exit status: 1 with stderr:
<stdin>:3:12: warning: 'as' test is always true case let b as Int: print("OK", b) ^ <stdin>:2:1: error: switch must be exhaustive switch a { ^ <stdin>:2:1: note: add missing case: '.none' switch a { ^ <stdin>:2:1: note: add missing case: '.some(_)' switch a { ^