Uniformative error message when missing a "self" while importing a module

[julienw]

Exemple code:

mod foo {
  mod hello {
    pub enum world {}
  }
  use hello::world;
}

fn main() {
}

Error is:

<anon>:6:7: 6:12 error: unresolved import `hello::world`. Maybe a missing `extern crate hello`? [E0432]
<anon>:6   use hello::world;
               ^~~~~
<anon>:6:7: 6:12 help: see the detailed explanation for E0432
error: aborting due to previous error
playpen: application terminated with error code 101

The compiler should detect that "self" is missing.

Note this is an error I do all the time as a beginner.

[SimonSapin]

Even without doing an analysis of what could have likely been intended this error message could mention that paths in use are absolute by default, unless they start with self:: or super::.

[frewsxcv]

Ran into this a few days ago, would love to the messaging here improved 👍

[birkenfeld]

The linked PR adds the information to the long diagnostics, at least.

Note that if you just have an use module; then the error message is markedly different:

error: unresolved import `modname`. There is no `modname` in the crate root [E0432]

I wonder if some consolidation would be in order.

[jseyfried]

Fixed in #36289.