anchor.diff:          _argProfileFor,
           _argLegacyStyle,
           _argFastBoot,
  +        _argLegacyWhitespace
         ].toSet();
         final unknownArgs = options.keys.toSet().difference(knownArgs);
         if (unknownArgs.isNotEmpty) {
  
positive.code:           'Whether to emit additional code that may be used by tooling '
            'in order to profile performance or other runtime information.',
      )
      ..addFlag(_argFastBoot,
          defaultsTo: null,
          help: 'Whether to support AngularDart v5\'s "fastBoot" functionality.');
  
    /// Whether to emit extra code suitable for testing and local development.
    final bool genDebugInfo;
  
negative.code:       log('Invalid value for "$_argFastBoot": $useFastBoot');
        useFastBoot = null;
      }
      var useLegacyWhitespace = options[_argLegacyWhitespace];
      if (useLegacyStyle != null && useLegacyStyle is! bool) {
        log('Invalid value for "$_argLegacyWhitespace": $_argLegacyWhitespace');
        useLegacyWhitespace = null;
      }
      return new CompilerFlags(
        genDebugInfo: debugMode ?? defaultTo.genDebugInfo,
        profileFor: _toProfile(profileFor, log) ?? defaultTo.profileFor,
        useLegacyStyleEncapsulation:
            useLegacyStyle ?? defaultTo.useLegacyStyleEncapsulation,
        useFastBoot: useFastBoot ?? defaultTo.useFastBoot,
        useNewPreserveWhitespace: useLegacyWhitespace != null
            ? !useLegacyWhitespace
            : defaultTo.useNewPreserveWhitespace,
      );
    }
  }
  