Implement trait upcasting #821
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I guess this is for r-a? But jack is working on switching it to use the new solver, and has made a lot of progress already. |
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@lqd yes, this is for r-a. I started looking into it since it blocks stabilization of trait upcasting (rust-lang/rust#134367 (comment)). |
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Ah I see, it seems worthwhile to land to unblock stabilization then. |
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@WaffleLapkin: Can you please unset the style edition? This is both churn, and more importantly this crate needs to build on stable. The edition is not stable, so unless you want to wait until edition 2024 is stable in February to land this, then it should be reverted. |
The rest of the code uses A/B, so use them here too.
Co-authored-by: Ryo Yoshida <[email protected]>
Co-authored-by: Ryo Yoshida <[email protected]>
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@compiler-errors forgot for a moment that 2024 edition is not stable yet, oops /_= I undid formatting changes. |
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Let's maybe wait for a review from someone who does understand it then 😆 I'll give this a look when I'm back from the bakery |
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heh, fair. (not that my approvals matters much anyways, i can't merge it!) |
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I'll take another look at this over the weekend. I've read through #796 a while ago and nothing seemed surprising at the time (just didn't put enough thought into it to feel completely confident). One note is that I think auto releases may currently be broken, so we'll have to follow up with a manual release, I think, to fix things. |
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I feel like what's missing here is a test with the super trait being under a binder (e.g. trait Principal where for<'a> Self: Super<'a>. I assume we can do this without modifying any of the test parsing code - if we can't, then I think it's okay to land this with just a FIXME added.
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does chalk represent dyn for<'a> Trait<'a>? I assume that forall<'a> dyn Trait + 'a is a distinct thing from dyn for<'a> Trait + 'a. If it can represent that then it would probably also be good to test dyn for<'a> Trait<'a> can be upcasted to dyn for<'a> Super<'a> given some trait Trait<'a>: Super<'a> in addition to the case of trait: for<'a> Super<'a>
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I think it should be able to (there is certainly ir for it, but I'm not sure exactly how to specify it in the parser). If you can't figure it out, I'll look at it this evening.
That's a good test to add for sure.
@jackh726 are you going to release a new version? 👀 |
This is based on #796, but with a few more changes.
cc @Veykril @lowr @jackh726