Bogus exception handling during build

Model:
	greetings+=Greeting*;
	
Greeting:
	'Hello' name=ID ('from' from=[Greeting])? '!';

public class MyDslScopeProvider extends AbstractMyDslScopeProvider {
	
	@Override
	public IScope getScope(EObject context, EReference reference) {
		if (true) {
			throw new ClassCastException("xxxxx");
		}
		return super.getScope(context, reference);
	}

}

Caused by: java.lang.ClassCastException: xxxxx
	at org.xtext.example.mydsl.scoping.MyDslScopeProvider.getScope(MyDslScopeProvider.java:21)
	at org.eclipse.xtext.linking.impl.DefaultLinkingService.getScope(DefaultLinkingService.java:59)
	at org.eclipse.xtext.linking.impl.DefaultLinkingService.getLinkedObjects(DefaultLinkingService.java:108)
	at org.eclipse.xtext.linking.lazy.LazyLinkingResource.getEObject(LazyLinkingResource.java:266)
	at org.eclipse.xtext.linking.lazy.LazyLinkingResource.getEObject(LazyLinkingResource.java:237)
	... 23 more
109185 [Worker-10: Building] ERROR org.eclipse.xtext.builder.clustering.CopiedResourceDescription  - java.lang.IllegalStateException: getReferenceDescriptions platform:/resource/demo/x.mydsl
java.lang.IllegalStateException: getReferenceDescriptions platform:/resource/demo/x.mydsl
	at org.eclipse.xtext.builder.clustering.CopiedResourceDescription.getReferenceDescriptions(CopiedResourceDescription.java:85)
	at org.eclipse.xtext.builder.builderState.BuilderStateUtil.copyReferenceDescriptions(BuilderStateUtil.java:60)
	at org.eclipse.xtext.builder.builderState.BuilderStateUtil.create(BuilderStateUtil.java:35)
	at org.eclipse.xtext.builder.clustering.ClusteringBuilderState.doUpdate(ClusteringBuilderState.java:269)
	at org.eclipse.xtext.builder.builderState.AbstractBuilderState.update(AbstractBuilderState.java:164)
	at org.eclipse.xtext.builder.impl.XtextBuilder.doBuild(XtextBuilder.java:521)
	at org.eclipse.xtext.builder.impl.XtextBuilder.addInfosFromTaskAndBuild(XtextBuilder.java:455)
	at org.eclipse.xtext.builder.impl.XtextBuilder.fullBuild(XtextBuilder.java:562)
	at org.eclipse.xtext.builder.impl.XtextBuilder.build(XtextBuilder.java:333)
	at org.eclipse.core.internal.events.BuildManager$2.run(BuildManager.java:1024)
	at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:45)
	at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:254)
	at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:311)
	at org.eclipse.core.internal.events.BuildManager$1.run(BuildManager.java:400)
	at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:45)
	at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:403)
	at org.eclipse.core.internal.events.BuildManager.basicBuildLoop(BuildManager.java:514)
	at org.eclipse.core.internal.events.BuildManager.basicBuildLoop(BuildManager.java:462)
	at org.eclipse.core.internal.events.BuildManager.build(BuildManager.java:544)
	at org.eclipse.core.internal.events.AutoBuildJob.doBuild(AutoBuildJob.java:161)
	at org.eclipse.core.internal.events.AutoBuildJob.run(AutoBuildJob.java:255)
	at org.eclipse.core.internal.jobs.Worker.run(Worker.java:63)

@szarnekow do we intentionally call BuilderStateUtil.create on copiedresourcedescription?

Reproduce the build with the shown MyDslScopeProvider and start at CopiedResourceDescription.getReferenceDescriptions, then follow BuilderStateUtil.copyReferenceDescriptions and BuilderStateUtil.create. Compare the original ClassCastException with the later IllegalStateException from XtextBuilder; done means the build no longer reports misleading exception handling for this failure.