Open Radar

 
Note: This issue is resolved in Xcode 6 Beta 2.

Summary:
The Swift REPL incorrectly allows you to change a constant defined with "let".

Steps to Reproduce:
1. Launch the Swift REPL from the command line:
$ xcrun swift
Welcome to Swift!  Type :help for assistance.

2. Define a constant:
  1> let a = 5
a: Int = 5

3. Try to assign a new value to a:
  2> a = 10


Expected Results:
I expect the REPL to show an error because assigning to constants is not allowed.

Actual Results:
There is no error. The value appears to have changed:

  3> println(a)
10

Version:
Xcode Version 6.0 (6A215l)
OS X 10.9.3 (13D65)

$ xcrun swift --version
Swift version 1.0 (swift-600.0.34.4.5)
Target: x86_64-apple-darwin13.2.0

Notes:
Note that this bug only appears when you launch the REPL without the "-integrated-repl" argument. When launched with "-integrated-repl", it behaves correctly:

$ xcrun swift -integrated-repl
Welcome to swift.  Type ':help' for assistance.
(swift) let a = 5
// a : Int = 5
(swift) a = 10
<REPL Input>:1:3: error: cannot assign to 'let' value 'a'
a = 10
~ ^

Discussed in the Dev Forums at https://devforums.apple.com/message/971654#971654.