Well, although I understand the complaint, I think it is the best option we have. The problem is that we are also
"recompiling" dependencies on save, e.g. if you have a class referencing a missing method in other class/file, and you
create the method (and save the file), the file that contains the reference to the missing method will also be
recompiled. So there are three possibilities:
-the current option
-update errors for the current file without save, update the dependencies on save - this would confuse the users, as the
tasklist would be partially updated without save.
-update the current file and dependencies without save (after the user pauses for a while) - this would be quite slow,
and would very likely cause big complaints from the users, as we might in general recompile quite a few files after each
typed character.

I also find it a bit weird that the errors don't show up in the task list as we compute them. I think it should work like this:

If the task list is in the "Current File" mode, show the errors as they appear in the file. I think this is straightforward.

In "All Projects" mode, I would say we should also show errors for the currently edited file immediately and show other errors as we compute them. I think 
users would quickly learn how it works: They make modification in a file and errors appear in task list. They fix it and save the file and new errors appear in 
the task list from the files depending on the edited one. That seems pretty slick to me.

This is ENH request.

Actually I still think this is a defect. 

I have an error in the tasklist. I click it in tasklist (to navigate to the editor), fix it and .. nothing happens.
Sure, after some time, I figure out that I need to save the file to actually see the changes, but still .. it feels wrong.

This old bug may not be relevant anymore. If you can still reproduce it in 8.2 development builds please reopen this issue.

Thanks for your cooperation,
NetBeans IDE 8.2 Release Boss