regression: inline, used attr no longer accepted in more places

[Mark-Simulacrum]

inline:

• https://crater-reports.s3.amazonaws.com/beta-1.51-1/beta-2021-02-14/reg/debug_iterator-0.1.0/log.txt
• https://crater-reports.s3.amazonaws.com/beta-1.51-1/beta-2021-02-14/gh/museun.debug_iterator/log.txt

used:

• https://crater-reports.s3.amazonaws.com/beta-1.51-1/beta-2021-02-14/gh/nickyc975.RustWebServer/log.txt

Filing primarily so that we can get this documented in release notes as a compatibility note (if it isn't already); cc @XAMPPRocky

[lcnr]

That's surprising, iirc the crater runs we did during the PRs didn't notice any regressions 🤔

[lcnr]

inline PR is #77015

[apiraino]

(removing I-prioritize autolabel added from bot)