t4727.scala:5: error: type mismatch;
 found   : Null
 required: Int
Note that implicit conversions are not applicable because they are ambiguous:
 both method Integer2intNullConflict in class LowPriorityImplicits of type (x: Null)Int
 and method Integer2int in object Predef of type (x: Integer)Int
 are possible conversion functions from Null to Int
Error occurred in an application involving default arguments.
    new C[Int]
    ^
one error found