tag	d2b653fc5b62db69ce05409da9d66f907ef1ff56
tagger	The Android Open Source Project <initial-contribution@android.com>	Thu May 04 16:18:13 2023 -0700
object	20b25e7980ca66c849b2358091bf2d3075981c7a

commit	20b25e7980ca66c849b2358091bf2d3075981c7a	[log] [tgz]
author	Android Build Coastguard Worker <android-build-coastguard-worker@google.com>	Wed Feb 01 11:01:43 2023 +0000
committer	Android Build Coastguard Worker <android-build-coastguard-worker@google.com>	Wed Feb 01 11:01:43 2023 +0000
tree	24220ebcf96ffa9804e838f8ac35890694f8dc59
parent	4789f9be294ff5d99cf135c249c6961330716e30 [diff]
parent	a38084eecd736860e92d10101b283e7cf34d288f [diff]

tree: 24220ebcf96ffa9804e838f8ac35890694f8dc59

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.