Nested use trees are not reachable

[euclio]

This causes an issue where the imports are not dumped in the save analysis data if it is configured to contain only reachable defs.

Steps to reproduce:

lib.rs:

#![crate_type = "lib"]

pub use private::*;

mod private {
    pub struct Struct1;
    pub struct Struct2;
}

pub use private2::{Struct3, Struct4};

mod private2 {
    pub struct Struct3;
    pub struct Struct4;
}

$ RUST_SAVE_ANALYSIS_CONFIG='{ "reachable_only": true, "full_docs": true, "pub_only": false, "distro_crate": false, "signatures": false, "borrow_data": false }' rustc -Zsave-analysis lib.rs

Notice that pub use private::*; will appear in the save analysis data, but neither import of Struct3 or Struct4.

The relevant reachability testing is here.

It seems to me that the privacy_access_levels query needs to be updated to consider the nested use tree as reachable?

cc @pietroalbini

[pietroalbini]

I'll look into this in a few hours.

[pietroalbini]

Sorry, I'm a bit busy these days, I'll try looking at this in the next few days.

[euclio]

No problem. I need to take a closer look because using the analysis data seemed to work as expected.

[pietroalbini]

Found the bug and fixed it locally. Tonight I'll add some tests and create a PR.