compile does not stop with error message

try compile the following line of code:

def main(args : Array):
    var c2 = java.util.Set[Int]() = ???

The dotty compiler 0.27.0-RC1 does not stop or it craches without giving an error message. I cannot say if it crashed or simply does not stop as I am using Metals on visual studion code. Problem is that Scastie times out after 30 seconds as well.