Open Radar

 
The attached script will cause Playgrounds to crash, and not work again until Xcode is reloaded

Steps to Reproduce:
1. Install Xcode 
2. Open a new playground
3. Copy and paste the following script:

struct A
{
    init()
    {
    }
}

struct B
{
    var a : [A]
    init()
    {
        a = []
    }
}

var b = [B](count: 4, repeatedValue: B())
var c = A()

b[0].a.append(c)


Expected Results:
No popup windows, no crashes.

The value of b might be shown as:
[{A}, {0 elements}, {0 elements}, {0 elements}]


Actual Results:
A pop-up window appears:

Communication with the playground service was interrupted unexpectedly.
The playground service "com.apple.dt.Xcode.Playground" may have generated a crash log.


Further typing causes another popup window:

Error running playground.
An error occurred while trying to communicate with a helper application. You may need to restart Xcode before playgrounds will run again.

Version:
Xcode Version 6.1.1 (6A2008a)
OS X Version 10.10.2 (14C94b)