Empty package object

[som-snytt]

If I create a package object in the empty package:

object `package` {
  implicit class sss(s: String) {
    def d: Double = s.toDouble
  }
}

then I have to import its members explicitly:

import `package`._

package x {
  object X { def f = "3.14".d }
}

If the empty package is allowed to have a package object, then the workaround also bends the rule that members of the empty package cannot be imported.

Edit: obviously this is more interesting if they're importing in a named package. Also, same behavior on dotty.

[som-snytt]

It's not obvious that members of the empty package are visible to members of packagings, although ordinary lexical scoping seems to suggest obviously yes:

object `package` {
  type MyString = String
}

class Limbo

package p {
  class C {
    val s: MyString = "hello, world"
    val limbo = new Limbo
  }
}
package q {
  import scala.util.chaining._

  object Test extends App {
    println(new p.C().pipe(c => (c.s, c.limbo)))
  }
}

In separate files, the class is visible to p.C but not MyString.

All this is contrary to Java, where members of the empty package are visible only to other members of the empty package, which is a kind of scratch space for experiments but must never accidentally leak into real code.

Similarly, the following works in one file but not two compiled together but not separately:

object `package` {
  implicit class sss(s: String) {
    def d: Double = s.toDouble
  }
}
class Limbo {
  def f = "3.14".d
}

Not sure if that was the point of the original issue, but it's clearly wrong.

It seems to me there is nothing extraordinary about a package object for the empty package. The problem is that access to the empty package is bungled in a couple of ways, both to top-level members and members of the package object.

Spec says: Top-level definitions outside a packaging are assumed to be injected into a special empty package. That package cannot be named and therefore cannot be imported. However, members of the empty package are visible to each other without qualification.

I wonder what doti says.

[som-snytt]

I corrected the last example, which scalac compiles together but not separately.

dotc also compiles them separately.

[som-snytt]

Per odersky no sane person does that.

These are REPL use cases, and no one uses the REPL that way anyway.