switch to std::task::ready!() where possible

[Muscraft]

In Rust 1.64.0, std::task::ready was stabilized. Using ready!() can make what is happening clearer in the code as it expands to roughly:

let num = match fut.poll(cx) {
    Poll::Ready(t) => t,
    Poll::Pending => return Poll::Pending,
};

This PR replaces places using Poll::Pending => return Poll::Pending with ready!() where appropriate.

I was unsure about how useful the new macro would be in one place in cargo/registry/index.rs, so I left it out and will add it in if needed.

Close #11128

r? @Eh2406

[Eh2406]

These all look like good improvements.
I agree with you that cargo/registry/index.rs, is significantly clearer as a match.

What do you think about changing cargo/sources/registry/http_remote.rs and cargo/sources/registry/remote.rs?

[Muscraft]

I think it makes sense to use ready!() in those two places, it makes them so you are matching once it is ready. I think theoretically cargo/registry/index.rs could probably have a similar structure:

match ready!(self.query_inner_with_online(dep, load, yanked_whitelist, f, false)?) {
    0 => {}
    _ => return Poll::Ready(Ok(())),
}

Which would make the whole thing:

if self.config.offline() {
    match ready!(self.query_inner_with_online(dep, load, yanked_whitelist, f, false)?) {
        0 => {}
        _ => return Poll::Ready(Ok(())),
    }
    // If offline, and there are no matches, try again with online.
    // This is necessary for dependencies that are not used (such as
    // target-cfg or optional), but are not downloaded. Normally the
    // build should succeed if they are not downloaded and not used,
    // but they still need to resolve. If they are actually needed
    // then cargo will fail to download and an error message
    // indicating that the required dependency is unavailable while
    // offline will be displayed.
}
self.query_inner_with_online(dep, load, yanked_whitelist, f, true)
    .map_ok(|_| ())

I'm not sold on this but I think it could be fine. I'll leave it up to you.

[Eh2406]

Maybe something like:

    if ready!(self.query_inner_with_online(dep, load, yanked_whitelist, f, false)?) > 0 {
        return Poll::Ready(Ok(())),
    }

[Eh2406]

@bors r+

And thank you!

[bors]

📌 Commit 0c2e0fe has been approved by Eh2406

It is now in the queue for this repository.

[bors]

⌛ Testing commit 0c2e0fe with merge dbd1c18...

[bors]

☀️ Test successful - checks-actions
Approved by: Eh2406
Pushing dbd1c18 to master...