reproduction steps

using Scala 2.13.3:

Scastie showing the warning: https://scastie.scala-lang.org/r3Fnc5YcSzeA91CKs06EtQ

// libraryDependencies += "com.github.alexarchambault" %% "scalacheck-shapeless_1.14" % "1.2.5"

import org.scalacheck.Arbitrary

final case class X(s: String)
object X {
  implicit val arb: Arbitrary[X] = org.scalacheck.derive.MkArbitrary[X].arbitrary
}

problem

Getting a warning:

Block result was adapted via implicit conversion (method apply) taking a by-name parameter

But the warning applies to the code generated by shapeless.Lazy macro, not user-written code. This makes it mandatory to disable the -Xlint:byname-implicit due to the massive amount of false positives whenever implicit derivation is used.