You are asking for Editor feature which would quitely lead to performance degradation of the editor. For any such feature the Editor might need to build/maintain Object Graph/Syntax Tree ( would this use AST in java world ) for java objects and then compare it with Dart's Syntax Tree.
Also different languages will put forward the same request example C#, Ruby, etc. There does not seem to be any sane way to validate the objects from different programming world within performance limits.
I can borrow some more points from below stackoverflow q/a on why its simpler to use JSON/XML rather than any other way to exchange data between java/c# world to dart world -\