

The completion is there and I'm happy with it:

But the Annex Class is still in Black ans no way to go to definition ("Cannot find declaration to got to" is displayed in tooltip)