"Unable to locate class file for inner class" (mixed compilation bug?)

[dwijnand]

(Reported by @elfprince13 as scala/bug#11062.)

I have two source files, one Java, one Scala.
The Java class definition is as follows:

public class HeapNode<Elem> extends Node<HeapNode<Elem>> implements Cloneable {
	volatile LazyBraunHeapLF.NodeEvalState<Elem> state;
	
	HeapNode(LazyBraunHeapLF.NodeEvalState<Elem> initState){
		state = initState;
	}
	
	@SuppressWarnings("rawtypes")
	public static final AtomicReferenceFieldUpdater<HeapNode, LazyBraunHeapLF.NodeEvalState> updateState 
					= AtomicReferenceFieldUpdater.newUpdater(HeapNode.class, LazyBraunHeapLF.NodeEvalState.class, "state");

	
}

The Scala source contains the following:

object LazyBraunHeapLF {
	
	class EmptyNode[E] extends HeapNode[E](Empty[E]()){
		marked = true
	}
	
	sealed trait Immediate[E]{ this: NodeEvalState[E] =>
		def force:NodeEvalState[E] with Immediate[E] = this
	}
	
	sealed abstract class NodeEvalState[E] {
		def force: NodeEvalState[E] with Immediate[E]
	}
	
	case class Empty[E]() extends NodeEvalState[E] with Immediate[E]
	// The remainder is commented out for a M(N)WE
}

Everything works fine with a clean build, or if the definition of class EmptyNode[E] is commented out; however, after roughly ~1 edit cycle, I get the following error message:

[error] Unable to locate class corresponding to inner class entry for NodeEvalState in owner LazyBraunHeapLF
[error] one error found
[error] (compile:compileIncremental) Compilation failed
[error] Total time: 2 s, completed Aug 8, 2018 11:30:33 AM

I'm using Scala 2.12.6 on Java 8. Notably, the class file in question exists on my file system.

[dlilljegren]

If you in the Java class do
import LazyBraunHeapLF.NodeEvalState

and replace then in the Java class replace LazyBraunHeapLF.NodeEvalState with just NodeEvalState it will work