test_deref.rs

use std::ops::Deref;

struct DerefExample<T> {
    value: T
}

impl<T> Deref for DerefExample<T> {
    type Target = T;

    fn deref(&self) -> &T {
            &self.value
        }
}

struct NonDeref<T> {
    value: T
}

fn main() {
    let x = DerefExample{ value: "abc" };
    let s1 : String = x.to_owned();

    let y = NonDeref{ value: "abc" };
    // let s2 : String = y.to_owned(); // <- エラー発生
}