Error when aridLayout adding , removing or list children


I have received the error when trying to insert a child, super strange
ERROR TypeError: this.gridLayout.insertChild is not a function

  let tmpLabel = new Label(); 
        tmpLabel.text = "TETETETETETE" ;
        tmpLabel.width = 100 ;
        tmpLabel.height = 100 ;          
(this.gridLayout as GridLayout).insertChild(tmpLabel,0) ;

This gridLayout is in the DrawerComponent if this meaning .


Please consider sharing a Playground project reproducing this issue.