anchor.diff:      ++ optional sqliteSupport sqlite
       ++ optional postgresqlSupport postgresql
       ++ optionals mysqlSupport [ mariadb zlib ];
  +
  +  buildNoDefaultFeatures = true;
  +  buildFeatures = optional sqliteSupport "sqlite"
  +    ++ optional postgresqlSupport "postgres"
  +    ++ optional mysqlSupport "mysql";
   
     checkPhase = ''
       runHook preCheck
  
positive.code: 
  let
    inherit (lib) optional optionals optionalString;
    features = optional sqliteSupport "sqlite"
      ++ optional postgresqlSupport "postgres"
      ++ optional mysqlSupport "mysql";
  in
  
  rustPlatform.buildRustPackage rec {
  
negative.code:     sha256 = "sha256-mRdDc4fHMkwkszY+2l8z1RSNMEQnrWI5/Y0Y2W+guQE=";
    };
  
    cargoSha256 = "sha256-sQ762Ss31sA5qALHzwkvwbfRXo00cCtqzQyoz3/zf6I=";
  
    nativeBuildInputs = [ installShellFiles pkg-config ];
  