Get the name of named capture group

[tisonkun]

Today I wrota program to catch group capture in a generic way:

let mut result = vec![];
for c in  regex.captures_iter(arg) {
    let mut cap = vec![];
    for m in c.iter() {
        if let Some(m) = m {
            // how to get the name?
            cap.push(<{ "name": ..., "text": m.as_str() }>);
        }
        cap.push(<null>);
    }
    result.push(cap);
}

When the match is not named, I'm OK to attach a null name field. But is it possible to get the name of named capture group?

Related - #955 and thus cc @BurntSushi @01mf02