I created, as I was instructed by a more senior developer, a new .sql file in Eclipse in a project folder buried somewhere in the entire application's overall project structure. When I tried to edit the file, Eclipse asked me whether I'm sure if I want to edit a derived file. I clicked "No" arbitrarily to make the popup go away and to be able to check the file's and project's properties just to be sure, because as far as I knew, the files in the project were not actually derived from anything.
Problem is, the file is now apparently locked for editing, and I don't see any way of unlocking it. In the properties, it is not marked as Read-only, nor is it in fact marked as Derived.
How do enable editing on this file again?
In the end, I deleted the file and created a new one with the same name, which is tedious, but it fixed the problem. I did not try closing and opening it again as howlger suggested, though that might have worked as well.