private var personDaoImpl: SysPersonDaoImpl? = null一般是申明的时候指定了可以为空 但实际为null时,kotlin无法智能转换 ,修改成:
private lateinit var personDaoImpl: SysPersonDaoImpl
smart cast 'xxx' to is impossible,because 'xxx' is a mutable property that could have been changed by this time
原文：https://www.cnblogs.com/caosq/p/11613253.html
