@Override
public void addReference(IReferencable reference) {
if (super.getReference() != null) {
throw new InternalException("addReference shouldn't be used twice");
}
super.addReference(reference);
}
public ImplicitReferenceElement(IReferencable reference, Grammar grammar) {
super(grammar);
if (reference == null) {
throw new InternalException("reference may not be null");
}
super.addReference(reference);
}