Add missing documentation

src/librustdoc/clean/inline.rs

@@ -227,6 +227,10 @@ pub(crate) fn item_relative_path(tcx: TyCtxt<'_>, def_id: DefId) -> Vec<Symbol>
     tcx.def_path(def_id).data.into_iter().filter_map(|elem| elem.data.get_opt_name()).collect()
 }
 
+/// Get the path to an item in a URL sense: we use it to generate the URL to the actual item.
+///
+/// In particular: we handle macro differently: if it's not a macro 2.0 oe a built-in macro, then
+/// it is generated at the top-level of the crate and its path will be `[crate_name, macro_name]`.
 pub(crate) fn get_item_path(tcx: TyCtxt<'_>, def_id: DefId, kind: ItemType) -> Vec<Symbol> {
     let crate_name = tcx.crate_name(def_id.krate);
     let relative = item_relative_path(tcx, def_id);

src/librustdoc/html/format.rs

@@ -410,6 +410,8 @@ fn generate_macro_def_id_path(
     Ok((url, item_type, fqp))
 }
 
+/// If the function succeeded, it will return the full URL to the item, its type and a `Vec`
+/// representing its `use` path.
 fn generate_item_def_id_path(
     mut def_id: DefId,
     original_def_id: DefId,