usedisplaythis::Display;pubusestd::error::Error;#[test]fntest_unused_qualifications(){#![deny(unused_qualifications)]// Expansion of derive(Error) macro can't know whether something like
// std::error::Error is already imported in the caller's scope so it must
// suppress unused_qualifications.
#[derive(Debug, Display)]#[display("...")]pubstructMyError;let_: MyError;}