26190497: Xcode 7.3: Accessing specular field of MDLScatteringFunction crashes playground (OS X and iOS)

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Description

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.dylibswift::_swift_getClass(void const*) + 33 frame #1: 0x0000000111af83d3 libswiftCore.dylibfindDynamicValueAndType(swift::OpaqueValue_, swift::Metadata const_, swift::OpaqueValue_&, swift::Metadata const_&, bool&) + 179
  frame 22108390: Swift 2.0b4: Allow assignment of nil to self in failable initializers to indicate failure #2: 0x0000000111af977c libswiftCore.dylib_dynamicCastToExistential(swift::OpaqueValue*, swift::OpaqueValue*, swift::Metadata const*, swift::ExistentialTypeMetadata const*, swift::DynamicCastFlags) + 60 frame #3: 0x0000000111af8d8f libswiftCore.dylibswift_dynamicCast + 671
  frame 22108127: Apple Music: CarPlay does not show the For You Playlists #4: 0x00000001119deaf1 libswiftCore.dylibgeneric 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.dylibfunction 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 (Swift.Array<protocol<>>, separator : Swift.String, terminator : Swift.String, toStream : inout A) -> () + 373
  frame 22108095: Changing account in Music app requires force-quit #6: 0x0000000111a73652 libswiftCore.dylibfunction 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.dylibSwift.print (Swift.Array<protocol<>>, separator : Swift.String, terminator : Swift.String) -> () + 29
  frame 22107434: Providing Generic Generator for protocol intermittently crashes compiler #8: 0x000000011b0d5995 $__lldb_expr14main + 661 at ModelIO.playground:7 frame #9: 0x000000010f4c2ab0 ModelIO frame #10: 0x000000010f4c59a1 ModelIOreabstraction thunk helper from @callee_owned () -> (@unowned ()) to @callee_owned (@in ()) -> (@out ()) + 17
  frame 22106545: automaticallyAdjustsScrollViewInsets doesn't change insets on iOS 9 #11: 0x000000010f4c5401 ModelIOpartial apply forwarder for reabstraction thunk helper from @callee_owned () -> (@unowned ()) to @callee_owned (@in ()) -> (@out ()) + 81 frame #12: 0x000000010f4c59d0 ModelIOreabstraction thunk helper from @callee_owned (@in ()) -> (@out ()) to @callee_owned () -> (@unowned ()) + 32
  frame 22105831: Application windows move erratically with two monitors #13: 0x000000010f4c5a07 ModelIOreabstraction thunk helper from @callee_owned () -> (@unowned ()) to @callee_unowned @convention(block) () -> (@unowned ()) + 39 frame #14: 0x000000010fee42ec CoreFoundationCFRUNLOOP_IS_CALLING_OUT_TO_A_BLOCK + 12
  frame 22104678: Xcode7-beta4 (7A165t): libtool does not support -ios_version_min link editor flag #15: 0x000000010fed9f75 CoreFoundation__CFRunLoopDoBlocks + 341 frame #16: 0x000000010fed96d2 CoreFoundation__CFRunLoopRun + 850
  frame 22103812: TestFlight does not support yet apps with watchOS 2 #17: 0x000000010fed90f8 CoreFoundationCFRunLoopRunSpecific + 488 frame #18: 0x0000000116a9ead2 GraphicsServicesGSEventRunModal + 161
  frame 22102418: El Capitan Terminal password autofill suggestion #19: 0x0000000110374f09 UIKitUIApplicationMain + 171 frame #20: 0x000000010f4c2f39 ModelIOmain + 1161
  frame 22100305: Safari does not see my valid Safari Developer cert #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.

Product Version: Xcode 7.3 (7D175)
Created: 2016-05-10T07:21:23.435440
Originated: 2016-05-10T00:20:00
Open Radar Link: http://www.openradar.me/26190497

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Modified: 2016-05-10T07:21:23.435650