def f x: = 1
      ^~ could not parse the endless method parameters

def f ... = 1
      ^~~ could not parse the endless method parameters

def f * = 1
      ^ could not parse the endless method parameters

def f ** = 1
      ^~ could not parse the endless method parameters

def f & = 1
      ^ could not parse the endless method parameters

def f *a = 1
       ^ could not parse the endless method parameters

def f **a = 1
        ^ could not parse the endless method parameters

def f &a = 1
       ^ could not parse the endless method parameters