Add regression test for https://bugs.swift.org/browse/SR-16076

Author: AnthonyLatsis

validation-test/compiler_crashers_2_fixed/sr16076.swift

@@ -0,0 +1,17 @@
+// RUN: %target-swift-frontend -emit-sil -O %s
+
+// REQUIRES: objc_interop
+import Foundation
+
+@objc protocol OptionalVar {
+    @objc optional var name: String { get }
+}
+
+extension NSObject: OptionalVar { }
+
+do {
+  let objects = [NSObject()] as Array<OptionalVar>
+
+  let names = objects.compactMap(\.name)
+  print("Names: \(names)")
+}