Converting Rc<Trait> types

2

Not automatically, you will need to implement methods on traits like this,

pub trait FrpNodeAny {
    fn update(&self);
    fn parents(&self) -> Vec<Rc<dyn FrpNodeAny>>;

    fn into_rc_any(self: Rc<Self>) -> Rc<FrpNodeAny>;
}

But this is burdensome on the user, the solution to this problem is yet another trait

pub trait IntoFrpNodeAny {
    fn into_rc_any(self: Rc<Self>) -> Rc<FrpNodeAny>;

    fn as_any(&self) -> &FrpNodeAny;
    fn as_any_mut(&mut self) -> &mut FrpNodeAny;

    // add methods for whatever pointer like type here
}

pub trait FrpNodeAny: IntoFrpNodeAny {
    fn update(&self);
    fn parents(&self) -> Vec<Rc<dyn FrpNodeAny>>;
}

// this is important, you can't move this implementation into the trait
// as default methods, because these coercions require `Sized` bounds
// which are provided here, but can't in the trait
impl<T: FrpNodeAny> IntoFrpNodeAny for T {
    fn into_rc_any(self: Rc<Self>) -> Rc<FrpNodeAny> { self }

    fn as_any(&self) -> &FrpNodeAny { self }
    fn as_any_mut(&mut self) -> &mut FrpNodeAny { self }
}

This way implementors of FrpNodeAny don't need to think about it, they just get it for free.

you can then use this like so,

pub fn magic<Out>(x: Rc<dyn FrpNode<Out>>) -> Rc<dyn FrpNodeAny> {
    x.into_rc_any()
}
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