Understanding Rust Error E0025: Field Bound Multiple Times in a Pattern

What is Rust Error E0025?

Rust error E0025 occurs when a field in a struct is bound multiple times within a single pattern. In Rust, each field of a struct can only be bound once in a pattern, and attempting to bind the same field more than once will result in this error.

Example of Erroneous Code

struct Foo {
    a: u8,
    b: u8,
}

fn main(){
    let x = Foo { a:1, b:2 };

    let Foo { a: x, a: y } = x;
    // error: field `a` bound multiple times in the pattern
}

In the above example, field 'a' is being bound two times in the pattern. This is against Rust's rule of binding each field only once in a pattern, and the compiler will throw error E0025.

How to Fix Rust Error E0025

To fix Rust Error E0025, ensure that each field is bound only once in a pattern. Double-check your code for any attempts to bind the same field more than once, and remove or modify these duplicate bindings. It's also possible that a similar field name was misspelled, causing the duplication.

Example of Corrected Code

struct Foo {
    a: u8,
    b: u8,
}

fn main(){
    let x = Foo { a:1, b:2 };

    let Foo { a: x, b: y } = x; // ok!
}

In this corrected example, each field 'a' and 'b' is bound only once in the pattern, complying with Rust's rule and avoiding error E0025.

Common Causes for Rust Error E0025