anchor.diff:  stdenv.mkDerivation rec {
   
     pname = "solc";
  -  version = "0.5.15";
  +  version = "0.6.8";
   
     # upstream suggests avoid using archive generated by github
     src = fetchzip {
       url = "https://github.com/ethereum/solidity/releases/download/v${version}/solidity_${version}.tar.gz";
  -    sha256 = "1nfvsaci5ja5ss603z04197wndwkvcq9nm5mdab1kpdr91djxh2y";
  +    sha256 = "1nxds6c10hjqjjk893qw2yljws57li0xigbf3ih85y8y6d587ph0";
     };
   
     postPatch = ''
  
positive.code: { stdenv, fetchzip, boost, cmake, ncurses, python2
  , z3Support ? true, z3 ? null, cvc4Support ? true, cvc4 ? null
  , cln ? null, gmp ? null
  }:
  
negative.code:   buildInputs = [ boost ]
      ++ stdenv.lib.optionals z3Support [ z3 ]
      ++ stdenv.lib.optionals cvc4Support [ cvc4 cln gmp ];
    checkInputs = [ ncurses python3 ];
  
    # Test fails on darwin for unclear reason
    doCheck = stdenv.hostPlatform.isLinux;
  