def visit_this_3(receiver, thing, arg1, arg2, arg3)
    if method_name = @cache[thing.class]
      return receiver.send(method_name, thing, arg1, arg2, arg3)
    end
    visit_this(receiver, thing, [arg1, arg2, arg3])
  end
def visit_this_3(receiver, thing, arg1, arg2, arg3)
    if method_name = @cache[thing.class]
      return receiver.send(method_name, thing, arg1, arg2, arg3)
    end
    visit_this(receiver, thing, [arg1, arg2, arg3])
  end
Visit an explicit receiver with 3 args
 (This is ~30% faster than calling the general method)