The requirement for a final ``++case _++`` clause is defensive programming. The clause should either take appropriate action, or contain a suitable comment as to why no action is taken.
== Noncompliant Code Example
----
param match {
case 1 => doSomething
case 2 => doSomethingElse
}
== Compliant Solution
case _ => throw new IllegalArgumentException(s"Unexpected param: $param")
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