Grunt compilation failure

Executing 'dockergento grunt exec' throws ' PHP Parse error:  syntax error, unexpected 'LinkRepositoryInterface' (T_STRING), expecting function (T_FUNCTION) or const (T_CONST) in /var/www/html/app/code/ffff/aaaa/Helper/Data.php on line 44
>> Exited with code: 255.
>> Error executing child process: Error: Process exited with code 255'
php -7.4 
node 7.3