ArrowAssoc warning in Scala 3.10

Play JSON Version (2.5.x / etc)

• 3.1.0-M10
• 3.0.6

API (Scala / Java / Neither / Both)

Scala

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

all

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

all

Library Dependencies

Expected Behavior

no warning

Actual Behavior

[warn]   6 |  val f = play.api.libs.json.Json.format[A]
[warn]     |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[warn]     |method ArrowAssoc in object Predef is deprecated since 3.10.0: Use `->` extension method instead.
[warn]     |---------------------------------------------------------------------------
[warn]     |Inline stack trace
[warn]     |- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
[warn]     |This location contains code that was inlined from JsMacroImpl.scala:713
[warn]     |- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
[warn]     |This location contains code that was inlined from JsMacroImpl.scala:713
[warn]      ---------------------------------------------------------------------------
[warn] one warning found

Reproducible Test Case

build.sbt

scalaVersion := "3.10.0-RC1"

libraryDependencies += "org.playframework" %% "play-json" % "3.1.0-M10"

scalacOptions += "-deprecation"

A.scala

package example

case class A(x: Int)

object A {
  val f = play.api.libs.json.Json.format[A]
}

Note

• https://github.com/scala/scala3/blob/3.10.0-RC1/library/src/scala/Predef.scala#L408-L411
• https://github.com/scala/scala3/pull/24728

Reproduce the warning with the provided build.sbt and A.scala using Scala 3.10.0-RC1 and play-json 3.1.0-M10. Start from the inline trace pointing to JsMacroImpl.scala:713 and compare it with the referenced Scala Predef change. Done means the Json.format[A] example compiles without the ArrowAssoc deprecation warning.