Crate pin_project

An attribute that would create a projection struct covering all the fields.

Examples

For 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: Unpin, U> Unpin for Foo<T, U> {} // Conditional Unpin impl

For 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

See unsafe_project and project for more details.

Attribute Macros

project	An attribute to support pattern matching.
unsafe_fields	An attribute that would create projections for each struct fields.
unsafe_project	An attribute that would create a projection struct covering all the fields.
unsafe_variants	An attribute that would create projections for each enum variants.