exit status: 1 with stderr:
<stdin>:2:1: error: type 'Optional<Wrapped>' does not conform to protocol 'CVarArg' extension Optional: CVarArg { ^ Swift.CVarArg:2:9: note: protocol requires property '_cVarArgEncoding' with type '[Int]' var _cVarArgEncoding: [Int] { get } ^ <stdin>:10:15: error: incorrect argument labels in call (have 'format:_:', expected 'repeating:count:') let s = String(format: "%@", a) ^~~~~~~ repeating count: <stdin>:10:30: error: cannot convert value of type 'Any?' to expected argument type 'Int' let s = String(format: "%@", a) ^ as! Int