[Bug] False Positive: Error building player because scripts have compile "errors" in editor

Double clicking the err does nothing -- there are no details whatsoever. In VS2017, no errors. Rebuild solution? Still no errors.

Restart Unity? Mystery error vanishes. This is a false-positive bug I've only seen this in 5.6f1 so far multiple times.

EDIT: Reported bug within Unity. Also note that this is the only error that shows -- other reports usually include a 2nd error and will not fix itself upon Unity restart. I am using services/collab.

EDIT 2: This time I had the bug, I restarted and instead of fixing itself, it showed the "real" error: Something really simple (I forgot an arg to a func that required an arg).

EDIT 3: Now that I'm thinking about it, I not only noticed this only happen in f1, I also got Visual Studio 2017 since f1 (from 2015). It could be a VS issue .... I've noticed VS2017 often take a long time to "catch up". After all, it said 0 errors within VS. Unity knew it was "something", but wasn't sure what. HOWEVER, note that Visual Studio did NOT restart or do anything at all and could not detect the error until Unity restarted. Strange...