Fix setting public properties

- This currently only works with ES5 engines
  - Fallback to follow so this will work with pre-ES5 engines
- As such, I do not recommend using this commit outside of ES5-compliant engines that work properly with getters/setters
  - This does NOT include IE8, as IE8 only works with getters/setters on DOM elements

lib/class.js

@@ -537,6 +537,25 @@ function attachPropInit( prototype, properties, members )
             // initialize the value with a clone to ensure that they do
             // not share references (and therefore, data)
             this[ prop ] = util.clone( prop_pub[ prop ] );
+
+            ( function( prop )
+            {
+                var inst = this;
+
+                // public properties, when set internally, must forward to the
+                // actual variable
+                inst_props.__defineSetter__( prop, function( val )
+                {
+                    inst[ prop ] = val;
+                } );
+
+                // since we're defining a setter, we'll need to define a getter
+                // to return the value, or we'll simply return undefined
+                inst_props.__defineGetter__( prop, function()
+                {
+                    return inst[ prop ];
+                } );
+            } ).call( this, prop );
         }
 
         var methods_protected = members[ 'protected' ],

test/test-class-visibility.js

@@ -50,9 +50,22 @@ var common = require( './common' ),
             // protected/private properties (for testing purposes)
             return this[ name ];
         },
+
+
+        /**
+         * Allows us to set a value from within the class
+         */
+        'public setValue': function( name, value )
+        {
+            this[ name ] = value;
+        },
     })();
 
 
+/**
+ * Public members are the only members added to the instance's prototype to be
+ * accessible externally
+ */
 ( function testPublicMembersAreAccessbileExternally()
 {
     assert.equal(
@@ -69,6 +82,67 @@ var common = require( './common' ),
 } )();
 
 
+/**
+ * For reasons that are discussed in the next test (writing to public
+ * properties), we need to make sure public members are available internally.
+ * Actually, we don't need to test public methods, really, but it's in there for
+ * good measure. Who knows what bugs may be introduced in the future.
+ *
+ * This ensures that the getter is properly proxying the value to us.
+ */
+( function testPublicMembersAreAccessibleInternally()
+{
+    assert.equal(
+        foo.getProp( 'pub' ),
+        pub,
+        "Public properties are accessible internally"
+    );
+
+    assert.equal(
+        foo.getProp( 'pubf' )(),
+        pub,
+        "Public methods are accessible internally"
+    );
+} )();
+
+
+/**
+ * This may sound like an odd test, but it's actually very important. Due to how
+ * private/protected members are implemented, it compromises public members. In
+ * fact, public members would not work internally without what is essentially a
+ * proxy via setters.
+ *
+ * This test is to ensure that the setter is properly forwarding writes to the
+ * object within the prototype chain containing the public values. Otherwise,
+ * setting the value would simply mask it in the prototype chain. The value
+ * would appear to have changed internally, but when accessed externally, the
+ * value would still be the same. That would obviously be a problem ;)
+ */
+( function testPublicPropertiesAreWritableInternally()
+{
+    var val = 'moomookittypoo';
+
+    // start by setting the value
+    foo.setValue( 'pub', val );
+
+    // we should see that change internally...
+    assert.equal(
+        foo.getProp( 'pub' ),
+        val,
+        "Setting the value of a public property internally should be " +
+            "observable /internally/"
+    );
+
+    // ...as well as externally
+    assert.equal(
+        foo.pub,
+        val,
+        "Setting the value of a public property internally should be " +
+            "observable /externally/"
+    );
+} )();
+
+
 ( function testProtectedAndPrivateMembersAreNotAccessibleExternally()
 {
     assert.equal(