use std::ptr;

struct MyCell<'a> {
    value: &'a i32,
}

impl<'a> MyCell<'a> {
    fn new(x: &'a i32) -> MyCell<'a> {
        MyCell {value: x}
    }
    fn get(&self) -> i32 {
        *self.value
    }
    fn set(&self, value: &'a i32) {
        unsafe {
            ptr::write(&self.value as *const _ as *mut _, value);
        }
    }
}

fn step<'a>(r_c1: &mut MyCell<'a>) {
    let val: i32 = 13;
    r_c1.set(&val);
    println!("step1 value: {}", r_c1.value);
}

fn main() {
    let x = 3;
    let mut cell = MyCell::new(&x);
    step(&mut cell);
    println!("end value: {}", cell.value);
}

MyCell::set 方法的value用 ’a 标记了，不是应该传入存活时间比MyCell本身长的值吗？为什么生命周期检测没有生效呢？