Add regression test for #89436

[Manishearth]

I never got around to adding such a test.

In general I think the yoke crate has a bunch of interesting testcases that exercise various edges of the algorithms here, it would be nice if we could simply depend on the crate and add some tests that exercise it, but I don't think that's possible. Do you or @eddyb think there's any use trying to upstream a bunch of common yoke minimal working example code to the testsuite and having a ton of yoke tests?

[rust-highfive]

r? @Mark-Simulacrum

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[eddyb]

it would be nice if we could simply depend on the crate and add some tests that exercise it, but I don't think that's possible

You could make it a dependency of rustc, heh.

But more seriously, how silly does adding it as a perf benchmark sound?
It's not as good but it can still detect regressions, and it might be genuinely useful if you're hitting e.g. trait system slower edge cases (though I doubt you have metaprogramming on the level of e.g. tower).

[jackh726]

@bors r+ rollup

[bors]

📌 Commit 62edbbe has been approved by jackh726

It is now in the queue for this repository.

[Manishearth]

@eddyb seems a bit silly but i'm open to it if the rust team is okay with perf benchmarks that are Actually Compiler Regression Tests

[Mark-Simulacrum]

We have a number of crates in cargotest that we fetch a pinned commit of and run cargo test in; that seems like a better fit here?

[Manishearth]

Yeah we could do that! I don't know if the yoke crate has full test coverage of the bugs, but I can make sure we do and go fix that.

(One of the reasons I'm wary of leaving this up to crater is that a lot of these things only show up when using the crate, i.e when building tests, which crater does do, but folks do tend to look at test failures less)