Ambiguous reference error compiling Scala with Java 9

Question

Currently I am facing the following compilation error in Scala against Java 9:

: ambiguous reference to overloaded definition,
both method putAll in class Properties of type (x$1: java.util.Map[_, _])Unit
and  method putAll in class Hashtable of type (x$1: java.util.Map[_ <: Object, _ <: Object])Unit
match argument types (java.util.Properties)
  newProps.putAll(props)

newProps is defined as:

  val newProps = new Properties

I tried variants of newProps.asInstanceOf[java.util.Map[...]] but got different compilation errors.

Any hint is welcome.

Answer 1

As @Ted pointed out this is a known issue. One workardound would be to subsitute putAll with something like this:

props.forEach((k, v) => newProps.put(k, v))

Note that by doing this your operation is not atomic anymore but most probably this is not important in your case.