The current JDT model builder, also called structure builder, needed for interoperability with Java in Eclipse, is currently using the Scala source to generate the required elements. To do this, it needs to parse the source and resolve the types, then duplicate some of the work done by the compiler to create a JDT elements which are equivalent to the Scala compiled classes.

The idea is to work of the compiled classes directly.
JDT is not able to directly read classes generated by the Scala compiler because it is making assumption about the classes. We need a JDT model builder able to correctly read compiled Scala classes.