try_v2 0.4.2

Provides a derive macro for `Try` ([try_trait_v2](https://rust-lang.github.io/rfcs/3058-try-trait-v2.html))
Documentation 
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use autocfg::AutoCfg;

extern crate autocfg;

fn main() {
    let ac = autocfg::new();
    stable_feature(&ac, "assert_matches");
    assert_matches_in_module(&ac);
    assert_matches_in_root(&ac);

    stable_feature(&ac, "let_chains");

    stable_feature(&ac, "if_let_guard");
}

fn stable_feature(ac: &AutoCfg, feature: &'static str) {
    let cfg = format!("stable_{feature}");
    let code = format!(
        r#"
    #![deny(stable_features)]
    #![feature({feature})]
    "#
    );

    autocfg::emit_possibility(&cfg);
    if ac.probe_raw(&code).is_err() {
        autocfg::emit(&cfg);
    }
}

fn assert_matches_in_root(ac: &AutoCfg) {
    let cfg = "assert_matches_in_root";
    let code = r#"
    #![allow(stable_features)]
    #![feature(assert_matches)]
    use std::assert_matches;

    fn main() {
        assert_matches!(Some(4), Some(_));
    }
        "#;
    autocfg::emit_possibility(cfg);
    if ac.probe_raw(code).is_ok() {
        autocfg::emit(cfg);
    }
}

fn assert_matches_in_module(ac: &AutoCfg) {
    let cfg = "assert_matches_in_module";
    let code = r#"
    #![allow(stable_features)]
    #![feature(assert_matches)]
    use std::assert_matches::assert_matches;

    fn main() {
        assert_matches!(Some(4), Some(_));
    }
        "#;
    autocfg::emit_possibility(cfg);
    if ac.probe_raw(code).is_ok() {
        autocfg::emit(cfg);
    }
}