Reorganize equivalence test helpers

tests/compiler/dart2js/kernel/impact_test.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.
 
 library dart2js.kernel.impact_test;
 
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/commandline_options.dart';
 import 'package:compiler/src/common.dart';
 import 'package:compiler/src/common/names.dart';
 import 'package:compiler/src/common/resolution.dart';
 import 'package:compiler/src/compiler.dart';
 import 'package:compiler/src/constants/expressions.dart';
 import 'package:compiler/src/elements/elements.dart';
 import 'package:compiler/src/elements/resolution_types.dart';
 import 'package:compiler/src/js_backend/backend.dart';
 import 'package:compiler/src/kernel/element_map.dart';
 import 'package:compiler/src/kernel/element_map_impl.dart';
 import 'package:compiler/src/resolution/registry.dart';
 import 'package:compiler/src/resolution/tree_elements.dart';
 import 'package:compiler/src/ssa/kernel_impact.dart';
 import 'package:compiler/src/serialization/equivalence.dart';
 import 'package:compiler/src/universe/call_structure.dart';
 import 'package:compiler/src/universe/feature.dart';
 import 'package:compiler/src/universe/use.dart';
 import 'package:expect/expect.dart';
 import 'package:kernel/ast.dart' as ir;
 import '../memory_compiler.dart';
-import '../serialization/test_helper.dart';
+import '../equivalence/check_helpers.dart';
+import 'test_helpers.dart';
 
 const Map<String, String> SOURCE = const <String, String>{
   // Pretend this is a dart2js_native test to allow use of 'native' keyword.
   'sdk/tests/compiler/dart2js_native/main.dart': r'''
 import 'dart:_foreign_helper';
 import 'dart:_js_helper';
 import 'dart:_interceptors';
 import 'dart:_native_typed_data';
 import 'dart:indexed_db';
 import 'dart:html';
@@ skipping 857 matching lines @@
         builder.registerFeature(Feature.THROW_EXPRESSION);
         break;
       default:
         builder.registerFeature(feature);
         break;
     }
   }
   impact.nativeData.forEach(builder.registerNativeData);
   return builder;
 }
-
-/// Visitor the performers unaliasing of all typedefs nested within a
-/// [ResolutionDartType].
-class Unaliaser
-    extends BaseResolutionDartTypeVisitor<dynamic, ResolutionDartType> {
-  const Unaliaser();
-
-  @override
-  ResolutionDartType visit(ResolutionDartType type, [_]) =>
-      type.accept(this, null);
-
-  @override
-  ResolutionDartType visitType(ResolutionDartType type, _) => type;
-
-  List<ResolutionDartType> visitList(List<ResolutionDartType> types) =>
-      types.map(visit).toList();
-
-  @override
-  ResolutionDartType visitInterfaceType(ResolutionInterfaceType type, _) {
-    return type.createInstantiation(visitList(type.typeArguments));
-  }
-
-  @override
-  ResolutionDartType visitTypedefType(ResolutionTypedefType type, _) {
-    return visit(type.unaliased);
-  }
-
-  @override
-  ResolutionDartType visitFunctionType(ResolutionFunctionType type, _) {
-    return new ResolutionFunctionType.synthesized(
-        visit(type.returnType),
-        visitList(type.parameterTypes),
-        visitList(type.optionalParameterTypes),
-        type.namedParameters,
-        visitList(type.namedParameterTypes));
-  }
-}
-
-/// Perform unaliasing of all typedefs nested within a [ResolutionDartType].
-ResolutionDartType unalias(ResolutionDartType type) {
-  return const Unaliaser().visit(type);
-}