Future unexpected_cfgs warning from derive(CheckedBitPattern)

[kpreid]

Use Rust nightly or beta (1.84.0-beta.1), bytemuck 1.20.0, and compile this trivial program:

#[derive(Clone, Copy, bytemuck::CheckedBitPattern)]
#[repr(C)]
struct Foo {}

to receive this warning:

warning: unexpected `cfg` condition value: `spirv`
 --> src/lib.rs:1:23
  |
1 | #[derive(Clone, Copy, bytemuck::CheckedBitPattern)]
  |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: expected values for `target_arch` are: `aarch64`, `arm`, `arm64ec`, `avr`, `bpf`, `csky`, `hexagon`, `loongarch64`, `m68k`, `mips`, `mips32r6`, `mips64`, `mips64r6`, `msp430`, `nvptx64`, `powerpc`, `powerpc64`, `riscv32`, `riscv64`, `s390x`, `sparc`, `sparc64`, `wasm32`, `wasm64`, `x86`, `x86_64`, and `xtensa`
  = note: see <https://doc.rust-lang.org/nightly/rustc/check-cfg/cargo-specifics.html> for more information about checking conditional configuration
  = note: `#[warn(unexpected_cfgs)]` on by default
  = note: this warning originates in the derive macro `bytemuck::CheckedBitPattern` (in Nightly builds, run with -Z macro-backtrace for more info)

[Lokathor]

@CryZe i think you added the spirv support? did the name change or something?

[zachs18]

The lint configurations for bytemuck/bytemuck_derive itself don't apply to crates using bytemuck's derive macros, so the cfg_attr(not(target_arch = "spirv"), derive(Debug)) for the FooBits type generated by derive(CheckedBitPattern) hits the lint, since spirv is not an in-tree target IIUC.