After doc_auto_cfg is gone, in the generated docs, nested structs do not receive the feature label anymore

[rodrigocfd]

Context

This issue came after this discussion in the Rust Users forum:

• https://users.rust-lang.org/t/doc-auto-cfg-is-gone-what-am-i-supposed-to-do/135070

Problem

After doc_auto_cfg being merged with doc_cfg, entities in nested modules do not receive the label anymore. I attached a zip with a minimal reproducible example:

broken-feats.zip

In the generated docs, both structs should have the feature label, but the nested one doesn't:

The command to generate the docs is:

RUSTDOCFLAGS="--cfg docsrs" cargo +nightly doc --all-features

Version

rustdoc 1.92.0 (ded5c06cf 2025-12-08)

[rodrigocfd]

Ping @GuillaumeGomez, who implemented this change in #138907.

[pheki]

The same issue happens with functions in extern blocks when the whole extern block is gated on the cfg:

#![feature(doc_cfg)]

unsafe extern "C" {
    #[cfg(feature = "banana")]
    pub fn doc_cfg_works();
}

#[cfg(feature = "banana")]
unsafe extern "C" {
    pub fn doc_cfg_doesnt_work();
}