varlink_derive-8.0.0 doesn't have any documentation.
Macro for generating modules from a varlink interface definition
It has the drawback, that most IDEs don't execute this and thus offer no code completion.
Examples:
use varlink_derive;
varlink!;
use crate VarlinkClientInterface;
/* ... */
use varlink_derive;
varlink_file!;
use crate VarlinkClientInterface;
/* ... */