[Test] Go through the runtime for the "as? NSObject" check.

This prevents runtime differences on as? from affecting this test.

Author: DougGregor

test/stdlib/BridgeIdAsAny.swift.gyb

@@ -196,6 +196,11 @@ testCases = [
 ]
 }%
 
+/// Whether this can be safely casted to NSObject
+func isNSObject<T>(_ value: T) -> Bool {
+  return (value as? NSObject) != nil
+}
+
 % for testName, type, valueExpr, testFunc, conformsToError, conformsToHashable in testCases:
 BridgeAnything.test("${testName}") {
   autoreleasepool {
@@ -207,7 +212,7 @@ BridgeAnything.test("${testName}") {
     let xInArray = [x]
     ${testFunc}(original: x, bridged: (_bridgeAnythingToObjectiveC(xInArray) as! [AnyObject])[0])
     ${testFunc}(original: x, bridged: (_bridgeAnythingToObjectiveC(xInArray) as? [AnyObject])![0])
-    if (x as? NSObject) != nil {
+    if isNSObject(x) {
       ${testFunc}(original: x, bridged: (_bridgeAnythingToObjectiveC(xInArray) as! [AnyObject])[0])
       ${testFunc}(original: x, bridged: (_bridgeAnythingToObjectiveC(xInArray) as? [AnyObject])![0])
     }
@@ -216,7 +221,7 @@ BridgeAnything.test("${testName}") {
     let xInDictValue = ["key" : x]
     ${testFunc}(original: x, bridged: (_bridgeAnythingToObjectiveC(xInDictValue) as! [String: AnyObject])["key"]!)
     ${testFunc}(original: x, bridged: (_bridgeAnythingToObjectiveC(xInDictValue) as? [String: AnyObject])!["key"]!)
-    if (x as? NSObject) != nil {
+    if isNSObject(x) {
       ${testFunc}(original: x, bridged: (_bridgeAnythingToObjectiveC(xInDictValue) as! [String: NSObject])["key"]!)
       ${testFunc}(original: x, bridged: (_bridgeAnythingToObjectiveC(xInDictValue) as? [String: NSObject])!["key"]!)
     }
@@ -228,7 +233,7 @@ BridgeAnything.test("${testName}") {
     // The NSObject version below can't test class LifetimeTracked.
     // ${testFunc}(original: x, bridged: (_bridgeAnythingToObjectiveC(xInDictKey) as! [(AnyObject & Hashable): String]).keys.first!)
     // ${testFunc}(original: x, bridged: (_bridgeAnythingToObjectiveC(xInDictKey) as? [(AnyObject & Hashable): String])!.keys.first!)
-    if (x as? NSObject) != nil {
+    if isNSObject(x) {
       ${testFunc}(original: x, bridged: (_bridgeAnythingToObjectiveC(xInDictKey) as! [NSObject: String]).keys.first!)
       ${testFunc}(original: x, bridged: (_bridgeAnythingToObjectiveC(xInDictKey) as? [NSObject: String])!.keys.first!)
     }