{ pkgs, haskellLib }:

with haskellLib;

self: super: {

  # This compiler version needs llvm 7.x.
  llvmPackages = pkgs.llvmPackages_7;

  # Disable GHC 8.8.x core libraries.
  array = null;
  base = null;
  binary = null;
  bytestring = null;
  Cabal = null;
  containers = null;
  deepseq = null;
  directory = null;
  filepath = null;
  ghc-boot = null;
  ghc-boot-th = null;
  ghc-compact = null;
  ghc-heap = null;
  ghc-prim = null;
  ghci = null;
  haskeline = null;
  hpc = null;
  integer-gmp = null;
  libiserv = null;
  mtl = null;
  parsec = null;
  pretty = null;
  process = null;
  rts = null;
  stm = null;
  template-haskell = null;
  terminfo = null;
  text = null;
  time = null;
  transformers = null;
  unix = null;
  xhtml = null;

  # Use the current git version of cabal-install.
  cabal-install = overrideCabal (super.cabal-install.overrideScope (self: super: { Cabal = self.Cabal-git; })) (drv: {
    src = pkgs.fetchFromGitHub {
      owner = "haskell";
      repo = "cabal";
      rev = "e98f6c26fa301b49921c2df67934bf9b0a4f3386";
      sha256 = "15nrkvckq2rw31z7grgbsg5f0gxfc09afsrqdfi4n471k630xd2i";
    };
    version = "20190510-git";
    editedCabalFile = null;
    postUnpack = "sourceRoot+=/cabal-install";
    jailbreak = true;
  });
  Cabal-git = overrideCabal super.Cabal_2_4_1_0 (drv: {
    src = pkgs.fetchFromGitHub {
      owner = "haskell";
      repo = "cabal";
      rev = "e98f6c26fa301b49921c2df67934bf9b0a4f3386";
      sha256 = "15nrkvckq2rw31z7grgbsg5f0gxfc09afsrqdfi4n471k630xd2i";
    };
    version = "20190510-git";
    editedCabalFile = null;
    postUnpack = "sourceRoot+=/Cabal";
  });

  # Ignore overly restrictive upper version bounds.
  async = doJailbreak super.async;
  ChasingBottoms = doJailbreak super.ChasingBottoms;
  cryptohash-sha256 = doJailbreak super.cryptohash-sha256;
  Diff = dontCheck super.Diff;
  doctest = doJailbreak super.doctest;
  hashable = doJailbreak super.hashable;
  hashable-time = doJailbreak super.hashable-time;
  integer-logarithms = doJailbreak super.integer-logarithms;
  lucid = doJailbreak super.lucid;
  parallel = doJailbreak super.parallel;
  quickcheck-instances = doJailbreak super.quickcheck-instances;
  setlocale = doJailbreak super.setlocale;
  split = doJailbreak super.split;
  tasty-expected-failure = doJailbreak super.tasty-expected-failure;
  test-framework = doJailbreak super.test-framework;
  th-lift = self.th-lift_0_8_0_1;
  hledger-lib = doJailbreak super.hledger-lib;  # base >=4.8 && <4.13, easytest >=0.2.1 && <0.3

  # These packages don't work and need patching and/or an update.
  primitive = overrideSrc (doJailbreak super.primitive) {
    version = "20180530-git";
    src = pkgs.fetchFromGitHub {
      owner = "haskell";
      repo = "primitive";
      rev = "97964182881aa0419546e0bb188b2d17e4468324";
      sha256 = "1p1pinca33vd10iy7hl20c1fc99vharcgcai6z3ngqbq50k2pd3q";
    };
  };
  tar = overrideCabal (appendPatch super.tar (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/tar-0.5.1.0.patch";
    sha256 = "1inbfpamfdpi3yfac59j5xpaq5fvh5g1ca8hlbpic1bizd3s03i0";
  })) (drv: {
    configureFlags = ["-f-old-time"];
    editedCabalFile = null;
    preConfigure = ''
      cp -v ${pkgs.fetchurl {url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/tar-0.5.1.0.cabal"; sha256 = "1lydbwsmccf2av0g61j07bx7r5mzbcfgwvmh0qwg3a91857x264x";}} tar.cabal
      sed -i -e 's/time < 1.9/time < 2/' tar.cabal
    '';
  });
  resolv = overrideCabal (overrideSrc super.resolv {
    version = "20180411-git";
    src = pkgs.fetchFromGitHub {
      owner = "haskell-hvr";
      repo = "resolv";
      rev = "a22f9dd900cb276b3dd70f4781fb436d617e2186";
      sha256 = "1j2jyywmxjhyk46kxff625yvg5y37knv7q6y0qkwiqdwdsppccdk";
    };
  }) (drv: {
    buildTools = with pkgs; [autoconf];
    preConfigure = "autoreconf --install";
  });
  dlist = appendPatch (doJailbreak super.dlist) (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/dlist-0.8.0.6.patch";
    sha256 = "0lkhibfxfk6mi796mrjgmbb50hbyjgc7xdinci64dahj8325jlpc";
  });
  vector-th-unbox = appendPatch super.vector-th-unbox (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/vector-th-unbox-0.2.1.6.patch";
    sha256 = "0169yf9ms1g5mmkc5l6hpffzm34zdrqdng4df02nbdmfgba45h19";
  });
  cabal-doctest = appendPatch  (doJailbreak super.cabal-doctest) (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/cabal-doctest-1.0.6.patch";
    sha256 = "0735mkxhv557pgnfvdjakkw9r85l5gy28grdwg929m26ghbf9s8j";
  });
  QuickCheck = appendPatch super.QuickCheck (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/QuickCheck-2.13.1.patch";
    sha256 = "138yrp3x5cnvncimrnhnkawz6clyk7fj3sr3y93l5szfr11kcvbl";
  });
  regex-base = appendPatch super.regex-base (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/regex-base-0.93.2.patch";
    sha256 = "01d1plrdx6hcspwn2h6y9pyi5366qk926vb5cl5qcl6x4m23l6y1";
  });
  regex-posix = appendPatch super.regex-posix (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/regex-posix-0.95.2.patch";
    sha256 = "006yli58jpqp786zm1xlncjsilc38iv3a09r4pv94l587sdzasd2";
  });
  th-abstraction = appendPatch (doJailbreak super.th-abstraction) (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/th-abstraction-0.2.11.0.patch";
    sha256 = "0czqfszfblz6bvsybcd1z5jijj79f9czqq6dn992wp2gibsbrgj3";
  });
  zlib = appendPatch super.zlib (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/zlib-0.6.2.patch";
    sha256 = "13fy730z9ihyc9kw3qkh642mi0bdbd7bz01dksj1zz845pr9jjif";
  });
  haskell-src-exts = appendPatch super.haskell-src-exts_1_21_0 (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/haskell-src-exts-1.21.0.patch";
    sha256 = "0alb28hcsp774c9s73dgrajcb44vgv1xqfg2n5a9y2bpyngqscs3";
  });
  optparse-applicative = appendPatch (doJailbreak super.optparse-applicative) (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/optparse-applicative-0.14.3.0.patch";
    sha256 = "068sjj98jqiq3h8h03mg4w2pa11q8lxkx2i4lmxivq77xyhlwq3y";
  });
  HTTP = appendPatch (doJailbreak super.HTTP) (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/HTTP-4000.3.13.patch";
    sha256 = "1fadi529x7dnmbfmls5969qfn9d4z954nc4lbqxmrwgirphkpmn4";
  });
  hackage-security = appendPatch (doJailbreak super.hackage-security) (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/hackage-security-0.5.3.0.patch";
    sha256 = "0l8x0pbsn18fj5ak5q0g5rva4xw1s9yc4d86a1pfyaz467b9i5a4";
  });
  happy = appendPatch super.happy (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/happy-1.19.9.patch";
    sha256 = "1zmcb7dgcwivq2mddcy1f20djw2kds1m7ahwsa4xpbbwnijc6zjx";
  });
  hedgehog = appendPatch super.hedgehog (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/hedgehog-0.6.1.patch";
    sha256 = "04xwznd3lfgracfz68ls6vfm19rhq8fb74r6ii0grpv6cx4rr21i";
  });
  easytest = self.easytest_0_3;
  regex-tdfa = appendPatch super.regex-tdfa (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/regex-tdfa-1.2.3.1.patch";
    sha256 = "1lhas4s2ms666prb475gaw2bqw1v4y8cxi66sy20j727sx7ppjs7";
  });
  unordered-containers = self.unordered-containers_0_2_10_0;
  attoparsec = appendPatch super.attoparsec (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/attoparsec-0.13.2.2.patch";
    sha256 = "13i1p5g0xzxnv966nlyb77mfmxvg9jzbym1d36h1ajn045yf4igl";
  });
  aeson = appendPatch (dontCheck super.aeson) (pkgs.fetchpatch {   # the test suite breaks the compiler
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/aeson-1.4.3.0.patch";
    sha256 = "1z6wmsmc682qs3y768r0zx493dxardwbsp0wdc4dsx83c0m5x66f";
  });
  cassava = appendPatch super.cassava (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/cassava-0.5.1.0.patch";
    sha256 = "11scwwjp94si90vb8v5yr291g9qwv5l223z8y0g0lc63932bp63g";
  });
  shakespeare = appendPatch super.shakespeare (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/shakespeare-2.0.20.patch";
    sha256 = "1dgx41ylahj4wk8r422aik0d7qdpawdga4gqz905nvlnhqjla58y";
  });
  lens = appendPatch (doJailbreak super.lens) (pkgs.fetchpatch {
    url = "https://raw.githubusercontent.com/hvr/head.hackage/master/patches/lens-4.17.1.patch";
    sha256 = "0w89ipi6dfkx5vlw4a64hh6fd0bm9hg33mwpghliyyxik5jmilv1";
  });

}