matching on std::net::AddrParseError triggers "use of unmarked library feature"

[crawford]

match Ipv4Addr::from_str(blah) {
    Ok(ip) => Ok(ip),
    Err(AddrParseError(_)) => Err("cannot parse address")
}

src/main.rs:84:32: 84:33 error: use of unmarked library feature
src/main.rs:84             Err(AddrParseError(_)) => Err("cannot parse address")
                                              ^
src/main.rs:84:32: 84:33 note: this is either a bug in the library you are using or a bug in the compiler - please report it in both places
src/main.rs:84             Err(AddrParseError(_)) => Err("cannot parse address")
                                              ^
src/main.rs:84:32: 84:33 note: use #![feature(unmarked_api)] in the crate attributes to override this
src/main.rs:84             Err(AddrParseError(_)) => Err("cannot parse address")
                                              ^
error: aborting due to previous error

$ rustc --version --verbose
rustc 1.1.0 (35ceea399 2015-06-19)
binary: rustc
commit-hash: 35ceea3997c79a3b7562e89b462ab76af5b86b22
commit-date: 2015-06-19
host: x86_64-unknown-linux-gnu
release: 1.1.0

$ cargo --version
cargo 0.3.0 (built 2015-07-08)

[tamird]

#27069

[steveklabnik]

since #27069 has been merged, i'm giving this a close