Update to syn-2

[maurer]

This won't test cleanly or go in yet, as it depends on synstructure updating to support syn-2 (this is trivial, but hasn't landed yet).

Uploading the code for review in case you have feedback before it's landable.

[tarcieri]

It might also be worth dropping synstructure. zeroize_derive isn't a particularly complicated proc macro.

Never mind, synstructure has been updated.

[maurer]

I missed the edit and wrote a commit removing the synstructure dep. Do you want me to drop that commit or leave it in?

[tarcieri]

Oh, if you’ve already done it one fewer dependency is great, thank you!

[tarcieri]

Hmm, seems like the zeroize tests are failing on fields that use #[zeroize(skip)] because they aren't being accessed.

I think you could go ahead and add #[allow(unused_variables)] to those fields?

[maurer]

Added the #[allow(unused_variables)], and put a #![deny(warnings)] into the zeroize derive test that was breaking - it had scrolled past clean locally because the warnings got pushed off the screen, but you must be overriding that in CI somewhere. That should make it fail locally for others.

[tarcieri]

We deny warnings in CI but allow them locally to make refactoring easier. I'd suggest removing the #![deny(warnings)].

[tarcieri]

Hmm, seems this will entail an MSRV bump for the derive feature. That's fine.

[tarcieri]

I opened #869 which does a 2021 edition upgrade for zeroize and zeroize_derive

[tarcieri]

@maurer if you rebase it should take care of the MSRV-related issues

[tarcieri]

Awesome, thanks!