{ pkgs }:

with import ./lib.nix { inherit pkgs; };

self: super: {

  # Disable GHC 7.8.x core libraries.
  array = null;
  base = null;
  binary = null;
  bin-package-db = null;
  bytestring = null;
  Cabal = null;
  containers = null;
  deepseq = null;
  directory = null;
  filepath = null;
  ghc-prim = null;
  haskeline = null;
  haskell2010 = null;
  haskell98 = null;
  hoopl = null;
  hpc = null;
  integer-gmp = null;
  old-locale = null;
  old-time = null;
  pretty = null;
  process = null;
  rts = null;
  template-haskell = null;
  terminfo = null;
  time = null;
  transformers = null;
  unix = null;
  xhtml = null;

  # mtl 2.2.x needs the latest transformers.
  mtl_2_2_1 = super.mtl_2_2_1.override { transformers = self.transformers_0_4_2_0; };

  # Idris requires mtl 2.2.x.
  idris = overrideCabal (super.idris.overrideScope (self: super: {
    mkDerivation = drv: super.mkDerivation (drv // { doCheck = false; });
    transformers = super.transformers_0_4_2_0;
    transformers-compat = disableCabalFlag super.transformers-compat "three";
    mtl = super.mtl_2_2_1;
  })) (drv: {
    jailbreak = true;           # idris is scared of lens 4.7
    patchPhase = "find . -name '*.hs' -exec sed -i -s 's|-Werror||' {} +";
  });                           # warning: "Module ‘Control.Monad.Error’ is deprecated"

}

// # packages relating to amazonka

(let
  amazonkaEnv = let self_ = self; in self: super: {
    mkDerivation = drv: super.mkDerivation (drv // {
      doCheck = false;
      hyperlinkSource = false;
      extraLibraries = (drv.extraLibraries or []) ++ [ (
        if builtins.elem drv.pname [
          "Cabal"
          "time"
          "unix"
          "directory"
          "process"
          "jailbreak-cabal"
        ] then null else self.Cabal_1_18_1_6
      ) ];
    });
    mtl = self.mtl_2_2_1;
    transformers = self.transformers_0_4_2_0;
    transformers-compat = overrideCabal super.transformers-compat (drv: { configureFlags = []; });
    aeson = disableCabalFlag super.aeson "old-locale";
    hscolour = super.hscolour;
    time = self.time_1_5_0_1;
    unix = self.unix_2_7_1_0;
    directory = self.directory_1_2_1_0;
    process = overrideCabal self.process_1_2_1_0 (drv: {
      coreSetup = true;
    });
    inherit amazonka-core amazonkaEnv amazonka amazonka-cloudwatch;
  };
  Cabal = self.Cabal_1_18_1_6.overrideScope amazonkaEnv;
  amazonka-core =
    overrideCabal (super.amazonka-core.overrideScope amazonkaEnv) (drv: {
      # https://github.com/brendanhay/amazonka/pull/57
      prePatch = "sed -i 's|nats >= 0.1.3 && < 1|nats|' amazonka-core.cabal";

      extraLibraries = (drv.extraLibraries or []) ++ [ Cabal ];
    });
  useEnvCabal = p: overrideCabal (p.overrideScope amazonkaEnv) (drv: {
    extraLibraries = (drv.extraLibraries or []) ++ [ Cabal ];
  });
  amazonka = useEnvCabal super.amazonka;
  amazonka-cloudwatch = useEnvCabal super.amazonka-cloudwatch;
in {
  inherit amazonka-core amazonkaEnv amazonka amazonka-cloudwatch;
})