use crate::{Edit, Patch};use parking_lot::Mutex;use std::{    mem,    sync::{Arc, Weak},}; #[derive(Default)]pub struct Topic<T>(Mutex<Vec<Weak<Mutex<Patch<T>>>>>); pub struct Subscription<T>(Arc<Mutex<Patch<T>>>); impl<T: Default, TDelta> Topic<T>where    T: 'static        + Copy        + Ord        + std::ops::Sub<T, Output = TDelta>        + std::ops::Add<TDelta, Output = T>        + std::ops::AddAssign<TDelta>        + Default,    TDelta: Ord + Copy,{    pub fn subscribe(&mut self) -> Subscription<T> {        let subscription = Subscription(Default::default());        self.0.get_mut().push(Arc::downgrade(&subscription.0));        subscription    }     pub fn publish(&self, edits: impl Clone + IntoIterator<Item = Edit<T>>) {        publish(&mut self.0.lock(), edits);    }     pub fn publish_mut(&mut self, edits: impl Clone + IntoIterator<Item = Edit<T>>) {        publish(self.0.get_mut(), edits);    }} impl<T: Default> Subscription<T> {    pub fn consume(&self) -> Patch<T> {        mem::take(&mut *self.0.lock())    }} fn publish<T, TDelta>(    subscriptions: &mut Vec<Weak<Mutex<Patch<T>>>>,    edits: impl Clone + IntoIterator<Item = Edit<T>>,) where    T: 'static        + Copy        + Ord        + std::ops::Sub<T, Output = TDelta>        + std::ops::Add<TDelta, Output = T>        + std::ops::AddAssign<TDelta>        + Default,    TDelta: Ord + Copy,{    subscriptions.retain(|subscription| {        if let Some(subscription) = subscription.upgrade() {            let mut patch = subscription.lock();            *patch = patch.compose(edits.clone());            true        } else {            false        }    });}