Variance error in copy method

[Krever]

Compiler version

3.3.3

Minimized code

sealed trait WIO[+Err, +Out] {

  def handleError[Err1,Out1 >: Out, ErrIn >: Err](
      f: ErrIn => WIO[Err1, Out1]
  ): WIO[Err1, Out1] = HandleError(f)

}

case class HandleError[+ErrOut, +Out, ErrIn](handleError: ErrIn => WIO[ErrOut, Out]) extends WIO[ErrOut, Out]

Output

The below output is taken from scastie execution

covariant type Out occurs in contravariant position in type [ErrOut, Out, ErrIn]: (Any => Playground.WIO[Any, Out]) =>
  Playground.WIO[Any, Out] of method copy$default$1

Expectation

I believe this is a bug due to the following reason:

• The variance error disappears when handleError method is removed.
• It compiles in Scala 2.
• The error points to the generated copy method
• I don't see why it would be a contravariant position

Sorry for the poor issue title, I couldn't think of a better one.

[som-snytt]

it does not yet compile in 3.4.0 but does compile in 3.4.2-RC1-bin-SNAPSHOT-git-a36849f