Question

I like Scala’s sys.error function – but I want to distinguish two cases: internal errors (e.g. database problem) and user errors (invalid input).

I tried extending Scala – but it doesn’t seem to work:

package scala

class UserException(msg: String) extends RuntimeException(msg)

package object err {

    def internal(message: String): Nothing =
        sys.error(message)

    def usr(message: String): Nothing =
        throw new UserException(message)
}

How should I define err.usr() to be able to use it without an explicit import?

Answer 1

You can’t, only scala.Predef is imported by default and it’s not user extensible in any useful way.