Update syn requirement from 1.0.81 to 2.0.6

[dependabot]

Updates the requirements on syn to permit the latest version.

Commits

• 7840102 Release 2.0.6
• e76d644 Merge pull request #1420 from dtolnay/nonbracemacro
• 6dcc480 Keep non-brace macro invocations in trailing expr position as Expr::Macro
• d12db40 Merge pull request #1419 from dtolnay/expectedsemi
• 69c5efc Improve error message on missing ';' between statements
• fd18254 Release 2.0.5
• 4df4c4e Merge pull request #1417 from dtolnay/exprmacro
• f591c40 Provide Expr::Macro even with features="full" off
• fb1062f Eliminate allow_struct args in non-full mode
• 99de683 Factor out Path::is_mod_style private method
• Additional commits viewable in compare view

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Fixes #249 > Note

Automatic rebases have been disabled on this pull request as it has been open for over 30 days.

[dependabot]

A newer version of syn exists, but since this PR has been edited by someone other than Dependabot I haven't updated it. You'll get a PR for the updated version as normal once this PR is merged.

[tyranron]

@JelteF @ilslv well, the problem of failing tests is dtolnay/syn#1414. syn::Path doesn't parse keywords as syn::Ident anymore, so we have a problem with parsing ref in our attributes. There are two ways of resolving this:

1. Replace ref with r#ref and leave the current parsing code "as is" (like serde_with does).
2. Preserve using ref, but rewrite attribute parsing to our own types.

I'd vote for the option 2, despite it requires more work. This also interferes with #248.

[ilslv]

@tyranron I definitely vote for option 2 too.

[JelteF]

I think r#ref looks extremly ugly. I'm hoping the syn maintainer will fix this regression: dtolnay/syn#1414

But in case they don't I think I'd prefer changing the name over impleminting our own parsing, i.e. changing the name tho reference or something not to r#ref

[JelteF]

Okay so after looking into it more, it seems that custom parsing would be fine too. As long as we only skip parsing the full list as as a meta list again. We can still use syn to parse the elements of the list though.

[JelteF]

Still maybe changing ref to reference is the nicer option. I definitely wouldn't have gone with ref over reference when creating this feature originally if it required writing custom parsing code. Now that it becomes a breaking change, it becomes a different question though. But I'd say it's a small enough breaking change, with an easy way of addressing it, that it shouldn't hurt too badly for the few users of this feature.

[tyranron]

@JelteF reference is too long, ref is just much more ergonomic.

Regarding custom parsing - I don't see this as a minus. Outside derive_more I do use custom parsing most of the time (even before syn 2.0), because it's much easier to read such code and understand, as the parsed stuff explicitly defined in meaningful types. The same why we prefer derive(Deserialize) on a struct rather than tinkering around serde_json::Value.

I will try to finish this PR in next few days.

[JelteF]

Alrigth sounds good, let's go with the custom parsing for ref then.

[JelteF]

@tyranron friendly ping :). I feel like we're super close to releasing 1.0

[tyranron]

@JelteF I'm super sorry, have been so overwhelmed on my job last weeks that couldn't even touch it. Now it seems I start getting some time for open source again, and getting derive_more released is my primary focus.

I've implemented minimal polyfill for parsing ref, it works now. However, some new problems arose from fmt macros. Will fix them tomorrow.

[tyranron]

@JelteF ping 🙃

[tyranron]

@JelteF ping