Make slice comparisons const #143925
Make slice comparisons const #143925
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oli-obk
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| let mut attrs = thin_vec![cx.attr_word(sym::automatically_derived, self.span),]; | ||
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| if self.is_const && self.is_staged_api_crate { |
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There's clearly something interesting going on here, please add a comment explaining what.
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I'm fine with this being a temporary solution. To me, we should change #[derive_const(PartialEq)] to something like #[derive(PartialEq(const))] (syntax to-be-bikeshedded), then we can have #[derive(PartialEq(const, unstable))] in all standard library crates.
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How does it know which feature gate to use...?
We're fairly close to actually enforcing feature stability on impls (#140399) so this question matters soon, IIUC.
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it doesn't. All derived const trait impls are under the derive_const feature gate
| @@ -115,11 +119,13 @@ where | |||
| // Implemented as explicit indexing rather | |||
| // than zipped iterators for performance reasons. | |||
| // See PR https://github.com/rust-lang/rust/pull/116846 | |||
| for idx in 0..self.len() { | |||
| let mut idx = 0; | |||
| while idx < self.len() { | |||
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This should get a FIXME(const-hack).
Also make it *only* usable on nightly
oli-obk
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| let mut attrs = thin_vec![cx.attr_word(sym::automatically_derived, self.span),]; | ||
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| if self.is_const && self.is_staged_api_crate { |
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I'm fine with this being a temporary solution. To me, we should change #[derive_const(PartialEq)] to something like #[derive(PartialEq(const))] (syntax to-be-bikeshedded), then we can have #[derive(PartialEq(const, unstable))] in all standard library crates.
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@bors r+ rollup |
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This needed a fix for
derive_const, too, as it wasn't usable in libcore anymore as trait impls need const stability attributes. I think we can't use the same system as normal trait impls whileconst_trait_implis still unstable.r? @fee1-dead
cc #143800