I've never seen this. Usually you don't have the LaTeX source of a paper you cite, you wouldn't know which label to use for the reference, when the cited paper

I've never seen this. Usually you don't have the LaTeX source of a paper you cite, you wouldn't know which label to use for the reference, when the cited paper is written in LaTeX at all. Or something changed quite a bit in recent years. Can you link to another paper's Figure 2.2 now, and have LaTeX error out if the link is broken? How does that work?