Understanding Rust Error E0559

Introduction to Rust Error E0559

Rust Error E0559 occurs when you specify an unknown field in an enum's structure variant. This error may be caused by a misspelling or a missing field. In this article, we will discuss the cause, solution, and examples to help you prevent and fix Error E0559.

Erroneous Code Example

#![allow(unused)]
fn main() {
    enum Field {
        Fool { x: u32 },
    }

    let s = Field::Fool { joke: 0 };
    // error: struct variant `Field::Fool` has no field named `joke`
}

In the above example, the `Field` enum has a single structure variant `Fool` with a `x: u32` field. When creating a new `Fool` instance with `Field::Fool { joke: 0 }`, the Rust compiler throws Error E0559 because the `joke` field is not defined.

Solution

To fix Error E0559, double-check the field names for typos and ensure the desired field exists in the enum's structure variant. In our example, we can fix the error by renaming the `joke` field to `x` or by adding the `joke: u32` field to the `Fool` structure variant.

Corrected Code Example

#![allow(unused)]
fn main() {
    enum Field {
        Fool { joke: u32 },
    }

    let s = Field::Fool { joke: 0 }; // ok!
}

In this corrected example, we added the `joke: u32` field to the `Fool` structure variant. Now the code compiles and runs successfully without encountering Error E0559.

Conclusion