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Add NonZeroXxx::from_mut #129

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SOF3 opened this issue Oct 29, 2022 · 1 comment
Closed

Add NonZeroXxx::from_mut #129

SOF3 opened this issue Oct 29, 2022 · 1 comment
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ACP-accepted API Change Proposal is accepted (seconded with no objections) api-change-proposal A proposal to add or alter unstable APIs in the standard libraries T-libs-api

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@SOF3
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SOF3 commented Oct 29, 2022

Proposal

Problem statement

Add a function to convert a &mut xxx to &mut NonZeroXxx.

Motivation, use-cases

My project requires working on a &mut NonZeroU32 (because only NonZeroU32 implements a certain trait I want to use), but the value actually came from a &mut u32 somewhere deep inside my data structures, so it would be inconvenient to create a separate NonZeroU32 and proxy back the result later on.

Solution sketches

For n: &mut i32, if *n != 0 is currently true, and we provide the aforementioned function to map this reference into a &mut NonZeroI32, since the original n cannot be dereferenced without dropping the new &mut NonZeroI32, it is safe to work with the &mut NonZeroI32 directly.

Links and related work

As this change is very simple, I have already implemented it in a libcore patch: rust-lang/rust#103730

What happens now?

This issue is part of the libs-api team API change proposal process. Once this issue is filed the libs-api team will review open proposals in its weekly meeting. You should receive feedback within a week or two.
@SOF3 SOF3 added api-change-proposal A proposal to add or alter unstable APIs in the standard libraries T-libs-api labels Oct 29, 2022
@SOF3 SOF3 mentioned this issue Oct 29, 2022
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@m-ou-se
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m-ou-se commented Dec 30, 2022

Sounds good. Accepted as unstable in rust-lang/rust#103730

@m-ou-se m-ou-se closed this as completed Dec 30, 2022
@SOF3 SOF3 mentioned this issue Dec 30, 2022
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@dtolnay dtolnay added the ACP-accepted API Change Proposal is accepted (seconded with no objections) label Nov 23, 2023
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Jan 20, 2024
@matthiaskrgr
Rollup merge of rust-lang#103730 - SOF3:nonzero-from-mut, r=Mark-Simu…
f1713b0 
…lacrum,dtolnay

Added NonZeroXxx::from_mut(_unchecked)?

ACP: rust-lang/libs-team#129
Tracking issue: rust-lang#106290
rust-timer added a commit to rust-lang-ci/rust that referenced this issue Jan 20, 2024
@rust-timer
Unrolled build for rust-lang#103730
628b151 
Rollup merge of rust-lang#103730 - SOF3:nonzero-from-mut, r=Mark-Simulacrum,dtolnay

Added NonZeroXxx::from_mut(_unchecked)?

ACP: rust-lang/libs-team#129
Tracking issue: rust-lang#106290
github-actions bot pushed a commit to rust-lang/miri that referenced this issue Jan 21, 2024
@matthiaskrgr
Rollup merge of #103730 - SOF3:nonzero-from-mut, r=Mark-Simulacrum,dt…
81e735f 
…olnay

Added NonZeroXxx::from_mut(_unchecked)?

ACP: rust-lang/libs-team#129
Tracking issue: #106290
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