forAllSystems = f: genAttrs allSystems (system: f system);

        {
          inherit rustChannel;
          rustc = rustChannel.minimal;
          cargo = rustChannel.minimal;
        };
      forAllSystems = f: genAttrs allSystems (system: f {
        inherit system;
        pkgs = import nixpkgs {
          inherit system;
          overlays = [
            (import rust-overlay)
            rustOverlay
          ];
        };
      });
    in
    {
      devShell = forAllSystems ({ system, pkgs, ... }:
        pkgs.mkShell {

          {
            inherit rustChannel;
            rustc = rustChannel.minimal;
          };
    in {
      devShell = forAllSystems (system:
        let rustDevOverlay = final: prev:
              {
                # rust-analyzer needs core source
                rustc-with-src = prev.rustc.override { extensions = [ "rust-src" ]; };
                # need the latest rustfmt to match apheleia's behaviour
                rustfmt = prev.rust-bin.nightly."2021-10-23".rustfmt;
              };
            pkgs = import nixpkgs {
              inherit system;
              overlays = [
                (import rust-overlay)
                rustOverlay
                rustDevOverlay
              ];
            };
        in pkgs.mkShell {

          buildInputs = with pkgs; [

          packages = with pkgs; [

            (rustChannel.default.override { extensions = [ "rust-src" ]; })

            # needs to be before rustc-with-src so that we're not using the bundled rustfmt
            rustfmt
            rust-analyzer rustc-with-src

        ({ system, pkgs, ... }:

        (system:

            pkgs = import nixpkgs {
              inherit system;
              overlays = [
                (import rust-overlay)
                rustOverlay
              ];
            };