pin-project
An attribute that would create a projection struct covering all the fields.
Usage
Add this to your Cargo.toml
:
[dependencies]
pin-project = "0.2.1"
Now, you can use pin-project:
use pin_project::unsafe_project;
The current version of pin-project requires Rust 1.33 or later.
Examples
Structs and enums are supported.
Structs
use pin_project::unsafe_project;
use std::pin::Pin;
#[unsafe_project(Unpin)]
struct Foo<T, U> {
#[pin]
future: T,
field: U,
}
impl<T, U> Foo<T, U> {
fn baz(mut self: Pin<&mut Self>) {
let this = self.project();
let _: Pin<&mut T> = this.future; // Pinned reference to the field
let _: &mut U = this.field; // Normal reference to the field
}
}
// Automatically create the appropriate conditional Unpin implementation.
// impl<T, U> Unpin for Foo<T, U> where T: Unpin {} // Conditional Unpin impl
Code like this will be generated
Enums
use pin_project::{project, unsafe_project};
use std::pin::Pin;
#[unsafe_project(Unpin)]
enum Foo<T, U> {
Future(#[pin] T),
Done(U),
}
impl<T, U> Foo<T, U> {
#[project] // Nightly does not need a dummy attribute to the function.
fn baz(mut self: Pin<&mut Self>) {
#[project]
match self.project() {
Foo::Future(future) => {
let _: Pin<&mut T> = future;
}
Foo::Done(value) => {
let _: &mut U = value;
}
}
}
}
// Automatically create the appropriate conditional Unpin implementation.
// impl<T, U> Unpin for Foo<T, U> where T: Unpin {} // Conditional Unpin impl
Code like this will be generated
See the documentation for more details.
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.