duplicates:

• SR-4475 JSONSerialization cannot serialize UInt8 on Linux

Issue Description:

The check in isValidJSONObject on Linux only checks for generic-width ints (Int, UInt) and not explicit sized widths (e.g. Int8)

            // object is Swift.String, NSNull, Int, Bool, or UInt
            if obj is String || obj is NSNull || obj is Int || obj is Bool || obj is UInt {
                return true
            }

As a result, this code behaves differently on Linux and Darwin:

import Foundation

let i64:Int64 = 1
let i:Int = 1

print( [JSONSerialization.isValidJSONObject(["int64":i64]),
  JSONSerialization.isValidJSONObject(["int":i])]) 

On Darwin, this prints

[true, true]

On Linux, this prints

[false, true]

Adding explicitly sized integer widths (Int64, Int8 etc.) into the isValidObject should fix the problem.