Tracking Issue for lazy_get

Feature gate: #![feature(lazy_get)]

This is a tracking issue for LazyCell/Lock::get[_mut](), allowing you to extract a reference from a Lazy only if it is initialized, approved in ACP rust-lang/libs-team#429.

Public API

impl<T, F> core::cell::LazyCell<T, F> {
    pub fn get(this: &Self) -> Option<&T>;
    pub fn get_mut(this: &mut Self) -> Option<&mut T>;
    pub fn force_mut(this: &mut Self) -> &mut T;
}
impl<T, F> std::sync::LazyLock<T, F> {
    pub fn get(this: &Self) -> Option<&T>;
    pub fn get_mut(this: &mut Self) -> Option<&mut T>;
    pub fn force_mut(this: &mut Self) -> &mut T;
}

Steps / History

ACP: LazyLock/Cell get_mut() and DerefMut libs-team#429
Implementation:
- Implement (part of) ACP 429: add DerefMut to Lazy[Cell/Lock] #129334
- Implement ACP 429: add Lazy{Cell,Lock}::get[_mut] and force_mut #130476
Final comment period (FCP)¹
Stabilization PR

Unresolved Questions

None yet.

https://std-dev-guide.rust-lang.org/feature-lifecycle/stabilization.html ↩

Rollup merge of rust-lang#130476 - workingjubilee:more-lazy-methods-t…

Unrolled build for rust-lang#130476

The docs for LazyLock::get[_mut] are backwards:

LazyLock::get:

Returns a mutable reference to the value if initialized, or None if not.

LazyLock::get_mut:

Returns a reference to the value if initialized, or None if not.

The examples are right through.

@jalil-salame

@jalil-salame Why is that backwards? That seems correct to me.

@jalil-salame

@jalil-salame Why is that backwards? That seems correct to me.

Get should get a reference not a mutable reference

Get mut should get a mutable reference not a reference

Rollup merge of rust-lang#134452 - jalil-salame:fix-lazy-cell-docs, r…

Unrolled build for rust-lang#134452

get/get_mut have been fixed. Can this be stabilized now?

Rollup merge of rust-lang#134452 - jalil-salame:fix-lazy-cell-docs, r…

@rfcbot

FCP to stabilize get. get_mut and force_mut.

@rfcbot merge

Rollup merge of rust-lang#150016 - usamoi:stabilize-lazy-get, r=jhpratt

Unrolled build for #150016

Migrate from once_cell::sync::Lazy to std::sync::LazyLock.

Rollup merge of #150016 - usamoi:stabilize-lazy-get, r=jhpratt

Migrate from once_cell::sync::Lazy to std::sync::LazyLock.

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Tracking Issue for `lazy_get` #129333

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Tracking Issue for lazy_get #129333

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jalil-salame commented on Nov 29, 2024

ChayimFriedman2 commented on Nov 29, 2024

jalil-salame commented on Nov 29, 2024

kornelski commented on Mar 8, 2025

Amanieu commented on Apr 29, 2025

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Tracking Issue for `lazy_get` #129333