Understanding Rust Error E0364: Private Item Re-export

Understanding Rust Error E0364

Rust Error E0364 occurs when attempting to publicly re-export a private item. This means that a private type or value was re-exported using pub use, but the item itself was not marked as public.

Example of Erroneous Code:

#![allow(unused)]
fn main() {
mod a {
    fn foo() {}

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

To resolve this error, make sure to mark the items you're re-exporting as public using the pub keyword.

Example of Corrected Code:

#![allow(unused)]
fn main() {
mod a {
    pub fn foo() {} // ok!

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

In this corrected example, the function foo is now correctly marked as public, which allows it to be re-exported without encountering Rust Error E0364.

Why does Rust have Error E0364?

This error enforces Rust's privacy rules, which help ensure that private items cannot accidentally be exposed to the public API. By requiring that private items be explicitly marked as public, this error contributes to Rust's safety guarantees and encourages proper encapsulation.

Tips for Avoiding Rust Error E0364

1. Always review the items you're re-exporting and ensure they've been marked as public. 2. Use visibility modifiers (pub, pub(crate), or pub(super)) to accurately define the visibility of your items. 3. Double-check your code for proper use of the pub keyword in both the item definition and the re-export statement.

In conclusion, Rust Error E0364 can be easily resolved by ensuring that items being publicly re-exported are marked with the pub keyword. By following Rust's privacy rules and visibility modifiers, you can avoid unintended exposure of private items.