{ pkgs, stdenv, ghc
, packageSetConfig ? (self: super: {})
, overrides ? (self: super: {})
, provideOldAttributeNames ? false
}:

with ./lib.nix;

let

  fix = f: let x = f x // { __unfix__ = f; }; in x;

  extend = rattrs: f: self: let super = rattrs self; in super // f self super;

  haskellPackages = self:
    let

      mkDerivation = pkgs.callPackage ./generic-builder.nix {
        inherit stdenv ghc;
        inherit (pkgs) fetchurl pkgconfig glibcLocales coreutils gnugrep gnused;
        inherit (self) jailbreak-cabal;
        hscolour = overrideCabal self.hscolour (drv: {
          isLibrary = false;
          noHaddock = true;
          hyperlinkSource = false;      # Avoid depending on hscolour for this build.
          postFixup = "rm -rf $out/lib $out/share $out/nix-support";
        });
      };

      overrideCabal = drv: f: drv.override (args: args // {
        mkDerivation = drv: args.mkDerivation (drv // f drv);
      });

      callPackageWithScope = scope: drv: args: (stdenv.lib.callPackageWith scope drv args) // {
        overrideScope = f: callPackageWithScope (fix (extend scope.__unfix__ f)) drv args;
      };

      defaultScope = pkgs // pkgs.xlibs // pkgs.gnome // self;
      callPackage = drv: args: callPackageWithScope defaultScope drv args;

    in
      import ./hackage-packages.nix { inherit pkgs stdenv callPackage; } self // {

        inherit ghc mkDerivation callPackage;

        ghcWithPackages = pkgs: callPackage ./with-packages-wrapper.nix { packages = pkgs self; };

      };

  compatLayer = if provideOldAttributeNames then import ./compat-layer.nix else (self: super: {});
  commonConfiguration = import ./configuration-common.nix { inherit pkgs; };

in

  fix (extend (extend (extend (extend haskellPackages commonConfiguration) packageSetConfig) overrides) compatLayer)