You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: caches.rs
    path of file: ./repos/rerun/crates/re_viewer_context/src
    
    the code of the file until where you have to start completion: use std::any::{Any, TypeId};

use ahash::HashMap;
use parking_lot::Mutex;

/// Does memoization of different objects for the immediate mode UI.
#[derive(Default)]
pub struct C
    
    pub fn entry<C: Cache + Default, R>(&self, f: impl FnOnce(&mut C) -> R) -> R {
        #[allow(clippy::unwrap_or_default)] // or_default doesn't work here.
        f(self
            .0
            .lock()
            .entry(TypeId::of::<C>())
            .or_insert(Box::<C>::default())
            .as_any_mut()
            .downcast_mut::<C>()
            .expect("Downcast failed, this indicates a bug in how `Caches` adds new cache types."))
    }