This is obvious enough to anyone who's already familiar with ZS, but would be totally opaque to someone coming in from years of Decorate (and ACS) where this was never an issue.
Can we get something like the following, to be displayed in the console (preferably with increased visibility) if GZDoom notices there are classes defined before it encounters any version definition?
This should give the current error messages a bit more context so people can help themselves, or at least have enough of a lead to where they should be looking in the wiki.ZScript warning: <path/filename of zscript lump>: Class defined with no version number previously provided. Will fall back to version 2.3.0. (Latest version is ____)