Globs in save-analysis do not contain exports in `value`

[euclio]

Uncovered by rust-dev-tools/rls-analysis#124.

For the following code:

pub use private::*;

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

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

The save analysis data for the glob use has an empty string for the value, when I would expect Struct1 and Struct2 would be in the string.

The theory is that the glob_map created by the librustc_resolve::Resolver only contains imports actually used inside the module, but the save analysis data wants to include exports as well. The glob_map is used to create the value field in the analysis here.

I'm happy to work and submit a PR for this, but I don't think that I understand enough about the resolve code to move forward, particularly around what causes an import to be considered "used". Could someone give me some help?

[euclio]

cc @nrc

[nrc]

@jseyfried would you be able to provide some help here please?

[jyn514]

Save-analysis has been removed from the compiler.