There are a number of bugs related to methods marked
extern. There was a “fix” some time ago that made them not error (but only in one place), but they’ve never actually worked. I’d like to make it so they actually error, since they don’t really make any sense.
extern is currently accepted on all function items, including inherent methods, associated functions and trait methods. Every use I’ve seen of this “feature” has been a mistake on the part of the user, either an accident due to copy-paste or a misunderstanding of what
extern means. I think it would be much clearer to just disallow them altogether, rather than try to get them to work.