Rust 为相同特征的特征对象使用 move 方法实现特征

我正在try 在具有相同特征的盒装特征对象上实现特征.我以前做过这样的特征，它的方法是&self，这很好用，但不是self.

// The purpose of this trait is to allow for converting any kind of "group" which might eg be nested tuples like below, and convert it into a flat Vec of Items
trait Group {
    fn into_vec(self) -> Vec<Box<dyn Item>>;
}

trait Item: Group {}

// Foo is an Item an can also be made into a group
struct Foo {}
impl Item for Foo {}
impl Group for Foo {
    fn into_vec(self) -> Vec<Box<dyn Item>> {
        vec![Box::new(self)]
    }
}

// impl Group for data structures which contain items or other nested structures containing items
impl<A: Group, B: Group> Group for (A, B) {
    fn into_vec(self) -> Vec<Box<dyn Item>> {
        let mut new_vec = Vec::new();
        new_vec.extend(self.0.into_vec().into_iter());
        new_vec.extend(self.1.into_vec().into_iter());
        new_vec
    }
}

// Can create a single group fine
fn get_group() -> impl Group {
    (Foo {}, (Foo {}, Foo {}))
}

// Sometimes I might want to return different groups from different braches so need to box them
// However I'm not sure how to implement this. self.into_vec() is an ifinite recursion, and can't deref self either.
impl Group for Box<dyn Group> {
    fn into_vec(self) -> Vec<Box<dyn Item>> {
        (*self).into_vec()
    }
}
fn get_group_conditonal(condition: bool) -> impl Group {
    if condition {
        Box::new((Foo {}, (Foo {}, Foo {}))) as Box<dyn Group>
    } else {
        Box::new(Foo {}) as Box<dyn Group>
    }
}

我意识到，在这个特定的示例中，我可以将fn get_*()个函数更改为返回Box<dyn Group>来解决问题.然而，API的其余部分具有将输入作为impl Group的函数.如果我不能impl Group for Box<dyn Group>，那么这将进入API的其余部分，并要求所有函数只接受盒装特征对象作为输入，而不是impl Group，如果可能的话，我想避免这种情况.