Pickling diff error for valid code

[ivan-klass]

Compiler version

3.7.0-RC1-SNAPSHOT, 8fe16fe
Found in #22824 (tests were green before moving from tests/run-deep-subtype to tests/run which seems to be used for pickling tests)

Minimized code

object Test {

  type Tup = (Int, Double, Boolean, String)

  val firstTruthy: [T <: Tuple.Union[Tup]] => Seq[T] => Option[T] = [T <: Tuple.Union[Tup]] => (seq: Seq[T]) => seq.find {
      case x: Int => x != 0
      case x: Double => x != 0.0
      case x: Boolean => x
      case x: String => x.nonEmpty
  }
}

Output

diff before-pickling.txt after-pickling.txt is

124,125c124,125
<       :[T <: scala.Int | scala.Double | (scala.Boolean | String)] => (seq: Seq[T]) => scala.Option[T]>@
<         tests/run/Tuple-mapKind.scala<128..309>
---
>       :[T <: scala.Tuple.Fold[(scala.Int, scala.Double, scala.Boolean, String), scala.Nothing, [x, y] =>> x | y]] => (
>         seq: Seq[T]) => scala.Option[T]>@tests/run/Tuple-mapKind.scala<128..309>

Expectation

No pickling diff error, same representation before and after