I just updated to safe 3.0 and it seems that a lot of functions where removed (e.g. all image-functions, file_get_contents, etc.).
Running phpstan now with this package will still issue warnings like "Function file_get_contents is unsafe to use. It can return FALSE instead of throwing an exception. Please add 'use function Safe\file_get_contents;' at the beginning of the file" even though the function do not exist any more in safe 3.0.