Fix broken handling of extern "ABI" blocks

ForeignModule is just such a terrible name for these.

Author: jyn514

src/librustdoc/clean/mod.rs

@@ -260,7 +260,8 @@ impl Clean<Vec<Item>> for hir::Item<'_> {
             }
             // TODO: this should also take the span into account (inner or outer)
             ItemKind::Mod(ref mod_) => NotInlined(mod_.clean(cx)),
-            ItemKind::ForeignMod(ref mod_) => NotInlined(mod_.clean(cx)),
+            // `extern "C" { ... }`
+            ItemKind::ForeignMod(ref mod_) => MaybeInlined::InlinedWithoutOriginal(mod_.clean(cx)),
             ItemKind::GlobalAsm(..) => MaybeInlined::InlinedWithoutOriginal(vec![]), // not handled
             ItemKind::TyAlias(ty, ref generics) => {
                 let rustdoc_ty = ty.clean(cx);
@@ -403,9 +404,9 @@ impl Clean<ItemKind> for hir::Mod<'_> {
     }
 }
 
-impl Clean<ItemKind> for hir::ForeignMod<'_> {
-    fn clean(&self, cx: &DocContext<'_>) -> ItemKind {
-        ModuleItem(Module { is_crate: false, items: self.items.clean(cx) })
+impl Clean<Vec<Item>> for hir::ForeignMod<'_> {
+    fn clean(&self, cx: &DocContext<'_>) -> Vec<Item> {
+        self.items.iter().map(|x| x.clean(cx)).collect()
     }
 }
 

src/librustdoc/formats/renderer.rs

@@ -82,7 +82,7 @@ crate fn run_format<T: FormatRenderer>(
             // recurse into the items of the module as well.
             let name = item.name.as_ref().unwrap().to_string();
             if name.is_empty() {
-                panic!("Unexpected module with empty name");
+                panic!("Unexpected module with empty name: {:?}", item);
             }
 
             cx.mod_item_in(&item, &name, &cache)?;