Error code E0405

The code refers to a trait that is not in scope.

Erroneous code example:

#![allow(unused)]
fn main() {
struct Foo;

impl SomeTrait for Foo {} // error: trait `SomeTrait` is not in scope
}

Please verify that the name of the trait wasn’t misspelled and ensure that it was imported. Example:

#![allow(unused)]
fn main() {
#[cfg(for_demonstration_only)]
// solution 1:
use some_file::SomeTrait;

// solution 2:
trait SomeTrait {
    // some functions
}

struct Foo;

impl SomeTrait for Foo { // ok!
    // implements functions
}
}