use collections::HashSet;use parking_lot::Mutex;use project::ProjectEntryId;use smol::channel;use std::sync::{Arc, Weak}; /// The set of entries that are currently being indexed.pub struct IndexingEntrySet {    entry_ids: Mutex<HashSet<ProjectEntryId>>,    tx: channel::Sender<()>,} /// When dropped, removes the entry from the set of entries that are being indexed.#[derive(Clone)]pub(crate) struct IndexingEntryHandle {    entry_id: ProjectEntryId,    set: Weak<IndexingEntrySet>,} impl IndexingEntrySet {    pub fn new(tx: channel::Sender<()>) -> Self {        Self {            entry_ids: Default::default(),            tx,        }    }     pub fn insert(self: &Arc<Self>, entry_id: ProjectEntryId) -> IndexingEntryHandle {        self.entry_ids.lock().insert(entry_id);        self.tx.send_blocking(()).ok();        IndexingEntryHandle {            entry_id,            set: Arc::downgrade(self),        }    }     pub fn len(&self) -> usize {        self.entry_ids.lock().len()    }} impl Drop for IndexingEntryHandle {    fn drop(&mut self) {        if let Some(set) = self.set.upgrade() {            set.tx.send_blocking(()).ok();            set.entry_ids.lock().remove(&self.entry_id);        }    }}