Internal error on Scala 2.13 given generic JsonValueCodec to be used transitively

[tribbloid]

Code example:

trait Imp0 {

  case class User(
      name: String,
      age: Int,
      path: Path = Path.of("http://google.com")
  )

  implicit def pojoCodec[T <: AnyRef]: JsonValueCodec[T] = {

    print_@("pojo")
    ???
  } // fallback to jackson here

  implicit lazy val pojoCodec2: JsonValueCodec[AnyRef] = { // only works iif JsonValueCodec is contravariant

    print_@("pojo")
    ???
  } // fallback to jackson here
}

object JsoniterFallbackExample extends Imp0 {

  // Generate codec for Person (automatically handles Address too)
  implicit lazy val personCodec: JsonValueCodec[User] = JsonCodecMaker.make
}

The intention is to use Jackson to handle Java Path which is not a Scala product type. When compiling, it generates the following error:

[Error] /home/peng/git/scalaspike/common/generic/src/test/scala/com/tribbloids/spike/generic/jsoniter/JsoniterFallbackExample.scala:34:72: Internal error: unable to find the outer accessor symbol of <$anon: com.github.plokhotnyuk.jsoniter_scala.core.JsonValueCodec>
one error found

What is "outer accessor symbol" here? Can the internal error stack trace be reported and potentially be used in telemetry?

[plokhotnyuk]

It is a known issue num. 3: https://github.com/plokhotnyuk/jsoniter-scala?tab=readme-ov-file#known-issues

What you see is an internal error from the scalac.

Feel free to mitigate in your code by moving your data classes out a trait or contribute some mitigations to jsoniter-scala macros (or even scalac if the root cause is in its side).