When having a SQL Statement with a CTE (i.e. WITH [...] SELECT [...]) and pressing/holding CTRL (e.g. in order to perform CTRL+C, or do to invoke go-to-definition by CTRL+click), SQL Developer pops up this message:
Please amend your code to something like [...]
I'm experiencing this same issue. Really slows me down when I'm in the middle of writing code that I know is not well formed yet because i'm not done writing it.
Known issue, this has been nuked for the next EA.