This bug was originally marked as duplicate of bug 219263, that is already resolved. This bug is still valid, so this seems to be another bug, but it might be related.
Build: NetBeans IDE Dev (Build 201309250002)
VM: Java HotSpot(TM) 64-Bit Server VM, 24.0-b56, Java(TM) SE Runtime Environment, 1.7.0_40-b43
aldobrucale: Renamed an interface
java.lang.AssertionError: unexpected type: <nulltype>
Created attachment 140457 [details]
Created attachment 144190 [details]
Created attachment 148459 [details]
clean and build on a maven project while the "Scanning projects" task was active
This old bug may not be relevant anymore. If you can still reproduce it in 8.2 development builds please reopen this issue.
Thanks for your cooperation,
NetBeans IDE 8.2 Release Boss