anchor.diff:          _argProfileFor,
           _argLegacyStyle,
           _argFastBoot,
  +        _argLegacyWhitespace
         ].toSet();
         final unknownArgs = options.keys.toSet().difference(knownArgs);
         if (unknownArgs.isNotEmpty) {
  
positive.code: const _argProfileFor = 'profile';
  const _argLegacyStyle = 'use_legacy_style_encapsulation';
  const _argFastBoot = 'fast_boot';
  
  /// Compiler-wide configuration (flags) to allow opting in/out.
  ///
  
negative.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.',
      )
      ..addFlag(
        _argLegacyWhitespace,
        defaultsTo: null,
        help: 'Whether to opt-in/out of the new preserveWhitespace: false',
        // It's not clear we will keep this flag through the 5.x final release.
        hide: true,
      );
  
    /// Whether to emit extra code suitable for testing and local development.
    final bool genDebugInfo;
  