Pass ClassHierarchy instead of creating it.

pkg/kernel/lib/transformations/mixin_full_resolution.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.transformations.mixin_full_resolution;
 
 import '../ast.dart';
 import '../class_hierarchy.dart';
 import '../clone.dart';
 import '../core_types.dart';
 import '../target/targets.dart' show Target;
 import '../type_algebra.dart';
 
-void transformLibraries(
-    Target targetInfo, CoreTypes coreTypes, List<Library> libraries) {
-  new MixinFullResolution(targetInfo, coreTypes).transform(libraries);
+void transformLibraries(Target targetInfo, CoreTypes coreTypes,
+    ClassHierarchy hierarchy, List<Library> libraries) {
+  new MixinFullResolution(targetInfo, coreTypes, hierarchy)
+      .transform(libraries);
 }
 
 /// Replaces all mixin applications with regular classes, cloning all fields
 /// and procedures from the mixed-in class, cloning all constructors from the
 /// base class.
 ///
 /// Super calls (as well as super initializer invocations) are also resolved
 /// to their targets in this pass.
 class MixinFullResolution {
   final Target targetInfo;
+  final CoreTypes coreTypes;
 
-  final CoreTypes coreTypes;
+  /// The [ClassHierarchy] that should be used after applying this transformer.
+  /// If any class was updated, in general we need to create a new
+  /// [ClassHierarchy] instance, with new dispatch targets; or at least let
+  /// the existing instance know that some of its dispatch tables are not
+  /// valid anymore.

[ahe, 2017/06/01 11:38:29]

This is a good practical work around for a complex issue that got me stumped.
Awesome!

   ClassHierarchy hierarchy;
 
-  MixinFullResolution(this.targetInfo, this.coreTypes);
+  MixinFullResolution(this.targetInfo, this.coreTypes, this.hierarchy);
 
   /// Transform the given new [libraries].  It is expected that all other
   /// libraries have already been transformed.
   void transform(List<Library> libraries) {
     if (libraries.isEmpty) return;
 
     var transformedClasses = new Set<Class>();
 
     // Desugar all mixin application classes by copying in fields/methods from
     // the mixin and constructors from the base class.
     var processedClasses = new Set<Class>();
     for (var library in libraries) {
       if (library.isExternal) continue;
 
       for (var class_ in library.classes) {
         transformClass(libraries, processedClasses, transformedClasses, class_);
       }
     }
 
-    // TODO(scheglov) Remove "program" once we switch to creating "hierarchy"
-    // and "coreTypes" outside and passing into the transformers.
-    var program = libraries.first.enclosingProgram;
-    hierarchy = new ClassHierarchy(program);
+    // If there are transformed classes, we need to update hierarchy.
+    if (transformedClasses.isNotEmpty) {
+      var program = libraries.first.enclosingProgram;
+      hierarchy = new ClosedWorldClassHierarchy(program);
+    }
 
     // Resolve all super call expressions and super initializers.
     for (var library in libraries) {
       if (library.isExternal) continue;
 
       for (var class_ in library.classes) {
         final bool hasTransformedSuperclass =
             transformedClasses.contains(class_.superclass);
 
         for (var procedure in class_.procedures) {
@@ skipping 279 matching lines @@
           return null;
         }
       }
 
       throw new Exception(
           'Could not find a generative constructor named "${constructor.name}" '
           'in lookup class "${lookupClass.name}"!');
     }
   }
 }