It fully makes things up, like nonexistent parameters to real functions. In the areas where it's accurate it's barely better than the existing autocomplete, tho

It fully makes things up, like nonexistent parameters to real functions. In the areas where it's accurate it's barely better than the existing autocomplete, though I have noticed it seems to deal a bit better with broken code (which also breaks Swift's compiler-based tooling). It can also generate larger things like type definitions a bit better, but Apple never really invested into autocomplete, so it's not really anything better than what other IDEs already had.