You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: build.rs
    path of file: ./repos/phaser/phaser/vendor/tokio
    
    the code of the file until where you have to start completion: use autocfg::AutoCfg;

fn main() {
    match AutoCfg::new() {
        Ok(ac) => {
            // The #[track_caller] attribute was stabilized in rustc 1.46.0.
            if ac.probe_rustc_version(1, 46) {
                autocfg::emit("tokio_track_caller")
 
    
fn main() {
    match AutoCfg::new() {
        Ok(ac) => {
            // The #[track_caller] attribute was stabilized in rustc 1.46.0.
            if ac.probe_rustc_version(1, 46) {
                autocfg::emit("tokio_track_caller")
            }
        }

        Err(e) => {
            // If we couldn't detect the compiler version and features, just
            // print a warning. This isn't a fatal error: we can still build
            // Tokio, we just can't enable cfgs automatically.
            println!(
                "cargo:warning=tokio: failed to detect compiler features: {}",
                e
            );
        }
    }
}