Always include Object and its members into 'inherited'.

pkg/analysis_server/lib/src/domains/analysis/implemented_dart.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library domains.analysis.implemented_dart;
 
 import 'package:analysis_server/src/protocol_server.dart' as protocol;
 import 'package:analysis_server/src/services/search/hierarchy.dart';
 import 'package:analysis_server/src/services/search/search_engine.dart';
 import 'package:analyzer/src/generated/element.dart';
 
 class ImplementedComputer {
   final SearchEngine searchEngine;
   final CompilationUnitElement unitElement;
 
   List<protocol.ImplementedClass> classes = <protocol.ImplementedClass>[];
   List<protocol.ImplementedMember> members = <protocol.ImplementedMember>[];
 
   Set<ClassElement> subtypes;
 
   ImplementedComputer(this.searchEngine, this.unitElement);
 
   compute() async {
     for (ClassElement type in unitElement.types) {
+      // always include Object and its members
+      if (type.supertype == null) {
+        _addImplementedClass(type);
+        type.accessors.forEach(_addImplementedMember);
+        type.fields.forEach(_addImplementedMember);
+        type.methods.forEach(_addImplementedMember);
+        continue;
+      }
+      // analyze ancestors
       subtypes = await getSubClasses(searchEngine, type);
       if (subtypes.isNotEmpty) {
         _addImplementedClass(type);
       }
       type.accessors.forEach(_addMemberIfImplemented);
       type.fields.forEach(_addMemberIfImplemented);
       type.methods.forEach(_addMemberIfImplemented);
     }
   }
 
@@ skipping 23 matching lines @@
       if (subtype.getMethod(name) != null) {
         return true;
       }
       if (subtype.getField(name) != null) {
         return true;
       }
     }
     return false;
   }
 }