Rust tells me that an import is unused, and then in the very same breath tells me that I should make that import

Here’s the code:

use crate::rooms::room::RoomInterface;

pub mod dogroom {
    pub struct R;

    impl RoomInterface for R {

    }
}

Here’s /rooms/mod.rs:

pub mod room {

    //  Irrelevant stuff
    
    pub trait RoomInterface {
        // stuff
    }

    // stuff

}

Here’s what it tells me:

I find it quite arcane that I import the very same thing it wants me to import, and yet it doesn’t work.

I’ve tried pretty much all the permutations of the use keyword, and I can’t make it work. What’s going on?

>Solution :

uses are scoped to the module that imports them, not the file they are in.
Move the import into the dogroom module:

pub mod dogroom {
    use crate::rooms::room::RoomInterface;

    pub struct R;

    impl RoomInterface for R {

    }
}

Alternatively, you might want the dogroom module to reuse everything from the parent module:

use crate::rooms::room::RoomInterface;
pub mod dogroom {
    use super::*;

    pub struct R;

    impl RoomInterface for R {

    }
}