def f() { [] }
    
def a = f();
_ =
  match (a)
  {
    | [x, _]
    | [] with x = 1 => x
  };

_ =
  match (a)
  {
    | [x, y]
    | [] with (x, y) = (1, 2) => x + y // Так нельзя 
    | [] with x = 1 with y = 2 => x + y // Так тоже
    | [] with x = 1, y = 2 => x + y // И так :(
  };