use std::marker::PhantomData;
use std::os::raw::c_void;
use std::mem::transmute;

struct Rute<'a> {
    _marker: PhantomData<&'a u32>,
}

#[derive(Copy, Clone)]
struct Widget<'a> {
    _marker: PhantomData<&'a u32>,
}

impl<'a> Widget<'a> {
    pub fn on_change<T>(&mut self, data: &'a mut T) -> &mut Widget<'a>
    where T: 'a,
    {
        unsafe {
            let user_data: *const c_void = transmute(data);
            println!("{:?}", user_data)
        }

        self
    }
}

impl<'a> Rute<'a> {
    pub fn create_widget(&'a mut self) -> Widget<'a> {
        Widget { _marker: PhantomData }
    }
}

fn main() {
    let mut rute = Rute { _marker: PhantomData };
    let mut foo = 1;

    {
        rute.create_widget().on_change(&mut foo);
        //rute.on_change(&mut foo);
    }
}