{ pkgs, haskellLib }:

with haskellLib;

self: super: {

  # Use the latest LLVM.
  inherit (pkgs) llvmPackages;

  # Disable GHC 8.4.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-prim = null;
  ghci = null;
  haskeline = null;
  hpc = null;
  integer-gmp = 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;

  # https://github.com/jcristovao/enclosed-exceptions/issues/12
  enclosed-exceptions = dontCheck super.enclosed-exceptions;

  # https://github.com/xmonad/xmonad/issues/155
  xmonad = addBuildDepend (appendPatch super.xmonad (pkgs.fetchpatch {
    url = https://github.com/xmonad/xmonad/pull/153/commits/c96a59fa0de2f674e60befd0f57e67b93ea7dcf6.patch;
    sha256 = "1mj3k0w8aqyy71kmc71vzhgxmr4h6i5b3sykwflzays50grjm5jp";
  })) self.semigroups;

  # https://github.com/xmonad/xmonad-contrib/issues/235
  xmonad-contrib = doJailbreak (appendPatch super.xmonad-contrib ./patches/xmonad-contrib-ghc-8.4.1-fix.patch);

  # This package desperately needs a maintainer.
  xmobar = super.xmobar.overrideScope (self: super: {
    hinotify = self.hinotify_0_3_9;  # https://github.com/jaor/xmobar/issues/356
    dbus = self.dbus_0_10_15;        # https://github.com/jaor/xmobar/issues/346
  });
  hinotify_0_3_9 = dontCheck (doJailbreak super.hinotify_0_3_9); # allow async 2.2.x

}