proc-macro-error is unmaintained

[jayvdb]

c.f. rustsec/advisory-db#2057

Perhaps your approach here is worth being an alternative? Is it ready to be published?

note https://crates.io/crates/proc-macro-error2 already exists, so that name cant be used.

[GnomedDev]

This fork is the same as my proc-macro-error2 but without the CI fixes and other cleanups due to MSRV bump.