Tracking Issue for ControlFlow::into_value

[scottmcm]

Feature gate: #![feature(control_flow_into_value)]

This is a tracking issue for the into_value method on ControlFlow<T, T>: https://doc.rust-lang.org/nightly/std/ops/enum.ControlFlow.html#method.into_value

Public API

// core::ops

impl<T> ControlFlow<T, T> {
    // hopefully const one day, but that needs `~const Destruct`
    // or precise drop calculations
    pub fn into_value(self) -> T;
}

Steps / History

• ACP: Add into_value for ControlFlow libs-team#474 (comment)
• Implementation: Added into_value function to ControlFlow<T, T> #137495
• Final comment period (FCP)¹
• Stabilization PR

Unresolved Questions

• None yet.

Footnotes

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

[scottmcm]

This has an approved ACP (cc @carbotaniuman), but wasn't implemented. Anyone interested? Adding one unstable function is one of the easiest ways to have a first PR!

[chenyukang]

@randyli
may be interested in taking it.

[madhav-madhusoodanan]

Hi @scottmcm
I've been studying the rust compiler and I'd love to put in effort towards this.

How should I approach this?

[Shourya742]

@rustbot claim

[madhav-madhusoodanan]

@Shourya742 hi, as you can see I was interested in working on this issue.

Would it be alright if I claim this?

[Shourya742]

@Shourya742 hi, as you can see I was interested in working on this issue.

Would it be alright if I claim this?

My bad .. I didn't read through the comment... You can claim it...
@rustbot release-assignment

[chenyukang]

@madhav-madhusoodanan
Great, you should add a new api for ControlFlow, probably here:

https://github.com/chenyukang/rust/blob/1a440d56d63458e4491f289c4950396f73304264/library/core/src/ops/control_flow.rs#L136

Don't forget the feature gate control_flow_into_value.

And read more details in rust-lang/libs-team#474 (comment) and https://std-dev-guide.rust-lang.org/

[madhav-madhusoodanan]

Got it, going through it now

[madhav-madhusoodanan]

Public API

// core::ops

impl ControlFlow<T, T> {
pub const fn into_value(self) -> T;
}

Just to clarify, is the public API supposed to be a const fn?
I was facing an issue with Destructor cannot be evaluated at compile-time with the const fn version

[madhav-madhusoodanan]

Nevermind, I was able to implement it as a const fn using the #[rustc_allow_const_fn_unstable(const_precise_live_drops)] feature.