struct Board;

struct Foo<'a>(&'a Board);
struct Bar;

trait Thing<'a> {}

impl<'a> Thing<'a> for Foo<'a> {}
impl<'a> Thing<'a> for Bar {}

fn do_thing<'a>(board: &'a Board, a: Box<dyn Thing<'a>>, b: Box<dyn Thing<'a>>) {

}

fn test() {
    let board = Board;
    let foo = Foo(&board);
    let bar = Bar;
    do_thing(&board, Box::new(foo), Box::new(bar));
}