regression: alloc::prelude removed

[Mark-Simulacrum]

#89898 removed alloc::prelude, which was unstable, but some crates depended on it with absolute paths (which is a known stability hole):

• https://crater-reports.s3.amazonaws.com/beta-1.57-1/beta-2021-10-22/reg/ceres-std-0.2.0/log.txt (cc @clearloop)
• https://crater-reports.s3.amazonaws.com/beta-1.57-rustdoc-1/beta-2021-10-22/reg/no_proto-0.9.60/log.txt

[Mark-Simulacrum]

I think we likely want to just close this but wanted to file it for awareness, but I don't expect even a relnotes inclusion since it's a pretty clear use of an unstable feature.

[nbdd0121]

How many crates are affected?

[Mark-Simulacrum]

1 -- with the usual caveat of "that Crater detected". But I expect breakage to be minimal, and the migration to a stable path for any affected uses should be fairly easy.

[jhpratt]

Given that this is only a single known crate with 90 all-time downloads, I'm inclined to close this as well. Unstable APIs are unstable for a reason.

That said, what can be done about this stability hole? I just checked the source code for the crate and it doesn't do anything out of the ordinary. Is there documentation of this bug somewhere?

[nbdd0121]

It's #15702

[jhpratt]

Wow, that's an old issue.

[m-ou-se]

Closing this, as the impact seems very minimal. A solution for #15702 would be nice.

[Mark-Simulacrum]

no-proto is also broken, cc @only-cliches -- discovered in the rustdoc crater run.

https://crater-reports.s3.amazonaws.com/beta-1.57-rustdoc-1/beta-2021-10-22/reg/no_proto-0.9.60/log.txt