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: lib.rs
    path of file: ./repos/linkerd2-proxy/linkerd/pool/p2c/src
    
    the code of the file until where you have to start completion: //! A pool that uses the power-of-two-choices algorithm to select endpoints.
//!
// Based on tower::p2c::Balance. Copyright (c) 2019 Tower Contributors

#![deny(rust_2018_idioms, clippy::disallowed_methods, clippy::disallowed_types)]
#![forbid(unsafe_code)]

use ahash::AHashMap;
use futures::prelude::*;
use linkerd_error::Error;
use linkerd_metrics::prom;
use linkerd_pool::Pool;
use linkerd_stack::{NewService, Service};
use rand::{rngs::SmallRng, thread_rng, Rng, SeedableRng};
use std::{
    collections::hash_map::Entry,
    net::SocketAddr,
    task::{Context, Poll},
};
use tower::{
    load::Load,
    ready_cache::{error::Failed, ReadyCache},
};

/// Dispatches requests to a pool of services selected by the
/// power-of-two-choices algorithm.
#[derive(Debug)]
pub struct P2cPool<T, N, Req, S> {
    new_endpoint: N,
    endpoints: AH
    
    async fn p2c_ready_index() {
        let _trace = linkerd_tracing::test::with_default_filter("trace");

        let addr0 = "192.168.10.10:80".parse().unwrap();
        let (svc0, mut h0) = tower_test::mock::pair::<(), ()>();
        h0.allow(0);

        let addr1 = "192.168.10.11:80".parse().unwrap();
        let (svc1, mut h1) = tower_test::mock::pair::<(), ()>();
        h1.allow(0);

        let addr2 = "192.168.10.12:80".parse().unwrap();
        let (svc2, mut h2) = tower_test::mock::pair::<(), ()>();
        h2.allow(0);

        let metrics = P2cMetrics::default();
        let mut pool = P2cPool::new(metrics, |(a, ())| {
            PeakEwma::new(
                if a == addr0 {
                    svc0.clone()
                } else if a == addr1 {
                    svc1.clone()
                } else if a == addr2 {
                    svc2.clone()
                } else {
                    panic!("unexpected address: {a}");
                },
                time::Duration::from_secs(1),
                1.0 * 1000.0 * 1000.0,
                CompleteOnResponse::default(),
            )
        });

        assert!(pool.ready().now_or_never().is_none());
        assert!(pool.next_idx.is_none());

        pool.reset_pool(vec![(addr0, ())]);
        assert!(pool.ready().now_or_never().is_none());
        assert!(pool.next_idx.is_none());

        h0.allow(1);
        assert!(pool.ready().now_or_never().is_some());
        assert_eq!(pool.next_idx, Some(0));

        h1.allow(1);
        h2.allow(1);
        pool.reset_pool(vec![(addr0, ()), (addr1, ()), (addr2, ())]);
        assert!(pool.next_idx.is_none());
        assert!(pool.ready().now_or_never().is_some());
        assert!(pool.next_idx.is_some());

        let call = pool.call(());
        let ((), respond) = tokio::select! {
            r = h0.next_request() => r.unwrap(),
            r = h1.next_request() => r.unwrap(),
            r = h2.next_request() => r.unwrap(),
        };
        respond.send_response(());
        call.now_or_never()
            .expect("call should be satisfied")
            .expect("call should succeed");

        assert!(pool.ready().now_or_never().is_some());
        assert!(pool.next_idx.is_some());
        assert_eq!(pool.pool.ready_len(), 2);
        assert_eq!(pool.pool.pending_len(), 1);

        let ctx = &mut Context::from_waker(futures_util::task::noop_waker_ref());
        assert_pending!(pool.poll_pool(ctx));

        h0.allow(1);
        h1.allow(1);
        h2.allow(1);

        assert_ready_ok!(pool.poll_pool(ctx));

        assert!(pool.next_idx.is_some());
        assert_eq!(pool.pool.ready_len(), 3);
        assert_eq!(pool.pool.pending_len(), 0);
    }