#[doc(hidden)] does not work for externally used macros #39436

If a macro is imported using use (via the use_extern_macros feature), its documentation cannot be hidden. For instance, if the code is:

extern crate serde_json;

#[doc(hidden)]
pub use serde_json::json;

The documentation for the json macro will appear in the rustdocs. Of course, the expected result is that the documentation does not appear.

cc @jseyfried @nrc @dtolnay