On Mon, Jun 29, 2026 at 5:52 AM Nika Krasnova <[email protected]> wrote: > > The standard library gained core::cfg_select! for exactly this (stable > since Rust 1.95.0): one macro that emits the first arm whose cfg > predicate holds. The kernel's MSRV is 1.85.0, so it is not yet > available.
We can use unstable features before the are stable -- from a quick look, `cfg_match!` (its previous name) has been there since Rust 1.74.0, with the new name since Rust 1.89.0, and with the latest behavior change since Rust 1.91.0. (I didn't take a close look, just going by the tracking issue). When something like this happens, we typically want to consider whether it makes sense to reuse (internally) the original (if it makes sense -- probably not here) or "forward"/re-export to the upstream one when behavior matches. For instance, instead of waiting for the MSRV bump, could we already use the upstream one since Rust 1.91.0? That means that we are already sure we are using the upstream one as-is. Or is there a reason to avoid that? Thanks! Cheers, Miguel
