//! [![github]](https://github.com/dtolnay/threadbound) [![crates-io]](https://crates.io/crates/threadbound) [![docs-rs]](https://docs.rs/threadbound)
//!
//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs
//!
//! <br>
//!
//! [`ThreadBound<T>`] is a wrapper that binds a value to its original thread.
//! The wrapper gets to be [`Sync`] and [`Send`] but only the original thread on
//! which the ThreadBound was constructed can retrieve the underlying value.
//!
//! [`ThreadBound<T>`]: struct.ThreadBound.html
//! [`Sync`]: https://doc.rust-lang.org/std/marker/trait.Sync.html
//! [`Send`]: https://doc.rust-lang.org/std/marker/trait.Send.html
//!
//! # Example
//!
//! ```
//! use std::marker::PhantomData;
//! use std::rc::Rc;
//! use std::sync::Arc;
//! use threadbound::ThreadBound;
//!
//! // Neither Send nor Sync. Maybe the index points into a
//! // thread-local interner.
//! #[derive(Copy, Clone)]
//! struct Span {
//! index: u32,
//! marker: PhantomData<Rc<()>>,
//! }
//!
//! // Error types are always supposed to be Send and Sync.
//! // We can use ThreadBound to make it so.
//! struct Error {
//! span: ThreadBound<Span>,
//! message: String,
//! }
//!
//! fn main() {
//! let err = Error {
//! span: ThreadBound::new(Span {
//! index: 99,
//! marker: PhantomData,
//! }),
//! message: "fearless concurrency".to_owned(),
//! };
//!
//! // Original thread can see the contents.
//! assert_eq!(err.span.get_ref().unwrap().index, 99);
//!
//! let err = Arc::new(err);
//! let err2 = err.clone();
//! std::thread::spawn(move || {
//! // Other threads cannot get access. Maybe they use
//! // a default value or a different codepath.
//! assert!(err2.span.get_ref().is_none());
//! });
//!
//! // Original thread can still see the contents.
//! assert_eq!(err.span.get_ref().unwrap().index, 99);
//! }
//! ```
use ;
use ;
/// ThreadBound is a Sync-maker and Send-maker that allows accessing a value
/// of type T only from the original thread on which the ThreadBound was
/// constructed.
///
/// Refer to the [crate-level documentation] for a usage example.
///
/// [crate-level documentation]: index.html
unsafe
// Send bound requires Copy, as otherwise Drop could run in the wrong place.
unsafe