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Tracking Issue for generic NonZero #120257

Closed
20 of 21 tasks
reitermarkus opened this issue Jan 23, 2024 · 34 comments
Closed
20 of 21 tasks

Tracking Issue for generic NonZero #120257

reitermarkus opened this issue Jan 23, 2024 · 34 comments
Labels
C-tracking-issue Category: A tracking issue for an RFC or an unstable feature. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. finished-final-comment-period The final comment period is finished for this PR / Issue. T-libs-api Relevant to the library API team, which will review and decide on the PR/issue.

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@reitermarkus
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reitermarkus commented Jan 23, 2024

Feature gate: #![feature(generic_nonzero)]

This is a tracking issue for replacing the distinct NonZero* types with a generic NonZero<T> type. This allows using NonZero with FFI type aliases instead of having weird type names like NonZero_c_ulonglong.

This replaces the following tracking issues:

Public API

use core::num::{NonZero, NonZeroU8};

assert_eq!(NonZero::new(33u8), NonZeroU8::new(33));

Steps / History

Unresolved Questions

  • None yet.

Footnotes

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

@reitermarkus reitermarkus added C-tracking-issue Category: A tracking issue for an RFC or an unstable feature. T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. labels Jan 23, 2024
GuillaumeGomez added a commit to GuillaumeGomez/rust that referenced this issue Jan 30, 2024
…=dtolnay

Remove `raw_os_nonzero` feature.

This feature is superseded by a generic `NonZero` type: rust-lang#120257

Closes rust-lang#82363.
rust-timer added a commit to rust-lang-ci/rust that referenced this issue Jan 30, 2024
Rollup merge of rust-lang#120295 - reitermarkus:remove-ffi-nonzero, r=dtolnay

Remove `raw_os_nonzero` feature.

This feature is superseded by a generic `NonZero` type: rust-lang#120257

Closes rust-lang#82363.
@reitermarkus
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@dtolnay, given the documentation issue, making NonZero::new and other constructors generic can really only be done during/after stabilization, so the only blocker I can see right now is stabilization itself. Can this enter FCP, or do we want to wait for #120486?

@dtolnay dtolnay added the I-libs-api-nominated Nominated for discussion during a libs-api team meeting. label Jan 31, 2024
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Feb 3, 2024
…ructors, r=dtolnay,oli-obk

Make `NonZero` constructors generic.

This makes `NonZero` constructors generic, so that `NonZero::new` can be used without turbofish syntax.

Tracking issue: rust-lang#120257

~~I cannot figure out how to make this work with `const` traits. Not sure if I'm using it wrong or whether there's a bug:~~

```rust
101 |         if n == T::ZERO {
    |            ^^^^^^^^^^^^ expected `host`, found `true`
    |
    = note: expected constant `host`
               found constant `true`
```

r? `@dtolnay`
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Feb 4, 2024
…ructors, r=dtolnay,oli-obk

Make `NonZero` constructors generic.

This makes `NonZero` constructors generic, so that `NonZero::new` can be used without turbofish syntax.

Tracking issue: rust-lang#120257

~~I cannot figure out how to make this work with `const` traits. Not sure if I'm using it wrong or whether there's a bug:~~

```rust
101 |         if n == T::ZERO {
    |            ^^^^^^^^^^^^ expected `host`, found `true`
    |
    = note: expected constant `host`
               found constant `true`
```

r? ``@dtolnay``
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Feb 5, 2024
…ructors, r=dtolnay,oli-obk

Make `NonZero` constructors generic.

This makes `NonZero` constructors generic, so that `NonZero::new` can be used without turbofish syntax.

Tracking issue: rust-lang#120257

~~I cannot figure out how to make this work with `const` traits. Not sure if I'm using it wrong or whether there's a bug:~~

```rust
101 |         if n == T::ZERO {
    |            ^^^^^^^^^^^^ expected `host`, found `true`
    |
    = note: expected constant `host`
               found constant `true`
```

r? ```@dtolnay```
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Feb 5, 2024
…ructors, r=dtolnay,oli-obk

Make `NonZero` constructors generic.

This makes `NonZero` constructors generic, so that `NonZero::new` can be used without turbofish syntax.

Tracking issue: rust-lang#120257

~~I cannot figure out how to make this work with `const` traits. Not sure if I'm using it wrong or whether there's a bug:~~

```rust
101 |         if n == T::ZERO {
    |            ^^^^^^^^^^^^ expected `host`, found `true`
    |
    = note: expected constant `host`
               found constant `true`
```

r? ````@dtolnay````
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Feb 5, 2024
…ructors, r=dtolnay,oli-obk

Make `NonZero` constructors generic.

This makes `NonZero` constructors generic, so that `NonZero::new` can be used without turbofish syntax.

Tracking issue: rust-lang#120257

~~I cannot figure out how to make this work with `const` traits. Not sure if I'm using it wrong or whether there's a bug:~~

```rust
101 |         if n == T::ZERO {
    |            ^^^^^^^^^^^^ expected `host`, found `true`
    |
    = note: expected constant `host`
               found constant `true`
```

r? `````@dtolnay`````
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Feb 6, 2024
…ructors, r=dtolnay,oli-obk

Make `NonZero` constructors generic.

This makes `NonZero` constructors generic, so that `NonZero::new` can be used without turbofish syntax.

Tracking issue: rust-lang#120257

~~I cannot figure out how to make this work with `const` traits. Not sure if I'm using it wrong or whether there's a bug:~~

```rust
101 |         if n == T::ZERO {
    |            ^^^^^^^^^^^^ expected `host`, found `true`
    |
    = note: expected constant `host`
               found constant `true`
```

r? `@dtolnay`
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Feb 6, 2024
…ructors, r=dtolnay,oli-obk

Make `NonZero` constructors generic.

This makes `NonZero` constructors generic, so that `NonZero::new` can be used without turbofish syntax.

Tracking issue: rust-lang#120257

~~I cannot figure out how to make this work with `const` traits. Not sure if I'm using it wrong or whether there's a bug:~~

```rust
101 |         if n == T::ZERO {
    |            ^^^^^^^^^^^^ expected `host`, found `true`
    |
    = note: expected constant `host`
               found constant `true`
```

r? ``@dtolnay``
bors added a commit to rust-lang-ci/rust that referenced this issue Feb 7, 2024
…ctors, r=dtolnay,oli-obk

Make `NonZero` constructors generic.

This makes `NonZero` constructors generic, so that `NonZero::new` can be used without turbofish syntax.

Tracking issue: rust-lang#120257

~~I cannot figure out how to make this work with `const` traits. Not sure if I'm using it wrong or whether there's a bug:~~

```rust
101 |         if n == T::ZERO {
    |            ^^^^^^^^^^^^ expected `host`, found `true`
    |
    = note: expected constant `host`
               found constant `true`
```

r? `@dtolnay`
bors added a commit to rust-lang-ci/rust that referenced this issue Feb 8, 2024
…ctors, r=dtolnay

Make `NonZero` constructors generic.

This makes `NonZero` constructors generic, so that `NonZero::new` can be used without turbofish syntax.

Tracking issue: rust-lang#120257

~~I cannot figure out how to make this work with `const` traits. Not sure if I'm using it wrong or whether there's a bug:~~

```rust
101 |         if n == T::ZERO {
    |            ^^^^^^^^^^^^ expected `host`, found `true`
    |
    = note: expected constant `host`
               found constant `true`
```

r? `@dtolnay`
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Feb 9, 2024
…ructors, r=Nilstrieb

Use `transmute_unchecked` in `NonZero::new`.

Tracking issue: rust-lang#120257

See rust-lang#120521 (comment).
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Feb 9, 2024
…ructors, r=Nilstrieb

Use `transmute_unchecked` in `NonZero::new`.

Tracking issue: rust-lang#120257

See rust-lang#120521 (comment).
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Feb 9, 2024
…ructors, r=Nilstrieb

Use `transmute_unchecked` in `NonZero::new`.

Tracking issue: rust-lang#120257

See rust-lang#120521 (comment).
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Feb 9, 2024
…ructors, r=Nilstrieb

Use `transmute_unchecked` in `NonZero::new`.

Tracking issue: rust-lang#120257

See rust-lang#120521 (comment).
rust-timer added a commit to rust-lang-ci/rust that referenced this issue Feb 9, 2024
Rollup merge of rust-lang#120809 - reitermarkus:generic-nonzero-constructors, r=Nilstrieb

Use `transmute_unchecked` in `NonZero::new`.

Tracking issue: rust-lang#120257

See rust-lang#120521 (comment).
github-actions bot pushed a commit to rust-lang/miri that referenced this issue Feb 10, 2024
…r=Nilstrieb

Use `transmute_unchecked` in `NonZero::new`.

Tracking issue: rust-lang/rust#120257

See rust-lang/rust#120521 (comment).
oli-obk added a commit to oli-obk/rust that referenced this issue Feb 13, 2024
…r=dtolnay

Use generic `NonZero` internally.

Tracking issue: rust-lang#120257
oli-obk added a commit to oli-obk/rust that referenced this issue Feb 13, 2024
…r=dtolnay

Make `NonZero::get` generic.

Tracking issue: rust-lang#120257

Depends on rust-lang#120521.

r? `@dtolnay`
@Alonely0
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Alonely0 commented Apr 11, 2024

Just a thought:

I think this could potentially be made user-extensable if there was an API that looked like:

pub trait Zeroable: Copy + StructuralPartialEq + Sized {
  const ZERO: Self;
}

pub struct NonZero<T: Zeroable>(T);

impl<T: Zeroable> NonZero<T> {
  const fn new(v: T) -> Option<Self> {
    if (v == T::ZERO) {
      None
    } else {
      Some(NonZero(v))
    }
  }
  // ...
}

Could we instead have it just be an unsafe marker auto trait (without the associated const), and later on have a WithNiche trait that'd be a generalization in which the niche may or may not be a zeroed bit pattern? Your proposal seems a bit weird to me, since the compiler should be able to create a zeroed bit pattern for any known type. Furthermore, this would allow us to move this particular issue forward while we deal with the complexity of user-defined niches in a separate RFC.

Bikeshed:

use core::mem::MaybeUninit;

unsafe auto trait InvalidZeroed: WithNiche {}
unsafe trait WithNiche {
    const NICHE: Self;
}

unsafe impl<T: InvalidZeroed> WithNiche for T {
    const NICHE: T = unsafe { MaybeUninit::zeroed().assume_init() };
}

@reitermarkus
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reitermarkus commented Apr 11, 2024

the compiler should be able to create a zeroed bit pattern for any known type

The problem is not creating the bit pattern, it's ensuring that pattern is used as a niche, which currently can only be done with #[rustc_layout_scalar_valid_range_{start,end}], i.e. not in user code.

Furthermore, this would allow us to move this particular issue forward

Creating a user-implementable Zeroable trait is not part of this tracking issue, so this is not a blocker in any case.

@RalfJung
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Indeed, any discussion of having user-defined NonZero types is off-topic in this tracking issue.

@rfcbot rfcbot added finished-final-comment-period The final comment period is finished for this PR / Issue. to-announce Announce this issue on triage meeting and removed final-comment-period In the final comment period and will be merged soon unless new substantive objections are raised. labels Apr 11, 2024
@rfcbot
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rfcbot commented Apr 11, 2024

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.

This will be merged soon.

@tmccombs
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Indeed, any discussion of having user-defined NonZero types is off-topic in this tracking issue.

I probably should have been more clear, but the reason I brought it up is I'm not sure if it is merged as is, if it would be possible to change it to allow user-defined NonZero types in the future in a backwards compatible way.

@reitermarkus
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if it would be possible to change it to allow user-defined NonZero types in the future in a backwards compatible way.

Yes, the ZeroablePrimitive trait is perma-unstable and sealed in order to avoid any compatibility issues.

GuillaumeGomez added a commit to GuillaumeGomez/rust that referenced this issue Apr 22, 2024
…e, r=dtolnay

Stabilize generic `NonZero`.

Tracking issue: rust-lang#120257

r? `@dtolnay`
rust-timer added a commit to rust-lang-ci/rust that referenced this issue Apr 23, 2024
Rollup merge of rust-lang#124230 - reitermarkus:generic-nonzero-stable, r=dtolnay

Stabilize generic `NonZero`.

Tracking issue: rust-lang#120257

r? `@dtolnay`
@dtolnay dtolnay closed this as completed Apr 23, 2024
github-actions bot pushed a commit to rust-lang/miri that referenced this issue Apr 23, 2024
RalfJung pushed a commit to RalfJung/rust-analyzer that referenced this issue Apr 27, 2024
RalfJung pushed a commit to RalfJung/rust-analyzer that referenced this issue Apr 27, 2024
Make `NonZero::get` generic.

Tracking issue: rust-lang/rust#120257

Depends on rust-lang/rust#120521.

r? `@dtolnay`
RalfJung pushed a commit to RalfJung/rust-analyzer that referenced this issue Apr 27, 2024
Use generic `NonZero` in tests.

Tracking issue: rust-lang/rust#120257

r? `@dtolnay`
RalfJung pushed a commit to RalfJung/rust-analyzer that referenced this issue Apr 27, 2024
…,wesleywiser

Move generic `NonZero` `rustc_layout_scalar_valid_range_start` attribute to inner type.

Tracking issue: rust-lang/rust#120257

r? `@dtolnay`
@apiraino apiraino removed the to-announce Announce this issue on triage meeting label Apr 29, 2024
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue May 8, 2024
…r=dtolnay

Generic `NonZero` post-stabilization changes.

Tracking issue: rust-lang#120257

r? `@dtolnay`
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue May 8, 2024
…r=dtolnay

Generic `NonZero` post-stabilization changes.

Tracking issue: rust-lang#120257

r? ``@dtolnay``
rust-timer added a commit to rust-lang-ci/rust that referenced this issue May 8, 2024
Rollup merge of rust-lang#124587 - reitermarkus:use-generic-nonzero, r=dtolnay

Generic `NonZero` post-stabilization changes.

Tracking issue: rust-lang#120257

r? ``@dtolnay``
github-actions bot pushed a commit to rust-lang/miri that referenced this issue May 11, 2024
Generic `NonZero` post-stabilization changes.

Tracking issue: rust-lang/rust#120257

r? ``@dtolnay``
flip1995 pushed a commit to flip1995/rust-clippy that referenced this issue May 16, 2024
Generic `NonZero` post-stabilization changes.

Tracking issue: rust-lang/rust#120257

r? ``@dtolnay``
flip1995 pushed a commit to flip1995/rust-clippy that referenced this issue May 24, 2024
Generic `NonZero` post-stabilization changes.

Tracking issue: rust-lang/rust#120257

r? ``@dtolnay``
workingjubilee added a commit to workingjubilee/rustc that referenced this issue Sep 19, 2024
Create `Atomic<T>` type alias

and use it in core/alloc/std where possible, ignoring test files for now.

This is step one, creating the alias from `Atomic<T>` to `AtomicT`. The next step of flipping this and aliasing `AtomicT` to `Atomic<T>` will have a bigger impact, since `AtomicT` imports can be dropped once `Atomic::new` is a usable name.

First commit is the true change. Second commit is mostly mechanical replacement of `AtomicT` type names with `Atomic<T>`.

See [how this was done for `NonZero`](rust-lang#120257) for the rough blueprint I'm following.

- ACP: rust-lang/libs-team#443 (comment)
- Tracking issue: rust-lang#130539
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