Tracking Issue for `const_destruct`

Feature gate: #![feature(const_destruct)]

This is a tracking issue for const_destruct, which enables the naming of the Destruct trait and its use in ~const bounds to allow dropping values in const contexts.

Public API

pub trait Destruct { }

Steps / History

• Implementation: It was already implemented, but it's getting a new feature gate in https://github.com/rust-lang/rust/pull/132329.
• Final comment period (FCP)^1
• Stabilization PR

Unresolved Questions

• Do we want to allow ~const bounds on const Drop impls?

I think we do, and sorely need them for const drop to ever be useful. See my justification in https://github.com/rust-lang/rust/pull/132329#discussion_r1838749569. We want to be able to implement a conditional drop impl like:

struct DropAndCall<F: Fn()>(F);

impl<F> const Drop for DropAndCall<F>
where
    F: ~const Fn(),
{
    fn drop(&mut self) {
        (self.0)(); // This should be allowed.
    }
}

This is what is implemented on nightly.

Start with the const_destruct feature gate and the implementation described in rust-lang/rust#132329, then read the linked stabilization guide. The implementation is marked complete; remaining work is to resolve whether ~const bounds belong on const Drop impls, complete the final comment period, and prepare a stabilization PR.