Why is this an issue?

The requirement for a final else 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

case param
  when 1
    do_something()
  when 2
    do_something_else()
end

Compliant solution

case param
  when 1
    do_something()
  when 2
    do_something_else()
  else
    handle_error('error_message')
end

Resources

• MITRE, CWE-478 - Missing Default Case in Switch Statement