Unstable ErrorKind in Stable branch

[dr-kernel]

Version
1.38

Platform
Linux 5.15.0-107-generic #117-Ubuntu SMP Fri Apr 26 12:26:49 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux

Description
Using a crate tokio-modbus which uses TcpStream to connect to a client. If this client isn't available (like the device is offline) I get the error:
Os { code: 113, kind: HostUnreachable, message: "No route to host" }
Looking up this "kind" is points me to rust-lang/rust#86442
https://github.com/rust-lang/rust/blob/a9c8887c7d548abc6c3e87f7d6fa02a0e95880bd/library/std/src/io/error.rs#L229-L230
This error is in the unstable branch. Why does TcpStream::connect() use this when I don't use the nightly?
tokio = { version = "1", features = ["full"] }
I couldn't actually find where this ErrorKind variant is throw aside from

tokio/tokio/src/net/tcp/socket.rs

Lines 638 to 641 in 9a75d6f

	#[cfg(unix)]
	if err.raw_os_error() != Some(libc::EINPROGRESS) {
	return Err(err);
	}

which is likely an OS error?

I expected to see this happen:
See one of the stable io::Error::ErrorKinds:

 | ErrorKind::ConnectionRefused
 | ErrorKind::ConnectionReset
 | ErrorKind::ConnectionAborted

or the like
The one that's being returned is appropriate but I cannot use it if i want to continue to use stable.

Instead, this happened:
Os { code: 113, kind: HostUnreachable, message: "No route to host" }

[dr-kernel]

Seems that this is a sync problem between stable and nightly use of ErrorKind. https://doc.rust-lang.org/stable/src/std/sys/pal/unix/mod.rs.html#261
I'll leave this open for now, but doesn't seem to be a tokio-rs problem but a rust std problem.

[Darksonn]

Tokio will often rely on the standard library for various kinds of logic, and when we do so, we are subject to the choices that the standard library makes. There isn't anything we can do about it.

Closing as wont-fix.