RA thinks that a called #[tokio::main] function returns a Future

[kennethuil]

rust-analyzer version: f94fa62 2022-05-30 stable

rustc version: rustc 1.60.0 (7737e0b5c 2022-04-04)

relevant settings: (eg. client settings, or environment variables like CARGO, RUSTUP_HOME or CARGO_HOME)

Cargo.toml:

[package]
name = "ra-issue"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
tokio = { version = "1.18", features = ["rt", "rt-multi-thread", "net", "macros"] }

main.rs:

use std::error::Error;

fn main() {
    // do_something_async is a non-async function that blocks on the tokio runtime
    // It returns a plain Result
    // Rust Analyzer thinks do_something_async returns a Future and puts a red squiggle here
    // but it compiles without errors
    let x: Result<_,_> = do_something_async();
    println!("async result is {:?}",x);
}

#[tokio::main]
async fn do_something_async() -> Result<(), Box<dyn Error + Send + Sync>> {
    println!("async stuff goes here...");
    Ok(())
}

[bjorn3]

What is your rust-analyzer configuration? Do you have rust-analyzer.procMacro.enable set to true? (should be by default)

[kennethuil]

"Proc Macro: Enable" is checked (in VSCode). So is "Proc Macro > Attributes: Enable". "Proc Macro: Ignored" is empty. settings.json has no settings overrides in it.

[flodiebold]

The tokio::main macro implementation in tokio-macros has #[cfg(not(test))] on it. Probably adding tokio-macros to rust-analyzer.cargo.unsetTest will help, I haven't tried it yet though.

[kennethuil]

{
    "rust-analyzer.cargo.unsetTest": [
        "core",
        "tokio-macros",
        "tokio_macros"
    ]
}

did not have any effect on the flagged error.

[flodiebold]

Adding both "tokio" and "tokio-macros" (with the -) does it, because the reexport in tokio is again cfg(test).

[flodiebold]

Fixed by #12599