Private items cannot be publicly re-exported. This error indicates that you attempted to pub use a type or value that was not itself public.

Erroneous code example:

mod a {
    fn foo() {}

    mod a {
        pub use super::foo; // error!
    }
}

The solution to this problem is to ensure that the items that you are re-exporting are themselves marked with pub:

mod a {
    pub fn foo() {} // ok!

    mod a {
        pub use super::foo;
    }
}

See the Use Declarations section of the reference for more information on this topic.