Function describe_unit_at 

pub fn describe_unit_at<'s>(
    text: &'s str,
    offset: usize,
    others: impl IntoIterator<Item = &'s str>,
) -> Option<String>

#1885: the module-doc hover for the unit name under offset in text (see unit_name_at), resolved against text itself, then others (the project’s other files), then the embedded first-party sources (so consumes bynk.cloudflare still names its unit). None when the cursor is not on a unit name, or no source declares it.