Tracking Issue for `OnceLock::new_init`

Feature gate: #![feature(once_lock_new_init)]

This is a tracking issue for OnceLock::new_init, as discussed in the ACP: https://github.com/rust-lang/libs-team/issues/817

Sister Tracking issue for OnceCell::new_init: https://github.com/rust-lang/rust/issues/159859

Currently, it is impossible to create an already initialized version of OnceLock:

• Without using the From<T> implementation for OnceLock<T>
• In a const context

This new method aims to solve both of these issues.

Public API

impl<T> OnceLock<T> {
    pub const fn new_init(init_value: T) -> OnceLockl<T>;
}

Steps / History

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

• ACP: rust-lang/libs-team#817
• Implementation: #160881
• Final comment period (FCP)^1
• Stabilization PR

Unresolved Questions

• Should the API name be new_init, or something else? Some alternatives: new_initialized, with_value, ...

Start by reading the implementation referenced as #160881 and the ACP at rust-lang/libs-team#817, then review the unresolved API naming question. The tracking work is done when the final comment period completes and a stabilization PR is opened.