Add typedef AST node boilerplate.

pkg/kernel/lib/type_environment.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 kernel.type_environment;
 
 import 'ast.dart';
 import 'class_hierarchy.dart';
 import 'core_types.dart';
 import 'type_algebra.dart';
 
@@ skipping 127 matching lines @@
 /// The part of [TypeEnvironment] that deals with subtype tests.
 ///
 /// This lives in a separate class so it can be tested independently of the SDK.
 abstract class SubtypeTester {
   InterfaceType get objectType;
   InterfaceType get rawFunctionType;
   ClassHierarchy get hierarchy;
 
   /// Returns true if [subtype] is a subtype of [supertype].
   bool isSubtypeOf(DartType subtype, DartType supertype) {
+    subtype = subtype.unalias;
+    supertype = supertype.unalias;
     if (identical(subtype, supertype)) return true;
     if (subtype is BottomType) return true;
     if (supertype is DynamicType ||
         supertype is VoidType ||
         supertype == objectType) {
       return true;
     }
     if (subtype is InterfaceType && supertype is InterfaceType) {
       var upcastType =
           hierarchy.getTypeAsInstanceOf(subtype, supertype.classNode);
@@ skipping 78 matching lines @@
       if (subtypeNameIndex == subtype.namedParameters.length) return false;
       NamedType subtypeParameter = subtype.namedParameters[subtypeNameIndex];
       // Termination: Both types shrink in size.
       if (!isSubtypeOf(supertypeParameter.type, subtypeParameter.type)) {
         return false;
       }
     }
     return true;
   }
 }