Macro cons_list 

macro_rules! cons_list {
    () => { ... };
    ($head:expr $(, $tail:expr)* $(,)?) => { ... };
}

Recursively expands to nested ConsList::cons(…) calls.

let list = cons_list![1, 2, 3];
// expands to:
// ConsList::cons(1, ConsList::cons(2, ConsList::cons(3, ConsList::nil())))