Implement BitOr and BitOrAssign for the NonZero integer types

[thomcc]

This provides overloaded operators for NonZero$Int | NonZero$Int, NonZero$Int | $Int, and $Int | NonZero$Int. It also provides BitOrAssign where self is NonZero$Int, for symmetry.

It's a pretty small conceptual addition, but is good becasue but avoids a case where the operation is obviously sound, but you'd otherwise need unsafe to do it.

In crates trying to minimize unsafe usage, this is unfortunate and makes working with NonZero types often not worth it, even if the operations you're doing are clearly sound.

I've marked these as stable as I've been told in the past that trait impls are automatically stable. I'm happy to change it to unstable if this wasn't correct information.

I'm not entirely confident what version I should have put down, so I followed https://www.whatrustisit.com. Hopefully it's correct for this.

Apologies in advance if this has come up before, but I couldn't find it.

[rust-highfive]

r? @shepmaster

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[thomcc]

I remember hearing that libcore was going to require safety annotations, so I added them even though they're trivial. I can remove them (or remove the duplicates) if it's extraneous or noisy.

I also used new_unchecked instead of just doing $Ty(...) (despite it being in scope) to call attention to the unsafety but similarly don't have strong opinions here.

[Centril]

r? @dtolnay

[dtolnay]

@rust-lang/libs: this adds the following stable impls, which rely on nonzero integers or'd together being nonzero and previously would have involved unsafe code to encode that knowledge:

impl BitOr<NonZeroU8> for NonZeroU8 {         // NonZeroU8 | NonZeroU8
    type Output = NonZeroU8;
}

impl BitOr<u8> for NonZeroU8 {                // NonZeroU8 | u8
    type Output = NonZeroU8;
}

impl BitOr<NonZeroU8> for u8 {                // u8 | NonZeroU8
    type Output = NonZeroU8;
}

impl BitOrAssign<NonZeroU8> for NonZeroU8 {}  // NonZeroU8 |= NonZeroU8
impl BitOrAssign<u8> for NonZeroU8 {}         // NonZeroU8 |= u8

and equivalent for u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize.

@rfcbot fcp merge

[rfcbot]

Team member @dtolnay has proposed to merge this. The next step is review by the rest of the tagged team members:

• @Amanieu
• @KodrAus
• @SimonSapin
• @dtolnay
• @sfackler
• @withoutboats

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

[Centril]

👋 @KodrAus @withoutboats @SimonSapin

[rfcbot]

🔔 This is now entering its final comment period, as per the review above. 🔔

[rfcbot]

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

The RFC will be merged soon.

[Amanieu]

@bors r+

[bors]

📌 Commit 6cdb825 has been approved by Amanieu