Unsafe code - Rust native support available now (?)

[cylewitruk]

The comment in the following code block pointing to a PR in rust-lang, which seems to have been superseded by merged PR 109698, maybe warrants a fresh look at the usage of unsafe here?

https://github.com/clap-rs/clap/blob/3aeea916e8e426e8389357a67d9b8f9a1fceba3e/clap_lex/src/ext.rs#L272C24-L272C24

[epage]

I wrote rust-lang/rust#109698 based on my work within clap. Our use of unsafe meets the new guidelines that will be stabilized this week. We'll update to the new API when 1.74 becomes our MSRV.