Function find_top_level_named_call 

fn find_top_level_named_call<'a>(
    s: &'a str,
    name: &[u8],
) -> Option<(&'a str, Vec<&'a str>, &'a str)>

Locate a top-level call name(a, b, …) and split it into (before, args, after). Returns None if no qualifying call exists at depth 0.