Error code E0774
derive
was applied on something which is not a struct, a union or an enum.
Erroneous code example:
#![allow(unused)] fn main() { trait Foo { #[derive(Clone)] // error! type Bar; } }
As said above, the derive
attribute is only allowed on structs, unions or
enums:
#![allow(unused)] fn main() { #[derive(Clone)] // ok! struct Bar { field: u32, } }
You can find more information about derive
in the Rust Book.