It's not clear from the documentation when particular features were inctoduces or deprecated

[yurivict]

Location

I am looking at the stdsimd feature documentation here.

It looks like this is a current feature based on this page: there are no deprecation notices.

But rust-nightly-1.80.0.20240507 doesn't have this feature:

error[E0635]: unknown feature `stdsimd`
  --> /wrkdirs/usr/ports/lang/frawk/work/frawk-0.4.7/cargo-crates/ahash-0.7.6/src/lib.rs:33:42

It isn't obvious whether it was deprecated or not and not obvious where to get this information in a centralized way.

Summary

Documentation doesn't say when particular features are introduces or deprecated.

[workingjubilee]

@yurivict the std::simd module, AKA feature(portable_simd), has no relationship to feature(stdsimd), due to a quirk of history.

Nightly features are unstable experiments and are subject to total removal if the experiment they represent does not pan out. You must update the ahash version to build that crate with a recent nightly compiler, or use a stable compiler, as the reason that ahash generates that error is because it tries to enable features by automatically detecting a nightly compiler, without those features explicitly being enabled.

[workingjubilee]

@yurivict Hm. I am not sure if this is something you raised out of personal puzzlement or as a FreeBSD committer. In the latter case, what might address your concern more thoroughly is that there is work on an implementation in rustc that will allow controlling what version that rustc appears to be when it compiles a crate, even if you choose to use a nightly compiler, making it easier to pin down dependencies that try to outwit the compiler.

The case of feature(stdsimd) is particularly ironic because the reason it broke is because we split the feature into a few features per architecture (it was a sort of "catch-all" bin of "SIMD intrinsics for ${target_arch}"), to... make it... easier to document and track them all......