`use` suggestions for local paths are missing `crate::` in edition 2018

[zackmdavis]

Consider the following program.

mod inner_mod {
    pub struct MyInnerStruct;
}

fn main() {
    let _s = MyInnerStruct {};
}

When compiled with --edition 2018 with the 6 July nightly, we get this error message:

error[E0422]: cannot find struct, variant or union type `MyInnerStruct` in this scope
 --> import_suggestion.rs:6:14
  |
6 |     let _s = MyInnerStruct {};
  |              ^^^^^^^^^^^^^ not found in this scope
help: possible candidate is found in another module, you can import it into scope
  |
1 | use inner_mod::MyInnerStruct;
  |

error: aborting due to previous error

For more information about this error, try `rustc --explain E0422`.

But if we take the suggestion literally (and continue using the 2018 edition), inner_mod is presumed to be a crate:

error[E0463]: can't find crate for `inner_mod`
 --> import_suggestion.rs:1:5
  |
1 | use inner_mod::MyInnerStruct;
  |     ^^^^^^^^^ can't find crate

error: aborting due to previous error

A pull request is forthcoming.