better property overriding field

frog/member.dart

 // Copyright (c) 2011, 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 formal parameter to a [Method]. */
 class Parameter {
   FormalNode definition;
 
   String name;
   Type type;
@@ skipping 360 matching lines @@
     var lhs = get_(context, node, target, isDynamic);
     value = value.convertTo(context, type, node, isDynamic);
     return new Value(type, '${lhs.code} = ${value.code}');
   }
 }
 
 class PropertyMember extends Member {
   MethodMember getter;
   MethodMember setter;
 
+  Member _overriddenField;
+
   bool _provideFieldSyntax = false;
 
   // TODO(jimhug): What is the right span for this beast?
   SourceSpan get span() => getter != null ? getter.span : null;
 
   bool get canGet() => getter != null;
   bool get canSet() => setter != null;
 
   bool get prefersPropertySyntax() => true;
   bool get requiresFieldSyntax() => false;
@@ skipping 13 matching lines @@
   PropertyMember(String name, Type declaringType): super(name, declaringType);
 
   bool override(Member other) {
     if (!super.override(other)) return false;
 
     // properties can override other properties and fields
     if (other.isProperty || other.isField) {
       // TODO(jimhug):
       // other.returnType.ensureAssignableFrom(returnType, null, true);
       if (other.isProperty) addFromParent(other);
+      else _overriddenField = other;
       return true;
     } else {
       world.error('property can only override field or property',
         span, other.span);
       return false;
     }
   }
 
   Value get_(MethodGenerator context, Node node, Value target,
       [bool isDynamic=false]) {
     if (getter == null) {
+      if (_overriddenField != null) {
+        return _overriddenField.get_(context, node, target, isDynamic);
+      }
       return target.invokeNoSuchMethod(context, 'get:$name', node);
     }
     return getter.invoke(context, node, target, Arguments.EMPTY);
   }
 
   Value set_(MethodGenerator context, Node node, Value target, Value value,
       [bool isDynamic=false]) {
+    if (setter == null) {
+      if (_overriddenField != null) {
+        return _overriddenField.set_(context, node, target, value, isDynamic);
+      }
+      return target.invokeNoSuchMethod(context, 'set:$name', node,
+        new Arguments(null, [value]));
+    }
     return setter.invoke(context, node, target, new Arguments(null, [value]),
       isDynamic);
   }
 
   addFromParent(Member parentMember) {
     // TODO(jimhug): Egregious Hack!
     if (parentMember is ConcreteMember) {
       parentMember = parentMember.baseMember;
     }
 
@@ skipping 1067 matching lines @@
   }
 
   void forEach(void f(Member member)) {
     factories.forEach((_, Map constructors) {
       constructors.forEach((_, Member member) {
         f(member);
       });
     });
   }
 }