You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: borrows.rs
    path of file: ./repos/creusot/creusot/tests/should_succeed/type_invariants
    
    the code of the file until where you have to start completion: extern crate creusot_contracts;
use creusot_contracts::{invariant::Invariant, *};

pub struc
    
pub fn frozen_dead<'a>(mut x: &'a mut NonZero, y: &'a mut NonZero) {
    let _a = &mut x.0;
    // here we have to resolve x
    // assert x.inv() fails: depends on ^a which is unknown
    #[allow(unused_assignments)]
    x = y;
    inc(_a); // assert old(x).inv()
}