DeriveWhere on packed structs causes `reference to packed field is unaligned` errors.

[stegaBOB]

All of the match statements internally that get references to the fields cause this issue. Currently the std lib detects if the struct is #[repr(packed)] and adds implicit Fields: Copy bounds to the derive and copies out all the fields instead. Serde does something similar. I think it should be relatively* straightforward to add that in here too. I'd be more than happy to PR that in if its something you would be willing to accept.

*it might actually be a bit more complicated. The self match destructuring might need to be replaced for this. Technically possible to add a Self: Copy bound and still match without the refs, but it wouldn't be optimal.

[ModProg]

Sounds reasonable. Feel free to give it a go and ask if you encounter anything strange.

[stegaBOB]

I'll try to get something out next week!