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Add const stability tracking for traits #16

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RalfJung opened this issue Nov 10, 2024 · 0 comments · May be fixed by rust-lang/rust#133999
Open

Add const stability tracking for traits #16

RalfJung opened this issue Nov 10, 2024 · 0 comments · May be fixed by rust-lang/rust#133999

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@RalfJung
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RalfJung commented Nov 10, 2024 •
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I think we should add support for #[rustc_const_(un)stable] attributes on traits. That would set a feature gate which would be required to

  • use this trait in a ~const Trait or const Trait bound
  • write a const impl for that trait
  • call any function from this trait in const context

(All of these also require the const_trait_impl feature gate on top of the per-trait feature gate.)

Currently we have a #[const_trait] attribute; every trait in a staged-api crate that has that attribute should then also be required to have a const stability attribute.

For now, making such a trait rustc_const_stable should be forbidden since the feature is not ready yet. Or maybe we rely on the extra gating with the const_trait_impl feature for that? Once a trait is rustc_const_stable, all its const impl must also be marked rustc_const_stable.
@RalfJung RalfJung mentioned this issue Nov 10, 2024
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@tyrone-wu tyrone-wu mentioned this issue Nov 10, 2024
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@fee1-dead fee1-dead mentioned this issue Nov 20, 2024
Merged
GuillaumeGomez added a commit to GuillaumeGomez/rust that referenced this issue Nov 21, 2024
@GuillaumeGomez
Rollup merge of rust-lang#133237 - fee1-dead-contrib:constadd, r=comp…
09bc5fa 
…iler-errors

Minimally constify `Add`

* This PR removes the requirement for `impl const` to have a const stability attribute. cc `@RalfJung` I believe you mentioned that it would make much more sense to require `const_trait`s to have const stability instead. I agree with that sentiment but I don't think that is _required_ for a small scale experimentation like this PR. rust-lang/project-const-traits#16 should definitely be prioritized in the future, but removing the impl check should be good for now as all callers need `const_trait_impl` enabled for any const impl to work.
* This PR is intentionally minimal as constifying other traits can become more complicated (`PartialEq`, for example, would run into requiring implementing it for `str` as that is used in matches, which runs into the implementation for slice equality which uses specialization)

Per the reasons above, anyone who is interested in making traits `const` in the standard library are **strongly encouraged** to reach out to us on the [Zulip channel](https://rust-lang.zulipchat.com/#narrow/channel/419616-t-compiler.2Fproject-const-traits) before proceeding with the work.

cc `@rust-lang/project-const-traits`

I believe there is prior approval from libs that we can experiment, so

r? project-const-traits
jhpratt added a commit to jhpratt/rust that referenced this issue Nov 22, 2024
@jhpratt
Rollup merge of rust-lang#133237 - fee1-dead-contrib:constadd, r=comp…
17a440e 
…iler-errors

Minimally constify `Add`

* This PR removes the requirement for `impl const` to have a const stability attribute. cc ``@RalfJung`` I believe you mentioned that it would make much more sense to require `const_trait`s to have const stability instead. I agree with that sentiment but I don't think that is _required_ for a small scale experimentation like this PR. rust-lang/project-const-traits#16 should definitely be prioritized in the future, but removing the impl check should be good for now as all callers need `const_trait_impl` enabled for any const impl to work.
* This PR is intentionally minimal as constifying other traits can become more complicated (`PartialEq`, for example, would run into requiring implementing it for `str` as that is used in matches, which runs into the implementation for slice equality which uses specialization)

Per the reasons above, anyone who is interested in making traits `const` in the standard library are **strongly encouraged** to reach out to us on the [Zulip channel](https://rust-lang.zulipchat.com/#narrow/channel/419616-t-compiler.2Fproject-const-traits) before proceeding with the work.

cc ``@rust-lang/project-const-traits``

I believe there is prior approval from libs that we can experiment, so

r? project-const-traits
jieyouxu added a commit to jieyouxu/rust that referenced this issue Nov 22, 2024
@jieyouxu
Rollup merge of rust-lang#133237 - fee1-dead-contrib:constadd, r=comp…
15d66c3 
…iler-errors

Minimally constify `Add`

* This PR removes the requirement for `impl const` to have a const stability attribute. cc ```@RalfJung``` I believe you mentioned that it would make much more sense to require `const_trait`s to have const stability instead. I agree with that sentiment but I don't think that is _required_ for a small scale experimentation like this PR. rust-lang/project-const-traits#16 should definitely be prioritized in the future, but removing the impl check should be good for now as all callers need `const_trait_impl` enabled for any const impl to work.
* This PR is intentionally minimal as constifying other traits can become more complicated (`PartialEq`, for example, would run into requiring implementing it for `str` as that is used in matches, which runs into the implementation for slice equality which uses specialization)

Per the reasons above, anyone who is interested in making traits `const` in the standard library are **strongly encouraged** to reach out to us on the [Zulip channel](https://rust-lang.zulipchat.com/#narrow/channel/419616-t-compiler.2Fproject-const-traits) before proceeding with the work.

cc ```@rust-lang/project-const-traits```

I believe there is prior approval from libs that we can experiment, so

r? project-const-traits
jieyouxu added a commit to jieyouxu/rust that referenced this issue Nov 23, 2024
@jieyouxu
Rollup merge of rust-lang#133237 - fee1-dead-contrib:constadd, r=comp…
569656a 
…iler-errors

Minimally constify `Add`

* This PR removes the requirement for `impl const` to have a const stability attribute. cc `@RalfJung` I believe you mentioned that it would make much more sense to require `const_trait`s to have const stability instead. I agree with that sentiment but I don't think that is _required_ for a small scale experimentation like this PR. rust-lang/project-const-traits#16 should definitely be prioritized in the future, but removing the impl check should be good for now as all callers need `const_trait_impl` enabled for any const impl to work.
* This PR is intentionally minimal as constifying other traits can become more complicated (`PartialEq`, for example, would run into requiring implementing it for `str` as that is used in matches, which runs into the implementation for slice equality which uses specialization)

Per the reasons above, anyone who is interested in making traits `const` in the standard library are **strongly encouraged** to reach out to us on the [Zulip channel](https://rust-lang.zulipchat.com/#narrow/channel/419616-t-compiler.2Fproject-const-traits) before proceeding with the work.

cc `@rust-lang/project-const-traits`

I believe there is prior approval from libs that we can experiment, so

r? project-const-traits
jieyouxu added a commit to jieyouxu/rust that referenced this issue Nov 23, 2024
@jieyouxu
Rollup merge of rust-lang#133237 - fee1-dead-contrib:constadd, r=comp…
75b8f43 
…iler-errors

Minimally constify `Add`

* This PR removes the requirement for `impl const` to have a const stability attribute. cc ``@RalfJung`` I believe you mentioned that it would make much more sense to require `const_trait`s to have const stability instead. I agree with that sentiment but I don't think that is _required_ for a small scale experimentation like this PR. rust-lang/project-const-traits#16 should definitely be prioritized in the future, but removing the impl check should be good for now as all callers need `const_trait_impl` enabled for any const impl to work.
* This PR is intentionally minimal as constifying other traits can become more complicated (`PartialEq`, for example, would run into requiring implementing it for `str` as that is used in matches, which runs into the implementation for slice equality which uses specialization)

Per the reasons above, anyone who is interested in making traits `const` in the standard library are **strongly encouraged** to reach out to us on the [Zulip channel](https://rust-lang.zulipchat.com/#narrow/channel/419616-t-compiler.2Fproject-const-traits) before proceeding with the work.

cc ``@rust-lang/project-const-traits``

I believe there is prior approval from libs that we can experiment, so

r? project-const-traits
rust-timer added a commit to rust-lang-ci/rust that referenced this issue Nov 23, 2024
@rust-timer
Unrolled build for rust-lang#133237
a9fa63d 
Rollup merge of rust-lang#133237 - fee1-dead-contrib:constadd, r=compiler-errors

Minimally constify `Add`

* This PR removes the requirement for `impl const` to have a const stability attribute. cc ``@RalfJung`` I believe you mentioned that it would make much more sense to require `const_trait`s to have const stability instead. I agree with that sentiment but I don't think that is _required_ for a small scale experimentation like this PR. rust-lang/project-const-traits#16 should definitely be prioritized in the future, but removing the impl check should be good for now as all callers need `const_trait_impl` enabled for any const impl to work.
* This PR is intentionally minimal as constifying other traits can become more complicated (`PartialEq`, for example, would run into requiring implementing it for `str` as that is used in matches, which runs into the implementation for slice equality which uses specialization)

Per the reasons above, anyone who is interested in making traits `const` in the standard library are **strongly encouraged** to reach out to us on the [Zulip channel](https://rust-lang.zulipchat.com/#narrow/channel/419616-t-compiler.2Fproject-const-traits) before proceeding with the work.

cc ``@rust-lang/project-const-traits``

I believe there is prior approval from libs that we can experiment, so

r? project-const-traits
@fee1-dead fee1-dead linked a pull request Dec 7, 2024 that will close this issue
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Implement trait const stability fee1-dead-contrib/rust
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@RalfJung