[SDK] Backwards-deployment support for Core Data's generics. (#3154)

rdar://problem/26825103

Author: jrose-apple

stdlib/public/SDK/CoreData/CMakeLists.txt

@@ -1,5 +1,6 @@
 add_swift_library(swiftCoreData ${SWIFT_SDK_OVERLAY_LIBRARY_BUILD_TYPES} IS_SDK_OVERLAY
   CoreData.swift
+  CoreData.mm
 
   SWIFT_MODULE_DEPENDS Foundation
   FRAMEWORK_DEPENDS CoreData)

stdlib/public/SDK/CoreData/CoreData.mm

@@ -0,0 +1,28 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+#import <CoreData/CoreData.h>
+
+// Make sure -conformsToProtocol: checks succeed even on older OSs.
+// This only works because NSFetchRequestResult doesn't have any method
+// requirements.
+
+#define CONFORMS_TO_NSFETCHREQUESTRESULT(TYPE) \
+@interface TYPE (_SwiftNSFetchRequestResult) <NSFetchRequestResult> \
+@end \
+@implementation TYPE (_SwiftNSFetchRequestResult) \
+@end
+
+CONFORMS_TO_NSFETCHREQUESTRESULT(NSNumber)
+CONFORMS_TO_NSFETCHREQUESTRESULT(NSDictionary)
+CONFORMS_TO_NSFETCHREQUESTRESULT(NSManagedObject)
+CONFORMS_TO_NSFETCHREQUESTRESULT(NSManagedObjectID)

test/1_stdlib/Inputs/CoreDataHelper/CoreDataHelper.h

@@ -0,0 +1,9 @@
+@import CoreData;
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface NSFetchRequest<__covariant ResultType: id<NSFetchRequestResult>> (SwiftTesting)
++ (NSArray<ResultType> *)testGettingSomeDictionaries;
+@end
+
+NS_ASSUME_NONNULL_END

test/1_stdlib/Inputs/CoreDataHelper/CoreDataHelper.m

@@ -0,0 +1,7 @@
+#import "CoreDataHelper.h"
+
+@implementation NSFetchRequest (SwiftTesting)
++ (NSArray<id<NSFetchRequestResult>> *)testGettingSomeDictionaries {
+  return @[ @{}, @{} ];
+}
+@end

validation-test/stdlib/CoreData.swift

@@ -0,0 +1,41 @@
+// RUN: rm -rf %t && mkdir -p %t
+
+// RUN: %target-clang %S/Inputs/CoreDataHelper/CoreDataHelper.m -c -o %t/CoreDataHelper.o -g -fmodules
+// RUN: %target-build-swift %s -import-objc-header %S/Inputs/CoreDataHelper/CoreDataHelper.h -Xlinker %t/CoreDataHelper.o -o %t/main
+// RUN: %target-run %t/main
+
+// REQUIRES: executable_test
+// REQUIRES: objc_interop
+
+import CoreData
+import StdlibUnittest
+
+var CoreDataTests = TestSuite("CoreData")
+
+CoreDataTests.test("conformsToProtocol") {
+  expectTrue(NSDictionary.conforms(to: NSFetchRequestResult.self))
+  expectTrue(NSManagedObject.conforms(to: NSFetchRequestResult.self))
+}
+
+CoreDataTests.test("downcasting") {
+  var dictionaries = NSFetchRequest<NSFetchRequestResult>.testGettingSomeDictionaries()
+  expectType([NSFetchRequestResult].self, &dictionaries)
+
+  let casted = dictionaries as? [[NSObject: AnyObject]]
+  expectNotEmpty(casted)
+  expectEqual([[:], [:]], casted!)
+  expectEqual([[:], [:]], dictionaries as! [[NSObject: AnyObject]])
+}
+
+CoreDataTests.test("bridging") {
+  var dictionaries = NSFetchRequest<NSDictionary>.testGettingSomeDictionaries()
+  expectType([NSDictionary].self, &dictionaries)
+  expectEqual([[:], [:]], dictionaries)
+
+  let casted = dictionaries as? [[NSObject: AnyObject]]
+  expectNotEmpty(casted)
+  expectEqual([[:], [:]], casted!)
+  expectEqual([[:], [:]], dictionaries as! [[NSObject: AnyObject]])
+}
+
+runAllTests()