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; }