Tracking Issue for pin_deref_mut

[jonhoo]

Feature gate: #![feature(pin_deref_mut)]

This is a tracking issue for Pin::as_deref_mut.

The feature adds the method as_deref_mut to Pin, which allow a safe transformation from a Pin<&mut Pin<P>> to a Pin<&mut P::Target>.

Public API

impl<'a, P: DerefMut> Pin<&'a mut Pin<P>> {
    pub fn as_deref_mut(self) -> Pin<&'a mut P::Target> { /* .. */ }
}

Steps / History

• Implementation: Remove P: Unpin bound on impl Future for Pin #81363
• Final comment period (FCP)
• Stabilization PR

Unresolved Questions

• None yet.

[RalfJung]

from a Pin<P>

It's from a Pin<&'a mut Pin<P>>, right? The nesting is a bit odd. But I guess it is what comes up in practice?

[jonhoo]

Ah, yes, sorry — fixed!

[coolreader18]

Are there any remaining blockers on this? It's a pretty useful function for blanket impls for traits with poll methods (e.g. Future already uses it in its impl<P> Future for Pin<P> impl).

[jonhoo]

Not that I know of — given it touches the Pin machinery, I suspect it should go through an actual FCP, but I'll let others be the judge of that :)