dup will dup binding state already saved so it will keep variable val…

…ues but they will be their own thing from that point onward

core/src/main/java/org/jruby/RubyBinding.java

@@ -108,7 +108,7 @@ public IRubyObject initialize(ThreadContext context) {
 
     @JRubyMethod
     public IRubyObject dup(ThreadContext context) {
-        return newBinding(context.runtime, binding.clone());
+        return newBinding(context.runtime, binding.dup(context));
     }
 
     @JRubyMethod(name = "initialize_copy", visibility = Visibility.PRIVATE)

core/src/main/java/org/jruby/parser/StaticScope.java

@@ -76,7 +76,7 @@
  * will point to the previous scope of the enclosing module/class (cref).
  * 
  */
-public class StaticScope implements Serializable {
+public class StaticScope implements Serializable, Cloneable {
     public static final int MAX_SPECIALIZED_SIZE = 50;
     private static final long serialVersionUID = 3423852552352498148L;
 

core/src/main/java/org/jruby/runtime/Binding.java

@@ -316,4 +316,11 @@ public BacktraceElement getBacktrace() {
                     // Can't use Frame.DUMMY because of circular static init seeing it before it's assigned
                     new Frame(),
                     Visibility.PUBLIC);
+
+    public Binding dup(ThreadContext context) {
+        Binding newBinding = new Binding(this);
+        DynamicScope scope = getEvalScope(context.runtime);
+        newBinding.evalScope = scope.dup();
+        return newBinding;
+    }
 }

core/src/main/java/org/jruby/runtime/DynamicScope.java

@@ -598,4 +598,8 @@ public DynamicScope cloneScope() {
             throw new RuntimeException("BUG: failed to clone scope type " + getClass().getName());
         }
     }
+
+    public DynamicScope dup() {
+        return newDynamicScope(staticScope.duplicate(), parent);
+    }
 }