Is the "at most once" modifier useful for these macros

[alok]

rust-lang/rust#56245

I implemented a version of hashmap and ended up having issues with trailing commas. Now that this is stable, would it be useful for this crate?

[bluss]

Very useful, but it's a question if the small gain (we already have a solution for trailing commas) is worth the Rust version requirement change.

[alok]

Maybe another year then? 😁