#[derive(Debug)]
struct MyStruct;

type MyFunction = FnOnce(MyStruct) -> Result<MyStruct, ()> + Send;

fn main() {
    let functions: Vec<Box<MyFunction>> = vec![Box::new(|s| -> Result<MyStruct, ()> { Ok(s) })];
    let s = functions
        .into_iter()
        .fold(Ok(MyStruct), |result_s, boxed_f| {
            result_s.and_then(|s| boxed_f(s))
            // Error here:        ^^^^^^^ cannot move a value of type std::ops::FnOnce(..)
            // But shouldn't it be moving the box which is `Sized`, not the function inside the box?
        });

    print!("{:?}", s);
}