inline ItemId method, clarify comments a bit

Author: CraftSpider

src/librustdoc/clean/types.rs

@@ -75,14 +75,6 @@ impl ItemId {
         }
     }
 
-    #[inline]
-    crate fn is_local_impl(self) -> bool {
-        match self {
-            ItemId::Blanket { impl_id, .. } => impl_id.is_local(),
-            ItemId::Auto { .. } | ItemId::DefId(_) | ItemId::Primitive(_, _) => false,
-        }
-    }
-
     #[inline]
     #[track_caller]
     crate fn expect_def_id(self) -> DefId {

src/librustdoc/json/mod.rs

@@ -171,10 +171,17 @@ impl<'tcx> FormatRenderer<'tcx> for JsonRenderer<'tcx> {
     /// the hashmap because certain items (traits and types) need to have their mappings for trait
     /// implementations filled out before they're inserted.
     fn item(&mut self, item: clean::Item) -> Result<(), Error> {
+        // We skip children of local blanket implementations, as we'll have already seen the actual
+        // generic impl, and the generated ones don't need documenting.
+        let local_blanket_impl = match item.def_id {
+            clean::ItemId::Blanket { impl_id, .. } => impl_id.is_local(),
+            clean::ItemId::Auto { .. }
+            | clean::ItemId::DefId(_)
+            | clean::ItemId::Primitive(_, _) => false,
+        };
+
         // Flatten items that recursively store other items
-        // We skip local blanket implementations, as we'll have already seen the actual generic
-        // impl, and the generated ones don't need documenting.
-        if !item.def_id.is_local_impl() {
+        if !local_blanket_impl {
             item.kind.inner_items().for_each(|i| self.item(i.clone()).unwrap());
         }