与this question类似，我被编译器宏扩展错误难倒了。
违规代码是：

/// send a command and wait for the response
///
/// 'dirty' macro that relies on outside context
macro_rules! send_and_receive {
    ($cmd: expr, $response_pat:pat => $r_block:block) => {
        send_command(&mut port, $cmd);

        for i in 0..3 {
            match receive_response(&mut port) {
                $response_pat => $r_block,
                r => {
                    eprintln!("got response: {r:?}");
                    continue;
                }
            };
        }
        panic!("missing response");
    }
}

其中预期的参数是一个枚举示例和一个“match like”表达式，如下所示：

send_and_receive!(
    Command::Thing { field: value /* etc */ },
    Response::ThingResponse { response_field1,  /* ... */ } => {
        do_stuff_here();
    }
);