Build fails on current nightly (1.74.0-nightly), due to known proc-macro2 issue

[64kramsystem]

On the current nightly (1.74.0-nightly), compilation fails with this error:

error[E0635]: unknown feature `proc_macro_span_shrink`
  --> /home/saverio/.cargo/registry/src/index.crates.io-6f17d22bba15001f/proc-macro2-1.0.56/src/lib.rs:92:30
   |
92 |     feature(proc_macro_span, proc_macro_span_shrink)
   |                              ^^^^^^^^^^^^^^^^^^^^^^

This issue is known and it has been solved in proc-macro2 v1.0.60, so I think the project should update the dependency.

[64kramsystem]

I've noticed that this has been fixed in mrml-ruby's master (9e0e75e); it'd be convenient if a new version with that commit was released, but for reference, it can also be worked around by using an env variable export RUSTUP_TOOLCHAIN=stable).

[jonian]

Hi @64kramsystem, thanks for the report. I have released a new version.