cycle with default arguments creates null field

[scabug]

class IdAndMsg(val id: Int,  val msg: String = "")

case object ObjA extends IdAndMsg(1)
case object ObjB extends IdAndMsg(2)

object IdAndMsg {
  val values = List(ObjA , ObjB)
}

object Test {
  def main(args: Array[String]): Unit = {
    ObjA
    println(IdAndMsg.values)
  }
}

/*
Output:
List(null, ObjB)
*/

The cycle is that if one references ObjA first, its superclass has a default argument which is retrieved from object IdAndMsg, which has a val which refers to ObjA, which is null.

It doesn't seem necessary - IdAndMsg.init$default$2 is a static method, but it creates IdAndMsg$ and populates the MODULE$ field so it can call IdAndMsg$.init$default$2. At least in the case of constants, the static method could return it directly and avoid loading the object.

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-5366?orig=1
Reporter: @paulp
Affected Versions: 2.8.1, 2.9.3, 2.10.6, 2.11.8, 2.12.0-RC1

[scabug]

@lrytz said:
I tried once implementing constructor defaults using static methods but it was not straightforward. I don't remember the details, in principle it could most likely be done.

[SethTisue]

remains reproducible in Scala 3.6.3

[som-snytt]

➜  scala-cli run --server=false -S 3.6.3 t5366.scala
-- Warning: /home/amarki/snips/t5366.scala:6:12 --------------------------------
6 |case object ObjA extends IdAndMsg(1)
  |            ^
  |Cyclic initialization: object ObjA -> object IdAndMsg -> object ObjA. Calling trace:
  |├── case object ObjA extends IdAndMsg(1)     [ t5366.scala:6 ]
  |│                            ^
  |├── object IdAndMsg {        [ t5366.scala:9 ]
  |│   ^
  |└── val values = List(ObjA , ObjB)   [ t5366.scala:10 ]
  |                      ^^^^
-- Warning: /home/amarki/snips/t5366.scala:9:7 ---------------------------------
9 |object IdAndMsg {
  |       ^
  |Cyclic initialization: object IdAndMsg -> object ObjB -> object IdAndMsg. Calling trace:
  |├── object IdAndMsg {        [ t5366.scala:9 ]
  |│   ^
  |├── val values = List(ObjA , ObjB)   [ t5366.scala:10 ]
  |│                            ^^^^
  |└── case object ObjB extends IdAndMsg(2)     [ t5366.scala:7 ]
  |                             ^
2 warnings found
List(null, ObjB)
➜  cat t5366.scala

//> using options -Ysafe-init-global