Case Class AnyVal Not Working with Json.reads/Json.writes

[cheeseng]

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Play JSON Version (2.5.x / etc)

3.0.2

API (Scala / Java / Neither / Both)

Scala

Operating System (Ubuntu 15.10 / MacOS 10.10 / Windows 10)

22.04.1-Ubuntu

JDK (Oracle 1.8.0_72, OpenJDK 1.8.x, Azul Zing)

openjdk version "17.0.9" 2023-10-17 OpenJDK Runtime Environment GraalVM CE 17.0.9+9.1 (build 17.0.9+9-jvmci-23.0-b22) OpenJDK 64-Bit Server VM GraalVM CE 17.0.9+9.1 (build 17.0.9+9-jvmci-23.0-b22, mixed mode, sharing)

Library Dependencies

None.

Expected Behavior

Please describe the expected behavior of the issue, starting from the first action.

The following should compile (works under Scala 2.13):

case class UserId(id:Long) extends AnyVal

object UserId {
  implicit val reads: Reads[UserId] = Json.reads[UserId]
  implicit val writes: Writes[UserId] = Json.writes[UserId]
}

Actual Behavior

It fails to compile under Scala 3.3.3:

Instance not found: 'ProductOf[UserId]'

Reproducible Test Case

Example included in the ticket.

[xuwei-k]

• https://github.com/scala/scala3/issues/17800

[cchantep]

Class with AnyVal is a rather a Value class than a Case class (and in fact I would not recommended make it a case class). There are dedicated macros for Value classes.