Tracking Issue for `is_disconnected` functions for mpsc and mpmc channels

Feature gate: #![feature(mpsc_is_disconnected)] and #![feature(mpmc_channel)]

This is a tracking issue for the is_disconnected methods on mpsc and mpmc channels.

With these methods you'll be able to check if all Sender/Receivers on a channel have disconnected.

Public API

#![feature(mpsc_is_disconnected)]

use std::sync::mpsc::channel;

let (tx, rx) = channel::<i32>();
assert!(!tx.is_disconnected());
drop(rx);
assert!(tx.is_disconnected());

Steps / History

(Remember to update the S-tracking-* label when checking boxes.)

• ACP: https://github.com/rust-lang/libs-team/issues/748
• Implementation: https://github.com/rust-lang/rust/pull/153170
• Final comment period (FCP)^1
• Stabilization PR

Unresolved Questions

• How can we document this so that users do not from race conditions.
• Will std get the ability to re-connect channels? If so what does that mean for this feature?
• Can we add a clippy feature to detect the if !tx.is_disconnected() { tx.send() } racing form.

Start with the public API and review the linked implementation PR, rust-lang/rust#153170. Then read the unresolved questions about race-condition documentation, reconnection semantics, and a possible Clippy check. Done means completing the final comment period and stabilization work for the mpsc and mpmc is_disconnected methods.