pin_project cannot be used with structs that hold mutable references about pin-project HOT 4 CLOSED

I also commented on rust-lang/rust#72477, but this way should fix it completely:

playground

#[pin_project::pin_project]
pub struct A<'a, R> {
    buf: &'a mut [u8],

    #[pin]
    stuff: R,
}

impl<'a> Foo<'a> {
    fn foo(mut self: std::pin::Pin<&mut Self>) {
        let this = self.project();
        let (_, rest) = std::mem::replace(&mut *this.buf, &mut []).split_at_mut(1);
        *this.buf = rest;
    }
}

from pin-project.

Hmm... I could reproduce this without pin-project (playground):

pub struct Foo<'a> {
    buf: &'a mut [u8],
}

impl<'a> Foo<'a> {
    fn foo(self: std::pin::Pin<&mut Self>) {
        self.buf = &mut self.buf[1..];
    }
}

I guess this related to rust-lang/rust#54934, but I'll look into this more.

from pin-project.

Ok, this looks like rust-lang/rust#72337 and can be fixed by adding lifetime 'a to std::pin::Pin<&mut Self>:

playground

  impl<'a, R> Foo<'a, R> {
-     fn foo(self: std::pin::Pin<&mut Self>) {
+     fn foo(self: std::pin::Pin<&'a mut Self>) {
          let this = self.project();
          *this.buf = &mut this.buf[1..];
      }
  }

from pin-project.

Oh. You're right, this isn't related to pin-project at all, sorry for having bothered you with it!

This being said, your solution unfortunately requires the Pin to be borrowed for the lifetime of the whole struct, which isn't the API I'm looking for, but I'm going to raise that point with the compiler directly.

Thank you! :D

from pin-project.