internal override void Defined(CodeGenContext context)
        {
            if (qualified)
                if (scope != null)
                {
                    // object result;
                    int result = context.CreateLocal("result", PrimitiveType.Object);
                    PERWAPI.CILLabel endLabel = context.NewLabel();
                    // try {
                    context.StartBlock(Clause.Try);
                    {
                        // result = Eval.const_defined(scope, vid, caller);
                        scope.GenCode(context);
                        context.ldstr(vid.ToString());
                        context.ldloc(0);
                        context.call(Runtime.Eval.const_defined);
                        context.stloc(result);
                        context.leave(endLabel);
                    }
                    TryBlock block = context.EndTryBlock();
                    // catch (System.Exception) {
                    context.StartBlock(Clause.Catch);
                    {
                        // result = null;
                        context.ldnull();
                        context.stloc(result);
                        context.leave(endLabel);
                    }
                    context.EndCatchBlock(Runtime.SystemExceptionRef, block);

                    context.CodeLabel(endLabel);
                    context.ldloc(result);
                    context.ReleaseLocal(result, true);
                }
                else
                {
                    context.ldsfld(Ruby.Compiler.Runtime.Init.rb_cObject);
                    context.ldstr(vid.ToString());
                    context.ldloc(0);
                    context.call(Runtime.Eval.const_defined);
                }
            else
            {
                context.ruby_cbase(parent_scope);
                context.ldstr(vid.ToString());
                context.ldloc(0);
                context.call(Runtime.Eval.const_defined);
            }
        }