Update syn requirement from 1.0.84 to 2.0.58

[dependabot]

Updates the requirements on syn to permit the latest version.

Release notes

Sourced from syn's releases.

2.0.58

• Support $ in custom_punctuation! macro (#1611)

Commits

• 81adad6 Release 2.0.58
• 7247053 Merge pull request #1611 from dtolnay/customdollar
• 990142f Support '$' in custom_punctuation macro
• 4753622 Merge pull request #1610 from dtolnay/sortpunct
• 36a7f67 Sort tokens in the same order between custom_punctuation_len and Token macro
• f104427 Update test suite to nightly-2024-03-31
• 9cea040 Release 2.0.57
• 3c07b78 Release 2.0.56
• 585df47 Merge pull request #1608 from BD103/deps-features
• d7650b2 chore: bump msrv to 1.60 (pt. 2)
• Additional commits viewable in compare view

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[Bromeon]

I thought this would be a not-too-hard change as advertised in the 2.0.0 release notes:

This release contains a batch of syntax tree improvements to incorporate ongoing Rust language development from the past 3.5 years since syn 1.

However, there's a ton of breaking changes, once you scroll down a bit. It also seems like gdnative is affected to a massive degree due to its heavy proc-macro use. I'm not sure if the upgrade is worth it just to stick to the ecosystem -- I would suggest we don't do it unless there are certain syn 2 features that we desperately need, or someone wants to dedicate the time to go through everything.

[chitoyuu]

I agree. syn can't cause semver conflicts in downstream crates unlike normal dependencies, because it's only linked into the proc-macro binary. Since the current implementation is still working well, there isn't really a reason to update "just to stick to the ecosystem", as you've said.

There's a possibility that at some point in the future, some fundamentally new syntax might be added that syn 1 can't handle, and update would become necessary, but I think that should be handled after the fact, if it happens and use cases exist for them together with gdnative.

Since there seems to be an agreement:

@dependabot ignore this major version

[dependabot]

OK, I won't notify you about version 2.x.x again, unless you re-open this PR.