False positive: enum became abstract

[lbergelson]

We see a false positive report of This class became abstract on an enum.

Previously the enum was a simple enum of the form

enum Thing {
  First,
  Second
}

It subsequently gained an abstract method:

enum Thing {
   First() {
     void doThing(){..}
   },
   Second(){
     void doThing(){..}
   }

  abstract void doThing(){}
}

We now get a false positive report the Thing is abstract despite the fact that by definition enums are concrete final classes.