bug: #[tracing::instrument] reorders async and unsafe keywords #2576
Description
Bug Report
Version
tracing v0.1.37
Platform
Darwin Parkers-MacBook-Pro.local 22.4.0 Darwin Kernel Version 22.4.0: Mon Mar 6 20:59:58 PST 2023; root:xnu-8796.101.5~3/RELEASE_ARM64_T6020 arm64
Crates
tracing
Description
Currently you cannot use the #[tracing::instrument] macro to instrument an unsafe async function. The problem is the macro re-orders the async and unsafe keywords in the wrong order.
Minimum Repro:
use tracing;
#[tracing::instrument]
async unsafe fn foo() -> usize {
42
}
This fails to compile with the error:
error: expected one of `extern` or `fn`, found keyword `async`
--> src/lib.rs:4:1
|
4 | async unsafe fn foo() -> usize {
| ^^^^^-------
| |
| expected one of `extern` or `fn`
| help: `async` must come before `unsafe`: `async unsafe`
|
= note: keyword order for functions declaration is `pub`, `default`, `const`, `async`, `unsafe`, `extern`
error: could not compile `playground` due to previous error
Using rust-analyzer you can see what this expands to:
unsafe async fn bar< >() -> usize {
{}
let __tracing_attr_span = tracing::span!(target:module_path!(),tracing::Level::INFO,"bar",);
let __tracing_instrument_future = async move {
#[allow(unreachable_code,clippy::diverging_sub_expression,clippy::let_unit_value,clippy::unreachable)]
if false {
let __tracing_attr_fake_return:usize = unreachable!("this is just for type inference, and is unreachable code");
return __tracing_attr_fake_return;
}{
42
}
};
if!__tracing_attr_span.is_disabled(){
tracing::Instrument::instrument(__tracing_instrument_future,__tracing_attr_span).await
}else {
__tracing_instrument_future.await
}
}
And indeed if you look at the first line of the expansion you can see unsafe async when it should be async unsafe.