Code shared from the Rust Playground

playground.rs

use std::io::{self, BufRead};

struct Migration<'a> {
    pub namespace:  &'a str,
}

impl<'a> Migration<'a> {
    pub fn len(&self) -> usize {
        self.namespace.chars().count()
    }
}

fn create_migration(namespace: &str) -> *mut () {
    let boxed = Box::new(Migration { namespace });
    Box::into_raw(boxed) as *mut _
}

fn main() {
    let stdin = io::stdin();
    let namespace = stdin.lock().lines().next().unwrap().unwrap();
    let migration = create_migration(&namespace);
    let unboxed: Migration<'_> = unsafe { *Box::from_raw(migration as _) };
    println!("{}", unboxed.len());
}