Description of problem: I'm using the last gnome-builder available (3.18.1-2.fc23). If I try to cut / copy and paste, it does not work. It's the same behaviour when it does by the primary selection or Ctrl+C/X and Ctrl+V. In fact, these actions should work only if the selection it does under another program (like Firefox). Select and paste only under gnome-builder editor not works.
Another information. Copy / Cut then paste only under gnome-builder editor works when I use right click + select action.
I have a similar issue with gedit in fact. With Fedora Rawhide and Gnome 3.19.4, Gedit seemed normal about that, but I can't install gnome-builder to test that for the moment.
I hope this has been resolved already, if not - please reopen bug.