Alternative @SidedProxy setter for Scala.

common/cpw/mods/fml/common/ILanguageAdapter.java

@@ -1,6 +1,8 @@
 package cpw.mods.fml.common;
 
 import java.lang.reflect.Field;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
 
 public interface ILanguageAdapter {
     public Object getNewInstance(FMLModContainer container, Class<?> objectClass, ClassLoader classLoader) throws Exception;
@@ -24,6 +26,51 @@ public interface ILanguageAdapter {
         @Override
         public void setProxy(Field target, Class<?> proxyTarget, Object proxy) throws IllegalArgumentException, IllegalAccessException, NoSuchFieldException, SecurityException
         {
+            try
+            {
+                // Check if the target class is a singleton, if so its
+                // implementation's class name is the actual classname
+                // postfixed with a $.
+                final Class<?> targetSingleton = Class.forName(proxyTarget.getName() + "$", true, proxyTarget.getClassLoader());
+
+                // Get the instance via the MODULE$ field which is
+                // automatically generated by the scala compiler for
+                // singletons.
+                final Object targetInstance = targetSingleton.getField("MODULE$").get(null);
+
+                // Find setter function. We do it this way because we can't
+                // necessarily use proxyTarget.getMethod(proxy.getClass()), as
+                // it might be a subclass and not the exact parameter type.
+                // All fields are private in scala, wrapped by a getter and
+                // setter named <fieldname> and <fieldname>_$eq. To those
+                // familiar with scala.reflect.BeanProperty: these will always
+                // be there, set<Fieldname> and get<Fieldname> will always
+                // only be generated *additionally*.
+                final String setterName = target.getName() + "_$eq";
+                for (Method setter : proxyTarget.getMethods())
+                {
+                    Class<?>[] setterParameters = setter.getParameterTypes();
+                    if (setterName.equals(setter.getName()) &&
+                            // Some more validation.
+                            setterParameters.length == 1 &&
+                            setterParameters[0].isAssignableFrom(proxy.getClass()))
+                    {
+                        // Here goes nothing... if this invocation fails we'll
+                        // just fall back to the original functionality.
+                        setter.invoke(targetInstance, proxy);
+                        return;
+                    }
+                }
+            }
+            catch (ClassNotFoundException e)
+            {
+                FMLLog.fine("This scala class is not a singleton (scala object), falling back to old proxy setter.");
+            }
+            catch (InvocationTargetException e)
+            {
+                FMLLog.fine("There's a problem with this proxy's setter, falling back to old proxy setter.");
+            }
+
             Field field = proxyTarget.getField("INSTANCE");
             Object scalaObject = field.get(null);
             target.set(scalaObject, proxy);