Feature gate: #![feature(drop_guard)]

This is a tracking issue for the core::mem::DropGuard API: a helper type that makes it easy to create impl Drop destructors inline.

Public API

#![feature(drop_guard)]

use std::mem::DropGuard;

{
    // Create a new guard around a string that will
    // print its value when dropped.
    let s = String::from("Chashu likes tuna");
    let mut s = DropGuard::new(s, |s| println!("{s}"));

    // Modify the string contained in the guard.
    s.push_str("!!!");

    // The guard will be dropped here, printing:
    // "Chashu likes tuna!!!"
}

Steps / History

(Remember to update the S-tracking-* label when checking boxes.)

• ACP: ACP: Add core::mem::WithDrop to associate a custom drop fn with some data libs-team#622
• Implementation: Add core::mem::DropGuard #144236
• Final comment period (FCP)¹
• Stabilization PR

Unresolved Questions

• What should the name of the type be? DropGuard, WithDrop and Dropper were some of the preferred options raised in the 2025-07-22 T-Libs-API call.
• Should the impl have a Clone impl? This can always be added in the future, but should be discussed further prior to stabilization.
• Should the Debug impl be transparent? This can always be added in the future, but should be discussed further prior to stabilization.