[SR-5923] JSONSerialization cannot cast positive number to UInt

[swift-ci]

Previous ID	SR-5923
Radar	None
Original Reporter	ylin (JIRA User)
Type	Bug
Status	Resolved
Resolution	Done

Environment

Ubuntu 14.04, Swift 4 09-17 snapshot

Additional Detail from JIRA

Votes	0
Component/s	Foundation
Labels	Bug
Assignee	None
Priority	Medium

md5: f28ac0e9fa50444fffe98dcea94a5965

Issue Description:

Ubuntu 14.04:

ylin@ylin-VirtualBox:~$ swift -I/home/ylin/.swiftenv/versions/4.0-DEVELOPMENT-SNAPSHOT-2017-09-17-a/usr/lib/swift/clang/include
Welcome to Swift version 4.0-dev (LLVM 2dedb62a0b, Clang b9d76a314c, Swift 56b2dc8eab). Type :help for assistance.
  1> import Foundation 
  2. let str = """ 
  3. { 
  4.     "id": 1111 
  5. } 
  6. """ 
  7. let obj = JSONSerialization.jsonObject(with: str.data(using: .utf8)!) 
  8.  
  9. (obj as! [String: Any])["id"] as! UInt64
Could not cast value of type 'Swift.Int' (0x7ffff7d81170) to 'Swift.UInt64' (0x7ffff7d80cc0).
Process 3169 stopped
* thread #​1, name = 'repl_swift', stop reason = signal SIGABRT
    frame #​0: 0x00007ffff6c8dc37 libc.so.6`__GI_raise(sig=6) at raise.c:56
Target 0: (repl_swift) stopped.
str: String = {
  _core = {
    _baseAddress = <extracting data from value failed>

    _countAndFlags = <extracting data from value failed>

    _owner = <extracting data from value failed>

  }
}
obj: Any = <extracting data from value failed>

Execution interrupted. Enter code to recover and continue.
Enter LLDB commands to investigate (type :help for assistance.)

macOS:

ylin@youming-mbpr:~/Swift/swift-html-entities$ swift
Welcome to Apple Swift version 4.0-dev (LLVM 2dedb62a0b, Clang b9d76a314c, Swift 56b2dc8eab). Type :help for assistance.
  1> import Foundation 
  2. let str = """ 
  3. { 
  4.     "id": 1111 
  5. } 
  6. """ 
  7. let obj = JSONSerialization.jsonObject(with: str.data(using: .utf8)!) 
  8.  
  9. (obj as! [String: Any])["id"] as! UInt64
$R0: UInt64 = 1111
str: String = "{\n    \"id\": 1111\n}"
obj: Any = {
  payload_data_0 = 0x00000001002086c0
  payload_data_1 = 0x0000000000000000
  payload_data_2 = 0x0000000000000000
  instance_type = 0x00000001014272c0 libswiftCore.dylib`InitialAllocationPool + 3072
}

First reported here: Kitura/Kitura-CredentialsGitHub#27

[belkadan]

cc @phausler

[belkadan]

My understanding is that this is just how JSONSerialization works on Linux. Rather than creating NSNumber intermediates, it creates Ints directly, and you can't use as! to go from one kind of integer to another in Swift. (Apple platforms add magic around NSNumber, but they still won't go from Int to UInt.)

[itaiferber]

That's correct. You'll need to get the value out as either an `Int` or a `Double`, and convert it from there

[spevans]

The as casting was fixed in 4.2 on Linux so this now works:

$ ~/swift-4.2.1-RELEASE-ubuntu18.04/usr/bin/swift
Welcome to Swift version 4.2.1 (swift-4.2.1-RELEASE). Type :help for assistance.
  1> import Foundation 
  2> let str = " { \"id\": 1111 } "
str: String = " { \"id\": 1111 } "
  3> let obj = JSONSerialization.jsonObject(with: str.data(using: .utf8)!) 
obj: [String : Any] = 1 key/value pair {
  [0] = {
    key = "id"
    value = {
      Foundation.NSValue = {
        Foundation.NSObject = {}
      }
      _base = {
        info = 265422848
        pad = 8388596
      }
      _pad = 36028745744779264
    }
  }
}
  4> (obj as! [String: Any])["id"] as! UInt64
$R0: UInt64 = 1111