Code shared from the Rust Playground

playground.rs

use std::ops::Index;

struct Foo<T> {
    val: T,
}

impl<T> Index<usize> for (&Foo<T>, &str) {
    type Output = T;

    fn index(&self, _: usize) -> &T {
        self.0.val
    }
}
    
fn main() {
    let foo: Foo<u32> = Foo { val: 123 };
    println!("{}", foo[0]);
}