Understanding Rust Error E0251

Introduction to Rust Error E0251

Rust Error E0251 occurs when two items with the same name are imported without rebinding one of them under a new local name. This article explores this error, demonstrating examples and providing solutions.

Error E0251 Example

Consider the following code, which triggers Rust Error E0251:

mod foo {
    pub struct baz;
}

mod bar {
    pub mod baz {}
}

use foo::baz;
use bar::*;

fn main() {}

In this example, the 'foo' and 'bar' modules each have an item named 'baz'. When the items are imported using 'use foo::baz;' and 'use bar::*;', the compiler throws Error E0251, as there now exist two items with the same name in the same namespace.

Resolving Error E0251

To resolve Rust Error E0251, rebind one of the items under a new local name. Below is the revised code that demonstrates this solution:

mod foo {
    pub struct baz;
}

mod bar {
    pub mod baz {}
}

use foo::baz;
use bar::baz as bar_baz;

fn main() {}

Here, 'use bar::baz as bar_baz;' renames 'baz' from the 'bar' module to 'bar_baz', preventing naming conflicts and thus resolving the error.

Alternative Solution

Another way to avoid Rust Error E0251 is to import the modules themselves, instead of the items within the modules. Consider the following alternative approach:

mod foo {
    pub struct baz;
}

mod bar {
    pub mod baz {}
}

use foo;
use bar;

fn main() {
    let _ = foo::baz;
    let _ = bar::baz;
}

By importing both modules with 'use foo;' and 'use bar;', naming conflicts are avoided, and their respective 'baz' items can be accessed using their fully qualified names ('foo::baz' and 'bar::baz').