tokio build broken for aarch64-apple-visionos

[coolbluewater]

Version
tokio 1.63

Platform
Building for aarch64-apple-visionos
Building on macos (if that helps)

Description
Tokio does not build for the recently added Rust visionos target aarch64-apple-visionos.
Building using

cargo +nightly build --target aarch64-apple-visionos -Zbuild-std

yields this error, and a number of others:

error: unsupported target for `mio::unix::pipe`
  --> /Users/xxx/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-0.8.11/src/sys/unix/pipe.rs:75:5
   |
75 |     compile_error!("unsupported target for `mio::unix::pipe`");
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0432]: unresolved imports `self::selector::event`, `self::selector::Event`, `self::selector::Events`, `self::selector::Selector`
  --> /Users/xxx/.cargo/registry/src/index.crates.io-6f17d22bba15001f/mio-0.8.11/src/sys/unix/mod.rs:18:37
   |
18 |     pub(crate) use self::selector::{event, Event, Events, Selector};
   |                                     ^^^^^  ^^^^^  ^^^^^^  ^^^^^^^^ no `Selector` in `sys::unix::selector`
   |                                     |      |      |
   |                                     |      |      no `Events` in `sys::unix::selector`
   |                                     |      no `Event` in `sys::unix::selector`
   |                                     no `event` in `sys::unix::selector`
   |

[Darksonn]

Adding a new target requires changes to both Tokio and mio. The changelog entry you saw added the changes needed in Tokio, but the changes in mio have still not happened, so it's not really supported yet.

[coolbluewater]

Can we please keep this open until fixed?

[coolbluewater]

@Darksonn wrote

Adding a new target requires changes to both Tokio and mio. The changelog entry you saw added the changes needed in Tokio, but the changes in mio have still not happened, so it's not really supported yet.

Also, what changelog entries are you referring to? I'm simply reporting that tokio does not build for this target.

[Darksonn]

We close issues when the relevant changes are merged, not when a release containing them is released.

[Darksonn]

The fix in Tokio happened in #6465.

[coolbluewater]

@Darksonn, the build of a fresh clone of the master branch is still broken so I don't understand what you mean.

[coolbluewater]

Your responses make no sense. Please read this issue again.

[Darksonn]

A fresh clone of Tokio's master branch will use a released version of mio, and not the latest master branch of mio.

[coolbluewater]

I get that. What I don't understand is you saying that "The fix in tokio happened in #6465".

That was not sufficient to make the build actually work. tokio needs to update to the version of mio that has the fix.
I opened another issue in mio and they replied with the version that has the fix.

This issue means that tokio does not build for vision os. Period. Fixing it means making the build actually work, not some small part of the work.

Your replies are obtuse and unhelpful, and not to the point.

[Darksonn]

No, Tokio does not need to update to that mio version because Tokio depends on a range of mio versions. We are not pinned to a specific release. Once mio makes a v0.8.x release containing VisionOS support, it will work with Tokio as-is. No further changes are needed in the Tokio repository.