unsupported proc macro punctuation character '_' from v1.0.69 -> v1.0.89

[Kreijstal]

I was trying to update this subdirectory https://github.com/pascalkuthe/OpenVAF/tree/master/sourcegen using cargo update... but for some reason what was allowed on 1.0.69 is now simply not allowed? I can't tell why it's detecting a rogue _. Is this a proc_macro2 bug?

[Veykril]

We've hit this in rust-analyzer as well where we were updating from 1.0.86 to latest (happened within a quote! invocation)

[Kreijstal]

We've hit this in rust-analyzer as well where we were updating from 1.0.86 to latest (happened within a quote! invocation)

It seems the bug gets in the way even on 1.0.69 to 1.0.70 weird!

[anjx123]

Seems to be due to a change made in this issue:

https://github.com/dtolnay/proc-macro2/issues/470

We are seeing the same issue with: '(' as well.

[Veykril]

Ah, the comments in that thread explain things actually. _ is an identifier in the proc-macro API (and in rust in general I believe), so the error here is actually correct.

[chrysn]

@anjx123: c2rust had that issue too, but has since just moved away from single parentheses in https://github.com/immunant/c2rust/pull/1197. (I don't know proc macros well enough to have an opinion on whether proc-macro broke c2rust without a semver bump or whether c2rust did already hold it wrong, just observed that their code looked simpler after the fix.)