Extract OrderedTypeSetBuilderBase from OrderedTypeSetBuilder

pkg/compiler/lib/src/elements/elements.dart

 // Copyright (c) 2012, 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 elements;
 
 import 'package:front_end/src/fasta/parser/async_modifier.dart'
     show AsyncModifier;
 
 import '../common.dart';
 import '../common/resolution.dart' show Resolution;
 import '../constants/constructors.dart';
 import '../constants/expressions.dart';
 import '../common_elements.dart' show CommonElements;
 import '../ordered_typeset.dart' show OrderedTypeSet;
 import '../resolution/scope.dart' show Scope;
 import '../resolution/tree_elements.dart' show TreeElements;
 import '../script.dart';
 import 'package:front_end/src/fasta/scanner.dart'
     show Token, isUserDefinableOperator, isMinusOperator;
 import '../tree/tree.dart' hide AsyncModifier;
 import '../universe/call_structure.dart';
 import 'package:front_end/src/fasta/scanner/characters.dart' show $_;
 import '../util/util.dart';
 import '../world.dart' show ClosedWorld;
 import 'entities.dart';
 import 'resolution_types.dart';
+import 'types.dart';
 import 'visitor.dart' show ElementVisitor;
 
 part 'names.dart';
 
 const int STATE_NOT_STARTED = 0;
 const int STATE_STARTED = 1;
 const int STATE_DONE = 2;
 
 class ElementCategory {
   /**
@@ skipping 1555 matching lines @@
   ResolutionInterfaceType get thisType;
   ClassElement get superclass;
 
   /// The direct supertype of this class.
   ResolutionDartType get supertype;
 
   /// Ordered set of all supertypes of this class including the class itself.
   OrderedTypeSet get allSupertypesAndSelf;
 
   /// A list of all supertypes of this class excluding the class itself.
-  Link<ResolutionDartType> get allSupertypes;
+  Link<InterfaceType> get allSupertypes;
 
   /// Returns the this type of this class as an instance of [cls].
   ResolutionInterfaceType asInstanceOf(ClassElement cls);
 
   /// A list of all direct superinterfaces of this class.
   Link<ResolutionDartType> get interfaces;
 
   bool get hasConstructor;
   Link<Element> get constructors;
 
@@ skipping 419 matching lines @@
   /// by a field.
   bool get isDeclaredByField;
 
   /// Returns `true` if this member is abstract.
   bool get isAbstract;
 
   /// If abstract, [implementation] points to the overridden concrete member,
   /// if any. Otherwise [implementation] points to the member itself.
   Member get implementation;
 }