allow-until

允许项目直到指定的 semver 版本，然后在编译时出错。

#[allow_until(version = ">= 1.0.x", reason = "struct is deprecated from version 1.0.x onwards")]
struct MyStruct {
    //....
}

或者使用 derive 宏

#[derive(AllowUntil)]
struct MyStruct {
    #[allow_until(version = ">= 1.0.x", reason = "member is deprecated from version 1.0.x onwards")]
    foo: usize
}

一旦 CARGO_PKG_VERSION 与给定的 semver 断言相匹配，宏将导致编译错误，因此提醒您更新/删除代码。