Add const stability tracking for traits #16
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GuillaumeGomez
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Nov 21, 2024
…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
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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~const Traitorconst Traitboundconst implfor that trait(All of these also require the
const_trait_implfeature 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_stableshould be forbidden since the feature is not ready yet. Or maybe we rely on the extra gating with theconst_trait_implfeature for that? Once a trait isrustc_const_stable, all itsconst implmust also be markedrustc_const_stable.The text was updated successfully, but these errors were encountered: