doc(cfg) doesn't inherit down onto trait impls in modules

[Nemo157]

I tried this code:

#![feature(doc_cfg)]

pub trait Foo {}

#[doc(cfg(feature = "foobar"))]
impl crate::Foo for usize {}

#[doc(cfg(feature = "foobar"))]
mod imp {
    impl crate::Foo for () {}
}

I expected to see this happen: both impls being highlighted as needing the foobar feature.

Instead, this happened: only the usize impl got the message:

Meta

rustdoc 1.50.0-nightly (825637983 2020-11-18)
binary: rustdoc
commit-hash: 8256379832b5ecb7f71e8c5e2018446482223c12
commit-date: 2020-11-18
host: x86_64-unknown-linux-gnu
release: 1.50.0-nightly

[Nemo157]

@rustbot modify labels: +T-rustdoc

[Nemo157]

@rustbot claim