release.nix

{ pkgs ? import <nixpkgs> { } }:

let
  overlayHaskellPackages = haskellPackages: overlay: haskellPackages.override (origAttrs: {
    overrides = pkgs.lib.composeExtensions (origAttrs.overrides or (_: _: {})) overlay;
  });

  name = baseNameOf (dirOf __curPos.file);

  haskellPackages = overlayHaskellPackages pkgs.haskellPackages (self: super: {
    "${name}" = super.callCabal2nix name ./. { };
  });

in haskellPackages.${name}

shell.nix

{ ... }@args: (import ./release.nix args).env