memory leak using 'case let x = y as NSString

Question

I was using a switch with a case let but found out it leaked memory. See the instruments screenshot below. Why is the switch case structure giving me a memory leak?

The code that was causing the memory leak:

switch theValue {
// Bool, Int, UInt, Float and Double are casted to NSNumber by default!
case let numValue as NSNumber:
    return (numValue, "NSNumber", false)
case let longValue as Int64:
    return (NSNumber(longLong: longValue), "NSNumber", false)
case let longValue as UInt64:
    return (NSNumber(unsignedLongLong: longValue), "NSNumber", false)
case let intValue as Int32:
    return (NSNumber(int: intValue), "NSNumber", false)
case let intValue as UInt32:
    return (NSNumber(unsignedInt: intValue), "NSNumber", false)
case let intValue as Int16:
    return (NSNumber(short: intValue), "NSNumber", false)
case let intValue as UInt16:
    return (NSNumber(unsignedShort: intValue), "NSNumber", false)
case let intValue as Int8:
    return (NSNumber(char: intValue), "NSNumber", false)
case let intValue as UInt8:
    return (NSNumber(unsignedChar: intValue), "NSNumber", false)
case let stringValue as NSString:
    return (stringValue, "NSString", false)
case let stringValue as String:
    return (NSString(string: stringValue), "NSString", false)
case let dateValue as NSDate:
    return (dateValue, "NSDate", false)
case let anyvalue as NSArray:
    return (anyvalue, valueType, false)
case let anyvalue as EVObject:
    if valueType.containsString("<") {
        return (anyvalue, swiftStringFromClass(anyvalue), true)
    }
    return (anyvalue, valueType, true)
case let anyvalue as NSObject:
    if valueType.containsString("<") {
        return (anyvalue, swiftStringFromClass(anyvalue), false)
    }
    // isObject is false to prevent parsing of objects like CKRecord, CKRecordId and other objects.
    return (anyvalue, valueType, false)
default:
    (parentObject as? EVObject)?.addStatusMessage(.InvalidType, message: "valueForAny unkown type \(valueType) for value: \(theValue).")
    print("ERROR: valueForAny unkown type \(valueType) for value: \(theValue).")
    return (NSNull(), "NSNull", false)
}

The memory leak was gone after converting it to:

if theValue is NSNumber {
    return (theValue as! NSNumber, "NSNumber", false)
}
if theValue is Int64 {
    return (NSNumber(longLong: theValue as! Int64), "NSNumber", false)
}
if theValue is UInt64 {
    return (NSNumber(unsignedLongLong: theValue as! UInt64), "NSNumber", false)
}
if theValue is Int32 {
    return (NSNumber(int: theValue as! Int32), "NSNumber", false)
}
if theValue is UInt32 {
    return (NSNumber(unsignedInt: theValue as! UInt32), "NSNumber", false)
}
if theValue is Int16 {
    return (NSNumber(short: theValue as! Int16), "NSNumber", false)
}
if theValue is UInt16 {
    return (NSNumber(unsignedShort: theValue as! UInt16), "NSNumber", false)
}
if theValue is Int8 {
    return (NSNumber(char: theValue as! Int8), "NSNumber", false)
}
if theValue is UInt8 {
    return (NSNumber(unsignedChar: theValue as! UInt8), "NSNumber", false)
}
if theValue is NSString {
    return (theValue as! NSString, "NSString", false)
}
if theValue is NSDate {
    return (theValue as! NSDate, "NSDate", false)
}
if theValue is NSArray {
    return (theValue as! NSArray, valueType, false)
}
if theValue is EVObject {
    if valueType.containsString("<") {
        return (theValue as! EVObject, swiftStringFromClass(theValue as! EVObject), true)
    }
    return (theValue as! EVObject, valueType, true)
}
if theValue is NSObject {
    if valueType.containsString("<") {
        return (theValue as! NSObject, swiftStringFromClass(theValue as! NSObject), true)
    }
    return (theValue as! NSObject, valueType, true)
}
(parentObject as? EVObject)?.addStatusMessage(.InvalidType, message: "valueForAny unkown type \(valueType) for value: \(theValue).")
print("ERROR: valueForAny unkown type \(valueType) for value: \(theValue).")
return (NSNull(), "NSNull", false)

Here is the screenshot where you can see the details about the leak:

Answer 1

This is a known issue. Initially it should have been fixed in Xcode 7.1 but apparently there is still a problem.

The bug is reported here: https://bugs.swift.org/browse/SR-1339?jql=text%20~%20%22switch%20case%20leak%22