anchor.diff:      );
     }
   
  +  /// Performs a device code grant.
     FutureOr<DeviceCodeResponse> deviceCodeGrant(Client client,
         Iterable<String> scopes, RequestContext req, ResponseContext res) async {
       var body = await req.parseBody().then((_) => req.bodyAsMap);
  
positive.code: 
    var value = data.containsKey(name) ? data[name]?.toString() : null;
  
    if (value?.isNotEmpty != true) {
      throw new AuthorizationException(
        new ErrorResponse(
          ErrorResponse.invalidRequest,
  
negative.code: 
        state = body['state']?.toString() ?? '';
  
        var grantType = await _getParam(req, 'grant_type', state, body: true, throwIfEmpty: false);
  
        if (grantType != 'authorization_code') {
          var match =
  