commit	aeebe1a3e16408a040c3100ae74c5be0edbd7c6e	[log] [tgz]
author	Chih-Hung Hsieh <chh@google.com>	Thu Oct 29 19:49:12 2020 +0000
committer	Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>	Thu Oct 29 19:49:12 2020 +0000
tree	55ba197683b0a0093a2767fcb1f576490157f8a1
parent	c017e76ff935d7c5111d24026e79fed4c2d2b22f [diff]
parent	57fbfaa560008e6518b456f0a2af3de7bd30c708 [diff]

tree: 55ba197683b0a0093a2767fcb1f576490157f8a1

README.md

pin-project

A crate for safe and ergonomic pin-projection.

Usage

Add this to your Cargo.toml:

[dependencies]
pin-project = "1"

The current pin-project requires Rust 1.37 or later.

Examples

#[pin_project] attribute creates projection types covering all the fields of struct or enum.

use pin_project::pin_project;
use std::pin::Pin;

#[pin_project]
struct Struct<T, U> {
    #[pin]
    pinned: T,
    unpinned: U,
}

impl<T, U> Struct<T, U> {
    fn method(self: Pin<&mut Self>) {
        let this = self.project();
        let _: Pin<&mut T> = this.pinned; // Pinned reference to the field
        let _: &mut U = this.unpinned; // Normal reference to the field
    }
}

code like this will be generated

To use #[pin_project] on enums, you need to name the projection type returned from the method.

use pin_project::pin_project;
use std::pin::Pin;

#[pin_project(project = EnumProj)]
enum Enum<T, U> {
    Pinned(#[pin] T),
    Unpinned(U),
}

impl<T, U> Enum<T, U> {
    fn method(self: Pin<&mut Self>) {
        match self.project() {
            EnumProj::Pinned(x) => {
                let _: Pin<&mut T> = x;
            }
            EnumProj::Unpinned(y) => {
                let _: &mut U = y;
            }
        }
    }
}

code like this will be generated

See documentation for more details, and see examples directory for more examples and generated code.

Related Projects

pin-project-lite: A lightweight version of pin-project written with declarative macros.

License

Licensed under either of

Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.