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Allow initializing NonZero with literals#143594

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Allow initializing NonZero with literals#143594
oli-obk wants to merge 3 commits intorust-lang:mainfrom
oli-obk:non-zero-literals

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@oli-obk oli-obk commented Jul 7, 2025

This basically implements rust-lang/rfcs#3786 by teaching the language about NonZero and the literals NonZero supports.

I believe it is a minor enough feature that it either doesn't need an RFC and can just be FCPed or it is a simple enough RFC that @rust-lang/lang could FCP it to set a precedent for doing this for other libcore types. Anything like this for user types would of course require a full RFC as there are many open questions around it that NonZero<T> just doesn't have.

@oli-obk oli-obk added T-lang Relevant to the language team needs-fcp This change is insta-stable, or significant enough to need a team FCP to proceed. labels Jul 7, 2025
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traviscross commented Jul 7, 2025

We'll also need to update the Reference for this, and the details in that PR would help form another basis for the FCP here.

cc @ehuss

@traviscross traviscross added the S-waiting-on-documentation Status: Waiting on approved PRs to documentation before merging label Jul 7, 2025
programmerjake
programmerjake reviewed Jul 7, 2025
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Comment thread tests/ui/mismatched_types/non_zero_assigned_something.rs Outdated
oli-obk
oli-obk commented Jul 7, 2025
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Comment thread tests/ui/mismatched_types/non_zero_assigned_oflo_lit.rs

fn main() {
let _: std::num::NonZero<u8> = 256;
//~^ ERROR literal out of range
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@oli-obk oli-obk Jul 7, 2025

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Here's the erroring example

@oli-obk oli-obk force-pushed the non-zero-literals branch 2 times, most recently from 8797188 to 94dadf4 Compare July 8, 2025 07:34
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rust-bors Bot added a commit that referenced this pull request Jul 8, 2025
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Auto merge of #143629 - oli-obk:limited-nonzero-coercion, r=<try>
4a4dd8e 
Limited nonzero coercion

coercing `NonZero<T>` to `T` if all the types are available at the cast site.

This is fairly limited, as (as the tests show), this does not allow "reborrowing" `&NonZero<T>` as `&T`. It also fails quickly if the types aren't fully clear at the coercion site, but only resolved later.

Also cannot aid in trait selection or similar, even if there is clearly only one option.

Related:

* #143594
* rust-lang/rfcs#3786

cc `@traviscross`
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bors commented Jul 17, 2025

☔ The latest upstream changes (presumably #144044) made this pull request unmergeable. Please resolve the merge conflicts.

@bors bors added the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Jul 17, 2025
@rustbot rustbot added the T-clippy Relevant to the Clippy team. label Nov 4, 2025
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bors commented Nov 16, 2025

☔ The latest upstream changes (presumably #148957) made this pull request unmergeable. Please resolve the merge conflicts.

@oli-obk oli-obk removed the T-clippy Relevant to the Clippy team. label Apr 23, 2026
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oli-obk commented Apr 23, 2026

We'll also need to update the Reference for this, and the details in that PR would help form another basis for the FCP here.

@sandersaares do you want to do this instead of your RFC?

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clarfonthey commented Apr 23, 2026

Small note, but while it doesn't have to be implemented in this PR, it's probably worth noting for later that NonZero<char> isn't supported here and should be, alongside NonZero<u8> with byte literals.

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