Error code E0777
A literal value was used inside #[derive].
Erroneous code example:
#![allow(unused)] fn main() { #[derive("Clone")] // error! struct Foo; }
Only paths to traits are allowed as argument inside #[derive]. You can find
more information about the #[derive] attribute in the Rust Book.
#![allow(unused)] fn main() { #[derive(Clone)] // ok! struct Foo; }