Add cross-references to synthesized inherited members

infra/indexer/frontend/ast_visitor.cc

@@ -852,6 +852,21 @@ void AddVirtualMethodLinksImpl(
   }
 }
 
+const clang::CXXRecordDecl* GetRecordForType(const clang::QualType& type) {
+  clang::QualType derived_type = type;
+  if (const auto* pointer_type = type->getAs<clang::PointerType>()) {
+    derived_type = pointer_type->getPointeeType();
+  }
+  if (derived_type->isDependentType()) {
+    return nullptr;
+  }
+  const auto* record_type = derived_type->castAs<clang::RecordType>();
+  CHECK(record_type);
+  const clang::Decl* decl = record_type->getOriginalDecl();
+  CHECK(decl);
+  return llvm::cast<clang::CXXRecordDecl>(decl);
+}
+
 }  // namespace
 
 bool AstVisitor::VisitCallExpr(const clang::CallExpr* expr) {
@@ -1659,9 +1674,34 @@ void AstVisitor::AddReferencesForExpr(const clang::Expr* expr) {
     decl = llvm::cast<clang::DeclRefExpr>(expr)->getDecl();
   } else if (llvm::isa<clang::MemberExpr>(expr)) {
     const auto* member_expr = llvm::cast<clang::MemberExpr>(expr);
-    decl = member_expr->getMemberDecl();
-    if (member_expr->getBase()) {
-      AddReferencesForExpr(member_expr->getBase());
+    const clang::ValueDecl* value_decl = member_expr->getMemberDecl();
+    decl = value_decl;
+    if (clang::Expr* base = member_expr->getBase()) {
+      AddReferencesForExpr(base);
+
+      // Check if the access is through an inheriting descendant, in which case
+      // we add a cross-reference to the corresponding synthetic entity.
+      //
+      // Skip the case of an explicit qualification (`instance.Base::method`)
+      // because it is commonly used for members not accessible through the
+      // instance directly (for disambiguation).
+      if (!member_expr->getQualifierLoc()) {
+        if (const auto* expr_record_decl =
+                GetRecordForType(base->IgnoreParenBaseCasts()->getType())) {
+          const clang::DeclContext* decl_context =
+              value_decl->getNonTransparentDeclContext();
+          // If the base expression is not of the same record type as the parent
+          // of the retrieved member...
+          if (const auto* record_decl =
+                  llvm::dyn_cast<clang::CXXRecordDecl>(decl_context);
+              record_decl && record_decl->getCanonicalDecl() !=
+                                 expr_record_decl->getCanonicalDecl()) {
+            // ...add synthetic entity cross-references.
+            AddSyntheticMemberReference(expr_record_decl, value_decl,
+                                        expr->getSourceRange());
+          }
+        }
+      }
     }
   } else if (llvm::isa<clang::LambdaExpr>(expr)) {
     decl = llvm::cast<clang::LambdaExpr>(expr)
@@ -1674,6 +1714,24 @@ void AstVisitor::AddReferencesForExpr(const clang::Expr* expr) {
   }
 }
 
+void AstVisitor::AddSyntheticMemberReference(
+    const clang::CXXRecordDecl* child_class,
+    const clang::ValueDecl* inherited_member, const clang::SourceRange& range) {
+  const EntityId base_member_entity_id = GetEntityIdForDecl(inherited_member);
+  if (base_member_entity_id == kInvalidEntityId) {
+    return;
+  }
+  const Entity& base_member_entity =
+      index_.GetEntityById(base_member_entity_id);
+  const Entity synthetic_inherited_member = Entity(
+      base_member_entity, GetNamePrefixForDeclContext(child_class, context_),
+      /*inherited_entity_id=*/base_member_entity_id);
+  const EntityId synthetic_inherited_member_id =
+      index_.GetEntityId(synthetic_inherited_member);
+  auto location_id = GetLocationId(range.getBegin(), range.getEnd());
+  (void)index_.GetReferenceId({synthetic_inherited_member_id, location_id});
+}
+
 void AstVisitor::AddDeclReferenceForSourceRange(const clang::SourceRange& range,
                                                 const clang::Decl* decl) {
   auto entity_id = GetEntityIdForDecl(decl, /*for_reference=*/true);

infra/indexer/frontend/ast_visitor.h

@@ -82,6 +82,9 @@ class AstVisitor : public clang::RecursiveASTVisitor<AstVisitor> {
       const clang::Decl* template_decl, const clang::Decl* original_decl);
   void SynthesizeInheritedMemberEntities(
       const clang::CXXRecordDecl* class_decl);
+  void AddSyntheticMemberReference(const clang::CXXRecordDecl* child_class,
+                                   const clang::ValueDecl* inherited_member,
+                                   const clang::SourceRange& range);
   void AddTypeReferencesFromLocation(LocationId location_id,
                                      const clang::Type *type,
                                      bool outermost_type = true);

infra/indexer/frontend/frontend_test.cc

@@ -2256,6 +2256,47 @@ TEST(FrontendTest, MoreCursedInheritance) {
 
   // Note that this link skips `C` because it is devoid of `moo(int)`.
   EXPECT_HAS_VIRTUAL_LINK(index, "B::moo(int)", "D::moo(int)");
+
+  // Qualified-name member accesses only create references to the base class
+  // entities...
+  EXPECT_HAS_REFERENCE(
+      index, Entity::Kind::kFunction, "A::", "foo", "()", "snippet.cc", 2, 2,
+      "snippet.cc", 19, 19, /*is_incomplete=*/false,
+      /*template_prototype_entity_id=*/std::nullopt,
+      /*implicitly_defined_for_entity_id=*/std::nullopt,
+      /*enum_value=*/std::nullopt, /*inherited_from_entity_id=*/std::nullopt,
+      /*virtual_method_kind=*/Entity::VirtualMethodKind::kNonPureVirtual);
+  EXPECT_HAS_REFERENCE(
+      index, Entity::Kind::kFunction, "B::", "foo", "()", "snippet.cc", 7, 7,
+      "snippet.cc", 19, 19, /*is_incomplete=*/false,
+      /*template_prototype_entity_id=*/std::nullopt,
+      /*implicitly_defined_for_entity_id=*/std::nullopt,
+      /*enum_value=*/std::nullopt, /*inherited_from_entity_id=*/std::nullopt,
+      /*virtual_method_kind=*/Entity::VirtualMethodKind::kNonPureVirtual);
+  // ...whereas an unqualified-name one also creates a reference to the
+  // synthesized inherited entity in the child.
+  EXPECT_HAS_REFERENCE(
+      index, Entity::Kind::kFunction, "C::", "bar", "()", "snippet.cc", 13, 13,
+      "snippet.cc", 21, 21, /*is_incomplete=*/false,
+      /*template_prototype_entity_id=*/std::nullopt,
+      /*implicitly_defined_for_entity_id=*/std::nullopt,
+      /*enum_value=*/std::nullopt, /*inherited_from_entity_id=*/std::nullopt,
+      /*virtual_method_kind=*/Entity::VirtualMethodKind::kNonPureVirtual);
+  EXPECT_HAS_REFERENCE(
+      index, Entity::Kind::kFunction, "D::", "bar", "()", "snippet.cc", 13, 13,
+      "snippet.cc", 21, 21, /*is_incomplete=*/false,
+      /*template_prototype_entity_id=*/std::nullopt,
+      /*implicitly_defined_for_entity_id=*/std::nullopt,
+      /*enum_value=*/std::nullopt, /*inherited_from_entity_id=*/
+      RequiredEntityId(
+          index, Entity::Kind::kFunction, "C::", "bar", "()", "snippet.cc", 13,
+          13, /*is_incomplete=*/false,
+          /*template_prototype_entity_id=*/std::nullopt,
+          /*implicitly_defined_for_entity_id=*/std::nullopt,
+          /*enum_value=*/std::nullopt,
+          /*inherited_from_entity_id=*/std::nullopt,
+          /*virtual_method_kind=*/Entity::VirtualMethodKind::kNonPureVirtual),
+      /*virtual_method_kind=*/Entity::VirtualMethodKind::kNonPureVirtual);
 }
 
 TEST(FrontendTest, InheritanceThroughTemplateInstantiation) {