docs generation ignoring 'no docs' for re-exported items

[jnqnfe]

Location

https://doc.rust-lang.org/std/ffi/enum.c_void.html

Summary

The core::ffi::c_void type, if you look at the underlying code, has an attribute #[cfg_attr(not(doc), repr(u8))] with a comment alongside it that reads as follows:

An implementation detail we don't want to show up in rustdoc

This detail indeed does not show up on the core::ffi::c_void page, however this type is re-exported as std::ffi::c_void where this detail is shown on the page. It seems that rustdoc ignores such do-not-document attributes for re-exported items.

[fmease]

Dupe of #114952 but the concrete issue regarding priv repr will be fixed much sooner, cc #116882