First attempt at fixing mixin bug

mixinfix1.patch

diff --git a/src/vm/jvm/runtime/org/perl6/nqp/sixmodel/reprs/P6Opaque.java b/src/vm/jvm/runtime/org/perl6/nqp/sixmodel/reprs/P6Opaque.java
index dc9fd60..9cb26cb 100644
--- a/src/vm/jvm/runtime/org/perl6/nqp/sixmodel/reprs/P6Opaque.java
+++ b/src/vm/jvm/runtime/org/perl6/nqp/sixmodel/reprs/P6Opaque.java
@@ -644,7 +644,7 @@ public class P6Opaque extends REPR {
         // Ensure target type is also P6opaque-based.
         if (!(newType.st.REPR instanceof P6Opaque))
             throw ExceptionHandling.dieInternal(tc, "P6opaque can only rebless to another P6opaque-based type");
-        
+
         // Ensure that the MROs overlap properly.
         P6OpaqueREPRData ourREPRData = (P6OpaqueREPRData)obj.st.REPRData;
         P6OpaqueREPRData targetREPRData = (P6OpaqueREPRData)newType.st.REPRData;
@@ -658,14 +658,15 @@ public class P6Opaque extends REPR {
         // If there's a different number of attributes, need to set up delegate.
         // Note the condition below works because we don't make an entry in the
         // class handles list for a type with no attributes.
-        if (ourREPRData.classHandles.length != targetREPRData.classHandles.length) {
+        P6OpaqueBaseInstance opaqueInstance = (P6OpaqueBaseInstance) obj;
+        if (ourREPRData.classHandles.length != targetREPRData.classHandles.length || opaqueInstance.delegate != null) {
             // Create delegate.
             SixModelObject delegate = newType.st.REPR.allocate(tc, newType.st);
             
             // Find original object.
             SixModelObject orig;
-            if (((P6OpaqueBaseInstance)obj).delegate != null)
-                orig = ((P6OpaqueBaseInstance)obj).delegate;
+            if (opaqueInstance.delegate != null)
+                orig = opaqueInstance.delegate;
             else
                 orig = obj;
             
@@ -679,7 +680,7 @@ public class P6Opaque extends REPR {
             catch (IllegalAccessException e) { throw new RuntimeException(e); }
 
             // Install.
-            ((P6OpaqueBaseInstance)obj).delegate = delegate;
+            opaqueInstance.delegate = delegate;
         }
         
         // Switch STable over to the new type.