tag	510db690ab4647075af79f67a19f782ffcb35790
tagger	The Android Open Source Project <initial-contribution@android.com>	Wed Jan 12 10:56:27 2022 -0800
object	23cb2ff21bdab68452044ca37cbc08382532d9e1

commit	23cb2ff21bdab68452044ca37cbc08382532d9e1	[log] [tgz]
author	android-build-team Robot <android-build-team-robot@google.com>	Fri Apr 30 01:06:45 2021 +0000
committer	android-build-team Robot <android-build-team-robot@google.com>	Fri Apr 30 01:06:45 2021 +0000
tree	468b171d04d12d79930f58d6efc7ec3a45854589
parent	35f3c1431a8b9d619636569eee698cfd8cfdb9cc [diff]
parent	4eafa0cc0e589d8dd142ef7d2c30718b0f9c0e5b [diff]

tree: 468b171d04d12d79930f58d6efc7ec3a45854589

README.md

pin-project

A crate for safe and ergonomic pin-projection.

Usage

Add this to your Cargo.toml:

[dependencies]
pin-project = "1"

Compiler support: requires rustc 1.37+

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 or MIT license at your option.

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.