internal interface Rule {
}

private class Rule<T> : Rule {
   //Properties & Other Stuff
}

void method() {
   //For simplicity I used string here. It can be anything when the code is in context
   Type _type = typeof(string);
   Rule[] _rules;

   //This is causing an error because _type could not be found
   _rules = new Rule<_type>[] { };
}