shell.nix

{ pkgs ? import <nixpkgs> { overlays = [ ]; }, doBenchmark ? false }:

let

  foo = builtins.fetchGit {
    url = "https://github.com/phadej/splitmix";
    rev = "fcf2d95181c0d4c39dbaf80cd28b6498f24e5f74";
    };

  bar = builtins.fetchGit {
    url = "https://github.com/idontgetoutmuch/random.git";
    rev = "023e812545d2fac849ae64058d64590a63d2fe89";
    ref = "avoid-name-clash";
    };

  f = { mkDerivation, base, random, splitmix, stdenv }:
      mkDerivation {
        pname = "nix-reverse-deps-of-haskell-package";
        version = "0.1.0.0";
        src = ./.;
        isLibrary = false;
        isExecutable = true;
        executableHaskellDepends = [ base random splitmix ];
        license = stdenv.lib.licenses.bsd3;
      };

  variant = if doBenchmark then pkgs.haskell.lib.doBenchmark else pkgs.lib.id;

  drv = variant (pkgs.haskellPackages.callPackage f { random = bar; splitmix = foo; });

in

  if pkgs.lib.inNixShell then drv.env else drv