Unhelpful error message for unresolved ident in (multiple) import

[burg]

When a multiple import fails, the error message does not specify which ident was not found. The squiggly arrow seems to always point to the beginning of the thing being imported, whether or not that was the unresolved part.

Examples (from rust-http-client)

Multi-line multiple import: (no line at all!)

/Users/burg/repos/servo/src/rust-http-client/http_client.rs:5:7: 8:2 error: failed to resolve import
/Users/burg/repos/servo/src/rust-http-client/http_client.rs:5 import std::net::ip::{
/Users/burg/repos/servo/src/rust-http-client/http_client.rs:6     get_addr, format_addr, ipv4, ipv6, IpAddr,
/Users/burg/repos/servo/src/rust-http-client/http_client.rs:7     ip_get_addr_err
/Users/burg/repos/servo/src/rust-http-client/http_client.rs:8 };

Single-line multiple import: (points to std::)

/Users/burg/repos/servo/src/rust-http-client/connection.rs:2:7: 2:59 error: failed to resolve import
/Users/burg/repos/servo/src/rust-http-client/connection.rs:2 import std::net::tcp::{tcp_err_data, tcp_connect_err_data};
                                                                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Single-line single import: (points to std::)

/Users/burg/repos/servo/src/rust-http-client/connection.rs:25:15: 25:41 error: failed to resolve import
/Users/burg/repos/servo/src/rust-http-client/connection.rs:25         import std::net::tcp::tcp_socket;
                                                                             ^~~~~~~~~~~~~~~~~~~~~~~~~~

[burg]

Duplicate of #3027