haskell-override-package-version-user

for ghc802 specifically:
  packageOverrides = pkgs: with pkgs; rec {
 
    haskell = pkgs.haskell // {
      packages = pkgs.haskell.packages // {
        ghc802 = pkgs.haskell.packages.ghc802.override {
          overrides = self: super:
            {
            ghc-syb-utils = pkgs.haskell.lib.dontCheck super.ghc-syb-utils;
            apply-refact = pkgs.haskell.lib.overrideCabal super.apply-refact (drv:  {version = ".."; sha256 = "..";});
          };
        };
      };
    };

for deault haskell package set:

  packageOverrides = pkgs: with pkgs; rec {
    haskellPackages = pkgs.haskellPackages.override {
      overrides = self: super:
      {
        ghc-syb-utils = pkgs.haskell.lib.dontCheck super.ghc-syb-utils;
        apply-refact = pkgs.haskell.lib.overrideCabal super.apply-refact (drv:  {version = ".."; sha256 = "..";});
      };
};
  };