implicits.scala:21: error: type mismatch;
 found   : Pos
 required: ?{val +: ?}
Note that implicit conversions are not applicable because they are ambiguous:
 most specific definition is: method pos2int in object Super of type (Pos)int
 yet alternative definition   method any2plus in object Sub of type (Any)Sub.Plus
 is defined in a subclass.
 Both definitions are possible conversion functions from Pos to ?{val +: ?}
  f(p+1)
    ^
one error found