Intra-doc links are unresolved on `pub use _ as _` items

[Veetaha]

I tried this code:

/// [`std::fs`]
pub use foo as foo2;

pub fn foo(){}

fn main() {}

I expected to see this happen:
If I run cargo +nightly doc I get no warnings/errors.

Instead, this happened:

$ cargo +nightly doc
 Documenting foo v0.1.0 (/home/veetaha/junk/rust-sandbox)
warning: unresolved link to `std::fs`
 --> src/main.rs:1:6
  |
1 | /// [`std::fs`]
  |      ^^^^^^^^^ unresolved link
  |
  = note: `#[warn(broken_intra_doc_links)]` on by default
  = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`

warning: 1 warning emitted

Note that if I remove pub from the use statement, no warnings are emitted...

Meta

rustc --version --verbose:

rustc 1.47.0-nightly (2d8a3b918 2020-08-26)
binary: rustc
commit-hash: 2d8a3b9181f41d3af9b9f016c5d73b2553e344bf
commit-date: 2020-08-26
host: x86_64-unknown-linux-gnu
release: 1.47.0-nightly
LLVM version: 11.0

rustdoc --version --verbose:

rustdoc 1.47.0-nightly (2d8a3b918 2020-08-26)
binary: rustdoc
commit-hash: 2d8a3b9181f41d3af9b9f016c5d73b2553e344bf
commit-date: 2020-08-26
host: x86_64-unknown-linux-gnu
release: 1.47.0-nightly
LLVM version: 11.0

[jyn514]

$ RUSTDOC_LOG=rustdoc::passes::collect=debug rustdoc +stage1 pub-use.rs 
2020-08-29T20:03:27.412092Z DEBUG rustdoc::passes::collect_intra_doc_links: attempting to resolve item without parent module: std::fs
warning: unresolved link to `std::fs`
 --> pub-use.rs:1:6
  |
1 | /// [`std::fs`]
  |      ^^^^^^^^^ unresolved link

This is a bug in rustdoc, it should resolve relative to the current module.

[jyn514]

This will break #75756 until fixed.

[jyn514]

For some reason tcx.parent() returns None on pub use items 🤔

[jyn514]

Hmm, even after that's fixed it doesn't display the documentation anywhere ... @Veetaha did you expect it to show up above the re-export?

Or on the index page for the module?

[Veetaha]

Well, I would expect it to appear at least somewhere :D
Might it be an oversight in rust or rustdoc design that it is allowed to write doc comments on items where these doc comments are not rendered?
At the very least (even if unrendered) I would expect validation of the intra-doc link happening...

[jyn514]

Right, #76082 fixes the incorrect error. If you don't have a preference I might put it on the pub use, although I wonder if maybe rustdoc should just give an error instead that you tried to put docs on a re-export.

[Veetaha]

Reexports are part of the crate's public API. I think it is reasonable to apply docs to them and have them rendered. We may collect more opinions on that before further decisions