pan class="boring">        match *self {
</span><span class="boring">            Cons(_, ref item) =&gt; Some(item),
</span><span class="boring">            Nil =&gt; None,
</span><span class="boring">        }
</span><span class="boring">    }
</span><span class="boring">}
</span><span class="boring">
</span>fn main() {
    let a = Rc::new(Cons(5, RefCell::new(Rc::new(Nil))));

    // aの最初の参照カウント = {}
    println!(&quot;a initial rc count = {}&quot;, Rc::strong_count(&amp;a));
    // a�