Fix invalid handling of nested items with --document-private-items

src/librustdoc/visit_ast.rs

@@ -10,6 +10,7 @@
 use rustc_middle::hir::nested_filter;
 use rustc_middle::ty::TyCtxt;
 use rustc_span::def_id::{CRATE_DEF_ID, LOCAL_CRATE};
+use rustc_span::hygiene::MacroKind;
 use rustc_span::symbol::{kw, sym, Symbol};
 use rustc_span::Span;
 
@@ -87,6 +88,7 @@ pub(crate) struct RustdocVisitor<'a, 'tcx> {
     inside_public_path: bool,
     exact_paths: DefIdMap<Vec<Symbol>>,
     modules: Vec<Module<'tcx>>,
+    is_importable_from_parent: bool,
 }
 
 impl<'a, 'tcx> RustdocVisitor<'a, 'tcx> {
@@ -107,6 +109,7 @@ pub(crate) fn new(cx: &'a mut core::DocContext<'tcx>) -> RustdocVisitor<'a, 'tcx
             inside_public_path: true,
             exact_paths: Default::default(),
             modules: vec![om],
+            is_importable_from_parent: true,
         }
     }
 
@@ -319,12 +322,24 @@ fn add_to_current_mod(
         renamed: Option<Symbol>,
         parent_id: Option<LocalDefId>,
     ) {
+        if self.is_importable_from_parent
+            // If we're inside an item, only impl blocks and `macro_rules!` with the `macro_export`
+            // attribute can still be visible.
+            || match item.kind {
+                hir::ItemKind::Impl(..) => true,
+                hir::ItemKind::Macro(_, MacroKind::Bang) => {
+                    self.cx.tcx.has_attr(item.owner_id.def_id, sym::macro_export)
+                }
+                _ => false,
+            }
+        {
             self.modules
                 .last_mut()
                 .unwrap()
                 .items
                 .insert((item.owner_id.def_id, renamed), (item, renamed, parent_id));
         }
+    }
 
     fn visit_item_inner(
         &mut self,
@@ -485,7 +500,22 @@ fn nested_visit_map(&mut self) -> Self::Map {
 
     fn visit_item(&mut self, i: &'tcx hir::Item<'tcx>) {
         self.visit_item_inner(i, None, None);
+        let new_value = if self.is_importable_from_parent {
+            matches!(
+                i.kind,
+                hir::ItemKind::Mod(..)
+                    | hir::ItemKind::ForeignMod { .. }
+                    | hir::ItemKind::Impl(..)
+                    | hir::ItemKind::Trait(..)
+            )
+        } else {
+            // Whatever the context, if it's an impl block, the items inside it can be used so they
+            // should be visible.
+            matches!(i.kind, hir::ItemKind::Impl(..))
+        };
+        let prev = mem::replace(&mut self.is_importable_from_parent, new_value);
         walk_item(self, i);
+        self.is_importable_from_parent = prev;
     }
 
     fn visit_mod(&mut self, _: &hir::Mod<'tcx>, _: Span, _: hir::HirId) {