tracing debug sigil does not compile in rc.4

[ChristopherBiscardi]

Crates that currently use the ?variable tracing syntax (the "? sigil") are currently unable to build on bevy rc.3. bevy_log is currently pulling in rc.4.

Note

there is currently a half-published rc.4 release that exists on crates.io so this issue may resolve itself.
edit: full rc.4 release is out and the issue is still present

#18782 seems to have introduced the issue.

Minimal Reproduction

use bevy::prelude::*;

fn main() {
    let thing = 3;
    trace!(?thing, "some message");
    App::new().add_plugins(DefaultPlugins).run();
}

Additional info

locking bevy_log to rc.3 "solves" the issue.

bevy = "0.16.0-rc.3"
bevy_log = "=0.16.0-rc.3"

❯ cargo run
   Compiling bevy-log-test v0.2.0 (/Users/chris/tmp/bevy-log-test)
error: expected expression, found `?`
 --> src/main.rs:5:12
  |
5 |     trace!(?thing, "some message");
  |            ^ expected expression

error: could not compile `bevy-log-test` (bin "bevy-log-test") due to 1 previous error

[cart]

That PR switched out the tracing macros for log macros. In my head it was only doing it for no_std environments, but that was an unconditional change.

I don't think we should be using log as our primary interface. tracing "is" the bevy logging interface, and I don't want to trade out the additional capabilities.

Given that tracing already has no_std support, and given that it will likely soon have no_atomic support, I think we revert this.

@bushrat011899

[bushrat011899]

Ahh damn yeah unfortunately I concur. I was falsely under the impression that tracing and log had similar support in their base macros, hence the unconditional swap.

I agree, let's swap back to tracing. Embedded targets will need to use the Bevy crates individually, but that's a small audience and easily worked with.

[cart]

Looks like your PRs landed, so we're just waiting for a release now?

tokio-rs/tracing#3199
tokio-rs/tracing#3246

If so we can probably plug that in in 0.17