def visit_this_1(receiver, thing, arg)
    if method_name = @cache[thing.class]
      return receiver.send(method_name, thing, arg)
    end
    visit_this(receiver, thing, [arg])
  end
def visit_this_1(receiver, thing, arg)
    if method_name = @cache[thing.class]
      return receiver.send(method_name, thing, arg)
    end
    visit_this(receiver, thing, [arg])
  end
Visit an explicit receiver with 1 args
 (This is ~30% faster than calling the general method)