Re-evaluate policy on lowest supported Rust version

[mulkieran]

Our current development (1.79) is almost a year ahead of our lowest supported (1.71) at this time. Do we have a reason to move up and are we able to move up?

[mulkieran]

We have a lint-related reason now. It's pretty minor, though. We merged a clippy allow that would have been done nicer in a build script. Here's the PR: stratis-storage/devicemapper-rs#928 . Had we been running a newer version of Rust we would have handled that differently, by emitting instructions in build.rs: https://blog.rust-lang.org/2024/05/06/check-cfg.html.

[mulkieran]

We have a more important reason that would require us to move up to 1.77.0, since bindgen 0.70.0 emits code for libcryptsetup which wasn't part of the standard library until 1.77.0. https://doc.rust-lang.org/std/mem/macro.offset_of.html# and https://github.com/stratis-storage/libcryptsetup-rs/actions/runs/10491531137/job/29060894678?pr=348 . No sign of any action in Fedora to update bindgen to new release, but could happen any time. Note that 1.77 is only a bit more than 4.5 months back.

[mulkieran]

I have a feeling that we'll be happy to move up as soon as Fedora puts out a release of bindgen 0.70.0.

[mulkieran]

We have another lint-related reason, reasons are still experimental in our lowest supported:

this Cargo does not support nightly features, but if you
switch to nightly channel you can pass
`-Zlints` to enable this feature.
 Downloading crates ...
  Downloaded termios v0.3.3
   Compiling stratisd v3.7.0 (/__w/stratisd/stratisd)
   Compiling termios v0.3.3
error[E0658]: lint reasons are experimental
  --> src/systemd/bindings.rs:11:5
   |
11 |     reason = "https://github.com/rust-lang/rust-bindgen/issues/2845"
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: see issue #54503 <https://github.com/rust-lang/rust/issues/54503> for more information