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: rc_lazy_list.rs
    path of file: ./repos/jaq/jaq-interpret/src
    
    the code of the file until where you have to start completion: use alloc::boxed::Box;
use alloc::rc::Rc;
use once_cell::unsync::Lazy;

#[derive(Clone)]
pub struct List<'a, T>(Rc<Lazy<Node<'a, T>, Eval<'a, T>>>);
struct Node<'a, T>(Option<(T, List<'a, T>)>);
type Eval<'a, T> = Box<dyn 
    
fn drop() {
    let list = List::from_iter(0..100_000);
    // clone() ensures that we keep a copy of the whole list around
    // sum() then evaluates the whole list
    assert_eq!(list.clone().sum::<u64>(), 4999950000);
    // at the end, a long, fully evaluated list is dropped,
    // which would result in a stack overflow without the custom `Drop` impl
    std::mem::drop(list);
}