anchor.diff:    # If enabled GHC will be build with the GPL-free but slower integer-simple
     # library instead of the faster but GPLed integer-gmp library.
   , enableIntegerSimple ? false, gmp
  -, version ? "8.1.20170106"
  +, version ? "8.3.20170808"
   }:
   
   let
  
positive.code:   src = fetchgit {
      url = "git://git.haskell.org/ghc.git";
      inherit rev;
      sha256 = "1h064nikx5srsd7qvz19f6dxvnpfjp0b3b94xs1f4nar18hzf4j0";
    };
  
    postPatch = "patchShebangs .";
  
negative.code: 
    commonBuildInputs = [ ghc perl autoconf automake happy alex python3 ];
  
    rev = "14457cf6a50f708eecece8f286f08687791d51f7";
  
    commonPreConfigure =  ''
      echo ${version} >VERSION
  