Reimplement ~const trait specialization#133325
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compiler-errors
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Nov 22, 2024
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| debug!("fulfill_implication: an impl for {:?} specializes {:?}", source_trait, target_trait); | ||
| // If the parent impl is const, then the specializing impl must be const. |
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Note to self: Actually I don't know if this is correct -- well, it's not sufficient.
const trait Bar {}
impl const Bar for T {}
const trait Foo {}
impl const Foo for T where T: ~const Bar {}
// specializing impl:
impl Foo for (T,) {}
The specializing impl satisfies (T,): ~const Bar because of the blanket impl, but it's still less const than the parent impl. I think we need to check that the specializing impl is also conditionally const, and then bail.
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not 100% confident that I can review the specialization impl, but the tests lgtm.
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lcnr
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Dec 2, 2024
| @@ -230,23 +231,26 @@ pub(super) fn specialization_enabled_in(tcx: TyCtxt<'_>, _: LocalCrate) -> bool | |||
| /// `impl1` specializes `impl2` if it applies to a subset of the types `impl2` applies | |||
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comment is outdated after your rename
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also, I feel like it's very helpful to explicitly write down "We therefore prove that the specializing impl implies the parent impl".
Because then it feels clear why we're instantiating the specializing impl with placeholders and the parent impl with existentials and prove all bounds of the parent impül
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@bors r=lcnr,fee1-dead |
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…iaskrgr Rollup of 6 pull requests Successful merges: - rust-lang#132723 (Unify `sysroot_target_{bin,lib}dir` handling) - rust-lang#133041 (Print name of env var in `--print=deployment-target`) - rust-lang#133325 (Reimplement `~const` trait specialization) - rust-lang#133395 (Add simd_relaxed_fma intrinsic) - rust-lang#133517 (Deeply normalize when computing implied outlives bounds) - rust-lang#133785 (Add const evaluation error UI test.) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of rust-lang#133325 - compiler-errors:const-spec, r=lcnr,fee1-dead Reimplement `~const` trait specialization Reimplement const specialization. We need this for `PartialEq` constification :) r? lcnr
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Reimplement const specialization. We need this for
PartialEqconstification :)r? lcnr