{ nixpkgs ? import <nixpkgs> {}, compiler ? "ghc882", doBenchmark ? false }:

let
  pkgs = import (builtins.fetchGit {
    name ="nixos-20.03-small";
    url = https://github.com/nixos/nixpkgs-channels/;
    ref = "nixos-20.03-small";
    rev = "afeaca75cf7bd6510699821202c25cbaf778b1ef";
  }) {};

  f = { mkDerivation, base, extra, ghc-lib, ghc-lib-parser
      , hashable, haskell-names, haskell-src-exts, ormolu, stdenv, syb
      , uniplate
      , containers
      , ghc-paths
      , cabal-install
      }:
      mkDerivation {
        pname = "arst";
        version = "0.1";
        src = ./.;
        isLibrary = false;
        isExecutable = true;
        executableHaskellDepends = [
          base extra ghc-lib ghc-lib-parser hashable haskell-names
          haskell-src-exts ormolu syb uniplate
          containers
          ghc-paths
          cabal-install
        ];
        license = stdenv.lib.licenses.mit;
      };

  haskellPackages = if compiler == "default"
                       then pkgs.haskellPackages
                       else pkgs.haskell.packages.${compiler};

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

  drv = variant (haskellPackages.callPackage f {});

in

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