rustc: error when both both defining and using a module should be more specific

[aturon]

Given the following setup,

use test;
mod test {}

rustc says

mod-usage.rs:1:5: 1:9 error: unresolved import (maybe you meant `test::*`?)
mod-usage.rs:1 use test;
                   ^~~~

I ran into this while refactoring, but I imagine newcomers getting used to the use/mod distinction (and the fact that mod automatically uses) would benefit from a message more like:

mod-usage.rs:1:5: 1:9 error: cannot import `test` because it was already defined:
mod-usage.rs:1 use test;
                   ^~~~ import
mod-usage.rs:2 mod test {}
                   ^~~~ definition

It's also a bit strange that double-imports are allowed, but the situation above isn't. RFC PR 116 could help regularize things.

[flaper87]

This has been fixed. The current error reported is:

test.rs:1:5: 1:9 error: import `test` conflicts with existing submodule [E0258]
test.rs:1 use test;
              ^~~~
test.rs:2:1: 2:12 note: note conflicting module here
test.rs:2 mod test {}
          ^~~~~~~~~~~
error: aborting due to previous error