`#[tokio::main]` proc macro attaches questionable spans to user code

[jonas-schievink]

Version
tokio-macros 1.8.2

Platform
n/a

Description

In the following code, the variable; statement has incorrect spans attached to itself:

#[tokio::main]
async fn main() {
    let variable = "";
    variable;
}

The spans of variable; point to tokio::runtime::Builder::new_multi_thread() in the output of the macro. This causes rust-analyzer to (correctly) highlight variable as a function call and to show the new_multi_thread function on hover.

Please consider not doing this, as it degrades IDE functionality.

[Darksonn]

Thanks for reporting this bug. You are correct that it seems to be using the wrong span. Perhaps the #[tokio::main] macro's span would be better?

[jonas-schievink]

Yeah, Span::call_site() should be a good default

[taiki-e]

These were intended to improve diagnostics (#3766), but I would accept a patch to improve compatibility with rust-analyzer as long as there are no diagnostics regressions.