Fix for issue #6259: also look for subclasses when checking if a typed selector applies to an eleme…

lib/compiler/implementation/world.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.
 
 part of dart2js;
 
 class World {
   final Compiler compiler;
   final Map<ClassElement, Set<ClassElement>> subtypes;
+  final Map<ClassElement, Set<ClassElement>> typesImplementedBySubclasses;
   final Set<ClassElement> classesNeedingRti;
   final Map<ClassElement, Set<ClassElement>> rtiDependencies;
   final FunctionSet userDefinedGetters;
   final FunctionSet userDefinedSetters;
 
   World(Compiler compiler)
       : subtypes = new Map<ClassElement, Set<ClassElement>>(),
+        typesImplementedBySubclasses =
+            new Map<ClassElement, Set<ClassElement>>(),
         userDefinedGetters = new FunctionSet(compiler),
         userDefinedSetters = new FunctionSet(compiler),
         classesNeedingRti = new Set<ClassElement>(),
         rtiDependencies = new Map<ClassElement, Set<ClassElement>>(),
         this.compiler = compiler;
 
   void populate() {
     void addSubtypes(ClassElement cls) {
       if (cls.resolutionState != STATE_DONE) {
         compiler.internalErrorOnElement(
             cls, 'Class "${cls.name.slowToString()}" is not resolved.');
       }
+
       for (DartType type in cls.allSupertypes) {
         Set<Element> subtypesOfCls =
           subtypes.putIfAbsent(type.element, () => new Set<ClassElement>());
         subtypesOfCls.add(cls);
       }
+
+      // Walk through the superclasses, and record the types
+      // implemented by that type on the superclasses.
+      DartType type = cls.supertype;
+      while (type != null) {
+        Set<Element> typesImplementedBySubclassesOfCls =
+          typesImplementedBySubclasses.putIfAbsent(
+              type.element, () => new Set<ClassElement>());
+        typesImplementedBySubclassesOfCls.addAll(cls.allSupertypes);
+        type = type.element.supertype;
+      }
     }
 
     compiler.resolverWorld.instantiatedClasses.forEach(addSubtypes);
 
     // Find the classes that need runtime type information. Such
     // classes are:
     // (1) used in a is check with type variables,
     // (2) dependencies of classes in (1),
     // (3) subclasses of (2) and (3).
 
@@ skipping 142 matching lines @@
   final SourceString name;
 
   MemberSet(SourceString this.name) : elements = new Set<Element>();
 
   void add(Element element) {
     elements.add(element);
   }
 
   bool get isEmpty => elements.isEmpty;
 }