Implicit and hiding warnings interact

[scabug]

From a test. You don't see the warning that the import is not respected because of the implicit error; unless you uncomment the other import and implicitly.

If errors suppress warnings, then it would be nice if there were a way to always display warnings, for example, under -Xfatal-warnings.

case class K(s: java.lang.String)
class C { implicit val k: K = K("OK?"); override def toString = "C(" + k.toString + ")" }

object Test extends App {
  // uncomment to show the warning
  //import concurrent.ExecutionContext.Implicits._
  //def x = implicitly[concurrent.ExecutionContext]
  val c = new C
  import c.k
  def g = implicitly[K]
  val k = 42
}

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-9850?orig=1
Reporter: @som-snytt
Affected Versions: 2.12.0-M5

[som-snytt]

The warning in question was

warning: imported `k` is permanently hidden by definition of value k in object

which is dubious and pertains to earlier bugs in implicit search.

The -Wunused import is always warned.

Scala 3 doesn't have lexical hiding of implicits.