Indirect covariant comparison involving a higher-kinded type argument fails

[neko-kai]

From zio/zio#8215

trait Container[T] {
  def getT(): T
}

trait Service[+O[_] <: Container[_]] {
  def giveHello: String
}

final case class AContainer[T](t: T) extends Container[T] {
  override def getT() = t
} 

final case class MyConcreteService() extends Service[AContainer] {
  def giveHello = "Concrete hello!"
}

object Example extends App {

  implicitly[MyConcreteService <:< Service[Container]] // true

  val left = izumi.reflect.Tag[MyConcreteService]
  val right = izumi.reflect.Tag[Service[Container]]

  println(left <:< right) // false
}

[jdegoes]

/bounty $500

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Attempt	Started (GMT+0)	Solution
🟢 @gkfabs	Feb 12, 2025, 3:20:52 AM	#519

[gkfabs]

/attempt #469

• use the code to create a unit test
• find the root cause

Algora profile	Completed bounties	Tech	Active attempts	Options
@gkfabs	1 ZIO bounty	Java, Scala, Ruby & more		Cancel attempt

[algora-pbc]

💡 @gkfabs submitted a pull request that claims the bounty. You can visit your bounty board to reward.