Product Version = NetBeans IDE 8.2 (Build 201705191307)
Operating System = Linux version 4.4.0-78-generic running on amd64
Java; VM; Vendor = 1.8.0_131
Runtime = Java HotSpot(TM) 64-Bit Server VM 25.131-b11

Reproducibility: Happens sometimes, but not always

STEPS:
  * Something is corrupt in the project
  * I have deleted the cache and resumed Netbeans the problem appears to be in the Gradle cache?
  * I have a gradle sub-project I've stripped down to two classes
  * A package abstract protected base class and a public abstract daughter (in the same package)
  * The exception below appears when I try to import the base-class in the daughter
  * not rocket science.

ACTUAL:
  False errors on local class 'extends' verb

--- stacktrace ---

java.lang.NullPointerException
	at org.netbeans.modules.java.hints.errors.CreateElement.getPossibleSourceGroups(CreateElement.java:573)
	at org.netbeans.modules.java.hints.errors.CreateElement.prepareCreateOuterClassFix(CreateElement.java:648)
	at org.netbeans.modules.java.hints.errors.CreateElement.analyzeImpl(CreateElement.java:447)
	at org.netbeans.modules.java.hints.errors.CreateElement.analyze(CreateElement.java:150)
	at org.netbeans.modules.java.hints.errors.CreateElement.run(CreateElement.java:135)
	at org.netbeans.modules.java.hints.infrastructure.CreatorBasedLazyFixList.compute(CreatorBasedLazyFixList.java:148)
	at org.netbeans.modules.java.hints.infrastructure.LazyHintComputation.run(LazyHintComputation.java:112)
	at org.netbeans.modules.java.hints.infrastructure.LazyHintComputation.run(LazyHintComputation.java:58)
[catch] at org.netbeans.modules.java.source.JavaSourceAccessor$CancelableTaskWrapper.run(JavaSourceAccessor.java:298)
	at org.netbeans.modules.parsing.impl.TaskProcessor.callParserResultTask(TaskProcessor.java:584)
	at org.netbeans.modules.parsing.impl.TaskProcessor$RequestPerformer.run(TaskProcessor.java:809)
	at org.openide.util.lookup.Lookups.executeWith(Lookups.java:304)
	at org.netbeans.modules.parsing.impl.TaskProcessor$RequestPerformer.execute(TaskProcessor.java:725)
	at org.netbeans.modules.parsing.impl.TaskProcessor$CompilationJob.run(TaskProcessor.java:686)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1443)
	at org.netbeans.modules.openide.util.GlobalLookup.execute(GlobalLookup.java:68)
	at org.openide.util.lookup.Lookups.executeWith(Lookups.java:303)
	at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2058)


--- end ---

EXPECTED:
  I would love it to WORK
  In any case there needs to be a way to clear Gradle and Netbeans state from the IDE