Im trying to write a basic nary tree, where I have several traits that are all intended to work on structs which will form the nodes of the tree. These structs will have mutable references to the other nodes of the tree, so I have included lifetime parameters in my trait definitions.

For instance, this is the trait which all the structs will implement:

pub trait Node<'a>: NodeClone {

    fn value(&self) -> String;

    fn parent(&self) -> Option<Box<dyn Node>>;

    fn children(&self) -> Vec<Box<dyn Node>>;

    fn set_parent(&mut self, parent: &mut Box<dyn Node>);

    fn push_child(&mut self, child: &mut Box<dyn Node>);

    fn to_string(&self, current: &mut String) -> String;
}

Anything which implements Node must also implement NodeClone, which looks like:

pub trait NodeClone { 

    fn clone_box(&self) -> Box<dyn Node>;
}

impl<'a, T> NodeClone for T where T: 'static + Node<'a> + Clone, {

    fn clone_box(&self) -> Box<dyn Node> {

        return Box::new(self.clone());
    }
}

impl<'a> Clone for Box<dyn Node<'a>> {

    fn clone(&self) -> Box<dyn Node<'a>> {

        return self.clone_box();
    }
}

This is one of the structs which will form the tree:

#[derive(Clone)]
pub struct Operation<'a> {

    pub parent: Option<&'a mut Box<dyn Node<'a>>>,

    pub children: Vec<&'a mut Box<dyn Node<'a>>>
}

When I then try and implement Node for Operation like:

impl<'a> Node<'a> for Operation<'a> 

I get the error that:

error[E0477]: the type `Operation<'a>` does not fulfill the required lifetime
  --> src/language/components/node/operation.rs:31:10
   |
31 | impl<'a> Node<'a> for Operation<'a> {
   |          ^^^^^^^^
   |
note: type must satisfy the static lifetime as required by this binding
  --> src/language/components/node.rs:15:21
   |
15 | pub trait Node<'a>: NodeClone {
   | 

When I change the implementation of Operation to include a static lifetime:

impl<'a> Node<'a> for Operation<'static>

The fields of my struct Operation give me the error that:

the trait bound `&mut Box<(dyn Node<'_> + 'static)>: Clone` is not satisfied

Im not sure which lifetime I should change and where to solve this. Please help!