Open Radar

 
Summary:
Provide a descriptive summary of the issue.

Steps to Reproduce:
1) Create an iOS playground
2) Paste in the following code:

	import UIKit
	import ModelIO
	let scatteringFunction = MDLScatteringFunction()
	print(scatteringFunction.specular)

Expected Results:
The playground should print the value of the specular field and, you know, not crash.

Actual Results:
The playground crashes with the following message on the console:
5/10/16 12:14:59.856 AM com.apple.dt.Xcode.Playground[13137]: IDEPlaygroundExecutionSessionThread(pid=13330) IDEPlaygroundExecution: Playground execution failed: Error Domain=IDEPlaygroundErrorDomain Code=3 "Execution was interrupted, reason: EXC_BAD_ACCESS (code=1, address=0x0).
The process has been left at the point where it was interrupted, use "thread return -x" to return to the state before expression evaluation." UserInfo={IDEPlaygroundExprCrashDate=2016-05-10 07:14:59 +0000, IDEPlaygroundExprCrashBacktrace=* thread #1: tid = 0x131b2a, 0x0000000111b25b31 libswiftCore.dylib`swift::_swift_getClass(void const*) + 33, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x0)
  * frame #0: 0x0000000111b25b31 libswiftCore.dylib`swift::_swift_getClass(void const*) + 33
    frame #1: 0x0000000111af83d3 libswiftCore.dylib`findDynamicValueAndType(swift::OpaqueValue*, swift::Metadata const*, swift::OpaqueValue*&, swift::Metadata const*&, bool&) + 179
    frame #2: 0x0000000111af977c libswiftCore.dylib`_dynamicCastToExistential(swift::OpaqueValue*, swift::OpaqueValue*, swift::Metadata const*, swift::ExistentialTypeMetadata const*, swift::DynamicCastFlags) + 60
    frame #3: 0x0000000111af8d8f libswiftCore.dylib`swift_dynamicCast + 671
    frame #4: 0x00000001119deaf1 libswiftCore.dylib`generic specialization <protocol<>, Swift._TeeStream<Swift.String, Swift._Stdout> with Swift._TeeStream<Swift.String, Swift._Stdout> : Swift.OutputStreamType in Swift> of Swift._print_unlocked <A, B where B: Swift.OutputStreamType> (A, inout B) -> () + 433
    frame #5: 0x0000000111a73185 libswiftCore.dylib`function signature specialization <Arg[0] = Owned To Guaranteed, Arg[1] = Owned To Guaranteed and Exploded, Arg[2] = Owned To Guaranteed and Exploded> of generic specialization <Swift._TeeStream<Swift.String, Swift._Stdout> with Swift._TeeStream<Swift.String, Swift._Stdout> : Swift.OutputStreamType in Swift> of Swift._print <A where A: Swift.OutputStreamType> (Swift.Array<protocol<>>, separator : Swift.String, terminator : Swift.String, toStream : inout A) -> () + 373
    frame #6: 0x0000000111a73652 libswiftCore.dylib`function signature specialization <Arg[0] = Owned To Guaranteed, Arg[1] = Owned To Guaranteed and Exploded, Arg[2] = Owned To Guaranteed and Exploded> of Swift.print (Swift.Array<protocol<>>, separator : Swift.String, terminator : Swift.String) -> () + 194
    frame #7: 0x00000001119e19bd libswiftCore.dylib`Swift.print (Swift.Array<protocol<>>, separator : Swift.String, terminator : Swift.String) -> () + 29
    frame #8: 0x000000011b0d5995 $__lldb_expr14`main + 661 at ModelIO.playground:7
    frame #9: 0x000000010f4c2ab0 ModelIO
    frame #10: 0x000000010f4c59a1 ModelIO`reabstraction thunk helper from @callee_owned () -> (@unowned ()) to @callee_owned (@in ()) -> (@out ()) + 17
    frame #11: 0x000000010f4c5401 ModelIO`partial apply forwarder for reabstraction thunk helper from @callee_owned () -> (@unowned ()) to @callee_owned (@in ()) -> (@out ()) + 81
    frame #12: 0x000000010f4c59d0 ModelIO`reabstraction thunk helper from @callee_owned (@in ()) -> (@out ()) to @callee_owned () -> (@unowned ()) + 32
    frame #13: 0x000000010f4c5a07 ModelIO`reabstraction thunk helper from @callee_owned () -> (@unowned ()) to @callee_unowned @convention(block) () -> (@unowned ()) + 39
    frame #14: 0x000000010fee42ec CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK__ + 12
    frame #15: 0x000000010fed9f75 CoreFoundation`__CFRunLoopDoBlocks + 341
    frame #16: 0x000000010fed96d2 CoreFoundation`__CFRunLoopRun + 850
    frame #17: 0x000000010fed90f8 CoreFoundation`CFRunLoopRunSpecific + 488
    frame #18: 0x0000000116a9ead2 GraphicsServices`GSEventRunModal + 161
    frame #19: 0x0000000110374f09 UIKit`UIApplicationMain + 171
    frame #20: 0x000000010f4c2f39 ModelIO`main + 1161
    frame #21: 0x0000000112d0492d libdyld.dylib`start + 1
, IDEPlaygroundExprCrashMessage=Execution was interrupted, reason: EXC_BAD_ACCESS (code=1, address=0x0).
The process has been left at the point where it was interrupted, use "thread return -x" to return to the state before expression evaluation., IDEPlaygroundExprCrashLineNumber=6, NSLocalizedDescription=Execution was interrupted, reason: EXC_BAD_ACCESS (code=1, address=0x0).
The process has been left at the point where it was interrupted, use "thread return -x" to return to the state before expression evaluation.}



Regression:
Unknown occurs on both iOS and OS X.