Implement subtype relation for kernel based elements.

pkg/compiler/lib/src/compiler.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 dart2js.compiler_base;
 
 import 'dart:async' show Future;
 
 import '../compiler_new.dart' as api;
 import 'closure.dart' as closureMapping show ClosureTask;
@@ skipping 16 matching lines @@
 import 'diagnostics/code_location.dart';
 import 'diagnostics/diagnostic_listener.dart' show DiagnosticReporter;
 import 'diagnostics/invariant.dart' show REPORT_EXCESS_RESOLUTION;
 import 'diagnostics/messages.dart' show Message, MessageTemplate;
 import 'dump_info.dart' show DumpInfoTask;
 import 'elements/elements.dart';
 import 'elements/entities.dart';
 import 'elements/modelx.dart' show ErroneousElementX;
 import 'elements/resolution_types.dart'
     show
-        DartTypes,
         ResolutionDartType,
         ResolutionDynamicType,
         ResolutionFunctionType,
         ResolutionInterfaceType,
         Types;
+import 'elements/types.dart' show DartTypes;
 import 'enqueue.dart' show Enqueuer, EnqueueTask, ResolutionEnqueuer;
 import 'environment.dart';
 import 'id_generator.dart';
 import 'io/source_information.dart' show SourceInformation;
 import 'js_backend/backend.dart' show JavaScriptBackend;
 import 'library_loader.dart'
     show
         ElementScanner,
         LibraryLoader,
         LibraryLoaderTask,
@@ skipping 1916 matching lines @@
   ResolutionFunctionType getLocalFunctionType(LocalFunctionElement function) {
     return function.type;
   }
 
   @override
   ResolutionDartType getUnaliasedType(ResolutionDartType type) {
     type.computeUnaliased(_resolution);
     return type.unaliased;
   }
 }