fn parse_externs(matches: &getopts::Matches) -> Result<Externs, String> {
let mut externs: BTreeMap<_, BTreeSet<_>> = BTreeMap::new();
for arg in &matches.opt_strs("extern") {
let mut parts = arg.splitn(2, '=');
let name = parts.next().ok_or("--extern value must not be empty".to_string())?;
fn parse_externs(matches: &getopts::Matches) -> Result<Externs, String> {
let mut externs: BTreeMap<_, BTreeSet<_>> = BTreeMap::new();
for arg in &matches.opt_strs("extern") {
let mut parts = arg.splitn(2, '=');
let name = parts.next().ok_or("--extern value must not be empty".to_string())?;