Support overriding fields with fields.

dart/lib/compiler/implementation/emitter.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.
 
 /**
  * A function element that represents a closure call. The signature is copied
  * from the given element.
  */
 class ClosureInvocationElement extends FunctionElement {
   ClosureInvocationElement(SourceString name,
@@ skipping 380 matching lines @@
       defineInstanceMember(namer.getName(member), codeBlock);
       codeBlock = compiler.codegenWorld.generatedBailoutCode[member];
       if (codeBlock !== null) {
         defineInstanceMember(compiler.namer.getBailoutName(member), codeBlock);
       }
       FunctionElement function = member;
       FunctionSignature parameters = function.computeSignature(compiler);
       if (!parameters.optionalParameters.isEmpty()) {
         addParameterStubs(member, defineInstanceMember);
       }
-    } else if (member.kind !== ElementKind.FIELD) {
+    } else if (member.kind === ElementKind.FIELD) {
+      SourceString name = member.name;
+      ClassElement cls = member.getEnclosingClass();
+      if (cls.lookupSuperMember(name) !== null) {
+        String fieldName = namer.instanceFieldName(cls, name);
+        defineInstanceMember(namer.getterName(cls.getLibrary(), name),
+                             'function() {\n  return this.$fieldName;\n }');
+        defineInstanceMember(namer.setterName(cls.getLibrary(), name),
+                             'function(x) {\n  this.$fieldName = x;\n }');
+      }
+    } else {
       compiler.internalError('unexpected kind: "${member.kind}"',
                              element: member);
     }
     emitExtraAccessors(member, defineInstanceMember);
   }
 
   Set<Element> emitClassFields(ClassElement classElement, StringBuffer buffer) {
     // If the class is never instantiated we still need to set it up for
     // inheritance purposes, but we can simplify its JavaScript constructor.
     bool isInstantiated =
@@ skipping 14 matching lines @@
       }
 
       if ((isInstantiated && !enclosingClass.isNative())
           || needsDynamicGetter
           || needsDynamicSetter) {
         if (isFirstField) {
           isFirstField = false;
         } else {
           buffer.add(", ");
         }
-        LibraryElement library = member.getLibrary();
         SourceString name = member.name;
-        String fieldName = namer.instanceFieldName(library, name);
+        String fieldName = namer.instanceFieldName(member.getEnclosingClass(),
+                                                   name);
         // Getters and setters with suffixes will be generated dynamically.
         buffer.add('"$fieldName');
         if (needsDynamicGetter || needsDynamicSetter) {
           if (needsDynamicGetter && needsDynamicSetter) {
             buffer.add(GETTER_SETTER_SUFFIX);
           } else if (needsDynamicGetter) {
             buffer.add(GETTER_SUFFIX);
           } else {
             buffer.add(SETTER_SUFFIX);
           }
@@ skipping 261 matching lines @@
   }
 
   void emitCallStubForGetter(Element member,
                              Set<Selector> selectors,
                              void defineInstanceMember(String invocationName,
                                                        String definition)) {
     String getter;
     if (member.kind == ElementKind.GETTER) {
       getter = "this.${namer.getterName(member.getLibrary(), member.name)}()";
     } else {
-      getter =
-          "this.${namer.instanceFieldName(member.getLibrary(), member.name)}";
+      String name = namer.instanceFieldName(member.getEnclosingClass(),
+                                            member.name);
+      getter = "this.$name";
     }
     for (Selector selector in selectors) {
       if (selector.applies(member, compiler)) {
         String invocationName =
             namer.instanceMethodInvocationName(member.getLibrary(), member.name,
                                                selector);
         SourceString callName = Namer.CLOSURE_INVOCATION_NAME;
         String closureCallName =
             namer.instanceMethodInvocationName(member.getLibrary(), callName,
                                                selector);
@@ skipping 257 matching lines @@
       mainBuffer.add('function init() {\n');
       mainBuffer.add('  $isolateProperties = {};\n');
       addDefineClassAndFinishClassFunctionsIfNecessary(mainBuffer);
       emitFinishIsolateConstructor(mainBuffer);
       mainBuffer.add('}\n');
       compiler.assembledCode = mainBuffer.toString();
     });
     return compiler.assembledCode;
   }
 }