Result box error tests

[U007D]

No description provided.

[rust-highfive]

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[cramertj]

@U007D Is there a reason this is in a separate PR from #47544 ?

[U007D]

Yes, because I messed something up? ;) Seriously, no, it's supposed to be integrated with the other PR. Let me look into what I button I fat-fingered...

(I figured out what happened. Github defaults to merging back to the rust-lang/master branch instead of my local fork's master, and I missed that. Sorry for the noise!)

[cramertj]

No problem!