Error Highlighting in project view: It has merely just begun, right? Follow

As it currently stands in 5261 it is more than useless, but
rightward confusing and dangerous.

If this feature should make it, IMHO there's an absolute
requirement to highlight errors in all dependent files, too.

For example if I simply change an interface's name (by
directly typing in the editor rather than refactoring),
all implementation classes (and recursively their packages)
should become highlighted in the project view automatically.

Currently each implementation class is highlighted only
after itself is opened in the editor - which is pretty
stupid: Usually I would open it only if I already knew there
were errors, which is brought to my attention only after I
opened the file...