rust-lang / rust · Issue No. 160492

`feature(doc_cfg)` doesn't recognize `derive` implementations under `cfg_attr`

Openby gendxopened Aug 4, 2026updated Aug 4, 20260 comments

T-rustdocC-bugneeds-triage

Description

Code

From the appendvec crate:

#![cfg_attr(docsrs, feature(doc_cfg))]

#[cfg_attr(feature = "get-size2", derive(GetSize))]
pub struct AppendStr {
    ...
}

Reproduction Steps

Documentation generated at https://docs.rs/appendvec/0.1.6/appendvec/struct.AppendStr.html#impl-GetSize-for-AppendStr.

Expected Outcome

I expected the impl GetSize for AppendStr to be labeled with "Available on crate feature get-size2 only.", as happens with a manually implemented trait.

Actual Output

The "available on create feature" label is missing.

Version

Whatever docs.rs used on 2026-08-04 (today).

Additional Details

N/A

Relay Analysis

View on GitHub

Relay reads this issue against the repository's contribution signals: the files it is likely to touch, how the maintainers triage work this size, and what the first contribution would exercise.

The full analysis for this issue is still being assembled. Until then, the description above and the thread on GitHub are the most reliable context.