One problem with this is that formatting now becomes a multi-file thing. You have now have to figure out what names actually refer to, which depends on building a project model to correctly resolve imports, etc....
Compare this with traditional formatters, which you can run on each single file individually, this is much more complex and also harder to parallelise.
Compare this with traditional formatters, which you can run on each single file individually, this is much more complex and also harder to parallelise.