Move exh checking case class tests in

[Cherry-picked 892f048]

Author: dwijnand

library/src/scala/annotation/newMain.scala

@@ -253,6 +253,7 @@ final class newMain extends MainAnnotation[FromString, Any]:
             case (arg +: t, "") => recurse(t, arg, acc)
             case (arg +: t, l) if l.length + 1 + arg.length <= maxLength => recurse(t, s"$l $arg", acc)
             case (arg +: t, l) => recurse(t, arg, acc :+ l)
+            case (_, _) => acc
           }
 
         recurse(argsUsage, "", Vector()).toList

i22590.arity2.scala renamed to tests/warn/i22590.arity2.scala

@@ -8,7 +8,7 @@ case class CC_B[B](a: B,b:T_B) extends T_A
 
 @main def test() = {
   val v_a: CC_B[Int] = null
-  val v_b: Int = v_a match {
+  val v_b: Int = v_a match { // warn: match may not be exhaustive.
     case CC_B(12, CC_A()) => 0
     case CC_B(_, CC_C()) => 0
   }

i22590.scala renamed to tests/warn/i22590.scala

@@ -3,7 +3,7 @@ case class CC_B[T](a: T) extends T_A
 
 @main def test() = {
   val v_a: CC_B[Int] = CC_B(10)
-  val v_b: Int = v_a match{
+  val v_b: Int = v_a match{ // warn: match may not be exhaustive.
     case CC_B(12) => 0
   }
 }