{
  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";

  outputs =
    inputs:
    let
      system = "x86_64-linux";
      pkgs = inputs.nixpkgs.legacyPackages.${system};
    in
    {
      devShells.${system}.default = pkgs.mkShell {
        packages = with pkgs; [
          rustc
          cargo
        ];
      };
    };
}

In reply to @curid:matrix.org
don't i need to learn what a function is first?

Didn't get any bites in the main channel --

I've been hoping to get this PR working for darwin -- a python / rust (via maturin / PyO3) project that I think just needs to enable the system feature of the libffi-sys crate (same fix as https://github.com/NixOS/nixpkgs/pull/368102).

Unfortunately in this case the libffi-sys crate is a few dependencies deep, and the parent packages don't expose any feature flags to enable libffi/system (which enables libffi-sys/system):

$ cargo tree -i libffi-sys
libffi-sys v3.2.0
├── deno_ffi v0.190.0
│   └── deno_runtime v0.211.0
│       └── vl-convert-rs v1.7.0 (/private/tmp/nix-build-python3.12-vl-convert-python-1.7.0.drv-0/source/vl-convert-rs)
│           ├── vl-convert v1.7.0 (/private/tmp/nix-build-python3.12-vl-convert-python-1.7.0.drv-0/source/vl-convert)
│           └── vl-convert-python v1.7.0 (/private/tmp/nix-build-python3.12-vl-convert-python-1.7.0.drv-0/source/vl-convert-python)
└── libffi v4.0.0
    └── deno_ffi v0.190.0 (*)

Any suggestions for enabling this feature flag a few dependency layers deep?