Auto merge of #99210 - Dylan-DPC:rollup-879cp1t, r=Dylan-DPC

Auto merge of #99210 - Dylan-DPC:rollup-879cp1t, r=Dylan-DPC

Rollup of 5 pull requests

Successful merges:

 - #98574 (Lower let-else in MIR)
 - #99011 (`UnsafeCell` blocks niches inside its nested type from being available outside)
 - #99030 (diagnostics: error messages when struct literals fail to parse)
 - #99155 (Keep unstable target features for asm feature checking)
 - #99199 (Refactor: remove an unnecessary `span_to_snippet`)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup