anchor.diff:        }
       }
   
  +    // If a named configuration was specified ensure no other options, which are
  +    // implied by the named configuration, were specified.
  +    if (configuration['named_configuration'] is String) {
  +      for (final optionName in _namedConfigurationOptions) {
  +        if (configuration.containsKey(optionName)) {
  +          final namedConfig = configuration['named_configuration'];
  +          _fail("The named configuration '$namedConfig' implies "
  +              "'$optionName'. Try removing '$optionName'.");
  +        }
  +      }
  +    }
  +
       // Apply default values for unspecified options.
       for (var option in _options) {
         if (!configuration.containsKey(option.name)) {
  
positive.code: 
    /// Given a set of parsed option values, returns the list of command line
    /// arguments that would reproduce that configuration.
    List<String> _reproducingCommand(Map<String, dynamic> data) {
      var arguments = <String>[];
  
      for (var option in _options) {
        var name = option.name;
        if (!data.containsKey(name) || _blacklistedOptions.contains(name)) {
          continue;
        }
  
  
negative.code:                 packageRoot: data["package_root"] as String,
                  suiteDirectory: data["suite_dir"] as String,
                  outputDirectory: data["output_directory"] as String,
                  reproducingArguments:
                      _reproducingCommand(data, namedConfiguration != null),
                  fastTestsOnly: data["fast_tests"] as bool,
                  printPassingStdout: data["print_passing_stdout"] as bool);
  
  