Feature Request: Rust support function override

I hope rust can support function override, In real development world. we import a library, and may be want to override one function of the library.

Example origin func

fn add_one(x: i32) -> i32 {
    x + 1
}

we want to add log in the function

fn add_one(x: i32) -> i32 {
   log('The input number was {} ', x);
   x + 1
}

We only want to override the function , not want to fork the whole library and modify the library.

[sfackler]

Feature requests should be made on https://github.com/rust-lang/rfcs.

[steveklabnik]

Yes, please file over there. Thanks!