参考 https://docs.soliditylang.org/en/v0.6.7/060-breaking-changes.html#semantic-and-syntactic-changes https://mirror.xyz/ninjak.eth/EroVZqHW1lfJFai3umiu4tb9r1ZbDVPOYC-puaZklAw https://blog.csdn.net/weixin_45719444/article/details/121161842