stdlib: Dictionary, Set: allow querying for a mismatched type when bridged

Swift's Dictionary and Set are typed, but when bridged to NSDictionary
and NSSet they should behave accordingly, that is, allow querying for
keys of arbitrary types.

rdar://problem/23679193

Author: gribozavr

stdlib/public/core/HashedCollections.swift.gyb

@@ -3275,7 +3275,9 @@ final internal class _Native${Self}StorageOwner<${TypeParametersDecl}>
   @warn_unused_result
   internal func bridgingObjectForKey(_ aKey: AnyObject)
     -> AnyObject? {
-    let nativeKey = _forceBridgeFromObjectiveC(aKey, Key.self)
+    guard let nativeKey = _conditionallyBridgeFromObjectiveC(aKey, Key.self)
+    else { return nil }
+
     let (i, found) = nativeStorage._find(
       nativeKey, startBucket: nativeStorage._bucket(nativeKey))
     if found {

test/1_stdlib/Inputs/DictionaryKeyValueTypesObjC.swift

@@ -113,6 +113,39 @@ class TestObjCKeyTy : NSObject, NSCopying {
   var serial: Int
 }
 
+// A type that satisfies the requirements of an NSDictionary key (or an NSSet
+// member), but traps when any of its methods are called.
+class TestObjCInvalidKeyTy {
+  init() {
+    _objcKeyCount.fetchAndAdd(1)
+    serial = _objcKeySerial.addAndFetch(1)
+  }
+
+  deinit {
+    assert(serial > 0, "double destruction")
+    _objcKeyCount.fetchAndAdd(-1)
+    serial = -serial
+  }
+
+  @objc
+  var description: String {
+    assert(serial > 0, "dead TestObjCInvalidKeyTy")
+    fatalError()
+  }
+
+  @objc
+  func isEqual(_ object: AnyObject!) -> Bool {
+    fatalError()
+  }
+
+  @objc
+  var hash : Int {
+    fatalError()
+  }
+
+  var serial: Int
+}
+
 var _objcValueCount = _stdlib_AtomicInt(0)
 var _objcValueSerial = _stdlib_AtomicInt(0)
 

validation-test/stdlib/Dictionary.swift

@@ -2558,6 +2558,11 @@ DictionaryTestSuite.test("BridgedToObjC.Verbatim.ObjectForKey") {
 
   expectEmpty(d.object(forKey: TestObjCKeyTy(40)))
 
+  // NSDictionary can store mixed key types.  Swift's Dictionary is typed, but
+  // when bridged to NSDictionary, it should behave like one, and allow queries
+  // for mismatched key types.
+  expectEmpty(d.object(forKey: TestObjCInvalidKeyTy()))
+
   for i in 0..<3 {
     expectEqual(idValue10, unsafeBitCast(
       d.object(forKey: TestObjCKeyTy(10)), to: UInt.self))

validation-test/stdlib/Set.swift

@@ -2154,12 +2154,37 @@ SetTestSuite.test("BridgedToObjC.Verbatim.Count") {
 }
 
 SetTestSuite.test("BridgedToObjC.Verbatim.Contains") {
-  let nss = getBridgedNSSetOfRefTypesBridgedVerbatim()
+  let s = getBridgedNSSetOfRefTypesBridgedVerbatim()
 
-  expectNotEmpty(nss.member(TestObjCKeyTy(1010)))
-  expectNotEmpty(nss.member(TestObjCKeyTy(2020)))
-  expectNotEmpty(nss.member(TestObjCKeyTy(3030)))
-  expectEmpty(nss.member(TestObjCKeyTy(4040)))
+  var v: AnyObject? = s.member(TestObjCKeyTy(1010))
+  expectEqual(1010, (v as! TestObjCKeyTy).value)
+  let idValue10 = unsafeBitCast(v, to: UInt.self)
+
+  v = s.member(TestObjCKeyTy(2020))
+  expectEqual(2020, (v as! TestObjCKeyTy).value)
+  let idValue20 = unsafeBitCast(v, to: UInt.self)
+
+  v = s.member(TestObjCKeyTy(3030))
+  expectEqual(3030, (v as! TestObjCKeyTy).value)
+  let idValue30 = unsafeBitCast(v, to: UInt.self)
+
+  expectEmpty(s.member(TestObjCKeyTy(4040)))
+
+  // NSSet can store mixed key types.  Swift's Set is typed, but when bridged
+  // to NSSet, it should behave like one, and allow queries for mismatched key
+  // types.
+  expectEmpty(s.member(TestObjCInvalidKeyTy()))
+
+  for i in 0..<3 {
+    expectEqual(idValue10,
+      unsafeBitCast(s.member(TestObjCKeyTy(1010)), to: UInt.self))
+
+    expectEqual(idValue20,
+      unsafeBitCast(s.member(TestObjCKeyTy(2020)), to: UInt.self))
+
+    expectEqual(idValue30,
+      unsafeBitCast(s.member(TestObjCKeyTy(3030)), to: UInt.self))
+  }
 
   expectAutoreleasedKeysAndValues(unopt: (3, 0))
 }