I know this will be a little unbelievable, I don't believe it myself, having been an IdeaJ used for many years and LOVING it, but...
I have a constants file which has a fairly large number of constants contained therein. I ran an "unused declarations" inspection on the file. the following constant was listed:
So I commented out the constant and compiled the project within IdeaJ. I got a compilation error in another file (within a different package). I jumped over to that file and sure enough it was being used - and IdeaJ had it marked as red.
So I deleted the comment in the constants file. And the red mark in the using file went away. I was able to compile file.
I went back to the constants file and did a "Find Usages" on the constant - and IdeaJ told me there were no usages found.
I went to the place the constant is being used and hit Ctrl-B to go to the definition and indeed it took me to the correct place! But another Find Usages failed to bring me back to the use!
I checked the module settings and there are no exclusions.
Any thoughts? Is this a bug?