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tagger	The Android Open Source Project <initial-contribution@android.com>	Tue May 07 10:55:49 2024 -0700
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committer	Android Build Coastguard Worker <android-build-coastguard-worker@google.com>	Thu Nov 16 00:13:39 2023 +0000
tree	570f6d6a8e622c88b6332edf44fa702561b2af53
parent	8014df694c6c591694dd9e0706ce7c100f654f21 [diff]
parent	4052a3c23a002a7fa935ed3df487fe97d954b0f6 [diff]

tree: 570f6d6a8e622c88b6332edf44fa702561b2af53

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 1.56+

Examples

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

use std::pin::Pin;

use pin_project::pin_project;

#[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 std::pin::Pin;

use pin_project::pin_project;

#[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 #[pin_project] attribute 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.