Yeah that's why I assumed case labels are actual line labels. I'm pretty sure labels do require source to point to, its other compilers playing nice that are allowing it. However I thought switch was an exception.
It must be because the compiler cannot decide what to do with it. It could point to the implicit compiler generated return, or the explicit next statement outside of the function. However every situation the error occurs is quite illogical and is probably a good hint to change things.