Syn/2.0

[weiznich]

This updates our dependency on syn to the latest 2.0 release. Also it removes the proc_macro_error crate as that requires syn 1.x

[pksunkara]

Would you mind if we use a forked version of proc_macro_error? We need that for clap also.

[pksunkara]

Why not? Wouldn't we want to check that all features work on minimal dep versions?

[weiznich]

Because --all-features would enable the nightly feature for diesel-derives, which in turn would enable an unstable rustc feature, which in turn will not compile on a stable release.
The feature list is equivalent to --all-features with the nightly feature removed.

[weiznich]

Would you mind if we use a forked version of proc_macro_error

I'm fine with using a forked version of that crate as long as:

• It's maintained by someone I trust. (Which is the case for the clap team for example)
• It's ready before we cut the next release.

There is another reasons why I moved away from proc_macro_error: The old implementation used to generate panic's to generate error messages in quite a few cases. That's not considered good practice anymore. You should rather use compile_error! instead. That's fixed by this PR, by having results and moving the error handling up to the top level.

[pksunkara]

I am willing to maintain it in either this org or clap org.

But before I start doing that, I would like to ask @epage's opinion first because clap is going to have the same issue.

[epage]

Would you mind if we use a forked version of proc_macro_error? We need that for clap also.

I already removed proc-macro-error from clap in clap-rs/clap#4777