Extract DartTypeVisitor and subclasses from resolution_types.

pkg/compiler/lib/src/serialization/equivalence.dart

 // Copyright (c) 2016, 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.
 
 /// Functions for asserting equivalence across serialization.
 
 library dart2js.serialization.equivalence;
 
 import '../closure.dart';
 import '../common/resolution.dart';
@@ skipping 616 matching lines @@
 
   @override
   bool visitWarnOnUseElement(
       WarnOnUseElement element1, WarnOnUseElement element2) {
     return strategy.testElements(element1, element2, 'wrappedElement',
         element1.wrappedElement, element2.wrappedElement);
   }
 }
 
 /// Visitor that checks for equivalence of [ResolutionDartType]s.
-class TypeEquivalence implements DartTypeVisitor<bool, ResolutionDartType> {
+class TypeEquivalence
+    implements ResolutionDartTypeVisitor<bool, ResolutionDartType> {
   final TestStrategy strategy;
 
   const TypeEquivalence([this.strategy = const TestStrategy()]);
 
   bool visit(ResolutionDartType type1, ResolutionDartType type2) {
     return strategy.test(type1, type2, 'kind', type1.kind, type2.kind) &&
         type1.accept(this, type2);
   }
 
   @override
@@ skipping 1494 matching lines @@
 }
 
 bool areMetadataAnnotationsEquivalent(
     MetadataAnnotation metadata1, MetadataAnnotation metadata2) {
   if (metadata1 == metadata2) return true;
   if (metadata1 == null || metadata2 == null) return false;
   return areElementsEquivalent(
           metadata1.annotatedElement, metadata2.annotatedElement) &&
       areConstantsEquivalent(metadata1.constant, metadata2.constant);
 }