MultiOccurrenceVariableRef s = MultiOccurrenceVariableRef.from(source);
MultiOccurrenceVariableRef d = MultiOccurrenceVariableRef.from(destination);
final Class<?> dc = destination.getOwner().rawType();
final Class<?> destinationElementClass = d.elementType().getRawType();
if (destinationElementClass == null) {
throw new MappingException("cannot determine runtime type of destination collection " + dc.getName() + "." + d.name());
}