deref_coercion.rs

deref_coercion.rs

struct Wrapper(String);

impl std::ops::Deref for Wrapper {
    type Target = String;

    fn deref(&self) -> &String {
        &self.0
    }
}

impl Wrapper {
    // This inherent method takes precedence over deref targets
    fn len(&self) -> usize {
        999
    }
}

fn main() {
    let w = Wrapper("hello".to_string());

    // 1. Calls the inherent method on `Wrapper`
    println!("Inherent method: {}", w.len()); // Outputs: 999

    // 2. Explicitly dereferencing to call the String's method
    println!("Explicit dereference: {}", (*w).len()); // Outputs: 5

    // 3. Alternative: Using full path syntax to call String's method
    println!("String trait method: {}", String::len(&w)); // Outputs: 5
}

https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=495a3ff016dd14191a112e24e121a3e8