Allow initializing NonZero with literals
#143594
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oli-obk
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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 |
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oli-obk
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Jul 7, 2025
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| fn main() { | ||
| let _: std::num::NonZero<u8> = 256; | ||
| //~^ ERROR literal out of range |
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Here's the erroring example
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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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This basically implements rust-lang/rfcs#3786 by teaching the language about
NonZeroand the literalsNonZerosupports.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.