improve resolve error messages

[jesse99]

import model::{msg, deregister_msg, foobar, register_msg};
src/handlers/get_query.rs:5 import model::{msg, deregister_msg, foobar, register_msg};
                                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

above error points to the wrong location and doesn't indicate the actual problem (which is foobar).

import foobar::{msg, deregister_msg, register_msg};

src/handlers/get_query.rs:5:7: 5:51 error: unresolved name
src/handlers/get_query.rs:5 import foobar::{msg, deregister_msg, register_msg};
                                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

points to the right place, but does not say that that name is the problem (again foobar).

[jdm]

Sounds very similar to #3004.

[bstrie]

This:

extern mod std;
use std::{json, rope, foobar, arc, arena};
use foobar::bazqux;
fn main() {}

Now gives:

res.rs:2:22: 2:29 error: failed to resolve import: std::foobar
res.rs:2 use std::{json, rope, foobar, arc, arena};
                               ^~~~~~~
res.rs:3:4: 3:19 error: unresolved name
res.rs:3 use foobar::bazqux;
             ^~~~~~~~~~~~~~~
res.rs:3:4: 3:19 error: failed to resolve import: foobar::bazqux
res.rs:3 use foobar::bazqux;
             ^~~~~~~~~~~~~~~
error: failed to resolve imports
error: aborting due to 4 previous errors

So I think this issue can be closed.