Add/improve code comments

Author: GuillaumeGomez

src/librustdoc/clean/mod.rs

@@ -2377,7 +2377,7 @@ fn filter_tokens_from_list(
     tokens
 }
 
-/// When inlining items, we merge its attributes (and all the reexports attributes too) with the
+/// When inlining items, we merge their attributes (and all the reexports attributes too) with the
 /// final reexport. For example:
 ///
 /// ```ignore (just an example)

src/librustdoc/clean/types.rs

@@ -956,6 +956,8 @@ pub(crate) trait AttributesExt {
                     .filter_map(|attr| Cfg::parse(attr.meta_item()?).ok())
                     .fold(Cfg::True, |cfg, new_cfg| cfg & new_cfg)
             } else if doc_auto_cfg_active {
+                // If there is no `doc(cfg())`, then we retrieve the `cfg()` attributes (because
+                // `doc(cfg())` overrides `cfg()`).
                 self.iter()
                     .filter(|attr| attr.has_name(sym::cfg))
                     .filter_map(|attr| single(attr.meta_item_list()?))
@@ -2387,6 +2389,7 @@ impl ImplKind {
 #[derive(Clone, Debug)]
 pub(crate) struct Import {
     pub(crate) kind: ImportKind,
+    /// The item being re-exported.
     pub(crate) source: ImportSource,
     pub(crate) should_be_displayed: bool,
 }

tests/rustdoc/reexport-doc-hidden-inside-private.rs

@@ -1,4 +1,4 @@
-// This test ensures that a re-export of  `#[doc(hidden)]` item inside a private
+// This test ensures that a re-export of `#[doc(hidden)]` item inside a private
 // module will still be displayed (the re-export, not the item).
 
 #![crate_name = "foo"]