Get rid of HIR const checker #133321
Get rid of HIR const checker #133321
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r? @wesleywiser rustbot has assigned @wesleywiser. Use |
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Some changes occurred to the CTFE machinery cc @rust-lang/wg-const-eval |
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I didn't even know we had another const checker... |
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| = note: see issue #87575 <https://github.com/rust-lang/rust/issues/87575> for more information | ||
| = help: add `#![feature(const_for)]` to the crate attributes to enable |
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This helpful hint seems to have been lost?
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Notably, enabling this gate is neither necessary nor sufficient under const traits. I should have noted that.
If and when we work out how cons stability works for const traits it may, but it's just misleading today.
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It's just quite frustrating to get a nightly feature error without any hint about what the feature gate is. If I first get an error saying to enable const_for, and then another error saying to enable const_trait_impl, that's a lot better IMO.
Or does the const_for gate not actually do anything right now?
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AFAICT it does not do anything.
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Ah. Then it should mention const_trait_impl, no?
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No. Iterator is not a const trait yet.
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Oh, I see.
Yeah then the new error is fine. Maybe entirely remove the const_for symbol (and the others that were used only in the HIR const checker).
| --> $DIR/try.rs:6:5 | ||
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| LL | x?; | ||
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| = note: see issue #74935 <https://github.com/rust-lang/rust/issues/74935> for more information | ||
| = help: add `#![feature(const_try)]` to the crate attributes to enable |
As far as I can tell, the HIR const checker was implemented in #66170 because we were not able to issue useful const error messages in the MIR const checker.
This seems to have changed in the last 5 years, probably due to work like #90532. I've tweaked the diagnostics slightly and think the error messages have gotten better in fact.
Thus I think the HIR const checker has reached the end of its usefulness, and we can retire it.
cc @RalfJung