在阅读开源代码的时候遇到多次 pub(crate) 语法，不知是啥意思？

举例 在mod.rs中：

pub(crate) use task_local::LocalsMap;

举例2：

#[derive(Eq, PartialEq, Clone, Copy, Hash, Debug)]
pub struct TaskId(pub(crate) usize);

impl TaskId {
    /// Generates a new `TaskId`.
    pub(crate) fn generate() -> TaskId {
        // TODO: find a good version to emulate u64 atomics on 32 bit systems.
        static COUNTER: AtomicUsize = AtomicUsize::new(1);

        let id = COUNTER.fetch_add(1, Ordering::Relaxed);
        if id > usize::max_value() / 2 {
            std::process::abort();
        }
        TaskId(id)
    }
}

impl fmt::Display for TaskId {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.0)
    }
}